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WPO202100038 Calculations 2022-08-19
Southwood Redevelopment — Village 2 ALBEMARLE COUNTY, VIRGINIA ROAD PLAN, WPO PLAN, & PRELIMINARY SUBDIVISION PLAT DESIGN CALCULATIONS & NARRATIVE JULY 89 2021 REVISED DECEMBER 3, 2021 REVISED APRIL 1, 2022 REVISED AUGUST 11, 2022 s TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Clint Shifflett, PE Timmons Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 434.327.1690 T CLINT W. Z S FFLET a Lic. N 44380 �49: 8/11/2022 G • Table of Contents Section Title 1. Project Narrative 2. LD-204 Inlet Calculations 3. LD-229 Pipe Calculations 4. LD-347 Hydraulic Grade Line Analysis 5. Virginia Runoff Reduction Method Worksheet Summary 6. Nutrient Credit Letter of Availability 7. Wet Pond Routing Calculations Project Narrative: This project includes the construction of two roads, a residential community, and associated utilities and landscaping. The limits of disturbance is 4.88 acres. Water Ouality: The current site is undeveloped. 4.88 acres was analyzed for water quality. The total TP load reduction required is 4.50 lbs/year. There will be 3.07 lbs/year to be treated via wet pond SWM A. The remaining 1.43 lbs/yr of required nutrient credits area shall be purchased from a DEQ-Approved Nutrient Credit Bank in Accordance with VA code 62.1-44.15:35. For the overall Southwood Redevelopment project, this brings the total phosphorous reduction provided on -site to 22.25 lbs/yr, and off -site nutrient credits to 4.10 lbs/yr. 79.61 % of the treatment is being achieved onsite. Water Ouantity The proposed stormwater conveyance system outfall enters a floodplain and discharges runoff into an established channel with less than 1 % of the contributing drainage area, in accordance with 9VAC25-870-66 section C.3. Wetpond SWM A has been analyzed to ensure adequate storage and routing. No further stormwater quantity measures have been provided as part of this development. Energy balance requirements will be met through the use of one wet pond. Flood protection requirements for the 10-year storm will be met by releasing the stormwater into the mapped floodplain, in accordance with 9VAC25-670-66, Section C.3.c. FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 1 OF 3 ROUTE PROJECT SoulhwoodVllage2 DESIGNER: MUD CHECKED: DATE 8/10/2022 UNITS:NGLISH INLET z P a Z xO x 66 " 3 w O`. w �.. F z 3 w 3.. rn± $ U3 ®FFDF 0,zSO �SF��" Se Inlets Only xza Y u m G r o 8 o �❑ ^F N 104 D1-2B 10 O. 120 0.73 0.0876 0.0001RIGHT 0.088 4 0.352 0 0.352 0.0390 0.0208 1.515 2.000 1.3201 0.0833 4.0048 1.000 3.50 0.1458 0.1666 5.325 6.000 1.878 1.000 0.352 0.000 1.514 106 DI-3B 6.000 0.080 0.69 0.0552 OIRIGHT 0.055 4 0.22 0.047 0.267 0.0450 0.0208 1.330 2.000 1.5038 0.0833 4.0048 1.000 3.50 0.1458 0.1666 4.949 6.000 1.212 1.000 0.267 0.000 1.329 108 DI-2B 10 0.180 0.73 0.1314 OIRIGHT 0.131 4 0.524 0 0.524 0.0430 0.0208 1.726 2.000 1.1587 0.0833 4.0048 1.000 3.50 0.1458 0.1666 6.480 6.000 1.543 1.000 0.524 0.000 1.725 110 DI-3B 6.000 0200 0.80 0.16 OIRIGHT 0.16 4 0.64 0 0.640 0.0450 0.0208 1.845 2.000 1.084 0.0833 4.0048 1.000 3.50 0.1458 0.1666 7.145 6.000 0.840 0.963 0.616 0.024 1.844 112 DI-2B 10 0 230 0.67 0.1541 OIRIGHT 0.154 4 0.616 0 0.616 0.0350 0.0208 1.906 2.000 1.0493 0.0833 4.0048 1.000 3.50 0.1458 0.1666 6.521 6.000 L534 1.000 0.616 0.000 1.905 114 DI-3B 6.000 0.070 0.72 0.0504 OIRIGHT 0.05 4 0.2 0 0.200 0.0477 0.0208 1.180 2.000 1.6949 0.0833 4.0048 1.000 3.50 0.1458 0.1666 4.461 6.000 L345 1.000 0.200 0.000 1.180 116 DI-1 2000 0.270 0.42 0.1134 Buk/Lt. 0.0001RIGHT 0.113 4 0.452 0 Buk/Lt. 0 4 0 0 Ahead/Rt. 0.452 0.001 2.000 2 0.452 1 467 T> 4.0 ft 118 DI-1 1.500 0.270 0.56 0.1512 0.0001RIGHT 0.151 4 0.604 0 0.604 0.0314 1.500 1.500 1.000 0.604 0.000 0.1218 BHt =0. 103' 122 DI-3C 6.000 0.090 0.58 0.0522 Buk/Lt. 0.0001RIGHT 0.052 4 0.208 0 0.0050 0.0208 1.827 2.000 1.0947 0.0833 4.0048 3.50 Buk/Lt. 0 4 0 0 Ahead/Rt. 0.208 0.0050 6 0.208 0.534 0.166 0.333 0.4985 2.534 2.141 Weir Flow 124 DI-2B 10 0.170 0.72 0.1224 O'RIGHT 0.122 4 0.488 0 0.488 0.0270 0.0208 1.834 2.000 1.0905 0.0833 4.0048 1.000 3.50 0.1458 0.1666 5.470 6.000 1.828 1.000 0.488 0.000 1.833 126 DI-2B 10 0.340 0.64 0.2176 OIRIGHT 0.218 4 0.872 0 0.872 0.0270 0.0208 3.083 2.000 0.6487 0.0833 4.0048 0.986 3.50 0.1458 0.1647 7.030 6.000 1.422 1.000 0.872 0.000 2.270 128 DI-3B 6.000 0.090 0.80 0.072 OIRIGHT 0.072 4 0.288 0 0.288 0.0409 0.0208 1.393 2.000 1.4358 0.0833 4.0048 L000 3.50 0.1458 0.1666 4.965 6.000 1208 1.000 0.288 0.000 1.392 INLETSOFT BY ENSOFTEC DATE: 8/10/2022 FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 2 OF 3 ROUTE PROJECT SoulhwoodVllage2 DESIGNER: MUD CHECKED: DATE 8/10/2022 UNITS:NGLISH INLET Z F a ❑ o x 3 kzO S w h w z 3 w 3 y rnR oz �z g va a� 'au ❑" Se Inlets Only YCaF F m ¢q o G cm so v S o �❑ ^nF. 132 DI-3B 6.000 0.070 0.73 0.0511 O'RIGHT 0.051 4 0.204 0 0.204 0.0350 0.0208 1.260 2.000 1.5873 0.0833 4.0048 1.000 3.50 0.1458 0.1666 4.099 6.000 1464 1.000 0.204 0.000 1.260 134 DI-3B 6.000 0.050 0.84 0.042 O'RIGHT 0.042 4 0.168 0 0.168 0.0270 0.0208 1.230 2.000 1.626 0.0833 4.0048 1.000 3.50 0.1458 0.1666 3.495 6.000 L717 1.000 0.168 0.000 1.230 136 DI-2B IO 0.090 0.75 0.0675 O'RIGHT 0.068 4 0.272 0 0.272 0.0270 0.0208 1.473 2.000 1.3578 0.0833 4.0048 1.000 3.50 0.1458 0.1666 4.279 6.000 2.337 1.000 0.272 0.000 1.473 138 DI-2B IO 0.290 0.80 0.232 0.00011UGHT 0.232 4 0.928 0 0.928 0.0100 0.0208 4.896 2.000 0.4085 0.0833 4.0048 0.893 3.50 0.1458 0.1511 5.641 6.000 L773 1.000 0.928 0.000 2.722 140 DI-3A 6.000 0.460 0.72 0.3312 Buk/Lt. 0.00011UGHT 0.331 4 1.324 0 0.001 0.0208 10.836 2.000 0.1846 0.0833 4.0048 3.50 Buk/Lt. 0 4 0 0 Ahead/Rt. 1.324 0.001 6 1.324 1.837 0.166 0.333 0.4985 3.837 7.358 T> 8.0 ft 202 DI-1 1.000 0.030 0.70 0.021 O'RIGHT 0.021 4 0.084 0 0.084 0.0600 0.0600 0.817 2.000 2.448 0.0833 1.3883 1.000 2.56 0.1066 0.1666 3.320 1.000 0.301 1.000 0.084 0.000 0.817 204 DI-1 1.000 0.030 0.44 0.0132 O'RIGHT 0.013 4 0.052 0 0.052 0.0500 0.0500 0.706 2.000 2.8329 0.0833 1.666 1.000 2.80 0.1166 0.1666 2.570 1.000 0.389 1.000 0.052 0.000 0.706 206 DI-1 1.000 0.030 0.44 0.0132 O'RIGHT 0.013 4 0.052 0 0.052 0.0500 0.0500 0.706 2.000 2.8329 0.0833 1.666 1.000 2.80 0.1166 0.1666 2.570 1.000 0.389 1.000 0.052 0.000 0.706 208 DI-1 1.000 0.040 0.41 0.0164 O'RIGHT 0.016 4 0.064 0 0.064 0.0500 0.0500 0.764 2.000 2.6178 0.0833 1.666 1.000 2.80 0.1166 0.1666 2.804 1.000 0.357 1.000 0.064 0.000 0.763 210 DI-1 1.000 0.050 0.42 0.021 Buk/Lt. 0.00011UGHT 0.021 4 0.084 0 Buk/Lt. 0 4 0 0 Ahead/Rt. 0.084 0.001 1.000 1 0.084 0.819 T> 8.0 ft 212 DI-1 1.000 0.080 0.44 0.0352 O'RIGHT 0.035 4 0.14 0 0.140 0.0300 1.000 1.000 1.000 0.140 0.000 0.1315 BHt.=0.051' 214 DI-1 1.000 0.080 0.47 0.0376 INLETSOFT BY ENSOFTEC DATE: 8/10/2022 FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 3 OF 3 ROUTE PROJECT SoulhwoodVllage2 DESIGNER: MUD CHECKED: DATE 8/10/2022 UNITS:NGLISH INLET a a 3 w w Fpz. a Qva Se Inlets Only C F Z rnW G �❑ ^FnF. '�YzaF F o cm v S kzO OUz g zk .wi p _ �% �• w 'iz O F m 0.0001RIGHT 0.038 4 0.152 0 0.152 0.0200 0.0300 L253 2.000 1.5962 0.0833 2.7767 1.000 3.28 0.1366 0.1666 3.063 1.000 0.326 1.000 0.152 0.000 L253 216 DI-1 1.000 0.040 0.58 0.0232 ORIGHT 0.023 4 0.092 0 0.092 0.0127 0.0550 L131 2.000 1.7683 0.0833 L5145 1.000 2.68 0.1116 0.1666 2.165 1.000 0462 1.000 0.092 0.000 L130 INLETSOFT BY ENSOFTEC DATE: 8/10/2022 47039-STRM 100 STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: LOCATION: COUNTY: Southwood Village 2 Albemarle Designed by: Checked by: UNITS ENGLISH PIPE NO FROM POINT TO POINT DRAIN. AREA "A" Acre (3) RUNOFF COEFF. "C" (4) CA TOTAL INLET TIME Minutes (7) RAIN FALL In/Hr (8) RUNOFF Q CFS (9) INVERT ELEVATIONS LENGTH of Pipe Ft. (12) SLOPE FOR. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Capacity CFS (15) Friction Slope Ft./Ft. VEL Vn Ft/Sec (16) FLOW TIME Min. (17) REMARKS (18) INCRE- MENT (5) ACCUM- ULATED (6) ADDTL CA UPPER END (10) LOWER END (11) REFERENCE (1) STA. REFERENCE (2) STA. 129 128 126 0.090 0.800 0.072 0.072 0.000 6.000 6.230 0.449 419.738 419.090 32.377 0.020 15.000 Circular 9.894 0.000 4.090 0.132 127 126 124 0.340 0.640 0.218 0.290 0.000 6.132 6.191 1.793 418.994 416.360 175.610 0.015 15.000 Circular 8.568 0.001 5.533 0.529 123 124 122 0.170 0.720 0.122 0.412 0.000 6.661 6.042 2.489 416.156 415.816 34.007 0.010 15.000 Circular 6.996 0.001 5.230 0.108 121 122 114 0.090 0.580 0.052 0.464 0.000 6.769 6.013 2.791 415.620 414.491 56.457 0.020 15.000 Circular 9.894 0.002 6.944 0.135 117 118 1 116 0.270 0.560 0.151 0.151 0.000 0.000 8.901 1.346 420.187 417.640 101.893 0.025 15.000 Circular 11.062 0.000 6.115 0.278 115 116 114 0.270 0.420 0.113 0.265 0.000 0.278 8.717 2.307 417.437 416.850 58.717 0.010 15.000 Circular 6.996 0.001 5.124 0.191 113 114 112 0.070 0.720 0.050 0.779 0.000 6.905 5.976 4.657 411.743 411.141 30.110 0.020 18.000 Circular 16.090 0.002 7.898 0.064 137 138 136 0.340 0.800 0.272 0.272 0.000 6.000 6.230 1.695 415.989 414.220 70.779 0.025 15.000 Circular 11.062 0.001 6.536 0.180 135 136 134 0.090 0.760 0.068 0.340 0.000 6.180 6.177 2.103 411.046 410.450 29.806 0.020 15.000 Circular 9.894 0.001 6.418 0.077 139 140 134 0.460 0.720 0.331 0.331 0.000 0.000 8.901 2.948 409.486 408.620 86.601 0.010 18.000 Circular 11.377 0.001 5.417 0.266 133 134 132 0.050 0.840 0.042 0.714 0.000 6.258 6.155 4.392 408.420 408.086 33.373 0.010 18.000 Circular 11,377 0.001 6.036 0.092 131 132 112 0.070 0.730 0.051 0.765 0.000 6.350 6.129 4.687 407.886 407.253 63.360 0.010 18.000 Circular 11,377 0.002 6.140 0.172 111 112 102 0.230 0.670 0.154 1.698 0.000 6.968 5.959 10.119 407.050 406.628 42.038 0.010 18.000 Circular 11.397 0.008 7.304 0.096 109 110 108 0.200 0.800 0.160 0.160 0.000 6.000 6.230 0.997 425.359 423.990 30.431 0.045 15.000 Circular 14.841 0.000 6.894 0.074 107 108 104 0.180 0.730 0.131 0.291 0.000 6.074 6.209 1.809 423.791 422.100 84.547 0.020 15.000 Circular 9.894 0.001 6.150 0.229 105 106 104 0.080 0.690 0.055 0.055 0.000 6.000 6.230 0.344 421.657 421.359 29.827 0.010 15.000 Circular 6.996 0.000 2.962 0.168 103 104 102 0.120 0.730 0.088 0.434 0.000 6.303 6.142 2.667 421.148 419.189 97.933 0.020 15.000 Circular 9.894 0.001 6.858 0.238 IOTA 102 100A 0.000 0.000 0.000 2.132 0.000 7.064 5.934 12.652 406.458 404.920 76.896 0.020 24.000 Circular 34.655 0.003 10.189 0.126 101 100A 100 0.000 0.000 0.000 2.132 0.000 7.190 5.901 12.582 404.824 404.000 41.209 0.020 24.000 Circular 34.655 0.003 10.174 0.068 47039-STRM 200 STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: LOCATION: COUNTY: Southwood Village 2 Albemarle Designed by: Checked by: UNITS ENGLISH PIPE NO FROM POINT TO POINT DRAIN. AREA "A" Acre (3) RUNOFF COEFF. "C" (4) CA TOTAL INLET TIME Minutes (7) RAIN FALL Inft (8) RUNOFF Q CFS (9) INVERT ELEVATIONS LENGTH of Pipe Ft. (12) SLOPE FOR. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Capacity CFS (15) Friction Slope Ft./Ft. VEL Vn Ft/Sec (16) FLOW TIME Min. (17) REMARKS (18) INCRE- MENT (5) ACCUM- ULATED (6) ADDTL CA UPPER END (10) LOWER END (11) REFERENCE (1) STA. REFERENCE (2) STA. 215 216 214 0.040 0.580 0.023 0.023 0.000 5.000 6.542 0.152 411.158 408.850 92.311 0.025 12.000 Circular 7.321 0.000 3.739 0.411 213 214 212 0.080 0.470 0.038 0.061 0.000 1 5.411 6.409 0.390 408.754 408.190 56.429 0.010 1 12.000 Circular 4.630 0.000 3.592 0.262 211 212 210 0.080 0.440 0.035 0.096 0.000 5.673 6.328 0.608 408.093 407.450 64.324 0.010 12.000 Circular 4.630 0.000 4.088 0.262 209 210 208 0.050 0.420 0.021 0.117 0.000 5.936 6.249 0.731 407.353 407.000 35.324 0.010 12.000 Circular 4.630 0.000 4.312 0.137 207 208 1 1 206 1 0.040 0.410 0.016 0.133 0.000 6.072 6.209 0.828 406.905 406.460 44.479 0.010 12.000 Circular 4.630 0.000 4.469 0.166 205 206 204 0.030 0.440 0.013 0.147 0.000 6.238 6.161 0.903 406.356 405.780 57.639 0.010 12.000 Circular 4.630 0.000 4.580 0.210 203 204 202 0.030 0.440 0.013 0.160 0.000 6.448 6.101 0.975 405.680 404.730 94.974 0.010 12.000 Circular 4.630 0.000 4.680 0.338 201 202 200 0.030 0.700 0.021 0.181 0.000 6.786 6.008 1.086 404.625 404.000 62.512 0.010 12.000 Circular 4.630 0.001 4.825 0.216 47039-STRM 100 HYDRAULIC GRADE LINE ANALYSIS INCIDENCE PROBABILITY 10 Year PROJECT: Southwood Village 2 DESIGNED BY: Checked: INLET OR JUNCTION INLET STATION OUTLET WATER SURFACE ELEV. DIA. PIPE Do (In) DESIGN DISCH. Qo (CFS) LENGTH PIPE Lo (Ft) FRICTION SLOPE, Sfo (FT/FT) FRICTION LOSS Hf (Ft) JUNCTION LOSS FINAL H (Ft) Inlet Water Surface Elevation Rim Elev Comments Vo Ho (Ft) Qi Vi QIVI Vi'2/2g Hi Angle HD Ht 1.3 Ht 0.5 Ht 100A 407.55 24 12.58 41.21 0.26% 0.11 10.17 0.4 12.65 10.19 128.91 1.61 0.56 26.8 0.48 1.45 0 TRUE 0.83 408.38 424.44 OK -16.06 102 408.38 24 12.65 76.9 0.27% 0.2 10.19 0.4 10.12 7.3 73.91 0.83 0.29 76.68 0.55 1.24 0 TRUE 0.82 409.21 424.24 OK -15.03 112 1 409.21 1 18 10.12 1 42.04 0.79% 1 0.33 7.3 0.21 4.66 7.9 36.78 0.97 0.34 80.61 0.64 1.19 0 TRUE 1 0.93 410.13 1 422.68 OK -12.55 114 412.34 18 4.66 30.11 0.17% 0.05 7.9 0.24 2.79 6.94 19.38 0.75 0.26 93.84 0.52 1.03 0 TRUE 0.56 412.91 422.87 OK -9.97 122 415.49 15 2.79 56.46 0.16% 0.09 6.94 0.19 2.49 5.23 13.02 0.42 0.15 61.44 0.24 0.57 0 TRUE 0.38 415.87 420.55 OK -4.68 124 416.82 15 2.49 34.01 0.13% 0.04 5.23 0.11 1.79 5.53 9.92 0.48 0.17 43.54 0.2 0.48 0.62 FALSE 0.66 417.48 420.87 OK -3.39 126 417.48 15 1.79 175.61 0.07% 0.12 5.53 0.12 0.45 4.09 1.83 0.26 0.09 66.95 0.16 0.37 0.48 TRUE 0.35 417.83 426.42 OK -8.59 128 420.09 15 0.45 32.38 0.00% 0 4.09 0.06 0 0 0 0 0 0 0 0.06 0.08 TRUE 0.04 420.13 427.06 OK -6.93 104 420.19 15 2.67 97.93 0.15% 0.14 6.86 0.18 1.81 6.15 11.13 0.59 0.21 20.24 0.15 0.53 0.7 TRUE 0.49 420.68 427.74 OK -7.06 108 423.1 15 1.81 84.55 0.07% 0.06 6.15 0.15 1 6.89 6.87 0.74 0.26 78.77 0.49 0.89 1.16 TRUE 0.64 423.74 431.14 OK -7.4 110 424.99 15 1 30.43 0.02% 0.01 6.89 0.18 0 0 0 0 0 0 0 0.18 0.24 TRUE 0.13 425.12 431.44 OK -6.33 106 1 1 422.36 1 15 1 0.34 1 29.83 1 0.00% 1 0 1 2.96 1 0.03 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.03 1 0.04 1 TRUE 1 0.02 1 422.38 1 427.77 1 OK -5.39 132 410.13 18 4.69 63.36 0.17% 0.11 6.14 0.15 4.39 6.04 26.51 0.57 0.2 25.14 0.17 0.51 0 TRUE 0.36 410.5 420.41 OK -9.92 134 410.5 18 4.39 33.37 0.15% 0.05 6.04 0.14 2.95 5.42 15.97 0.46 0.16 41.98 0.28 0.58 0 TRUE 0.34 410.84 419.14 OK -8.3 136 411.45 15 2.1 29.81 0.09% 0.03 6.42 0.16 1.69 6.54 11.08 0.66 0.23 90 0.46 0.86 1.11 TRUE 1 0.58 412.03 418.72 OK -6.69 138 415.22 15 1.69 70.78 0.06% 0.04 6.54 0.17 0 0 0 0 0 0 0 0.17 0.22 TRUE 0.15 415.37 420.64 1 OK -5.27 140 1 1 410.84 1 18 1 2.95 1 86.6 1 0.07% 1 0.06 1 5.42 1 0.11 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.11 1 0.15 1 TRUE 1 0.13 1 410.97 1 416.3 1 OK -5.33 116 417.85 1 15 1 2.31 1 58.72 1 0.11% 1 0.06 1 5.12 1 0.1 1 1.35 1 6.12 1 8.23 1 0.58 1 0.2 1 26.58 1 0.17 1 0.48 1 0.62 1 TRUE 1 0.38 1 418.23 1 421.87 1 OK -3.64 118 418.64 1 15 1 1.35 1101.891 0.04% 1 0.04 1 6.12 1 0.15 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0.15 1 0.19 1 TRUE 1 0.13 1 418.77 1 424.94 OK -6.17 47039-STRM 200 PROJECT: Southwood Village 2 DESIGNED BY: HYDRAULIC GRADE LINE ANALYSIS INCIDENCE PROBABILITY 10 Year Checked: INLET OR JUNCTION INLET STATION OUTLET WATER SURFACE ELEV. DIA. PIPE Do (In) DESIGN DISCH. Do (CFS) LENGTH PIPE Lo (Ft) FRICTION SLOPE, Sfo (FT/FT) FRICTION LOSS Hf (Ft) JUNCTION LOSS FINAL H (Ft) Inlet Water Surface Elevation Rim Elev Comments Vo Ho (Ft) Qi Vi QIVI Vi'2/2g Hi Angle HD Ht 1.3 Ht 0.5 Ht 202 407.55 12 1.09 62.51 0.06% 0.03 4.82 0.09 0.97 4.68 4.56 0.34 0.12 38.32 0.15 0.36 0 TRUE 0.21 407.76 410.21 OK -2.45 204 407.76 12 0.97 94.97 0.04% 0.04 4.68 0.09 0.9 4.58 4.14 0.33 0.11 32.52 0.11 0.31 0 TRUE 0.2 407.96 408.11 OK -0.15 206 1 407.96 1 12 0.9 1 57.64 0.04% 1 0.02 4.58 0.08 0.83 4.47 3.7 0.31 0.11 29.5 0.11 0.3 0 TRUE 1 0.17 408.13 1 410.78 OK -2.65 208 408.13 12 0.83 44.48 0.03% 0.01 4.47 0.08 0.73 4.31 3.15 0.29 0.1 14.39 0.05 0.23 0 TRUE 0.13 408.26 409.83 OK -1.57 210 408.26 12 0.73 35.32 0.02% 0.01 4.31 0.07 0.61 4.09 2.48 0.26 0.09 41.98 0.11 0.27 0 TRUE 0.15 408.41 409.48 OK -1.07 212 408.41 12 0.61 64.32 0.02% 0.01 4.09 0.06 0.39 3.59 1.4 0.2 0.07 29.91 0.07 0.21 0.27 TRUE 0.14 408.55 410.59 OK -2.04 214 408.99 12 0.39 56.43 0.01% 0 3.59 0.05 0.15 3.74 0.57 0.22 0.08 8.06 0.03 0.15 0.2 TRUE 0.1 409.09 413.84 OK -4.74 216 409.65 12 0.15 92.31 0.00% 0 3.74 0.05 0 0 0 0 0 0 0 0.05 0.07 FALSE 0.07 409.72 415.19 OK -5.46 Virginia Runoff Reduction Method! Mrksheet DEq Virginia Runoff Reduction Method New Development Compliance Spreadsheet - Version 3.0 BMP Design Specifications List: 2013 Draft Stds & Specs Site Summary Project Title: Southwood Village 2 Date: 44651 Total Rainfall= 431nches Site Land Cover Summary A soils BSoils CSoils DSOUS Totals %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 2.38 0.00 0.00 2.38 49 Impervious Cover (acres) 1 0.00 2.50 0.00 0.00 2.50 51 4.88 100 Site Tv and Land Cover Nutrient Loads Site Rv 0.58 Treatment Volume ft 10,349 TP Load (lb/yr) 6.50 TN Load (lb/yr) 46.52 Total TP Load Reduction Required (lb/yr) 4.50 Site Compliance Summary Total Runoff Volume Reduction (ft) 0 Total TP Load Reduction Achieved (lb/yr) 3.07 Total TN Load Reduction Achieved (lb/yr) 13.18 Remaining Post Development TP Load 3.43 (lb/yr) Remaining TP Load Reduction (lb/yr) 143 Required ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Drainage Area Summary DA. A D.A. B DA. C D.A. D D.A. E Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acres) 2.03 0.00 0.00 0.00 0.00 2.03 Impervious Cover (acres) 2.41 0.00 0.00 0.00 0.00 2.41 Total Area (acres) 4.44 0.00 0.00 0.00 0.00 4.44 Drainage Area Compliance Summary DA. A D.A. B DA. C D.A. D DA. E Total TP Load Reduced (Ib/vr) 3.07 0.00 0.00 0.00 0.00 3.07 Summary Prior Virginia Runoff Reduction Method Worhsheet TN Load Reduced (lb/yr) 1 13.18 1 0.00 1 0.00 1 0.00 1 0.00 1 13.18 Drainage Area A Summary Land Cover Summan A Solis BSolls CSoils DSolis Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 2.03 0.00 0.00 2.03 46 Impervious Cover (acres) 1 0.00 2.41 0.00 0.00 2.41 54 4.44 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area [over Credits I Volume (Tt ( Upstream to Practice (16s) (16/yr) (Ih/yr) Treatmentto be (acres) Area (acres) practices (Ihz) Employed Total Impervious Cover Treated (acres) 2.41 Total Turf Area Treated (acres) 2.03 Total TP Load Reduction Achieved in D.A. (lb/yr) 3.07 Total TN Load Reduction Achieved in D.A. (lb/yr) 13.18 Drainage Area B Summary Land Cover Summary A Soils BSoils CSoils DSolis Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 1 0.00 0.00 0.00 0.00 0 Impervious Cover (acres) 1 0.00 1 0.00 0.00 0.00 0.00 0 0.00 BMP Selections Managed Turf Impervious BMPTreatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area Cover Credit I z Volume (ft ( Upstream to Practice (16s) (16/yr) (Ih/yr) Treatmentto 6e (acres) Area (acres) practices (Ihz) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (lb/yr) 0.00 Total TN Load Reduction Achieved in D.A. (lb/yr) 0.00 Summary Print Virginia Runoff Reduction Method Worhsheet Drainage Area C Summary Land Cover Summary A Soils BSolls CSolls DSolls Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 coo o Managed Turf (acres) 1 0.00 1 0.00 0.00 1 0.00 coo I o Impervious Cover (acres) 1 0.00 1 0.00 0.00 1 0.00 coo I o 0.00 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area Cover Credit I Volume (fts ( Upstream to Practice (Ihs) (16/yr) (Ih/yr) Treatmentto 6e (acres) Area (acres) practices (Ihs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (lh/yr) 0.00 Total TN Load Reduction Achieved in D.A. (lh/yr) 0.00 Drainage Area D Summary Land Cover Summan A Soils B Soils C Soils D Soils Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 1 0.00 0.00 1 0.00 0.00 1 0 Impervious Cover (acres) 1 0.00 1 0.00 0.00 1 0.00 0.00 1 0 0.00 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area Cover Credit I Volume (fts) Upstream to Practice (Ihs) (16/yr) (Ih/yr) Treatmentto 6e (acres) Area (acres) practices (Ihs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (lh/yr) 0.00 Total TN Load Reduction Achieved in D.A. (lh/yr) 0.00 Drainage Area E Summary Summary Print Virginia Runoff Reduction Method VVorksheet Land Cover Summary A Soils BSoils CSolls DSo0s Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 1 0.00 1 0.00 0.00 1 0.00 0.00 1 0 Impervious Cover (acres) 1 0.00 1 0.00 0.00 1 0.00 0.00 1 0 0.00 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Practice Credit Area Cover Credit I a Volume (Tt) Upstream to Practice (Ihs) (16/yr) (Ih/yr) Tre6e (acres) Area (acres) practices (Ihz) EmployEmployedd Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. 0.00 (Ih/yr) Total TN Load Reduction Achieved in D.A. 0.00 (Ih/yr) Runoff Volume and CN Calculations 1-yearstorm 2-year storm 10-year storm Target Rainfall Event (in) I 0.00 0.00 0.00 Drainage Areas RV & CN Drainage Area A Drainage Area B Drainage Area C Drainage Area D Drainage Area E CN 81 0 0 0 0 RR (f?) 0 0 0 0 0 1-year return period RV wa RR (. -in) 0.00 0.00 0.00 0.00 0.00 RV w RR (wnln) 0.00 0.00 0.00 0.00 0.00 CN adjoined 100 0 0 0 0 2-year return period RV wo RR (.in) 0.00 0.00 0.00 0.00 0.00 RV w RR (wsin) 0.00 0.00 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 10-year return period RVwa RR 0.00 0.00 Ow 0.00 0.00 -(--in) RR RV w (wsin) 0.00 0.00 0.00 0.00 0.00 CN adju:tee 100 0 0 0 0 Summary Print ECOSYSTEM SERVICES, LLC 1739 Allied Street, Suite A Charlottesville, VA 22903 540.578.4296 www.ecosystemservices.us ion@ecosystemservices.us December 3,1011 Catherine Gayner Project Engineer II TIMMONS GROUP 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 RE: Nutrient Offset Credit — Credit Availability Letter Project Name: Southwood Redevelopment Village 2 Project Address: Hickory Street, Charlottesville, VA 22902 Project TMP: 09A1-00-00-001E0/ Project WPO: 2021-00038 Project HUC: 02080204 Bank HUC: 02080204 Bank Address: 1705 Lambs Road, Charlottesville, VA 22901 Dear Ms. Gayner, We appreciate the opportunity to provide a credit availability letter for 1.48 pounds of phosphorus for the above referenced project. This letter is to certify that as of today, December 3rd, 2021, Ivy Creek Nutrient Bank has 119.21 pounds of phosphorus (TP), 183.55 pounds of nitrogen (TN), and 37,591.32 pounds of TSS available for transfer to those entities requiring offsets in accordance with the Chesapeake Bay Watershed Nutrient Credit Exchange Program (VA Code § 62.1-44.19:14 et seq.). Those offsets are also transferable in accordance with the Virginia stormwater offset program (VA Code § 62.1-44.15:35) and the Virginia Soil and Water Conservation Board's Guidance Document on Stormwater Nonpoint Nutrient Offsets approved on July 23, 2009, to those regulated entities qualifying for nutrient credits. We can certainly accommodate your needs and could offer to fulfil the order of 1.48 pounds of phosphorus. Please feel free to contact us with any questions. I hope we have the opportunity to work together on this project. Sincerely, Ecosystem Services, LLC By: Jonathan R. Roller, AOSE PSS CNMP Manager —Authorized Representative 1S 11S Pre Site Post Routed 12P SWM A Subcat Reach on Link Routing Diagram for Southwood Village 2 Prepared by Timmons Group, Printed 3/31/2022 FHydroCADq) 10.10-4a s/n 08663 ® 2020 HydroCAD Software Solutions LLC Southwood Village 2 Prepared by Timmons Group Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 2.340 61 >75%Grass cover, Good, HSG B (1S, 11S) 2.410 98 Paved parking, HSG B (11S) 4.140 60 Woods, Fair, HSG B (1S) 8.890 71 TOTAL AREA Printed 3/31/2022 Southwood Village 2 Prepared by Timmons Group Soil Listing (all nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 8.890 HSG B 1S, 11S 0.000 HSG C 0.000 HSG D 0.000 Other 8.890 TOTAL AREA Printed 3/31/2022 Southwood Village 2 Prepared by Timmons Group Ground Covers (all nodes) Printed 3/31/2022 HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover 0.000 2.340 0.000 0.000 0.000 2.340 >75% Grass cover, Good 0.000 2.410 0.000 0.000 0.000 2.410 Paved parking 0.000 4.140 0.000 0.000 0.000 4.140 Woods, Fair 0.000 8.890 0.000 0.000 0.000 8.890 TOTAL AREA Subcatchment Numbers Southwood Village 2 Type 11 24-hr 1-YR Rainfall=3.05" Prepared by Timmons Group Printed 3/31/2022 HydroCAD® 10.10-4a s/n 08663 ©2020 HydroCAD Software Solutions LLC Paoe 5 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentlS: Pre Site Runoff Area=4.450 ac 0.00% Impervious Runoff Depth>0.30" Tc=6.0 min CN=60 Runoff=1.93 cfs 0.111 of Subcatchment11S: Post Routed Runoff Area=4.440 ac 54.28% Impervious Runoff Depth>1.24" Tc=6.0 min CN=81 Runoff=10.36 cfs 0.458 of Pond 12P: SWM A Peak Elev=406.49' Storage=12,610 cf Inflow=10.36 cfs 0.458 of Outflow=0.32 cfs 0.215 of Total Runoff Area = 8.890 ac Runoff Volume = 0.569 of Average Runoff Depth = 0.77" 72.89% Pervious = 6.480 ac 27.11% Impervious = 2.410 ac Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 1-YR Rainfall=3.05" Printed 3/31/2022 Summary for Subcatchment 1S: Pre Site Runoff = 1.93 cfs @ 12.00 hrs, Volume= 0.111 af, Depth> 0.30" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.05 Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.140 60 Woods, Fair, HSG B 4.450 60 Weighted Average 4.450 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph ❑ Runoff 2 1.93 cfs Type II 24-hr 1-YR Rainfall=3.05" Runoff Area=4.450 ac Runoff Volume=oj 11 of Runoff Depth>0.30" LL Tc=6.0 min CN=60 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 1-YR Rainfall=3.05" Summary for Subcatchment 11S: Post Routed Runoff = 10.36 cfs @ 11.97 hrs, Volume= 0.458 af, Depth> 1.24" Printed 3/31/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-YR Rainfall=3.05 Area (ac) CN Description 2.410 98 Paved parking, HSG B 2.030 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.440 81 Weighted Average 2.030 45.72% Pervious Area 2.410 54.28% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph N �Y 5 - 3 I I LL 5 I I I I _L _J I I 4 I I I I I I -I -I 3 I I I I I I I I I I 2 ❑Runoff f] Type II 24-hr - TYR Rainfall=3.05'�- "--- Runoff Area=4.440 ac Runoff Vo�ump=0.458 of Runoff Depth?1.24'r Tc=6',0 rnin CN='81 ------------- 10 11 12 13 14 15 16 17 18 19 Time (hours) Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 1-YR Rainfall=3.05" Summary for Pond 12P: SWM A Printed 3/31/2022 Inflow Area = 4.440 ac, 54.28% Impervious, Inflow Depth > 1.24" for 1-YR event Inflow = 10.36 cfs @ 11.97 hrs, Volume= 0.458 of Outflow = 0.32 cfs @ 14.70 hrs, Volume= 0.215 af, Atten= 97%, Lag= 163.4 min Primary = 0.32 cfs @ 14.70 hrs, Volume= 0.215 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 406.49' @ 14.70 hrs Surf.Area= 6,099 sf Storage= 12,610 cf Plug -Flow detention time= 241.9 min calculated for 0.215 of (47% of inflow) Center -of -Mass det. time= 157.6 min ( 951.8 - 794.2 ) Volume Invert Avail.Storage Storage Description #1 404.00' 30,673 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,040 0 0 406.50 6,110 12,688 12,688 407.50 7,030 6,570 19,258 409.00 8,190 11,415 30,673 Device Routing Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 406.75' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=0.32 cfs @ 14.70 hrs HW=406.49' (Free Discharge) 1=Culvert (Passes 0.32 cfs of 20.43 cfs potential flow) �2=Orifice/Grate (Orifice Controls 0.32 cfs @ 7.43 fps) 3=Orifice/Grate ( Controls 0.00 cfs) =Broad -Crested Rectangular Weir( Controls 0.00 cfs) Southwood Village 2 Preaared by Timmons C 114" 5 Pond 12P: SWM A I I 10. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ------------ I I I I I I I I I I I I I I II IJ Type/1 24-hr 1-YR Rainfall=3.05" Printed 3/31/2022 I I I I --- lnf10"W Are'a=4.-440 Ad Peakk EIIev-4g6.49' --- toragwF011Z§1 Q_cf _ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I cfs ------r--- 0.32 7 8 g 10 11 12 13 Time (hours) Pond 12P: SWM A Stage -Discharge I I I I Broad -Crested Rectangular Weir m 407 Orifice/Grate a 0 m I I w 406 V I I 405 404 a 0 I I I I I I I I I I I I I I I I I I I I I I I Discharge (cfs) ■ Inflow ■ Primary ❑ Primary Southwood Village 2 Preaared by Timmons C Type 11 24-hr 1-YR Rainfall=3.05" Printed 3/31/2022 r n..-- A n Pond 12P: SWM A Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 ■ Surface I I I I I I I I I I I I I I ■ Storage 409 I I I I I I I u I I u I 408 I I I I I I I I I I I -__I I I I I I ____ I I I u I I I u I I I 1 1 y 407 I I I I I I I I I I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 t O �� I I I I I I I I I 1 I I I 1 ] 406 I I I I I I I I I I I I 1 1 W I I I I I I I I I ---r---r- I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I 1 I I I 1 405 r---r---rr- I II I II II I I I I---r- r-�-r---r---I-T--r---r---r I I I I I I I I I I I I i � I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 Custom Stage Data I I I I I I I I I 1 404 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet) Southwood Village 2 Type 11 24-hr 10-YR Rainfall=5.58" Prepared by Timmons Group Printed 3/31/2022 HydroCAD® 10.10-4a s/n 08663 ©2020 HydroCAD Software Solutions LLC Paae 11 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentlS: Pre Site Runoff Area=4.450 ac 0.00% Impervious Runoff Depth>1.48" Tc=6.0 min CN=60 Runoff=12.57 cfs 0.550 of Subcatchment11S: Post Routed Runoff Area=4.440 ac 54.28% Impervious Runoff Depth>3.26" Tc=6.0 min CN=81 Runoff=26.28 cfs 1.206 of Pond 12P: SWM A Peak Elev=407.50' Storage=19,265 cf Inflow=26.28 cfs 1.206 of Outflow=20.42 cfs 0.880 of Total Runoff Area = 8.890 ac Runoff Volume = 1.756 of Average Runoff Depth = 2.37" 72.89% Pervious = 6.480 ac 27.11% Impervious = 2.410 ac Southwood Village 2 Prepared by Timmons Group Type ll 24-hr 10-YR Rainfall=5.58" Summary for Subcatchment 1S: Pre Site Runoff = 12.57 cfs @ 11.98 hrs, Volume= 0.550 af, Depth> 1.48" Printed 3/31/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, l 0.05 hrs Type II 24-hr 10-YR Rainfall=5.58" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.140 60 Woods, Fair, HSG B 4.450 60 Weighted Average 4.450 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph 14 fT -------- 12 57 ■ Runoft Type-O-Z4.1hr ____ 1__L___ J__ L _ I____1 10-YR RainM11:0 .58" -------- ---- --- ---- ----I ---- 4---- Runbff Are&4.450 c1c --I--- ---- --- ------------ ---- --- 'IRupoff,-V-0= =01550,at- Runoff-Depth l:418"-- Tc=660-niin - I I I I I I I -r -, -r PN=i60 - I I I I I I _____ I _____ I _____ I _____________ I I I I I I I I I I I I I I I I I I I I I I 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 10-YR Rainfall=5.58" Summary for Subcatchment 11S: Post Routed Runoff = 26.28 cfs @ 11.97 hrs, Volume= 1.206 af, Depth> 3.26" Printed 3/31/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.58" Area (ac) CN Description 2.410 98 Paved parking, HSG B 2.030 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.440 81 Weighted Average 2.030 45.72% Pervious Area 2.410 54.28% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph I 28 26 26 I I I I 24 I I I I 22 26 I I I I 18 I I I I I I ---------------------------- V 16 I I I I I I 3 0 14 I I I I I I 12 ___ I____I____I____ I____I____ I_ ,6 I I I I 8 I I I I I 6 _I___ -I _I____. I I _ I_ I Type II 24-hr 10-YR Rainfall=5.58rr Runoff Area=4.440 ac Runoff Volume=1.206 of ------------------------------------ ------Runoff Depth>3 26"_- I -I I I Ir I --- CN=81-- I___ I T -r -7 -r -I - i ____I____J---- _---- ____I__ �I I 10 11 12 13 14 15 16 17 18 19 Time (hours) ❑ Runoff Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 10-YR Rainfall=5.58" Summary for Pond 12P: SWM A Printed 3/31/2022 Inflow Area = 4.440 ac, 54.28% Impervious, Inflow Depth > 3.26" for 10-YR event Inflow = 26.28 cfs @ 11.97 hrs, Volume= 1.206 of Outflow = 20.42 cfs @ 12.03 hrs, Volume= 0.880 af, Atten= 22%, Lag= 3.7 min Primary = 20.42 cfs @ 12.03 hrs, Volume= 0.880 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 407.50' @ 12.03 hrs Surf.Area= 7,031 sf Storage= 19,265 cf Plug -Flow detention time= 103.8 min calculated for 0.880 of (73% of inflow) Center -of -Mass det. time= 39.9 min ( 813.1 - 773.2 ) Volume Invert Avail.Storage Storage Description #1 404.00' 30,673 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,040 0 0 406.50 6,110 12,688 12,688 407.50 7,030 6,570 19,258 409.00 8,190 11,415 30,673 Device Routing Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 406.75' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=19.70 cfs @ 12.03 hrs HW=407.48' (Free Discharge) 1=Culvert (Passes 19.70 cfs of 22.12 cfs potential flow) �2=Orifice/Grate (Orifice Controls 0.38 cfs @ 8.85 fps) 3=Orifice/Grate (Weir Controls 19.32 cfs @ 2.80 fps) =Broad -Crested Rectangular Weir( Controls 0.00 cfs) Southwood Village 2 Preaared by Timmons C Type/1 24-hr 10-YR Rainfall=5.58" Printed 3/31/2022 Pond 12P: SWM A Hydrograph I i ____I__ I ■Inflow 26.28CfS --- ■Primary --- Jn%DwArpa- 4A4Q�ic- I I I I I I I I I I I I I I I ---J--- LI ---Pe* r;Iev=4Q7.-50`- ,, I----I----1------ 20.42 cfs -- --------r---,----r--- Sto ra gp-=1,9,;65- ct - - - - I I, I, I I I I I I I I I I I , I I I I I I I i I I I I I I I I I I I I I I , I I I I I I I I I I I I I I I I I I I I � i I I I I I I -I -♦ -I F _I _I _+ _I -F -y -F I I I I I I I I I I I 11 12 13 Time (hours) Pond 1213: SWM A Stage -Discharge ❑ Primary Discharge (cfs) Southwood Village 2 Preaared by Timmons C Type/1 24-hr 10-YR Rainfall=5.58" Printed 3/31/2022 r n..-- A c Pond 12P: SWM A Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 ■ Surface I I I I I I I I I I I I I I ■ Storage 409 I I I I I I I u I I u I 408 I I I I I I I I I I I —__I I I I I I ____ I I I u I I I u I I I 1 1 y 407 I I I I I I I I I I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 t O �� I I I I I I I I I 1 I I I 1 ] 406 I I I I I I I I I I I I 1 1 W I I I I I I I I I ---r---r- I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I 1 I I I 1 405 r---r---rr- I II I II II I I I I---r- r-�-r---r---I-T--r---r---r I I I I I I I I I I I I i � I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 Custom Stage Data I I I I I I I I I 1 404 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet) Southwood Village 2 Type 11 24-hr 100-YR Rainfall=9.16" Prepared by Timmons Group Printed 3/31/2022 HydroCAD® 10.10-4a s/n 08663 ©2020 HydroCAD Software Solutions LLC Paae 17 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentlS: Pre Site Runoff Area=4.450 ac 0.00% Impervious Runoff Depth>3.88" Tc=6.0 min CN=60 Runoff=32.44 cfs 1.438 of Subcatchment11S: Post Routed Runoff Area=4.440 ac 54.28% Impervious Runoff Depth>6.41" Tc=6.0 min CN=81 Runoff=49.61 cfs 2.373 of Pond 12P: SWM A Peak Elev=407.87' Storage=21,928 cf Inflow=49.61 cfs 2.373 of Outflow=48.64 cfs 2.042 of Total Runoff Area = 8.890 ac Runoff Volume = 3.811 of Average Runoff Depth = 5.14" 72.89% Pervious = 6.480 ac 27.11% Impervious = 2.410 ac Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 100-YR Rainfall=9.16" Summary for Subcatchment 1S: Pre Site Runoff = 32.44 cfs @ 11.97 hrs, Volume= 1.438 af, Depth> 3.88" Printed 3/31/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.16" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.310 61 >75% Grass cover, Good, HSG B 4.140 60 Woods, Fair, HSG B 4.450 60 Weighted Average 4.450 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site Hydrograph --- ---- ---- ---- '------------------------------- 36 __J____1____I____1____. 1 ❑Runoff 34 32.44 cfs 32 I I I I ----------'-------------------- �1- -- Type II 24-hr 30 _ ' ` - r --,-- - 10D-YR Rainfalfr9f6" 28 I I - 26 ------------------------------ ---- ---Tt-unbff-Areal=4.4ra01�- 24 22 -- -- ---1__Vb�u_mg=1Al63 'a�= _J _1 _I _1 _L _J _I w 26 V3- ; ffpth 88" ----;--;-- -------+-L'8 1 --- ---- I 1 c=6� rriin 1 iL 16 __I____r____�___r____r___r______1____r____r___r____r___�____ r____ 14 I 1 1 1 1 1 1,-'IV V 12 1 1 1 1 1 _-y----r--------______r___y____t____ 10 1 1 1 1 1 8 I I I I I I I I I I _J _1 _I _1 _I _1 _L _J _L _J _1 I 1 1 4 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 100-YR Rainfall=9.16" Summary for Subcatchment 11S: Post Routed Runoff = 49.61 cfs @ 11.97 hrs, Volume= 2.373 af, Depth> 6.41" Printed 3/31/2022 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.16" Area (ac) CN Description 2.410 98 Paved parking, HSG B 2.030 61 >75% Grass cover, Good, HSG B 0.000 60 Woods, Fair, HSG B 4.440 81 Weighted Average 2.030 45.72% Pervious Area 2.410 54.28% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph 45 35 N 30 � LL 25 i 20 _L _J 15 ❑ Runoff f] Type _1.1.24-hr 100-YR Rainfall=9.16rr Runoff Areal=4.440 ac Runoff Volume=2.373'af Runoff Depth>6.41" Tc=6.0 min -------- r---- CN=81 ---------- ------------- 10 11 12 13 14 15 16 17 18 19 Time (hours) Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 100-YR Rainfall=9.16" Summary for Pond 12P: SWM A Printed 3/31/2022 Inflow Area = 4.440 ac, 54.28% Impervious, Inflow Depth > 6.41" for 100-YR event Inflow = 49.61 cfs @ 11.97 hrs, Volume= 2.373 of Outflow = 48.64 cfs @ 11.99 hrs, Volume= 2.042 af, Atten= 2%, Lag= 1.3 min Primary = 48.64 cfs @ 11.99 hrs, Volume= 2.042 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 407.87' @ 11.99 hrs Surf.Area= 7,318 sf Storage= 21,928 cf Plug -Flow detention time= 71.2 min calculated for 2.042 of (86% of inflow) Center -of -Mass det. time= 27.4 min ( 785.0 - 757.6 ) Volume Invert Avail.Storage Storage Description #1 404.00' 30,673 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 404.00 4,040 0 0 406.50 6,110 12,688 12,688 407.50 7,030 6,570 19,258 409.00 8,190 11,415 30,673 Device Routing Invert Outlet Devices #1 Primary 400.94' 18.0" Round Culvert L= 86.8' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 400.94' / 399.20' S= 0.0200 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf #2 Device 1 404.00' 2.5" W x 2.5" H Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 406.75' 36.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 407.50' 45.0' long x 9.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.46 2.55 2.70 2.69 2.68 2.68 2.67 2.64 2.64 2.64 2.65 2.64 2.65 2.65 2.66 2.67 2.69 Primary OutFlow Max=47.12 cfs @ 11.99 hrs HW=407.86' (Free Discharge) 1=Culvert (Barrel Controls 22.73 cfs @ 12.86 fps) �2=Orifice/Grate (Passes < 0.40 cfs potential flow) 3=Orifice/Grate (Passes < 35.83 cfs potential flow) =Broad -Crested Rectangular Weir (Weir Controls 24.39 cfs @ 1.51 fps) Southwood Village 2 Preaared by Timmons C Type/1 24-hr 100-YR Rainfall=9.16" Printed 3/31/2022 Pond 12P: SWM A ----; --- ,----;----; ----it----; --- ;----; --- I I I I C Dfs,l I -i ll-- - - 4cfs _-ln%awe V��444Q4-e--- - ---Peak EIIev=4Q7.Q7' - - Storage=21-,q2V-p I I I I I I I I I I I I I I I I I I I I I I I - I I- r I- I I I I I I I I I I I I I I 11 12 13 14 15 Time (hours) Pond 1213: SWM A Stage -Discharge Discharge (cfs) ■ Inflow ■ Primary ❑ Primary Southwood Village 2 Preaared by Timmons C Type/1 24-hr 100-YR Rainfall=9.16" Printed 3/31/2022 Pond 12P: SWM A Stage -Area -Storage Surface/Horizontal/Wetted Area (sq-ft) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 ■ Surface I I I I I I I I I I I I I I ■ Storage 409 I I I I I I I u I I u I 408 I I I I I I I I I I I -__I I I I I I ____ I I I u I I I u I I I 1 1 y 407 I I I I I I I I I I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 t O �� I I I I I I I I I 1 I I I 1 ] 406 I I I I I I I I I I I I 1 1 W I I I I I I I I I ---r---r- I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I 1 I I I 1 405 r---r---rr- I II I II II I I I I---r- r-�-r---r---I-T--r---r---r I I I I I I I I I I I I i � I I I I I I I I I I I I I I I I I 1 1 I I I 1 I I I 1 Custom Stage Data I I I I I I I I I 1 404 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet)