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Home My WebLink AboutWPO202000034 Calculations WPO VSMP 2023-01-04 BELVEDERE PHASE 5 H&H Calculations BELVEDERE PHASE 5 Tax Map Parcels 62-16D January 4th, 2023 LOCATION: Albemarle, Virginia DEVELOPER: New Belvedere, Inc 610 West Rio Road Charlottesville, VA 22901 PREPARED BY: Dustin Greene, PE Roudabush, Gale &Associates 999 Second Street SE Charlottesville, VA 22902 INDEX Executive Summary 2 Drainage Area Summaries 3 VRRM Spreadsheet 4 Post-developed Hydrographs 5-8 Routed Dry Pond 9-12 • CpLTF/o s q11401.41111:161c: ODUSTIN E.GREENE C� Lic.No.55833 4/11 4F BELVEDERE PHASE 5 Executive Summary: The purpose of this amendment is to show that the private storm sewer system for lots 245-254 was not constructed in accordance with the approved plans. The backs of the townhouses and yards are no longer draining to the retention basin as shown on sheet 3 of VSMP amendment#3 of Belvedere phase IIB (WPO201600071). The rears of these lots now drain to the fire road dry pond as shown on sheet A18.2 of this VSMP (WPO202000034) submittal. Changes to the outlet structure ensure that the regulated storms are below the approved, post-developed flows,thus satisfying water quantity requirements. Per conversation with county engineer 6/7/22 0.18 lbs/yr of nutrient credits will be used to offset the phosphorous removal that would have been generated from the drainage going to the retention pond. The original nutrient purchase of 9 68 lbs/yr of phosphorous per year and the remaining 0.18 lbs do not exceed the 10 lbs/yr of phosphorous that would trigger onsite compliance strategies along with offsite requirements. BELVEDERE PHASE 5 PRE-DEVELOPED POA#2 AREA=2.68 AC CN = 65 Tc= 9.9 min POST-DEVELOPED POA#2 AREA= 2.74 AC CN = 69 Tc= 9.9min UPDATED POST-DEVELOPED POA#2 AREA=2.96 AC CN = 69 Tc= 9.9min data Input cells Project Name: BELVEDERE PHASES CLEAR ALL Date: 6/9/2022 _ constant values 9MP Uraign Sprci/icutiurrs List:: 2013 Draft Stds&Specs calculation cells final results Site Information Post-Development Project (Treatment Volume and Loads) Land Cover (acres) A Soils _ B Soils C Soils I.)Soils Totals Forest/Open Space(acres)••undisturbed, 0.00 piutrcted lurrat/uperr spate uu it4uiesled land Managed Turf(acres)--disturbed,graded lot 0.20 yards or other tort to be mowed/managed 0.20 Impervious Coder(acres) 0.10 0.10 0.30 Constants Runoff Coefflclents 4Rv) __ Annual Ramlell Ombra) 43 A Soils 8 Soils C Soils 1 U Soils_ -_. Target Rainfall Event(Inches) 1 00 Furest/Open Space 0 02 U 03 U U4 • U 0'. total Phosphorus(TP)EMI.png/L) 0.2b Managed Tuft 0 15 0 lU It 2. t►P. total Nruugen(IN)kW(urg/L) - 1.86 bnpeiviuus Cuvri 0.95 0.95 I/'r'. II PS taw(TP Load(Ib/our/yr) 0.41 Pi witless cortecnun tactut) 0.90 Post-Development Requirement for Site Area TP Load Reduction Required(Ib/yr) 0.18 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2023 Wednesday,01/4/2023 Hyd. No. 65 Post Dev to POA#2 Hydrograph type = SCS Runoff Peak discharge = 2.616 cfs Storm frequency = 1 yrs Time to peak = 722 min Time interval = 2 min Hyd. volume = 7,540 cuft Drainage area = 2.960 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 9.90 min Total precip. = 3.02 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Post Dev to POA#2 Q (cfs) Hyd. No. 65 -- 1 Year Q (cfs) 3.00 - - 3.00 2.00 — 2.00 1.00 1.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 65 Time (min) 6 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc v2023 Wednesday,01/4/2023 Hyd. No. 65 Post Dev to POA#2 Hydrograph type = SCS Runoff Peak discharge = 4.252 cfs Storm frequency = 2 yrs Time to peak = 722 min Time interval = 2 min Hyd. volume = 11,580 cuft Drainage area = 2.960 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 9.90 min Total precip. = 3.65 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Post Dev to POA#2 0 (cfs) Hyd. No. 65 -- 2 Year 0 (cfs) 5.00 5.00 4.00 4.00 3.00 3.00 2.00 2.00 1.00 1.00 0.00 - - 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 65 Time (min) 7 . Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2023 Wednesday,01 /4/2023 Hyd. No. 65 Post Dev to POA#2 Hydrograph type = SCS Runoff Peak discharge = 9.921 cfs Storm frequency = 10 yrs Time to peak = 722 min Time interval = 2 min Hyd. volume = 25,966 cuft Drainage area = 2.960 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 9.90 min Total precip. = 5.52 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Post Dev to POA#2 Q (cfs) Hyd. No. 65-- 10 Year Q (cfs) 10.00 10.00 8.00 - 8.00 6.00 6.00 4.00 - - . 4.00 2.00 2.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 65 Time (min) 8 • Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2023 Wednesday,01 /4/2023 Hyd. No. 65 Post Dev to POA#2 Hydrograph type = SCS Runoff Peak discharge = 22.50 cfs Storm frequency = 100 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 58,423 cuft Drainage area = 2.960 ac Curve number = 69 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 9.90 min Total precip. = 9.07 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Post Dev to POA#2 Q (cfs) Hyd. No. 65-- 100 Year Q (cfs) 24.00 24.00 20.00 20.00 16.00 16.00 12.00 12.00 8.00 8.00 4.00 4.00 0.00 - — - 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 65 Time (min) 9 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2023 Wednesday,01/4/2023 Hyd. No. 66 AB Fire Road Basin Hydrograph type = Reservoir Peak discharge = 0.749 cfs Storm frequency = 1 yrs Time to peak = 736 min Time interval = 2 min Hyd. volume = 7,531 cuft Inflow hyd. No. = 65 - Post Dev to POA#2 Max. Elevation = 427.38 ft Reservoir name = Fire road basin AB Max. Storage = 1,879 cuft Storage Indication method used. AB Fire Road Basin Q (cfs) Hyd. No. 66-- 1 Year Q (cfs) 3.00 3.00 2.00 2.00 1.00 1.00 0.00 J — 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) Hyd No. 66 Hyd No. 65 Total storage used = 1,879 tuft 10 . Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2023 Wednesday,01 /4/2023 Hyd. No. 66 AB Fire Road Basin Hydrograph type = Reservoir Peak discharge = 1.002 cfs Storm frequency = 2 yrs Time to peak = 736 min Time interval = 2 min Hyd. volume = 11,571 cuft Inflow hyd. No. = 65 - Post Dev to POA#2 Max. Elevation = 427.88 ft Reservoir name = Fire road basin AB Max. Storage = 3,446 cuft Storage Indication method used. AB Fire Road Basin Q (cfs) Hyd. No. 66 --2 Year Q (cfs) 5.00 5.00 4.00 - 4.00 3.00 3.00 2.00 2.00 1.00 1.00 0.00 - — 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) Hyd No. 66 Hyd No. 65 Total storage used = 3,446 cuft 11 . Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2023 Wednesday,01/4/2023 Hyd. No. 66 AB Fire Road Basin Hydrograph type = Reservoir Peak discharge = 1.529 cfs Storm frequency = 10 yrs Time to peak = 744 min Time interval = 2 min Hyd. volume = 25,957 cuft Inflow hyd. No. = 65 - Post Dev to POA#2 Max. Elevation = 429.37 ft Reservoir name = Fire road basin AB Max. Storage = 9,855 cuft Storage Indication method used. AB Fire Road Basin Q (cfs) Hyd. No. 66 -- 10 Year Q (cfs) 10.00 10.00 8.00 8.00 6.00 6.00 4.00 4.00 2.00 2.00 0.00 - - 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) Hyd No. 66 Hyd No. 65 Total storage used = 9,855 cuft 12 - Hydrograph Report Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc v2023 Wednesday,01 /4/2023 Hyd. No. 66 AB Fire Road Basin Hydrograph type = Reservoir Peak discharge = 2.202 cfs Storm frequency = 100 yrs Time to peak = 756 min Time interval = 2 min Hyd. volume = 58,414 cuft Inflow hyd. No. = 65 - Post Dev to POA#2 Max. Elevation = 432.26 ft Reservoir name = Fire road basin AB Max. Storage = 26,219 cuft Storage Indication method used. AB Fire Road Basin Q (cfs) Hyd. No. 66 -- 100 Year Q (cfs) 24.00 24.00 20.00 20.00 16.00 16.00 12.00 - 12.00 8.00 8.00 4.00 4.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) Hyd No. 66 Hyd No. 65 Total storage used = 26,219 cuft Pond Report 13 Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2023 Wednesday,01 /4/2023 Pond No. 19 - Fire road basin AB Pond Data Contours-User-defined contour areas.Average end area method used for volume calculation.Begining Elevation=426.50 ft Stage I Storage Table Stage(ft) Elevation(ft) Contour area(sqft) Incr.Storage(cuft) Total storage(cult) 0.00 426.50 120 0 0 0 50 427.00 2,607 682 682 1 50 428.00 3,711 3,159 3,841 3 50 430.00 5,084 8,795 12,636 5 50 432.00 6,559 11,643 24,279 7 50 434.00 8,275 14,834 39,113 9.50 436 00 10,296 18,571 57,684 11 50 438 00 12,656 22,952 80,636 13 50 440 00 15,799 28,455 109,091 Culvert/Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise(in) = 15.00 6.00 0.00 0.00 Crest Len(ft) = 12.57 0 00 0 00 0.00 Span(in) = 15.00 6.00 0.00 0.00 Crest El.(ft) = 432.50 0.00 0.00 0.00 No.Barrels = 1 1 0 0 Weir Coeff. = 3.33 3.33 3.33 3.33 Invert El.(ft) = 426.10 426 50 0.00 0.00 Weir Type = 1 --- --- Length(ft) = 186.47 0.70 0 00 0 00 Multi-Stage = Yes No No No Slope(%) = 11.79 0.00 0.00 n/a N-Value = .012 .013 .013 n/a Orifice Coeff. = 0.60 0 60 0 60 0.60 Exfil.(in/hr) = 0.000(by Wet area) Multi-Stage = n/a Yes No No TW Elev.(ft) = 0.00 Note'CulvertiOnfice outflows are analyzed under inlet(lc)and outlet(oc)control Weir nsers checked for onfice conditions(ic)and submergence(s) Stage(ft) Stage/Discharge Elev(ft) 14.00 440.50 12.00 438.50 10.00 - 436.50 8.00 - - 434.50 6.00 - - 432.50 4.00 430.50 2.00 428.50 0.00 - 426.50 0.00 2 00 4 00 6 00 8.00 10.00 12.00 14.00 16 00 18.00 20.00 22.00 Discharge(cfs) Total Q