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HomeMy WebLinkAboutWPO202100057 Calculations 2021-12-13Pantops Shopping Center Enterprise Car Wash STORMWATER MANAGEMENT CALCULATIONS PACKET Date of Calculations December 13, 2021 SCOTT/R. CULLIN: Lic. No. 035791 12/13/21 PREPARED BY: COLLINS ENG11,1I=ERING 200 GARRETT STREET, SUITE K CHARLOTTESVILLE, VA 22902 434.293.3719 PH 434.293.2813 FX www.collins-engineering.com SCS TR-55 Calculations (Note, all of the areas and land covers listed for the SCS Method stormwater quantity computations differ with the VRRM Method computations for stormwater quality. This is because drainage areas differ from limits of disturbance. Drainage Areas do encompass the entirety of the limits of disturbance) Soils Mapping (Source: NRCS Web Soil Survey Online Database) Soils Table (Source: NRCS Web Soil Survey Online Database) Albemarle County, Virginia (VA003) Albemarle County, Virginia (VA003) 0 Map Unit Percent of Symbol Map Unit Name Act 71C Rabun clay 14.3% loam, 7 to 15 percent slopes 88 Udorthents, 85.7% loamy, 2 to 25 percent slopes Totals for Area of 100.0% Interest Note: The NRCS web soil survey has catorgized this parcel's soil types as having primarily type D soils. As a result, the following calculations take this into consideration. Precipitation Data (Source: NOAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14 Point Precipitation Frequency Estimates) e � TertaF // 6 4 I oQ� I I I , Y I I 1 I I 1 I Qa 1 - �WOm Ploe_maL — SOOR ' POINT PRECIPITATION FREQUENCY (PF) ESTIMATES WIT" WA CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION NOAAAIIas 14. Volume 2, Version I PDSbased precipitation frequency estimates with 90% confidence Intervals (in Inches)l AvaaOe recullenca interval (yeas) auane"0+ 00 10 0® 1W 2W ® 1069 2441r (2.T2J;/0) (UW4.12) (4.208-26) (4 5-6.20) (6.04] W) (6: 68.80) p5 --00.1) (9.01a-11.6) 1 (106- 3.0) 1 (118-157) SCS TR-55 Calculations and Pre -Development Hydrographs U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 2: Runoff Curve Number and Runoff Project: Enterprise Car Rental Designed By: LMW, PE Location: Pantops Shopping Center Checked By: SRC, PE Check One: Present X Developed X 1. Runoff curve Number (CN) FL-ENG-21A 06/04 Date: 12/13/2021 Date: 12/13/2021 Cover description CN (weighted) _Calculated Drainage Area Soil name and hydrologic (Cover type, treatment, and hydrologic condition; percent CN Area Product of CN total product/ 'S' Description group (Appendix A) impervious; unconnected/ connected impervious area ratio) (Acres) x Area total area Value ON DA A Impervious Areas 98 0.13 13.0 (Pre-ReDev.) B Woods & Grass Combo in Good Condition 58 0.09 5.2 69 4.41 Lawns in Good Condition (75%+Groundcover) 61 0.33 20.0 Impervious Areas 98 0.38 37.3 ON DA A B Woods & Grass Combo in Good Condition 55 0.00 0.0 87 1.55 (Post-ReDev.) Lawns in Good Condition (75%+Groundcover) 61 0.17 10.4 EX PARKING LOT Impervious Areas 98 1.72 168.6 DRAINAGE B Woods & Grass Combo in Good Condition 55 0.00 0.0 98 0.25 (For Pipe Outfall) Lawns in Good Condition (75%+Groundcover) 61 0.02 1.2 2. Runoff 1-Year Storm 2-Year Storm 10-Year Storm 300-Year Storm Drainage Area Description Frequency -years 1 2 10 100 n/a Rainfall, P (24 hour)- inches 3.03 3.67 5.54 9.11 n/a Runoff, Cl- inches 0.70 1.08 2.39 5.36 ON DA A (Pre-ReDev.) Runoff, Cl- inches 1.73 2.30 4.03 7.48 ON DA A (Post-ReDev.) Runoff, Cl- inches 2.75 3.39 5.25 8.82 EX PARKING LOT DRAINAGE (For Pipe Outfall) U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 3: Time of Concentration (TJ or Travel Time (Tt) Project: Enterprise Car Rental Location: Pantops Shopping Center Check One: Present X Developed X Check One: Tc X Tt Designed By: UMW, PE Checked By: SRC, PE Through subarea n/a ON DAA ON DAA (Pre-ReDev.) (post - Segment ID: Sheet Flow: (Applicable to T. only) 1 Surface description (Table 3-1) Smooth Surface Smooth Surface 2 Manning's roughness coeff., n (Table 3-1 0.011 0.011 3 Flow length, L (total L < 100) (ft) 13 12 4 Two-year 24-hour rainfall, Pz (in.) 3.7 3.7 5 Land slope, s (ft/ft) 0.02 0.02 6 Compute Tt = [0.007(n•L)o.8] / Pz .5 s.a 0.00 0.00 Shallow Concentrated Flow 7 Surface description (paved or unpaved) Unpaved Paved 8 Flow Length, L (ft) 110 132 9 Watercourse slope, s (ft/ft) 0.080 0.027 10 Average velocity, V (Figure 3-1) (ft/s) 4.5 3.3 11 Tt=L/3600•V 0.01 0.01 Shallow Concentrated Flow: 7 Surface description (paved or unpaved) 8 Flow Length, L (ft) 9 Watercourse slope, s (ft/ft) 30 Average velocity, V (Figure 3-1) (ft/s) 11 Tt=L/3600•V Channel Flow: 12 Cross sectional Flow area, a (ft) 13 Wetted perimeter, P. (ft) 14 Hydraulic radius, r= a/Pw (ft) 15 Channel Slope, s (ft/ft) 16 Manning's Roughness Coeff, n 17 V= [ 1.49r2"so 5]/n 18 Flow length, L (ft) 19 Tt= L / 3600•V 20 Watershed or subarea T. or Tt (Add Tt in steps 6, 11 and 19) 0.00 0.00 0.10 1 0.10 FL-ENG-21A 06/04 Date: 12/13/2021 Date: 12/13/2021 U.S. Department of Agriculture Natural Resources Conservation Service TR 55 Worksheet 4: Graphical Peak Discharge Method Project: Enterprise Car Rental Designed By: UMW, PE Date: 12/13/2021 Location: Pantops Shopping Center Checked By: SRC, PE Date: 12/13/2021 Check One: Present X Developed X 1. Data Drainage Area Description Drainage Area Description Drainage Area Description ON DAA (Pre-ReDev.) ON DAA (Post-ReDev.) EX PARKING LOT DRAINAGE (For Pipe Outfall) Drainage Area (Am) in miles' 0.0009 0.0009 0.0027 Runoff curve number CN= 69 87 98 Time of concentration(Tc)= 0.10 0.10 0.10 Rainfall distribution type= II II II Pond and swamp areas spread throughout the watershed= 0 0 0 2. Frequency -years 1 2 10 1 2 10 1 2 10 3. Rainfall, P (24 hour)- inches 3.03 3.67 5.54 3.03 3.67 5.54 3.03 3.67 5.54 4. Initial Abstraction, la -inches 0.88 0.88 0.88 0.31 0.31 0.31 0.05 0.05 0.05 5. Compute la/P 0.29 0.24 0.16 0.10 0.08 0.06 0.02 0.01 0.01 6. Unit peak discharge, Qu-am/in Out of Range. See Hydrogmphs for Flows. Routed through Underground Detention Out of Range. See Hydmgraphs for Flows. ]. Runoff, Q from Worksheet 2-inches 0.70 1.08 2.39 1.73 2.30 4.03 2.75 3.39 5.25 8. Pond and Swamp adjustment factor, Fp 1 1 1 1 1 1 1 1 1 9. Peak Discharge, Qp- cfs where Qp-Qu Am Q Fp 0.61 0.91 2.03 0.24 0.83 2.01 7.55 9.30 14.42 WATERSHED SUMMARY FOR (ONSITE) CHANNEL & FLOOD PROTECTION ANALYSIS ON Area, ac. 1-year Flow, cfs 2-year Flow, cfs 10-year Flow, cfs ON DAA(Pre-ReDev.) ON DAA(Post-ReDev.) Existing Parking Lot Drainage i 69 0.55 0.61 0.91 2.03 95 0.55 0.24 0.83 2.01 98 1.74 7.55 9.30 14.42 OUTFALL PIPE ANALYSIS Chi Area, ac. 1-year Flow, cis 2-year Flow, cfs 10-year Flow, ds ON DAA(Post-REDev.) Existing Parking Lot Drainage 87 0.55 0.24 0.83 2.01 98 1.74 7.55 9.30 14.42 Total 7.79 10.13 16.43 1-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am*Q (mi2-in) ONDAA 0.10 0.10 0.29 0.0006 (Pre-ReDev.) Hydrograph Time (hrs.) 1-yr Discharges (cfs) 0.0 0.00 11.0 0.01 11.3 0.02 11.6 0.03 11.9 0.19 12.0 0.39 12.1 0.61 12.2 0.37 12.3 0.13 12.4 0.09 12.5 0.08 12.6 0.06 12.7 0.05 12.8 0.05 13.0 0.04 13.2 0.04 13.4 0.03 13.6 0.03 13.8 0.03 14.0 0.02 14.3 0.02 14.6 0.02 15.0 0.02 15.5 0.02 16.0 0.01 16.5 0.01 17.0 0.01 17.5 0.01 18.0 0.01 19.0 0.01 20.0 0.01 22.0 0.01 26.0 0.00 0.70 0.60 0.50 0.40 0.30 0.20 0.10 SCS TR-55 Pre-ReDevelopment Unit Hydrograph (ON DA A) 5.0 10.0 15.0 20.0 25.0 30.0 Worksheet 5b (Modified for Clarity): Basic watershed Data 2-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am•Q (mil -in) ONDAA 0.10 0.10 0.24 0.0009 (Pre-ReDev.) Hydrograph Time (hrs.) 2-yr Discharges (cfs) 0.0 0.00 11.0 0.01 11.3 0.02 11.6 0.03 11.9 0.23 12.0 0.57 12.1 0.91 12.2 0.54 12.3 0.20 12.4 0.15 12.5 0.13 12.6 0.11 12.7 0.09 12.8 0.08 13.0 0.07 13.2 0.06 13.4 0.05 13.6 0.05 13.8 0.05 14.0 0.04 14.3 0.04 14.6 0.04 15.0 0.03 15.5 0.03 16.0 0.03 16.5 0.02 17.0 0.02 17.5 0.02 18.0 0.02 19.0 0.02 20.0 0.01 22.0 0.01 26.0 0.00 1.00 0.90 0.80 0.70 0.60 0.50 0.a0 0.30 0.20 0.10 0.00 SCS TR-55 Pre-ReDevelopment Unit Hydrograph (ON DA A) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Worksheet 5b (Modified for Clarity): Basic watershed Data 10-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am•Q (mil -in) ONDAA 0.10 0.10 0.16 0.0021 (Pre-ReDev.) Hydrograph Time (hrs.) 10-yr Discharges (cfs) 0.0 0.00 11.0 0.03 11.3 0.05 11.6 0.08 11.9 0.58 12.0 1.28 12.1 2.03 12.2 1.22 12.3 0.45 12.4 0.32 12.5 0.27 12.6 0.23 12.7 0.19 12.8 0.17 13.0 0.15 13.2 0.13 13.4 0.12 13.6 0.11 13.8 0.10 14.0 0.09 14.3 0.08 14.6 0.07 15.0 0.07 15.5 0.06 16.0 0.05 16.5 0.05 17.0 0.05 17.5 0.04 18.0 0.04 19.0 0.04 20.0 0.03 22.0 0.03 26.0 0.00 2.50 2.00 1.50 1.00 0.50 0.00 SCS TR-55 Pre-ReDevelopment Unit Hydrograph (ON DA A) Worksheet 5b (Modified for Clarity): Basic watershed Data 1-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am*Q (mi2-in) EX PARKING LOT 0.10 0.10 0.02 0.0075 DRAINAGE (For Pipe Outfall) Hydrograph Time (hrs.) 1-yr Discharges (cfs) 0.0 0.00 11.0 0.18 11.3 0.25 11.6 0.40 11.9 2.50 12.0 4.84 12.1 7.55 12.2 4.66 12.3 1.62 12.4 1.10 12.5 0.92 12.6 0.78 12.7 0.64 12.8 0.57 13.0 0.49 13.2 0.43 13.4 0.38 13.6 0.34 13.8 0.31 14.0 0.28 14.3 0.25 14.6 0.24 15.0 0.22 15.5 0.19 16.0 0.17 16.5 0.16 17.0 0.15 17.5 0.14 18.0 0.13 19.0 0.11 20.0 0.10 22.0 0.09 26.0 0.00 IWIIIIIIIIIIIII 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 SCS TR-55 Pre-ReDevelopment Unit Hydrograph (Ex Pking DA) 2-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am*Q (mi2-in) EX PARKING LOT 0.10 0.10 0.01 0.0092 DRAINAGE (For Pipe Outfall) Hydrograph Time (hrs.) 2-yr Discharges (cfs) 0.0 0.00 11.0 0.22 11.3 0.31 11.6 0.49 11.9 3.08 12.0 5.96 22.1 9.30 12.2 5.74 12.3 2.00 12.4 1.35 12.5 1.13 12.6 0.96 12.7 0.79 12.8 0.70 13.0 0.61 13.2 0.52 13.4 0.47 13.6 0.42 13.8 0.39 14.0 0.35 14.3 0.31 14.6 0.29 15.0 0.27 15.5 0.24 16.0 0.21 16.5 0.19 17.0 0.18 17.5 0.17 18.0 0.17 19.0 0.14 20.0 0.12 22.0 0.11 26.0 0.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 SCS TR-55 Pre-ReDevelopment Unit Hydrograph (Ex Pking DA) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Worksheet 5b (Modified for Clarity): Basic watershed Data 10-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below Subarea Tc (hrs.) Tt (hr.) la / P Am•Q (mil -in) EX PARKING LOT 0.10 0.10 0.01 0.0143 DRAINAGE (For Pipe Outfall) Hydrograph Time (hrs.) 10-yr Discharges (cfs) 0.0 0.00 11.0 0.34 11.3 0.49 11.6 0.76 11.9 4.77 12.0 9.24 12.1 14.42 12.2 8.90 12.3 3.10 12.4 2.10 12.5 1.76 12.6 1.49 12.7 1.23 12.8 1.09 13.0 0.94 13.2 0.81 13.4 0.73 13.6 0.66 13.8 0.60 14.0 0.54 14.3 0.49 14.6 0.46 15.0 0.41 15.5 0.37 16.0 0.33 16.5 0.30 17.0 0.29 17.5 0.27 18.0 0.26 19.0 0.21 20.0 0.19 22.0 0.17 26.0 0.00 16.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 c SCS TR-55 Pre-ReDevelopment Unit Hydrograph (EX Pking DA) Post -Development Site Hydrographs and Proposed Underground Detention System Analysis (The following routing calculations and outflow hydrographs reflect the post - development attenuation in Subarea A from the proposed underground detention facility) Post -Development DA A (From Underground Detention Routings) Hydrograph Time (hrs.) 1-yr Discharges (cfs) 0.0 0.00 11.0 0.08 11.3 0.09 11.6 0.11 11.9 0.20 12.0 0.23 12.1 0.24 12.2 0.24 12.3 0.24 12.4 0.23 12.5 0.23 12.6 0.23 12.7 0.22 12.8 0.22 13.0 0.21 13.2 0.20 13.4 0.19 13.6 0.17 13.8 0.16 14.0 0.15 14.3 0.12 14.6 0.10 15.0 0.07 15.5 0.05 16.0 0.04 16.5 0.04 17.0 0.04 17.5 0.04 18.0 0.03 19.0 0.03 20.0 0.03 22.0 0.02 26.0 0.00 0.30 0.25 0.20 0.15 0.10 1 0.05 0.00 Outflow Hydrograph (ON DA A) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Post -Development DA A (From Underground Detention Routings) Hydrograph Time (hrs.) 2-yr Discharges (cfs) 0.0 0.00 11.0 0.10 11.3 0.11 11.6 0.12 11.9 0.22 12.0 0.52 12.1 0.83 12.2 0.45 12.3 0.33 12.4 0.27 12.5 0.24 12.6 0.24 12.7 0.23 12.8 0.23 13.0 0.22 13.2 0.21 13.4 0.20 13.6 0.19 13.8 0.18 14.0 0.17 14.3 0.15 14.6 0.13 15.0 0.10 15.5 0.07 16.0 0.06 16.5 0.05 17.0 0.05 17.5 0.05 18.0 0.04 19.0 0.04 20.0 0.03 22.0 0.03 26.0 0.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Outflow Hydrograph (ON DA A) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Post -Development DA A (From Underground Detention Routings) Hydrograph Time (hrs.) 10-yr Discharges (cfs) 0.0 0.00 11.0 0.12 11.3 0.14 11.6 0.16 11.9 1.24 12.0 2.01 12.1 1.61 12.2 1.09 12.3 0.59 12.4 0.43 12.5 0.34 12.6 0.29 12.7 0.26 12.8 0.24 13.0 0.24 13.2 0.23 13.4 0.22 13.6 0.22 13.8 0.21 14.0 0.20 14.3 0.19 14.6 0.17 15.0 0.15 15.5 0.13 16.0 0.10 16.5 0.08 17.0 0.08 17.5 0.07 18.0 0.07 19.0 0.06 20.0 0.05 22.0 0.05 26.0 0.00 2.50 2.00 1.50 1.00 0.50 0.00 Outflow Hydrograph (ON DA A) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 BasinFlow printout INPUT: Basin: Enterprise Car Wash UGD 0 Contour Areas Elevation(ft) Area(sf) Computed Vol.(cy) 2 Storage Pipes Storage pipe 0 name: Detention Pipe diameter (in) 48.000 length (ft) 80.000 invert (ft) 344.000 angle 0.287 volume (cy) 37.234 Storage pipe 1 name: name diameter (in) 48.000 length (ft) 80.000 invert (ft) 344.000 angle 0.287 volume (cy) 37.234 Start—Elevation(ft) 5 Outlet Structures Outlet structure 0 Orifice 344.00 Vol.(cy) 0.00 name: Barrel area (sf) 1.227 diameter or depth (in) 15.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 343.900 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 0.600 invert (ft) 344.000 multiple 2 discharge into riser Outlet structure 2 Orifice name: Mid -Flow Orifice area (sf) 0.292 diameter or depth (in) 6.000 width for rect. (in) 7.000 coefficient 0.600 invert (ft) 346.330 multiple 1 discharge into riser Outlet structure 3 Orifice name: Overflow Weir area (sf) 0.654 diameter or depth (in) 10.950 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 347.600 multiple 1 discharge into riser Outlet structure 4 Orifice name: Emergency Bypass area (sf) 0.785 diameter or depth (in) 12.000 width for rect. (in) 0.000 coefficient 0.600 invert (ft) 347.000 multiple 1 discharge out of riser 4 Inflow Hydrographs Hydrograph 0 SCS name: 1-yr 24-hr SCS TR-55 Design Storm Area (acres) 0.550 CN 87.000 Type 2 rainfall, P (in) 3.030 time of conc. (hrs) 0.1000 time increment (hrs) 0.0200 time limit (hrs) 30.000 fudge factor 1.00 routed true peak flow (cfs) 1.232 peak time (hrs) 11.917 volume (cy) 130.435 Hydrograph 1 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) Hydrograph 2 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) 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) OUTPUT: 2-yr 24-hr SCS 0.550 87.000 2 3.670 0.1000 0.0200 30.000 1.00 true 1.630 11.917 172.599 10-yr 24-hr SCS 0.550 87.000 2 name 2 5.540 0.1000 0.0200 30.000 1.00 true 2.846 11.917 301.344 6.810 0.1667 0.0200 30.000 1.00 false 3.319 11.950 391.230 TR-55 Design Storm TR-55 Design Storm 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 name (not routed) Peaks: 1-yr 24-hr SCS TR-55 Design Storm 1.226 at 11.92 (hrs) 0.241 at 12.12 (hrs) 346.317 at 12.14 (hrs) 39.979 Peaks: 2-yr 24-hr SCS TR-55 Design Storm 1.623 at 11.92 (hrs) 0.826 at 12.06 (hrs) 346.741 at 12.06 (hrs) 49.864 Peaks: 10-yr 24-hr SCS TR-55 Design Storm 2.833 at 11.92 (hrs) 2.008 at 12.02 (hrs) 347.777 at 12.02 (hrs) 70.154 Mon Dec 13 12:16:05 EST 2021 Channel and Flood Protection Compliance 9 VAC 25-870-66 Section B: Channel Protection Utilizing a 1-inch Orifice "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 stormwaterflow 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 13.3.a. In accordance with the following methodology: Q Ano.ee < I.F. * (Q Pre -oe.el.pe ! * (RV Pre-oewloped ) ) / (RV .—I.ped) * Q 1r re.eioped oxsne Q Ano.ee < 7.79 cis Where: QPRoeremped= 0.61 cls (From TR-55) CN PRoeremped= 69 (From Curve Number Summary) S Pre, xvHuped= 4.41 (From SCS TR-55 eq. 2-4) RV Pre -oael.pe!= 0.70 in. (From SCS TR-55 eq. 2-3) A Pm13—loped= 0.55 ac. (From Worksheet4 Watershed Summary) CN Posr-oereloped!= 85 (From Curve Number Summary) S port —loped = 1.76 (From SCS TR-55 eq. 2-4) RV Po,1.1oped= 1.61 in. (From SCS TR-55 eq. 2-3) A oe„eloped = 0.55 ac. (From Worksheet 4 Watershed Summary) I.F. = 0.90 (Factor of Safety) Q P-13—loped Omae= 7.55 cis (From TR-55) Q. eloped = 7.79 cis Section B.4 Limits of Analysis The analysis terminates at Post -Development Subarea A since subsection B.3.a is met. 9 VAC 25-870-66 Onsite Site Outfall #1 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.b.: The point of discharge "releases a postdevelopment peak flow rate for the 10-year 24-hour storm event that is less than the predevelopment peak flow rate from the 10-year 24-hour storm event. Downstream stormwater conveyance systems do not require any additional analysis to show compliance with flood protection criteria if this option is utilized." Pre -Development Onsite DA A + Ex Parking Lot Draiange 10-yr SCS 24-hr Peak Flow (cfs) = 16.45 Post -Development Onsite DA A + Ex Parking Lot Draiange 10-yr SCS 24-hr Peak Flow (cfs) = 16.43 Section C.3 Limits of Analysis The analysis terminates at the Subarea A since subsection C.2.b is met. Existing Outfall Pipe Adequacy Analysis Table S: Pipe Design Table PIPE DESIGN a=0.013 for RCP n=0.01 for HDPE npa Hydrology Pipe n E In LL LL p UGD 3TR1 See SLS Mal i5 and UGD RoNingn M Rmv Cm,..S. 201 30392 3�36] 2]A 001 0.006] 15 5.. •21 011 F. UGD Routing STR.1 OUT 16 d3 303 L5 339.00 Us 001 0.0660 18 N. 1690 0as Frcm SCSHytlre92phs Hydraulic Grade Line Calculation Design Year: l0 Project: Prrterprise Car Wash lob N: 112066 Prepared by. LMW srAwox suxrnceecevi :w .................................... ..., .g ¢ w o� v. o.•n Lo'rz ....n .. . . i3W .xncx x, n �.........', sn ,.. nnu x . 'w�cr WA U. suxrwa 33920 82.63 18 16A3 0.021 1,72 16.9 11 $3R7 2.0 42 8.46 0.3 0.10 0 0 121 1.57 N/A 3.30 342.34467 27.14 15 201 0001 002 4 2 01UGD 31 4.1 127 0.3 0.09 0 0 0.16 0 21 N/A 023 344. Hydraulic Grade Line Page 1 DEQ Virginia Runoff Reduction Method Water Quality Calculations (COMPLIANCE IS MET THROUGH THE BEST MANAGEMENT PRACTICES OF PURCHASING NUTRIENT CREDITS. PLEASE NOTE, THE AREAS SHOWN IN THE VRRM SPREADSHEET ARE DIFFERENT TO THOSE AREAS SHOWN IN THE SCS METHOD CALCULATIONS FOR STORMWATER QUANTITY.) mr, a-, d.od Re-.eme., andamue�pmadomm, - 0 20� Enaft EHMP Stddladd-d Sgamnamon, Projea N-: treumm. .1 .�Io - .., �Ioo,dd, ed. ld"eodi Imear Ded�10,dnv,m PMJ� No Site Information _ Post-Demelopment Project (Treatment Volume and I-oads) Eme, Tmal Di,lu,bad �a. Cha�k un-onv"? No ae.-Imuna. Landeovar Aeol, .�Ik C�11, Deol, �-D-eb;dnena laudd Onnu JaCred Auoll 'V--- .n.n. du... C...deno, (a�) A- .-. 1-1 Cumn, I- a- �d a- I.a XTEMPM—MAMITWOMM S -7-P, . an -u-d .1-1 � an de 023 020 % M­d 11 �2 TIMISMI �Coao -P ona de de .13 ead N.dTuI and M­d- 3ee .11 ell " a :.3, M—A %I-W- me F.-'-- W-1 Oad a.. Tramerwout Volume and Natrona Load TreatMent Volume and NUIrent LOad — u-n—d— ..133 T- V" .32� -t I'll, P.1 D-p-nt -.1 .... . ... .1 el, F F-.. P-t D-­W X. p ­-.7. nI V.1 IV t, L Laul de_,.� .... � d,ed (wo) llh* d", P­ 111d -"ou* d,.I.d lwu== Poet -Development Requirement ftr She Area Site Results (Water Quality Compliance) Area Checks D.A. A D.A. B D.A. C D.A. D D.A. E AREA CHECK FOREST/OPEN SPACE (ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac) 0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED [ac) 0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA (ac) 0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA TREATED (ac) 0.00 0.00 0.00 0.00 0.00 OK. AREA CHECK Site Treatment Volume (ft3) T,aoB Runoff Reduction Volume and TP By Drainage Area RUNOFF REDUCTION VOLUME ACHIEVED (fe)l 0 0 0 0 0 0 TP LOAD AVAILABLE FOR REMOVAL (Ib/yr) D.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REDUCTION ACHIEVED (Ib/yr) D.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REMAINING (Ib/yr) 0.00 0.00 0.00 0.00 11 0.00 0.00 NITROGEN LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 Total Phosphorus FINAL POST -DEVELOPMENT TP LOAD(Ib/yr) 1 0.88 TP LOAD REDUCTION REQUIRED (Ib/yr) 0.46 TP LOAD REDUCTION ACHIEVED (Ib/yr) 0.00 TP LOAD REMAINING (Ib/yr): 0.88 REMAINING TP LOAD REDUCTION REQUIRED (Ib/yr): 0.46