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WPO201800088 Calculations 2019-07-18
PROJECT MANAGEMENT CIVIL ENGINEERING LAND PLANNING ENGINEERING C May 31, 2019 Mr. John Anderson Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Regarding: WPO 201800088 Pantops Corner VSMP Major Amendment Dear John, g Enclosed is the stormwater calculation packet for Pantops Corner. The development property has an area of 6.67 acres and will improve an offsite right-of-way area of an additional 0.15 acres, bringing the applicable site area (also called the development area) to 6.82 acres. The proposed stormwater design meets the runoff requirements set forth in 9VAC25-870-96, 9VAC25-870-97, and 9VAC25-870-98, the VSMP Type IIC Stormwater Management regulations. This site is designed under the Type IIC regulations because it has an active permit that was approved under these regulations which is now being amended. The current county approval is WPO 201400028 and the current land disturbance permit is #VAR10E170. SWM Quantity 9VAC25-870-97 and 9VAC25-870-98 require that the 2-yr and 10-yr peak post -development site runoff at each channel not exceed the 2-yr and 10-yr peak pre -development runoff. We analyzed the areas within the development area for runoff compliance. To achieve post -development peak flow rates that do not exceed pre -development flow rates, the majority of the site runoff will be piped to an underground detention system consisting of 472 linear feet of 96" perforated CMP pipes embedded in #57 stone. This strategy allows site runoff at the two identified points of analysis (POA 1 & POA 2), to comply with 9VAC25-870-97 and 9VAC25-870-98. There is a 0.38 acre onsite area which does not drain to a point of analysis per 9VAC25-870-97 and 9VAC25-870-98. This area drains to inlets along Route 250 and outlets directly into the Rivanna River. We analyzed this area Per 9VAC25-840-40, sections 19-b(1) & 19-b(2)(c), which states "The applicant shall demonstrate that the total drainage area to the point of analysis within the channel is 100 times greater than the contributing drainage area of the project in question... Pipes and storm sewer systems shall be analyzed by the use of a 10-year storm to verify that stormwater will be contained within the pipe or system." This requires storm sewer capacity analysis to the point where the added drainage from the site is 1/100 of the total drainage area. The total drainage area at the point of discharge into the Rivanna River is thousands of acres and qualifies as the limits of analysis due as it is over 100x larger than the added 0.38 acre drainage area. To demonstrate storm sewer capacity to this point, we demonstrated that the Rte. 250 storm sewer can contain the 10-year storm utilizing the VDOT LD-347 hydraulic grade line analysis. This shows that the 10-year storm is contained within the Rte. 250 storm sewer, so the 0.38 acres complies with 9VAC25-840-40-19 for channel flooding and protection. APPROVEU by the Albemarle County Commur a neat Department Date File SWM Quality To achieve nutrient treatment compliance per 9VAC25-870-96, we analyzed the land cover changes for the development area and input the post -development land cover into the DCR Appendix 5D worksheets. The worksheets show that an amount of 8.49 lbs. of phosphorous removal is required for this development. An amount of 8.49 lbs. of phosphorous credits will be purchased from a VADEQ-approved Nutrient Bank to satisfy this requirement. Site Runoff Quantity Totals Storm Events and Associated Peak Runoff Rates Pre-Dev Post-Dev POA 1 POA 1 Pre-Dev Post-Dev POA 2 POA 2 2-Year 4.09 cfs 4.03 cfs 1.20 1.01 cfs 10-Year 12.32 cfs 12.18 cfs 3.44 2.37 cfs If you have any questions please do not hesitate to contact me at: Justin anshimp-engineerinq.com or by phone at 434-299-9843. Contents: Pre -Development Calculations: Pre-Dev POA Drainage Map Pre-Dev HydroCAD Report Time of Concentration Calculations Post-Dev Runoff Quantity Calculations: Post-Dev Drainage Summary Spreadsheet Post-Dev Ditch and Structure Drainage Map Post-Dev POA Drainage Map Post-Dev HydroCAD Report VDOT LD-204 Inlet Capacity VDOT LD-229 Culvert Capacity Route 250 Inlet Analysis Rte. 250 Inlet Comparison Spreadsheet Pre-Dev Rte. 250 Inlet Drainage Map Post-Dev Rte. 250 Inlet Drainage Map Downstream Rte. 250 Inlet Map Rte. 250 VDOT LD-229 Culvert Capacity Rte. 250 VDOT LD-347 Hydraulic Grade Line Post-Dev Runoff Quality Calculations: Post-Dev Land Cover Map Appendix 5D Worksheets Nutrient Credit Letter of Availability Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre -Development Calculations: Pre-Dev POA Drainage Map Pre-Dev HydroCAD Report Time of Concentration Calculations PANTOPS CORNER PRE—DEV POA DRAINAGE MAP \` `` � \ r ., .::: .i: .E:'.:.i':e: ;::;.. ;. •,;,. ,:y^.' ..: ..:..:.:::...::...: .. ..:. "" .. ... -•-, �-- _. rf It \ ... :...:.... ..:..1. :.:.. ...::::: so-• ..� :::::: � :-.� ::::: •::i � .::::::o-.:::;:p:?42 ..' :ii:ii:E•.%:� i� iEs i:i:i:i ':i::� �E:er•a:E:ia• ::::� i:• 2:i� :: � ::i:� �' ::s• .::o- •s::::::, .. ,....." '` , ; . \ .....: -.,.. , ..7 ..:..:T':ar'.::..:....:: >•::..>:>:-l•`:.:.:.::::.:...� :::.:.::r .::::y.1`:.,o-o-:.o-....:. •... :::x<:.:M' al — , RIX ll \ \ •::.:i; .:.. {:{'.::..: :....::...:.:...?�....fy'...:.::::t:#::tt> •:t::::<>�iiiit€ _ o \ \::F:,Y.:t:.'::�:.::,rr:.:��`...::::�?`:::::::�:�.:::�:>. ::f€>.......-:...�t::.. r I \ \ ,, i::•":•^t•.k:?s:: ice.. as— ,.\\ 1 7r'...i`•�:2iE:i'fEEEFi•Xss f / / ! 1 t \ 1 1 ..,/ / � \ .C.— ..•`` ._,_, "'\ `'\ -�.• -.. �"' — •— —_ _ -". '_ �: ��� \ i :d 7�,l;ffS!'; .:: € l'If / 1 .� •l f / .f -�.. \ 1 t — / �' "�. '� -'—� \i --•"�'- — — -- — �\ 11 \ :fit. l�.E::Es ,:i?si?`•EFEF>f�°�'" f f f f f r l — � � _ v"O. \ �•� �. �iii3�:��¢i3;iif??: � / l 1/ / ; I f �\402 \.., � \ALL / ...�''" �.. `-.; `\ �'•- � _— \ 1 '-. I1I i:i tt •h ( i v t v v { 1 v ` v v < / ` l v 1 k 'v t f T.M. 78-5A o\ ( LAND COVER DATA TO POA 1: ,� 5., 25 AC T i.2OTA� 1 \`` ``\1' �i"''k'i?`is` ii€€;:•. f l{ll 11 1{\ tl 't I \l 5 AC IMP WOODS HSG B: 0.72 AC 1 \ TURF HSG B: 4.28 AC 7t8;-58G1 ` t I I J,1/, IMPERVIOUS: 0.25 AC \ ` \\ \\\ t..'1` r>[>fiEi::d'S;IE;titiE:'.�i:,`•':: ` I 1 •�pp / 1 / \ t J41V / I / ! TOTAL. 5.25 AC if JJ TO POA 2: WOODS HSG B: 0.39 AC -_ \`���`.;`\ t ,\ `\\ ' \ '� ' , \ \`____, -\- - - - - - - _ = 1' TURF HSG B: 0.66 AC fit I TO RTE354,1 IMPERVIOUS: 0.10 AC N. `\\\\`\\, 0.46 AC TO TOTAL: 1.15 AC , ``\ [:. ~`� ` \ ` \ `` \` —__--- -- _ � `\ / — 'j _ !ii Note: 0.46 Acre Predev Area to Rte \ \ \ \ \ \ ♦ \ i:.. `\ I ii... I: s i ilSsi [€€I'•i[i:::: tE::s ::..... ' `\ 1! J 1 •�•• �.� ( 250 is included in Rte 250 Drainage f 390. Calculations and not analyzed with a ri POA. Refer to note on Postdev POA \ , �: Drainage Map 1.15 AC TOT 0.10 At, IMP` ` ` '' - - 37o `\ Y HYDROLOGIC DATA _, z;�\ T.M. 78-5F TO POA 1: ToC= 13.2 min � /- 4.09 cfs 2 YR ` 4 1 51 I1 = o. _ Qio—YR= 12.32 cfs �C , 1. o -+ T.M. 78-5 Q100-YR= 31.73 cfs om -:: :i:iai:ri:isai �• o �I --- ocrJ3i TOPOA2: O 02-YR= 1.20 cfs l , Qio—YR— 3.44 cfs k ' Q100-YR= 8.64 cfs 347.8 �Ny ` 1 { POA 2+ b , `v ___--- ! 1 \ , \ \ 62 ! `\ ``\T.M. 78-s513 I 80 0 80 160 240 356. \ ` \ N, \ STON RO INv ` `\ \1 Scale: 1 =80 \ \1 , y po �/TF OINr Ro 10 5 is Predev DA To POA 1 Subcat Reach on Link zs Predev DA to POA 2 PREDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 2 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Predev DATo POA 1 Runoff Area=5.250 ac 4.76% Impervious Runoff Depth=0.69" Tc=13.2 min CN=62 Runoff=4.09 cfs 0.303 of Subcatchment 2S: Predev DA to POA 2 Runoff Area=1.150 ac 8.70% Impervious Runoff Depth=0.69" Tc=6.9 min CN=62 Runoff=1.20 cfs 0.066 of Total Runoff Area = 6.400 ac Runoff Volume = 0.369 of Average Runoff Depth = 0.69" 94.53% Pervious = 6.050 ac 5.47% Impervious = 0.350 ac PREDEV Type 11 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 1 S: Predev DA To POA 1 Runoff = 4.09 cfs @ 12.08 hrs, Volume= 0.303 af, Depth= 0.69" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.66" Area (ac) CN Description 0.720 55 Woods, Good, HSG B 0.250 98 Impervious 4.280 61 >75% Grass cover, Good, HSG B 5.250 62 Weighted Average 5.000 95.24% Pervious Area 0.250 4.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.2 Direct Entry, Subcatchment 1 S: Predev DA To POA 1 Hydrograph 4 Type II 24-hr 2-YR Rainfall=3.66" Runoff Area=5.250 ac 3 Runoff Volume=0.303 of Runoff Depth=0.69" LL 2 1 Tc=13.2 min CN=62 5 6 7 8 9 1011 12131415 1617181920212223242526272829303132333435363738394041 42434445464748 Time (hours) ® Runoff 8 PREDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HvdroCADO 9.10 s/n 07054 © 2011 HvdroCAD Software Solutions LLC Paae 4 Summary for Subcatchment 2S: Predev DA to POA 2 Runoff = 1.20 cfs C@ 12.00 hrs, Volume= 0.066 af, Depth= 0.69" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 2-YR Rainfall=3.66" Area (ac) CN Description 0.390 55 Woods, Good, HSG B 0.100 98 Impervious 0.660 61 >75% Grass cover, Good, HSG B 1.150 62 Weighted Average 1.050 91.30% Pervious Area 0.100 8.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.9 Direct Entry, Subcatchment 2S: Predev DA to POA 2 Hydrograph Type II 24-hr 2-YR Rainfall=3.66" Runoff Area=1.150 ac Runoff Volume=0.066 of Runoff Depth=0.69" 0 LL Tc=6.9 min ■ CN=62 5 6 7 8 9 1011 12131415 1617181920 2122232425262728 29303132 333435363738394041 42434445464748 Time (hours) ■ Runoff 9 PREDEV Type 1124-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 5 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Predev DA To POA 1 Runoff Area=5.250 ac 4.76% Impervious Runoff Depth=1.78" Tc=13.2 min CN=62 Runoff=12.32 cfs 0.780 of Subcatchment 2S: Predev DA to POA 2 Runoff Area=1.150 ac 8.70% Impervious Runoff Depth=1.78" Tc=6.9 min CN=62 Runoff=3.44 cfs 0.171 of Total Runoff Area = 6.400 ac Runoff Volume = 0.951 of Average Runoff Depth = 1.78" 94.53% Pervious = 6.050 ac 5.47% Impervious = 0.350 ac 10 PREDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 1 S: Predev DA To POA 1 Runoff = 12.32 cfs @ 12.06 hrs, Volume= 0.780 af, Depth= 1.78" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.720 55 Woods, Good, HSG B 0.250 98 Impervious 4.280 61 >75% Grass cover, Good, HSG B 5.250 62 Weighted Average 5.000 95.24% Pervious Area 0.250 4.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.2 Direct Entry, Subcatchment 1 S: Predev DA To ! A 1 Hydrograph Type II 24-hr 10-YR Rainfall=5.54" Runoff Area=5.250 ac Runoff Volume=0.780 of 7 Runoff Depth=1.78" 6 1 Tc=13.2 min 51 1 ■ CN=62 5 6 7 8 9 101112131415161718192021222324252627282930313233343536373839404142434445464748 Time (hours) ■ Runoff it PREDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 0 2011 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: Predev DA to POA 2 Runoff = 3.44 cfs @ 11.99 hrs, Volume= 0.171 af, Depth= 1.78" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.390 55 Woods, Good, HSG B 0.100 98 Impervious 0.660 61 >75% Grass cover, Good, HSG B 1.150 62 Weighted Average 1.050 91.30% Pervious Area 0.100 8.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.9 Direct Entry, Subcatchment 2S: Predev DA to POA 2 Hydrograph Type II 24-hr 10-YR 31 1 ■ Rainfall=5.54" Runoff Area=1.150 ac Runoff Volume=0.171 of 2 Runoff Depth=1.78" Tc=6.9 min CN=62 5 6 7 8 9 1011 1213141516171819202122232425262728293031323334353637383940c 42434445464748 Time (hours) ® Runoff im PREDEV Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 8 Time span=5.00-48.00 hrs, dt=0.05 hrs, 861 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Predev DA To POA 1 Runoff Area=5.250 ac 4.76% Impervious Runoff Depth=4.43" Tc=13.2 min CN=62 Runoff=31.73 cfs 1.937 of Subcatchment 2S: Predev DA to POA 2 Runoff Area=1.150 ac 8.70% Impervious Runoff Depth=4.43" Tc=6.9 min CN=62 Runoff=8.64 cfs 0.424 of Total Runoff Area = 6.400 ac Runoff Volume = 2.361 of Average Runoff Depth = 4.43" 94.53% Pervious = 6.050 ac 5.47% Impervious = 0.350 ac 13 PREDEV Type // 24-hr 100-YR Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 1 S: Predev DA To POA 1 Runoff = 31.73 cfs @ 12.05 hrs, Volume= 1.937 af, Depth= 4.43" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.720 55 Woods, Good, HSG B 0.250 98 Impervious 4.280 61 >75% Grass cover, Good, HSG B 5.250 62 Weighted Average 5.000 95.24% Pervious Area 0.250 4.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.2 Direct Entry, Subcatchment 1 S: Predev DA To POA 1 Hydrograph 30 Type II 24-hr 100-YR 28 Rainfall=9.10" 26 Runoff Area=5.250 ac 24 22 Runoff Volume=1.937 of 18 Runoff Depth=4.43" 16 Tc=13.2 min d14 ,� CN=62 5 6 7 8 9 101112131415161718192021222324252627282930313233343536373839404142434445464748 Time (hours) ® Runoff 14 PREDEV Type 1124-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 2S: Predev DA to POA 2 Runoff = 8.64 cfs @ 11.98 hrs, Volume= 0.424 af, Depth= 4.43" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.390 55 Woods, Good, HSG B 0.100 98 Impervious 0.660 61 >75% Grass cover, Good, HSG B 1.150 62 Weighted Average 1.050 91.30% Pervious Area 0.100 8.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.9 Direct Entry, Subcatchment 2S: Predev DA to POA 2 Hydrograph Type II 24-hr 100-YR 8 Rainfall=9.10" Runoff Area=1.150 ac 6 Runoff Volume=0.424 of 5 Runoff Depth=4.43" LL 4 Tc=6.9 min CN=62 3 5 6 7 8 9 1011 1213 1415 161718192021222324 2526272829303132 3334353637 38394041 42434445 464748 Time (hours) ® Runoff 15 PANTOPS CORNER Time of Concentration Calculations PREDEV TOC: POA 1 55 ft overland flow 29.1% slope 0.35 C-value 5.5 min Seelye Chart 405 ft s. c. flow -woods 3.5% slope 1.3 fps velocity 5.2 min. NEH Figure 15-4 590 ft Channel 64 ft height 2.5 min. Kirpich Chart TOC= 13.2 min. PREDEV TOC: POA 2 50 ft overland flow 24.0% slope 0.35 C-value 5.5 min Seelye Chart 297 ft s. c. flow -woods 6.1% slope 4.7 fps velocity 1.1 min. NEH Figure 15-4 195 ft Channel - Pipe 9 ft height 0.3 min. Kirpich Chart TOC= 6.9 min. 16 PRE-DEV TOC NOMOGRAPHS PREDEV TOC TO POA 1 PREDEV TOC TO POA 2 w w w z a= U- O J 2 0 z w J r1 Paved q 0 z 300 It Bare w 0 200 Soil Poor 1� Grass w �_ 3 \Surface a w Average a .4 z Grass 100 Surface ►- 90 \ a 80 nse Grass \ Z \ 0 50 .V 40 30 20 IN 35 30 25 20 N w z z 0.5 _ 1.0 w o I5 2.0 (n / z 0 .0 z �- w a 1 L) a: 20 W a. z OVERLAND FLOW TIME (Seelye Chart) Source: Data Book for Civil Engineers, E.E. Seelye z 10 0 U U \ w J 91 z 8 VA Plate 5-1 17 1.0( 0.9( 0.8( 0.7( 0.6( J161 0.4( 0.30 mm r, 0.10 0.09 0.08 0.07 0 0.06 0.05 0.04 0.03 0.02 0.01 0.005 L 0 VA, C4 m 't ua Co ti o0 q o N m co ti00 m o Velocity (ft1s) IN TRAVEL TIME FOR CHANNEL FLOW (Kirpich Chart) H (feet) 500 TC (min.) 200 100 100 L (feet) 10000 Fxamp 50 v l e 5000 > o > L c c ¢ L r C u Note: o a (1) For use with n rat channels; 4Z a o v c (2) For paved channels, iply 4- o v 10 10 Tt by 0.2 1000 V) £ 5 0 5 0 L 01 2 ,y 100 1 1 TIME OF CONCENTRATION OF SMALL DRAINAGE BASINS Source: VDOT Plate 5-3 19 Post-Dev Runoff Quantity Calculations: Post-Dev Drainage Summary Spreadsheet Post-Dev Ditch and Structure Drainage Map Post-Dev POA Drainage Map Post-Dev HydroCAD Report VDOT LD-204 Inlet Capacity VDOT LD-229 Culvert Capacity 20 Pantops Corner Inlet Drainage Area Summary Impervious C 0.9 Pervious C 0.3 To Area Impervious Turf C A D2 72,525 47,501 25,024 0.69 1.66 A13 29,364 26,085 3,279 0.83 0.67 Al2 3,007 2,230 777 0.74 0.07 A11C 6,130 5,372 758 0.83 0.14 A11B 10,470 8,117 2,353 0.77 0.24 A11 14,820 12,506 2,314 0.81 0.34 A10 2,440 1,970 470 0.78 0.06 A9A 11,545 9,455 2,090 0.79 0.27 A9Z 17,301 16,920 381 0.89 0.40 A9Y 5,203 3,771 1,432 0.73 0.12 A9 10,881 6,920 3,961 0.68 0.25 A8 3,919 1,489 2,430 0.53 0.09 A6 13,431 12,382 1,049 0.85 0.31 B1A 17,401 11,962 5,439 0.71 0.40 B7 50,958 40,963 9,995 0.78 1.17 66 1,903 1,664 239 0.82 0.04 B5 13,914 10,504 3,410 0.75 0.32 B3 7,080 4,224 1 2,856 0.66 0.16 B2 25,726 23,902 1,824 0.86 0.59 C4 6,960 3,042 3,918 0.56 0.16 C3 15,020 7,371 7,649 0.59 0.34 C2 28,971 22,983 l 5,988 0.78 0.67 A13INLET 3,410 2,631 779 0.76 0.08 B7INLET 7,203 3,711 3,492 0.61 0.17 21 s i J t �o .�RANTOPS CORNTER l I 1 \I �\ I - -- - -- -, \ mamy�i . �--' _' INLET DRAINAGE MAP //' ,' ✓ -' -' i� / ,/ i' //' //' / I [.i j 1 ,` - _-------------------------- i i -' -- �'' / / / '( / / _ _ — ♦ .4 _ — _ -- _ _ _ / Y _ g. 0C IMP/ / i �� >/� ���� 'l!.": . f � � � ■ j i "40(pa s� . „r. �.r-�sa. vxs+r.._ _..0 � � 4 / 1 / / / i' f �i'S '-� �R'I __ —..—� • f i K.j' ■ 1 TO INLET BT /,(,— 11 ■1 1 h / / �� �.. ,..� j--..:t _— — v ` ,`✓ ./ _� 0.22 ACRE5 / / / � j �. - � � I ._ _ "_— . " " '� ■ I $12 AC IMF `x _ _, "r � I � CN c ■ CR■S {�try•. ��•:i� itI p In 0. AfEA TO B2 �x 0.32`ES \ , (P ; ' t ■I .59 ACRES I I �' /' //���i!� ■I i I— C) I /0.55 AC IMP I 1 �°'�r�` ♦■• i i it ■I i i� ; I:, W CO a) 9 I I II III j ,"- — ♦ ■ ♦ .rlrf;R[w[i i'ie'p. }i r,5 s..ell r I ■I I I 'I' IX (D � ;I �Bi N 11 I 1V - I '` � I• I I � 1 I I I � , i Ji I AREA TO B � I■ . , . i ♦ _ ♦ 1.16 ACRE `.: r �� i■ Q �- , ��J�'"-I �� / r~- °' BG`■ a� S �'1// i■ I II 1 / - " ,r -J :_ s rc I I 11 i I � I ; � : �f,�', � t 1 -� ,:< i 1 � 1"- � �_ ■ `-� � "� .93 AC IMP' loop// � r 1, �r i■ i I i �'�� t----i I I �� I _ " 'f I I 1 rig 1 I 1 1 '� I �`v" ■ o`ii I i/ �,�IJ � �Is ---- f t j __ op r� � [ � I i I�—I � iEATO 10Is � ' ✓i t''/ - -- � .�; ,� I I��� � \� 1 1 I I 1 1 I I j i ,�/I✓ �I Y 1 �.P 1 4 v� vv_JJ � �� I � ',- =i� �1 A Irip ate/. i Ei� 0�13 ra V \ � I _ V1 Ci A"f'I-J .^,� vv v v V �� /� �� I ail --� I ♦ ��,;'. 0,AC I�f �' f '*1 ♦ -`� �`v %� 0.4�QCRES s, 101, Q. y ACIMP — - -- v AREA TO A8A 0.2 A�� _ iaae�e-_�-__ • �� 0_07INLETACRES A v v v v 0.27,,�4CRES AR _ ».. rowLEra�a �09-107 ��1" I 0.22 AC JMP 1� A�iJMP 7 - _� o.oe ac Inns - - ��\ D1 `- --- --�- v .._,1 . 0.05 AC IMP s // i%f `�����♦ %�....rf r....... .f .. \ ���� • f ■ Z��f, rrfY�fi�Fi�i..I I I \\ \ �� AREA TO A6`, 3g ".��%``,N- \\\ I \ \\ \ \\ \ \ \\ \ 0.31 ACRES ♦ • \ - --- -- _ -- __ ?--�- - �------- I I \� \\ \\\ \ \\\ \ \\ \\\ J r-- 0.28 AC IMP iy\\ i �} ��►.. /' i `\ 4 --- \ 211 444444 \�\` VAS • A\•\"�' A� `�V A\ - ,� / , �, - ° F - 0 09� ♦ vvvv Vv vvv\ vv v vv vv \ ��i i2 v ''00 �� I ♦ AREA TO Al / / ■ - "� - 0.33 ACRES ■ ��� �� AREA A11Ci '� ��`` '�%ll�%f�`�5'ff ♦ ■ I 6 r I rn 11 L M a� /,r?t,+ O A B� 0.14 A S / 0 2$ 71�c <f Fes. 'i A ROS�D V \ I AC 1 P 1�- A �R-� 0.19 ,+�:0, \ AREA TO A92 - /tjj --■ / _i °s ` r ■ / o , \\ �\ ` \ \ \Olir�1�1�EL\�%IA ' ■ �� ��tz i �t I i 0.40 ACRES \ v v �� vvv A `y � 0.39 AC IMP,r,! \ _ _ �v ` v `�A A ` �` �— _ A . � ;-;* - i• .ram' — m _ V A v — ' f.uu ............ ♦ I 1 v vAv \ .v : ; `ate v ■ �, -, a �� .•k... _,; � C2 INSET DETAIL o s r t r ■ � \ ' � I � ( I III � � `. 1 � 1 C3 ■ w 1 1 111� v A� — _ 1 �1 AREA TO EX" \\� 0.69 ACRES I • ■ i I ♦ I I I I I `\ �`.� f 0.53 AC IMP ' \ II13 r�i I Cv 1 r:, f:fA ♦ i s N ISLE INSET DETAIL —j THIS PAGE 60 0 60 120 1 B 0 ���; ' `•' ��� ` �`- ����j '� ems! ';►� - A x" ♦y y /�> G ----- o4b" 22 Scale: 1"=60' \\\ ~\ % r AREA TO EX C2" \ �� -� ' PANTOPS CORNTER POSTDEV POA DRAINAGE MAP � I1 i ONSITE POSTDEV �(/ / \\ l -------=�-�_ �-j I - -�_ - - -- - --- - _- -- - - -- ---- -- - - DRAINAGE INFO POAOATO POA 1:TO DETENTION , --J •--__J i it ''•., r -tJ '-- J- `i _".,`w._. ' ' JJ v 4.72 AC IMPERVIOUS -��-6-- _ 0.84 AC TURF HSG B �\ \ + , // -�i ii1, ill-�i �-' / /I '.,// _ •1 --•'J :'f:=•..,, I i r Y '/ ``' � �', ,;" a.'o� = p �i j i 5.56 AC TOTAL I; -/C J / X1J- BYPASS 1 TOPE, r- � :a..� . � ;� � 0.01 AC IMPERVIOUS � P t �•- lri� _ -i �� --- ��:�r I � � - 1 1 I / � - - _ __- -. -. 0.34 A � vA ;l lS rl';l 0.35 �"6 A� TOTAL � Jrl r �'--_� 4.72 AC I �- •.r %//l / u ; OD C TOTAB t BYPASS 2 0.03 AC V � - '_� �A`w wv ., t, , r. y I F_i •-_- �. 1 / / 'r,, .. "`��I r� Irr ,t C ' \ ` `., ♦ � \ \� \ \ \ , ,,,' I; .,,,� a _, `�� [: � '` I l is i• .•• J - __ __ - ' _ , /'' IMPERVIOUS - y. - -- 0.04 AC TOTAL ;� AC TURF T r oiflf _ {� I S E y/ ---OT r-- - ---- --- -- --- --- 250v -�� ------ --- ��'� ; � �, TO POA 2: IMPERVIOUS0.13 AC f T AC TURF HSG B r `\ 0.52 AC TOTAL . •'- �i 1 -.-. `/ i ••••••• .. ",, _ ail Note: the 0.38 Acre Site Area which flows to U \ �•. �'1 ' Rte 250 inlets discharges ' urges into the R vanna r River andmeetsthe limitsofanalysis per - 9VAC25-840-40, 19-b(1) & 19-b(2)(c) See 4 __ I - Rte 2 Inlet Analysis which shows the �V AC --; ;; i _ - '; �� ; /� I I _ I adequacy of the storm drains to the point i of discharge into the Rivanna River. \' 4 �\ A- 0TO _---_ t �'"..A'QW �'11t I 1 - - - �_ HYDROLOGIC DATA ,;,,,,0 ; I f I i f �= c--r--� -- -- \; POA 1 Assumed ToC to Detention = 6.0 min --- \► �,-- ; 1 1 1 ;1�\\;, ___ _ - Assumed Bypass ToC = 6.0 min ', ,, i � �'---__-______=---------= \ 02-YR= 4.03 cfs �-----��-\ ' Q 12.18 cfs •`, `\' \ it \ MID-- — �� '� i 1 I 1\ \ \\ , 10—YR= Q100-YR= 73.28 cfs - --- 11 i ' I rI'Q POA 2 Assumed ToC - 5.0 min ; � 02-YR— 1.01 cfs l\PQA, '1 ' Il �(I \ - - 010-YR= 2.37 cfs �\ - --- -- --_ Q100-YR= 5.31 cfs 80 0 80 160 240 III - \ o I Scale: 1' =80'23 Postdev nsite to 30S Dete tion Bypass 1 2P 4S \Dete t on Bypass 2 5L [Zi7_"I Subcat Reach on Link (6S) Postdev O site to POA 2 7L POA 2 24 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 2 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Postdev Onsite to Runoff Area=5.560 ac 84.89% Impervious Runoff Depth=2.79" Tc=6.0 min CN=92 Runoff=25.97 cfs 1.293 of Pond 2P: Detention Peak Elev=359.24' Storage=0.527 of Inflow=25.97 cfs 1.293 of Outflow=3.95 cfs 1.293 of Subcatchment 3S: Bypass 1 Runoff Area=0.350 ac 2.86% Impervious Runoff Depth=0.44" Tc=6.0 min CN=56 Runoff=0.20 cfs 0.013 of Subcatchment 4S: Bypass 2 Runoff Area=0.040 ac 75.00% Impervious Runoff Depth=2.51" Tc=6.0 min CN=89 Runoff=0.17 cfs 0.008 of Link 5L: POA 1 Inflow=4.03 cfs 1.314 of Primary=4.03 cfs 1.314 of Subcatchment 6S: Postdev Onsite to POA 2 Runoff Area=0.560 ac 25.00% Impervious Runoff Depth=1.00" Tc=5.0 min CN=68 Runoff=1.01 cfs 0.046 of Link 7L: POA 2 Inflow=1.01 cfs 0.046 of Primary=1.01 cfs 0.046 of Total Runoff Area = 6.510 ac Runoff Volume = 1.360 of Average Runoff Depth = 2.51" 24.73% Pervious = 1.610 ac 75.27% Impervious = 4.900 ac 25 POSTDEV Type 11 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paqe 3 Summary for Subcatchment 1 S: Postdev Onsite to Detention Runoff = 25.97 cfs @ 11.97 hrs, Volume= 1.293 af, Depth= 2.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-YR Rainfall=3.66" _ Area a (ac) CN Description 0.840 61 >75% Grass cover, Good, HSG B 4.720 98 Impervious 5.560 92 Weighted Average 0.840 15.11 % Pervious Area 4.720 84.89% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, 28 1 3, LL 1 Subcatchment 1 S: Postdev Onsite to Detention Hydrograph Type II 24-hr 2-YR Rainfall=3.66" Runoff Area=5.560 ac Runoff Volume=1.293 of Runoff Depth=2.79" Tc=6.0 min CN=92 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 26 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 4 Summary for Pond 2P: Detention Inflow Area = 5.560 ac, 84.89% Impervious, Inflow Depth = 2.79" for 2-YR event Inflow = 25.97 cfs @ 11.97 hrs, Volume= 1.293 of Outflow = 3.95 cfs @ 12.18 hrs, Volume= 1.293 af, Atten= 85%, Lag= 12.5 min Primary = 3.95 cfs @ 12.18 hrs, Volume= 1.293 of Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 359.24' @ 12.18 hrs Surf.Area= 0.143 ac Storage= 0.527 of Plug -Flow detention time= 75.0 min calculated for 1.293 of (100% of inflow) Center -of -Mass det. time= 75.0 min ( 864.9 - 789.8 ) Volume Invert Avail.Storage Storage Description #1 354.00' 0.297 of 12.00'W x 22.001 x 9.00'H Prismatoid x 23.6 1.287 of Overall - 0.545 of Embedded = 0.743 of x 40.0% Voids #2 354.00' 0.545 of 96.0" D x 20.01 Pipe Storage x 23.6 Inside #1 #3 362.00' 0.005 of 8.00'D x 4.00'H Vertical Cone/Cylinder 0.846 of Total Available Storage Device Routinq Invert Outlet Devices #1 Primary 354.00' 30.0" Round Culvert L= 13.9' Ke= 0.400 Inlet / Outlet Invert= 354.00' / 352.37' S= 0.1173 '/' Cc= 0.900 n= 0.012 #2 Device 1 354.00' 7.5" Vert. Orifice/Grate C= 0.600 #3 Device 1 358.20' 3.0" W x 8.0" H Vert. Orifice/Grate C= 0.600 #4 Device 1 360.72' 1.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #5 Primary 363.00' 8.0' long x 3.00' rise Sharp -Crested Rectangular Weir 2 End Contraction(s) 9.0' Crest Height Primary OutFlow Max=3.95 cfs @ 12.18 hrs HW=359.24' (Free Discharge) 1=Culvert (Passes 3.95 cfs of 50.58 cfs potential flow) 2=Orifice/Grate (Orifice Controls 3.28 cfs @ 10.69 fps) 3=Orifice/Grate (Orifice Controls 0.67 cfs @ 4.01 fps) 4=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) S=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 27 POSTDEV Type 11 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 5 H V 3 0 LL Pond 2P: Detention Hydrograph 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ■ Inflow ■ Primary 28 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADOO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 3S: Bypass 1 Runoff = 0.20 cfs @ 12.00 hrs, Volume= 0.013 af, Depth= 0.44" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-YR Rainfall=3.66" Area (ac) CN Description 0.340 55 Woods, Good, HSG B 0.010 98 Impervious 0.350 56 Weighted Average 0.340 97.14% Pervious Area 0.010 2.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Bypass 1 Hydrograph 0.22 ®Runoff 0.21 02 0.20 cfs Type II 24-hr 2-YR 0.19 0.18 Rainfall=3.66" 0.17 0.16 Runoff Area=0.350 ac 0.15 0.14 Runoff Volume=0.013 of y 0.13 0.12 Runoff Depth=0.44" 3 0.11 ,° 0.1 Tc=6.0 min 0.09 0.08 CN=56 0.03 0.01 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 6668 7072 Time (hours) 29 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 4S: Bypass 2 Runoff = 0.17 cfs @ 11.97 hrs, Volume= 0.008 af, Depth= 2.51" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-YR Rainfall=3.66" Area (ac) CN Description 0.010 61 >75% Grass cover, Good, HSG B 0.030 98 Impervious 0.040 89 Weighted Average 0.010 25.00% Pervious Area 0.030 75.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Bypass 2 Hydrograph 0.19 ®Runoff 0.18 0.17 0.1 cts Type II 24-hr 2-YR 0.16 0.15 Rainfall=3.66" 014 Runoff Area=0.040 ac 0.13 0.12 Runoff Volume=0.008 of 0.1 Runoff Depth=2.51" L 009 LL Tc=6.0 min 0.08 0.07 CN=89 0.03 0.01 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) 30 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 8 Summary for Link 5L: POA 1 Inflow Area = 5.950 ac, 80.00% Impervious, Inflow Depth = 2.65" for 2-YR event Inflow = 4.03 cfs Qa 12.14 hrs, Volume= 1.314 of Primary = 4.03 cfs Qa 12.14 hrs, Volume= 1.314 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 5L: POA 1 Hydrograph 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) IN Inflow ■ Primary 31 POSTDEV Type 1124-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 6S: Postdev Onsite to POA 2 Runoff = 1.01 cfs @ 11.97 hrs, Volume= 0.046 af, Depth= 1.00" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-YR Rainfall=3.66" Area (ac) CN Description 0.420 58 Woods/grass comb., Good, HSG B 0.140 98 Impervious (road) 0.560 68 Weighted Average 0.420 75.00% Pervious Area 0.140 25.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Postdev Onsite to POA 2 Hydrograph Type II 24-hr 2-YR Rainfall=3.66" Runoff Area=0.560 ac Runoff Volume=0.046 of Runoff Depth=1.00" 0 LL I I Tc=5.0 min 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) 0 Runoff 32 POSTDEV Type // 24-hr 2-YR Rainfall=3.66" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 10 Summary for Link 7L: POA 2 Inflow Area = 0.560 ac, 25.00% Impervious, Inflow Depth = 1.00" for 2-YR event Inflow = 1.01 cfs @ 11.97 hrs, Volume= 0.046 of Primary = 1.01 cfs @ 11.97 hrs, Volume= 0.046 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs U 3 0 LL Link 7L: POA 2 Hydrograph 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ■ Inflow ® Primary 33 POSTDEV Type 1124-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADOO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 11 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Postdev Onsite to Runoff Area=5.560 ac 84.89% Impervious Runoff Depth=4.62" Tc=6.0 min CN=92 Runoff=41.55 cfs 2.140 of Pond 2P: Detention Peak Elev=362.85' Storage=0.834 of Inflow=41.55 cfs 2.140 of Outflow=11.81 cfs 2.140 of Subcatchment 3S: Bypass 1 Runoff Area=0.350 ac 2.86% Impervious Runoff Depth=1.33" Tc=6.0 min CN=56 Runoff=0.80 cfs 0.039 of Subcatchment 4S: Bypass 2 Runoff Area=0.040 ac 75.00% Impervious Runoff Depth=4.29" Tc=6.0 min CN=89 Runoff=0.29 cfs 0.014 of Link 5L: POA 1 Inflow=12.18 cfs 2.193 of Primary=12.18 cfs 2.193 of Subcatchment 6S: Postdev Onsite to POA 2 Runoff Area=0.560 ac 25.00% Impervious Runoff Depth=2.27" Tc=5.0 min CN=68 Runoff=2.37 cfs 0.106 of Link 7L: POA 2 Inflow=2.37 cfs 0.106 of Primary=2.37 cfs 0.106 of Total Runoff Area = 6.510 ac Runoff Volume = 2.299 of Average Runoff Depth = 4.24" 24.73% Pervious = 1.610 ac 75.27% Impervious = 4.900 ac 34 POSTDEV Type 1124-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment 1 S: Postdev Onsite to Detention Runoff = 41.55 cfs @ 11.97 hrs, Volume= 2.140 af, Depth= 4.62" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.840 61 >75% Grass cover, Good, HSG B 4.720 98 Impervious 5.560 92 Weighted Average 0.840 15.11 % Pervious Area 4.720 84.89% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1 S: Postdev Onsite to Detention Hydrograph 40. Type II 24-hr 10-YR 36 Rainfall=5.54" 32 Runoff Area=5.560 ac 28 Runoff Volume=2.140 of 24 Runoff Depth=4.62" 0 22 LL 20 Tc=6.0 min 18 16 CN=92 14 12 10 8 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 35 POSTDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 13 Summary for Pond 2P: Detention Inflow Area = 5.560 ac, 84.89% Impervious, Inflow Depth = 4.62" for 10-YR event Inflow = 41.55 cfs @ 11.97 hrs, Volume= 2.140 of Outflow = 11.81 cfs @ 12.10 hrs, Volume= 2.140 af, Atten= 72%, Lag= 7.8 min Primary = 11.81 cfs @ 12.10 hrs, Volume= 2.140 of Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 362.85' @ 12.10 hrs Surf.Area= 0.144 ac Storage= 0.834 of Plug -Flow detention time= 72.8 min calculated for 2.139 of (100% of inflow) Center -of -Mass det. time= 72.9 min ( 849.0 - 776.1 ) Volume Invert Avail.Storage Storage Description #1 354.00' 0.297 of 12.00'W x 22.001 x 9.00'H Prismatoid x 23.6 1.287 of Overall - 0.545 of Embedded = 0.743 of x 40.0% Voids #2 354.00' 0.545 of 96.0" D x 20.01 Pipe Storage x 23.6 Inside #1 #3 362.00' 0.005 of 8.00'D x 4.00'H Vertical Cone/Cylinder 0.846 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 354.00' 30.0" Round Culvert L= 13.9' Ke= 0.400 Inlet / Outlet Invert= 354.00' / 352.37' S= 0.1173 '/' Cc= 0.900 n= 0.012 #2 Device 1 354.00' 7.5" Vert. Orifice/Grate C= 0.600 #3 Device 1 358.20' 3.0" W x 8.0" H Vert. Orifice/Grate C= 0.600 #4 Device 1 360.72' 1.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #5 Primary 363.00' 8.0' long x 3.00' rise Sharp -Crested Rectangular Weir 2 End Contraction(s) 9.0' Crest Height Primary Out low Max=11.81 cfs @ 12.10 hrs HW=362.84' (Free Discharge) 1=Culvert (Passes 11.81 cfs of 69.79 cfs potential flow) 12=Orifice/Grate (Orifice Controls 4.31 cfs @ 14.06 fps) 3=Orifice/Grate (Orifice Controls 1.67 cfs @ 10.00 fps) 4=Sharp-Crested Rectangular Weir (Weir Controls 5.82 cfs @ 4.77 fps) 5=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 36 POSTDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 14 U 3 0 LL Pond 2P: Detention Hydrograph 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ■ Inflow ■ Primary 37 POSTDEV Type 1124-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment 3S: Bypass 1 Runoff = 0.80 cfs @ 11.98 hrs, Volume= 0.039 af, Depth= 1.33" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.340 55 Woods, Good, HSG B 0.010 98 Impervious 0.350 56 Weighted Average 0.340 97.14% Pervious Area 0.010 2.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Bypass 1 Hydrograph 0.8 Type II 24-hr 10-YR 0.75 0.7 Rainfall=5.54" 0.65 Runoff Area=0.350 ac 0.6 0.55 Runoff Volume=0.039 of 05 Runoff Depth=1.33" 3 0.45 0.4 Tc=6.0 min 0.35 0.3 CN=56 0.25 0.2 0.15 0.1 0.05 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 38 POSTDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 16 Summary for Subcatchment 4S: Bypass 2 Runoff = 0.29 cfs @ 11.97 hrs, Volume= 0.014 af, Depth= 4.29" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.010 61 >75% Grass cover, Good, HSG B 0.030 98 Impervious 0.040 89 Weighted Average 0.010 25.00% Pervious Area 0.030 75.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Bypass 2 Hydrograph 0.32 0.3 0.2s crs 0.28 Type 1124-h r 10-YR 0.26 Rainfall=5.54" 0.24 0.22 Runoff Area=0.040 ac 0.2 Runoff Volume=0.014 of 018 Runoff Depth=4.29" 3 0.16 M 0.14 Tc=6.0 min 0.12 CN=89 0.1 0. 0. 0. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 39 POSTDEV Type 1124-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 17 Summary for Link 5L: POA 1 Inflow Area = 5.950 ac, 80.00% Impervious, Inflow Depth = 4.42" for 10-YR event Inflow = 12.18 cfs @ 12.09 hrs, Volume= 2.193 of Primary = 12.18 cfs @ 12.09 hrs, Volume= 2.193 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs 1 1 1 1 Link 5L: POA 1 Hydrograph 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) IN Inflow ■ Primary 40 POSTDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 18 Summary for Subcatchment 6S: Postdev Onsite to POA 2 Runoff = 2.37 cfs @ 11.96 hrs, Volume= 0.106 af, Depth= 2.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-YR Rainfall=5.54" Area (ac) CN Description 0.420 58 Woods/grass comb., Good, HSG B 0.140 98 Impervious (road) 0.560 68 Weighted Average 0.420 75.00% Pervious Area 0.140 25.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Postdev Onsite to POA 2 Hydrograph Type II 24-hr 10-YR 2 Rainfall=5.54" Runoff Area=0.560 ac Runoff Volume=0.106 of Runoff Depth=2.27" 3 L I Tc=5.0 min 11 1 ■ CN=68 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 41 POSTDEV Type // 24-hr 10-YR Rainfall=5.54" Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 19 Summary for Link 7L: POA 2 Inflow Area = 0.560 ac, 25.00% Impervious, Inflow Depth = 2.27" for 10-YR event Inflow = 2.37 cfs @ 11.96 hrs, Volume= 0.106 of Primary = 2.37 cfs @ 11.96 hrs, Volume= 0.106 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 7L: POA 2 Hydrograph 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) IN Inflow ■ Primary 42 POSTDEV Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 20 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: Postdev Onsite to Runoff Area=5.560 ac 84.89% Impervious Runoff Depth=8.13" Tc=6.0 min CN=92 Runoff=70.60 cfs 3.769 of Pond 2P: Detention Peak Elev=364.59' Storage=0.845 of Inflow=70.60 cfs 3.769 of Outflow=70.49 cfs 3.776 of Subcatchment 3S: Bypass 1 Runoff Area=0.350 ac 2.86% Impervious Runoff Depth=3.68" Tc=6.0 min CN=56 Runoff=2.31 cfs 0.107 of Subcatchment 4S: Bypass 2 Runoff Area=0.040 ac 75.00% Impervious Runoff Depth=7.77" Tc=6.0 min CN=89 Runoff=0.50 cfs 0.026 of Link 5L: POA 1 Inflow=73.28 cfs 3.909 of Primary=73.28 cfs 3.909 of Subcatchment 6S: Postdev Onsite to POA 2 Runoff Area=0.560 ac 25.00% Impervious Runoff Depth=5.17" Tc=5.0 min CN=68 Runoff=5.31 cfs 0.241 of Link 7L: POA 2 Inflow=5.31 cfs 0.241 of Primary=5.31 cfs 0.241 of Total Runoff Area = 6.510 ac Runoff Volume = 4.143 of Average Runoff Depth = 7.64" 24.73% Pervious- 1.610 ac 75.27% Impervious = 4.900 ac 43 POSTDEV Type 1124-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 21 Summary for Subcatchment 1 S: Postdev Onsite to Detention Runoff = 70.60 cfs @ 11.97 hrs, Volume= 3.769 af, Depth= 8.13" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.840 61 >75% Grass cover, Good, HSG B 4.720 98 Impervious 5.560 92 Weighted Average 0.840 15.11 % Pervious Area 4.720 84.89% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1 S: Postdev Onsite to Detention Hydrograph 70 Type II 24-hr 100-YR 65 Rainfall=9.10" 60 55 Runoff Area=5.560 ac 50 Runoff Volume=3.769 of ZW 45 40 Runoff Depth=8.13" v iz 3 35 Tc=6.0 min 30 CN=92 25 I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 44 Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 22 Summary for Pond 2P: Detention Inflow Area = 5.560 ac, 84.89% Impervious, Inflow Depth = 8.13" for 100-YR event Inflow = 70.60 cfs @ 11.97 hrs, Volume= 3.769 of Outflow = 70.49 cfs @ 11.97 hrs, Volume= 3.776 af, Atten= 0%, Lag= 0.0 min Primary = 70.49 cfs @ 11.97 hrs, Volume= 3.776 of Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 364.59' @ 11.97 hrs Surf.Area= 0.144 ac Storage= 0.845 of Plug -Flow detention time= 56.2 min calculated for 3.768 of (100% of inflow) Center -of -Mass det. time= 57.9 min ( 820.0 - 762.1 ) Volume Invert Avail.Storage Storage Description #1 354.00' 0.297 of 12.00'W x 22.001 x 9.00'H Prismatoid x 23.6 1.287 of Overall - 0.545 of Embedded = 0.743 of x 40.0% Voids #2 354.00' 0.545 of 96.0" D x 20.01 Pipe Storage x 23.6 Inside #1 #3 362.00' 0.005 of 8.00'D x 4.00'H Vertical Cone/Cylinder 0.846 of Total Available Storage Device Routinq Invert Outlet Devices #1 Primary 354.00' 30.0" Round Culvert L= 13.9' Ke= 0.400 Inlet / Outlet Invert= 354.00' / 352.37' S= 0.1173 '/' Cc= 0.900 n= 0.012 #2 Device 1 354.00' 7.5" Vert. Orifice/Grate C= 0.600 #3 Device 1 358.20' 3.0" W x 8.0" H Vert. Orifice/Grate C= 0.600 #4 Device 1 360.72' 1.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s) #5 Primary 363.00' 8.0' long x 3.00' rise Sharp -Crested Rectangular Weir 2 End Contraction(s) 9.0' Crest Height Primary Out low Max=70.37 cfs @ 11.97 hrs HW=364.59' (Free Discharge) 1=Culvert (Passes 19.13 cfs of 77.37 cfs potential flow) 2=Orifice/Grate (Orifice Controls 4.73 cfs @ 15.43 fps) 3=Orifice/Grate (Orifice Controls 1.97 cfs @ 11.84 fps) 4=Sharp-Crested Rectangular Weir (Weir Controls 12.43 cfs @ 6.43 fps) 5=Sharp-Crested Rectangular Weir (Weir Controls 51.23 cfs @ 4.21 fps) 45 POSTDEV Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 23 Pond 2P: Detention Hydrograph Time (hours) ■ Inflow ■ Primary 46 POSTDEV Type 1124-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 24 Summary for Subcatchment 3S: Bypass 1 Runoff = 2.31 cfs @ 11.98 hrs, Volume= 0.107 af, Depth= 3.68" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.340 55 Woods, Good, HSG B 0.010 98 Impervious 0.350 56 Weighted Average 0.340 97.14% Pervious Area 0.010 2.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Bypass 1 Hydrograph Type II 24-hr 100-YR z Rainfall=9.10" Runoff Area=0.350 ac Runoff Volume=0.107 of Runoff Depth=3.68" 0 LL I I Tc=6.0 min 1 1 ■ CN=56 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 47 POSTDEV Type 11 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 25 Summary for Subcatchment 4S: Bypass 2 Runoff = 0.50 cfs @ 11.97 hrs, Volume= 0.026 af, Depth= 7.77" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.010 61 >75% Grass cover, Good, HSG B 0.030 98 Impervious 0.040 89 Weighted Average 0.010 25.00% Pervious Area 0.030 75.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Bypass 2 Hydrograph Type II 24-hr 100-YR 0.45 Rainfall=9.10" 04 Runoff Area=0.040 ac 0.35 Runoff Volume=0.026 of 03 Runoff Depth=7.77" 3 0.25 Tc=6.0 min 0.2 CN=89 0.15 0.1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 48 POSTDEV Type 1124-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 26 Summary for Link 5L: POA 1 Inflow Area = 5.950 ac, 80.00% Impervious, Inflow Depth = 7.88" for 100-YR event Inflow = 73.28 cfs @ 11.97 hrs, Volume= 3.909 of Primary = 73.28 cfs @ 11.97 hrs, Volume= 3.909 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 5L: POA 1 Hydrograph 0 2 4 5 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) IN Inflow ■ Primary 49 POSTDEV Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 27 Summary for Subcatchment 6S: Postdev Onsite to POA 2 Runoff = 5.31 cfs @ 11.96 hrs, Volume= 0.241 af, Depth= 5.17" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-YR Rainfall=9.10" Area (ac) CN Description 0.420 58 Woods/grass comb., Good, HSG B 0.140 98 Impervious (road) 0.560 68 Weighted Average 0.420 75.00% Pervious Area 0.140 25.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Postdev Onsite to POA 2 Hydrograph 5 Type II 24-hr 100-YR Rainfall=9.10rr Runoff Area=0.560 ac 4 Runoff Volume=0.241 of 3 3 Runoff Depth=5.17rr Tc=5.0 min 50 CN=68 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ® Runoff 47i1 POSTDEV Type // 24-hr 100-YR Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 5/31/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 28 Summary for Link 7L: POA 2 Inflow Area = 0.560 ac, 25.00% Impervious, Inflow Depth = 5.17" for 100-YR event Inflow = 5.31 cfs @a 11.96 hrs, Volume= 0.241 of Primary = 5.31 cfs @ 11.96 hrs, Volume= 0.241 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 7L: POA 2 Hydrograph v 4 � o o 1 v If 14 o 10 zu z2 Z4 zb Zb 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) ■ Inflow ■ Primary 61 Pantops Corner LD-204 Stormwater Inlet Computations Inlets on Grade Only Sag Inlets Only E d Qp- 0 0 m o m Q aEi O_ o U >. E °>' O N o o N N « C N ~ O E O - L m O) C U N X h 3 N U C Q C N N U N U O F- J y N O N D_ W ci U if U = a a (3 a a U) o o a a i5 U o 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 ft ac in/hr cfs cfs tots)Y' Y' '/' ft ft cfs cfs ft ft ft) D2 DI-313 10 1.66 0.69 1.15 4.0 4.62 0.00 4.62 0.013 0.030 0.020 0.08 0.27 0.5 0.54 7.57 7.5 8.65 0.00 8.65 0.41 0.5 0.82 14.60 A13 DI-38 8 0.08 0.76 0.06 4.0 0.24 0.00 0.24 0.013 0.061 0,020 0.08 1.20 0.14 100.0% 0.24 0.00 7.5 0.45 0.00 0.45 1.52 0.15 95.9% 0.43 0.02 Al2 DI-313 8 0.07 0.74 0.05 4.0 0.21 0.00 0.21 0.013 0.061 0.020 0.08 1.14 0.14 100.0% 0.21 0.00 7.5 0.39 0.02 0.40 0.08 1.45 0.15 100.0% 0.39 0.00 Ai1C DI-38 4 0.14 0.83 0.12 4.0 0.46 0.00 0.46 0.013 0.061 0.020 0.08 0.09 0.5 0.18 3.10 7.5 0.87 0.00 0.87 0.08 0.14 0.5 0.27 3.97 A118 DI-38 8 0.24 0.77 0.18 4.0 0.74 0.00 0.74 0.013 0.061 0.020 0.08 0.09 0.5 0.18 6.00 7.5 1.38 0.00 1.38 0.08 0.14 0.5 0.28 6.32 All DI-31B 14 0.34 0.81 0.27 4.0 1.10 0.00 1.10 0.013 0.061 0.020 0.08 2.29 0.17 100.0% 1.10 0.00 7.5 2.06 0.00 2.06 4.28 0.21 100.0% 2.06 0.00 A10 DI-313 10 0.06 0.78 0.04 4.0 0.18 0.00 0.18 0.013 0.067 0.020 0.08 1.02 0.14 100.0% 0.18 0.00 7.5 0.33 0.00 0.33 1.30 0.15 100.0% 0.33 0.00 A9A DI-38 10 0.27 0.79 0.21 4.0 0.84 0.00 0.84 0.013 0.020 0.020 0.08 0.18 0.5 0.37 3.20 7.5 1.57 0.00 1.57 0.23 0.5 0.45 5.22 A9Z DI-3C 6 0.40 0.89 0.35 4.0 1.41 0.00 1.41 0.013 0.133 0.020 0.08 0.16 0.5 0.32 2.00 7.5 2.64 0.00 2.64 0.24 0.5 0.48 4.76 A9Y DI-313 12 0.12 0.73 0.09 4.0 0.35 0.00 0.35 0.013 0.133 0.020 0.08 1.17 0.14 100.0% 0.35 0.00 7.5 0.66 0.00 0.66 1.48 0.15 100.0% 0.66 0.00 A9 DI-313 12 0.25 0.68 0.17 4.0 0.68 0.00 0.68 0.013 0.133 0.020 0.08 1.50 0.15 100.0% 0.68 0.00 7.5 1.28 0.00 1.28 1.90 0.16 95.8% 1.22 0.05 A8 DI-313 10 0.09 0.53 0.05 4.0 0.19 0.00 0.19 0.013 0.133 0.020 0.08 0.93 0.14 100.0% 0.19 0.00 7.5 0.36 0.05 0.41 1.24 0.15 100.0% 0.41 0.00 A6 DI-38 14 0.31 0.85 0.26 4.0 1.05 0.00 1.05 0.013 0.015 0.040 - 4.08 0.16 100.0% 1.05 0.00 7.5 1.97 0.00 1.97 5.17 0.21 100.0% 1.97 0.00 B1A DI-38 10 0,40 0.71 0.28 4.0 1.14 0.00 1.14 0.013 0.040 0.020 0.08 0.19 0.5 0.38 1.55 7.5 2.13 0.00 2.13 0.23 0.5 0.47 3.50 87 DI-313 10 0.17 0.61 0.10 4.0 0.40 0.00 0.40 0.013 0.073 0.020 0.08 1.36 0.15 100.0% 0.40 0.00 7.5 0.76 0.00 0.76 1,76 0.16 100.0% 0.76 0.00 B6 DI-3B 10 0.04 0.82 0.04 4.0 0.14 0.00 0.14 0.013 0.073 0.020 0,08 0.93 0.14 100.0% 0.14 0.00 7.5 0.27 0.00 0.27 1.18 0.14 100.0% 0.27 0.00 B5 DI-3B 10 0.32 0.75 0.24 4.0 0.96 0.00 0.96 0.013 0.016 0.020 0.08 0.20 0.5 0.40 3.97 7.5 1.80 0.00 1.80 0.24 0.5 0.48 6.09 B3 DI-313 10 0.16 0.66 0.11 4,0 0.43 0.00 0.43 0.013 0.040 0.020 0.08 4.26 0.09 100.0% 0.43 0.00 7.5 0.80 0.00 0.80 5.39 0.11 100.0% 0.80 0.00 82 DI-3B 10 0.59 0.86 0.51 4.0 2.03 0.00 2.03 0.013 0.040 0.020 0.08 0.21 0.5 0.42 4.55 7.5 3.80 0.00 3.80 0.25 0.5 0.51 6.72 C4 DI-3B 10 0.16 0.56 0.09 4.0 0.36 0.00 0.36 0.013 0.040 0.020 0.08 1.47 0.15 100.0% 0.36 0.00 7.5 0.67 0.00 0.67 1.85 0.16 100.0% 0.67 0.00 C3 DI-3B 10 0.34 0,59 0.20 4.0 0.82 0.20 1.02 0.013 0.040 0.020 0.08 2.70 0.17 100.0% 1.02 0.00 7.5 1.54 1.11 2.65 5.83 0.24 85.4% 2.26 0.39 C2 EX. DI-38 8 0.67 0.78 0.52 4.0 2.06 0.00 2.06 0.013 0.020 0.020 0.08 5.85 0.25 90.1% 1.86 0.20 7.5 3.87 0.00 3.87 8,11 0.30 71.3% 2.76 1.11 Postdev 8-20P EX, DI-313 10 0.43 0.74 0.32 4.0 1.28 0.00 1.28 0.013 0.030 0.020 0.08 3.88 0.20 100.0% 1.28 0.00 7.5 2.40 0.00 2.40 1 5.99 0.24 100.0% 2.40 0.00 52 LD-229 Storm Drain Design Computations Pantops Corner From Structure To Structure Catch. Area (ac) Runoff Coef Increment AC Accum. AC Total TOC (min) Total Intensity (in/hr) Total Flow (cfs) Up Invert Elev. Down Invert Elev. Pipe Length (ft) Invert Slope % Pipe Diameter (in) Pipe Capacity (cfs) Velocity (f+ Flow time Increment 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 D2 D1" 1.66 0.69 1.15 1.15 5.00 6.81 7.86 390.20 389.70 34.31 1.46% 15 8.5 7.8 0.07 A13 Al2 0.67 0.83 0.56 0.56 5.00 6.81 3.82 385.50 378.00 107.73 6.96% 15 18.9 12.3 0.15 Al2 A11 0.07 0.74 0.05 0.61 5.15 6.77 4.15 377.80 376.20 40.74 3.93% 15 14.3 10.3 0.07 Al 1 C Al 1 B 0.14 0.83 0.12 0.12 5.00 6.81 0.79 383.00 381.70 102.00 1.27% 15 7.9 4.1 0.41 A11 B A11 A 0.24 0.77 0.18 0.30 5.41 6.69 2.01 381.50 380.20 85.59 1.52% 15 9.3 6.4 0.22 A11A A11 0.00 0.00 0.00 0.30 5.64 6.63 1.99 380.00 376.20 124.03 3.06% 15 12.2 7.1 0.29 A11 A10 0.34 0.81 0.27 0.89 5.21 6.75 5.99 376.00 373.70 69.94 3.29% 18 18.8 10.0 0.12 A10 A9 0.06 0.78 0.04 0.93 5.33 6.72 6.25 373.50 363.00 95.30 11.02% 18 38.7 17.7 0.09 A9A A9 0.27 0.79 0.21 0.21 5.00 6.81 1.43 370.00 363.00 49.97 14.01 % 15 26.2 11.4 0.07 A9Z A9Y 0.40 0.89 0.35 0.35 5.00 6.81 2.40 365.30 363.60 13.14 12.94% 12 13.7 12.9 0.02 A9Y A9 0.12 0.73 0.09 0.44 5.02 6.81 2.99 362.90 362.50 22.21 1.80% 15 9.4 6.8 0.05 A9 A8 0.25 0.68 0.17 1.75 5.07 6.79 11.89 362.30 360.60 45.30 3.75% 18 22.0 9.4 0.08 A8 A7 0.09 0.53 0.05 1.80 5.15 6.77 12.17 360.40 359.70 67.88 1.03% 24 24.9 8.2 0.14 A7 A6 0.00 0.00 0.00 1.80 5.29 6.73 12.10 359.50 357.90 153.65 1.04% 24 25.0 8.2 0.31 A6 A5 0.31 0.85 0.26 2.06 5.60 6.64 13.69 357.70 356.90 72.05 1.11 % 24 25.7 8.4 0.14 A4 A3 11.71 354.00 352.13 15.92 11.75% 30 152.3 18.4 0.01 A3 A2 11.71 350.93 348.71 54.10 4.10% 30 90.0 12.7 0.07 A2 Al 11.71 340.52 340.00 20.24 2.57% 30 71.7 10.7 0.03 B7 B6 1.17 0.78 0.92 0.92 5.00 6.81 6.23 378.50 378.00 25.00 2.00% 15 9.9 8.5 0.05 B6 B5 0.04 0.82 0.04 0.95 5.05 6.80 6.46 377.80 376.20 134.79 1.19% 15 7.6 7.0 0.32 B5 B4 0.32 0.75 0.24 1.19 5.37 6.71 7.99 376.00 375.50 24.90 2.01 % 18 16.2 9.1 0.05 B4 B3 0.00 0.00 0.00 1.19 5.42 6.69 7.98 375.30 372.70 100.38 2.59% 18 18.4 10.0 0.17 B3 B2 0.16 0.66 0.11 1.30 5.58 6.65 8.63 372.50 363.20 145.91 6.37% 18 28.7 14.2 0.17 B2 B1 0.59 0.86 0.51 1.81 5.75 6.60 11.91 363.00 359.00 40.28 9.93% 18 35.9 18.2 0.04 B1A B1 0.40 0.71 0.28 0.28 5.00 6.81 1.94 361.50 359.00 19.80 12.63% 15 24.9 12.0 0.03 C4 C3 0.16 0.56 0.09 0.09 5.00 6.81 0.61 350.11 349.53 59.18 0.98% 15 7.0 3.4 0.29 C3 C2 0.34 0.59 0.20 0.29 5.29 6.73 1.98 349.33 348.66 67.51 0.99% 15 7.0 4.2 0.27 C2 EX. Cl 0.67 0.78 0.52 0.52 5.56 6.65 3.43 348.46 347.80 112.83 0.58% 15 5.3 3.4 0.55 'Ex. Storm Sewer Downstream D1 is adequate. See Rte 250 LD-347 53 Route 250 Inlet Analysis Rte. 250 Inlet Comparison Spreadsheet Pre-Dev Rte. 250 Inlet Drainage Map Post-Dev Rte. 250 Inlet Drainage Map Downstream Rte. 250 Inlet Map Rte. 250 VDOT LD-229 Culvert Capacity Rte. 250 VDOT LD-347 Hydraulic Grade Line 54 Route 250 Inlet Drainage Area Summary Impervious C 0.9 Pervious C 0.3 To Area Impervious Turf C A Predev D1 73,060 42,275 30,785 0.65 1.68 Postdev D1 72,525 47,501 25,024 0.69 1.66 Predev 8-20P 21,778 10,675 11,103 0.59 0.50 Postdev 8-20P j 18,870 13,802 5,068 0.74 0.43 8-21P 24,860 21,800 3,060 0.83 0.57 8-3P 17,920 15,500 2,420 0.82 0.41 8-4P 11,110 10,200 910 0.85 0.26 7-21P 14,240 13,000 1,240 0.85 0.33 7-22P 35,454 32,000 3,454 0.84 0.81 7-18P 43,700 40,000 3,700 0.85 1.00 7-11P 5,562 5,562 0 0.90 0.13 7-10P 54,970 52,000 2,970 0.87 1.26 7-4P 6,315 6,315 0 0.90 0.14 7-2P 26,984 26,984 0 0.90 0.62 7-3 P 00 0 0 0.00 0.00 7-1P 14,060 13,000 1,060 0.85 0.32 6-13P 15,145 14,000 1,145 0.85 0.35 6-16P 8,080 8,080 0 0.90 0.19 Rte 250 Inlet Drainage Areas computed with GIS topographic info. Rte 250 Storm Sewer Data obtained from VDOT archives. Ref. VDOT Project # 0250-002-105 Construction Plans 55 ,k r ------------- k ili r(� 1„y i IJ o 1 �I4EDEV TO 8.4'JOP ;0.40 ACRES 1 _-____ - 0.25 AC IMP - - - ` _- '--- - PREDEV TO D1 i / ---`---------- - -- - - - — - O -- -- -- ---- "-------- — �_. --- --_ ---- -- - -- _ - --- — ------ - ----- �--' , — _ �Q.9T AC IMP STIR, T — — I 8-20121 / r i i / 1 I 1 1 1 k l \ 1 \ \t I 1 , r 1 PREDEV DRAINAGE INFO TO PREDEV D1: TURF HSG B: 0.71 AC IMPERVIOUS: 0.97 AC TOTAL: 1.68 AC TO PREDEV 8-20P: TURF HSG B: 0.25 AC IMPERVIOUS: 0.25 AC TOTAL: 0.50 AC HYDROLOGIC DATA TO PREDEV D1: Assumed ToC = 5.0 min . Q2-YR= 5.61 cfs Q10_YR= 7.39 cfs TOTAL TO PREDEV 8-20P: Q2-YR= 9.39 cfs Q10_YR= 12.42 cfs l PANTOPS CORNTER PRE—DEV DRAINAGE MAP RTE 250 INLETS _J 1 -Ji - \ I \ t \ J' 0 56 :1 1 :1 160 41 i1 POSTDEV DRAINAGE INFO TO POSTEV D2 & D1: TURF HSG B: 0.57 AC IMPERVIOUS: 1.09 AC TOTAL: 1.66 AC TO POSTEV 8-20P: TURF HSG B: 0.11 AC IMPERVIOUS: 0.32 AC TOTAL: 0.43 AC HYDROLOGIC DATA TO POSTEV D2 & D1: Assumed ToC = 5.0 min 02-YR= 5.96 cfs Q10-YR= 7.89 cfs TOTAL TO POSTEV 8-20P: Q2-YR= 9.86 cfs Q10-YR= 13.04 cfs PANTOPS CORNTER POST—DEV DRAINAGE MAP RTE 250 INLETS 57 / / i I STR 6-17 I / F kFFe�Pj i / / / i I / STR 6-13P / i / / / / / / i 6P STR 7-1 P STR 7-31 STR 7-2P STR 7-1 1 Q� 7-1 7 11 1 100 200 300 %%% 11 STATE ROUTE 250 O W IJ /r STR 7-21 F PANTOPS CORNTER EXISTING DRAINAGE MAP RTE 250 INLETS --- 7j-- ---- r /If-------- J / i �. / Aar T 6-21 - ------ - P jSEEPaSYFSEP 250 DRAINAGE MAP) m 03 m z v v -u W O v O C m v v D z O CA N n O z m A FATE ROUTE 250 I r� mm 11 m v r 58 Rte 250 LD-229 Pint- r"'n- From To Design Catch. Runoff Increment Accum. Total Total Total Up Down Pipe Invert Pipe Pipe Velocity Flow time Structure Structure Storm Area Coef AC AC TOC Intensity Flow Invert Invert Length Slope Diameter Capacity Increment (ac) (min) (in/hr) (cfs) Elev. Elev. (ft) % (in) (cfs) (ft/s) (min) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Preclt,v D1 8 22P 2-yr 3 70 Postdev D1 8-22P 2-yr 1.66 0.69 1.15 1.15 5.00 5.17 5.96 389.50 377.60 263.0 4.52% 15 13.70 10.8 0.41 10-yr 5.00 6.81 7.86 11.6 0.38 8-21 P 8-20P 2-yr 0.57 0.83 0.47 0.47 5.00 5.17 2.44 377.80 377.60 8.0 2.50% 15 10.20 6.8 0.02 (Flow to inlet did not change) 10-yr 5.00 6.81 3.21 7.0 0.02 'reel{;v 8.2O== Postdev 8-20P 8-4P 2-yr 0.43 0.74 0.32 1.95 5.41 5.07 9.86 377.60 368.00 224.0 4.29% 18 21.80 11.4 0.33 10-yr 5.38 6.70 13.04 12.9 0.29 a Flow at 8-20P 2-yr 2-yr 0.47 10-yr 10-yr 0.62 Postdev Downstream Flows: 8-4P 7-22P 10-yr 0.67 0.82 0.55 2.50 5.67 6.62 16.55 367.10 361.00 291.0 2.10% 18 15.22 8.6 0.56 7-22P 7-18P 10-yr 1.14 0.84 0.96 3.46 6.23 6.47 22.41 357.37 348.87 200.0 4.25% 18 21.66 12.3 0.27 7-18P 7-3P 10-yr 1.00 0.85 0.85 4.31 6.50 6.40 27.62 348.39 342.50 147.0 4.01% 18 18.16 10.3 0.24 7-3P 7-1 P 10-yr 2.15 0.90 1.90 6.21 6.74 6.34 39.40 339.78 338.04 55.0 3.16% 24 40.21 14.6 0.06 7-1 P 6-16P 10-yr 0.32 0.85 0.28 6.49 6.80 6.33 41.05 335.40 330.40 95.0 5.26°/ 24 51.88 18.3 0.09 6-16P 6-17P 10-yr 0.53 0.85 0.46 6.95 6.89 6.31 43.84 330.30 312.10 79.0 23.04% 24 108.59 32.7 0.04 59 Rte 250 Inlets LD-347 Hydraulic Grade Line n = 0.013 Inlet Number 1 Outlet Water Surface Elev.' 2 Do 3 Oc 4 L„ 5 Sfo% 6 Hf 7 Junction Loss Final H 19 Inlet Water Surface Elev. 20 Rim. Elev 21 Vo (8) Ho (9) O, (10) V; (11) O;V; (12) H, (13) Angle (14) Ho (is) Ht (16) 1.3`Ht (17) 0.51-It (18) 6-16P 313.70 2.00 43.84 79.00 3.757% 2.968 32.69 4.9781 41.05 18.30 751.3 1.820 15 0.988 7.786 10.754 324.45 338.65 7-1P 332.00 2.00 41.05 95.00 3.294% 3.130 18.30 2.2361 39.40 14.59 574.9 1.157 40 1.421 4.814 7.944 339.94 343.58 7-3P 339.94 2.00 39.40 55.00 3.035 % 1.669 14.59 0.1983 27.62 10.28 284.0 0.574 5 0.098 0.871 2.540 342.48 345.50 7-18P 343.70 1.50 27.62 147.00 6.917 % 10.169 10.28 0.0985 22.41 12.25 274.5 0.816 5 0.140 1.054 0.5269 10.695 354.40 354.57 7-22P 354.40 1.50 22.41 200.00 4.552% 9.105 12.25 0.1165 16.55 8.60 142.4 0.402 3 0.057 0.576 0.2879 9.393 363.79 364.37 8-4P 363.79 1.50 16.55 291.00 2.484% 7.230 8.60 0.0459 13.04 12.90 168.2 0.904 1 0.103 1.054 0.5269 7.756 371.54 371.70 Postdev 8-20P 371.54 1.50 13.04 224.00 1.542% 3.453 11.40 0.0807 12.42 12.00 149.1 1 0.783 1 0.089 0.953 4.406 375.95 381.60 Postdev D1 378.60 1.25 7.86 263.00 1.480% 3.892 11.60 1.2537 7.86 7.75 60.9 0.326 69 0.560 2.140 1.0698 4.962 383.56 393.60 .a ua as L - V--1 UI -U- LIM -!i Wdteu tduwdter ur ure invert uut. M Post-Dev Runoff Quality Calculations: Post-Dev Land Cover Map Appendix 5D Worksheets Nutrient Credit Letter of Availability m PANTOPS CORNTER POST DEVELOPMENT LAND COVER MAP If SITE BOUNDARY u U IMPERVIOUS (TYP.) � I 1 AREA�w 0 ROW RENTS) � 80 0 80 160 240 Scale:i0 I.•A•: .•L7•: .•C1.:1 0 OFFSITE AREA (RTE 250 ROW IMPROVEMENTS) !i I ! f i APPLICABLE AREA: 6.67 AC ONSITE + ' 0.15 AC OFFSITE I I 6.82 AC TOTAL ONSITE AREA: J 1 1 1� IMPERVIOUS (TYP.) __--_�— --___— ! _a I\ L� - t a — t y. s __-_____-_-__-__ -- '______' - ----____ ---, --_ _.-.-- -- _ _ —____________ ;T e � _ ill 5.11 AC IMP 1.56 AC DERV OFFSITE AREA: 0.12 AC IMP 0.03 AC DERV TOTAL AREA: 5.23 AC IMP 1.59 AC DERV 62 STEP 1 Pantops Corner - Appendix 5D Nutrient Requirement Spreadsheet Worksheet 1 page 1 of 3 Determine the applicable area (A) and the post -developed impervious cover (Ipost). (6.67 acres onsite + 0.15 acres Applicable Area (A)* = 6.82 acres offsite ROW improvements Post -development impervious cover: Total = 5.23 acres Ipost = (total post -development impervious cover - A) x 100 = 76.7% * The area subject to the criteria may vary from locality to locality. Therefore, consult the locality for proper determination of this value. STEP 2 Determine the average land cover condition (Iwatershed) or the existing impervious cover (Iexisting). Average land cover condition If the locality has determined land cover conditions for individual watersheds within its jurisdiction, use the watershed specific value determined by the locality as Iwatershed- Iwatershed — % Otherwise, use the Chesapeake Bay default value: lwatershed = 16% 63 PERFORMANCE -BASED WATER QUALITY CALCULATIONS WnrkchPPt 1 page 2 of 3 Existing impervious cover (IPv;,i„a): Determine the existing impervious cover of the development site if present. Existing impervious cover: Total = 0.27 acres 'existing = (total existing impervious cover = A*) x 100 = 4% * The area should be the same as used in STEP 1 STEP 3 Determine the appropriate development situation. The site information determined in STEP 1 and STEP 2 provide enough information to determine the appropriate development situation under which the performance criteria will apply. Check (�) the appropriate development situation as follows: Situation 1: This consists of land development where the existing percent impervious cover (IeX„t;ng) is less than or equal to the average land cover condition (Iwatershed) and the proposed improvements will create a total percent impervious cover (Ipo,t) which is less than or equal to the average land cover condition (Iwatershed)- Ipost < Iwatershed 64 PERFORMANCE -BASED WATER QUALITY CALCULATIONS Worksheet 1 page 3 of 3 Situation 2: This consists of land development where the existing percent impervious cover (Iexisting) is less than or equal to the average land cover condition (Iwatershed) and the proposed improvements will create a total percent Situation 3: Situation 4: impervious cover (Ipost) which is greater than the average land cover condition (Iwatershed)- Iexisting < Iwatershed ; and Ipost > Iwatershed This consists of land development where the existing percent impervious cover (Iexisting) is greater than the average land cover condition (Iwatershed)• Iexisting 4.0% > Iwatershed 16.0% ;and This consists of land development where the existing percent impervious cover (Iexisting) is served by an existing stormwater management BMP(s) that addresses water quality. If the proposed development meets the criteria for development Situation 1, than the low density development is considered to be the BMP and no pollutant removal is required. The calculation procedure for Situation 1 stops here. If the proposed development meets the criteria for development Situations 2, 3, or 4, then proceed to STEP 4 on the appropriate worksheet. 65 Pantops Corner - Appendix 5D Nutrient Requirement Spreadsheet Worksheet 2 page 1 of 3 Summary of Situation 2 criteria: from calculation procedure STEP 1 thru STEP 3, Worksheet 1: Applicable area (A)* = 6.82 acres Ipost = (total post -development impervious cover _ A) x 100 = 76.7% (watershed = % or lwatershed= 16% lexisting = (total existing impervious cover _ A*) x 100 = 3.96% (existing 4.0 % < (watershed 16.0 % ; and (post 76.7 % > Iwatershed 16.0 % STEP 4 Determine the relative pre -development pollutant load (Lpre). Lpre(watershed) = [0.05 + (0.009 x Iwatershed)] x A x 2.28 (Equation 5-16) where: Lpre(watershed) = relative pre -development total phosphorous load (pounds per year) (watershed = average land cover condition for specific watershed or locality or the Chesapeake Bay default value of 16% (percent expressed in whole numbers) A = applicable area (acres) Lpre(watershed) _ [0.05+ (0.009 x 16.0%)] x 6.82 x 2.28 3.02 pounds per year 66 PERFORMANCE -BASED WATER QUALITY CALCULATIONS Worksheet 2 page L or 3 STEP 5 Determine the relative post -development pollutant load (Lpost). Lpost = [0.05 + (0.009 x IposJ] x A x 2.28 (Equation 5-21) where: Lpost = relative post -development total phosphorous load (pounds per year) Ipost = post -development percent impervious cover (percent expressed in whole numbers) A = applicable area (acres) Lpost = [0.05 + (0.009 x 76.7%)] x 6.82 x 2.28 11.51 pounds per year STEP 6 Determine the relative pollutant removal requirement (RR). RR = Lpost - Lpre(watershed) RR = 11.51 - 3.02 8.49 pounds per year STEP 7 Identify best management practice (BMP) for the site. 1. Determine the required pollutant removal efficiency for the site: EFF = ( RR / I.tost ) x 100 where• EFF — (Equation 5-22) required pollutant removal efficiency (percent expressed in whole numbers) RR = pollutant removal requirement (pounds per year) Lpost = relative post -development total phosphorous load (pounds per year) EFF = (8.49 - 11.51) x 100 74 % 67 PERFORMANCE -BASED WATER QUALITY CALCULATIONS Worksheet 2 page 3 of 3 2. Select BMP(s) from Table 5-14 and locate on the site: BMP 1: Bioretention filter 3. Determine the pollutant load entering the proposed BMP(s): LBMP = [0.05 + (0.009 x IBMA x A x 2.28 (Equation 5-23) where: LBMP = relative post -development total phosphorous load entering proposed BMP (pounds per year) IBMP = post -development percent impervious cover of BMP drainage area (percent expressed in whole numbers) A = drainage area of proposed BMP (acres) LBMP1 = [0.05+ (0.009 x x 2.28 0.00 pounds per year 4. Calculate the pollutant load removed by the proposed BMP(s): Lremoved = EffBMP x LBMP (Equation 5-24) where: 1removed = post -development pollutant load removed by proposed BMP (pounds per year) EffBMP = pollutant removal efficiency of BMP (expressed in decimal form) LBMP = relative post -development total phosphorous load entering proposed BMP (pounds per year) Lremoved/BMP1 = 0.65 x 0.00 = 0.00 pounds per year 5. Calculate the total pollutant load removed by the BMP(s): Lremoved/total = Lremove&BMP1 (Equation 5-25) 0.00 pounds per year 6. Verify Compliance: Lremoved/total —> RR 0.00 >_ 8.49 68 Rivanna River Nutrient Bank May 31, 2019 kcajie bucker. 1' 1 l . 0\ ii keanenshimp-en ing_eering com Plioti : 434.299.9843 Certificate No. James-039 Project Name: Pantops Corner Location: Albemarle County, Tax Map 78 Parcels 5A, 513, 5E, & 58G1 Owner: Pantops Corner LC 12704 Crimson Ct Ste. 101 Henrico Va, 23233 Credit Amount Desired: 8.49 lbs Project HUC: 020802040401 Rivanna River -Meadow Creek Dear Keane, This letter is to confirm the availability of authorized Nutrient Credits sufficient to meet your projects requirements of 8.49 Nutrient Credits at our above referenced nutrient offset credit bank facility (the `Bank"), which is registered with the Virginia Department of Environmental Quality (DEQ. These Nutrient Credits are generated and managed under the terms of the Reduction Implementation Plan for the Bank dated November 2017, which was authorized by the Virginia Department of Environmental Quality (DEQ) on September 5, 2018. The Bank has been authorized to provide Nutrient Credits for use in the James River watershed. These credits are transferable to those entities regulated under DEQ's Storm Water Management program in accordance with VA Code 62.1-44.15:27. If we can provide further assistance please feel free to contact our office. Hotel Street Capital, LLC, Bank Sponsor By Its Manager Thomas James Ross II 540-687-0171 Rivanna River Nutrient Offset Trading Bank, 31 Garrett Street, Warrenton, Virginia 20186 69 Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report 70 USDA United States Department of Agriculture o NRCS 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 FebruaP7�19, 2014 38' Y 14" N 38° 1' 59" N Custom Soil Resource Report Map —Hydrologic Soil Group h N N i[s.wu 723390 723440 723490 723540 723590 723640 3 3 N Map Scale: 1: 2,150 if printed on A portrait (8.5" x 11") sheet. N 91 N Meters n 0 30 60 120 180 ^ Feet /V 0 100 200 400 600 Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84 19 r� N N N V 38' 2' 14' N 38o 1' 59" N 72 Custom Soil Resource Report MAP LEGEND MAP INFORMATION Area of Interest (AOI) ■ C The soil surveys that comprise your AOI were mapped at 1:15,800. 0 Area of Interest (AOI) ■ C/D Soils ■ D Warning: Soil Map may not be valid at this scale. Soil Rating Polygons A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause °/D Water Features misunderstanding of the detail of mapping and accuracy of soil line Streams and Canals placement. The maps do not show the small areas of contrasting ® B soils that could have been shown at a more detailed scale. Transportation B/D ++4 Rails Please rely on the bar scale on each map sheet for map C A/ Interstate Highways measurements. C/D US Routes D Source of Map: Natural Resources Conservation Service _. Major Roads Web Soil Survey LIRL: http:/twebsoilsurvey.nres.usda.gov 0 Not rated or not available Local Roads Coordinate System: Web Mercator (EPSG:3857) Soil Rating Lines Background 9 Maps from the Web Soil Survey are based on the Web Mercator w A Aerial Photography projection, which preserves direction and shape but distorts A/D distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate B calculations of distance or area are required. . B/D This product is generated from the USDA-NRCS certified data as of C the version date(s) listed below. ..tir C/D D Soil Survey Area: Albemarle County, Virginia Survey Area Data: Version 10, Dec 11, 2013 Not rated or not available Soil Rating Points Soil map units are labeled (as space allows) for map scales 1:50,000 ■ A or larger. ■ A/D Date(s) aerial images were photographed: May 10, 2010—Jun 4, ■ B 2011 ■ B/D The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background - -Afn imagery displayed on these maps. As a result, some minor shifting S nrl9 ring Y ' 1 M 20 73 Custom Soil Resource Report Table —Hydrologic Soil Group Hydrologic Soil Group-- Summary by Map Unit — Albemarle County, Virginia (VA003) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 12C Catoctin silt loam, 7 to 15 B 0.6 3.8% percent slopes 12D Catoctin silt loam, 15 to B 1.2 7.9% 25 percent slopes 23B Davidson clay loam, 2 to B 6.6 42.9% 7 percent slopes 23C Davidson clay loam, 7 to B 1.2 8.0% 15 percent slopes 79B Starr silt loam, 2 to 7 B 0.4 2.6% percent slopes 88 Udorthents, loamy 5.3 34.8% Totals for Area of Interest 15.3 100.0% Rating Options —Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff.- None Specified Tie -break Rule: Higher 21 74 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.gov/wps/portal/nres/ detail/national/soils/?cid=nres142p2_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/ n res/detail/national/soils/?cid=n res 142 p2_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/n res/detai I/national/soils/?cid=n res 142 p2_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/main/national/ landuse/forestry/pub/ 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=stelprdb1043084 22 75 Custom Soil Resource Report United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 43041. http://www.nres.usda.gov/wps/portal/ n res/detai I/soils/scientists/?cid= n res 142 p2_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. http://www. nres. usda.gov/wps/portal/nres/detail/national/soils/? cid= n res 142 p2_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 23 76 NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* Ai Latitude: 38.03470, Longitude:-78.4530 Elevation: 396.01 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)1 Average recurrence interval (years) '10 25 50 100� 20�0 500 1000 F5-;�in 0.353 0.420 0.4920.553 0.623 0.677 0.728 0.775 0.832 0.878 (0.318-0.392) (0.379-0.466) (0.443-0.545) (0.497 0.613) (0.557-0.687) (0.603-0.746) (0.645-0.802) (0.682 0.854) (0.724 0.919) (0.758 0.974) 10-min 0.564 0.672 0.788 0.885 0.993 1.08 1.16 1.23 1.32 1.38 (0.508-0.626) (0.606 0.745) (0.709-0.873) (0.795 0.980) (0.888-1.10) (0.961-1.19) 1 (1.02-1.27) 1 (1.08-1.35) 1 (1.15-1.45) (1.19 1.53) 15-min 0.705 0.844 0.996 1.26 1.37 1.46 1.55 1.66 1.74 (0.635-0.783) (0.762 0.937) (0.897-1.10)F1;112 0-.24)1 (1.13-1.39) 1 (1.22-1.51) 1 (1.29-1.61) (1.36 1.71) 1 (1.44-1.83) (1.50 1.93) 30-mm 0.966Fl�l7 1.42 1.62 1.86 2.06 2.24 2.41 2.64 2.81 (0.870-1.07)-1.29)1 (1.27-1.57) 1 (1.46-1.80) 1 (1.67-2.06) 1 (1.83 2.27) 1 (1.98-2.47) (2.12-2.66) 1 (2.30-2.91) (2.43-3.12) F60-mm 1.21 1.46 1.82 11 2.48 2.79 3.08 3.39 3.78 4.11 (1.09-1.34) (1.32-1.62) (1.63-2.01) F2. 0 2.34) (2,22-2.74) 1 (2.48-3.07) 1 (2.73-3.40) 1 (2.98 3.73) 1 (3.29-4..18) 1 (3.54-4.55) F2-hr 1.45 1.76 2.19 2.58 3.07 3.48 3.91 4.35 4.96 5.47 (1.27-1.66) (1.54 2.00) (1.93-2.50) 1 (2.27-2.93) 1 (2.68-3.48) 1 (3.03 3.94) 1 (3.37-4.42) 1 (3.73-4.91) 1 (4.20 5.60) 1 (4.59 6.20) 3-hr 1.59 1.92 2.40 2.81 3.35 3.81 4.28 4.76 5.43 6.00 (1.39-1.82) 1 (1.68-2.20) 1 (2.10-2.76) 1 (2.45 3.22) 1 (2.91-3.83) (3.29-4.34) 1 (3.67 4.87) 1 (4.05 5.43) 1 (4.57-6.20) (4.99 6.86) F6-hr 2.02 2.43 3.02 3.56 4.28 4.91 5.57 6.28 7.28 8.17 (1.79-2.29) 1 (2.15-2.76) 1 (2.66-3.43) 1 (3..12-4.03) 1 (3.73-4.84) (4.25-5.53) 1 (4.77 6.28) 1 (5.32-7.08) (6.09-8.22) (6.74 9.23) 12-hr 2.53 3.05 3.80 4.51 5.48 6.36 7.30 8.33 ) (6 9.85 2 11.2 ) (2.24-2.90) (2.69-3.50) (3.34-4.35) (3.95-5.15) (4.76-6.24) (5.47-7.22) (6.20-8.27) (6.99-9.43 ) (9.09-12.7 4-hr 3.03 3.66 4.68 5.54 6.81 7.90 29.40 10.4 12.4 ) F( 14.1 ) (2.72-3.40) (3.29 4.12) (4.19-5.26) (4.94-6.20) (6.03-7.59) (6.95 8.79) (7.94-10.1) (9.00 11.6) (10.5-13.8 11.8 15.7 F2-day 3.57 4.33 5.51 6.48 7.88 9.06 10.3 11.7 13.8 15.5 (3.20 3.99) (3.89-4.84) (4.93-6.15) (5.78 7.22) (6.99-8.77) (7.98-10.1) (9.04-11.5) 1 (10.2-13.1) 1 (11.8-15.4) 1 (13.1 17.3) 3-da 3.80 4.61 5.86 6.88 8.37 9.62 11.0 12.4 14.6 16.4 (3.45-4.21) (4.18-5.11) 1 (5.30-6.49) (6.22-7.61) 1 (7.52-9.24) (8.58 10.6) 1 (9.72-12.1) 1 (10.9 13.7) 1 (12.7-16.2) 1 (14.1 18.2) 4-day 4.03 4.89 6.21 7.29 8.86 10.2 11.6 13.1 15.4 17.3 (3.70-4.44) (4.47-5.37) 1 (5.68-6.82) 1 (6.65 8.00) 1 (8.05-9.71) 1 (9.19-11.2) 1 (10.4 12.7) 1 (11.7-14.4) 1 (13.5-16.9) 1 (15.0-19.1) 7-day 4.69 5.64 7.06 8.22 9.89 11.3 12.8 14.4 16.7 18.6 (4.31-5.11) (5.19-6.16) 1 (6.47-7.70) 1 (7.52 8.96) 1 (9.00-10.8) 1 (10.2 12.3) 1 (11.5-13.9) 1 (12.8 15.7) 1 (14.7-18.3) 1 (16.2 20.4) [10-day 5.31 6.38 7.88 9.10 10.8 12.2 13.7 15.3 17.5 19.4 [(4.91-5.75) (5.89 6.90) (7.27-8.52) (8.37 9.84) (9.91-11.7) (11.1 13.2) (12.4-14.8) (13.8 16.6) (15.6-19.0) (17.1 21.1) F20-day 6.98 8.32 10.1 11.4 13.3 14.7 16.2 17.7 19.8 21.4 (6.53 7.47) (7.80 8.91) (9.41-10.8) 1 (10.7-12.2) 1 (12.3-14.2) 1 (13.6-15.7) 1 (15.0-17.4) 1 (16.3-19.0) (18.1 21.3) 1 (19.4-23.1) F30-day 8.56 10.1 12.0 13.4 15.3 16.7 18.0 19.4 21.1 22.5 (8.06-9.11) (9.55 10.8) (11.3-12.8) (12.6 14.3) (14.3-16.2) (15.6-17.7) (16.8 19.2) (18.0-20.6) Fo9.5 22.6) (20.7-24.1) F45-day 10.7 12.6 14.8 16.4 18.4 19.9 21.4 22.8 24.6 26.0 (10.1-11.3) 1 (11.9-13.4) 1 (13.9-15.6) 1 (15.4-17.3) 1 (17.3-19.5) (18.7-21.1) 1 (20.0-22.7) 1 (21.3 24.2) 1 (22.9-26.2) 1 (24.0 27.7) 60-day 12.5 14.8 17.0 18.7 20.9 22.5 24.0 25.5 27.3 28.7 1 (11.9-13.2) (14.0-15.6) (16.1-18.0) (17.7-19.8) (19.7-22.1) (21.2-23.7) (22.6-25.4) F(23.9-27.0) (25.5-29.0) 1 (26.7-30.5) 1 Precipitation frequency (PF) estimates in this table are 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 (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 and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Too PF graphical 77 PDS-based depth -duration -frequency (DDF) curves Latitude: 38.03470, Longitude:-78-45301 30 25 - - - c z 20 5 ... .. 0 c c c c c L s E m ro ro ro ra m m ro m pp N n'� �b N v ro ro ro ro ro ro ro ro -po 6 � fG tD '-i fV N A 4 r, O N M � lD Duration 30 25 c CL 10 IL 5 0 1 2 5 10 25 50 100 200 500 1000 Average recurrence interval (years) NOAA Atlas 14, Volume 2. Version 3 Created (GMT): Wed Jun 20 14:39:59 2018 Back to To Maps & aerials Small scale terrain Average recurrence interval (years) — 1 2 — 5 10 25 50 100 200 500 1000 Duration — 54ft — 2-day — 104r4n — 3-day 15-mat — 4- * — 30-rrun — 7-day — 60n — 10-day 24W — 20-day — 34v — 30-day — 64W — 45-day — 124y — 80-day — 244Y 78 scale terrain Washington, D.C. H,n0 ' 'IR:,INI Filch ' Lrin.ld.i!rc� � Large scale map ary I: ` An r � • , , �* w oton tirginia A ;ti , Fliso urq !1 t rgmia Richrmn Lynchburg Blacksburg Rwncke 100km F"--� NDripl 60mi Large scale aerial 79