Phase A - Alternatives Analysis Report - Urban Drainage and Flood ...

PHASE A – ALTERNATIVES ANALYSIS REPORTMajor Drainageway Planning Update for Hidden Lake-Bates LakeMeeting MinutesHidden Lake – Bates LakeMajor Drainageway Planning UpdateMonday May 19, 2008, 2:30pm – 4:00 pm at UDFCDAttendees:Ken MacKenzie UDFCD 303-455-6277 kam@udfcd.orgShea Thomas UDFCD 303-455-6277 sthomas@udfcd.orgKelly Hargadin Adams County 303-453-8766 khargadin@co.adams.co.usGeorgia Simpson City of Arvada 720-898-7646 gsimpson@arvada.orgJohn Burke City of Westminster 303-430-2400 x2126 jburke@ci.westminster.co.usRobert Krehbiel Matrix Design Group 303-572-0200 robertk@matrixdesigngroup.comTim Fairbank Matrix Design Group 303-572-0200 tim_fairbank@matrixdesigngroup.comWilson Wheeler Matrix Design Group 303-572-0200 wilson_wheeler@matrixdesigngroup.comJenn Newby Matrix Design Group 303-572-0200 jennifer_newby@matrixdesigngroup.com1. PurposeReview Draft Baseline Hydrology Report2. Updated Near-Term Project Scheduled. May 23 – Baseline Hydrology Reporte. June 11 – Benefit-Cost Calculationsf. June 18 – Draft Phase A Report3. Data Gatheringg. Received at the meeting:i. Shoenberg Farms Commercial Center Drainage Reportii. Shoenberg Shopping Center – Wal-Mart Drainage Study4. Hydrologyh. Rainfall depths have increased since the 1975 study was completed.i. The C T values in CUHP have been changed since the 1975 study due to a change in the shape of thehydrograph.j. Impervious values for land use taken from the UDFCD criteria manual. Correlation of other land usetypes to imperviousness based upon actual imperviousness of similar development. Table 2-2 summarizesthe future imperviousness. Figure 2-2 shows future land use categories, Figure 2-3 shows futureimperviousness. Composite imperviousness of the 1975 study was 53.8%; current study is 56.8%.k. Variable % imperviousness for Bates Lake. Use 100% in the 100-year model. Could use less than 100%in lesser storm events.l. Some Sub-Basins are less than 90 acres. Combine basins as a check. Calibrate smaller sub-basins to bewithin 10% of the combined basins. Adjust C T , C P and Horton’s coefficients to calibrate flows.m. Comments on the draft information are due by Friday May 23. Send comments to: Tim Fairbank, with acc: to Shea Thomas.5. Alternatives Analysisn. Develop 4 to 5 alternatives per reach. Typical considerations are:i. Do nothingii. Detention (new or enhanced)iii. Improved conveyanceiv. Water quality enhancemento. Examples of reaches are:i. Hidden Lake Drainageway: Headwater to Sheridanii. Hidden Lake Drainageway: Sheridan to Lowelliii. Hidden Lake Drainageway: Adjacent to Lowelliv. Hidden Lake Drainageway: Lake Sangraco to Clear Creekv. Bates Lake Drainageway: Headwater to 60 thvi. Bates Lake Drainageway: 60 th to 58 thvii. Bates Lake Drainageway: Along future RTD Gold Line6. Websitef. Matrix to host the web site. UDFCD to provide link.g. Need to post project description, Baseline Hydrology Report, list of contacts, meeting minutes, maps,project description, schedule, and a way to get added to an information distribution list.h. Public Meeting latter half of July. Post cards need to arrive 1 week before the meeting. One week isneeded by UDFCD to compile the address list. Post public meeting notice on the web site by about July 4.i. Website will remain through project completion and a few months beyond.7. Actions Itemsp. Steering Committee Comments on Draft Baseline Hydrology Report by May 23.q. Arvada Parks & Rec Maintenance Superintendent to comment on Bates Lake if the pond fills in lesserstorm events.r. Matrix to set up website by May 23.s. Matrix to finalize Baseline Hydrology Report by May 23.t. Matrix to prepare Hydraulic Model.