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HomeMy WebLinkAboutWPO202100038 Calculations 2021-07-09Southwood Redevelopment — Village 2 ALBEMARLE COUNTY, VIRGINIA ROAD PLAN, WPO PLAN, & PRELIMINARY SUBDIVISION PLAT DESIGN CALCULATIONS & NARRATIVE JULY 89 2021 0Soso 0• TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Clint Shifflett, PE Timmons Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 434.327.1690 CLINT W. S F LET • Lit. N . 54330 7/8/2021 NAL Table of Contents Section Title 1. Project Narrative 2. LD-204 Inlet Calculations 3. LD-229 Pipe Calculations 4. LD-347 Hydraulic Grade Line Analysis 5. Virginia Runoff Reduction Method Worksheet Summary 6. Wet Pond Routing Calculations Project Narrative: This project includes the construction of two roads, a residential community, and associated utilities and landscaping. The limits of disturbance is 4.88 acres. Water Ouality: The current site is undeveloped. 4.88 acres was analyzed for water quality. The total TP load reduction required is 4.67 lbs/year. There will be 3.19 lbs/year to be treated via wet pond SWM A. The remaining 1.48 lbs/yr of required nutrient credits area shall be purchased from a DEQ-Approved Nutrient Credit Bank in Accordance with VA code 62.1-44.15:35. For the overall Southwood Redevelopment project, this brings the total phosphorous reduction provided on -site to 21.81 lbs/yr, and off -site nutrient credits to 5.13 lbs/yr. 77.98% of the treatment is being achieved onsite. Water Ouantity The proposed stormwater conveyance system outfall enters a floodplain and discharges runoff into an established channel with less than 1 % of the contributing drainage area, in accordance with 9VAC25-870-66 section C.3. Wetpond SWM A has been analyzed to ensure adequate storage and routing. No further stormwater quantity measures have been provided as part of this development. Energy balance requirements will be met through the use of one wet pond. Flood protection requirements for the 10-year storm will be met by releasing the stormwater into the mapped floodplain, in accordance with 9VAC25-670-66, Section C.3.c. Virginia Runoff Reduction Method! Worksheet DEC, Virginia Runoff Reduction Method New Development Compliance Spreadsheet - Version 3.0 BMP Design Specifications List: 2013 Draft Stds & Specs Site Summary Project Title: Southwood Village Date: 44376 Total Rainfall = 43 inches Site Land Cover Summary A soils BSoils CSoils DSolis Totals %of Total Forest/Open(acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 2.28 0.00 0.00 2.28 47 Impervious Cover (acres) 1 0.00 2.60 0.00 0.00 2.60 53 4.88 100 Site Tv and Land Cover Nutrient Loads She Rv 0.60 Treatment Volume ft 10,618 TP Load (lb/yr) 6.67 TN Load (lb/yr) 47.73 Total TP Load Reduction Required (lb/yr) 4.67 Site Compliance Summary Total Runoff Volume Reduction (ft) 0 Total TP Load Reduction Achieved (lb/yr) 3.19 Total TN Load Reduction Achieved (Ib/yr) 13.70 Remaining Post Development TP Load 3.48 (Ib/yr) Remaining TP Load Reduction (lb/yr) 148 Required Drainage Area Summary DA. A D.A. B D.A. C D.A. D D.A. E Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acres) 2.04 0.00 0. 00 0.00 0.00 2.04 Impervious Cover (acres) 2.52 0.00 0.D0 0.00 0.00 2.52 Total Area (acres) 4.56 0.00 0.00 0.00 0.00 4.56 Drainage Area Compliance Summary LA. A D.A. B D.A. C D.A. D DA. E Total TP Load Reduced (lb/yr) 3.19 0.00 0.00 0.00 0.00 3.19 Summary Print Virginia Runoff Reduction Method Worksheet TN Load Reduced (lb/yr) 1 13.70 1 0.00 1 0.00 1 0.00 1 0.00 1 13.70 Drainage Area A Summary Land Cover Summary A Soils BSoils CSolls DSoils Total %ofTotal Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 2.04 0.00 1 0.00 2.04 45 Impervious Cover (acres) 1 0.00 2.52 0.00 1 0.00 2.52 55 ) 4.56 BMP Selections Managed Turf Impervious Cover BMPTreatment TIP Load from Untreated TIP Load TPRemoved TPRemaining Downstream Practice Credit Area Credit Area s Volume (k) Upstream to Practice (Ibs) (Ib/yr) (Ih/yr) Treatment to be (acres) (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 2.52 Total Turf Area Treated (acres) 2.04 Total TP Load Reduction Achieved in D.A. 3.19 Ib/ r Total TN Load Reduction Achieved in D.A. 13.70 Ib/ r Drainage Area B Summary Land Cover Summary A Soils BSolls CSolls DSolls Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 0.00 0.00 0.00 0.00 0.00 0 Impervious Cover (acres) 0.00 0.00 0.00 0.00 0.00 1 0 1 0.00 BMP Selections Managed Turf Impervious Cover BMP Treatment TIP Load from Downstream Practice Credit Area Credit Area s Volume (k) Upstream I Untreated TIP Load to Practice (Ibs) TPRemoved (Ib/yr) TPRemaining (Ih/yr) Treatment to he (aces) (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TIP Load Reduction Achieved in D.A. (Ib/yr) 0.00 Total TN Load Reduction Achieved in D.A. (Ib/yr) 0.00 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area C Summary Land Cover Summary A Soils BSolls CSolls DSolls Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 0.00 0.00 0.00 0.00 0.00 0 Impervious Cover (acres) 0.00 0.00 0.00 0.00 0.00 0 1 0.00 BMP Selections Managed Turf Impervious Cover BMP TP TP Load from UntreatedTP TP Removed TP Remaining Downstream Practice Credit Area Credit Area s Volume (k) Upstream e(lbs) to Practice (Ibs (lb/yr) (lb/yr) Treatment to he (ayes) (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (Ib/yr) 0.00 Total TN Load Reduction Achieved in D.A. (Ib/yr) 0.00 Drainage Area D Summary Land Cover Summary A Soils BSolls CSOOs DSolls Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(acres) 0.00 0.00 0.00 1 0.00 0.00 1 0 Impervious Cover (acres) 0.00 0.00 0.00 1 0.00 0.00 1 0 1 0.00 BMP Selections Managed Turf Impervious Cover BMPTreatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area Credi[Area s Volume (k) Upstream to Practice (Ibs) (Ib/yr) (Ih/yr) Treatment to he (acres) (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. Ib r 0.00 Total TN Load Reduction Achieved in D.A. Ib r 0.00 Summary Print Virginia Runoff Reduction Methotl Worksheet Drainage Area E Summary Land Cover Summary A Soils BSolis CSolls DSoils Total %of Total Forest/Open(acres) 0.00 0.00 DOD 0.00 0.00 0 Managed Turf (acres) 0.00 0.00 0.00 0.00 0.00 0 Impervious Cover (acres) 0.00 0.00 0.00 0.00 0.00 0 1 0.00 BMP Selections Managed Turf Impervious Cover BMP Treatment TIP Load from Untreated TIP Load TIP Removed TP Remaining Downstream Practice Credit Area Credit Area s Volume (k) Upstream to Practice (Ibs) (Ib/yr) (Ih/yr) Treatment to he (acres) (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TIP Load Reduction Achieved in D.A. 0.00 Ib/ r Total TN Load Reduction Achieved in D.A. 0.00 Ib/ r .__._.__..__._.__..__._.__..__._.__..__._.__..__._..__._.__..__._.__..__._.__..__._.__..__._.__..__._.__..__._.__..__._.__..__._.__, Runoff Volume and CN Calculations 1- arstorm 2-yearstorm 10-yearstorm Target Rainfall Event (in) 1 0.00 0.00 0.00 Drainage Areas RV&CN Drainage Area Drainage Area Drainage Area Drainage Area Drainage Arm ON 81 0 0 0 0 RR (fta) 0 0 0 0 0 1-year return period RV wo RR(m-in) 0.0) 0.W 0.00 0.00 0.00 Rvw RR(we-in) 0.00 0.W 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 2-year return period W wo RR(.4n) 0.00 0.00 0.00 0.00 0.00 RVw RR(we-in) 0.00 0.00 0.00 0.00 0.00 CN adjuted 100 0 0 0 0 10-year return period W wo RR(w n) 0.00 0.W OAO 0.00 0.00 RVw RR(ws-in) 0.00 0.W 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 Summary Print 1S 11S Pre Site ezpost Routed 12 SWM A Subcat Reach on Link Routing Diagram for Southwood village 2 Prepared by Timmons Group, Printed 7/6/2021 HydroCAD®10.00-20 s/n 10074 0 2017 HydroCAD Software Solutions LLC Southwood Village 2 Prepared by Timmons G Type 1124-hr 1-YR Rainfall=3.05" Printed 7/6/2021 Summary for Subcatchment 1S: Pre Site Runoff = 1.98 cfs @ 12.00 hrs, Volume= 0.113 af, Depth> 0.30" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.05 Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.250 60 Woods, Fair, HSG B 4.560 60 Weighted Average 4.560 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph 2-Type II 24-hr 1-YR Rainfall=3.05" Runoff Area=4.560 ac Runoff Volume=0.113 of Runoff Depth>0.30" Tc=6.0 min CN=60 0 5 6 7 8 9 10 11 12 13 14 15 76 17 18 19 20 Time (houm) ■ RUWff Southwood Village 2 Prepared by Timmons G Type 1124-hr 1-YR Rainfall=3.05" Summary for Subcatchment 11S: Post Routed Runoff = 11.15 cfs @ 11.97 hrs, Volume= 0.495 af, Depth> 1.30" Printed 7/6/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.05 Area (ac) CN 2.560 98 Paved parking, HSG B 2.000 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.560 82 Weighted Average 2.000 43.86% Pervious Area 2.560 56.14% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph ■ Runoff Time (hours) Southwood Village 2 Prepared by Timmons G Type 1124-hr 1-YR Rainfall=3.05" Summary for Pond 12P: SWM A Printed 7/6/2021 Inflow Area = 4.560 ac, 56.14% Impervious, Inflow Depth > 1.30" for 1-YR event Inflow = 11.15 cfs @ 11.97 hrs, Volume= 0.495 of Outflow = 0.34 cfs @ 14.68 hrs, Volume= 0.229 af, Atten= 97%, Lag= 162.1 min Primary = 0.34 cfs @ 14.68 hrs, Volume= 0.229 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 406.79' @ 14.68 hrs Surf.Area= 5,739 sf Storage= 13,737 cf Plug -Flow detention time= 242.3 min calculated for 0.229 of (46% of inflow) Center -of -Mass det. time= 158.8 min ( 950.6 - 791.8 ) Volume Invert Avail.Storage Storage Description #1 404.00' 27,850 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,110 0 0 409.00 7,030 27,850 27,850 Device Routing Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 #3 Device 1 406.80' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=0.34 cfs @ 14.68 hrs HW=406.79' (Free Discharge) 1_Cu lvert (Passes 0.34 cfs of 20.96 cfs potential flow) �2=Orifice/Grate (Orifice Controls 0.34 cfs @ 7.89 fps) 3=Orifice/Grate ( Controls 0.00 cfs) =Broad -Crested Rectangular Weir ( Controls 0.00 cfs) Southwood Village 2 Prepared by Timmons 1 Type 11 24-hr 1-YR Rainfall=3.05" Printed 7/6/2021 '. Hydrograph ......M ME .-..- MOMMEM WNW ..... , ME .. ... --- ------ ---- ------1 , ------- WMMMM1► MENOMONEE Pond 12P: SWM A Stage -Discharge Discharge ids) ■ Infloa ■ Primary ❑ Primary Southwood Village 2 Prepared by Timmons 1 Pond 12P: SWM A Stage -Area -Storage a a Type 11 24-hr 1-YR Rainfall=3.05" Printed 7/6/2021 FE—S—Uff—a—Wil ■ Storage Southwood Village 2 Prepared by Timmons G Type/1 24-hr 10-YR Rainfall=5.58" Printed 7/6/2021 Summary for Subcatchment 1S: Pre Site Runoff = 12.88 cfs @ 11.98 hrs, Volume= 0.564 af, Depth> 1.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.58" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.250 60 Woods, Fair, HSG B 4.560 60 Weighted Average 4.560 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph ■ Rurwff 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Southwood Village 2 Prepared by Timmons G Type/1 24-hr 10-YR Rainfall=5.58" Summary for Subcatchment 11S: Post Routed Runoff = 27.65 cfs @ 11.97 hrs, Volume= 1.275 af, Depth> 3.36" Printed 7/6/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.58" Area (ac) CN 2.560 98 Paved parking, HSG B 2.000 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.560 82 Weighted Average 2.000 43.86% Pervious Area 2.560 56.14% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph ■ Rurwff Time (hours) Southwood Village 2 Prepared by Timmons G Type/1 24-hr 10-YR Rainfall=5.58" Summary for Pond 12P: SWM A Printed 7/6/2021 Inflow Area = 4.560 ac, 56.14% Impervious, Inflow Depth > 3.36" for 10-YR event Inflow = 27.65 cfs @ 11.97 hrs, Volume= 1.275 of Outflow = 25.93 cfs @ 12.01 hrs, Volume= 0.959 af, Atten= 6%, Lag= 2.5 min Primary = 25.93 cfs @ 12.01 hrs, Volume= 0.959 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 407.61' @ 12.01 hrs Surf.Area= 6,216 sf Storage= 18,616 cf Plug -Flow detention time= 96.7 min calculated for 0.956 of (75% of inflow) Center -of -Mass det. time= 36.5 min ( 807.5 - 771.0 ) Volume Invert Avail.Storage Storage Description #1 404.00' 27,850 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,110 0 0 409.00 7,030 27,850 27,850 Device Routing Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 #3 Device 1 406.80' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=24.79 cfs @ 12.01 hrs HW=407.59' (Free Discharge) 1_Cu lvert (Passes 21.92 cfs of 22.29 cfs potential flow) �2=Orifice/Grate (Orifice Controls 0.39 cfs @ 8.99 fps) 3=Orifice/Grate (Weir Controls 21.53 cfs @ 2.90 fps) =Broad -Crested Rectangular Weir (Weir Controls 2.86 cfs @ 0.73 fps) Southwood Village 2 Prepared by Timmons 1 30 28 26 24 22 20 18 16 3 LL 14 12 ,o 8 6 4 2 0 Type 1124-hr 10-YR Rainfall=5.58" Printed 7/6/2021 Pond 12P: SWM A Hydrograph MMMMM 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Pond 12P: SWM A Stage -Discharge Discharge (c,$) ■ Inflow ■ Primary ❑ Primary Southwood Village 2 Prepared by Timmons 1 Pond 12P: SWM A Stage -Area -Storage a a Type 1124-hr 10-YR Rainfall=5.58" Printed 7/6/2021 FE—S—Uff—a—Wil ■ Storage Southwood Village 2 Prepared by Timmons G Type/1 24-hr 100-YR Rainfall=9.16" Printed 7/6/2021 Summary for Subcatchment 1S: Pre Site Runoff = 33.24 cfs @ 11.97 hrs, Volume= 1.473 af, Depth> 3.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.16" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.250 60 Woods, Fair, HSG B 4.560 60 Weighted Average 4.560 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph ■ Rurwff 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Southwood Village 2 Prepared by Timmons G Type/1 24-hr 100-YR Rainfall=9.16" Summary for Subcatchment 11S: Post Routed Runoff = 51.60 cfs @ 11.96 hrs, Volume= 2.482 af, Depth> 6.53" Printed 7/6/2021 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.16" Area (ac) CN 2.560 98 Paved parking, HSG B 2.000 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.560 82 Weighted Average 2.000 43.86% Pervious Area 2.560 56.14% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph ■ Rurwff Time (hours) Southwood Village 2 Prepared by Timmons G Type II 24-hr 100-YR Rainfall=9.16" Summary for Pond 12P: SWM A [82] Warning: Early inflow requires earlier time span Printed 7/6/2021 Inflow Area = 4.560 ac, 56.14% Impervious, Inflow Depth > 6.53" for 100-YR event Inflow = 51.60 cfs @ 11.96 hrs, Volume= 2.482 of Outflow = 50.92 cfs @ 11.98 hrs, Volume= 2.161 af, Atten= 1%, Lag= 1.2 min Primary = 50.92 cfs @ 11.98 hrs, Volume= 2.161 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 407.89' @ 11.98 hrs Surf.Area= 6,384 sf Storage= 20,427 cf Plug -Flow detention time= 67.4 min calculated for 2.154 of (87% of inflow) Center -of -Mass det. time= 26.5 min ( 782.3 - 755.8 ) Volume Invert Avail.Storage Storage Description #1 404.00' 27,850 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,110 0 0 409.00 7,030 27,850 27,850 Device Routino Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 #3 Device 1 406.80' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=49.15 cfs @ 11.98 hrs HW=407.88' (Free Discharge) 1_Cu lvert (Barrel Controls 22.75 cfs @ 12.88 fps) �2=Orifice/Grate (Passes < 0.41 cfs potential flow) 3=Orifice/Grate (Passes < 34.42 cfs potential flow) =Broad -Crested Rectangular Weir (Weir Controls 26.40 cfs @ 1.56 fps) Southwood Village 2 Prepared by Timmons 1 Pond 12P: SWM A Hydrograph Time (hours) Pond 12P: SWM A Stage -Discharge Discharge (ds) Type 1124-hr 100-YR Rainfa&9.16" Printed 7/6/2021 ■ Inflow ■ Primary ❑ Primary Southwood Village 2 Prepared by Timmons 1 Pond 12P: SWM A Stage -Area -Storage a a Type 1124-hr 100-YR Rainfa&9.16" Printed 7/6/2021 FE—S—Uff—a—Wil ■ Storage