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HomeMy WebLinkAboutWPO201600053 Calculations WPO VSMP 2016-08-22 PHONE(434)977-0205 FAX(434)296-5220 `o;' FAX ROUDABUSH, GALE &ASSOCIATES, INC. A PROFESSIONAL CORPORATION LAND SURVEYING Serving Virginia Since 1956 ENGINEERING 914 MONTICELLO ROAD LAND PLANNING CHARLOTTESVILLE,VIRGINIA WILLIAM J.LEDBETTER,L.S. 22902 J.CLINT HARMON,L.S. DAVID M.ROBINSON,P.E. DAVID A.JORDAN,L.S. AMMY M.GEORGE,L.A. BRIAN D.JAMISON,L.S. KRISTOPHER C.WINTERS,L.S. STORMWATER DESIGN REPORT FOR: OLD TRAIL VILLAGE-BALLARD POND CONVERSION PREPARED FOR: MARCH MOUNTAIN PROPETIES LLC CONTACT: DAVE BROCKMAN 1005 HEATHERCROFT CIRCLE, SUITE 100 CROZET VA 22932 PREPARED BY: ROUDABUSH, GALE &ASSOCIATES, INC. 914 MONTECELLO RD CHARLOTTESVILLE, VA 22902 liv,AI-TH Op rr a �I� `d J 5-; Ji my L. Taggart • No. 022841 2 •~ DATE: ,<v�.a AUGUST 22, 2016 SS/ONAL ti1:: PRE-DEVELOPMENT CONDITIONS 2-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 3.68 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Pre 20.60 57 0.15 0.15 Computed Results: Peak Discharge (Qp) : 8.42 cfs Time to Peak: 12.10 hrs Runoff Volume: 0.37 acre-ft 10-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 5.57 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Pre 20.60 57 0.15 0.15 Computed Results: Peak Discharge (Qp) : 42.82 cfs Time to Peak: 12.10 hrs Runoff Volume: 1.45 acre-ft 100-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 9.14 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Pre 20.60 57 0.15 0.15 Computed Results: Peak Discharge (Qp) : 124.76 cfs Time to Peak: 12.10 hrs Runoff Volume: 4.12 acre-ft POST-DEVELOPMENT CONDITIONS 2-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 3.68 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Post 23.80 69 0.25 0.25 Computed Results: Peak Discharge (Qp) : 22.70 cfs Time to Peak: 12.30 hrs Runoff Volume: 1.17 acre-ft 10-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 5.57 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Post 23.80 69 0.25 0.25 Computed Results: Peak Discharge (Qp) : 59.86 cfs Time to Peak: 12.20 hrs Runoff Volume: 2.96 acre-ft 100-YR Runoff Hydrograph: TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type: Type II Rainfall Depth: 9.14 in Base Flow: 0.00 cfs Ia/P Interpolation: Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-Post 23.80 69 0.25 0.25 Computed Results: Peak Discharge (Qp) : 134.08 cfs Time to Peak: 12.20 hrs Runoff Volume: 6.63 acre-ft POST-DEVELOPMENT ROUTED CONDITIONS 2-YR Reservoir Routing: Storage Indication Method Results: Inflow Peak Flow: 22.70 cfs Inflow Peak Time: 12.30 hr Routed Peak Flow: 5.13 cfs Routed Peak Time: 12.85 hr Maximum Pond Storage: 0.8269 acre-feet Maximum Pond Elevation: 667.94 ft 10-YR Reservoir Routing: Storage Indication Method Results: Inflow Peak Flow: 59.86 cfs Inflow Peak Time: 12.20 hr Routed Peak Flow: 52.47 cfs Routed Peak Time: 12.35 hr Maximum Pond Storage: 1.1640 acre-feet Maximum Pond Elevation: 669.02 ft 100-YR Reservoir Routing: Storage Indication Method Results: Inflow Peak Flow: 134.08 cfs Inflow Peak Time: 12.20 hr Routed Peak Flow: 128.62 cfs Routed Peak Time: 12.30 hr Maximum Pond Storage: 1.6277 acre-feet Maximum Pond Elevation: 670.39 ft DESIGN PARAMETERS Multiple Outlet Design Outflow Total Discharge: 388.07 cfs Water Surface Elevation: 672.00 ft Tailwater Elevation: 0.00 ft Detention Base Elevation: 0.00 ft Outlet #1: Riser, Drop Pipe Riser Top Elev: 667.75 ft Riser Base Elev: 663.00 ft Riser Diameter: 48.00 in Orifice Coefficient: 0.60 Weir Coefficient: 3.33 Culvert Length: 95.00 ft Culvert Diameter: 24.00 in Culvert Invert In: 662.00 ft Culvert Friction Coefficient: 0.01 Culvert Entrance Loss Coefficient: 0.10 Discharge: 145.83 cfs Outlet #2: Spillway, Weir Shape: Trapezoidal Side Slope Ratio (V:H) : 2.00 Crest Length: 10.00 ft Invert Elevation: 669.25 ft Coefficient: 3.33 Number of Openings: 1 Discharge: 242.24 cfs Velocity: 7.02 ft/s STAGE-STORAGE REPORT Elev(Ft) Storage(CF) Storage(CY) Storage(Acre-Ft) Area(SF) Area(Acre) 662.900 0.000 0.000 0.000 0.000 0.000 663.000 159.000 5.889 0.004 3180.000 0.073 664.000 4323.000 160.111 0.099 5148.000 0.118 666.000 16815.000 622.778 0.386 7344.000 0.169 668.000 36574.000 1354.593 0.840 12415.000 0.285 670.000 64279.000 2380.704 1.476 15290.000 0.351 672.000 97959.000 3628.111 2.249 18390.000 0.422 674.000 138066.000 5113.556 3.170 21717.000 0.499 • SWM RETENTION POND DESIGN SUMMARY Top of Dam: 672.00 ft Toe of Dam: 663.00 ft Design High Water: 670.39 ft (100-YR) Crest of Riser: 667.75 ft Emergency Spillway: 669.25 ft Riser Diameter: 48.00 in Trash Rack Diameter: 72.00 in Trash Rack Height: 21.00 in Barrel Length: 95.00 ft Barrel Diameter: 24.00 in Barrel Invert In: 663.00 ft Barrel Invert Out: 662.00 ft Treatment Volume Required: 32,035 ft3 (VRRM Spreasheet) Treatment Volume Provided: 34,104 ft3 DIRT VOLUME REPORT Cut volume: 43,670.5 C.F. , 1,617.43 C.Y. Fill volume: 48,107.8 C.F. , 1,781.77 C.Y. Area in Cut : 25,843.0 S.F. , 0.59 Acres Area in Fill: 19,622.3 S.F. , 0.45 Acres Area exactly in daylight: 2,488.2 S.F. , 0.06 Acres Total inclusion area: 47,953.5 S.F. , 1.10 Acres Average Cut Depth: 1.69 feet Average Fill Depth: 2.45 feet Cut to Fill ratio: 0.91 Import Volume: 164.3 C.Y. Elevation Change To Reach Balance: -0.093 Volume Change Per .1 ft: 177.6 C.Y. Cut (C.Y.) / Area (acres) : 1469.24 Fill (C.Y.) / Area (acres) : 1618.52 Max Cut: 5.201 at 11421053.195,3910836.185 Max Fill: 8.000 at 11421128.646,3910828.733 Max Cut: 5.980 at 11421114.578,3910787.28 Max Fill: 10.000 at 11421151.200,3910822.006