PDF (53.8 MB) - Urban Drainage and Flood Control District

Happy Canyon Creek Major Drainageway Plan 

Alternative Analysis August 2013 

COLORADO 

Town of 

Parker COLORADO

Muller Engineering Company, Inc. 

Happy Canyon Creek Major Drainageway Plan - DRAFT 

TABLE OF CONTENTS 

SECTION 1 – INTRODUCTION 

1.1 Authorization ............................................................................................................................ 1-1 

1.2 Purpose and Scope .................................................................................................................. 1-1 

1.3 Planning Process ...................................................................................................................... 1-1 

1.4 Mapping and Surveys ............................................................................................................. 1-3 

1.5 Data Collection .......................................................................................................................... 1-3 

1.6 Acknowledgements ................................................................................................................. 1-3 

SECTION 2 – STUDY AREA DESCRIPTION 

2.1 Project Area ............................................................................................................................... 2-1 

2.2 Land Use ...................................................................................................................................... 2-1 

2.3 Reach Description ................................................................................................................... 2-2 

2.4 Flood History ............................................................................................................................. 2-6 

2.5 Environmental Assessment.................................................................................................. 2-6 

SECTION 3 – HYDROLOGIC ANALYSIS 

3.1 Overview ..................................................................................................................................... 3-1 

3.2 Design Rainfall .......................................................................................................................... 3-1 

3.3 Subwatershed Characteristics ............................................................................................ 3-2 

3.4 Hydrograph Routing ............................................................................................................... 3-2 

3.5 Previous Studies ....................................................................................................................... 3-3 

3.6 Model Calibration .................................................................................................................... 3-3 

3.7 Results of Analysis ................................................................................................................... 3-5 

SECTION 4 – HYDRAULIC ANALYSIS 

4.1 Evaluation of Existing Facilities .......................................................................................... 4-1 

4.2 Flood Hazards ........................................................................................................................... 4-4 

4.3 Previous Analysis .................................................................................................................... 4-5 

SECTION 5 – ALTERNATIVE ANALYSIS 

5.1 Alternative Development Process ..................................................................................... 5-1 

5.2 Criteria and Constraints ........................................................................................................ 5-1 

5.3 Alternative Categories ........................................................................................................... 5-2 

5.4 Alternative Hydrology and Hydraulics ............................................................................ 5-3 

5.5 Alternative Costs ...................................................................................................................... 5-6 

5.6 Alternative Plans ..................................................................................................................... 5-6 

5.6.1 Detention Alternatives ............................................................................................. 5-6 

5.6.2 Channel and Crossing Alternatives .................................................................... 5-13 

5.7 Qualitative Evaluation of Alternatives .......................................................................... 5-23 

SECTION 6 – RECOMMENDED PLAN 

6.1 Plan Description ...................................................................................................................... 6-1 

6.2 Plan Cost ..................................................................................................................................... 6-3 

6.3 Water Quality Impacts .......................................................................................................... 6-3 

6.3 Operations and Maintenance .............................................................................................. 6-4 

6.4 Environmental and Safety Assessment ........................................................................... 6-4 

SECTION 8 – REFERENCES ............................................................................................................................ 8-1 

LIST OF TABLES 

Table 1-1 Project Meetings ................................................................................................................ 1-2 

Table 1-2 Project Participants ......................................................................................................... 1-4 

Table 2-1 Major Crossing Inventory ............................................................................................... 2-6 

Table 3-1 Point Rainfall Depths ....................................................................................................... 3-1 

Table 3-2 Area Adjustment Factors ................................................................................................ 3-1 

Table 3-3 Model Calibration ............................................................................................................. 3-4 

Table 3-4 Comparison to Previous Studies .................................................................................. 3-5 

Table 4-1 Structure Flooding Evaluation ..................................................................................... 4-2 

Table 4-2 Crossing Capacity Evaluation ........................................................................................ 4-3 

Table 4-3 Roadway Overtopping Depths ...................................................................................... 4-4 

Table 4-4 Grandview Estates Analysis and Preliminary Design Summary ...................... 4-6 

Table 5-1 Channel Alternatives Screening Matrix .................................................................... 5-4 

Table 5-2 Detention and Other Alternatives Screening Matrix ............................................ 5-5 

Table 5-3 Additional Cost Allowances ........................................................................................... 5-6 

Table 5-4 Detention Alternatives Cost Summary ...................................................................... 5-9 

Table 5-5 Reach 1 Channel Cost Summary ................................................................................. 5-13 

Table 5-6 Reach 2a Channel Cost Summary .............................................................................. 5-13 

Table 5-7 Reach 2b Channel Cost Summary .............................................................................. 5-13 

Table 5-8 Reach 2b Crossing Cost Summary ............................................................................. 5-13 

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Table 5-9 Reach 3 Channel Cost Summary ................................................................................ 5-14 

Table 5-10 Reach 3 Crossing Cost Summary ................................................................................ 5-14 





Table 5-15 Reach 7a Channel Cost Summary .............................................................................. 5-15 

Table 5-16 Reach 7b Channel Cost Summary .............................................................................. 5-16 

Table 5-17 Reach 7b Crossing Cost Summary ............................................................................. 5-16 

Table 5-18 Reach 7b Benefit/Cost Analysis ...................................................................................... 5-17 





Table 5-23 Channel Operation and Maintenance Costs ........................................................... 5-18 

Table 5-24 Relative Costs of Alternatives ..................................................................................... 5-23 

Table 5-25 Alternative Grandview Estates Structure Flooding ............................................ 5-24 

Table 6-1 Recommended Plan Costs by Jurisdiction ................................................................ 6-3 

Table 6-2 Recommended Plan Cost Estimate Summary .......................................................... 6-8 

Table B-1 Rainfall Distributions ...................................................................................................... B-3 

Table B-2 CUHP Input ............................................................................................................. B-4 to B-7 

Table B-3 Detention Rating Curves .............................................................................. B-11 to B-12 

Table B-4 Peak Flows ......................................................................................................... B-13 to B-15 

Table B-5 Runoff Volumes – Existing Development................................................................ B-16 

Table B-6 Runoff Volumes – Future Development .................................................................. B-17 

Table B-7 Sample SWMM Input ...................................................................................... B-22 to B-40 

Table B-8 Sample SWMM Output ................................................................................... B-41 to B-54 

Table C-1 Channel Roughness Values ............................................................................................. C-1 

Table F-1 Unit Costs .............................................................................................................................. F-1 

Table F-2 Detention Alternative Peak Flow Rates and Volumes ............................. F-2 to F-3 

Table F-3 Detention Alternative A Cost Estimate ....................................................................... F-8 

Table F-4 Detention Alternative B Cost Estimate ....................................................................... F-9 

Table F-5 Detention Alternative C Cost Estimate .................................................................... F-10 

Table F-6 Channel Quantity Summary by Reach....................................................... F-11 to F-12 

LIST OF FIGURES 

Figure 2-1 Vicinity Map ........................................................................................................................ 2-1 

Figure 5-1 Detention Alternatives – Reach 1-3 .......................................................................... 5-10 



Figure 5-4 Channel Alternatives – Reach 1-3 .............................................................................. 5-19 



Figure 5-7 Channel Improvement Unit Cost Comparison ...................................................... 5-22 

Figure 6-1 Recommended Plan – Reach 1-3 .................................................................................. 6-5 



Figure B-1 Interactive Hydrology Map – Upper Watershed .................................................... B-1 

Figure B-2 Interactive Hydrology Map – Lower Watershed .................................................... B-2 

Figure B-3 SWMM Schematic – Happy Canyon Creek ................................................................. B-8 

Figure B-4 SWMM Schematic – Upper Tributaries ...................................................................... B-9 

Figure B-5 SWMM Schematic – Lower Tributaries .................................................................... B-10 

Figure B-6 Hydrographs – Existing Development ..................................................................... B-18 

Figure B-7 Hydrographs – Future Development ........................................................................ B-19 

Figure B-8 Peak Flow Diagram – Existing Development ......................................................... B-20 

Figure B-9 Peak Flow Diagram – Future Development ........................................................... B-21 

Figure B-10 Peak Flow Diagram – Model Calibration ................................................................. B-55 

Figure C-1 HEC-RAS Sections .................................................................................................. C-2 to C-5 

Figure C-2 Floodplain and Problem Areas – Reach 1-3 ............................................................. C-6 



Figure E-1 Wetland & Riparian Areas – Reach 1-3 ..................................................................... E-1 



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Figure F-1 Detention Alternative Peak Flow Diagram – 100-Year Event ............................ F-4 

Figure F-2 Detention Alternative Peak Flow Diagram – 10-Year Event ............................... F-5 

Figure F-3 Detention Alternative Peak Flow Diagram – 2-Year Event ................................. F-6 

Figure F-4 Detention Alternative Peak Flow Diagram – Water Quality Event ................... F-7 

LIST OF APPENDICES 

Appendix A 

Appendix B 

Appendix C 

Appendix D 

Appendix E 

Appendix F 

Project Correspondence 

Hydrologic Analysis 

Hydraulic Analysis 

Legal Opinion 

Wetland and Riparian Inventory 

Alternatives Analysis 

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SECTION 1 – INTRODUCTION 

1.1 Authorization 

The Urban Drainage and Flood Control District (UDFCD), in agreement with Douglas County, the City 

of Lone Tree, the Town of Parker, and the Southeast Metro Stormwater Authority (SEMSWA), 

contracted with Muller Engineering Company, Inc. to conduct a Major Drainageway Plan (MDP) and 

Flood Hazard Area Delineation (FHAD) for Happy Canyon Creek. The work is authorized under 

UDFCD Agreement No. 11-11.06, dated April 18, 2012. 

Amendment 1 (Agreement No. 11-11.06A), dated September 18, 2012, added a FHAD for Badger 

Gulch to the scope. Amendment 2 (Agreement No. 11-11.06B), dated ___________, authorized a study of 

the impacts of detention sizing and layout within the City of Lone Tree on the timing of peak flows 

on Happy Canyon Creek, revisions to the report that resulted from the study, and various minor 

additional tasks. 

1.2 Purpose and Scope 

The Happy Canyon Creek watershed was last studied in the Happy Canyon Creek Watershed Outfall 

Systems Planning Study (OSP), published in August 1993 by Kiowa Engineering Corporation. The 

Happy Canyon Creek regulatory floodplain was established in a 1977 FHAD prepared by Howard, 

Needles, Tammen & Bergendoff that included Happy Canyon Creek and Badger Gulch (a tributary to 

Happy Canyon Creek), along with Newlin, Baldwin, Sulphur, and Tallman Gulches. Several Letter of 

Map Revision (LOMR) updates to the floodplain have been incorporated since the 1977 FHAD. 

UDFCD typically updates master plans every 20-30 years based on requests and support from local 

governments. Development is actively occurring in the lower portion of the Happy Canyon 

watershed, and development projections for the middle portion of the watershed in the City of Lone 

Tree have changed significantly since 1993 with the formulation of the RidgeGate Planned 

Development District (PDD). This update is therefore well-timed to help guide channel and 

detention improvements in conjunction with development. In addition, there seem to be 

inconsistencies in the hydrologic basis for the floodplain mapping; because this update includes a 

FHAD, inconsistencies in floodplain hydrology along Happy Canyon Creek will be eliminated. 

The overall scope of work for the MDP includes the following main tasks: 

1. Meet periodically with the project sponsors and other stakeholders to exchange information 

and to solicit input and direction; 

2. Set up and maintain a project web site to present information and receive input from 

interested parties; 

3. Collect and review available reports and studies related to existing and proposed stormwater 

facilities, local hydrology, floodplains, current and future land use, and water quality; 

4. Review the 1993 hydrologic model and modify to run on the newest versions of CUHP and 

SWMM, to reflect current imperviousness conditions and updated projections of future 

imperviousness based on recent zoning changes, to include current publicly-maintained 

regional detention facilities, and to reflect other stormwater facilities and watershed 

conditions that currently exist; 

5. Perform hydraulic calculations necessary to assess the adequacy of existing stormwater 

facilities and to size alternative improvement plans; 

6. Identify existing and potential future drainage, erosion, water quality, and flooding problems 

in the project area, including a general identification of wetland and riparian zones and 

potential detention sites; 

7. Formulate and evaluate conceptual alternative plans to address drainage, erosion, water 

quality, and flood hazard problems associated with the drainageway, considering probable 

costs, water quality effects, and maintenance aspects; 

8. Prepare a draft alternatives analysis report to document the formulation and evaluation of 

alternative plans and to recommend a preferred alternative, review with project sponsors 

and stakeholders, and revise to address the comments received; 

9. Undertake a conceptual design of the selected alternative and prepare drawings and 

probable cost information for the plan, documenting in a draft, then final conceptual design 

report; and 

10. Participate in formal presentations of the study results at two public meetings. 

1.3 Planning Process 

Based on input from the project sponsors and on observations of the current condition of various 

reaches of Happy Canyon Creek, the following main objectives for this master plan were identified: 

• Preserve/establish channel equilibrium by maintaining balance of water flow and sediment 

movement to the extent possible 

• Eliminate inconsistencies / improve the accuracy of the floodplain delineation 

• Address floodplain concerns in Grandview Estates 

August 2013 Page 1-1 Alternative Analysis



• Address severely degraded channel reaches 

• Develop conceptual design improvements to be implemented with adjacent development 

• Reduce peak flow rates for minor storm events by providing regional full-spectrum 

detention, incorporating infiltration measures, or other means 

• Develop this plan with the involvement and buy-in of major property owners such as 

RidgeGate 

• Reduce impacts of livestock to channel stability and water quality 

• Maintain a watershed approach to the plan 

• Achieve the objectives of project sponsors and numerous project stakeholders while 

preserving a natural channel character and supporting riparian vegetation communities and 

resident wildlife habitat 

Periodic meetings were held to gather input from project sponsors and stakeholders. A summary of 

project meetings is shown in Table 1-1; meeting minutes are included in Appendix A. 

A public meeting was held on June 12, 2013 at the Parker Recreation Center to present the draft 

Alternative Analysis. Invitations were sent to residents and property owners within 300’ of Happy 

Canyon Creek, and email notification was provided to agencies identified by the project sponsors as 

additional project stakeholders. Meeting minutes and the attendance roster are included in 

Appendix A. 

Table 1-1 

Project Meetings 

Meeting Date Purpose 

Kickoff Meeting May 3, 2012 

Progress Meeting #2 June 12, 2012 

Progress Meeting #3 September 10, 2012 

Progress Meeting #4 October 11, 2012 

Progress Meeting #5 October 30, 2012 

Review project scope and project approach, identify 

information needs 

Hydrology status update, review land use 

assumptions, introduce stakeholders 

Review Draft Baseline Hydrology comments, initial 

discussion of FHAD and alternatives analysis 

Working meeting for FHAD and alternatives analysis; 

identify survey needs and initial areas of concern 

Review initial FHAD results including roughness 

sensitivity analysis; discuss FHAD and alternatives 

issues 

Progress Meeting #6 April 4, 2013 Review Draft Alternative Analysis comments 

Public Meeting June 12, 2013 Present Draft Alternative Analysis for public comment 




1.4 Mapping and Surveys 

Mapping data sources used for the Happy Canyon Creek MDP included the following: 

• Color aerial photography was provided by UDFCD. The photography was generated as part of 

the Denver Region Aerial Photography Project (DRAPP) by the Denver Region Council of 

Governments (DRCOG). Photographs are from spring 2010, meet 1”=200’ horizontal mapping 

standards, and have a resolution of 1 foot. 

• 2-foot interval topography within the northern project area (north of Lincoln Avenue) was 

obtained from the Denver Democratic National Convention (DNC) LIDAR Survey compiled by 

Sanborn Geospatial on July 25, 2008. 

• 2-foot interval topography along the main stem of Happy Canyon Creek south of Lincoln 

Avenue and along Badger Gulch was provided by UDFCD. The topography was prepared by 

Landmark Mapping, Ltd. at a scale of 1”=100” and was based on aerial photography dated 

December 17, 2011 (Happy Canyon) and October 2012 (Badger Gulch). 

• 5-foot interval topography in Douglas County was provided by the County and was used to 

delineate watershed boundaries and define subwatershed and channel properties south of 

Lincoln Avenue. The source of the mapping was Merrick & Company’s 1996 Digital Elevation 

Model (DEM) “Mass Points.” 

1.5 Data Collection 

Numerous reports, studies, and design plans were reviewed and utilized in the preparation of this 

report. A listing of the primary references is as follows; a full listing is included in the References 

section at the end of this report. 

• 1977 Flood Hazard Area Delineation, Happy Canyon Creek, Badger Gulch, Newlin Gulch, 

Baldwin Gulch, Sulphur Gulch, Tallman Gulch (Howard, Needles, Tammen & Bergendoff) 

• 1993 Happy Canyon Creek Watershed Outfall Systems Planning Study (Kiowa Engineering 

Corporation) 

• 2001 Phase I Design Report, Happy Canyon Creek Channel Restoration [in Grandview 

Estates] (HDR, Inc.) 

1.6 Acknowledgements 

This report could not have been prepared without the participation and support of the following 

project sponsors and stakeholders. We are grateful for their contributions. 

• Ground survey of stream crossings on main stem Happy Canyon Creek and was provided by 

UDFCD. Survey was conducted by Accurate EngiSurv, LLC in December 2011 (Happy 

Canyon). Additional ground survey of structures and other various sensitive areas was 

conducted in November 2012. 

All mapping is on the Colorado State Plane Central Zone projection, horizontal datum NAD83, and 

vertical datum NAVD 1988. 

Existing parcel boundaries, zoning, jurisdictional boundaries, and Digital Flood Insurance Rate Map 

(DFIRM) data were provided by Douglas County and SEMSWA in Geographic Information System 

(GIS) format. SEMSWA data also included existing storm infrastructure within their jurisdiction. 




Table 1-2 

Project Participants 

Project Sponsors 

Shea Thomas 

Brad Robenstein 

Greg Weeks 

Ward Mahanke 

Tom Williams 

Jacob James 

Monica Bortolini 

Project Stakeholders 

Stacey Thompson 

Bryan Ruth 

Ken Linhardt 

Denise Denslow 

Brad Meyering 

Charlie Fagan 

Bill Ruzzo 

Agency 

Urban Drainage and Flood Control District 

Douglas County 

City of Lone Tree 

representing City of Lone Tree 

Town of Parker 


Southeast Metro Stormwater Authority 

Agency 

Arapahoe County 

representing Rampart Range Metro District 



City of Castle Pines 

Castle Pines North Metro District 

Cherry Creek Basin Water Quality Authority 




SECTION 2 – STUDY AREA DESCRIPTION 

2.1 Project Area 

Happy Canyon Creek originates in the City of Castle 

Pines, south of the Denver metropolitan area and west 

of I-25. The creek flows in a northeasterly direction 

through unincorporated Douglas County, crossing I-25 

near Surrey Ridge. It then passes through the 

RidgeGate PDD in the City of Lone Tree before joining 

with its major tributary, Badger Gulch, just south of 

Lincoln Avenue within the Meridian International 

Business Center. North of Lincoln, Happy Canyon 

Creek flows through Grandview Estates, then through 

the Compark development adjacent to E-470. 

Compark extends to the Douglas-Arapahoe county 

line, and is primarily within the Town of Parker’s 

current and future annexation boundaries. Happy 

Canyon Creek then enters Arapahoe County in the 

Dove Valley Business Park, crosses Jordan Road into 

the Southcreek subdivision, and finally empties into 

Cherry Creek just south of Broncos Parkway in the 

Cherry Creek Valley Ecological Park. Watershed limits, 

jurisdictional boundaries, and major landmarks are 

shown in Figures B-1 and B-2. 

Happy 

Canyon 

Creek 

Watershed 

Figure 2-1. Vicinity Map 

The Happy Canyon Creek watershed is approximately 10.2 miles in length and has an average width 

of 2.1 miles for most of its length, tapering to 0.5 miles wide at the north end. The total area is 17.5 

square miles or 11,200 acres. Approximately 40% of this area is developed. The highest and lowest 

points are 6680 and 5668 feet above mean sea level, respectively; the average watershed slope is 

1.8%. Underlying soils are hydrologic group C through much of the watershed, with type B soils 

increasing to the north and a few small areas of type A near the Douglas-Arapahoe county line. A 

map of soil classifications is included in Appendix B. 

Happy Canyon Creek is UDFCD Project Reuse watershed #4609; Badger Gulch is Project Reuse 

watershed #4610. 

The Major Drainageway Plan project area includes Happy Canyon Creek from the northern 

boundary of Castle Pines to the confluence with Cherry Creek. Though channel improvements in 

Castle Pines and on the tributaries are not within the scope of this plan, potential locations for new 

or improved detention throughout the watershed will be considered. 

2.2 Land Use 

Land use within the Happy Canyon Creek watershed covers a wide range from agricultural and open 

space to high density city center. Existing development conditions are generally based on visual 

assessment of the aerial photography provided by UDFCD, and future development conditions are 

based on information provided by project sponsors and stakeholders, including planning 

documents, zoning, master drainage plans, and direct input. In a few cases, roads were identified 

separately in land use analysis: the I-25 and E-470 corridors are reflected as 50% impervious to 

reflect separation between travel lanes and additional right-of-way included in the corridor, while 

Castle Pines Parkway, RidgeGate Parkway, and Lincoln Avenue are assumed 100% impervious (50% 

build-out of RidgeGate Parkway is reflected in the existing condition). All other existing or planned 

roads are assumed to be accounted for in the impervious values of adjacent development. 

The overall existing weighted impervious value for the Happy Canyon Creek watershed is 15.9%. 

Future development is projected to increase watershed imperviousness to 36.3%. The interactive 

hydrology map in Appendix B shows existing and future land use boundaries and impervious values 

(Figures B-1 and B-2). 

Upper Watershed: West of I-25 

The upper watershed includes approximately one third of the total area and is essentially fully 

developed. The City of Castle Pines is primarily small lot residential, with some medium lot 

residential and a small commercial area along Castle Pines Parkway near I-25. Small lot residential 

developments were grouped by density based on visual assessment, and an average % impervious 

was assigned to each group ranging from 40% to 60%. Undeveloped commercial parcels, golf 

courses, and other open space areas were assigned 2%, school sites were assigned 50%, and 

commercial areas were assigned 80%. Outside of Castle Pines, unincorporated Douglas County is 

dominated by large lot residential. Areas were separated into two groups based on lot size and 

average imperviousness values of 10% and 15% were calculated for the two groups. For future 

conditions, undeveloped areas were assumed to develop according to the surrounding areas. 

The weighted impervious values for the upper watershed are 21.6 % for existing development and 

22.5 % for future development. 

Middle Watershed: I-25 to Lincoln Avenue 

The middle watershed, which represents nearly half of the total watershed area, is largely 

undeveloped. This area will see significant growth, however, within the planned RidgeGate 

development in the City of Lone Tree’s jurisdiction. RidgeGate is a 3500 acre planned development 

that extends from the eastern edge of Lone Tree west across I-25 to Yosemite Street. Land use 

within RidgeGate will run the gamut from an ultra-dense city center just east of I-25 to rural 

residential and dedicated open space. Within the Happy Canyon Creek watershed, future land use is 

based on the PDD document and is largely residential mixed use. Impervious values for the various 




mixed use/residential planning areas were calculated based on maximum allowable ratios of 

commercial and multi-family residential development indicated in the PDD, with 85% applied to 

commercial areas, 80% for multi-family residential, and 50% for single family residential in the 

remaining area. Other land uses and their associated % impervious values within RidgeGate include 

city center (95%), commercial mixed use (85%), institutional (50%), rural residential (15%), central 

community park (10%), and open space (2%). RidgeGate Parkway, which has been constructed at 

half of its ultimate design width, is reflected as 50% impervious in the existing condition and 100% 

in the future. 

South of RidgeGate, unincorporated Douglas County is zoned for agricultural use. This area is slated 

for another planned development, Freshfields, under the same landowner/developer as RidgeGate; 

however, planning for Freshfields has not yet begun and development is not expected to begin until 

RidgeGate is built out. Because that timeline exceeds the expected life of this plan, no future 

development is reflected. 

Several other planned developments are located within the middle watershed. Surrounded on three 

sides by RidgeGate, Meridian Commons is a mixed-use/residential filing of the Meridian 

International Business Center (Meridian.) East of Lone Tree, Meridian Filing No. 7 is under active 

development. Sierra Ridge is located along the west side of Chambers Road and is currently 

undeveloped. Future land use for each of these planned developments is based on master drainage 

plans. 

Overall weighted impervious values for the middle watershed are 9.8 % for existing development 

and 36.8 % for future development. 

Lower Watershed: Lincoln Avenue to Cherry Creek 

North of Lincoln Avenue, Happy Canyon Creek bisects Grandview Estates, an established large lot 

residential area in unincorporated Douglas County. Impervious values are set at 15% for both 

existing and future conditions. East of Grandview Estates, Chambers Reservoir is currently under 

construction. For the purpose of this study, the reservoir is assumed complete and is reflected as 

100% impervious. West of Peoria Street lies additional Meridian planned development. 

Undeveloped industrial/business parks are located between Meridian and Grandview Estates. North 

of Grandview Estates, the Compark planned development spans both sides of E-470 to the Douglas- 

Arapahoe County line. Portions of Compark north of E-470 are within the Town of Parker; the area 

south of E-470 is a proposed annexation to the Town. Future impervious values for Meridian and 

Compark planned development areas are based on master drainage plans. Industrial/business parks 

are assumed to develop to 80% impervious. 

North of Compark, the Happy Canyon Creek watershed crosses into Arapahoe County. The Dove 

Valley Business Park stretches from the county line to Jordan Road and is largely undeveloped. 

Future development is reflected as 80% impervious. East of Jordan Road, the creek is flanked by 

residential development in the Southcreek subdivision. 

Weighted impervious values for the lower watershed are 19.6% for existing development and 

54.2% for future development. 

2.3 Reach Description 

The Happy Canyon Creek channel character varies widely along its length. The character of each 

segment is heavily influenced by the surrounding land use; because land use varies by jurisdiction, 

the creek is easily divided into nine distinct reaches at the jurisdictional boundaries. A description of 

each reach follows; reach limits are shown in Figures B-1 and B-2. 

Reach 1 – Castle Pines 

Within the City of Castle Pines, Happy Canyon Creek lies within a dedicated open space corridor 

adjacent to Monarch Boulevard. The channel is generally stable and well-vegetated, with significant 

wetland growth supported by a base flow. Five online regional detention ponds are located within 

Castle Pines on Happy Canyon Creek and its tributaries; the ponds are maintained by the Castle 

Pines North Metro District (CPNMD). The two mainstem ponds are located at Castle Pines Parkway 

(CPNMD Pond #11) and near the city limit (CPNMD Pond #12). In the lower portion of the reach 

downstream of Pond #12, Happy Canyon Creek has not been stabilized and is experiencing severe 

bank erosion and channel degradation as relatively clear water from the stabilized channel 

upstream enters an unimproved, 

natural channel. Though Reach 1 

is not officially included in the 

study area, the plan addresses the 

degradation at the downstream 

end of the reach and considers 

opportunities for detention 

improvements within Castle 

Pines for the benefit of the 

downstream watershed. 

Reach 1 




Reach 2 Reach 3 Reach 4 

Reach 2 – Douglas County South 

Immediately downstream of Castle Pines, the severe channel degradation observed in the lower 

portion of Reach 1 continues over a distance of approximately 850 feet, then transitions to a 

moderately stable, well-vegetated stream as it passes through large lot development in 

unincorporated Douglas County. Any future stabilization of the eroded areas will have the potential 

to shift the degradation downstream as it reduces the quantity of sediment being supplied to 

downstream reaches. UDFCD and Douglas County have implemented a project that constructed 

several low-flow grade control structures downstream of Oak Hills Drive. 

Major crossings include a box culvert at Oak Hills Drive and a small double-barrel CMP culvert at 

Clydesdale Road. Most homes sit well above the channel, however there are a few structures sited 

relatively low that pose a floodplain concern. Because the channel is located on private property 

through most of this reach, access is limited. 

Reach 3 – I-25 Corridor 

Reach 3 is located adjacent to the west side of I-25 and is overall the most damaged reach of Happy 

Canyon Creek. There is severe erosion downstream of the confluence with the Oak Hills Tributary, 

and the channel is constricted between I-25 and Surrey Drive with steep banks on both sides and 

failed slope paving along the east (I-25) bank. At the downstream end of this reach, bridges allow 

Happy Canyon Creek to cross under I-25 and the east frontage road. 

Reach 4 – Lone Tree South 

East of I-25, reach 4 is characterized by wide meanders and fairly dense natural vegetation in the 

overbanks. In many areas, the creek is flanked by high bluffs on one side, with an open, gentle 

floodplain on the other. The upper portion of the reach shows moderate channel erosion; this 

transitions to slight aggradation in the middle of the reach. The RidgeGate property is currently used 

for livestock operations; damage to the channel from the cattle is apparent, with trampled banks 

unable to support vegetation immediately adjacent to the channel. The recently constructed 

RidgeGate Parkway crosses the creek via a bridge. 




Reach 5 Reach 6 Reach 7 

Reach 5 – Meridian Commons 

Midway between RidgeGate Parkway and Lincoln Avenue, a 2700’ reach of Happy Canyon Creek 

runs adjacent to Meridian Commons, passing back and forth along the property line between 

Meridian Commons and RidgeGate. Though the natural channel character mimics reach 4, this reach 

is fenced off from livestock. As a result, the overall channel health is much improved, with healthy 

wetland vegetation along the low flow channel. This reach was stabilized during development with 

several check structures and a sloping grouted boulder drop structure at the downstream end. 

Reach 6 – Lone Tree North 

Beyond Meridian Commons, Happy Canyon again runs through Lone Tree in the future RidgeGate 

area to West Parker Road at the city limit. With the continuation of unrestricted livestock access in 

Lone Tree, creekside vegetation is again limited and bank stability suffers. The channel bottom is 

moderately stable with evidence of substantial sediment transport. The crossing at West Parker 

Road is a bridge. Note: West Parker Road, from Lincoln Avenue south in Lone Tree, was renamed to 

First Street in 2012. However, consistent with historical knowledge and most of the available area 

maps, the West Parker Road name has been used throughout this report. 

Reach 7 – Douglas County North (Grandview Estates) 

Beyond West Parker Road, Happy Canyon Creek crosses through a corner of Meridian Village in 

unincorporated Douglas County before passing through the Lincoln Avenue bridge and into 

Grandview Estates. The Meridian Village portion of the reach has been stabilized with two sloping 

grouted boulder drop structures and is in good condition. Grandview Estates is a large lot residential 

development north of Lincoln Avenue in unincorporated Douglas County. A segment of the reach, 

from Lincoln Avenue to Birch Avenue, is located within Douglas County Open Space. The remainder 

of reach 7 crosses private residential lots with no drainage easement and limited channel access. 

There is a bridge crossing at Birch Avenue and a triple 48” CMP culvert crossing at Dogwood 

Avenue. The base flow disappears within this reach, and there is evidence of aggradation in the 

wide, sandy channel bottom. 

Reach 7 was the subject of a 2001 study and initial phase of design by HDR, Inc. for Douglas County 

and UDFCD. The HDR project had “dual goals of flood control and bank and streambed stabilization.” 

At the time, there were numerous flooding concerns related to the Dogwood crossing and the 

Grandview Tributary, as well as channel and bank stabilization issues and aesthetic considerations 

due to debris that had been placed along the banks by the residents in stabilization efforts. Several 

projects have been completed since the HDR study; outstanding issues are discussed further in 

Section 4 of this report. 




Reach 8 – Town of Parker 

Happy Canyon Creek takes a sharp turn to the east as it exits Grandview Estates, and meanders 

widely before crossing under dual bridges at E-470. The dry, sandy bottom continues through this 

reach, and the channel takes a sharp turn to the west before crossing under a bridge at Chambers 

Road. Bank stability at this bend is a potential concern. There is very little if any wetland vegetation 

in this reach, as there is no base flow to support it. Reach 8 is primarily undeveloped at this point, 

but lies within several planned developments. A future bridge crossing for Belford Avenue, just 

south of E-470, will connect two proposed Town of Parker annexations: Compark Village South and 

Chambers Highpoint, located on the west and east sides of the creek, respectively. North of E-470, 

various filings of Compark are located within current Town of Parker boundaries. Drainage tracts 

and/or easements have been, or will be, dedicated throughout the planned developments. The 

channel invert through Compark has been stabilized with drop structures at each crossing and 

several check structures. 

Reach 9 – Arapahoe County 

The final reach of Happy Canyon Creek extends from the Douglas-Arapahoe County line to its 

confluence with Cherry Creek. West of Jordan Road, it passes through the Dove Valley Business Park, 

which is largely undeveloped. Channel stabilization measures and an access trail have been 

implemented along one developed parcel that is adjacent to the creek, and there is a sloping grouted 

boulder drop structure upstream of the bridge at Jordan Road. East of Jordan, the creek is located in 

a wide Arapahoe County open space tract between two built out residential developments that are 

part of the Southcreek subdivision. Three sloping grouted boulder drop structures and a concrete 

box culvert pedestrian crossing were constructed with the development. 

Happy Canyon joins Cherry Creek just upstream of the Broncos Parkway bridge, within the Cherry 

Creek Valley Ecological Park. Historically, the creek paralleled the east side of Jordan Road for a 

distance before turning to the east toward Cherry Creek. In 1975, the channel was realigned and the 

confluence moved approximately 2000’ upstream to its current location. The channel character in 

reach 9 is unappealing, with its wide sandy bottom, straight alignment, and dry, upland plains 

vegetation. 

Reach 8 Reach 9 




Table 2-1 

Major Crossing Inventory 

Crossing Location Reach Type 

Oak Hills Drive Reach 2 – Douglas County South Double 6’x8’ Box Culvert 

Clydesdale Road Reach 2 – Douglas County South Double 72” CMP Culvert 

Interstate 25 Reach 3 – I-25 Corridor Single Span Bridge 

I-25 Frontage Road Reach 3 – I-25 Corridor Single Span Bridge 

Ridgegate Parkway Reach 4 – Lone Tree South Single Span Bridge 

West Parker Road Reach 6 – Lone Tree North Double Span Bridge 

Lincoln Avenue Reach 6 – Lone Tree North Triple Span Bridge 

Birch Avenue Reach 7 – Grandview Estates Double Span Bridge 

Dogwood Avenue Reach 7 – Grandview Estates Triple 48” CMP 

E-470 Reach 8 – Compark Two Single Span Bridges 

Chambers Road Reach 8 – Compark Single Span Bridge 

Jordan Road Reach 9 – Arapahoe County Single Span Bridge 

desire to protect this reach in as natural a state as possible, not only for habitat benefit, but also for 

water quality through a meandering riparian ribbon. The upper zone, from Castle Pines to I-25, was 

seen as less valuable to wildlife than the middle zone, with less extensive riparian vegetation in the 

ponderosa pine forest. Wetland vegetation within Castle Pines seems to have increased substantially 

since this time. Overall, the value of maintaining a preserved open space corridor through the 

drainageway was emphasized for the benefit of wildlife habitat. This approach is in line with the 

local jurisdictions’ policies of floodplain preservation and creation of open space corridors. 

No federally threatened or endangered species have been identified within the project area; 

however, a project site-specific review should be conducted prior to implementing any 

recommended improvements. In addition, any work along the creek corridor should consider nonprotected 

species in the area and avoid impacts during sensitive periods such as nesting/mating 

season. 

2.4 Flood History 

There is limited information on history of flooding along Happy Canyon Creek, though there are 

many published accounts of flooding on nearby Cherry Creek. Much of the Happy Canyon Creek 

channel is located within open space tracts that provide adequate floodplain capacity; areas of flood 

concern are primarily located within Grandview Estates. Residents mentioned various high flow 

events causing overtopping of local streets and/or flood waters approaching their homes over the 

years; the 1993 OSP indicates previous accounts of road overtopping during heavy rainfall events. 

There are no stream gages on Happy Canyon Creek. 

2.5 Environmental Assessment 

Wetland zones are present along much of Happy Canyon Creek, though they markedly decrease in 

the downstream portions of the watershed where there is no base flow. An inventory of wetland and 

riparian areas is included in Appendix E. 

The 1993 OSP includes correspondence from the Colorado Division of Wildlife (DOW) regarding 

wildlife habitat within the watershed. The DOW described three different zones of vegetation with 

varying wildlife value. The lower zone, from Lincoln Avenue to Cherry Creek, was described as 

relatively dry with sparse riparian vegetation and only marginal wildlife value. The potential for 

creation of wetlands was noted, as the floodplain is wide and open. The middle zone, from I-25 to 

Lincoln Avenue, was described as the most valuable reach for wildlife, with “a broad band of riparian 

vegetation including an abundance of willows and cottonwoods.” The DOW commented on the 




SECTION 3 – HYDROLOGIC ANALYSIS 

3.1 Overview 

In watersheds where hydrologic models exist, master planning efforts generally utilize the existing 

models as a starting point for baseline hydrology, with revisions made as necessary to reflect 

changes in the watershed and to update the models to current software. For Happy Canyon Creek, 

hydrologic models from the 1993 OSP were provided by UDFCD. Electronic AutoCAD or GIS files 

were not available for the subwatershed delineation. While reviewing and attempting to recreate the 

boundaries based on the Hydrological Basin Map from the 1993 report, it became apparent that a 

number of changes would need to be made in order to reflect recent or upcoming development, 

position design points at desired locations such as detention ponds and road crossings, and to meet 

as closely as possible UDFCD’s guidelines on subwatershed size, which include a target size of 90- 

100 acres with a maximum size of 130 acres. As a result, though the 1993 boundaries were used as a 

guide, a new subwatershed delineation was performed. These watersheds were evaluated using 

UDFCDs Colorado Urban Hydrograph Procedure (CUHP) 2005, version 1.3.3 (release date January 

2010). Hydrographs generated in CUHP were then routed through the Environmental Protection 

Agency’s (EPA) Storm Water Management Model (SWMM), version 5.0.021. Due to the numerous 

changes that would have been needed to reflect the updated delineation, the design team elected to 

create a new SWMM model as well rather than update the previous model. This facilitated numerous 

improvements to the model to make it more user-friendly with the current software, including a 

revised naming scheme for subwatersheds, conveyance elements, and design points; layout of the 

SWMM model elements in the graphical user interface (GUI) over a background image of the 

watershed; and updating SWMM node elevations to match the project mapping. 

3.2 Design Rainfall 

One-hour point rainfall depths for the 2-, 5-, 10-, 25-, 50-, and 100-year storm events were obtained 

from UDFCD rainfall maps for the project area and compared with the values used in the 1993 OSP. 

Current values are slightly lower than those used in 1993 for all but the 50-year storm, as shown in 

Table 3-1. Because the Happy Canyon Creek watershed is greater than 10 square miles, UDFCD 

criteria require use of a 3-hour storm with area adjustment. In order to calculate the 3-hour storm 

distribution, 6-hour point rainfall depths were also obtained from UDFCD rainfall maps and are 

included in Table 3-1. Design rainfall distributions for both the 2-hour and 3-hour storm were then 

calculated within CUHP based on the distributions identified in the Urban Storm Drainage Criteria 

Manual (USDCM), with the areal adjustment also incorporated into the 3-hour distribution. Area 

adjustment factors for the 3-hour design storm are shown in Table 3-2; rainfall distributions for 

both design storm durations and all return periods are listed in Table B-1, Appendix B. 

Table 3-1 

Point Rainfall Depths 

Table 3-2 

Area Adjustment Factors 

Time 

(min) 

Storm 

Event 

One-Hour 

(1993 OSP) 

10-20 Square Mile Area Adjustment Factor 

2-, 5-, and 10-Year 

Design Rainfall 

Rainfall Depth (in) 

One-Hour 

Six-Hour 

2-year 1.06 0.95 1.42 

5-year 1.43 1.40 1.97 

10-year 1.66 1.63 2.26 

25-year N/A 1.98 2.80 

50-year 2.26 2.28 3.06 

100-year 2.60 2.58 3.42 

25-, 50-, and 100-Year 

Design Rainfall 

5 1.00 1.00 

10 1.00 1.00 

15 1.00 1.00 

20 0.90 1.00 

25 0.90 0.90 

30 0.90 0.90 

35 1.00 0.90 

40 1.00 1.00 

45 1.00 1.00 

50 1.00 1.00 

55 1.00 1.00 

60 1.00 1.00 

65-120 1.00 1.00 

125-180 1.00 1.00 




3.3 Subwatershed Characteristics 

Subwatershed characteristics were defined according to the revised delineation and current 

mapping and land use information. For each subwatershed, the flow path from the highest point in 

the basin was determined from the project mapping and used to define the length and distance to 

centroid. The length-weighted slope along the flow path was then calculated according to the 

method described in the USDCM. Existing and future imperviousness was determined based on the 

land use assumptions outlined in Section 2.2. Hydrologic soil group classifications were determined 

via the Natural Resources Conservation Service Web Soil Survey, and weighted values were 

calculated for initial and final infiltration rates as well as for the Horton’s decay coefficient. 

Depression losses in pervious and impervious areas were set at 0.5 and 0.1, respectively, to match 

the values used in the 1993 OSP. 

A total of 130 subwatersheds were defined. Areas ranged from 24 acres to 129 acres, with an 

average size of 86 acres. 

3.4 Hydrograph Routing 

A new SWMM model was created for routing of the hydrographs generated in CUHP. Channel 

geometry was approximated from the project mapping, utilizing 2’ interval topography north of 

Lincoln Avenue and along the main stem south of Lincoln, and 5’ interval topography in the 

remainder of the watershed. Where only 5’ topography was available, channel geometry used in the 

1993 OSP was referenced as well. Pipe elements were defined along tributary channels in locations 

where review of design plans indicated that the channel is or will be piped for long distances. An 

overflow channel was added for the Grandview Tributary from Lincoln Avenue to the confluence 

with Happy Canyon Creek; storm sewer was installed in this reach in 2010, but the capacity is less 

than the 100-year event until a planned detention pond upstream of Lincoln Avenue is constructed. 

All other piped reaches were assumed to carry the 100-year event; pipe diameters were set large 

enough to not constrict flow in the SWMM model. SWMM determines channel slopes based on the 

segment length and elevations of upstream and downstream nodes; node elevations were defined 

based on the project mapping. Manning’s n values were calculated according to the procedures 

outlined in the USDCM. Design points were placed at the downstream end of each subwatershed, 

with additional points included to reflect flow rates before and after the confluence with each 

tributary channel. 

Fourteen existing regional detention ponds have been identified as eligible for inclusion in the 

baseline hydrology. Five of these are located in the City of Castle Pines and are maintained by the 

Castle Pines North Metro District: CPNMD Ponds #9, #10, #11, #12, and #20. Ponds #9 and #10 are 

located on the Oak Hills Tributary, just upstream and downstream of Monarch Blvd, respectively. 

Both ponds are 10-Yr/100-Yr ponds with a reinforced concrete pipe (RCP) flared end section (FES) 

controlling the lower stage and a drop box controlling the upper stage. Design reports and as-built 

drawings were utilized to generate the storage and discharge curves. 

CPNMD Pond #20 is located on the Monarch Tributary, which joins the Oak Hills Tributary near the 

city limit. Pond #20 was constructed as a water quality (WQ)/10-Year/100-Year pond; however, the 

water quality orifice has been removed. Record drawings and the Phase III Drainage Report were 

used to determine the storage and discharge curves; discharge is based on the current condition (no 

water quality orifice). Pond #20 is UDFCD maintenance eligible; the remaining nine facilities are not. 

CPNMD Pond #11 is located on the main stem of Happy Canyon Creek, just upstream of Castle Pines 

Parkway. This pond was included in the 1993 OSP baseline hydrology, but has been retrofitted since 

that time to a 10-Year/100-Year pond, with three large diameter orifices providing the first stage 

control and a drop box with orifice plates on the three outlet pipes providing second stage control. 

The storage curve was defined based on the 2’ interval project channel topography, and the 

discharge curve was generated based on the project crossing survey. 

CPNMD Pond #12 is located downstream of Pond #11 at the Castle Pines city limit. A weir upstream 

of the outlet seems to provide flow measurement capabilities; the outlet is a quintuple pipe single 

stage outlet. The storage curve was defined based on the 2’ interval project channel topography, and 

the discharge curve was generated based on the project crossing survey. 

The Meridian Metropolitan District owns and maintains six ponds located in various filings of the 

Meridian International Business Center. Meridian Village Pond 1 is located just south of Lincoln 

Avenue adjacent to the confluence of Happy Canyon Creek and Badger Gulch. This offline facility has 

three cells that are designed to function as a single pond; the storage curve was taken from the 

Phase III Drainage Report and the discharge curve was generated based on the construction 

drawings. 

Stepping Stone Ponds D1 and D3 are located on the Grandview Tributary in Meridian Filing No. 7 to 

the south of RidgeGate Parkway/Main Street. These ponds are under construction at the time of this 

report. Storage curves are from the Phase III Drainage Report, and discharge curves were generated 

based on the construction drawings. 

Meridian Ponds 4A, 4B, and 4C are located on the Green Acres Tributary in Meridian Filings 4/5, 

adjacent to Peoria Street. An interim version of Pond 4A is currently in place, but plans have been 

approved for the expansion and addition of two additional ponds in series. They are included in the 

baseline hydrology because construction is expected to occur during the timeframe of this master 

plan. Storage and discharge curves are based on information provided in the Phase III Master 

Drainage Report. 




Another facility on the Green Acres Tributary is the E-470 Pond, located immediately upstream of its 

namesake. It is unclear if this facility was intentionally designed as a pond or if it merely provides 

inadvertent storage; the pond is controlled by a 12’x10’ concrete box culvert with no formal outlet 

structure, and provides little peak flow attenuation. However, because the pond was included in the 

1993 OSP baseline hydrology, it has been included in the baseline hydrology for this MDP. 

Finally, the Stonegate Tributary has two online regional detention ponds: the Stonegate Pond and 

the Chambers Reservoir WQ Pond. The Stonegate Pond is located at the southwest corner of Lincoln 

Avenue and Chambers Road. It was initially constructed as a WQ/10-Year/100-Year pond to provide 

treatment for Chambers Road, but is being expanded and converted to full spectrum detention for 

the upstream portion of the Sierra Ridge planned development. The baseline hydrology reflects the 

expanded FSD version of the pond, which is under construction at the time of this report. The 

storage curve was taken from the Phase III Drainage Report, and the discharge curve was generated 

based on the construction drawings. 

The Chambers WQ Pond is a full spectrum detention pond recently constructed just upstream of the 

in-progress Chambers Reservoir. Storage and discharge curves were taken from the Phase III 

Drainage Report for the Chambers Dam & Reservoir. 

Stage-area and stage-discharge curves for all detention ponds are included in Table B-3, Appendix B. 

For each return period and each development condition, the SWMM model was run with both a 2- 

hour and a 3-hour design storm applied uniformly over the entire watershed. Results from the 2- 

hour run were used for all design points in all tributary basins and for all main stem design points 

upstream of Badger Gulch. Results from the 3-hour model run were used for all main stem design 

points downstream of Badger Gulch, where the accumulated drainage area exceeds 10 square miles. 

3.5 Previous Studies 

Happy Canyon Creek was previously analyzed in the 1977 FHAD and the 1993 OSP. The FHAD 

included a portion of Badger Gulch and established the regulatory FEMA flow rates. Hydrographs 

were based on a 24-hour design storm with a Type IIA SCS rainfall distribution; peak discharges 

were calculated with the Soil Conservation Service’s computer programs WSP2 and TR20. According 

to the 1993 OSP, the FHAD study assumed fairly uniform land use throughout the watershed, with a 

future development weighted average of 20% impervious. The study extended upstream to I-25. 

The 1993 OSP utilized 2-hour and 3-hour design storms. Hydrographs were generated with the PC 

version of CUHP and routed through UDSWM2-PC. The future development imperviousness was 

28%. The two design storms were applied differently in the OSP than in this study: the 3-hour storm 

results were used for all main stem design points, including those above Badger Gulch. 

Table 3-4 includes peak flow rates from both studies. Regulatory flow rates in Douglas County 

mirror the FHAD. The Arapahoe County FIS lists a single flow rate of 3690 cfs for the 100-year event 

on Happy Canyon Creek. The source of this flow rate is unknown: it does not match any known 

studies, and documentation within the FIS is unclear. Examination of the FEMA effective mapped 

floodplain within Arapahoe County at the confluence of Cherry Creek with Happy Canyon Creek 

indicates that it is based on the 1993 OSP future development condition, which has a 100-year peak 

of 7303 cfs. 

3.6 Model Calibration 

Standard practice for master planning studies on previously studied watersheds includes calibration 

of the hydrologic model to reconcile the results within 10% of the previously published data. This 

practice ensures that changes in baseline hydrology are due to changes within the watershed or 

updates to criteria rather than differences in software. Calibration is generally done through 

adjustment of Cp and/or Ct values in CUHP, which impact the peak flow rates and the time to peak, 

respectively. This study targeted the 1993 OSP existing condition peak flow rates for reconciliation. 

A calibration model was prepared that mimicked the 1993 existing conditions impervious values 

and utilized the same 100-year 2-hour and 3-hour rainfall distributions as the 1993 OSP. Initial 

results were significantly higher, with a downstream 100-year peak of 7500 cfs vs. 5279 in the 1993 

OSP. The models compared favorably upstream of the Oak Hills Tributary. Because this study 

utilized newly created models rather than modifications of the previous models, the 1993 CUHP and 

SWMM data was converted to the current software utilizing UDFCD’s CUHP SWMM Converter. This 

converted model indicated a downstream peak flow rate of 6200 cfs, indicating that the difference is 

partially attributed to software differences and partially attributed to the model construction, which 

may include differences in watershed discretization, definition of subwatershed parameters, or 

definition of SWMM element parameters. An overall review of subwatershed and SWMM element 

parameters was conducted to verify that no large-scale, persistent differences existed between the 

1993 and current models; the two seemed comparable. 

As another point of reference, results were compared with the unit peak flow rates for Cottonwood 

Creek as published in a 2010 OSP. The Cottonwood Creek watershed abuts the Happy Canyon Creek 

watershed to the north and has similar characteristics to the Happy Canyon Creek watershed. To 

avoid differences based on development conditions and detention in the watershed, the historic 

conditions Cottonwood Creek model was used for comparison; this model reflects 2% impervious 

throughout the watershed and no detention facilities. (Weighted average imperviousness for the 

1993 existing conditions model is 5.4%). Cottonwood Creek’s watershed area is approximately 8 

square miles, so the peaks are based on a 2-hour design storm with no areal adjustment. Unit peak 

flows for Cottonwood Creek were determined based on accumulated drainage area, then applied to 

the drainage area at various design points on Happy Canyon Creek and plotted against 2-hour design 

storm results for the calibration model. This comparison indicated a difference of 10-15% between 

the Oak Hills Tributary and Badger Gulch, with good correlation upstream of the Oak Hills Tributary. 




At the direction of UDFCD, Cp values were adjusted in CUHP for all subwatersheds except those 

contributing to the design point immediately upstream of the Oak Hills Tributary confluence. Several 

trials indicated that an adjustment factor of 0.65 (multiplied with the normal calculated Cp values) 

provided good correlation between the 2-hour design storm calibration model and the Cottonwood 

Creek historic conditions model. This factor was then applied to the 3-hour design storm and the 

results compared with the 1993 OSP published values. The calibrated model peak flow rates range 

from 25% lower than the 1993 OSP at the upstream end of the watershed to 22% higher at the 

downstream end of the watershed. Results of the calibration effort are indicated in Table 3-3; a peak 

flow diagram of the various models utilized is included at the end of Appendix B. 

Cottonwood 

OSP unit 

peak for 

similar 

drainage 

area 

Table 3-3 

Model Calibration 

A B C D E F G 

1993 

Model, 

Current 

Unadjusted 

Calibration 

Model 

Unadjusted 

Calibration 

Model 

Cottonwood 

OSP 

equivalent 

Station 

Location 

Tributary 

Area 

1993 

Published 

Values Software (3-Hour) (2-Hour) peaks 

Delta 

(D-E)/E 

Calibrated 

Model 

(2-Hour) 

Delta 

(F-E)/E 

Calibrated 

Model 

(3-Hour) 

Delta 

(G-A)/A 

(ft) (ac) (cfs/ac) (cfs) (cfs) (cfs) (cfs) (cfs) (%) (cfs) (%) (cfs) (%) 

0 Cherry Creek 5279 6200 7501 9650 8589 6750 28% 

2600 Green Acres Tributary (D/S) 5357 6262 7514 9666 8590 6752 26% 

2600 Green Acres Tributary (U/S) 4940 5710 6903 8875 7866 6182 25% 

10500 Stonegate Tributary (D/S) 4961 5735 7005 9011 7979 6269 26% 

10500 Stonegate Tributary (U/S) 4961 5735 6896 8865 7848 6167 24% 

16200 Grandview Tributary (D/S) 4939 5626 6847 8804 7774 6109 24% 

16200 Grandview Tributary (U/S) 4939 5626 6523 8374 7388 5812 18% 

20100 Badger Gulch (D/S) 4705 5355 6467 8302 7319 5756 22% 

20100 Badger Gulch (U/S) 3831 4350 5057 6494 5813 4565 19% 

22600 3831 4350 5055 6491 5811 4562 19% 

32000 Ridgegate Parkway 5233 1.08 3873 4241 4831 6191 5652 10% 5519 -2% 4337 12% 

43600 I-25 4209 1.15 3922 3947 4324 5511 4840 14% 4889 1% 3854 -2% 

46100 Oak Hills Tributary (D/S) 3965 1.15 3733 3784 4155 5289 4560 16% 4699 3% 3706 -1% 

46100 Oak Hills Tributary (U/S) 2014 1.37 2318 2352 2085 2699 2759 -2% 2699 -2% 2085 -10% 

54500 Oak Hills Drive 1780 1694 1765 2279 2279 1765 -1% 

54500 1185 1059 1238 1616 1616 1238 4% 

61000 Castle Pines Parkway 835 723 762 968 968 762 -9% 

62500 Pond 353 Outflow 385 327 344 414 414 344 -11% 

62500 Pond 353 Inflow 688 470 548 766 766 548 -20% 

Note: all peak flow rates shown are based on a 100-year storm and 1993 existing development conditions. 




3.7 Results of Analysis 

Once the calibration effort was completed, the model was updated to reflect current existing and 

future development conditions, current rainfall point values and distributions, and to incorporate 

existing regional detention facilities described in Section 3.4. Happy Canyon Creek was then 

analyzed for the 2-, 5-, 10-, 25-, 50-, and 100-year storm events under existing and future 

development conditions, and with both 3-hour and 2-hour design storms. Peak flow rates at each 

design point are listed in Table B-4. Runoff volumes and accumulated drainage areas at key locations 

are listed in Tables B-5 and B-6. Hydrographs at key locations for the 2-year and 100-year events, 

are shown in Figures B-6 and B-7. Peak flow profiles for all storm events on the main stem of Happy 

Canyon Creek are shown in Figures B-8 and B-9. All tables and figures reflect 3-hour storm results 

downstream of Lincoln Avenue (confluence with Badger Gulch) and 2-hour storm results for the 

remainder of the watershed. 

primarily due to the use of a 2-hour design storm versus the 3-hour design storm used in the 1993 

OSP. Downstream of Lincoln Avenue, both studies use a 3-hour design storm; higher peak flow rates 

are due in part to the increases seen in the calibration effort, described above, and in part to the 

increased development projections (future imperviousness of 28% in the 1993 OSP versus 36% in 

the current study.) 

In comparison with the 1977 FHAD, the current study predicts nearly 40% greater peak flow rates. 

These differences are attributed primarily to the different design rainfalls used (SCS 24-hour rainfall 

distribution in the FHAD versus 2-hour and 3-hour storms per current USDCM guidelines) and to the 

increased development projections (20% future imperviousness in the FHAD versus 36% in the 

current study). 

Table 3-4 summarizes the results in comparison to the previous studies. The current study indicates 

peak flow rates averaging 25% higher than the 1993 OSP. Upstream of Lincoln Avenue, this is 

Table 3-4 

Comparison to Previous Studies 

Location 

FHAD 

Cross 

Section 

OSP 

Design 

Point 

Current 

Design 

Point 

1977 

FHAD 

100-Yr 

2-Yr 

Existing 

100-Yr 

Existing 

1993 OSP Current Study 

2-Yr 

Future 

100-Yr 

Future 

2-Yr 

Existing 

100-Yr 

Existing 

2-Yr 

Future 

100-Yr 

Future 

(cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) 

% Increase 

from 1993 

OSP* 

% Increase 

from 1977 

FHAD* 

Cherry Creek 60 228 HC999 6744 63 5279 741 7303 322 8161 836 9234 26% 37% 

Jordan Road 56 217 HC036 6800 73 5357 741 7344 326 8166 828 9228 26% 36% 

E-470 49 213 HC033 5700 89 4961 467 6523 309 7702 652 8474 30% 49% 

Dogwood Ave / Grandview Trib 43 208 HC029 5650 97 4939 428 6390 313 7502 624 8245 29% 46% 

Lincoln Avenue D/S of Badger Gulch 33A 207 HC026 5520 102 4705 346 6044 311 7079 572 7663 27% 39% 

Lincoln Avenue U/S of Badger Gulch 33 190 HC025 4070 103 3831 231 4729 316 5897 465 6247 32% 53% 

Ridgegate Parkway 11 186 HC021 4240 118 3873 224 4771 370 5555 452 5726 20% 35% 

I-25 3 179 HC016 4390 139 3922 227 4739 407 4899 433 4920 4% 12% 

Oak Hills Tributary 160 HC014 141 3733 222 4527 407 4700 430 4708 4% 

Oak Hills Drive 172 HC009 117 1780 119 2030 352 2598 372 2591 28% 

Castle Pines Parkway (1300' N) 165 HC004 85 835 85 910 251 1259 251 1259 38% 

*Comparisons are based on 

100-Yr Future development 

conditions 




SECTION 4 – HYDRAULIC ANALYSIS 

4.1 Evaluation of Existing Facilities 

Hydraulic analysis of the channel and existing road crossings was performed using HEC-RAS v.4.1.0 

software. Hydraulic sections are located so as to represent the topography of the channel; the 

average spacing is approximately 150-feet, with larger spacing (up to maximum of 500 feet) or 

additional sections as needed. Left, right, and channel reach lengths were determined initially with 

the aid of software, and have been adjusted as necessary, particularly in areas with sharp channel 

radii. While an effort was made to keep the horizontal layout of the hydraulic cross-sections straight, 

some cross-sections were “bent” at one or more locations to remain generally perpendicular to the 

centerline alignment and the overall flood flow areas in highly meandering reaches. 

Ineffective flow areas were added as indicated by the presence of structures or the surrounding 

topography of the channel. Contraction and expansion coefficients are typically 0.1 and 0.3, 

respectively, however, these values were increased to 0.3 and 0.5 at and surrounding many 

hydraulic structures. Cross-sections surrounding the hydraulic structures were placed so as to 

model the expansion and contraction losses into the structure in accordance with the HEC-RAS 

Hydraulic Reference Manual (typically a 2:1 expansion and 1:1 contraction). Hydraulic structures 

were incorporated based on the ground survey information. 

Bank stations are set to model a narrow (typically 10 to 15-feet wide) main channel with vegetated 

overbanks in most locations, so that the channel typically conveys the 2-year flow or less before 

spilling into the overbanks. Manning’s ‘n’ values were estimated based on site visits. In some 

reaches, adjustments were made to reflect future channel conditions as estimated based on 

increasing development from future upstream development or by future channel improvements. 

A summary table of Manning’s ‘n’ values is included in Appendix C, along with representative HEC- 

RAS cross sections. 

The 100-year floodplain was delineated based on the future development, existing infrastructure 

hydrology developed for the project. The hydraulic model was also run with existing condition peak 

flow rates; the two hydraulic profiles were compared and generally exhibited less than one half foot 

difference in base flood elevation, so a separate existing condition floodplain was not delineated. The 

future conditions floodplain is shown in Figures C-2 through C-5. 

Flooding at existing structures was evaluated based on the lowest adjacent ground (LAG) elevation 

relative to the base flood elevation for both the current regulatory floodplain and the draft FHAD 

floodplain. Additional ground survey was obtained in select areas; where detailed survey was not 

conducted, the LAG elevations were estimated based on the project topography. Structures were 

identified within the floodplain in Reach 5 and Reach 7. 

• Reach 5 – Meridian Commons: One home along the left bank at the upstream end of this 

reach is within the 100-year FHAD floodplain based on both existing and future peak flow 

rates. Flooding depths based on the LAG are less than 0.5 feet, with the base flood elevation 

(BFE) below the finished floor elevation. This home is not in the current regulatory 

floodplain. 

• Reach 7 – Grandview Estates: Eleven homes and numerous outbuildings are impacted in 

the 100-year event. The majority of these structures are located north of Dogwood Avenue, 

where channel capacity is extremely limited. Flooding depths vary from less than 0.5 feet to 

4.8 feet, with six of the twelve below one foot. 

It appears that none of these homes are on record as being within the current regulatory 

floodplain; the impacted lots appear to have been undeveloped at the time of the 1977 FHAD. 

The 1993 OSP did not include floodplain analysis, but the 1977 FHAD floodplain was 

superimposed on the new mapping; though review of the OSP mapping shows several homes 

that appear to be impacted, the report states that “there are no habitable structures within 

the 100-year floodplain.” Review of the DFIRM relative to the mapping for this project 

indicates six impacted homes: three in Zone AE and three in Zone X (shaded), representing 

100-year shallow flooding. Comparison of the published BFEs with structure elevations 

indicates an additional five impacted homes that are not currently delineated. 

A summary of existing structure impacts is shown in Table 4-1. 

Road crossings were also evaluated using the HEC-RAS model. There are twelve road crossings of 

Happy Canyon Creek; nine bridges and three culverts. Of the nine bridges, eight have sufficient 

capacity to pass the 100-year event. Two of these, Lincoln Avenue and Birch Avenue, lack freeboard 

(are in pressure flow) in the 100-year event. The bridge at West Parker Road has capacity for the 

25-year event. The three culvert crossings are all undersized; Oak Hills Drive provides 25-year 

capacity, Clydesdale Road passes the 2-year event, and Dogwood Avenue provides less than 2-year 

capacity. A private access drive for the Xcel substation located along Reach 4 in Lone Tree also 

provides less than 2-year capacity. A summary of the crossing sizes and capacities is included in 

Table 4-2. 

There are two trail crossings located within the project reach; these were also tabulated in Table 4- 

2. A low flow crossing for the E-470 bike trail provides limited capacity for the base flow; a culvert 

crossing for the Happy Canyon regional trail near the confluence with Cherry Creek provides 2-year 

capacity. 




Table 4-1 

Structure Flooding Evaluation 

Address 

Surveyed 

LAG 

Low 

LiDAR 

Elev. 

FHAD 

100-Year BFE 

DFIRM 

(Regulatory) 

Delta 

(FHAD-DFIRM) 

Freeboard (F) or Depth (D) 

FHAD DFIRM DFIRM Notes 

MERIDIAN COMMONS 

10320 Nottingham Dr. 5930.37 5931.0 5930.81 -- -- 0.44 D -- DFIRM Zone A (no detailed study) 

GRANDVIEW ESTATES 

3592 Dogwood Ave. -- 5813.0 5815.11 5813.95 1.16 2.11 D 0.95 D DFIRM Zone AE 

3771 Elm Ave. 5800.83 5800.0 5801.10 5800.32 0.78 0.27 D 0.51 F 

12666 4th St. -- 5808.0 5808.19 5807.48 0.71 0.19 D 0.52 F 

12706 4th St. -- 5806.0 5806.43 5806.55 -0.13 0.43 D 0.55 D No flooding reflected in DFIRM delineation 

12746 4th St. -- 5804.0 5804.83 5805.19 -0.36 0.83 D 1.19 D No flooding reflected in DFIRM delineation 

12786 4th St. 5802.50 5802.0 5803.18 5803.11 0.07 0.68 D 0.61 D No flooding reflected in DFIRM delineation 



12863 5th St. -- 5796.0 5797.39 5797.97 -0.58 1.39 D 1.97 D DFIRM Zone AE 

12907 5th St. -- 5794.5 5795.39 5796.35 -0.96 0.89 D 1.85 D DFIRM Zone AE 

12908 5th St. 5794.19 5794.0 5795.39 5796.35 -0.96 1.20 D 2.16 D DFIRM Zone X (shaded) (1977 FHAD 100-yr shallow flooding) 

12948 5th St. -- 5795.0 5794.21 5795.13 -0.92 0.79 F 0.13 D DFIRM Zone X (shaded) (1977 FHAD 100-yr shallow flooding) 

12990 5th St. -- 5788.0 5785.87 5787.27 -1.41 2.13 F 0.73 F DFIRM Zone X (shaded) (1977 FHAD 100-yr shallow flooding) 

-- = No data available Total # impacted homes 12 10 




Station 

Location 

Crossing 

No. 

Table 4-2 

Crossing Capacity Evaluation 

Description Capacity Condition / Notes 

54950 Oak Hills Drive 10 Double 6'x8' Box Culvert 25-YR 

Sediment deposition in west cell; overtopping flows spread into the open field to the east before spilling back into 

the channel to the north 

48100 Clydesdale Road 11 Double 72" CMP 2-YR Steep roadway fill slope is susceptible to erosion during overtopping 

43400 I-25 12 Single Span Concrete Bridge 100-YR Channel degradation under bridge has potential for undermining of north bridge abutments 

43200 I-25 Frontage Road 13 Single Span Concrete Bridge 500-YR Good Condition 

32000 RidgeGate Parkway 14 Single Span Concrete Bridge 500-YR Good Condition 

30550 Xcel Substation Access Drive 15 Quadruple 3'x6' Box Culvert



4.2 Flood Hazards 

Roadway overtopping for a major drainageway is prohibited by both the Douglas County Storm 

Drainage Design and Technical Criteria Manual and the Arapahoe County Stormwater Management 

Manual. As noted above, several roadway crossings along Happy Canyon Creek provide less than 

100-year capacity and therefore pose a significant flood hazard. In addition, two roadways 

experience shallow flooding in the 100-year event. A summary of the overtopping depths for the 10- 

year, 50-year, and 100-year events at major crossings is included in Table 4-3 below. The Xcel 

substation access drive was not included in this tabulation as it is not a public road and a secondary 

access route to the substation is also provided from RidgeGate Parkway. 

Table 4-3 

Roadway Overtopping Depths 

Overtopping Depth (ft) 

Station Location 

Reach 

No. 

Jurisdiction 2-YR 10-YR 50-YR 100-YR 

54950 Oak Hills Drive 2 Douglas County -- -- 1.0 1.4 

48100 Clydesdale Road 2 Douglas County -- 1.2 2.6 3.2 

21250 West Parker Road 6 City of Lone Tree -- -- 0.3 1.0 

15800 Dogwood Avenue 7 Douglas County 1.4 2.3 3.2 3.6 

20100 Lincoln Avenue 7 Douglas County -- -- --



Reach 3, located adjacent to I-25, is another severely degraded reach. Though the floodplain width 

through this reach has always been limited due to the steep topography, construction of I-25 further 

constricted the Happy Canyon Creek floodplain and reduced the stream length by eliminating 

meanders in the channel. The constricted floodplain combined with increased flow rates from 

upstream development and from I-25 itself have led to channel instability in this reach, with the 

potential to threaten the integrity of I-25. There are numerous instances of slope paving failure, and 

a sheet pile failure where the Oak Ridge tributary crosses below the interstate. Ongoing bank scour 

is evident through recent bank collapses. Happy Canyon makes a 90-degree turn to cross under the 

I-25 bridge; the channel invert has scoured several feet along the north (outer) side of the bridge 

crossing, potentially threatening the bridge abutment. 

A second exposed utility is located just upstream of 

Birch Avenue in Grandview Estates in an area of 

localized channel degradation. The type and size of 

the utility are unknown. Channel degradation in 

this area is also apparent at the pier for the Birch 

Avenue bridge; the paint line is 2-3 feet above the 

channel invert. This degradation may pose a hazard 

to the bridge structure. 

Flood hazards and problem areas are identified in 

Figures C-2 through C-4. 

4.3 Previous Analyses 

Paint line indicates possible degradation below 

Birch Avenue bridge 

Previous hydraulic analyses along Happy Canyon Creek include the 1977 FHAD, the 1993 OSP, and 

the 2001 analysis and preliminary design of channel improvements within Grandview Estates, 

completed by HDR. 

Failed slope paving along Happy Canyon 

Creek below I-25 barrier wall. 

Channel scour below I-25 bridge; original 

invert to right 

Active cattle grazing along Reaches 4 and 6 in the City of Lone Tree poses a water quality hazard to 

the watershed as a result of cattle manure in the stream bed and overbanks. During field 

investigations, manure was noticed as far north as E-470, two miles beyond the grazing area. It is 

likely that, during large storm events, manure is 

washed down Happy Canyon Creek into Cherry 

Creek, eventually reaching Cherry Creek Reservoir. 

With a single cow producing 12 tons of manure per 

year, this is potentially a significant nutrient 

source for the Reservoir. In addition to the water 

quality impacts, the cattle threaten the health of 

the stream by trampling the banks, killing off the 

wetland and riparian vegetation adjacent to the 

channel and leaving the banks vulnerable to 

Cattle near Happy Canyon Creek in Lone Tree 

erosion. 

The FHAD identified few flood hazards along Happy Canyon Creek, as most of the watershed was 

undeveloped at the time. Crossings at Dogwood Avenue, Birch Avenue, and old West Parker Road 

(now Lincoln Avenue) within Grandview Estates were undersized at the time; bridges have since 

been installed at Birch and Lincoln. It appears the Dogwood crossing has also been replaced, though 

not with sufficient capacity; the FHAD identifies a triple culvert crossing consisiting of one 36” CMP 

and two 36”x60” CMP arches while the current crossing is a triple 48” CMP. Existing development at 

the time was outside the floodplain limits. 

The 1993 OSP identified inadequately sized road crossings at Clydesdale Road, Lincoln Avenue, and 

Dogwood Avenue. As mentioned above, the Lincoln Avenue crossing has since been replaced with a 

bridge. West Parker Road was found to be adequately sized based on a 100-year peak of 3800 cfs; 

the increased peak of 6200 cfs in this study exceeds the structure capacity. Floodplain delineation 

was not performed for the 1993 OSP; structure flooding was based on the floodplain limits 

established in the 1977 FHAD, which was superimposed on the OSP mapping. According to the text, 

structure flooding was limited to barns and other outbuildings within Grandview Estates, though 

review of the OSP plan drawings shows three homes within the boundary. 

The HDR study built upon the findings of the 1993 OSP with regards to flood hazards; additional 

problem areas within Grandview Estates were noted including areas of bank instability and channel 

degradation. Multiple phases of construction were identified and prioritized; several of these 




projects have been completed to date. A summary of the proposed improvements by reach and 

implementation status is included in Table 4-4. 

Table 4-4 

Grandview Estates Analysis and Preliminary Design Summary - HDR, 2001 

Improvements Implemented 

Reach Problem Areas Recommended Improvements 

(Year) 

Downstream 

Boundary to 

Elm Street 

Properties within 

100-year 

floodplain, 

channel 

aggradation 

Excavation of a subchannel within 

main channel; 4' drop structure; bank 

regrading; work at primitive Elm 

Street crossing to reduce backwater 

None 

Elm Street to 

Dogwood 

Crossing 

Minor bank 

instabilities 

Minor bank protection; low flow 

channel relocation 

None 

Dogwood 

Crossing 

Undersized 

crossing resulting 

in split flow and 

shallow flooding 

area 

5' drop structure; double 72" culvert 

(2-year capacity); lower Dogwood 

profile to contain overtopping at 

channel, eliminating split flow 

None (Improvements were 

included in Phase I Final Design, 

but were not constructed due to 

unwillingness of property 

owner to grant an easement) 

Dogwood 

Crossing to 

Birch Street 

Banks stabilized 

by residents with 

debris, non-native 

soils 

Bank stabilization; aesthetic 

improvements; two check structures; 

low flow channel relocation 

Bank stabilization, drop 

structure, low flow channel 

relocation for 400' reach 

upstream of confluence with 

Grandview Tributary (2011) 

Birch Street to 

Lincoln Street 

Significant erosion 

of channel banks 

and invert 

Two check structures and one drop 

structure; maintenance access trail 

Constructed as Phase I 

Improvements (2002) 

Grandview 

Tributary 

Flooding of 

numerous 

properties 

Construct ditches and culverts 

adequate to pass 100-year flow (based 

on future construction of detention 

facility upstream of Lincoln Avenue) 

42" storm sewer and ditch 

improvements sized for 

Grandview Pond design release 

rate of 75 cfs (2009). 

Grandview Pond is not yet 

constructed in its final 

configuration. 




SECTION 5 – ALTERNATIVE ANALYSIS 

5.1 Alternative Development Process 

Three classifications of alternatives were developed for Happy Canyon Creek: detention 

improvements, channel improvements, and crossing improvements. Alternatives were evaluated on 

a reach by reach basis, with consideration for the pairing of channel and detention improvements 

based on the impact of additional detention on the degree of channel improvements necessary. 

5.1.1 Detention Alternatives 

Detention alternatives were developed with an aim toward neutralizing the impacts of development 

within the watershed. While all jurisdictions within the watershed require detention and water 

quality treatment for any new development, it is often provided on an on-site basis rather than a 

regional basis. On-site facilities can be effective in reducing storm peaks and improving water 

quality, however their size limits their impact on a watershed-wide level. Additionally, because 

operation and maintenance is the responsibility of individual property owners for on-site facilities, 

it is difficult to ensure that their effectiveness does not diminish with time. For these reasons, 

UDFCD policy precludes consideration of the impact of on-site facilities in the master planning 

process. Regional or sub-regional facilities provide greater impact due to their increased size and 

are more reliable due to regularly scheduled maintenance. Regional facilities, therefore, are a key 

solution to improving water quality and flood control from a master planning perspective. Private 

landowners benefit from regional facilities as well, as they can eliminate the need for on-site 

detention and water quality capture volume (WQCV). 

Reduction of flows from the many small runoff events to storms slightly larger than the 2-year event 

is considered of primary significance, as flows near the 2-year return period are considered 

important channel-forming discharges and occur frequently enough to cause substantial impacts to 

streams. Therefore, detention alternatives aim to reduce peak flow rates for all storm events to 

historic levels. Currently developed areas were examined for adequacy of existing regional 

detention; retrofits and new facilities were explored to address inadequacies. Planned regional 

detention in areas of future development was reviewed, and additions or modifications were 

considered to improve the effectiveness of future detention. 

5.1.2 Channel Alternatives 

Channel improvement alternatives were developed to address areas of concern within the channel, 

including degraded or unstable reaches, threats to existing infrastructure, limited channel 

conveyance, and floodplain concerns. Improvements targeted varying levels of channel stabilization, 

from a traditional fully stabilized approach to a softer, more strategic approach. Hydraulic 

evaluation of channel capacity was performed as necessary, and was based on the peak flow rates 

developed during the hydrologic analysis. 

5.1.3 Crossing Improvements 

Improvements to roadway crossings with less than 100-year capacity are included in the alternative 

analysis. New crossings were assumed to be the same type as the existing crossing (e.g. culvert or 

bridge), with the exception of Dogwood Avenue. Douglas County provided guidance on the two 

desired alternatives for Dogwood: replacement with a steel truss bridge that will span the 100-year 

floodplain, and permanent closure of Dogwood to allow removal of the crossing. 

5.2 Criteria and Constraints 


Detention improvements aim to provide Full Spectrum Detention within the watershed where 

possible. Full Spectrum Detention combines 100-year detention with the capture of Excess Urban 

Runoff Volume (EURV), or the additional runoff over historic levels that results from urban 

development. By capturing this excess runoff and releasing it slowly, peak flows from a range of 

events from small, frequently occurring storms through large, extreme flood events are maintained 

near pre-development levels. As with WQCV facilities, EURV facilities capture and treat the “first 

flush,” or the initial runoff from any storm event which will carry a substantial pollutant load; 

however, EURV facilities have approximately double the treatment capacity of WQCV facilities. 

Douglas County, the City of Lone Tree, and Arapahoe County have adopted Full Spectrum Detention 

as the minimum detention requirement for all new developments and the Town of Parker is 

currently updating its criteria to require Full Spectrum Detention. 


Channel improvements consider the criteria presented in the Urban Storm Drainage Criteria Manual, 

the Douglas County Storm Drainage Design and Technical Criteria Manual, the Town of Parker Storm 

Drainage and Environmental Criteria Manual, and the Arapahoe County Stormwater Management 

Manual. These criteria include recommendations on channel slope and drop structure height, as well 

as the overall approach to channel restoration. All jurisdictions favor natural channel preservation 

and restoration to engineered channels. This approach seeks to maintain a wide, shallow floodplain 

and make use of healthy riparian vegetation to help stabilize the channel, reduce stream velocities, 

and improve water quality. 

5.2.3 Crossing Alternatives 

Overtopping of any roadway at a major drainageway crossing in the 100-year event is prohibited 

under the criteria presented in both Douglas County’s Storm Drainage Design and Technical Criteria 

Manual and Arapahoe County’s Stormwater Management Manual. Proposed crossing improvements 

provide 100-year capacity according to criteria, including freeboard at bridge crossings. 




5.3 Alternative Categories 

Several categories of alternatives were developed for each of the major improvement classifications: 

detention improvements and channel improvements. 


Methods considered for adding or improving detention facilities or otherwise reducing peak flow 

rates within the watershed include planned detention facilities, retrofits to existing detention 

facilities, management of existing facilities, and new detention facilities. 

Planned Detention Facilities 

Some areas of future development within the watershed include plans for regional detention to be 

incorporated with development. Representatives of the Rampart Range Metro District, who are 

involved as stakeholders in this master planning effort, have indicated that the RidgeGate 

development in the City of Lone Tree will utilize regional facilities to meet the Full Spectrum 

Detention criteria required by the city. A regional detention facility has been designed and approved 

for the Sierra Ridge development in Douglas County, south of Lincoln Avenue. Finally, the Compark 

South development located south of E-470 in the Town of Parker Annexation zone has preliminary 

plans for regional detention at the E-470 Pond location for the portion of their development within 

the Green Acres Tributary. 

Retrofits to Existing Detention Facilities 

Potential retrofits to existing detention facilities were considered, with an aim to provide EURV for 

the upstream contributing area. Providing additional detention to reduce peak flows in the 100-year 

event to levels below pre-development conditions was also considered in selected locations where 

additional storage capacity is available. The retrofit category also includes consideration of existing 

facilities that are not currently recognized as flood detention facilities, but provide some attenuation 

of flows that could potentially be incorporated into the master plan hydrology. 

New Full Spectrum Detention Facilities 

Additional new facilities were considered in areas lacking regional detention and/or areas where a 

roadway embankment provides opportunity for additional storage. 


A number of channel improvement alternatives were considered to address the existing conditions 

observed along mainstem Happy Canyon Creek. These were formulated to rehabilitate existing 

degraded channels, to increase the conveyance of reaches and crossings that have limited capacity, 

and to protect and reinforce channels that are relatively stable today, but could deteriorate in the 

future. 

Protect and Reinforce Currently Stable Channel Reaches 

Much of Happy Canyon Creek is in a state of quasi-equilibrium and has not yet experienced severe 

degradation, and desirable riparian vegetation exists along most of the middle portion of the 

watershed. Alternatives within these reaches were considered to protect the beneficial functions 

and character of the creek and reinforce the channel against future deterioration. Four specific 

alternative concepts were explored. 

Alternative S1 represents the most extensive improvements with the highest level of stability and 

highest cost. Grade control structures are envisioned as “full-width” structures, extending across the 

entire channel bottom and tying into the high banks on either side of the creek. Alternative S1 

consists of full-width grade control structures based on an assumed long-term equilibrium slope of 

0.3 percent along the entire reach of channel, installing riprap protection on a portion of the outer 

banks and active channel banks, undertaking a moderate amount of regrading of slopes, and 

revegetating the disturbed channel area with riparian and upland seeding and plantings. 

Alternative S2 reduces the size of the structures from full-width drops to low flow drops tying into 

the banks of the active channel, allowing larger flows to be conveyed on the vegetated overbanks 

flanking the active channel. This alternative depends on the root strength and shear resistance of the 

overbank vegetation to remain stable at the existing gradient of the overbank (varies from 

approximately 0.5 percent in the downstream reaches to 1.1 percent in the upstream reaches). 

Riprap bank protection, slope grading, and revegetation are unchanged from Alternative S1. 

Alternative S3 is the same as Alternative S2, but with fewer drops based on a channel slope 

approximately halfway between the existing stream gradient and the assumed long-term 

equilibrium slope of 0.3 percent. This alternative reflects the lesser degree of degradation and 

slope-flattening that may be associated the reduced runoff peaks of the more effective detention 

alternatives. The amount of riprap bank protection assumed is slightly less than in Alternative S2. 

Alternative S4 represents the most modest set of channel improvements with the lowest cost. It 

assumes that the low flow drops and riprap protection of Alternative S3 would only be necessary 

over about half the reach length, and that half of the reach would be able to remain generally stable 

in its current condition. This alternative is based on making limited proactive improvements in 

selected areas most prone to erosion with the intent of keeping channel erosion from progressing to 

severe levels. The alternative, which follows an approach implemented on McMurdo Gulch, would 

require regular monitoring of channel conditions by the local jurisdictions and a rediness to 

implement improvements where and when they are needed. 

Rehabilitate Existing Degraded Channels 

The reaches of Happy Canyon Creek that have experienced severe degradation are planned to be 

rehabilitated by filling the channel bottom to pre-erosion levels (on the order of 4 to 8 vertical feet), 

constructing full-width grade control structures to maintain the raised elevation with a channel 




slope of 0.3 percent, installing riprap lining on outer banks and otherwise taking steps to stabilize 

high eroding banks, and revegetating the disturbed channel area. 

In recognition of the benefit associated with maintaining a moderate level of sediment source and 

transport in these reaches (over-restraining sediment movement may promote degradation 

immediately downstream of the improvements), the channel is envisioned to be filled slightly 

steeper than the predicted equilibrium slope and the sides of the active channel will be left relatively 

soft. 

Two alternatives were considered for degraded reaches: Alternative D1 represents the more 

stabilized approach with a higher level of bank protection, and Alternative D2 reflects a more 

moderate approach to bank protection based on decreased peak flow rates during frequent storms 

as a result of detention improvements. 

Increase Flood Conveyance where Capacity is Limited 

Where the conveyance capacity of Happy Canyon Creek is limited, alternatives providing additional 

capacity were considered. Each of the alternatives depends on improvements to the Dogwood 

crossing – either a 100-year capacity bridge or elimination of the crossing and closure of Dogwood. 

Alternative F1 consists of constructing a 100-year capacity channel with full width grade control 

structures based on a long-term equilibrium slope of 0.3 percent, installing riprap lining on outer 

banks in high velocity areas, and re-vegetating the disturbed channel area. 

Alternative F2 features a smaller channel about half the width of the 100-year channel that is sized 

to convey the 10-year event without structure flooding. Like Alternative F1, it would include full 

width (for the smaller width) grade control structures based on a long-term equilibrium slope of 0.3 

percent, installing riprap lining on outer banks, and re-vegetating the disturbed channel area. 

Alternative F3 provides stabilization improvements to the existing channel, but does not seek to 

increase the flood capacity of the creek. The improvements consist of small grade control structures 

on the existing active channel based on a long-term equilibrium slope of 0.3 percent, a modest 

amount of riprap bank protection, and revegetation of the disturbed channel area. 

Table 5-1 summarizes the alternative categories evaluated for each channel reach; Table 5-2 

summarizes detention improvements and other factors such as crossings and maintenance access. 

5.4 Alternative Hydrology and Hydraulics 

Detention alternatives were evaluated with EPA SWMM. Stage-area and stage-discharge curves were 

developed utilizing the Basin and Outlet worksheets in the UD-Detention spreadsheet, version 2.31, 

and entered into the project SWMM model. Results were generated for the 100-year, 10-year and 2- 

year storm events based on the future development condition CUHP hydrographs from the baseline 

hydrology analysis. In order to determine the target release rates at each detention facility and to 

gauge the overall performance of detention alternatives, historic flow rates for the three return 

periods were also calculated. A historic condition CUHP model was created by setting the 

imperviousness to 2.0% for each subwatershed. These hydrographs were then routed through a 

historic condition SWMM model, which excludes all detention facilities and assumes trapezoidal 

channel conveyance elements where the existing condition SWMM model includes pipes. 

In addition to the 100-year, 10-year, and 2-year events, a water quality event was simulated in order 

to evaluate the impact of the detention alternatives on smaller, more frequent storms. A new rainfall 

distribution was generated utilizing a one-hour rainfall depth of 0.5 inches with a 2-year hyetograph 

pattern (this is the smallest return period recognized by CUHP). Based on studies conducted for 

Douglas County, impervious values for large-lot developments within the watershed were set to 

2.0% to reflect the conclusion that no significant runoff flows off these lots will occur during a water 

quality event. In addition, developed areas with onsite water quality facilities were set to 2.0% 

impervious to reflect the effects of onsite WQCV. The resultant hydrographs from this water quality 

event CUHP model were then routed through the existing condition and alternative SWMM models. 

It should be noted that, because UDFCD does not recognize onsite facilities in master planning nor 

runoff reductions for large lots, this is purely an illustrative analysis. 

Hydraulic evaluations for stream crossings were performed using HEC-RAS. Culverts were assumed 

for Oak Hills Drive and Clydesdale Road, with consideration given for minimum cover requirements. 

Bridges were assumed for West Parker Road and Dogwood Avenue, with freeboard provided 

according to Douglas County criteria. An upstream drop structure and channel excavation was 

assumed at Dogwood Avenue in order to provide the necessary capacity. 

For the evaluation of channel conveyance improvements in Grandview Estates, normal depth 

calculations were performed in order to select channel dimensions for the desired channel capacity. 

The channel section template was then incorporated along with grade control into the HEC-RAS 

floodplain model, and the resulting water surface profile compared with structure elevations in 

order to determine the impacts to structure flooding. 

Overtopping spillway elevations at CPNMD Pond #12 were determined using weir flow calculations 

with a weir coefficient of 3.0. One foot of freeboard was provided to reduce the likelihood that the 

sanitary lift station would be flooded. 

Road crossings that exhibit shallow flooding in the draft FHAD analysis were addressed through 

reduction of peak flows as a result of detention improvements, or by channel conveyance 

improvements in the vicinity of the crossing. 




Table 5-1 

Channel Alternatives Screening Matrix 

STABLE CHANNEL 

ALTERNATIVES 

DEGRADED 

CHANNEL 

ALTERNATIVES 

FLOOD CONVEYANCE 

ALTERNATIVES 

S1: Full-width grade control, 

0.3% slope, moderate bank 

protection 

S2: Low-flow grade control, 

0.3% slope, bank protection 

S3: Low-flow grade control, 

0.4%-0.6% slope, minor 

bank protection 

S4: Partial implementation 

of S3 based on wait-and-see 

approach 

D1: Restore channel invert, 

full-width grade control, 

0.3% slope, extensive bank 

protection 

D2: Restore channel invert, 

full-width grade control, 

0.3% slope, moderate bank 

protection 

F1: 100-year capacity 

channel, full-width grade 

control, 0.3% slope, 

extensive bank protection in 

high velocity areas 

F2: 10-year capacity 

channel, full-width grade 

control, 0.3% slope, 

extensive bank protection in 

high velocity areas 

F3: No flood reduction, lowflow 

grade control, 0.3% 

slope, moderate bank 

protection 

Castle Pines 

REACH 

1a 

NOT IN STUDY 

REACH 

1b 


South 

REACH 

2a 

REACH 

2b 

I-25 Corridor 

 

 

Lone Tree 

South 

Meridian 

Commons 

Lone Tree 

North 

REACH 3 REACH 4 REACH 5 REACH 6 


North 

REACH 

7a 

REACH 

7b 

Town of 

Parker 

Arapahoe 

County 

REACH 8 REACH 9 

 

 

 

 

 

 

 




Table 5-2 

Detention and Other Alternatives Screening Matrix 

Castle Pines 


South 

I-25 Corridor 

Lone Tree 

South 

Meridian 

Commons 

Lone Tree 

North 

Douglas County North 

Town of 

Parker 

Arapahoe 

County 

REACH 

1a 

REACH 1b 

REACH 

2a 

REACH 

2b 

REACH 3 REACH 4 REACH 5 REACH 6 

REACH 

7a 

REACH 

7b 

REACH 8 REACH 9 

REGIONAL DETENTION 

ALTERNATIVES 

Planned Detention Facilities 

Retrofits to Existing 

Detention Facilities 

New Full Spectrum 

Detention Facilities 

CPNMD 

Ponds 

Beverly Hills 

Tributary 

Beverly Hills Stock 

Pond 

Oak Ridge 

Tributary 

RidgeGate RidgeGate Sierra Ridge Compark 

Chambers & Meridian 

Reservoirs 

Green Acres Tributary 

Green Acres 

Tributary 

CROSSING IMPROVEMENTS 

MAINTENANCE ACCESS / 

EASEMENTS 

OTHER CONSIDERATIONS 

NOT IN STUDY 

Provide 

maintenance 

access; 

property 

owned by 

Public 

Service Co. 

Eliminate 

flooding at 

sanitary 

sewer lift 

station 

Oak Hills Drive 

Clydesdale Road 

Provide 

maintenance 

access; obtain 

easements from 

private property 

owners 

I-25 Bridge 

(Stabilization) 

Stabilize 

Downstream 

Portion of Oak 

Hills Tributary 

Provide 

maintenance 

access; 

property to be 

open space 

corridor 

Incorporate 

cattle 

management 

for water 

quality 

enhancement 

and less 

rigorous 

channel 

stabilization 

alternatives 

West Parker 

Road 

Provide 

maintenance 

access; 


open space 

corridor 

Incorporate 

cattle 

management 

for water 

quality 

enhancement 

and less 

rigorous 

channel 

stabilization 

alternatives 

Dogwood Avenue 

(Improve or Remove) 

Provide 

maintenance 

access; 

obtain 

easements 

from private 

property 

owners 

E-470 Trail 

Crossing 

Provide 

maintenance 

access; 


open space 

corridor 

Stabilize 

Downstream 

Portion of 

Stonegate 

Tributary 

New 

pedestrian 

bridge for 

Happy Canyon 

Trail 

connection 

Provide 

maintenance 

access; 


open space 

corridor 

Incorporate 

cattle 

management 

for water 

quality 

enhancement; 

improve 

function of 

existing subregional 

ponds 




5.5 Alternative Costs 

Cost estimates for the alternatives were developed using UDFCD’s master planning cost estimating 

spreadsheet, UD-MP Cost, Version 1.1. The spreadsheet includes set unit costs for various capital 

improvement items based on 2009 costs with an adjustment for inflation; the annual inflation rate 

assumed was 3.0%. Unit costs are shown in 

Table F-1. Capital improvement costs 

include set allowances for mobilization 

(5%) and for stormwater management and 

erosion control (5%), and user-defined 

costs for dewatering, traffic control, and 

utility relocation. Dewatering was set at 

2.5% of the capital improvement cost; lump 

sums for traffic control were added for 

crossing improvements. No utility 

relocation was assumed. Allowances for 

other costs were added as shown in Table 

5-3. No right of way costs for access and maintenance easements were included. Proposed 

improvements are assumed to be mutually beneficial to private landowners and local jurisdictions; 

in such cases, easements are generally granted when the improvements are constructed. 

5.6 Alternative Plans 

Table 5-3 

Additional Cost Allowances 

Item 

% of Capital 

Improvement 

Cost 

Engineering 15% 

Legal/Administrative 5% 

Contract Admin/Construction 

Management 

10% 

Contingency 25% 


Detention Alternatives that were considered are shown in Figures 5-1 through 5-3, and include 

existing and proposed detention facilities located on or adjacent to Happy Canyon Creek as well as 

on several tributary channels. Where the impact of a specific pond was in question, the facility was 

evaluated by running the SWMM model with and without the proposed improvement; alternatives 

that were considered but discarded due to limited impact are indicated. Potential new facilities or 

improvements to existing facilities were then grouped into three overall detention alternatives 

based on the type of improvements provided in each one. Peak inflow and outflow rates and storage 

volumes at each pond for each alternative are listed in Table F-2 alongside baseline hydrology and 

historic values. Peak flow diagrams for the 100-year, 10-year, 2-year, and water quality storm events 

are included as Figures F-1 through F-4; each diagram includes existing and future baseline 

hydrology, historic flow rates, and the three detention alternatives. 

Costs for detention alternatives were determined using the unit costs and multipliers established in 

UD-MP Cost. In order to effectively tabulate the costs for each individual facility in each alternative, 

the calculations were performed in a separate spreadsheet. Costs for new or fully reconfigured 

detention facilities were estimated using a complete-in-place unit cost per acre-foot, which would 

include excavation and embankment, outlet structures, maintenance access, overflow spillways, 

forebays and low-flow channel improvements, and revegetation. While this approach was applied 

uniformly, experience indicates that the cost to volume ratio should decrease for larger facilities; 

therefore, the total estimated costs for large detention facilities may be more conservative than for 

smaller facilities. This is especially true for the 100-year online peak-shaving ponds, which would 

only require a downstream embankment and large culvert crossing in order to construct as planned. 

Costs for retrofits were calculated based on varying assumed costs for outlet works improvements, 

with an allowance for revegetation where appropriate. 

Detailed cost estimates for each detention alternative are included in Appendix F. 

Detention Alternative A 

This essentially represents a “no-action” scenario, reflecting only planned full spectrum detention 

that will be publically owned and maintained. This includes facilities in the Sierra Ridge 

development, under the oversight of the Sierra Ridge Metropolitan District, in the RidgeGate 

development, under the oversight of the Rampart Range Metropolitan District, and in Compark 

South in the Town of Parker. 

The Grandview Pond is located in Sierra Ridge immediately upstream of Lincoln Avenue, on the 

Grandview Tributary. Final design has been completed and construction plans approved by Douglas 

County. Storage and discharge curves are based on updated design plans dated May 2012. 

A full-spectrum detention facility is proposed on the Green Acres Tributary in Compark South, at the 

location of the E-470 pond. As described earlier, the existing pond is not a formal pond but merely a 

large culvert crossing under E-470 that was described as a pond in the 1993 OSP. The conceptual 

drainage plan for the development indicates a water quality/100-year detention pond at this site; 

for this analysis, the sizing has been revised to reflect full spectrum detention for the contributing 

area within Compark South and within Grandview Estates. 

Two distinct types of ponds are shown within the RidgeGate development: offline EURV ponds and 

online 100-year peak-shaving ponds. Initially, a few large offline full spectrum detention ponds were 

assumed within this development. These ponds had been sized through iteration to match the 

existing conditions hydrology peak flow rates on Happy Canyon Creek and Badger Gulch. With 

approval of the project sponsors, additional analysis was done to determine the impact of offline 

detention on peak flow timing in the channel. The analysis modeled offline FSD ponds in comparison 

with offline EURV ponds that bypass the 100-year peaks, and found that the offline FSD ponds delay 

100-year peaks such that their timing then corresponded with the channel peak, thereby causing an 

overall increase in the 100-year channel peaks. As a result of this analysis, the approach to detention 

within RidgeGate was changed to avoid placing 100-year detention offline, and instead utilizing 

online peak shaving ponds to reduce 100-year peaks. While online detention facilities are not 

generally recommended in this study in order to allow sediment movement within the channel, the 

peak shaving ponds are proposed to be configured as an embankment with a large culvert that 




produces some flow attenuation in large events but allows smaller flows to pass through. Because 

these facilities are located within the floodplain, they are expected to have minimal impact on 

developable area. 

A total of 10 offline EURV ponds and two online 100-year ponds are shown; however, the actual 

number and location of facilities can be adjusted as needed based on the layout and timing of 

development. The number and placement is not significant to the results, as long as the offline ponds 

allow flows in excess of the EURV to pass unrestricted and the online ponds are configured to allow 

sediment movement in the channel. 

The capital improvement cost associated with Alternative A estimated using the methods described 

above is $18.3 million, with a total project cost of $28.4 million. As mentioned, these costs are 

viewed as conservative, especially in regards to the online 100-year ponds in RidgeGate. 

Detention Alternative B 

Alternative B includes the planned facilities described in Alternative A, and adds retrofits to existing 

detention facilities and formalization of existing detention volume. 

Retrofits to CPNMD ponds #9, 10, 11, and 20 are included, with each sized to provide EURV for the 

upstream contributing area. CPNMD Pond #12 is modeled with conveyance improvements to 

prevent flooding of the adjacent sanitary sewer lift station. These improvements consist of lowering 

the existing overflow spillway embankment by approximately 2’ to provide 1’ of freeboard in the 

100-year event; this results in a loss of 3.7 acre feet of storage. The cost for these improvements is 

not included in the detention costs; because it is for the purpose of improving conveyance rather 

than providing additional detention, it is instead reflected in the channel alternative costs. 

Retrofits to two sub-regional facilities in Arapahoe County are reflected in the cost estimates for 

Alternative B, however, the ponds are not included in the SWMM model as their contributing areas 

are too small to be eligible for inclusion in master plan hydrology. SEMSWA has indicated that these 

ponds do not perform well, and retrofits to improve their function are desired. 

In addition to retrofits, the formalization of existing detention volume was explored for this 

alternative. An existing stock pond is located on the Beverly Hills Tributary immediately upstream of 

the confluence with Happy Canyon Creek; during field investigation of this pond, no evidence of 

overtopping was seen. No outlet to the pond was found (or is expected), which indicates that peak 

flows from the Beverly Hills Tributary seldom reach Happy Canyon Creek. Though this pond may not 

be the only reason for this phenomenon, it seems reasonable to incorporate this pond into the 

hydrology so that it’s benefit can be reflected in the downstream peak flow rates. The pond is 

located on Douglas County property and was modeled based on the existing storage volume and 

overflow spillway, with a 2” diameter outlet pipe assumed to reflect infiltration of the volume below 

the spillway. To formalize this pond, a geotechnical investigation of the embankment is 

recommended; an outlet structure could be provided if desired (costs are based on the standard 

$45,600/af, which is quite conservative for this case). 

Two additional existing facilities were considered for this alternative. The Chambers and Meridian 

reservoirs are reflected in the baseline hydrology as brim full with 100% imperviousness over the 

permanent pool. In actuality, these ponds typically operate with freeboard that would allow rain 

falling on the surface and on the areas around the pond to be captured. The SWMM model was 

modified to reflect such a condition at each pond to determine the potential benefit of an operating 

agreement establishing a minimum freeboard: in the 100-year event, there was zero benefit to 

Happy Canyon Creek from the Meridian Reservoir and less than 1% benefit from the Chambers 

Reservoir. These were therefore discarded as alternatives. 

Resulting peak flow rates for Alternative B are nearly identical to Alternative A in the 100-year event 

as the retrofits are aimed at providing EURV where 100-year detention already exists. Peaks are 

markedly reduced in the 10-year and 2-year events, which drop below existing along much of the 

channel. Peak flow rates for the water quality event are approximately half of the Alternative A 

peaks. 

The capital improvement cost associated with Alternative B is $18.7 million, with a total project cost 

of $29.0 million. The incremental project cost above the “no action” Alternative A is $0.6 million. 

Detention Alternative C 

The maximum detention improvements are reflected in Alternative C, which includes the planned 

and retrofitted facilities in Alternatives A and B as well as several new facilities and further 

modification to existing facilities. 

For Alternative C, CPNMD Pond #12 is assumed to be reconstructed with a new embankment 

located just upstream of the sanitary lift station; this configuration provides additional volume to 

reach the calculated EURV for the upstream contributing area while eliminating the undesirable 

levee condition at the sanitary sewer lift station. The volume needed to reduce 100-year peak flow 

rates to pre-development levels cannot be provided at this facility; Alternative C also reflects further 

restriction of the 100-year outlets at CPNMD Pond #11 in order to detain the 100-year peak 

discharge to levels below pre-development conditions. This partially offsets the higher peaks 

downstream while still providing substantial freeboard (over 8 feet) to Castle Pines Parkway. 

A new facility on the Beverly Hills Tributary at Charter Oaks Drive is included in this alternative. 

There are two existing crossings of Charter Oaks from two flow paths that converge on the 

downstream side; an existing detention pond is located at the east crossing and provides 10-Yr/100- 

Yr detention for the large shopping complex upstream and for the existing elementary school to the 

east. The west crossing is unrestricted, and the land on this side is owned by the Castle Pines North 

Metro District and is planned as a park. A middle school is currently under construction on the high 




ground between the two crossings. The two low areas could be connected to form a U-shaped pond 

around the middle school. This facility would treat the most heavily developed portion of this 

subwatershed, and would reduce peaks on Happy Canyon Creek for all storm events. In addition, 

reductions in peak flows on the Beverly Hills Tributary would be beneficial in dealing with flooding 

and conveyance issues along the tributary. Channel improvements and replacement of a crossing at 

Oakwood Drive have been conceptually designed to reduce flooding at homes along the tributary; a 

preliminary check of the existing Oakwood crossing capacity indicates that replacement may not be 

required if the Charter Oaks pond is constructed upstream. 

Excavation of the Beverly Hills Stock Pond to increase its volume was considered, but the 100-year 

benefit was low and the level of disturbance to this well-vegetated area seemed inappropriate to the 

spirit of this plan, which aims to minimize impacts in stable areas. This alternative was therefore 

discarded. 

A new facility was considered on the Oak Ridge Tributary just upstream of I-25, straddling CDOT 

right of way and Douglas County property. The available volume at this location is limited due to 

steep grades and freeboard requirements at I-25, so this pond was ineffective in the 100-year event. 

An existing water quality pond treats the highway runoff at this location and the rest of the basin is 

undeveloped; with no apparent benefit of this facility, it was discarded as an alternative. 

Alternative C reflects additional 100-year peak flow reduction provided through the RidgeGate 

development. The discharge curves for ponds HC522, HC525, and BG511 were modified to reflect 

smaller culverts and an overtopping spillway, and a fourth pond was added near I-25 (HC519). 

These ponds aim to reduce 100-year peak flow rates as much as possible below pre-development 

levels in order to relieve flooding issues in Grandview Estates. Though this alternative reflects an 

additional 164 acre-feet of storage over Alternative A, the impact on developable area within 

RidgeGate is minimal based on the conceptual pond locations shown: with the steep natural banks 

and large footprints of the ponds, the increased ponding area outside the floodplain for ponds 

HC522, HC525, and BG511 totals approximately 10 acres, and pond HC519 is located entirely within 

planned open space. (Of course, RidgeGate may choose to locate ponds differently and/or may 

change the planned land usage, and the overlot grading of the adjacent areas may impact – positively 

or negatively – the available ponding depth at any given location.) 

A new facility is proposed on the Green Acres Tributary within the Airport 320 industrial park, 

which is currently undeveloped. This facility would provide FSD for the contributing area 

downstream of Meridian Pond 4A, and would “close the loop” on regional detention on the Green 

Acres Tributary upstream of E-470, with all areas in this reach being treated by a regional facility. 

The upstream Meridian ponds reduce 100-year peak flows below pre-development conditions, so 

additional 100-year attenuation was not sought in this facility. 

Another new facility on the Green Acres Tributary is included in Alternative C, located within the 

Dove Valley Business Park in Arapahoe County. This area is largely undeveloped, and though the 

master drainage plan reflects onsite and/or subregional detention, the landowners have a desire to 

implement regional detention instead. Several scenarios were considered in the sizing of this pond, 

as the upstream Compark North development is not served by regional detention. If sized for the 

entire upstream contributing area below the E-470 pond, this facility would require 43 acre-feet of 

EURV and up to 71 acre-feet in total, including 100-year detention. A facility of this size cannot be 

accommodated in this location. The WQCV for the same area was calculated, as well as WQCV, EURV, 

and 100-year volumes for the two subwatersheds that encompass the Dove Valley Business Park 

(H210 and H220). The WQCV for the area below the E-470 pond and the EURV for subwatersheds 

H210 and H220 are both approximately 14 acre-feet. This compares favorably with the total 

proposed detention volume reflected in Dove Valley’s master drainage plan of 16.8 acre-feet (for 

areas draining to the Green Acres Tributary). Based on a conceptual layout of this facility, a water 

surface elevation of 5717.0 corresponds with approximately 15 acre-feet of storage; this was chosen 

as the top of the extended detention (EURV or WQCV) volume. No additional 100-year volume is 

assumed (though the SWMM model reflects some additional storage as higher flows are routed over 

a spillway); though the resultant 100-year peak flow rates at this location are approximately 200 cfs 

higher than historic, there are no downstream impacts as this facility is at the mouth of the tributary, 

and the timing of flows on Happy Canyon Creek are such that delay of the 100-year peak on Green 

Acres would actually increase the peak on Happy Canyon. 

Alternative C significantly reduces peak flow rates for all storm events. In the 2-year event, the 

largest reductions are seen through the degraded channel reaches in the upstream portion of the 

watershed as a result of the incorporation of EURV in CPNMD Pond #12. In the downstream portion 

of the watershed, additional detention on the Green Acres Tributary actually delays peaks such that 

a greater increase on Happy Canyon is seen at the tributary when compared with existing 

conditions; however, this may be beneficial in reducing aggradation in the lower reach. Similar 

results are seen for the water quality event, with the upper reaches dropping near the zero-flow 

historic condition. In this smaller event, the delayed peak phenomenon is not seen at Green Acres as 

the additional extended detention minimizes runoff from the tributary. 

In the 100-year event, the largest reduction is seen in the lower portion of the watershed, 

downstream of the proposed peak-shaving facilities in RidgeGate. This produces peak flow rates 

through Grandview Estates that are well below the estimated historic peaks and are within 

approximately 100-200 cfs of the peaks reported in the 1977 FHAD, which were 5520 at Lincoln 

Ave. and 5700 at E-470. 10-year peaks are approximately halfway between the existing and historic 

peaks. 

The capital improvement cost associated with Alternative C is $32.5 million, with a total project cost 

of $50.4 million. The incremental project cost based on $51,000/acre-foot above the “no action” 




Alternative A is $22 million, however $14 million of this is due to the increased detention in 

RidgeGate and is exceedingly conservative for the additional improvements needed. 

Costs for each detention alternative including operations and maintenance are summarized in Table 

5-4. 

In each of the three detention alternatives, new or modified facilities are located within 10,000 feet 

of runways at Centennial Airport. These include the Airport 320 Pond, the E-470 pond, and 

RidgeGate Pond HC525. Generally, FAA guidelines restrict uses that could attract wildlife within this 

zone, including detention ponds that will store water for an extended period of time. UDFCD has 

prepared a memorandum addressing this matter, which has been included in Appendix A. 

Table 5-4 

Detention Alternatives Cost Summary 

Capital Cost 

Contingency 

Engineering / 

Administration 

/ Legal Total Cost 

Annual 

O&M 

Total Cost 

Including 

Present Worth 

of 50 Years 

O&M 

Alternative A $ 18,348,044 $ 4,587,011 $ 5,504,413 $ 28,439,468 $ 145,000 $ 32,170,275 

Alternative B $ 18,681,315 $ 4,670,329 $ 5,604,395 $ 28,956,038 $ 155,000 $ 32,944,142 

Alternative C $ 32,512,917 $ 8,128,229 $ 9,753,875 $ 50,395,022 $ 175,000 $ 54,897,720 




5.6.2 Channel and Crossing Alternatives 

Channel alternatives for each reach are shown in Figures 5-4 through 5-6 and discussed below. 

Though channel alternatives were generally considered independently of detention alternatives, 

some pairing was assumed in order to reduce channel costs based on lower anticipated peak flow 

rates. Detailed cost information and assumed quantities are included in Appendix F. 

Once costs for each reach were developed using UD-MP Cost, the total was then divided by the reach 

length to obtain a unit cost per linear foot of channel (reflecting capital costs plus contingency). This 

unit cost provides a point of comparison between different alternatives and various reaches. 

Reach 1b – Castle Pines 

The portion of Happy Canyon Creek within the limits of the City of Castle Pines is not officially within 

the limits of this study; however, the severe channel degredation in the lower portion of the reach 

(downstream of the CNPMD Pond #12 outfall) begins within City limits and cannot reasonably be 

excluded from this study. Because this is a degraded reach, Alternatives D1 and D2 were considered. 

Grade control is a priority in this reach to protect an exposed high pressure gas main. Though bank 

stabilization is recommended in both alternatives, either would aim to allow this reach to continue 

to serve as a moderate sediment source for the channel. This reach would greatly benefit from Full 

Spectrum Detention improvements upstream as there is currently no attenuation of peak flows from 

small storm events, including the 2-year. Costs for this reach include excavation required to lower 

the embankment at CPNMD Pond #12 to provide overtopping capacity without flooding the adjacent 

sanitary lift station; this portion of the cost could be eliminated with the new pond embankment 

provided in Detention Alternative C. 

Table 5-5 

Reach 1b Channel Cost Summary 

Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 

Alternative D1 $0.55 M $0.14 M $0.16 M $0.85 M $1,364 


Reach 2a – Douglas County South (upper) 

The degradation that begins in Reach 1 extends into the first portion of Reach 2. Because the channel 

transitions to a more stable condition partway through the reach, it was subdivided into a degraded 

section and a relatively stable section. As with Reach 1, Alternatives D1 and D2 were considered. 

Bank stabilization methods should continue to allow some source material to be carried from this 

reach downstream. The channel is located on private property with no formal access; a maintenance 

trail was included in the cost estimate. 

Table 5-6 

Reach 2a Channel Cost Summary 

Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 

Alternative D1 $0.46 M $0.11 M $0.14 M $0.71 M $670 

Alternative D2 $0.37 M $0.09 M $0.11 M $0.57 M $544 

Reach 2b – Douglas County South (lower) 

As Reach 2b continues to the north, it transitions to a relatively stable channel; alternatives S1 

through S4 were considered for this reach. As with Reach 2a, maintenance access is lacking through 

this residential area. Two overtopping culvert crossings are located in this reach: Oak Hills Drive and 

Clydesdale Road. Neither causes flooding of any structures. Oak Hills Drive requires a triple 18’ x 6’ 

box culvert to pass the 100-year event; this size was not recognized by UD-MP Cost, so the cost was 

calculated based on a 9’ x 6’ culvert with six cells. Clydesdale Road requires a double 14’ x 8’ box 

culvert to pass the 100-year event, with some re-profiling of the road required to provide adequate 

cover. 

Table 5-7 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 

Alternative S1 $4.44 M $1.11 M $1.33 M $6.88 M $539 




Table 5-8 

Reach 2b Crossing Cost Summary 

Capital 

Cost 

Contingency 

Contingency 

Contingency 

Contingency 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

Oak Hills Drive $354,369 $88,592 $106,311 $549,271 

Clydesdale Road $523,368 $130,842 $157,010 $811,220 




Reach 3 – I-25 Corridor 

Reach 3 is the last of three severely degraded reaches of Happy Canyon Creek. This reach parallels I- 

25 and was in part relocated for its construction; the channel degradation is beginning to threaten 

the integrity of the Interstate highway. There are several instances of failed slope paving and some 

failed sheet piling at the outfall of the Oak Ridge Tributary. The Oak Hills Tributary also joins Happy 

Canyon Creek within this reach; the degraded channel condition also extends up this tributary and 

threatens the Oak Hills crossing of Surrey Road. This reach would benefit from upstream minor 

storm detention improvements on the mainstem as well as on the two tributaries. Though Surrey 

Road parallels the channel through this reach, it is located well above the channel; a lower 

maintenance access road is needed for improved access. Property ownership through this reach is 

primarily the Surrey Ridge homeowners association, with some private properties and some CDOT 

right of way. While the I-25 bridge has adequate capacity, the invert has degraded along the north 

side of the bridge, which represents the outer bank at the sharp 90-degree bend leading into the 

channel. A current preliminary design effort for the Douglas County east-west trail has examined 

this situation and concluded that the desire to pass the trail through this bridge prohibits filling the 

channel to raise this invert; instead, the project proposes a concrete slab floor beneath the bridge to 

prevent further degradation. 

Table 5-9 

Reach 3 Channel Cost Summary 

Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 



Table 5-10 

Reach 3 Crossing Cost Summary 

I-25 Bridge 

Improvements 

Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

$200,250 $50,063 $60,075 $310,388 

Reach 4 –Lone Tree South 

Beyond I-25, Happy Canyon once again transitions to a relatively stable channel. Cattle impacts are a 

consideration in this reach, with damage to the streambanks resulting from unrestrained grazing 

access. Because the low-flow drop concept included in Alternatives S2, S3, and S4 relies on healthy, 

resistant overbank vegetation to function well, these alternatives include installation of cattle 

fencing along both sides of the creek in order to protect the riparian benches. Periodic access to the 

creek would be provided for watering the cattle. Without fencing, the full width drops included in 

Alternative S1 would likely be required to stabilize the channel. It is expected that a floodplain 

corridor will be defined as the area develops; costs for a maintenance trail along the corridor were 

included. 

Table 5-11 


CapitalCost 

Contingency 

Contingency 

Contingency 

Eng,/Admin/Legal 

ReachCost 

Channel 

Cost/LF 





Reach 5 –Meridian Commons 

Because it is fenced off from the adjacent grazing areas, Reach 5 is quite stable with good overbank 

vegetation. Though grade control was implemented with development, some additional grade 

control is recommended due to minor headcutting. There is an existing gravel maintenance road 

west of the channel; no maintenance costs were assumed. Though one home has been identified 

within the 100-year floodplain based on lowest adjacent grade, conveyance improvements were not 

specifically considered as the base flood elevation is below the finished floor of the structure’s walkout 

basement; the floodplain impact could be eliminated by raising the lowest adjacent grade and/or 

by implementing detention improvements upstream. 

Table 5-12 


Capital 

Cost 

Contingency 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 








Reach 6 –Lone Tree North 

Reach 6 is once again located within a cattle grazing area, and exhibits similar characteristics to 

Reach 4. Cattle fencing was included in the costs for Alternatives S2 through S4, and a maintenance 

trail was included in all four alternatives. West Parker Road is an overtopping bridge crossing 

located at the downstream end of the reach, within Lone Tree’s city limits. A total span of 180’ is 

required to pass the 100-year event with the required freeboard, and some revisions to the road 

profile are required to eliminate a low point just north of the bridge. Based on the reductions in 100- 

year peaks associated with Detention Alternative C, it is likely this span could be reduced. While it is 

expected that the road may be widened in the future to accommodate additional traffic loads with 

the development of RidgeGate, the cost estimate assumes the existing width. 

Table 5-13 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 





Table 5-14 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

West Parker Road $631,906 $157,977 $189,572 $979,455 

Reach 7a –Douglas County North (upper) 

Reach 7 is another reach that warranted splitting into two sub-reaches based on differences in 

channel condition. The upper portion, stretching from West Parker Road to Birch Avenue, is 

moderately stable with generally adequate capacity. There are some concerns in Reach 7a: 

floodplain modeling indicates that Lincoln Avenue overtops in the 100-year event due to channel 

flow spilling into Meridian Village Pond 1 through the pond’s emergency spillway. This results in 

elevated water surface conditions within the pond, which spill over a low point in Lincoln to the 

west of Happy Canyon Creek. Channel costs include excavation below an existing drop structure 

located just upstream of Lincoln; the drop has been partially buried due to aggradation, and 

excavation would restore its design drop height. The reduction in 100-year peak flows associated 

with Detention Alternative C would eliminate the need to increase capacity through excavation. 

Another concern in this reach is an exposed utility located just upstream of Birch Avenue and 

degradation of the channel invert through the Birch Avenue crossing; while no new grade control 

was identified for this reach, grade control downstream of Birch in Reach 7b should resolve these 

issues. 

Because Alternatives S1 and S2 differ only in the assumed sizing of grade control, these alternatives 

reflect the same cost for this reach as no additional grade control is needed. 

Table 5-15 

Reach 7a Channel Cost Summary 

Capital 

Cost 

Contingency 

Contingency 

Contingency 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 





Reach 7b –Douglas County North (lower) 

The lower portion of Reach 7 presents numerous floodplain concerns as Happy Canyon Creek passes 

through private residential properties in Grandview Estates. The development predates all other 

development within the watershed, and it is apparent that little thought was given to this major 

drainageway when the land was subdivided. Floodplain analysis indicates that 11 homes are 

impacted in the 100-year event as a result of inadequate channel capacity and a severely undersized 

crossing at Dogwood Avenue. Flood conveyance alternatives F1, F2, and F3 were considered for this 

reach. Alternative F1 provides a 100-year channel with a top width of 120’ to 140’. Approximately 

70,000 cubic yards of excavation is required to provide a 100-year channel. Alternative F2 provides 

10-year capacity, and alternative F3 includes only minor channel stabilization with no capacity 

improvements. 

A portion of this reach just north of Cottonwood Avenue, between Birch and Dogwood, is quite 

narrow with steep banks and exhibits high velocities up to 18 feet/sec. Extensive bank protection is 

provided in Alternatives F1 and F2, with a more modest approach in Alternative F3. 

Dogwood crossing improvements include two alternatives, at the direction of Douglas County: 

replacement of the crossing with a steel truss bridge that spans the 100-year floodplain, and 

removal of the crossing and permanent closure of the street at this location. Both alternatives would 

address the channel concerns; removal would change traffic patterns in the development but would 

still maintain multiple access points for all residents. While the channel costs are tabulated 




separately from the crossing costs, it should be noted that Alternative F1, F2, and F3 all rely on 

implementation of one of the two Dogwood improvement options in order to provide the intended 

capacity. 

Maintenance access is lacking in this reach; from Birch to Cottonwood the channel parallels 3 rd 

Street, but the remainder of the reach is generally inaccessible. A maintenance trail is included in the 

alternative costs; however, residents have been resistant to allowing access along their private 

property in the past. 

Table 5-16 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 

Alternative F1 $5.04 M $1.26 M $1.51 M $7.81 M $1,212 

Alternative F2 $2.66 M $0.67 M $0.80 M $4.13 M $641 

Alternative F3 $1.59 M $0.40 M $0.48 M $2.46 M $382 

Table 5-17 

Reach 7b Crossing Cost Summary 

Alt. 1 

Alt. 2 


Bridge 


Removal 

Capital 

Cost 

Contingency 

Contingency 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

$576,725 $144,181 $173,018 $893,924 

$37,458 $9,364 $11,237 $58,060 

Because the channel conveyance improvements rely on the improvements at the Dogwood crossing, 

the analysis was conducted pairing each of the three channel alternatives with each of the two 

Dogwood alternatives. For the purposes of the flood damage reduction benefit/cost analysis, the 

cost of the minimum required level of stream stabilization measures (Alternative F3) was deducted 

from the reach costs so that the remaining cost was representative of flood conveyance 

improvements. Annualized costs for the improvements were calculated based on an interest rate of 

3.0 percent and a period of 50 years. The results of the analysis are shown in Table 5–18; flood 

damage calculations are included in Appendix F. 

Reach 8 –Town of Parker 

Reach 8 passes through Town of Parker annexation areas south of E-470 and current town 

boundaries north of E-470. The wide, sandy channel bottom is aggrading through this reach, but will 

likely require grade control in the future as upstream degradation is reduced, shifting the channel 

equilibrium. South of E-470, the channel is unimproved with no maintenance access; costs for a trail 

are included, but not land acquisition as a floodplain corridor will be required for development. An 

existing low flow double 24” RCP trail crossing at E-470 appears to pose maintenance issues, acting 

as a sediment trap for the channel. Crossing improvement costs include replacement with a 10’ x 3’ 

box culvert. North of E-470, some grade control and bank protection has been implemented along 

with a recreational / maintenance trail. 

The outfall of the pipe that diverts the Stonegate Tributary around Chambers Reservoir is located 

just east of the E-470 trail crossing; the channel reach from the outfall to the confluence with Happy 

Canyon Creek is unstable and actively degrading. The floodplain also expands at this point before 

contracting to pass under E-470; the Town of Parker has indicated a desire to channelize Happy 

Canyon Creek here to avoid sedimentation in the ineffective flow areas. Costs include a large amount 

of fill in the ineffective floodplain area and extension of the Stonegate Tributary pipe to the filled 

channel edge. 

Benefit/Cost Analysis for Flood Damage Reduction 

The reach costs for the three channel conveyance alternatives in Grandview were compared against 

the associated flood damage reduction to estimate a benefit/cost ratio for each alternative. Flood 

damages were calculated in accordance with UDFCD’s 1977 Methodology for Evaluation of 

Feasibility: Multijurisdictional Urban Drainage and Flood Control Projects. Annualized flood damages 

were estimated by determining water surface elevations at each structure for a given return period 

event, comparing them to the structure elevation, finding a depth of flooding, using depth-damage 

curves published by FEMA to estimate damages as a percent of the structure value, and multiplying 

by the valuation of each structure. This process was repeated for each return period for the three 

alternatives and the flood damages were plotted against probability, then integrated to find the 

annualized flood damage potential. 




Table 5-18 

Reach 7b Benefit/Cost Analysis 

Dogwood Alternative 1: 100-Year Bridge 

Channel Alternative F1: 

100-yr Channel Improvements 




Low Flow Stabilization Improvements 

Dogwood Alternative 2: Crossing Removal 






Low Flow Stabilization Improvements 

Total 

Reach Cost 

* Cost annualized using a Capital Recovery A/P of 0.03887 

Less Min. Stream 

Stabilization 

Improvement 

Crossing Cost 

Net Alternative 

Cost 

Annualized Cost* 

Average Annual Flood 

Damage Reduction 

Benefit/ Cost 

Ratio 

$7,812,970 -$2,464,394 $893,924 $6,242,499 $242,646 $25,545 0.11 

$4,130,709 -$2,464,394 $893,924 $2,560,238 $99,516 $21,135 0.21 

$2,464,394 -$2,464,394 $893,924 $893,924 $34,747 $8,670 0.25 

$7,812,970 -$2,464,394 $58,060 $5,406,635 $210,156 $25,545 0.12 

$4,130,709 -$2,464,394 $58,060 $1,724,375 $67,026 $21,135 0.32 

$2,464,394 -$2,464,394 $58,060 $58,060 $2,257 $8,670 3.84 

Table 5-19 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 





Table 5-20 


Capital 

Cost 

Contingency 

Contingency 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

E-470 Trail $14,344 $3,586 $4,303 $22,234 

Reach 9 –Arapahoe County 

The final reach of Happy Canyon Creek lies in Arapahoe County, within SEMSWA’s jurisdiction. Like 

Reach 8, Reach 9 is aggrading but will likely require additional grade control in the future. Upstream 

of Jordan Road, capacity improvements have been implemented adjacent to the ACWWA- 

Cottonwood WSD Joint Water Purification Plant (JWPP). Downstream of Jordan, the engineered 

channel may experience capacity issues in the future as development increases base flows, allowing 

more vegetation to take hold in this dry sandy reach; however, this will be offset by peak flow 

reductions associated with any of the detention alternatives. Project sponsors indicated cattle are a 

problem in the undeveloped portions of this reach as well; fencing has been included for cattle 

management. Channel costs assume some excavation of a low-flow channel to improve the character 

of this reach. Maintenance access is provided along most of the reach with the Happy Canyon Creek 

trail, with a gap extending from the county line to the JWPP property. Trail costs are included to 

close this gap, as well as a pedestrian/light truck bridge crossing that will be required to complete 

the linkage. Though the FHAD indicates shallow flooding at Jordan Road based on future condition 

peak flows, no conveyance improvements have been reflected as the reductions in 100-year peaks 

associated with detention already planned within the watershed (as represented in Detention 

Alternative A) will prevent this condition from ever materializing. 




Table 5-21 


Capital 

Cost 

Eng,/ 

Admin/ 

Legal 

Reach 

Cost 

Channel 

Cost/LF 





Table 5-22 


Capital 

Cost 

Contingency 

Contingency 

Eng,/ 

Admin/ 

Legal 

Total 

Cost 

Happy Canyon Trail $225,000 $56,250 $67,500 $348,750 

Capital costs for all the reaches are compared on a lineal foot basis in Figure 5-7 for all channel 

alternatives. This figure, which is color coded to match the types of improvements shown in Figures 

5-4 through 5-6, shows that the expected costs for the currently degraded reaches (in orange) are 

relatively high and that there is not much opportunity to develop alternatives that lower the cost 

substantially. Relatively high costs for the Grandview reach (in gray) are also shown for the 

alternatives that provide significant flood damage reduction. A lower cost alternative is possible, but 

the flood damage reduction is modest and results from improvements at Dogwood rather than in the 

channel. Figure 5-7 indicates that the alternative costs for reaches that are relatively stable (in 

green) are generally the lowest on a lineal foot basis and illustrate a wide cost range depending on 

the extent of stabilization measures needed. 

Annual operations and maintenance costs for all reaches were calculated based on a cost of 

$0.50/LF and are summarized in Table 5-21 below. 

Table 5-23 

Channel Operation and Maintenance Costs 

Reach No. 

Reach Description 

Length 

(ft) 

Total Annual 

Cost 

Present Worth - 

50 Years O&M 

1 Castle Pines 500 $ 250 $ 6,432 

2a Douglas County South (upper) 850 $ 425 $ 10,935 

2b Douglas County South (lower) 10300 $ 5,150 $ 132,508 

3 I-25 Corridor 5050 $ 2,525 $ 64,967 

4 Lone Tree South 13950 $ 6,975 $ 179,465 

5 Meridian Commons 3000 $ 1,500 $ 38,595 

6 Lone Tree North 4900 $ 2,450 $ 63,038 

7a Douglas County North (upper) 2550 $ 1,275 $ 32,805 

7b Douglas County North (lower) 5200 $ 2,600 $ 66,897 

8 Town of Parker/Stonegate Trib 8720 $ 4,360 $ 112,181 

9 Arapahoe County 5000 $ 2,500 $ 64,324 

Totals 60020 $ 30,010 $ 772,148 




$1,600 

Figure 5-7 

Channel Improvement Unit Cost Comparison 

Capital Cost per LF 

$1,400 

$1,200 

$1,000 

$800 

$600 

Reach 9 

Reach 8 

Reach 7b 

Reach 7a 

Reach 6 

Reach 5 

Reach 4 

Reach 3 

Reach 2b 

Reach 2a 

Reach 1 

$400 

$200 

$0 

000+00 100+00 200+00 300+00 400+00 500+00 600+00 700+00 

Station 

Degraded Channel - ALT D1 Degraded Channel - ALT D2 Stable Channel - ALT S1 

Stable Channel - ALT S2 Stable Channel - ALT S3 Stable Channel - ALT S4 

Grandview Channel - ALT F1 Grandview Channel - ALT F2 Grandview Channel - ALT F3 




5.7 Qualitative Evaluation of Alternatives 

This section summarizes advantages and disadvantages of alternatives and provides a discussion 

leading to the selection of a recommended plan. 

5.7.1 Relative Costs 

Of the three categories of improvements in the Happy Canyon Creek watershed – regional detention, 

channel reclamation/enlargement, and crossing improvements – the greatest potential cost burden 

is associated with channel reclamation. The table below shows the sum of the reach costs for the 

most extensive alternative plans and the least extensive, indicating the difference in cost between 

the two. 

Table 5-24 

Relative Costs of Alternatives 

Channel 

Improvements 

Detention 

Improvements 

Crossing 

Improvements 

Most Extensive Alternatives $56,400,000 $50,400,000 $3,900,000 

Least Extensive Alternatives $22,800,000 $28,400,000 $3,100,000 

Difference $33,600,000 $22,000,000 $800,000 

5.7.2 Reducing Channel Improvement Measures 

Implementing the least extensive channel improvements, if adequate, has the potential of saving 

$33.6 million compared to the most extensive improvements based on the alternative cost 

estimates. In addition, the least extensive channel improvements reduce disturbance to the creek 

corridor and help to preserve natural riparian vegetation and habitat. Therefore, it is worthwhile to 

take measures – as recommended in sections 5.7.3 through 5.7.5 – that increase the likelihood that 

the least extensive channel improvements will suffice to maintain a healthy, relatively stable creek. 

5.7.3 Full Spectrum Detention and 100-Year Peak Flow Reduction 

One measure that has the potential to reduce the extent of the work in the creek is implementing an 

effective Full Spectrum Detention approach for the watershed – one that reduces peak runoff during 

frequent storms to levels similar to historic conditions. Of the detention alternatives, Alternative C 

effectively neutralizes increased peak flows from urbanization in Castle Pines and produces the 

closest match to historic flows in the water quality event and 2-year event. Reduction of 100-year 

peak flow rates helps address floodplain issues in Grandview Estates by providing additional 

detention volume where it can be done with minimal impact to the surrounding properties. The 

increased investment to move from the planned detention of Alternative A to the enhanced 

approach of Alternative C based on the costs above is $22 million; this is less than the potential 

savings in channel work if a less extensive set of channel improvements is possible. The actual 

savings are likely greater based on the over-conservative nature of the detention cost estimates. 

5.7.4 Cattle Fencing 

Another measure that is focused on reducing the scope of improvements necessary in the Happy 

Canyon Creek channel is installing fencing to control cattle in Reaches 4 and 6. Unrestricted cattle 

access impacts creek banks and riparian vegetation and weakens the corridor’s resistance to 

erosion. Fencing to keep cattle out of riparian corridors except at periodic watering stations has 

been shown to restore stream bank vegetation and improve the stability of creeks and floodplains. 

One such fencing project, implemented several years ago by Douglas County Open Space in Prairie 

Canyon Ranch, has effectively reduced cattle access and has led to a dramatic improvement in the 

health and stability of Cherry Creek. 

Cattle control fencing has an estimated installation cost of about $2 per lineal foot, or approximately 

$83,000 to fence both sides of Happy Canyon Creek along Reaches 4 and 6 in addition to establishing 

watering stations about every quarter mile. In approximate terms, the potential savings in stream 

reclamation that the fencing could create might be as much as the difference between Alternative S1 

(full-width drops) and Alternative S2 (low flow drops), or $5.9 million for Reaches 4 and 6. 

5.7.5 Sediment Management 

Based on thorough observations along the entire study reach, Happy Canyon Creek is characterized 

by a relatively high sediment transport load, allowing the stream to maintain longitudinal gradients 

from 0.5 percent in the lower watershed up to 1.1 percent in the upper reaches at something close to 

equilibrium conditions, more-or-less. Alternatives that avoid drastic changes in sediment supply 

and transport from existing conditions – either higher or lower – are important in reducing the 

tendency for the Creek to degrade or aggrade and, therefore, reducing the measures and costs 

necessary to stabilize the creek. 

For this reason, the regional detention alternatives considered avoid locating EURV or full-spectrum 

detention facilities on mainstem Happy Canyon Creek. Regional extended detention facilities on the 

mainstem would trap a lot of sediment – requiring frequent maintenance operations to remove – 

and would set up cycles of channel degradation downstream as currently exhibited by the 

degradation downstream of CPNMD Pond #12. The only on-line detention facilities considered were 

100-year “peak shaving” facilities that have relatively large culvert outlets that would still allow 

sediment to pass. 

Also, channel alternatives developed to reclaim existing degraded reaches are intended to re-create 

a natural, somewhat soft creek corridor and to avoid structurally constraining these reaches to the 

point where there is no longer any in-reach sediment supply. It is desirable to address erosion and 

reduce the amount of sediment moving downstream, but not to take the sediment supply suddenly 

to zero, or downstream reaches may react with accelerated degradation. The goal is to maintain 

moderate levels of sediment supply in the near term to reduce the magnitude of downstream 

degradation and over time to allow the sediment supply along the entire study reach to decrease in a 

balanced fashion. 




5.7.6 Dogwood Avenue Crossing 

If it is acceptable, elimination of the Dogwood crossing would save an estimated $800,000 compared 

to construction of a new 100-year capacity bridge over Happy Canyon Creek. Removal of the 

Dogwood crossing would reduce potential flood damages in Grandview Estates and has a 

benefit/cost ratio greater than one, indicating that the benefits outweigh the costs. 

5.7.7 Grandview Estates Conveyance Improvements 

Of the three conveyance improvement alternatives, the greatest reduction in flood damages is 

associated with Alternative F1. This alternative also has the greatest cost and the lowest 

benefit/cost ratio. A modest reduction in flood damages is associated with Alternative F3 based on 

the removal of the existing Dogwood crossing. This alternative has the lowest net cost and highest 

benefit/cost ratio. Alternative F2, the 10-year channel, represents an approach that is in the middle 

of the other two alternatives both in its benefits and costs; it provides over 80 percent of the damage 

reduction of Alternative F1 for just over half the cost. 

While all of the flood damage calculations are based on the future conditions peak flows reflected in 

the FHAD update, pairing of channel improvements with Detention Alternative C can further reduce 

flooding. Table 5-25 shows the estimated structure flooding based on no channel improvements, 

removal or replacement of the Dogwood crossing, and removal or replacement of Dogwood paired 

with Alternative F2 for both the future conditions peak flow rates and the Detention Alternative C 

peak flow rates. 

Table 5-25 

Alternative Grandview Estates Structure Flooding 

Freeboard (F) or Flooding Depth (D) 

Future Conditions Peak Flows Detention Alternative C Peak Flows 

Dogwood 

Crossing 

Removed 

10-YR 

Channel 

(Alt F2) & 

Dogwood 

Removed 

Dogwood 

Crossing 

Removed 

10-YR 

Channel 

(Alt F2) & 

Dogwood 

Removed 

Existing 

Existing 

Address 

Channel 

Channel 

3592 Dogwood Ave. 2.11 D 2.82 F 3.24 F 1.66 D 4.69 F 4.67 F 

3771 E. Elm Ave. 0.27 D 0.28 D 1.95 F 1.63 F 1.63 F 2.57 F 

12666 4th St. 0.19 D 0.16 2 D 0.17 2 D 1.57 3 F 1.61 F 1.49 F 

12706 4th St. 0.43 D 0.43 2 D 0.37 2 D 1.14 F 1.14 F 0.77 F 

12746 4th St. 0.83 D 0.84 D 1.75 F 0.51 F 0.51 F 0.82 F 

12786 4th St. 0.68 D 0.69 D 0.19 F 0.70 F 0.70 F 1.59 F 

12787 5th St. 3.82 D 3.83 D 2.49 D 2.18 D 2.18 D 1.29 D 

12823 5th St. 1.24 D 1.26 D 0.69 F 0.73 F 0.73 F 1.63 F 

12863 5th St. 1.39 D 1.33 D 0.55 D 0.85 D 0.85 D 0.36 F 

12907 5th St. 0.89 D 0.89 D 0.56 D 0.35 D 0.35 D 0.02 F 

12908 5th St. 1.20 D 1.20 D 0.87 D 0.66 D 0.66 D 0.29 1 D 

Total # Impacted Homes 11 8-10 4-6 5-6 4 1 

1Home located in unlikely ineffective flow area. Assume no innundation. 

2Possibility that homes are protected by a natural berm since there would be no spill flow from Dogwood overtopping. 

3Shallow flooding from Dogwood not included in depth calculation. 




SECTION 6 – RECOMMENDED PLAN 

6.1 Plan Description 

The recommended plan, shown in Figures 6-1 through 6-3, consists of the following elements: 

1. Detention Alternative C. The maximum detention approach is recommended because it 

most effectively reduces peak runoff during frequent and large, infrequent storms to levels 

similar to historic conditions. This in turn reduces stresses imposed on Happy Canyon Creek 

during runoff events and allows a more modest program of stabilization improvements to be 

implemented. The maximum detention alternative also provides the most water quality 

treatment via extended detention, and significantly reduces 100-year peaks through the 

flood-prone Grandview Estates. EURV and FSD detention facilities are recommended to be 

located offline from mainstem Happy Canyon Creek to attenuate increased peak flows prior 

to entry into the creek and to avoid dramatic imbalances in sediment movement and stream 

equilibrium. Online peak-shaving ponds within RidgeGate are recommended to maximize 

100-year detention, minimize impact to developable area, and avoid “stacking” the 

development’s peaks with the main channel peaks. 

2. Reclamation of degraded reaches. It is recommended that the portions of Happy Canyon 

Creek that have experienced severe degradation be rehabilitated as soon as possible. This 

includes the eroded length of channel downstream of CPNMD Pond #12 in Reaches 1 and 2 

and the I-25 Corridor (Reach 3). Risks to an exposed high pressure gas line in Reach 1 and to 

I-25 in Reach 3 make these repairs an immediate priority; in addition, if the degradation 

continues, the damage will grow worse and the reclamation improvements will need to be 

more extensive and costly. To help diminish a cycle of rapid downstream degradation, it is 

recommended that the channel be filled slightly steeper than the predicted equilibrium slope 

and the sides of the active channel be left relatively soft to maintain a moderate sediment 

supply in these reaches. It is recommended that this approach be refined based on further 

evaluations, including quantitative sediment equilibrium analyses over the anticipated range 

of flow conditions. With the implementation of Detention Alternative C and the resultant 

reduction in peak flows during frequent events, Channel Alternative D2 can be applied to 

these reaches. 

3. Timed, incremental approach to keep reaches stable. One of the most important benefits 

of this major drainageway plan will be to coordinate a strategy to protect the 8 miles of 

Happy Canyon Creek that are currently in a relatively stable condition (several reaches are 

already severely degraded and require more immediate, substantial stabilization measures). 

If not managed well, these currently stable reaches could deteriorate quickly. The 

recommended approach has a number of characteristics. It is: 

• Incremental. Reclamation improvements are tailored to meet the current and nearterm 

needs of the stream rather than totally re-constructing channels for assumed 

long-term conditions. Improvements seek to be small and surgical, reinforcing weak 

points but preserving stable areas of the floodplain. 

• Timed. Improvements are to be implemented at “just the right time” – proactively 

addressing “hot spots” soon after early signs of instability are observed rather than in 

a delayed manner to repair major degradation after it has already occurred. 

• Distributed. Since Happy Canyon Creek is a system that responds to actions in 

individual sub-reaches, improvements are intended to be implemented in a 

coordinated approach and distributed throughout the study reach based on the 

condition and needs of the creek in any given year. Otherwise, too many dollars may 

be spent on completely stabilizing one reach to a level that may not be needed for 

years into the future, while others are left unprotected and vulnerable to impact with 

the potential to create a downstream ripple effect of impacts. 

• Progressive. Since Happy Canyon Creek will respond to changes in the watershed 

over time, there may be a need for follow-up phases of work within the same reaches, 

adding grade control as the stream adjusts to a flatter equilibrium slope or addressing 

new “hot spots” of bed or bank erosion. 

• Managed. Annual stream inventories are recommended to observe signs of instability 

that need to be addressed and to assess how initial reinforcement improvements are 

functioning, how revegetation establishment is progressing, and whether any signs of 

additional instability are noticed in reaches addressed in initial improvements. The 

results of the monitoring are to be used by UDFCD and the local jurisdictions to plan 

for subsequent improvement measures. 

The four alternatives identified for the relatively stable reaches of Happy Canyon Creek 

represent a progression of channel improvements that may be necessary both over time and 

with increasing stress from developed runoff conditions. Potential improvements that may 

be necessary could start with the more modest stabilization measures of Alternative S4 (or 

even less) and move through Alternatives S3, S2, and perhaps ultimately to the measures of 

Alternative S1 if time and stresses call for more and more stabilization. 

If the stresses imposed on the creek are managed well – with the maximum Full-Spectrum 

Detention Alternative C and other recommended measures – it is possible that lesser 

stabilization measures will suffice to allow these reaches to maintain a relatively steep 

equilibrium slope even over the long term. In this case, Alternative S4 may represent all the 

channel stabilization work that is ever needed. If additional measures become necessary, 




they could be implemented in timed, incremental approach. This strategy of identifying less 

extensive work for initial implementation will stretch out funding requirements over time 

and promote a “just enough” approach to protecting and reclaiming Happy Canyon Creek. 

4. Cattle Fencing. It is recommended that fencing be installed as soon as possible to protect the 

riparian corridor of Happy Canyon Creek in Lone Tree (Reach 4 and 6) from cattle impacts. 

The fencing is envisioned as barbed wire fencing running the length of these reaches on both 

sides of the creek corridor with periodic (approximately quarter mile) watering stations. The 

intent is to reduce nutrient loading associated with cow waste and to reduce damage to the 

creek banks and vegetation that weaken the floodplain’s natural resistance to erosion. It is 

expected that the investment in cattle fencing will more than pay for itself in reduced stream 

stabilization measures. 

5. Conveyance improvements in Grandview Estates. The decision regarding the level of 

improvements to be implemented in Grandview Estates will need to be carefully thought out 

based on the goals of the local community, Douglas County, and UDFCD. From a hydraulic 

perspective, the two alternatives at Dogwood Avenue are equivalent, but the benefit/cost 

ratio strongly favors removal. Therefore, based on hydraulic analysis and on the measureable 

floodplain benefit to be gained with minimal investment, removal of the crossing is 

recommended. However, this recommendation does not account for the numerous other 

factors that must be considered by Douglas County before making any final decisions, such as 

traffic movement, neighborhood impacts, emergency service access, and public opinion. As 

evidenced by the residents’ comments submitted after the public meeting, removal of the 

crossing may not be a palatable option for the County. In addition to addressing Dogwood 

Avenue, it also seems reasonable to consider constructing some level of channel 

improvements to gain an additional reduction in potential flood damages. Alternative F2, the 

10-year channel, represents an approach that is in the middle of the other two alternatives 

both in its benefits and costs. For this reason, Alternative F2 is the recommended alternative 

for Reach 7b. When paired with Detention Alternative C, the total number of impacted homes 

within Grandview Estates, can be reduced from eleven to just one. 

6. Crossing improvements. It is recommended that existing undersized crossings be enlarged 

and upgraded based on the priorities of the local jurisdictions. The exception would be the 

Dogwood Avenue crossing, which, as discussed above, is recommended to be removed. 

7. Runoff reduction practices. Although not identified as a specific alternative to evaluate, it is 

recommended that all new developments in the watershed employ runoff reduction 

practices. These practices consist of reducing areas of imperviousness, using porous 

pavements, and directing runoff from roofs and pavement to vegetated areas such as grass 

buffers and swales. Arapahoe County / SEMSWA requires adherence to the “20/10 rule” in 

all developments tributary to a regional water quality facility, which requires that 20% of the 

impervious area be disconnected and drain through a receiving pervious area that is at least 

10% of the contributing impervious area in size. 

8. Funding and implementation. Several unique aspects of the recommended plan deserve 

special consideration with respect to funding and implementation. These are associated with 

improvements in Castle Pines and Lone Tree. 

Castle Pines 

Although there will be benefits to Castle Pines and the Metro District associated with 

retrofitting Full Spectrum Detention into the existing Castle Pines detention facilities, 

significant benefits will also accrue to the downstream jurisdictions. Therefore, it is 

recommended that a coordinated funding plan be developed that seeks to apportion costs 

equitably between Castle Pines and downstream jurisdictions. 

Lone Tree 

As with Castle Pines, the Alternative C detention improvements recommended in Lone Tree 

provide additional benefit to downstream jurisdictions by going beyond the minimum 

required detention represented in Alternatives A and B. Because the landowner will be 

required to implement detention with development, cost-sharing with the local jurisdictions 

may be a means of maximizing the potential benefit of the online peak-shaving ponds without 

putting undue burden on the landowner. 

It is recommended that a plan be developed to fund and implement stream improvements in 

Lone Tree over the long term based on the “timed, incremental” approach discussed above. 

One approach to accomplish this is to determine the appropriate amount and timing of 

contributions from the developer and have them reserved in a fund that could be managed by 

UDFCD and Lone Tree to implement improvements as they are needed over time. 

For these reaches and the other reaches that are relatively stable today, the plan 

recommends establishing long term budgets based on Alternative S2 (more or less) and 

implementing a plan similar to Alternative S4 as an initial set of improvements. 

This point can be illustrated by considering example practices in McMurdo Gulch, a major 

tributary draining to Cherry Creek upstream of Happy Canyon Creek. In one portion of 

McMurdo Gulch, an adjacent developer was required to construct a full 100-year channel 

with 100-year grade control structures at the outset of development. One of these structures 

is shown below in the photo to the left. In another portion of McMurdo Gulch, the first phase 

of a timed, incremental set of improvements was constructed. A representative reach of 

improvements is shown in the photo to the right. The latter approach was installed more 

surgically, preserving valuable existing riparian vegetation, and as an initial phase of 

improvements, was much less costly than the full 100-year approach installed by the 




developer. The recommended plan for Happy Canyon Creek promotes the latter approach in 

reaches that are relatively stable today. 

6.3 Water Quality Impacts 

The recommended plan addresses water quality impacts in a number of significant ways. The plan 

represents a watershed-wide strategy to implement UDFCD’s Four Step Process for water quality 

protection. These steps are: 

1. Employ runoff reduction practices. 

2. Implement effective water quality detention. 

3. Stabilize drainageways. 

4. Implement source control practices. 

Developer-constructed 100-year drop 

structure on McMurdo Gulch 

6.2 Plan Cost 

Phase 1 of timed, incremental improvements 

on McMurdo Gulch 

The total estimated costs for the recommended plan are tabulated by jurisdiction in Table 6-1. For 

stable channels, the improvement costs for Alternative S2 are reflected in the budget costs and 

Alternative S4 are reflected in the implementation costs. 

Table 6-1 

Recommended Plan Costs by Jurisdiction (including O&M) 

City of Castle 

Pines 

Douglas 

County 

City of Lone 

Tree 

Town of 

Parker 

Detention 

Costs 

Crossing 

Costs 

Channel 

Costs - 

Budget 

Channel 

Costs - 

Implement 

Total Cost - 

Budget 

Total Cost - 

Implement 

$ 3,508,631 $ 0 $ 828,363 $ 828,363 $ 4,336,994 $ 4,336,994 

$ 9,815,715 $ 1,418,551 $20,316,674 $15,514,412 $31,550,940 $26,748,678 

$36,649,374 $ 1,289,842 $14,524,736 $ 8,237,962 $52,463,953 $46,177,178 

$ 1,353,733 $ 22,234 $ 4,504,273 $ 2,635,474 $ 5,880,240 $ 4,011,441 

SEMSWA $ 2,541,079 $ 348,750 $ 2,029,594 $ 1,266,941 $ 4,919,423 $ 4,156,770 

A summary of costs by channel reach and by detention facility is shown in Table 6-2. 

Employ runoff reduction practices 

The recommended plan encourages adoption of runoff reduction practices in newly developing 

areas. As shown in the recent Large Lot Runoff Study conducted for Douglas County, the capacity for 

infiltration and filtering in vegetated areas during frequent storms such as the water quality event is 

substantial. Taking advantage of this capacity decreases stormwater infrastructure and reduces 

stresses on Happy Canyon Creek and its tributaries. 

Implement effective water quality detention 

The recommended detention plan (Alternative C) maximizes the implementation of Full Spectrum 

Detention in the watershed. Since Full Spectrum Detention provides extended detention based on 

the excess urban runoff volume (EURV) – more than twice the water quality capture volume (WQCV) 

for a given area – much more than the required WQCV is being provided in the plan for settling and 

treatment of runoff. 

The effectiveness of the recommended detention plan during the water quality event can be 

observed in Figure F-4. Runoff peaks during the water quality event are very low throughout the 

study reach. Because the recommended Full Spectrum Detention approach will significantly reduce 

peak flows during frequent events, erosive forces on the creek will be controlled and softer, more 

vegetative measures can be taken to reclaim the stream. Helping to control stream erosion through 

Full Spectrum Detention is a major water quality benefit of the recommended plan. 

Stabilize drainageways 

Measures recommended to protect and reclaim Happy Canyon Creek are not just intended to 

promote the stability of the creek, but to create and preserve natural floodplain processes that 

enhance water quality. These processes include connecting the creek to its floodplain, encouraging 

runoff to spread out over vegetated overbanks during storm events for treatment via infiltration and 

filtering. The benefits of such a stream reclamation approach for water quality were documented in 

a report entitled Stream Reclamation, Water Quality Benefit Evaluation – Interim Status Report, dated 

June 16, 2011, prepared for the Cherry Creek Basin Water Quality Authority. 




Implement source control practices 

An example of the plan’s focus on source control measures is the recommendation for cattle fencing 

to protect the creek in Reaches 4, 6, and 9. With a single cow capable of producing 12 tons of 

manure per year, this is potentially a significant nutrient source for Cherry Creek Reservoir, in 

addition to the impacts of the cattle on the stream banks and vegetation. Fencing is a proven means 

of controlling these impacts at their source. 

Overall, the goal of protecting and enhancing water quality in the Happy Canyon Creek watershed 

and in the receiving waters downstream is a primary driver in the development of the 

recommended plan. 

6.4 Operations and Maintenance 

Ongoing operations and maintenance are an essential component of the recommended plan. 

Provision of a maintenance access trail along the entire length of the study reach has been made. 

New and retrofitted Full Spectrum Detention facilities will require attention to the outlet works and 

debris grate design to reduce maintenance requirements. 

Estimates of operations and maintenance costs have been made both for detention facilities and the 

mainstem of Happy Canyon Creek. A present worth valuation of these annual costs was made based 

on a period of 50 years and an inflation rate of 3.0 percent. Operations and maintenance costs are 

included in Table 6-2. 

6.5 Environmental and Safety Assessment 

Serious environmental and safety concerns have been observed in several severely degraded 

reaches of Happy Canyon Creek, specifically in the reach downstream of Castle Pines Pond #12 and 

along I-25. It is recommended that these reaches be rehabilitated as soon as possible to mitigate the 

environmental and safety concerns. The recommended plan is focused on taking strategic measures 

to promote the stability of the remaining reaches of Happy Canyon Creek and keep the degradation 

already experienced in the creek from occurring elsewhere. 


Engineering / Legal / 

Engineering / Legal / 

Recommended Total Capital Cost - Contract / Const. Contingency 

Total Capital Cost - Contract / Const. Contingency 

Reach Jurisdiction Alternative 

Budget 

30% 25% Total Cost - Budget Implement 

30% 25% 

Channel Costs 

Reach 1b - Castle Pines City of Castle Pines Alternative D2 $ 530,278 $ 159,083 $ 132,569 $ 821,931 $ 530,278 $ 159,083 $ 132,569 $ 821,931 $ 250 $ 6,432 $ 828,363 $ 828,363 

Reach 2a - Douglas County South (upper) Douglas County Alternative D2 $ 369,780 $ 110,934 $ 92,445 $ 573,158 $ 369,780 $ 110,934 $ 92,445 $ 573,158 $ 425 $ 10,935 $ 584,094 $ 584,094 

Reach 2b - Douglas County South (lower) Douglas County Alternative S2/S4 $ 4,133,867 $ 1,240,160 $ 1,033,467 $ 6,407,493 $ 1,334,943 $ 1,240,160 $ 333,736 $ 2,908,839 $ 5,150 $ 132,508 $ 6,540,001 $ 3,041,347 

Reach 3 - I-25 Corridor Douglas County Alternative D2 $ 4,068,609 $ 1,220,583 $ 1,017,152 $ 6,306,345 $ 4,068,609 $ 1,220,583 $ 1,017,152 $ 6,306,345 $ 2,525 $ 64,967 $ 6,371,312 $ 6,371,312 

Reach 4 - Lone Tree South City of Lone Tree Alternative S2/S4 $ 7,178,373 $ 2,153,512 $ 1,794,593 $ 11,126,479 $ 3,109,337 $ 2,153,512 $ 777,334 $ 6,040,183 $ 6,975 $ 179,465 $ 11,305,943 $ 6,219,648 

Reach 5 - Meridian Commons Douglas County Alternative S2/S4 $ 1,070,118 $ 321,035 $ 267,530 $ 1,658,683 $ 414,664 $ 321,035 $ 103,666 $ 839,365 $ 1,500 $ 38,595 $ 1,697,278 $ 877,960 

Reach 6 - Lone Tree North City of Lone Tree Alternative S2/S4 $ 2,035,971 $ 610,791 $ 508,993 $ 3,155,755 $ 1,075,588 $ 610,791 $ 268,897 $ 1,955,276 $ 2,450 $ 63,038 $ 3,218,793 $ 2,018,314 

Reach 7a - Douglas County North (upper) Douglas County Alternative S2/S4 $ 576,502 $ 172,951 $ 144,125 $ 893,578 $ 189,070 $ 172,951 $ 47,267 $ 409,288 $ 1,275 $ 32,805 $ 926,383 $ 442,093 

Reach 7b - Douglas County North (lower) Douglas County Alternative F2 $ 2,664,974 $ 799,492 $ 666,243 $ 4,130,709 $ 2,664,974 $ 799,492 $ 666,243 $ 4,130,709 $ 2,600 $ 66,897 $ 4,197,606 $ 4,197,606 

Reach 8 - Town of Parker Town of Parker Alternative S2/S4 $ 2,833,607 $ 850,082 $ 708,402 $ 4,392,091 $ 1,338,568 $ 850,082 $ 334,642 $ 2,523,293 $ 4,360 $ 112,181 $ 4,504,273 $ 2,635,474 

Reach 9 - Arapahoe County SEMSWA Alternative S2/S4 $ 1,267,916 $ 380,375 $ 316,979 $ 1,965,270 $ 657,794 $ 380,375 $ 164,448 $ 1,202,617 $ 2,500 $ 64,324 $ 2,029,594 $ 1,266,941 

Crossing Costs 

Oak Hills Drive Douglas County Triple 18' x 6' Box $ 354,369 $ 106,311 $ 88,592 $ 549,271 $ 549,271 $ 549,271 

Clydesdale Road Douglas County Double 14' x 8' Box $ 523,368 $ 157,010 $ 130,842 $ 811,220 $ 811,220 $ 811,220 

I-25 Bridge Improvements City of Lone Tree Concrete Slab Floor $ 200,250 $ 60,075 $ 50,063 $ 310,388 $ 310,388 $ 310,388 

West Parker Road City of Lone Tree 180' Span Bridge $ 631,906 $ 189,572 $ 157,977 $ 979,455 $ 979,455 $ 979,455 

Dogwood Avenue Douglas County Removal $ 37,458 $ 11,237 $ 9,364 $ 58,060 $ 58,060 $ 58,060 

E-470 Trail Town of Parker 10' x 3' Box $ 14,344 $ 4,303 $ 3,586 $ 22,234 $ 22,234 $ 22,234 

Happy Canyon Trail SEMSWA Ped/Light Truck Bridge $ 225,000 $ 67,500 $ 56,250 $ 348,750 $ 348,750 $ 348,750 

Detention Costs 

Charter Oaks Pond City of Castle Pines Alternative C $ 508,100 $ 152,430 $ 127,025 $ 787,555 $ 5,000 $ 128,649 $ 916,203 $ 916,203 

CPNMD Pond 11 City of Castle Pines Alternative C $ 57,476 $ 17,243 $ 14,369 $ 89,088 $ 5,000 $ 128,649 $ 217,736 $ 217,736 

CPNMD Pond 12 City of Castle Pines Alternative C $ 1,129,110 $ 338,733 $ 282,278 $ 1,750,121 $ 5,000 $ 128,649 $ 1,878,770 $ 1,878,770 




Beverly Hills Stock Pond Douglas County Alternative C $ 169,367 $ 50,810 $ 42,342 $ 262,518 $ 5,000 $ 128,649 $ 391,167 $ 391,167 

RidgeGate Ponds HC551, HC552, HC553, 

HC554, HC561 

City of Lone Tree Alternative C $ 3,048,598 $ 914,579 $ 762,150 $ 4,725,327 $ 5,000 $ 128,649 

Page 6-8 

$ 4,853,976 $ 4,853,976 

RidgeGate Pond HC519 City of Lone Tree Alternative C $ 2,822,776 $ 846,833 $ 705,694 $ 4,375,303 $ 5,000 $ 128,649 $ 4,503,951 $ 4,503,951 

RidgeGate Pond HC522 City of Lone Tree Alternative C $ 3,838,975 $ 1,151,693 $ 959,744 $ 5,950,412 $ 5,000 $ 128,649 $ 6,079,060 $ 6,079,060 

RidgeGate Ponds HC562, HC563, BG551, 

BG552, BG553 

Table 6-2 

Recommended Plan Cost Estimate Summary 

City of Lone Tree Alternative C $ 4,290,620 $ 1,287,186 $ 1,072,655 $ 6,650,460 $ 5,000 $ 128,649 

$ 6,779,109 $ 6,779,109 

RidgeGate Pond HC525 City of Lone Tree Alternative C $ 5,306,819 $ 1,592,046 $ 1,326,705 $ 8,225,569 $ 5,000 $ 128,649 $ 8,354,218 $ 8,354,218 

RidgeGate Pond BG511 City of Lone Tree Alternative C $ 3,838,975 $ 1,151,693 $ 959,744 $ 5,950,412 $ 5,000 $ 128,649 $ 6,079,060 $ 6,079,060 

Meridian Pond 4C Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Meridian Pond 4B Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Meridian Pond 4A Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Airport 320 Pond Douglas County Alternative C $ 1,580,755 $ 474,226 $ 395,189 $ 2,450,170 $ 5,000 $ 128,649 $ 2,578,818 $ 2,578,818 

Stepping Stone Pond D1 Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Stepping Stone Pond D3 Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Grandview Pond Douglas County Alternative C $ 3,669,609 $ 1,100,883 $ 917,402 $ 5,687,894 $ 5,000 $ 128,649 $ 5,816,542 $ 5,816,542 

Meridian Village Pond 1 Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Stonegate Pond Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

Chambers WQ Pond Douglas County Alternative C $ - $ - $ - $ - $ 5,000 $ 128,649 $ 128,649 $ 128,649 

E470 Pond Town of Parker Alternative C $ 790,377 $ 237,113 $ 197,594 $ 1,225,085 $ 5,000 $ 128,649 $ 1,353,733 $ 1,353,733 

Dove Valley Pond SEMSWA Alternative C $ 1,354,932 $ 406,480 $ 338,733 $ 2,100,145 $ 5,000 $ 128,649 $ 2,228,794 $ 2,228,794 

JWPP Pond SEMSWA Alternative C $ 17,738 $ 5,321 $ 4,435 $ 27,494 $ 5,000 $ 128,649 $ 156,142 $ 156,142 

Ladera Pond SEMSWA Alternative C $ 17,738 $ 5,321 $ 4,435 $ 27,494 $ 5,000 $ 128,649 $ 156,142 $ 156,142 

Totals $ 61,229,607 $ 18,368,882 $ 15,307,402 $ 94,905,891 $ 15,753,604 $ 8,018,998 $ 3,938,401 $ 27,711,004 $ 165,010 $ 4,245,658 $ 99,151,549 $ 85,431,061 

Total Cost - 

Implement 

Annual O&M 

Present Worth of 

50 Years of O&M 

Total Including 

O&M - Budget 

Total Including 

O&M - Implement



SECTION 8 – REFERENCES 

Carroll and Lange, Inc. Castle Pines North Preliminary Drainage Plan. 

Carroll and Lange, Inc. Compark Green Acres Tributary Drainage Improvements/Construction Plans. 

Prepared for the E-470 Business Metropolitan District. Record Copy for August 1999. 

Carroll and Lange, Inc. Compark Green Acres Tributary Drainage Improvements/Construction Plans 

Phase II. Prepared for the Compark Business Campus Metropolitan District. Record Copy for 

August 2003. 

Carroll and Lange, Inc. Compark Happy Canyon Creek: Drainage Improvement Plans for Chambers 

Road Bridge Construction. Prepared for the E-470 Business Metropolitan District. Record 

Copy for March 2000. 

Carroll and Lange, Inc. Compark Happy Canyon Creek North: Drainage Improvement Plans. Prepared 

for the E-470 Business Metropolitan District. Record Copy for March 2000 with re-approval 

through May 2002. 

Carroll and Lange, Inc. Construction Plans for Castle Pines North Filing No. 16. July 2000. 

Carroll and Lange, Inc. Flood Insurance Study for Compark Green Acres Tributary. Prepared for the 

Federal Emergency Management Agency. November 1999. 

Carroll and Lange-Manhard Consulting, Ltd. Compark Village Development Plan – Third Amendment. 

December 2011. 

Carroll and Lange-Manhard Consulting, Ltd. Conceptual Drainage Report: Compark South. Prepared 

for the Vickers Trust Office. October 2011 with revisions through December 2011. 

Carroll and Lange, Inc. Phase III Drainage Report for Castle Pines North Filing No. 16. Prepared for 

Village Homes of Colorado, Inc. March 1997 with revisions through April 1999. 

Carroll and Lange, Inc. Preliminary Drainage Study Castle Pines North Filings 1-15. Prepared for The 

Writer Corporation. July 1984. Revised October 1984. 

Civil Resources, LLC. Chambers Reservoir Project. Prepared for the United Water and Sanitation 

District. Record Copy for August 2010. 

Civil Resources, LLC. Phase III Drainage Report for Chambers Dam and Reservoir. Prepared for the 

United Water and Sanitation District. September 2010. 

CVL Consultants of Colorado, Inc. Sierra Ridge Filing 1. June 2008. 

CVL Consultants of Colorado, Inc. Sierra Ridge Filing 1: Phase III Drainage Report. Prepared for the 

Sierra Ridge Metropolitan District. June 2007 with revisions through June 2008. 

EDAW. Meridian International Business Center 13 th Amendment. July 2011. 

Felsburg, Holt, and Ullevig. Chambers Road/West Mainstreet Improvements Drainage Details. 

January 2006. 

Greenhorne and O’Mara, Inc. Happy Canyon Creek at Oak Hills Drive. December 1994. 

HDR Engineering, Inc. Construction Drawings for Dogwood Reach Bank Stabilization. Prepared for 

the Urban Drainage and Flood Control District and Douglas County. July 2011. 

HDR Engineering, Inc. Construction Drawings for Grandview Tributary Improvements. Prepared for 

the Urban Drainage and Flood Control District and Douglas County. September 2009. 

HDR Engineering, Inc. Phase One Construction Drawings for Happy Canyon Creek. Prepared for the 

Urban Drainage and Flood Control District and Douglas County. July 2002. 

HDR Engineering, Inc. Phase I Design Report: Happy Canyon Creek Channel Restoration. Prepared for 

the Urban Drainage and Flood Control District and Douglas County, 2001. 

J.F. Sato and Associates. Happy Canyon Creek at Surrey Ridge. Prepared for Douglas County and the 

Urban Drainage and Flood Control District. January 2011. 

Kiowa Engineering Corporation. Happy Canyon Creek Watershed Outfall Systems Planning Study. 

Prepared for the Urban Drainage and Flood Control District, Douglas County, and Arapahoe 

County. November 1991. 

Kirkham, Michael, and Associates. Lincoln Avenue Improvements. April 1994. 

Martin/Martin Consulting Engineers. Meridian Office park Filings 4 and 5 Master Plan Update. April 

2006. 

MB Consulting, Inc. C.P.N. Filing No. 27 Phase III Drainage Plan. Prepared for Lynx Land, LLC. 

August 1999. 

MB Consulting, Inc. Phase III Drainage Report for Castle Pines North Filing No. 27. Prepared for Lynx 

Land, LLC. January 2000. 




Meurer and Associates. Castle Pines North Metropolitan District Phase II Stormwater Permit. 

December 2002. 

Mulhern MRE, Inc. Design Report for Happy Canyon Creek Channel Improvements Upstream from 

Jordan Road. Prepared for the Cottonwood Water and Sanitation District, the Arapahoe 

County Water and Wastewater Authority, and Richard P. Arber Assoc., Inc. March 2007 

Muller Engineering Company, Inc. Happy Canyon Creek Channel Stabilization Construction Drawings. 

July 2006 

Muller Engineering Company, Inc. Oak Hills Tributary Improvements Construction Drawings. January 

2003. 

Peak Civil Consultants, Inc. 2 nd Amendment Study to Meridian Office Park Filings 4 and 5 Phase III 

Master Drainage Report. November 2010 with revisions through February 2012. 

Peak Civil Consultants, Inc. Phase III Drainage Report for Stepping Stone Filing No. 1 and Stepping 

Stone Circle. June 2012. 

Peak Civil Consultants, Inc. Stepping Stone Filing No. 1 Phase III Drainage Plan. May 2012. 

Peak Civil Consultants, Inc. Stepping Stone Street, Area Grading, and Storm Sewer Construction Plans. 

March 2013. 

Taranto, Stanton and Tagge Consulting Engineers. Castle Pines North Metropolitan District. July 

1984. 

Urban Drainage and Flood Control District. Urban Storm Drainage Criteria Manual, Volumes I & II. 

2001 Edition with revisions through April 2008. 


Muller Engineering Company, Inc. Happy Canyon Creek Major Drainageway Plan 

APPENDIX A 

PROJECT CORRESPONDENCE

MEETING 

MEMORANDUM 

Project 

Happy Canyon Creek MDP & FHAD 

Sponsors 

UDFCD / Douglas County / City of Lone Tree / 

Town of Parker / SEMSWA 

Meeting Location 

SEMSWA 

Attendees 

See attached list 

Purpose 

Happy Canyon Creek MDP & FHAD Kick-off Meeting 

MULLER ENGINEERING COMPANY, INC. 

CONSULTING ENGINEERS 

777 SOUTH WADSWORTH BLVD., SUITE 4-100 

LAKEWOOD, COLORADO 80226 

(303) 988-4939 

Meeting Date 

May 3, 2012 

Issue Date 

May 10, 2012 

Revised May 15, 2012 

MEC Project No. 

12-010.01 

Minutes Prepared By 

Andy Pultorak 

Routing 

ASP / MDC / JTW 

Action Items 

All action items are requested to be completed by May 24, 2012 unless otherwise noted. 

Muller Action Items: 

1. Melanie will send an email to the project stakeholders to inform them of the project and invite them to 

future progress meetings. 

2. Muller will check with Charlie Fagan with Castle Pines North Metro District to see if there are design 

plans available for Castle Pines Ponds 10 and 11. 

3. Muller will begin work on the project website and submit for review by all parties prior to publishing. 

4. Muller will work with the Douglas County GIS department to obtain 2030 future land use and impervious 

GIS files. Douglas County GIS will also provide 5-foot resolution topographic mapping for the project 

area south of the Parker 2008 DNC LiDAR boundary. 

5. Muller will work with the SEMSWA GIS department to obtain future land use and impervious GIS files, 

as well as additional LiDAR data files required for hydraulic modeling. 

Ridgegate/Rampart Range Metro District Action Items: 

1. Ridgegate & Rampart Range Metro District will look to see if they have better topographic mapping 

within their portion of the watershed and provide any such mapping to Muller. 

2. Bryan will provide Muller with an updated 4 th amendment to the Planned Development Application for 

the Ridgegate development east of I-25. Bryan will continue to provide updates to Muller as they occur. 

3. Bryan will look for proposed land use information on the Douglas County property south of Ridgegate, 

which is owned by the same group as Ridgegate. 

Douglas County Action Items: 

1. Brad will provide design plans for the UDFCD sponsored bank stabilization project which is nearing 

completion in Grandview Estates to Muller. 

2. Brad will provide record drawings of Happy Canyon channel improvements in the Compark development 

to Muller. 

Happy Canyon Creek MDP & FHAD – Kickoff Meeting – Meeting Minutes 

May 3, 2012 

3. Brad will provide design drawings currently in review for the Meridian Pond at Peoria on the Green Acres 

Tributary to Muller. 

4. Brad will check to see if the County has drawings for Castle Pines North Ponds 9, 10, and 11 and if so will 

provide them to Muller. 

5. Brad will check to see if the Sierra Ridge Metro District should be included in future meetings. 

Parker Action Items: 

1. Kamal will provide any applicable land use and future imperviousness information for Parker’s portion of 

the watershed. 

2. Kamal will provide draft information on the proposed Compark South development, including land use, 

proposed channel improvements, and information on a possible new bridge for E-470 over Happy Canyon 

Creek. 

Lone Tree Action Items: 

1. Ward will provide Muller with contacts from City of Castle Pines for invitation to all future meetings. 

UDFCD Action Items: 

1. Shea will discuss adding Badger Gulch Tributary to the floodplain study with Bill DeGroot. 

2. Shea will provide Muller with contact info for Landmark Mapping. 

3. Shea will provide Muller with the updated UDFCD DFHAD Guidelines, which are not yet published. 

SEMSWA Action Items: 

1. Monica will provide any applicable land use and future imperviousness information for SEMSWA’s 

portion of the watershed. 

2. Monica will revisit discussions with SEMSWA’s water quality group on “semi-regional” offline water 

quality BMPs and see if they are appropriate for mentioning in the MDP. The MDP could include a 

prototype BMP. (This item will not impact baseline hydrology, and can be completed at a later date if 

desired.) 

Discussion 

THE FOLLOWING IS OUR UNDERSTANDING OF THE SUBJECT MATTER COVERED IN THIS 

CONFERENCE. IF THIS DIFFERS WITH YOUR UNDERSTANDING, PLEASE NOTIFY US 

IMMEDIATELY. 

1. REVIEW OF PROJECT APPROACH AND SPONSOR ISSUES AND CONCERNS 

a. Melanie introduced the project and introductions were made. Melanie presented Muller’s approach to 

the project, which is to follow the UDFCD guidelines for a MDP and FHAD, with a special emphasis 

on preserving the character of the watershed and preventing steam degradation in the future. The key 

phrase was “an ounce of prevention is worth a pound of cure.” A key area of focus will be the 

movement of sediment in the creek, which will require maintaining equilibrium as illustrated with 

Lane’s balance. 

b. Project sponsor and stakeholder issues were discussed. The key issues discussed will be considered as 

the project develops: 

SEMSWA: Monica asked that no alternatives be eliminated without consideration by all the 

sponsors, including SEMSWA. Monica had concerns with the un-natural character of the 

channel through Southcreek. Monica also had concerns regarding the accuracy of the 

floodplain through Southcreek, and thought that the regulatory floodplain BFEs might be 3- 

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May 3, 2012 

 

 

 

 

 

feet higher than the actual floodplain model due to a possible error in datum conversion. 

Monica though this error might extend to the floodplain on Badger Gulch and expressed 

interest in modeling Badger Gulch as part of this study. Monica also requested that the plan 

consider semi-regional water quality BMPs which could be installed in cooperation with 

developers as a more effective alternative to onsite treatment. Shea recommended that the 

MDP not reflect actual planned locations of these BMPs, but that the report could include 

discussion of this approach as well as a prototype BMP. 

Town of Parker: Kamal discussed the pending annexation of the Compark South development 

by the Town. Parker desires to maintain a good relationship with Grandview Estates as the 

southern neighbor to this expansion – there are some concerns about the proposed noise/visual 

barrier from a channel and floodplain perspective. Kamal also mentioned the steep channel 

banks in the existing Parker reach through Compark. 

Douglas County: Brad expressed concern with the accuracy of the regulatory floodplain 

through Grandview Estates. There are also a couple of severely degraded channel reaches 

within Douglas County’s jurisdiction. 

City of Lone Tree: With the entire Happy Canyon watershed within Lone Tree’s boundaries 

as a part of the planned Ridgegate development, Greg stated a desire to involve Ridgegate in 

the entire process to ensure their buy-in to the final plan. The plan should also allow flexibility 

for Ridgegate to alter the character of the creek to match their vision for the development. 

Ridgegate: Bryan stated that the development is very interested in being allowed to discharge 

stormwater into Happy Canyon at historic rates (vs. overdetention). The current development 

plans show a linear open space/regional park planned around Happy Canyon Creek. 

Ridgegate is currently planning on online regional detention. However, plans for this portion 

of Ridgegate are still very conceptual, so the project is well-timed. 

UDFCD: Shea would like to balance the needs of the upstream communities with the 

concerns of the communities downstream. She expressed an interest in keeping the project 

moving and working to find common ground between the various sponsors and stakeholders. 

Shea stated that Bill DeGroot will meet with the project team once the hydraulics phase 

commences to give some pointers and to discuss the updated FHAD guidelines. Shea also 

suggested using a single interactive PDF as an alternative to the many different maps required 

in Appendix B of the MDP submittal. 

c. In the project interview, Muller proposed the idea of performing some soil analysis to expand on a 

recent Douglas County infiltration study. Jim provided more background on this study, which 

demonstrated an infiltration response similar to a soil of Hydrologic Group A in an area classified by 

the NRCS as Hydrologic Group C/D. Jim suggested that research could be done in conjunction with 

the Happy Canyon MDP to reclassify portions of the basin and potentially reduce the peak flood flows 

for the watershed. There was general agreement that more research would need to be done on this 

topic before use of soil classifications other than those developed by NRCS could be defended. 

Therefore, it was decided that this MDP would use the NRCS soil classifications. However, it was 

also decided that the report could make mention of the Douglas County soil analysis, and in particular 

note that the peak runoff rates developed for this MDP could be conservative as a result. 

d. New DFHAD guidelines will soon be released by UDFCD (see Action Items). Muller will check 

FEMA’s 30% rule, which prohibits the use of future land use assumptions for a regulatory floodplain 

if the future peak flow rates exceed the existing peak flows by more than 30% and result in a 

difference of more than 0.5’ in the BFE. If this is the case, Muller may need to develop hydraulic 

models for the existing flows, which will become the regulatory model, and for the future conditions 

flows to be used for planning. Jim suggested that, while the FHAD model will reflect current channel 

conditions related to infrastructure, the hydraulic model could use a non-degraded channel section to 

model BFEs in areas where the channel has recently degraded. Jim also mentioned that the hydraulic 

model could use future roughness values to account for a more developed condition where frequent 

runoff produces more vegetation, and therefore, more roughness. Shea has discussed these items with 

Bill DeGroot and provided Muller input via email; Muller will review this correspondence prior to 

floodplain modeling. 

 

As a follow-up to this item, the direction from Bill was that accounting for degradation by 

modifying/raising the channel invert in the model cannot be included, as FEMA closely 

checks the model invert compared to existing grade topography. The n value issue may be 

easier to accommodate, so we can work with the sponsors to use future assumed n values for 

the FHAD. In areas where the stream invert is badly degraded, the master plan can look at a 

‘floodplain preservation for restored stream’ option. 

e. Muller will evaluate the shear stresses produced by flood events to help determine potential erosion 

problems and recommend soft channel improvements. 

f. Muller will look into the impacts of cattle grazing on the Ridgegate property. Some negative impacts 

to the stream have already been identified, and the project team will consider fence as a temporary 

measure to keep cattle from damaging the creek and to improve water quality. Bryan thought 

Ridgegate would be open to discussing cattle management, as it could reduce the cost of stream 

stabilization in the future. 

g. The study will analyze and recommend runoff reduction methods such as infiltration techniques and 

minimizing directly connected impervious area for future developments, including Ridgegate and 

Compark South. Bryan thought Ridgegate would be open to this approach. 

2. IDENTIFY STAKEHOLDERS 

a. Arapahoe County: SEMSWA’s portion of the watershed is in unincorporated Arapahoe County; 

Stacey Thompson should be included in all meetings that include SEMSWA. 

b. Ridgegate / Rampart Range Metro District (RRMD): Bryan Ruth and Ken Linhardt of Merrick & 

Company will represent Ridgegate, along with Denise Denslow, the RRMD Manager. Ridgegate 

should be included in all progress meetings. Any additional coordination regarding cattle management 

would be handled through Merrick. 

c. City of Castle Pines: Ward asked that Brad Meyering with Castle Pines be invited to all future 

meetings (see Action Items). Ward stated that Castle Pines has removed “North” from its name. 

d. Castle Pines North Metro District (CPNMD): Muller has been in contact with Charlie Fagan at 

CPNMD and will invite him to future meetings. Several existing ponds are maintained by CPNMD 

and may be considered for retrofitting as a part of the plan. 

e. Cherry Creek Basin Water Quality Authority (CCBWQA): Bill Ruzzo should be invited once the 

baseline hydrology is complete. 

f. CDOT: A portion of the channel is in CDOT ROW; a separate meeting will be held with CDOT 

following completion of the baseline hydrology. 

g. Sierra Ridge Metro District: Brad will check to determine if they should be included as a stakeholder. 

(see Action Items). 

3. PROJECT SCHEDULE 

a. Melanie distributed copies of a project schedule, showing milestones and progress meetings. 

b. Shea requested that Muller keep the schedule updated throughout the course of the project and that 

updates be reflected on the project website. 

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May 3, 2012 

4. PROJECT WEBSITE 

a. Shea said that the project website could be similar in design and content to the Cottonwood Creek 

OSP website which Muller created. 

b. Muller will prepare the website and send it to the project team for review prior to publishing. 

c. The website should include the sponsor agency names and logos (not individual contact 

information). Stakeholders will be mentioned in the project description. There will be a comment 

page on the website which will be directed to Melanie. Melanie will forward comments and 

concerns received though the comment page to Shea, who will distribute to the sponsors as 

appropriate. 

5. MAPPING 

study, Shea approved the inclusion of the proposed modifications in the baseline hydrology. Brad will 

provide additional design information on this pond. 

d. Melanie identified information needed to appropriately model the existing publically maintained 

detention ponds listed above. See Action Items for additional information. If design or as-built 

information for CPN Ponds 9, 10, and 11 is not available, additional survey will be needed. 

7. NEXT MEETING 

Melanie concluded the meeting asking for additional comments and questions. As there were none, the next 

progress meeting was scheduled for Thursday, June 7 th at 9:30 at the SEMSWA offices. 

END OF MINUTES 

a. The following mapping has been received by Muller: 

1. LiDAR: 2’ contours north of Lincoln Ave. 

2. Landmark survey: 2’ contours along the mainstem corridor south of LiDAR 

coverage. 

3. Detailed ground survey of all mainstem crossings. 

b. Muller will obtain the 5-foot contour mapping from Douglas County GIS (see Action 

Items). 

c. Bryan will check to see if there is more detailed mapping available for the Ridgegate 

development (see Action Items). 

d. Adding Badger Gulch to the FHAD study was discussed. It was generally agreed that it 

would be beneficial for the project to study this tributary. It will be necessary to obtain 2’ 

aerial mapping and a crossing survey of Badger Gulch if the floodplain is to be studied. 

e. Additional mapping may be necessary to incorporate existing detention ponds into the 

baseline hydrology. See further discussion below. 

6. HYDROLOGY UPDATE 

a. Melanie reviewed the steps necessary to update the existing hydrology for the basin: 1) Convert 

CUHP/SWMM files from 1993 OSP, 2)Update subwatershed boundaries and characteristics 

(excluding % imp.), 3) Calibrate to 1993 OSP, 4) Update impervious values for existing and future 

land use, and 5) Add eligible publically maintained detention ponds. Shea agreed that these were the 

appropriate steps to follow. 

b. Melanie noted the Ridgegate development and Compark South as two currently undeveloped portions 

of the watershed where development is planned. Muller will need Planned Development Application 

documents and other resources showing the planned development to accurately reflect the future 

runoff potential of these developments in this study (see Action Items). 

c. Melanie presented a summary table prepared by Muller of the publically maintained detention ponds 

identified within the watershed (see attached). It was generally agreed that the following existing 

ponds shown on the table would be included in the baseline hydrologic analysis: 

E-470 Pond 

Chambers Reservoir Detention Pond 

Stonegate Pond (@ Lincoln Ave.) 

CPN Ponds 9, 10, 11, 12, and 20. 

Melanie noted that the Meridian Pond at Peoria is currently planned for expansion and will incorporate 

full-spectrum detention. Since the pond improvements will likely be complete before the end of this 

5 

6 

Page A-3

HAPPY CANYON CREEK MDP & FHAD 

KICKOFF MEETING 

Date: May 3, 2012 

Location: SEMSWA 

ATTENDEES 

NAME AGENCY PHONE EMAIL 

Ward Mahanke City of Lone Tree 303-792-0557 ward.mahanke@cityoflonetree.com 

Brad Robenstein Douglas County 303-660-7490 brobenst@douglas.co.us 

Kamal Ouda Town of Parker 303-840-9546 kouda@parkeronline.org 

Monica Bortolini SEMSWA 303-858-8844 mbortolini@semswa.org 

Shea Thomas UDFCD 303-455-6277 sthomas@udfcd.org 

Bryan Ruth 

Rampart Range Metro. 

District 303-353-3621 bryan.ruth@merrick.com 

Greg Weeks City of Lone Tree 303-662-8112 greg.weeks@cityoflonetree.com 

Melanie Chenard Muller Engineering 303-988-4939 mchenard@mullereng.com 

Jim Wulliman Muller Engineering 303-988-4939 jwulliman@mullereng.com 


DETENTION POND SUMMARY 

updated 5/10/12 

Information Availability/Needs 

Pond Description Stream Jurisdiction Maintained By Outlet Type Volume Outlet Spillway Notes 

E470 Pond 

Green Acres Douglas County (Parker 

inverts/slope from 

Parker (in future) 100-Yr LIDAR topo 

Tributary Annexation) 

d/s design plans 

LIDAR Included in 1993 OSP 

NEEDED 

NEEDED 

NEEDED 

Meridian Pond @ Green Acres 

WQCV/10- 

To be expanded / 

Douglas County Meridian 

(Expansion Design (Expansion Design (Expansion Design 

Peoria 

Tributary 

Yr/100-Yr (?) 

retrofitted 

Plans) 

Plans) 

Plans) 

Chambers Reservoir Stonegate 

Detention Pond Tributary 

Douglas County ? EURV/100-Yr Design Plans Design Plans Design Plans 

Stonegate Pond (@ 

Lincoln Ave.) 

Stonegate 

Tributary 


CPN Pond 9 Oak Hill Tributary Castle Pines North 

CPN Pond 10 Oak Hill Tributary Castle Pines North 

CPN Pond 11 

CPN Pond 12 

CPN Pond 20 

Happy Canyon 

Creek 

Happy Canyon 

Creek 

Castle Pines North 

Castle Pines North 

Monarch Tributary Castle Pines North 

Sierra Ridge 

Metro District 

CPN Metro 

District 

CPN Metro 


CPN Metro 


CPN Metro 


CPN Metro 


WQCV/10- 

Yr/100-Yr 

LIDAR / Design 

Plans 

Design Plans 

10-Yr/100-Yr (?) NEEDED NEEDED 

10-Yr/100-Yr (?) 

10-Yr/100-Yr 

Erosion Control 

Plan 

NEEDED - extend 

LM survey 

NEEDED 

Design Plans 

Erosion Control 

Plan 

NEEDED 

Crossing Survey Landmark Survey Included in 1993 OSP 

100-Yr Landmark survey Crossing Survey Landmark Survey 

WQCV/10- 

Yr/100-Yr 

Record Dwgs Record Dwgs Record Dwgs 

UDFCD Maintenance 

Eligible 

Andy Pultorak Muller Engineering 303-988-4939 apultorak@mullereng.com 

Page A-4

MEETING 

MEMORANDUM 

Project 


Sponsors 




SEMSWA 

Attendees 






(303) 988-4939 

Meeting Date 

June 12, 2012 

Issue Date 

June 25, 2012 

Revised June 28, 2012 


12-010.01 


Andy Pultorak 

Routing 


Purpose 

Happy Canyon Creek MDP & FHAD Progress Meeting #2 

Action Items 

All action items are requested to be completed by July 2, 2012 unless otherwise noted. 


1. Muller will continue work on the Draft Baseline Hydrology submittal. The anticipated submittal date for 

the baseline hydrology is July 10, 2012. 

2. Melanie will send a meeting invite for Progress Meeting #3 to all sponsors and stakeholders. 

3. Melanie will send an email to Shea requesting a copy of the LOMR submittal for the Ridgegate Parkway 

crossing. Shea will forward this email to David Mallory (UDFCD). 

4. Melanie will send a copy of the project powerpoint presentation (shown at the meeting) to Brad Meyering. 

5. Melanie will verify the rainfall amounts used in the 1993 OSP. 

6. Muller will post the subwatershed boundaries for review and comment by all parties. 

7. Muller will review SEMSWA GIS data for % impervious values in Arapahoe County, and will follow up 

with Monica and Stacey on the assumptions in this area. 

8. Muller will continue work on the project website and submit for review by all parties prior to publishing. 

It is anticipated that the project website will be up and running in the next few weeks. 

RidgeGate/Rampart Range Metro District Action Items: 

1. Bryan will provide anticipated average impervious values for the mixed residential areas shown in the 

Planned Development Application (PDA) for the RidgeGate property. 

2. Bryan will continue to provide Muller with any updates to the PDA for RidgeGate. 


1. Brad R. will provide anticipated land use and future impervious information for various parcels and 

developments within the watershed, including Airport 320, Vista Pointe Technicenter, and Highfield 

Business Park. 


1. Shea will continue to discuss adding Badger Gulch Tributary to the floodplain study with Bill DeGroot. 

Happy Canyon Creek MDP & FHAD – Progress Meeting #2 – Meeting Minutes 

June 12, 2012 

2. Shea will provide Muller with the updated UDFCD DFHAD Guidelines, which are not yet published. 

3. Shea will provide Muller with the technical appendix checklist. 

4. Shea will provide Muller with draft guidelines for interactive PDFs. 

Arapahoe County Action Items: 

1. Stacey will provide Muller with planned land use information for the future business park near Jordan Rd. 

Discussion 


CONFERENCE. IF THIS DIFFERS WITH YOUR UNDERSTANDING, PLEASE NOTIFY US 

IMMEDIATELY. 

1. INTRODUCE STAKEHOLDERS; PROJECT OVERVIEW 

a. Melanie introduced the project and introductions were made. Melanie presented Muller’s approach to 

the project, which is to follow the UDFCD guidelines for a MDP and FHAD, with a special emphasis 

on preserving the character of the watershed and preventing steam degradation in the future. The key 

phrase was “an ounce of prevention is worth a pound of cure.” A key area of focus will be the 

movement of sediment in the creek, which will require maintaining equilibrium as illustrated with 

Lane’s balance. 

b. A number of stakeholders were present who were not present at the kickoff meeting: Denise Denslow 

(representing Rampart Range Metro District); Stacey Thompson (Arapahoe County); Brad Meyering 

(City of Castle Pines); and Ken Linhardt (representing RidgeGate). Shea explained that specific 

stakeholder issues had been discussed at the kickoff meeting. She asked that the stakeholders who 

were not present at the kickoff please voice any areas of concern or issues in the watershed to UDFCD 

or Muller as soon as possible. These issues will be considered as the project develops. 

2. HYDROLOGY STATUS UPDATE 

a. Melanie explained that the starting point for the baseline hydrology update is the 1993 OSP. The only 

basin map available from the 1993 study is an 11x17 drawing of showing the entire watershed; no 

CAD files are available. Though the 1993 map was used as a guide, Muller generally re-delineated the 

entire watershed using the project mapping and numerous drainage plans/reports for developed or 

soon-to-develop areas to more accurately reflect developed drainage patterns. This effort also brought 

the subwatershed sizes into line with UDFCD recommendations (max. 130 acres, average 90-100 

acres); previous subwatersheds ranged from 7-270 acres, while the current delineation ranges from 24- 

133 acres. Melanie asked for comments on the delineation prior to completing the baseline hydrology; 

Greg requested that the map be provided in PDF format following the meeting to facilitate 

sponsor/stakeholder review (see Action Items). 

b. Melanie explained that the CUHP model has been updated based on the new delineation, with the 

1993 OSP existing % impervious values. 

a. Muller will use this CUHP model with a calibration SWMM model to match the peak 

runoff generated with that of the 1993 OSP. Once the CUHP/SWMM model is adjusted 

to match the 1993 OSP output, impervious values for both the existing and future 

conditions will be updated (see Item 3) to generate the baseline SWMM models. 

b. Melanie presented a summary table of the initial CUHP output. She noted that excess 

precipitation averaged across the watershed in her model (1.25 in) matched the 1993 OSP 

(1.22 in) closely. Melanie noted that the table was based on a three hour storm; the 

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June 12, 2012 


June 12, 2012 

SWMM model will incorporate both 2-hour and 3-hour storms due to the size of the 

watershed. 

c. Currently, rainfall depths from the 1993 OSP are being used; Muller will verify that these 

are appropriate (see Muller Action Items). 

c. Muller is in the process of completing a revised SWMM model based on the updated sub-watershed 

boundaries. The model has been updated to the current software (EPA SWMM 5.0), and is being 

cleaned up to make it more user friendly. 

3. FUTURE DEVELOPMENT / IMPERVIOUSNESS 

a. Melanie had reviewed existing development within the watershed, and had identified parcels and lots 

which remain undeveloped. She had prepared a CAD presentation which took the project team 

through each undeveloped area from south to north. The applicable stakeholders were then able to 

discuss the anticipated development at each parcel or lot. The results of these discussions will be used 

to establish peak flowrates for the future land use baseline hydrology. The results of the discussions 

are summarized below: 

a. Castle Pines 

i. Scattered vacant lots would generally be built similar to the surrounding houses. 

ii. Brad M. said that the City had plans for a park area north of Castle Pines Parkway and 

east of Yorkshire Drive. Shea asked Melanie to use the UDFCD impervious value for 

parks. 

iii. Brad M. said that there is planned commercial development in the empty lots to the south 

of the planned park. 

b. Douglas County South 

i. Scattered vacant lots would generally be built similar to the surrounding houses. 

ii. There is an area zoned A1 (agricultural) and a single parcel >100 acres that could 

potentially be subdivided; Muller will assume large lot similar to the surrounding areas; 

Brad R. will confirm (see Douglas County Action Items). 

iii. 

The Freshfields area, located between I-25 and Lone Tree, is currently zoned A1 

(agricultural). Planning for this area of development has not yet begun; the property 

owner is the same as RidgeGate, and will likely wait until RidgeGate is built out to begin 

developing Freshfields (probably at least a 20-30 year timeframe). Shea recommended 

that this study maintain A1 land use for the future condition; if this study is still in effect 

when development occurs, the developers will match peak flow rates from this study. 

c. Lone Tree 

i. Bryan had provided Muller with the 4 th Amendment to the PDA for RidgeGate. Melanie 

reviewed the % impervious assumptions for each land use: 

1. City Center – 95%: The project team thought this value was reasonable. 

2. Commercial Mixed Use – 85%: No comments. 

3. Residential Mixed Use – 75%: Denise thought that this value could vary 

significantly because the zoning allowed flexibility in the type of development. 

Ken and Bryan thought that it would be possible to come up with a good average 

value based on development that has occurred in RidgeGate west of I-25 (see 

RidgeGate Action Items). 

4. Institutional – 50%: Planned high school / middle school. The project team 

thought this value was reasonable. 

5. Open Space – 2%: OK for most locations, but should be increased to 10% in the 

center park. 

ii. 

Muller will account for the impervious area of the planned roadways in the future land 

use hydrology (in RidgeGate and elsewhere in the watershed, as applicable). 

d. Douglas County North 

i. Proposed Meridian development – individual parcels generally have a maximum of 75% 

in Douglas County, 70% in Parker based on drainage plans/reports for those areas. Muller 

will continue to refer to the drainage plans to account for lower % impervious areas. 

ii. Sierra Ridge – 50% based on the drainage report for that development. 

iii. Business Parks: Airport 320, Vista Pointe Technicenter, Highfield Business Park: Brad R. 

will review and provide additional guidance (see Douglas County Action Items). 

e. Compark 

i. Parker Annexation – 60% west of HCC and 20% to east per drainage plans. 

ii. Parker – zoned Business Commercial – Muller will choose appropriate values based on 

UDFCD guidelines and current development 

iii. Douglas County – Muller will assume similar to existing development 

f. Arapahoe County 

i. Business Park: Muller will review GIS data to see if it includes future % impervious 

values; Stacey will look for additional information (see Muller and Arapahoe County 

Action Items). 

4. RIDGEGATE DEVELOPMENT DISCUSSION 

a. Ken expressed an interest in Muller’s investigation into online vs. offline detention, as both options 

were being considered. Shea clarified that the Clean Water Act requires treatment before 

stormwater reaches the channel, which generally prohibits online water quality facilities. 

SEMSWA/Arapahoe County gets around this by requiring onsite treatment of some sort in addition 

to regional water quality. Online flood control facilities are not a problem in this regard. 

b. Ken stated that RidgeGate is currently planning 2 regional facilities; one in the central park, and one 

at the downstream end of the site (near the confluence with Badger Gulch). They are currently 

generally leaning toward offline detention, though these two facilities could be online. The general 

plan called for grading over the tributaries but leaving the Happy Canyon floodplain intact, with the 

exception of the road crossings. Drainage from the development will likely be conveyed to the 

ponds by means of a storm sewer network. 

c. Ken stated that it would be 8 or 9 months until RidgeGate begins a Master Drainage Report for the 

area in the Happy Canyon watershed. Since this study will progress faster than that, assumptions for 

this study will be made based on the PDA and input from Ken/Bryan. During the alternatives 

analysis, Muller will look at online vs. offline detention; the results can help guide RidgeGate in the 

development of their master drainage plan. If RidgeGate begins planning sooner, Ken and Bryan 

will keep Muller updated. The first area likely to develop will be the area immediately south of the 

Meridian residential development. 

d. Greg mentioned that Lone Tree is currently reviewing their ordinances, and are looking at O&M 

requirements that will allow the City to maintain private facilities if the HOAs don’t keep up on 

maintenance. This may allow future private facilities to be counted toward master-planned 

detention. All future detention facilities within RidgeGate will be owned and controlled by the 

Metropolitan Districts, and will therefore also be counted toward master-planned detention. 

e. Shea stated that it was not within Muller’s scope-of-work to consider offline water quality pond 

locations. She asked Muller to generally consider offline water quality detention in the master plan 

but look for areas suitable for online 100-YR detention. 

f. A 10 MGD wastewater treatment plant is planned in the northeast corner of the development. The 

site will occupy approximately 10 acres. 

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June 12, 2012 

5. PROJECT SCHEDULE 

a. Melanie stated that she planned to submit the draft baseline hydrology to the project team in 

approximately 4 weeks (around July 10, 2012). The schedule provides three weeks for sponsors and 

stakeholders to review. The group will not plan to meet again until after the review period. 

b. Shea mentioned that adjustments to the mapping had resulted in some delays to the schedule. 

c. Shea asked Muller to proceed with the best available information for future imperviousness without 

excessive delay waiting for stakeholder input. 

6. PROJECT WEBSITE 

Melanie said that the project website is in progress and will be completed for sponsor and stakeholder review 

in the next few weeks (see Muller Action Items). 

7. OTHER ITEMS 

a. Ken noted a LOMR was completed 2-3 years ago by FHU for the Ridgegate Parkway bridge over 

Happy Canyon (see Muller Action Items). 

b. The team also noted that a LOMR had been completed for the Richmond Merdian development – this 

was 8 or more years ago, and should be incorporated into the Douglas County DFIRM, which dates 

from 2005. 

c. Muller should show the conceptual street layouts and crossing locations for RidgeGate as dashed to 

denote that this information is subject to change. 


The next progress meeting was scheduled for Monday, August 20, 2012 at 2:00pm at the SEMSWA offices. 


5 

Page A-7

MEETING 

MEMORANDUM 

Project 


Sponsors 




SEMSWA 

Attendees 






(303) 988-4939 

Meeting Date 

September 10, 2012 

Issue Date 

October 3, 2012 


12-010.01 


Andy Pultorak, Melanie Chenard 

Routing 


Purpose 


Action Items 


1. Muller will address sponsor comments on the Baseline Hydrology and post the updated report to Dropbox 

for sponsor review. 

2. Melanie will send a meeting invite for Progress Meeting #4 to all sponsors and stakeholders. 

3. Andy will provide Stacey Thompson with a figure showing the draft floodplain delineation near the water 

treatment facility south of Jordan Rd. on the Happy Canyon mainstem. 

4. Melanie will review the draft Rock Creek MDP for guidance on interactive hydrologic maps. 

5. Muller will contact additional stakeholders identified by the project sponsors. 

6. Muller will coordinate with Brad Robenstein (Douglas County) to obtain grading plan / LOMR 

information at the north end of Chambers Reservoir and to determine the construction time frame of 

Meridian Ponds 4A-4C. 


1. Shea will provide Muller with the updated UDFCD DFHAD Guidelines and checklist. 

2. Shea will review the new UDFCD rainfall data (as posted on the UDFCD website) and determine if there 

is any impact to the Happy Canyon hydrology. 

3. Shea will discuss the following items with Bill DeGroot and instruct Muller accordingly: 

a. What starting WSEL should be used at Cherry Creek for 10, 50, and 500-year Happy Canyon 

Creek FP? 

b. What flowrate/WSEL should be assumed in Green Acres Trib. if the mainstem spills into it in a 

100- or 500-year? 

c. What steps should be taken (if any) at locations where the meander of the low-flow channel does 

not match the floodplain centerline? 

d. Where flow spills from the main channel into a side channel, should the spill flow be subtracted 

from the main channel if the spill is significant? 

e. Should Muller model the proposed channel improvements at I-25 for the Douglas County East- 

West trail if construction is not expected until late in 2013? 



4. UDFCD will review the draft mainstem cross-section locations workmaps provided by Muller and provide 

any comments. 

5. UDFCD will provide LiDAR mapping for Badger Gulch to Muller once data processing is finished. 

Discussion 


CONFERENCE. IF THIS DIFFERS WITH YOUR UNDERSTANDING, PLEASE NOTIFY US. 

1. INTRODUCTIONS 

2. DRAFT BASELINE HYDROLOGY COMMENTS 

The group discussed the overall results of the baseline hydrology and the calibration effort. The initial 

results indicated significantly higher peak flows than the 1993 OSP though the 1993 % impervious was 

matched and the subwatershed and conveyance element parameters were very similar to the 1993 model. 

Because the Happy Canyon Creek watershed is adjacent to the Cottonwood Creek watershed and should 

exhibit similar flow characteristics, the results were compared with the 2010 Cottonwood Creek OSP 

hydrology based on pre-development conditions on both watersheds. Ultimately, the Happy Canyon Creek 

model was calibrated to match Cottonwood Creek peak flows by adjusting Cp values (see the report for 

additional discussion). The resultant peak flows, prior to updates for existing and revised future conditions, 

still exceed the 1993 OSP but compare favorably with the 1977 FHAD, which are the regulatory flow 

rates. Muller will add the FHAD peak flow rates to Figure B-10 in the report and will provide some 

additional discussion of the differences in hydrology between this master plan and the 1977 FHAD. 

Bill Ruzzo inquired if the hydrology would be revisited if the increased peak flow rates have detrimental 

floodplain impacts. Shea indicated that this is a possibility. 

Additional discussion of specific comments is summarized below. 

a. SEMSWA has new aerial photography dated Spring 2012. Because the coverage is limited to 

Arapahoe County and changes in this portion of the watershed are limited, the 2010 aerial 

photography provided by UDFCD will continue to be used for the project. 

b. Greg Weeks provided Muller with a conceptual alignment for the future Belford Ave. bridge crossing 

over Happy Canyon Creek south of E-470. The area to the east of Happy Canyon, north of Grandview 

Estates, is another Town of Parker annexation area (Chambers High Point) – information is available 

on the Town’s website. 

c. In response to some SEMSWA comments, Muller clarified the peak flow rates at the confluence with 

Cherry Creek: 

• Arapahoe County FIS published 100-year peak = 3690 cfs for Happy Canyon Creek. The source 

of this flow rate is unknown; it does not match any known studies. 

• Mapped floodplain appears to be based on the 1993 OSP 100-year future conditions peak of 7303 

cfs rather than the FIS published value. 

• 1977 FHAD (future conditions) = 6744 cfs 

• Current study (future conditions) = 9238 cfs 

The discrepancies seem to be limited to the Arapahoe County portion of the channel; the remainder of 

the floodplain appears to be based on the 1977 FHAD hydrology. 

d. Lone Tree had commented on modeling of piped reaches in SWMM model. The report stated that the 

pipe sizes had been artificially enlarged in the SWMM model to convey the entire peak flow, since 

overtopping a piped reach could cause instabilities in the model. Actual capacities will be evaluated 

for any insufficiencies during the alternatives evaluation. 

1 

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Page A-8





e. In response to Town of Parker comments, Muller clarified the E-470 Pond configuration. The pond is 

controlled by a 12’ x 10’ CBC with no outlet structure and provides little attenuation. However, 

because it was included in the 1993 OSP as a pond, it has been left in the baseline hydrology model in 

its current configuration. Modifications will be considered for the alternatives analysis. 

f. Chambers Reservoir is currently modeled as 100% impervious with no freeboard (provides no 

storage/attenuation). Douglas County commented that the design report describes a 38-39 acre basin 

self-contained in the reservoir. Because there is no known operating agreement guaranteeing that the 

design freeboard be available for flow attenuation, Shea directed Muller to maintain this condition for 

the baseline hydrology. The alternatives analysis can consider formalizing any available reservoir 

storage. The same situation applies to the Meridian golf course pond located just north of Lincoln 

Avenue along the western watershed boundary. 

g. Meridian Ponds 4A and 4B are currently included in the baseline hydrology based on future 

configuration (construction was expected to occur prior to completion of the MDP). Douglas County 

has reported that final approval has been delayed; Brad will follow up and determine an estimated 

construction time frame. Construction needs to begin prior to finalization of the MDP to include the 

ponds in the baseline hydrology. A third pond, 4C, was not initially included in the baseline hydrology 

because a previous report indicated a design volume of only 2 acre-feet. The correct design volume is 

4.5 acre-feet and the pond is online; subwatershed boundaries will be adjusted to reflect the correct 

contributing area and the pond will be added to the model (subject to construction time frame). 

h. CPNMD Pond #20 is missing the water quality orifice and has been modeled as such. Shea confirmed 

that this is appropriate as the orifice plate has likely been discarded and likely will not be reinstalled. 

i. Lone Tree encountered burrowing owls and nesting eagles during construction of the Ridgegate 

Parkway bridge; Muller will expand on the discussion of wildlife within the report. 

j. Lone Tree had questioned the slight drop in 100-year existing condition peak flow rates at Badger 

Gulch. Upon further review of the models, Muller discovered an error in the Existing, 100-Year, 3- 

Hour storm CUHP run. As a result, existing condition peak flow rates downstream of Badger Gulch 

will be revised (will increase) in the final baseline hydrology. Lone Tree had also questioned the jump 

in peak flow rates at the confluence of Badger Gulch in regards to the requirement to provide 

EURV/100-year facilities in RidgeGate. UDFCD policy does not allow consideration of future 

detention for establishment of baseline hydrology, so the future development hydrology assumes full 

development with no additional detention facilities beyond those currently in place. Shea explained 

that this policy is due to the fact that UDFCD has no control over development criteria for local 

jurisdictions, and cannot guarantee that current requirements will be upheld. However, UDFCD has 

worked with local governments to prepare IGAs (inter-governmental agreements) that guarantee the 

construction of detention facilities concurrently with development, and then reflected those detention 

facilities in the future development hydrology. For this project, the value of an IGA to reflect future 

detention will be determined as the impact of the increased flow rates on the floodplain delineation is 

known. 

k. Urban Drainage is reconsidering the value of public meetings in the master planning process and may 

eliminate public meetings from the scope of this project. 

3. OTHER BASELINE HYDROLOGY ITEMS 

a. Melanie noted that a new rainfall spreadsheet has been posted to the UDFCD website. The revisions 

seem to indicate use of a 6-hour storm for a watershed of this size. Muller will continue to use the 3- 

hour storm according to the USDCM unless otherwise instructed; Shea will review the updates with 

Ken MacKenzie but does not expect to make any changes to the rainfall for this project. 

b. Arapahoe County has provided some additional information in the Dove Valley / Southcreek areas; 

additional revisions to the baseline hydrology will be made as needed. 

c. Melanie asked if there were any comments on the Interactive PDF. Shea said that for future projects 

the PDF should be on one sheet and could be made larger than 11x17 in order to fit the entire 

watershed on one panel. Muller does not need to change the panel layout for this project. Greg Weeks 

(Lone Tree) asked if there would be a way to print a portion of the panel and still see the legend; Shea 

is not currently requiring this capability for the hydrology maps. 

d. Monica indicated a desire to have a single paper copy of the final MDP report at the completion of the 

project as the electronic format is not suitable in all situations. Some of the other project sponsors 

agreed; Shea will consider adding this to future MDP contracts. 

4. FHAD 

a. Andy introduced the FHAD portion of the project. Since the completion of the draft Baseline 

Hydrology submittal, Muller had begun preliminary work on the FHAD for the mainstem of Happy 

Canyon. 

The original FHAD scope encompasses the Happy Canyon mainstem from Castle Pines Pond 

12 to Cherry Creek (11.3 miles). 

Draft hydraulic cross-section layouts had been completed. The draft layout included 330 crosssections 

at an average spacing of 180-ft. Andy noted that this was very detailed, especially 

when compared to the DFHAD guidelines recommended maximum spacing of 500-feet. The 

spacing between the draft hydraulic cross-sections never exceeds 300-feet. Andy noted that the 

recent Cottonwood Creek FHAD cross-sections were spaced at an average of 120-ft, but he 

attributed the tighter spacing to a more urbanized watershed with more hydraulic structures. 

The mainstem includes modeling of 14 crossings. Shea reminded Muller to include the 

recommended four cross-sections at each structure to appropriately model the expansion and 

contraction losses in and out of the structures. Jim said that the draft section locations showed 

more than the four sections at some crossings due to unusual grading or hydraulic structures 

near the crossings. He said that in these cases ineffective flow areas would be used on the 

floodplain fringes based on appropriate expansion/contraction ratios. 

Andy noted that the mainstem has a 1.1% average thalweg slope. 

Shea said that changes to the DFHAD guidelines had been formalized, and she said she would 

give Muller a copy of the new guidelines and checklist. Andy noted that he had been working 

from a draft version dated April 2012. 

b. Shea stated that Badger Gulch had been flown by Merrick the previous week. She anticipated 

receiving the processed LiDAR data sometime in the next few weeks. 

c. Muller had prepared a chart comparing the peak flows in for existing conditions and future 

watershed conditions along the mainstem. Andy noted the following key items: 

Upstream of Lincoln Ave. / Badger Gulch 

Less than 30% increase to future peak over existing peak flowrates 

Preliminary modeling shows less than 0.5-foot rise in future WSELs over existing WSELs 

Downstream of Lincoln Ave. / Badger Gulch 

Less than 30% increase to future peak over existing peak flowrates 

Preliminary modeling shows localized areas exceeding 0.5-foot rise in future WSELs over 

existing WSELs 

Shea noted that a separate FIRM is usually triggered by either the 30% rule or the 0.5-foot rule. 

However, she noted that the preliminary modeling indicated that the areas downstream of 

Lincoln Ave. exceeding 0.5-feet of increase appeared too localized to warrant a separate FIRM. 

For now the team will proceed under the assumption that a separate FIRM will not be required. 

d. Cross section layout 

Muller gave rollplot workmaps showing the draft cross-section layouts to UDFCD for review 


e. Bank stations 

3 

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Page A-9





Muller intends to set the bank stations based on the relatively narrow existing base-flow 

channel. Muller will determine the extent of the base-flow channel by inspecting the terrain 

data, aerial imagery, and field conditions. 

f. Manning’s n values 

Muller will use the existing channel conditions as a basis for manning’s ‘n’ values. In areas 

where development is expected to bring more frequent flows to the channel, Muller will 

consider increasing the ‘n’ values in the model to account for the future vegetative condition. 

Muller will base the hydraulic sections on existing channel condition, including any incision or 

headcutting reflected by the mapping. 

g. Muller had prepared a Google Earth layer showing the draft hydraulic cross-section locations, the 

regulatory floodplain boundaries, and a rough “first cut” of the floodplain extents based on the 

baseline hydrology. Discussion centered around the following areas of the mainstem: 

Andy asked Shea for guidance on the starting WSEL assumptions at the Cherry Creek 

confluence. Shea recommended using a 10-year WSEL in Cherry Creek for the Happy Canyon 

100-year. She will check with Bill on recommendations for the 10-, 50-, and 500-year events 


Andy noted an area of channel between Jordan Rd. and Chambers Rd. where the Green Acres 

tributary paralleled the mainstem for about a half-mile. Based on preliminary modeling, he 

anticipated that the berm could overtop in a 500-year flood on the mainstem. Shea will check 

with Bill for guidance on how the spill should be modeled, including what assumptions should 

be made regarding the WSEL and flow rate in the Green Acres Trib. during overtopping (see 

Action Items). In this same area, the recently constructed water treatment plant appeared to be 

close to the preliminary floodplain delineation. Muller will coordinate with Stacey Thompson 

(Arapahoe County) to obtain CLOMR/LOMR documentation for the treatment plant and 

incorporate this into the FHAD model (see Action Items). 

Andy noted a pond north of Chambers Rd., which Tom Williams (Parker) said was a water 

quality pond hydraulically connected to the mainstem. It will therefore be mapped as floodplain. 

The LiDAR data indicated a spill flow in the right overbank near the location of the Chambers 

Reservoir project. The aerial photography indicates that this area has been regraded since the 

LiDAR data was collected. Tom Williams (Parker) suggested coordinating with Brad 

Robenstein (Douglas County) to obtain updated grading for the area. A LOMR was also 

prepared on the Stonegate Tributary for the reservoir grading. 

Andy noted several areas in RidgeGate and Meridian where the sinuous nature of the channel 

resulted in a meandering low-flow channel which was different from the flood flow centerline. 

Andy stated that the centerline had been drawn on the low-flow channel in accordance with the 

DFHAD guidelines, but asked Shea to determine whether the centerline was acceptable in the 

major floods (see Action Items). Andy noted that the longer low-flow path would result in some 

overestimation of WSEL in the major floods, but that he would make the overbank reach 

lengths shorter to reflect the flood flows, which would somewhat reduce the effect of the longer 

centerline. 

Muller had taken a preliminary look at spill flow locations at several points along the project. 

The spill just south of Ridgegate Parkway had already been mapped as Zone A by FEMA. Greg 

Weeks (Lone Tree) noted that the developer would probably have to address the spill flow, 

since the spill returns to the main channel in a manner which could cause significant bank 

erosion. It was recommended that Muller not subtract the spill flow from the main channel flow, 

even if this is conservative for the existing case. Shea will check with Bill for general rules 

about spill flow modeling (see Action Items). 

5. OTHER ITEMS 

a. Melanie informed the team of a design project for the Douglas County east-west trail, which would 

likely be crossing I-25 at Happy Canyon. The trail project is slated for construction in 2013, and would 

probably incorporate grade control for Happy Canyon downstream of the Surrey Ridge bridge. Shea 

will discuss with Bill but generally felt that the trail project was coming too late to be modeled as part of 

the FHAD (see Action Items). 

b. Additional potential stakeholders such as ACWWA, various metro districts, development groups, etc. 

will be identified by the sponsors and contacted by Muller to alert them of the project and determine 

their interest in participating. Shea has been in communication with CDOT and is waiting to hear who 

the appropriate contact is; CDOT will be met with separately once the Alternatives Analysis is 

underway. 

6. SCHEDULE 

Muller had prepared an updated schedule for the meeting. Melanie noted that the FHAD had a 16 week 

timeframe to draft submittal. She had modified the schedule to incorporate a preliminary FHAD submittal 

in accordance with the DFHAD guidelines. She anticipated 12-weeks to the preliminary submittal. Shea 

stated that the reason the preliminary submittal wasn’t mentioned in the contract is that the FHAD 

schedule is optimistic and will likely require more submittals than those listed in the guidelines. She said 

that she expected the FHAD to take longer than the master plan. Monica noted that submitting the FHAD 

after the master plan allows final changes and comments to be addressed. 


There was unfinished business on the agenda, so the team decided to meet to discuss the rest of the agenda 

at a later date. Melanie will coordinate with the Sponsors and Stakeholders to determine a suitable time. 


5 

6 

Page A-10

Page A-11

MEETING 

MEMORANDUM 

Project 






(303) 988-4939 

Meeting Date 




Discussion 



Sponsors 




MEC Office 

Attendees 


Issue Date 



12-010.01 



Routing 


Purpose 


ACTION ITEMS: 

Items completed as of issue date have been noted. 


1. Muller will analyze the impact of existing vs. future roughness values on the floodplain in Grandview 

Estates and in Southcreek. The findings of this analysis will be presented at the next progress meeting. 

2. Muller will prepare a list of additional ground survey needs for the FHAD and give this list to Shea. 

3. Muller will extend the FHAD model upstream to include all of CPNMD Pond #12. 

4. Muller will prepare a figure showing the overtopping of Dogwood Ave. for Douglas County. (complete) 

5. Muller will contact the list of additional potential stakeholders once the revised baseline hydrology has 

been accepted and posted on the project website. 


1. Shea will coordinate survey of the additional items for the FHAD as requested by Muller. 

2. Shea will provide Muller with the Badger Gulch LiDAR survey. (complete) 

3. Shea will provide Muller with a CDOT contact for the I-25 reach. 


1. Brad will provide Muller with construction plans for the Badger Gulch channel improvements at Meridian 

Village. (complete) 

2. Brad will investigate the LOMR schedule for the Badger Gulch improvements. 

3. Brad will provide Muller with the grading plan for fills on the west side of Happy Canyon from the 

Chambers Reservoir excavation. (complete) 

Arapahoe County Action Items: 

1. Monica will pursue as-built information for the Joint Water Purification Plant. 

1. DRAFT BASELINE HYDROLOGY STATUS 

a. Muller has addressed comments on the draft baseline hydrology, but wanted to review two topics prior 

to finalizing the revisions: 

Meridian Ponds 

Pond 4C has been added to the baseline hydrology; Melanie asked for any updates on the 

construction timeframe that would impact whether the three ponds are included in the baseline 

hydrology. Brad Robenstein reported that Meridian met with Douglas County on October 10; the 

ponds have gone through one maintenance eligibility review, and Meridian will be completing the 

constructing drawings soon. The construction timeframe is still unknown; Brad guesses maybe 

early next year. All three are expected to be built together. Muller will leave the ponds in the 

baseline hydrology; Brad will provide any updates as the project progresses. 

Floodplain impacts 

There was some discussion at the last meeting of the possibility of modifying the baseline 

hydrology based on floodplain impacts resulting from increased peak flow rates. (Modifications 

would potentially include further calibration, adding future detention in RidgeGate, etc.) Melanie 

wondered if the group wanted to pursue this discussion further based on initial FHAD modeling 

results to be presented. Shea directed Muller to go ahead and re-issue the hydrology without 

further modification; any consideration of future changes would come later in the project. 

Based on this input, the baseline hydrology will be completed and posted next week. 

2. FHAD 

a. Field Visit Results / Roughness Evaluation 

Muller has visited a number of key areas along the length of the mainstem as part of the FHAD 

modeling effort. The site visit examined key crossings and recorded existing channel roughness 

values. Muller also evaluated the possibility of future increases to channel roughness. In a number of 

areas, Muller proposes to use future, increased roughness values to simulate the effect of increased 

baseflow caused by upstream development. Andy showed a tabulation of existing and future roughness 

values by station and offered to make the table available to the project sponsors and stakeholders for 

review. 

b. Addressed UDFCD XS Comments 

Andy has addressed comments on the cross-section locations provided by UDFCD on September 19th. 

The changes included removing two secondary channels and modeling these areas as a single, wide 

floodplain. 

c. Badger Gulch mapping status 

Shea expects to send the Badger Gulch LiDAR mapping to Muller by October 15 th . 

d. Areas of Interest 

Lift Station at Castle Pines 

Charlie said that the sanitary lift station adjacent to Pond #12 (8100 Monarch Blvd.) is the most 

critical lift station for CPNMD; all 9 district lift stations flow to this one. The draft FHAD 

sections model the adjacent pond embankment and show the lift station will be inundated by the 

100-year floodplain. Bill DeGroot asked that the model be extended upstream to model the entire 

pond. Jim commented that the emergency spillway of the pond is only slightly lower (0.5’) than 

the rest of the embankment and doesn’t provide much protection for the lift station. The MDP will 

1 

Page A-12 

2





 

 

 

 

 

 

make recommendations for protecting the lift station. Shea will obtain ground survey of the pond 

embankment. 

Split flow south of Ridgegate Parkway 

Andy had removed the secondary channel model south of Ridgegate Parkway per UDFCD 

comments. The split flow will be modeled with cross-sections spanning the entire floodplain 

including the secondary channel. The split flow will likely be removed during development. 

Badger Gulch development including new crossing 

The Merrick LiDAR mapping for Badger Gulch should incorporate the improved flood channel 

through the new Meridian Village development. Brad R. will provide development plans for use in 

modeling the new ConSpan bridge crossing and channel improvements in the Meridian Village 

reach. A CLOMR was prepared for this work; Brad will check on the timing of the LOMR to 

determine if additional survey will be needed at the crossing. Andy had already obtained a LOMR 

for the Ridgegate Parkway crossing of Badger Gulch, which he will use to model the crossing. 

Andy will recommend additional ground survey for Badger Gulch. 

Grandview Estates 

The updated floodplain through Grandview Estates shows more structures inundated than the 

current DFIRM. In particular, there is a spill northwest of Dogwood Ave. not shown in the 

DFIRM. Andy suggested that part of this increase is due to the increased peak runoff computed in 

the Baseline Hydrology, but that this reach was also modeled with future ‘n’ values which are 

rougher than the existing channel condition due to the expectation of a persistent base flow in the 

future. The group discussed whether it would be appropriate to reflect increased future roughness 

if the increase adversely impacts the floodplain. The sponsors instructed Muller to perform a 

sensitivity analysis demonstrating the impact to existing structures of using existing ‘n’ values vs. 

the elevated future values. Muller requested additional ground survey of a non-levee embankment 

upstream of Birch Ave. which is close to overtopping. A spill in this location would combine with 

the floodplain for the Grandview Tributary; however, Muller would not need to consider the 

combined flows as the Grandview Pond will be constructed next year, and will eliminate the 

Grandview Trib floodplain. 

Chambers Reservoir grading 

There was a small secondary channel upstream of E-470 which was filled during the construction 

of the Chambers Reservoir. The secondary channel was visible but not mapped in the 1977 FHAD 

or DFIRM. Brad R. had provided Andy with the proposed grading plan for the embankment, 

which Andy had used to delineate the new floodplain. The Chambers Reservoir embankment did 

not result in any adverse floodplain impacts. Additional fill material was placed on the west bank; 

Brad will provide the grading plan. 

Joint Water Purification Plant 

Andy had refined the ‘n’ value estimate for this reach after the field visit, noting the general lack 

of vegetation with the exception of short, bunch-type grasses. The reach is currently modeled 

based on a slightly higher future roughness. The Joint Water Purification Plant appears to be out 

of the 100-year floodplain. However, Andy noted that the 2008 LiDAR survey used in this area 

was taken during construction of the plant and did not capture floodplain improvements such as a 

flood wall and pedestrian trail bench. A CLOMR was prepared for this work, but the LOMR has 

never been completed. Monica will pursue as-built information for this reach; if no information is 

available, Andy will recommend additional ground survey in this area. 

Southcreek Development 

Andy had increased roughness values in Southcreek slightly to account for future channel 

improvements which would increase vegetative density. Because the floodplain is quite close to 

the back of the residential lots, Muller will perform a sensitivity analysis in this reach as well, 

varying the roughness values to determine a maximum future roughness before negatively 

impacting the surrounding structures. 

e. Floodway 

Bill DeGroot noted the floodways should be made equal to the floodplain in areas where the 

floodplain is already channelized, as a floodway would not be meaningful in these areas. Andy 

suggested that Muller will investigate implementing a floodway in the Grandview Estates area. He 

noted that the majority of the mainstem floodplain is confined to the main channel. 

f. FHAD Approach 

Bill DeGroot gave an overview of the UDFCD FHAD review process: 

Submittal 1: Review of hydraulic calculations, workmaps, tables and profiles (no report). 

Reviewed only by UDFCD. 

Submittal 2: Total package including report and hydraulics (corrected based on review 

comments from Submittal 1). Submitted to sponsors and stakeholders for review. 

Submittal 3: Final revision based on comment received from Submittals 1 and 2. 

There are sometimes multiple iterations of a single submittal. 

Making FHAD regulatory: FHAD study is too large for a LOMR, must be incorporated in PMR 

submittal. UDFCD has been working to streamline this process; Bill hopes that soon several 

FHAD studies will be made regulatory each year. 

3. ALTERNATIVES EVALUATION 

Summary tables of detention pond and channel reach considerations for the alternatives analysis were 

distributed to the group. There was insufficient time to review all of the information, but some items were 

discussed as follows. 

a. CPNMD Detention Ponds 

Though the Castle Pines reach is outside of the study limits, Muller would like to examine retrofits to 

the CPNMD ponds (main stem and tributary ponds) to reduce peak flow rates downstream, especially 

in small, frequent storm events. Though the downstream communities would be the primary 

beneficiaries, the retrofits would also benefit Castle Pines by improving maintenance at their facilities 

and addressing floodplain concerns at the sanitary lift station adjacent to Pond #12. Charlie and Brad 

Meyering both indicated a willingness to consider retrofits; Muller will coordinate further to 

determine any specific maintenance or other concerns to be addressed in retrofit plans. 

b. Stock pond embankment at Beverly Hills Tributary 

During a recent field visit, Muller noted an existing embankment adjacent to Happy Canyon Creek at 

the confluence with the Beverly Hills Tributary. It is likely an old stock pond embankment; it appears 

that it fully captures Beverly Hills runoff, as there is no evidence of flow entering the main channel at 

this point. Muller would like to consider formalizing the storage provided at this location. The parcel 

is owned by Douglas County. Bill Ruzzo cautioned against making assumptions about the condition of 

the embankment; if included in the master plan, a geotechnical investigation would be included in the 

plan recommendations. 

c. Sediment movement within Happy Canyon Creek / overall approach to channel stabilization 

Immediately downstream of Castle Pines, the Douglas County South reach currently exhibits extreme 

bank erosion. Along with the I-25 ROW reach, this is the primary source for sediment moving 

throughout the creek. While conventional approaches may prioritize substantial channel stabilization 

and bank protection in these damaged reaches, Muller’s experience indicates that this would merely 

shift the problem, resulting in rapid degradation of the next reach downstream. This progression 

would continue until the entire channel has been stabilized, an effort that would be quite costly and 

take years to complete. Muller would like to take a different approach on Happy Canyon by 

3 

Page A-13 

4



implementing minimal stabilization measures in the damaged reaches and allowing continued bank 

erosion to provide a sediment source where there are minimal property damage risks associated with 

continued erosion. This approach would aim to minimize long-term channel stabilization 

requirements in the downstream channel, which is generally in a state of dynamic equilibrium 

(balance of erosion and deposition). The group seemed open to this approach, but had cautionary 

tales of severe degradation on Piney Creek. Muller will continue to explore this approach as an 

alternative to conventional channel stabilization. 

d. Cattle impacts in RidgeGate 

Reaches 4 and 6, Lone Tree South and North, show signs of deterioration due to cattle impacts. 

Muller would like to explore managing cattle access to the creek as a strategy to preserve/restore a 

healthy channel condition in these reaches, as well as to reduce water quality impacts of cow manure 

in the creek corridor. Bryan was unsure if the property owner would be willing to bear the cost of 

fencing, etc. to manage access, and wondered what authority the local jurisdictions would have to 

enforce such a requirement. Bill Ruzzo mentioned the Cherry Creek Basin Water Quality Authority’s 

ability to regulate nonpoint source (NPS) pollution as a part of CR-72, which may enable 

municipalities to enforce nonpoint source controls as well. (As a follow-up to the meeting, Bill 

reviewed CR-72 and found that it does delegate NPS control to local governments.) Regardless of the 

enforcement authority, Muller strongly feels that cattle management would be in the landowner’s best 

interest as protection of the creek would reduce channel stabilization costs required as the property 

develops. Muller will include a comparison of the channel stabilization costs with and without cattle 

management in the study to make a case for RidgeGate’s voluntary participation in cattle 

management. 

4. ADDITIONAL STAKEHOLDERS / PUBLIC CONTACT 

a. Muller has been provided contact information for the following stakeholders, and will reach out to 

them once the revised baseline hydrology has been posted on the project website. Muller will continue 

to work with the project sponsors to identify any additional potential stakeholders. 

ACWWA 

Dove Valley Business Park Associates 

Dove Valley Metro District 

Centennial Airport 

Parker Jordan Metro District 

Arapahoe County Open Spaces 

Compark Development 

Chambers Highpoint Development 

b. Shea will provide Muller with a CDOT contact so that a separate meeting can be scheduled in the near 

future. 

5. PROJECT WEBSITE – http://projects.udfcd.org/happycanyon 

6. PROJECT SCHEDULE / NEXT MEETING 

The next meeting was scheduled for Tuesday, October 30 th at 9:00 am at SEMSWA. 

Draft Alternatives Analysis submittal anticipated mid-November 

1 st FHAD submittal mid to late November (pending Badger Gulch survey) 


5 

Page A-14

DRAFT BASELINE HYDROLOGY COMMENTS 

Draft baseline hydrology was submitted to the project sponsors on August 2, 2012 for review. 

Comments were received on August 28, 2012 in the form of an annotated PDF copy of the report. 

Select comments have been reproduced below; responses are italicized. Minor comments/corrections 

were addressed in the revision but are not listed here. 

UDFCD Comments: 

Table 3-4 

You had a great explanation for why flows are different from the 1993 study and how 

we calibrated to them, but I don't think you've covered the difference from the 1977 

FHAD. 

Additional discussion comparing the results to the 1977 FHAD has been added. 

Section 3.4 

The Chambers Reservoir and Meridian golf course pond were both modeled with 100% 

imperviousness and no storage; this would reflect brim-full conditions with no freeboard. 

Upon discussion with UDFCD, it was determined that this is appropriate as the project 

sponsors have no authority regarding the operation of these facilities. These facilities can 

be examined during the alternatives analysis to determine whether formalized storage 

volume would be beneficial to the plan. 

Final approval for the expansion of Meridian Pond 4A and construction of Pond 4B has 

been delayed. There is also a Pond 4C in series that we should consider including. 

For the present, Ponds 4A and 4B are still included in the baseline hydrology. As additional 

information regarding the construction time frame becomes available, the inclusion of 

these ponds will be reevaluated. Pond 4C has been added and subwatershed boundaries 

adjusted to reflect the appropriate contributing area. 

Table B-2 

There are several subbasins that exceed the recommended 4:1 shape ratio for CUHP 

(E210, G100, H160, A315, A375, A270). Please check the cfs/acre against other 

subbasins with similar %I to make sure you aren't getting a falsely high flow rate from 

these subbasins. 

According to the USDCM, “…whenever catchment length is increased faster than its area, 

the storm hydrograph peak will tend to decrease.” The concern, therefore, is falsely low 

flow rates from these subbasins. We reviewed unit discharge and length:width ratios and 

found that, in some cases, the unit flow rate is indeed lower than subbasins with similar 

imperviousness. However, because the subbasin delineation matches the topography and 

longer subbasins will naturally have less concentration of flow, we feel that the unit 

discharges are appropriate. Adjusting the basin delineation to avoid exceeding the 

recommended shape ratio would require one of the following measures: 

1. Combining adjacent long subbasins. This would result in subbasins which 

exceed the maximum allowable size of 130 acres. 

2. Further dividing long subbasins. This would reduce subbasin size well below the 

recommended 90-acre minimum, and may result in falsely high flow rates as 

CUHP tends to overestimate peak flows from small subbasins. 

3. Deviating from the topography. This would not give an accurate representation 

of the flow patterns within the watershed. 

Because the flow rates seem appropriate and any adjustments would produce further 

undesirable results, we recommend maintaining the current delineation. 

Douglas County Comments: 

Section 2.2 

The Chambers Reservoir drainage report outlined a 38-39 acre basin that was self 

contained within the reservoir. Did we assume that runoff from the reservoir would be 

conveyed downstream? 

City of Lone Tree Comments: 

Section 2.5 

Section 3.4 

Are there threatened or endangered species in the area of Ridgegate Parkway and 

bridges? Wasn't there some issue for construction (burrowing owls, eagle nesting)? 

Additional discussion of considerations for non-protected species has been added. 

Is it a valid assumption to increase pipe diameters in the SWMM model to prevent flow 

constriction? What impacts if not true? Are not the "actual" pipe sizes potentially 

available? 

Based on the reference documents reviewed for this project, piped reaches were sized to 

carry the 100-year peak flow. Though most of the pipe sizes are available, many appear 

insufficient due to changed hydrology and/or the standard assumption of full future 

development without additional detention infrastructure. In order to avoid attenuation 

due to inadvertent storage at culvert entrances or volume losses from the system, the pipes 

were upsized as needed within the SWMM model to reflect the design intent of 100-year 

peak flow passage without impacting the timing of peak flows. 

As a UDFCD eligible pond, isn't the WQ orifice for CPNMD Pond #20 REQUIRED to be reinstalled? 

If so, how was pond modeled (with or without the WQ orifice)? What, if any, 

sensitivity difference downstream? 

Though the pond is UDFCD maintenance eligible, it is currently maintained by CPNMD. 

The whereabouts of the water quality orifice plate are unknown; it is likely that a new 

orifice plate would need to be fabricated. This pond will be evaluated for retrofits during 

the alternatives analysis stage; it is therefore reasonable to wait until a selected plan has 

been identified before fabricating and installing a new orifice plate. The pond was 

modeled without the water quality orifice. The downstream sensitivity will be evaluated 

with the alternatives analysis. 

Page A-15

Figure B-8 

Figure B-9 

Please clarify/explain what is happening at the confluence with Badger Gulch. How 

does flow for 100 yr DROP, when for smaller storms it increases? 

An error was discovered in the 100-year, 3-hour, existing conditions CUHP run that 

resulted in artificially low peak flow rates downstream of Badger Gulch. The error has 

been corrected and the peak flow now increases at this location. 

Comparing the relative growth in flow rate at this node between existing and future 

conditions, the relative increase for each storm event was fairly consistent for the 2, 5, 

10, 25 and 50 yr events. However, there was a LARGE differential increase for the 100 

yr event. If we are providing plans for regional detention (in RidgeGate) for the 

EURV/100 yr facilities, please explain why this large jump is occurring. It looks like it 

might be coming from the Badger Gulch segment, is that correct? Why? 

See response to Figure B-8 comment above; the corrected flow rates reflect consistent 

growth for the 100-year event as well. In accordance with UDFCD policy, the future 

development conditions reflect future imperviousness with existing infrastructure; 

therefore, regional detention within RidgeGate is not reflected. 

Town of Parker Comments 

Section 2.3 

Section 3.4 

Reach 8 - May want to include discussion on future bridge planned (Belford Ave). 

crossing Happy Canyon here. 

Mention of the future bridge has been added. The text and figures have also been updated 

to reflect the Chambers Highpoint annexation area located east of the creek. 

Is the E-470 Pond a formalized detention pond or inadvertent storage due to the 

culvert? 

The E-470 Pond was listed as an existing 36 acre-foot pond in the 1993 OSP. There is no 

outlet structure; it is not clear if the existing 10’ x 12’ box culvert was intentionally sized to 

provide peak flow attenuation or if the storage is inadvertent. However, because it was 

included in the 1993 plan, the project team decided to include it in the baseline hydrology 

for this plan as well. A formal detention pond is planned for this location as part of the 

Compark Village South PD; modifications will be considered in the alternatives analysis. 

SEMSWA Comments 

Section 1.4 

Section 3.2 

Section 3.4 

Discuss Badger Gulch survey? 

Discussion of the Badger Gulch survey will be added once the survey has been provided. 

Will the 500-year rainfall depths be in the FHAD? 

Yes, 500-year rainfall depths will be included in the separate FHAD report. 

Re: Pond #20 - Are none of the rest maintenance eligible and is this why their status 

was not mentioned? 

None of the other nine ponds are maintenance eligible. 

Section 3.5 So does it appear that the floodplain matches a flow rate of 3690 or a larger flow rate - 

indicating that 3690 is a typo of some kind? 

The HEC-RAS model for the Southcreek LOMR, which was provided to Muller for use on the 

Cherry Creek at Eco Park project, included the FIS flow rate of 3690 cfs as well as the 1993 

OSP published future flow rate of 7303 cfs. Based on review of available LOMR 

documentation, the mapped floodplain appears to match the higher 7303 OSP flow rate. 

Table 3-4 

I assume that 3690 cfs does not match the developed conditions flow rate from the OSP 

and is why you stated that the source of the 3690 cfs is unknown? 

The 1993 OSP peak flow is 7303; the 1977 FHAD peak flow is 6744. Both the 1995 and 

2010 Arapahoe County FISs state that “The hydrologic and hydraulic analyses for 

portions of First, Piney, Murphy, Lone Tree, Happy Canyon, Cottonwood and Littles Creeks 

and Lee Gulch were performed by J.F. Sato and Associates, for the Federal Emergency 

Management Agency (FEMA), under Contract No. EMW84-C-1631. This work was 

completed in August 1985 (References 10, 11, 12, 13, 14, 15, and 16).” However, the 

references listed include a 1977 Happy Canyon Creek FHAD (attributed to Gingery 

Associates rather than HNTB) and no reports by J.F. Sato. 

The 1977 FHAD values are Future conditions, right? 

Correct. The FHAD only included future development conditions; however, the projected 

land use was less dense at that time than 1993 or current projections. 

Table B-4 

It does not appear that the E-470 pond has much of an impact on the existing conditions 

hydrology. Were any modifications to the pond assumed in future conditions? 

Future conditions baseline hydrology includes future development with existing 

infrastructure; therefore no modifications were assumed. However, modifications will be 

considered in the alternatives analysis phase. 

Figure B-10 

Big difference between the 1977 FHAD and the FIS curves – what will this do to the 

extent of the floodplain? Is the FEMA effective delineation for the 3690 or 7303 cfs? 

Maybe we can guess as the FHAD modeling gets done. 

See responses to Section 3.5 comments. Though the floodplain seems to be based on the 

higher OSP flow rate, this study still reflects a substantial increase to over 9200 cfs; the 

floodplain impacts will be evaluated in the FHAD, and the alternatives analysis will seek 

to mitigate the increased peaks through additional detention. 

Page A-16

MEETING 

MEMORANDUM 

Project 






(303) 988-4939 

Meeting Date 




Castle Pines Action Items: 

1. Brad will investigate the exposed utility downstream of CPNMD Pond #12. (Complete) 

Discussion 

Sponsors 




SEMSWA 

Attendees 

Shea Thomas / UDFCD 

Monica Bortolini / SEMSWA 

Tom Williams / Town of Parker 

Brad Robenstein / Douglas County 

Greg Weeks / City of Lone Tree 

Brad Meyering / City of Castle Pines 

Charlie Fagan / Castle Pines North Metro Dist. 

Bill Ruzzo / CCBWQA 

Bryan Ruth / Rampart Range Metro Dist. 

Stacey Thompson / Arapahoe County 

Lanae Raymond / SEMSWA 

Jim Wulliman / Muller 

Melanie Chenard / Muller 

Andy Pultorak / Muller 

Purpose 


ACTION ITEMS: 


Issue Date 

November 2, 2012 


12-010.01 



Routing 




1. OUTSTANDING ITEMS 

a. Baseline Hydrology acceptance 

The revised Baseline Hydrology was submitted on 10/18. Shea confirmed that she reviewed the report 

to ensure all comments were addressed; Muller can now post the update on the project website. 

b. Stakeholder contact info 

Muller was holding off on contacting the additional stakeholders until the revised Baseline Hydrology 

was accepted and posted on the website. This effort will now proceed: a few contacts are still needed. 

Brad Robenstein confirmed that Randy Gabriel would be the contact for Meridian, and will provide a 

contact for Sierra Ridge Metro District. Shea does not yet have a contact at CDOT; Muller will pursue 

identifying the appropriate contact. Brad Meyering noted that CDOT is revising their region 

boundaries, so there may be some shuffling of CDOT staff. 

c. Survey needs 

Two potential survey items were outstanding at the previous meeting: the new Badger Gulch crossing 

at Bristleridge and the Joint Water Purification Plant (JWPP). Brad R. has provided design drawings 

for the Badger Gulch crossing and will be sending as-built drawings as soon as he receives them 

(complete as of issue date); so no additional survey is needed at this location. Andy spoke with Ron 

Lambert of Mulhern MRE, who prepared the construction drawings for the channel improvements at 

the JWPP. The area has been flown, but the data has not been processed to generate the final survey 

results due to funding limitations. Ron could try to move this forward, but it could take some time to 

get funding approved. To avoid delaying the FHAD, UDFCD will go ahead and obtain ground survey 

here. Muller will add this area to the survey request and submit to Shea ASAP. 

2. FHAD / ALTERNATIVES DISCUSSION 

a. Reach 7: Douglas County North 


1. Muller will post accepted Baseline Hydrology on the project website. 

2. Muller will pursue contact information for CDOT and contact additional stakeholders. 

3. Muller will finalize survey request and provide to UDFCD. (Complete) 


1. Shea will discuss with Bill DeGroot whether a DFIRM will be required. (Complete) 

2. Shea will obtain additional survey as requested by Muller. 


1. Brad will provide as-built information at the Bristleridge crossing when he receives it. (Complete) 

2. Brad will provide direction for alternatives to be considered at the Dogwood crossing. (Complete) 

3. Brad will provide construction drawings for the Meridian Village detention ponds adjacent to Lincoln 

Ave. (Complete) 

 

Grandview Estates flooded structures / roughness sensitivity analysis 

As discussed at Progress Meeting #4, Muller has performed a sensitivity analysis to determine the 

impact of utilizing future channel roughness values within Grandview Estates. A summary of the 

structure flooding is as follows: 

Basis of Floodplain 

# of Impacted 

Structures 

FEMA regulatory 8 

Current study – future 

peaks and existing 

roughness 

Current study – future 

peaks and future 

roughness 

Manning’s n 

(channel – overbank) 

20 0.035-0.040 

26 0.040-0.050 

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The structure count is based on examination of the aerial photo, and may include some 

nonhabitable structures that will be removed from the final count. Andy noted that the regulatory 

floodplain would probably include a few more structures if plotted on current mapping based on 

the BFEs. However, most of the increase in impacted structures is due to the higher peak flow. 

The regulatory flow rates are around 5500 cfs and are based on the 1977 FHAD, which had a 24- 

hour SCS rainfall distribution and lower projected development within the watershed. The current 

projected 100-year peaks are over 7500 cfs, based on current rainfall criteria and updated 

projected development. Based on the high sensitivity to increased n values in this reach, Shea 

directed Muller to utilize existing roughness values throughout Grandview Estates. 

Dogwood Crossing 

The Dogwood crossing is quite undersized and is a significant cause of flooding. The existing 

crossing consists of (3) 48” CMPs. The 1993 OSP recommended (4) 72” CMPs, which would 

have provided 10-year capacity based on 1993 peak flows. HDR completed a study of Grandview 

Estates in the early 2000s, and recommended (2) 72” CMPs to provide 2-year capacity, along with 

lowering of the road profile to contain overtopping above the crossing. Currently, overtopping 

flows spread to the east, causing flooding along a low area that runs parallel to the channel. 

According to HDR’s preliminary design report, this crossing was selected to be part of the first 

phase of improvements along with the channel improvements through the open space just north of 

Lincoln. However, the final construction plans excluded the crossing. Brad Robenstein reported 

that, at the time, one of the adjacent property owners was unwilling to grant Douglas County an 

easement, so the county was unable to proceed with the crossing. Following the last progress 

meeting, Muller had discussed with Brad the possibility of removing the crossing entirely, 

creating dead ends on either side of the creek. Several of the east-west roads in Grandview dead 

end without crossing the creek. Brad is meeting with other county officials on October 31 to 

discuss whether permanent removal is feasible. 

Update: Based on the aforementioned meeting, Brad directed Muller to examine two alternatives 

for this crossing: a 100-year capacity bridge and removal of the crossing. 

Lincoln Avenue 

Andy has identified a potential flooding issue at the Lincoln Avenue crossing. In the 100-year 

event, backwater from the Lincoln Avenue bridge causes flows to overtop the spillway of the 

adjacent Meridian Village detention pond to the east. This is one of a complex of three ponds 

along the south side of Lincoln: two are located between Happy Canyon Creek and Meridian 

Village Parkway, and a third is located east of Meridian Village Parkway. The spill into the pond 

complex results in overtopping of both Lincoln and MV Pkwy, as both roads have sags adjacent to 

the ponds. The overtopping at Lincoln flows northward into the open space parcel and rejoins 

Happy Canyon Creek, and the overtopping at MV Pkwy is contained by the pond – no additional 

structures are impacted. Melanie noted that the drop structure located immediately upstream of 

Lincoln had a design height of 8’; the topo reflects a lesser drop. Brad R. noted that there has been 

quite a lot of sedimentation downstream of the drop, so its height may indeed be reduced. Muller 

will request additional survey of the drop, the pond spillway, and the berm along the north edge of 

the pond in order to verify the overtopping. Brad will provide design drawings of the pond. 

Brad confirmed that Muller should include maintenance easement acquisition within Grandview 

Estates in the alternatives analysis. 

 

Muller has identified 100-year overtopping at the West Parker Road bridge. A Parker Water and 

Sanitation District wastewater treatment plant is proposed for the northwest corner of this 

crossing. 

b. Reach 8: Parker 

 

 

 

The trail crossing upstream of E-470 is a culvert crossing that appears to have maintenance issues 

due to sedimentation. Per Tom, the E-470 Authority is responsible for any maintenance of their 

trails. Muller will look at a new crossing at this location. 

The outfall from the Stonegate Tributary is a badly eroding channel downstream of the piped 

segment at Chambers Reservoir. Ideally, this channel would have been stabilized with the 

installation of the piped segment. Future improvements are likely when the Belford Ave. crossing 

of Happy Canyon creek is constructed; however, this crossing is only at the conceptual level and 

the time frame is uncertain, so measures should be taken to stabilize the channel in the interim. 

Muller will provide photos to Brad R. and will include improvements in the plan. 

Muller will consider online detention in the lower, stabilized portion of the watershed to reduce 

sediment accumulation in the downstream reach of creek. The Chambers Road embankment could 

be a potential location; however, Andy has identified an overtopping spill flow in the 500-year 

event, so any proposed detention here could have potential for flooding issues. Muller will review 

other potential locations for this alternative. 

c. Reach 9: Arapahoe County 

 

 

 

Southcreek 

Muller has completed the roughness sensitivity analysis in this reach, and has found that a slight 

increase in Manning’s n values (from existing values of 0.030 to 0.040) does not adversely impact 

the floodplain. A greater increase to 0.060 would result in flooding at the homes that back to the 

creek. Muller will use 0.040 in the FHAD to allow for a limited increase in vegetation. The 10’ 

deep channel section through this reach has a wide benched area 5’ above the channel bottom. 

Excavation in these benched areas could provide the additional conveyance that would be needed 

to offset further increase in vegetation within the reach to acoid impacting the homes; Muller will 

continue to look at options to improve the channel character in this reach. 

Dove Valley Business Park / JWPP 

Lanae expressed interest in improving the function of the detention pond just north of the JWPP 

and wondered if that could be worked into this plan. If Muller proposes online detention in the 

lower watershed, Jordan Road would be a potential location; this could then replace the JWPP 

pond as well as the numerous other ponds proposed within the Dove Valley Business Park. There 

is a wide drainage tract in this area; development plans call for relocation of the Green Acres 

Tributary to allow for an offline pond near the existing confluence with Happy Canyon. An online 

regional pond could be located within the drainage tract and could serve both Happy Canyon 

Creek and the Green Acres Tributary. Muller will explore this alternative further. 

There are several other small detention ponds in the area that Lanae would like to see improved; 

while this plan will not specifically address these ponds, some discussion of watershed controls 

can be included in the text. 

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4





d. Reach 5: Meridian Commons 

Muller has identified potential flooding at homes adjacent to the creek at Meridian Commons. Brad R. 

noted that the LOMR in this area did not show much freeboard at these homes with the lower 

regulatory flow rates. Muller will request additional survey at these homes to verify impacts. 

e. Reach 1: Castle Pines 

 

 

 

As previously discussed, Muller will propose improvements at CPNMD Pond #12 to improve 

detention as well as to reduce flood hazards at the adjacent sanitary lift station. Because the pond 

embankment is not a certified levee, the lift station may still be located in the mapped floodplain 

even if the embankment is modified to prevent flooding. As an alternative, the downstream pond 

embankment could be moved upstream of the lift station, which would allow the channel and the 

floodplain to be lower than the lift station. 

Update: Following the meeting, Shea clarified that the FHAD will stop at the Castle Pines 

corporate boundary. Castle Pines currently has no mapped floodplain and is not an NFIP 

community. The MDP can still model this area and recommend floodplain improvements, but it 

will be excluded from the FHAD. 

Bill described that the Cherry Creek Basin Water Quality Authority regulations require secondary 

containment at sanitary lift stations within the basin, as well as numerous other standards. The 

Authority is researching this facility to determine whether the standards apply, or if it was 

constructed prior to adoption of the standards and is therefore grandfathered. Because it could 

pose a water quality issue for the watershed, it would be appropriate to include 

discussion/recommendations at the lift station in the report; Bill offered to help write this section 

once he understands how it fits within the standards. The Authority is also compiling a list of 

other lift stations within the basin. Charlie mentioned that Kennedy/Jenks maintains this lift 

station: his contact is Greg Sekera. 

Muller discovered an exposed utility line just downstream of the Pond #12 embankment. The 

channel has degraded significantly in this area; there is 6-8’ of vertical drop from the pond outlet 

to the exposed utility approximately 20’ downstream. This area is located within the boundary of 

Castle Pines, but is part of the Public Service transmission line corridor; neither the City of Castle 

Pines, the Castle Pines North Metro District, nor Douglas County maintain the channel in this 

location. Brad M. and Brad R. will follow up to try to identify the utility line and bring it to the 

attention of the appropriate party. 

Update: The line has been identified as an Xcel Energy 6” high pressure gas main. It is located in 

Xcel-owned property within the City of Castle Pines corporate boundary. Melanie will lead the 

coordination effort with Xcel. 

g. Other Alternatives Evaluation Topics 

Muller has prepared a matrix of the alternatives to be examined in each reach. Two approaches to 

overall channel stabilization will be explored: a minimal approach that maintains a steeper 

equilibrium slope with greater sediment movement; and a fully stabilized approach that provides a 

flatter slope with reduced sediment movement and stabilized banks. 

The proposed channel alternatives will be accompanied by detention recommendations in an 

effort to get peak flows for all storm events reduced to or near historic levels. 

Melanie inquired if the Alternative maps will be standard format or something similar to the 

interactive baseline hydrology maps. Shea has not yet prepared a prototype for alternative maps, 

so Muller can stick with the format specified in the contract. 

h. DFIRM 

Shea mentioned that, because the peak flows are >30% greater than the regulatory peak flows, a 

separate DFIRM will be triggered. Muller was under the impression that no DFIRM would be 

needed because the existing vs. future peak flows differ by less than 30%. In fact, when the 

hydrologic models are run with 2% imperviousness throughout the watershed and no detention 

ponds to simulate historic peaks, the difference appears less than 30%. Shea will discuss this 

further with Bill DeGroot. 

Update: Per Shea, the DFIRM will not be required as long as the increase in flows is adequately 

explained in the FHAD. 


The revised baseline hydrology will be posted ASAP. Meeting minutes are also available on the website. 


Survey needs will be submitted ASAP, as the survey results will influence both the FHAD and the 

Alternatives Analysis. 

Muller will proceed to completion of the 1 st FHAD submittal and Draft Alternatives Analysis. 

Expected submittal date is late November or early December, depending on when survey results 

are obtained. 

The next meeting will be held following sponsor review of the Draft Alternatives Analysis. Muller 

will coordinate with the group once the review schedule has been set. 

Public meetings will be discussed at the next meeting; though UDFCD is moving away from 

public meetings for master plans, this plan will likely warrant a meeting due to the impacts to 

residential properties. 


f. Reach 2: Douglas County South 

 

 

Muller has identified overtopping at the Oak Hills Drive and Clydesdale Road crossings. The 

alternatives analysis will include improved crossings. 

Just upstream of its confluence with Happy Canyon Creek, the Oak Hills Tributary crosses Surrey 

Road with (2) 72” CMPs. This crossing is severely degraded, with 6-8’ of vertical drop from the 

end of the CMPs. The 1993 OSP includes recommendations for a larger crossing. Muller will 

review and restate or revise these recommendations in this plan, and proposed improvements on 

Happy Canyon will consider how Happy Canyon ties into Oak Hills and the proposed Surrey 

Road crossing. 

5 

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6

MEETING 

MEMORANDUM 

Project 


Sponsors 




SEMSWA 

Attendees 


Monica Bortolini / SEMSWA 

Jacob James / Town of Parker 



Brad Meyering / City of Castle Pines 

Charlie Fagan / Castle Pines North Metro Dist. 

Bill Ruzzo / CCBWQA 

Bryan Ruth / Rampart Range Metro Dist. 


Lanae Raymond / SEMSWA 



Purpose 


ACTION ITEMS: 






(303) 988-4939 

Meeting Date 

April 4, 2013 

Issue Date 

April 30, 2013 


12-010.01 


Melanie Chenard 

Routing 



1. If UDFCD requests based on Shea’s discussion with Bill DeGroot, Muller will perform additional analysis 

to quantify the floodplain impact associated with an IGA that commits to the implementation of regional 

full-spectrum detention in RidgeGate. 

2. Muller will review the impact of the Chambers Reservoir and Meridian Reservoir alternatives 

independently to evaluate their benefit. 

3. Muller will send Bryan the historic conditions CUHP/SWMM model. 

4. Muller will schedule a meeting with CDOT to review issues along the I-25 reach. 

5. Muller will send UDFCD a shapefile representing a 300’ offset from the stream centerline for the public 

meeting mailing list. Completed. 

6. Muller will update the project website before the public meeting. 


1. Shea will write a section for the report discussing the FAA guidelines as they apply to the proposed 

improvements. 

2. Shea will discuss with Bill DeGroot any possible negative aspects of an IGA with RidgeGate. 


April 4, 2013 

3. Shea will look into whether unimproved channels can be maintenance eligible. 

4. Shea will discuss with UDFCD staff the concept of apportioning the cost of improvements based in part 

on downstream benefit. Shea will also discuss the concept of prioritizing projects based on their impact in 

the watershed and implementing the recommended timed, incremental approach to stream improvements. 

5. Shea will send invitations for the public meeting once the date, time, and location are set. 


1. Brad R. will provide Muller with plans for the newly designed Meridian Village pond upstream of Main 

Street. Completed. 

2. Brad R. will provide Muller with any information on detention in the Castle Oaks area. Completed. 

Town of Parker Action Items: 

1. Jacob will look into potential locations for the public meeting. 

SEMSWA Action Items: 

1. Lanae will provide Muller with plans for the Ladera and JWPP ponds. 

CCBWQA Action Items: 

1. Bill will provide Muller with any information on detention in the Castle Oaks area. Completed. 

2. Bill will provide Muller with comments on the Alternative Analysis. Completed. 

Castle Pines Action Items: 

1. Brad M. and Charlie will review the Alternative Analysis and provide any comments to Muller and 

UDFCD. 

2. Brad M. will provide Muller with any information on detention in the Castle Oaks area. Completed. 

Discussion 



1. ALTERNATIVE ANALYSIS 

a. Review Comments 

Melanie had identified a number of comments that required further discussion or clarification; selected 

discussion items are presented below. 

Structures in floodplain: Shea confirmed that the lowest adjacent grade elevation will determine if 

structures are in the floodplain. For the home in Meridian Commons, Muller should state that the 

first floor is above the floodplain. 

Grandview Estates Floodplain: Muller will show the 100-year floodplain based on the 10-year 

channel alternative in Grandview Estates. 

Detention in Arapahoe County: Muller did not include any regional detention facilities in the 

alternative analysis in Arapahoe County: the development area is relatively small, the developers 

have planned for a number of small facilities, and there are no floodplain concerns to be addressed 

in the final reach. Stacey would like Muller to reconsider in order to promote the use of regional 

detention by developers; Muller will review the volume and drainage area of the proposed 

facilities in Dove Valley and coordinate with Shea on possible addition to the plan. Lanae would 

like Muller to include improvements to the Ladera Pond and JWPP in the plan. The Ladera Pond, 

located on the west side of Happy Canyon Creek at the confluence with Cherry Creek, is currently 

HOA owned and maintained. The JWPP pond, located just north of the JWPP at Jordan Road, is 

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April 4, 2013 


April 4, 2013 

 

 

 

 

 

 

maintained by SEMSWA. SEMSWA would like to improve the function of both facilities and 

would therefore like them to be discussed, as master planned items are more likely to be 

constructed. Shea clarified that these ponds are too small to include in the master plan hydrology, 

but agreed to include retrofit improvements in the master plan to allow SEMSWA to budget for 

them. Lanae will provide Muller with the design plans for both ponds for reference. 

Maintenance access and easements: When developing the alternative costs, Muller included costs 

for easement acquisition as well as maintenance trail construction in residential reaches. In 

developer-owned reaches, only costs for the maintenance trail construction were included, as it 

was assumed that the developer would be required to grant easements to the local jurisdiction as 

development occurs. The sponsors prefer not to list easement costs, as this creates an expectation 

of payment with the property owners; the reality is that easements are often granted in exchange 

for the channel improvements to be constructed. Muller will remove all easement costs from the 

Alternative Analysis. 

Meridian Village Pond: This pond, located just south of Lincoln Avenue adjacent to Happy 

Canyon Creek, was not on Muller’s radar during the baseline hydrology and had not been 

mentioned by the sponsors as a possible regional facility. The pond was examined due to 

floodplain issues during the preliminary FHAD modeling and found to be eligible for inclusion in 

the baseline hydrology, as it is a regional pond that is publicly owned and maintained (by the 

Meridian Metro District). Muller will add it to the baseline hydrology model and revise the peak 

flow rates accordingly. 

Reservoirs: Chambers Reservoir and Meridian Reservoir are modeled in the baseline hydrology as 

100% impervious assuming they are brim-full. Based on earlier sponsor input, the two facilities 

were included in the Alternative Analysis as “Manage as Detention” alternatives. From the 

modeling perspective, this means that the reservoir and the area draining directly to the reservoir 

were excluded from the alternative hydrology. Politically, this would require an agreement with 

the owners regarding the operation of the reservoirs to maintain a minimum amount of freeboard 

so that no downstream storm runoff is generated from this area or at least to not change the 

geometry and capacity of the emergency spillway, maintaining the attenuation provided by the 

facilities assuming the reservoirs are brim full at the start of the storm. The group is uncertain of 

the worth of these alternatives; Muller will look at the impact of each facility independently to 

provide the sponsors with additional detail on the benefit of managing each facility. 

Grandview Pond: Previous improvements to the Grandview Tributary were sized based on the 

design release rate for the future pond; however Muller discovered that the pond design reflected 

onsite detention for a portion of the upstream contributing area within Meridian Village. Because 

the onsite ponds cannot be included in the master plan hydrology, this resulted in undersized 

improvements downstream of the pond. Brad R. just signed design plans for a new full spectrum 

detention pond treating approximately 200 acres upstream of Main Street; he will provide these 

plans to Muller to include in the alternative hydrology. Muller will determine if the additional 

facility will provide sufficient volume to meet the design assumptions for the tributary 

improvements. 

Beverly Hills Tributary Detention: Muller proposed a new detention facility on the Beverly Hills 

Tributary adjacent to Charter Oaks Drive in Castle Pines. Brad R. pointed out that there are 

existing facilities in this area that could potentially be converted to full spectrum and taken over 

by Castle Pines or CPNMD. Brad M. and Bill mentioned that an existing pond was recently 

enlarged for the expansion of the Montessori school; Bill reviewed the plans for the CCBWQA. 

Bill, Brad M., and Brad R. will all provide Muller with any information they can find regarding 

detention in this area. 

Cattle Mangement: In addition to the cattle grazing along the RidgeGate reach, Stacey and 

Monica mentioned that grazing also occurs in the Arapahoe County portion of the watershed, on 

the property south of the JWPP. Discussion in the report of cattle management in this area would 

be beneficial – though the cattle do not water at the creek due to the absence of a base flow in this 

reach, the manure still poses a water quality issue. 

E-470 pedestrian bridge: A suggestion was made to recommend that any redesign of the 

pedestrian bridge consider streamlining or other methods to reduce sedimentation in the vicinity. 

Airport Proximity: Several proposed detention facilities are located within a 10,000’ radius of the 

end of a runway; FAA guidelines require that standing water drain within 48 hours. However, 

there are multiple existing, larger, permanent water storage facilities within this radius. Shea will 

write a section for Muller to include in the report regarding this matter. 

Green Acres Tributary Floodplain: There is currently a gap in the floodplain delineation for the 

Green Acres Tributary: it is not included in the Arapahoe County DFIRM, but is shown in 

Douglas County. Muller had modeled a portion of this tributary to evaluate overflows from Happy 

Canyon Creek; the FHAD comments include instruction for Muller to expand the Green Acres 

Tributary floodplain to tie in with the Douglas County DFIRM. 

Detention inflows/outflows: A comment was made that at least one pond showed outflows 

greater than inflows. Muller will check this. 

Historic Model: RRMD requested to review the historic conditions CUHP/SWMM model. 

Melanie explained that it is the same as the baseline hydrology model, except with the % 

impervious for all subwatersheds set to 2% and all detention facilities removed. Muller will send 

the model to Bryan to review. 

CCBWQA Comments: Bill will be providing review comments to Muller in the next week. 

Comments will include some discussion of sediment transport and pose the question of whether 

quantitative sediment transport modeling of HCC would be beneficial. Jim mentioned that 

Muller’s assessment of stability of the creek as well as recommendations for improvements are 

heavily influenced by sediment transport considerations; however, these are based on qualitative 

analyses using observations of degradational and aggradational tendencies and application of 

geomorphic principles. The methods described in the report – offline detention, phased 

improvements, provision of full spectrum detention – are intended to minimize sudden, drastic 

changes to the sediment transport within the channel and keep the system relatively in balance as 

the creek shifts over time to a lower energy / lower sediment transport system. The benefit of 

quantitative sediment transport modeling can be further discussed by the sponsors. 

b. Detention in RidgeGate 

 

 

Melanie explained how the RidgeGate ponds were sized. Because the subwatershed boundaries do 

not always follow the development boundaries, the contributing area for the three ponds includes 

some areas outside RidgeGate and excludes some areas within RidgeGate. Rather than calculating 

volumes based on the contributing areas, the pond curves were iterated within the SWMM model 

to result in releases that match the existing conditions hydrology at that location. Since there is 

very little additional development assumed upstream of RidgeGate, the existing and future peak 

flow rates entering RidgeGate are essentially the same. However, flows in HCC are significantly 

influenced by proposed modifications to upstream ponds within Castle Pines. Therefore, the plan 

will not establish set release rates at the downstream end of the development, as they will vary 

based on the implementation of upstream detention improvements. Muller will include additional 

discussion in the report to provide direction for the developers on the sizing of the RidgeGate 

ponds. 

The group has previously discussed the concept of an inter-governmental agreement (IGA) 

between RidgeGate/Rampart Range Metro District and UDFCD to allow the RidgeGate ponds to 

be reflected in the baseline hydrology. Muller’s initial exploration of this issue indicates that the 

benefit would be limited; the peak flows would be reduced by less than 10% and there would still 

be substantial flooding in Grandview Estates. Due to the complexity of the flow splits/flooding in 

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April 4, 2013 


April 4, 2013 

Grandview Estates and the expectation of limited impact on the floodplain, Muller has not 

completed a detailed assessment of the floodplain impact of an IGA. 

The sponsors shared the opinion that, though the benefit would be limited, the IGA is still worth 

pursuing if there is no down side. Shea will discuss this further with Bill DeGroot to see if he has 

any objections to an IGA; if Bill is on board, Muller will perform some additional analysis to 

quantify the benefit that such an agreement would provide. 

c. S4 Alternative Approach 

The group discussed the S4 alternative approach presented in the report, which assumes a phased 

implementation based on channel condition. This approach would require active monitoring of 

channel condition so that improvements can be planned as soon as problem areas develop, before 

the conditions become severe. If properly implemented, it could result in a lesser degree of 

stabilization necessary – and therefore a lower cost – over the life of the master plan. Melanie 

noted that the S4 alternative approach needs to be paired with the most extensive detention 

concept in order to reduce peak runoff rates during frequent events. 

This approach would allow channel improvements within new developments to be limited to those 

that address immediate needs, with developers contributing funds in lieu of full stabilization; these 

funds could then be utilized for additional improvements as needed based on the regular channel 

monitoring. This concept will need further discussion by the sponsors. 

Bill mentioned that on other watersheds, he has found the threshold imperviousness to be 8-12%, 

at which point the channel begins to react to development. This threshold could be the trigger for 

implementing channel improvements within new development. 

If unimproved channels could be maintenance eligible, the local jurisdictions would be able to 

partner with UDFCD to implement improvements as they are needed. Shea will look into whether 

unimproved channels can be maintenance eligible. 

d. Apportioning of Costs based on Downstream Benefits 

The group discussed the concept of apportioning project costs in part based on downstream 

benefits. In some areas, this may be a good approach to implementing the plan improvements; for 

example, although retrofitting ponds in Castle Pines provides some benefit to the city and 

CPNMD, additional benefit would accrue in downstream reaches since the reduction of peaks 

during small storm events would reduce erosional stresses on the creek. 

Though the sponsors were in favor of this type of approach, they were uncertain if they would be 

allowed to fund improvements outside their jurisdiction. This approach will require additional 

consideration. The formation of a separate watershed entity was suggested. 

Shea will discuss the concept internally with UDFCD staff and provide Muller with some 

additional feedback. 

e. Castle Pines Reach 

 

 

Based on the latest communication, Xcel does not intend to do any work to protect the exposed 

gas line in the near future. They have tested the pipe condition and do not see an immediate 

concern. 

Brad M. and Charlie did not provide comments on the Alternative Analysis; neither has had a 

chance to review it yet. Melanie and Jim summarized the proposed improvements, which include 

outlet structure retrofits at Ponds 9, 10, 11, and 20; construction of a new embankment at Pond 12, 

located upstream of the lift station; and channel improvements through the Xcel property. It was 

requested that the report emphasize the benefit associated with enlarging Pond 11 in terms of 

addressing capacity problems downstream at the lift station. In general, no concerns or objections 

were raised; if Brad or Charlie have any additional comments upon review of the report, they will 

provide them to Muller. 

f. I-25 Corridor 

Upon further examination of the property ownership along I-25, it became apparent that little of 

the channel lies within CDOT ROW. North of the Clydesdale Road crossing, the channel crosses 

a few residential properties and a parcel owned by the Surrey Ridge HOA. The largest segment of 

channel is owned by Surrey Overlook Development, LLC. At the northern end of the reach, the 

channel does enter CDOT ROW, with small segments crossing into parcels owned by Parker 

Water and Sanitation District and RidgeGate. 

Muller has looked at the highway drainage along this reach; there are two locations where large 

concentrations of flow outfall into Happy Canyon Creek. Muller would like to propose 

improvements to help reduce peak runoff and provide water quality treatment, including 

modification of the existing failed pond approximately 600’ south of the Happy Canyon bridge 

crossing, near the end of a long reach of median. 

Muller will proceed with scheduling a meeting with CDOT to discuss the channel condition along 

I-25 as well as the potential for improvements to address the highway runoff. The CDOT contact 

is Carrie DeJiacomo-Wiedner. 

2. FHAD STATUS UPDATE 

a. UDFCD returned comments on the preliminary submittal to Muller at the meeting. 

b. The next step is the Draft Submittal, which will be reviewed by all project sponsors. The Draft 

Submittal includes a draft of the FHAD report in addition to the technical information provided for the 

preliminary submittal. 

3. STAKEHOLDER CONTACTS 

a. Stakeholders identified by the sponsors were contacted via email in March. The only response Muller 

has received is from a resident of Grandview Estates regarding the Dogwood crossing removal; the 

resident was referred to Brad R. for further information. 

b. Muller will continue to update the stakeholders as project milestones are reached. 

4. PUBLIC MEETING 

a. A public meeting will be held for this plan before the Alternative Analysis is finalized. The invite list 

will include property owners near the channel as well as the list of stakeholders. Melanie will provide 

UDFCD with a shapefile that reflects a 300’ offset from the channel centerline; Shea will generate the 

mailing list. 

b. Jacob will look into potential meeting locations within the Town of Parker, including the Recreation 

Center at Challenger Park, which is located near Lincoln Ave. and Jordan Rd. 

c. Muller will ensure the project website is up to date before the invitations are sent. 

d. The meeting will be a presentation format. 


a. Muller will work on addressing the Alternative Analysis comments but will not finalize/post the report 

on the website until after the public meeting. Once the Alternative Analysis is finalized, the sponsors 

will determine the Selected Plan. 

b. Muller will also proceed with the Draft FHAD submittal, and will aim to submit this during the 

Selected Plan development process. 

c. The next progress meeting will be to review the Selected Plan and kick off the Conceptual Design; it 

will be scheduled at a later date. 


5 

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Page A-22

Cherry Creek Basin Water Quality Authority 

8390 East Crescent Parkway, Suite 500 

Greenwood Village, Colorado 80111 

(P) 303.779.4525 (F) 303.773.2050 

In paragraph 5.7.5, the report suggests avoiding creek corridor improvements that result in “overstabilization”. 

Whereas what this means is not clear, the Authority does not believe “overstabilizing” 

a channel is possible. If the channel lacks adequate sediment transport capabilities 

because it’s "too flat", then the channel is not stable. This is an example of why we need a better 

understanding of sediment transport to support what seems to be a logical approach to maintain 

stability in the drainage system. 

April 9, 2013 

Ms. Shea Thomas, P.E. 

Urban Drainage & Flood Control District 

2480 W. 26 th Avenue, Suite 156 B 

Denver, CO 80211 

Re: Happy Canyon Creek Major Drainageway Plan Alternative Analysis 

Dear Ms. Thomas: 

The Cherry Creek Basin Water Quality Authority (Authority) appreciates the opportunity to provide 

comments on the Happy Canyon Creek Major Drainage Plan Alternatives Analysis (Alternatives 

Plan) prepared by Muller Engineering Company (MEC) dated February 2013. The report was 

reviewed and comments provided on a pdf version of the report, which also contained comments 

from SEMSWA, and is submitted under separate cover. 

The Authority finds the report to be very comprehensive and well organized, presenting new 

concepts and approaches to solving drainage, flood control, and water quality problems associated 

with an urbanizing watershed. MEC is to be complimented on a thorough analysis and approach. 

The Authority has some fundamental questions along with suggestions regarding project approaches, 

which are discussed below under the headings of sediment transport and channel reclamation. 

Sediment Transport 

Channel Reclamation. 

The approaches to alternatives for Happy Canyon Creek relies on providing detention ponds 

distributed throughout the watershed that are designed to capture excess urban runoff volume 

(EURV) and slowly release the runoff into the drainageways. There is a good body of knowledge 

that suggests detention ponds designed to provide EURV will help stabilize downstream channel 

providing drainage and flood control benefits and water quality protection. The channel alternatives 

are then based the “wait and see” approach along with implementing “strategic” improvements when 

field evidence shows signs of instability in the channel. 

If the project sponsors support the recommendation in the report, then local governments will need 

to implement long-term monitoring and establish a funding mechanism to be ready and able to make 

strategic channel improvements, otherwise there may be negative water quality impacts to the Happy 

Canyon and Cherry Creek watersheds. 

We hope that our comments and suggestions are helpful to the project sponsors in making their 

selection of the preferred alternatives for Happy Canyon Creek. 

Respectfully submitted 

William P. Ruzzo, PE 

For the Cherry Creek Basin Water Quality Authority 

Channel stabilization\reclamation alternatives are based on qualitative assessments of the sediment 

transport regimes that are expected to occur as development and drainage improvements are 

implemented with urbanization. The report provides sound logic for the sediment transport 

assumptions which lead to specific channel stabilization alternatives and recommendations. 

However, the qualitative approach to sediment transport has been used in other master drainage 

plans that led to considerable capital improvement costs with less than adequate results. 

The Authority believes that a different approach is needed for sediment transport analysis in 

planning studies, such as a quantitative analysis or sediment/erosion monitoring. Either or both 

approaches would improve our understanding of sediment dynamics created by urbanization leading 

to long-term solutions with less risk of failures. Solving sediment transport questions will improve 

drainage and flood control projects and provide for improved water quality. 

Cc: 

Chuck Reid, CCBWQA Manager 

Melanie Chenard, Muller Engineering Company 

1 

2 

Page A-23

MEETING 

MEMORANDUM 

Project 


Sponsors 




Parker Recreation Center 

17301 E Lincoln Ave, Parker, CO 80134 

Project Sponsors in Attendance 


Ken MacKenzie / UDFCD 

Jacob James / Town of Parker 

Tom Williams / Town of Parker 






Andy Pultorak / Muller 

Members of the Public in Attendance 

See attached sign-in sheet 

Purpose 

Happy Canyon Creek MDP & FHAD Public Meeting 

Discussion 





(303) 988-4939 

Meeting Date 

June 12, 2013 

Issue Date 

June 18, 2013 


12-010.01 


Melanie Chenard 

Andy Pultorak 

Routing 




1. PRESENTATION 

Ken explained the function of UDFCD and gave an overview of the master planning process. He 

introduced the project sponsors and engineers. Jim, Melanie, and Andy then gave a presentation on the 

project, including the following topics: 

Watershed overview: Melanie gave an overview of the watershed, which extends from Castle 

Pines to the confluence with Cherry Creek in the Dove Valley Business Park. Current 

development varies, from the built-out Castle Pines to undeveloped land, with large lot residential, 

business parks, and several planned developments. The largest source of future development will 

be RidgeGate, in the City of Lone Tree, located generally east of I-25 and south of Lincoln 

Avenue. Melanie took a poll of meeting attendees; almost all were residents of Grandview Estates, 

with one resident of Meridian Commons and one representative for Arapahoe County property 

owners. 

Hydrology Update: Melanie explained that the first step in the master plan process is to update the 

hydrology based on current standards of practice and current development conditions and 

Happy Canyon Creek MDP & FHAD – Public Meeting – Meeting Minutes 

June 12, 2013 

 

 

 

projections. Melanie showed a peak flow chart for existing and future development conditions, 

and compared these with the current regulatory peak flow rates which were based on the Flood 

Hazard Area Delineation completed in 1977. The updated peak flows are notably higher. Melanie 

explained that while the updated hydrology reflects existing publically maintained detention 

ponds, UDFCD policy does not generally allow master plans to reflect detention that will be 

required with new development. In this case, however, in an effort to reduce the impact of the 

future RidgeGate development on the downstream peak flow rates, the plan sponsors are working 

with the developer to form an intergovernmental agreement (IGA) that will set the terms for 

detention improvements in RidgeGate so that they can be reflected in the future peak flow rates. 

Also, Muller is doing some additional analysis to further define the criteria to be established in the 

IGA in an effort to maximize the reduction in peak flow rates that will be seen from the 

RidgeGate detention ponds and therefore minimize the impact on the downstream communities. 

Alternative Development: Jim discussed Muller’s approach to the project, which emphasizes 

preserving the character of the watershed and reducing steam degradation in the future. The key 

phrase was “an ounce of prevention is worth a pound of cure.” A key area of focus is maintaining 

the delicate balance between water flow and sediment movement within the creek. To help with 

the water flow portion of this balance, the study will look at Full Spectrum Detention, which is a 

relatively new approach to detention that aims to capture the excess runoff from developed areas 

for all storm events, including the frequent, smaller storms that tend to cause significant damage to 

sandy creeks. For channel improvements, Jim stated that much of the channel is in relatively good 

condition, so the study will focus on preserving these undamaged channel reaches and making 

small repairs with limited disturbance with more significant channel improvements in localized 

unstable or limited capacity reaches. 

Problem Areas / Recommended Plan: Melanie went through the watershed noting problem areas 

and recommended improvements reach by reach. The upper watershed has two severely 

degrading reaches (at the north end of Castle Pines and along I-25), undersized crossings at Oak 

Hills Drive and Clydesdale Rd., and flooding concerns at a sanitary lift station in Castle Pines. 

The plan will also recommend retrofitting several existing detention ponds and a few new ponds. 

The middle portion of the watershed, dominated by the RidgeGate development, is currently used 

for cattle grazing. This poses a water quality concern as well as a stream stability concern; the plan 

recommends fencing to limit access. Andy then discussed flooding issues in Grandview Estates 

(see below) before Melanie continued with the lower watershed in Parker and Arapahoe County 

where the lack of vegetation is an issue from aesthetic and water quality perspectives. Peak flow 

diagrams for the 100-year and 2-year event were shown to illustrate the plan’s benefit in reducing 

flows nearer historic pre-development levels. 

Grandview Estates: Andy discussed floodplain issues identified in Grandview Estates. He noted 

that the regulatory floodplain (DFIRM) shows a number of properties already in the floodplain. 

Andy showed a draft floodplain delineation based on the hydrology update in progress; he stated 

that this floodplain would go through a second draft submittal before the final submittal. After the 

final submittal, he noted that the floodplain would still not be regulatory until submitted and 

reviewed by FEMA in a separate process. The draft floodplain delineation shows thirteen 

properties with one or more structures impacted by the floodplain. The regulatory and draft 

floodplain delineations both show overtopping of Dogwood Ave. Andy noted that the culverts at 

Dogwood Ave. are much smaller than is necessary to convey major storms. This causes a backup 

of water south of the road in a major storm, and the overtopping of the road causes flooding of 

several structures. The draft recommendation of the study is to remove the Dogwood Ave. 

crossing, which will eliminate the structure flooding at Dogwood. From a floodplain management 

perspective, removing the Dogwood crossing is the most cost effective alternative evaluated. 

Replacing the culverts with a bridge or very large box culverts was analyzed as a second 

1 

2 

Page A-24


June 12, 2013 


June 12, 2013 

alternative, but the initial cost of bridge or culvert construction outweighs the benefit of the flood 

hazard reduction. Andy noted that the channel north of Elm Ave. is poorly defined and 

significantly undersized for the major storm, causing flooding of structures along 5 th St. The draft 

study recommendation is to construct a 10-year capacity channel to convey more frequent storms. 

However, approximately seven homes would remain in the regulatory floodplain. A 100-year 

capacity channel was also evaluated, but the 100-year channel would be significantly deeper and 

wider than the 10-year alternate. The recommended alternative is a compromise between 

providing more conveyance for storm flows and respecting the integrity of the adjacent lots where 

the channel would be constructed. Andy noted that constructing a 10-year channel will 

dramatically reduce flooding impacts during smaller, more frequent storms. 

2. QUESTION AND ANSWER 

Following the presentation, Ken moderated a question and answer session. Unless noted, questions were 

answered by Ken, Jim, or Melanie. 

Q: A resident of Grandview Estates suggested adding more culverts under Dogwood to alleviate flooding 

concerns. Another resident suggested that a detention pond could be created upstream of Dogwood 

Ave. to attenuate the peak flows and reduce flooding damage. 

A: Ken stated that additional culverts would not be enough to convey the 100-year peak flood of around 

8,000 cfs. Melanie noted that a detention pond of sufficient size to attenuate the large peak flood would 

cover several blocks (dozens of homes). 

Q: A resident expressed concern that removing the Dogwood crossing would make it difficult for the fire 

department to respond to an emergency. The same resident noted that her house had been destroyed in 

a fire because water to fight the fire was not available. The resident noted that the development does 

not have fire hydrants. 

A: Steve Standridge, the Emergency Manager for the South Metro Fire District, was present at the meeting 

(standing in for Kevin Milan, the South Metro Fire Marshal). He stated that, all things being equal, the 

fire department always prefers two or more access points. However, whether Dogwood is removed or 

not, he assured residents that it would not significantly impact South Metro’s ability to respond to an 

emergency. 

Q: A resident noted that Dogwood Ave. was paved by the County to address issues with rutting because of 

the volume of traffic. He noted that people have been getting stuck on dirt roads throughout Grandview 

Estates during rainstorms and wondered if the fire department was aware if their equipment would get 

stuck as well. He complained that if Dogwood were removed, there would be less stable access during 

rainstorms. 

A: Steve (South Metro Fire District) commented that South Metro operates in many areas with 

unimproved road access, and that they currently serve several locations that have one way in and out. 

Since every rainstorm is different, South Metro has to evaluate their ability to use a dirt road during 

every storm and, in some cases, find alternate access. He noted that the recommendations of the study 

will need to go through an internal review at South Metro, taking numerous factors into account, before 

providing their official position on any changes in access. Jim noted that, in large storms, Dogwood 

may be unpassable in its current configuration due to overtopping. 

Q: A resident expressed concern that Douglas County had violated County criteria by paving and doing 

other repairs to the Dogwood crossing, since the crossing has limited capacity and is overtopped by a 

major drainageway. He suggested that the County should have replaced the crossing already because 

of this. 

A: Brad noted that Grandview Estates was platted in the 1950’s, before the County had established criteria 

for overtopping of road crossings. He noted that the criteria are enforced with new development, but 

that the County is not always able to bring older crossings up to current standards. 

Q: There was a general consensus amongst Grandview Estates residents that the loss of the Dogwood Ave. 

crossing would adversely impact their community. Many comments were received on this topic. The 

concerns were related to fire and other emergency vehicle access, traffic patterns & safety, access 

during rainstorms, and division of the community. The assembled residents voiced the sentiment that 

eliminating the flooding caused by Dogwood Ave. should be a County priority. The residents further 

voiced that the crossing should be replaced with a bridge to preserve access. Several residents thought 

that developers upstream should pay for these improvements. 

A: Ken stated that the Engineer’s recommended plan would not necessarily be the selected plan. He stated 

that the Urban Drainage and Flood Control District would work with Douglas County to select the 

conceptual design plan based on public comments as well as the Engineer’s recommended alternatives. 

He noted previous instances where public comment has overruled the Engineer’s recommendation. Jim 

stated that the Engineer’s recommendations focus on solving flooding problems in the most cost 

effective manner compared to the associated reduction in flood damages. UDFCD and the County will 

consider many other factors in selecting the conceptual plan for the watershed. 

Q: A resident speculated that the flooding problems north of Elm Ave. could be solved by excavating the 

channel bottom and adding riprap and grade control structures. The resident suggested that the project 

team look at a recent project for Sand Creek in Commerce City for guidance. The assembled residents 

generally supported constructing a 100-year channel north of Dogwood Ave. to solve all structure 

flooding problems. The residents suggested that the adjacent homeowners would grant drainage 

easements for the channel. 

A: Jim explained that the draft alternative analysis recommends the construction of a channel north of 

Dogwood Ave. The channel would include riprap bank protection and grade control (drop structures) to 

stabilize and armor the channel against future degradation. Melanie further clarified that a 100-year 

channel was evaluated, but the channel size would be quite significant, with a top width over 100 feet, 

and have a sizeable impact on the private properties on which the channel is located. The current 

recommendation is for a channel with capacity for the 10-year event, which will solve minor flooding 

issues with a substantially smaller channel cross section and less impact to the private properties. 

Q: A resident asked if the study had considered the impact of ACWWA’s (Arapahoe County Water and 

Wastewater) application to take water out of Happy Canyon Creek north of Grandview Estates (at 

Chambers Reservoir). 

A: Jim responded that we were not aware of this, but that we would follow up with ACWWA and 

incorporate any findings or recommendations in the final study. Potential impacts on Grandview 

Estates of any diversion downstream could include trapping of sediment, creating additional channel 

aggradation and backwater within the development; any diversion should be planned to allow free 

movement of sediment through the channel. 

Q: A resident had a concern about the recent project on the Grandview Tributary. In 2008, the County 

constructed roadside ditches and a 42-inch pipe along 4 th Street from Lincoln to Happy Canyon Creek 

just south of Dogwood Ave. The resident commented that prior to construction, the tributary flows 

running north along 4 th Street would then head west along Cottonwood Ave. to Happy Canyon Creek. 

The project impacted the grades at the intersection such that 4 th Street is now too high to allow the 

cross flow onto Cottonwood. With the additional flow continuing north on 4 th , it has caused new 

flooding issues for homes along 4 th Street. 

3 

4 

Page A-25


June 12, 2013 

A: Brad explained that the improvements are intended to provide 100-year capacity once the Grandview 

Pond is constructed just south of Lincoln in the Sierra Ridge development. At the time of construction, 

the pond plans had been approved and the County thought construction was imminent; unfortunately, 

the downturn in the economy delayed development and therefore delayed the pond construction. 

Currently, flows are diverted into the new 42-inch pipe until they overtop a weir wall around an 

existing 84-inch cross culvert under Lincoln Ave. Brad stated that the County will be providing some 

improvement in the interim by raising the weir wall around the old 84-inch culvert and sending more 

water into the new 42-inch culvert, reducing the undesirable surface flow along 4 th street. He noted that 

development is picking up again; Sierra Ridge is currently constructing a pond on the Stonegate 

Tributary to the east so they can begin developing in that area. Brad also noted that the County has 

worked with Sierra Ridge to detain significantly more than the required amount of runoff for their 

development in order to further attenuate flows from the 500 acre upstream watershed and provide the 

maximum reduction of flows through Grandview Estates. 

Q: A number of residents were concerned that the Plan might include a pedestrian/bike trail along Happy 

Canyon Creek through Grandview Estates. The residents voiced their opposition to a public trail along 

the Creek through their community. 

A: Melanie stated that the Plan does not recommend or even consider a public trail along the Creek 

through Grandview Estates. Ken clarified that permanent “flowage” easements would be required for 

UDFCD participation in the funding of improvements in order to allow future channel maintenance; 

however these easements would not grant access to the public. 

3. OTHER COMMENTS 

 

 

A resident complained that the County has allowed berms to be built along the channel which 

disrupt flood flows and create a hazard. 

A number of residents expressed a desire to include measures to further prevent public access to 

the Creek through Grandview Estates. 


Melanie noted the comments page and welcomed any additional comments on the MDP or FHAD. 

Meeting minutes are also available on the website. 


5 

Page A-26

Page A-27

From: 

To: 

Subject: 

Date: 

 

 

 

 

From: 

Kevin Milan 

To: 

Melanie D. Chenard 

Subject: Public Meeting - 6/12 

Date: 

Monday, June 03, 2013 3:07:38 PM 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ms. Chenard, 

Last month the fire chief & I were asked to attend a homeowners meeting in Grandview Estates. 

An area of concern for these citizens was the drainage project, which I believe you are holding an 

informational meeting for at the Parker Recreation Center. I am interested in attending since I 

believe the homeowners will be asking about emergency access. I’m not a fan of surprises, so I was 

1) wondering if you believe my attendance is appropriate and 2) curious if you and I could discuss 

so neither of us is put in the hot seat if I do attend. Please let me know your thoughts on this 

matter. 

Thank you, 

Kevin 

 

 

 

 

 

 

Disclaimer: This email message and all attachments are for the sole use of the 

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intended recipient, please contact the sender by reply e-mail and destroy all copies 

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transmission. If verification is required, please request a hard-copy version. 

Page A-28

From: 

To: 

Subject: 

Date: 

jfb85@hughes.net 


Comment from Happy Canyon Website 

Thursday, June 06, 2013 4:11:31 PM 

From: 

To: 

Subject: 

Date: 

jlshuford@msn.com 



Thursday, June 13, 2013 10:58:06 AM 

Name: Jon Bauer 

Company: 

Phone: 3037902609 

E-Mail: jfb85@hughes.net 

Comments: I won't be able to attend the public meeting, but wanted to provide the following for your 

consideration. Happy Canyon Creek flows through our property just north of Castle Pines. We've lived 

here almost 30 years and have seen a lot of change to the creek and its environs in that time. One of 

the biggest is the flow and accompanying vegetation growth. 25 years ago, Happy Canyon was a much 

"drier" creek - flow was not always continuous, a lot of it being subsurface (even including some 

pockets of "quicksand"). Today, due I suspect to more development and increased runoff, the flow 

here is continuous and year round. Much more vegetation has grown and the area has become a real 

magnet for wildlife - a good thing! But it has also meant one other important change. With the 

increased flow it eliminated the many pockets and pools of water that used to be in the creek and 

thereby significantly reduced the number of mosquitoes breeding there. Being down by the creek is 

much more pleasant today than it was a couple of decades ago. Point here being that I am concerned 

about any plan you might have that would reduce the current natural or normal flow of this creek. In 

our neighborhood (and elsewhere, I suspect)the creek also flows through parks and other areas where 

kids play and people walk their dogs, etc. We don't need any plan that would inadvertently support or 

encourage an increase in the mosquito (or other noxious bug) population. Please take that in to 

consideration - Thanks! 

Name: James Shuford 

Company: Grandview Estates 

Phone: 303-840-6207 

E-Mail: jlshuford@msn.com 

Comments: Hi Melanie, 

I attended the Happy Canyon Creek Major Dranageway Plan meeting on 06/12/13. We spoke briefly 

after the meeting. You had some screens that showed the 100 year flood plain as part of your 

presentation. It showed very distinctly my home at 12946 N. 4th Steet. It showed where my home 

would be in relation to the 100 year flood plain boundaries. I have been briefly reviewing your 

documents this morning and I can't find the pictures you shared last night, at least not to the level of 

detail I am looking for. I saw the pictures on pages, 34, 42, and 145 but I don't think they are same 

unless you had expanded the detail on them. Can you send me those pictures from the presentation last 

night so I can show my wife who was unable to attend the meeting? 

I will continue to review your project plans. Thanks for the information, I appreciate it. 

Jim Shuford 

Page A-29

From: 

To: 

Subject: 

Date: 

chb@bucknam.com 



Friday, June 14, 2013 6:02:58 PM 

From: 

To: 

Subject: 

Date: 

sdeuell@bw-legal.com 



Friday, June 14, 2013 8:18:30 PM 

Name: Charles H. Bucknam 

Company: Grandview Estates Homeowners Association 

Phone: 303-805-1690 

E-Mail: chb@bucknam.com 

Comments: At the meeting, it was obvious that Lincoln and Dogwood formed dams the way that the 

cross Happy Canyon Creek. The proposed removal of the bridge at Dogwood is unacceptable to the 

residents in Grandview Estates. We will loose one block of precious paved roadway for the benefit of 

about 1.5 blocks of residents, two blocks north will still be flooded every 100 years! We use the bridge 

every day. The proposal would benefit one day in a hundred years. Too high a cost for the benefit. At 

the last round of meetings to gain the easements we were told they would put in a box culvert bridge 

to solve the problem at Dogwood. It is tie for the County Commissioners to step up and put in the 

causeway that is needed at the Dogwood crossing. 

Thanks 

CHB 

Name: Don and Sharon Deuell 


Phone: 303 592-8331 (office) 

E-Mail: sdeuell@bw-legal.com 

Comments: We support retaining the Dogwood access - possibly box culverts in Grandview or adding 

rip/rap as suggested or another creek treatment/bridge as was done on Birch. We realize you are 

looking at the larger picture as it concerns Happy Canyon Creek, but found it disappointing that other 

options for the creek and Dogwood seemingly had to be dragged out at the meeting we attended on 

Wednesday. Your presentation made it appear there was only one option. There were some good 

suggestions from homeowners which we hope you considered with an open mind. In spite of the fact 

that this subdivision has been around since the 1950s, Grandview and its water is continuously being 

compromised by the newer Stonegates and Meridians of the world. We think our 200+ families are 

worth serious consideration of the reasonable and substantiated requests you heard at the meeting. By 

the way, the creek runs through one end of our two acre lot and we are aware of the lot erosion about 

which you spoke. Thank you. 

Page A-30

From: 

To: 

Subject: 

Date: 

catchcabo@aol.com 



Friday, June 14, 2013 10:13:52 PM 

From: 

To: 

Subject: 

Date: 

conniestoffel@msn.com 



Monday, June 24, 2013 11:35:53 AM 

Name: Frank and Roberta McLister 

Company: GrandView Estates 

Phone: 303-884-3669 

E-Mail: catchcabo@aol.com 

Comments: My wife, Roberta, and I live at 12985 N. 4th St. in Grandview Estates. I have lived in the 

old stone house there at the far north end of 4th St. since 1974. Bobbi joined me in 1983 and we have 

lived there since. Dogwood has always given us an option to go either east or west where 4th dead 

ends at Dogwood whether to visit neighbors or just enjoying our rural residential neighborhood...It is 

one of only two thru east - west streets in all of Grandview Estates - Birch is the other. We believe that 

the overload on Birch will cause serious problems as the traffic increases two - three fold. This is 

compounded by the fact that there is a one way bridge on Birch which the majority of drivers must 

navigate. Have you ever heard of the exression "don't fix it if it ain't broke? Lgic tells us that the 

necessary fix on widening the bridge on Birch would be wasted County money compared to the fix on 

Dogwood. 

Name: Connie Stoffel 

Company: Grand View Estates 

Phone: 720-842-1441 

E-Mail: conniestoffel@msn.com 

Comments: My concern is by closing this road to solve the problem of the cost of a bridge is the 

problems it would cause if it wasn't installed. Dogwood is the only paved road that goes all the way 

through the subdivision. It was paved due to difficulty in maintaining and high traffic flow. If closed 

residence will be driving through side streets that are not paved having to zigzag through the 

neighborhood to get to there respective homes. Are they then going to pave all of those streets. This 

also could potentially be dangerous to kids on the side streets. If Mag chloride is put down as a dust 

suppressant instead of paving the side streets it would be extremely slimy and slick when wet. There is 

unknowns about environmental impact on water and wildlife for the long term. It will cause vehicles to 

erode and when mag chloride breaks down it could come up with the dust and be in the air. Or there 

could be an adequate bridge. Connie Stoffel 

Thank you for your attention to this matter, 

Frank and Roberta McLister, 

12985 N. 4th St. 

Parker, CO. 

303 884-3669 

Page A-31

From: 

To: 

Subject: 

Date: 

jrico@oppenheimerfunds.com 



Wednesday, June 26, 2013 10:46:15 AM 

From: 

To: 

Subject: 

Date: 

kristin.rico@live.com 



Wednesday, June 26, 2013 10:44:07 AM 

Name: Jose A. Rico 

Company: Grand View Estates, Parker CO 

Phone: 773-620-7940 

E-Mail: jrico@oppenheimerfunds.com 

Comments: To Whom this may Concern: 

I'm writing to object and voice my concern regarding the closure of Dogwood Avenue located in Grand 

View Estates, Parker. 

As a homeowner in this community, I know firsthand how the closure of this central street would 

negatively impact our neighborhood. Dogwood Avenue is a main artery and would seriously threaten our 

vital emergency routes. It is concerning that our community was never consulted prior to this proposal. 

My house is located near Birch Street, thus meaning I would be significantly impacted by the closure of 

Dogwood as the traffic near my home would drastically increase! Not to mention create dust, delays 

and waste! 

This proposal, in my opinion, is careless as GVE residents consider Dogwood Avenue an imperative 

street in our community. 

Please consider replacing the bridge on Dogwood Avenue instead (paid for by Douglas county). 

Name: Kristin Rico 

Company: Grand View Estates- closure of Dogwood Ave 

Phone: 773.243.7286 

E-Mail: kristin.rico@live.com 

Comments: To Whom this may Concern: 

I'm writing to object and voice my concern regarding the closure of Dogwood Avenue located in Grand 

View Estates, Parker. 

As a homeowner in this community, I know firsthand how the closure of this central street would 

negatively impact our neighborhood. Dogwood Avenue is a main artery and would seriously threaten our 

vital emergency routes. It is concerning that our community was never consulted prior to this proposal. 

My house is located near Birch Street, thus meaning I would be significantly impacted by the closure of 

Dogwood as the traffic near my home would drastically increase! Not to mention create dust, delays 

and waste! 

This proposal, in my opinion, is careless as GVE residents consider Dogwood Avenue an imperative 

street in our community. 

Please consider replacing the bridge on Dogwood Avenue instead (paid for by Douglas county). 

I urge you to reconsider this proposal! 

I urge you to reconsider this proposal! 

Thank you for your time, 

Jose A. Rico 

Thank you for your time, 

Kristin Rico 

12303 Second Street 

Parker, CO 80134 

(773) 243-7286 

Page A-32

From: 

To: 

Subject: 

Date: 

mkhickman@msn.com 



Saturday, June 29, 2013 9:50:15 AM 

From: 

To: 

Subject: 

Date: 

rdjbsievers@hotmail.com 



Monday, July 08, 2013 8:38:32 AM 

Name: Karen M. Hickman 


Phone: 303-419-7179 

E-Mail: mkhickman@msn.com 

Comments: While the residents of Grandview Estates appreciate the extent of this project encompassing 

many subdivisions and municipalities in Douglas County, it is a little disconcerting that we were not 

asked to participate in this study since we would be directly affected by the closure of Dogwood Avenue 

as recommended by Muller Engineering. 

Dogwood Avenue is our main artery connecting both sides of Grandview Estates. Even the fire dept. 

has indicated that to close this road would be a threat to our safety in the event of a fire or other major 

emergency. 

Name: Debi Sievers 


Phone: 

E-Mail: rdjbsievers@hotmail.com 

Comments: I use the bridge on Dogwood, between 4th and 5th streets on a regular basis. It is one of 

my main entrance and exit routs in or out of this neighborhood. Traffic in this neighborhood is already 

limited due to the fact that you can only enter it on the South side, and the creek runs through it. 

Closing any of the streets in this neighborhood would create more of a risk should an emergency arise. 

If you need to repair the bridge than the repair work should be done, but the crossing should not be 

closed permanently. 

While many residents use the one lane Birch St. bridge to gain access to eastbound Lincoln Ave. via the 

light at 3rd St., they then use the 6th St. access via Dogwood Ave. to return to their homes. I can't 

imagine the additional traffic on the Birch St. bridge, if Dogwood Ave. were closed. 

In addition, mail delivery, trash pickup, Fed Ex/UPS deliveries, recreational access (foot traffic), etc. 

would all be sharing the same one-lane bridge off of 3rd and Birch St. with automobile traffic in order 

to gain access to the entire community. This is not acceptable and poses other risks. (Just an FYI. 

The Chaparral High School men's and women's track teams train in our neighborhood and regularly use 

Dogwood for access to and from their main training area on Elm St. I can't imagine them also having 

to use the Birch St. bridge.) 

I would think that prior to Mueller Engineering making their recommendation, they would have 

conducted some sort of traffic study within our subdivision. 

While many residents haven't yet had time to understand all of the issues involved, apparently one 

option is to leave Dogwood as is with the risk of a possible 100 year flood taking out the entire culvert. 

Another option would be to install a two-lane bridge on Dogwood Ave. While this would be the best 

option, I believe that the residents might be amiable to a one-lane bridge vs. total closure. However, I 

would think that a study would need to be done to determine whether lines of sight were adequate for 

safe passage - particularly at night. I know that a traffic light at 1st. St. and Lincoln wasn't approved 

due to the steep grade of eastbound Lincoln Ave. 

Thank you for your consideration of this issue for our community. 

Page A-33

From: 

To: 

Subject: 

Date: 

samstedman@me.com 



Friday, July 05, 2013 10:52:11 AM 

From: 

To: 

Subject: 

Date: 

lcbigbey@q.com 



Thursday, July 18, 2013 8:13:55 PM 

Name: Sandra Stedman 

Company: Grandview 

Phone: 303 840-3765 

E-Mail: samstedman@me.com 

Comments: I am strongly opposed to the option of closing Dogwood as part of the Happy Canyon 

Drainage Project. Grandview is already experiencing access challenges with various streets not allowing 

through traffic and with the elimination of the left turn into and out of 6th Street. Closure of Dogwood 

would cause a 50% decrease in east/west access, leaving Birch as the single east/west route. This is 

cause for serious concern, particularly with respect to emergency services. While I know emergency 

service providers would eventually reach the residents-in-need, it is inevitable that services to some 

parts of our community would be delayed due to the limited access. 

Name: Carol Bigbey 

Company: Grand View Estates 

Phone: 303-841-8328 

E-Mail: lcbigbey@q.com 

Comments: I am not pleased that you made a decision to close down the bridge on Dogwood. We use 

that street every time we come home from 6th st. It was very inconsiderate to make such a decision 

when we, at Grand View Estates didn't have knowledge that it was being voted on and the ones who 

did vote don't even live here. We pay plenty of taxes on projects that we don't use but yet when it 

comes to our place, we don't even get a say so. You people need to think this over again and let us 

folks have a say. The traffic uses Dogwood alot. As a matter of fact, I support a two lane bridge, not 

like the single lane on Birch. That will be large impact on that bridge. We deserve to have some 

consideration in keeping and updating our bridge. 

Page A-34

From: 

To: 

Subject: 

Date: 

doniley@ileycpa.com 



Thursday, July 18, 2013 8:56:53 PM 

From: 

To: 

Subject: 

Date: 

colohills@msn.com 



Friday, July 19, 2013 3:19:04 PM 

Name: Don & Mary Iley 

Company: 

Phone: 

E-Mail: doniley@ileycpa.com 

Comments: We are residents of Grandview Estates and oppose the engineers' recommendation to close 

Dogwood Avenue. Instead, we support the Grandview Estates Homeowners Association's preferred 

option for flood control, which is replacing the Dogwood Avenue crossing with a proper two-lane bridge 

that spans the required gulch. We are extremely concerned about the disruption of daily traffic patterns 

and emergency vehicle response times with the proposed option of closing Dogwood. We are 

particularly concerned with the necessary increased traffic on Birch as a result of any closure of 

Dogwood, given our proximity to Birch and that it is our ONLY egress from our home. (Our home is on a 

dead-end street.). The single-lane bridge on Birch is hardly adequate for all the increased traffic. Our 

neighborhood has been here a VERY LONG time and had NO INPUT in this decision. THIS IS HARDLY 

FAIR. 

Name: Frank Hill 


Phone: 303-841-4559 

E-Mail: colohills@msn.com 

Comments: I wish to express my concern to the proposal made by Brad Robenstein of Douglas County 

Public Works to close Dogwood Avenue in Grandview Estates. As a resident of Grandview who lives in 

the northwest quadrant of the development this closure puts me at greater risk for emergency 

assistance response from the fire station located at Lincoln Ave. and S. Peoria St. 

I would add it is unconscionable that the very community this proposal adversely impacts was not 

invited or provided the opportunity to give input to this proposal! 

Frank Hill 

3772 E Elm Ave 

Parker, CO 80314 

(Grandview Estates) 

Page A-35

From: 

To: 

Subject: 

Date: 

whitemary44@yahoo.com 



Friday, July 19, 2013 1:58:11 PM 

From: 

To: 

Subject: 

Date: 

lbmcjs@msn.com 



Saturday, July 20, 2013 8:28:42 AM 

Name: mary f white 

Company: grandview estates 

Phone: 3038413882 

E-Mail: whitemary44@yahoo.com 

Comments: I live on the corner of 3rd and dogwood. I would have to go back north out of the way to 

get out of the neighborhood. I have lived here since Jun of 1970 and was not was not allowed to give 

input when this was proposed. this has been a main artery since I have lived here. I have lived here for 

43 years and this will threaten my lively hood. emergency and fire routes are threatened. build a bridge 

for the drainage problem. 

Name: Lorren Smith 


Phone: 

E-Mail: lbmcjs@msn.com 

Comments: I am disturbed by the recommnendation of closing Dogwood ave. in Grandview Estates 

given that no one was afforded the opportunity for input on this decision. I am certain there are other 

improvements that need to be made in this project and wonder if the fact that Grandview has been in 

existence far longer than the city of Lonetree and the city af Parker has expanded to our border in 

recent years. Should not the oldest of communities involved be granted the right to have required 

"fixes" and not just shut down because of an "poor design" decision which was made fifty or sixty years 

ago? 

I am asking you to please reconsider this decision and help those who live in one of the oldest 

subdivisions in Douglas County. 

Page A-36

From: 

To: 

Subject: 

Date: 

heritagelawn@centurylink.net 



Monday, July 22, 2013 12:56:45 PM 

Name: Cameron Brown 


Phone: 

E-Mail: heritagelawn@centurylink.net 

Comments: I completely oppose the road closure of Dogwood. It is one of two roads that go all the 

way through our neighboorhood from east to west. We really need to keep it open for the people in 

this area for any and all driving purposes including emergency vehicles. I believe a two lane bridge is 

an option and I would strongly agree with that. We need to keep Dogwood open for a number of 

reasons!!! 

Page A-37

TO: 

Study Sponsors and Stakeholders 

M E M O R A N D U M 

FROM: Shea Thomas, P.E. 

Senior Project Engineer, Master Planning Program 

SUBJECT: 

FAA Guidelines 

DATE: June 19, 2013 

In Advisory Circular 150/5200-33, the Federal Aviation Administration (FAA) recommends that 

wildlife-attracting uses be located 10,000 feet beyond the end of airport runways. While the 

types of wildlife-attracting uses are not specified, examples of incompatible land uses include 

putrescible-waste disposal operations, wastewater treatment facilities, artificial marshes, 

wastewater discharge and sludge disposal, and wetland mitigation that provides habitat for 

hazardous wildlife (particularly waterfowl). Also noted are some land uses that may be 

compatible with safe airport operations provided they are designed appropriately, including 

water detention or retention facilities. Further guidance for detention facilities specifies the 

following design recommendations: 

 

 

 

 

 

 

 

Minimize the surface area of standing water. 

Increase the depth of the facility and make it more linear to achieve capacity without 

increasing surface area. 

If a two-chambered design is necessary, there should be at least a ½-1 percent gradient 

from the upper to lower pond, making sure that the outlet/control structure is at the 

absolute lowest point. 

Place riprap or quarry spalls on the side and bottom of the ponds (similar to a French 

drain) to prevent waterfowl from feeding on emergent vegetation. 

If vegetation is required for water treatment, a uniform mix of forest or shrub/scrub 

vegetation should be established at a density such that areas of standing water are 

eliminated or minimized by the vegetative canopy. 

If an erosion mix is needed, use a vegetative mix that is not an attractive food source for 

waterfowl or other flocking birds (i.e., one that does not include high quantities of millet 

or clover). 

Netting or overhead wires can be used for short-term construction projects such as 

sediment catch basins, but waterfowl and birds can still see the open water and may come 

to investigate the area. This also creates a maintenance issue. 

The Urban Drainage and Flood Control District recognizes the concern of the FAA regarding 

waterfowl habitat and complies with the distance requirements and also the maximum 48-hour 

detention period in most cases. 

Happy Canyon Creek currently shows extensive signs of degradation in the upper reaches of the 

watershed. With plenty of development left to occur in the majority of the watershed, more 

frequent stormwater runoff will exacerbate the problem. Therefore, Full Spectrum Detention, 

which controls the release from a detention pond to closely mimic the pre-development release 

rates for a wide spectrum of storm events, is crucial for the entire watershed. Like a typical water 

quality extended detention pond, a Full Spectrum Detention pond drains the water quality 

capture volume in 40 hours. The maximum detention period for a Full Spectrum Detention pond 

is longer since it releases a volume roughly equivalent to the 2-year event in 72 hours. However, 

this additional detention time and volume would not happen with a frequency sufficient to attract 

waterfowl. 

There are currently 12 existing regional detention ponds in the watershed. The Happy Canyon 

Creek Major Drainageway Plan recommends retrofitting 6 of the existing ponds with an outlet 

structure that will release detained water at the Full Spectrum Detention rates. The plan also calls 

for an additional 9 Full Spectrum Detention ponds to be constructed as development occurs. Two 

of these ponds (Airport 320 Pond and Ridgegate Pond 2) are located within the 10,000 foot 

radius from the end of the Centennial Airport southern runway. 

Due to the importance of watershed-wide full spectrum detention, UDFCD is waiving the FAA 

guidelines for the two ponds due to the fact that there are multiple existing facilities within the 

10,000 foot radius that are a much more likely source for waterfowl habitat. Meridian Reservoir 

and Inverness Reservoir are large water bodies with a significant permanent water surface area. 

Meridian Golf Course and Inverness Golf Course contain smaller permanent water features. 

There are also numerous small on-site detention basins similar to the ones proposed in the master 

plan with an extended detention feature to provide water quality. The ponds will be designed to 

drain in no more than 72 hours and will follow the design recommendations listed above. 

1 | P age 

2 | P age 

Page A-38

3 | P age 

Page A-39

DRAFT ALTERNATIVE ANALYSIS COMMENTS 

Draft alternative analysis was submitted to the project sponsors on March 1, 2013 for review. 

Comments were received on March 27, 2013 in the form of an annotated PDF copy of the report. 

Additional comments were provided by CCBWQA on April 9, 2013. Select comments have been 

reproduced or paraphrased below; responses are italicized. Comments/corrections not requiring 

additional clarification were addressed in the revision but are not listed here. 

Urban Drainage and Flood Control District (UDFCD) Comments: 

Section 5.6.2 “Costs for this reach include excavation required to lower the embankment at CPNMD 

Reach 1 Pond #12 to provide overtopping capacity without flooding the adjacent sanitary lift 

station.” Weren't these costs already included in the detention alternative? 

We considered where to include this cost and determined that it is best reflected in the 

channel costs rather than the detention costs. Though this work is related to a detention 

facility, it is not a detention improvement as it results in reduced storage capacity. 

Instead, we consider it a channel improvement that addresses a flooding issue. Once we 

move on to conceptual design of the selected plan, there will not be a desire to 

differentiate between the channel alternatives and detention alternatives, and we may 

reevaluate how we present these costs. 

Douglas County Comments: 

Section 5.6.1 “Meridian Village includes 319 acres tributary to the Grandview Pond; detention for 

most of this area will be provided in private onsite facilities, with two small publically 

owned facilities providing a combined 100-year volume of 5.5 acre-feet.” Grandview 

Pond design was based on assumption that Meridian ponds would be metro district 

maintained. Douglas County to investigate. 

Additional information was provided on two proposed detention ponds in Meridian’s 

Stepping Stone development. These ponds have sufficient contributing area and capacity 

to warrant including in the master plan and will be maintained by the Meridian Metro 

District. Subwatershed boundaries and land use have been revised to better reflect the 

proposed development, and the ponds have been incorporated into the model. Because the 

ponds are currently under construction, they have been reflected in the baseline 

hydrology. With these additions, the Grandview Pond release now corresponds with the 

design flow rate for the downstream improvements. 

(re: Charter Oaks pond) There are a couple of existing on-site ponds just upstream that 

could potentially be converted to Full Spectrum ponds. Would CPNMD consider taking 

those over? Do the benefits of all the additional detention on this tributary exceed the 

costs to implement the detention? 

Plans for the existing pond adjacent to the Montessori school were provided and reviewed. 

The existing pond reflects minimal downstream benefit when added to the SWMM model 

(though the model’s basins do not correspond with the pond’s contributing area). We had 

planned to abandon the idea of a pond at this location, but were then made aware of 

downstream flooding and crossing capacity concerns on the Beverly Hills Tributary. To aid 

in these situations, the existing pond could potentially be connected with the low area to 

the west of the Montessori school under construction; the school site will include an offsite 

pond adjacent to the road, which could form the center of the “U” shaped pond. Though 

such a facility would provide some benefit to Happy Canyon Creek, the benefit would 

mostly be recognized on the Beverly Hills Tributary channel. Because conveyance and 

floodplain improvements on the tributary are not a part of this scope, we have not 

associated a channel cost savings with these improvements, though initial analysis 

indicates that the planned culvert replacement at Oakwood Lane may not be necessary. 

Section 5.6.2 Do these costs reflect that the lower portion of Reach 2b has been stabilized by Douglas 

Reach 2b County and the UDFCD or are the typical costs applied to the entire reach length? 

Drop structure costs are based on the number of vertical feet of drop needed based on 

upstream and downstream invert elevations, a design slope, and the total vertical feet of 

existing drop structures. Other improvement items such as riprap and earthwork are 

applied along the entire reach based on average cross sectional dimensions. These 

assumptions can be refined for the conceptual design if appropriate/desired. 

Figure 5-1 

(re:Reach 3) Is Alternative D2 adequate considering the close proximity of I-25 and the 

need for that bank to remain very stable? 

The improvements assumed for Alternative D2 are still quite substantial, representing 

85% of the D1 costs; we feel the per linear foot costs are appropriate for a reach of this 

nature. This alternative is intended to be paired with the recommended detention 

improvements upstream; if the timing of such improvements would significantly lag 

channel improvements, Alternative D1 may be needed to provide additional protection in 

the near term. 

Town of Parker Comments 

Section 5.6 

Some clarification is requested regarding the E-470 Detention Pond…..The Town 

requests revising the language in the document related to modification of the E-470 

Detention Pond (Compark South). 

The report and models have been revised to reflect a single proposed configuration for the 

E-470 pond, with sizing based on the upstream contributing area within Compark South 

and Grandview Estates. The resulting volume for Alternative C decreases slightly due to 

the addition of the Airport 320 pond (the higher volume was used for cost estimating). 

Page A-40

Southeast Metro Stormwater Authority (SEMSWA) Comments 

Section 4.1 

Section 5.3 

Table 5-1 

Figure 5-2 

Figure 5-3 

(re: Happy Canyon regional trail crossing) Where is this? 

As stated in the text, the crossing is located near the confluence with Cherry Creek. 

Existing trails have been added to Figures C-2 through C-4. 

(re: Alternative F2) It would be good to know how much floodplain fringe area would 

still be needed for the 100-year event for this alternative. 

A recommended plan floodplain has been added to the recommended plan figures; this 

floodplain reflects the reduced peak flows that result from Detention Alternative A. While 

we did not delineate the floodplain under every scenario, we did evaluate the structure 

flooding under a variety of scenarios to present additional information on the benefit 

associated with each contributing factor. 

“Stable Channel Alternative S4: Partial implementation of SE based on wait-and-see 

approach” We think this is an interesting concept and an interesting way to budget for 

it. Any thoughts on how this could be facilitated in practice? 

This approach would require regular monitoring of the stream condition and the ability to 

react fairly quickly when problem areas develop. Additional discussion will be provided in 

the conceptual design report if this approach is chosen for the selected plan. 

(re: Meridian Reservoir) The gray color for a pond isn't listed in the legend. Isn't this a 

proposed pond? or was your intent to label it differently - like approved future pond or 

something like that. Same with Chambers Reservoir? 

The Meridian Reservoir is not intentionally shaded gray; this is merely the coloring of the 

permanent water surface in the aerial photo. The Chambers Reservoir was intentionally 

shaded gray to produce a similar look, as it is not yet filled and is therefore not visible in 

the aerial photo. The gray color is not added to the legend as there are also existing stock 

ponds that exhibit a similar look but are not part of the alternative analysis. 

Did you consider if making the Ladera Pond a regional facility would be beneficial? It is 

currently a sub-regional pond (serves more than one property) and it accepts "public" 

flows from roadway drainage. 

The tributary area to the Ladera Pond is approximately 45 acres, which is well below the 

130 acres generally required to define a regional facility. Because it is offline and at the 

bottom of the watershed, it would not provide any beneficial impact to peak flow rates 

within the channel if incorporated into the hydrologic model. As a result, this pond is not a 

good candidate for a regional pond. Retrofit improvements have been added at SEMSWA’s 

request. 

Did you consider if making the JWPP pond a regional facility would be beneficial? It is 

currently a sub-regional pond (serves more than one property) and it accepts "public" 

flows from roadway drainage. 

The tributary area to the JWPP Pond is approximately 10 acres, and the volume is less 

than 1 acre-foot. As with the Ladera Pond, it is not a good candidate for a regional pond 

due to the small size and location in the watershed. Retrofit improvements have been 

added at SEMSWA’s request. 

Section 5.6.2 “Oak Hills Drive requires a triple 18’ x 6’ box culvert to pass the 100-year event; this 

Reach 2b size was not recognized by UD-MP Cost, so the cost was calculated based on a 9’ x 6’ 

culvert with six cells.” Is this appropriate? 

Though 18’x6’ is not a common box culvert size, it is a constructible size. There is not 

sufficient clearance to increase the rise, allowing a common size. Since the cost as shown 

cannot be calculated with UD-MP Cost, the closest approximation possible was made. The 

resultant cost will reflect some excess concrete for the additional center walls; for the 

conceptual level of this study, the difference is not significant. 

Section 5.6.2 Did you evaluate how much reduction in capacity there is due to aggradation at this 

Reach 9 time? 

We did not evaluate the capacity reduction as there are no significant floodplain concerns 

in this reach. 

Figure 5-6 

Section 6.1 

Table 6-2 

A crossing of the Green Acres Tributary may also be necessary with development. 

Tributary improvements are not included in this plan, with the exception of some 

degradation on tributaries immediately adjacent to the main stem. 

Can you please include the existing and proposed trail with a typical x-section in the 

conceptual design report figures? 

The existing and proposed trails will be shown in plan view and a typical cross section will 

be included for the conceptual design. 

(re: cattle fencing) SEMSWA thanks you for including this in the plan. We have need for 

this all over Dove Valley! 

Per the discussion at the comment review meeting, fencing has been added to the cost 

estimate for Reach 9. 

Where is the cost for the low flow channel? 

The cost is incorporated into the channel improvement costs for each of the stable channel 

alternatives in this reach. Table F-6 indicates the earthwork quantities assumed, which 

include the low-flow channel. We can provide a more detailed breakdown in the 

conceptual design report. 

Page A-41

Arapahoe County Comments 

Section 5.3.1 Will typical sections be provided for the channel alternatives? 

Typical sections are not provided for the alternative analysis, but will be included in the 

conceptual design. 

Section 6.1 

Figure 6-3 

Has this coordinated funding plan been executed on other projects? How is this done? 

If this is the recommendation, it would seem that the apportioned costs would need to 

be identified in this study for the downstream jurisdictions for planning, budgeting, etc. 

This concept warrants further discussion. 

To our knowledge, this approach has not yet been taken on other projects. Additional 

discussion of how this could be implemented can be provided in the conceptual design 

report if the project sponsors would like to pursue this approach. 

Regional detention (FSD) is not proposed within Arapahoe County. The Dove Valley 

Business Park is largely undeveloped. With this plan, Dove Valley will not need to 

provide any detention with development - is this correct? A sub-regional detention 

pond was identified in the Dove Valley Master Development Plan that would serve a 

portion of the Business Park. It is understood that the sub-regional pond cannot be 

included in this study, but is it assumed that the sub-regional facility will still be 

provided with development? If Dove Valley does not need to provide any detention with 

development, is there a minimum level of regional detention that needs to be in place 

upstream before Dove Valley can develop without detention? 

The draft plan assumed Dove Valley would provide onsite detention as reflected in their 

master drainage plan. A regional facility has now been added; the proposed facility is not 

a true regional FSD facility as it is not sized for the entire upstream watershed; however, 

100-year peak flows are not a concern downstream of this facility so we think the 

proposed facility could satisfy Dove Valley’s detention requirements if Arapahoe County / 

SEMSWA are satisfied as well. 

SEMSWA may already know/have the answer to this, but how would system 

development fees be established for the timed, incremental approach to the channel 

improvements? If budgeting (and assessing?) is based on the ultimate improvements, 

and improvements are implemented on the wait and see approach with the potential 

that less than ultimate is all that is necessary, how will the fees reconciled? 

This will be a good topic of discussion for the project sponsors; additional discussion can 

be included in the conceptual design report. 

Table F-2 

A 10’ wide x 2’ deep channel was assumed along the entire reach for cost estimating 

purposes; this can be refined in the conceptual design report if excavation through Dove 

Valley is not needed/desired. 

Was regional detention (FSD) considered as an alternative in Arapahoe County 

upstream of S Jordan Road? 

Initially, detention in this area was considered but not developed as an alternative for 

several reasons: 

• A regional facility is ideally sized for all contributing area below the next upstream 

facility; there is no regional detention for Compark downstream of E-470, so a 

regional FSD facility in Arapahoe County would be quite large (>70 af). 

• Master drainage plans are in place for Compark and Dove Valley and reflect onsite 

or multi-lot ponds; it was assumed that this was the developers’ preference. 

• There is no existing embankment that facilitates the construction of a large pond 

(Jordan Road could not be used due to the confluence with Happy Canyon Creek 

and the desire to avoid online detention on Happy Canyon). 

• There are no floodplain concerns downstream that would benefit from reduced 

100-year peak flows. 

However, as a result of the comments provided herein and discussions with DAB 

Engineering, representing the Dove Valley Business Park, an online regional facility has 

been shown within the Park. See the revised report text for a discussion of sizing. 

Section 5.6.2 Do the costs include recommended improvements to the existing trail crossing within 

Reach 9 Reach 9? 

There are no recommended improvements to the existing trail crossing. The crossing has 

2-year capacity, which is assumed sufficient for a crossing of this nature. 

Figure C-4 

Will the Green Acres floodplain mapping be extended upstream of the Arapahoe- 

Douglas County line, or is this the upstream limit? 

Muller modeled this portion of the Green Acres floodplain in order to determine if there 

was spill flow from Happy Canyon. As there is not, Muller had intended to trim this portion 

of the mapping; however, because there is currently a gap in the floodplain delineation 

along the Green Acres Tributary in Arapahoe County, at the request of the sponsors the 

floodplain will be extended to tie in to the floodplain in Douglas County. Muller would like 

to note that the Arapahoe County floodplain will be based on the current hydrology, which 

will differ from the Douglas County floodplain. Additional information will be provided in 

the FHAD report. 

For clarification, is the low flow channel excavation recommended for the entire reach, 

or just through Southcreek? 

Page A-42

Rampart Range Metro District (RRMD) Comments 

Section 5.6 

The full spectrum detention ponds in Lone Tree appear to make sense in principal. 

However, the ponds and sizing calculations do not appear in the SWMM model or the 

report, respectively, since the report covers the Existing and Future conditions only. 

The RRMD would like to review the pond sizing information. 

The pond layout has been revised for the resubmittal, and now reflects offline EURV ponds 

and online 100-year peak shaving ponds. The offline EURV ponds were sized using the UD- 

Detention spreadsheet based on the contributing area and % impervious for each pond, 

with the model reflecting spillways at the top of the EURV to allow larger storms to bypass 

the ponds without 100-year detention. The 100-year ponds are controlled by a large 

culvert opening, with the size determined by trial and error to produce the desired release 

rate and/or ponding depth. Muller will provide RRMD with the spreadsheets utilized in the 

alternatives development for review. Stage-storage and stage-discharge curves for 

proposed ponds will generally be provided in the conceptual design, though it may be to 

RRMD’s benefit to exclude specific details on ponds in RidgeGate in favor of more general 

development guidelines to allow maximum flexibility. 

Section 5.3 

Section 5.5 

Appendix D 

Because Chambers Reservoir is a water supply facility, getting a long term commitment 

to "limit storage" might be challenging. as they will want to maximize storage without 

concern for flood events. 

Both the Chambers Reservoir and Meridian Reservoir were further evaluated to identify 

the specific benefit of recognizing detention volume within each on the watershed 

downstream. Due to limited benefit, this is no longer included in the recommended plan. 

We are finding that these projects are highly specialized and costing closer to 40% of 

Capital 

The cost allowances are the standard values to be used in master plan cost estimating. 

While these may be low, some of the other standard costs may be conservatively high: for 

example, all drop structures are represented as grouted boulder though the preference is 

for “softer” (and less costly) drops through much of the study area. Cost estimating 

practices are set by UDFCD to provide consistency between master plans. 

Why is a 1998 legal opinion included? 

This is the standard legal opinion that is included in every UDFCD master plan. 

The RRMD would recommend looking at the possibility of accounting for the City of 

Lone Tree required full spectrum detention in the Future model as it could impact the 

downstream floodplain and structure replacement requirements. 

The concept of an inter-governmental agreement (IGA) to allow future detention within 

the RidgeGate development in Lone Tree to be reflected in the FHAD flow rates was 

pursued with the revisions to this report. The benefit would be limited, however, as the 

difference between the existing and future conditions peak flow rates downstream of 

RidgeGate is approximately 600 cfs, which is less than 10% of the future peak. This 

translates to an average reduction in BFEs of 0.2’ at downstream flooded structures, and 

would at best avoid inclusion of two structures in the floodplain. The project sponsors 

opted not to further pursue an IGA with RRMD. 

4/9/2013 Comment Letter - Sediment Transport section: 

The concepts discussed in the MDP relative to sediment movement are based on thorough 

observation of channel equilibrium, degradation, aggradation, and bank erosion, along 

with the application of geomorphic principles. We feel this type of qualitative evaluation is 

appropriate for this level of planning. However, we are supportive of using quantitative 

analyses to confirm and refine concepts as the MDP moves into implementation. 

Cherry Creek Basin Water Quality Authority (CCBWQA) Comments 

Section 2.1 

Section 2.3 

List of abbreviations? 

PDD is defined as Planned Development District in Section 1.2. A list of abbreviations has 

not been added at this time but will be considered for the final MDP. 

Because the problems are not totally consistent with the reach limits, perhaps Figures 

B-1 and B-2 could be annotated. 

Problem areas are identified in Figures C-2 through C-4. 

Page A-43

FINAL ALTERNATIVE ANALYSIS COMMENTS 

Final alternative analysis was submitted to the project sponsors on August 5, 2013 for review. 

Additional comments were received on August 21, 2013 in the form of an annotated PDF copy of the 

report. Select comments have been reproduced or paraphrased below; responses are italicized. 

Comments/corrections not requiring additional clarification were addressed in the revision but are 

not listed here. 

City of Lone Tree Comments 

Table 5-25 Should there be one additional OPTION shown for each of the two categories - e.g. - 10- 

Yr Channel (Alt. F2, without Dogwood Crossing Removed???? 

At the direction of Douglas County, only two options were considered for Dogwood: 

removal and replacement with a bridge, and removal and closure of the road. 

Hydraulically, the two options are the same, as both remove the existing Dogwood 

crossing from the 100-year floodplain. The structure flooding depths indicated with 

Dogwood removed, therefore, represent both Dogwood options. 

Southeast Metro Stormwater Authority (SEMSWA) Comments 

Figure 6-1 

Why no proposed maintenance trail for Reaches 1B through 3, Beverly Hills Trib or Oak 

Hills Trib? 

Reaches 2A through 3 are private property, so we did not include a permanent access trail. 

Access along tributaries is outside the scope of this study. A trail in Reach 1B will be added 

during conceptual design. 

Figures 6-2,3 Why no proposed maintenance trail on Badger Gulch? Why no proposed maintenance 

trail on Green Acres Trib? Is there any need for us to plan for a crossing here? (on Green 

Acres Trib) 

Access along tributaries is outside the scope of this study, as are crossings on tributaries. 

Arapahoe County Comments 

Figure 6-2 

(re: Dove Valley Pond) In light of [recent] discussion …at the Sand Creek MDP progress 

meeting. Will the WQ Pond remain in the Recommended Plan, with the understanding 

that UDFCD will not participate in this improvement? Or, is it appropriate to keep this 

improvement in the Recommended Plan, so that SEMSWA could design and construct 

this facility as part of the MDP? 

Per UDFCD, since the pond will not provide any flood control, it is outside the scope of a 

UDFCD flood control master plan. Therefore, it will not be modeled in the final plan and no 

conceptual design will be provided. It will, however, be shown in the plan along with the 

other ponds SEMSWA previously requested be added (Ladera and JWPP). 

Additional discussion should be included in the report to indicate that areas not 

tributary to this regional water quality facility will still need to provide on-site WQCV 

with development, unless additional regional or sub-regional WQ is planned to serve 

these areas. 

This statement applies to numerous areas to be developed within the watershed; we plan 

to cover this topic in the conceptual design section, along with supplemental treatment for 

areas that are tributary to regional water quality facilities, as required by local criteria 

(i.e. 20/10 rule). 

Please include a separate water quality facility that would serve development within 

the Town of Parker. 

The Town of Parker has not indicated a desire for an online regional water quality facility; 

existing master drainage plans call for on-site detention. We will plan on including some 

discussion of detention in the area and its impact on the sizing of the downstream Dove 

Valley pond at the next progress meeting, for the conceptual design report. 

Rampart Range Metro District (RRMD) Comments 

We have concerns with Alternative C (the recommend alternative) which suggests that RidgeGate 

should incorporate additional on-channel “Peak Shaving Ponds”, and increase the size of the proposed 

on-channel ponds, for the purpose of reducing runoff from upstream development in order to get 

back to historic runoff levels. Specifically, we have the following concerns:urpose of reducing runoff 

from upstream development in order to get back to historic runoff levels. Specifically, we have the 

following concerns: 

a. For ponds HC522, HC525, and BG511, it is unknown at this time if the additional detention could 

remain in designated open space or if it would encroach into areas identified on the RidgeGate PDD as 

developable land, thus reducing the available developable land. 

b. Pond HC519 is proposed for the sole purpose of providing on-channel detention to account for 

undetained runoff from upstream development. While the pond appears to be located in open space 

as designated by the RidgeGate PPD, the open space is part of the Schweiger Ranch. The pond as 

depicted on Figure 5-2 in the report, appears to encroach into the Ranch property creating a 

floodplain on a historic landmark protected by Douglas County. 

c. The cost for an additional on-channel pond (HC519) and the costs to increase the size of the 

other ponds (HC522, HC525, and BG511) may not be eligible for RRMD funding since the costs are not 

related to the RidgeGate development, but rather, impacts from upstream development. That being 

said, the additional costs may be off-set by the potential savings mentioned in the report from limiting 

the channel improvements if the Alternative C ponds are in place, but this is yet to be determined. 

The locations and configurations of ponds are flexible, and can be altered to avoid impact on developable 

land or on the Schweiger Ranch property. Language was added to the report regarding potential costsharing 

for the additional detention provided in Alternative C.



APPENDIX B 

HYDROLOGIC ANALYSIS

NAME: P:\12-010.01 Happy Canyon Creek MDP & FHAD UDFCD\CAD\12010-HYDROLOGY MAPS.dwg DATE: JUL 19, 2013 TIME: 9:48 AM 

. 

. 

No. 

DATE 

REVISIONS 

APPR. 


777 SOUTH WADSWORTH BLVD. 4-100 

LAKEWOOD, COLORADO 

80226 (303) 988-4939 

DESIGN 

DRAWN 

CHECK 

MDC 

JHK 

JTW 

HAPPY CANYON CREEK 

MAJOR DRAINAGEWAY PLAN 

INTERACTIVE HYDROLOGY MAP 

BASELINE SUBWATERSHED EXISTING HYDROLOGY FUTURE SOIL STUDY SURVEY LAND AREA BOUNDARIES 

SWMM USE 

ROUTING 

DATE 

JULY 2013 

FIGURE NO. 

B-1

. 

. 

NAME: P:\12-010.01 Happy Canyon Creek MDP & FHAD UDFCD\CAD\12010-HYDROLOGY MAPS.dwg DATE: JUL 19, 2013 TIME: 9:48 AM 

No. 

DATE 

REVISIONS 

APPR. 


777 SOUTH WADSWORTH BLVD. 4-100 

LAKEWOOD, COLORADO 

80226 (303) 988-4939 

DESIGN 

DRAWN 

CHECK 

MDC 

JHK 

JTW 


MAJOR DRAINAGEWAY PLAN 

INTERACTIVE HYDROLOGY MAP 

BASELINE SUBWATERSHED EXISTING HYDROLOGY FUTURE SOIL STUDY SURVEY LAND AREA BOUNDARIES 

SWMM USE 

ROUTING 

DATE 

JULY 2013 

FIGURE NO. 

B-2



Table B-1 

Rainfall Distributions 

3-Hour Design Storm 

2-Hour Design Storm 

Time Rainfall Depth (in) Rainfall Depth (in) 

(Hr:Min) 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 

0:05 0.0185 0.0273 0.0318 0.0251 0.0289 0.0252 0.0190 0.0280 0.0326 0.0257 0.0296 0.0258 

0:10 0.0371 0.0505 0.0588 0.0676 0.0778 0.0755 0.0380 0.0518 0.0603 0.0693 0.0798 0.0774 

0:15 0.0768 0.1188 0.1303 0.0965 0.1112 0.1157 0.0798 0.1218 0.1337 0.0990 0.1140 0.1187 

0:20 0.1462 0.2088 0.2384 0.1544 0.1778 0.2012 0.1520 0.2142 0.2445 0.1584 0.1824 0.2064 

0:25 0.2284 0.3413 0.3973 0.2896 0.3335 0.3522 0.2375 0.3500 0.4075 0.2970 0.3420 0.3612 

0:30 0.1279 0.1775 0.1907 0.4826 0.5558 0.6289 0.1330 0.1820 0.1956 0.4950 0.5700 0.6450 

0:35 0.0576 0.0792 0.0890 0.2317 0.2668 0.3522 0.0599 0.0812 0.0913 0.2376 0.2736 0.3612 

0:40 0.0463 0.0601 0.0683 0.1544 0.1778 0.2012 0.0475 0.0616 0.0701 0.1584 0.1824 0.2064 

0:45 0.0278 0.0491 0.0604 0.0965 0.1112 0.1560 0.0285 0.0504 0.0619 0.0990 0.1140 0.1600 

0:50 0.0278 0.0491 0.0509 0.0965 0.1112 0.1258 0.0285 0.0504 0.0522 0.0990 0.1140 0.1290 

0:55 0.0278 0.0410 0.0509 0.0618 0.0711 0.1006 0.0285 0.0420 0.0522 0.0634 0.0730 0.1032 

1:00 0.0278 0.0410 0.0509 0.0618 0.0711 0.1006 0.0285 0.0420 0.0522 0.0634 0.0730 0.1032 

1:05 0.0278 0.0410 0.0509 0.0618 0.0711 0.1006 0.0285 0.0420 0.0522 0.0634 0.0730 0.1032 

1:10 0.0185 0.0410 0.0509 0.0463 0.0534 0.0503 0.0190 0.0420 0.0522 0.0475 0.0547 0.0516 

1:15 0.0185 0.0341 0.0509 0.0463 0.0534 0.0503 0.0190 0.0350 0.0522 0.0475 0.0547 0.0516 

1:20 0.0185 0.0300 0.0397 0.0347 0.0400 0.0302 0.0190 0.0308 0.0408 0.0356 0.0410 0.0310 

1:25 0.0185 0.0300 0.0302 0.0347 0.0400 0.0302 0.0190 0.0308 0.0310 0.0356 0.0410 0.0310 

1:30 0.0185 0.0300 0.0302 0.0270 0.0311 0.0302 0.0190 0.0308 0.0310 0.0277 0.0319 0.0310 

1:35 0.0185 0.0300 0.0302 0.0270 0.0311 0.0302 0.0190 0.0308 0.0310 0.0277 0.0319 0.0310 

1:40 0.0185 0.0205 0.0302 0.0270 0.0311 0.0302 0.0190 0.0210 0.0310 0.0277 0.0319 0.0310 

1:45 0.0185 0.0205 0.0302 0.0270 0.0311 0.0302 0.0190 0.0210 0.0310 0.0277 0.0319 0.0310 

1:50 0.0185 0.0205 0.0302 0.0270 0.0311 0.0302 0.0190 0.0210 0.0310 0.0277 0.0319 0.0310 

1:55 0.0146 0.0205 0.0270 0.0270 0.0311 0.0302 0.0095 0.0210 0.0277 0.0277 0.0319 0.0310 

2:00 0.0126 0.0177 0.0207 0.0270 0.0311 0.0302 0.0095 0.0182 0.0212 0.0277 0.0319 0.0310 

2:05 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:10 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:15 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:20 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:25 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:30 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:35 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:40 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:45 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:50 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

2:55 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

3:00 0.0107 0.0098 0.0098 0.0147 0.0089 0.0080 

Page B-3



Subwatershed ID 

Table B-2 

CUHP Input 

Length- 

Weighted % Impervious Depression Storage Infiltration 

Area Dist to Centroid Length 

Weighted 

Slope Existing Future Pervious Impervious 

Initial 

Rate 

Decay 

Coeff. 

acres sq mi ft mi ft mi ft/ft % % watershed in watershed in in/hr 1/second in/hr 

Final 

Rate 

Corresponding 

Basin IDs - 1993 

OSP 

Happy Canyon Creek 

A100 73 0.11434 1351 0.256 3537 0.670 0.0534 43.1 43.1 0.5 0.1 3 0.0018 0.5 38 

A105 110 0.17226 3267 0.619 5375 1.018 0.0449 20.3 20.3 0.5 0.1 3 0.0018 0.5 77,99 

A110 77 0.12066 515 0.098 2180 0.413 0.0459 48.0 48.0 0.5 0.1 3 0.0018 0.5 19,20,23,99 

A120 109 0.16982 686 0.130 3712 0.703 0.0361 48.0 48.0 0.5 0.1 3 0.0018 0.5 20,21,22 

A125 75 0.11706 1326 0.251 2822 0.534 0.0352 48.0 48.0 0.5 0.1 3 0.0018 0.5 23 

A130 47 0.07297 723 0.137 2237 0.424 0.0335 28.0 28.0 0.5 0.1 3 0.0018 0.5 23,24 

A134 119 0.18605 1560 0.295 3524 0.667 0.0467 29.0 29.0 0.5 0.1 3 0.0018 0.5 25 

A135 102 0.16012 1953 0.370 4408 0.835 0.0405 32.0 32.0 0.5 0.1 3 0.0018 0.5 26 

A140 117 0.18228 1252 0.237 4074 0.772 0.0454 31.7 32.0 0.5 0.1 3.075 0.0018 0.505 27 

A150 115 0.17973 760 0.144 3939 0.746 0.0432 16.0 16.0 0.5 0.1 3.15 0.0018 0.51 27,28 

A160 107 0.16740 1111 0.210 3157 0.598 0.0489 11.0 11.0 0.5 0.1 3.225 0.0018 0.515 33 

A170 87 0.13580 1451 0.275 2833 0.537 0.0410 9.0 10.0 0.5 0.1 3.225 0.0018 0.515 35 

A180 85 0.13343 834 0.158 4019 0.761 0.0375 7.2 10.0 0.5 0.1 3.375 0.0018 0.525 36 

A190 89 0.13915 753 0.143 3143 0.595 0.0472 8.5 10.1 0.5 0.1 3.3 0.0018 0.52 36,39 

A195 76 0.11838 2655 0.503 4667 0.884 0.0403 13.9 14.0 0.5 0.1 3.15 0.0018 0.51 39 

A200 89 0.13978 905 0.171 3273 0.620 0.0421 14.0 14.0 0.5 0.1 3.15 0.0018 0.51 40 

A210 83 0.12988 2407 0.456 4265 0.808 0.0325 19.8 20.0 0.5 0.1 3 0.0018 0.5 40 

A215 118 0.18400 2407 0.456 4388 0.831 0.0515 7.0 7.0 0.5 0.1 3 0.0018 0.5 46 

A220 96 0.15036 1070 0.203 4835 0.916 0.0355 6.4 18.6 0.5 0.1 3 0.0018 0.5 47 

A230 30 0.04679 362 0.068 1738 0.329 0.0398 10.4 11.2 0.5 0.1 3 0.0018 0.5 50 

A234 85 0.13317 1519 0.288 2641 0.500 0.0535 2.0 12.3 0.5 0.1 3 0.0018 0.5 48 

A235 97 0.15135 1349 0.255 3383 0.641 0.0524 2.8 3.0 0.5 0.1 3 0.0018 0.5 49 

A240 87 0.13610 722 0.137 3989 0.756 0.0522 10.0 24.0 0.5 0.1 3 0.0018 0.5 51,52 

A245 33 0.05176 813 0.154 1788 0.339 0.0621 10.2 10.2 0.5 0.1 3 0.0018 0.5 57 

A250 41 0.06351 1283 0.243 2776 0.526 0.0353 11.2 39.3 0.5 0.1 3 0.0018 0.5 57 

A260 103 0.16066 2005 0.380 4316 0.817 0.0226 9.1 28.9 0.5 0.1 3.225 0.0018 0.515 59 

A263 77 0.12082 2139 0.405 4170 0.790 0.0516 2.0 20.0 0.5 0.1 3.15 0.0018 0.51 54 

A264 98 0.15259 2770 0.525 5425 1.027 0.0489 2.0 24.0 0.5 0.1 3.225 0.0018 0.515 53 

A265 51 0.08003 1344 0.255 3461 0.656 0.0529 2.0 68.0 0.5 0.1 3.375 0.0018 0.525 53,55 

A270 96 0.15054 5036 0.954 7405 1.402 0.0280 2.4 37.8 0.5 0.1 3.075 0.0018 0.505 56 

A275 87 0.13558 1103 0.209 2831 0.536 0.0551 14.6 63.4 0.5 0.1 3.075 0.0018 0.505 59,60 

A276 41 0.06437 664 0.126 2735 0.518 0.0385 10.0 81.8 0.5 0.1 3 0.0018 0.5 60 

Page B-4




Length- 



Weighted 


Initial 

Rate 

Decay 

Coeff. 


Final 

Rate 

Corresponding 


OSP 

A280 128 0.19954 1820 0.345 4206 0.797 0.0506 3.0 60.5 0.5 0.1 3.225 0.0018 0.515 58,60,61 

A285 41 0.06428 1200 0.227 3168 0.600 0.0473 3.0 57.0 0.5 0.1 3 0.0018 0.5 62 

A290 129 0.20186 1681 0.318 3935 0.745 0.0264 6.2 57.0 0.5 0.1 3.6 0.0018 0.54 60,61,62,64,65 

A295 53 0.08333 591 0.112 1999 0.379 0.0338 23.6 56.3 0.5 0.1 3.375 0.0018 0.525 65,119 

A300 116 0.18133 1671 0.316 3575 0.677 0.0227 38.0 39.0 0.5 0.1 3.525 0.0018 0.535 64,65,67,68 

A304 100 0.15610 2184 0.414 5131 0.972 0.0307 4.4 75.9 0.5 0.1 3 0.0018 0.5 63 

A305 46 0.07226 1591 0.301 3513 0.665 0.0306 2.0 65.5 0.5 0.1 3.225 0.0018 0.515 63 

A310 79 0.12298 1319 0.250 3803 0.720 0.0161 3.7 48.1 0.5 0.1 4.05 0.0018 0.57 68 

A314 82 0.12862 3023 0.573 5569 1.055 0.0278 4.3 73.8 0.5 0.1 3.15 0.0018 0.51 66 

A315 72 0.11236 2151 0.407 5480 1.038 0.0298 2.7 61.2 0.5 0.1 4.125 0.0018 0.575 66 

A320 57 0.08854 1462 0.277 3838 0.727 0.0155 15.8 48.2 0.5 0.1 4.05 0.0018 0.57 69 

A325 85 0.13339 1309 0.248 3434 0.650 0.0223 58.4 71.1 0.5 0.1 3.75 0.0018 0.55 98 

A330 101 0.15815 1367 0.259 5006 0.948 0.0192 16.2 23.4 0.5 0.1 3.9 0.0018 0.56 69,71 

A340 111 0.17409 2928 0.555 5986 1.134 0.0190 9.0 44.6 0.5 0.1 3.225 0.0018 0.515 70,71 

A345 39 0.06108 1800 0.341 3495 0.662 0.0145 17.8 17.8 0.5 0.1 4.425 0.0018 0.595 71,105 

A350 64 0.10010 1083 0.205 3730 0.706 0.0195 15.0 15.0 0.5 0.1 3.75 0.0018 0.55 112 

A360 116 0.18064 2061 0.390 5222 0.989 0.0154 14.6 15.0 0.5 0.1 4.2 0.0018 0.58 112 

A370 74 0.11627 668 0.127 3471 0.657 0.0176 20.7 40.5 0.5 0.1 4.275 0.0018 0.585 112 

A375 92 0.14318 3142 0.595 6499 1.231 0.0220 14.0 24.5 0.5 0.1 3.9 0.0018 0.56 109 

A380 113 0.17678 1414 0.268 4057 0.768 0.0143 8.6 77.6 0.5 0.1 4.525 0.00158 0.675 114 

A390 111 0.17297 2356 0.446 5082 0.963 0.0157 24.7 48.5 0.5 0.1 4.075 0.00158 0.645 115 

A395 33 0.05118 530 0.100 1406 0.266 0.0261 23.0 80.0 0.5 0.1 4.5 0.0018 0.6 116 

A400 107 0.16644 1482 0.281 3918 0.742 0.0261 55.4 65.8 0.5 0.1 3.6 0.0018 0.54 118 

Beverly Hills Tributary 

B100 73 0.11348 798 0.151 1987 0.376 0.0469 44.4 71.8 0.5 0.1 3 0.0018 0.5 29 

B110 83 0.12911 1052 0.199 2796 0.530 0.0480 28.5 28.5 0.5 0.1 3 0.0018 0.5 29,30,31 

B120 76 0.11855 1052 0.199 3362 0.637 0.0410 24.8 24.8 0.5 0.1 3.075 0.0018 0.505 32 

B130 72 0.11212 1233 0.234 4808 0.911 0.0371 9.5 10.8 0.5 0.1 3.225 0.0018 0.515 32,34 

B134 24 0.03817 191 0.036 1546 0.293 0.0154 40.3 40.3 0.5 0.1 3 0.0018 0.5 37 

B135 126 0.19620 2196 0.416 4472 0.847 0.0396 15.4 15.8 0.5 0.1 3 0.0018 0.5 37 

Oak Hills Tributary 

C100 96 0.15070 1267 0.240 2684 0.508 0.0454 2.5 3.0 0.5 0.1 3 0.0018 0.5 2 

C110 105 0.16355 888 0.168 3334 0.631 0.0495 9.0 9.0 0.5 0.1 3 0.0018 0.5 2 

C120 66 0.10323 1452 0.275 3578 0.678 0.0373 13.0 13.0 0.5 0.1 3 0.0018 0.5 2 

C125 113 0.17616 2179 0.413 4534 0.859 0.0429 8.0 8.0 0.5 0.1 3 0.0018 0.5 1 

C130 111 0.17419 1171 0.222 3322 0.629 0.0326 36.0 36.0 0.5 0.1 3 0.0018 0.5 3 

Page B-5




Length- 



Weighted 


Initial 

Rate 

Decay 

Coeff. 


Final 

Rate 

Corresponding 


OSP 

C140 54 0.08476 616 0.117 3090 0.585 0.0375 26.0 26.0 0.5 0.1 3 0.0018 0.5 6 

C150 58 0.09093 1435 0.272 3333 0.631 0.0243 2.8 3.0 0.5 0.1 3 0.0018 0.5 6,10 

C153 125 0.19544 1319 0.250 3758 0.712 0.0439 33.0 33.0 0.5 0.1 3 0.0018 0.5 4,18 

C154 97 0.15211 1120 0.212 2836 0.537 0.0396 43.0 43.0 0.5 0.1 3 0.0018 0.5 4,5,7 

C155 76 0.11855 1646 0.312 3436 0.651 0.0453 31.0 31.0 0.5 0.1 3 0.0018 0.5 5,7 

C159 110 0.17231 1265 0.240 3613 0.684 0.0487 29.0 29.0 0.5 0.1 3 0.0018 0.5 8,9,13 

C160 115 0.17934 650 0.123 2856 0.541 0.0504 7.5 8.0 0.5 0.1 3 0.0018 0.5 9,10,11,13 

C170 108 0.16852 1561 0.296 4566 0.865 0.0316 11.0 11.0 0.5 0.1 3 0.0018 0.5 14 

C175 100 0.15692 1826 0.346 4218 0.799 0.0454 8.0 8.0 0.5 0.1 3 0.0018 0.5 12,15 

C180 44 0.06861 680 0.129 3284 0.622 0.0405 14.8 15.0 0.5 0.1 3 0.0018 0.5 15 

C185 111 0.17376 2188 0.414 4310 0.816 0.0490 7.7 10.5 0.5 0.1 3 0.0018 0.5 16 

C190 76 0.11850 1418 0.269 4044 0.766 0.0311 10.7 15.0 0.5 0.1 3 0.0018 0.5 17 

Oak Ridge Tributary 

D100 120 0.18741 1488 0.282 3591 0.680 0.0398 9.0 9.0 0.5 0.1 3 0.0018 0.5 41,42 

D110 112 0.17483 1496 0.283 3267 0.619 0.0301 11.0 11.0 0.5 0.1 3 0.0018 0.5 43 

D120 73 0.11483 550 0.104 3204 0.607 0.0467 10.0 10.0 0.5 0.1 3 0.0018 0.5 44 

D130 80 0.12517 1488 0.282 3124 0.592 0.0500 24.0 24.0 0.5 0.1 3 0.0018 0.5 45 

Badger Gulch 

E100 97 0.15101 1551 0.294 3708 0.702 0.0304 2.0 2.0 0.5 0.1 3 0.0018 0.5 72,74 

E105 53 0.08243 1122 0.212 2532 0.480 0.0389 2.0 2.0 0.5 0.1 3 0.0018 0.5 73 

E110 83 0.12948 1034 0.196 2470 0.468 0.0454 2.0 2.0 0.5 0.1 3 0.0018 0.5 73,74,75,76,78 

E120 78 0.12137 1068 0.202 3492 0.661 0.0418 2.0 2.0 0.5 0.1 3 0.0018 0.5 78,79 

E125 73 0.11481 1604 0.304 3032 0.574 0.0498 2.0 2.0 0.5 0.1 3 0.0018 0.5 80 

E130 82 0.12879 766 0.145 3651 0.691 0.0451 2.0 2.0 0.5 0.1 3 0.0018 0.5 80,82 

E135 102 0.15893 1738 0.329 3569 0.676 0.0481 2.0 2.0 0.5 0.1 3 0.0018 0.5 81 

E140 91 0.14215 724 0.137 2798 0.530 0.0344 2.0 2.0 0.5 0.1 3 0.0018 0.5 83,87 

E150 67 0.10449 959 0.182 2835 0.537 0.0517 2.0 2.0 0.5 0.1 3.075 0.0018 0.505 88 

E155 127 0.19834 2452 0.464 4538 0.859 0.0513 2.0 2.0 0.5 0.1 3 0.0018 0.5 84 

E160 122 0.19091 1451 0.275 3478 0.659 0.0376 2.0 52.6 0.5 0.1 3.825 0.0018 0.555 89 

E170 99 0.15500 1248 0.236 2859 0.541 0.0597 2.0 68.3 0.5 0.1 3.9 0.0018 0.56 90,91 

E180 44 0.06812 1706 0.323 2785 0.527 0.0254 2.0 70.0 0.5 0.1 4.2 0.0018 0.58 93 

E183 119 0.18666 2518 0.477 4516 0.855 0.0542 2.0 6.0 0.5 0.1 3.375 0.0018 0.525 5 

E184 73 0.11392 1747 0.331 3842 0.728 0.0530 2.0 17.4 0.5 0.1 3.75 0.0018 0.55 86 

E185 128 0.19940 1890 0.358 5506 1.043 0.0388 2.0 41.7 0.5 0.1 3.6 0.0018 0.54 92 

E190 61 0.09504 657 0.124 2749 0.521 0.0262 2.0 54.4 0.5 0.1 3.75 0.0018 0.55 95,96 

E200 108 0.16838 2866 0.543 4594 0.870 0.0230 5.4 42.1 0.5 0.1 3.75 0.0018 0.55 95,96,97 

Page B-6




Length- 



Weighted 


Initial 

Rate 

Decay 

Coeff. 


Final 

Rate 

Corresponding 


OSP 

E204 42 0.06605 1067 0.202 2541 0.481 0.0294 2.0 71.6 0.5 0.1 3 0.0018 0.5 94 

E205 100 0.15620 1948 0.369 4214 0.798 0.0320 35.2 52.8 0.5 0.1 3.15 0.0018 0.51 94 

E210 96 0.14956 2674 0.507 5765 1.092 0.0159 9.2 49.3 0.5 0.1 3.825 0.0018 0.555 98 

Grandview Tributary 

F100 93 0.14511 800 0.152 2700 0.511 0.0308 2.0 56.8 0.5 0.1 3 0.0018 0.5 100 

F110 105 0.16378 880 0.167 2240 0.424 0.0234 6.5 52.5 0.5 0.1 3 0.0018 0.5 100,101,103 

F120 124 0.19354 1990 0.377 3526 0.668 0.0282 38.3 55.6 0.5 0.1 3.075 0.0018 0.505 101,102,103 

F125 70 0.10874 1339 0.254 3288 0.623 0.0252 2.0 50.0 0.5 0.1 3.675 0.0018 0.545 101,103,104 

F130 107 0.16717 1518 0.287 3294 0.624 0.0217 4.7 51.4 0.5 0.1 3.675 0.0018 0.545 104 

F140 54 0.08509 2009 0.380 4129 0.782 0.0215 19.6 19.6 0.5 0.1 4.05 0.0018 0.57 105 

Stonegate Tributary 

G100 112 0.17554 3093 0.586 6705 1.270 0.0154 2.0 50.0 0.5 0.1 3.075 0.0018 0.505 107 

G105 43 0.06657 1219 0.231 3081 0.584 0.0194 50.0 50.0 0.5 0.1 3.825 0.0018 0.555 107 

G110 73 0.11451 1596 0.302 3413 0.646 0.0227 22.8 22.8 0.5 0.1 4.05 0.0018 0.57 108,111 

G120 87 0.13633 2412 0.457 4933 0.934 0.0215 50.5 68.3 0.5 0.1 4.5 0.0018 0.6 111 

Green Acres Tributary 

H100 122 0.19127 1349 0.255 5346 1.013 0.0122 51.2 72.6 0.5 0.1 3 0.0018 0.5 119,67,121 

H110 98 0.15386 557 0.105 1981 0.375 0.0186 44.4 46.4 0.5 0.1 3 0.0018 0.5 120,124 

H115 55 0.08578 691 0.131 1531 0.290 0.0131 44.4 44.4 0.5 0.1 3 0.0018 0.5 119,120 

H120 59 0.09167 1533 0.290 2500 0.473 0.0165 19.5 63.0 0.5 0.1 3 0.0018 0.5 120,123 

H130 36 0.05656 810 0.153 2112 0.400 0.0172 15.2 56.9 0.5 0.1 3 0.0018 0.5 123,124 

H140 36 0.05631 1750 0.331 3054 0.578 0.0235 3.5 75.0 0.5 0.1 3.375 0.0018 0.525 123,124,125 

H145 116 0.18173 2457 0.465 5742 1.088 0.0167 10.2 79.6 0.5 0.1 3.075 0.0018 0.505 68,124 

H150 98 0.15282 637 0.121 2590 0.491 0.0323 2.0 80.0 0.5 0.1 3.6 0.0018 0.54 125 

H160 107 0.16661 3461 0.655 6975 1.321 0.0172 5.2 37.7 0.5 0.1 3.675 0.0018 0.545 125,129 

H170 73 0.11465 1902 0.360 4331 0.820 0.0214 10.0 32.3 0.5 0.1 3.75 0.0018 0.55 128 

H180 93 0.14542 1094 0.207 3929 0.744 0.0191 21.1 45.7 0.5 0.1 3.75 0.0018 0.55 131 

H185 118 0.18474 1850 0.350 5098 0.966 0.0219 19.0 73.3 0.5 0.1 3 0.0018 0.5 130,132 

H190 96 0.15048 561 0.106 2865 0.543 0.0348 43.8 77.6 0.5 0.1 3.375 0.0018 0.525 132,133 

H200 83 0.12951 1236 0.234 3650 0.691 0.0189 23.4 80.0 0.5 0.1 3.9 0.0018 0.56 132,133,114,134 

H205 64 0.10061 820 0.155 1900 0.360 0.0349 35.8 80.0 0.5 0.1 3.75 0.0018 0.55 132,133,134 

H210 120 0.18689 1520 0.288 3320 0.629 0.0222 4.9 78.6 0.5 0.1 3.8 0.00169 0.59 133,115,134,135 

H220 50 0.07869 1530 0.290 2490 0.472 0.0269 4.4 64.0 0.5 0.1 3.55 0.00158 0.61 135,116 

Page B-7



Table B-3 

Detention Rating Curves 

Storage Curve Outlet Curve Storage Curve Outlet Curve Storage Curve Outlet Curve 

Elevation Stage Area Stage Discharge Elevation Stage Area Stage Discharge Elevation Stage Area Stage Discharge 

(ft) (ft) (sq ft) (ft) (cfs) (ft) (ft) (sq ft) (ft) (cfs) (ft) (ft) (sq ft) (ft) (cfs) 

CPNMD Pond #11 (SWMM element HC310) CPNMD Pond #9 (SWMM element OH310) CPNMD Pond #10 (SWMM element OH320) 

6345 0 0 0.0 0.0 6310 0 2178 0 0.4 6282 0 0 0 0.0 

6346 1 500 1.0 23.0 6312 2 6970 1 9.8 6284 2 2480 1 5.5 

6348 3 2100 3.0 133 6314 4 10890 2 25.2 6286 4 4690 2 20.9 

6350 5 8900 5.0 228 6316 6 17424 3 43.8 6288 6 9440 3 41.7 

6352 7 28400 7.0 292 6318 8 23958 4 55.6 6290 8 12470 4 65.0 

6354 9 39800 9.0 348 6320 10 30492 5 65.3 6292 10 22280 5 80.0 

6356 11 51900 11.0 388 6322 12 45302 6 73.7 6294 12 33380 6 92.5 

6358 13 63700 13.0 423 6324 14 60113 7 81.2 6296 14 46200 7 104 

6360 15 75300 15.0 456 6326 16 74923 8 88.1 6298 16 62250 8 114 

6362 17 89000 17.0 487 6328 18 91476 9 94.6 6299 17 78300 9 123 

6364 19 103200 19.0 516 6330 20 104544 10 101 6300 18 94350 10 211 

6366 21 120600 21.0 543 11 106 6303 21 142500 11 412 

6368 23 137100 23.0 569 12 112 12 441 

CPNMD Pond #12 (SWMM element HC320) 12.1 112 13 463 

6296.8 0.0 4000 0.0 0.0 13 195 14 484 

6298 1.2 8100 1.2 130 14 317 15 505 

6300 3.2 34300 3.2 375 15 330 16 524 

6302 5.2 71700 5.2 528 16 343 17 543 

6304 7.2 104500 7.2 648 17 355 18 561 

6306 9.2 135300 9.2 749 18 367 19 579 

6308 11.2 166100 11.2 2069 19 379 20 596 

CPNMD Pond #20 (SWMM element MT300) 20 390 21 613 

6319.4 0.0 10 0.0 0.00 Meridian Village Pond 1 (SWMM element HC326) 

6320.0 0.6 675 0.6 0.10 5838 0 0 0 0.00 

6321.7 2.3 22100 2.3 9.99 5840 2 41140 2 0.73 

6322.0 2.6 26600 2.6 12.1 5841 3 58420 3 1.7 

6324.0 4.6 63500 4.6 24.2 5842 4 75700 4 17.7 

6325.2 5.8 111375 5.8 28.8 5844 6 139340 6 22.2 

6326.0 6.6 143275 6.6 65.3 5846 8 180260 8 73 

6326.5 7.1 149750 7.1 105 5848 10 220000 10 82 

6328.0 8.6 164325 8.6 263 

6328.6 9.2 169550 9.2 279 

6329.6 10.2 178825 10.2 303 

6330.6 11.2 188100 11.2 627 

6331.6 12.2 197375 12.2 1279 

Page B-11



Storage Curve Outlet Curve Storage Curve Outlet Curve Storage Curve Outlet Curve 

Elevation Stage Area Stage Discharge Elevation Stage Area Stage Discharge Elevation Stage Area Stage Discharge 

(ft) (ft) (sq ft) (ft) (cfs) (ft) (ft) (sq ft) (ft) (cfs) (ft) (ft) (sq ft) (ft) (cfs) 

Chambers Reservoir WQ Pond (SWMM element SG320) Meridian Pond 4A (SWMM element GA311) Stepping Stone Pond D1 (SWMM element GV301) 

5837.2 0 0 0.0 0 5888.5 0 11333 0.0 0.0 6007.5 0 10 0.0 0.0 

5838 0.8 334 0.8 0.4 5889 0.5 15901 0.5 0.0 6008 0.5 2672 0.5 1.3 

5840 2.8 47285 2.8 2.2 5890 1.5 34312 1.5 0.11 6009 1.5 13483 1.5 13.20 

5840.3 3.1 51599 3.1 2.5 5891 2.5 52329 2.5 0.51 6010 2.5 27296 2.5 30.90 

5842 4.8 88359 4.8 3.7 5892 3.5 64920 3.5 1.06 6011 3.5 44579 3.5 52.20 

5844 6.8 110216 6.8 64.7 5893 4.5 70257 4.5 1.73 6012 4.5 66756 4.5 71.20 

5846 8.8 124039 8.8 75.1 5894 5.5 75559 5.5 58.1 6013 5.5 76808 5.5 86.4 

5848 10.8 137906 10.8 2671 5895 6.5 79701 6.5 219 6014 6.5 86899 6.5 99 

5849 11.8 145138 11.8 4890 5896 7.5 83843 7.5 290 6015 7.5 96990 7.5 151 

Stonegate Pond (SWMM element SG310) 5897 8.5 87985 8.5 337 6016 8.5 107081 8.5 484 

5886.3 0 260 0.0 0.00 Meridian Pond 4B (SWMM element GA310) Stepping Stone Pond D3 (SWMM element GV302) 

5887 1 4340 0.7 0.13 5891.5 0 0 0.0 0.0 5973.5 0 76487 0.0 0.0 

5888 2 9086 1.7 0.40 5892 0.5 348 0.5 3.26 5974 0.5 114069 0.5 0.21 

5889 3 24864 2.7 0.75 5893 1.5 5730 1.5 16.9 5975 1.5 122270 1.5 0.5 

5890 4 52193 3.7 1.18 5894 2.5 24126 2.5 36.5 5976 2.5 131136 2.5 13.7 

5891 5 77199 4.7 1.66 5895 3.5 53961 3.5 60.4 5977 3.5 138533 3.5 87.0 

5892 5.7 94517 5.7 2.20 5896 4.5 92234 4.5 75.7 5978 4.5 147406 4.5 193.8 

5893 6.7 105201 6.7 7.05 5897 5.5 126509 5.5 118 5979 5.5 157864 5.5 207 

5894 7.7 112546 7.7 32.5 5898 6.5 146888 6.5 147 5980 6.5 167217 6.5 220 

5895 8.7 120451 8.7 41.8 5899 7.5 153323 7.5 161 5981 7.5 176570 7.5 390 

5896 9.7 127914 9.7 43.9 5900 8.5 159889 8.5 173 5982 8.5 185923 8.5 915 

5897 10.7 135421 10.7 45.8 5901 9.5 166733 9.5 185 5983 9.5 195276 9.5 1677 

5898 11.7 147109 11.7 47.7 5902 10.5 173678 10.5 197 

5899 12.7 160614 12.7 49.5 5903 11.5 180632 11.5 207 

E-470 Pond (SWMM element GA350) 5904 12.5 187664 12.5 217 

5782 0 200 0 103 5905 13.5 194696 13.5 452 

5784 2 21000 2 291 5906 14.5 201728 14.5 677 

5786 4 58900 4 531 Meridian Pond 4C (SWMM element GA309) 

5788 6 115100 6 813 5917 0 10 0 0.00 

5790 8 192300 8 1134 5918 1 2120 1 9.22 

5792 10 269600 10 1467 5919 2 15960 2 26.1 

5920 3 33760 3 55.3 

5921 4 42906 4 94.6 

5922 5 51523 5 160 

5923 6 60321 6 258 

5924 7 78033 7 268 

5925 8 184401 8 278 

5926 9 190000 9 437 

5927 10 195600 10 711 

Page B-12



SWMM 

Node 

Table B-4 

Peak Flows 

EXISTING DEVELOPMENT 

FUTURE DEVELOPMENT 

Station Channel 

Design 100-YR 50-YR 25-YR 10-YR 5-YR 2-YR 100-YR 50-YR 25-YR 10-YR 5-YR 2-YR 

(ft) Reach 

Landmark 

Storm (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) 


HC999 0 9 Cherry Creek 3-hr 8161 5910 4237 2095 1166 322 9234 6970 5236 3049 1994 836 

HC037 2500 9 Jordan Road (D/S) 3-hr 8168 5915 4241 2100 1173 326 9233 6969 5236 3049 1994 832 

HC036 2700 9 Jordan Rd (U/S) / Green Acres Trib (D/S) 3-hr 8166 5914 4240 2100 1173 326 9228 6964 5231 3046 1991 828 

HC035 2700 9 Green Acres Tributary (U/S) 3-hr 7621 5502 3923 1915 1047 283 8449 6324 4704 2669 1705 656 

HC034 7300 8 Chambers Road 3-hr 7693 5558 3979 1963 1093 301 8489 6355 4740 2691 1724 664 

HC033 10500 8 E-470 / Stonegate Tributary (D/S) 3-hr 7702 5569 3997 1982 1114 309 8474 6344 4740 2691 1728 652 

HC032 10500 8 Stonegate Tributary (U/S) 3-hr 7593 5488 3937 1954 1100 304 8354 6249 4670 2656 1708 633 

HC031 12700 8 Grandview Estates / Compark South Boundary 3-hr 7552 5460 3922 1953 1106 308 8302 6211 4648 2647 1705 625 

HC030 14600 7 Elm Avenue (extended) 3-hr 7523 5440 3914 1955 1114 312 8269 6189 4639 2646 1710 625 

HC029 16200 7 Grandview Tributary (D/S) 3-hr 7502 5425 3905 1953 1115 313 8245 6172 4630 2643 1710 624 

HC028 16200 7 Grandview Tributary (U/S) 3-hr 7161 5190 3745 1904 1093 306 7776 5803 4339 2461 1592 578 

HC027 17400 7 Cottonwood Avenue (extended) 3-hr 7097 5144 3714 1891 1088 305 7689 5734 4288 2431 1573 569 

HC026 20100 7 Lincoln Ave / Badger Gulch (D/S) 3-hr 7079 5132 3715 1899 1102 311 7663 5717 4287 2434 1580 572 

HC025 20100 6 Badger Gulch (U/S) 2-hr 5897 4340 3166 1734 1088 316 6247 4689 3511 2073 1394 465 

HC024 22600 6 1100' W of West Parker Road 2-hr 5884 4331 3162 1739 1100 325 6223 4670 3502 2069 1396 469 

HC023 25600 6 East boundary of Meridian Commons 2-hr 5801 4273 3130 1738 1117 339 6066 4540 3410 2006 1361 462 

HC022 28800 5 West boundary of Meridian Commons 2-hr 5668 4174 3068 1712 1119 356 5871 4382 3299 1929 1314 454 

HC021 32000 4 Ridgegate Parkway 2-hr 5555 4094 3020 1698 1125 370 5726 4263 3216 1870 1280 452 

HC020 32800 4 2-hr 5476 4040 2981 1683 1120 370 5627 4183 3149 1826 1251 444 

HC019 36800 4 2-hr 5369 3962 2932 1662 1117 376 5481 4066 3062 1767 1214 434 

HC018 40000 4 2-hr 5169 3817 2846 1630 1117 396 5212 3858 2918 1684 1169 432 

HC017 42000 4 2-hr 5124 3783 2831 1623 1120 406 5158 3815 2896 1671 1166 438 

HC016 43500 3 I-25 2-hr 4899 3628 2708 1570 1099 407 4920 3647 2757 1603 1133 433 

HC015 44600 3 2-hr 4879 3614 2697 1566 1098 408 4899 3633 2747 1598 1132 435 

HC014 46100 3 Oak Hills Tributary (D/S) 2-hr 4700 3488 2598 1520 1078 407 4708 3497 2636 1543 1105 430 

HC013 46100 3 Oak Hills Tributary (U/S) 2-hr 3012 2254 1698 1045 773 308 3017 2260 1730 1064 796 332 

HC012 49300 2 2-hr 2948 2203 1676 1032 775 329 2950 2205 1705 1053 797 352 

HC011 51200 2 2-hr 2858 2143 1624 1010 767 335 2857 2144 1648 1030 788 358 

HC010 52200 2 2-hr 2676 2022 1519 965 744 332 2674 2021 1539 983 763 355 

HC009 54300 2 500' N of Oak Hills Drive / Beverly Hills Tributary (D/S) 2-hr 2598 1969 1475 954 746 352 2591 1964 1497 971 763 372 

HC008 54500 2 Beverly Hills Tributary (U/S) 2-hr 1832 1415 1028 693 560 273 1834 1416 1029 694 561 274 

HC007 56700 2 2-hr 1733 1350 985 668 548 281 1734 1351 986 669 549 281 

HC006 58700 2 2-hr 1591 1258 928 633 527 281 1592 1258 929 633 528 282 

HC005 59600 1 Castle Pines City Limit / CPNMD Pond #12 Outflow 2-hr 1408 1132 853 587 495 270 1409 1133 853 587 495 270 

HC320 59600 1 CPNMD Pond #12 Inflow 2-hr 1517 1269 1056 700 554 277 1518 1270 1057 701 554 277 

HC004 61000 1 Tenby Way 2-hr 1259 1067 898 614 492 251 1259 1067 898 614 492 251 

HC003 62500 1 Castle Pines Parkway / CPNMD Pond #11 Outflow 2-hr 491 449 408 321 273 153 491 449 408 321 273 153 

HC310 62500 1 CPNMD Pond #11 Inflow 2-hr 1001 808 644 409 310 154 1001 808 644 409 310 154 

HC002 64000 1 2-hr 635 513 410 264 201 103 635 513 410 264 201 103 

HC001 64700 1 Monarch Blvd. 2-hr 356 288 229 140 104 50 356 288 229 140 104 50 

Page B-13



SWMM 

Node 





(ft) Reach 



HC124 2-hr 52 38 28 13 7 0.8 119 101 85 59 50 31 

HC123 2-hr 82 61 45 20 11 1.4 183 155 131 93 78 49 

HC122 2-hr 38 29 21 9 5 0.5 76 63 52 35 28 16 

HC119 2-hr 136 101 74 31 16 1.0 200 157 122 66 45 18 

HC117 2-hr 205 155 114 49 25 1.5 231 177 133 62 36 6 

HC116 2-hr 99 75 56 25 13 0.8 124 96 74 37 24 6 

HC104 2-hr 304 244 193 115 82 36 304 244 193 115 82 36 

HC103 2-hr 279 231 187 126 97 52 279 231 187 126 97 52 

GREEN ACRES TRIBUTARY 

GA999 70000 Confluence w/ Happy Canyon 2-hr 882 667 507 253 165 69 1446 1182 986 669 545 317 

GA012 71400 2-hr 844 640 488 257 169 70 1377 1125 940 640 521 304 

GA011 73700 Chambers Road 2-hr 740 563 434 240 166 73 1199 979 819 559 454 265 

GA010 76300 Compark Boulevard 2-hr 580 431 332 191 158 64 976 800 667 454 367 213 

GA009 77200 E-470 (D/S) 2-hr 495 368 293 187 176 86 861 710 589 396 320 200 

GA008 77700 E-470 (U/S) / E-470 Pond Outflow 2-hr 420 332 269 171 141 70 688 567 470 319 249 144 

GA350 77700 E-470 Pond Inflow 2-hr 422 332 270 171 115 47 725 586 479 319 250 144 

GA007 79200 2-hr 355 287 240 159 110 46 522 430 357 287 229 118 

GA006 82600 NW Corner of Grandview Estates (approx.) 2-hr 320 265 228 158 114 50 457 383 322 267 218 115 

GA005 84600 2-hr 288 247 217 157 115 51 385 335 297 241 201 111 

GA004 86000 Peoria Street / Meridian Pond 4A Outflow 2-hr 212 193 176 137 106 50 224 207 193 164 141 81 

GA311 86000 Meridian Pond 4A Inflow 2-hr 213 194 178 139 111 65 226 208 194 166 143 87 

GA003 86600 Meridian Pond 4B Outflow 2-hr 201 182 165 132 106 63 212 195 178 151 132 80 

GA310 86600 Meridian Pond 4B Inflow 2-hr 420 324 303 203 155 79 477 366 335 256 204 112 

GA002 87000 Mt Belford Avenue / Meridian Pond 4C Outflow 2-hr 361 276 264 182 141 74 394 301 271 212 169 92 

GA309 87000 Meridian Pond 4C Inflow 2-hr 499 410 334 215 169 91 540 450 371 249 202 115 

GA001 89600 Lincoln Avenue 2-hr 197 162 133 87 69 39 232 196 165 116 98 61 

STONEGATE TRIBUTARY 

SG999 90000 Confluence w/ Happy Canyon 2-hr 131 98 75 46 36 22 143 110 92 62 51 32 

SG003 94500 Chambers Reservoir WQ Pond Outflow 2-hr 65 50 36 16 4 3 69 61 42 18 6 3 

SG320 94500 Chambers Reservoir WQ Pond Inflow 2-hr 139 109 86 47 33 17 140 109 86 47 34 17 

SG002 97500 Lincoln Avenue 2-hr 64 52 43 27 21 12 66 53 44 28 22 13 

SG001 97300 Stonegate Pond Outflow 2-hr 21 9 4 2 1.0 0.2 41 35 26 11 5 2 

SG310 97300 Stonegate Pond Inflow 2-hr 62 45 33 15 7 0.5 126 103 84 54 43 23 

GRANDVIEW TRIBUTARY 

GV999 110000 Confluence w/ Happy Canyon 2-hr 394 277 215 123 76 30 629 482 374 221 163 96 

GV004 112900 Lincoln Avenue 2-hr 364 269 207 104 68 27 604 463 359 214 169 93 

GV003 116500 Meridian Filing No. 7 / Sierra Ridge Boundary 2-hr 290 209 165 94 68 32 475 365 284 173 129 74 

GV002 120100 Main Street / Stepping Stone Pond D3 Outflow 2-hr 133 90 58 9 0 0 198 169 136 85 60 13 

GV302 120100 Stepping Stone Pond D3 Inflow 2-hr 210 165 127 61 35 5 337 287 241 166 136 80 

GV001 121200 Stepping Stone Pond D1 Outflow 2-hr 78 64 51 25 14 1 119 94 84 65 57 36 

GV301 121200 Stepping Stone Pond D1 Inflow 2-hr 128 98 73 33 18 1 249 208 172 119 96 55 

Page B-14



SWMM 

Node 





(ft) Reach 



BADGER GULCH 

BG999 130000 Confluence w/ Happy Canyon 2-hr 1522 1087 767 308 128 19 1856 1398 1053 572 405 214 

BG011 133900 500' E of West Parker Road (extended) 2-hr 1489 1065 753 303 127 22 1789 1343 1008 539 383 204 

BG010 138500 Ridgegate Parkway 2-hr 1362 976 692 273 114 4 1571 1168 868 438 308 169 

BG009 140300 Confluence with East Fork 2-hr 1321 948 674 268 113 4 1513 1122 832 414 276 152 

BG008 142800 2-hr 1053 761 545 221 97 4 1136 841 619 296 180 107 

BG007 144800 2-hr 972 706 509 210 95 4 1019 750 549 249 129 53 

BG006 147200 Lone Tree City Limit 2-hr 870 636 462 195 90 3 870 636 462 195 90 3 

BG005 149000 2-hr 693 509 372 156 74 3 693 509 372 156 74 3 

BG004 150900 2-hr 592 438 321 135 66 3 592 438 321 135 66 3 

BG003 152600 2-hr 400 298 219 93 47 2 400 298 219 93 47 2 

BG002 154100 2-hr 247 185 137 58 30 1.4 247 185 137 58 30 1.4 

BG001 155300 2-hr 149 113 84 37 20 1.2 149 113 84 37 20 1.2 

BG111 2-hr 40 30 22 10 5 0.3 90 76 64 45 38 23 

BG109 2-hr 169 126 93 36 17 1.3 201 154 116 53 31 9 

OAK RIDGE TRIBUTARY 

OR999 180000 I-25 / Confluence w/ Happy Canyon 2-hr 482 361 270 130 77 17 482 361 270 130 77 17 

OR003 183100 2-hr 386 291 217 101 59 11 386 291 217 101 59 11 

OR002 184400 2-hr 287 218 164 77 46 9 287 218 164 77 46 9 

OR001 187000 2-hr 157 121 92 44 27 6 157 121 92 44 27 6 

OAK HILLS TRIBUTARY 

OH999 160000 Confluence w/ Happy Canyon 2-hr 1374 1057 803 366 239 92 1381 1062 807 371 243 94 

OH010 162300 2-hr 1328 1025 783 352 233 92 1331 1028 786 354 235 93 

OH009 163400 Sorrell Road 2-hr 1200 938 727 319 212 88 1200 939 728 319 213 89 

OH008 166800 Surrey Road / Heather Drive 2-hr 1051 839 663 278 192 87 1051 839 664 278 192 87 

OH007 168100 Castle Pines City Limit 2-hr 940 772 626 258 181 85 940 772 626 258 181 85 

OH006 169500 2-hr 767 650 545 218 157 70 767 651 546 218 157 70 

OH005 170700 Serena Drive / CPNMD Pond #10 Outflow 2-hr 424 386 349 121 95 39 424 386 350 121 95 39 

OH320 170700 CPNMD Pond #10 Inflow 2-hr 430 386 350 126 96 39 430 386 351 126 96 39 

OH004 171800 Monarch Blvd / CPNMD Pond #9 Outflow 2-hr 384 345 317 112 85 31 385 346 317 112 85 31 

OH310 171800 CPNMD Pond #9 Inflow 2-hr 622 475 360 177 110 32 623 477 361 177 110 32 

OH003 174000 2-hr 448 342 257 118 68 12 450 343 258 119 69 12 

OH002 175900 2-hr 264 202 151 69 39 6 265 203 152 69 39 6 

OH001 177000 2-hr 115 88 66 29 16 1.2 116 89 66 30 16 1.4 

MT110 CPNMD Pond #20 Outflow 2-hr 265 203 153 77 48 24 265 203 153 77 48 24 

MT300 CPNMD Pond #20 Inflow 2-hr 444 363 291 179 136 67 444 363 291 179 136 67 

MT100 2-hr 251 205 163 98 73 34 251 205 163 98 73 34 

BEVERLY HILLS TRIBUTARY 

BH999 Confluence w/ Happy Canyon 2-hr 920 724 561 305 213 83 989 791 623 364 266 120 

BH003 Oakwood Lane 2-hr 656 527 415 245 178 78 732 597 479 312 240 123 

BH002 Suffolk Lane 2-hr 514 414 328 205 152 71 594 491 400 278 219 122 

BH001 Charter Oaks Drive 2-hr 317 265 212 138 105 54 418 363 304 223 182 111 

BH100 I-25 2-hr 100 83 66 43 32 16 100 83 66 43 32 16 

Page B-15



SWMM 

Node 

Table B-5 

Runoff Volumes – Existing Development 

Cumulative 


Station 

Drainage 

Area 

Design 100-YR 50-YR 25-YR 10-YR 5-YR 2-YR 

(ft) (ac) Landmark 

Storm (cf) (in) (cf) (in) (cf) (in) (cf) (in) (cf) (in) (cf) (in) 

HC999 0 11,193 Cherry Creek 3-hr 62,461,967 1.54 47,857,312 1.18 36,422,019 0.90 19,856,686 0.49 12,177,226 0.30 5,007,397 0.12 

HC036 2700 11,053 Jordan Rd (U/S) / Green Acres Trib (D/S) 3-hr 61,474,785 1.53 47,041,640 1.17 35,744,120 0.89 19,390,268 0.48 11,813,052 0.29 4,785,568 0.12 

HC035 2700 9,628 Green Acres Tributary (U/S) 3-hr 53,184,390 1.52 40,590,281 1.16 30,739,471 0.88 16,513,554 0.47 9,913,353 0.28 3,863,971 0.11 

HC033 10500 9,404 E-470 / Stonegate Tributary (D/S) 3-hr 52,085,559 1.53 39,784,638 1.17 30,150,379 0.88 16,258,870 0.48 9,746,211 0.29 3,783,433 0.11 

HC032 10500 9,088 Stonegate Tributary (U/S) 3-hr 50,179,909 1.52 38,282,929 1.16 28,963,793 0.88 15,547,648 0.47 9,251,571 0.28 3,517,854 0.11 

HC029 16200 8,743 Grandview Tributary (D/S) 3-hr 48,348,845 1.52 36,900,743 1.16 27,930,690 0.88 15,038,944 0.47 8,957,045 0.28 3,394,967 0.11 

HC028 16200 8,190 Grandview Tributary (U/S) 3-hr 45,339,070 1.53 34,614,899 1.16 26,207,781 0.88 14,136,680 0.48 8,429,244 0.28 3,187,799 0.11 

HC026 20100 7,938 Lincoln Ave / Badger Gulch (D/S) 3-hr 44,004,151 1.53 33,608,911 1.17 25,458,799 0.88 13,763,561 0.48 8,220,214 0.29 3,114,560 0.11 

HC025 20100 6,009 Badger Gulch (U/S) 2-hr 35,386,513 1.62 27,325,961 1.25 20,826,378 0.95 11,909,483 0.55 7,423,636 0.34 2,670,020 0.12 

HC021 32000 5,234 Ridgegate Parkway 2-hr 31,117,425 1.64 24,103,021 1.27 18,423,819 0.97 10,680,600 0.56 6,731,837 0.35 2,441,534 0.13 

HC016 43500 4,210 I-25 2-hr 25,602,934 1.68 19,985,589 1.31 15,392,903 1.01 9,183,169 0.60 5,970,960 0.39 2,315,957 0.15 

HC014 46100 3,966 Oak Hills Tributary (D/S) 2-hr 24,261,036 1.69 18,975,576 1.32 14,643,981 1.02 8,797,614 0.61 5,764,820 0.40 2,278,674 0.16 

HC013 46100 2,014 Oak Hills Tributary (U/S) 2-hr 12,659,590 1.73 9,992,087 1.37 7,782,370 1.06 4,820,348 0.66 3,268,899 0.45 1,409,195 0.19 

HC009 54300 1,591 500' N of Oak Hills Drive / Beverly Hills Tributary (D/S) 2-hr 10,262,774 1.78 8,165,134 1.41 6,409,269 1.11 4,077,590 0.71 2,836,752 0.49 1,283,666 0.22 

HC008 54500 1,138 Beverly Hills Tributary (U/S) 2-hr 7,416,011 1.79 5,918,405 1.43 4,660,028 1.13 2,993,854 0.72 2,103,504 0.51 973,255 0.24 

HC005 59600 829 Castle Pines City Limit / CPNMD Pond #12 Outflow 2-hr 5,668,091 1.88 4,587,333 1.52 3,660,779 1.22 2,455,168 0.82 1,791,967 0.60 886,004 0.29 

HC003 62500 369 Castle Pines Parkway / CPNMD Pond #11 Outflow 2-hr 2,578,406 1.92 2,099,034 1.57 1,684,677 1.26 1,149,382 0.86 852,834 0.64 436,490 0.33 

Page B-16



SWMM 

Node 

Table B-6 

Runoff Volumes – Future Development 

Cumulative 


Station 

Drainage 

Area 

Design 100-YR 50-YR 25-YR 10-YR 5-YR 2-YR 

(ft) (ac) Landmark 

Storm (cf) (in) (cf) (in) (cf) (in) (cf) (in) (cf) (in) (cf) (in) 

HC999 0 11,193 Cherry Creek 3-hr 73,983,567 1.82 59,852,291 1.47 48,531,007 1.19 31,877,858 0.78 23,539,200 0.58 13,042,502 0.32 

HC036 2700 11,053 Jordan Rd (U/S) / Green Acres Trib (D/S) 3-hr 72,828,898 1.82 58,863,138 1.47 47,676,792 1.19 31,236,471 0.78 23,010,385 0.57 12,700,021 0.32 

HC035 2700 9,628 Green Acres Tributary (U/S) 3-hr 61,267,159 1.75 49,010,127 1.40 39,222,844 1.12 24,944,057 0.71 17,868,841 0.51 9,421,958 0.27 

HC033 10500 9,404 E-470 / Stonegate Tributary (D/S) 3-hr 59,535,010 1.74 47,549,279 1.39 37,974,090 1.11 24,037,645 0.70 17,118,843 0.50 8,932,713 0.26 

HC032 10500 9,088 Stonegate Tributary (U/S) 3-hr 57,270,622 1.74 45,673,561 1.38 36,410,905 1.10 22,952,276 0.70 16,269,265 0.49 8,416,469 0.26 

HC029 16200 8,743 Grandview Tributary (D/S) 3-hr 55,303,842 1.74 44,150,372 1.39 35,235,005 1.11 22,301,182 0.70 15,841,244 0.50 8,201,200 0.26 

HC028 16200 8,190 Grandview Tributary (U/S) 3-hr 51,252,088 1.72 40,777,391 1.37 32,414,367 1.09 20,310,492 0.68 14,277,049 0.48 7,259,722 0.24 

HC026 20100 7,938 Lincoln Ave / Badger Gulch (D/S) 3-hr 49,675,583 1.72 39,519,557 1.37 31,411,175 1.09 19,685,298 0.68 13,828,071 0.48 7,016,068 0.24 

HC025 20100 6,009 Badger Gulch (U/S) 2-hr 38,802,619 1.78 30,877,697 1.42 24,255,605 1.11 15,438,803 0.71 10,775,158 0.49 4,982,965 0.23 

HC021 32000 5,234 Ridgegate Parkway 2-hr 32,768,652 1.72 25,822,796 1.36 20,082,953 1.06 12,385,411 0.65 8,351,774 0.44 3,551,810 0.19 

HC016 43500 4,210 I-25 2-hr 25,819,009 1.69 20,210,999 1.32 15,610,224 1.02 9,406,427 0.62 6,182,339 0.40 2,458,244 0.16 

HC014 46100 3,966 Oak Hills Tributary (D/S) 2-hr 24,421,656 1.70 19,142,974 1.33 14,805,552 1.03 8,963,633 0.62 5,922,487 0.41 2,387,020 0.17 

HC013 46100 2,014 Oak Hills Tributary (U/S) 2-hr 12,785,288 1.75 10,122,826 1.38 7,908,854 1.08 4,950,281 0.68 3,392,892 0.46 1,497,297 0.20 

HC009 54300 1,591 500' N of Oak Hills Drive / Beverly Hills Tributary (D/S) 2-hr 10,369,923 1.80 8,276,358 1.43 6,517,337 1.13 4,188,289 0.73 2,942,881 0.51 1,362,375 0.24 

HC008 54500 1,138 Beverly Hills Tributary (U/S) 2-hr 7,421,663 1.80 5,924,350 1.43 4,665,560 1.13 2,999,659 0.73 2,108,982 0.51 976,526 0.24 

HC005 59600 829 Castle Pines City Limit / CPNMD Pond #12 Outflow 2-hr 5,669,835 1.88 4,589,151 1.52 3,662,404 1.22 2,456,891 0.82 1,793,641 0.60 887,267 0.29 

HC003 62500 369 Castle Pines Parkway / CPNMD Pond #11 Outflow 2-hr 2,578,406 1.92 2,099,034 1.57 1,684,677 1.26 1,149,382 0.86 852,834 0.64 436,490 0.33 

Page B-17



Figure B-6 

Hydrographs – Existing Development 

Confluence with Cherry Creek 

SWMM Element HC999 



9000 

8000 

8000 

7000 

Flow (cfs) 

7000 

6000 

5000 

4000 

3000 

2000 

100-Year 

10-Year 

2-Year 

Flow (cfs) 

6000 

5000 

4000 

3000 

2000 

100-Year 

10-Year 

2-Year 

1000 

1000 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

6000 

I-25 


1600 

Castle Pines City Limit 


Flow (cfs) 

5000 

4000 

3000 

2000 

1000 

100-Year 

10-Year 

2-Year 

Flow (cfs) 

1400 

1200 

1000 

800 

600 

400 

200 

100-Year 

10-Year 

2-Year 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

Page B-18



Figure B-7 

Hydrographs – Future Development 

Flow (cfs) 

10000 

9000 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

Confluence with Cherry Creek 


0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

100-Year 

10-Year 

2-Year 

Flow (cfs) 

9000 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 



0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

100-Year 

10-Year 

2-Year 

6000 

I-25 


1600 

Castle Pines City Limit 


Flow (cfs) 

5000 

4000 

3000 

2000 

1000 

100-Year 

10-Year 

2-Year 

Flow (cfs) 

1400 

1200 

1000 

800 

600 

400 

200 

100-Year 

10-Year 

2-Year 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

0 

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 

Time (H:M) 

Page B-19



10000 

Figure B-8 

Peak Flow Diagram – Existing Development 

100-YR 

9000 

50-YR 

Peak Flow (cfs) 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

Cherry Creek 

Jordan Road 

(Green Acres Trib) 

E-470 (Stonegate Trib) 


Lincoln Ave 

(Badger Gulch) 

Ridgegate Parkway 

I-25 

Oak Hills and Oak Ridge Tributaries 

Oak Hills Drive (Beverly Hills Trib) 

25-YR 

10-YR 

5-YR 

2-YR 

Castle Pines City Limit (CPNMD Pond #12) 

Castle Pines Parkway (CPNMD Pond #11) 

Monarch Blvd. 

1000 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page B-20



Figure B-9 

Peak Flow Diagram – Future Development 

10000 


9000 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

Cherry Creek 

Jordan Road 




Lincoln Ave 



I-25 



100-YR 

50-YR 

25-YR 

10-YR 

5-YR 

2-YR 



Monarch Blvd. 

1000 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page B-21



Table B-7 

Sample SWMM Input 

[TITLE] 


BASELINE HYDROLOGY SWMM MODEL 

100-YR, 3-HR STORM, FUTURE DEVELOPMENT 

[OPTIONS] 

FLOW_UNITS CFS 

INFILTRATION HORTON 

FLOW_ROUTING KINWAVE 

START_DATE 01/01/2005 

START_TIME 00:00:00 

REPORT_START_DATE 01/01/2005 

REPORT_START_TIME 00:00:00 

END_DATE 01/05/2005 

END_TIME 00:00:00 

SWEEP_START 01/01 

SWEEP_END 12/31 

DRY_DAYS 0 

REPORT_STEP 00:01:00 

WET_STEP 00:05:00 

DRY_STEP 01:00:00 

ROUTING_STEP 0:00:30 

ALLOW_PONDING NO 

INERTIAL_DAMPING PARTIAL 

VARIABLE_STEP 0.75 

LENGTHENING_STEP 0 

MIN_SURFAREA 0 

NORMAL_FLOW_LIMITED BOTH 

SKIP_STEADY_STATE NO 

FORCE_MAIN_EQUATION H-W 

LINK_OFFSETS DEPTH 

MIN_SLOPE 0 

[FILES] 

USE INFLOWS "P:\12-010.01 Happy Canyon Creek MDP & FHAD 

UDFCD\Hydrology\CUHP\FUTURE\HappyCanyon_FU_100_3-hr_CUHP Output.txt" 

[EVAPORATION] 

;;Type Parameters 

;;---------- ---------- 

CONSTANT 0.0 

DRY_ONLY NO 

[JUNCTIONS] 

;; Invert Max. Init. Surcharge Ponded 

;;Name Elev. Depth Depth Depth Area 

;;-------------- ---------- ---------- ---------- ---------- ---------- 

A100 6401 0 0 0 0 

A105 6401 0 0 0 0 

A110 6386 0 0 0 0 

A120 6347 0 0 0 0 

A125 6361 0 0 0 0 

A130 6319 0 0 0 0 

A134 6387 0 0 0 0 

A135 6319 0 0 0 0 

A140 6306 0 0 0 0 

A150 6281 0 0 0 0 

A160 6258 0 0 0 0 

A170 6239 0 0 0 0 

A180 6201 0 0 0 0 

A190 6190 0 0 0 0 

A195 6190 0 0 0 0 

A200 6161 0 0 0 0 

A210 6109 0 0 0 0 

A215 6095 0 0 0 0 

A220 6095 0 0 0 0 

A230 6086 0 0 0 0 

A234 6084 0 0 0 0 

A235 6069 0 0 0 0 

A240 6068 0 0 0 0 

A245 6047 0 0 0 0 

A250 6051 0 0 0 0 

A260 5991 0 0 0 0 

A263 6066 0 0 0 0 

A264 6066 0 0 0 0 

A265 6006 0 0 0 0 

Page B-22



A270 5966 0 0 0 0 

A275 5971 0 0 0 0 

A276 5971 0 0 0 0 

A280 5961 0 0 0 0 

A285 6016 0 0 0 0 

A290 5929 0 0 0 0 

A295 5993 0 0 0 0 

A300 5886 0 0 0 0 

A304 5971 0 0 0 0 

A305 5891 0 0 0 0 

A310 5870 0 0 0 0 

A314 5916 0 0 0 0 

A315 5870 0 0 0 0 

A320 5870 0 0 0 0 

A325 5836 0 0 0 0 

A330 5815 0 0 0 0 

A340 5809 0 0 0 0 

A345 5809 0 0 0 0 

A350 5795 0 0 0 0 

A360 5781 0 0 0 0 

A370 5760 0 0 0 0 

A375 5760 0 0 0 0 

A380 5737 0 0 0 0 

A390 5698 0 0 0 0 

A395 5696 0 0 0 0 

A400 5668 0 0 0 0 

B100 6381 0 0 0 0 

B110 6316 0 0 0 0 

B120 6301 0 0 0 0 

B130 6239 0 0 0 0 

B134 6361 0 0 0 0 

B135 6239 0 0 0 0 

BG001 6275 0 0 0 0 

BG002 6240 0 0 0 0 

BG003 6195 0 0 0 0 

BG004 6160 0 0 0 0 

BG005 6125 0 0 0 0 

BG006 6085 0 0 0 0 

BG007 6045 0 0 0 0 

BG008 6015 0 0 0 0 

BG009 5975 0 0 0 0 

BG010 5947 0 0 0 0 

BG011 5885 0 0 0 0 

BG109 6055 0 0 0 0 

BG111 5947 0 0 0 0 

BG999 5835 0 0 0 0 

BH001 6380 0 0 0 0 

BH002 6315 0 0 0 0 

BH003 6300 0 0 0 0 

BH100 6360 0 0 0 0 

BH999 6238 0 0 0 0 

C100 6441 0 0 0 0 

C110 6396 0 0 0 0 

C120 6351 0 0 0 0 

C125 6351 0 0 0 0 

C130 6311 0 0 0 0 

C140 6283 0 0 0 0 

C150 6246 0 0 0 0 

C153 6376 0 0 0 0 

C154 6307 0 0 0 0 

C155 6256 0 0 0 0 

C159 6246 0 0 0 0 

C160 6216 0 0 0 0 

C170 6171 0 0 0 0 

C175 6171 0 0 0 0 

C180 6150 0 0 0 0 

C185 6150 0 0 0 0 

C190 6109 0 0 0 0 

D100 6281 0 0 0 0 

D110 6221 0 0 0 0 

D120 6196 0 0 0 0 

D130 6109 0 0 0 0 

E100 6276 0 0 0 0 

E105 6276 0 0 0 0 

E110 6241 0 0 0 0 

E120 6196 0 0 0 0 

E125 6196 0 0 0 0 

E130 6161 0 0 0 0 

E135 6161 0 0 0 0 

E140 6126 0 0 0 0 

E150 6086 0 0 0 0 

E155 6086 0 0 0 0 

Page B-23



E160 6046 0 0 0 0 

E170 6021 0 0 0 0 

E180 5981 0 0 0 0 

E183 6056 0 0 0 0 

E184 6056 0 0 0 0 

E185 5981 0 0 0 0 

E190 5948 0 0 0 0 

E200 5891 0 0 0 0 

E204 5948 0 0 0 0 

E205 5886 0 0 0 0 

E210 5836 0 0 0 0 

F100 6008 0 0 0 0 

F110 5978 0 0 0 0 

F120 5906 0 0 0 0 

F125 5906 0 0 0 0 

F130 5853 0 0 0 0 

F140 5809 0 0 0 0 

G100 5887 0 0 0 0 

G105 5885 0 0 0 0 

G110 5842 0 0 0 0 

G120 5760 0 0 0 0 

GA001 5950 0 0 0 0 

GA002 5916 0 0 0 0 

GA003 5893 0 0 0 0 

GA004 5888 0 0 0 0 

GA005 5864 0 0 0 0 

GA006 5843 0 0 0 0 

GA007 5792 0 0 0 0 

GA008 5780 0 0 0 0 

GA009 5772 0 0 0 0 

GA010 5762 0 0 0 0 

GA011 5736 0 0 0 0 

GA012 5721 0 0 0 0 

GA999 5707 0 0 0 0 

GV001 6007 0 0 0 0 

GV002 5973 0 0 0 0 

GV003 5905 0 0 0 0 

GV999 5808 0 0 0 0 

H100 5951 0 0 0 0 

H110 5919 0 0 0 0 

H115 5919 0 0 0 0 

H120 5896 0 0 0 0 

H130 5892 0 0 0 0 

H140 5865 0 0 0 0 

H145 5865 0 0 0 0 

H150 5844 0 0 0 0 

H160 5793 0 0 0 0 

H170 5783 0 0 0 0 

H180 5783 0 0 0 0 

H185 5816 0 0 0 0 

H190 5763 0 0 0 0 

H200 5737 0 0 0 0 

H205 5737 0 0 0 0 

H210 5722 0 0 0 0 

H220 5708 0 0 0 0 

HC001 6400 0 0 0 0 

HC002 6385 0 0 0 0 

HC003 6340 0 0 0 0 

HC004 6318 0 0 0 0 

HC005 6300 0 0 0 0 

HC006 6280 0 0 0 0 

HC007 6257 0 0 0 0 

HC008 6238 0 0 0 0 

HC009 6237 0 0 0 0 

HC010 6200 0 0 0 0 

HC011 6189 0 0 0 0 

HC012 6160 0 0 0 0 

HC013 6108 0 0 0 0 

HC014 6107 0 0 0 0 

HC015 6094 0 0 0 0 

HC016 6085 0 0 0 0 

HC017 6067 0 0 0 0 

HC018 6045 0 0 0 0 

HC019 6000 0 0 0 0 

HC020 5965 0 0 0 0 

HC021 5955 0 0 0 0 

HC022 5923 0 0 0 0 

HC023 5885 0 0 0 0 

HC024 5864 0 0 0 0 

HC025 5835 0 0 0 0 

HC026 5834 0 0 0 0 

HC027 5814 0 0 0 0 

Page B-24



HC028 5808 0 0 0 0 

HC029 5807 0 0 0 0 

HC030 5794 0 0 0 0 

HC031 5780 0 0 0 0 

HC032 5759 0 0 0 0 

HC033 5758 0 0 0 0 

HC034 5736 0 0 0 0 

HC035 5706 0 0 0 0 

HC036 5698 0 0 0 0 

HC037 5695 0 0 0 0 

HC103 6360 0 0 0 0 

HC104 6386 0 0 0 0 

HC116 6083 0 0 0 0 

HC117 6068 0 0 0 0 

HC119 6065 0 0 0 0 

HC122 6015 0 0 0 0 

HC123 5970 0 0 0 0 

HC124 5915 0 0 0 0 

HC999 5667 0 0 0 0 

MT100 6375 0 0 0 0 

MT110 6300 0 0 0 0 

OH001 6440 0 0 0 0 

OH002 6395 0 0 0 0 

OH003 6350 0 0 0 0 

OH004 6309 0 0 0 0 

OH005 6281 0 0 0 0 

OH006 6255 0 0 0 0 

OH007 6245 0 0 0 0 

OH008 6215 0 0 0 0 

OH009 6170 0 0 0 0 

OH010 6149 0 0 0 0 

OH999 6108 0 0 0 0 

OR001 6280 0 0 0 0 

OR002 6220 0 0 0 0 

OR003 6195 0 0 0 0 

OR999 6108 0 0 0 0 

SG001 5885 0 0 0 0 

SG002 5884 0 0 0 0 

SG003 5839 0 0 0 0 

SG999 5759 0 0 0 0 

[OUTFALLS] 

;; Invert Outfall Stage/Table Tide 

;;Name Elev. Type Time Series Gate 

;;-------------- ---------- ---------- ---------------- ---- 

HC-OUTFALL 5666 FREE NO 

[DIVIDERS] 

;; Invert Diverted Divider 

;;Name Elev. Link Type Parameters 

;;-------------- ---------- ---------------- ---------- ---------- 

GV004 5852 F14-Overflow OVERFLOW 0 0 0 0 

[STORAGE] 

;; Invert Max. Init. Storage Curve Ponded Evap. 

;;Name Elev. Depth Depth Curve Params Area Frac. Infiltration Parameters 

;;-------------- -------- -------- -------- ---------- -------- -------- -------- -------- -------- ----------------------- 

GA309 5917 10 0 TABULAR GA309-STORAGE-EX 0 0 

GA310 5894 14.5 0 TABULAR GA310-STORAGE-EX 0 0 



HC310 6345 23 0 TABULAR HC310-STORAGE-EX 0 0 


MT300 6301 12.2 0 TABULAR MT300-STORAGE-EX 0 0 

OH310 6310 20 0 TABULAR OH310-STORAGE-EX 0 0 

OH320 6282 21 0 TABULAR OH320-STORAGE-EX 0 0 

SG310 5886 13 0 TABULAR SG310-STORAGE-EX 0 0 

SG320 5840 12 0 TABULAR SG320-STORAGE-EX 0 0 


GV301 6007.5 8.5 0 TABULAR GV301-STORAGE-EX 0 0 

GV302 5973.5 9.5 0 TABULAR GV302-STORAGE-EX 0 0 

[CONDUITS] 

;; Inlet Outlet Manning Inlet Outlet Init. Max. 

;;Name Node Node Length N Offset Offset Flow Flow 

;;-------------- ---------------- ---------------- ---------- ---------- ---------- ---------- ---------- ---------- 

A100-DF A100 HC001 10 0.01 0 0 0 0 

A105-DF A105 HC001 10 0.01 0 0 0 0 

A11 HC001 HC002 730 .087 0 0 0 0 

A110-DF A110 HC002 10 0.01 0 0 0 0 

A12 HC002 HC310 1650 .093 0 0 0 0 

A120-DF A120 HC310 10 0.01 0 0 0 0 

Page B-25



A125-DF A125 HC103 10 0.01 0 0 0 0 

A13 HC003 HC004 1350 .077 0 0 0 0 

A130 HC103 HC004 1340 .102 0 0 0 0 

A130-DF A130 HC004 10 0.01 0 0 0 0 

A134-DF A134 HC104 10 0.01 0 0 0 0 

A135 HC104 HC004 2540 .099 0 0 0 0 

A135-DF A135 HC004 10 0.01 0 0 0 0 

A14 HC004 HC320 1270 .063 0 0 0 0 

A140-DF A140 HC320 10 0.01 0 0 0 0 

A15 HC005 HC006 710 .089 0 0 0 0 

A150-DF A150 HC006 10 0.01 0 0 0 0 

A16 HC006 HC007 1700 .067 0 0 0 0 

A160-DF A160 HC007 10 0.01 0 0 0 0 

A17 HC007 HC008 1460 .069 0 0 0 0 

A170-DF A170 HC008 10 0.01 0 0 0 0 

A18 HC009 HC010 2520 .069 0 0 0 0 

A180-DF A180 HC010 10 0.01 0 0 0 0 

A19 HC010 HC011 940 .064 0 0 0 0 

A190-DF A190 HC011 10 0.01 0 0 0 0 

A195-DF A195 HC011 10 0.01 0 0 0 0 

A20 HC011 HC012 1850 .069 0 0 0 0 

A200-DF A200 HC012 10 0.01 0 0 0 0 

A21 HC012 HC013 3070 .071 0 0 0 0 

A210-DF A210 HC013 10 0.01 0 0 0 0 

A215-DF A215 HC015 10 0.01 0 0 0 0 

A22 HC014 HC015 1410 .051 0 0 0 0 

A220-DF A220 HC015 10 0.01 0 0 0 0 

A23 HC015 HC016 1080 .051 0 0 0 0 

A230-DF A230 HC016 10 0.01 0 0 0 0 

A234-DF A234 HC116 10 0.01 0 0 0 0 

A235 HC116 HC117 2280 .052 0 0 0 0 

A235-DF A235 HC117 10 0.01 0 0 0 0 

A24 HC016 HC017 1290 .064 0 0 0 0 

A240-DF A240 HC017 10 0.01 0 0 0 0 

A245-DF A245 HC018 10 0.01 0 0 0 0 

A25 HC017 HC018 1980 .060 0 0 0 0 

A250-DF A250 HC018 10 0.01 0 0 0 0 

A26 HC018 HC019 3070 .068 0 0 0 0 

A260-DF A260 HC019 10 0.01 0 0 0 0 

A263-DF A263 HC119 10 0.01 0 0 0 0 

A264-DF A264 HC119 10 0.01 0 0 0 0 

A265 HC119 HC019 1810 0.111 0 0 0 0 

A265-DF A265 HC019 10 0.01 0 0 0 0 

A27 HC019 HC020 3050 .056 0 0 0 0 

A270-DF A270 HC020 10 0.01 0 0 0 0 

A275-DF A275 HC020 10 0.01 0 0 0 0 

A276-DF A276 HC020 10 0.01 0 0 0 0 

A28 HC020 HC021 1120 .053 0 0 0 0 

A280-DF A280 HC021 10 0.01 0 0 0 0 

A285-DF A285 HC122 10 0.01 0 0 0 0 

A29 HC021 HC022 2900 .059 0 0 0 0 

A290 HC122 HC022 2820 0.116 0 0 0 0 

A290-DF A290 HC022 10 0.01 0 0 0 0 

A295 A295 HC022 1110 .016 0 0 0 0 

A30 HC022 HC023 3080 .063 0 0 0 0 

A300-DF A300 HC023 10 0.01 0 0 0 0 

A304-DF A304 HC123 10 0.01 0 0 0 0 

A305 HC123 HC023 2660 0.111 0 0 0 0 

A305-DF A305 HC023 10 0.01 0 0 0 0 

A31 HC023 HC024 2550 .056 0 0 0 0 

A310-DF A310 HC024 10 0.01 0 0 0 0 

A314-DF A314 HC124 10 0.01 0 0 0 0 

A315 HC124 HC024 1530 0.035 0 0 0 0 

A315-DF A315 HC024 10 0.01 0 0 0 0 

A32 HC024 HC025 2340 .065 0 0 0 0 

A320-DF A320 HC025 10 0.01 0 0 0 0 

A325-DF A325 HC326 10 0.01 0 0 0 0 

A33 HC026 HC027 2730 .050 0 0 0 0 

A330-DF A330 HC027 10 0.01 0 0 0 0 

A34 HC027 HC028 900 .048 0 0 0 0 

A340-DF A340 HC028 10 0.01 0 0 0 0 

A345-DF A345 HC028 10 0.01 0 0 0 0 

A35 HC029 HC030 1560 .052 0 0 0 0 

A350-DF A350 HC030 10 0.01 0 0 0 0 

A36 HC030 HC031 1900 .052 0 0 0 0 

A360-DF A360 HC031 10 0.01 0 0 0 0 

A37 HC031 HC032 2000 .060 0 0 0 0 

A370-DF A370 HC032 10 0.01 0 0 0 0 

A375-DF A375 HC032 10 0.01 0 0 0 0 

A38 HC033 HC034 3000 .050 0 0 0 0 

A380-DF A380 HC034 10 0.01 0 0 0 0 

A39 HC034 HC035 4580 .053 0 0 0 0 

Page B-26



A390-DF A390 HC035 10 0.01 0 0 0 0 

A395-DF A395 HC037 10 0.01 0 0 0 0 

A40 HC037 HC999 2600 .060 0 0 0 0 

A400-DF A400 HC999 10 0.01 0 0 0 0 

B100-DF B100 BH001 10 0.01 0 0 0 0 

B11 BH001 BH002 1740 .116 0 0 0 0 

B110-DF B110 BH002 10 0.01 0 0 0 0 

B12 BH002 BH003 1230 .072 0 0 0 0 

B120-DF B120 BH003 10 0.01 0 0 0 0 

B13 BH003 BH999 2060 .106 0 0 0 0 

B130-DF B130 BH999 10 0.01 0 0 0 0 

B134-DF B134 BH100 10 0.01 0 0 0 0 

B135 BH100 BH999 3220 0.01 0 0 0 0 

B135-DF B135 BH999 10 0.01 0 0 0 0 

BG999-DF BG999 HC026 10 0.01 0 0 0 0 

BH999-DF BH999 HC009 10 0.01 0 0 0 0 

C100-DF C100 OH001 10 0.01 0 0 0 0 

C11 OH001 OH002 1130 .12 0 0 0 0 

C110-DF C110 OH002 10 0.01 0 0 0 0 

C12 OH002 OH003 1890 .087 0 0 0 0 

C120-DF C120 OH003 10 0.01 0 0 0 0 

C125-DF C125 OH003 10 0.01 0 0 0 0 

C13 OH003 OH310 2230 .07 0 0 0 0 

C130-DF C130 OH310 10 0.01 0 0 0 0 

C14 OH004 OH320 1070 .088 0 0 0 0 

C140-DF C140 OH320 10 0.01 0 0 0 0 

C150-DF C150 OH007 10 0.01 0 0 0 0 

C153-DF C153 MT100 10 0.01 0 0 0 0 

C154 MT100 MT300 1950 0.01 0 0 0 0 

C154-DF C154 MT300 10 0.01 0 0 0 0 

C155 MT110 OH006 1690 .08 0 0 0 0 

C155-DF C155 OH006 10 0.01 0 0 0 0 

C159-DF C159 OH007 10 0.01 0 0 0 0 

C15A OH005 OH006 1410 .078 0 0 0 0 

C15B OH006 OH007 1110 .054 0 0 0 0 

C16 OH007 OH008 1360 .082 0 0 0 0 

C160-DF C160 OH008 10 0.01 0 0 0 0 

C17 OH008 OH009 3400 .064 0 0 0 0 

C170-DF C170 OH009 10 0.01 0 0 0 0 

C175-DF C175 OH009 10 0.01 0 0 0 0 

C18 OH009 OH010 1090 .073 0 0 0 0 

C180-DF C180 OH010 10 0.01 0 0 0 0 

C185-DF C185 OH010 10 0.01 0 0 0 0 

C19 OH010 OH999 2280 .074 0 0 0 0 

C190-DF C190 OH999 10 0.01 0 0 0 0 

D100-DF D100 OR001 10 0.01 0 0 0 0 

D11 OR001 OR002 2630 .093 0 0 0 0 

D110-DF D110 OR002 10 0.01 0 0 0 0 

D12 OR002 OR003 1270 .088 0 0 0 0 

D120-DF D120 OR003 10 0.01 0 0 0 0 

D13 OR003 OR999 3120 .092 0 0 0 0 

D130-DF D130 OR999 10 0.01 0 0 0 0 

E100-DF E100 BG001 10 0.01 0 0 0 0 

E105-DF E105 BG001 10 0.01 0 0 0 0 

E11 BG001 BG002 1730 .093 0 0 0 0 

E110-DF E110 BG002 10 0.01 0 0 0 0 

E12 BG002 BG003 1500 .103 0 0 0 0 

E120-DF E120 BG003 10 0.01 0 0 0 0 

E125-DF E125 BG003 10 0.01 0 0 0 0 

E13 BG003 BG004 1710 .085 0 0 0 0 

E130-DF E130 BG004 10 0.01 0 0 0 0 

E135-DF E135 BG004 10 0.01 0 0 0 0 

E14 BG004 BG005 1900 .080 0 0 0 0 

E140-DF E140 BG005 10 0.01 0 0 0 0 

E15 BG005 BG006 1800 .086 0 0 0 0 

E150-DF E150 BG006 10 0.01 0 0 0 0 

E155-DF E155 BG006 10 0.01 0 0 0 0 

E16 BG006 BG007 2310 .076 0 0 0 0 

E160-DF E160 BG007 10 0.01 0 0 0 0 

E17 BG007 BG008 1890 .072 0 0 0 0 

E170-DF E170 BG008 10 0.01 0 0 0 0 

E18 BG008 BG009 2640 .071 0 0 0 0 

E180-DF E180 BG009 10 0.01 0 0 0 0 

E183-DF E183 BG109 10 0.01 0 0 0 0 

E184-DF E184 BG109 10 0.01 0 0 0 0 

E185 BG109 BG009 2660 0.102 0 0 0 0 

E185-DF E185 BG009 10 0.01 0 0 0 0 

E19 BG009 BG010 1780 .070 0 0 0 0 

E190-DF E190 BG010 10 0.01 0 0 0 0 

E20 BG010 BG011 4500 .070 0 0 0 0 

E200-DF E200 BG011 10 0.01 0 0 0 0 

E204-DF E204 BG111 10 0.01 0 0 0 0 

Page B-27



E205 BG111 BG011 3210 0.115 0 0 0 0 

E205-DF E205 BG011 10 0.01 0 0 0 0 

E21 BG011 BG999 3820 .066 0 0 0 0 

E210-DF E210 BG999 10 0.01 0 0 0 0 

F100-DF F100 GV301 10 0.01 0 0 0 0 

F11 GV001 GV302 2200 0.016 0 0 0 0 

F110-DF F110 GV302 10 0.01 0 0 0 0 

F12 GV002 GV003 3690 .016 0 0 0 0 

F120-DF F120 GV003 10 0.01 0 0 0 0 

F125-DF F125 GV003 10 0.01 0 0 0 0 

F13 GV003 GV004 3590 .076 0 0 0 0 

F130-DF F130 GV004 10 0.01 0 0 0 0 

F14 GV004 GV999 2920 .016 0 0 0 0 

F140-DF F140 GV999 10 0.01 0 0 0 0 

F14-Overflow GV004 GV999 2920 .082 0 0 0 0 

G10 SG001 SG002 120 .016 0 0 0 0 

G100-DF G100 SG310 10 0.01 0 0 0 0 

G105-DF G105 SG002 10 0.01 0 0 0 0 

G11 SG002 SG320 2290 .108 0 0 0 0 

G110-DF G110 SG320 10 0.01 0 0 0 0 

G12 SG003 SG999 4140 .016 0 0 0 0 

G120-DF G120 SG999 10 0.01 0 0 0 0 

GA999-DF GA999 HC036 10 0.01 0 0 0 0 

GV999-DF GV999 HC029 10 0.01 0 0 0 0 

H100-DF H100 GA001 10 0.01 0 0 0 0 

H11 GA001 GA309 2000 .016 0 0 0 0 

H110-DF H110 GA309 10 0.01 0 0 0 0 

H115-DF H115 GA309 10 0.01 0 0 0 0 

H12 GA002 GA310 1250 .016 0 0 0 0 

H120-DF H120 GA310 10 0.01 0 0 0 0 

H13 GA003 GA311 470 .051 0 0 0 0 

H130-DF H130 GA311 10 0.01 0 0 0 0 

H14 GA004 GA005 1460 .084 0 0 0 0 

H140-DF H140 GA005 10 0.01 0 0 0 0 

H145-DF H145 GA005 10 0.01 0 0 0 0 

H15 GA005 GA006 1980 .068 0 0 0 0 

H150-DF H150 GA006 10 0.01 0 0 0 0 

H16 GA006 GA007 3370 .082 0 0 0 0 

H160-DF H160 GA007 10 0.01 0 0 0 0 

H17 GA007 GA350 1450 .054 0 0 0 0 

H170-DF H170 GA350 10 0.01 0 0 0 0 

H18 GA008 GA009 1360 .016 0 0 0 0 

H180-DF H180 GA350 10 0.01 0 0 0 0 

H185 H185 GA009 1970 .016 0 0 0 0 

H19 GA009 GA010 940 .065 0 0 0 0 

H190-DF H190 GA010 10 0.01 0 0 0 0 

H20 GA010 GA011 2530 .062 0 0 0 0 

H200-DF H200 GA011 10 0.01 0 0 0 0 

H205 H205 GA011 660 .016 0 0 0 0 

H21 GA011 GA012 2300 .051 0 0 0 0 

H210-DF H210 GA012 10 0.01 0 0 0 0 

H22 GA012 GA999 1360 .062 0 0 0 0 

H220-DF H220 GA999 10 0.01 0 0 0 0 

HC008-DF HC008 HC009 10 0.01 0 0 0 0 

HC013-DF HC013 HC014 10 0.01 0 0 0 0 

HC025-DF HC025 HC026 10 0.01 0 0 0 0 

HC028-DF HC028 HC029 10 0.01 0 0 0 0 

HC032-DF HC032 HC033 10 0.01 0 0 0 0 

HC035-DF HC035 HC036 10 0.01 0 0 0 0 

HC036-DF HC036 HC037 10 0.01 0 0 0 0 

HC117-DF HC117 HC017 10 0.01 0 0 0 0 

HC999-DF HC999 HC-OUTFALL 10 0.01 0 0 0 0 

OH999-DF OH999 HC014 10 0.01 0 0 0 0 

OR999-DF OR999 HC014 10 0.01 0 0 0 0 

SG999-DF SG999 HC033 10 0.01 0 0 0 0 

[OUTLETS] 

;; Inlet Outlet Outflow Outlet Qcoeff/ Flap 

;;Name Node Node Height Type QTable Qexpon Gate 

;;-------------- ---------------- ---------------- ---------- --------------- ---------------- ---------- ---- 

GA309-OUT GA309 GA002 0 TABULAR/DEPTH GA309-DISCHARGE-EX NO 




GV301-OUT GV301 GV001 0 TABULAR/DEPTH GV301-DISCHARGE-EX NO 

GV302-OUT GV302 GV002 0 TABULAR/DEPTH GV302-DISCHARGE-EX NO 

HC310-OUT HC310 HC003 0 TABULAR/DEPTH HC310-DISCHARGE-EX NO 



MT300-OUT MT300 MT110 0 TABULAR/DEPTH MT300-DISCHARGE-EX NO 

OH310-OUT OH310 OH004 0 TABULAR/DEPTH OH310-DISCHARGE-EX NO 

OH320-OUT OH320 OH005 0 TABULAR/DEPTH OH320-DISCHARGE-EX NO 

Page B-28



SG310-OUT SG310 SG001 0 TABULAR/DEPTH SG310-DISCHARGE-EX NO 

SG320-OUT SG320 SG003 0 TABULAR/DEPTH SG320-DISCHARGE-EX NO 

[XSECTIONS] 

;;Link Shape Geom1 Geom2 Geom3 Geom4 Barrels 

;;-------------- ------------ ---------------- ---------- ---------- ---------- ---------- 

A100-DF DUMMY 0 0 0 0 1 

A105-DF DUMMY 0 0 0 0 1 

A11 TRAPEZOIDAL 10 5 4 4 1 

A110-DF DUMMY 0 0 0 0 1 


A120-DF DUMMY 0 0 0 0 1 

A125-DF DUMMY 0 0 0 0 1 



A130-DF DUMMY 0 0 0 0 1 

A134-DF DUMMY 0 0 0 0 1 

A135 TRAPEZOIDAL 10 15 10 10 1 

A135-DF DUMMY 0 0 0 0 1 


A140-DF DUMMY 0 0 0 0 1 


A150-DF DUMMY 0 0 0 0 1 


A160-DF DUMMY 0 0 0 0 1 


A170-DF DUMMY 0 0 0 0 1 


A180-DF DUMMY 0 0 0 0 1 


A190-DF DUMMY 0 0 0 0 1 

A195-DF DUMMY 0 0 0 0 1 


A200-DF DUMMY 0 0 0 0 1 


A210-DF DUMMY 0 0 0 0 1 

A215-DF DUMMY 0 0 0 0 1 


A220-DF DUMMY 0 0 0 0 1 


A230-DF DUMMY 0 0 0 0 1 

A234-DF DUMMY 0 0 0 0 1 


A235-DF DUMMY 0 0 0 0 1 


A240-DF DUMMY 0 0 0 0 1 

A245-DF DUMMY 0 0 0 0 1 


A250-DF DUMMY 0 0 0 0 1 


A260-DF DUMMY 0 0 0 0 1 

A263-DF DUMMY 0 0 0 0 1 

A264-DF DUMMY 0 0 0 0 1 


A265-DF DUMMY 0 0 0 0 1 


A270-DF DUMMY 0 0 0 0 1 

A275-DF DUMMY 0 0 0 0 1 

A276-DF DUMMY 0 0 0 0 1 


A280-DF DUMMY 0 0 0 0 1 

A285-DF DUMMY 0 0 0 0 1 



A290-DF DUMMY 0 0 0 0 1 

A295 CIRCULAR 4 0 0 0 1 


A300-DF DUMMY 0 0 0 0 1 

A304-DF DUMMY 0 0 0 0 1 


A305-DF DUMMY 0 0 0 0 1 


A310-DF DUMMY 0 0 0 0 1 

A314-DF DUMMY 0 0 0 0 1 


A315-DF DUMMY 0 0 0 0 1 


A320-DF DUMMY 0 0 0 0 1 

A325-DF DUMMY 0 0 0 0 1 


A330-DF DUMMY 0 0 0 0 1 


Page B-29



A340-DF DUMMY 0 0 0 0 1 

A345-DF DUMMY 0 0 0 0 1 


A350-DF DUMMY 0 0 0 0 1 


A360-DF DUMMY 0 0 0 0 1 


A370-DF DUMMY 0 0 0 0 1 

A375-DF DUMMY 0 0 0 0 1 


A380-DF DUMMY 0 0 0 0 1 


A390-DF DUMMY 0 0 0 0 1 

A395-DF DUMMY 0 0 0 0 1 


A400-DF DUMMY 0 0 0 0 1 

B100-DF DUMMY 0 0 0 0 1 

B11 TRAPEZOIDAL 10 15 4 4 1 

B110-DF DUMMY 0 0 0 0 1 


B120-DF DUMMY 0 0 0 0 1 


B130-DF DUMMY 0 0 0 0 1 

B134-DF DUMMY 0 0 0 0 1 


B135-DF DUMMY 0 0 0 0 1 

BG999-DF DUMMY 0 0 0 0 1 

BH999-DF DUMMY 0 0 0 0 1 

C100-DF DUMMY 0 0 0 0 1 

C11 TRAPEZOIDAL 10 20 4 10 1 

C110-DF DUMMY 0 0 0 0 1 


C120-DF DUMMY 0 0 0 0 1 

C125-DF DUMMY 0 0 0 0 1 


C130-DF DUMMY 0 0 0 0 1 


C140-DF DUMMY 0 0 0 0 1 

C150-DF DUMMY 0 0 0 0 1 

C153-DF DUMMY 0 0 0 0 1 


C154-DF DUMMY 0 0 0 0 1 


C155-DF DUMMY 0 0 0 0 1 

C159-DF DUMMY 0 0 0 0 1 

C15A TRAPEZOIDAL 10 10 3 3 1 

C15B TRAPEZOIDAL 10 10 3 3 1 


C160-DF DUMMY 0 0 0 0 1 


C170-DF DUMMY 0 0 0 0 1 

C175-DF DUMMY 0 0 0 0 1 


C180-DF DUMMY 0 0 0 0 1 

C185-DF DUMMY 0 0 0 0 1 


C190-DF DUMMY 0 0 0 0 1 

D100-DF DUMMY 0 0 0 0 1 

D11 TRAPEZOIDAL 10 10 5 5 1 

D110-DF DUMMY 0 0 0 0 1 


D120-DF DUMMY 0 0 0 0 1 


D130-DF DUMMY 0 0 0 0 1 

E100-DF DUMMY 0 0 0 0 1 

E105-DF DUMMY 0 0 0 0 1 

E11 TRAPEZOIDAL 10 10 4 4 1 

E110-DF DUMMY 0 0 0 0 1 


E120-DF DUMMY 0 0 0 0 1 

E125-DF DUMMY 0 0 0 0 1 


E130-DF DUMMY 0 0 0 0 1 

E135-DF DUMMY 0 0 0 0 1 


E140-DF DUMMY 0 0 0 0 1 


E150-DF DUMMY 0 0 0 0 1 

E155-DF DUMMY 0 0 0 0 1 


E160-DF DUMMY 0 0 0 0 1 


Page B-30



E170-DF DUMMY 0 0 0 0 1 


E180-DF DUMMY 0 0 0 0 1 

E183-DF DUMMY 0 0 0 0 1 

E184-DF DUMMY 0 0 0 0 1 


E185-DF DUMMY 0 0 0 0 1 


E190-DF DUMMY 0 0 0 0 1 


E200-DF DUMMY 0 0 0 0 1 

E204-DF DUMMY 0 0 0 0 1 


E205-DF DUMMY 0 0 0 0 1 


E210-DF DUMMY 0 0 0 0 1 

F100-DF DUMMY 0 0 0 0 1 

F11 CIRCULAR 5 0 0 0 1 

F110-DF DUMMY 0 0 0 0 1 

F12 CIRCULAR 9 0 0 0 1 

F120-DF DUMMY 0 0 0 0 1 

F125-DF DUMMY 0 0 0 0 1 

F13 TRAPEZOIDAL 10 10 5 5 1 

F130-DF DUMMY 0 0 0 0 1 

F14 CIRCULAR 3.5 0 0 0 1 

F140-DF DUMMY 0 0 0 0 1 

F14-Overflow TRAPEZOIDAL 10 6 20 20 1 

G10 CIRCULAR 6 0 0 0 1 

G100-DF DUMMY 0 0 0 0 1 

G105-DF DUMMY 0 0 0 0 1 

G11 TRAPEZOIDAL 10 10 4 4 1 

G110-DF DUMMY 0 0 0 0 1 

G12 CIRCULAR 6 0 0 0 1 

G120-DF DUMMY 0 0 0 0 1 

GA999-DF DUMMY 0 0 0 0 1 

GV999-DF DUMMY 0 0 0 0 1 

H100-DF DUMMY 0 0 0 0 1 

H11 CIRCULAR 6 0 0 0 1 

H110-DF DUMMY 0 0 0 0 1 

H115-DF DUMMY 0 0 0 0 1 

H12 CIRCULAR 6 0 0 0 1 

H120-DF DUMMY 0 0 0 0 1 

H13 TRAPEZOIDAL 10 5 20 20 1 

H130-DF DUMMY 0 0 0 0 1 


H140-DF DUMMY 0 0 0 0 1 

H145-DF DUMMY 0 0 0 0 1 


H150-DF DUMMY 0 0 0 0 1 


H160-DF DUMMY 0 0 0 0 1 


H170-DF DUMMY 0 0 0 0 1 

H18 RECT_CLOSED 10 12 0 0 1 

H180-DF DUMMY 0 0 0 0 1 

H185 CIRCULAR 5 0 0 0 1 


H190-DF DUMMY 0 0 0 0 1 


H200-DF DUMMY 0 0 0 0 1 



H210-DF DUMMY 0 0 0 0 1 


H220-DF DUMMY 0 0 0 0 1 

HC008-DF DUMMY 0 0 0 0 1 

HC013-DF DUMMY 0 0 0 0 1 

HC025-DF DUMMY 0 0 0 0 1 

HC028-DF DUMMY 0 0 0 0 1 

HC032-DF DUMMY 0 0 0 0 1 

HC035-DF DUMMY 0 0 0 0 1 

HC036-DF DUMMY 0 0 0 0 1 

HC117-DF DUMMY 0 0 0 0 1 

HC999-DF DUMMY 0 0 0 0 1 

OH999-DF DUMMY 0 0 0 0 1 

OR999-DF DUMMY 0 0 0 0 1 

SG999-DF DUMMY 0 0 0 0 1 

[LOSSES] 

;;Link Inlet Outlet Average Flap Gate 

;;-------------- ---------- ---------- ---------- ---------- 

Page B-31



[CURVES] 

;;Name Type X-Value Y-Value 

;;-------------- ---------- ---------- ---------- 

;MERIDIAN POND 4C DESIGN 

;(construction underway/imminent at time of study) 

;Stage-discharge curve from 2/2012 Phase III Drainage Report 

;2nd Amendment Study to Meridian Office Park Filings 4 & 5 (Peoria Place-Filing 4 Amendment) 

;(extrapolated for top 2' based on 50' weir @ el. 5925) 

GA309-DISCHARGE-EX Rating 0 0.00 

GA309-DISCHARGE-EX 1 9.22 




GA309-DISCHARGE-EX 5 160 






;MERIDIAN POND 4B DESIGN 




;(extrapolated for top 2' based on 150' spill weir @ elev. 5904) 

GA310-DISCHARGE-EX Rating 0.0 0.0 

GA310-DISCHARGE-EX 0.5 3.26 





GA310-DISCHARGE-EX 5.5 118 










;MERIDIAN POND 4A DESIGN 




GA311-DISCHARGE-EX Rating 0.00 0.0 










;E-470 POND EXISTING 

;Stage-discharge calculated with UD-Detention based on construction drawings for Compark Green Acres Tributary 

GA350-DISCHARGE-EX Rating 0 103 






;STEPPING STONE POND D1 EXISTING 

;(construction underway at time of study) 

;Stage-discharge calculated with UD-Detention from 3/2013 Phase III Drainage Report for Stepping Stone and 

Stepping Stone Circle 

GV301-DISCHARGE-EX Rating 0.0 0.00 

GV301-DISCHARGE-EX 0.5 1.30 











Page B-32



;Stage-discharge calculated with UD-Detention from 3/2013 Phase III Drainage Report for Stepping Stone and 

Stepping Stone Circle 

GV302-DISCHARGE-EX Rating 0.0 0.00 











;CPNMD POND #11 EXISTING 

;Stage-discharge calculalted with UD-Detention based on survey/field measurements of outlet 

HC310-DISCHARGE-EX Rating 0.0 0.0 

HC310-DISCHARGE-EX 1.0 23.0 

HC310-DISCHARGE-EX 3.0 133 












;Stage-discharge calculalted with UD-Detention based on survey/field measurements of outlet & spillway 

embankment 

HC320-DISCHARGE-EX Rating 0 0.00 







;MERIDIAN VILLAGE POND 1 - EXISTING 

;Stage-discharge calculated with UD-Detention based on 8/2005 construction drawings 

HC326-DISCHARGE-EX Rating 0.0 0.00 








;Stage-discharge curve calculated with UD-Detention based on Record drawings 

MT300-DISCHARGE-EX Rating 0.0 0.00 

MT300-DISCHARGE-EX 0.6 0.10 






MT300-DISCHARGE-EX 7.1 105 







;Stage-discharge curve calculated with UD-Detention based on As-built drawings 

OH310-DISCHARGE-EX Rating 0.0 0.42 

OH310-DISCHARGE-EX 1.0 9.81 











Page B-33














;Stage-discharge curve calculated with UD-Detention based on As-built drawings 

OH320-DISCHARGE-EX Rating 0.0 0.00 






















;STONEGATE POND EXISTING 

;(under construction at time of report) 

;Stage-Discharge calculated with UD-Detention based on May 2012 construction drawings 

SG310-DISCHARGE-EX Rating 0.0 0.00 

SG310-DISCHARGE-EX 0.7 0.13 













;CHAMBERS RES WQ POND EXISTING 

;Stage-discharge from Phase III Drainage Report for Chambers Dam & Reservoir 

SG320-DISCHARGE-EX Rating 0 0 







SG320-DISCHARGE-EX 10.8 2671 

SG320-DISCHARGE-EX 11.8 4890 

;MERIDIAN POND 4C DESIGN 


;Stage-area curve from 2/2012 Phase III Drainage Report 


;(top 2' of curve extrapolated) 

GA309-STORAGE-EX Storage 0 10 

GA309-STORAGE-EX 1 2120 










Page B-34



;MERIDIAN POND 4B DESIGN 




;(top 2' of curve extrapolated) 


GA310-STORAGE-EX 0.5 348 





GA310-STORAGE-EX 5.5 126509 

GA310-STORAGE-EX 6.5 146888 

GA310-STORAGE-EX 7.5 153323 

GA310-STORAGE-EX 8.5 159889 

GA310-STORAGE-EX 9.5 166733 

GA310-STORAGE-EX 10.5 173678 

GA310-STORAGE-EX 11.5 180632 

GA310-STORAGE-EX 12.5 187664 

GA310-STORAGE-EX 13.5 194696 

GA310-STORAGE-EX 14.5 201728 

;MERIDIAN POND 4A DESIGN 














;E-470 POND EXISTING 

;Stage-area based on 2' DNC LIDAR topography 









;Stage-area from 3/2013 Phase III Drainage Report for Stepping Stone and Stepping Stone Circle 

;(top 1' extrapolated) 

GV301-STORAGE-EX Storage 0.0 10 

GV301-STORAGE-EX 0.5 2672 








GV301-STORAGE-EX 8.5 107081 



;Stage-area from 3/2013 Phase III Drainage Report for Stepping Stone and Stepping Stone Circle 


GV302-STORAGE-EX Storage 0.0 76487 

GV302-STORAGE-EX 0.5 114069 

GV302-STORAGE-EX 1.5 122270 

GV302-STORAGE-EX 2.5 131136 

GV302-STORAGE-EX 3.5 138533 

GV302-STORAGE-EX 4.5 147406 

GV302-STORAGE-EX 5.5 157864 

GV302-STORAGE-EX 6.5 167217 

GV302-STORAGE-EX 7.5 176570 

GV302-STORAGE-EX 8.5 185923 

GV302-STORAGE-EX 9.5 195276 


;Stage-area based on 2012 2' Channel Topo provided by UDFCD 

HC310-STORAGE-EX Storage 0 0 

HC310-STORAGE-EX 1 500 

Page B-35















;Stage-area based on 2012 2' Channel Topo provided by UDFCD 

HC320-STORAGE-EX Storage 0 4000 

HC320-STORAGE-EX 1.2 8100 



HC320-STORAGE-EX 7.2 104500 

HC320-STORAGE-EX 9.2 135300 

HC320-STORAGE-EX 11.2 166100 

;MERIDIAN VILLAGE POND - EXISTING 

;Stage-area from 10/2005 Phase III Drainage Report, MIBC Filing 7 


HC326-STORAGE-EX Storage 0.0 0 




HC326-STORAGE-EX 6.0 139340 

HC326-STORAGE-EX 8.0 180260 

HC326-STORAGE-EX 10.0 220000 


;Stage-area from CPN Filing No. 16 Phase III Drainage Report 

MT300-STORAGE-EX Storage 0.0 10 

MT300-STORAGE-EX 0.6 675 




MT300-STORAGE-EX 5.8 111375 

MT300-STORAGE-EX 6.6 143275 

MT300-STORAGE-EX 7.1 149750 

MT300-STORAGE-EX 8.6 164325 

MT300-STORAGE-EX 9.2 169550 

MT300-STORAGE-EX 10.2 178825 

MT300-STORAGE-EX 11.2 188100 

MT300-STORAGE-EX 12.2 197375 


;Stage-area information from CPN Filing 27 Phase III Drainage Report 

OH310-STORAGE-EX Storage 0 2178 

OH310-STORAGE-EX 2 6970 











;Stage-area information from CPN Filing 27 Phase III Drainage Report 

OH320-STORAGE-EX Storage 0 0 












;STONEGATE POND EXISTING 

;(under construction at time of report) 

;Stage-Area from 8/2012 Supplement to Phase III Drainage Report, Sierra Ridge Filing 1 

SG310-STORAGE-EX Storage 0.0 260 

Page B-36



SG310-STORAGE-EX 0.7 4340 






SG310-STORAGE-EX 6.7 105201 

SG310-STORAGE-EX 7.7 112546 

SG310-STORAGE-EX 8.7 120451 

SG310-STORAGE-EX 9.7 127914 

SG310-STORAGE-EX 10.7 135421 

SG310-STORAGE-EX 11.7 147109 

SG310-STORAGE-EX 12.7 160614 

;CHAMBERS RES WQ POND EXISTING 

;Stage-area from Phase III Drainage Report for Chambers Dam & Reservoir 

SG320-STORAGE-EX Storage 0 0 





SG320-STORAGE-EX 6.8 110216 

SG320-STORAGE-EX 8.8 124039 

SG320-STORAGE-EX 10.8 137906 

SG320-STORAGE-EX 11.8 145138 

[REPORT] 

INPUT NO 

CONTROLS NO 

SUBCATCHMENTS ALL 

NODES ALL 

LINKS ALL 

[TAGS] 

[MAP] 

DIMENSIONS 0.000 0.000 10000.000 10000.000 

Units None 

[COORDINATES] 

;;Node X-Coord Y-Coord 

;;-------------- ------------------ ------------------ 

A100 3241.979 855.615 

A105 2854.278 882.353 

A110 3230.386 1131.458 

A120 3314.850 1506.269 

A125 2841.497 1530.905 

A130 3226.867 1775.500 

A134 2338.229 1622.408 

A135 2790.466 1909.236 

A140 3001.628 2050.010 

A150 3390.517 2013.057 

A160 3313.091 2403.705 

A170 3515.454 2634.223 

A180 3804.041 2994.957 

A190 4032.799 3033.670 

A195 4314.348 3024.871 

A200 3881.467 3454.233 

A210 4090.868 3716.425 

A215 4616.802 4132.542 

A220 4004.774 4317.511 

A230 4365.191 4619.445 

A234 3777.644 4570.483 

A235 4245.505 4828.895 

A240 4732.408 4403.195 

A245 4495.757 4977.141 

A250 4762.126 4732.859 

A260 4728.327 5182.511 

A263 5166.648 4463.954 

A264 4937.777 4556.882 

A265 5162.188 4947.220 

A270 5311.794 4994.822 

A275 4910.538 5457.672 

A276 5123.235 5697.440 

A280 5526.684 5268.195 

A285 5801.417 5056.025 

A290 5766.366 5675.105 

A295 5442.117 6079.367 

A300 6025.827 6207.998 

A304 6020.387 5502.126 

A305 6312.665 6035.510 

A310 6458.718 6491.511 

Page B-37



A314 6251.823 5804.284 

A315 6633.018 6059.438 

A320 6712.666 6592.059 

A325 7307.007 6386.166 

A330 7033.777 6797.412 

A340 7216.840 7244.667 

A345 7418.624 6845.258 

A350 7487.273 7477.655 

A360 7566.322 7681.520 

A370 7726.502 8008.120 

A375 7930.367 7660.717 

A380 8169.775 8244.772 

A390 8388.618 8952.616 

A395 8215.771 9470.285 

A400 8542.697 9502.334 

B100 3899.064 1536.184 

B110 4006.404 1796.616 

B120 4097.907 2032.413 

B130 3872.668 2361.473 

B134 4502.109 2310.305 

B135 4185.910 2381.034 

BG001 5159.327 3063.017 

BG002 5256.980 3364.591 

BG003 5297.190 3623.083 

BG004 5486.750 3904.551 

BG005 5653.334 4197.509 

BG006 5831.406 4447.384 

BG007 5997.990 4792.040 

BG008 6256.481 4990.217 

BG009 6575.288 5165.417 

BG010 6674.898 5395.681 

BG011 7047.932 6076.448 

BG109 6555.183 4590.991 

BG111 6957.591 5349.390 

BG999 7120.014 6579.168 

BH001 3835.275 1684.394 

BH002 3950.160 2040.538 

BH003 3987.498 2278.925 

BH100 4404.031 2335.774 

BH999 3889.727 2662.003 

C100 1710.024 1907.476 

C110 1937.023 2187.265 

C120 2102.432 2417.783 

C125 1688.908 2558.557 

C130 2223.686 2919.466 

C140 2646.173 2917.531 

C150 2769.350 3236.033 

C153 2403.337 2299.884 

C154 2775.762 2603.270 

C155 2918.923 2903.454 

C159 3159.999 2940.407 

C160 3039.691 3352.512 

C170 3580.562 3551.015 

C175 3362.362 3895.912 

C180 3767.088 3675.952 

C185 3538.330 4156.344 

C190 4018.375 3932.613 

D100 4713.795 2544.479 

D110 4671.562 3051.267 

D120 4641.648 3417.280 

D130 4456.315 3894.531 

E100 5027.389 2878.082 

E105 5353.569 2860.546 

E110 5023.881 3176.204 

E120 5483.162 3304.264 

E125 4996.260 3584.437 

E130 5148.587 3840.129 

E135 5605.568 3592.597 

E140 5451.881 4097.181 

E150 5543.005 4396.395 

E155 5940.143 4041.418 

E160 5713.632 4672.625 

E170 6314.629 4705.615 

E180 6327.232 5150.872 

E183 6437.926 4117.582 

E184 6292.400 4382.794 

E185 6632.415 4887.377 

E190 6463.852 5320.056 

E200 6670.497 5736.056 

E204 6907.049 5126.597 

E205 7086.676 5722.456 

E210 6950.670 6327.684 

Page B-38



F100 7103.718 4831.656 

F110 7398.333 5140.299 

F120 7222.967 5634.831 

F125 7580.713 5838.255 

F130 7636.830 6381.888 

F140 7633.323 6879.927 

G100 7830.212 6286.800 

G105 8015.154 6426.081 

G110 7930.924 6918.332 

G120 8043.822 7743.885 

GA001 6000.862 6633.076 

GA002 6072.297 6970.936 

GA003 6285.513 7179.096 

GA004 6358.439 7255.647 

GA005 6615.498 7425.784 

GA006 6845.268 7649.810 

GA007 7270.343 8014.571 

GA008 7516.121 8123.624 

GA009 7517.149 8235.330 

GA010 7583.056 8423.532 

GA011 7980.157 8756.506 

GA012 8220.132 9144.957 

GA999 8277.921 9359.214 

GV001 7249.574 5112.599 

GV002 7390.973 5306.151 

GV003 7445.543 6027.056 

GV999 7508.496 7198.421 

H100 5827.403 6471.391 

H110 6143.109 6763.041 

H115 5757.977 6786.826 

H120 6070.394 7168.669 

H130 6182.079 7354.309 

H140 6425.070 7389.022 

H145 6486.950 6966.429 

H150 6603.163 7577.679 

H160 7036.321 7861.420 

H170 7149.515 7645.596 

H180 7468.513 7973.231 

H185 7106.750 8273.507 

H190 7286.858 8431.921 

H200 7635.497 8653.782 

H205 7726.053 8907.338 

H210 8095.822 9091.468 

H220 8163.770 9340.189 

HC001 3033.951 1153.050 

HC002 3074.160 1305.273 

HC003 3133.267 1655.245 

HC004 3097.137 1925.653 

HC005 3229.255 2132.447 

HC006 3355.629 2241.588 

HC007 3559.550 2462.742 

HC008 3761.866 2660.034 

HC009 3799.166 2710.570 

HC010 3918.567 3094.610 

HC011 4073.662 3218.112 

HC012 4128.307 3567.918 

HC013 4232.563 4071.200 

HC014 4246.756 4145.401 

HC015 4366.619 4384.197 

HC016 4468.195 4597.864 

HC017 4634.675 4720.320 

HC018 4722.763 5007.450 

HC019 5118.399 5247.074 

HC020 5352.530 5579.414 

HC021 5570.042 5538.794 

HC022 5867.469 5925.302 

HC023 6279.458 6276.931 

HC024 6704.932 6437.370 

HC025 7063.295 6607.528 

HC026 7109.504 6650.308 

HC027 7310.451 7121.932 

HC028 7433.994 7193.101 

HC029 7498.561 7222.871 

HC030 7620.743 7523.436 

HC031 7755.734 7816.394 

HC032 7964.880 7992.621 

HC033 8003.779 8025.963 

HC034 8212.402 8540.170 

HC035 8382.559 9324.969 

HC036 8365.436 9380.142 

HC037 8405.389 9406.777 

HC103 2948.859 1670.491 

Page B-39



HC104 2600.259 1741.837 

HC116 4093.767 4651.305 

HC117 4519.938 4757.797 

HC119 5018.593 4927.030 

HC122 5845.767 5346.361 

HC123 6055.432 5791.541 

HC124 6528.497 6099.402 

HC999 8610.979 9877.506 

MT100 2551.433 2462.742 

MT110 2787.640 2853.083 

OH001 1842.016 2092.237 

OH002 1933.924 2316.263 

OH003 2123.485 2666.663 

OH004 2459.524 2936.643 

OH005 2652.653 3024.822 

OH006 2906.700 3115.116 

OH007 3071.288 3232.473 

OH008 3255.105 3433.522 

OH009 3691.668 3815.515 

OH010 3886.973 3930.401 

OH999 4182.931 4094.422 

OR001 4630.855 2841.863 

OR002 4441.295 3287.043 

OR003 4360.875 3536.919 

OR999 4289.072 4076.879 

SG001 7984.492 6652.571 

SG002 8041.971 6672.499 

SG003 8042.947 7244.839 

SG999 7994.408 7984.209 

HC-OUTFALL 8648.047 9929.739 

GV004 7571.917 6664.669 

GA309 6044.220 6953.319 

GA310 6272.636 7127.170 

GA311 6350.044 7203.309 

GA350 7518.776 8095.402 

HC310 3113.339 1593.345 

HC320 3204.363 2086.720 

MT300 2664.704 2752.438 

OH310 2383.955 2925.841 

OH320 2582.131 3033.187 

SG310 7978.147 6608.157 

SG320 8041.596 7203.309 

HC326 7198.256 6585.311 

GV301 7199.458 5050.747 

GV302 7368.830 5265.449 

[VERTICES] 

;;Link X-Coord Y-Coord 

;;-------------- ------------------ ------------------ 

F14-Overflow 7533.192 6698.069 

G12 8177.512 7824.099 

[BACKDROP] 

FILE "P:\12-010.01 Happy Canyon Creek MDP & FHAD UDFCD\Hydrology\SWMM\SWMM_image.jpg" 

DIMENSIONS 1236.939 0.000 8763.061 10000.000 

Page B-40



Table B-8 

Sample SWMM Output 

EPA STORM WATER MANAGEMENT MODEL - VERSION 5.0 (Build 5.0.020) 

-------------------------------------------------------------- 


BASELINE HYDROLOGY SWMM MODEL 

100-YR, 3-HR STORM, FUTURE DEVELOPMENT 

********************************************************* 

NOTE: The summary statistics displayed in this report are 

based on results found at every computational time step, 

not just on results from each reporting time step. 

********************************************************* 

**************** 

Analysis Options 

**************** 

Flow Units ............... CFS 

Process Models: 

Rainfall/Runoff ........ NO 

Snowmelt ............... NO 

Groundwater ............ NO 

Flow Routing ........... YES 

Ponding Allowed ........ NO 

Water Quality .......... NO 

Flow Routing Method ...... KINWAVE 

Starting Date ............ JAN-01-2005 00:00:00 

Ending Date .............. JAN-05-2005 00:00:00 

Antecedent Dry Days ...... 0.0 

Report Time Step ......... 00:01:00 

Routing Time Step ........ 30.00 sec 

WARNING 08: elevation drop exceeds length for Conduit A320-DF 

************************** Volume Volume 

Flow Routing Continuity acre-feet 10^6 gal 

************************** --------- --------- 

Dry Weather Inflow ....... 0.000 0.000 

Wet Weather Inflow ....... 0.000 0.000 

Groundwater Inflow ....... 0.000 0.000 

RDII Inflow .............. 0.000 0.000 

External Inflow .......... 1698.367 553.438 

External Outflow ......... 1719.840 560.436 

Internal Outflow ......... 0.000 0.000 

Storage Losses ........... 0.000 0.000 

Initial Stored Volume .... 0.000 0.000 

Final Stored Volume ...... 2.778 0.905 

Continuity Error (%) ..... -1.428 

******************************** 

Highest Flow Instability Indexes 

******************************** 

Link OH320-OUT (7) 

Link C15A (7) 

Link OH310-OUT (7) 

Link C14 (6) 

Link C15B (6) 

************************* 

Routing Time Step Summary 

************************* 

Minimum Time Step : 30.00 sec 

Average Time Step : 30.00 sec 

Maximum Time Step : 30.00 sec 

Percent in Steady State : 0.00 

Average Iterations per Step : 1.00 

****************** 

Node Depth Summary 

****************** 

--------------------------------------------------------------------- 

Average Maximum Maximum Time of Max 

Depth Depth HGL Occurrence 

Node Type Feet Feet Feet days hr:min 

--------------------------------------------------------------------- 

A100 JUNCTION 0.00 0.00 6401.00 0 00:00 

A105 JUNCTION 0.00 0.00 6401.00 0 00:00 

A110 JUNCTION 0.00 0.00 6386.00 0 00:00 

A120 JUNCTION 0.00 0.00 6347.00 0 00:00 

A125 JUNCTION 0.00 0.00 6361.00 0 00:00 

Page B-41



A130 JUNCTION 0.00 0.00 6319.00 0 00:00 

A134 JUNCTION 0.00 0.00 6387.00 0 00:00 

A135 JUNCTION 0.00 0.00 6319.00 0 00:00 

A140 JUNCTION 0.00 0.00 6306.00 0 00:00 

A150 JUNCTION 0.00 0.00 6281.00 0 00:00 

A160 JUNCTION 0.00 0.00 6258.00 0 00:00 

A170 JUNCTION 0.00 0.00 6239.00 0 00:00 

A180 JUNCTION 0.00 0.00 6201.00 0 00:00 

A190 JUNCTION 0.00 0.00 6190.00 0 00:00 

A195 JUNCTION 0.00 0.00 6190.00 0 00:00 

A200 JUNCTION 0.00 0.00 6161.00 0 00:00 

A210 JUNCTION 0.00 0.00 6109.00 0 00:00 

A215 JUNCTION 0.00 0.00 6095.00 0 00:00 

A220 JUNCTION 0.00 0.00 6095.00 0 00:00 

A230 JUNCTION 0.00 0.00 6086.00 0 00:00 

A234 JUNCTION 0.00 0.00 6084.00 0 00:00 

A235 JUNCTION 0.00 0.00 6069.00 0 00:00 

A240 JUNCTION 0.00 0.00 6068.00 0 00:00 

A245 JUNCTION 0.00 0.00 6047.00 0 00:00 

A250 JUNCTION 0.00 0.00 6051.00 0 00:00 

A260 JUNCTION 0.00 0.00 5991.00 0 00:00 

A263 JUNCTION 0.00 0.00 6066.00 0 00:00 

A264 JUNCTION 0.00 0.00 6066.00 0 00:00 

A265 JUNCTION 0.00 0.00 6006.00 0 00:00 

A270 JUNCTION 0.00 0.00 5966.00 0 00:00 

A275 JUNCTION 0.00 0.00 5971.00 0 00:00 

A276 JUNCTION 0.00 0.00 5971.00 0 00:00 

A280 JUNCTION 0.00 0.00 5961.00 0 00:00 

A285 JUNCTION 0.00 0.00 6016.00 0 00:00 

A290 JUNCTION 0.00 0.00 5929.00 0 00:00 

A295 JUNCTION 0.03 1.93 5994.93 0 00:37 

A300 JUNCTION 0.00 0.00 5886.00 0 00:00 

A304 JUNCTION 0.00 0.00 5971.00 0 00:00 

A305 JUNCTION 0.00 0.00 5891.00 0 00:00 

A310 JUNCTION 0.00 0.00 5870.00 0 00:00 

A314 JUNCTION 0.00 0.00 5916.00 0 00:00 

A315 JUNCTION 0.00 0.00 5870.00 0 00:00 

A320 JUNCTION 0.00 0.00 5870.00 0 00:00 

A325 JUNCTION 0.00 0.00 5836.00 0 00:00 

A330 JUNCTION 0.00 0.00 5815.00 0 00:00 

A340 JUNCTION 0.00 0.00 5809.00 0 00:00 

A345 JUNCTION 0.00 0.00 5809.00 0 00:00 

A350 JUNCTION 0.00 0.00 5795.00 0 00:00 

A360 JUNCTION 0.00 0.00 5781.00 0 00:00 

A370 JUNCTION 0.00 0.00 5760.00 0 00:00 

A375 JUNCTION 0.00 0.00 5760.00 0 00:00 

A380 JUNCTION 0.00 0.00 5737.00 0 00:00 

A390 JUNCTION 0.00 0.00 5698.00 0 00:00 

A395 JUNCTION 0.00 0.00 5696.00 0 00:00 

A400 JUNCTION 0.00 0.00 5668.00 0 00:00 

B100 JUNCTION 0.00 0.00 6381.00 0 00:00 

B110 JUNCTION 0.00 0.00 6316.00 0 00:00 

B120 JUNCTION 0.00 0.00 6301.00 0 00:00 

B130 JUNCTION 0.00 0.00 6239.00 0 00:00 

B134 JUNCTION 0.00 0.00 6361.00 0 00:00 

B135 JUNCTION 0.00 0.00 6239.00 0 00:00 

BG001 JUNCTION 0.05 2.38 6277.38 0 00:56 

BG002 JUNCTION 0.06 2.90 6242.90 0 01:00 

BG003 JUNCTION 0.08 3.64 6198.64 0 01:03 

BG004 JUNCTION 0.10 4.34 6164.34 0 01:06 

BG005 JUNCTION 0.11 4.62 6129.62 0 01:08 

BG006 JUNCTION 0.13 5.11 6090.11 0 01:11 

BG007 JUNCTION 0.15 5.46 6050.46 0 01:13 

BG008 JUNCTION 0.16 5.75 6020.75 0 01:15 

BG009 JUNCTION 0.19 6.43 5981.43 0 01:18 

BG010 JUNCTION 0.19 6.42 5953.42 0 01:22 

BG011 JUNCTION 0.18 6.10 5891.10 0 01:30 

BG109 JUNCTION 0.07 3.06 6058.06 0 00:55 

BG111 JUNCTION 0.05 2.51 5949.51 0 00:43 

BG999 JUNCTION 0.19 6.07 5841.07 0 01:37 

BH001 JUNCTION 0.03 3.36 6383.36 0 00:32 

BH002 JUNCTION 0.03 3.16 6318.16 0 00:37 

BH003 JUNCTION 0.04 3.01 6303.01 0 00:42 

BH100 JUNCTION 0.00 0.47 6360.47 0 00:34 

BH999 JUNCTION 0.05 2.86 6240.86 0 00:51 

C100 JUNCTION 0.00 0.00 6441.00 0 00:00 

C110 JUNCTION 0.00 0.00 6396.00 0 00:00 

C120 JUNCTION 0.00 0.00 6351.00 0 00:00 

C125 JUNCTION 0.00 0.00 6351.00 0 00:00 

C130 JUNCTION 0.00 0.00 6311.00 0 00:00 

C140 JUNCTION 0.00 0.00 6283.00 0 00:00 

C150 JUNCTION 0.00 0.00 6246.00 0 00:00 

C153 JUNCTION 0.00 0.00 6376.00 0 00:00 

C154 JUNCTION 0.00 0.00 6307.00 0 00:00 

C155 JUNCTION 0.00 0.00 6256.00 0 00:00 

C159 JUNCTION 0.00 0.00 6246.00 0 00:00 

C160 JUNCTION 0.00 0.00 6216.00 0 00:00 

C170 JUNCTION 0.00 0.00 6171.00 0 00:00 

C175 JUNCTION 0.00 0.00 6171.00 0 00:00 

C180 JUNCTION 0.00 0.00 6150.00 0 00:00 

C185 JUNCTION 0.00 0.00 6150.00 0 00:00 

C190 JUNCTION 0.00 0.00 6109.00 0 00:00 

Page B-42



D100 JUNCTION 0.00 0.00 6281.00 0 00:00 

D110 JUNCTION 0.00 0.00 6221.00 0 00:00 

D120 JUNCTION 0.00 0.00 6196.00 0 00:00 

D130 JUNCTION 0.00 0.00 6109.00 0 00:00 

E100 JUNCTION 0.00 0.00 6276.00 0 00:00 

E105 JUNCTION 0.00 0.00 6276.00 0 00:00 

E110 JUNCTION 0.00 0.00 6241.00 0 00:00 

E120 JUNCTION 0.00 0.00 6196.00 0 00:00 

E125 JUNCTION 0.00 0.00 6196.00 0 00:00 

E130 JUNCTION 0.00 0.00 6161.00 0 00:00 

E135 JUNCTION 0.00 0.00 6161.00 0 00:00 

E140 JUNCTION 0.00 0.00 6126.00 0 00:00 

E150 JUNCTION 0.00 0.00 6086.00 0 00:00 

E155 JUNCTION 0.00 0.00 6086.00 0 00:00 

E160 JUNCTION 0.00 0.00 6046.00 0 00:00 

E170 JUNCTION 0.00 0.00 6021.00 0 00:00 

E180 JUNCTION 0.00 0.00 5981.00 0 00:00 

E183 JUNCTION 0.00 0.00 6056.00 0 00:00 

E184 JUNCTION 0.00 0.00 6056.00 0 00:00 

E185 JUNCTION 0.00 0.00 5981.00 0 00:00 

E190 JUNCTION 0.00 0.00 5948.00 0 00:00 

E200 JUNCTION 0.00 0.00 5891.00 0 00:00 

E204 JUNCTION 0.00 0.00 5948.00 0 00:00 

E205 JUNCTION 0.00 0.00 5886.00 0 00:00 

E210 JUNCTION 0.00 0.00 5836.00 0 00:00 

F100 JUNCTION 0.00 0.00 6008.00 0 00:00 

F110 JUNCTION 0.00 0.00 5978.00 0 00:00 

F120 JUNCTION 0.00 0.00 5906.00 0 00:00 

F125 JUNCTION 0.00 0.00 5906.00 0 00:00 

F130 JUNCTION 0.00 0.00 5853.00 0 00:00 

F140 JUNCTION 0.00 0.00 5809.00 0 00:00 

G100 JUNCTION 0.00 0.00 5887.00 0 00:00 

G105 JUNCTION 0.00 0.00 5885.00 0 00:00 

G110 JUNCTION 0.00 0.00 5842.00 0 00:00 

G120 JUNCTION 0.00 0.00 5760.00 0 00:00 

GA001 JUNCTION 0.06 3.03 5953.03 0 00:46 

GA002 JUNCTION 0.09 4.17 5920.17 0 01:13 

GA003 JUNCTION 0.08 1.86 5894.86 0 02:16 

GA004 JUNCTION 0.18 2.10 5890.10 0 02:05 

GA005 JUNCTION 0.21 2.63 5866.63 0 01:27 

GA006 JUNCTION 0.22 2.62 5845.62 0 01:37 

GA007 JUNCTION 0.24 3.34 5795.34 0 01:07 

GA008 JUNCTION 0.20 4.26 5784.26 0 01:16 

GA009 JUNCTION 0.22 4.34 5776.34 0 01:14 

GA010 JUNCTION 0.23 4.56 5766.56 0 01:10 

GA011 JUNCTION 0.25 5.17 5741.17 0 01:10 

GA012 JUNCTION 0.26 5.46 5726.46 0 01:11 

GA999 JUNCTION 0.26 5.45 5712.45 0 01:13 

GV001 JUNCTION 0.05 2.31 6009.31 0 01:14 

GV002 JUNCTION 0.18 2.29 5975.29 0 01:24 

GV003 JUNCTION 0.22 3.82 5908.82 0 01:07 

GV999 JUNCTION 0.29 3.50 5811.50 0 00:34 

H100 JUNCTION 0.00 0.00 5951.00 0 00:00 

H110 JUNCTION 0.00 0.00 5919.00 0 00:00 

H115 JUNCTION 0.00 0.00 5919.00 0 00:00 

H120 JUNCTION 0.00 0.00 5896.00 0 00:00 

H130 JUNCTION 0.00 0.00 5892.00 0 00:00 

H140 JUNCTION 0.00 0.00 5865.00 0 00:00 

H145 JUNCTION 0.00 0.00 5865.00 0 00:00 

H150 JUNCTION 0.00 0.00 5844.00 0 00:00 

H160 JUNCTION 0.00 0.00 5793.00 0 00:00 

H170 JUNCTION 0.00 0.00 5783.00 0 00:00 

H180 JUNCTION 0.00 0.00 5783.00 0 00:00 

H185 JUNCTION 0.06 3.05 5819.05 0 00:46 

H190 JUNCTION 0.00 0.00 5763.00 0 00:00 

H200 JUNCTION 0.00 0.00 5737.00 0 00:00 

H205 JUNCTION 0.03 2.00 5739.00 0 00:37 

H210 JUNCTION 0.00 0.00 5722.00 0 00:00 

H220 JUNCTION 0.00 0.00 5708.00 0 00:00 

HC001 JUNCTION 0.07 3.97 6403.97 0 00:41 

HC002 JUNCTION 0.07 3.96 6388.96 0 00:43 

HC003 JUNCTION 0.08 3.68 6343.68 0 01:01 

HC004 JUNCTION 0.08 4.00 6322.00 0 00:47 

HC005 JUNCTION 0.14 6.40 6306.40 0 00:58 

HC006 JUNCTION 0.14 6.39 6286.39 0 01:00 

HC007 JUNCTION 0.09 5.06 6262.06 0 01:03 

HC008 JUNCTION 0.05 3.02 6241.02 0 01:06 

HC009 JUNCTION 0.09 5.16 6242.16 0 01:03 

HC010 JUNCTION 0.10 5.13 6205.13 0 01:08 

HC011 JUNCTION 0.12 6.12 6195.12 0 01:09 

HC012 JUNCTION 0.13 6.32 6166.32 0 01:12 

HC013 JUNCTION 0.13 6.29 6114.29 0 01:17 

HC014 JUNCTION 0.36 10.76 6117.76 0 01:19 

HC015 JUNCTION 0.36 10.75 6104.75 0 01:21 

HC016 JUNCTION 0.33 9.38 6094.38 0 01:23 

HC017 JUNCTION 0.29 8.26 6075.26 0 01:25 

HC018 JUNCTION 0.17 6.59 6051.59 0 01:27 

HC019 JUNCTION 0.43 13.50 6013.50 0 01:31 

HC020 JUNCTION 0.45 13.48 5978.48 0 01:35 

HC021 JUNCTION 0.42 11.73 5966.73 0 01:36 

HC022 JUNCTION 0.23 7.66 5930.66 0 01:40 

HC023 JUNCTION 0.21 6.64 5891.64 0 01:44 

Page B-43



HC024 JUNCTION 0.19 5.96 5869.96 0 01:48 

HC025 JUNCTION 0.19 5.95 5840.95 0 01:52 

HC026 JUNCTION 0.43 10.29 5844.29 0 01:50 

HC027 JUNCTION 0.43 10.38 5824.38 0 01:54 

HC028 JUNCTION 0.40 10.38 5818.38 0 01:55 

HC029 JUNCTION 0.41 10.61 5817.61 0 01:55 

HC030 JUNCTION 0.41 10.61 5804.61 0 01:57 

HC031 JUNCTION 0.36 8.09 5788.09 0 02:00 

HC032 JUNCTION 0.32 7.87 5766.87 0 02:04 

HC033 JUNCTION 0.43 9.27 5767.27 0 02:04 

HC034 JUNCTION 0.45 9.94 5745.94 0 02:08 

HC035 JUNCTION 0.45 9.89 5715.89 0 02:16 

HC036 JUNCTION 0.00 0.00 5698.00 0 00:00 

HC037 JUNCTION 0.38 8.00 5703.00 0 02:15 

HC103 JUNCTION 0.02 2.40 6362.40 0 00:36 

HC104 JUNCTION 0.03 2.38 6388.38 0 00:39 

HC116 JUNCTION 0.05 3.07 6086.07 0 00:47 

HC117 JUNCTION 0.05 3.02 6071.02 0 00:57 

HC119 JUNCTION 0.07 3.05 6068.05 0 00:54 

HC122 JUNCTION 0.04 2.06 6017.06 0 00:45 

HC123 JUNCTION 0.07 3.02 5973.02 0 00:47 

HC124 JUNCTION 0.04 1.45 5916.45 0 00:54 

HC999 JUNCTION 0.38 7.99 5674.99 0 02:19 

MT100 JUNCTION 0.01 0.77 6375.77 0 00:42 

MT110 JUNCTION 0.07 2.35 6302.35 0 01:16 

OH001 JUNCTION 0.02 1.44 6441.44 0 00:50 

OH002 JUNCTION 0.05 3.11 6398.11 0 00:52 

OH003 JUNCTION 0.08 3.88 6353.88 0 00:57 

OH004 JUNCTION 0.09 3.28 6312.28 0 01:34 

OH005 JUNCTION 0.12 4.00 6285.00 0 01:24 

OH006 JUNCTION 0.16 5.24 6260.24 0 01:18 

OH007 JUNCTION 0.17 5.24 6250.24 0 01:21 

OH008 JUNCTION 0.15 4.68 6219.68 0 01:15 

OH009 JUNCTION 0.17 4.83 6174.83 0 01:23 

OH010 JUNCTION 0.16 4.82 6153.82 0 01:25 

OH999 JUNCTION 0.15 4.15 6112.15 0 01:30 

OR001 JUNCTION 0.04 2.27 6282.27 0 00:50 

OR002 JUNCTION 0.05 2.21 6222.21 0 01:03 

OR003 JUNCTION 0.09 4.29 6199.29 0 01:02 

OR999 JUNCTION 0.10 4.26 6112.26 0 01:11 

SG001 JUNCTION 0.24 1.44 5886.44 0 02:45 

SG002 JUNCTION 0.26 1.73 5885.73 0 01:44 

SG003 JUNCTION 0.26 1.53 5840.53 0 02:46 

SG999 JUNCTION 0.26 1.53 5760.53 0 02:50 

HC-OUTFALL OUTFALL 0.00 0.00 5666.00 0 00:00 

GV004 DIVIDER 0.30 3.79 5855.79 0 01:18 

GA309 STORAGE 0.18 8.63 5925.63 0 01:13 

GA310 STORAGE 0.40 11.65 5905.65 0 02:15 

GA311 STORAGE 2.61 6.53 5895.53 0 02:05 

GA350 STORAGE 0.13 4.97 5785.97 0 01:16 

HC310 STORAGE 0.23 16.81 6361.81 0 01:01 

HC320 STORAGE 0.16 10.13 6311.13 0 00:58 

MT300 STORAGE 0.35 8.55 6309.55 0 01:16 

OH310 STORAGE 0.47 18.95 6328.95 0 01:34 

OH320 STORAGE 0.35 11.21 6293.21 0 01:24 

SG310 STORAGE 2.76 8.48 5894.48 0 02:45 

SG320 STORAGE 2.22 7.38 5847.38 0 02:45 

HC326 STORAGE 1.07 6.82 5844.82 0 02:00 

GV301 STORAGE 0.14 6.78 6014.28 0 01:13 

GV302 STORAGE 1.17 4.66 5978.16 0 01:24 

******************* 

Node Inflow Summary 

******************* 

------------------------------------------------------------------------------------- 

Maximum Maximum Lateral Total 

Lateral Total Time of Max Inflow Inflow 

Inflow Inflow Occurrence Volume Volume 

Node Type CFS CFS days hr:min 10^6 gal 10^6 gal 

------------------------------------------------------------------------------------- 

A100 JUNCTION 237.67 237.67 0 00:37 3.864 3.864 

A105 JUNCTION 144.72 144.72 0 00:52 4.863 4.863 

A110 JUNCTION 372.80 372.80 0 00:32 4.216 4.216 

A120 JUNCTION 462.81 462.81 0 00:34 5.938 5.938 

A125 JUNCTION 270.06 270.06 0 00:36 4.096 4.096 

A130 JUNCTION 116.59 116.59 0 00:38 2.194 2.194 

A134 JUNCTION 293.11 293.11 0 00:39 5.638 5.638 

A135 JUNCTION 224.05 224.05 0 00:42 4.971 4.971 

A140 JUNCTION 313.49 313.49 0 00:38 5.638 5.638 

A150 JUNCTION 241.26 241.26 0 00:40 4.841 4.841 

A160 JUNCTION 194.39 194.39 0 00:42 4.287 4.287 

A170 JUNCTION 134.43 134.43 0 00:45 3.446 3.446 

A180 JUNCTION 137.10 137.10 0 00:44 3.348 3.348 

A190 JUNCTION 168.60 168.60 0 00:41 3.514 3.514 

A195 JUNCTION 83.01 83.01 0 00:55 3.133 3.133 

A200 JUNCTION 167.12 167.12 0 00:42 3.698 3.698 

A210 JUNCTION 111.91 111.91 0 00:51 3.657 3.657 

A215 JUNCTION 115.63 115.63 0 00:56 4.631 4.631 

A220 JUNCTION 131.08 131.08 0 00:48 4.184 4.184 

A230 JUNCTION 51.31 51.31 0 00:42 1.221 1.221 

Page B-44



A234 JUNCTION 118.75 118.75 0 00:47 3.509 3.509 

A235 JUNCTION 109.73 109.73 0 00:51 3.680 3.680 

A240 JUNCTION 159.07 159.07 0 00:42 3.962 3.962 

A245 JUNCTION 46.73 46.73 0 00:46 1.339 1.339 

A250 JUNCTION 60.45 60.45 0 00:48 2.088 2.088 

A260 JUNCTION 126.55 126.55 0 00:52 4.809 4.809 

A263 JUNCTION 87.86 87.86 0 00:53 3.370 3.370 

A264 JUNCTION 104.48 104.48 0 00:56 4.383 4.383 

A265 JUNCTION 100.41 100.41 0 00:43 3.173 3.173 

A270 JUNCTION 80.56 80.56 0 01:10 4.876 4.876 

A275 JUNCTION 220.88 220.88 0 00:38 5.250 5.250 

A276 JUNCTION 106.49 106.49 0 00:39 2.790 2.790 

A280 JUNCTION 266.66 266.66 0 00:42 7.556 7.556 

A285 JUNCTION 73.15 73.15 0 00:45 2.392 2.392 

A290 JUNCTION 246.90 246.90 0 00:44 7.393 7.393 

A295 JUNCTION 137.96 137.96 0 00:37 3.055 3.055 

A300 JUNCTION 185.62 185.62 0 00:46 5.817 5.817 

A304 JUNCTION 177.44 177.44 0 00:47 6.537 6.537 

A305 JUNCTION 74.58 74.58 0 00:48 2.827 2.827 

A310 JUNCTION 118.93 118.93 0 00:48 4.161 4.161 

A314 JUNCTION 115.96 115.96 0 00:54 5.308 5.308 

A315 JUNCTION 98.66 98.66 0 00:52 4.192 4.192 

A320 JUNCTION 72.43 72.43 0 00:52 2.998 2.998 

A325 JUNCTION 175.97 175.97 0 00:43 5.361 5.361 

A330 JUNCTION 108.39 108.39 0 00:54 4.350 4.350 

A340 JUNCTION 117.00 117.00 0 01:00 5.899 5.899 

A345 JUNCTION 25.89 25.89 0 01:09 1.543 1.543 

A350 JUNCTION 62.62 62.62 0 00:55 2.566 2.566 

A360 JUNCTION 91.58 91.58 0 01:05 4.497 4.497 

A370 JUNCTION 123.21 123.21 0 00:44 3.669 3.669 

A375 JUNCTION 66.39 66.39 0 01:10 3.979 3.979 

A380 JUNCTION 225.85 225.85 0 00:44 7.265 7.265 

A390 JUNCTION 135.51 135.51 0 00:53 5.691 5.691 

A395 JUNCTION 95.60 95.60 0 00:37 2.161 2.161 

A400 JUNCTION 212.67 212.67 0 00:43 6.476 6.476 

B100 JUNCTION 405.49 405.49 0 00:32 4.628 4.628 

B110 JUNCTION 218.14 218.14 0 00:38 3.898 3.898 

B120 JUNCTION 163.33 163.33 0 00:41 3.458 3.458 

B130 JUNCTION 92.07 92.07 0 00:50 2.866 2.866 

B134 JUNCTION 96.42 96.42 0 00:34 1.263 1.263 

B135 JUNCTION 183.88 183.88 0 00:48 5.330 5.330 

BG001 JUNCTION 0.00 142.59 0 00:56 0.000 5.627 

BG002 JUNCTION 0.00 235.88 0 01:00 0.000 8.800 

BG003 JUNCTION 0.00 382.47 0 01:03 0.000 14.530 

BG004 JUNCTION 0.00 566.29 0 01:06 0.000 21.515 

BG005 JUNCTION 0.00 662.33 0 01:08 0.000 25.011 

BG006 JUNCTION 0.00 830.91 0 01:11 0.000 32.349 

BG007 JUNCTION 0.00 973.97 0 01:13 0.000 39.168 

BG008 JUNCTION 0.00 1085.83 0 01:15 0.000 45.295 

BG009 JUNCTION 0.00 1446.53 0 01:18 0.000 62.176 

BG010 JUNCTION 0.00 1502.23 0 01:21 0.000 65.601 

BG011 JUNCTION 0.00 1712.07 0 01:30 0.000 79.987 

BG109 JUNCTION 0.00 192.95 0 00:55 0.000 7.507 

BG111 JUNCTION 0.00 87.28 0 00:43 0.000 2.696 

BG999 JUNCTION 0.00 1776.02 0 01:37 0.000 85.323 

BH001 JUNCTION 0.00 405.49 0 00:32 0.000 4.628 

BH002 JUNCTION 0.00 574.82 0 00:38 0.000 8.583 

BH003 JUNCTION 0.00 707.13 0 00:42 0.000 12.082 

BH100 JUNCTION 0.00 96.42 0 00:34 0.000 1.263 

BH999 JUNCTION 0.00 952.09 0 00:50 0.000 21.779 

C100 JUNCTION 111.46 111.46 0 00:50 3.664 3.664 

C110 JUNCTION 150.36 150.36 0 00:46 4.187 4.187 

C120 JUNCTION 69.76 69.76 0 00:54 2.737 2.737 

C125 JUNCTION 110.63 110.63 0 00:56 4.472 4.472 

C130 JUNCTION 212.03 212.03 0 00:42 5.581 5.581 

C140 JUNCTION 94.87 94.87 0 00:43 2.508 2.508 

C150 JUNCTION 47.46 47.46 0 01:03 2.211 2.211 

C153 JUNCTION 242.55 242.55 0 00:42 6.116 6.116 

C154 JUNCTION 186.53 186.53 0 00:42 5.138 5.138 

C155 JUNCTION 111.50 111.50 0 00:47 3.652 3.652 

C159 JUNCTION 192.90 192.90 0 00:43 5.223 5.223 

C160 JUNCTION 195.04 195.04 0 00:42 4.553 4.553 

C170 JUNCTION 107.50 107.50 0 00:55 4.390 4.390 

C175 JUNCTION 96.88 96.88 0 00:56 3.984 3.984 

C180 JUNCTION 54.50 54.50 0 00:49 1.851 1.851 

C185 JUNCTION 116.01 116.01 0 00:54 4.507 4.507 

C190 JUNCTION 81.73 81.73 0 00:54 3.197 3.197 

D100 JUNCTION 150.37 150.37 0 00:50 4.798 4.798 

D110 JUNCTION 141.48 141.48 0 00:50 4.555 4.555 

D120 JUNCTION 119.14 119.14 0 00:43 2.965 2.965 

D130 JUNCTION 121.33 121.33 0 00:46 3.643 3.643 

E100 JUNCTION 89.59 89.59 0 00:57 3.640 3.640 

E105 JUNCTION 53.31 53.31 0 00:54 1.987 1.987 

E110 JUNCTION 103.63 103.63 0 00:48 3.121 3.121 

E120 JUNCTION 82.49 82.49 0 00:53 2.925 2.925 

E125 JUNCTION 71.82 71.82 0 00:55 2.767 2.767 

E130 JUNCTION 99.78 99.78 0 00:49 3.104 3.104 

E135 JUNCTION 101.45 101.45 0 00:55 3.831 3.831 

E140 JUNCTION 121.02 121.02 0 00:47 3.426 3.426 

E150 JUNCTION 77.58 77.58 0 00:50 2.502 2.502 

E155 JUNCTION 112.31 112.31 0 01:00 4.781 4.781 

E160 JUNCTION 253.32 253.32 0 00:41 6.731 6.731 

Page B-45



E170 JUNCTION 261.43 261.43 0 00:38 6.099 6.099 

E180 JUNCTION 72.02 72.02 0 00:48 2.699 2.699 

E183 JUNCTION 110.38 110.38 0 00:57 4.519 4.519 

E184 JUNCTION 83.95 83.95 0 00:52 2.988 2.988 

E185 JUNCTION 195.39 195.39 0 00:48 6.517 6.517 

E190 JUNCTION 135.20 135.20 0 00:40 3.402 3.402 

E200 JUNCTION 131.98 131.98 0 00:54 5.490 5.490 

E204 JUNCTION 87.28 87.28 0 00:43 2.696 2.696 

E205 JUNCTION 165.60 165.60 0 00:47 5.625 5.625 

E210 JUNCTION 106.78 106.78 0 00:58 5.144 5.144 

F100 JUNCTION 241.48 241.48 0 00:38 5.392 5.392 

F110 JUNCTION 258.95 258.95 0 00:38 5.912 5.912 

F120 JUNCTION 231.77 231.77 0 00:44 7.120 7.120 

F125 JUNCTION 116.55 116.55 0 00:46 3.777 3.777 

F130 JUNCTION 194.63 194.63 0 00:44 5.867 5.867 

F140 JUNCTION 41.26 41.26 0 01:07 2.239 2.239 

G100 JUNCTION 122.04 122.04 0 01:01 6.215 6.215 

G105 JUNCTION 61.32 61.32 0 00:49 2.302 2.302 

G110 JUNCTION 79.18 79.18 0 00:53 3.106 3.106 

G120 JUNCTION 125.80 125.80 0 00:52 5.315 5.315 

GA001 JUNCTION 0.00 225.28 0 00:46 0.000 7.854 

GA002 JUNCTION 0.00 378.82 0 01:13 0.000 16.081 

GA003 JUNCTION 0.00 208.55 0 02:16 0.000 19.614 

GA004 JUNCTION 0.00 221.06 0 02:05 0.000 21.511 

GA005 JUNCTION 0.00 375.50 0 01:27 0.000 31.665 

GA006 JUNCTION 0.00 443.14 0 00:50 0.000 38.236 

GA007 JUNCTION 0.00 506.41 0 01:07 0.000 43.842 

GA008 JUNCTION 0.00 668.18 0 01:16 0.000 52.181 

GA009 JUNCTION 0.00 836.25 0 01:14 0.000 59.786 

GA010 JUNCTION 0.00 947.14 0 01:10 0.000 66.135 

GA011 JUNCTION 0.00 1163.11 0 01:10 0.000 76.012 

GA012 JUNCTION 0.00 1334.96 0 01:11 0.000 83.925 

GA999 JUNCTION 0.00 1402.30 0 01:12 0.000 86.920 

GV001 JUNCTION 0.00 113.64 0 01:14 0.000 5.392 

GV002 JUNCTION 0.00 195.92 0 01:24 0.000 10.827 

GV003 JUNCTION 0.00 455.43 0 01:07 0.000 21.705 

GV999 JUNCTION 0.00 604.04 0 01:25 0.000 30.391 

H100 JUNCTION 225.28 225.28 0 00:46 7.854 7.854 

H110 JUNCTION 186.13 186.13 0 00:43 5.324 5.324 

H115 JUNCTION 117.60 117.60 0 00:41 2.926 2.926 

H120 JUNCTION 100.10 100.10 0 00:47 3.547 3.547 

H130 JUNCTION 67.89 67.89 0 00:44 2.103 2.103 

H140 JUNCTION 55.81 55.81 0 00:50 2.333 2.333 

H145 JUNCTION 186.42 186.42 0 00:51 7.772 7.772 

H150 JUNCTION 318.79 318.79 0 00:36 6.511 6.511 

H160 JUNCTION 95.94 95.94 0 01:07 5.256 5.256 

H170 JUNCTION 76.46 76.46 0 00:56 3.442 3.442 

H180 JUNCTION 153.01 153.01 0 00:46 4.877 4.877 

H185 JUNCTION 217.92 217.92 0 00:46 7.618 7.618 

H190 JUNCTION 314.61 314.61 0 00:36 6.335 6.335 

H200 JUNCTION 175.41 175.41 0 00:43 5.502 5.502 

H205 JUNCTION 192.41 192.41 0 00:37 4.281 4.281 

H210 JUNCTION 276.48 276.48 0 00:41 7.832 7.832 

H220 JUNCTION 89.36 89.36 0 00:45 2.969 2.969 

HC001 JUNCTION 0.00 343.36 0 00:41 0.000 8.727 

HC002 JUNCTION 0.00 613.00 0 00:37 0.000 12.947 

HC003 JUNCTION 0.00 484.06 0 01:01 0.000 18.936 

HC004 JUNCTION 0.00 1223.85 0 00:47 0.000 36.054 

HC005 JUNCTION 0.00 1361.65 0 00:58 0.000 41.721 

HC006 JUNCTION 0.00 1536.04 0 00:59 0.000 46.565 

HC007 JUNCTION 0.00 1670.36 0 01:02 0.000 50.918 

HC008 JUNCTION 0.00 1764.87 0 01:06 0.000 54.505 

HC009 JUNCTION 0.00 2486.76 0 01:03 0.000 76.284 

HC010 JUNCTION 0.00 2565.33 0 01:08 0.000 79.891 

HC011 JUNCTION 0.00 2738.54 0 01:09 0.000 86.582 

HC012 JUNCTION 0.00 2825.38 0 01:12 0.000 90.385 

HC013 JUNCTION 0.00 2890.04 0 01:17 0.000 94.259 

HC014 JUNCTION 0.00 4507.25 0 01:19 0.000 179.070 

HC015 JUNCTION 0.00 4688.73 0 01:21 0.000 187.891 

HC016 JUNCTION 0.00 4707.68 0 01:22 0.000 189.121 

HC017 JUNCTION 0.00 4932.72 0 01:24 0.000 200.347 

HC018 JUNCTION 0.00 4984.45 0 01:27 0.000 203.945 

HC019 JUNCTION 0.00 5241.16 0 01:31 0.000 219.929 

HC020 JUNCTION 0.00 5379.92 0 01:34 0.000 232.890 

HC021 JUNCTION 0.00 5474.33 0 01:36 0.000 240.460 

HC022 JUNCTION 0.00 5613.12 0 01:39 0.000 253.566 

HC023 JUNCTION 0.00 5799.67 0 01:43 0.000 269.079 

HC024 JUNCTION 0.00 5950.71 0 01:48 0.000 283.005 

HC025 JUNCTION 0.00 5973.04 0 01:51 0.000 286.205 

HC026 JUNCTION 0.00 7662.68 0 01:50 0.000 376.889 

HC027 JUNCTION 0.00 7688.03 0 01:54 0.000 381.325 

HC028 JUNCTION 0.00 7775.72 0 01:55 0.000 388.775 

HC029 JUNCTION 0.00 8244.66 0 01:55 0.000 419.166 

HC030 JUNCTION 0.00 8268.40 0 01:57 0.000 421.764 

HC031 JUNCTION 0.00 8301.31 0 02:00 0.000 426.400 

HC032 JUNCTION 0.00 8353.18 0 02:04 0.000 434.125 

HC033 JUNCTION 0.00 8473.21 0 02:04 0.000 451.101 

HC034 JUNCTION 0.00 8488.38 0 02:08 0.000 458.532 

HC035 JUNCTION 0.00 8448.02 0 02:16 0.000 464.651 

HC036 JUNCTION 0.00 9227.02 0 02:15 0.000 551.571 

HC037 JUNCTION 0.00 9232.25 0 02:15 0.000 553.732 

HC103 JUNCTION 0.00 270.06 0 00:36 0.000 4.096 

Page B-46



HC104 JUNCTION 0.00 293.11 0 00:39 0.000 5.638 

HC116 JUNCTION 0.00 118.75 0 00:47 0.000 3.509 

HC117 JUNCTION 0.00 221.69 0 00:55 0.000 7.247 

HC119 JUNCTION 0.00 192.09 0 00:54 0.000 7.753 

HC122 JUNCTION 0.00 73.15 0 00:45 0.000 2.392 

HC123 JUNCTION 0.00 177.44 0 00:47 0.000 6.537 

HC124 JUNCTION 0.00 115.96 0 00:54 0.000 5.308 

HC999 JUNCTION 0.00 9233.48 0 02:19 0.000 560.394 

MT100 JUNCTION 0.00 242.55 0 00:42 0.000 6.116 

MT110 JUNCTION 0.00 258.07 0 01:16 0.000 11.256 

OH001 JUNCTION 0.00 111.46 0 00:50 0.000 3.664 

OH002 JUNCTION 0.00 254.30 0 00:52 0.000 7.882 

OH003 JUNCTION 0.00 430.86 0 00:57 0.000 15.144 

OH004 JUNCTION 0.00 378.41 0 01:34 0.000 20.782 

OH005 JUNCTION 0.00 418.30 0 01:24 0.000 23.297 

OH006 JUNCTION 0.00 752.36 0 01:18 0.000 38.224 

OH007 JUNCTION 0.00 914.87 0 01:14 0.000 45.664 

OH008 JUNCTION 0.00 1017.32 0 01:15 0.000 50.231 

OH009 JUNCTION 0.00 1157.66 0 01:23 0.000 58.883 

OH010 JUNCTION 0.00 1281.01 0 01:24 0.000 65.260 

OH999 JUNCTION 0.00 1327.80 0 01:30 0.000 68.582 

OR001 JUNCTION 0.00 150.37 0 00:50 0.000 4.798 

OR002 JUNCTION 0.00 274.77 0 00:59 0.000 9.470 

OR003 JUNCTION 0.00 369.50 0 01:02 0.000 12.476 

OR999 JUNCTION 0.00 462.14 0 01:08 0.000 16.228 

SG001 JUNCTION 0.00 39.77 0 02:45 0.000 6.215 

SG002 JUNCTION 0.00 62.98 0 01:44 0.000 8.516 

SG003 JUNCTION 0.00 67.72 0 02:46 0.000 11.670 

SG999 JUNCTION 0.00 136.39 0 01:28 0.000 16.977 

HC-OUTFALL OUTFALL 0.00 9233.48 0 02:19 0.000 560.394 

GV004 DIVIDER 0.00 580.11 0 01:14 0.000 27.737 

GA309 STORAGE 0.00 522.91 0 00:44 0.000 16.081 

GA310 STORAGE 0.00 459.32 0 01:11 0.000 19.614 

GA311 STORAGE 0.00 222.09 0 01:44 0.000 21.720 

GA350 STORAGE 0.00 701.80 0 01:08 0.000 52.181 

HC310 STORAGE 0.00 965.26 0 00:39 0.000 18.936 

HC320 STORAGE 0.00 1473.28 0 00:49 0.000 41.721 

MT300 STORAGE 0.00 428.48 0 00:43 0.000 11.256 

OH310 STORAGE 0.00 597.97 0 01:00 0.000 20.782 

OH320 STORAGE 0.00 423.00 0 01:13 0.000 23.296 

SG310 STORAGE 0.00 122.04 0 01:01 0.000 6.215 

SG320 STORAGE 0.00 134.57 0 01:03 0.000 11.670 

HC326 STORAGE 0.00 175.97 0 00:43 0.000 5.361 

GV301 STORAGE 0.00 241.48 0 00:38 0.000 5.392 

GV302 STORAGE 0.00 327.34 0 00:42 0.000 11.285 

********************** 

Node Surcharge Summary 

********************** 

Surcharging occurs when water rises above the top of the highest conduit. 

--------------------------------------------------------------------- 

Max. Height Min. Depth 

Hours Above Crown Below Rim 

Node Type Surcharged Feet Feet 

--------------------------------------------------------------------- 

A100 JUNCTION 96.01 0.000 0.000 

A105 JUNCTION 96.01 0.000 0.000 

A110 JUNCTION 96.01 0.000 0.000 

A120 JUNCTION 96.01 0.000 0.000 

A125 JUNCTION 96.01 0.000 0.000 

A130 JUNCTION 96.01 0.000 0.000 

A134 JUNCTION 96.01 0.000 0.000 

A135 JUNCTION 96.01 0.000 0.000 

A140 JUNCTION 96.01 0.000 0.000 

A150 JUNCTION 96.01 0.000 0.000 

A160 JUNCTION 96.01 0.000 0.000 

A170 JUNCTION 96.01 0.000 0.000 

A180 JUNCTION 96.01 0.000 0.000 

A190 JUNCTION 96.01 0.000 0.000 

A195 JUNCTION 96.01 0.000 0.000 

A200 JUNCTION 96.01 0.000 0.000 

A210 JUNCTION 96.01 0.000 0.000 

A215 JUNCTION 96.01 0.000 0.000 

A220 JUNCTION 96.01 0.000 0.000 

A230 JUNCTION 96.01 0.000 0.000 

A234 JUNCTION 96.01 0.000 0.000 

A235 JUNCTION 96.01 0.000 0.000 

A240 JUNCTION 96.01 0.000 0.000 

A245 JUNCTION 96.01 0.000 0.000 

A250 JUNCTION 96.01 0.000 0.000 

A260 JUNCTION 96.01 0.000 0.000 

A263 JUNCTION 96.01 0.000 0.000 

A264 JUNCTION 96.01 0.000 0.000 

A265 JUNCTION 96.01 0.000 0.000 

A270 JUNCTION 96.01 0.000 0.000 

A275 JUNCTION 96.01 0.000 0.000 

A276 JUNCTION 96.01 0.000 0.000 

A280 JUNCTION 96.01 0.000 0.000 

A285 JUNCTION 96.01 0.000 0.000 

A290 JUNCTION 96.01 0.000 0.000 

Page B-47



A300 JUNCTION 96.01 0.000 0.000 

A304 JUNCTION 96.01 0.000 0.000 

A305 JUNCTION 96.01 0.000 0.000 

A310 JUNCTION 96.01 0.000 0.000 

A314 JUNCTION 96.01 0.000 0.000 

A315 JUNCTION 96.01 0.000 0.000 

A320 JUNCTION 96.01 0.000 0.000 

A325 JUNCTION 96.01 0.000 0.000 

A330 JUNCTION 96.01 0.000 0.000 

A340 JUNCTION 96.01 0.000 0.000 

A345 JUNCTION 96.01 0.000 0.000 

A350 JUNCTION 96.01 0.000 0.000 

A360 JUNCTION 96.01 0.000 0.000 

A370 JUNCTION 96.01 0.000 0.000 

A375 JUNCTION 96.01 0.000 0.000 

A380 JUNCTION 96.01 0.000 0.000 

A390 JUNCTION 96.01 0.000 0.000 

A395 JUNCTION 96.01 0.000 0.000 

A400 JUNCTION 96.01 0.000 0.000 

B100 JUNCTION 96.01 0.000 0.000 

B110 JUNCTION 96.01 0.000 0.000 

B120 JUNCTION 96.01 0.000 0.000 

B130 JUNCTION 96.01 0.000 0.000 

B134 JUNCTION 96.01 0.000 0.000 

B135 JUNCTION 96.01 0.000 0.000 

C100 JUNCTION 96.01 0.000 0.000 

C110 JUNCTION 96.01 0.000 0.000 

C120 JUNCTION 96.01 0.000 0.000 

C125 JUNCTION 96.01 0.000 0.000 

C130 JUNCTION 96.01 0.000 0.000 

C140 JUNCTION 96.01 0.000 0.000 

C150 JUNCTION 96.01 0.000 0.000 

C153 JUNCTION 96.01 0.000 0.000 

C154 JUNCTION 96.01 0.000 0.000 

C155 JUNCTION 96.01 0.000 0.000 

C159 JUNCTION 96.01 0.000 0.000 

C160 JUNCTION 96.01 0.000 0.000 

C170 JUNCTION 96.01 0.000 0.000 

C175 JUNCTION 96.01 0.000 0.000 

C180 JUNCTION 96.01 0.000 0.000 

C185 JUNCTION 96.01 0.000 0.000 

C190 JUNCTION 96.01 0.000 0.000 

D100 JUNCTION 96.01 0.000 0.000 

D110 JUNCTION 96.01 0.000 0.000 

D120 JUNCTION 96.01 0.000 0.000 

D130 JUNCTION 96.01 0.000 0.000 

E100 JUNCTION 96.01 0.000 0.000 

E105 JUNCTION 96.01 0.000 0.000 

E110 JUNCTION 96.01 0.000 0.000 

E120 JUNCTION 96.01 0.000 0.000 

E125 JUNCTION 96.01 0.000 0.000 

E130 JUNCTION 96.01 0.000 0.000 

E135 JUNCTION 96.01 0.000 0.000 

E140 JUNCTION 96.01 0.000 0.000 

E150 JUNCTION 96.01 0.000 0.000 

E155 JUNCTION 96.01 0.000 0.000 

E160 JUNCTION 96.01 0.000 0.000 

E170 JUNCTION 96.01 0.000 0.000 

E180 JUNCTION 96.01 0.000 0.000 

E183 JUNCTION 96.01 0.000 0.000 

E184 JUNCTION 96.01 0.000 0.000 

E185 JUNCTION 96.01 0.000 0.000 

E190 JUNCTION 96.01 0.000 0.000 

E200 JUNCTION 96.01 0.000 0.000 

E204 JUNCTION 96.01 0.000 0.000 

E205 JUNCTION 96.01 0.000 0.000 

E210 JUNCTION 96.01 0.000 0.000 

F100 JUNCTION 96.01 0.000 0.000 

F110 JUNCTION 96.01 0.000 0.000 

F120 JUNCTION 96.01 0.000 0.000 

F125 JUNCTION 96.01 0.000 0.000 

F130 JUNCTION 96.01 0.000 0.000 

F140 JUNCTION 96.01 0.000 0.000 

G100 JUNCTION 96.01 0.000 0.000 

G105 JUNCTION 96.01 0.000 0.000 

G110 JUNCTION 96.01 0.000 0.000 

G120 JUNCTION 96.01 0.000 0.000 

H100 JUNCTION 96.01 0.000 0.000 

H110 JUNCTION 96.01 0.000 0.000 

H115 JUNCTION 96.01 0.000 0.000 

H120 JUNCTION 96.01 0.000 0.000 

H130 JUNCTION 96.01 0.000 0.000 

H140 JUNCTION 96.01 0.000 0.000 

H145 JUNCTION 96.01 0.000 0.000 

H150 JUNCTION 96.01 0.000 0.000 

H160 JUNCTION 96.01 0.000 0.000 

H170 JUNCTION 96.01 0.000 0.000 

H180 JUNCTION 96.01 0.000 0.000 

H190 JUNCTION 96.01 0.000 0.000 

H200 JUNCTION 96.01 0.000 0.000 

H210 JUNCTION 96.01 0.000 0.000 

H220 JUNCTION 96.01 0.000 0.000 

Page B-48



HC036 JUNCTION 96.01 0.000 0.000 

GA309 STORAGE 1.50 2.634 1.366 

GA310 STORAGE 3.33 5.655 2.845 

HC310 STORAGE 1.13 6.811 6.189 

HC320 STORAGE 0.21 0.129 1.871 

OH310 STORAGE 2.48 8.952 1.048 

OH320 STORAGE 1.70 1.213 9.787 

SG310 STORAGE 96.01 8.481 4.519 

HC326 STORAGE 96.01 6.819 3.181 

GV301 STORAGE 96.01 6.778 1.722 

*********************** 

----------------------------------------------------------- 

Flow Avg. Max. Total 

Freq. Flow Flow Volume 

Outfall Node Pcnt. CFS CFS 10^6 gal 

----------------------------------------------------------- 

HC-OUTFALL 99.84 217.10 9233.48 560.394 

----------------------------------------------------------- 

System 99.84 217.10 9233.48 560.394 

********************* 

Node Flooding Summary 

********************* 

No nodes were flooded. 

********************** 

Storage Volume Summary 

********************** 

-------------------------------------------------------------------------------------------- 

Average Avg E&I Maximum Max Time of Max Maximum 

Volume Pcnt Pcnt Volume Pcnt Occurrence Outflow 

Storage Unit 1000 ft3 Full Loss 1000 ft3 Full days hr:min CFS 

-------------------------------------------------------------------------------------------- 

GA309 6.770 1 0 494.915 65 0 01:13 378.82 

GA310 31.074 2 0 1221.709 69 0 02:15 208.55 

GA311 89.614 16 0 354.296 63 0 02:05 221.06 

GA350 2.748 0 0 171.725 16 0 01:16 668.18 

HC310 5.616 0 0 613.209 47 0 01:01 484.06 

HC320 8.393 1 0 703.940 70 0 00:58 1361.65 

MT300 14.940 1 0 624.911 49 0 01:16 258.07 

OH310 12.305 1 0 723.813 87 0 01:34 378.41 

OH320 2.617 0 0 111.539 13 0 01:24 418.30 

SG310 81.834 7 0 513.385 45 0 02:45 39.77 

SG320 67.273 6 0 445.378 43 0 02:45 67.72 

HC326 36.169 3 0 493.992 45 0 02:00 42.92 

GV301 4.419 1 0 298.914 64 0 01:13 113.64 

GV302 126.841 9 0 594.099 42 0 01:24 195.92 

*********************** 

Outfall Loading Summary 

******************** 

Link Flow Summary 

******************** 

----------------------------------------------------------------------------- 

Maximum Time of Max Maximum Max/ Max/ 

|Flow| Occurrence |Veloc| Full Full 

Link Type CFS days hr:min ft/sec Flow Depth 

----------------------------------------------------------------------------- 

A100-DF DUMMY 237.67 0 00:37 

A105-DF DUMMY 144.72 0 00:52 

A11 CONDUIT 341.97 0 00:43 4.15 0.10 0.40 

A110-DF DUMMY 372.80 0 00:32 

A12 CONDUIT 585.45 0 00:42 4.55 0.10 0.31 

A120-DF DUMMY 462.81 0 00:34 

A125-DF DUMMY 270.06 0 00:36 

A13 CONDUIT 483.74 0 01:06 4.69 0.09 0.37 

A130 CONDUIT 257.44 0 00:41 3.87 0.05 0.23 

A130-DF DUMMY 116.59 0 00:38 

A134-DF DUMMY 293.11 0 00:39 

A135 CONDUIT 258.32 0 00:52 3.28 0.03 0.22 

A135-DF DUMMY 224.05 0 00:42 

A14 CONDUIT 1219.02 0 00:50 5.29 0.14 0.40 

A140-DF DUMMY 313.49 0 00:38 

A15 CONDUIT 1359.99 0 01:00 6.31 0.33 0.64 

A150-DF DUMMY 241.26 0 00:40 

A16 CONDUIT 1522.76 0 01:03 6.05 0.25 0.51 

A160-DF DUMMY 194.39 0 00:42 

A17 CONDUIT 1656.35 0 01:06 4.69 0.11 0.30 

A170-DF DUMMY 134.43 0 00:45 

A18 CONDUIT 2462.39 0 01:08 6.44 0.27 0.51 

A180-DF DUMMY 137.10 0 00:44 

A19 CONDUIT 2561.27 0 01:10 5.58 0.19 0.42 

A190-DF DUMMY 168.60 0 00:41 

Page B-49



A195-DF DUMMY 83.01 0 00:55 

A20 CONDUIT 2728.87 0 01:12 7.33 0.38 0.61 

A200-DF DUMMY 167.12 0 00:42 

A21 CONDUIT 2803.13 0 01:17 7.67 0.41 0.63 

A210-DF DUMMY 111.91 0 00:51 

A215-DF DUMMY 115.63 0 00:56 

A22 CONDUIT 4503.19 0 01:21 8.74 0.20 0.54 

A220-DF DUMMY 131.08 0 00:48 

A23 CONDUIT 4685.38 0 01:23 7.58 0.14 0.47 

A230-DF DUMMY 51.31 0 00:42 

A234-DF DUMMY 118.75 0 00:47 

A235 CONDUIT 114.39 0 00:57 3.50 0.07 0.30 

A235-DF DUMMY 109.73 0 00:51 

A24 CONDUIT 4702.97 0 01:25 7.20 0.10 0.41 

A240-DF DUMMY 159.07 0 00:42 

A245-DF DUMMY 46.73 0 00:46 

A25 CONDUIT 4922.38 0 01:27 6.99 0.08 0.29 

A250-DF DUMMY 60.45 0 00:48 

A26 CONDUIT 4964.94 0 01:32 7.90 0.11 0.33 

A260-DF DUMMY 126.55 0 00:52 

A263-DF DUMMY 87.86 0 00:53 

A264-DF DUMMY 104.48 0 00:56 

A265 CONDUIT 190.06 0 01:01 3.70 0.06 0.30 

A265-DF DUMMY 100.41 0 00:43 

A27 CONDUIT 5228.38 0 01:35 10.56 0.39 0.67 

A270-DF DUMMY 80.56 0 01:10 

A275-DF DUMMY 220.88 0 00:38 

A276-DF DUMMY 106.49 0 00:39 

A28 CONDUIT 5377.29 0 01:36 8.99 0.27 0.59 

A280-DF DUMMY 266.66 0 00:42 

A285-DF DUMMY 73.15 0 00:45 

A29 CONDUIT 5458.48 0 01:40 8.64 0.16 0.38 

A290 CONDUIT 67.22 0 01:02 2.77 0.02 0.20 

A290-DF DUMMY 246.90 0 00:44 

A295 CONDUIT 137.89 0 00:38 23.00 0.47 0.48 

A30 CONDUIT 5590.77 0 01:44 7.95 0.12 0.33 

A300-DF DUMMY 185.62 0 00:46 

A304-DF DUMMY 177.44 0 00:47 

A305 CONDUIT 170.33 0 00:59 3.48 0.05 0.30 

A305-DF DUMMY 74.58 0 00:48 

A31 CONDUIT 5775.04 0 01:48 6.60 0.09 0.30 

A310-DF DUMMY 118.93 0 00:48 

A314-DF DUMMY 115.96 0 00:54 

A315 CONDUIT 115.84 0 00:56 7.38 0.01 0.15 

A315-DF DUMMY 98.66 0 00:52 

A32 CONDUIT 5936.02 0 01:52 7.48 0.11 0.30 

A320-DF DUMMY 72.43 0 00:52 

A325-DF DUMMY 175.97 0 00:43 

A33 CONDUIT 7635.76 0 01:54 8.14 0.20 0.51 

A330-DF DUMMY 108.39 0 00:54 

A34 CONDUIT 7685.71 0 01:55 8.51 0.22 0.52 

A340-DF DUMMY 117.00 0 01:00 

A345-DF DUMMY 25.89 0 01:09 

A35 CONDUIT 8238.37 0 01:57 9.44 0.26 0.53 

A350-DF DUMMY 62.62 0 00:55 

A36 CONDUIT 8249.60 0 02:00 6.87 0.11 0.40 

A360-DF DUMMY 91.58 0 01:05 

A37 CONDUIT 8284.00 0 02:04 7.42 0.12 0.39 

A370-DF DUMMY 123.21 0 00:44 

A375-DF DUMMY 66.39 0 01:10 

A38 CONDUIT 8437.59 0 02:09 8.06 0.17 0.46 

A380-DF DUMMY 225.85 0 00:44 

A39 CONDUIT 8400.62 0 02:16 7.89 0.21 0.49 

A390-DF DUMMY 135.51 0 00:53 

A395-DF DUMMY 95.60 0 00:37 

A40 CONDUIT 9208.84 0 02:19 8.05 0.14 0.40 

A400-DF DUMMY 212.67 0 00:43 

B100-DF DUMMY 405.49 0 00:32 

B11 CONDUIT 356.79 0 00:37 4.53 0.08 0.31 

B110-DF DUMMY 218.14 0 00:38 

B12 CONDUIT 544.46 0 00:42 3.61 0.06 0.27 

B120-DF DUMMY 163.33 0 00:41 

B13 CONDUIT 624.22 0 00:51 3.48 0.04 0.28 

B130-DF DUMMY 92.07 0 00:50 

B134-DF DUMMY 96.42 0 00:34 

B135 CONDUIT 95.23 0 00:37 15.16 0.00 0.05 

B135-DF DUMMY 183.88 0 00:48 

BG999-DF DUMMY 1776.02 0 01:37 

BH999-DF DUMMY 952.09 0 00:50 

C100-DF DUMMY 111.46 0 00:50 

C11 CONDUIT 110.15 0 00:56 2.59 0.02 0.14 

C110-DF DUMMY 150.36 0 00:46 

C12 CONDUIT 251.25 0 00:58 4.25 0.08 0.31 

C120-DF DUMMY 69.76 0 00:54 

C125-DF DUMMY 110.63 0 00:56 

C13 CONDUIT 426.62 0 01:03 5.16 0.12 0.39 

C130-DF DUMMY 212.03 0 00:42 

C14 CONDUIT 378.36 0 01:37 4.67 0.10 0.33 

C140-DF DUMMY 94.87 0 00:43 

C150-DF DUMMY 47.46 0 01:03 

C153-DF DUMMY 242.55 0 00:42 

C154 CONDUIT 242.23 0 00:43 19.56 0.00 0.08 

Page B-50



C154-DF DUMMY 186.53 0 00:42 

C155 CONDUIT 256.87 0 01:22 3.85 0.03 0.23 

C155-DF DUMMY 111.50 0 00:47 

C159-DF DUMMY 192.90 0 00:43 

C15A CONDUIT 418.24 0 01:28 4.77 0.13 0.40 

C15B CONDUIT 752.02 0 01:21 5.59 0.23 0.52 

C16 CONDUIT 912.29 0 01:18 4.57 0.10 0.38 

C160-DF DUMMY 195.04 0 00:42 

C17 CONDUIT 996.30 0 01:25 5.13 0.15 0.46 

C170-DF DUMMY 107.50 0 00:55 

C175-DF DUMMY 96.88 0 00:56 

C18 CONDUIT 1156.59 0 01:25 6.11 0.21 0.48 

C180-DF DUMMY 54.50 0 00:49 

C185-DF DUMMY 116.01 0 00:54 

C19 CONDUIT 1271.27 0 01:30 4.78 0.12 0.41 

C190-DF DUMMY 81.73 0 00:54 

D100-DF DUMMY 150.37 0 00:50 

D11 CONDUIT 142.46 0 01:03 3.18 0.03 0.22 

D110-DF DUMMY 141.48 0 00:50 

D12 CONDUIT 273.15 0 01:05 3.03 0.03 0.22 

D120-DF DUMMY 119.14 0 00:43 

D13 CONDUIT 364.14 0 01:11 4.94 0.13 0.43 

D130-DF DUMMY 121.33 0 00:46 

E100-DF DUMMY 89.59 0 00:57 

E105-DF DUMMY 53.31 0 00:54 

E11 CONDUIT 140.67 0 01:03 3.10 0.04 0.24 

E110-DF DUMMY 103.63 0 00:48 

E12 CONDUIT 234.70 0 01:05 3.79 0.06 0.29 

E120-DF DUMMY 82.49 0 00:53 

E125-DF DUMMY 71.82 0 00:55 

E13 CONDUIT 381.18 0 01:08 4.31 0.10 0.36 

E130-DF DUMMY 99.78 0 00:49 

E135-DF DUMMY 101.45 0 00:55 

E14 CONDUIT 564.10 0 01:11 4.80 0.15 0.43 

E140-DF DUMMY 121.02 0 00:47 

E15 CONDUIT 659.73 0 01:13 5.07 0.17 0.46 

E150-DF DUMMY 77.58 0 00:50 

E155-DF DUMMY 112.31 0 01:00 

E16 CONDUIT 825.77 0 01:17 5.39 0.21 0.51 

E160-DF DUMMY 253.32 0 00:41 

E17 CONDUIT 970.23 0 01:18 5.63 0.24 0.54 

E170-DF DUMMY 261.43 0 00:38 

E18 CONDUIT 1077.64 0 01:21 5.78 0.27 0.57 

E180-DF DUMMY 72.02 0 00:48 

E183-DF DUMMY 110.38 0 00:57 

E184-DF DUMMY 83.95 0 00:52 

E185 CONDUIT 188.34 0 01:07 3.74 0.06 0.30 

E185-DF DUMMY 195.39 0 00:48 

E19 CONDUIT 1443.06 0 01:22 6.34 0.35 0.64 

E190-DF DUMMY 135.20 0 00:40 

E20 CONDUIT 1468.84 0 01:32 5.02 0.16 0.46 

E200-DF DUMMY 131.98 0 00:54 

E204-DF DUMMY 87.28 0 00:43 

E205 CONDUIT 75.88 0 01:09 2.48 0.03 0.23 

E205-DF DUMMY 165.60 0 00:47 

E21 CONDUIT 1699.13 0 01:37 6.42 0.34 0.61 

E210-DF DUMMY 106.78 0 00:58 

F100-DF DUMMY 241.48 0 00:38 

F11 CONDUIT 113.51 0 01:16 12.86 0.43 0.46 

F110-DF DUMMY 258.95 0 00:38 

F12 CONDUIT 195.90 0 01:27 15.42 0.14 0.25 

F120-DF DUMMY 231.77 0 00:44 

F125-DF DUMMY 116.55 0 00:46 

F13 CONDUIT 447.17 0 01:18 4.22 0.10 0.38 

F130-DF DUMMY 194.63 0 00:44 

F14 CONDUIT 108.25 0 03:08 12.53 1.08 1.00 

F140-DF DUMMY 41.26 0 01:07 

F14-Overflow CONDUIT 467.61 0 01:26 5.43 0.03 0.27 

G10 CONDUIT 39.77 0 02:45 7.62 0.13 0.24 

G100-DF DUMMY 122.04 0 01:01 

G105-DF DUMMY 61.32 0 00:49 

G11 CONDUIT 61.89 0 01:51 2.17 0.02 0.17 

G110-DF DUMMY 79.18 0 00:53 

G12 CONDUIT 67.72 0 02:50 11.96 0.14 0.25 

G120-DF DUMMY 125.80 0 00:52 

GA999-DF DUMMY 1402.30 0 01:12 

GV999-DF DUMMY 604.04 0 01:25 

H100-DF DUMMY 225.28 0 00:46 

H11 CONDUIT 225.01 0 00:47 15.73 0.51 0.51 

H110-DF DUMMY 186.13 0 00:43 

H115-DF DUMMY 117.60 0 00:41 

H12 CONDUIT 378.76 0 01:14 18.06 0.83 0.70 

H120-DF DUMMY 100.10 0 00:47 

H13 CONDUIT 208.52 0 02:18 3.91 0.01 0.19 

H130-DF DUMMY 67.89 0 00:44 

H14 CONDUIT 221.02 0 02:12 2.55 0.02 0.21 

H140-DF DUMMY 55.81 0 00:50 

H145-DF DUMMY 186.42 0 00:51 

H15 CONDUIT 371.64 0 01:37 2.91 0.03 0.26 

H150-DF DUMMY 318.79 0 00:36 

H16 CONDUIT 410.47 0 01:07 2.83 0.03 0.25 

H160-DF DUMMY 95.94 0 01:07 

Page B-51



H17 CONDUIT 504.69 0 01:10 4.17 0.09 0.33 

H170-DF DUMMY 76.46 0 00:56 

H18 CONDUIT 668.03 0 01:18 13.09 0.40 0.43 

H180-DF DUMMY 153.01 0 00:46 

H185 CONDUIT 217.62 0 00:47 17.38 0.69 0.61 

H19 CONDUIT 835.84 0 01:16 5.07 0.19 0.43 

H190-DF DUMMY 314.61 0 00:36 

H20 CONDUIT 943.17 0 01:16 5.41 0.21 0.46 

H200-DF DUMMY 175.41 0 00:43 

H205 CONDUIT 190.80 0 00:39 3.71 0.01 0.20 

H21 CONDUIT 1159.70 0 01:15 5.59 0.26 0.52 

H210-DF DUMMY 276.48 0 00:41 

H22 CONDUIT 1334.12 0 01:13 5.93 0.29 0.55 

H220-DF DUMMY 89.36 0 00:45 

HC008-DF DUMMY 1764.87 0 01:06 

HC013-DF DUMMY 2890.04 0 01:17 

HC025-DF DUMMY 5973.04 0 01:51 

HC028-DF DUMMY 7775.72 0 01:55 

HC032-DF DUMMY 8353.18 0 02:04 

HC035-DF DUMMY 8448.02 0 02:16 

HC036-DF DUMMY 9227.02 0 02:15 

HC117-DF DUMMY 221.69 0 00:55 

HC999-DF DUMMY 9233.48 0 02:19 

OH999-DF DUMMY 1327.80 0 01:30 

OR999-DF DUMMY 462.14 0 01:08 

SG999-DF DUMMY 136.39 0 01:28 

GA309-OUT DUMMY 378.82 0 01:13 

GA310-OUT DUMMY 208.55 0 02:16 

GA311-OUT DUMMY 221.06 0 02:05 

GA350-OUT DUMMY 668.18 0 01:16 

GV301-OUT DUMMY 113.64 0 01:14 

GV302-OUT DUMMY 195.92 0 01:24 

HC310-OUT DUMMY 484.06 0 01:01 

HC320-OUT DUMMY 1361.65 0 00:58 

HC326-OUT DUMMY 42.92 0 02:00 

MT300-OUT DUMMY 258.07 0 01:16 

OH310-OUT DUMMY 378.41 0 01:34 

OH320-OUT DUMMY 418.30 0 01:24 

SG310-OUT DUMMY 39.77 0 02:45 

SG320-OUT DUMMY 67.72 0 02:46 

************************* 

Conduit Surcharge Summary 

************************* 

---------------------------------------------------------------------------- 

Hours Hours 

--------- Hours Full -------- Above Full Capacity 

Conduit Both Ends Upstream Dnstream Normal Flow Limited 

---------------------------------------------------------------------------- 

A100-DF 0.01 0.01 0.01 96.01 0.01 

A105-DF 0.01 0.01 0.01 96.01 0.01 

A110-DF 0.01 0.01 0.01 96.01 0.01 

A120-DF 0.01 0.01 0.01 96.01 0.01 

A125-DF 0.01 0.01 0.01 96.01 0.01 

A130-DF 0.01 0.01 0.01 96.01 0.01 

A134-DF 0.01 0.01 0.01 96.01 0.01 

A135-DF 0.01 0.01 0.01 96.01 0.01 

A140-DF 0.01 0.01 0.01 96.01 0.01 

A150-DF 0.01 0.01 0.01 96.01 0.01 

A160-DF 0.01 0.01 0.01 96.01 0.01 

A170-DF 0.01 0.01 0.01 96.01 0.01 

A180-DF 0.01 0.01 0.01 96.01 0.01 

A190-DF 0.01 0.01 0.01 96.01 0.01 

A195-DF 0.01 0.01 0.01 96.01 0.01 

A200-DF 0.01 0.01 0.01 96.01 0.01 

A210-DF 0.01 0.01 0.01 96.01 0.01 

A215-DF 0.01 0.01 0.01 96.01 0.01 

A220-DF 0.01 0.01 0.01 96.01 0.01 

A230-DF 0.01 0.01 0.01 96.01 0.01 

A234-DF 0.01 0.01 0.01 96.01 0.01 

A235-DF 0.01 0.01 0.01 96.01 0.01 

A240-DF 0.01 0.01 0.01 96.01 0.01 

A245-DF 0.01 0.01 0.01 96.01 0.01 

A250-DF 0.01 0.01 0.01 96.01 0.01 

A260-DF 0.01 0.01 0.01 96.01 0.01 

A263-DF 0.01 0.01 0.01 96.01 0.01 

A264-DF 0.01 0.01 0.01 96.01 0.01 

A265-DF 0.01 0.01 0.01 96.01 0.01 

A270-DF 0.01 0.01 0.01 96.01 0.01 

A275-DF 0.01 0.01 0.01 96.01 0.01 

A276-DF 0.01 0.01 0.01 96.01 0.01 

A280-DF 0.01 0.01 0.01 96.01 0.01 

A285-DF 0.01 0.01 0.01 96.01 0.01 

A290-DF 0.01 0.01 0.01 96.01 0.01 

A300-DF 0.01 0.01 0.01 96.01 0.01 

A304-DF 0.01 0.01 0.01 96.01 0.01 

A305-DF 0.01 0.01 0.01 96.01 0.01 

A310-DF 0.01 0.01 0.01 96.01 0.01 

A314-DF 0.01 0.01 0.01 96.01 0.01 

A315-DF 0.01 0.01 0.01 96.01 0.01 

Page B-52



A320-DF 0.01 0.01 0.01 96.01 0.01 

A325-DF 0.01 0.01 0.01 96.01 0.01 

A330-DF 0.01 0.01 0.01 96.01 0.01 

A340-DF 0.01 0.01 0.01 96.01 0.01 

A345-DF 0.01 0.01 0.01 96.01 0.01 

A350-DF 0.01 0.01 0.01 96.01 0.01 

A360-DF 0.01 0.01 0.01 96.01 0.01 

A370-DF 0.01 0.01 0.01 96.01 0.01 

A375-DF 0.01 0.01 0.01 96.01 0.01 

A380-DF 0.01 0.01 0.01 96.01 0.01 

A390-DF 0.01 0.01 0.01 96.01 0.01 

A395-DF 0.01 0.01 0.01 96.01 0.01 

A400-DF 0.01 0.01 0.01 96.01 0.01 

B100-DF 0.01 0.01 0.01 96.01 0.01 

B110-DF 0.01 0.01 0.01 96.01 0.01 

B120-DF 0.01 0.01 0.01 96.01 0.01 

B130-DF 0.01 0.01 0.01 96.01 0.01 

B134-DF 0.01 0.01 0.01 96.01 0.01 

B135-DF 0.01 0.01 0.01 96.01 0.01 

BG999-DF 0.01 0.01 0.01 96.01 0.01 

BH999-DF 0.01 0.01 0.01 96.01 0.01 

C100-DF 0.01 0.01 0.01 96.01 0.01 

C110-DF 0.01 0.01 0.01 96.01 0.01 

C120-DF 0.01 0.01 0.01 96.01 0.01 

C125-DF 0.01 0.01 0.01 96.01 0.01 

C130-DF 0.01 0.01 0.01 96.01 0.01 

C140-DF 0.01 0.01 0.01 96.01 0.01 

C150-DF 0.01 0.01 0.01 96.01 0.01 

C153-DF 0.01 0.01 0.01 96.01 0.01 

C154-DF 0.01 0.01 0.01 96.01 0.01 

C155-DF 0.01 0.01 0.01 96.01 0.01 

C159-DF 0.01 0.01 0.01 96.01 0.01 

C160-DF 0.01 0.01 0.01 96.01 0.01 

C170-DF 0.01 0.01 0.01 96.01 0.01 

C175-DF 0.01 0.01 0.01 96.01 0.01 

C180-DF 0.01 0.01 0.01 96.01 0.01 

C185-DF 0.01 0.01 0.01 96.01 0.01 

C190-DF 0.01 0.01 0.01 96.01 0.01 

D100-DF 0.01 0.01 0.01 96.01 0.01 

D110-DF 0.01 0.01 0.01 96.01 0.01 

D120-DF 0.01 0.01 0.01 96.01 0.01 

D130-DF 0.01 0.01 0.01 96.01 0.01 

E100-DF 0.01 0.01 0.01 96.01 0.01 

E105-DF 0.01 0.01 0.01 96.01 0.01 

E110-DF 0.01 0.01 0.01 96.01 0.01 

E120-DF 0.01 0.01 0.01 96.01 0.01 

E125-DF 0.01 0.01 0.01 96.01 0.01 

E130-DF 0.01 0.01 0.01 96.01 0.01 

E135-DF 0.01 0.01 0.01 96.01 0.01 

E140-DF 0.01 0.01 0.01 96.01 0.01 

E150-DF 0.01 0.01 0.01 96.01 0.01 

E155-DF 0.01 0.01 0.01 96.01 0.01 

E160-DF 0.01 0.01 0.01 96.01 0.01 

E170-DF 0.01 0.01 0.01 96.01 0.01 

E180-DF 0.01 0.01 0.01 96.01 0.01 

E183-DF 0.01 0.01 0.01 96.01 0.01 

E184-DF 0.01 0.01 0.01 96.01 0.01 

E185-DF 0.01 0.01 0.01 96.01 0.01 

E190-DF 0.01 0.01 0.01 96.01 0.01 

E200-DF 0.01 0.01 0.01 96.01 0.01 

E204-DF 0.01 0.01 0.01 96.01 0.01 

E205-DF 0.01 0.01 0.01 96.01 0.01 

E210-DF 0.01 0.01 0.01 96.01 0.01 

F100-DF 0.01 0.01 0.01 96.01 0.01 

F110-DF 0.01 0.01 0.01 96.01 0.01 

F120-DF 0.01 0.01 0.01 96.01 0.01 

F125-DF 0.01 0.01 0.01 96.01 0.01 

F130-DF 0.01 0.01 0.01 96.01 0.01 

F14 2.52 2.58 2.54 2.63 2.58 

F140-DF 0.01 0.01 0.01 96.01 0.01 

G100-DF 0.01 0.01 0.01 96.01 0.01 

G105-DF 0.01 0.01 0.01 96.01 0.01 

G110-DF 0.01 0.01 0.01 96.01 0.01 

G120-DF 0.01 0.01 0.01 96.01 0.01 

GA999-DF 0.01 0.01 0.01 96.01 0.01 

GV999-DF 0.01 0.01 0.01 96.01 0.01 

H100-DF 0.01 0.01 0.01 96.01 0.01 

H110-DF 0.01 0.01 0.01 96.01 0.01 

H115-DF 0.01 0.01 0.01 96.01 0.01 

H120-DF 0.01 0.01 0.01 96.01 0.01 

H130-DF 0.01 0.01 0.01 96.01 0.01 

H140-DF 0.01 0.01 0.01 96.01 0.01 

H145-DF 0.01 0.01 0.01 96.01 0.01 

H150-DF 0.01 0.01 0.01 96.01 0.01 

H160-DF 0.01 0.01 0.01 96.01 0.01 

H170-DF 0.01 0.01 0.01 96.01 0.01 

H180-DF 0.01 0.01 0.01 96.01 0.01 

H190-DF 0.01 0.01 0.01 96.01 0.01 

H200-DF 0.01 0.01 0.01 96.01 0.01 

H210-DF 0.01 0.01 0.01 96.01 0.01 

H220-DF 0.01 0.01 0.01 96.01 0.01 

HC008-DF 0.01 0.01 0.01 96.01 0.01 

Page B-53



HC013-DF 0.01 0.01 0.01 96.01 0.01 

HC025-DF 0.01 0.01 0.01 96.01 0.01 

HC028-DF 0.01 0.01 0.01 96.01 0.01 

HC032-DF 0.01 0.01 0.01 96.01 0.01 

HC035-DF 0.01 0.01 0.01 96.01 0.01 

HC036-DF 0.01 0.01 0.01 96.01 0.01 

HC117-DF 0.01 0.01 0.01 96.01 0.01 

HC999-DF 0.01 0.01 0.01 96.01 0.01 

OH999-DF 0.01 0.01 0.01 96.01 0.01 

OR999-DF 0.01 0.01 0.01 96.01 0.01 

SG999-DF 0.01 0.01 0.01 96.01 0.01 

Analysis begun on: Thu Aug 01 01:18:49 2013 

Analysis ended on: Thu Aug 01 01:18:55 2013 

Page B-54



Figure B-10 

Peak Flow Diagram – Model Calibration 

8000 

7000 

6000 


1993 OSP (Published Values) 

1993 OSP (Run on Current Software) 

Unadjusted Calibration Model 

Unadjusted Calibration Model, 2-Hr Storm 

Equivalent Cottonwood Historic Peak 

Calibration Model, 0.65*Cp 

Calibration Model, 2-Hr, 0.65*Cp 

1977 FHAD / FEMA Effective 


5000 

4000 

3000 

2000 

1000 

Confluence w/ Cherry Creek 

Jordan Road (Green Acres Tributary) 

E-470 (Stonegate Tributary) 


Lincoln Ave (Badger Gulch) 


I-25 

Oak Hills Drive (Beverly Hills Tributary) 

ALL PEAK FLOW RATES SHOWN ARE BASED 

ON A 100-YEAR STORM AND 1993 

EXISTING DEVELOPMENT CONDITIONS, 

WITH THE EXCEPTION OF THE 1977 FHAD, 

WHICH IS BASED ON FUTURE 

DEVELOPMENT AS PREDICTED IN 1977. 

Castle Pines Parkway (CPNMD Pond 11) 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page B-55


APPENDIX C 

HYDRAULIC ANALYSIS

Existing Channel Condition Future Condition Adjustment 

Station to Station Reach No. Description n-left n-channel n-right n-left n-channel n-right Existing Channel Remarks: Future Conditions Remarks 

Meandering with vertical banks and Future improvements will reduce turbulence of 

59597 56400 1/2 Downstream of Castle Pines 0.08 0.05 0.08 0.1 0.045 0.1 

significant erosion of low-flow. 

low-flow but increase vegetative density in 

56100 55800 2 Douglas County South 0.08 0.045 0.05 0.1 0.045 0.05 Grassy, wide ROB 

overbanks. 

55500 54982 2 Douglas County South 0.1 0.05 0.1 

Meandering with 0-4' of incision. Dense, 

healthy veg. Some vertical banks. 


Flat, grassy ROB at confluence with 

Beverly Hills Trib. 


Meandering with 0-4' of incision. Dense, 

healthy veg. 

48088 43553 3 I-25 Corridor 0.1 0.05 0.1 Narrow and incised 

43472 43193 3 I-25 Bridge (Crossing 12) See XS 

43094 40259 4 Lone Tree South 0.04 0.03 0.035 0.05 0.035 0.045 Overgrazed area, sparse short veg. 


35402 33481 4 Lone Tree South 0.035 0.045 0.035 0.045 0.045 0.045 Turbulent, sharply meandering low-flow 


32010 31933 4 Ridgegate Pkwy (Crossing 14) See XS 


29469 26100 5 Merdian 0.05 0.04 0.05 

Willows and shurbs with large mature 

cottonwoods 

25802 21423 6 Lone Tree North 0.035 0.03 0.035 0.045 0.035 0.045 Overgrazed area, sparse short veg. 

21274 21001 6 Lone Tree North 0.05 0.04 0.05 

Primarily medium density grasses with 

stands of shrubs. 

20839 20809 7 Grouted Boulder Drop Structure 0.1 0.1 0.1 

20700 20211 7 Douglas County North 0.06 0.06 0.06 Willows and medium density grasses 

20135 20007 7 Lincoln Ave. (Crossing 17 & Drop) See XS 

19929 18641 7 Grandview Estates 0.035 0.03 0.035 

Isolated stands of trees and medium 

density grasses 

18540 18469 7 Birch Ave. (Crossing 18) See XS 

18378 16933 7 Grandview Estates (recent channel project) 0.025 0.03 0.025 0.035 0.03 0.035 

16791 10595 7/8 Grandview Estates / Compark South 0.035 0.03 0.035 

10548 10326 8 E-470 (Crossing 21) See XS 

10157 7422 8 Compark North 0.04 0.035 0.04 0.05 0.04 0.05 

7377 7261 8 Chambers Rd. (Crossing 22) See XS 

7158 2879 9 JWPP Reach 0.03 0.03 0.03 0.04 0.035 0.04 


2767 2718 9 JWPP Reach 0.03 0.03 0.03 0.04 0.035 0.04 

2654 2530 9 Jordan Rd. (Crossing 23) See XS 

2400 2298 9 Southcreek Trapezoidal Channel 0.03 0.035 0.03 0.035 0.04 0.035 






Table C-1 

Channel Roughness Values 


Overbanks relatively bare due to recent 

channel project. 

sparse, bunchy veg with sandy, aggraded 

low-flow. 


low-flow. 


low-flow. 


low-flow. 


low-flow. 


low-flow. 


low-flow. 

Future runoff increases and elimination of cattle 

grazing will result in increased veg. density 

Future runoff increases will increase veg. density 

Future runoff increases will increase veg. density 

Page C-1

6270 

Happy Canyon FHAD Plan: Happy Canyon FHAD 2/19/2013 


RS = 56400 Reach 2 RS = 53400 Reach 2 

.1 . .1 

.08 .04 .08 

045 6232 

Legend 

Legend 

6268 

WS 500YR 

WS 100YR 

6230 

WS 500YR 

WS 100YR 

6266 

WS 50YR 

6228 

WS 50YR 

6264 

WS 10YR 

Ground 

6226 

WS 10YR 

Ground 

Elevation (ft) 

6262 

6260 

Bank Sta 


6224 

6222 

Ineff 

Bank Sta 

6258 

6220 

6256 

6218 

6254 

6216 

6252 

0 50 100 150 200 250 300 350 

6214 

0 100 200 300 400 

6185 

Station (ft) 

Station (ft) 




.08 .04 .08 

.1 .05 .1 

6130 

Legend 

Legend 

6180 

WS 500YR 

WS 100YR 

WS 50YR 

6125 

WS 500YR 

WS 100YR 

WS 50YR 

6175 

WS 10YR 

Ground 

6120 

WS 10YR 

Ground 


6170 

6165 

Bank Sta 


6115 

Bank Sta 

6160 

6110 

6155 

6105 

6150 

0 50 100 150 200 250 300 350 

6100 

0 50 100 150 200 250 300 350 

Station (ft) 

Station (ft) 

1 

Page C-2

6030 




.045 . .045 

.045 .035 .045 

035 5965 

Legend 

WS 500YR 

Legend 

WS 500YR 

6025 

WS 100YR 

WS 50YR 

5960 

WS 100YR 

WS 50YR 

WS 10YR 

Ground 

5955 

WS 10YR 

Ground 


6020 

6015 

Bank Sta 


5950 

Ineff 

Bank Sta 

5945 

6010 

5940 

6005 

0 100 200 300 400 500 

5935 

0 100 200 300 400 500 600 700 

5945 

Station (ft) 

Station (ft) 




.05 .04 .05 

.045 .035 .045 

5880 

Legend 

Legend 

5940 

WS 500YR 

WS 100YR 

WS 50YR 

5875 

WS 500YR 

WS 100YR 

WS 50YR 

5935 

WS 10YR 

WS 10YR 

Ground 

Ground 


5930 

5925 

Ineff 

Bank Sta 


5870 

5865 

Bank Sta 

5920 

5860 

5915 

5910 

0 50 100 150 200 250 300 350 

5855 

0 200 400 600 800 

Station (ft) 

Station (ft) 

2 

Page C-3

5850 



RS = 19255 non-levee natural embankment in ROB Reach 7 RS = 15498 Low point in LOB (modeled as IEFA) Reach 7 

.035 .03 .035 

.035 .03 .035 

5820 

Legend 

WS 500YR 

Legend 

WS 500YR 

5845 

WS 100YR 

WS 50YR 

WS 10YR 

5815 

WS 100YR 

WS 50YR 

WS 10YR 

Ground 

Ground 


5840 

Levee 

Bank Sta 


5810 

5805 

Ineff 

Bank Sta 

5835 

5800 

5830 

0 200 400 600 800 1000 1200 

5795 

0 200 400 600 800 1000 1200 

5775 

Station (ft) 

Station (ft) 



RS = 9910 Reach 8 RS = 5700 Pond in ROB (modeled as IEFA) Reach 8 

.05 .04 .05 

.04 . .04 

5755 

035 

Legend 

Legend 

WS 500YR 

WS 100YR 

5750 

WS 500YR 

WS 100YR 

5770 

WS 50YR 

WS 10YR 

5745 

WS 50YR 

WS 10YR 

Ground 

Ground 


5765 

Bank Sta 


5740 

5735 

Ineff 

Bank Sta 

5760 

5730 

5725 

5755 

0 100 200 300 400 500 600 700 

Station (ft) 

3 

5720 

0 200 400 600 800 1000 

Station (ft) 

Page C-4

5700 

5698 

5696 


RS = 1800 Reach 9 

.035 .04 .035 

Legend 

WS 500YR 

WS 100YR 

WS 50YR 

WS 10YR 


5694 

5692 

5690 

Ground 

Bank Sta 

5688 

5686 

5684 

0 100 200 300 400 500 

Station (ft) 

4 

Page C-5



APPENDIX D 

LEGAL OPINION

Page D-1

Page D-2

Page D-3

Page D-4


APPENDIX E 

WETLAND AND RIPARIAN INVENTORY



APPENDIX F 

ALTERNATIVES ANALYSIS

Table F-1 

Unit Cost Data 

Unit Cost Unit Cost 

Item Unit 2009 Current Yr. 

Hydraulic Structures 

Grouted Boulders, 36-inch CY $250.00 $281.38 

Riprap, Type M CY $60.00 $67.53 

Soil Riprap, Type M CY $65.00 $73.16 

Excavation, Complete-in-Place CY $12.00 $13.51 

Bedding, Granular Type II CY $50.00 $56.28 

Grout CY $275.00 $309.51 

Check Structure, Concrete LF $220.00 $340.00 

Channel Improvements 

Soil Riprap, Type VL CY $50.00 $56.28 

Soil Riprap, Type L CY $55.00 $61.90 

Soil Riprap, Type M CY $60.00 $67.53 

Soil Riprap, Type H CY $70.00 $78.79 

Soil Riprap, Type VH CY $85.00 $95.67 

Excavation, Low Range CY $12.00 $13.51 

Excavation, Mid Range CY $15.00 $16.88 

Excavation, High Range CY $25.00 $28.14 

Detention/Water Quality Facilities 

Excavation, Low Range CY $12.00 $13.51 

Excavation, Mid Range CY $15.00 $16.88 

Excavation, High Range CY $25.00 $28.14 

Outlet Works* EA varies 

Water Quality Appurtenances* EA varies 

Detention (Complete-in-Place) AC-FT $45,600.00 $51,323.20 

Landscaping and Recreation Improvements 

Wetlands Plantings ACRE $25,000.00 $28,137.72 

Reclamation & seeding (native grasses) ACRE $1,000.00 $1,125.51 

Trail/Path, Concrete (10' Width) LF $40.00 $45.02 

Trail/Path, Crusher Fines (10' Width) LF $10.00 $11.26 

Removals 

Removal of culvert pipe (D

Table F-2 

Detention Alternative Peak Flow Rates and Volumes 

Pond Description 

Jurisdiction / Reach 

SWMM 

Element 

HISTORIC 

2- year 10-year 100-year 

flow flow flow 

(cfs) (cfs) (cfs) 

inflow 

(cfs) 

2-Year 

outflow 

(cfs) 

BASELINE HYDROLOGY - FUTURE DEVELOPMENT 

volume 

(af) 

inflow 

(cfs) 

10-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

100-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

2-Year 

outflow 

(cfs) 

volume 

(af) 

DETENTION ALTERNATIVE A 

inflow 

(cfs) 

10-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

100-Year 

outflow 

(cfs) 

volume 

(af) 

CPNMD Pond 11 City of Castle Pines HC310 2.5 124 526 154 153 0.1 409 321 1.9 1001 491 15.0 154 153 0.1 409 321 1.9 1001 491 15.0 

CPNMD Pond 12 City of Castle Pines HC320 5.0 262 1147 277 270 0.6 701 587 5.4 1518 1409 16.4 277 270 0.6 701 587 5.4 1518 1409 16.4 

CPNMD Pond 20 City of Castle Pines MT300 2.1 66 264 67 24 2.6 179 77 7.9 444 265 14.8 67 24 2.6 179 77 7.9 444 265 14.8 

CPNMD Pond 9 City of Castle Pines OH310 2.5 120 517 32 31 0.3 177 112 5.3 623 385 17.9 32 31 0.3 177 112 5.3 623 385 17.9 

CPNMD Pond 10 City of Castle Pines OH320 2.6 132 576 39 39 0.1 126 121 1.3 430 424 2.7 39 39 0.1 126 121 1.3 430 424 2.7 

Beverly Hills Stock Pond Douglas County (South) BH504 2.5 136 627 

Charter Oak Pond City of Castle Pines BH501 1.3 39 145 

RidgeGate Pond HC519 City of Lone Tree HC519 10.1 1014 4969 

RidgeGate Pond HC522 City of Lone Tree HC522 10.0 1047 5238 387 376 2.1 1941 1901 10.9 5957 5679 45.5 

RidgeGate Pond HC525 City of Lone Tree HC525 9.4 1058 5421 346 341 1.5 2022 1967 12.5 6039 5850 47.2 

RidgeGate Pond BG511 City of Lone Tree BG511 4.1 288 1467 9 9 0.0 410 402 2.0 1697 1463 21.3 

Meridian Pond 4C Douglas County (North) GA309 1.6 62 263 115 92 1.6 249 212 3.4 540 394 11.8 115 92 1.6 249 212 3.4 540 394 11.8 

Meridian Pond 4B Douglas County (North) GA310 1.8 74 311 112 80 3.2 256 151 9.7 477 212 29.3 112 80 3.2 256 151 9.7 477 212 29.3 

Meridian Pond 4A Douglas County (North) GA311 2.0 81 344 87 81 6.5 166 164 7.5 226 224 8.2 87 81 6.5 166 164 7.5 226 224 8.2 

Airport 320 Pond Douglas County (North) GA506 2.1 110 512 

E470 Pond Town of Parker GA350 2.0 125 622 144 144 0.0 319 319 0.6 725 688 4.2 144 124 7.4 319 315 9.4 725 684 13.5 

Dove Valley Pond Arapahoe County GA599 2.0 157 876 

Stepping Stone Pond D1 Douglas County (North) GV301 1.1 33 128 55 36 0.8 119 65 2.3 249 119 7.1 55 36 0.8 119 65 2.3 249 119 7.1 

Stepping Stone Pond D3 Douglas County (North) GV302 1.7 63 263 80 13 6.6 166 85 9.7 337 198 14.1 80 13 6.6 166 85 9.7 337 198 14.1 

Grandview Pond Douglas County (North) GV504 2.2 109 513 93 7 12.3 214 55 29.8 603 76 64.8 

Meridian Village Pond 1 Douglas County (North) HC326 0.6 16 78 47 14 3.2 90 20 6.2 181 45 11.6 47 14 3.2 90 20 6.2 181 45 11.6 

Stonegate Pond Douglas County (North) SG310 0.5 15 62 23 2 3.5 54 11 7.6 126 41 12.1 23 2 3.5 54 11 7.6 126 41 12.1 

Chambers Reservoir WQ 

Pond 

Douglas County (North) SG320 0.7 28 140 17 3 2.1 47 18 5.1 140 69 10.7 17 3 2.1 47 18 5.1 140 69 10.7 

Page F-2

Table F-2 (cont.) 

Detention Alternative Peak Flow Rates and Volumes 


Jurisdiction / Reach 

SWMM 

Element 

HISTORIC 

2- year 10-year 100-year 

flow flow flow 

(cfs) (cfs) (cfs) 

inflow 

(cfs) 

2-Year 

outflow 

(cfs) 

volume 

(af) 

DETENTION ALTERNATIVE B 

inflow 

(cfs) 

10-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

100-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

2-Year 

outflow 

(cfs) 

volume 

(af) 

DETENTION ALTERNATIVE C 

inflow 

(cfs) 

10-Year 

outflow 

(cfs) 

volume 

(af) 

inflow 

(cfs) 

100-Year 

outflow 

(cfs) 

volume 

(af) 

CPNMD Pond 11 City of Castle Pines HC310 2.5 124 526 

CPNMD Pond 12 City of Castle Pines HC320 5.0 262 1147 

CPNMD Pond 20 City of Castle Pines MT300 2.1 66 264 

CPNMD Pond 9 City of Castle Pines OH310 2.5 120 517 

CPNMD Pond 10 City of Castle Pines OH320 2.6 132 576 

Beverly Hills Stock Pond Douglas County (South) BH504 2.5 136 627 

Charter Oak Pond City of Castle Pines BH501 1.3 39 145 




RidgeGate Pond BG511 City of Lone Tree BG511 4.1 288 1467 

Meridian Pond 4C Douglas County (North) GA309 1.6 62 263 

Meridian Pond 4B Douglas County (North) GA310 1.8 74 311 

Meridian Pond 4A Douglas County (North) GA311 2.0 81 344 

Airport 320 Pond Douglas County (North) GA506 2.1 110 512 

E470 Pond Town of Parker GA350 2.0 125 622 

Dove Valley Pond Arapahoe County GA599 2.0 157 876 

Stepping Stone Pond D1 Douglas County (North) GV301 1.1 33 128 

Stepping Stone Pond D3 Douglas County (North) GV302 1.7 63 263 

Grandview Pond Douglas County (North) GV504 2.2 109 513 

Meridian Village Pond 1 Douglas County (North) HC326 0.6 16 78 

Stonegate Pond Douglas County (North) SG310 0.5 15 62 

154 9 8.2 409 177 11.5 1001 524 20.2 154 9 8.2 409 177 11.5 1001 366 25.9 

136 136 0.2 431 416 1.6 1506 1411 12.5 136 5 14.3 431 414 16.1 1363 1317 19.5 

67 4 5.2 179 74 9.1 444 258 15.7 67 4 5.2 179 74 9.1 444 258 15.7 

32 3 3.5 177 158 6.9 623 390 18.9 32 3 3.5 177 158 6.9 623 390 18.9 

11 3 1.1 176 175 2.1 437 437 3.1 11 3 1.1 176 175 2.1 437 437 3.1 

121 83 3.6 368 339 5.4 996 976 7.3 49 28 3.2 212 189 4.6 696 694 6.4 

111 2 3.7 223 27 5.8 418 92 8.7 

91 90 0.3 1167 1154 5.8 4911 4588 49.4 

236 233 1.1 1650 1619 9.0 5891 5616 44.7 95 95 1.0 1308 1260 17.3 5134 5026 67.6 

212 211 0.7 1738 1702 10.5 5964 5781 46.5 98 97 0.8 1339 1288 19.3 5287 4759 93.9 

9 9 0.0 410 402 2.0 1697 1463 21.3 9 9 0.0 410 291 9.4 1697 1107 67.2 

115 92 1.6 249 212 3.4 540 394 11.8 115 92 1.6 249 212 3.4 540 394 11.8 

112 80 3.2 256 151 9.7 477 212 29.3 112 80 3.2 256 151 9.7 477 212 29.3 

87 81 6.5 166 164 7.5 226 224 8.2 87 81 6.5 166 164 7.5 226 224 8.2 

116 32 23.5 268 246 26.2 461 422 27.6 

144 124 7.4 319 315 9.4 725 684 13.5 45 26 6.5 258 252 8.7 554 542 12.0 

279 174 16.1 550 457 18.2 1154 1062 23.8 

55 36 0.8 119 65 2.3 249 119 7.1 55 36 0.8 119 65 2.3 249 119 7.1 

80 13 6.6 166 85 9.7 337 198 14.1 80 13 6.6 166 85 9.7 337 198 14.1 

93 7 12.3 214 55 29.8 603 76 64.8 93 7 12.3 214 55 29.8 603 76 64.8 

47 14 3.2 90 20 6.2 181 45 11.6 47 14 3.2 90 20 6.2 181 45 11.6 

23 2 3.5 54 11 7.6 126 41 12.1 23 2 3.5 54 11 7.6 126 41 12.1 

Chambers Reservoir WQ 

Pond 

Douglas County (North) SG320 0.7 28 140 

17 3 2.1 47 18 5.1 140 69 10.7 17 3 2.1 47 18 5.1 140 69 10.7 

Page F-3

Figure F-1 

Detention Alternatives Peak Flow Diagram - 100-Year Event 

10000 

EXISTING 

FUTURE 

9000 

HISTORIC 

ALT-A 


8000 

7000 

6000 

5000 

4000 

3000 

2000 

Cherry Creek 

Jordan Road 




Lincoln Ave 



I-25 




ALT-B 

ALT-C 


Monarch Blvd. 

1000 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page F-4

4000 

Figure F-2 


EXISTING 


3500 

3000 

2500 

2000 

1500 

1000 

500 

Cherry Creek 

Jordan Road 




Lincoln Ave 



I-25 





FUTURE 

HISTORIC 

ALT-A 

ALT-B 

ALT-C 

Monarch Blvd. 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page F-5

Figure F-3 


EXISTING 

1000 

FUTURE 


900 

800 

700 

600 

500 

400 

300 

Cherry Creek 

Jordan Road 




Lincoln Ave 



I-25 





HISTORIC 

ALT-A 

ALT-B 

ALT-C 

200 

100 

Monarch Blvd. 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page F-6

350 

Figure F-4 

Detention Alternatives Peak Flow Diagram - WQ Event 

FUTURE 


300 

250 

200 

150 

100 

50 

Cherry Creek 

Jordan Road 




Lincoln Ave 



I-25 




HISTORIC 

ALT-A 

ALT-B 

ALT-C 


Monarch Blvd. 

0 

0 10000 20000 30000 40000 50000 60000 70000 

Station (ft) 

Page F-7

Table F-3 

Detention Alternative A Cost Estimate 



Mob (5%) Stormwater 

Mgmt & EC (5%) 

Engineering 

Legal / Admin 

Contract Admin 

/ Const Mgmt 

Contingency 

Subtotal Total Capital Cost Total 

Unit Cost $ 51,323.20 varies $ 1,125.51 

10% 15% 5% 10% 25% 

SWMM 

Element 

Vol 

(AF) 

Cost 

Qty 

(EA) 

Unit Cost 

Cost 

Area 

(AC) 

Cost Cost Cost Cost Cost Cost 

CPNMD Pond 11 HC310 $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - 

CPNMD Pond 12 HC320 $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - 

CPNMD Pond 20 MT300 $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - 

CPNMD Pond 9 OH310 $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - 

CPNMD Pond 10 OH320 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Douglas County South 

Beverly Hills Stock Pond BH504 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Lone Tree South 

RidgeGate Ponds HC551, HC552, 

HC553, HC554, HC561 

varies 54 $ 2,771,453 

$ - $ - $ 2,771,453 $ 277,145 $ 3,048,598 $ 457,290 $ 152,430 $ 304,860 $ 762,150 $ 4,725,327 

RidgeGate Pond HC522 HC522 46 $ 2,360,867 

$ - $ - $ 2,360,867 $ 236,087 $ 2,596,954 $ 389,543 $ 129,848 $ 259,695 $ 649,238 $ 4,025,279 

Lone Tree North 


BG551, BG552, BG553 

varies 76 $ 3,900,563 

$ - $ - $ 3,900,563 $ 390,056 $ 4,290,620 $ 643,593 $ 214,531 $ 429,062 $ 1,072,655 $ 6,650,460 


$ - $ - $ 2,463,514 $ 246,351 $ 2,709,865 $ 406,480 $ 135,493 $ 270,986 $ 677,466 $ 4,200,291 

RidgeGate Pond BG511 BG511 22 $ 1,129,110 

$ - $ - $ 1,129,110 $ 112,911 $ 1,242,021 $ 186,303 $ 62,101 $ 124,202 $ 310,505 $ 1,925,133 


Meridian Pond 4C GA309 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Meridian Pond 4B GA310 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Meridian Pond 4A GA311 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Stepping Stone Pond D1 GV301 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Grandview Pond GV504 65 $ 3,336,008 

$ - $ - $ 3,336,008 $ 333,601 $ 3,669,609 $ 550,441 $ 183,480 $ 366,961 $ 917,402 $ 5,687,894 

Meridian Village Pond 1 HC326 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Stonegate Pond SG310 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Chambers WQ Pond SG320 $ - 

$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


Complete-In-Place 

Pond (AF) 

Outlet Works 

Reclamation & 

Seeding 

E470 Pond GA350 14 $ 718,525 

$ - $ - $ 718,525 $ 71,852 $ 790,377 $ 118,557 $ 39,519 $ 79,038 $ 197,594 $ 1,225,085 

Reach 

Total 

$ - 

$ - 

$ 8,750,606 

$ 12,775,884 

$ 5,687,894 

$ 1,225,085 

ALTERNATIVE A TOTAL $ 18,348,044 

Total # of Ponds 29 Annual Maintenance Cost $ 5,000 Total Annual Cost $ 145,000 

P/A for 50 Years at 3% Annual Inflation 25.7297 Total Present Worth of 50 Years Maintenance 

$ 

$ 

28,439,468 

3,730,807 

ALTERNATIVE A TOTAL WITH 50 YEARS MAINTENANCE $ 32,170,275 

Page F-8

Table F-4 

Detention Alternative B Cost Estimate 





Engineering 

Legal / Admin 


/ Const Mgmt 

Contingency 

Subtotal Total Capital Cost Total 


10% 15% 5% 10% 25% 

SWMM 

Element 

Vol 

(AF) 

Cost 

Qty 

(EA) 

Unit Cost 

Cost 

Area 

(AC) 


CPNMD Pond 11 HC310 $ - 1 $ 50,000 $ 50,000 2 $ 2,251 $ 52,251 $ 5,225 $ 57,476 $ 8,621 $ 2,874 $ 5,748 $ 14,369 $ 89,088 

CPNMD Pond 12 HC320 $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - $ - 

CPNMD Pond 20 MT300 $ - 1 $ 10,000 $ 10,000 $ - $ 10,000 $ 1,000 $ 11,000 $ 1,650 $ 550 $ 1,100 $ 2,750 $ 17,050 

CPNMD Pond 9 OH310 $ - 1 $ 25,000 $ 25,000 2 $ 2,251 $ 27,251 $ 2,725 $ 29,976 $ 4,496 $ 1,499 $ 2,998 $ 7,494 $ 46,463 

CPNMD Pond 10 OH320 $ - 1 $ 25,000 $ 25,000 2 $ 2,251 $ 27,251 $ 2,725 $ 29,976 $ 4,496 $ 1,499 $ 2,998 $ 7,494 $ 46,463 


Beverly Hills Stock Pond BH504 3 $ 153,970 

$ - $ - $ 153,970 $ 15,397 $ 169,367 $ 25,405 $ 8,468 $ 16,937 $ 42,342 $ 262,518 



HC553, HC554, HC561 

varies 54 $ 2,771,453 

$ - $ - $ 2,771,453 $ 277,145 $ 3,048,598 $ 457,290 $ 152,430 $ 304,860 $ 762,150 $ 4,725,327 


$ - $ - $ 2,360,867 $ 236,087 $ 2,596,954 $ 389,543 $ 129,848 $ 259,695 $ 649,238 $ 4,025,279 



BG551, BG552, BG553 

varies 76 $ 3,900,563 

$ - $ - $ 3,900,563 $ 390,056 $ 4,290,620 $ 643,593 $ 214,531 $ 429,062 $ 1,072,655 $ 6,650,460 


$ - $ - $ 2,463,514 $ 246,351 $ 2,709,865 $ 406,480 $ 135,493 $ 270,986 $ 677,466 $ 4,200,291 


$ - $ - $ 1,129,110 $ 112,911 $ 1,242,021 $ 186,303 $ 62,101 $ 124,202 $ 310,505 $ 1,925,133 



$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ 3,336,008 $ 333,601 $ 3,669,609 $ 550,441 $ 183,480 $ 366,961 $ 917,402 $ 5,687,894 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


E470 Pond GA350 14 $ 718,525 

$ - $ - $ 718,525 $ 71,852 $ 790,377 $ 118,557 $ 39,519 $ 79,038 $ 197,594 $ 1,225,085 



Pond (AF) 

Outlet Works 

Reclamation & 

Seeding 

JWPP Pond $ - 1 $ 15,000 $ 15,000 1 $ 1,126 $ 16,126 $ 1,613 $ 17,738 $ 2,661 $ 887 $ 1,774 $ 4,435 $ 27,494 

Ladera Pond $ - 1 $ 15,000 $ 15,000 1 $ 1,126 $ 16,126 $ 1,613 $ 17,738 $ 2,661 $ 887 $ 1,774 $ 4,435 $ 27,494 

Reach 

Total 

$ 199,064 

$ 262,518 

$ 8,750,606 

$ 12,775,884 

$ 5,687,894 

$ 1,225,085 

$ 54,988 

ALTERNATIVE B TOTAL $ 18,681,315 



$ 

$ 

28,956,038 

3,988,104 

ALTERNATIVE B TOTAL WITH 50 YEARS MAINTENANCE $ 32,944,142 

Page F-9

Table F-5 

Detention Alternative C Cost Estimate 





Engineering 

Legal / Admin 


/ Const Mgmt 

Subtotal 

Total Capital Cost 


10% 15% 5% 10% 25% 

SWMM 

Element 

Vol 

(AF) 

Cost 

Qty 

(EA) 

Unit Cost 

Cost 

Area 

(AC) 

Contingency 


Charter Oaks Pond BH501 9 $ 461,909 $ - $ - $ 461,909 $ 46,191 $ 508,100 $ 76,215 $ 25,405 $ 50,810 $ 127,025 $ 787,555 

CPNMD Pond 11 HC310 $ - 1 $ 50,000 $ 50,000 2 $ 2,251 $ 52,251 $ 5,225 $ 57,476 $ 8,621 $ 2,874 $ 5,748 $ 14,369 $ 89,088 

CPNMD Pond 12 HC320 20 $ 1,026,464 $ - $ - $ 1,026,464 $ 102,646 $ 1,129,110 $ 169,367 $ 56,456 $ 112,911 $ 282,278 $ 1,750,121 

CPNMD Pond 20 MT300 $ - 1 $ 10,000 $ 10,000 $ - $ 10,000 $ 1,000 $ 11,000 $ 1,650 $ 550 $ 1,100 $ 2,750 $ 17,050 

CPNMD Pond 9 OH310 $ - 1 $ 25,000 $ 25,000 2 $ 2,251 $ 27,251 $ 2,725 $ 29,976 $ 4,496 $ 1,499 $ 2,998 $ 7,494 $ 46,463 

CPNMD Pond 10 OH320 $ - 1 $ 25,000 $ 25,000 2 $ 2,251 $ 27,251 $ 2,725 $ 29,976 $ 4,496 $ 1,499 $ 2,998 $ 7,494 $ 46,463 


Beverly Hills Stock Pond BH504 3 $ 153,970 

$ - $ - $ 153,970 $ 15,397 $ 169,367 $ 25,405 $ 8,468 $ 16,937 $ 42,342 $ 262,518 



HC553, HC554, HC561 


Pond (AF) 

Outlet Works 

Reclamation & 

Seeding 

varies 54 $ 2,771,453 

$ - $ - $ 2,771,453 $ 277,145 $ 3,048,598 $ 457,290 $ 152,430 $ 304,860 $ 762,150 $ 4,725,327 


$ - $ - $ 2,566,160 $ 256,616 $ 2,822,776 $ 423,416 $ 141,139 $ 282,278 $ 705,694 $ 4,375,303 


$ - $ - $ 3,489,978 $ 348,998 $ 3,838,975 $ 575,846 $ 191,949 $ 383,898 $ 959,744 $ 5,950,412 

Total 

Reach 

Total 

$ 2,736,740 

$ 262,518 

$ 15,051,042 



BG551, BG552, BG553 

$ 20,826,441 

varies 76 $ 3,900,563 

$ - $ - $ 3,900,563 $ 390,056 $ 4,290,620 $ 643,593 $ 214,531 $ 429,062 $ 1,072,655 $ 6,650,460 


$ - $ - $ 4,824,381 $ 482,438 $ 5,306,819 $ 796,023 $ 265,341 $ 530,682 $ 1,326,705 $ 8,225,569 


$ - $ - $ 3,489,978 $ 348,998 $ 3,838,975 $ 575,846 $ 191,949 $ 383,898 $ 959,744 $ 5,950,412 



$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 

Airport 320 Pond GA506 28 $ 1,437,050 

$ - $ - $ 1,437,050 $ 143,705 $ 1,580,755 $ 237,113 $ 79,038 $ 158,075 $ 395,189 $ 2,450,170 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ 3,336,008 $ 333,601 $ 3,669,609 $ 550,441 $ 183,480 $ 366,961 $ 917,402 $ 5,687,894 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


$ - $ - $ - $ - $ - $ - $ - $ - $ - $ 

- 


E470 Pond GA350 14 $ 718,525 

$ - $ - $ 718,525 $ 71,852 $ 790,377 $ 118,557 $ 39,519 $ 79,038 $ 197,594 $ 1,225,085 


Dove Valley Pond GA599 24 $ 1,231,757 

$ - $ - $ 1,231,757 $ 123,176 $ 1,354,932 $ 203,240 $ 67,747 $ 135,493 $ 338,733 $ 2,100,145 

JWPP Pond $ - 1 $ 15,000 $ 15,000 1 $ 1,126 $ 16,126 $ 1,613 $ 17,738 $ 2,661 $ 887 $ 1,774 $ 4,435 $ 27,494 

Ladera Pond $ - 1 $ 15,000 $ 15,000 1 $ 1,126 $ 16,126 $ 1,613 $ 17,738 $ 2,661 $ 887 $ 1,774 $ 4,435 $ 27,494 

$ 8,138,063 

$ 1,225,085 

$ 2,155,133 

ALTERNATIVE C TOTAL $ 32,512,917 



ALTERNATIVE C TOTAL WITH 50 YEARS MAINTENANCE 

Page F-10 

$ 

$ 

$ 

50,395,022 

4,502,698 

54,897,720

Table F-6 

Channel Quantity Summary by Reach 

Channel Alternatives D1, S1, F1 

Degraded Channels Stable Channels Limited Flood Capacity Channels 

Add'l No. of 

Upstream 

Type M Soil Type M Soil 

6' Dia. 

Concrete 

Reach 

Existing Slope Add'l Vert. 

Average 

Crest 

Type M Soil 

Earthwork 

Grass Grass 

Crusher 

Reach 

Downstream Upstream Reach Elev. 

Type of 

Drop 

Normal Depth 

Riprap Riprap Earthwork Earthwork 

Wetlands Wetlands 

48"Dia Manhole & 

Trail Easement 

Reach Name 

Length 

Vert. Drop between Drop 

Drop 

Width 

Riprap 

Volume 

Width Area 

Fines Trail 

No. 

Station Station Diff. (ft) 

Drop 

Structures 

(Crest depth) 

Thickness Volume Width (ft) Depth (ft) 

Width (ft) Area (ac) 

Pipe (ft) 48" FES 

Length Width 

(ft) 

Height (ft) Drops Needed (ft) 

Height (ft) 

(ft) 

Width (ft) 

(CY) 

(ft) (ac) 

Length (LF) 

Needed 

(ft) 

(ft) (CY) 

(ea) 

(LF) 

Castle Pines 1 500 59250 59750 14.0 0.0 0.3% 12.5 Full Width 4.0 3 24.0 4.0 36 2 1333 50 3 2778 40 0.5 80 0.9 500 0 0.0 


South (u/s) 


South (d/s) 

2a 850 58400 59250 10.0 0.0 0.3% 7.5 Full Width 4.0 2 24.0 4.0 36 2 2267 50 4 6296 40 0.8 80 1.6 850 120 2.3 

2b 10300 48100 58400 132.0 25.0 0.3% 76.1 Full Width 4.0 19 24.0 4.0 24 2 18311 24 2 18311 30 7.1 40 9.5 10300 120 28.4 

I-25 Right of Way 3 5050 43050 48100 62.0 0.0 0.3% 46.9 Full Width 4.0 12 40.0 5.0 48 2 17956 70 4 52370 60 7.0 0.0 5050 140 16.2 

Lone Tree South 4 13950 29100 43050 152.0 0.0 0.3% 110.2 Full Width 4.0 28 60.0 5.0 36 2 37200 50 2 51667 30 9.6 40 12.8 13950 0 0.0 

Meridian 

Commons 

5 3000 26100 29100 38.0 6.0 0.3% 23.0 Full Width 4.0 6 60.0 5.0 16 2 3556 24 2 5333 30 2.1 40 2.8 0 0 0.0 

Lone Tree North 6 4900 21200 26100 37.0 0.0 0.3% 22.3 Full Width 4.0 6 60.0 5.0 36 2 13067 50 2 18148 30 3.4 40 4.5 4900 0 0.0 

Easement 

Area (ac) 2 

Cattle 

Fence (LF) 

@$2/LF 


North (u/s) 

7a 2550 18650 21200 21.0 14.0 0.3% -0.7 Full Width 4.0 0 80.0 5.0 30 2 5667 24 2 4533 30 1.8 40 2.3 0 0 0.0 


North (mid) 

7b 1 1100 17550 18650 15.0 1.9 0.3% 9.8 Full Width 4.0 2 80.0 5.0 66 2 5378 60 2.5 6111 80 2.0 60 1.5 0 140 3.5 


North (d/s) 

7b 1 4100 13450 17550 31.0 7.2 0.3% 11.5 Full Width 4.0 3 80.0 5.0 66 2 20044 100 4.5 68333 80 7.5 60 5.6 4100 140 13.2 

Town of Parker 8 1 8450 5000 13450 64.5 5.8 0.3% 33.4 Full Width 4.0 8 90.0 5.0 24 2 15022 24 2 15022 30 5.8 40 7.8 2400 0 0.0 

Town of Parker - 

Stonegate Trib 

8 1 270 250 5 12500 250 1.5 200 1 0 0.0 

Arapahoe County 9 5000 0 5000 48.3 23.6 0.3% 9.7 Full Width 4.0 2 100.0 5.0 24 2 8889 24 2 8889 30 3.4 40 4.6 0 1500 0 0.0 

Notes: 

1. Quantities summed in UD-MP Cost; reach costs reflect both segments. 

2. Easements not included in cost estimate 

Channel Alternative S2 

Reach Name 

Reach 

No. 

Reach 

Length 

(ft) 

Downstream 

Station 

Upstream 

Station 

Reach Elev. 

Diff. (ft) 

Existing 

Vert. Drop 

Height (ft) 

Slope 

between 

Drops 

Add'l Vert. 

Drop 

Needed (ft) 

Type of 

Drop 

Average 

Drop 

Height (ft) 

Add'l No. of 

Drop 

Structures 

Needed 

Crest 

Width 

(ft) 

Upstream 

Normal Depth 

(Crest depth) 

(ft) 

Type M Soil 

Riprap 

Width (ft) 


South (d/s) 

2b 10300 48100 58400 132.0 25.0 0.3% 76.1 Low Flow 3.0 25 16.0 3.0 24 2 18311 24 2 18311 30 7.1 40 9.5 10300 120 28.4 

Lone Tree South 4 13950 29100 43050 152.0 0.0 0.3% 110.2 Low Flow 3.0 37 16.0 3.0 36 2 37200 50 2 51667 30 9.6 40 12.8 13950 0 0.0 30690 

Meridian 

Commons 

5 3000 26100 29100 38.0 6.0 0.3% 23.0 Low Flow 3.0 8 16.0 3.0 16 2 3556 24 2 5333 30 2.1 40 2.8 0 0 0.0 

Lone Tree North 6 4900 21200 26100 37.0 0.0 0.3% 22.3 Low Flow 3.0 7 16.0 3.0 36 2 13067 50 2 18148 30 3.4 40 4.5 4900 0 0.0 10780 


North (u/s) 

7a 2550 18650 21200 21.0 14.0 0.3% -0.7 Low Flow 3.0 0 16.0 3.0 30 2 5667 24 2 4533 30 1.8 40 2.3 0 0 0.0 

Town of Parker 8 1 8450 5000 13450 64.5 5.8 0.3% 33.4 Low Flow 3.0 11 16.0 3.0 24 2 15022 24 2 15022 30 5.8 40 7.8 2400 0 0.0 



8 1 270 250 5 12500 250 1.5 200 1 0 0.0 

Arapahoe County 9 5000 0 5000 48.3 23.6 0.3% 9.7 Low Flow 3.0 3 16.0 3.0 24 2 8889 24 2 8889 30 3.4 40 4.6 0 1500 0 0.0 11000 

Notes: 



Type M Soil 

Riprap 

Thickness 

(ft) 

Type M Soil 

Riprap 

Volume 

(CY) 

Earthwork 

Width (ft) 

Earthwork 

Depth (ft) 

Earthwork 

Volume 

(CY) 

Wetlands 

Width (ft) 


Area (ac) 

Grass 

Width 

(ft) 

Grass 

Area 

(ac) 

48"Dia 

Pipe (ft) 

6' Dia. 

Manhole & 

48" FES 

(ea) 

Crusher 

Fines Trail 

Length (LF) 

Concrete 

Trail 

Length 

(LF) 

Easement 

Width 

Easement 

Area (ac) 

2 

Cattle 

Fence (LF) 

@$2/LF 

Page F-11

Channel Alternatives S3, F2 

Reach Name 

Reach 

No. 

Reach 

Length 

(ft) 

Downstream 

Station 

Upstream 

Station 

Reach Elev. 

Diff. (ft) 

Existing 

Vert. Drop 

Height (ft) 

Slope 

between 

Drops 

Add'l Vert. 

Drop 

Needed (ft) 

Type of 

Drop 

Degraded Channels Stable Channels Limited Flood Capacity Channels 

Average 

Drop 

Height (ft) 

Add'l No. of 

Drop 

Structures 

Needed 

Crest 

Width 

(ft) 

Upstream 

Normal Depth 

(Crest depth) 

(ft) 

Type M Soil 

Riprap 

Width (ft) 


South (d/s) 

2b 10300 48100 58400 132.0 25.0 0.6% 45.2 Low Flow 3.0 15 16.0 3.0 8 2 6104 12 2 9156 30 7.1 40 9.5 10300 120 28.4 


Meridian 

Commons 

5 3000 26100 29100 38.0 6.0 0.6% 14.0 Low Flow 3.0 5 16.0 3.0 8 2 1778 20 2 4444 30 2.1 40 2.8 0 0 0.0 



North (u/s) 

7a 2550 18650 21200 21.0 14.0 0.3% -0.7 Low Flow 3.0 0 16.0 3.0 8 2 1511 40 2 7556 30 1.8 40 2.3 0 0 0.0 


North (mid) 

7b 1 1100 17550 18650 15.0 1.9 0.3% 9.8 Full Width 4.0 2 40.0 4.0 30 2 2444 60 2.5 6111 80 2.0 60 1.5 0 80 2.0 


North (d/s) 

7b 1 4100 13450 17550 31.0 7.2 0.3% 11.5 Full Width 4.0 3 40.0 4.0 30 2 9111 60 3 27333 80 7.5 60 5.6 4100 80 7.5 




8 1 270 250 5 12500 250 1.5 200 1 0 0.0 


Notes: 



Channel Alternatives D2, S4, F3 

Add'l No. of 

Upstream 

Type M Soil Type M Soil 

6' Dia. 

Concrete 

Reach 

Existing Slope Add'l Vert. 

Average 

Crest 

Type M Soil 

Earthwork 

Grass Grass 

Crusher 

Reach 

Downstream Upstream Reach Elev. 

Type of 

Drop 

Normal Depth 

Riprap Riprap Earthwork Earthwork 

Wetlands Wetlands 

48"Dia Manhole & 

Trail Easement 

Reach Name 

Length 

Vert. Drop between Drop 

Drop 

Width 

Riprap 

Volume 

Width Area 

Fines Trail 

No. 

Station Station Diff. (ft) 

Drop 

Structures 

(Crest depth) 

Thickness Volume Width (ft) Depth (ft) 

Width (ft) Area (ac) 

Pipe (ft) 48" FES 

Length Width 

(ft) 

Height (ft) Drops Needed (ft) 

Height (ft) 

(ft) 

Width (ft) 

(CY) 

(ft) (ac) 

Length (LF) 

Needed 

(ft) 

(ft) (CY) 

(ea) 

(LF) 

Castle Pines 1 500 59250 59750 14.0 0.0 0.3% 12.5 Full Width 4.0 3 24.0 4.0 18 2 667 50 5 4630 40 0.5 80 0.9 500 0 0.0 


South (u/s) 


South (d/s) 

2a 850 58400 59250 10.0 0.0 0.3% 7.5 Full Width 4.0 2 24.0 4.0 18 2 1133 50 4 6296 40 0.8 80 1.6 850 120 2.3 

2b 10300 48100 58400 132.0 25.0 0.8% 22.5 Low Flow 3.0 8 16.0 3.0 4 2 3052 6 2 4578 30 7.1 40 9.5 10300 120 28.4 

I-25 Right of Way 3 5050 43050 48100 62.0 0.0 0.3% 46.9 Full Width 4.0 12 40.0 5.0 24 2 8978 70 4 52370 60 7.0 0.0 5050 140 16.2 


Meridian 

Commons 

5 3000 26100 29100 38.0 6.0 0.8% 8.0 Low Flow 3.0 3 16.0 3.0 4 2 889 10 2 2222 30 2.1 40 2.8 0 0 0.0 



North (u/s) 

7a 2550 18650 21200 21.0 14.0 0.3% -0.7 Low Flow 3.0 0 16.0 3.0 4 2 756 20 2 3778 30 1.8 40 2.3 0 0 0.0 


North (mid) 

7b 1 1100 17550 18650 15.0 1.9 0.3% 9.8 Low Flow 3.0 3 16.0 3.0 16 2 1304 20 2 1630 40 1.0 60 1.5 0 50 1.3 


North (d/s) 

7b 1 4100 13450 17550 31.0 7.2 0.3% 11.5 Low Flow 3.0 4 16.0 3.0 16 2 4859 20 2 6074 40 3.8 60 5.6 4100 50 4.7 




8 1 270 250 5 12500 250 1.5 200 1 0 0.0 


Notes: 



Table F-6 

Channel Quantity Summary by Reach (cont.) 

Type M Soil 

Riprap 

Thickness 

(ft) 

Type M Soil 

Riprap 

Volume 

(CY) 

Earthwork 

Width (ft) 

Earthwork 

Depth (ft) 

Earthwork 

Volume 

(CY) 


Width (ft) 


Area (ac) 

Grass 

Width 

(ft) 

Grass 

Area 

(ac) 

48"Dia 

Pipe (ft) 

6' Dia. 

Manhole & 

48" FES 

(ea) 

Crusher 

Fines Trail 

Length (LF) 

Concrete 

Trail 

Length 

(LF) 

Easement 

Width 

Easement 

Area (ac) 

Easement 

Area (ac) 

Cattle 

Fence (LF) 

@$2/LF 

Cattle 

Fence (LF) 

@$2/LF 

Page F-12

Damage Estimate ‐ FHAD Q's w/ No Channel Improvements 

2‐Year Event 




Structure 

Appraised 

Flooding 

Depth, d 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth, d 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure # Address Structure Type Value 1 

1 12786 N. 4th St. Ranch, basement $541,963 0.69 19 $103,695 

2 12787 N. 5th St. 2‐Story, basement $226,378 0.02 7 $15,711 2.54 24 $53,566 3.83 29 $65,941 

3 12823 N. 5th St. 2‐Story, basement $151,300 0.65 12 $18,209 1.26 16 $24,733 

4 3771 E. Elm Ave. Split Level $204,484 0.28 6 $11,804 

5 12908 N. 5th St. Split Level, basement $131,985 0.76 13 $17,622 1.20 17 $21,878 

6 3592 Dogwood Ave. Split Level, basement $173,940 0.82 14 $24,080 1.72 20 $34,580 2.11 22 $38,339 

7 12666 4th St. Split Level $133,127 0.17 5 $6,599 

8 12706 4th St. Split Level, basement $165,738 0.43 11 $17,608 


10 12863 5th St. Ranch, basement $115,751 0.97 22 $25,627 1.33 26 $29,630 

11 12907 5th St. Split Level $224,104 0.45 7 $15,532 0.89 10 $21,910 

Structure/ 

Content 

Damage 

Total $2,176,355 $0 $39,791 $165,137 $352,349 

1 Obtained from Arapahoe and Douglas County Assessor's Office 

2 Based on modified FIA depth‐damage curve, September 1970 

Depth‐Damage Curve Trendline Equations 

Ranch, b % = 0.0816d 3 ‐ 1.715d 2 + 13.223d + 10.853 

Split Level, b % = 0.0785d 3 ‐ 1.2809d 2 + 9.608d + 6.7552 

2‐story, b % = 0.0439d 3 ‐ 0.9114d 2 + 8.6857d + 6.7622 

Ranch 

% = 0.1043d 3 ‐ 1.9575d 2 + 13.807d + 8.835 

Split Level % = 0.0408d 3 ‐ 0.7681d 2 + 7.4406d + 3.7343 

2‐Story % = 0.0923d 3 ‐ 1.5542d 2 + 11.161d + 2.5804 

Page F-13

Damage Estimate ‐ FHAD Q's w/ ALT F2 Channel Improvements 

2‐Year Event 10‐Year Event 

50‐Year Event 100‐Year Event 

Structure # Address Structure Type Value 1 Depth, d Damage, % 2 Damage Depth, d Damage, % 2 Damage Depth Damage, % 2 Damage Depth Damage, % 2 Damage 

Structure 

Appraised Flooding 

Percent 

Structure/ 

Content 

Structure/ 

Content Flooding 

Percent 

Structure/ 

Content 

Structure/ 


Percent 

Structure/ 

Content 

Structure/ 


Percent 

Structure/ 

Content 

Structure/ 

Content 

1 12786 N. 4th St. Ranch, basement $541,963 


3 12823 N. 5th St. 2‐Story, basement $151,300 

4 3771 E. Elm Ave. Split Level $204,484 

5 12908 N. 5th St. Split Level, basement $131,985 0.87 14 $18,737 

6 3592 Dogwood Ave. Split Level, basement $173,940 

7 12666 4th St. Split Level $133,127 

8 12706 4th St. Split Level, basement $165,738 

9 12746 4th St. Split Level $107,585 

10 12863 5th St. Ranch, basement $115,751 0.55 18 $20,440 


Total $2,176,355 $0 $0 $17,638 $109,370 

Damage Estimate ‐ FHAD Q's w/ ALT F3 Channel Improvements 


10‐Year Event 50‐Year Event 100‐Year Event 

Structure 

Appraised 


Depth, d 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth, d 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure/ 

Content 

Damage 


Depth 

Percent 

Structure/ 

Content 

Damage, % 2 

Structure # Address Structure Type Value 1 

1 12786 N. 4th St. Ranch, basement $541,963 0.69 19 $103,695 

2 12787 N. 5th St. 2‐Story, basement $226,378 0.03 7 $15,896 2.54 24 $53,566 3.83 29 $65,941 


4 3771 E. Elm Ave. Split Level $204,484 0.28 6 $11,804 

5 12908 N. 5th St. Split Level, basement $131,985 0.75 13 $17,519 1.20 17 $21,878 

6 3592 Dogwood Ave. Split Level, basement $173,940 


8 12706 4th St. Split Level, basement $165,738 0.43 11 $17,608 


10 12863 5th St. Ranch, basement $115,751 0.96 22 $25,510 1.33 26 $29,630 

11 12907 5th St. Split Level $224,104 0.44 7 $15,380 0.89 10 $21,910 

Structure/ 

Content 

Damage 

Total $2,176,355 $0 $15,896 $130,184 $313,916 

1 Obtained from Arapahoe and Douglas County Assessor's Office 

2 Based on modified FIA depth‐damage curve, September 1970 

Page F-14

Page F-15

Page F-16

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