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HomeMy WebLinkAboutWPO202100038 Calculations 2022-10-28Southwood Redevelopment — Village 2 ALBEMARLE COUNTY, VIRGINIA ROAD PLAN, WPO PLAN, & PRELIIVIINARY SUBDIVISION PLAT DESIGN CALCULATIONS & NARRATIVE JULY 89 2021 REVISED DECEMBER 39 2021 REVISED APRIL 19 2022 REVISED AUGUST 11, 2022 .00000 0 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 EpL.r n nF CLINT W. S FFLET Lic. N 54300 8/11/2022 APPROVED by the Albemarle County Community Development Department Date 10/27/22 File �NF?n9h91 Mr13R 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 1.431bs/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 SouthwoodVllage2 DESIGNER: MJD CHECKED: DATE 8/1012022 UNITS:NGLISH INLET o F F `^ ps ia_ O G U U w E = z_ o c u >o� }a'o �u s� wU �U a- z `F ��. zti Uw p^ <� y m� 3 F �w °' ,� 3 y �.$ o V o U" y� Z ww F a $ w k`�' zLL a`✓ x'� UU `a U'i - _ Sa Inlets Only Z w Z u= o n a� oc o -� n c` ❑ a 104 DI-2B 10 0.120 0.73 0.0876 0.000'RIGHT 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 D1-3B 6-000 0.080 0.69 0.0552 O'RIGHT 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 0.190 0.73 0.1314 O'RIGHT 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 O'RIGHT 0.16 4 064 0 0640 0.0450 0.0208 L845 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 1.8" 112 DI-2B 10 0.230 0.67 0.1541 O'RIGHT 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 1.534 1.000 0.616 0.000 1.905 114 D1-3B 6.000 0.070 0.72 0.0504 O'RIGHT 0.05 4 02 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 4A61 6.000 L345 1.000 0.200 0.000 1.180 116 DI-1 2.000 0.270 0.42 0.1134 Back/Lt. 0.009RIGHT 0.113 4 0.452 0 Back/Lt. 0 4 0 0 Ahead/Rt. 0A52 0.001 2.000 2 0.452 L467 T> 4.0 R 118 DI-1 1.500 0.270 0.56 0.1512 0.009RIGHT 0. 151 4 0604 0 0.604 0.0314 1.500 1.500 1.000 0.604 0.000 0.1218 BF[[.-O. 103' 122 DI-3C 6.000 0.090 0.58 0.0522 Back/Lt. 0.009RIGHT 0.052 4 0.208 0 0.0050 0.0208 1.827 2.000 1.0947 0.0833 4.0048 3.50 Back/Lt. 0 4 0 0 Ahead/Rt. 0.208 0.0050 6 0208 0.534 0.166 0.333 0A985 2.534 2.141 Weir Flow 124 D1-2B 10 0.170 0.72 0.1224 O'RIGHT 0.122 4 0488 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 5A70 6.000 1.828 1.000 0A88 0.000 1.833 126 D1-2B 10 0.340 0.64 0.2176 O'RIGHT 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 D1-3B 6.000 0.090 0.80 0.072 O'RIGHT 0.072 4 0.288 0 0.288 0.0409 0.0208 1.393 2.000 1.4358 0.0833 4.0048 1.000 3.50 0.1458 0.1666 4.965 6.000 1.208 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 SouthwoodVllage2 DESIGNER: MJD CHECKED: DATE 8/1012022 UNITS:NGLISH �--__-- ---®---�--__-- ---®__- ®® .III 1 �.I ®®-------------------------__-® -----------® III -----------�--�-������� ®--__-- ---®-----__-- -_-®--_--___- ---®---�--__-- -_-®_-_ INLETSOFT BY ENSOFTEC DATE: 8/10/2022 FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 3 OF 3 ROUTE PROJECT SouthwoodVllage2 DESIGNER: MJD CHECKED: DATE 8/1012022 UNITS:NGLISH INLET g� Sa Inlets Only 0a'o 2 ^uF R 5F - `uF�. a$ W,�o=c= -�'G �❑�1 U z 3 Uu. Uam'i � `uO _--6 a �� J^ fYy. �OU oO yZU p j w C C Z C a t Ox 3 H 0.000'RIGHT 0.038 4 0.152 0 0.152 0.0200 0.0300 1.253 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 1.253 216 DI-1 I.000 0.040 0.58 00232 O'RIGHT 0 023 4 0 092 0 0.092 0.0127 0.0550 1.131 2.000 1.7683 0.0833 1 5145 1.000 2.68 0.1116 0.1666 2.165 1.000 0.462 L000 0.092 0 000 1.130 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..MENT (4) CA TOTAL INLET TIME Minutes (7) RAIN FALL In" (8) RUNOFF Q CFS (9) INVERT ELEVATIONS LENGTH of Pipe Ft. (12) SLOPE Ft./Ft. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Capacity CFS (15) Friction Slope FtJFt. VEL Vn Ft/Sec (16) FLOW TIME Min. (17) REMARKS (I8) INCRE- (5) ACC 4- 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 1 6.191 1 1.793 418.994 416.360 1 175.610 0.015 15.000 Circular 8.568 1 0.001 5.533 1 0.529 123 124 1 122 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 0.135 117 118 116 1 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 6A18 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 1 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 IOIA 102 IOOA 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 10.1891 0.126 101 IOOA 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 1 10.1741 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..MENT (4) CA TOTAL INLET TIME Minutes (7) RAIN FALL In" (8) RUNOFF Q CFS (9) INVERT ELEVATIONS LENGTH of Pipe Ft. (12) SLOPE Ft./Ft. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Capacity CFS (15) Friction Slope FtJFt. VEL Vn Ft/Sec (16) FLOW TIME Min. (17) REMARKS (18) INCRE- (5) ACC 4- 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 5.411 1 6.409 1 0.390 408.754 408.190 1 56.429 0.010 1 12.000 Circular 1 4.630 1 0.000 3.592 1 0.262 211 212 1 210 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 0.137 207 208 206 1 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 1 0.181 0.000 1 6.786 6.008 1.086 404.625 404.000 62.512 1 0.010 12.000 Circular 4.630 0.001 1 4.825 0.216 47039-STRM 100 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 DIM Vi'2/2g Hi Angle H4 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 -6.33 106 422.36 1 15 1 0.34 1 29.83 1 0.00% 0 2.96 1 0.03 0 0 0 0 0 0 0 0.03 1 0.04 1 TRUE 1 0.02 1422.38 427.77 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% 1 0.03 6.42 0.16 1.69 1 6.54 11.08 0.66 0.23 1 90 0.46 0.86 1.11 TRUE 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 1 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 1410.97 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 DIM 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 Marro! Wor"neet 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= 43 inches Site Land Cover Summary A soils BSoils CSails DSoils 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 1 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 fts 10,349 TP Load (lb/yr) 6.50 IN Load (lb/yr) 46.52 Total TP Load Reduction Required (lb/yr) 4.50 Site Compliance Summary Total Runoff Volume Reduction (W) 0 Total TP Load Reduction Achieved (lb/yr) 3.07 Total TN Load Reduction Achieved (lb/yr) 13.18 Remaining Post Development TP Load (lb/yr) 3.43 Remaining TP Load Reduction (lb/yr) Required 1.43 ---------------------------------------------------------------------------- Drainage Area Summary D.A. A D.A. B D.A. C D.A. D D.A. E Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf (acres) 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 D.A. A D.A. B D.A. C D.A. D D.A. E Total TP Load Reduced (Ib/yr) 1 3.07 0.00 0.00 0.00 0.00 3.07 Summary Print Virginia Runoff Reduction Method Worksneet TN Load Reduced (Ib/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 Summary A Soils BSoils CSoils DSoils Total %of Total Forest/Open (acres( 0.00 0.00 0.00 OAO 0.00 0 Managed Turf (acres) 1 0.00 2.03 0.00 OAO 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 CoveArea ( s) Volume ft Upstream to Practice Ibs ( ) Ib r ( /y) Ib r ( /y) Treatmentbe (acres) (acres) Area (acres( practices (lbs) Employed Employ d Total Impervious Cover Treated (acres) 2.41 Total Turf Area Treated (acres) 2.03 Total TP Load Reduction Achieved in D.A. 3.07 (lb/yr) Total TN Load Reduction Achieved in D.A. 13.18 (lb/yr) Drainage Area B Summary Land Cover Summary A Soils BSoils CSoils DSoils Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.D0 0 Managed Turf(acres) 1 0.00 1 0.00 0.00 1 0.00 0.00 0 Impervious Cover (acres) I 0.00 I DOO 0.00 1 0.00 0.00 1 0 1 0.00 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load mo TP Removed TP Remaining Downstream Practice Credit Area Cover Credit I Volume ( ft s) Upstream to Practice ( Ibs) ( Ib r ( Ib/yr) Treatment to be (acres) Area (acres) practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (Ib/yr) 0.00 Total TN Load Reduction Achieved in D.A. (lb/yr) 0.00 Summary Print Virginia Runoff Reduction Method Worisheet Drainage Area C Summary Land Cover Summary A Soils BSoils CSoils Dsoils 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 OAO 1 0.00 1 0 Impervious Cover (acres) I O.00 1 0.00 0.00 1 a00 1 0.00 1 0 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 (it') Upstream to Practice (Ib (16/yr) (Ib/yr) Treatmentbe (acres) Area (acres) Practices (Ibs) Employs) 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. (Ib/yr) 0.00 Drainage Area D Summary Land Cover Summary A Soils BSoils CSoils Lolls 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 O.DO 1 0.00 1 0 Impervious Cover (acres) 1 0.00 1 0.00 0.00 1 0.00 1 0.00 1 0 I 0.00 I BMP Selections Managed Turf Impervious TP Load from Downstream BMP Treatment Untreated TP Load TP Removed TP Remaining Practice Credit Area Cover Credit I Volume(it') Upstream to Practice Qbs) (Ib/yr) Qb/yr) Treatment to be (acres) Area (acres) Practices (Ibs( 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 Drainage Area E Summary Summary Print Virginia Runoff Reduction Method Worksneet Land Cover Summary A Solis BSoils CSo0s n1lis Total %of Total Forest/Open (acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf (acres) 0.00 0.00 0.00 0.00 0.00 0 Impervious Cover (acres) 0.00 0.00 0.00 D.00 0.00 0 0.00 BMP Selections Managed Turf Impervious BMP Treatment TP Load from Untreated TP Load TPRemovn! TPRemaining Downstream Practice Credit Area Cover Credit I volume (k') Upstream to Practice (Has) (Ib/yr) (Ib/yr) I Treatment to be (acres) Area (acres) Practices (Ibs) Employed Total Impervious Cover Treated (acres) 0.00 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. (ib/yr) 0.00 Total TN Load Reduction Achieved in D.A. (lb/ 0.00 Runoff Volume and ON Calculations 1-year storm 2-year storm 10-year storm Target Rainfall Event (in) I 0.D0 0.00 0.00 Drainage Areas RV&CN Drainage AreaA Drainage Areali Drainage AreaC Drainage Area Drainage Area CN 81 0 0 0 0 RR (k') 0 0 0 0 0 1-year return period RV wo FUR (..In) 0.00 0.00 0.00 0.00 0.00 RVw RR(weln) 0.00 0.00 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 2-year return period RV vro FUR (wean) 0.00 0.00 0.00 0.00 0.00 RVw M(wsdn) 0.00 0.00 ofic) 0.00 0.00 CN adjusted Im 0 0 0 10-year return period RV wo RR lws-Inl 0.00 O.m I 0.00 0.00 avw M(wsin) 0.W o.m om 0.00 O.00 cN adjusted too 0 0 0 0 Smwy Part ECOSYSTEM SERVICES, LLC 1739 Allied Street, Suite A Charlottesville, VA 22903 540.578.4296 www.ecosystemservices.us jonaecosystemservices.us December 3, 2021 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: 09A1-00-00-001EO/ 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 3`', 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 �ost Routed 12P SWM A Subcat Reach °� Link Routing Diagram for Southwood Village 2 Prepared by Timmons Group, Printed 3/31/2022 FydroCAWD 10.104a a/n 08663 0 2020 HytlroCAD 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 HydroCAD® 10.10-4a s/n 08663 © 2020 HydroCAD Software Solutions LLC Printed 3/31/2022 Page 4 Ground Covers (all nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 2.340 0.000 0.000 0.000 2.340 >75% Grass cover, Good 1S, 11S 0.000 2.410 0.000 0.000 0.000 2.410 Paved parking 11S 0.000 4.140 0.000 0.000 0.000 4.140 Woods, Fair 1S 0.000 8.890 0.000 0.000 0.000 8.890 TOTAL AREA Southwood Village 2 Type/1 24-hr 1-YR Rainfall=3.05" Prepared by Timmons Group Printed 3/31/2022 HydroCADO 10.10-4a s/n 08663 © 2020 HydroCAD Software Solutions LLC Paae 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 Subcatchment1 S: 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 Subcatchmentl IS: 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 1213: 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 Descriotion 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) (f /ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site ❑ Runoff Type II 24-hr 1-YR Rainfall=3.05" Runoff Area=4.450 ac Runoff Volume=0.111 of Runoff Depth>0.30" 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" Printed 3/31/2022 Summary for Subcatchment 11S: Post Routed Runoff = 10.36 cfs @ 11.97 hrs, Volume= 0.458 af, Depth> 1.24" 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 Descriotion 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 Description Direct Entry, Subcatchment 11S: Post Routed Hydrograph 1 10.36 cfs I Type II 24-hr 1-YR Rainfall=3.05'r Runoff Area=4.440 ac Runoff Volume=0.458 of Runoff Depth>1.24" Tc=6.0 min I CN=81 --------------------- _ I___ I I _1___ I 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) -I ■ Rumffi 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 '/' 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-C rested Rectangular Weir( Controls 0.00 cfs) Southwood Village 2 Prepared by Timmons C rj Type/1 24-hr 1-YR Rainfall=3.05" Printed 3/31/2022 Pond 12P: SWM A Inflow Area=4.440 ac Peak Elev=406.49' Storage=12,610 cf I I I I I I I I I I I � I I I I I I 1 I - 1 -i I I I 1 I I I I I 1 I I 0.32 cfs 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Pond 12P: SWM A Stage -Discharge Discharge (cfs) ■ Inflow ❑ Primary ❑ Primary Southwood Village 2 Prepared by Timmons C Pond 12P: SWM A Type/1 24-hr 1-YR Rainfall=3.05" Printed 3/31/2022 Stage -Area -Storage oee/Horizonta: ied Area(sq-R) 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 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet) Surface ❑ Storage Southwood Village 2 Type/1 24-hr 10-YR Rainfall=5.58" Prepared by Timmons Group Printed 3/31/2022 HydroCADO 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 Subcatchment 1 S: 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 Subcatchmentl IS: 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 1213: 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/1 24-hr 10-YR Rainfall=5.58" Printed 3/31/2022 Summary for Subcatchment 1S: Pre Site Runoff = 12.57 cfs @ 11.98 hrs, Volume= 0.550 af, Depth> 1.48" 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 Descriotion 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) (f /ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site 13 11c.O' ua 12 Type II 24-hr 11 10-YR Rainfall=5.58" 10 Runoff Area=4.450 ac 9 Runoff Volume=0.550 of 8 Runoff Depth>1.48" LL s Tc=6.0 min 5 CN=60 2 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) ❑ Runoff Southwood Village 2 Prepared by Timmons Group Type/1 24-hr 10-YR Rainfall=5.58" Printed 3/31/2022 Summary for Subcatchment 11S: Post Routed Runoff = 26.28 cfs @ 11.97 hrs, Volume= 1.206 af, Depth> 3.26" 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 Descriotion 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 Description 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph ❑ Runoff 2826.28 cfs 26 Type II 24-hr 24 10-YR Rainfall=5.58" 20 Runoff Area=4.440 ac 18 Runoff Volume=1.206 of 16 Runoff Depth>3.26" c 14 Tc=6.0 min ,a CN=81 8 6 4 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 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 '/' 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-C rested Rectangular Weir( Controls 0.00 cfs) Southwood Village 2 Prepared by Timmons C rj Type /l 24-hr 10-YR Rainfall=5.5811 Printed 3/31/2022 Pond 12P: SWM A Inflow Area=4.440 ac- Peak Elev=407.50`- Storage=19,265 cf - I I I I I I I 1 I I I I I I 1 I I I I I I 1 I I I I I I I I _t _I _T _I _t __I _r I I I I 1 1 I I I I 1 1 I____I____ I____I____ 17 ___ I I 1 I I 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) Pond 12P: SWM A Stage -Discharge Discharge (cfs) ■ hfiow ■ Primary ❑ Primary Southwood Village 2 Prepared by Timmons C Pond 12P: SWM A Type /l 24-hr 10-YR Rainfall=5.58" Printed 3/31/2022 Stage -Area -Storage oee/Horizonta: ied Area(sq-R) 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 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet) ❑ Surface ® Storage Southwood Village 2 Type/1 24-hr 100-YR Rainfall=9.16" Prepared by Timmons Group Printed 3/31/2022 HydroCADO 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 Subcatchment1 S: 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 Subcatchmentl IS: 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 1213: 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" Printed 3/31/2022 Summary for Subcatchment 1S: Pre Site Runoff = 32.44 cfs @ 11.97 hrs, Volume= 1.438 af, Depth> 3.88" 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 Descriotion 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) (f /ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Pre Site ❑ Runoff 34- 32.44 cfs 32 Type II 24-hr 28 100-YR Rainfall=9.16" 26 Runoff Area=4.450 ac 22 Runoff Volume=1.438 of 20 Runoff Depth>3.88" 3 18 16 Tc=6.0 min 14 CN=60 12 10 8 6 4 2 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 100-YR Rainfall=9.16" Printed 3/31/2022 Summary for Subcatchment 11S: Post Routed Runoff = 49.61 cfs @ 11.97 hrs, Volume= 2.373 af, Depth> 6.41" 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 Descriotion 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 Description 6.0 Direct Entry, Subcatchment 11S: Post Routed Hydrograph 49.61 cfs 50 Type II 24-h_r_ 45 100-YR Rainfall=9.16" 40 Runoff Area=4.440 ac 35 Runoff Volume=2.373 of 30 Runoff Depth>6.41" LL 25 Tc=6.0 min 20 CN=81 10 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) ❑ Runoff 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 '/' 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-C rested Rectangular Weir (Weir Controls 24.39 cfs @ 1.51 fps) Southwood Village 2 Prepared by Timmons C Pond 12P: SWM A 49 - ---- T ---- r Type 11 24-hr 100-YR Rainfall=9.16" Printed 3/31/2022 LLC Paae 21 Inflow Area=4.440 ac Peak Elev=407.87' Storage=21,928 cf 5 6 7 8 9 16 11 12 13 14 15 16 17 18 19 20 Time (hours) Pond 12P: SWM A Stage -Discharge Discharge (cfs) ■ Inflow ■ Primary ❑ Primary Southwood Village 2 Prepared by Timmons C Pond 12P: SWM A Type 11 24-hr 100-YR Rainfall=9.16" Printed 3/31/2022 Stage -Area -Storage oee/Horizonta: ied Area(sq-R) 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 0 5,000 10,000 15,000 20,000 25,000 30,000 Storage (cubic -feet) ❑ Surface ® Storage