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HomeMy WebLinkAboutWPO202100007 Stormwater Management Maintenance Agree. 2022-02-07BROOKHILL STORMWATER MANAGEMENT CALCULATIONS PACKET SCOTT R. INS Lic. No. 035791 -1- 2/4/22 GJ ?ONAL (WPO 20210007- Blocks 16-17) Date of Calculations January 21, 2021 Revised On June 9, 2021 Revised On July 30, 2021 Revised On October 14, 2021 Revised On February 4, 2022 I:1:1W-AW:loil :1'ii COLLINS ENGINEERING 200 GARRETT STREET, SUITE K CHARLOTTESVILLE, VA 22902 434.293.3719 PH 434.293.2813 FX www.collins-engineering.com SCS TR-55 Calculations Soils Table (Source: NRCS Web Soil Survey Online Database) Albemarle County, Virginia (VA003) Map Unit Map Uni[ Name Percent of en Symbol cen OI 16 Codorus silt 2.6% loam, 0 to 2 percent slopes, occasionally Flooded 27B Elioak loam, 2 24.7% to 7 percent slopes 27C Elioak loam, 7 20.5% to 15 percent slopes 28133 Elioak clay 0.2% loam, 15 to 25 percent slopes, severely eroded 34B Glenelg loam, 2 8.5% to 7 percent slopes 34C Glenelg loam, 7 9.2% to 15 percent slopes 34D Glenelg loam, 3.0% 15 to 25 percent slopes 39D Hazel loam, 15 25.9% to 25 percent slopes 39E Hazel loam, 25 3.5% to 45 percent slopes 95 Hatboro silt 2.0% loam, 0 to 2 percent slopes, occasionally Flooded Totals for Area of 100.0% Interest Note: The soils' properties witin this development are predominantly (96%+/-) composed of hydrologic soil group type B soils. Precipitation Data (Source: NCAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates) p,� O Map pehwood � Terrain 84a T�Orn p09e * J n a r a3o° u t PO 0 Y 3° 6 d e 1 I\ e °`gym Polo Uno, C o c Q pa 0 ° v K N C O` O a F `>C Q 4 °C COr �a M° 0.4km d.2m7 -n. .v l:an ehrnnM POINT PRECIPITATION FREQUENCY (PF) ESTIMATES WITH 90% CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION NOAA Atlas 14, V011lme 2. Version 3 PDS-based precipitation frequency estimates with 90% confidence intervals (in Inches)' Avera90 rawn Fb al (yens) Duration 1 2 5 10 25 50 100 200 500 1000 DODOOOOOOO 244r 3.00 3.63 12.693.38) 1 (3.26A.09) 4.64 (4.155.21) SA8 1 (4.896.15) 6.74 7.81 11 (5.97-7.53) (6.87-8.71) 8.99 (7.85-10.0) 10.3 (8.89-11.4) 12.3 13S (10.4-13.6) (11.7-15.5) U.S. Department of Agriculture Natural Resources Conservation Service Project: Brookhill Location: Blocks 16-17 Check One: Present % Developed 1. Runoff curve Number (CN) TR 55 Worksheet 2: Runoff Curve Number and Runoff Designed By: FGM, PE Checked By: SRC, PE FL-ENG-21A 06/04 Date: 6/9/2021 Date: 6/9/2021 Cover description CN (weighted) _Calculated'S' Drainage Area Soil name and hydrologic (Cover type,treatment, and hydrologic condition; percent CN Area Product of ON x total product/ Description group (Appendix A) impervious; unconnected/connected impervious area ratio) (Acres) Area total area Value Analyzed as Woods in Good Condition DAA (for Blocks 16& 17's Energy Balance) 55 6.37 350.4 55 8.18 (Pre-Dev.) B Analyzed as Woods In Good Condition (for Final Buildout) 55 7.75 426.3 55 8.18 Impervious Areas 98 3.68 360.8 DAA (Post-Dev.) B Lawns In Good Condition 61 2.69 164.0 82 2.14 Woods In Good Condition 55 0.00 0.0 Impervious Areas 98 4.65 456.2 DAA (Final Buildout) B Lawns in Good Condition 61 3.10 188.8 83 2.02 Woods In Good Condition 55 0.00 0.0 Analyzed as Woods in Good Condition DA B (for Blocks 16 & 17's Energy Balance) 55 12.36 668.8 55 8.18 (Pre-Dev.) B Analyzed as Woods in Good Condition (for Final Buildout) 55 20.08 1304.4 55 8.18 Impervious Areas 98 6.87 673.1 DAB B Lawns in Good Condition fit 5.29 322.8 82 2.21 (Post-Dev.) Woods in Good Condition 55 1 0.00 0.0 Impervious Areas 98 11.90 1166.5 DA B B Lawns in Good Condition fit 8.18 498.8 83 2.06 (Final Buildout) Woods in Good Condition 55 0.00 0.0 Impervious Areas 98 0.59 58.0 DAC B Lawns in Good Condition fit 0.95 57.8 72 3.96 (Pre-Dev.) Woods in Good Condition 55 0.33 18.2 Impervious Areas 98 1.02 99.6 DAC B Lawns in Good Condition fit 0.75 46.0 81 2.38 (Post-Dev.) Woods in Good Condition 55 0.10 5.5 2. Runoff 1-Year Storm 2-Year Storm 30-Year Storm Drainage Area Description Frequency -years 1 2 10 n a Rainfall, P(24 hour) -inches 3.00 3.63 5.48 n/a Runoff, Q-inches 0.19 0.39 1.23 DAA(Pre-Dev.) Runoff, Q-Inches 1.40 1.92 3.55 DAA(Post-Dev.) Runoff, Q-inches 1.46 1.99 3.63 DA A(Final Buildout) Runoff, 0- inches 0.19 0.39 1.23 DAB(Pre-Dev.) Runoff, Q-Inches 1.37 1.88 3.50 DA B (Post-Dev.) Runoff, Q-inches 1.44 1.96 3.60 DA B(Final Buildout) Runoff, 4-inches 0.79 1.19 2.54 DA C (Pre -De¢) Runoff, Q- inches 1.30 1.80 3.39 DAC (Post-Dev.) U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 3: Time of Concentration (T,) or Travel Time (Tj Pmjec[: Brookhill Location: Blocks 16-17 Check One: Present X Developed X Check One: T, X T, Segment ID Sheet Flow: (Applicable to T, only) 1 Surface description (Table 3-1) 2 Manning's roughness coeff., n (Table 3-1 3 Flow length, L (total L < 100) (ft) 4 Two-year 24-hour rainfall, Pr(in.) 5 Land slope, s (ft/ft) 6 Compute T,= ]0.007(n•L)oa] / Pi 3 sn4 Shallow Concentrated Flow: Surface description (paved or unpaved) 8 Flow Length, L (ft) 9 Watercourse slope, s(ft/ft) 10 Average velocity, V (Figure 3-I) (ft/s) 11 T,= L/ 3600•V Channel Flow: 12 Cress sectional Flow area, a (ft) 13 Wetted perimeter, P. (ft) 14 Hydraulic radius, r= a/P„ (ft) 15 Channel Slope, s (ft/ft) 16 Manning's Roughness Coeff, n 17 V=[1.49rV3s05]/n 38 Flow length, L (k) 19 T, L/3600`V 20 Watershed or subarea T, or T, (Add T, in steps 6,11 and 19) Note: The shoretest SCS Tc is 0.10 hrs. Designed By: FGM, PE Checked By: SRC, PE Through subarea n/a FL-ENG-23A O6/04 Date: 10/14/2021 Date: 10/14/2021 DAA DAA DAA DAB DAB DAB DAC DAC (Pre-Dev.) (Post-Dev.) (Final Buildout) (Pre-0ev.) (Port-Dev.) (Final Buildout) (Pre -De,) (Post-Oev.) Dense Dense Dense Dense Dense Dense Dense Dense Grass Grass Grass Grass Grass Grass Grass Grass 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 300 SO SO 100 100 300 100 20 3.63 3.63 3.63 3.63 3.63 3.63 3.63 3.63 0.02 0.04 0.04 0.04 0.07 0.07 0.09 0.30 0.135 1 0.10 0.10 0.17 0.135 0.135 0.12 0.02 Unpaved Unpaved Unpaved Unpaved Unpaved 650 1150 215 215 75 0.14 0.07 0.04 0.04 0.20 6.3 4.3 3.2 3.2 7.2 0.029 0.07 0.019 0.019 0.00 o v o d o+ o+ q+ q+ a d+ a d+ a x a x x x E I c o E 0'�°o iu o isU �U iu q@r iu m@, `o `o `o o n „� o n N o o. o. _ N a b UJ N V1 a, n 0.16 1 0.12 1 0.12 1 0.24 1 0.17 1 0.12 1 0.13 1 0.10 U.S. Department of Agrlakure Natural Resources Comereatlon Service Project: Brookhill Location: BIak516-12 Check One: Present % Da.loped % TR 55 Worlaheet 4: Graphical Peak Discharge Method Designed By: FGM, PE Checked By: SRC, PE Date: 2/4/2022 Date: 2/4/2022 1. Data Drainage Area Description Drainage Area Description Drainage Area Description Drainage Area Descnption Drainage Area Descriptbn Drainage Area Description Drainage Area Decription Drainage Area D¢cdptlon Drainage Area Descrl"n Drainage Area Decripion DAA (pre-0¢V.) Pre -Der. DAA (For FIPal Buildout) DAA Upoat-Dev.) DAA (Final Buildout) DAB (Pre-Dev.) Pre -Der. DAB (For Fire I BYIWout) DAB (Post-Dev.) DAB (Final Buildout) DAC (Pre-Day.) DAC (Pont-Day.) Drainage Area (Am) In mlks2= 0.0100 0.0121 0.0100 0.0121 0.01" 0.0314 0.0190 0.0314 0.0029 0.0029 Runoff curee number CN= 55 55 82 83 55 55 82 83 22 81 Time of concentration(TQ= 0.16 0.16 0.12 0.12 0.24 0.24 0.12 0.12 0.13 0.10 Rainfall distribution type= II II II II II II II II II II Ford and swamp area55p.d throughout the watershed= 0 0 0 0 0 0 0 0 0 0 2. Frequency -years 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 1 1 2 10 3. R¢Infall, P)24 hourE Inches 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 3.00 3.63 5.48 4. Initial Abstraction, la -inches 1.64 LIES 1.64 1.64 1.64 1.64 0.43 0.43 0.43 0.40 0.40 0.40 1.64 1.64 1.64 1.64 1.64 1.64 0." 0.44 0." 0.41 0.41 0.41 O.79 On O.79 0.48 0.48 0.48 S. Compute la/P 0.55 O.45 0.30 0.55 0.45 0.30 0.14 0.12 0.08 0.13 0.11 0.07 0.55 0.45 0.30 0.55 0.45 0.30 0.15 0.12 0.08 0.14 0.11 0.08 0.26 0.22 0.14 0.16 0.13 0.09 6. Unit peak O."Ne. Qu-am/In 425 550 T25 425 550 T25 925 950 950 925 950 950 350 450 650 350 450 650 825 825 850 825 825 850 875 875 BUD 925 925 1000 2. Runoff, Q from Worksheet 2-inches 0.19 0.39 1.23 0.19 0.39 1.23 1.40 1.92 3.55 1.46 1.% 3.63 0.19 0.39 1.23 0.19 0.39 1.23 1.32 1.88 3.50 1.44 1.96 3.60 O.79 1.19 2.54 1.30 1.80 3.39 B. Pond and Swamp adjustment factor, Fp 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 9. Peak Discharge, Qp-ch where Qp=Qu Am Q Fp 0.82 2.14 9.48 1.00 2.60 11.53 See Routing Cakulatki See Routing Colahtions 1.30 3.34 15.17 2.14 5.51 25.05 See Routing Calculations See Routing Cokulations 2.02 3.03 6.69 3.20 5.12 9.91 WATERSHED SUMMARY FOR SUBAREA A Area, 1-year Flow, 2-year Flow, 10-year Flow, CHI an. cfs cis cfs DAA(Pre-Da.) 55 6.32 0.82 2.14 9.48 DAA (Post -De,) 82 6.32 0.09 0.14 24.35 CHI Ar¢a, I -War Flow, 2-War Flow, 10-year Flow, ac. ch cfs ch Pre0ev. DAA)For Final Buildout) 55 2.25 1.00 2.60 11.53 OAA)Final Bulltlout) 83 2.25 0.13 2.94 32.52 WATERSHED SUMMARY FOR SUBAREA B CHI Area, 1-year Flaw, 2-year Flow, 10-year Flow, ac. cfs eft cis DA B)Pre-Dev.) 55 12.16 1.30 3.34 15.12 DA B)Post-Dev) 1 82 12.16 0.2 0.21 9.14 Area, 1-year Flow, 2-year Flow, 10-year Flow, CHI at. cfs cfs cis Pra-D¢V. DA B)PorFirelBuildout) 55 20.08 2.14 5.51 25.05 DA B(Final Buildout) 83 20.08 0.22 7.75 25.32 WATERSHED SUMMARY FOR SUBAREA C CHI Area, 1-year Flow, 2-year Flow, 10-year Flow, an. cfs cfs cfs DA C Fre-Dal) A 1.82 2.02 3.03 6.69 DAC)Post-Der.) 81 1.82 3.20 5.12 9.91 Channel & Flood Protection Calculations 9 VAC 25-870-66 (Point of Analysis 'A'- For Proposed Watershed) Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.1.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section B.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity shall be calculated either.." a. or b." Section B.3.a. In accordance with the following methodology: Under no condition shall Q Developed be greater than Q Pre -Developed nor shall Q Developed be required to be less than that calculated in the equation: Q Allowed 15- (Q Forest * RV Forest ) / RV Developed Q Allowed Where: QForest = CN Forest= S Forest RV Forest= CN Post -Developed= S Post -Developed = RV Post -Developed = Q Developed < 0.11 cfs Section B.4 Limits of Analysis 0.82 cfs (From Worksheet 4 Watershed Summary) 55 (From Worksheet 4 Watershed Summary) 8.18 (From SCS TR-55 eq. 2-4) 0.19 in. (From SCS TR-55 eq. 2-3) 82 (From Worksheet 4 Watershed Summary) 2.14 (From SCS TR-55 eq. 2-4) 1.40 in. (From SCS TR-55 eq. 2-3) 0.09 cfs (For Proposed Development) The analysis terminates at the onsite subarea since subsection B.3.a is met. 9 VAC 25-870-66 (Point of Analysis'A'- For Final Buildout) Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.1.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section B.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity shall be calculated either.." a. or b." Section B.3.a. In accordance with the following methodology: Under no condition shall Q Developed be greater than Q Pre -Developed nor shall Q Developed be required to be less than that calculated in the equation: Q Allowed 15- (Q Forest * RV Forest ) / RV Developed Q Allowed Where: QForest = CN Forest= S Forest RV Forest= CN Post -Developed= S Post -Developed = RV Post -Developed = Q Developed < 0.13 cfs Section B.4 Limits of Analysis 1.00 cfs (From Worksheet 4 Watershed Summary) 55 (From Worksheet 4 Watershed Summary) 8.18 (From SCS TR-55 eq. 2-4) 0.19 in. (From SCS TR-55 eq. 2-3) 83 (From Worksheet 4 Watershed Summary) 2.02 (From SCS TR-55 eq. 2-4) 1.46 in. (From SCS TR-55 eq. 2-3) 0.13 cfs (For Full Buildout) The analysis terminates at the onsite subarea since subsection B.3.a is met. 9 VAC 25-870-66 (Point of Analysis W) Section C: Flood Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic methodologies:" Section C.2.a.: Concentrated stormwater flow to stormwater conveyance systems that currently experience localized flooding [i.e. the floodplain] during the 10-year 24-hour storm event shall confine the postdevelopment peak flow rate from the 10-year 24-hour storm event within the stormwater conveyance system [i.e. the detention facilities] to avoid the localized flooding. Detention of stormwater or downstream improvements may be incorporated into the approved land -disturbing activity to meet this criterion." Please note, the detention facilities contain the 10-yr design storm, herby satisifying this criterion. 10-yr 24-hr SCS Design Storm's Peak WSE = 371.27 ft (For Proposed Plan) 10-yr 24-hr SCS Design Storm's Peak WSE = 371.40 ft (For Final Buildout) SWM Facility Top of Dam Elevation = 373.00 ft Section C.3 Limits of Analysis "...Stormwater conveyance systems shall be analyzed for compliance with flood protection criteria to a point where" either a, b or c are met. Section C.3.c.: "The stormwater conveyance system [i.e. the facilities' outfall] enters a mapped floodplain or other flood -prone area, adopted by ordinance, of any locality." 9 VAC 25-870-66 (Point of Analysis'B'- For Proposed Plan) Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.1.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section B.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity shall be calculated either.." a. or b." Section B.3.a. In accordance with the following methodology: Under no condition shall Q Developed be greater than Q Pre -Developed nor shall Q Developed be required to be less than that calculated in the equation: Q Allowed 15- (Q Forest * RV Forest ) / RV Developed Q Allowed Where: QForest = CN Forest= S Forest RV Forest= CN Post -Developed= S Post -Developed = RV Post -Developed = Q Developed < 0.18 cfs Section B.4 Limits of Analysis 1.30 cfs (From Worksheet 4 Watershed Summary) 55 (From Worksheet 4 Watershed Summary) 8.18 (From SCS TR-55 eq. 2-4) 0.19 in. (From SCS TR-55 eq. 2-3) 82 (From Worksheet 4 Watershed Summary) 2.21 (From SCS TR-55 eq. 2-4) 1.37 in. (From SCS TR-55 eq. 2-3) 0.18 cfs (For Proposed Watershed) The analysis terminates at the onsite subarea since subsection B.3.a is met. 9 VAC 25-870-66 (Point of Analysis'B'- For Final Buildout) Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.1.b. "The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance systems in subdivision 3 of this subsection shall be met." Section B.3 "... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity shall be calculated either.." a. or b." Section B.3.a. In accordance with the following methodology: Under no condition shall Q Developed be greater than Q Pre -Developed nor shall Q Developed be required to be less than that calculated in the equation: Q Allowed 15- (Q Forest * RV Forest ) / RV Developed Q Allowed Where: QForest = CN Forest= S Forest RV Forest= CN Post -Developed= S Post -Developed = RV Post -Developed = Q Developed < 0.29 cfs 2.14 cfs (From Worksheet 4 Watershed Summary) 55 (From Worksheet 4 Watershed Summary) 8.18 (From SCS TR-55 eq. 2-4) 0.19 in. (From SCS TR-55 eq. 2-3) 83 (From Worksheet 4 Watershed Summary) 2.06 (From SCS TR-55 eq. 2-4) 1.44 in. (From SCS TR-55 eq. 2-3) = 0.27 cfs (For Full Buildout Watershed) Section B.4 Limits of Analysis The analysis terminates at the onsite subarea since subsection B.3.a is met. 9 VAC 25-870-66 (Point of Analysis W) Section C: Flood Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic methodologies:" Section C.2.a.: Concentrated stormwater flow to stormwater conveyance systems that currently experience localized flooding [i.e. the floodplain] during the 10-year 24-hour storm event shall confine the postdevelopment peak flow rate from the 10-year 24-hour storm event within the stormwater conveyance system [i.e. the UGD system] to avoid the localized flooding. Detention of stormwater or downstream improvements may be incorporated into the approved land -disturbing activity to meet this criterion." Please note, UGD System W contains the 10-yr design storm, herby satisifying this criterion. 10-yr 24-hr SCS Design Storm's Peak WSE = 361.64 ft (For Proposed Plan) 10-yr 24-hr SCS Design Storm's Peak WSE = 362.49 ft (For Final Buildout) SWM Facility Top of Dam Elevation = 364.00 ft Section C.3 Limits of Analysis "...Stormwater conveyance systems shall be analyzed for compliance with flood protection criteria to a point where" either a, b or c are met. Section C.3.c.: "The stormwater conveyance system [i.e. the UGD system's outfall] enters a mapped floodplain or other flood -prone area, adopted by ordinance, of any locality." 9 VAC 25-870-66 (Point of Analysis 'C') Section B: Channel Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet the criteria in subdivision 1, 2 or 3 of this subsection..." Section B.1: Manmade stormwater conveyance systems "When stormwater from a development is discharged to a manmade stormwater conveyance system, following the land -disturbing activity, either..." a. or b. shall be met: Section B.1.a. "The manmade stormwater conveyance system shall convey the postdevelopment peak flow rate from the two-year 24-hour storm event without causing erosion of the system. " Note, the 2-yr 24-hour design storm's peak flow rate is not erosive in the concrete storm sewer and the rirpap lined stream's bed below the double 60"x60" concrete box culverts. This conclusion is logical since the storm sewer and manmade riprap were designed for storms in excess of the 2-year design storm and were recently approved with adequacies. Section B.4.a. Limits of Analysis Stormwater conveyance systems shall be analyzed for compliance with channel protection criteria to a point where, based on land area, the site's contributing drainage area is less than or equal to 1.0% of the total watershed area. Note, post -development subarea C's contributing drainage area is less than 1% of the overall watershed draining to the point of analysis (i.e. the riprap lined stream's bed below the double 60"x60" concrete box culverts). 9 VAC 25-870-66 (Point of Analysis'C') Section C: Flood Protection "Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic methodologies:" Section C.2.a.: Concentrated stormwater flow to stormwater conveyance systems that currently experience localized flooding [i.e. the floodplain] during the 10-year 24-hour storm event shall confine the postdevelopment peak flow rate from the 10-year 24-hour storm event within the stormwater conveyance system [i.e. the storm sewer] to avoid the localized flooding." Please note, the storm sewer's hydraulic grade line calculations have been provided showing the peak back water elevations do not overtop the inlets, herby satisifying this requirement. This is consistent with logic since storm sewer systems are designed for the 10-year storm events. Section C.3 Limits of Analysis "...Stormwater conveyance systems shall be analyzed for compliance with flood protection criteria to a point where" either a, b or c are met. Section C.3.c.: "The stormwater conveyance system [i.e. the downstream storm sewer] enters a mapped floodplain or other flood -prone area, adopted by ordinance, of any locality." Underground Detention System 'A' Routing Calculations (Subarea A- Proposed Development) Note: The following routing calculations are for the upper Underground Detention Basin 'A'. These routing calculations were used to generate outflow hydrographs, which were later used for the inflow hydrographs in the lower Dry Detention Basin 'A' routings. Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Proposed Development BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Proposed Development 13 Contour Areas Elevation(ft) Area(sf) 371.50 1328.00 372.00 1328.00 373.00 2228.00 374.00 2528.00 375.00 2703.00 376.00 2798.00 377.00 2828.00 378.00 2798.00 379.00 2703.00 380.00 2528.00 381.00 2228.00 382.00 1328.00 383.00 1328.00 Start_Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice Computed Vol •(cy) 0.0 24.6 89.7 177.7 274.6 376.5 480.6 584.8 686.7 783.5 871.6 936.7 985.9 371.50 Vol.(cy) 0.00 name: Low -Flow Orifice area (sf) 0.049 diameter or depth (in) 3.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 372.000 multiple 2 discharge into riser Page 1 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Proposed Development Outlet structure 1 Orifice name: Emergency Overflow in Weir Plate area (sf) 2.461 diameter or depth (in) 21.240 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 380.170 multiple 1 discharge into riser Outlet structure 2 Weir name: Access Manhole for Inspection diameter (in) 30.000 side angle 0.000 coefficient 3.000 invert (ft) 388.400 multiple 1 discharge into riser Outlet structure 3 Orifice name: Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 371.970 multiple 1 discharge out of riser Outlet structure 4 Orifice name: Emergency Bypass Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 379.500 multiple 2 discharge through dam Page 2 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Proposed Development 3 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS Design Storm Area (acres) 6.370 CN 82.000 Type 2 rainfall, P (in) 3.000 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 10.780 peak time (hrs) 11.922 volume (cy) 1179.963 Hydrograph 1 SCS name: 2-yr 24-hr SCS Design Storm Area (acres) 6.370 CN 82.000 Type 2 rainfall, P (in) 3.630 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 14.778 peak time (hrs) 11.922 volume (cy) 1617.630 Hydrograph 2 SCS name: 10-yr 24-hr SCS Design Storm Area (acres) 6.370 CN 82.000 Type 2 rainfall, P (in) 5.480 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 27.451 peak time (hrs) 11.922 volume (cy) 3004.907 Page 3 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Proposed Development OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr SCS Design Storm inflow (cfs) 10.761 at 11.92 (hrs) discharge (cfs) 0.921 at 12.42 (hrs) water level (ft) 377.601 at 12.50 (hrs) storage (cy) 543.372 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr SCS Design Storm inflow (cfs) 14.752 at 11.92 (hrs) discharge (cfs) 1.425 at 12.32 (hrs) water level (ft) 379.637 at 12.32 (hrs) storage (cy) 749.131 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr SCS Design Storm inflow (cfs) 27.403 at 11.92 (hrs) discharge (cfs) 26.260 at 11.96 (hrs) water level (ft) 380.811 at 11.96 (hrs) storage (cy) 855.752 Wed Feb 02 15:49:28 EST 2022 Page 4 Underground Detention System 'A' Outflow Hydrographs, Proposed Development (Used for the Lower Dry Detention Basin 'A' inflow hydrographs) Post -Development DA A (Proposed Development) Outflow Hydrograph From UGD A's Routings Tim.(hrs) Outflow(tf5) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.00 3.0 0.01 3.5 0.04 4.0 0.07 4.5 0.09 5.0 0.10 5.5 0.11 6.0 0.12 6.5 0.13 7.0 0.14 7.5 0.16 8.0 0.17 8.5 0.18 9.0 0.21 9.5 0.23 10.0 0.25 10.5 0.29 11.0 0.34 11.5 0.41 11.9 0.71 12.0 0.86 12.1 0.90 12.2 0.91 12.3 0.92 12.4 0.92 12.5 0.92 13.0 0.91 13.5 0.89 14.0 0.86 14.5 0.83 15.0 0.80 15.5 0.76 16.0 0.73 16.5 0.69 17.0 0.66 17.5 0.62 18.0 0.58 18.5 0.54 19.0 0.50 19.5 0.46 20.0 0.41 20.5 0.37 21.0 0.33 21.5 0.28 22.0 0.24 22.5 0.20 23.0 0.16 23.5 0.12 24.0 0.10 24.5 0.02 25.0 0.01 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 l00 a s0 0.60 0.40 0.20 0 00 -0.20 Outflow Hydrograph (1-yr Design Storm) 0A 5.0 30.0 15.0 200 25.0 30.0 35.0 Post -Development DA A (Proposed Development) Outflow Hydrograph From UGD A's Routings Tim.(hrs) Outflow(tf5) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.06 3.0 0.10 3.5 0.11 4.0 0.13 4.5 0.15 5.0 0.16 5.5 0.17 6.0 0.18 6.5 0.20 7.0 0.21 7.5 0.22 8.0 0.23 8.5 0.25 9.0 0.28 9.5 0.30 10.0 0.33 10.5 0.37 11.0 0.42 11.5 0.50 11.9 0.83 12.0 1.01 12.1 1.06 12.2 1.16 12.3 1.43 12.4 1.38 12.5 127 13.0 1.07 13.5 1.05 14.0 1.02 14.5 0.99 15.0 0.96 15.5 0.93 16.0 0.90 16.5 0.87 17.0 0.83 17.5 0.80 18.0 0.76 18.5 0.72 19.0 0.69 19.5 0.65 20.0 0.61 20.5 0.57 21.0 0.53 21.5 0.49 22.0 0.45 22.5 0.41 23.0 0.37 23.5 0.34 24.0 0.30 24.5 0.23 25.0 0.14 25.5 0.05 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 1.20 100 0.80 0.60 0.40 0m Outflow Hydrograph (2-yr Design Storm) 1.0 100 15.0 20.0 25.0 30.0 35.0 Post -Development DA A (Proposed Development) Outflow Hydrograph From UGD A's Routings Tim.(hrs) Outflow(tfs) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.11 2.0 0.18 2.5 0.21 3.0 0.23 3.5 0.25 4.0 0.27 4.5 0.28 5.0 0.30 5.5 0.32 6.0 0.33 6.5 0.35 7.0 0.36 7.5 0.38 8.0 0.39 8.5 0.41 9.0 0.45 9.5 0.48 10.0 0.51 10.5 0.56 11.0 0.63 11.5 0.73 11.9 16.39 1L0 26.26 12.1 18.15 12.2 5.68 12.3 3.64 12.4 2.79 12.5 2.24 13.0 1.31 13.5 1.12 14.0 1.07 14.5 1.05 15.0 1.04 15.5 1.02 16.0 1.00 16.5 0.97 17.0 0.95 17.5 0.92 18.0 0.90 18.5 0.87 19.0 0.84 19.5 0.81 20.0 0.78 20.5 0.75 21.0 0.72 21.5 0.69 22.0 0.66 22.5 0.63 23.0 0.60 23.5 0.57 24.0 0.54 24.5 0.48 25.0 0.43 25.5 0.36 26.0 0.30 26.5 0.22 27.0 0.13 27.5 0.04 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 3000 25.00 2000. 1500 10.00 5.00 o.m 500 Outflow Hydrograph (10-yr Design Storm) 0.0 5.0 10.0 150 20.0 250 300 35.0 Underground Detention System 'A' Routing Calculations (Subarea A- Full Buildout) Note: The following routing calculations are for the upper Underground Detention Basin 'A'. These routing calculations were used to generate outflow hydrographs, which were later used for the inflow hydrographs in the lower Dry Detention Basin 'A' routings. Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Full Buildout BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Full Buildout 13 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 371.50 1328.00 0.0 372.00 1328.00 24.6 373.00 2228.00 89.7 374.00 2528.00 177.7 375.00 2703.00 274.6 376.00 2798.00 376.5 377.00 2828.00 480.6 378.00 2798.00 584.8 379.00 2703.00 686.7 380.00 2528.00 783.5 381.00 2228.00 871.6 382.00 1328.00 936.7 383.00 1328.00 985.9 Start_Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice 371.50 Vol.(cy) 0.00 name: Low -Flow Orifice area (sf) 0.049 diameter or depth (in) 3.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 372.000 multiple 2 discharge into riser Page 1 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Full Buildout Outlet structure 1 Orifice name: Emergency Overflow in Weir Plate area (sf) 2.461 diameter or depth (in) 21.240 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 380.170 multiple 1 discharge into riser Outlet structure 2 Weir name: Access Manhole for Inspection diameter (in) 30.000 side angle 0.000 coefficient 3.000 invert (ft) 388.400 multiple 1 discharge into riser Outlet structure 3 Orifice name: Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 371.970 multiple 1 discharge out of riser Outlet structure 4 Orifice name: Emergency Bypass Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 379.500 multiple 2 discharge through dam Page 2 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Full Buildout 3 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS Design Storm Area (acres) 7.750 CN 83.000 Type 2 rainfall, P (in) 3.000 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 13.758 peak time (hrs) 11.922 volume (cy) 1505.929 Hydrograph 1 SCS name: 2-yr 24-hr SCS Design Storm Area (acres) 7.750 CN 83.000 Type 2 rainfall, P (in) 3.630 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 18.721 peak time (hrs) 11.922 volume (cy) 2049.202 Hydrograph 2 SCS name: 10-yr 24-hr SCS Design Storm Area (acres) 7.750 CN 83.000 Type 2 rainfall, P (in) 5.480 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 34.347 peak time (hrs) 11.922 volume (cy) 3759.736 Page 3 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea A Full Buildout OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr SCS Design Storm inflow (cfs) 13.733 at 11.92 (hrs) discharge (cfs) 1.051 at 12.50 (hrs) water level (ft) 379.248 at 12.56 (hrs) storage (cy) 711.352 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr SCS Design Storm inflow (cfs) 18.688 at 11.92 (hrs) discharge (cfs) 10.811 at 12.06 (hrs) water level (ft) 380.281 at 12.06 (hrs) storage (cy) 809.389 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr SCS Design Storm inflow (cfs) 34.287 at 11.92 (hrs) discharge (cfs) 33.674 at 11.94 (hrs) water level (ft) 381.051 at 11.94 (hrs) storage (cy) 875.685 Wed Feb 02 15:45:36 EST 2022 Page 4 Underground Detention System 'A' Outflow Hydrographs, Full Buildout (Used for the Lower Dry Detention Basin 'A' inflow hydrographs) Post -Development DA A (Full Buildout( Outflow Hydrograph From UGD A's Routings Tim.(hrs) Outflow(tfs) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.04 3.0 0.08 3.5 0.10 4.0 0.11 4.5 0.13 5.0 0.14 5.5 0.16 6.0 0.17 6.5 0.18 7.0 0.19 7.5 0.21 8.0 0.22 8.5 0.23 9.0 0.26 9.5 0.29 10.0 0.31 10.5 0.35 11.0 0.40 11.5 0.48 11.9 0.80 ILO 0.96 12.1 1.02 12.2 1.03 12.3 1.04 12.4 1.05 12.5 1.05 13.0 1.04 13.5 1.02 14.0 1.00 14.5 0.97 15.0 0.94 15.5 0.91 16.0 0.87 16.5 0.84 17.0 0.80 17.5 0.77 18.0 0.73 18.5 0.69 19.0 0.66 19.5 0.62 20.0 0.58 20.5 0.54 21.0 0.50 21.5 0.46 22.0 0.42 22.5 0.38 23.0 0.34 23.5 0.30 24.0 0.26 24.5 0.18 25.0 0.09 25.5 0.01 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 1.20 1.00 0.80 0.0 0.40 0.20 coo -0.20 Outflow Hydrograph (1-yr Design Storm) M 5.0 100 15,0 20.0 2s.0 30.0 35.0 Post -Development DA A (Full Buildout( Outflow Hydrograph From UGD A's Routings Tim.(hrs) Outflow(tfs) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.08 2.5 0.12 3.0 0.15 3.5 0.17 4.0 0.18 4.5 0.20 5.0 0.21 5.5 0.22 6.0 0.24 6.5 0.25 7.0 0.26 7.5 0.28 8.0 0.29 8.5 0.31 9.0 0.34 9.5 0.36 10.0 0.39 10.5 0.43 11.0 0.49 11.5 0.58 11.9 0.94 12.0 10.76 12.1 10.81 12.2 3.96 12.3 2.45 12.4 1.88 12.5 1.55 13.0 1.10 13.5 1.06 14.0 1.04 14.5 1.02 15.0 0.99 15.5 0.97 16.0 0.94 16.5 0.91 17.0 0.87 17.5 0.84 18.0 0.81 18.5 0.78 19.0 0.74 19.5 0.71 20.0 0.67 20.5 0.64 21.0 0.60 21.5 0.56 22.0 0.53 22.5 0.49 23.0 0.46 23.5 0.42 24.0 0.39 24.5 0.33 25.0 0.26 25.5 0.17 26.0 0.08 26.5 0.01 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 14.00 12 00 MOO 8.00 6.00 4.00 2.00 0.00 - 0.0 200 Outflow Hydrograph (2-yr Design Storm) 5.0 IDA 15.0 20.0 25.0 30.0 35.0 Post -Development DA A (Full Buildout) Outflow Hydrograph From UGD A's Routings Time (hrs) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.07 1.5 0.18 2.0 0.23 2.5 0.26 3.0 0.29 3.5 0.31 4.0 0.32 4.5 0.34 5.0 0.36 5.5 0.38 6.0 0.39 6.5 0.41 7.0 0.43 7.5 0.45 8.0 0.47 8.5 0.49 9.0 0.52 9.5 0.56 10.0 0.60 10.5 0.65 11.0 0.72 11.5 0.84 11.9 30.68 iL9 33.67 12.1 22.70 12.2 6.83 12.3 4.66 12.4 3.60 12.5 2.87 13.0 1.56 13.5 1.25 14.0 1.11 14.5 1.07 15.0 1.06 15.5 1.05 16.0 1.03 16.5 1.01 17.0 0.99 17.5 0.97 18.0 0.95 18.5 0.93 19.0 0.90 19.5 0.88 20.0 0.85 20.5 0.82 21.0 0.79 21.5 0.77 22.0 0.74 22.5 0.71 23.0 0.68 23.5 0.66 24.0 0.63 24.5 0.58 25.0 0.53 25.5 0.47 26.0 0.41 26.5 0.35 27.0 0.28 27.5 0.20 28.0 0.11 28.5 0.02 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 30 oa 25.00 2000 15.00 1000 500 coo 0.0 500 Outflow Hydrograph (10-yr Design Storm) 5.0 10.0 15.0 20.0 25.0 30.0 35.0 Dry Detention Basin 'A' Routing Calculations (Subarea A- Proposed Development) Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Proposed Development BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Proposed Development 21 Contour Areas Elevation(ft) Area(sf) 363.00 88.00 363.50 197.00 364.00 371.00 364.50 578.00 365.00 815.00 365.50 1081.00 366.00 1368.00 366.50 1675.00 367.00 1995.00 367.50 2220.00 368.00 2426.00 368.50 2672.00 369.00 2924.00 369.50 3189.00 370.00 3518.00 370.50 3816.00 371.00 4117.00 371.50 4437.00 372.00 4762.00 372.50 5099.00 373.00 5448.00 Start_Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice name: area (sf) diameter or depth (in) width for rect. (in) coefficient invert (ft) multiple Computed Vol 363.00 Vol.(cy) •(cy) 0.0 2.6 7.7 16.5 29.3 46.8 69.4 97.5 131.5 170.5 213.5 260.7 312.5 369.1 431.1 499.0 572.5 651.7 736.8 828.1 925.7 Str. A9- Lower Outfall 1.227 15.000 0.000 0.500 362.800 1 discharge out of riser Page 1 Am Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Proposed Development Outlet structure 1 Orifice name: Str. A7- Upper Outfall area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 364.550 multiple 1 discharge out of riser Outlet structure 2 Orifice name: Low -Flow Orifice area (sf) 0.009 diameter or depth (in) 1.250 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 363.000 multiple 1 discharge into riser Outlet structure 3 Weir name: Str. A8, Riser diameter (in) 60.000 side angle 0.000 coefficient 3.300 invert (ft) 370.670 multiple 1 discharge into riser transition at (ft) 1.519 orifice coef. 0.500 orifice area (sf) 19.635 Outlet structure 4 Weir name: Emergency Spillway length (ft) 30.000 side angle 75.964 coefficient 3.300 invert (ft) 371.670 multiple 1 discharge through dam Page 2 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Proposed Development 4 Inflow Hydrographs Hydrograph 0 Curve name: 1yr SCS TR-55 24-hr Design Storm - time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 1yr 24hr SCS TR-55 DA A Proposed volume (cy) 1124.04 routed true time in hours true Hydrograph 1 Curve name: 2yr SCS TR-55 24-hr Design Storm - time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 2yr 24hr SCS TR-55 DA A Proposed volume (cy) 1561.08 routed true time in hours true Hydrograph 2 Curve name: time incr (minlhrs) time limit (minlhrs) file: Hydrograph.txt volume (cy) routed time in hours Hydrograph 3 SCS name: Area (acres) CN Type rainfall, P (in) time of conc. (hrs) time increment (hrs) time limit (hrs) fudge factor routed peak flow (cfs) peak time (hrs) volume (cy) Proposed Development Buildout Inflow Hydrograph.txt Proposed Development Buildout Inflow Hydrograph.txt 10yr SCS TR-55 24-hr Design Storm- 0.01 720.00 10yr 24hr SCS TR-55 DA A Proposed 3300.04 true true 100yr SCS TR-55 24-hr Design 6.370 82.000 2 8.990 0.1200 0.0200 30.000 1.00 true 53.189 11.922 5822.219 Page 3 Proposed Development Buildout Inflow Storm- Proposed Development Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Proposed Development OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 1 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 2 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 3 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Peaks: 1yr SCS TR-55 24-hr Design Storm- Proposed Development 0.921 at 12.45 (hrs) 0.094 at 15.15 (hrs) 370.651 at 15.77 (hrs) 520.605 Peaks: 2yr SCS TR-55 24-hr Design Storm- Proposed Development 1.425 at 12.32 (hrs) 0.138 at 14.38 (hrs) 370.679 at 14.38 (hrs) 524.674 Peaks: 10yr SCS 26.260 at 24.352 at 371.273 at 614.922 Peaks: 100yr SCS 53.096 at 51.448 at 371.664 at 678.874 Wed Feb 02 16:45:23 EST 2022 TR-55 24-hr Design Storm- Proposed Development 11.96 (hrs) 11.98 (hrs) 11.98 (hrs) TR-55 24-hr Design Storm- Proposed Development 11.92 (hrs) 11.94 (hrs) 11.94 (hrs) Page 4 Dry Detention Basin 'A' Routing Calculations (Subarea A- Final Buildout) Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Full Buildout BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Full Buildout 21 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 363.00 88.00 0.0 363.50 197.00 2.6 364.00 371.00 7.7 364.50 578.00 16.5 365.00 815.00 29.3 365.50 1081.00 46.8 366.00 1368.00 69.4 366.50 1675.00 97.5 367.00 1995.00 131.5 367.50 2220.00 170.5 368.00 2426.00 213.5 368.50 2672.00 260.7 369.00 2924.00 312.5 369.50 3189.00 369.1 370.00 3518.00 431.1 370.50 3816.00 499.0 371.00 4117.00 572.5 371.50 4437.00 651.7 372.00 4762.00 736.8 372.50 5099.00 828.1 373.00 5448.00 925.7 Start_Elevation(ft) 363.00 Vol.(cy) 0.00 5 Outlet Structures Outlet structure 0 Orifice name: Str. A9- Lower Outfall area (sf) 1.227 diameter or depth (in) 15.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 362.800 multiple 1 discharge out of riser Page 1 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Full Buildout Outlet structure 1 Orifice name: Str. A7- Upper Outfall area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 364.550 multiple 1 discharge out of riser Outlet structure 2 Orifice name: Low -Flow Orifice area (sf) 0.011 diameter or depth (in) 1.438 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 363.000 multiple 1 discharge into riser Outlet structure 3 Weir name: Str. A8, Riser diameter (in) 60.000 side angle 0.000 coefficient 3.300 invert (ft) 370.670 multiple 1 discharge into riser transition at (ft) 1.519 orifice coef. 0.500 orifice area (sf) 19.635 Outlet structure 4 Weir name: Emergency Spillway length (ft) 30.000 side angle 75.964 coefficient 3.300 invert (ft) 371.670 multiple 1 discharge through dam Page 2 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Full Buildout 4 Inflow Hydrographs Hydrograph 0 Curve name: lyr SCS TR-55 24-hr Design Storm- Full Buildout time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 1yr 24hr SCS TR-55 DA A Full Buildout Inflow Hydrograph.txt volume (cy) 1460.91 routed true time in hours true Hydrograph 1 Curve name: 2yr SCS TR-55 24-hr Design Storm- Full Buildout time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 2yr 24hr SCS TR-55 DA A Full Buildout Inflow Hydrograph.txt volume (cy) 2036.84 routed true time in hours true Hydrograph 2 Curve name: 10yr SCS TR-55 24-hr Design Storm- Full Buildout time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 10yr 24hr SCS TR-55 DA A Full Buildout Inflow Hydrograph.txt volume (cy) 4219.58 routed true time in hours true Hydrograph 3 SCS name: 100yr SCS TR-55 24-hr Design Storm- Full Buildout Area (acres) 7.750 CN 83.000 Type 2 rainfall, P (in) 8.990 time of conc. (hrs) 0.1200 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 65.878 peak time (hrs) 11.922 volume (cy) 7211.198 Page 3 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea A Full Buildout OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 1 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 2 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 3 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Peaks: lyr SCS TR-55 24-hr Design Storm- Full Buildout 1.051 at 12.49 (hrs) 0.125 at 14.57 (hrs) 370.670 at 15.03 (hrs) 523.391 Peaks: 2yr SCS TR-55 24-hr Design Storm- Full Buildout 10.811 at 12.06 (hrs) 2.936 at 12.23 (hrs) 370.813 at 12.23 (hrs) 544.384 Peaks: 10yr SCS 33.674 at 32.520 at 371.401 at 635.483 Peaks: 100yr SCS 65.763 at 66.055 at 371.792 at 700.707 Wed Feb 02 16:45:00 EST 2022 TR-55 24-hr Design 11.94 (hrs) 11.95 (hrs) 11.95 (hrs) Storm- Full Buildout TR-55 24-hr Design Storm- Full Buildout 11.92 (hrs) 11.94 (hrs) 11.94 (hrs) Page 4 Level Spreader 'A' Calculations LEVEL SPREADER 'A' DESIGN (Full Buildout) Per VSMH Chpt. 11, Section 11.5.3 Step 1 Area = 7.75 ac. (Eqn 11.11) Tv= 18,286 cf Q,= 0.65 watershed inches (From Worksheet 2) CN = 83 Step 2 Tc = 0.12 hrs Step 3 la = 0.40 la/P= 0.40 q "= 750 csm/in A= 0.012mi2 q PT ,= 5.9 cfs NOTES: q P, is the Treatment Volume peak discharge, or the peak flow rate for the 1-inch rainfall event. The dry basin's lower / Treatment Volume outfall is set at the basin's floor elevation. Per the VA DEQ Specification #2, page 14, the Level Spreader should be designed per the following: "Where the Conserved Open Space is a mix of grass and forest (or re -forested), establish the Level Spreader length by computing a weighted average of the lengths required for each vegetation type." 90%+/- Native Grasses/groundcover below tree canopy at a LS length of 13 ft per 1 cfs 30%+/- Forest groundcover below tree canopy at a LS length of 40 ft per 1 cfs Site Specific / Weighted Average LS length = 15.7 ft per 1 cfs Min. LS'B' Design Length= 93 ft (94' Proposed) Note: Max. LS Length = 130 ft Min. LS Length = 13 ft Underground Detention System '13' Routing Calculations (Subarea B- Proposed Development) Note: The following routing calculations are for the upper Underground Detention Basin 'B'. These routing calculations were used to generate outflow hydrographs, which were later used for the inflow hydrographs in the lower Dry Detention Basin 'B' routings. Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Proposed Development BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Proposed Development 13 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 371.50 1584.00 0.0 372.00 1584.00 29.3 373.00 2689.00 107.6 374.00 3058.00 213.9 375.00 3272.00 331.1 376.00 3389.00 454.5 377.00 3426.00 580.7 378.00 3389.00 706.9 379.00 3272.00 830.2 380.00 3058.00 947.4 381.00 2689.00 1053.8 382.00 1584.00 1132.0 383.00 1584.00 1190.7 Start_Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice 371.50 Vol.(cy) 0.00 name: Low -Flow Orifice area (sf) 0.545 diameter or depth (in) 10.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 372.000 multiple 2 discharge into riser Page 1 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Proposed Development Outlet structure 1 Orifice name: Emergency Overflow in Weir Plate area (sf) 2.461 diameter or depth (in) 21.240 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 380.170 multiple 1 discharge into riser Outlet structure 2 Weir name: Access Manhole for Inspection diameter (in) 30.000 side angle 0.000 coefficient 3.000 invert (ft) 388.400 multiple 1 discharge into riser Outlet structure 3 Orifice name: Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 371.970 multiple 1 discharge out of riser Outlet structure 4 Orifice name: Emergency Bypass Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 379.500 multiple 2 discharge through dam Page 2 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Proposed Development 3 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS Design Storm Area (acres) 12.160 CN 82.000 Type 2 rainfall, P (in) 3.000 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 18.977 peak time (hrs) 11.961 volume (cy) 2252.353 Hydrograph 1 SCS name: 2-yr 24-hr SCS Design Storm Area (acres) 12.160 CN 82.000 Type 2 rainfall, P (in) 3.630 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 26.016 peak time (hrs) 11.961 volume (cy) 3087.808 Hydrograph 2 SCS name: 10-yr 24-hr SCS Design Storm Area (acres) 12.160 CN 82.000 Type 2 rainfall, P (in) 5.480 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 48.327 peak time (hrs) 11.961 volume (cy) 5735.928 Page 3 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Proposed Development OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr SCS Design Storm inflow (cfs) 18.975 at 11.96 (hrs) discharge (cfs) 8.669 at 12.12 (hrs) water level (ft) 376.342 at 12.12 (hrs) storage (cy) 497.501 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr SCS Design Storm inflow (cfs) 26.014 at 11.96 (hrs) discharge (cfs) 10.516 at 12.14 (hrs) water level (ft) 378.193 at 12.14 (hrs) storage (cy) 731.046 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr SCS Design Storm inflow (cfs) 48.323 at 11.96 (hrs) discharge (cfs) 44.202 at 12.02 (hrs) water level (ft) 381.012 at 12.02 (hrs) storage (cy) 1054.987 Tue Feb 01 11:47:20 EST 2022 Page 4 Underground Detention System 'B' Outflow Hydrographs, Proposed Development (Used for the Lower Dry Detention Basin 'B' inflow hydrographs) Post -Development DA B (Proposed Development) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.00 3.0 0.00 3.5 0.00 4.0 0.00 4.5 0.00 5.0 0.00 5.5 0.00 6.0 0.00 6.5 0.00 7.0 0.00 7.5 0.00 8.0 0.00 8.5 0.00 9.0 0.06 9.5 0.14 10.0 0.22 10.5 0.44 11.0 0.82 11.5 1.64 11.9 6.21 12.0 8.15 12.1 8.67 12.2 8.45 12.3 7.89 12.4 7.22 12.5 6.48 13.0 2.46 13.5 0.77 14.0 0.40 14.5 0.23 15.0 0.16 15.5 0.09 16.0 0.04 16.5 0.01 17.0 0.00 17.5 0.00 18.0 0.00 18.5 0.00 19.0 0.00 19.5 0.00 20.0 0.00 20.5 0.00 21.0 0.00 21.5 0.00 22.0 0.00 22.5 0.00 23.0 0.00 23.5 0.00 24.0 0.00 24.5 0.00 25.0 0.00 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 10 00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 1,0000 Outflow Hydrograph (1-yr Design Storm) 50 loa 15,0 20.0 ssa 3aa 35.0 Post -Development DA B (Proposed Development) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.00 3.0 0.00 3.5 0.00 4.0 0.00 4.5 0.00 5.0 0.00 5.5 0.00 6.0 0.00 6.5 0.02 7.0 0.04 7.5 0.07 8.0 0.09 8.5 0.17 9.0 0.31 9.5 0.40 10.0 0.53 10.5 0.85 11.0 1.39 11.5 2.17 11.9 7.47 12.0 9.78 12.1 10.52 12.2 10.36 12.3 9.86 12.4 9.24 12.5 8.56 13.0 4.74 13.5 1.69 14.0 0.78 14.5 0.53 15.0 0.42 15.5 0.30 16.0 0.21 16.5 0.14 17.0 0.10 17.5 0.07 18.0 0.04 18.5 0.02 19.0 0.00 19.5 0.00 20.0 0.00 20.5 0.00 21.0 0.00 21.5 0.00 22.0 0.00 22.5 0.00 23.0 0.00 23.5 0.00 24.0 0.00 24.5 0.00 25.0 0.00 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 12.60 low am 6.00 4.W 2.00 0.m 200 Outflow Hydrograph (2-yr Design Storm) 0.0 5.0 10.0 150 20.0 250 300 35.0 Post -Development DA B (Proposed Development) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.04 2.0 0.10 2.5 0.13 3.0 0.16 3.5 0.18 4.0 0.21 4.5 0.26 5.0 0.30 5.5 0.37 6.0 0.42 6.5 0.49 7.0 0.54 7.5 0.61 8.0 0.66 8.5 0.85 9.0 1.15 9.5 1.31 10.0 1.56 10.5 2.02 11.0 2.66 11.5 3.83 11.9 10.65 1Lo 44.20 12.1 39.45 12.2 15.93 12.3 11.66 12.4 11.22 12.5 10.69 13.0 7.59 13.5 4.39 14.0 2.17 14.5 1.56 15.0 1.32 15.5 1.09 16.0 0.88 16.5 0.73 17.0 0.65 17.5 0.57 18.0 0.50 18.5 0.43 19.0 0.35 19.5 0.29 20.0 0.22 20.5 0.18 21.0 0.16 21.5 0.14 22.0 0.13 22.5 0.12 23.0 0.11 23.5 0.10 24.0 0.08 24.5 0.00 25.0 0.02 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 50 00 40 00 MOO 20 00 MOO OM -Moo Outflow Hydrograph (10-yr Design Storm) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 Underground Detention System 'B' Routing Calculations (Subarea B- Full Buildout) Note: The following routing calculations are for the upper Underground Detention Basin 'B'. These routing calculations were used to generate outflow hydrographs, which were later used for the inflow hydrographs in the lower Dry Detention Basin 'B' routings. Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Full Buildout BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Full Buildout 13 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 371.50 1584.00 0.0 372.00 1584.00 29.3 373.00 2689.00 107.6 374.00 3058.00 213.9 375.00 3272.00 331.1 376.00 3389.00 454.5 377.00 3426.00 580.7 378.00 3389.00 706.9 379.00 3272.00 830.2 380.00 3058.00 947.4 381.00 2689.00 1053.8 382.00 1584.00 1132.0 383.00 1584.00 1190.7 Start_Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice 371.50 Vol.(cy) 0.00 name: Low -Flow Orifice area (sf) 0.545 diameter or depth (in) 10.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 372.000 multiple 2 discharge into riser Page 1 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Full Buildout Outlet structure 1 Orifice name: Emergency Overflow in Weir Plate area (sf) 2.461 diameter or depth (in) 21.240 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 380.170 multiple 1 discharge into riser Outlet structure 2 Weir name: Access Manhole for Inspection diameter (in) 30.000 side angle 0.000 coefficient 3.000 invert (ft) 388.400 multiple 1 discharge into riser Outlet structure 3 Orifice name: Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 371.970 multiple 1 discharge out of riser Outlet structure 4 Orifice name: Emergency Bypass Outfall to Dry Basin area (sf) 4.909 diameter or depth (in) 30.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 379.500 multiple 2 discharge through dam Page 2 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Full Buildout 3 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS Design Storm Area (acres) 20.080 CN 83.000 Type 2 rainfall, P (in) 3.000 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 32.873 peak time (hrs) 11.961 volume (cy) 3901.652 Hydrograph 1 SCS name: 2-yr 24-hr SCS Design Storm Area (acres) 20.080 CN 83.000 Type 2 rainfall, P (in) 3.630 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 44.732 peak time (hrs) 11.961 volume (cy) 5309.184 Hydrograph 2 SCS name: 10-yr 24-hr SCS Design Storm Area (acres) 20.080 CN 83.000 Type 2 rainfall, P (in) 5.480 time of conc. (hrs) 0.1700 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 82.070 peak time (hrs) 11.961 volume (cy) 9740.817 Page 3 Brookhill Blocks 16-17- Upper UGD System Routing of Subarea B Full Buildout OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of Peaks: 1-yr 24-hr SCS Design Storm inflow (cfs) 32.870 at 11.96 (hrs) discharge (cfs) 15.647 at 12.12 (hrs) water level (ft) 379.960 at 12.12 (hrs) storage (cy) 942.910 Hydrograph 1 Routing Summary of Peaks: 2-yr 24-hr SCS Design Storm inflow (cfs) 44.728 at 11.96 (hrs) discharge (cfs) 39.192 at 12.02 (hrs) water level (ft) 380.854 at 12.02 (hrs) storage (cy) 1039.107 Hydrograph 2 Routing Summary of Peaks: 10-yr 24-hr SCS Design Storm inflow (cfs) 82.062 at 11.96 (hrs) discharge (cfs) 81.203 at 11.98 (hrs) water level (ft) 382.675 at 11.98 (hrs) storage (cy) 1171.587 Tue Feb 01 11:48:48 EST 2022 Page 4 Underground Detention System 'B' Outflow Hydrographs, Full Buildout (Used for the Lower Dry Detention Basin 'B' inflow hydrographs) Part -Development DA B (Full Buildout) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.00 2.0 0.00 2.5 0.00 3.0 0.00 3.5 0.00 4.0 0.01 4.5 0.02 5.0 0.04 5.5 0.08 6.0 0.11 6.5 0.15 7.0 0.18 7.5 0.22 8.0 0.25 8.5 0.37 9.0 0.56 9.5 0.68 10.0 0.85 10.5 1.26 11.0 1.86 11.5 2.78 11.9 8.54 12.0 10.87 12.1 15.65 12.2 12.10 12.3 11.27 12.4 10.67 12.5 10.02 13.0 6.40 13.5 2.77 14.0 1.23 14.5 0.84 15.0 0.69 15.5 0.53 16.0 0.40 16.5 0.31 17.0 0.26 17.5 0.20 18.0 0.17 18.5 0.12 19.0 0.08 19.5 0.05 20.0 0.02 20.5 0.01 21.0 0.00 21.5 0.00 22.0 0.00 22.5 0.00 23.0 0.00 23.5 0.00 24.0 0.00 24.5 0.00 25.0 0.00 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 is 00 1600 la ao 12M 10 ao am s.ao a ao ao 000 200 00 Outflow Hydrograph (1-yr Design Storm) so 10,0 150 20.0 25.0 30.0 35.0 Part -Development DA B (Full Buildout) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (ds) 0.0 0.00 0.5 0.00 1.0 0.00 1.5 0.01 2.0 0.05 2.5 0.08 3.0 0.11 3.5 0.13 4.0 0.15 4.5 0.20 5.0 0.24 5.5 0.29 6.0 0.34 6.5 0.40 7.0 0.45 7.5 0.52 8.0 0.56 8.5 0.73 9.0 1.01 9.5 1.16 10.0 1.40 10.5 1.88 11.0 2.45 11.5 3.61 11.9 10.18 ILO 39.19 12.1 28.74 12.2 15.07 12.3 11.59 12.4 11.12 12.5 10.56 13.0 7.35 13.5 4.05 14.0 2.03 14.5 1.39 15.0 1.17 15.5 0.95 16.0 0.77 16.5 0.63 17.0 0.56 17.5 0.48 18.0 0.42 18.5 0.35 19.0 0.29 19.5 0.23 20.0 0.16 20.5 0.13 21.0 0.11 21.5 0.10 22.0 0.09 22.5 0.08 23.0 0.07 23.5 0.06 24.0 0.05 24.5 0.00 25.0 0.00 25.5 0.00 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 4s o0 40.00 35 00 3000 25.00 20.00 ss.00 1000 500 000 50000 Outflow Hydrograph (2-yr Design Storm) 50 10,9 150 20.0 25.0 30.0 35.0 Part -Development DA B (Full Buildout) Outflow Hydrograph From UGD B's Routings Time (h.) Outflow (cN) 0.0 0.00 0.5 0.00 1.0 0.39 1.5 0.52 2.0 0.57 2.5 0.62 3.0 0.68 3.5 0.73 4.0 0.78 4.5 0.88 5.0 0.96 5.5 1.08 6.0 1.17 6.5 1.29 7.0 1.38 7.5 1.51 8.0 1.58 8.5 1.84 9.0 2.15 9.5 2.37 10.0 2.68 10.5 3.30 11.0 4.20 11.5 5.83 11.9 63.62 Izo 81.20 12.1 52.80 12.2 24.24 12.3 15.64 12.4 12.24 12.5 11.53 13.0 9.36 13.5 6.89 14.0 4.52 14.5 2.95 15.0 2.43 15.5 2.16 16.0 1.92 16.5 1.69 17.0 1.56 17.5 1.42 18.0 1.31 18.5 1.18 19.0 1.04 19.5 0.92 20.0 0.78 20.5 0.70 21.0 0.66 21.5 0.64 22.0 0.61 22.5 0.59 23.0 0.56 23.5 0.54 24.0 0.51 24.5 0.00 25.0 0.62 25.5 0.36 26.0 0.00 26.5 0.00 27.0 0.00 27.5 0.00 28.0 0.00 28.5 0.00 29.0 0.00 29.5 0.00 30.0 0.00 30.5 0.00 31.0 0.00 90 00 MOO 20 00 6000 50 00 c0 00 30 00 MOB 10 a0 OM -Moo 0'0 Outflow Hydrograph (10-yr Design Storm) 5.0 10.0 15.0 20.0 25.0 30.0 35.0 Dry Detention Basin 'B' Routing Calculations (Subarea B- Proposed Development) Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Proposed Development BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Proposed Development 8 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 350.00 2672.00 0.0 352.00 3816.00 239.0 354.00 5127.00 569.1 356.00 6609.00 1002.6 358.00 8268.00 1552.4 360.00 10105.00 2231.8 362.00 12089.00 3052.7 364.00 14178.00 4024.5 Start—Elevation(ft) 4 Outlet Structures Outlet structure 0 Orifice 350.00 Vol.(cy) 0.00 name: Barrel area (sf) 7.069 diameter or depth (in) 36.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 346.500 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low -Flow Orifice area (sf) 0.017 diameter or depth (in) 1.750 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 350.000 multiple 1 discharge into riser Page 1 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Proposed Development Outlet structure 2 Weir name: Riser diameter (in) 60.000 side angle 0.000 coefficient 3.300 invert (ft) 361.330 multiple 1 discharge into riser transition at (ft) 1.519 orifice coef. 0.500 orifice area (sf) 19.635 Outlet structure 3 Weir name: Emergency Spillway length (ft) 50.000 side angle 75.964 coefficient 3.300 invert (ft) 362.330 multiple 1 discharge through dam Page 2 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Proposed Development 4 Inflow Hydrographs Hydrograph 0 Curve name: 1-yr SCS TR-55 24-hr Design Storm- Proposed Development time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 1yr 24hr SCS TR-55 DA B Proposed Buildout Inflow Hydrograph.txt volume (cy) 1488.31 routed true time in hours true Hydrograph 1 Curve name: 2-yr SCS TR-55 24-hr Design Storm- Proposed Development time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 2yr 24hr SCS TR-55 DA B Proposed Buildout Inflow Hydrograph.txt volume (cy) 2239.91 routed true time in hours true Hydrograph 2 Curve name: time incr (minlhrs) time limit (minlhrs) file: Hydrograph.txt volume (cy) routed time in hours Hydrograph 3 SCS name: Area (acres) CN Type rainfall, P (in) time of conc. (hrs) time increment (hrs) time limit (hrs) fudge factor routed peak flow (cfs) peak time (hrs) volume (cy) 10-yr SCS TR-55 24-hr Design 0.01 720.00 Storm- Proposed Development 10yr 24hr SCS TR-55 DA B Proposed Buildout Inflow 5049.20 true true 100-yr SCS TR-55 24-hr Design Storm 12.160 82.000 2 8.990 0.1700 0.0200 30.000 1.00 true 93.637 11.961 11113.730 Page 3 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Proposed Development OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 1 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 2 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 3 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Peaks: 1-yr SCS 8.669 at 0.182 at 357.453 at 1389.752 Peaks: 2-yr SCS 10.516 at 0.206 at 359.566 at 2072.767 Peaks: 10-yr SCS 44.202 at 9.144 at 361.639 at 2893.660 TR-55 24-hr Design 12.12 (hrs) 13.95 (hrs) 14.84 (hrs) TR-55 24-hr Design 12.14 (hrs) 14.53 (hrs) 15.96 (hrs) Storm- Proposed Development Storm- Proposed Development TR-55 24-hr Design Storm- Proposed Development 12.02 (hrs) 12.62 (hrs) 12.62 (hrs) Peaks: 100-yr SCS TR-55 24-hr Design Storm 93.629 at 11.96 (hrs) 89.261 at 11.98 (hrs) 362.559 at 11.98 (hrs) 3308.932 Thu Oct 07 14:06:51 EDT 2021 Page 4 Dry Detention Basin 'B' Routing Calculations (Subarea B- Full Buildout) Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Full Buildout BasinFlow printout INPUT: Basin: Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Full Buildout 8 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 350.00 2672.00 0.0 352.00 3816.00 239.0 354.00 5127.00 569.1 356.00 6609.00 1002.6 358.00 8268.00 1552.4 360.00 10105.00 2231.8 362.00 12089.00 3052.7 364.00 14178.00 4024.5 Start—Elevation(ft) 4 Outlet Structures Outlet structure 0 Orifice 350.00 Vol.(cy) 0.00 name: Barrel area (sf) 7.069 diameter or depth (in) 36.000 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 346.500 multiple 1 discharge out of riser Outlet structure 1 Orifice name: Low -Flow Orifice area (sf) 0.020 diameter or depth (in) 1.938 width for rect. (in) 0.000 coefficient 0.500 invert (ft) 350.000 multiple 1 discharge into riser Page 1 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Full Buildout Outlet structure 2 Weir name: Riser diameter (in) 60.000 side angle 0.000 coefficient 3.300 invert (ft) 361.330 multiple 1 discharge into riser transition at (ft) 1.519 orifice coef. 0.500 orifice area (sf) 19.635 Outlet structure 3 Weir name: Emergency Spillway length (ft) 50.000 side angle 75.964 coefficient 3.300 invert (ft) 362.330 multiple 1 discharge through dam Page 2 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Full Buildout 4 Inflow Hydrographs Hydrograph 0 Curve name: 1-yr SCS TR-55 24-hr Design Storm- Full Buildout time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 1yr 24hr SCS TR-55 DA B Full Buildout Inflow Hydrograph.txt volume (cy) 3036.95 routed true time in hours true Hydrograph 1 Curve name: 2-yr SCS TR-55 24-hr Design Storm- Full Buildout time incr (minlhrs) 0.01 time limit (minlhrs) 720.00 file: 2yr 24hr SCS TR-55 DA B Full Buildout Inflow Hydrograph.txt volume (cy) 4607.74 routed true time in hours true Hydrograph 2 Curve name: time incr (minlhrs) time limit (minlhrs) file: volume (cy) routed time in hours Hydrograph 3 SCS name: Area (acres) CN Type rainfall, P (in) time of conc. (hrs) time increment (hrs) time limit (hrs) fudge factor routed peak flow (cfs) peak time (hrs) volume (cy) 10-yr SCS TR-55 24-hr Design Storm- Full Buildout 0.01 720.00 10yr 24hr SCS TR-55 DA B Full Buildout Inflow Hydrograph.txt 10503.70 true true 100-yr SCS TR-55 24-hr Design Storm 20.080 83.000 2 8.990 0.1700 0.0200 30.000 1.00 true 157.411 11.961 18682.996 Page 3 Brookhill Blocks 16-17- Lower Dry Basin Routing of Subarea B Full Buildout OUTPUT: Routing Method: storage -indication Hydrograph 0 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 1 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 2 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Hydrograph 3 Routing Summary of inflow (cfs) discharge (cfs) water level (ft) storage (cy) Peaks: 1-yr SCS 15.647 at 0.273 at 361.120 at 2673.314 Peaks: 2-yr SCS 39.192 at 7.752 at 361.605 at 2878.774 Peaks: 10-yr SCS 81.203 at 75.323 at 362.488 at 3275.557 TR-55 24-hr Design 12.12 (hrs) 14.41 (hrs) 15.16 (hrs) TR-55 24-hr Design 12.02 (hrs) 12.82 (hrs) 12.82 (hrs) Storm- Full Buildout Storm- Full Buildout TR-55 24-hr Design Storm- Full Buildout 11.98 (hrs) 11.99 (hrs) 11.99 (hrs) Peaks: 100-yr SCS TR-55 24-hr Design Storm 157.397 at 11.96 (hrs) 157.153 at 11.96 (hrs) 362.835 at 11.96 (hrs) 3439.686 Thu Oct 07 14:02:43 EDT 2021 Page 4 Subarea C's Analysis of the Storm Sewer System (For Subarea C's Channel & Flood Protection Compliance) This analysis shows the 10-year hydraulic grade lines do not overtop the inlets, and the pipes are adequately sized for their runoff, hereby confirming the 10-year design storm is confined within the stormwater conveyance system. Also, the runoff is not erosive on concrete lined pipes and manmade riprap located in the stream's bed. Table 8: Pipe Design Table PIPE DESIGN n=0.013 for RCP n=0.01 for HDPE Pipe Hydrology Pipe y Lip! R, run: 4B -Out 4B 4 0.23 O.W 0.138 0.138 5.W 6.67 0.92 0.6 3W.W 3W.10 40.2 0.01 0."7 15 4.68 2.37 0.28 4 BB 0.29 O.W 0.145 0.2W 6.W 6.W 0.92 0.76 3W.W 345.W 117.4 0.01 0.OW3 15 12.64 5.54 0.35 BB K 0.22 O.W 0.110 0.543 6.W 6.25 0.69 1.64 345.W 344.43 64.9 0.01 0.0088 15 6.06 4.16 0.26 B7 B6 0.14 0.81 0.113 1.OW 6.61 6.18 0.70 4.97 344.33 343.10 111.2 0.01 0.0111 15 6.81 6.04 0.31 B6 B5 0.20 0.69 0.138 1.218 8.92 6.09 O.B4 5.74 343.W 342.2r 43.5 0.01 0.01W 15 8.37 7.32 0.10 B5 B3 0.16 0.W 0.109 1.518 7.02 6.W 0.W 7.73 342.17 U1.Q 48.3 0.01 0.0155 15 8.04 7.46 0.11 B3 B2 0.W 0.90 0.000 1.548 7.13 6.03 O.W ]]3 338.33 337.52 21.5 0.01 0.03r8 15 12.% 10.71 0.W B2 OUT 0.W 0.90 0.000 1.548 7.16 6.02 O.W )]3 337d2 336.W 41.3 0.01 0.0223 15 9.65 8]1 0.08 Pipe run: B4-B5 B4 I B5 0.29 0.76 0.220 0.220 6.W 6.W 1.40 1.40 342.W 342.2r 13.2 0.01 0.0235 15 9.90 5.65 0.04 P" run: B9-B8 B9 I W 0.25 O.W 0.1W 0.1W 6.W 8.35 0.95 0.95 348.W 348.W 71.4 0.01 0.0116 15 6.W 3.88 0.31 Pipe run: B10-B7 B10 I K 0.53 O.W 0.424 0.424 6.W 6.35 2.69 2.69 349.W W.% 119.6 0.01 0.02W 15 9.W 6.73 0.W Hydraulic Grade Line Calculation Design Year: 10 Protect: BH Blks 16-17 Job #: 182150 Prepared by: FGM, PE •RIM— • •, •,I Sf. Af MCTM•..�YNAIINLFT—WAM zw V. Ho • Hydraulic Grade Line Page I Storm Sewer Analysis of the SWM Facilities' Outfalls Table 8: Pipe Design Table PIPE DESIGN n=0.013 for RCP n=0.01 for HDPE Pipe Hydrology Pipe Lip! N Pipe run: St, A8 (Dry DetenWn S,*rn'A') - ON AB A6 ].]5 0.65 5.038 5.038 7.W 6.07 30.56 26.67 366.55 359.89 WA 0.01 O.OnO 30 12330 19A5 OAS A6 Ad 0.00 0.90 0.000 5.038 ].OS 6.05 O.00 26.67 359.M 359.09 160.0 0.01 O.W 30 3].]O 8.33 0.28 Ad P2 0.00 0.90 0.000 5.038 7.33 5.98 0.00 26.67 359.89 358.71 56.9 0.01 0.W 30 31.62 ].1] 0.13 P2 OI 0.00 0.90 0.000 5.038 7.d6 5.95 O.00 26.67 358.61 35 M 71.9 0.01 O.O 30 3].]O 8.33 0.16 RM run: Dry Detent'ron Basin'B'- Out BB6 BM 0.00 o.90 0.O 0.000 5.00 6.67 0.00 75.32 316.59 365.10 82.8 0.01 0.0130 36 98.86 15.v OA9 BM BB2 0.00 0.90 0.000 0.000 5.09 6.66 0.00 75.32 366.65 363.66 68.1 0.01 0.0210 36 125.65 18.67 0.% BB2 OUT 0.00 0.90 O.O 0." 5.13 6.62 O.00 75.32 363.16 363.00 7.9 0.01 0.0 3fi 122b2 18.15 0.01 Plpe mn: Str. AB (Dry DetentWn Syatem'A') - level Spreader AB L3 ].]5 0.65 1 5.0. 5.038 7.00 6.07 30.56 5.85 362.80 362.61 SB.8 0.01 O.O O 15 5.86 5A6 0.18 Hydraulic Grade Line Calculation Design Year: 10 Protect: BH Blks 16-17 Job #: 182150 Prepared by: FGM, PE INLET STATION OUTLET WATER' SURFACE ELEV Lo j a oI Nfa r ZW V. Ho QJN VIN Q; V, V 2g H, ANGI F H, Ht 13H 5Ht FINAL H INLET WATER 1 SURFACE ELEV RIM ELEV A8 0.00 180 0.00 0.11 NA 0.06 0.31 362.32 370.75 345.40 7.85 36 75.32 0.011 0.09 10.7 0.4 BB2 75.3 10.7 802.603 1.8 0.62 0 0.00 1.06 N/A 0.53 IA9 346.59 348.00 346.59 4805 36 75.32 OOLI 0.52 10.7 0A BB4 75.3 10.7 802.603 L8 0 62 0 0 00 1 06 N/A 0.53 1.19 347.77 357.33 347.80 82.80 36 75.32 0.O11 0.90 10.7 0.4 BB6 0.00 0 000 0A4 NA 0.22 1.19 348.99 361.33 300.25 71.92 30 26.67 0.004 0.26 5.4 0.1 A2 26.7 5A 144.907 O.5 0.16 0 0 028 N/A OA4 0.40 36065 362.35 360.71 56.88 30 26 67 0 004 020 5.4 0.1 A4 26.7 SA 144.907 0.5 0.16 91 0.3209 0.60 N/A 0.30 0.50 36121 363.70 361.21 14000 30 26 67 0O04 0.50 5.4 0.1 A6 26.7 5A 144.907 O.5 0.16 147 0.3209 0.60 N/A 0.30 0.80 36202 369.20 362.02 60A0 30 26 67 0 004 022 5A 0.1 A8 0.00 1 180 1 0 1 0.11 1 NA 0.06 1 0.31 362.32 370.75 Hydraulic Grade Line Page I Riprap Lined Outlet Protection Calculations OttrL-eT PPoT cr:Ca-u 'CJESY(:4j �; �jU6ARCcA R liiE Fo•uawluG cALcuNT8at1y [o NSE�.`J +-`-Ly N•'S4\At4E TIE L_c-vEL s'('Ri;.AdErA's LAW-Ftcw �i.�il xs CLo66Gn ANO ALL Rw.mi-� zs (tn.arc�9 '� TxE ourr-nu-/ @aT.Sr QXo'TE<.r;(CN % qe' a4.'35 cT-s CP0.aPn5Ed 1�wN�� oa,36w _ LAO crs CQkovieycS A FACV aG SAFE) PCB C�p�E 3.\g-1 , �fPTH OF S�sNE, d = 1:5 x STor r 'pmAkrZTER, 8\AtS%M L6S" C riPrA� 6'; x TW ) ��03.AM4TEK 'p FR Vr'�SCFt `�!-PGCE 3.1$-�1 Aso = aHowr��6R C1S0 M-t Nsrtvx R,CLU,vNE.vdG. e) a Fj�� M rN4 AvA IZ006N Lp t Vg Q.4 LA) 'pvwnc 6%- �Ua.16-17 l'A IaMaC RE.n�4 ON s�glsl R&,0&0,P- 7/30IilI {'LvvS40 1`14 'A\t4i'dN eo-1-Go a+ 'o ILI I;ra �NiTM A K1Ar. 9-cc�^410 6Nl VO)m CLP S Al, 't-G-1 STCNE 35 QRC9?a40 \�So- 0. / i�1c�a.EccR a Si Z FZWAL t'CUCaJ 35 vpaT c L., A9 Co-t kVAPR P wi,K A 00'rR aF �8" clx do� Ae'+7 T� FiL•TE, fA09PZc. v+.V1<caLAYKE.h'f, RzQaaa -ro'8t FLAT, 64' LCArd; &" N�Avc u.zsD7M5 CAT QgP£ Ov-,KAL`} AnAn 16' Cp, t W ow c-" L6T QRdi rccT.y aN, . S UQA(LE JL QlA' q,lW crs C?ACNUF aft SA^J X PioE Qt.ATFALL 'OaAAln IGA = -Y TW > VaL CUAMETEIL LP = 36' Oes�u 11c*wv�A Ma.N : (ieea+Ar�bae4En d,+` 6", eL, AS, EC-1 STCNE C3 iaj 01*OyL'� '4 Fx NA6. "gE5ei4tl Si V CL. A1, ��^L RiVAAP w' N A �Vo 4�P- lu" At,*D A •�S+-'[a' h uNr)C0.60.4ACAaC , PYeaAP Tt+ 3t 'FLAT I V'� (,.ON('r NO NAvE w'C.iittl5 of i' Cac PC@� cv:rf.ALL, ANO A7/ (KT ENO OF OBIT L0T TXOA*&. o\)) I Z� N DESIGN OF OUTLET PROTECTION FROM A ROUND PIPE FLOWING FULL MAXIMUM fAILWATER CONDITION TM 0.5 DIAMETER) 110 00, Pi outlet —T Min Tw - Do + 0.4La a P Diameter DO La 90 SDO 70 Ok 60 so leo"AA I _ 30 20 Reco�nded Min. 0. Wd 109 1 2 0 �0 go lio, 120 T 50 T 100 200 500 Discharge, ft?/sec. L Cl 2 ai Virginia Runoff Reduction Method Water Quality Calculations (For the Proposed Plan) This analysis is for the proposed plan and shows its water quality compliance. Please note, the level spreader was designed for the more stringent final buildout's higher treatment volume. The final buildout's higher treatment volume can be viewed in the next section entitled ' Reduction Method Water Quality Calculations (For the Final Buildout)'. MQWgIMn RumlyReJURM MCMotl New Qevebpmem Canpffi—SpeatlsM1eel-Ven n30 ❑ W21 BMV Standards and Spe flcns M1013 Mal WManHWsx SpaMlulbns vmlett Name: BrookHill Blocks 1&17 lVroiwsed %an) l wce: 1/0/303 amvoearyn spxipanimrstist M1302h5tds LSpe Site Information PoSt-Development Project (Treatment Volume and loads) lamQw laveal •Soik I Biala I cLk I soih myay.�svwlaeal-v s.as uexr/eceeavazmeerxeuee Nne iws �aio+*asl+aeal-eewxe. eraemim ss.sl m,a/ma.agae ss.n ary tavi Ral g034 v1.Ta coniar dllaneal 43 ml.maal �altvl EMclmn/0 0.16 ganlSMggaLlme/Il Leh was llMwreMl a.al Pj lunl nenknfxtnl 090 Forert/openspaa Lorerlxrea) s.as WngM1bi Prlf^rert) 0.03 %forert I>% ManaptlTuh(merlaresl 13.51 WeyMetl R,(tl l 010 %FUnagtlTud a9% I,w-Lover laved go.>a Pr(mceMousl 095 %Impemw¢ 3a% sra area lxreal Bv>0 Runo Goo fideMs IRvl 003 T emvw.me lamanl ] 111a Tres M.mvm.melatian.sl ae,e91 Te bae llh/yal 3pZ dm�atamra®Ik lun daYiuulle O�eMW MeP w�mnm��mam�xm� noa A1w SWmvxMV BeM Man en�Rm[M:ee RR�RwaXReNMan eeµ�n mn. enlM SIN µIM vm..IM •� w 0000 000� 00000 00000 00©00 0©000 am000 0�000 00000 00000 ©0000 00000 00000 00000 00000 00000 0000m 00000 00000 oo��® 00000 0©000 Site Results (Water Quality Compliance) Area Checks D.A. A DA. B D.A. C D.A. D D.A. E AREA CHECK FOREST/OPEN SPACE (ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac) 3.68 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED (ac) 3.68 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA (ac) 2.69 0.00 0.00 0.00 0.00 OK. MANAGEDTURFAREATREATED(ac) 2.69 0.00 0.00 0.00 0.00 OK. AREA CHECN Site Treatment Volume (ft') 0 Runoff Reduction Volume and TP By Drainage Area D.A. A DA. B D.A. C D.A. D D.A. E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED (ft)jj 10,983 0 0 0 0 10,983 TP LOAD AVAILABLE FOR REMOVAL (Ib/yr) 9.20 0.00 0.00 0.00 0.00 9.20 TP LOAD REDUCTION ACHIEVED (Ib/yr) 6.89 0.00 0.00 0.00 0.00 6.89 TP LOAD REMAINING (Ib/yrl 2.31 0.00 0.00 0.00 0.00 2.31 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 49.31 0.00 0.00 0.00 0.00 49.31 Total Phosphorus FINAL POST -DEVELOPMENT TP LOAD (Ib/yr) 30.72 TP LOAD REDUCTION REQUIRED (Ib/yr) 17.72 TP LOAD REDUCTION ACHIEVED (Ib/yr) 6.89 TP LOAD REMAINING (Ib/yr): 23.83 REMAINING TP LOAD REDUCTION REQUIRED (Ib/yr): 10.83 Total Nitrogen (For Information Purposes) POST -DEVELOPMENT LOAD(Ib/yr) 219.75 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 49.31 REMAINING POST -DEVELOPMENT NITROGEN LOAD (Ib/yr) 170.44 Virginia Runoff Reduction Method Water Quality Calculations (For the Final Buildout) This analysis was used to obtain the more stringent/larger design treatment volume for the level spreader. Since the final buildout of Brookhill will likely introduce additional impervious areas & runoff directed to the level spreader with the construction of the future Block 18, the level spreader was overdesigned with this plan to meet the following final buildout's requirements. Please see the previous section entitled 'Virginia Runoff Reduction Method Water Quality Calculations (For the Proposed Plon)' for this plan's water quality compliance. umInWA as n mmm.m.rw�.a �ea�emnn rwnmMm�*mmmx ..nuaetl�l wn SermwaterR lMana mem R.I. IRR = R..W R uRbnj urvy.a�. v n ur r�inwY ue�a�ev vev amrme Pe[tln mn 4man mry MCMervr prvnM1w rv'a nm[� �[MoNry arveiN eln�a'W`amlK�vn�rin�ven.IMle R_ All �o��00000mmmm� �o��00000mmmm� o��00000mmmm� �o��00000mmmm� 11. all o��0000ammmm� o��0000®mmmm� w.,Po �o��0000©mmmm� o��00000mmmm� ®��0000®mmmm� 0��00000m�mm� ®m�mm ommmm ommmm ommmm ommmm mmmmm M, ommmm ommmm ommmm ©m�mm ommmm ommmm ommmm