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WPO202000017 Stormwater Management Maintenance Agree. 2021-06-07
SHIMP ENGINEERING, P.C. Design Focused Engineering Stormwater Management Plan Calculation Packet Proffit Road Townhomes South Prepared by. Shimp Engineering WPO-2020-00017 June 07, 2021 O�w Gfp c�. O ? U N IMP Y ic. No 4 183 �SS�ONAL ENG 912 E High SL Charlortesville, VA 22902 1 434.227. 5140 1 shimp engineering com SHIMP ENGINEERING, P.C. Design Focused Engineering June 7.2021 County of Albemarle Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Regarding: Proffit Road Townhomes South Stormwater Management Plan Dear David, The purpose of this project is to build 40 single family attached units on the southern side of Profflt Road. The total area of disturbance is 3.34 acres. Water Quantity: Runoff from the site in the predevelopment condition is analyzed at one point labeled POA. The post - development condition runoff is collected and piped to an underground detention system comprised of StormTech MC-4500 chambers and an isolation row, which outlets to POA. The proposed storm sewer will outlet into an existing channel further downstream. Runoff from the site will be released at rates that comply with the energy balance equation set forth in 9VAC25-870-66-B(3). The calculations are summarized in the table below. Please note that a small portion of the drainage area to POA is from offsite. The flow from offsite was included in the energy balance equation, but no improvement factor was applied to offsite areas. PROFFIT ROAD TOWNHOMES SOUTH 24 Hr 1 year Storm: Qa 'I.F.•( i'RV., )/Rva Qa ''(Qr RV�)/R� Ilrema Area: POA 1. 0.13 RVpp¢,. - OA2 JM XQy - 0.41 cfs RV�— 0.015 Q�0A0 cfs Prt Deveb v[ Pos[ Deveb o[ 10 r Z61 7.55 Water Quality According to the VRRM spreadsheet included in this packet, the target phosphorus load reduction is 3.14 lb/yr. The StormTech chambers with the isolator row are rated for 40%phosphorous removal, resulting in 1.91 Iblyr phosphorous removal. The remaining phosphorous load 1.30 Iblyr will be effectively reduced by the purchase of nutrient credits. SHIMP ENGINEERING, P.C. Design Focused Engineering Contents: Water Quantity Calculations: Pre -Development Drainage Area Map Pre -Development Hydro CAD Report Post -Development Drainage Area Maps Post -Development Inlets Drainage Area Maps Temp. SCC Drainage Area Map Post -Development HydroCAD Report Energy Balance Equations TOC Calculations Nomographs VDOT LD-204 VDOT LD-209 VDOT LD-347 VDOT LD-268 Water Quality Calculations: Pre -Development VRRM Landuse Map Post -Development VRRM Landuse Map VRRM Redevelopment Spreadsheets Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report SHIMP ENGINEERING, P.C. Design Focused Engineering Water Quantity Calculations: Pre -Development Drainage Area Map Pre -Development Hydro CAD Report Post -Development Drainage Area Maps Post -Development Inlets Drainage Area Maps Temp. SCC Drainage Area Map Post -Development HydroCAD Report Energy Balance Equations TOC Calculations Nomographs VDOT LD-204 VDOT LD-209 VDOT LD-347 VDOT LD-268 1S 2S Pre-Dev Onsite Pre-Dev Offsite 3L POA1 Subcat Reach On Link Drainage Diagram for Pre Development Prepared by SHIMP ENGINEERING, P.C., Printed 6/4/2021 HydroCAD® 9.10 s/n 07054 0 2011 HydroCAD Software Solutions LLC Pre Dev DA to POA Pre Development Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.480 55 Woods, Good, HSG B (1S, 2S) 2.880 61 >75% Grass cover, Good, HSG B (1S, 2S) 0.330 98 Paved parking, HSG B (1S, 2S) 3.690 64 TOTAL AREA Pre Dev DA to POA Pre Development Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 3.690 HSG B 1S, 2S 0.000 HSG C 0.000 HSG D 0.000 Other 3.690 TOTAL AREA Pre Dev DA to POA Pre Development Type II24-hr I yr, 24 hr Rainfall=2.97" Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 4 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Pre-Dev Onsite Subcatchment 2S: Pre-Dev Offsite Link 3L: POM Runoff Area=3.150 ac 9.84% Impervious Runoff Depth=0.46" Tc=18.0 min CN=64 Runoff=1.20 cfs 0.120 of Runoff Area=0.540 ac 3.70% Impervious Runoff Depth=0.35" Tc=18.0 min CN=61 Runoff=0.13 cfs 0.016 of Inflow=1.34 cfs 0.136 of Primary=1.34 cfs 0.136 of Total Runoff Area = 3.690 ac Runoff Volume = 0.136 of Average Runoff Depth = 0.44" 91.06 % Pervious = 3.360 ac 8.94 % Impervious = 0.330 ac Pre Dev DA to POA Pre Development Type II 24-hr I yr, 24 hr Rainfall=2.97" Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 5 Summary for Subcatchment 1S: Pre-Dev Onsite Runoff = 1.20 cfs @ 12.15 hrs, Volume= 0.120 af, Depth= 0.46" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" 0.360 55 Woods, Good, HSG B 2.480 61 >75% Grass cover, Good, HSG B 0.310 98 Paved parking, HSG B 3.150 64 Weighted Average 2.840 90.16% Pervious Area 0.310 9.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.0 Direct Entry, Summary for Subcatchment 2S: Pre-Dev Mite Runoff = 0.13 cfs @ 12.16 hrs, Volume= 0.016 af, Depth= 0.35" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" Area (ac) CN Description 0.400 61 >75% Grass cover, Good, HSG B 0.020 98 Paved oarldne. HSG B !9 0.540 61 Weighted Average 0.520 96.30% Pervious Area 0.020 3.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.0 Direct Entry, Summary for Link 3L: POM Inflow Area = 3.690 ac, 8.94% Impervious, Inflow Depth = 0.44" for 1 yr, 24 hr event Inflow = 1.34 cfs @ 12.15 hrs, Volume= 0.136 of Primary = 1.34 cfs @ 12.15 hrs, Volume= 0.136 af, Atten= 0%, lag= 0.0 min Primary outflow = Inflow, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs Pre Dev DA to POA Pre Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 6 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Pre-Dev Onsite Subcatchment 2S: Pre-Dev Offsite Link 3L: POM Runoff Area=3.150 ac 9.84% Impervious Runoff Depth=1.87 Tc=18.0 min CN=64 Runoff-6.64 cfs 0.490 of Runoff Area=0.540 ac 3.70% Impervious Runoff Depth=1.63" Tc=18.0 min CN=61 Runoff=0 97 cfs 0.074 of Inflow=7.61 cfs 0.563 of Primary=7.61 cfs 0.563 of Total Runoff Area = 3.690 ac Runoff Volume = 0.563 of Average Runoff Depth =1.83" 91.06 % Pervious = 3.360 ac 8.94 % Impervious = 0.330 ac Pre Dev DA to POA Pre Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6/4/2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 7 Summary for Subcatchment 1S: Pre-Dev Onsite Runoff = 6.64 cfs @ 12.12 hrs, Volume= 0.490 af, Depth= 1.87" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr Rainfall=5.43" 0.360 55 Woods, Good, HSG B 2.480 61 >75% Grass cover, Good, HSG B 0.310 98 Paved parking, HSG B 3.150 64 Weighted Average 2.840 90.16% Pervious Area 0.310 9.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.0 Direct Entry, Summary for Subcatchment 2S: Pre-Dev Mite Runoff = 0.97 cfs @ 12.12 hrs, Volume= 0.074 af, Depth= 1.63" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr Rainfall=5.43" Area (ac) CN Description 0.400 61 >75% Grass cover, Good, HSG B 0.020 98 Paved oarldne. HSG B !9 0.540 61 Weighted Average 0.520 96.30% Pervious Area 0.020 3.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.0 Direct Entry, Summary for Link 3L: POM Inflow Area = 3.690 ac, 8.94% Impervious, Inflow Depth = 1.83" for 10 yr, 24 hr event Inflow = 7.61 cfs @ 12.12 hrs, Volume= 0.563 of Primary = 7.61 cfs @ 12.12 hrs, Volume= 0.563 af, Atten= 0%, lag= 0.0 min Primary outflow = Inflow, Time Span-- 0.00-36.00 hrs, dt= 0.05 hrs rM Onsite Trea 1S Onsite Treated Onsittn[reated 5P StormTech\ POA Subcat Reach Aon Link 4S ite Untreated Post Dev DA to POA Post Development Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.120 55 Woods, Good, HSG B (1S) 1.630 61 >75% Grass cover, Good, HSG B (1S, 2S, 3S, 4S) 1.920 98 (2S) 0.023 98 Paved parking, HSG B (1S, 3S) 3.693 80 TOTAL AREA Post Dev DA to POA Post Development Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 1.773 HSG B 1S, 2S, 3S, 4S 0.000 HSG C 0.000 HSG D 1.920 Other 2S 3.693 TOTAL AREA Post Dev DA to POA Post Development Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 4 Pipe Listing (all nodes) Line# Node In -Invert Out -Invert Length Slope n Diam/Width Height Fill Number (feet) (feet) (feet) (ft/ft) (inches) (inches) (inches) 1 5P 516.72 516.10 77.4 0.0080 0.012 24.0 0.0 0.0 Post Dev DA to POA Post Development Type II24-hr I yr, 24 hr Rainfall=2.97" Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 5 Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Offsite Treated Subcatchment 2S: Onsite Treated Subcatchment 3S: Onsite Untreated Subcatchment 4S: Offsite Untreated Pond SP: StormTech Link 6L: POA Runoff Area=0.330 ac 6.06% Impervious Runoff Depth=0.35" Tc=5.0 min CN=61 Runoff=0.15 cfs 0.010 of Runoff Area=2.860 ac 67.13% Impervious Runoff Depth=1.64" Tc=5.0 min CN=86 Runoff=8.37 cfs 0.390 of Runoff Area=0.293 ac 1.02% Impervious Runoff Depth=0.35" Tc=5.0 min CN=61 Runoff--O. 14 cfs 0.009 of Runoff Area=0.210 ac 0.00% Impervious Runoff Depth=0.35" Tc=18.0 min CN-61 Runoff=0.05 cfs 0.006 of Peak Elev=520.86' Storage=9,440 cf hrtlow=8.50 cfs 0.400 of Outflow=0.28 cfs 0.400 of hrtlow=0.40 cfs 0.415 of Primary=0.40 cfs 0.415 of Total Runoff Area = 3.693 ac Runoff Volume = 0.415 of Average Runoff Depth = 1.35" 47.39 % Pervious =1.750 ac 52.61 % Impervious =1.943 ac Post Dev DA to POA Post Development Type II 24-hr I yr, 24 hr Rainfall=2.97' Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 6 Summary for Subcatchment 1S: Offsite Treated Runoff = 0.15 cfs @ 11.99 hrs, Volume= 0.010 af, Depth= 0.35" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" 0.190 61 >75% Grass cover, Good, HSG B 0.020 98 Paved parldng, HSG B 0.120 55 Woods, Good, HSG B 0.330 61 Weighted Average 0.310 93.94% Pervious Area 0.020 6.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: Onsite Treated Runoff = 8.37 cfs @ 11.96 hrs, Volume= 0.390 af, Depth= 1.64" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" Area (ac) CN Description * 1.920 98 0.940 61 >75% Grass cover, Good, HSG B 2.860 86 Weighted Average 0.940 32.87% Pervious Area 1.920 67.13% Impervious Area Tc Length Slope Velocity Capacity Description 5.0 Direct Entry, Summary for Subcatchment 3S: Onsite Untreated Runoff = 0.14 cfs @ 11.99 hrs, Volume= 0.009 af, Depth= 0.35" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" Post Dev DA to POA Post Development Type II 24-hr I yr, 24 hr Rainfall=2.97" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 7 Area (ac) CN Description 0.290 61 >75% Grass cover, Good, HSG B 0.003 98 Paved Darkine. HSG B 0.293 61 Weighted Average 0.290 98.98% Pervious Area 0.003 1.02% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 4S: Mite Untreated Runoff = 0.05 cfs @ 12.16 hrs, Volume= 0.006 af, Depth= 0.35" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 1 yr, 24 hr Rainfall=2.97" Area (ac) CN Description 0.210 61 >75% Grass cover, Good, HSG B 0.210 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 18.0 Direct Entry, Summary for Pond 5P: StormTech Inflow Area = 3.190 ac, 60.82% Impervious, Inflow Depth = 1.50" for 1 yr, 24 hr event Inflow = 8.50 cfs @ 11.96 hrs, Volume= 0.400 of Outflow = 0.28 cfs @ 13.99 hrs, Volume= 0.400 af, Atten= 97%, Lag-- 121.9 min Primary = 0.28 cfs @ 13.99 hrs, Volume= 0.400 of Routing by Stor-Ind method, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 520.86' @ 13.99 hrs Surf.Area= 4,748 sf Storage= 9,440 cf Plug -Flow detention time= 385.1 min calculated for 0.399 of (100% of inflow) Center -of -Mass det. time= 385.2 min (1,209.4 - 824.2 ) Volume Invert Avail.Storage Storage Description #1 516.72' 919 cf 36.0" D x 130.0'L Pipe Storage S= 0.0098 T #2 517.50' 11,919 cf 47.46'W x 99.80'L x 8.30'H STONE STORAGE 39,313 cf Overall - 9,515 cf Embedded = 29,798 cf x 40.0% Voids #3 519.50' 9,158 cf StorntTech MC-4500 x 86 Inside #2 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 =106.5 cf Overall Size=100.0"W x 60.0"H x 4.33'L with 0.3 l'Overlap #4 519.50' 357 cf StorntTech MC-4500 Cap x 10 Inside #2 Effective Size= 63.5"W x 59.0"H => 15.25 sf x 2.341 = 35.7 cf Overall Size= 90.2"W x 59.4"H x 2.921 with 0.58' Overlap Post Dev DA to POA Post Development Type II 24-hr I yr, 24 hr Rainfall=2.97" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 8 22,353 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 516.72' 24.0" Round Culvert 1= 77.4' Ke= 0.600 Wet/ Outlet Invert= 516.72' / 516.10' S= 0.0080 7 Cc= 0.900 n= 0.012 #2 Device 1 516.72' 2.3" Vert. Orifice/Grate-1-YR C=0.600 #3 Device 1 520.90' 24.0" W x 5.5" H Vert. Orifice/Grate-10-YR C= 0.600 #4 Primary 523.27' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 2.00 Width (feet) 5.00 5.00 Primary OutFlow Max-0.28 cfs @ 13.99 hrs HW=520.86' (Free Discharge) 1=Culvert (Passes 0.28 cfs of 25.14 cfs potential flow) L2=Orifice/Grate-1-YR (Orifice Controls 0.28 cfs @ 9.68 fps) 3=Orifice/Grate-10-YR ( Controls 0.00 cfs) =Custom Weir/Orifice ( Controls 0,00 cfs) Summary for Link 6L: POA Inflow Area = 3.693 ac, 52.61 % Impervious, Inflow Depth = 1.35" for 1 yr, 24 hr event Inflow = 0.40 cfs @ 12.01 hrs, Volume= 0.415 of Primary = 0.40 cfs @ 12.01 hrs, Volume= 0.415 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Post Dev DA to POA Post Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 9 Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Offsite Treated Subcatchment 2S: Onsite Treated Subcatchment 3S: Onsite Untreated Subcatchment 4S: Offsite Untreated Pond SP: StormTech Link 6L: POA Runoff Area=0.330 ac 6.06% Impervious Runoff Depth=1.63" Tc=5.0 min CN=61 Runoff=0.95 cfs 0.045 of Runoff Area=2.860 ac 67.13% Impervious Runoff Depth=3.87" Tc=5.0 min CN=86 Runoff--19.05 cfs 0.922 of Runoff Area=0.293 ac 1.02% Impervious Runoff Depth=1.63" Tc=5.0 min CN=61 Runoff=0.85 cfs 0.040 of Runoff Area=0.210 ac 0.00% Impervious Runoff Depth=1.63" Tc=18.0 min CN=61 Runoff=0.38 cfs 0.029 of Peak P1ev=523.27' Storage=17,008 cf hdlow=19.99 cfs 0.967 of Outflow=6.81 cfs 0.967 of In low=7.55 cfs 1.036 of Primary=7.55 cfs 1.036 of Total Runoff Area = 3.693 ac Runoff Volume =1.036 of Average Runoff Depth = 3.37" 47.39 % Pervious =1.750 ac 52.61 % Impervious =1.943 ac Post Dev DA to POA Post Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 © 2011 HydroCAD Software Solutions LLC Paee 10 Summary for Subcatchment 1S: Offsite Treated Runoff = 0.95 cfs @ 11.97 hrs, Volume= 0.045 af, Depth= 1.63" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr RainfaM.43" 0.190 61 >75% Grass cover, Good, HSG B 0.020 98 Paved parldng, HSG B 0.120 55 Woods, Good, HSG B 0.330 61 Weighted Average 0.310 93.94% Pervious Area 0.020 6.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: Onsite Treated Runoff = 19.05 cfs @ 11.95 hrs, Volume= 0.922 af, Depth= 3.87" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 firs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr RainfaM.43" Area (ac) CN Description * 1.920 98 0.940 61 >75% Grass cover, Good, HSG B 2.860 86 Weighted Average 0.940 32.87% Pervious Area 1.920 67.13% Impervious Area Tc Length Slope Velocity Capacity Description 5.0 Direct Entry, Summary for Subcatchment 3S: Onsite Untreated Runoff = 0.85 cfs @ 11.97 hrs, Volume= 0.040 af, Depth= 1.63" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr Rainfall=5.43" Post Dev DA to POA Post Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 11 Area (ac) CN Description 0.290 61 >75% Grass cover, Good, HSG B 0.003 98 Paved Darkine. HSG B 0.293 61 Weighted Average 0.290 98.98% Pervious Area 0.003 1.02% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 4S: Mite Untreated Runoff = 0.38 cfs @ 12.12 hrs, Volume= 0.029 af, Depth= 1.63" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 10 yr, 24 hr Rainfall=5.43" Area (ac) CN Description 0.210 61 >75% Grass cover, Good, HSG B 0.210 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 18.0 Direct Entry, Summary for Pond 5P: StormTech Inflow Area = 3.190 ac, 60.82% Impervious, Inflow Depth = 3.64" for 10 yr, 24 hr event Inflow = 19.99 cfs @ 11.95 hrs, Volume= 0.967 of Outflow = 6.81 cfs @ 12.08 hrs, Volume= 0.967 af, Atten= 66%, Lag-- 7.3 min Primary = 6.81 cfs @ 12.08 hrs, Volume= 0.967 of Routing by Stor-Ind method, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 523.27' @ 12.08 hrs Surf.Area= 4,737 sf Storage= 17,008 cf Plug -Flow detention time= 232.8 min calculated for 0.966 of (100% of inflow) Center -of -Mass det. time= 233.3 min (1,033.6 - 800.3 ) Volume Invert Avail.Storage Storage Description #1 516.72' 919 cf 36.0" D x 130.0'L Pipe Storage S= 0.0098 T #2 517.50' 11,919 cf 47.46'W x 99.80'L x 8.30'H STONE STORAGE 39,313 cf Overall - 9,515 cf Embedded = 29,798 cf x 40.0% Voids #3 519.50' 9,158 cf StorntTech MC-4500 x 86 Inside #2 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 =106.5 cf Overall Size=100.0"W x 60.0"H x 4.33'L with 0.3 l'Overlap #4 519.50' 357 cf StorntTech MC-4500 Cap x 10 Inside #2 Effective Size= 63.5"W x 59.0"H => 15.25 sf x 2.341 = 35.7 cf Overall Size= 90.2"W x 59.4"H x 2.921 with 0.58' Overlap Post Dev DA to POA Post Development Type II 24-hr 10 yr, 24 hr Rainfall=5.43" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 12 22,353 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 516.72' 24.0" Round Culvert 1= 77.4' Ke= 0.600 Wet/ Outlet Invert= 516.72' / 516.10' S= 0.0080 7 Cc= 0.900 n= 0.012 #2 Device 1 516.72' 2.3" Vert. Orifice/Grate-1-YR C=0.600 #3 Device 1 520.90' 24.0" W x 5.5" H Vert. Orifice/Grate-10-YR C= 0.600 #4 Primary 523.27' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 2.00 Width (feet) 5.00 5.00 Primary OutFlow Max=6.77 cfs @ 12.08 hrs HW=523.25' (Free Discharge) 1=Culvert (Passes 6.77 cfs of 33.34 cfs potential flow) L2=Orifice/Grate-1-YR (Orifice Controls 0.35 cfs @ 12.21 fps) 3=Orifice/Grate-10-YR (Orifice Controls 6.42 cfs @ 7.00 fps) =Custom Weir/Orifice ( Controls 0.00 cfs) Summary for Link 6L: POA Inflow Area = 3.693 ac, 52.61 % Impervious, Inflow Depth = 3.37" for 10 yr, 24 hr event Inflow = 7.55 cfs @ 12.06 hrs, Volume= 1.036 of Primary = 7.55 cfs @ 12.06 hrs, Volume= 1.036 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Post Dev DA to POA Post Development Type II24-hr 100yr, 24 hr Rainfall=8.90" Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 0 2011 HydroCAD Software Solutions LLC Paee 13 Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Offsite Treated Subcatchment 2S: Onsite Treated Subcatchment 3S: Onsite Untreated Subcatchment 4S: Offsite Untreated Pond SP: StormTech Link 6L: POA Runoff Area=0.330 ac 6.06% Impervious Runoff Depth=4.14" Tc=5.0 min CN=61 Runoff=2.46 cfs 0.114 of Runoff Area=2.860 ac 67.13% Impervious Runoff Depth=7.21" Tc=5.0 min CN=86 Runoff--34.11 cfs 1.717 of Runoff Area=0.293 ac 1.02% Impervious Runoff Depth=4.14" Tc=5.0 min CN=61 Runoff=2.19 cfs 0.101 of Runoff Area=0.210 ac 0.00% Impervious Runoff Depth=4.14" Tc=18.0 min CN=61 Runoff=1.02 cfs 0.073 of Peak Elev=524.68' Storage=20,238 cf hdlow=36.56 cfs 1.831 of Outflow=36.01 cfs 1.831 of Inflow=38.78 cfs 2.005 of Primary=38.78 cfs 2.005 of Total Runoff Area = 3.693 ac Runoff Volume = 2.005 of Average Runoff Depth = 6.52" 47.39 % Pervious =1.750 ac 52.61 % Impervious =1.943 ac Post Dev DA to POA Post Development Type II 24-hr 100yr, 24 hr Rainfall=8.90" Prepared by SHIMP ENGINEERING, P.C. Printed 6M2021 HydroCAD® 9.10 On 07054 0 2011 HydroCAD Software Solutions LLC Paee 14 Summary for Subcatchment 1S: Offsite Treated Runoff = 2.46 cfs @ 11.96 hrs, Volume= 0.114 af, Depth= 4.14" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 100yr, 24 hr Rainfall=8.90" 0.190 61 >75% Grass cover, Good, HSG B 0.020 98 Paved parldng, HSG B 0.120 55 Woods, Good, HSG B 0.330 61 Weighted Average 0.310 93.94% Pervious Area 0.020 6.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: Onsite Treated Runoff = 34.11 cfs @ 11.95 hrs, Volume= 1.717 af, Depth= 7.21" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 100yr, 24 hr Rainfall=8.90" Area (ac) CN Description * 1.920 98 0.940 61 >75% Grass cover, Good, HSG B 2.860 86 Weighted Average 0.940 32.87% Pervious Area 1.920 67.13% Impervious Area Tc Length Slope Velocity Capacity Description 5.0 Direct Entry, Summary for Subcatchment 3S: Onsite Untreated Runoff = 2.19 cfs @ 11.96 hrs, Volume= 0.101 af, Depth= 4.14" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 100yr, 24 hr Rainfall=8.90" Post Dev DA to POA Post Development Type II 24-hr 100yr, 24 hr Rainfall=8.90" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 15 Area (ac) CN Description 0.290 61 >75% Grass cover, Good, HSG B 0.003 98 Paved Darkine. HSG B 0.293 61 Weighted Average 0.290 98.98% Pervious Area 0.003 1.02% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 4S: Mite Untreated Runoff = 1.02 cfs @ 12.11 hrs, Volume= 0.073 af, Depth= 4.14" Runoff by SCS TR-20 method, UH=SCS, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Type H 24-hr 100yr, 24 hr Rainfall=8.90" Area (ac) CN Description 0.210 61 >75% Grass cover, Good, HSG B 0.210 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fdft) (ft(sec) (cfs) 18.0 Direct Entry, Summary for Pond 5P: StormTech Inflow Area = 3.190 ac, 60.82% Impervious, Inflow Depth = 6.89" for 100yr, 24 hr event Inflow = 36.56 cfs @ 11.95 hrs, Volume= 1.831 of Outflow = 36.01 cfs @ 11.97 hrs, Volume= 1.831 af, Atten= 2%, Lag= 1.2 min Primary = 36.01 cfs @ 11.97 hrs, Volume= 1.831 of Routing by Stor-Ind method, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 524.68' @ 11.97 hrs Surf.Area= 4,737 sf Storage= 20,238 cf Plug -Flow detention time=148.1 min calculated for 1.830 of (100% of inflow) Center -of -Mass det. time=148.7 min ( 932.1 - 783.4 ) Volume Invert Avail.Storage Storage Description #1 516.72' 919 cf 36.0" D x 130.0'L Pipe Storage S= 0.0098 T #2 517.50' 11,919 cf 47.46'W x 99.80'L x 8.30'H STONE STORAGE 39,313 cf Overall - 9,515 cf Embedded = 29,798 cf x 40.0% Voids #3 519.50' 9,158 cf StorntTech MC-4500 x 86 Inside #2 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 =106.5 cf Overall Size=100.0"W x 60.0"H x 4.33'L with 0.3 l'Overlap #4 519.50' 357 cf StorntTech MC-4500 Cap x 10 Inside #2 Effective Size= 63.5"W x 59.0"H => 15.25 sf x 2.341 = 35.7 cf Overall Size= 90.2"W x 59.4"H x 2.921 with 0.58' Overlap Post Dev DA to POA Post Development Type II 24-hr 100yr, 24 hr Rainfall=8.90" Prepared by SHIMP ENGINEERING, P.C. Printed 6n12021 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paee 16 22,353 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 516.72' 24.0" Round Culvert 1= 77.4' Ke= 0.600 Wet/ Outlet Invert= 516.72' / 516.10' S= 0.0080 7 Cc= 0.900 n= 0.012 #2 Device 1 516.72' 2.3" Vert. Orifice/Grate-1-YR C=0.600 #3 Device 1 520.90' 24.0" W x 5.5" H Vert. Orifice/Grate-10-YR C= 0.600 #4 Primary 523.27' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 2.00 Width (feet) 5.00 5.00 Primary OutFlow Max=34.10 cfs @ 11.97 hrs HW=524.61' (Free Discharge) 1=Culvert (Passes 8.62 cfs of 37.23 cfs potential flow) L2=Orifice/Grate-1-YR (Orifice Controls 0.39 cfs @ 13.44 fps) 3=Orifice/Grate-10-YR (Orifice Controls 8.24 cfs @ 8.99 fps) =Custom Weir/Orifice (Weir Controls 25.47 cfs @ 3.79 fps) Summary for Link 6L: POA Inflow Area = 3.693 ac, 52.61 % Impervious, Inflow Depth = 6.52" for 100yr, 24 hr event Inflow = 38.78 cfs @ 11.97 hrs, Volume= 2.005 of Primary = 38.78 cfs @ 11.97 hrs, Volume= 2.005 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span-- 0.00-48.00 hrs, dt= 0.05 hrs PROFFIT ROAD TOWNHOMES SOUTH Area: I POA 24 Hr 1 year Storm: = 0.13 = 0.12 lMaXQde,eloped = 0.41 cfs = 0.415 jQde..l p d = 0.40 cfs Pre Development Post I Development 10 yr 1 7.611 7.55 PROFFIT ROAD TOWNHOMES SOUTH Time of Concentration Calculations PRE DEVELOPMENT TOC 100 ft Overland Flow 4.10% slope 0.35 C-value 1 10.9 min ISeelye Chart 484.0 ft S.C. Flow 2.25% slope 1.1 fps velocity 7.1 min. NEH Figure 15-4 0.0 ft Channel** 0.0 ft height 1 0.0 min. Kirpich Chart TOC=j 18.0 min. ** There is no Channel on site. All ToC's assumed to be 5 minutes. This assumption dictates very conservative design factors. TOC 5.0 MINUTES POST DEVELOPMENT (OFFSITE UNTREATED) TOC 36.0 ft Overland Flow 3.86% sloe 0.35 C-value 7.8 min ISeelye Chart 583.0 ft S.C. Flow 1.85% sloe 0.9 fps velocity I 10.2 min. INEH Figure 15-4 0.0 ft Channel** 0.0 ft height 1 0.0 1 min. I Kirpich Chart TOC=j 18.0 min. >- ere is no Uhannel on site. .1 v Roved y 0 z o .e 300 I— 7 IcZ.7T��: w u_ 200 Soil Poor Grass \SurfaceLLJ Average Grass 6 w U-,5 a x =_ y U Z 90 9 \ a SO Dense 70 Grass z \ N 60 \ J 0 50 V -� 40 x 30 z w J 20 m 35 30 F1 20 w F z_ z z 0.5 w _ w IA o 15 j 2.0 0 / a z o 5.0 z �- 10cr i 20 w 0. w OVERLAND FLOW TIME (Seelye Chart) z 10 U 0 9�w J z 7 V Source: Data Book for Civil Engineers. E.E. Seelye Plate 5-1 1.00 0.90 0.80 0.70 0.60 0.40 0.30 0.20 0.09 0. 0.08 0.07 0 0.06 n 0.05 0.04 0.03 0.02 0.01 0.005 0 2 ci ca v �q 19�i-oo ao c� w v c ctimao d d d d d ddd.: Velocity (ft(s) PROFFIT ROAD TOWNHOMES SOUTH Modified LD-268 Roadside and Median Ditch Desi n Form Side Slope I Min Slope iVft I Max Slope ft/t I I I I I Earth I Protective Lining SCC C A CA TOC — :1 L — :1 R Design Storm Intensity (in/hr) a (cis) Allowable Velocity (fps) n=.03 EC-2 or EC-3: n=.05 Paved: n=.015 INCR ACC Vel.' On T Velocity' I Depth" On Depth 1 0.60 1.60 1 0.96 1 0.96 1 5 1 3 1 3 1 0.01 1 0.03 1 2-Yr 1 5.17 1 4.97 1 4 0.25 1 2.89 1 0.86 "NOTES: The SCC is temporary for this site and only necessary during E&S Phase 2 SHIMP ENGINEERING, P.C. Design Focused Engineering Water Quality Calculations: Pre -Development VRRM Landuse Map Post -Development VRRM Landuse Map VRRM Redevelopment Spreadsheets Drainage Area A Drainage Area A Land Cover (acres) Land Cover A Soils BSoils CSoils DSoils Rv Forest/Open Space (acres) 0.00 Managed Turf (acres) 1.25 t1l. 0.20 Impervious Cover (acres) 1.94 0.95 Total Phosphorus Available for Removal in D.A. A (lb/yr) 4.77 Total Post Development Treatment Volume in D.A. A (ft) 7,598 Stormwater Best Management Practices (RR= Runoff Reduction) Runoff Managed Turf Impervious Volume from Runoff Remaining Total BMP Phosphorus Phosphorus Untreated Phosphorus Remaining Practice Reduction Credit Area Cover Credit Upstream Reduction Runoff Treatment Removal Load from Phosphorus Removed By Phosphoro Credit (%) (acres) Area (acres) practice (kal (ft) Volume fts ( ) Volume ka ( 1 Efficiency W (%) Upstream Load to Practice (lb) s Load (lb) 14. Manufactured Treatment Practices (lb) Practice (lb) 14.a. Manufactured Treatment Device- 0 1.25 1.94 0 0 7,598 7,598 40 0.00 4.77 1.91 2.86 Hydrodynamic TOTAL IMPERVIOUS COVER TREATED(ac) 1.94 AREACHECK:OK. TOTAL MANAGED TURF AREA TREATED(ac) 1.25 AREACHECK:OK. TOTAL PHOSPHORUS REMOVAL REQUIRED ON SITE (lb/yr) 3.20 TOTAL PHOSPHORUS AVAILABLE FOR REMOVAL IN D.A. A (lb/yr) 4.77 TOTAL PHOSPHORUS REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr) 1.91 TOTAL PHOSPHORUS REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr) 0.00 TOTAL PHOSPHORUS LOAD REDUCTION ACHIEVED IN D.A. A (lb/yr) 1.91 TOTAL PHOSPHORUS REMAINING AFTER APPLYING BMP LOAD REDUCTIONS IN D.A. A (lb/yr) 2.87 SEE WATER QUALITY COMPLIANCE TAB FOR SITE COMPLIANCE CALCULATIONS NITROGEN REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A (Ib/yr) 0.00 NITROGEN REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A. A (Ib/yr) 0.00 TOTAL NITROGEN REMOVED IN D.A. A (Ib/yr) 0.00 Site Results (Water Quality Compliance) Area Checks D.A. A D.A. B D.A. C D.A. D D.A. E AREA CHECK FOREST/OPEN SPACE (ac) 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac) 1.94 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED (ac) 1.94 0.00 E0.00 0.00 T MANAGED TURF AREA (ac) 1.25 0.00 0.00 MANAGED TURF AREA TREATED (ac) 1.25 0.00 0.00 0.00 OK. AREA CHECK Site Treatment Volume (ft3) 7,706 Runoff Reduction Volume and TP By Drainage Area D.A. A D.A. B D.A. C D.A. D D.A. E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED (ft) 0 1 0 0 0 0 TP LOAD AVAILABLE FOR REMOVAL (Ib/yr) 4.77 0.00 0.00 0.00 0.00 4.77 TP LOAD REDUCTION ACHIEVED (Ib/yr) 1.91 0.00 0.00 0.00 0.00 1.91 TP LOAD REMAINING (Ib/yr) 2.87 0.00 0.00 0.00 0.00 2.87 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) D.00 0.00 0.00 0.00 0.00 0.00 Total Phosphorus FINAL POST-DEVELOPMENTTP LOAD(Ib/yr) 4.84 TP LOAD REDUCTION REQUIRED (Ib/yr) 3.20 TP LOAD REDUCTION ACHIEVED (Ib/yr) 1.91 TP LOAD REMAINING (Ib/yr): 2.93 REMAINING TP LOAD REDUCTION REQUIRED (Ib/yr): 1.30 Total Nitrogen (For Information Purposes) POST -DEVELOPMENT LOAD(Ib/yr) 1 34.64 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 REMAINING POST -DEVELOPMENT NITROGEN LOAD (Ib/yr) 34.64 Virginia Runoff Reduction Method Worksheet DEC, Virginia Runoff Reduction Method Re -Development Compliance Spreadsheet - Version 3.0 LIMP Design Specifications List: 2013 Draft Stds & Specs Site Summary Project Title: Proffit South Date: 44351 Total Rainfall (in): 43 Total Disturbed Acreage: 3.34 Site Land Cover Summary Pre-ReDevelopment Land Cover (acres) Asoils BSolls CSolls DSolis Totals %of Total Forest/Open (acres) if 0.37 0.00 0.00 0.37 11 Managed Turf(acres)0.00 2.72 0.00 0.00 2.72 81 Impervious Cover (acres) 0.00 0.25 0.00 0.00 0.25 7 3.34 100 Post-ReDevelopment Land Cover (acres) Asoils BSoih CSolls DSoils Totals %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(acres) 0.00 1.40 0.00 0.00 1.40 42 Impervious Cover (acres) 0.00 1.94 0.00 0.00 1.94 58 3.34 100 Site TV and Land Cover Nutrient Loads Final Port -Development Post- post- Pre- Adjusted Pre- (Post-ReDevelopment ReDevelopment Developmentrvlous ReDevelopment &New lm pe ) (New Impervious) Site Rv 0.64 0.31 0.95 0.31 Treatment Volume(fts) 7,706 1,879 5,828 1,879 TP Load(lb/yr) 4.84 1.18 3.66 1.18 Total TP Load Reduction Required (lb/yr) 3.20 0.24 2.97 Final Post -Development Load (Post-ReDevelopment & New Impervious) Pre- ReDevelopment TN Load (Ib/yr) 34.64 12.93 Pre- ReDevelopment Final Post -Development Post-ReDevelopment TP TP Load per acre TP Load per acre Load per acre (lb/acre/yr) (lb/acre/yr) (lb/acre/yr) 0.72 LAS 0.72 Summary Print Virginia Runoff Reduction Method Worksheet Site Compliance Summary Maximum% Reduction Required Below 20% Pre-ReDevelopment Loatl Total Runoff Volume Reduction (k') 0 Total TP Load Reduction Achieved (lb/yr) 1.91 Total TN Load Reduction Achieved (lb/yr) 0.00 Remaining Post Development TP Load 2.93 (lb/yr) Remaining TP Load Reduction (lb/yr) 1.30 Required Summary Print Virginia Runoff Reduction Method Worksheet 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) 1.25 0.00 0.00 0.00 0.00 1.25 Impervious Cover(acres) 1.94 0.00 0.00 0.00 0.00 1.94 Total Area (acres) 3.19 0.00 0.00 0.00 0.00 3.19 Drainage Area Compliance Summary DA. A D.A. B DA. C D.A. D D.A. E Total TR Load Reduced (lb/yr) 1 1.91 0.00 1 0.00 1 0.00 0.00 1.91 TN Load Reduced (lb/yr) 1 0.00 0.00 1 0.00 1 0.00 0.00 0.00 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary A Soils B So"s [ solb D Soils Total %of Total Forest/Open (acres) D. D. 0.00 0.00 0.. 0 Man aged Turf(acres) 0.00 1.25 0.00 0.00 1.25 39 Impervious Cover (acres) 1 0.00 1.94 0.00 0.00 1.94 61 3.19 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Treatment Practice Credit Area Cover Credit volume (fc') Upstream to Practice (Ihs) (Ib/yr) (Ih/yr) to be Employed (acres) Area (acres) Practices (Ihs) 14.a. Manufactured Treatment Device- Hydrodynamic 1.25 1.94 7,597.59 0.00 4.77 1.91 2.86 Total Impervious Cover Treated(acres) 1.94 Total Turf Area Treated (acres) 1.25 Total TP Load Reduction Achieved in D.A. (Ib/yr) 1.91 Total TN Load Reduction Achieved in D.A. (lb/yr) 0.00 Summary Print Virginia Runoff Reduction Method Worksheet ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Runoff Volume and CN Calculations 1-year storm 2-year storm 10-year storm Target Rainfall Euent(in) I 0.00 0.00 0.00 Drainage Areas RV & CN Drainage Area A Drainage Area B Drainage Area C Drainage Area D Drainage Area E CN 84 0 0 0 0 RR (fta) 0 0 0 0 0 I -year return period RV wo RR(wzin) 0.00 0.00 0.00 0.00 0.00 RV w RR(wsin) 0.00 0.00 0.00 0.00 0.00 CN ad)ueted 100 0 0 0 0 2-year return period RVwo RR(ws-in) 0.00 0.00 0.00 0.00 0.00 RV w RR (wean) 0.00 0.00 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 10-year return period RVwo RR(Zin) 0.00 0.00 0.00 0.00 0.00 RV w RR(wzn) 0.00 0.00 0.00 0.00 0.00 04 adjusted 100 0 0 0 0 Summary Print SHIMP ENGINEERING, P.C. Design Focused Engineering Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report USDA United States Department of Agriculture MRCS Natural Resources Conservation Service A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Albemarle County, Virginia November 1 2019 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrGs.usda.govtwps/ portal/nres/main/soils/healthn and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https:Hoffices.sc.egov.usda.gov/locator/app?agency=nres) or your NRCS State Soil Scientist (http://www.nrGs.usda.govtwps/portal/nres/detail/soils/contactus/? cid=nres 142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface................................................................ SoilMap.............................................................. SoilMap........................................................... Legend............................................................. Map Unit Legend .............................................. Map Unit Descriptions ...................................... Albemarle County, Virginia ........................... 27B—Elioak loam, 2 to 7 percent slopes.. .2 .5 ..6 ..7 .8 .8 10 10 C! Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. M' 7W N 3 TWN Custom Soil Resource Report N Soil Map N N fn T25010 7250G0 725= 72510D 7251M 72510D 725190 DI 3 3 q iF p Map Smie:1:1,270 rn5' Ded m A pDbat(8.x 1175bBt q N Meters 0 15 30 W 9D A0 50 700 Z00 3r Mapproedb:WebMammr Cmc rdnz�:WGSB4 Edgdrs:UTMZm17NWGS84 6 A n Y I I 3 7'WN MAPLEGEND Area of Interest (AOQ O Area of Interest (AOI) Solis Soil Map Unit Polygons N Soil Map Unit Lines Soil Map Unit Points Special Point Features V Blowout ® Borrow Pit Clay Spot O Closed Depression Gravel Pit Gravelly Spot O Landfill A. Lava Flow Marsh or swamp Mine or Quarry O Miscellaneous Water O Perennial Water y Rock Outcrop + Saline Spot Sandy Spot Severely Eroded Spot Q Sinkhole Slide or Slip J, Sodic Spot Custom Soil Resource Report MAP INFORMATION g Spoil Area The soil surveys that comprise your AOI were mapped at 1:15,800. o Stony Spot W Very Stony Spot Warning: Soil Map may not be valid at this scale. wet Spot Enlargement of maps beyond the scale of mapping can cause Other misunderstanding of the detail of mapping and accuracy of soil Special Line Features line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed Water Features scale. Streams and Canals Transportation Please rely on the bar scale on each map sheet for map �..ry Rails measurements. N Interstate Highways Source of Map: Natural Resources Conservation Service ti US Routes Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Major Roads Local Roads Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts Background distance and area. A projection that preserves area, such as the . Aerial Photography Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Albemarle County, Virginia Survey Area Data: Version 13, Sep 17, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: May 20, 2019—Aug 1, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. V1 Custom Soil Resource Report Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 27B Elioak loam, 2 to 7 percent slopes 4.0 100.0% Totals for Area of Interest 4.0 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic Gass. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncentrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. R9 Custom Soil Resource Report An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha -Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. W Custom Soil Resource Report Albemarle County, Virginia 2713—Elioak loam, 2 to 7 percent slopes Map Unit Setting National map unit symbol: kb8y Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost -free period: 195 to 231 days Farmland classification: All areas are prime farmland Map Unit Composition Elioak and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Elioak Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down -slope shape: Convex Across -slope shape: Convex Parent material: Residuum weathered from mica schist Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 39 inches: silty clay H3 - 39 to 79 inches: silt loam Properties and qualities Slope: 2 to 7 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 6.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 2e Hydrologic Soil Group: B Hydric soil rating: No 10 11/112019 Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* E ,.. Latitude: 38.1309°, Longitude:-78.4283° FW�WI Elevation: 538.71 ft** " source: ESRI Maps "" source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) Duration 7 2 5 10 25 50 1 100 00 200 500 1000 0.349 F 0.416 F 0.489 F 0.551 F 0.621 F 0.677 F 0.729 F 0.778 F 0.839 F 0.889 5-min (0 315-0.386) (0.376-0.461) (0.441-0.541) (0.495-0.609) (0.556-0.685) (0.603-0.745) (0.645-0.802) (0.694-0.858) (0.730-0.928) (0.78-0.986) 10-min (g_503-0617) (0.602-0 38) (0.707-0866) (0.79-0.974) (0.886---11.09) (0.960-18.19) (1.03127) (1.09-21336) (1. 5-3L47) (1214.55) 0.697 0.837 0.991 1.11 1.25 1.36 1.46 1.56 1.67 1.76 15-min (0.629-0.772) (0.756-0.928) (0.894-1.10) 1 (1.00-1.23) 1 (1.12-1.38) 1 (1.22-1.50) 1 (1.30-1.61) 1 (1.37-1.72) 1 (1.45-1.85) 1 (1.51-1.95) 0.955 1.16 1.41 1.61 1.86 2.06 2.24 2.42 2.66 2.85 30-min (0.862-1.06) 1 (1.05-1.28) 1 (1.27-1.56) 1 (1.45-1.79) 1 (1.66-2.05) 1 (1.83-2.26) 1 (1.99-2.47) 1 (2.13-2.67) 1 (2.31-2.94) (2.45-3.16) 1.19 1.45 1.81 2.10 2.48 2.78 3.09 3.40 3.82 4.15 60-min (1.08-1.32) 1 (1.31-1.61) 1 (1.63-2.00) 1 (1.89-2.32) 1 (2.22-2.73) 1 (2.48-3.07) 1 (2.74-3.40) 1 (2.99-3.75) 1 (3.32-4.22) 1 (3.58-4.61) 1.43 1.74 2.18 2.56 3.06 3.47 3.90 4.35 4.99 5.52 2-hr (1.27-1.62) 1 (1.54-1.97) 1 (1.93-2.46) 1 (2.27-2.88) 1 (2.69-3.43) 1 (3.04-3.90) 1 (3.39-4.38) 1 (3.75-4.89) 1 (4.25-5.61) 1 (4.8-6.23) 1.57 1.90 2.38 2.79 3.33 3.79 4.27 4.77 5.47 6.07 3-hr (1.38-1.79) 1 (1.67-2.17) 1 (2.09-2.71) 1 (2.45-3.18) 1 (2.91-3.79) 1 (3.29-4.30) 1 (3.68-4.84) 1 (4.07-5.41) 1 (4.61-6.22) 1 (5.D6-6.91) 1.99 2.41 2.99 3.52 4.23 4.86 5.52 6.23 7.26 8.17 6-hr (1.77-2.26) 1 (2.13-2.74) 1 (2.64-3.39) (3.09-3.99) (3.69-4.80) (4.21-5.49) (4.73-6.24) (5.29-7.05) (6.07-8.22) (6.73-9.26) 2.49 3.01 3.75 4.44 5.40 6.26 7.20 8.23 9.76 11.1 12-hr (2.21-2.85) 1 (2.66-3.44) 1 (3.31-4.29) (3.90-5.06) (4.70-6.14) (5.40-7.11) (6.13-8.17) (6.91-9.33) (8.04-11.1) (9.02-12.7) 2997 3.60 4.60 5.43 6.67 7.73 8.90 10.2 12.1 13.8 24-hr (2.67-3.35) (3.23-4.05) (4.11-5.17) (4.84-6.10) (5.91-7.47) (6.80-8.64) (7.76-9.93) (8.79-11.3) (10.3-13.5) (11.5-15.3) 2-day (3. 6391) (3. 3-4.74) (4.85 6002) (5. 8--374.07) (6.86 8?57) (7. 3 9684) (8.86- 12) (9.97- 2.7) (115315.0) (12.t8-16.9) 3.73 4.52 5.74 6.74 8.20 9.41 10.7 12.2 14.2 16.0 3-day (3.39-4.14) 1 (4.10-5.01) 1 (5.20-6.36) 1 (6.09-7.46) 1 (7.36-9.06) 1 (8.40-10.4) 1 (9.50-11.9) 1 (10.7-13.4) 1 (12.4-15.8) 1 (13.7-17.8) 3.96 4.79 6.08 7.15 8.68 9.97 11.4 12.9 15.0 16.9 4-day (3.62-4.37) 1 (4.38-5.29) 1 (5.55-6.71) 1 (6.50-7.86) 1 (7.86-9.54) 1 (8.97-11.0) 1 (10.1-12.5) 1 (11.4-14.1) 1 (13.2-16.6) 1 (14.6-18.7) 4.60 5.54 6.92 8.06 9.69 11.0 12.5 14.1 16.3 18.2 7-day (4.21-5.05) 1 (5.07-6.07) 1 (6.33-7.59) 1 (7.35-8.83) 1 (8.79-10.6) 1 (9.97-12.1) 1 (11.2-13.7) 1 (12.5-15.4) 1 (14.3-17.9) 1 (15.8-20.0) 5.22 6.27 7.73 B.93 10.6 12.0 13.4 15.0 17.1 18.9 10day (4.80-5.68) (5.77-6.81) (7.11-8.40) (8.19-9.69) (9.69-11.5) (10.9-13.0) (12.1-14.6) (13.4-16.3) (15.2-18.7) (16.6-20.7) 6.86 8.19 9.89 11.2 13.0 14.5 15.9 17.4 19.4 21.0 20-0ay P� (6.41-7.38) (7.65-8.80) (9.22-10.6) (10.4-12.0) (12.1-14.0) (13.4-15.5) (14.7-17.1) (15.9-18.7) (17.7-20.9) (19.0-22.7) 8.42 9.98 11.8 13.2 15.0 16.4 17.7 19.0 20.8 22.1 30rlay (7.91-8.99) 1 (9.38-10.7) 1 (11.1-12.6) 1 (12.4-14.1) 1 (14.0-16.0) 1 (15.3-17.5) 1 (16.5-18.9) 1 (17.6-20.3) 1 (19.1-22.3) 1 (20.2-23.7) 22.4 IF 45tlay (9.91---11.2) (11.172--13.2) (13.14 5.4) (15..1---17.0) (17.10-19.2) (18.t4- 0.8) (196�2.3) (20.9- 3.8) (2244 5.8) (2325-27.2) 12.4 14.5 16.8 18.4 20.6 22.1 23.6 25.0 26.8 28.1 BOrlay (11.7-13.1) (13.7-15.4) (15.8-17.7) (17.4-19.5) (19.4-21.7) (20.8-23.4) (22.2-25.0) (23.5-26.5) (25.0-28.4) (26.1-29.9) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top hftps://hdsc.nws.noaa.gov/hdsolpfds/pfds_Printpage.html?lat=38.1309&Ion=-78.4283&data=depth&units=english&series=pds 1/4