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Home My WebLink AboutWPO201500083 Calculations Stormwater Management Plan 2015-12-21 WPO 2006-39 STORM WATER MANAGEMENT VOLUME CALCULATIONS FOR MINOR SITE PLAN AMENDMENT EARLYSVILLE BUSINESS PARK DATED: October 8, 2015 REV: December 21, 2015 LOCATION: Tax Map 32, Parcel 21A Albemarle County, Virginia OWNER: 4F, LLC Earlysville, VA 22901 PREPARED BY: Meridian Planning Group, LLC 440 Premier Circle, Ste 200 Charlottesville, VA 22901 434.882.0121 PRE-DEVELOPMENT HYDROGRAPHS Drainage Area A A soils B Soils C Soils D Soils Area (acres) 0.,00, Forest/Open Space-undisturbed, protected forest/open space or reforested land CN 30 55 70 77 Managed Turf-disturbed, graded for yards Area (acres) 0 0f 924 .6:'? or other turf to be mowed/managed CN 39 61 74 80 Area (acres) 0 00 x.83 0.00 0.00 Impervious Cover CN 98 98 98 98 Weighted CN 1-year storm RVDeveioped (in)with no Runoff Reduction ": 0 RVDeve,oped (in)with Runoff Reduction 0 Adjusted CN 61: DA-A Pre-Development: 1-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type Type II Rainfall Depth 3.50 in Base Flow 0.00 cfs la/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-A 25.10 65 0.40 0.40 Computed Results: Peak Discharge (Qp) 14.60 cfs Time to Peak 12.40 hrs Runoff Volume 0.85 acre-ft POST-DEVELOPMENT HYDROGRAPHS Drainage Area B A soils B Soils C Soils D Soils Forest/Open Space-undisturbed, protected Area (acres) 6,00 tl Oa,„ COO 0'.00,440` forest/open space or reforested land CN 30 55 70 77 Managed Turf-disturbed, graded for yards Area (acres) ,0.00' 320 00 . .�_ 0.00 or other turf to be mowed/managed CN 39 61 74 80 Area (acres) s. 0) P.qV Q£lid:,..., f100 Impervious Cover . CN 98 ' 98 98 98 Weighted CN 1-year storm RVDeveloped (in)with no Runoff Reduction 1J RVDeveioped (in)with Runoff Reduction 3 ` Adjusted CN 7 ,,.. DA-B: 1-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type ..Type II Rainfall Depth 3.50 in Base Flow 0.00 cfs la/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-B DA-C 11.62 76 0.27 0.27 Computed Results: Peak Discharge (Qp) ... 16.37 cfs Time to Peak 12.20 hrs Runoff Volume 0.83 acre-ft DA-B: 2-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type ..Type II Rainfall Depth 3.70 in Base Flow 0.00 cfs Ia/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-B DA-C 11.62 76 0.27 0.27 Computed Results: Peak Discharge (Qp) ... 18.56 cfs Time to Peak 12.20 hrs Runoff Volume 0.92 acre-ft DA-B: 10-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type ..Type II Rainfall Depth 5.60 in Base Flow 0.00 cfs Ia/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-B DA-C 11.62 76 0.27 0.27 Computed Results: Peak Discharge (Qp) ... 37.28 cfs Time to Peak 12.20 hrs Runoff Volume 1.84 acre-ft DA-B: 100-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type ..Type II Rainfall Depth ... 7.60 in Base Flow 0.00 cfs la/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-B DA-C 11.62 76 0.27 0.27 Computed Results: Peak Discharge (Qp) ... 61.80. cfs Time to Peak 12.20 hrs Runoff Volume 3.06 acre-ft Drainage Area C A soils _B Soils C Soils D Soils Forest/Open Space-undisturbed, protected Area (acres) 0 . .. 0.00;` `0 Q 1Q� . forest/open space or reforested land CN 30 55 70 77 Managed Turf-disturbed, graded for yards Area (acres) or other turf to be mowed/managed CN 39 ' 61 74 80 Area (acres) m 00 Impervious Cover CN 98 98 98 98 Weighted CN .. ,. . 1ear storm RVDeveloped (in)with no Runoff Reduction 0 RVDeveloped (in)with Runoff Reduction Adjusted CN 6'6. '',v0 :: DA-C: 1-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type Type II Rainfall Depth 3.50 in Base Flow 0.00 cfs Ia/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-C none 13.48 56 0.45 0.45 Computed Results: Peak Discharge (Qp) ... 1.83 cfs Time to Peak 12.60 hrs DA-C: 2-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type Type II Rainfall Depth 3.70 in Base Flow 0.00 cfs la/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-C none 13.48 56 0.45 0.45 Computed Results: Peak Discharge (Qp) ... 2.19 cfs Time to Peak 12.60 hrs DA-C: 10-Year 24-Hour Runoff Hydrograph TR-55 Tabular Hydrograph Method Input Data: Rainfall Distribution Type Type II Rainfall Depth 5.60 in Base Flow 0.00 cfs la/P Interpolation Off Subarea Downstream Area CN Tc Tt Name Subareas (acre) (hr) (hr) DA-C none 13.48 56 0.45 0.45 Computed Results: Peak Discharge (Qp) ... 12.63 cfs Time to Peak 12.50 hrs BASIN AND OUTLET PARAMETERS PRIMARY OUTLET DESIGN Outflow Total Discharge: 58.73 cfs Water Surface Elevation: 568.00 ft Tailwater Elevation: 559.80 ft Detention Base Elevation: 0.00 ft Outlet#1: Riser, Drop Pipe Riser Top Elev: 566.50 ft Riser Base Elev: 563.00 ft Riser Diameter: 48.00 in Orifice Coefficient: 0.60 Weir Coefficient: 3.33 Culvert Length: 35.00 ft Culvert Diameter: 24.00 in Culvert Invert In: 562.83 ft Culvert Friction Coefficient: 0.01 Culvert Entrance Loss Coefficient: 0.10 Discharge: 49.73 cfs Outlet#2: Orifice, Orifice Shape: Circular Diameter: 15.00 in Invert Elevation: 563.00 ft Coefficient: 0.60 Number of Openings: 1 Discharge: 11.63 cfs Velocity: 9.47 ft/s Stage (ft) Discharge (cfs) 563.50 0.00 564.50 3.91 565.00 5.52 565.50 6.93 566.00 8.09 566.50 9.10 567.00 24.81 567.50 52.70 STAGE-STORAGE REPORT Elev(Ft) Storage(CF) Area(SF) 563.00 127.1 2541 564.00 3045.1 3295 566.00 11314.0 4974 568.00 23167.0 6879 EMERGENCY OUTLET DESIGN Outflow Total Discharge: 61.08 cfs Water Surface Elevation: 568.00 ft Tailwater Elevation: 0.00 ft Detention Base Elevation: 0.00 ft Outlet#1: Spillway, Weir Shape: Trapezoidal Side Slope Ratio (V:H): 2.00 Crest Length: 10.00 ft Invert Elevation: 566.75 ft Coefficient: 3.33 Number of Openings: 1 Discharge: 61.08 cfs Velocity: 4.60 ft/s POST-DEVELOPMENT ROUTED HYDROGRAPHS DA-B: 1-Year 24-Hour Routed Hydrograph Inflow Peak Flow 16.37 cfs Inflow Peak Time 12.20 hr Routed Peak Flow 9.19 cfs Routed Peak Time 12.45 hr Maximum Pond Storage 0.2744 acre-feet Maximum Pond Elevation .566.05 ft DA-B: 2-Year 24-Hour Routed Hydrograph Inflow Peak Flow 18.56 cfs Inflow Peak Time 12.20 hr Routed Peak Flow 9.84 cfs Routed Peak Time 12.46 hr Maximum Pond Storage 0.3145 acre-feet Maximum Pond Elevation .566.40 ft DA-B: 10-Year 24-Hour Routed Hydrograph Inflow Peak Flow 37.28 cfs Inflow Peak Time 12.20 hr Routed Peak Flow 37.02 cfs Routed Peak Time 12.30 hr Maximum Pond Storage 0.4134 acre-feet Maximum Pond Elevation .567.13 ft DA-B: 100-Year 24-Hour Routed Hydrograph Inflow Peak Flow 57.27 cfs Inflow Peak Time 12.31 hr Routed Peak Flow 57.16 cfs Routed Peak Time 12.33 hr Maximum Pond Storage 0.4478 acre-feet Maximum Pond Elevation .567.38 ft ENERGY BALANCE CALCULATIONS Drainage Areas B&C Combined A soils B Soils C Soils D Soils ) (acres Forest/Open Space-undisturbed, protected Area forest/open space or reforested land CN 30 55 70 77 Managed Turf-disturbed, graded for yards Area (acres) {)00 8' 4.,, 0,0 or other turf to be mowed/managed CN 39 61 74 80 Area (acres) 0,00 `4 z... _ 5'. 9 0.00 . Impervious Cover CN 98 98 98 98 Weighted CN 6 1-year storm RVDeveloped (in)with no Runoff Reduction OAP, RVDeveloped (in)with Runoff Reduction 0.80 Adjusted CN 56 DA-B Routed and DA-C: Combined 1-Year 24-Hour Runoff Hydrograph Peak Discharge (Qp) 10.85 cfs Time to Peak 12.50 hrs DA-B Routed and DA-C: Combined 2-Year 24-Hour Runoff Hydrograph Peak Discharge (Qp) 12.03 cfs Time to Peak 12.50 hrs DA-B Routed and DA-C: Combined 10-Year 24-Hour Runoff Hydrograph Peak Discharge (Qp) 44.55 cfs Time to Peak 12.50 hrs x g x o m CO m 4 N- u_ w m mE.; W VI VI VI VI VI VI VI x 7 m I ° 00 '1.4' m o.1 O d OT .N a) O C I U) a) rn c U r-- c a) a O m c i E U 3 g J, a O o tri W a ° 3 N J L m R o r C O Q C 11,3 > a) I— :LI O 2 >- U co E Q o - O o L E ate,, O g 2 ... .0 a) n °- - CO Na) Cl) d v O C W c '> >, c co o O U co • _2' c O V Z L (p O O c g � 0 d n N Cl)V 'a Na 0 J a m CO fi Cl) c N 'V C. � m O E - 8, m a _ _ o a C'! r' a) o () > °= a"- a�i O a o a) U < c °' C N �o? a� m c c Ts co co cn co a) co @ U v aa)O o m Z as 15$1,a)L E w w w w w w w 3 ur c a-0 - ° a O 'C 00oP2 >- >- >- >- >- >- >- in-i OCoa) c-awna �I— c -0 o _c� � r-a c .+. .- d E 2 o c Eu) ` E u) J 2 a)• C3'E m a £a) m m W > 3 0 oco Ec E Z E c T a o o 0 0 z V) ° S a) -,134- om ••- o co - c 2 000 Qo_ N w> a) c'_ 2 c _ '= t a)Z E. c� La' 2 c 2 2 U R ' 'yooNx 3oEso .a) 9, o f >, Cl). v a) a) a a) C °) 3NL5 S YE ' .xE U C c c c . g = aca2 d 8 c .2 c d a° E EDI Jaz > aa))Cr y my °, E c ax w 8 8 5L- /.N,� V # L fa a3 • U) V a , >'• a) a) 3a) S o E Y > '° 0 O a) Cl) Cl) a) a) a) Cl) o• (n Q-OE a m m C O N. - a) .2 N t0 2 N at 2 N f0 2 . 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