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Home My WebLink AboutWPO201800077 Calculations 2022-04-12OLD TRAIL VILLAGE ALBEMARLE COUNTY, VIRGINIA EROSION CONTROL & STORMWATER MANAGEMENT PLAN BLOCK 32 (WP0201800077) AMENDMENT #3 DESIGN CALCULATIONS He NARRATIVE APRIL 5, 2022 • f • TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Jeremy Fox, P.E. Timmons Group 608 Preston Ave, Suite 200. Charlottesville, VA 22903 434.327.1681 ,ALTH OF Gr IEREMY L. FOX y Lic. No. 60786 04/05/2022 4� Table of Contents Section Title 1 Project Narrative 2 Water Quantity Compliance Summary 3 Water Quality Compliance Summary 4 Hydro Express Grass Channel Calculations 5 HydroCAD Calculations (Grass Channel/Biofilter/ED Pond) 6 DCR Performance Based WQ Calculations PROJECT NARRATIVE This plan proposes a third amendment to WP0201800077, originally approved 05/23/2019. In this amendment, a grass channel will be added directly upstream of the proposed biofilter to provide additional treatment as well as runoff reduction. The purpose of the amendment is to decrease the biofilter size directly behind the houses and reduce the required maintenance of such a large bioretention footprint. The media depth of the biofilter has been increased to 42" from 36" and provides adequate water quality and quantity requirements when paired with the proposed upstream grass channel and downstream extended detention. All drainage areas remain unchanged from the approved plan and calculations have been used to coincide accordingly. WATER QUANTITY: The original approved stormwater management plan was designed and analyzed under the IIC stormwater management criteria. Per approved plan, the pre -developed condition produces a maximum 2-year flow rate of 9.28 cfs and a maximum 10-year flow rate of 27.36 cfs. These values can be found on sheet C1.2 of the amendment. Per the proposed amendment, the post -developed routed condition produces a maximum 2-year flow rate of 7.05 cfs and a maximum 10-year flow rate of 9.50 cfs. These values can be found on sheet C2.1 as well as in the HydroCAD calculations provided herein. WATER QUALITY: The original approved stormwater management plan was designed and analyzed under the IIC stormwater management criteria. Per approved plan, the phosphorus load removal requirement is 7.88 Ib/yr for the development. The removal rate of 8.04 Ibtyr was achieved by the implementation of a biofilter and extended detention. With the proposed addition of a grass channel, the removal rate increases to 9.83 Ib/yr and provides a 'treatment train' for the development. These values and calculations can be found on sheet C2.0 of the amendment. Channel Report Hydraflow Express Extension for Autodesk®AutoCAD® Civil 31D9 by Autodesk, Inc. GRASS CHANNEL (2-YR) Trapezoidal Bottom Width (ft) = 6.00 Side Slopes (z:1) = 3.00, 3.00 Total Depth (ft) = 1.50 Invert Elev (ft) = 659.00 Slope (%) = 4.00 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 7.03 Elev (ft) Section 661.00 660.50 659.50 659.00 658.50 Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s) Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) Friday, Apr 1 2022 = 0.80 = 7.030 = 6.72 = 1.05 = 11.06 = 0.33 = 10.80 = 0.82 2 4 6 8 10 12 14 16 18 20 Reach (ft) Depth (ft) 2.00 1.50 1.00 0.50 M _n rn Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3138 by Autodesk, Inc. GRASS CHANNEL (10-YR) Trapezoidal Bottom Width (ft) = 6.00 Side Slopes (z:1) = 3.00, 3.00 Total Depth (ft) = 1.50 Invert Elev (ft) = 659.00 Slope (%) = 4.00 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 12.27 Elev (ft) Section 661.00 660.50 659.50 659.00 658.50 Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s) Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) Friday, Apr 1 2022 = 1.07 = 12.27 = 9.85 = 1.25 = 12.77 = 0.47 = 12.42 = 1.09 2 4 6 8 10 12 14 16 18 20 Reach (ft) Depth (ft) 2.00 1.50 1.00 0.50 M _n rn DA 1 A - EE /ioretention32 Total Post Subcat Reach Aon Llnk (3S 1 B - GRASS CHANNEL & BIOFILTER F8R] CHANNEL Post Prepared by Timmons Group Printed 4/4/2022 Rainfall Events Listing (selected events) Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 1-Year NOAA24-hr D Default 24.00 1 3.00 2 2 2-Year NOAA 24-hr D Default 24.00 1 3.60 2 3 10-Year NOAA 24-hr D Default 24.00 1 5.50 2 4 100-Year NOAA 24-hr D Default 24.00 1 9.00 2 Post NOAA 24-hr D 1-Year Rainfall=3.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 1S: DA 1A - ED POND Runoff = 7.42 cfs @ 12.20 hrs, Volume= 0.603 af, Depth> 1.07" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=3.00" Area (ac) CN Description 3.240 98 Paved parking, HSG B 3.530 61 >75% Grass cover, Good, HSG B 6.770 79 Weighted Average 3.530 52.14% Pervious Area 3.240 47.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.0 Direct Entry, Tc (Amendmentl) Subcatchment 1S: DA 1A - ED POND Hydrograph 71 k NOAA 24-hr D 1-Year Rainfall=3.00" 6 Runoff Area=6.770 ac 5 Runoff Volume=0.603 of 4 Runoff Depth>1.07" Tc=12.0 min 34 1 1 ffA CN=79 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) ❑ Runoff Post NOAA 24-hr D 1-Year Rainfall=3.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 3S: DA 1 B - GRASS CHANNEL & BIOFILTER Runoff = 5.41 cfs @ 12.23 hrs, Volume= 0.480 af, Depth> 1.59" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 1-Year Rainfall=3.00" Area (ac) CN Description 2.520 98 Paved parking, HSG B 1.090 61 >75% Grass cover, Good, HSG B 3.610 87 Weighted Average 1.090 30.19% Pervious Area 2.520 69.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.5 Direct Entry, (FAA)Tc Subcatchment 3S: DA 1B - GRASS CHANNEL & BIOFILTER Hydrograph N u ❑ Runoff c 3 LL -------------------------- 2 -- -------------------- NOAA 24-hr D 1-Year Rainfall=3.00" Runoff Area=3.610 ac Runoff Volume=0.480 of Runoff Depth>1.59" Tc=14.5 min CN=87 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post NOAA 24-hr D 1-Year Rainfall=3.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Reach 8R: GRASS CHANNEL Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 1.59" for 1-Year event Inflow = 5.41 cfs @ 12.23 hrs, Volume= 0.480 of Outflow = 5.25 cfs @ 12.28 hrs, Volume= 0.478 af, Atten= 3%, Lag= 3.4 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 0.98 fps, Min. Travel Time= 1.9 min Avg. Velocity = 0.35 fps, Avg. Travel Time= 5.3 min Peak Storage= 599 cf @ 12.25 hrs Average Depth at Peak Storage= 0.68' , Surface Width= 10.07' Bank -Full Depth= 1.50' Flow Area= 15.8 sf, Capacity= 23.94 cfs 6.00' x 1.50' deep channel, n= 0.200 Side Slope Z-value= 3.0 7' Top Width= 15.00' Length= 110.0' Slope= 0.0409 T Inlet Invert= 659.50', Outlet Invert= 655.00' Reach 8R: GRASS CHANNEL Hydrograph ❑ InHow ❑ Outflow 2 Inflow Area=3.610 ac Avg. Flow Depth=0.68' Max Vet=0.98 fps n=0.200 L=110.0' S=0.0409 '/' Capacity=23.94 cfs 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post Timmons N c YL 0 G NOAA 24-hr D 1-Year Rainfall=3. 00 " Reach 8R: GRASS CHANNEL Stage -Discharge Discharge (cfs) Reach 8R: GRASS CHANNEL Stage -Storage Storage (cubic -feet) Printed 4/4/2022 ❑ Primary ❑ Storage Post Timmons NOAA 24-hr D 1-Year Rainfall=3.00" Summary for Pond 5P: Bioretention32 Printed 4/4/2022 Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 1.59" for 1-Year event Inflow = 5.25 cfs @ 12.28 hrs, Volume= 0.478 of Outflow = 4.55 cfs @ 12.37 hrs, Volume= 0.474 af, Atten= 13%, Lag= 5.0 min Discarded = 4.55 cfs @ 12.37 hrs, Volume= 0.474 of Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 651.20' @ 12.37 hrs Surf.Area= 2,356 sf Storage= 1,677 cf Plug -Flow detention time= 9.9 min calculated for 0.474 of (99% of inflow) Center -of -Mass det. time= 6.7 min ( 805.5 - 798.9 ) Volume Invert Avail.Storage Storage Description #1 649.25' 8,099 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic -feet) (cubic -feet) 649.25 2,356 0.0 0 0 650.75 2,356 40.0 1,414 1,414 651.75 2,356 25.0 589 2,003 653.50 2,356 25.0 1,031 3,033 655.00 2,356 25.0 884 3,917 656.00 2,927 100.0 2,642 6,558 656.50 3,235 100.0 1,541 8,099 Device Routing Invert Outlet Devices #1 Discarded 649.25' 12.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Discarded 655.50' 6.3' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #3 Primary 655.50' 6.0' long Sharp -Crested Rectangular Weir 0 End Contraction(s) #4 Discarded 655.00' 0.50 cfs Exfiltration when above 655.00' Discarded OutFlow Max=4.51 cfs @ 12.37 hrs HW=651.17' (Free Discharge) 1=Orifice/Grate (Orifice Controls 4.51 cfs @ 5.74 fps) 2=Sharp-Crested Rectangular Weir( Controls 0.00 cfs) =Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=649.25' (Free Discharge) t3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) Post NOAA 24-hr D 1-Year Rainfall=3.00" Prepared by Timmons Group Printed 4/4/2022 Pond 5P: Bioretention32 Hydrograph :Y3E 14�5 r___r___r___r_I I I I I I I I I I 4- 3- 0 LL I I I 14 -Inflow Area=3.610 ac Peak Elev=651.20' Storage=1,677 cf I I I 5 6 7 8 9 10 11 12 13 14 15 16 17 Time (hours) Pond 5P: Bioretention32 Stage-Discharge -------`----- IL Sharp-Crested Rectangular Wda i 656VSharp,-fCre _ - - - - - gular Weir z n lu duun I I I I I I I I I I I I I I I I 654-I I I I I I I _------------------------------------ IIII I I I I I I I I I I I c658------------T-----T------------------r----- .�I I I I I q dI I I I I I I w 652 I I I I I I I I I I I I I 651 I I I I I I I -I -I -� I I I I I I I I I I I I I I I 650 Discharge (cfe) ■ Inflow Outflow ■ Discarded � Prlmary F Total ■ Discarded El Primary Post Timmons Custom Stage Data NOAA 24-hr D 1-Year Rainfall=3. 00 " Pond 5P: Bioretention32 Stage -Area -Storage Surface/Horizontal/Wetted Area 800 1,000 1,200 1,400 1,600 1,800 2, -------------------- 4,000 5,000 6,000 Storage (cubic -feet) 2,400 Printed 4/4/2022 ■ Surface ■ Storage Post Timmons NOAA 24-hr D 1-Year Rainfall=3.00" Summary for Pond 6P: Pond Printed 4/4/2022 Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 0.70" for 1-Year event Inflow = 7.42 cfs @ 12.20 hrs, Volume= 0.603 of Outflow = 5.82 cfs @ 12.29 hrs, Volume= 0.602 af, Atten= 22%, Lag= 5.4 min Primary = 5.82 cfs @ 12.29 hrs, Volume= 0.602 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 645.58' @ 12.29 hrs Surf.Area= 826 sf Storage= 1,383 cf Plug -Flow detention time= 2.1 min calculated for 0.602 of (100% of inflow) Center -of -Mass det. time= 1.5 min ( 818.0 - 816.5 ) Volume Invert Avail.Storage Storage Description #1 642.00' 31,663 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 642.00 57 0 0 644.00 376 433 433 646.00 945 1,321 1,754 648.00 1,780 2,725 4,479 650.00 2,825 4,605 9,084 652.00 4,099 6,924 16,008 654.00 5,570 9,669 25,677 655.00 6,402 5,986 31,663 Device Routing Invert Outlet Devices #1 Primary 642.00' 36.0" Round Culvert L= 105.0' RCP, end -section conforming to fill, Ke= 0.500 Inlet / Outlet Invert= 642.00' / 640.25' S= 0.0167 '/' Cc= 0.900 n= 0.013, Flow Area= 7.07 sf #2 Device 1 642.25' 8.0" Vert. Orifice/Grate X 2.00 C= 0.600 Limited to weir flow at low heads #3 Device 1 651.00' 16.0' long Sharp -Crested Rectangular Weir End Contraction(s) #4 Primary 653.00' 25.0' long x 14.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.64 2.67 2.70 2.65 2.64 2.65 2.65 2.63 Primary OutFlow Max=5.81 cfs @ 12.29 hrs HW=645.57' (Free Discharge) 1=Culvert (Passes 5.81 cfs of 48.95 cfs potential flow) �2=Orifice/Grate (Orifice Controls 5.81 cfs @ 8.32 fps) 3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) = B road-C rested Rectangular Weir( Controls 0.00 cfs) Post Timmons 6 T 6 5 3 4 0 LL 3 2 i c 0 w m W NOAA 24-hr D 1-Year Rainfall=3. 00 " Printed 4/4/2022 Pond GP: Pond Hydrograph zu as f ow', krga- a j80 $c - Peak Ele-v=f45.58'-- 5 d, %or$ a=1 383:cf 1 12 13 Time (hours) Pond 6P: Pond Stage -Discharge Discharge (cts) ■ Inflow ■ Pdmary ■ Pdmary Post Timmons Pond 6P: Pond NOAA 24-hr D 1-Year Rainfall=3. 00 " Printed 4/4/2022 Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 41500 5,000 5,500 6,000 ■ Surface ■ Storage __ I I I I I I I II I I I I I I I II II II I I I 654 I I I I I I I II I I I I I I I I I I I I 653 I I I I I I I I I I I I I I n I I I I n I I I I I I I I I I I I I I I I I I I I 652 I I I I I I I I I I II I I I I I I I I I 651 I I I I I I II _rr__ _r__rr___n___,r___rr__r_r_ I I I I I II I I I I r _,T__ I I I I I I_y_ - _ I__ ___I__I__I __I -I - 650 I I I I I I I I I I I I I I. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 649 TY--Y-_ YT u o u � 648 I I I I I II I I I I I I I I I I I I I I I I I I � __ 14__4 _�__'�___'____I_1___4-I-_J__�'___u___�r___I_'__�_'_4__a II J-- W 647 � I I I I I I III I I I I I I I I I II n I I I I I I I I I 646 i -Tr T-T-T I I I -TT I I -ll -I I -r-I -T -r7 -O -1r II I I I I I I I I I I I -I-i I I I I I I I 645 I I I I I I I II I I I I I I I I I II I I I I I I I I I 644 I I I I I I I -T --1 - II I I I I I I I I I 1 1 1 11Y I I -I-Y -Y-Y- I I -YT I I I I I Custom Stage Data Storage (cubic -feet) Post NOAA 24-hr D 1-Year Rainfall=3.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Link 7L: Total Post Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 0.70" for 1-Year event Inflow = 5.82 cfs @ 12.29 hrs, Volume= 0.602 of Primary = 5.82 cfs @ 12.29 hrs, Volume= 0.602 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 7L: Total Post Hydrograph ❑ Inflow ❑ Primary Time (hours) Post NOAA 24-hr D 2-Year Rainfall=3.60" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 1S: DA 1A - ED POND Runoff = 10.38 cfs @ 12.20 hrs, Volume= 0.841 af, Depth> 1.49" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.60" Area (ac) CN Description 3.240 98 Paved parking, HSG B 3.530 61 >75% Grass cover, Good, HSG B 6.770 79 Weighted Average 3.530 52.14% Pervious Area 3.240 47.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.0 Direct Entry, Tc (Amendmentl) Subcatchment 1S: DA 1A - ED POND ❑ Runoff ? NOAA 24-hr D 2-Year Rainfall=3.60"-- Runoff Area=6.770 ac - Runoff Volume=0.;841,af- Runoff Depth-;)l:49tF- "--- Tc=12.0 min - 4;N=19-- L-- --- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post NOAA 24-hr D 2-Year Rainfall=3.60" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 3S: DA 1 B - GRASS CHANNEL & BIOFILTER Runoff = 7.03 cfs @ 12.23 hrs, Volume= 0.630 af, Depth> 2.09" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 2-Year Rainfall=3.60" Area (ac) CN Description 2.520 98 Paved parking, HSG B 1.090 61 >75% Grass cover, Good, HSG B 3.610 87 Weighted Average 1.090 30.19% Pervious Area 2.520 69.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.5 Direct Entry, (FAA)Tc Subcatchment 3S: DA 1B - GRASS CHANNEL & BIOFILTER Hydrograph NOAA 24-hr D 6 2-Year Rainfall=3.60" Runoff Area=3.610 ac 5 Runoff Volume=0.630 of 4 Runoff Depth>2.09' Tc=14.5 min 3 CN=87 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) ❑ Runoff Post NOAA 24-hr D 2-Year Rainfall=3.60" Prepared by Timmons Group Printed 4/4/2022 Summary for Reach 8R: GRASS CHANNEL Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 2.09" for 2-Year event Inflow = 7.03 cfs @ 12.23 hrs, Volume= 0.630 of Outflow = 6.83 cfs @ 12.28 hrs, Volume= 0.628 af, Atten= 3%, Lag= 3.2 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 1.07 fps, Min. Travel Time= 1.7 min Avg. Velocity = 0.37 fps, Avg. Travel Time= 5.0 min Peak Storage= 719 cf @ 12.25 hrs Average Depth at Peak Storage= 0.78' , Surface Width= 10.70' Bank -Full Depth= 1.50' Flow Area= 15.8 sf, Capacity= 23.94 cfs 6.00' x 1.50' deep channel, n= 0.200 Side Slope Z-value= 3.0 7' Top Width= 15.00' Length= 110.0' Slope= 0.0409 T Inlet Invert= 659.50', Outlet Invert= 655.00' Reach 8R: GRASS CHANNEL Hydrograph Inflow Area=3.610 ac Avg. Flow Depth=0.78' Max Vet=1.07 fps n=0.200 L=110.0' S=0.0409 '/' Capacity=23.94 cfs 0 5 6 7 8 9 10 11 12 13 14 Time (hours) 19 20 ❑ Inflow ❑ Outflow Post Timmons N c YL 0 G NOAA 24-hr D 2-Year Rainfall=3.60" Reach 8R: GRASS CHANNEL Stage -Discharge Discharge (cfs) Reach 8R: GRASS CHANNEL Stage -Storage Storage (cubic -feet) Printed 4/4/2022 ❑ Primary ❑ Storage Post Timmons NOAA 24-hr D 2-Year Rainfall=3.60" Summary for Pond 5P: Bioretention32 Printed 4/4/2022 Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 2.09" for 2-Year event Inflow = 6.83 cfs @ 12.28 hrs, Volume= 0.628 of Outflow = 5.82 cfs @ 12.37 hrs, Volume= 0.623 af, Atten= 15%, Lag= 5.3 min Discarded = 5.82 cfs @ 12.37 hrs, Volume= 0.623 of Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 652.12' @ 12.37 hrs Surf.Area= 2,356 sf Storage= 2,218 cf Plug -Flow detention time= 9.2 min calculated for 0.621 of (99% of inflow) Center -of -Mass det. time= 6.4 min ( 798.2 - 791.7 ) Volume Invert Avail.Storage Storage Description #1 649.25' 8,099 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic -feet) (cubic -feet) 649.25 2,356 0.0 0 0 650.75 2,356 40.0 1,414 1,414 651.75 2,356 25.0 589 2,003 653.50 2,356 25.0 1,031 3,033 655.00 2,356 25.0 884 3,917 656.00 2,927 100.0 2,642 6,558 656.50 3,235 100.0 1,541 8,099 Device Routing Invert Outlet Devices #1 Discarded 649.25' 12.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Discarded 655.50' 6.3' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #3 Primary 655.50' 6.0' long Sharp -Crested Rectangular Weir 0 End Contraction(s) #4 Discarded 655.00' 0.50 cfs Exfiltration when above 655.00' Discarded OutFlow Max=5.78 cfs @ 12.37 hrs HW=652.08' (Free Discharge) 1=Orifice/Grate (Orifice Controls 5.78 cfs @ 7.36 fps) 2=Sharp-Crested Rectangular Weir( Controls 0.00 cfs) =Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=649.25' (Free Discharge) t3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) Post NOAA 24-hr D 2-Year Rainfall=3.60" Prepared by Timmons Group Printed 4/4/2022 i4- 3- 2- 0 5 656 655 654 1 c 653- e m W 652 Pond 5P: Bioretention32 Hydrograph Inflow Area=3.610 ac Peak Elev=652.12' Storage=2,218 cf I I I I I I I I I I I I I I I I I I I I I I I I 7 8 9 10 11 12 13 14 15 16 17 Time (hours) Pond 5P: Bioretention32 Stage -Discharge Sharp -Crested Rectangular RectanVar Weir nlu Guun I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I Orifice/Grate Discharge (cfe) ■ Inflow Ou flow ■ Discarded 0 Primary F Total ■ Discarded El Primary Post Timmons Custom Stage Data NOAA 24-hr D 2-Year Rainfall=3.60" Pond 5P: Bioretention32 Stage -Area -Storage Surface/Horizontal/Wetted Area 800 1,000 1,200 1,400 1,600 1,800 2, -------------------- 4,000 5,000 6,000 Storage (cubic -feet) 2,400 Printed 4/4/2022 ■ Surface ■ Storage Post Timmons NOAA 24-hr D 2-Year Rainfall=3.60" Summary for Pond 6P: Pond Printed 4/4/2022 Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 0.97" for 2-Year event Inflow = 10.38 cfs @ 12.20 hrs, Volume= 0.841 of Outflow = 7.05 cfs @ 12.32 hrs, Volume= 0.840 af, Atten= 32%, Lag= 7.3 min Primary = 7.05 cfs @ 12.32 hrs, Volume= 0.840 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 646.98' @ 12.32 hrs Surf.Area= 1,353 sf Storage= 2,878 cf Plug -Flow detention time= 2.8 min calculated for 0.837 of (100% of inflow) Center -of -Mass det. time= 2.3 min ( 811.0 - 808.6 ) Volume Invert Avail.Storage Storage Description #1 642.00' 31,663 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 642.00 57 0 0 644.00 376 433 433 646.00 945 1,321 1,754 648.00 1,780 2,725 4,479 650.00 2,825 4,605 9,084 652.00 4,099 6,924 16,008 654.00 5,570 9,669 25,677 655.00 6,402 5,986 31,663 Device Routing Invert Outlet Devices #1 Primary 642.00' 36.0" Round Culvert L= 105.0' RCP, end -section conforming to fill, Ke= 0.500 Inlet / Outlet Invert= 642.00' / 640.25' S= 0.0167 '/' Cc= 0.900 n= 0.013, Flow Area= 7.07 sf #2 Device 1 642.25' 8.0" Vert. Orifice/Grate X 2.00 C= 0.600 Limited to weir flow at low heads #3 Device 1 651.00' 16.0' long Sharp -Crested Rectangular Weir End Contraction(s) #4 Primary 653.00' 25.0' long x 14.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.64 2.67 2.70 2.65 2.64 2.65 2.65 2.63 Primary OutFlow Max=7.02 cfs @ 12.32 hrs HW=646.95' (Free Discharge) 1=Culvert (Passes 7.02 cfs of 63.20 cfs potential flow) �2=Orifice/Grate (Orifice Controls 7.02 cfs @ 10.06 fps) 3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) = B road-C rested Rectangular Weir( Controls 0.00 cfs) Post Timmons 0 LL i c 0 w m W NOAA 24-hr D 2-Year Rainfall=3.60" Printed 4/4/2022 Pond GP: Pond Hydrograph -Inflpw Area=_1A.30G A�C --- Pehk_EleV=646.98' _ ----II, -Sforage�2,678_6f _ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I -I - I -I - I -I 1 12 13 Time (hours) Pond 6P: Pond Stage -Discharge Discharge (cts) ■ Inflow ■ Primary ■ Primary Post Timmons Pond 6P: Pond NOAA 24-hr D 2-Year Rainfall=3.60" Printed 4/4/2022 Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 41500 5,000 5,500 6,000 ■ Surface ■ Storage __ I I I I I I I II I I I I I I I II 11 II I I I 654 I I I I I I I II I I I I I I I I I I I I 653 I I I I I I I I I I I I I I n I I I I n I I I I I I I I I I I I I I I I I I I I 652 I I I I I I I I I I II I I I I I I I I I 651 1 I I I 1 1 II _rr__ _r__rr___n___,r___rr__r_r_ 1 1 I 1 1 11 11 1 1 1 r -IT __ 1 1 I I I I_y_ - _ I__ ___I__I__I--I-1 - 650 1 I 1 I I I 1 1 1 1 1 1 1 1. I 1 1 I 1 11 1 I 1 1 I 1 1 11 11 11 1 1 1 1 1 1 I I I 1 1 I I I 649 TY--Y-_ 1 1 1 YT 1 u 1 1 1 1 1 11 1 1 1 1 1 0 1 1 1 1 u 1 1 1 1 1 11 1 1 1 1 1 � 648 1 I 1 1 1 II 1 1 1 1 I 1 1 11 11 1 1 1 1 I I I � __ 14__4 1 _�__'�___'____1_1---4-1-_J__�'___u___�r___1_'__�_'_4__a 1 1 II 1 1 1 1 1 11 11 1 1 1 1 J-- W 647 � 1 I 1 1 1 1 1 1 1 1 1 III 1 I 1 1 I 1 1 11 II 1 1 1 1 1 n 11 1 1 1 1 1 1 1 I I I 1 1 646 i —Tr T—T—T I I I —TT I I —ll —I I —r—I —T —r7 —O —1r II I I I I I I I I I I I —I—i I I I I I I I 645 1 I 1 I 1 1 1 1 1 1 1 1 II 1 I 1 1 I 1 1 11 II 1 1 1 1 1 11 1 1 1 1 1 1 1 I I I 1 1 644 I I I I I I I —T ——11 — II I I I I I I I 11 1 1 1I 1 I —I— —1 I 1 I —YT 1 I I I I I Custom Stage Data Storage (cubic -feet) Post NOAA 24-hr D 2-Year Rainfall=3.60" Prepared by Timmons Group Printed 4/4/2022 Summary for Link 7L: Total Post Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 0.97" for 2-Year event Inflow = 7.05 cfs @ 12.32 hrs, Volume= 0.840 of Primary = 7.05 cfs @ 12.32 hrs, Volume= 0.840 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 7L: Total Post Hydrograph FE ]—I n—fl.—. ❑ Primary Time (hours) Post NOAA 24-hr D 10-Year Rainfall=5.50" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 1S: DA 1A - ED POND Runoff = 20.44 cfs @ 12.20 hrs, Volume= 1.677 af, Depth> 2.97" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.50" Area (ac) CN Description 3.240 98 Paved parking, HSG B 3.530 61 >75% Grass cover, Good, HSG B 6.770 79 Weighted Average 3.530 52.14% Pervious Area 3.240 47.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.0 Direct Entry, Tc (Amendmentl) Subcatchment 1S: DA 1A - ED POND - ■Runoff 21 I 20 4{8 I 20 ----I----I--__I_____I___ ___I____ I____INOAA 1a I ---,-----------,-- -,--- T---- T---- r 10•aar RainfalTSM„-- 17 16 --- -'- - ------'-------------'--- I_ I_ I_ I_ _ I I I I I I ---I -------- ---J----1----1----J----L---J--- ------- Runbff-Ared=&.77Daac- ;4 ; ---;--------i--------;r---='I----'IRunoffyolum0=1,';617?af - 13 12 ___i____i____I____i____�____I__. ---------------- ---- --- -- -Runoff Depth>2.97" 11 ------ ------'--------'----'-- -'-T----'-T----T Tc=12.0 min 6 -, -T -I -T -r -T -I -T 7 ______ _ __I I I I I I I I I I I I I I q ____�____ 1___ J____1_. I 2 ------------ -----'---------------'---- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post NOAA 24-hr D 10-Year Rainfall=5.50" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 3S: DA 1 B - GRASS CHANNEL & BIOFILTER Runoff = 12.27 cfs @ 12.22 hrs, Volume= 1.128 af, Depth> 3.75" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 10-Year Rainfall=5.50" Area (ac) CN Description 2.520 98 Paved parking, HSG B 1.090 61 >75% Grass cover, Good, HSG B 3.610 87 Weighted Average 1.090 30.19% Pervious Area 2.520 69.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.5 Direct Entry, (FAA)Tc 5 Subcatchment 3S: DA 1B - GRASS CHANNEL & BIOFILTER Hydrograph I I ---r---i----r---T- ❑Runoff d: I NOAA 24-hr D 10-Year Rainfall=5.50" Runoff Area=3.610 ac - -Runoff Volume=1.128 of Runoff Depth>3.75" Tc=14.5 min -- CN=87 _T _I _T 5 6 7 8 9 19 11 12 13 14 15 16 17 18 19 20 Time (hours) Post NOAA 24-hr D 10-Year Rainfall=5.50" Prepared by Timmons Group Printed 4/4/2022 Summary for Reach 8R: GRASS CHANNEL [821 Warning: Early inflow requires earlier time span Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 3.75" for 10-Year event Inflow = 12.27 cfs @ 12.22 hrs, Volume= 1.128 of Outflow = 11.95 cfs @ 12.27 hrs, Volume= 1.125 af, Atten= 3%, Lag= 2.7 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 1.26 fps, Min. Travel Time= 1.5 min Avg. Velocity = 0.45 fps, Avg. Travel Time= 4.1 min Peak Storage= 1,065 cf @ 12.24 hrs Average Depth at Peak Storage= 1.06' , Surface Width= 12.34' Bank -Full Depth= 1.50' Flow Area= 15.8 sf, Capacity= 23.94 cfs 6.00' x 1.50' deep channel, n= 0.200 Side Slope Z-value= 3.0 7' Top Width= 15.00' Length= 110.0' Slope= 0.0409 T Inlet Invert= 659.50'. Outlet Invert= 655.00' Reach 8R: GRASS CHANNEL Hydrograph 12 � 11 I ----r--------r-- , A".T� ow-Dept&1,06'- ------ I I I I I 1 19 , --- �11-- --11,---+1----III---- ----III- -- -11----11, --MaxVe1=1.26-fps- 9 11 11 11 11 1 L----1 L -- n�0.200 8 -I y1 7 -;------------------7L=-11-01 LL 6 I I I I I I I I I 5 11,---1----11----;---J1-JI----11`Dapacity 4 ____T____I____f___y y_--1____T____ I____r___ I I I I I I I 1 1 1 3 I I I I I 1 1 1 1 1 2 _1 _I _L _L _1 _J _L I I I I I I I I I 1 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) ❑ Inflow OUWM Post Timmons I c YL 0 a NOAA 24-hr D 10-Year Rainfall=5.50" Reach 8R: GRASS CHANNEL Stage -Discharge Discharge (cfs) Reach 8R: GRASS CHANNEL Stage -Storage Storage (cubic -feet) Printed 4/4/2022 ❑ Primary ❑ Storage Post Timmons NOAA 24-hr D 10-Year Rainfall=5.50" Summary for Pond 5P: Bioretention32 [611 Hint: Exceeded Reach 8R outlet invert by 0.18' @ 12.40 hrs Printed 4/4/2022 Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 3.74" for 10-Year event Inflow = 11.95 cfs @ 12.27 hrs, Volume= 1.125 of Outflow = 9.32 cfs @ 12.38 hrs, Volume= 1.119 af, Atten= 22%, Lag= 6.6 min Discarded = 9.32 cfs @ 12.38 hrs, Volume= 1.119 of Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 655.19' @ 12.38 hrs Surf.Area= 2,463 sf Storage= 4,370 cf Plug -Flow detention time= 8.4 min calculated for 1.119 of (99% of inflow) Center -of -Mass det. time= 6.3 min ( 782.6 - 776.3 ) Volume Invert Avail.Storage Storage Description #1 649.25' 8,099 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic -feet) (cubic -feet) 649.25 2,356 0.0 0 0 650.75 2,356 40.0 1,414 1,414 651.75 2,356 25.0 589 2,003 653.50 2,356 25.0 1,031 3,033 655.00 2,356 25.0 884 3,917 656.00 2,927 100.0 2,642 6,558 656.50 3,235 100.0 1,541 8,099 Device Routing Invert Outlet Devices #1 Discarded 649.25' 12.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Discarded 655.50' 6.3' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #3 Primary 655.50' 6.0' long Sharp -Crested Rectangular Weir 0 End Contraction(s) #4 Discarded 655.00' 0.50 cfs Exfiltration when above 655.00' Discarded OutFlow Max=9.31 cfs @ 12.38 hrs HW=655.17' (Free Discharge) 1=Orifice/Grate (Orifice Controls 8.81 cfs @ 11.21 fps) 2=Sharp-Crested Rectangular Weir( Controls 0.00 cfs) =Exfiltration (Exfiltration Controls 0.50 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=649.25' (Free Discharge) L3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) Post 656 655 654 c 653- e m W 652 Timmons NOAA 24-hr D 10-Year Rainfall=5.50" Printed 4/4/2022 Pond 5P: Bioretention32 Hydrograph � ---r---r---T---T---T---1---1----I----I----I----r---r---r---T--- , 11.95as I ----tnfIIDw:IIAr a=&610ic- �. I ---Peak] lIev=6�5AI r 9.32 ch I I tbralge=4,37Q I I I I I I I I I I ___ I I___ I I___ , , r I I I I I I I I I I I I I I ' I I I I _1 _1 _1 _J _I _I _I _L _L _L ' I I I I I I , —r —T —T —T —1 1 12 13 14 15 16 17 Time (hours) Pond 5P: Bioretention32 Stage -Discharge Sharp -Crested Rectangular RectanVar Weir nlu tluun I I I I I I ------------------------------------ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I Orifice/Grate Discharge (cfe) ■ Inflow ■ Outflow ■ Discarded ■ Pdmary ■ Total ■ Discarded ■ Primary Post Timmons NOAA 24-hr D 10-Year Rainfall=5.50" Pond 5P: Bioretention32 Stage -Area -Storage Surface/Horizontal/Wetted Area 400 600 800 1,000 1,200 1,400 1,600 1,800 2,� Custom Stage Data -------------------- 4,000 5,000 6,000 Storage (cubic -feet) 2,400 Printed 4/4/2022 ■ Surface ■ Storage Post Timmons NOAA 24-hr D 10-Year Rainfall=5.50" Summary for Pond 6P: Pond Printed 4/4/2022 Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 1.94" for 10-Year event Inflow = 20.44 cfs @ 12.20 hrs, Volume= 1.677 of Outflow = 9.50 cfs @ 12.41 hrs, Volume= 1.676 af, Atten= 54%, Lag= 12.7 min Primary = 9.50 cfs @ 12.41 hrs, Volume= 1.676 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 650.58' @ 12.41 hrs Surf.Area= 3,192 sf Storage= 10,816 cf Plug -Flow detention time= 6.9 min calculated for 1.676 of (100% of inflow) Center -of -Mass det. time= 6.6 min ( 798.4 - 791.7 ) Volume Invert Avail.Storage Storage Description #1 642.00' 31,663 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 642.00 57 0 0 644.00 376 433 433 646.00 945 1,321 1,754 648.00 1,780 2,725 4,479 650.00 2,825 4,605 9,084 652.00 4,099 6,924 16,008 654.00 5,570 9,669 25,677 655.00 6,402 5,986 31,663 Device Routing Invert Outlet Devices #1 Primary 642.00' 36.0" Round Culvert L= 105.0' RCP, end -section conforming to fill, Ke= 0.500 Inlet / Outlet Invert= 642.00' / 640.25' S= 0.0167 '/' Cc= 0.900 n= 0.013, Flow Area= 7.07 sf #2 Device 1 642.25' 8.0" Vert. Orifice/Grate X 2.00 C= 0.600 Limited to weir flow at low heads #3 Device 1 651.00' 16.0' long Sharp -Crested Rectangular Weir End Contraction(s) #4 Primary 653.00' 25.0' long x 14.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.64 2.67 2.70 2.65 2.64 2.65 2.65 2.63 Primary OutFlow Max=9.50 cfs @ 12.41 hrs HW=650.57' (Free Discharge) 1=Culvert (Passes 9.50 cfs of 90.48 cfs potential flow) �2=Orifice/Grate (Orifice Controls 9.50 cfs @ 13.60 fps) 3=S harp-C rested Rectangular Weir( Controls 0.00 cfs) = B road-C rested Rectangular Weir( Controls 0.00 cfs) Post NOAA 24-hr D 10-Year Rainfall=5.50" Prepared by Timmons Group Printed 4/4/2022 HydroCAD® 10.10-4a s/n 08663 © 2020 HydroCAD Software Solutions LLC Page 33 Pond 6P: Pond Hydrograph ■ Inflow �Pnma ry 22 _____________ 1----___� ____� 20 as crs----------1-------�---J----'---- 21 �,'' -----------'-------�----(nfiQw-Are;3=4}0:300AQ_ 20 ___�____I____7____1____r—i--------r-rIr-ter--- 19 ,, ___ J___J____ 1___J____ L___ J_. .__I i , -4 -I -i -I -Y -y I 17 {}y d ,8 1 _I _L Jiora V i',' 1s ___-____I____7____1____r___�_. 14 13 — 12i ___r____I____r___�____r___ 3 „ ,' ___ J___J____1___J____ L___J_. ._J____I____ J___J____ L___ J____ L___ ' 9 8 _L _J _L -I -i -I -h -y -F i ,' 4 , 1 ___7____I____7____I____r___ __r_ _I_ r- _I____r___�____r___ 3 I I i c 0 m m w 1 12 13 Time (hours) Pond 6P: Pond Stage -Discharge Discharge (cfs) ■ Primary Post Timmons Pond 6P: Pond NOAA 24-hr D 10-Year Rainfall=5.50" Printed 4/4/2022 Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 ■ Surface ■ Storage __ I I I I I I I II I I I I I I I II II II I I I 654 I I I I I I I II I I I I I I I I I I I I 653 I I I I I I I I I I I I I I n I I I I n I I I I I I I I I I I I I I I I I I I I 652 I I I I I I I I I I II I I I I I I I I I 651 I I I I I I II _rr__ _r__rr___n___,r___rr__r_r_ I I I I I II I I I I r _,T__ I I I I I I_y_ - _ I__ ___I__I__I __I -I - 650 I I I I I I I I I I I I I. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ` 649 TY--Y-_ YT u C o u � 648 I I I I I II I I I I I I I I I I I I I I I I I I � 14__4 II 'I____I_1___4-I-_J__�'___u___�r___I_'__�_'_4__a J-- W 647 I I I I I I II I I I I I I I I I II n I I I I I I I I I 646 i -Tr T-T-T I I I -TT I I -ll -I I -r-I -T -r7 -O II I I I I I I I I I -1r I I -I-i I I I I I I I 645 I I I I I I I II I I I I I I I I I II I I I I I I I I I 644 I I I I I I I -T --1 II I I I I I I I I I 1 1 1 - 11Y I I -I-Y -Y-Y- I I -YT I I I I I Custom Stage Data 14,000 16,000 18.001 Storage (cubic -feet) Post NOAA 24-hr D 10-Year Rainfall=5.50" Prepared by Timmons Group Printed 4/4/2022 HydroCAD@ 10.10-4a s/n 08663 @ 2020 HydroCAD Software Solutions LLC Page 35 Summary for Link 7L: Total Post Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 1.94" for 10-Year event Inflow = 9.50 cfs @ 12.41 hrs, Volume= 1.676 of Primary = 9.50 cfs @ 12.41 hrs, Volume= 1.676 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 7L: Total Post Hydrograph ❑Inflow eso cr: ❑ Primary p 5 LL 4 3 ___ 2 1 , T 1 12 13 14 Time (hours) Post NOAA 24-hr D 100-Year Rainfall=9.00" Timmons Summary for Subcatchment 1S: DA 1A - ED POND Runoff = 39.78 cfs @ 12.20 hrs, Volume= 3.373 af, Depth> 5.98" Printed 4/4/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 100-Year Rainfall=9.00" Area (ac) CN Description 3.240 98 Paved parking, HSG B 3.530 61 >75% Grass cover, Good, HSG B 6.770 79 Weighted Average 3.530 52.14% Pervious Area 3.240 47.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.0 Direct Entry, Tc (Amendmentl) Subcatchment 1S: DA 1A - ED POND Hydrograph 44 -------------------------- _y _+ _1 _+ 42 ' 1 1 1 1 4 ___J____1____1__-- 38 1 32 ____11____ T____11____I 1 28 -- -. -1 -Y -1 -Y 2 I ___,____T____� ___1_. __r ____1___ jo I 1---- S 24 -----------1---- 1 1 1 -- 1- 22 -J _1 _I _1 _I -J 1 18 16 ----I--------I--__ _ 1 1 I 1 1 ' ____1__-- _.- - �. __1____+____�___+____+____1____+____ ■Runoff �I --- NOAA 24-h D_ - -100-Year Rainfall=9.00"- ---r----T---- Runoff Area=6.770 ac - Runoff Volume=3.373,af-- Runoff Depth>5.98- _I _1 _L _J T/_�L� //�I J/J� -1 -Y Y -Y- c=12,0-nIn- - -----;- -- ; CN=79 1 I I I I ------------------ 1 1 1 I I I 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post NOAA 24-hr D 100-Year Rainfall=9.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Subcatchment 3S: DA 1 B - GRASS CHANNEL & BIOFILTER Runoff = 21.83 cfs @ 12.22 hrs, Volume= 2.074 af, Depth> 6.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs NOAA 24-hr D 100-Year Rainfall=9.00" Area (ac) CN Description 2.520 98 Paved parking, HSG B 1.090 61 >75% Grass cover, Good, HSG B 3.610 87 Weighted Average 1.090 30.19% Pervious Area 2.520 69.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.5 Direct Entry, (FAA)Tc 15 14 13 12 11 10 , Subcatchment 3S: DA 1B - GRASS CHANNEL & BIOFILTER Hydrograph ----------------------------------- ----- ------------------- I I I I I I I I I 2183c I -1 -T -I -T I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I T I I __I____+____�___+____+____I____+____ ■Runoff _ -I -I I-- 140"-2th�-U- I_ _ I I I __I__ I I I I I I ____ __ ___ ______ _ _ tunbff=Are=3.fi1D-ac- -+-Runoff Deij3_th _6.8i9_'`- - •_T`-L J 5 -1 n -I I�14LV-I1'rr L_ J____L___-I___-1___ -------'T----PN=87 - - ----T----I - -I ---- ----T---- 1---- 1____L--- J____L---- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Post Timmons NOAA 24-hr D 100-Year Rainfall=9.00" Summary for Reach 8R: GRASS CHANNEL [821 Warning: Early inflow requires earlier time span Printed 4/4/2022 Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 6.89" for 100-Year event Inflow = 21.83 cfs @ 12.22 hrs, Volume= 2.074 of Outflow = 21.32 cfs @ 12.26 hrs, Volume= 2.070 af, Atten= 2%, Lag= 2.3 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 1.48 fps, Min. Travel Time= 1.2 min Avg. Velocity = 0.57 fps, Avg. Travel Time= 3.2 min Peak Storage= 1,612 cf @ 12.24 hrs Average Depth at Peak Storage= 1.43' , Surface Width= 14.56' Bank -Full Depth= 1.50' Flow Area= 15.8 sf, Capacity= 23.94 cfs 6.00' x 1.50' deep channel, n= 0.200 Side Slope Z-value= 3.0 7' Top Width= 15.00' Length= 110.0' Slope= 0.0409 T Inlet Invert= 659.50'. Outlet Invert= 655.00' Reach 8R: GRASS CHANNEL Hydrograph I I ---- T---- I ---- r___ 24 - - -I_ 23 22 ___ _________I__ 21.32 cfs _y1__�FriO�{ e�=3 to 21 - - -�-- -------------------- - Avg. Flo - - w Depthl-1.43'- 18 --- ---+------_-_-_- ----II - - Max Vet=1.48 fps= 17 -a _i _I _4 _a _a _L 16 ___�_---r---r----r---r---�- /{ n-O.200- a 13 r ---L r___r I r--- r_ --L--------L---L r____r___- L-.----; L=110;0' 3 12 ___�_---r -T -I -r -r �----r---�----r---r----r---r--- O 11 LL ___l__ __I____1____I____L___J _J _L___1____I_ JwTrw�I,rwAw L� �_ �V.V'TV -I - 9 -- L ---L--------; ---LI -LI----Oapac*=�21$4-c�ft- 8 ------------T---- ----Y---r 7 --_ �_- ------L--------L----I -----------------L--------L--_ 6 -Y 5 ---�i _--------------'--------� 8 I I _ 2 1 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (horns) ■ laow 10 oullim Post Timmons I c YL 0 a NOAA 24-hr D 100-Year Rainfall=9.00" Reach 8R: GRASS CHANNEL Stage -Discharge Discharge (cfs) Reach 8R: GRASS CHANNEL Stage -Storage Storage (cubic -feet) Printed 4/4/2022 ❑ Primary ❑ Storage Post Timmons NOAA 24-hr D 100-Year Rainfall=9.00" Summary for Pond 5P: Bioretention32 [611 Hint: Exceeded Reach 8R outlet invert by 0.92' @ 12.30 hrs Printed 4/4/2022 Inflow Area = 3.610 ac, 69.81 % Impervious, Inflow Depth > 6.88" for 100-Year event Inflow = 21.32 cfs @ 12.26 hrs, Volume= 2.070 of Outflow = 21.03 cfs @ 12.28 hrs, Volume= 2.062 af, Atten= 1%, Lag= 1.4 min Discarded = 15.56 cfs @ 12.28 hrs, Volume= 1.970 of Primary = 5.47 cfs @ 12.28 hrs, Volume= 0.092 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 655.93' @ 12.28 hrs Surf.Area= 2,885 sf Storage= 6,346 cf Plug -Flow detention time= 7.3 min calculated for 2.062 of (100% of inflow) Center -of -Mass det. time= 5.8 min ( 768.4 - 762.6 ) Volume Invert Avail.Storage Storage Description #1 649.25' 8,099 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic -feet) (cubic -feet) 649.25 2,356 0.0 0 0 650.75 2,356 40.0 1,414 1,414 651.75 2,356 25.0 589 2,003 653.50 2,356 25.0 1,031 3,033 655.00 2,356 25.0 884 3,917 656.00 2,927 100.0 2,642 6,558 656.50 3,235 100.0 1,541 8,099 Device Routing Invert Outlet Devices #1 Discarded 649.25' 12.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #2 Discarded 655.50' 6.3' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #3 Primary 655.50' 6.0' long Sharp -Crested Rectangular Weir 0 End Contraction(s) #4 Discarded 655.00' 0.50 cfs Exfiltration when above 655.00' Discarded OutFlow Max=15.42 cfs @ 12.28 hrs HW=655.92' (Free Discharge) 1=Orifice/Grate (Orifice Controls 9.39 cfs @ 11.96 fps) 2=Sharp-Crested Rectangular Weir(Weir Controls 5.53 cfs @ 2.12 fps) =Exfiltration (Exfiltration Controls 0.50 cfs) Primary OutFlow Max=5.34 cfs @ 12.28 hrs HW=655.92' (Free Discharge) L3=S harp-C rested Rectangular Weir(Weir Controls 5.34 cfs @ 2.12 fps) Post NOAA 24-hr D 100-Year Rainfall=9.00" Prepared by Timmons Group Printed 4/4/2022 O LL 5 656 655 654 1 c 653- e m W 652 Pond 5P: Bioretention32 Hydrograph 7 8 9 10 11 12 13 Time (hours) i-------li ---� --- i nffbw':A fta=:C10 -4 --- Peak-060:05:9;3' StbraoLe=6,346 Id _ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 15 16 17 Pond 5P: Bioretention32 Stage -Discharge Sharp -Crested Rectangular RectanVar Weir nlu tluun I I I I I I ------------------------------------ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I Orifice/Grate Discharge (cfe) IN Inflow .Outflow ■ Discarded MP ■ Total ■ Discarded ■ Pdmary Post Timmons NOAA 24-hr D 100-Year Rainfall=9.00" Pond 5P: Bioretention32 Stage -Area -Storage Surface/Horizontal/Wetted Area 400 600 800 1,000 1,200 1,400 1,600 1,800 2,� Custom Stage Data -------------------- 4,000 5,000 6,000 Storage (cubic -feet) 2,400 Printed 4/4/2022 ■ Surface ■ Storage Post Timmons NOAA 24-hr D 100-Year Rainfall=9.00" Summary for Pond 6P: Pond [881 Warning: Qout>Qin may require smaller dt or Finer Routing Printed 4/4/2022 Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 4.01" for 100-Year event Inflow = 41.67 cfs @ 12.22 hrs, Volume= 3.466 of Outflow = 43.94 cfs @ 12.22 hrs, Volume= 3.464 af, Atten= 0%, Lag= 0.2 min Primary = 43.94 cfs @ 12.22 hrs, Volume= 3.464 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 651.76' @ 12.22 hrs Surf.Area= 3,944 sf Storage= 15,029 cf Plug -Flow detention time= 7.2 min calculated for 3.464 of (100% of inflow) Center -of -Mass det. time= 6.9 min ( 779.8 - 772.9 ) Volume Invert Avail.Storage Storage Description #1 642.00' 31,663 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 642.00 57 0 0 644.00 376 433 433 646.00 945 1,321 1,754 648.00 1,780 2,725 4,479 650.00 2,825 4,605 9,084 652.00 4,099 6,924 16,008 654.00 5,570 9,669 25,677 655.00 6,402 5,986 31,663 Device Routing Invert Outlet Devices #1 Primary 642.00' 36.0" Round Culvert L= 105.0' RCP, end -section conforming to fill, Ke= 0.500 Inlet / Outlet Invert= 642.00' / 640.25' S= 0.0167 '/' Cc= 0.900 n= 0.013, Flow Area= 7.07 sf #2 Device 1 642.25' 8.0" Vert. Orifice/Grate X 2.00 C= 0.600 Limited to weir flow at low heads #3 Device 1 651.00' 16.0' long Sharp -Crested Rectangular Weir End Contraction(s) #4 Primary 653.00' 25.0' long x 14.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.64 2.67 2.70 2.65 2.64 2.65 2.65 2.63 Primary OutFlow Max=41.22 cfs @ 12.22 hrs HW=651.71' (Free Discharge) 1=Culvert (Passes 41.22 cfs of 97.52 cfs potential flow) �2=Orifice/Grate (Orifice Controls 10.16 cfs @ 14.55 fps) 3=S harp-C rested Rectangular Weir(Weir Controls 31.06 cfs @ 2.76 fps) = B road-C rested Rectangular Weir( Controls 0.00 cfs) Post NOAA 24-hr D 100-Year Rainfall=9.00" Prepared by Timmons Group Printed 4/4/2022 4Z 40 38 36 34 32 30 28 26 24 LL 22 20 18 16 14 12 10 a 6 4 2 0 5 i c 0 m m w Pond GP: Pond Hydrograph ---1 ---- r--- T----I- ---r T I _4 _I _T _I -r -T -r I _4 _I -T -I I �.8L �6 I I y��( -Q'-W rep"g-M1 __�Lf .380-ac- ___J____L_-_J_ _I----1--_I----L--^/�-J----L--- I I IPe Ele�6��.7C' - _1 _I _L _J _� _Ij�\\jj _I LJ!_J/A//� _L -1 -I -T - -r -r -1 IY��I � �i9- J____ I____ 1___J---- L--- J- -_J____I_ } --I J____ I____ 1___J---- L___ J_ ._J____I____ 1___J____L--- J____ L___ I I I ___J_ ._!____I____ J___J____ L___ J____ L___ I ____7____I__--r---r- ______1____7____I____r___y____r___ J____I____ 1___I---- L --- J- I I I I I I _L1-__I____L___J____L__- I I I I I I _y _I _{ I I I I I I I I I I I I I I I I I I I I I ____I____I____I____I____ I I I I I 7 8 9 10 11 12 13 14 Time (hours) Pond 6P: Pond Stage -Discharge Discharge (cfs) ■ Inflow ■ Primary ■ Primary Post Timmons Pond 6P: Pond NOAA 24-hr D 100-Year Rainfall=9.00" Printed 4/4/2022 Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 ■ Surface ■ Storage __ I I I I I I I II I I I I I I I II II II I I I 654 I I I I I I I II I I I I I I I I I I I I 653 I I I I I I I I I I I I I I n I I I I n I I I I I I I I I I I I I I I I I I I I 652 I I I I I I I I I I II I I I I I I I I I 651 I I I I I I II _rr__ _r__rr___n___,r___rr__r_r_ I I I I I II I I I I r _,T__ I I I I I I_y_ - _ I__ ___I__I__I __I -I - 650 I I I I I I I I I I I I I. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ` 649 TY--Y-_ YT u C o u � 648 I I I I I II I I I I I I I I I I I I I I I I I I � 14__4 II 'I____I_1___4-I-_J__�'___u___�r___I_'__�_'_4__a J-- W 647 I I I I I I II I I I I I I I I I II n I I I I I I I I I 646 i -Tr T-T-T I I I -TT I I -ll -I I -r-I -T -r7 -O II I I I I I I I I I -1r I I -I-i I I I I I I I 645 I I I I I I I II I I I I I I I I I II I I I I I I I I I 644 I I I I I I I -T --1 II I I I I I I I I I 1 1 1 - 11Y I I -I-Y -Y-Y- I I -YT I I I I I Custom Stage Data 14,000 16,000 18.001 Storage (cubic -feet) Post NOAA 24-hr D 100-Year Rainfall=9.00" Prepared by Timmons Group Printed 4/4/2022 Summary for Link 7L: Total Post Inflow Area = 10.380 ac, 55.49% Impervious, Inflow Depth > 4.00" for 100-Year event Inflow = 43.94 cfs @ 12.22 hrs, Volume= 3.464 of Primary = 43.94 cfs @ 12.22 hrs, Volume= 3.464 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs 'n 28 26 24 LL 22 20 18 16 14 12 10 8 6 4 2 Link 7L: Total Post Hydrograph Ir-------r- 4394 ca L_-- 4394 ch 7---- I____r___,_ 1___J____ L___J_ I I I I I _L __J_ I I I I I L___J_ I I I I I I _Y _7 I —T —I 1---1____L___J_ I I I I I I I L___L____L___L_ I I I I I I I I ____________ Inflow Area=1r0.380ac _J _L _J _L I 1 —1 —I —T —I —r —l —r __!____ I____ 1___J---- L___ J____ L___ I 1 I____ L___J---- L___ J____ L___ I —y —I —+ —1 —r _y —r J _ _L _J _L I 1___I____ L___J____ L___ I I I I I I I 1 12 13 14 Time (hours) ❑ Inflow ❑ Primary VA DCR SWPP Performance Based Water Quality Calculation Procedure Project: ON -Block 32 Locality: Albemarle Co. Date: 4/4/2022 14:48 Step 1 Determine the applicable area A and the post -developed impervious cover (lpost). Applicable area (A) = 1 452152.8 s.f. or 10.380 acres Post -development impervious cover: structures = s.f. or 0.000 acres parking lot = s.f. or 0.000 acres roadway = s.f. or 0.000 acres impervious = 239580 s.f. or 5.500 acres s.f. or 0.000 acres s.f. or 0.000 acres Total = 239580 s.f. or 5.500 acres hr = (total post -development impervious cover+A) x 100 = 53% Step 2 Determine the average land cover condition (I� or the existing impervious cover Average land cover condition If the locality has determined land cover conditions for individual watersheds within its jurisdiction, use the watershed specific value determined by the locality as Iwatershed. Iw,W, 0% Otherwise, use the Chesapeake Bay default value: 16% Existing impervious cover (k" �„): Determine the existing impervious cover of the development site if present. Pre -development impervious cover: structures = s.f. or 0.000 acres parking lot = s.f. or 0.000 acres roadway = s.f. or 0.000 acres other s.f. or 0.000 acres Concrete s.f. or 0.000 acres s.f. or 0.000 acres Total = 0 s.f. or 0.000 acres 1,, —(total existing impervious cover<A)x 100= 0% - The area should be the same as used in STEP 1. Step 3 Determine the appropriate development situation The site information determined in STEP 1 and STEP 2 provide enough information to determine the appropriate development situation under which the performance criteria will apply. Check U the appropriate development situation as follows: No Situation 1: This consists of land development where the existing percent impervious cover (1 is less than or equal to the average land cover condition ([watershed) and the proposed improvements will create a total percent impervious cover (Ipost) which is less than or equal to the avera a land cover condition ([watershed). <_ Iw,,,,,h,e 78% False IPOOF-53% Yes Situation 2: This consists of land development where the existing percent impervious cover ({,;a) is less than or equal to the average land cover condition ([watershed) and the proposed improvements will create a total percent impervious cover (Ipost) which is eater than the avera land cover condition (Iwatershed). True I :mfi s 0% <I.,k�ro,e 16% and True Ipa,� 53% > I...rshm F 78% No Situation 3: This consists of land development where the existing percent impervious cover (t,,;#;,) is greater than the average land cover condition watershed). False Iema.r 0% > L,n•.,h,a 78% No --]Situation 4: This consists of land development where the existing percent impervious cover (t,,;#;,) is served by an existing stormwater management BMP(s) that addresses water quality. If the proposed development meets the criteria for development Situation 1, than the low density development is considered to be the BMP and no pollutant removal is required. The calculation procedure for Situation 1 stops here. If the proposed development meets the criteria for development Situations 2, 3, or 4, then proceed to STEP 4 on the appropriate worksheet. VA DCR SWPP Performance Based Water Quality Calculation Procedure Project: OTV-Block 32 Locality'. Albemarle Co. Date: 04-Apr-22 Summary of Situation 2 criteria_ from calculation procedure STEP 1 thm STEP 3 Worksheet I Area= 10.38 at. V^a�- 53% t.vav — 16% t exuding 0% Stem 4 Determine the relative pre-developmem pollutant load (1,,.} Based on Ed tm, Impervious Cover I Lr„le. ,,,-[0.05+(0009x1mm)]x Ax228 (Equation5-16) where: Lyy,.a;,el = relative pre -development total phosphorous load (pounds per year) 4vi - Iverng m,im,Noama covN naaem exaNad in wM1ole nlwlua) A = applicable area (scros) LPelnaa%�=1005+(o009x 0% )I x 10.38 x2.28 1.18 pounds per year 2L,„... smt=[005+(0009xlw„-,,d)]x Ax228 (Equafion Sl6) SITUATION Ilur 1..�.nnR 6% 51.-1. 16% and F 53% >I..ueeea F 16% SITUATION 3 False 1,.u,l.a o% I ''- 16% SITUATION d False 4.ama BMP CURRENTLY IN 4 PLACE? NO where: Ley,) = relative pre -development total phosphorous load (pounds per year) L-v. J - average taiiii om fti- rune Nciae wnmFM a t-h,,r.cF.,udre a,, defm value of Re. nav- eeaessM in w le—k-a A = applicable area (scros) Largw,una.al=[005+(0009x 16% )I x 10.38 x2.28 pounds per year $Mo 5 Determine the relative port -development pollutant load (Ipd. L� _ [005 +(0-009 x 1.)] x A x 228 (Equafion 5-21) where: Ls„ = relative post -development total phosphorous load (pounds per year) Iw, = post -development impervious cover (percent expressed in whole numbers) A = applicable roes (acres) L,u,=[0.05+(0009x 53% A x 10.38 x2.28 pounds per year Step 6 Determine the relative pollutant removal requirement (RR). RR= L�-(09ALyq p RR = 12.5 - 1A RR= 11.60 pounds per year or RR = LPm-Lyq,,,l„sml RR = 12.5 - 4.6 pounds per year Use RR= ].66 (lessor value) Step 9 Identify best management practice (BMP) for the site. 1. Determine the required pollutant removal efficiency for the site: EFF — (RE. Ly ) x l0) (Equation 5-22) where: EFF = required pollutant removal efficiency RE = pollutant removal requirement(pounds per year) Lm, = relative post -development total phosphorous load, Equation 5-21 (pounds per year) EFF = ].88 I 12.6] x 100= 63% 2 Select BMP(s) from Table 5-14 and locate on the site Orairage Impervious Type Efficiency Am.Kf) Area(sf.) Gesodpfion: BhIP 1: BhIP 2: BW 3: BW 4: BW 5: BMPA BMPB BMPC BMPB BMPE 3- Determine the pollutant load entering the pmposed BMP(s)- Lane = [OM +(0009 x law)) x APwsne x 2 28 (Equation 5-23) where: Law = relative post -development total phosphorous load entering proposed BMP (pounds per year) Iaxm = post -development Iscmerd impervious cover b proposed BMP (percent expressed in whole numbers) Apmpaxw = drainage men to proposed BMP (acres) I.. — [0 05 + (0.009 x 70% B x 3.61 x2.28 = 5.58 pounds per year Lan.=[005+(0.009x 70% B x 3.61 x2.28 = 5.58 pounds per year Lane. —[005+(0.009x 81% A x 6.]] x2.28 = 12.06 pounds per year Lau.=[005+(0.009x 0% B x B.ou x2.28 = 0.00 pounds per year Lanes=[005+(0.009x 0% B x B.ou x2.28 = 0.00 pounds per year 4. Calculate the pollutant load removed by the proposed BMP(s): LRm, . = Effene x Laue (Equation 5-24) wiaxe: l,,,,s,,, = post -development total phosphorous load removed by proposed BMP (pounds per year) Effsne = pollutant removal efficiency of BMP (expressed in decimal form) Lame = relative post -development total phosphorous load entering proposed BMP, Equation 5-23 (pounds per year) Lmm... aam. — 1 ]9 Pounds per War removed L..mo.... 5.02 Pounds per War removed L..mm... 3.01 Pounds per War removed Lmm... aan. — 0.00 Pounds per year remov dl Gress Swale 32 15M51.6 109]]1.2 Biufiaer io 15M51.6 109]]1.2 Extended 0 25 296901.E 230580 Lv.wwaemr = 0.00 Pounds Par War removed] 5. Calculate Its, total pollutant load removed by the BMP(s): L,ei+L„,.wm�smn+L„,_Wm.+. .(Equation 5-25) where: L� = total pollutant load removed by proposed BMPs (pounds per year) L..owsrae, = pollutant load removed by proposed BMP No- 1, Equation 5-24 L._Wmee = pollutant load removed by proposed BMP No- 2, Equation 5-24 L._Wmm = pollutant load removed by proposed BMP No. 3, Equation 5-24 L,,..., , — 8.83 Tatal Pounds Par year removed] Verify wmpliance: L„.u„a,,, IItit L,m,o„�y, — 9.83 Total Pounds Par war removed] Req'd Removal= ].88 Total Pounds Per year removed] OK, Removal Rats Exceetlstl