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WPO201900062 Calculations 2021-12-30
ENGINEERING HYDROLOGY AND HYDRAULIC CALCULATIONS BOOKLET FOR SOUTHWOOD - PHASE 1 CLEAN EARTH FILL— NORTH AREA TMP 90A1-1D ALBEMARLE COUNTY, VIRGINIA DECEMBER 23, 2021 PON OWNER: SOUTHWOOD CHARLOTTESVILLE, LLC WILLIAM THIESSEN 609-651-6404 wthiessen(a)cvillehabitat. org ENGINEER: 30 SCALE, LLC MICHAEL MYERS, PE, CFM 434-242-2866 mike(a)30scale.com Py z� 0 9 Lic. No. 33028 12/23/2021 Sr ONAL t TABLE OF CONTENTS STORMWATER MANAGEMENT/BMP NARRATIVE 3 LAND COVER CONDITIONS 5 STORM SEWER PIPE DESIGN AND INLET CALCULATIONS 6 OUTLET PROTECTION CALCULATIONS 8 NOAA ATLAS 14 PRECIPITATION VALUES 9 APPENDICES: A. ARMY CORPS APPROVAL LETTER (EMAIL) B. HYDRAFLOW REPORT- EXTENDED DETENTION POND C. VRRM SPREADSHEETS D. NUTRIENT CREDIT AVAILABILITY LETTER E. NRCS SOILS REPORT STORMWATER MANAGEMENT NARRATIVE PROJECT DESCRIPTION THE PURPOSE OF THIS PROJECT IS TO PERFORM CLEAN EARTH FILL OPERATIONS IN AN APPROXIMATE 1-ACRE GULLY LOCATED IN BETWEEN FIN COURT AND IRIS COURT, BOUNDED ON THE SOUTH BY BITTERNUT LANE AND ENDING AT THE WATER PROTECTION ORDINANCE BUFFER ON THE NORTH. BASED ON SITE VISITS AND CORRESPONDENCE WITH THE US ARMY CORPS OF ENGINEERS (ACOE), THE LIMITS OF DISTURBANCE COVERED BY THIS PLAN IS OUTSIDE OF ANY PROTECTED ELEMENTS OF A "WATERS OF THE UNITED STATES', AND THEREFORE NO ACOE PERMITTING OR REPORTING IS REQUIRED. ALSO, NO DISTURBANCE OF THE WATER PROTECTION ORDINANCE BUFFER IS PROPOSED AND THERE IS NO 100-YEAR FLOODPLAIN WITHIN THE LIMITS OF DISTURBANCE. FOLLOWING THE CLEAN EARTH FILL OPERATIONS, RUNOFF FROM THE FILL AREA WILL FLOW OVERLAND TO THE EXTENDED DETENTION POND. THE EXISTING RUNOFF FROM THE STORM SEWER ON BITTERNUT LANE WILL CONTINUE TO FLOW VIA STORM SEWER PIPE, AND WILL BYPASS THE EXTENDED DETENTION FACILITY AND OUTFALL INTO RIP -RAP OUTLET PROTECTION BEFORE ENTERING THE WATER PROTECTION ORDINANCE BUFFER. CHANNEL PROTECTION CHANNEL PROTECTION IS MET BY COMPLYING WITH 9VAC25-870-66(B)1b. THE PEAK 1-YEAR, 24-HOUR DEVELOPED DISCHARGE RATE IS LESS THAN THE MAXIMUM ALLOWABLE RUNOFF RATE FOR CONCENTRATED DISCHARGE USING THE ENERGY BALANCE CRITERIA. REFER TO ENERGY BALANCE SUMMARY ON THIS SHEET AND HYDRAULIC AND HYDROLOGIC COMPUTATIONS BOOKLET FOR SUPPORTING CALCULATIONS. Q1 MAXIMUM ALLOWABLE RUNOFF = 0.90 CFS Q1 POST -DEVELOPED = 0.71 CFS OK FLOOD PROTECTION FLOOD PROTECTION IS MET BY COMPLIANCE WITH 9VAC25-870-66(C)2B. THE PEAK 10-YEAR, 24-HOUR (10% AEP) COMBINED DEVELOPED DISCHARGE RATE HAS BEEN REDUCED TO BE LESS THAN THE PRE -DEVELOPMENT 10-YEAR, 24- HOUR DISCHARGE RATE FOR THE ENTIRE 6.28-ACRE DRAINAGE AREA TO THE POINT OF ANALYSIS. THE FOLLOWING PEAK RATES ARE TAKEN FROM THE Page 3 of 12 HYDRAFLOW CALCULATIONS REPORT LOCATED IN THE APPENDICES OF THIS BOOKLET: Q10 PRE -DEVELOPED = 24.3 CFS Q10 POST DEVELOPED = 19.5 CFS OK WATER QUALITY COMPLIANCE NARRATIVE WATER QUALITY WILL BE MET BY THE EXTENDED DETENTION POND AND THE PURCHASING NUTRIENT CREDITS. A LETTER OF AVAILABILITY HAS BEEN PROVIDED ON SHEET 9 OF THE SITE PLAN FOR 0.43 LBSNR OF SUPPLEMENTAL PHOSPHORUS REMOVAL. THE NUTRIENT CREDITS WILL BE PURCHASED PRIOR TO WPO AMENDMENT APPROVAL. THE EXTENDED DETENTION POND WILL BE PRIVATELY OWNED AND MAINTAINED AND BE SUBJECT TO A STORMWATER MANAGEMENT MAINTENANCE AGREEMENT. Page 4 of 12 LAND COVER CALCULATIONS NOTE: HAZEL AND ELIOAK SOILS ARE NRCS "B" SOILS PRE -DEVELOPMENT COMPOSITE CN CALCULATIONS LAND COVER (AC) CN CN*A COMPOSITE CN ROADWAY/SIDEWALKS/DRIVEWAYS 0.26 98 ROOFTOP 0.25 98 GRAVEL TRAIL 0.09 98 TOTAL IMPERVIOUS 0.60 98 58.8 WOODS 1.68 55 92.4 LAWN 0.05 61 3.1 TOTAL AREA 2.33 AC 154.3 66 L (FT) HI ELEV LO ELEV SLOPE SHEET FLOW 100 489.5 481.5 8.0% SHALLOW CONCENTRATED FLOW 89 481.5 472.0 10.7% CHANNEL FLOW 658 472.0 431.0 6.2% TC = 7.2 MIN POST -DEVELOPMENT COMPOSITE CN CALCULATIONS LAND COVER (AC) CN CN*A COMPOSITE CN ROADWAY/SIDEWALKS/DRIVEWAYS 0.26 98 ROOFTOP 0.25 98 GRAVELTRAIL 0.09 98 TOTAL IMPERVIOUS 0.60 98 58.8 WOODS 0.62 55 34.1 LAWN 1.11 61 67.7 TOTAL AREA 2.33 AC 160.6 69 L (FT) HI ELEV LO ELEV SLOPE SHEET FLOW 100 489.5 481.5 8.0% SHALLOW CONCENTRATED FLOW 89 481.5 472.0 10.7% CHANNEL FLOW 642 472.0 431.0 6.4% TC = 7.2 MIN NOTE: USE 5-MINUTE TIME OF CONCENTRATION FOR 2.33-ACRE DRAINAGE AREA FLOWING TO PONC OFFSITE COMPOSITE CN CALCULATIONS LAND COVER (AC) CN CN*A COMPOSITE CN ROADWAY/SIDEWALKS/DRIVEWAYS ROOFTOP 1.41 0.32 98 98 TOTAL IMPERVIOUS WOODS LAWN 1.73 2.16 0.06 98 55 61 169.5 118.8 3.7 TOTAL AREA 3.95 AC 292.0 74 Page 5 of 12 u LL m rn� m y � U N N N O V O N fi LL M V u Z r r r r r M M M M M C O O O O O O O O O O O N O W O N Z ❑ F n m N M O M 6 M O O ' y O N IL V r N O W ' y N N O J LL M W N 1(J M In Z (O (O (O 4n (O Q Z w y M M M M 0 a U r Lu U N a 7 co CO N r .. <o U U v w rn r <o � a C U r r o d U 2 U n n r o O a Q o 0 Z w 2 U m w r o O M M o O W y Q M O O N O W vc, Q V M N N NG LL O0 h V M N N c LL Page 6 of 12 Inlet Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Dec 24 2021 CURB INLETS 4 AND 5 Curb Inlet Calculations Location = Sag Compute by: Q vs Depth Curb Length (ft) = 16.00 (2) 8-FT THROATS Max Depth (in) = 6 Throat Height (in) = 6.00 Grate Area (sqft) _ -0- Highlighted Grate Width (ft) _ -0- Q Total (cfs) = 10.50 Grate Length (ft) _ -0- Q Capt (cfs) = 10.50 Q Bypass (cfs) _ -0- Gutter Depth at Inlet (in) = 5.98 Slope, Sw (ft/ft) = 0.080 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 18.92 Local Depr (in) _ -0- Gutter Vel (ft/s) _ -0- Gutter Width (ft) = 2.00 Bypass Spread (ft) _ -0- Gutter Slope (%) _ -0- Bypass Depth (in) _ -0- Gutter n-value = -0- u1 dimm,aoo. ioW NOTE: CURB INLETS 4 AND 5 WERE MODELED TOGETHER SINCE THEY ARE EACH LOCATED IN A SUMP ON OPPOSITE SIDES OF BITTERNUT LANE. COMBINED, THESE INLETS PROVIDE ADEQUATE CAPACITY TO CONVEY THE 2-YEAR DESIGN STORM WITHOUT OVERTOPPING THE CURB. THE ULTIMATE DESIGN OF SOUTHWOOD PHASE 2 WILL HONOR THE LOCATIONS OF INLETS 4 AND 5; AND SUPPLEMENTAL STORM SEWER DESIGN AT THAT TIME WILL REDUCE THE OVERLAND FLOWS ULTIMATELY FLOWING TO INLETS 4 AND 5. Page 7 of 12 1992 3.18 J LL Sm MA rs§_--ai - LN}� sa a a�i -1BE ---ENEM Source: USDA-SCS d G r Gb J G z mm � a z Plate 3.18-3 II1 - 164 Page 8 of 12 12/24/21, 8:53 AM Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* Latitude: 38.0008°, Longitude: ®-78.52350 ! Elevation: 455.13 ft** "source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)" a I Oura6on D0000rage0 1 2 5 f0 35 50 D000 100 o 100 500 1000 Smin 0.310]--0.391 0.3]7-0465 0.441 Ob44 OA95-0.610 0.555-0.1685 0.601-0]M 0.641-0798 0.678-0.1851 0.720-0.914 0.752-0968 10m1n 0.506-0.624 0.604-07" 0.707-0.871 0.792-0.976 0.885-1.09 0.95 -1.19 1.02-1.2 1.08-1.3 1.144.45 1.19-1.52 1.72 15m1n 0.6320.780 0.759-0.93 0.894-1.10 1.00-1.24 1.12438 1.21�50 1.29-L80 1.36-1.70 1A38182 1.49-1.91 1,11 2.62 30m1n 0.8678L0 1.OSL29 1.2]--1.5 1.4SL79 1.66-2.05 1.82-228 1.97-2.48 2.11-2.85 2.28-2.90 2: l-8.10 3.7 60m1n 1.W1.33 1.32�82 1.63-2.01 1.89-2.33 2.21A2.73 2.47-3.08 2.2-3.38 .96-3.71(3.274.16) 3: 2�52 2Jrr 1.28-1.85 1.53-599 1.92-2.49 .252.92 2.88-3.48 .00-3.93 3.354.39 .68-4.88 4.153.58 4: 30.14 34rr 1.38-1.82 1.8792.19 2.09-2.75 .44-3.21 2.90-3.82 .274.32 3.6".85 4.02-5A0 4.52-0.15 4.94-8.80 67 1: 9-2.29 .15-2]8 2.67--3.42 .13-4.03 3.73-4.83 42 ".53 4: 8-0.2 5.32-7.0 6.08-8.20 6. 2020 3.55 3.07 3.83 4.53 5.51 6.39 3 8.37 9.89 11.3 13-hr 225-292 2.]1-3.51 3.36-438 3.97-5.17 4]90.2 5,50-7,25.31 (7.020,1 8.13-112 9.11-12.824-hr 3.05 3.89 4.72 5.68 6.86 7.95 6 105 125 10.2n4.23-528 4.98i13 608-]62 7,01-8,83 #(613.8 102 (9.07-118 (10.6-13.8 11.9-152-day 3.59 4.36 5." 6.52 7.94 9.12 .4 11.8 13.9 156 (323-4.01) (3.91-4.87) (4.96-6A9) (5.82-]27) (703-883) (8,03-10.1) 11.6) 1 (10.2-13d) (tt9-15.5) (132-17A) 3.-1 4.84 5.69 6 8.-9 9.-1 11.0 125 14.1 16.5 (348-024) (4213.13 ) (534-652 ) 7 (6.26-765) (757-929) (864-10] ) ( 9.]8-122) (11.0-13.8 ) (127-162 ) (141-183) d.067F 4.92 76.25 7 F 9 711 183-214 (373-446J1 (4.51-5.40) (5726 -975) (925-2) ( 10.151]1 LB) .5) (13165-.15]0) (15117-.1491)] 4.72 5.68 7.10 8.26- 9.94 11.3 12.8 16A 16.8 18.] 7�y (434-513) (5.230.18) (652-772) (758-899) (9.06-108) (103-12.3) (115-13.9) (12.9-15.7) (148-183) (163-205) 5.30 B.N 7.92 9.14� 10.9 12.1 13.8 1S3 17.6 19.4 10-0ay (494-577) (5.94-0.93) (732-855) (843-986) (9.98-11.7) (112-132) (12.5-149) (13.8-16.6) (157-191) (172-211) 7.02 8.37 10.1 11.5 1&3 14.8 16 3-7 17.8 19.9 21.5 20-0ay (658-750) (7.85-8.95) (947-108) (10 L123) (12.4-14.2) (13]-15.8) (15.1-174) (18.4-19.1) (182-214) (195-232) 8.61 10.2 12.1 13.5 1S3 16.8 18.1 194 21.3 22.6 3 ay FF (811-916) (9.62-10.9 ) (114-12.8) (123-143) (14.4-16.3 ) (157-17.8 ) ( 16.9-193) (18.1-20.8) (197-22 (208-242) 10.7 12.7 14.6 66.4 1S5 20.0 21 -5-1 22.9 24.7 26.1 SY (102-114) 1 (12.0-13A) 11 (140-151) 11 (155-174) 1 (17.4-19.6) 11 (188-21.2) 11 (20.2-228) 1 (21.4-2A.3) (230-263) (242-278) 12.6 14.8 1].1 16.8 21.0 22.6 24.2 25.6 27.5 28.8 -0ay (12 fr133) (14.1-15.8) (162-181) (178-199) (19.9-22.2) (213-239) (227-255) (24.1-2].i) (257-291) (269-308) 1 Precipitation frequency (PF) estimates in this table am based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (far a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are rot checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Backto Top PF graphical Page 9 of 12 hftps://hdsc.nws.noaa.govlhdsc/pfds/pfds_Printpage.html?lat=38.0008&Ion=-78.5235&data=depth&units=english&series=pds 113 12/24/21, 8:53 AM Precipitation Frequency Data Server PDS-based depth -duration -frequency (DDF) curves Latitude: 38.0008'. Longitude:-78.5235' W 5 A.K.p rscuaenca Meru) (Yar) — 1 2 — s 10 25 so 100 200 — bo0 1000 0 ter' L C E C E C E ry L L Lry LC N N N N N N N N R N h � y 4 uEf Ills p p p OOfd[IOn Duration 24w —'"M — 3Esy - tbmin — sorry — 30aen — 74ay — O"M — 10-aay — 2Ar — 20Eay — "r — 65Lay — 121a — 6"W — 2L Average recurrence interval (years) NOAA Atlas 16. volume 2. Version 3 Created (GMT): M Dec 2413:53:06 2021 Back to Top Maps & aerials Small scale terrain Large scale terrain Washington, D.C.' Haai-nburg . �uncre1 VIRGINIA ~ IA I IN.'r iynclAurg ti Ric rbu9 Roaloke t,00xm Page 10 of 12 hftps://hdsc.nws.noaa.gov/hdsc/pfds/pfds_Printpage.html?lat=38.0008&Ion=-78.5235&data=depth&units=english&series=pds 2/3 12/24/21, 8:53 AM Precipitation Frequency Data Server Large scale map �rndn elacxsmny rewnoxe 100k. 60mi Back to Top US DeoaWneM M Commerce National Oceanic antl Atmospheric AtlminisbWion Nat anal Weather Saw National Water Center 1325 East West Highway Silver Spnng, MD 20910 Questions?: HOSC Q wcYnnc®nn Disdaimer An s mM1 Page 11 of 12 hftps://hdsc.nws.noaa.govlhdsc/pfds/pfds_Printpage.html?lat=38.0008&Ion=-78.5235&data=depth&units=english&series=pds 3/3 12/24/21, 8:53 AM Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* Latitude: 38.0008e, Longitude: ®-78.52350 ! Elevation: 455.13 ft** "source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1 Average recurrence Interval Duratlm 1 2 8 10 11 35 50 O�O�O 100 500 1000 92 Smin 3.80-4.89 4.52-5.58 5.29-6.53 5.91-1.31 6.W8.22 .21-8.93 ].89-9.58 8.1 02 8.84911.0 9.02- 1.8 69 10m1n 3.OY3.]4 3.62i.46 4.24-5.23 4. 5386 5.31-0.55 5: d-].11 6.17.61 6.45-8.09 6.83-8.88 .11-9.14 15m1n 2.53-3.12 .OF3]4 3.58-4.40 4.014.94 6.48-5.54 4.84-8.00 5.15-0.42 5.43-0.80 5: 3-].28 5.95--7.85 ��IO (1. .14) .10-2.58 2.54-3.13 .90-3.58 3.32d 10 .65-4.52 3.954.91 4.2 �30 4.56-5.79 462-8.20 BOmin 168-133 1.321.82 1.63-2.01 1.89-2.33 2.21-2.73 .4]-]3..08 2.M-3.38 .96-3.71 32 74.18 3: 2�.52 2Jrr 0.632 824 0.766-0998 0.958-1.26 1.13�48 1.33-1.73 1.50-1.98 1.6]r-x2.20 1.&S2.44 2.08-2.78 2.26-3.07 34rr 0.480-0.805 0.55".731 0 0.6 915 0.813-1.0 0.964-12 44 1.09-1. 1.21A1.61 1.34-1.80 1.51-205 1.84-228 Bfir 0.299-0.382 0.380-0.481 0.448-0.5]2 0.5 2-06]3 0.24-0.80 0.]100-0.923 0.]9]9-110.0 0.889-1.18 1.02=13 1.12�50 12-hr 0.18&0242 0225-0292 0.2]9-0.383 0.330-0429 0.39 0920 0.456-0.602 0.51]�0990 0.582�-0]88 0.8]5-0.1931 0756-1.06 W-hr 0.114-0.142) 0.138-01]2 0.106-0.220 0.208-0259 0.25 � 18 (0.2 2-0268 0.333 O423) 0.3 8-0.481 (0.M3-0.15]8)11(0.496-0655 0.05 0.091 0.115 6.136 0.168 0.190 021] Q746 0.289 0325 2:;; (0067-0084) (0.081-0.101) (0.103-0129) (0.121-0151) (0.14]-0.184) (0.167-0211) 0.189-0241) (0.213-0274) (0.247-032) (0274-0362) 0.053 0.066 0.082 6.096 0.117 0.136 F 0.153 a174 0.264 6.229 (0.048-0059) (0.059-0.071) (0M4-0091) (0.08]-0106) (0.105-0.129) (0120-0148) 0.lM O169) (0.153-0.192) (0.177-0225) (0.196-0254) 0042 0.051 0.065 6.076 0.093 0.10] 0.121 0.108 0.161 6.181 4by (0.03LOO 6) (0.047-0.056) .060-0 (0671)070- (0.0084) (0.084-0.102) (017)096-0.1 0.109-0.133) (0.123-0.151) (0.142-0.177) (0.157-0.192) 0028 0.034 0.042 6.049 0.059 0.067 0.076 0.086 0.100 0.111 7ylay (0.026-0.031) (0.031-0.037) (0.039-0046) (0.045-0053) (0.054-0664) (M61-0.0]3) 0.(69-0083) (0.077-0.094) (0088-0.109) (069Y0.122) 0.022 0.027 0.033 6.038 0.045 0.051 0.057 0.064 0.6]3 6.081 10-0ay (0.021-0024) (0.025-0.029) (0.031-0038).035- (00 W) (0.042-0.049) (0047-0055) 0.052-0062) (0.058-0069) (0065-0079) (OID2-0088) 0.015 0.017 0.021 6.024 0.028 0.031 0.034 0.03] 0.641 6.045 20-0ay (0014-0016) (0.016-0.019) (0.020-0023) (020 O026) (0.026-0.030) (0029-0033) 0.031 -0OM) (0.034-0040) (0038-0045) (0641-0048) 0.012 0.014 0.01] 6.019 0.021 0.023 0.025 0.02] 0.606 6.031 00-0ay (0.011-0 013) (0.013-0.015) (0.016-0 018) (0.018-0 020) (0.20-0.023) (D 022-0 025) 0.023-0 027) (0.025-0 029) (0 27-0 02) (0629-0 034) 0.010 002770.014 6.015 0.017 0.019 0.020 0.021 0.621 6.02d 65-0ay (0.009-0011) (0.011-0.012) (0.013-0015) (0.014-0016) (0.016-0.018) (0017-0020) 0.019-0021) (0.020-0.23) (0.021-0024) (0622-0026) 0.009 0.010 0.012 6.013 0.015 0.016 0.017 a018 1 0.019 1 0.020 60-0ay (0008-0009) (0.010-0.011) (0.011-0.013) (0.012-0014) (0.014-0.015) (0.015-0017) (0016-0D18) (0.017-0.019) (0.018-0020) (0619-0021) 1 Precipitation frequency (PF) estimates in this table am based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 9D% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates antl may be higher than currently valid PMP values. Please refer to flc A Atlas 14 document for more information. Back to Top PF graphical Page 12 of 12 https://hdsc.nws.noaa.govlhdsc/pfds/pfds_Printpage.html?lat=38.0008&Ion=-78.5235&data=intensity&units=english&series=pds 1/3 APPENDIX A ARMY CORPS APPROVAL LETTER (EMAIL) APPENDIX B HYDRAFLOW REPORT FOR EXTENDED DETENTION POND APPENDIX C APPENDIX D NUTRIENT CREDIT AVAILABILITY LLETTER APPENDIX E NRCS SOILS REPORT Mike Myers From: Pero, Vincent D CIV USARMY CENAO (USA) <Vincent.D.Pero@usace.army.mil> Sent: Wednesday, December 8, 2021 6:33 AM To: Mike Myers; William Thiessen; RJ Wright Cc: Frank Pohl; Andrew Vinisky; Bryan Rieckmann Subject: RE: Southwood - Proposed Fill in Northern Gully MINAM Thanks for showing me around the site. No permit is required from my office to fill the northern gully. The Corps determination for that area only is that it is a drainage channel and not a water of the U.S. Thanks and let me know if you need anything more from my office at this time Vinny Vinny Pero U.S. Army Corps of Engineers Norfolk District Western Virginia Regulatory Section Charlottesville Field Office 920 Gardens Boulevard, Suite 103-B Charlottesville, Virginia 22901 757-297-0011 (temp while teleworking) The Norfolk District is committed to providing the highest level of support to the public. In order for us to better serve you, please complete our Customer Satisfaction Survey at: https://regulatory.ops.usace.armV.mil/ords/f?p=136:4 From: Mike Myers <mike@30scale.com> Sent: Thursday, December 2, 2021 7:22 PM To: Pero, Vincent D CIV USARMY CENAO (USA) <Vincent.D.Pero@usace.army.mil>; William Thiessen <wthiessen@cvillehabitat.org>; RJ Wright <rjwright@faulconerconstruction.com> Cc: Frank Pohl <fpohl@albemarle.org>; Andrew Vinisky <avinisky@cvillehabitat.org>; Bryan Rieckmann <brieckma nn@fauIcon erconstruction.com> Subject: [Non-DoD Source] Southwood - Proposed Fill in Northern Gully Vinny, Thanks for meeting up with Bill (Habitat for Humanity), RJ Wright (Faulconer Construction) and me this morning at Southwood to walk the site and discuss our plan to fill the northern gully with excess dirt from Village 1 in an effort to reduce costs for trucking off excess dirt. Based on our site meeting this morning, it is our understanding that the proposed fill operations will not require a Corps permit. However, I wanted to make sure you had the various maps so that you could provide Albemarle County and us written confirmation. Our goal is to perform the fill operations in 1 Q of 2022 so that we can coordinate with the Village 1 construction schedule. I have provided snapshots of the various maps below and here is a L LINK to the full-size pdfs of each of these. Thanks very much, and please let me know if you have any questions or if you need clarification on anything, great to see you this morning, Mike PS to Frank and Matt, Once we hear back from Vinny, we would like to schedule a meeting with you (onsite preferably) so we can review our proposal in the field prior to formal submission of the E&S Plan. I will follow up with you, but wanted you to be aware of our plans and schedule. Feel free to reach out with questions as well, Mike Michael Myers, PE, CFM 30 Scale, LLC C: 34-242-2866 1 Web: 30Scale.com MAPS/EXHIBITS/PHOTOS Marked -Up WSSI WOTUS MAP — NORTHERN GULLY N 6. ie,s CNx,w3lnn wAa l (e98T M.nuN) ara suety O.An..fion Msnw'. E.N 6 T6. Ro .On.Sp FpW wttl, w.a pabn STREAM REACH CI NORTHERN STUDY S. bm WOTUSh....a, AREA BOUNDARY 9 NWSSI'sopnaw.9b orE.ary 1pN.w.M nvvs E,IC1Mf aeenea n uplsrM DFa Sace.n 1n 9. NpvinWM 13,1"9l61 Na (Sfli. 1 ..en. 9u1 wrle I..uxes TV FE—' S) 9pcoc Wm tNa -- C6 E12� NORTHERN +o ss...w,wYu GULLY TO BE'a� il,.s. nwawoa wel.. use + FILLED C'1 E6 (NOT[s9 1.fn. _ Wuwna'Ee O [uxexl mSNS6.b 0 „ —' rol vehlHa 6v IM COE, I E Marked -up Albemarle County GIS Map showing approximate location of fill, storm sewer and E83S z i 90 1 Conceptual Fill Plan 3 Photo of "Ski Slope" in Village 1 — Excess dirt to be placed in northern gully "ski slope" Excess dirt from Village 1 to be placed in northern gully 51 APPENDIX A ARMY CORPS APPROVAL LETTER (EMAIL) APPENDIX B HYDRAFLOW REPORT FOR EXTENDED DETENTION POND APPENDIX C VRRM SPREADSHEETS APPENDIX D NUTRIENT CREDIT AVAILABILITY LLETTER APPENDIX E NRCS SOILS REPORT Hydraflow Table of Contents NEW SWIM ROUTINGS - NG.gpw Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Watershed Model Schematic...................................................................................... 1 1 -Year HydrographReports................................................................................................................... 2 Hydrograph No. 1, SCS Runoff, PRE-DEVELOPMENT.......................................................... 2 TR-55 Tc Worksheet........................................................................................................... 3 Hydrograph No. 2, SCS Runoff, POST-DEVELOPMENT........................................................ 4 Hydrograph No. 4, SCS Runoff, PRE-DEV POND................................................................... 5 Hydrograph No. 5, SCS Runoff, POST-DEV TO POND. .......................................................... 6 Hydrograph No. 7, Reservoir, ROUTING................................................................................. 7 PondReport - POND........................................................................................................... 8 Hydrograph No. 9, SCS Runoff, OFFSITE............................................................................... 9 Hydrograph No. 11, Combine, COMBINED OUTFLOW........................................................ 10 10 - Year HydrographReports................................................................................................................. 11 Hydrograph No. 1, SCS Runoff, PRE-DEVELOPMENT........................................................ 11 Hydrograph No. 2, SCS Runoff, POST-DEVELOPMENT...................................................... 12 Hydrograph No. 4, SCS Runoff, PRE-DEV POND................................................................. 13 Hydrograph No. 5, SCS Runoff, POST-DEV TO POND. ........................................................ 14 Hydrograph No. 7, Reservoir, ROUTING............................................................................... 15 Hydrograph No. 9, SCS Runoff, OFFSITE............................................................................. 16 Hydrograph No. 11, Combine, COMBINED OUTFLOW........................................................ 17 100 - Year HydrographReports................................................................................................................. 18 Hydrograph No. 1, SCS Runoff, PRE-DEVELOPMENT........................................................ 18 Hydrograph No. 2, SCS Runoff, POST-DEVELOPMENT...................................................... 19 Hydrograph No. 4, SCS Runoff, PRE-DEV POND................................................................. 20 Hydrograph No. 5, SCS Runoff, POST-DEV TO POND. ........................................................ 21 Hydrograph No. 7, Reservoir, ROUTING............................................................................... 22 Hydrograph No. 9, SCS Runoff, OFFSITE............................................................................. 23 Hydrograph No. 11, Combine, COMBINED OUTFLOW........................................................ 24 IDFReport.................................................................................................................. 25 Watershed Model Schematic I HydraFlow Hydrographs Extension for Autodesk® Civil 3138 by Autodesk, Inc. v2022 Legend �d- 0ri gin Description 1 SCS Runoff PRE -DEVELOPMENT 2 SCS Runoff POST -DEVELOPMENT 4 SCS Runoff PRE-DEV POND 5 SCS Runoff POST-DEV TO POND 7 Reservoir ROUTING 9 SCS Runoff OFFSITE 11 Combine COMBINED OUTFLOW Project: NEW SWM ROUTINGS - NG.gpw Friday, 12 124 / 2021 Hydrograph Report 2 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 1 PRE -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 1 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = TR55 Total precip. = 3.05 in Storm duration = 24 hrs Q (Cfs) 10.00 It . m 4.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE -DEVELOPMENT Hyd. No. 1 -- 1 Year Friday, 12 / 24 / 2021 = 9.216 cfs = 720 min = 21,431 cuft = 74 = Oft = 7.20 min = Type II = 484 Q (cfs) 10.00 4.00 2.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 1 Time (min) 3 TR55 Tc Worksheet Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 1 PRE -DEVELOPMENT Description A B C Totals Sheet Flow Manning's n-value = 0.150 0.011 0.011 Flow length (ft) = 100.0 0.0 0.0 Two-year 24-hr precip. (in) = 3.36 0.00 0.00 Land slope (%) = 8.00 0.00 0.00 Travel Time (min) = 5.49 + 0.00 + 0.00 = 5.49 Shallow Concentrated Flow Flow length (ft) = 89.00 0.00 0.00 Watercourse slope (%) = 3.30 0.00 0.00 Surface description = Unpaved Paved Paved Average velocity (ft/s) =2.93 0.00 0.00 Travel Time (min) = 0.51 + 0.00 + 0.00 = 0.51 Channel Flow X sectional flow area (sqft) = 1.00 0.00 0.00 Wetted perimeter (ft) = 2.00 0.00 0.00 Channel slope (%) = 6.20 0.00 0.00 Manning's n-value = 0.025 0.015 0.015 Velocity (ft/s) =9.33 0.00 0.00 Flow length (ft) ({0))658.0 0.0 0.0 Travel Time (min) = 1.18 + 0.00 + 0.00 = 1.18 Total Travel Time, Tc.............................................................................. 7.20 min Hydrograph Report 4 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 2 POST -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 1 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = User Total precip. = 3.05 in Storm duration = 24 hrs Q (Cfs) 10.00 It . m 4.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor POST -DEVELOPMENT Hyd. No. 2 -- 1 Year Friday, 12 / 24 / 2021 = 9.791 cfs = 720 min = 22,651 cult = 75 = Oft = 7.20 min = Type II = 484 Q (cfs) 10.00 4.00 2.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 2 Time (min) Hydrograph Report 5 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 4 PRE-DEV POND Hydrograph type = SCS Runoff Storm frequency = 1 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 3.05 in Storm duration = 24 hrs Q (Cfs) 3.00 r it 1.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE-DEV POND Hyd. No. 4 -- 1 Year 120 240 360 480 600 720 840 960 Hyd No. 4 Friday, 12 / 24 / 2021 = 2.081 cfs = 718 min = 4,510 cuft = 66 = Oft = 5.00 min = Type II = 484 Q (cfs) 3.00 2.00 1.00 0.00 1080 1200 1320 1440 1560 Time (min) Hydrograph Report Lj Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 5 POST-DEV TO POND Hydrograph type = SCS Runoff Storm frequency = 1 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 3.05 in Storm duration = 24 hrs Q (Cfs) 3.00 r It 1.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor POST-DEV TO POND Hyd. No. 5 -- 1 Year 120 240 360 480 600 720 840 960 Hyd No. 5 Friday, 12 / 24 / 2021 = 2.663 cfs = 718 min = 5,524 tuft = 69 = Oft = 5.00 min = Type II = 484 Q (cfs) 3.00 2.00 1.00 0.00 1080 1200 1320 1440 1560 Time (min) Hydrograph Report 7 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 7 ROUTING Hydrograph type = Reservoir Peak discharge = 0.712 cfs Storm frequency = 1 yrs Time to peak = 724 min Time interval = 2 min Hyd. volume = 5,522 cuft Inflow hyd. No. = 5 - POST-DEV TO POND Max. Elevation = 432.37 ft Reservoir name = POND Max. Storage = 1,374 cuft Storage Indication method used Q (cfs) 3.00 r It 1.00 0.00 0 120 240 Hyd No. 7 360 480 600 — Hyd No. 5 ROUTING Hyd. No. 7 -- 1 Year 720 Q (cfs) 3.00 2.00 1.00 0.00 840 960 1080 1200 1320 1440 1560 ® Total storage used = 1,374 cuft Time (min) Pond Report $ Hydrafiow Hydrographs Extension for Autodesk® Civil 3DO by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Pond No. 1 - POND Pond Data Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation - 431.50 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sgft) Incr. Storage (cult) Total storage (cuft) 0.00 431.50 1,073 0 0 3.50 435.00 2,131 5,502 5,502 5.50 437.00 2,875 4,987 10,489 6.50 438.00 3,284 3,077 13,566 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in) = 36.00 6.00 0.00 0.00 Crest Len (ft) = 12.57 2.00 Inactive 0.00 Span (in) = 36.00 6.00 0.00 0.00 Crest El. (ft) = 438.00 435.00 0.00 0.00 No. Barrels = 1 1 0 0 Weir Coeff. = 3.33 3.33 3.33 3.33 Invert El. (ft) = 431.50 431.50 0.00 0.00 Weir Type = 1 Red Red -- Length (ft) = 40.00 1.00 0.00 0.00 Multi -Stage = Yes No No No Slope (%) = 1.00 1.00 0.00 n/a N-Value = .013 .013 .013 n/a Orifice Coeff. = 0.60 0.60 0.60 0.60 Exfil.(in/hr) = 0.000 (by Wet area) Multi -Stage = n/a Yes No No TW Elev. (ft) = 0.00 Stage (ft) 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0.00 4.00 Total Q Note: Culvertl0rifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir nears checked for orifice conditions (ic) and submergence (a). Stage / Discharge 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 Elev (ft) 438.50 437.50 436.50 435.50 434.50 433.50 432.50 1 431.50 40.00 Discharge (cfs) I Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 9 OFFSITE Hydrograph type = SCS Runoff Peak discharge = 5.797 cfs Storm frequency = 1 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 13,480 cult Drainage area = 3.950 ac Curve number = 74 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.30 min Total precip. = 3.05 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 Q (Cfs) 6.00 5.00 4.00 3.00 r M 1.00 OFFSITE Hyd. No. 9 -- 1 Year Q (cfs) 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 9 Time (min) 10 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 11 COMBINED OUTFLOW Hydrograph type = Combine Peak discharge = 6.436 cfs Storm frequency = 1 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 19,002 cult Inflow hyds. = 7, 9 Contrib. drain. area = 3.950 ac Q (cfs 7.00 I 11 5.00 4.00 c 11 r 11 1.00 Q (cfs) 7.00 . 11 5.00 4.00 3.00 2.00 1.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) — Hyd No. 11 —Hyd No. 7 —Hyd No. 9 Hydrograph Report 11 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 1 PRE -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 10 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = TR55 Total precip. = 5.58 in Storm duration = 24 hrs Q (cfs) 30.00 25.00 20.00 15.00 10.00 5.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE -DEVELOPMENT Hyd. No. 1 -- 10 Year Friday, 12 / 24 / 2021 = 28.25 cfs = 718 min = 64,628 cult = 74 = Oft = 7.20 min = Type II = 484 Q (cfs) 30.00 25.00 20.00 15.00 10.00 5.00 0.00 ' 1 1— 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 1 Time (min) Hydrograph Report 12 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 2 POST -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 10 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = User Total precip. = 5.58 in Storm duration = 24 hrs Q (cfs) 30.00 25.00 20.00 15.00 10.00 5.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor POST -DEVELOPMENT Hyd. No. 2 -- 10 Year Friday, 12 / 24 / 2021 = 29.17 cfs = 718 min = 66,733 cult = 75 = Oft = 7.20 min = Type II = 484 Q (cfs) 30.00 25.00 20.00 15.00 10.00 5.00 0.00 ' 1 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 2 Time (min) Hydrograph Report 13 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 4 PRE-DEV POND Hydrograph type = SCS Runoff Storm frequency = 10 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 5.58 in Storm duration = 24 hrs Q (Cfs) 10.00 It . M 4.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE-DEV POND Hyd. No. 4 -- 10 Year Friday, 12 / 24 / 2021 = 8.459 cfs = 718 min = 16,919 cuft = 66 = Oft = 5.00 min = Type II = 484 Q (cfs) 10.00 12 M 4.00 2.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 4 Time (min) Hydrograph Report 14 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 5 POST-DEV TO POND Hydrograph type = SCS Runoff Storm frequency = 10 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 5.58 in Storm duration = 24 hrs Q (Cfs) 10.00 It . M 4.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor POST-DEV TO POND Hyd. No. 5 -- 10 Year Friday, 12 / 24 / 2021 = 9.441 cfs = 718 min = 18,942 cuft = 69 = Oft = 5.00 min = Type II = 484 Q (cfs) 10.00 12 M 4.00 2.00 0.00 1 1 1 1 1 1 1 1 1 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 5 Time (min) Hydrograph Report 15 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 7 ROUTING Hydrograph type = Reservoir Peak discharge = 2.945 cfs Storm frequency = 10 yrs Time to peak = 724 min Time interval = 2 min Hyd. volume = 18,940 cult Inflow hyd. No. = 5 - POST-DEV TO POND Max. Elevation = 435.31 ft Reservoir name = POND Max. Storage = 6,285 cuft Storage Indication method used Q (cfs) 10.00 It 4.00 r Kt 0.00 0 120 240 Hyd No. 7 ROUTING Hyd. No. 7 -- 10 Year 360 480 600 — Hyd No. 5 720 Q (cfs) 10.00 to 4.00 2.00 ' 0.00 840 960 1080 1200 1320 1440 1560 ® Total storage used = 6,285 cuft Time (min) Hydrograph Report 16 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 9 OFFSITE Hydrograph type = SCS Runoff Storm frequency = 10 yrs Time interval = 2 min Drainage area = 3.950 ac Basin Slope = 0.0 % Tc method = User Total precip. = 5.58 in Storm duration = 24 hrs Q (cfs) 18.00 15.00 12.00 • m . M 3.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor OFFSITE Hyd. No. 9 -- 10 Year Friday, 12 / 24 / 2021 = 17.77 cfs = 718 min = 40,650 cult = 74 = Oft = 8.30 min = Type II = 484 Q (cfs) 18.00 15.00 12.00 M M 3.00 0.00 ' 1 1— 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 9 Time (min) 17 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 11 COMBINED OUTFLOW Hydrograph type = Combine Peak discharge = 19.54 cfs Storm frequency = 10 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 59,590 cult Inflow hyds. = 7, 9 Contrib. drain. area = 3.950 ac Q (cfs 21.00 18.00 15.00 12.00 '• o t . �� 3.00 COMBINED OUTFLOW Hyd. No. 11 -- 10 Year Q (cfs) 21.00 18.00 15.00 12.00 • t] 3.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Time (min) — Hyd No. 11 —Hyd No. 7 —Hyd No. 9 Hydrograph Report 18 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 1 PRE -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 100 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = TR55 Total precip. = 9.16 in Storm duration = 24 hrs Q (cfs) 60.00 50.00 40.00 30.00 20.00 10.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE -DEVELOPMENT Hyd. No. 1 -- 100 Year Friday, 12 / 24 / 2021 = 58.67 cfs = 718 min = 136,209 tuft = 74 = Oft = 7.20 min = Type II = 484 Q (cfs) 60.00 50.00 40.00 30.00 20.00 10.00 0.00 1 1 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 Hyd No. 1 Time (min) Hydrograph Report 19 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 2 POST -DEVELOPMENT Hydrograph type = SCS Runoff Storm frequency = 100 yrs Time interval = 2 min Drainage area = 6.280 ac Basin Slope = 0.0 % Tc method = User Total precip. = 9.16 in Storm duration = 24 hrs Q (cfs 60.00 50.00 40.00 30.00 20.00 10.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor Friday, 12 / 24 / 2021 = 59.72 cfs = 718 min = 139,047 cuft = 75 = Oft = 7.20 min = Type II = 484 Q (cfs) 60.00 50.00 40.00 30.00 20.00 10.00 0.00 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 Hyd No. 2 Time (min) Hydrograph Report 20 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 4 PRE-DEV POND Hydrograph type = SCS Runoff Storm frequency = 100 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 9.16 in Storm duration = 24 hrs Q (cfs) 21.00 18.00 15.00 12.00 • 11 3.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor PRE-DEV POND Hyd. No. 4 -- 100 Year Friday, 12 / 24 / 2021 = 19.48 cfs = 716 min = 39,459 cult = 66 = Oft = 5.00 min = Type II = 484 Q (cfs) 21.00 18.00 15.00 12.00 • oe M 3.00 0.00 ' 1 1— 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 Hyd No. 4 Time (min) Hydrograph Report 21 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 5 POST-DEV TO POND Hydrograph type = SCS Runoff Storm frequency = 100 yrs Time interval = 2 min Drainage area = 2.330 ac Basin Slope = 0.0 % Tc method = User Total precip. = 9.16 in Storm duration = 24 hrs Q (cfs) 21.00 18.00 15.00 12.00 • 11 3.00 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor POST-DEV TO POND Hyd. No. 5 -- 100 Year Friday, 12 / 24 / 2021 = 20.84 cfs = 716 min = 42,432 cuft = 69 = Oft = 5.00 min = Type II = 484 Q (cfs) 21.00 18.00 15.00 12.00 • oe M 3.00 0.00 ' 1 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 Hyd No. 5 Time (min) Hydrograph Report 22 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 7 ROUTING Hydrograph type = Reservoir Peak discharge = 17.34 cfs Storm frequency = 100 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 42,430 cult Inflow hyd. No. = 5 - POST-DEV TO POND Max. Elevation = 436.74 ft Reservoir name = POND Max. Storage = 9,836 cuft Storage Indication method used Q (cfs) 21.00 18.00 15.00 12.00 • 11 . m 3.00 ROUTING Hyd. No. 7 -- 100 Year Q (cfs) 21.00 18.00 15.00 12.00 • to 3.00 0.00 ' I 10.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 7 — Hyd No. 5 ® Total storage used = 9,836 cuft Time (min) Hydrograph Report 23 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Hyd. No. 9 OFFSITE Hydrograph type = SCS Runoff Storm frequency = 100 yrs Time interval = 2 min Drainage area = 3.950 ac Basin Slope = 0.0 % Tc method = User Total precip. = 9.16 in Storm duration = 24 hrs Q (Cfs) 40.00 30.00 20.00 10.00 0.00 0 120 240 Hyd No. 9 Peak discharge Time to peak Hyd. volume Curve number Hydraulic length Time of conc. (Tc) Distribution Shape factor OFFSITE Hyd. No. 9 — 100 Year 360 480 600 720 840 Friday, 12 / 24 / 2021 = 36.90 cfs = 718 min = 85,673 cult = 74 = Oft = 8.30 min = Type II = 484 Q (cfs) 40.00 30.00 20.00 10.00 0.00 960 1080 1200 1320 1440 Time (min) 24 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Friday, 12 / 24 / 2021 Hyd. No. 11 COMBINED OUTFLOW Hydrograph type = Combine Peak discharge = 53.47 cfs Storm frequency = 100 yrs Time to peak = 720 min Time interval = 2 min Hyd. volume = 128,103 cuft Inflow hyds. = 7, 9 Contrib. drain. area = 3.950 ac Q (cfs lif 60.00 50.00 40.00 30.00 20.00 10.00 Q (cfs) 60.00 50.00 40.00 30.00 20.00 10.00 0.00 0.00 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 Hyd No. 11 — Hyd No. 7 — Hyd No. 9 Time (min) Hydraflow Rainfall Report 25 Hydrafiow Hydrographs Extension for Autodesk® Civil 3130 by Autodesk, Inc. v2022 Return Period Intensity -Duration -Frequency Equation Coefficients (FHA) (Yrs) B D E (NIA) 1 0.0000 0.0000 0.0000 --- 2 53.4281 12.5000 0.8941 ----- 3 0.0000 0.0000 0.0000 ------- 5 75.7517 14.2000 0.8271 ------- 10 50.0721 10.7000 0.7889 ------- 25 103.3028 16.6000 0.8227 ------- 50 116.5747 17.3000 0.8234 ------- 100 124.5731 17.6000 0.8144 ----- File name: SampleFHA.idf Intensity = B I (Tc + D)AE Friday, 12 / 24 / 2021 Return Period Intensity Values (in/hr) (Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 SO 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2 4.13 3.30 2.76 2.38 2.09 1.87 1.69 1.55 1.43 1.32 1.24 1.16 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5 6.58 5.43 4.65 4.08 3.64 3.30 3.02 2.79 2.59 2.42 2.28 2.15 10 5.70 4.59 3.87 3.36 2.98 2.69 2.46 2.26 2.10 1.96 1.84 1.74 25 8.25 6.95 6.03 5.34 4.81 4.38 4.03 3.73 3.48 3.26 3.08 2.91 50 9.05 7.66 6.67 5.92 5.34 4.87 4.48 4.16 3.88 3.64 3.43 3.25 100 9.83 8.35 7.30 6.49 5.87 5.36 4.94 4.59 4.29 4.03 3.80 3.60 Tc = time in minutes. Values may exceed 60. PreciD. file name: SamDle.DCD Storm Rainfall Precipitation Table (in) Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr SCS 24-hour 3.05 3.69 0.00 3.30 5.58 5.77 6.80 9.16 SCS 6-Hr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff -1st 0.00 0.00 0.00 2.75 0.00 0.00 6.50 0.00 Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Custom 0.00 0.00 0.00 2.80 0.00 0.00 6.00 0.00 APPENDIX A ARMY CORPS APPROVAL LETTER (EMAIL) APPENDIX B HYDRAFLOW REPORT FOR EXTENDED DETENTION POND APPENDIX C APPENDIX D NUTRIENT CREDIT AVAILABILITY LLETTER APPENDIX E NRCS SOILS REPORT DEQViMinia RunoffReduaion Method Re -Development Compliance Spreadsheet - Version 3.0 1326H1 BMP standards and 5pdeficatons M 2013 Draft BMP Standards and Spee icHions Project Name: SOUTHWOOD. FILL IN NORTHERN AREA WEDGE data input cells Date: 12/17/2021 constantvalues Linear Development Project? No calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) -4 2.33 Check: BMP Design Specificaffons List 2013 Draft Stds&Specs Pre-ReDevelopmentland Cover (acres) • t®'. 0 Linearpmlect? Land coverareos enteredcorrectly? Total disturbed area entered? No SI SI ASplls BYils CSoils OSoili Totals Foren/Open spare laves) - undisturbed foresVopenspace 1.68 168 Moment! Turf (aves)- disturbed, graded for yards or other Wrt to be maws/managM 0.05 0.05 ImpeMous Cover laves) 0.60 0.60 2.33 Post -Development land Cover (acres( Amos asons cSOS DSoils rounds Forest/Open spare hoped - undisturbed, protected tore:Vopen space or refarestea land 0.62 0.62 Marged Turf laves)- disturbed, graded for yams or ether Wrf to be mawM/managM 1.11 1.11 Impervious Coverlasres) 0.60 0.60 Asset Ciledr OK. OK. Oa. OK. 2.33 • Fofest/Open spare areas must be promised in accomance with the Virginia Runoff Reduction Method Constants Runoff Coefcients(Rv) Annual Runfill(inches) 43 Asolls Broils CSoils o5ons aged Rainfall E•vent(incres) 1.00 ForesVOpen Space 0.02 0.03 O.00 0.05 oral Phosphorus(Tp) par(mF/U 0.26 Manag H Turf 0.15 0.20 0.22 0.25 oral Nhmges(M) EMC(mg/L) 1.86 Impervious Cover D.95 1 0.95 1 0.95 1 0.95 arietT Lead(lb/ameMl 0.41 Pj(m itless correction factor) M90 LAND COVER SUMMARY PRE -REDEVELOPMENT• COVER SUMMARY POSTDEVELOPMENT Land (over summarµpre Door lnver5ummarµpos[(Final) Local C0.T/SummatµPosf 71 Land cover summary -Poi, PmReaevedopment United Mjusted, Non Space. B New Impervious pwORea¢selopnpm pastDevelopmentNew Impervious ForoVitpen Space Cover(acres) 1.68 1.68 F.mWOpen Space Cmmr(acres) 062 Fmoompen Spare trivialities) MR laminated M.(forest) 0.03 0.03 Weighted M.(fones0 0.03 Weighted Rrjmost) 0.03 is robot 22% 72% %Forest 2296 %Forst 229g Managetl Turf Cover (apes) 0.05 0.05 Manag H Turf Caver (aces) 1.11 Managed Turf Cover (acre) 1.11 Weighed Adrum 0.20 0.20 Weighted Rv hi 0.20 WeyMed be(torR 0.20 %Managed TmF 2% 2% %Managed TmF 48% %Managed Tuff OR% Impennmu Ccer-Wrred 0.63 0.60 Impendam Cvue.la[re:) 0.60 ReCev.lmper iw: raerbra—) 060 Newlmpeniouscover 0.00 (arena) RNimpennausl 0b5 0.95 RNimpennaus) 0.95 RNlmMmous) 095 Rv(impemious) — %Impe"mus 26% 26% %Impervmus 26% "balaw'iaus 26% Fatal SNe Ame Imes) 2.33 2.33 Final Sae Area lav(s) 2.33 .1�s. ea Area s.Fe 0.22 0.22 Final Pent Dev She Re 0.35 ReOev Lb Rv 035 Treatment Volume and Nutrient Load Treatment Volume and Post-Reoevelopment Nutrient Load PrMeDevelopment Treatment Volume Final Post-oevelopment Part.Melapmem (acre a) 0.0525 0.0525 Treatment Volume 0.0676 Treatment Volume 096T6 Treatmem Volume (..-a) (cum -a) MEME (mea) PrMeDevela [heatmen[Valume Amen Final Pmt-0evelapment Port-Reoe.Immem .1henNapmem Imbicfem) 2,288 2,299 Treatment Volume 2,992 Treatment tnt Volume 2,902 Treatment Volume(ablc — (cubic local (cubic local Feed acre weempmem R toad Pre-ReDevelopment lP load Final Post- POSFarrMvdo,orent (b 1 /vrl 1.94 l.44 DevelapmeA` load 1.85 toad OF) 195 Ib 1 h+l Iro/vrl (IblWr cAReOeeblmemm PmReOereluvmemlP Wad lrer zrrc Finzl P,—realuvmem TF II6/arre/M nsz osz wad Pa, acre Vre wad Per arre Oa/am/nl II6/am/M Razehre lP Wad (I a/yr) r. aeJnem Reyuirea IaatlWacreM aPPRM mPre'andenowerrenuarea.amenne pemwr 0.% (aNw'P.e- N1M land maMnai in, new imps vbm cw.rl ov aovmvm wal 'Adjuvedloed.Sumem, Pre Reavelopmenimmiceeorm.peramn Manse r0e—Vemeo spare m ance.ped Tp load Reduction Required for 0.70 IF TP bad Rednedom Required For New 0 turjf areape rmo edjm newlmpemmuc raver. Redeveloped Area Wool Area((b/yr) Ib/yrl is ronsl4en[x9M Post-ReOzvebpment acreage (minus oveage of remeadlamlacreape vnpemous verf Column Ishows load reduceem rMuriementfor new mommoues cover(bnsed m new devebprnent bad bmq OAl Ibs/acre lb m), Post-Development Loatl Retluc[ion Required (lb/yr) 0.]0 Nitrogen Loads (Informational Purposes Only( Lir IPart-oe Mrnrlm TN load PrPReDerelncomem TN Load (mhr) 10.29 IPortAmeveloFarm axev lmperviaml 13.z3 (lb/yr) Drainage Area A tav la[rtal M, J—� uviparual�l iavlq , Mmn A-11INa b namwal In Dl A pE/yh * Pnn oeuelaoneminamem�aume In of AlM1 Ars Stormwater Best Management Practices (RR = Runoff Retluction) nn,naarereenn tic Pmoh—n Pn[u[e Inn rtuv Art <I—) ela m n wewra nnanunt wv ream Pnmpwwwe ree By nWn bre(IN _ x rtot" Artala[revl acre IN) aee I I-)wme —W) d,N) a�ev(I (IN ra ph) rmWmnNnnurtv .a wkm .nunalmw.e wkm o��00000mmmm� nn lllal o��0000©mmmm� Jet) RN rtupq ., a R� Tm.,.NNB.FMEBxR,Bx,NxPA,N, P.ryN (l I Tarul«a TIME E:FOUPIDO UERE MEMED WON RUNOFF RMUMOA o..ucTecsixos.= SfEWATfR QNPIITI' COMGIIANCE TAB fOR LTE COMPLIANCE CAICIIIAiWNS ,lame Mxl o��00000mmmm� o��00000mmmm� �dheMMl .. o��00000mmmm� ED,,,, MEALALED AxIA.AIA,M-ED WE) xEEACH... TOME MmMBRUS REMOVAL FLOURED OM x,E (l,/P) D Anaya n/vn FEEFULANDANEORUS REMOVED ROOM RUNOFF REDUCTION MAFTMFElNOAAJHWI TOMLP A.ABar T Sx om SREM INws AnERAr LnNGRMx LOADRFMffMewPAA(NMI SEE WATER QUALT' COMPLIANCE TAB FOR SITE COMPLIANCE CALCMATIONI lie/P xmas[xxENREM aa wmla A.AFn/,lI imM xrtmsEx xEMw[o ix of A �e/N� TOTAL RUNOFF AMAJODON WN AA(M) xFRmxREMwW wNx MINmrFEoorooN.xA<.IEEB ix B.AIN/y) sEF waTFF auaury romvuaxcFTaB FOF n rz u¢uunoxs Bgoe, MAE 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) 0.62 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac) 0.60 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED (ac) 0.60 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA (ac) 1.11 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA TREATED (ac) 1.11 0.00 0.00 0.00E 0.00 OK. AREA CHECK Site Treatment Volume (ft;) 2,942 Runoff Reduction Volume and TP By Drainage Area RUNOFF REDUCTION VOLUME (n3) 0 0 TP WAD AVAILABLE FOR REMOVAL (Ib/yr) 1.81 0.00 ���� 0.00 0.00 0.00 1.81 CHIEVEACHIEVED TP WAD REDUCTION ACHIEVED (Ib/yr) 0.27 0.00 0.00 0.00 0.00 0.27 TP LOAD REMAINING (Ib/yr) 1.54 0.00 0.00 0.00 0.00 1.54 NITROGEN WAD REDUCTION ACHIEVED (Ib/yr) 1.29 0.00 0.00 0.00 0.00 1.29 Total Phosphorus FINAL POST -DEVELOPMENT TP LOAD(Ib/yr) 1.85 TP WAD REDUCTION REQUIRED (Ib/yr) 0.70 TP WAD REDUCTION ACHIEVED (Ib/yr) 0.27 TP WAD REMAINING (Ib/yr): 1.58 REMAINING TP LOAD REDUCTION REQUIRED (Ib/yr): 0.43 Total Nitrogen (For Information Purposes) POST -DEVELOPMENT LOAD(Ib/yr) r 13.23 NITROGEN WAD REDUCTION ACHIEVED (Ib/yr)j 1.29 REMAINING POST -DEVELOPMENT NITROGEN LOAD (Ib/yr) 11.93 Virginia Runoff Reduction Method Woftheet DEQ Virginia Runoff Reduction Method Re -Development Compliance Spreadsheet - Version 3.0 LIMP Design Specifications List: 2013 Draft Sods & Spea Site Summary Project Title: SOUTHWOOD - FILL IN NORTHERN AREA WEDGE Date: 44547 Total Rainfall (in): 43 Total Disturbed Acreage: 2.33 Site Land Cover Summary Pre-ReDevelopment Land Cover (acres) Asails BSolis CSoils DSoils Totals %of Total Forest/Open (acres) 0.00 1.68 0.00 0.00 1.68 72 Managed Turf (acres) 0.00 0.05 0.00 0.00 0.05 2 Impervious Cover (acres) 0.00 0.60 0.00 0.00 0.60 26 2.33 100 Post-ReDevelopment Land Cover (acres) Asolls BSolis CSoils DSoils Totals %of Total Forest/Open (acres) 0.00 0.62 0.00 0.00 0.62 27 Managed Turf (acres) 0.00 1.11 0.00 0.00 1.11 48 Impervious Cover (acres) 0.00 0.60 0.00 0.00 0.60 26 Forest/Open Space areas must be protected in accordance with the Virginia Runoff Reduction Method 2.33 100 Site Tv and Land Cover Nutrient Loads Final Post -Development Post- Post- Adjusted Pre- (Post-ReDevelopment ReDevelopment Development ReDevelopment & New Im Impervious) P ) (New Impervious) Site Rv 0.35 0.35 - 0.27 Treatment Volume(fta) 2,942 2,942 - 2,288 TP Load(lb/yr) 1.85 1.85 -- 1.44 Total TP Load Reduction Required (lb/yr) 0.70 0.70 0 Final Port -Development Load (Port-ReDevelopment & New Impervious) Pre- ReDevelopment TN Load (lb/yr) 13.23 10.29 Pre ReDevelopment Final Post -Development Post-ReDevelopment TP TP Load per acre TP Load per acre Load per acre (Ih/acre/yr) (lb/acre/yr) (lb/acre/yr) 0.62 0.79 0.79 Summary Print Virginia Runoff Reduction Method Wcaftheet Site Compliance Summary Maximum% Reduction Required Below 20 Pre-ReDevelopment Load Total Runoff Volume Reduction (ft) 0 Total TP Load Reduction Achieved (lb/yr) 0.27 Total TN Load Reduction Achieved (lb/yr) 1.29 Remaining Post Development TP Load 1.58 (lb/yr) Remaining TP Load Reduction (lb/yr) 0.43 Required Summary Print Virginia Runoff Reduction Method Wrifthest ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Drainage Area Summary D.A. A D.A. B D.A. C D.A. D D.A. E Total Forest/Open (acres) 0.62 0.00 0.00 0.00 0.00 0.62 Managed Turf(acres) 1.11 0.00 0.00 0.00 0.00 1.11 Impervious Cover (acres) 0.60 0.00 0.00 0.00 0.00 0.60 Total Area (acres) 2.33 0.00 0.00 0.00 0.00 2.33 Drainage Area Compliance Summary D.A. A DA. B DA C D.A. D D.A. E Total TP Load Reduced (lb/yr) 0.27 0.00 1 0.00 1 0.00 0.00 0.27 TN Load Reduced (lb/yr) 1.29 0.00 10.00 10.00 0.00 1.29 Virginia Runoff Reduction Method Wmksheel Runoff Volume and CN Calculations 1-yearstorm 2-yearstorm 10-yearstorm Target Rainfall Event (in) 1 0.00 0.00 0.00 Drainage Areas RV&CN Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area CN 69 0 0 0 0 RR (ft') 0 0 0 0 0 1-year return period RV wo RR (.,,in) IN 0.00 0.00 0.00 0.00 RV w RR(ws-in) 0.00 0.00 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 2-year return period RV wo RR (.sin) 0.00 0.00 0.00 0.00 0.00 RV w RR(ws-in) 0.00 0.00 0.00 0.00 0.00 CN adjusted 100 0 0 0 0 10-year return period RV wa RR (.sin) 0.00 0.00 0.00 0.00 0.00 M/w RR(.s-in) 0.00 0.00 0.00 0.00 0.00 CN atljustetl 100 0 0 0 0 Summary Print APPENDIX A ARMY CORPS APPROVAL LETTER (EMAIL) APPENDIX B HYDRAFLOW REPORT FOR EXTENDED DETENTION POND APPENDIX C APPENDIX D NUTRIENT CREDIT AVAILABILITY LLETTER APPENDIX E NRCS SOILS REPORT %%h-VIRGINIA NUTRIENT HANK P.O. Box 142 Penn Laird, VA 22846 • (540) 217-4079 - www.VireiniaNutrientBank.com December 23, 2021 Michael Myers, PE, CFM 30 Scale, LLC 871 Justin Drive Palmyra, VA 22963 Re: Nutrient Credit Availability - Southwood - Northern Area Wedge - Site Plan Mr. Myers, The Virginia Nutrient Bank (VNB) is pleased to confirm availability 041t pounds per year of phosphorus offsets (nutrient credits) for the Southwood - Northern Area Wedge site plan located at a portion of Tax Map 90A1-ID at the intersection of Bittemut Lane, Fin Court and Iris Court in Albemarle County. The project drains to HUC: 02080204. VNB has approval from the Virginia Department of Environmental Quality (VDEQ) for Nonpoint Source Offset Generation Certification. VNB is approved to transfer nutrient credits in accordance with the Chesapeake Bay Watershed Nutrient Credit Exchange Program (VA Code 62.1-44.19:14 et seq). These 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 regulator entities qualifying for nutrient offsets. VNB is managing the Upper James Nutrient Bank in Nelson County that will generate approximately 155.31 pounds of phosphorus reduction and roughly 555.15 pounds of nitrogen reduction per year within the 02080203 HUC. VNB will retire 0.431 pounds of phosphorus credits and corresponding nitrogen credits from the Upper James Nutrient Bank in accordance with the Nutrient Offset Certification regulations. Respectfully, �• 06-Z't64 Gordon D. Weirich Virginia Nutrient Bank, LLC gordon@virginianutrientbank.com 1 540-217-4079 APPENDIX A ARMY CORPS APPROVAL LETTER (EMAIL) APPENDIX B HYDRAFLOW REPORT FOR EXTENDED DETENTION POND APPENDIX C APPENDIX D NUTRIENT CREDIT AVAILABILITY LLETTER APPENDIX E NRCS SOILS REPORT USDA United States Department of Agriculture N RCS Natural Resources Conservation Service A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Albemarle County, Virginia December 21, 2021 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrGs.usda.govtwps/ portal/nres/main/soils/healthn and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https:Hoffices.sc.egov.usda.gov/locator/app?agency=nres) or your NRCS State Soil Scientist (http://www.nrGs.usda.govtwps/portal/nres/detail/soils/contactus/? cid=nres 142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface.................................................................... How Soil Surveys Are Made ................................. SoilMap.................................................................. SoilMap............................................................... Legend................................................................. MapUnit Legend .................................................. Map Unit Descriptions .......................................... Albemarle County, Virginia ............................... 2713—Elioak loam, 2 to 7 percent slopes...... 27C—Elioak loam, 7 to 15 percent slopes.... 39D—Hazel loam, 15 to 25 percent slopes.. References............................................................. ................ 2 ................5 ................ 8 ................9 ..............10 .............. 11 ...............11 ..............13 .............. 13 .............. 14 ..............15 ..............16 C! How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil -vegetation -landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 Custom Soil Resource Report scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil -landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil -landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field -observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. IM Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. ow . y� w. .ij�,t '>t �+LSF�rr.,�� •.Sjn y'r - �� �: 27 r >. . G, AilJ ilk XP ,• �+i _ ivy u �/' �Ai ��' n ql MAPLEGEND Area of Interest (AOO O Area of Interest (AOI) Solis Soil Map Unit Polygons N Soil Map Unit Lines Soil Map Unit Points Special Point Features V Blowout ® Borrow Pit Clay Spot O Closed Depression Gravel Pit Gravelly Spot O Landfill A. Lava Flow Marsh or swamp Mine or Quarry O Miscellaneous Water O Perennial Water y Rock Outcrop + Saline Spot Sandy Spot Severely Eroded Spot Q Sinkhole Slide or Slip J, Sodic Spot Custom Soil Resource Report MAP INFORMATION g Spoil Area The soil surveys that comprise your AOI were mapped at 1:15,800. o Stony Spot W Very Stony Spot Warning: Soil Map may not be valid at this scale. wet Spot Enlargement of maps beyond the scale of mapping can cause Other misunderstanding of the detail of mapping and accuracy of soil Special Line Features line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed Water Features scale. Streams and Canals Transportation Please rely on the bar scale on each map sheet for map �..ry Rails measurements. N Interstate Highways Source of Map: Natural Resources Conservation Service ti US Routes Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Major Roads Local Roads Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts Background distance and area. A projection that preserves area, such as the . Aerial Photography Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Albemarle County, Virginia Survey Area Data: Version 15, Sep 13, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Oct 14, 2019—Oct 15, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 10 Custom Soil Resource Report Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 27B Elioak loam, 2 to 7 percent slopes 3.4 46.5% 27C Elioak loam, 7 to 15 percent slopes 2.3 31.1% 39D Hazel loam, 15 to 25 percent slopes 1.7 22.5% Totals for Area of Interest 7.4 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or 11 Custom Soil Resource Report landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha -Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. iv Custom Soil Resource Report Albemarle County, Virginia 2713—Elioak loam, 2 to 7 percent slopes Map Unit Setting National map unit symbol: kb8y Elevation: 360 to 790 feet Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost -free period: 195 to 231 days Farmland classification: All areas are prime farmland Map Unit Composition Elioak and similar soils: 80 percent Estimates are based on observations, Description of Elioak descriptions, and transects of the mapunit. Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down -slope shape: Convex Across -slope shape: Convex Parent material: Residuum weathered from mica schist Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 39 inches: silty clay H3 - 39 to 79 inches: silt loam Properties and qualities Slope: 2 to 7 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat) (0.20 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Moderately high to high Available water supply, 0 to 60 inches: Moderate (about 6.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 2e Hydrologic Soil Group: B Hydric soil rating: No 13 Custom Soil Resource Report 27C—Elioak loam, 7 to 15 percent slopes Map Unit Setting National map unit symbol: kb8z Elevation: 340 to 820 feet Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost -free period: 195 to 231 days Farmland classification: Farmland of statewide importance Map Unit Composition Elioak and similar soils: 80 percent Estimates are based on observations, Description of Elioak descriptions, and transects of the mapunit. Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down -slope shape: Convex Across -slope shape: Convex Parent material: Residuum weathered from mica schist Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 39 inches: silty clay H3 - 39 to 79 inches: silt loam Properties and qualities Slope: 7 to 15 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat) (0.20 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Moderately high to high Available water supply, 0 to 60 inches: Moderate (about 6.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Hydric soil rating: No 14 Custom Soil Resource Report 39D—Hazel loam, 15 to 25 percent slopes Map Unit Setting National map unit symbol: kbb3 Elevation: 310 to 1,300 feet Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost -free period: 195 to 231 days Farmland classification: Not prime farmland Map Unit Composition Hazel and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Hazel Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down -slope shape: Convex Across -slope shape: Convex Parent material: Residuum weathered from graywacke sandstone and mica schist Typical profile H1 - 0 to 10 inches: loam H2 - 10 to 20 inches: loam H3 - 20 to 30 inches: channery loam H4 - 30 to 79 inches: bedrock Properties and qualities Slope: 15 to 25 percent Depth to restrictive feature: 20 to 40 inches to lithic bedrock Drainage class: Excessively drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: Low (about 4.1 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B Hydric soil rating: No 15 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nres.usda.govAvps/portal/ nres/deta i I/nations I/soi Is/?cid=n res 142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www. nres.usda.gov/wps/portal/nres/detail/national/soils/?cid=nres142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www. nres.usda.gov/wps/portal/nres/detail/national/soils/?cid=nres142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/ home/?cid=nres 142 p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/ detail/national/landuse/rangepasture/?cid=stelprd b1043084 16 Custom Soil Resource Report United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nres.usda.gov/wps/portal/ nres/detail/soils/scientists/?cid=nres 142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. hftp://www.nres.usda.gov/wps/portal/nres/detail/national/soils/? cid=n res 142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/lnternet/FSE—DOCUMENTS/nrcsl42p2_052290.pdf ivil