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

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PHASE A – ALTERNATIVES ANALYSIS REPORTMajor Drainageway Planning Update for Hidden Lake-Bates LakeBates Lake is actually a 9-acre dry parkland area graded with a sump, capable of short-term storage ofapproximately 22 acre-feet of stormwater during a rainfall event. To the community, this appears as atypical park known as Homestead Park. During a rain event, the storm pipes reach capacity and begin to fillthe sump until the storm subsides and the storm pipes can convey the flow. Maintenance personnel state thatBates Lake stores water for a brief period each year.wetland areas. An inventory of the wetlands and riparian zones within the study area can be seen on FiguresE-1 through E-X in Appendix E.The project area was split into six individual reaches, four of which are in the Hidden Lake watershed(designated as “H”) and two of which are in the Bates Lake watershed (designated as “B”). The extents ofeach reach can be seen on Figure 2-4.• Reach H-1 extends from the Hidden Lake watershed headwaters, near the intersection of Carr Streetand 69 th Place to the intersection of Sheridan Boulevard and 69 th Avenue.• Reach H-2 is dominated by Hidden Lake itself and extends from the intersection of SheridanBoulevard and 69 th Avenue to the outlet of Hidden Lake.• Reach H-3 is immediately adjacent to Lowell Boulevard and extends from the outlet of HiddenLake to where the existing 96-inch CMP storm sewer discharges to Lake Sangraco.• Reach H-4 is dominated by Lake Sangraco itself and extends from where the existing 96-inch CMPstorm sewer discharges to Lake Sangraco, through Lake Sangraco, and the open channel east of theLake Sangraco outlet to Clear Creek.• Reach B-1 extends from the Bates Lake watershed headwaters, near the intersection of Pierce Streetand 67 th Avenue, to the intersection of Sheridan Boulevard and the Union Pacific Railroad.• Reach B-2 is immediately north and adjacent to the Union Pacific Railroad and extends from whereSheridan Boulevard crosses the railroad to where Tennyson Street crosses the railroad.2.5 Flood HistoryThere is limited data on historic flooding within this drainage basin. Reports are anecdotal and no data hasbeen presented documenting flood damages. Minor flooding is known to occur on Sheridan Boulevard near69 th Avenue where the Hidden Lake drainageway passes under the roadway in a culvert. The existing twin6’ x 4’ reinforced concrete box culvert under Sheridan can convey approximately a 5-year flood eventbefore overtopping occurs. Local criteria for this culvert recommend 100-year capacity for arterial roadwaystructures over major drainageways. Some minor flooding immediately upstream of this intersection on theHidden Lake drainageway has also been reported.FEMA has established a Zone A floodplain along the west side of Lowell Blvd. between 64 th Ave. and 67 thAve. The Zone A floodplain extends into Hidden Lake. These floodplains can be seen on FEMA FloodInsurance Rate Map (FIRM) Numbers 08001C0583H and 08059C0208E. Lake Sangraco, Lake L’Nor, andAloha Beach Lake are designated by FEMA as Zone AE on FIRM Numbers 08001C0591H and08001C6592H. See Figure 2-5 for current FEMA FIRM floodplain limits.2.6 Wetland and Riparian ZonesQuality wetlands and riparian zones exist along the perimeters of Hidden Lake and Lake Sangraco. Thereare additional wetlands within the drainageway west of the intersection of Sheridan Boulevard and 69 thAvenue. Grace Church built an access roadway across the Hidden Lake watershed’s main flow path andinstalled a 24” corrugated metal pipe (CMP) culvert. The existing 24” CMP is undersized to convey stormflows and storm runoff ponds up west of the access road, which has expanded the wetlands that existed atthat location prior to the construction of the access road. The alternatives should consider impacts to these2-2
P I E R C E S TW A D S W O R T H B DW 7 6 T H A VB R A D B U R N B DZ U N I S TlhW 7 2 N D A VW 7 0 T H A VS H E R I D A N B DE S T E S S THiddenLakeP E C O S S TH A VW 6 6 T H A VP I E R C E S TF E D E R A L B L V DC-3W 6 4 T H A VW 6 4 T H A VGordonLake93 56%ACW 6 2 N D A VG A R R I S O N S TL A M A R S TJim BakerReservoirC A R R S TLakeSangracoW 6 0 T H A VkW 5 8 T H A VDeweyLakeW A D S W O R T H B DW 5 6 T H A VBURLINGTON NORTHERN SANTA FET E N N Y S O N S TT E J O N S TW 5 3 R D A V5 2 N D A VW 5 2 N D A VE L P A S O B DP E C O S S TK S TW 5 6 T H A VW 7 6 T H A Vr e e k C a n a lCW 6 8 T H A VrC l e aw e rC r e e kBURLINGTON NORTHERN SANTA FEoLC l e a rt c hh e r D isF ihcti n D iaR o c k y M o u n tF E D E R A L B DL O W E L L B DW 7 4 T H A VW 7 2 N D A VW 6 8 T H A VW 6 2 N D A VO B E R O N R DG R A N D V I E W A VI N D E P E N D E N C E S TJ E F F E R S O N C O U N T YA D A M S C O U N T YJ E F F E R S O N C O U N T YA D A M S C O U N T YH-1499 44%ACB-7165 56%ACH-15147 69%ACUNION PACIFIC RAILROADH-250 35%ACH-3157 49%ACH-1111 43%ACH-796 38%ACH-889 46%ACH-4121 48%ACH-9118 62%ACH-683 50%ACH-5111 47%ACH-11156 78%ACH-10117 53%ACH-1298 48%ACB-182 49%ACB-697 57%ACH-1358 48%ACB-2110 54%ACB-3121 72%ACBatesLakeB-4105 65%ACB-829 81%ACH-1683 75%ACB-9133 72%ACB-549 76%ACC-2162 56%ACC-162 45%ACD E N V E R C O U N T Y28736C-5120 49%ACC-4111 95%AC76e e kC rraeC lC r o k eCa n alUNION PACIFIC RAILROADe erD i t c hr cC h uhi n e C a n a lF a r mr s H i geOberonLakesOberonLakesa l s t o n CRBURLINGTON NORTHERN SANTA FE0 1,000 2,000FeetFIGURE 2-1FUTURE LAND USE MAPHIDDEN LAKE AND BATES LAKE2-3SubbasinCounty BoundaryLegendLand Use CategoriesBusiness - Commercial Areas Residential:IndustrialIndustrial - Light AreasOpen SpaceParks, CemeteriesT-MU-30WaterR-0R-2AR-3R-3-XR-5R-MU-30R-S-4FILE: \\Tartarus\gis\GIS_Projects\UDFCD_Hidden_Lake\08.155.006\active\apps\HiddenLake_Future_Land_Use_Map.mxd, 7/25/2008, chris_martin
Page 1 and 2: MAJOR DRAINAGEWAY PLANNINGUPDATE FO
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Page 17 and 18: CP I E R C E S TW A D S W O R T H B
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Page 25 and 26: Figure 3-3 Hidden Lake Peak Dischar
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Page 35 and 36: 48121830X1948W 76TH AV2724818242415
Page 37 and 38: W 72ND AV273324W 70TH AV722760W 69T
Page 39 and 40: LegendHEC-RAS CenterlineMajor Basin
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Page 43 and 44: 18HiddenLakeWADSWORTH BD1830X1953LA
Page 45 and 46: 1230TENNYSON ST9624SHERIDAN BDWOLFF
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Page 55 and 56: 48121830X1948W 76TH AV2724218182424
Page 57 and 58: LegendHEC-RAS CenterlineMajor Basin
Page 59 and 60: 18HiddenLake18WADSWORTH BD1830X1953
Page 63 and 64: APPENDIX AMeeting MinutesPHASE A -
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PHASE A - ALTERNATIVES ANALYSIS REP
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APPENDIX BHydrologic AnalysisPHASE
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Identification#ElementTypeLocationP
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APPENDIX CHydraulic AnalysisPHASE A
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Table C-1 HEC-RAS Summary TablePHAS
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Jim Baker Reservoir SpillwayPHASE A
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APPENDIX DLegal OpinionPHASE A - AL
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APPENDIX EEnvironmental InventoryPH
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APPENDIX FDamage AnalysisPHASE A -
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