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WPO201700029 Calculations 2019-10-22
Contents: Runoff Quality Calculations: VRRM Re -Development Spreadsheet Pre-Dev Calculations: Pre-Dev Drainage Map Pre-Dev HydroCAD Report Post-Dev Runoff Quantity Calculations: Post-Dev Drainage Map Post-Dev HydroCAD Report Original SWM Calculations: Original SWM Letter Original Post-Dev SWM Map Original VRRM Spreadsheet Original Post-Dev HydroCAD Report APPROVED by the Albemarle County Community Do 'Iopr�enDepartment Date D L Z File ZDl GL'Pc7 2F� r ��oa�9 Runoff Quality Calculations: VRRM Development Spreadsheet Virginia Runoff Reduction Method New Development Worksheet - v2.8 - June 2014 To be used w/ 2011 BMP Standards and Specifications Site Data I I I_ Project Name: Hillbrook Subdivision AS -BUILT Date: 06/27/2019 data input cells _ calculation cells constant values _ 1. Post -Development Project & Land Cover Information Constants Annual Rainfall (inches) Target Rainfall Event (inches) 1.00 Phosphorus EMC mg/L 0.26 Nitrogen EMC m /L 1.86 Target Phosphorus Target Load (lb/acre/yr) 0.41 Pi 0.90 Land Cover acres A soils B Soils C Soils I D Soils Totals Forest/Open Space (acres) -- undisturbed, protected forest/open space or reforested land 0.00 0.54 0.00 0.54 Managed Turf (acres) -- disturbed, graded for yards or other turf to be mowed/managed OM 1.26 O.00 0.00 1.26 Impervious Cover (acres) 0.00 O.73 0100 0-00 0.73 Total 2.53 Rv Coefficients A soils B Soils C Soils D Soils Forest/Open Space 0.02 0.03 0.04 0.05 Managed Turf 0.15 0.20 0.22 0.25 Impervious Cover 0.95 0.95 0.95 0.95 Land Cover Summary Forest/Open Space Cover acres 0.54 Weighted Rv forest 0.03 % Forest 220/io Managed Turf Cover acres -- ' 1.26 Weighted Rv turf 0.20 % Managed Turf 50% Impervious Cover acres 0.73 Rv(impervious) 0.95 % Impervious 29% - Total Site Area acres 2.53 Site Rv 0.38 Post-Develo ment Treatment Volume acre-ft 8 ost- eve opment reatment o ume cu131c feet) =` 3,476 Post Development Load (TP) (Ib/ r 2.18 Post Develo ment Load TN Ib/ r 15.6 Total Load (TP) Reduction Required (lb/yr) 1.15 4 ri o 0. o 0 i8$ 0 o Q o Q o a b ti o. o 0 J"a rl 8 8 8 8 8 8 8 8 8 8 8 8 o a n 6 O � 2 22 n ozR - op _ f 8 8 8 c 0 b 0 mna p p q q d ti b O O ti 0 O q O O O O G O • t) b O tl cl O 'd` O jw 0 0 0 C1 C C 4 p CS OO 0 O O I p N N cal ro O O os_. b h t0 III � i I II I , I c Iz 1 w Z I j 3 Ii E 1 E k a O �0 o 8 8$$ 0 8 S $ 8 S 8 8 8 S $ 8$ 8$% 8 8 8 y 1 I i j g A o y O O O 4 • O O a O Q 0 0 O iJ O 0 0 o a q o O C o O O O Q E•$ a y e o C a O O O qO a I m - m� o a d o a o o d o g�' c c o 0 0 0 0 o ei o r3 q I1 I i I 8 8 8 o S S $ e 8 8 S 8 8 S S 8 8$ � I n � i m ae o Ea` 8 8 8$ � O O O O O o o O O O O O O O O a Q a a ,n N N N N P o S� 11 0a d caP4 o o tla aq o o o 4 o o - 44 a � �I , I i I r O I 0 0 o P o Ii I a E;$ Iw io 'g-5 �.� Wo- Ig w�a V I I i al 2 itW i Stgy� IC � og ai aC4n 1J c w Itl1 <° w ro E a v N N v v ® 8 8 ��' G I B i< z � 'i � � O O 8 c ° o 8 c 0 o O O 00 o 8 8 c I ~ „>pV a•$W < LL ~1 3 q � Q la- W - 5 � .� � 6 � � N € � § 5 $ € v � E ffr, 5 5 ,� 5 € € � fr fr � Yfr. 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O m r C 9 8 C t a 3 9 a c Ia m> ' o .0 `o G p, a �O LO �'I> C a' o>C C am > 3 m O NITm � a m >I� O m0 � m OI Q' � ' O v U w v' U m m'= E = a f I o f ImM o 0o)ouo E E E E E O' Cc m o mm a c a E E p:3 o: a E I E w> 0`Uf > O > it > w u c u c o o c o c ww t_n m m d m m m W m m X m m w o m m m m m m m m m m m v a 0' a C C O C E.O C C O C C O C CIO m l w C N C o 0 W 'a a WE 810 d' CO Ali I LLL Virginia Runoff Reduction Method Worksheet Virginia Runoff Reduction Method New Development Worksheet - v2.8 - June 2014 Site Data Summary Total Rainfall = 43 inches Site Land Cover Summary A Soils B Soils C Soils D Soils Total %of Total Forest (acres) 0.00 0.541 0.001 0.001 0.541 21.52 Turf (acres) 0.001 1.261 0.001 0.001 1.261 49.74 Impervious (acres) 0.001 0.731 0.001 0.001 0.731 28.73 i L.SiI lUU. UUI Site Rv 0.38 Post Development Treatment Volume (ft3) 3476 Post Development TP Load (lb/yr) 2.18 Post Development TN Load (lb/yr) 15.62 Total TP Load Reduction Required (lb/yr) 1.15 Total Runoff Volume Reduction (ft) 207 Total TP Load Reduction Achieved (lb/yr) 0 Total TN Load Reduction Achieved (lb/yr) 1.86 Adjusted Post Development TP Load (lb/yr) 2.05 Remaining Phosphorous Load Reduction (Lb/yr) Required 1.02 Drainage Area Summary D.A. A D.A. B D.A. C D.A. D D.A. E Total Forest (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf (acres) 0.53 0.15 0.00 0.00 0.00 0.68 Impervious (acres) 0.46 ' 0.09 0.00 0.00 0.00 0.55 1.23 Drainage Area Compliance Summary D.A. A D.A. B D.A. C I D.A. D I D.A. E I Total TP Load Red. (lb/yr) 0.10 0.03 O.Ool 0.001 0.001 0.13 TN Load Red. (lb/yr) 1.39 0.461 0.001 0.001 0.001 1.86 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary A Soils B Soils C Soils D Soils Total % of Total Forest (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf (acres) 0.00 0.53 0.00 0.00 0.53 53.54 Impervious (acres) 0.00 0.46 0.00 0.00 0.46 46.46 BMP Selections I U.yy1 Practice Credit Area (acres) Downstream Practice 2.a. Simple Disconnection to A/B Soils (Spec #1) impervious 0.09 None acres disconnected Total Impervious Cover Treated (acres) 0.09 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. A (lb/yr) 0.10 Total TN Load Reduction Achieved in D.A. A (lb/yr) 1.39 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area B Summary Land Cover Summary A Soils B Soils C Soils D Soils Total % of Total Forest (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf (acres) 0.00 0.15 0.00 0.00 0.1s 62.50 Impervious (acres) 0.00 0.09 0.00 0.00 0.09 37.50 BMP Selections 1 0.241 Practice Credit Area (acres) Downstream Practice 2.a. Simple Disconnection to A/B Soils (Spec #1) impervious 0.03 None acres disconnected Total Impervious Cover Treated (acres) 0.03 Total Turf Area Treated (acres) 0.00 Total TIP Load Reduction Achieved in D.A. A (lb/yr) 0.03 Total TN Load Reduction Achieved in D.A. A (lb/yr) 0.46 Summary Print Virginia Runoff Reduction Method Worksheet Channel and Flood Protection Weighted CN 1-year storm Adjusted CN 2-year storm Adjusted CN 10-year storm Adjusted CN Target Rainfall Event (in) 3.01 3.65 5.51 D.A. A CN 78 77 771 77 D.A. B CN 75 74 74 74 D.A. C CN 0 #N/A #N/A #N/A D.A. D CN 0 #N/A #N/A #N/A D.A. E CN 0 #N/A #N/A #N/A Summary Print Pre -Development Calculations: Pre -Development Drainage Map Pre-Dev HydroCAD Report HILLBROOK PRE -DEVELOPMENT SWM MAP DEVELOPMENT AREA j A 0,=.1.62 C,FS )c powpat "r-- -+> 4P 40P D.A. 2 FS TE P.A. I 2 ONS -1 i0� . ITE 0.510•1,856 AC. 8 AC. 0.328 A IMPO roc=14.6 MIN. F I 9.4 MIN. To C 0-5. 1 Q,=0.32 CM, I so S, 9,,1=\0.23 CFS F RV=0.042 AF R, '1-0.017 AF DEVELOPMENT AREA 41p# IMPERVIOUS Ilk Area 1 Time of Concentration slope —value 13.2 Seelye Chart 200 ft overland flow 7.7% 0.35 C min 128 ft s. c. flow —woods 8.2% slope 1.4 fps velocity 1.4 min. NEH Figure 15-4 14.6 min. Area 2 Time of Concentration lope 0.35 C—volue 9.1 min Seelye Chart 88 ft overland flow 10.3% s `� o 223 ft swole 12 ft height 0.3 min. Kirpich Chart 9.4 min. 40 0 40 80 120 Scale: I"=40' A Pre -Development Hillbrook Pre -Development Type // 24-hr lyr Rainfall=3. 01 " Prepared by Shimp Engineering Printed 6/27/2019 HvdroCADO10.00-25 s/n M21870 © 2019 HvdroCAD Software Solutions LLC Paae 5 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A.1 Runoff Area=1.856 ac 0.00% Impervious Runoff Depth>0.27" Tc=14.6 min CN=58 Runoff=0.32 cfs 0.042 of Subcatchment2: D.A.2 Onsite Runoff Area=0.568 ac 0.00% Impervious Runoff Depth>0.37" Tc=9.4 min CN=61 Runoff=0.23 cfs 0.017 of Subcatchment3: D.A.2Offsite Runoff Area=0.510 ac 64.31% Impervious Runoff Depth>1.59" Tc=5.0 min CN=85 Runoff=1.50 cfs 0.068 of Link 4: D.A.2 inflow=1.62 cfs 0.085 of Primary=1.62 cfs 0.085 of Total Runoff Area = 2.934 ac Runoff Volume = 0.128 of Average Runoff Depth = 0.52" 88.82% Pervious = 2.606 ac 11.18% Impervious = 0.328 ac Pre -Development Hillbrook Pre -Development Type // 24-hr IOyrRainfali=5.51" Prepared by Shimp Engineering Printed 6/27/2019 HvdroCAD010.00-25 s/n M21870 © 2019 HvdroCAD Software Solutions LLC Paoe 10 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A.1 Runoff Area=1.856 ac 0.00% Impervious Runoff Depth>1.45" Tc=14.6 min CN=58 Runoff=3.29 cfs 0.225 of Subcatchment2: D.A.2 Onsite Runoff Area=0.568 ac 0.00% Impervious Runoff Depth>1.68" Tc=9.4 min CN=61 Runoff=1.47 cfs 0.080 of Subcatchment3: D.A.2 Offsite Runoff Area=0.510 ac 64.31 % Impervious Runoff Depth>3.84" Tc=5.0 min CN=85 Runoff=3.48 cfs 0,163 of Link 4: D.A.2 Inflow=4.67 cfs 0.243 of Primary=4.67 cfs 0,243 of Total Runoff Area = 2.934 ac Runoff Volume = 0.467 of Average Runoff Depth =1.91" 88.82% Pervious = 2.606 ac 11.18% Impervious = 0.328 ac Pre -Development Hillbrook Pre -Development Type // 24-hr 100yr Rainfall* 10" Prepared by Shimp Engineering Printed 6/27/2019 HydroCAD®10.00-25 s/n M21870 ©2019 HydroCAD Software Solutions LLC Paae 15 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A.1 Runoff Area=1.856 ac 0.00% Impervious Runoff Depth>3.91" Tc=14.6 min CN=58 Runoff=9.52 cfs 0.605 of Subcatchment2: D.A.2 Onsite Runoff Area=0.568 ac 0.00% Impervious Runoff Depth>4.29" Tc=9.4 min CN=61 Runoff=3.85 cfs 0.203 of Subcatchment3: D.A.2 Offsite Runoff Area=0.510 ac 64.31% Impervious Runoff Depth>7.27" Tc=5.0 min CN=85 Runoff=6.31 cfs 0.309 of Link 4: D.A.2 Inflow=9.66 cfs 0.512 of Primary=9.66 cfs 0.512 of Total Runoff Area = 2.934 ac Runoff Volume =1.118 of Average Runoff Depth = 4.57" 88.82% Pervious = 2.606 ac 11.18% Impervious = 0.328 ac Post-Dev Runoff Quantity Calculations: Post-Dev Drainage Map Post-Dev HydroCAD Report PEAK DISCHARGE: i UNDETAINED 1.62 CY_ -- PRE -DEVELOPMENT ON -SITE / W W - 0 3'CF`S REQUIRED REDUCTION 4it W W 0.169 ACL �!� w,, y� 1.47 C F ALLOWABLE DEVELOPM(NT AREA 0.054 AC. IMF. JY� W W W{/ W W W W W W W W W J W W W W W W W W W W W W W W W W W y J4W v W W W R A S E F LJ O, f W •V W W W W W W W W W W � J• 1 ♦Y W W 1 RV=0.012/AF p W W W W W .Y W W W I W ♦ W W W tt 1 W W J W J+ W W W♦ W W W W W j1 W 1 W W J. •Y W W� W W W W / / .. ' I' W III W •3 W IILf,- y� W I •L D.A\'B }` •Y `W 1-UNDETAINED W W W I •Y W •Y W W W p Ij1r W OFFSITE W W W W I WO S W 4W W W W j��\ r W W W W W AIYJU 0.328 AC \ W W\ 1 f W W W W W W W W W W I �i O.0� \ W W .Y \\W\. W W—/7•Y • • 11 W 0.208 AC. IMP. 1 11 ,fff ' W `I ! t � / '.,, ���~� �-a- q-. >_ `� _ _-�- f'//J/{�(�,� \ ` �"y W W \ ® I W Y IJ• Y C W� W W W♦ �� I j /� \- - 1 �-_ _ �y _ ,— �! , � /\ \`� W W W W W � L W W •Y W W W W I W W W W W ® W W W W � . � ' t W W W •Y �, � � � � W W JW W W W W •1' W J• W W I Y W W W W •L p i 1 � �— � W W W W W W W .Y W W � W W W h (1 �W W W W W W W� W W� `I I I �� � (W � W W W W •Y W W W 1` W W W W W W W W W `t IS W P.�! 1\ `.``ael� ��bn r�$sn% W W _ W W •Y { \ DEVELOPMENT AREA / lW .Y W W I .i• �y rr --- w .Y �/ ® u• W The 1— yr & 10— yr ��! A� r/ ' post —development flows �� W W •Y W have been reduced from I. W WW ' ' w pre —development flows to rAI)J / W y W y the open space. W W See table below: 1 �W 1 + I v W W W W •Y / •Y W W •Y W 11 W W W W +!• IW W W �w-�l � W J• W W W W •Y 'jam H -b' J. W W W W W •Y W W -A• W �.•� W` W W •Y J• W W W W W W W W W W 1 W W W W W W W OFFSITE ' W W Y W� •• W W W W W W W W W W Y • ", W � W W W W W W W W v. W W DETAINED Y W W APr- ORIG IAL SHEET - 1 1 w .Y •� 0.182 AC. 1 W y FLOW AREA 0.1 �O AC. IMP■ W W W TI OF CONCENTRATION=5.0 MINUTES 0.246 C. TOTAL W` W UNLESS OTHERISE NOTED TOC=11.6 MIN. \ 1 40 0 40 80 120 Q1=0.10 CFS RV=0.016 AF 1� Scale: 1 "=40' HILLBROOK POST -DEVELOPMENT SWM MAP 1` I I Sheetf low Runoff Flow Rates 1-yr 10-yr (cfs] (cfs] Pre-Dev Post-Dev Pre-Dev Post-Dev 0.32 0.53 1 3.29 2.62 The VRRM Spreadsheet was used to determine the Adjusted CN values. Simple Disconnections were counted for both the sheet flow area and the detention area, as shown on the map. REVISED: 8-26-2019 HSG B PRESERVED WOODS W W W W MANAGED W W W W LAWN W W W W W W W W IMPERVIOUS SIMPLE DISCONNECTION SWM DIVIDE STORM DIVIDE SIMPLE DISCONNECTION — DIVIDE Hillbrook Subdivision Post -Development HydroCAD Report "As -Built" Offsite Detained 8-15-2019 12S Original heetflow Area '8}D.A. B (New Sheet w) Onsite Undetained 11. Flow at Open Space Onsite Detained SubcatReach on Link Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr lyr Rainfall=3. 01 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADD 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paoe 2 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A. B (New Sheetflow) Runoff Area=0.240 ac 0.00% Impervious Runoff Depth>0.91" Tc=11.6 min CN=74 Runoff=0.31 cfs 0.018 of Subcatchment 2: D.A. A Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>1.07" Tc=10.0 min CN=77 Runoff=1.63 cfs 0.089 of Pond 3: Vault Peak Elev=496.64' Storage=9 cf Inflow=1.63 cfs 0.089 of Primary=1.63 cfs 0.089 of Secondary=0.00 cfs 0.000 of Outflow=1.63 cfs 0.089 of Pond 4: Detention Peak EIev=491.40' Storage=1,692 cf Inflow=1.63 cfs 0.089 of Outflow=0.13 cfs 0.086 of Subcatchment 5: Onsite Detained Runoff Area=0.325 ac 35.69% Impervious Runoff Depth>0.91" Tc=5.0 min CN=74 Runoff=0.55 cfs 0.025 of Subcatchment 6: Offsite Detained Runoff Area=0.182 ac 76.92% Impervious Runoff Depth>1.91" Tc=5.0 min CN=89 Runoff=0.63 cfs 0.029 of Pond 7: Detention Peak EIev=491.98' Storage=585 cf Inflow=1.17 cfs 0.054 of Outflow=0.32 cfs 0.054 of Subcatchment 8: Onsite Undetained Runoff Area=0.169 ac 31.95% Impervious Runoff Depth>0.86" Tc=5.0 min CN=73 Runoff=0.27 cfs 0.012 of Subcatchment 9: Offsite Undetained Runoff Area=0.328 ac 63.41% Impervious Runoff Depth>1.52" Tc=5.0 min CN=84 Runoff=0.93 cfs 0.042 of Link 10: Inlet X4 Inflow=1.47 cfs 0.107 of Primary=1.47 cfs 0.107 of Link 11: Flow at Open Space Inflow=0.53 cfs 0.121 of Primary=0.53 cfs 0.121 of Subcatchment 12S: Original Sheetf low Area Runoff Area=0.800 ac 0.00% Impervious Runoff Depth>0.25" Tc=11.6 min CN=57 Runoff=0.13 cfs 0.016 of Total Runoff Area = 3.034 ac Runoff Volume = 0.231 of Average Runoff Depth = 0.91" 82.93% Pervious = 2.516 ac 17.07°/a Impervious = 0.518 ac Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCAD® 9.10 s/n 07054 O 2011 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 1: D.A. B (New Sheetflow) Runoff = 0.31 cfs @ 12.05 hrs, Volume= 0.018 af, Depth> 0.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.240 74 Sheet Flow Adjusted CN 0.240 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 1.63 cfs @ 12.02 hrs, Volume= 0.089 af, Depth> 1.07" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.990 77 Adjusted CN 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Pond 3: Vault Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth> 1.07" for 1 yr event Inflow = 1.63 cfs @ 12.02 hrs, Volume= 0.089 of Outflow = 1.63 cfs @ 12.03 hrs, Volume= 0.089 af, Atten= 0%, Lag= 0.1 min Primary = 1.63 cfs @ 12.03 hrs, Volume= 0.089 of Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 496.64' @ 12.03 hrs Surf.Area= 16 sf Storage= 9 cf Plug -Flow detention time= 0.1 min calculated for 0.089 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 854.5 - 854.4 ) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.001 x 6.74'H 4'x4' Vault Storage Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr lyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCAD@ 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Page 4 Device Routing Invert Outlet Devices #1 Primary 496.00' 15.0" Round STM 5-6 L= 180.5' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 495.10' S= 0.0050 '/' Cc= 0.900 n= 0.011 #2 Device 1 496.00' 24.0" W x 3.0" H Vert. Weir Plate Orifice C= 0.600 #3 Secondary 497.45' 15.0" Round STM 3-4 L= 71.5' Ke= 0.100 Inlet / Outlet Invert= 497.45' / 490.20' S= 0.1014 '/' Cc= 0.900 n= 0.011 #4 Device 3 496.10' 15.0" Round STM 4-5 L= 16.1' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 496.10' S=-0.0062 '/' Cc= 0.900 n= 0.011 Primary OutFlow Max=1.63 cfs @ 12.03 hrs HW=496.64' (Free Discharge) t1=STM 5-6 (Barrel Controls 1.63 cfs @ 3.72 fps) L2=Weir Plate Orifice (Passes 1.63 cfs of 1.73 cfs potential flow) econdary OutFlow Max=0.00 cfs @ 0.00 hrs HW=496.10' (Free Discharge) STM 3-4 ( Controls 0.00 cfs) =STM 4-5 ( Controls 0.00 cfs) Summary for Pond 4: Detention Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth > 1.07" for 1yr event Inflow = 1.63 cfs @ 12.03 hrs, Volume= 0.089 of Outflow = 0.13 cfs @ 12.97 hrs, Volume= 0.086 af, Atten= 92%, Lag= 56.9 min Primary = 0.13 cfs @ 12.97 hrs, Volume= 0.086 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 491.40' @ 12.97 hrs Surf.Area= 1,714 sf Storage= 1,692 cf Plug -Flow detention time= 148.8 min calculated for 0.086 of (97% of inflow) Center -of -Mass det. time= 130.8 min ( 985.3 - 854.5 ) Volume Invert Avail.Storage Storage Description #1 489.70' 2,936 cf Gravel (Prismatic) Listed below (Recalc) 9,256 cf Overall - 1,917 cf Embedded = 7,339 cf x 40.0% Voids #2 489.70' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 = 106.5 cf Overall Size= 100.0"W x 60.0"H x 4.331 with 0 31' Overlap 4,852 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.70 1,714 0 0 495.10 1,714 9,256 9,256 Device Routing Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr l yr Rainfall=3.01 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paae 5 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 #2 Primary 489.70' 3.0" Round Culvert L= 110.0' Ke= 0.800 Inlet / Outlet Invert= 489.70' / 488.00' S= 0.0155 '/' Cc= 0.900 n= 0.015 Primary OutFlow Max=0.13 cfs @ 12.97 hrs HW=491.40' (Free Discharge) Ll =Emergency Spillway ( Controls 0.00 cfs) 2=Culvert (Barrel Controls 0.13 cfs @ 2.56 fps) Summary for Subcatchment 5: Onsite Detained Runoff = 0.55 cfs @ 11.97 hrs, Volume= 0.025 af, Depth> 0.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.116 98 Impervious 0.209 61 >75% Grass cover, Good. HSG B 0.325 74 Weighted Average 0.209 64.31 % Pervious Area 0.116 35.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6: Offsite Detained Runoff = 0.63 cfs @ 11.96 hrs, Volume= 0.029 af, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1 yr Rainfall=3.01 " Area (ac) CN Description 0.140 98 Impervious 0.042 61 >75% Grass cover, Good, HSG B 0.182 89 Weighted Average 0.042 23.08% Pervious Area 0.140 76.92% Impervious Area Tc Length Slope Velocity Capacity Description min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr 1 yr Rainfall=3.01 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 6 Summary for Pond 7: Detention Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 1.27" for 1 yr event Inflow = 1.17 cfs @ 11.96 hrs, Volume= 0.054 of Outflow = 0.32 cfs @ 12.08 hrs, Volume= 0.054 af, Atten= 72%, Lag= 7.2 min Primary = 0.32 cfs @ 12.08 hrs, Volume= 0.054 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 491.98' @ 12.08 hrs Surf.Area= 454 sf Storage= 585 cf Plug -Flow detention time= 12.1 min calculated for 0.054 of (100% of inflow) Center -of -Mass det. time= 11.3 min ( 844.1 - 832.8 ) Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.01 15" Storage S= 0.0025 7' #2 490.41' 1,470 cf 48.0" D x 39.0148" Storage S= 0.0025 7' x 3 1,541 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 489.00' 15.0" Round Pipe 2-1 L= 124.2' Ke= 0.600 Inlet / Outlet Invert= 489.00' / 482.80' S= 0.0499 '/' Cc= 0.900 n= 0.011 #2 Device 1 489.97' 3.0" Vert. 1-yr Orifice C= 0.600 #3 Device 1 492.00' 46.0" W x 3.5" H Vert. 10-yr Orifice C= 0.600 Primary OutFlow Max=0.32 cfs @ 12.08 hrs HW=491.98' (Free Discharge) Li=Pipe 2-1 (Passes 0.32 cfs of 8.50 cfs potential flow) 1:3=10-yr 2=1-yr Orifice (Orifice Controls 0.32 cfs @ 6.61 fps) Orifice ( Controls 0.00 cfs) Summary for Subcatchment 8: Onsite Undetained Runoff = 0.27 cfs @ 11.97 hrs, Volume= 0.012 af, Depth> 0.86" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr lyr Rainfall=3.01" Area (ac) CN Description 0.115 61 >75% Grass cover, Good, HSG B 0.054 98 Impervious 0.169 73 Weighted Average 0.115 68.05% Pervious Area 0.054 31.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr 1 yr Rainfall=3.01 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paoe 7 Summary for Subcatchment 9: Offsite Undetained Runoff = 0.93 cfs @ 11.96 hrs, Volume= 0.042 af, Depth> 1.52" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.120 61 >75% Grass cover, Good, HSG B 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59% Pervious Area 0.208 63.41 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area = 1.004 ac, 51.59% Impervious, Inflow Depth > 1.28" for 1yr event Inflow = 1.47 cfs @ 11.97 hrs, Volume= 0.107 of Primary = 1.47 cfs @ 11.97 hrs, Volume= 0.107 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Link 11: Flow at Open Space Inflow Area = 2.030 ac, 0.00% Impervious, Inflow Depth > 0.71 " for 1 yr event Inflow = 0.53 cfs @ 12.06 hrs, Volume= 0.121 of Primary = 0.53 cfs @ 12.06 hrs, Volume= 0.121 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Subcatchment 12S: Original Sheetflow Area Runoff = 0.13 cfs @ 12.09 hrs, Volume= 0.016 af, Depth> 0.25" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type 11 24-hr 1 yr Rainfall=3.01 " Area (ac) CN Description 0.246 61 >75% Grass cover, Good, HSG B 0.554 55 Woods, Good, HSG B 0.800 57 Weighted Average 0.800 100.00% Pervious Area Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 ( Type 1124-hr lyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 8 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 9 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A. B (New Sheetflow) Runoff Area=0.240 ac 0.00% Impervious Runoff Depth>2.77" Tc=11.6 min CN=74 Runoff=0.97 cfs 0.055 of Subcatchment 2: D.A. A Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>3.05" Tc=10.0 min CN=77 Runoff=4.65 cfs 0.251 of Pond 3: Vault Peak Elev=497.93' Storage=29 cf Inflow=4.65 cfs 0.251 of Primary=3.24 cfs 0.238 of Secondary=1.41 cfs 0.014 of Outflow=4.65 cfs 0.251 of Pond 4: Detention Peak EIev=495.01' Storage=4,792 cf Inflow=3.24 cfs 0.238 of Outflow=0.71 cfs 0.191 of Subcatchment 5: Onsite Detained Runoff Area=0.325 ac 35.69% Impervious Runoff Depth>2.77" Tc=5.0 min CN=74 Runoff=1.67 cfs 0.075 of Subcatchment 6: Offsite Detained Runoff Area=0.182 ac 76.92% Impervious Runoff Depth>4.26" Tc=5.0 min CN=89 Runoff=1.34 cfs 0.065 of Pond 7: Detention Peak EIev=492.56' Storage=852 cf Inflow=4.00 cfs 0.153 of Outflow=3.80 cfs 0.153 of Subcatchment 8: Onsite Undetained Runoff Area=0.169 ac 31.95% Impervious Runoff Depth>2.68" Tc=5.0 min CN=73 Runoff=0.84 cfs 0.038 of Subcatchment 9: Offsite Undetained Runoff Area=0.328 ac 63.41% Impervious Runoff Depth>3.74" Tc=5.0 min CN=84 Runoff=2.19 cfs 0.102 of Link 10: Inlet X4 Inflow=6.52 cfs 0.293 of Primary=6.52 cfs 0.293 of Link 11: Flow at Open Space Inflow=2.62 cfs 0.338 of Primary=2.62 cfs 0.338 of Subcatchment 12S: Original Sheetflow Area Runoff Area=0.800 ac 0.00% Impervious Runoff Depth>1.38" Tc=11.6 min CN=57 Runoff=1.50 cfs 0.092 of Total Runoff Area = 3.034 ac Runoff Volume = 0.678 of Average Runoff Depth = 2.68" 82.93% Pervious = 2.516 ac 17.07% Impervious = 0.518 ac Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 1: D.A. B (New Sheetflow) Runoff = 0.97 cfs @ 12.04 hrs, Volume= 0.055 af, Depth> 2.77" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type 11 24-hr 10yr Rainfall=5.51 " Area (ac) CN Description 0.240 74 Sheet Flow Adjusted CN 0.240 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 4.65 cfs @ 12.02 hrs, Volume= 0.251 af, Depth> 3.05" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51 " Area (ac) CN Description 0.990 77 Adjusted CN 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Pond 3: Vault Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth> 3.05" for 10yr event Inflow = 4.65 cfs @ 12.02 hrs, Volume= 0.251 of Outflow = 4.65 cfs @ 12.02 hrs, Volume= 0.251 af, Atten= 0%, Lag= 0.1 min Primary = 3.24 cfs @ 12.02 hrs, Volume= 0.238 of Secondary = 1.41 cfs @ 12.02 hrs, Volume= 0.014 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 497.93' @ 12.02 hrs Surf.Area= 16 sf Storage= 29 cf Plug -Flow detention time= 0.1 min calculated for 0.251 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 824.4 - 824.3) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.001 x 6.74'H 4'x4' Vault Storage Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 11 Device Routing Invert Outlet Devices #1 Primary 496.00' 15.0" Round STM 5-6 L= 180.5' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 495.10' S= 0.0050 '/' Cc= 0.900 n= 0.011 #2 Device 1 496.00' 24.0" W x 3.0" H Vert. Weir Plate Orifice C= 0.600 #3 Secondary 497.45' 15.0" Round STM 3-4 L= 71.5' Ke= 0.100 Inlet / Outlet Invert= 497.45' / 490.20' S= 0.1014 '/' Cc= 0.900 n= 0.011 #4 Device 3 496.10' 15.0" Round STM 4-5 L= 16.1' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 496.10' S=-0.0062 '/' Cc= 0.900 n= 0.011 Primary OutFlow Max=3.24 cfs @ 12.02 hrs HW=497.93' (Free Discharge) L7=STM 5-6 (Passes 3.24 cfs of 6.11 cfs potential flow) L2=Weir Plate Orifice (Orifice Controls 3.24 cfs @ 6.47 fps) gecondary OutFlow Max=1.40 cfs @ 12.02 hrs HW=497.93' (Free Discharge) t =STM 3-4 (Inlet Controls 1.40 cfs @ 3.22 fps) =STM 4-5 (Passes 1.40 cfs of 5.59 cfs potential flow) Summary for Pond 4: Detention Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth > 2.88" for 10yr event Inflow = 3.24 cfs @ 12.02 hrs, Volume= 0.238 of Outflow = 0.71 cfs @ 12.39 hrs, Volume= 0.191 af, Atten= 78%, Lag= 22.6 min Primary = 0.71 cfs @ 12.39 hrs, Volume= 0.191 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.01' @ 12.39 hrs Surf.Area= 1,714 sf Storage= 4,792 cf Plug -Flow detention time= 263.9 min calculated for 0.191 of (80% of inflow) Center -of -Mass det. time= 180.9 min ( 1,011.3 - 830.4 ) Volume Invert Avail.Storage Storage Description #1 489.70' 2,936 cf Gravel (Prismatic) Listed below (Recalc) 9,256 cf Overall - 1,917 cf Embedded = 7,339 cf x 40.0% Voids #2 489.70' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 = 106.5 cf Overall Size= 100.0"W x 60.0"H x 4.331 with 0.31' Overlap 4,852 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.70 1,714 0 0 495.10 1,714 9,256 9,256 Device Routing Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paqe 12 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 #2 Primary 489.70' 3.0" Round Culvert L= 110.0' Ke= 0.800 Inlet / Outlet Invert= 489.70' / 488.00' S= 0.0155 7' Cc= 0.900 n= 0.015 Primary OutFlow Max=0.42 cfs @ 12.39 hrs HW=495.01' (Free Discharge) 1=Emergency Spillway (Weir Controls 0.24 cfs @ 0.27 fps) L2=Culvert (Barrel Controls 0.18 cfs @ 3.75 fps) Summary for Subcatchment 5: Onsite Detained Runoff = 1.67 cfs @ 11.96 hrs, Volume= 0.075 af, Depth> 2.77" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51 " Area (ac) CN Description 0.116 98 Impervious 0.209 61 >75% Grass cover. Good. HSG B 0.325 74 Weighted Average 0.209 64.31 % Pervious Area 0.116 35.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6: Offsite Detained Runoff = 1.34 cfs @ 11.96 hrs, Volume= 0.065 af, Depth> 4.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Descriotion 0.140 98 Impervious 0.042 61 >75% Grass cover, Good, HSG B 0.182 89 Weighted Average 0.042 23.08% Pervious Area 0.140 76.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 13 Summary for Pond 7: Detention Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 3.63" for 10yr event Inflow = 4.00 cfs @ 11.98 hrs, Volume= 0.153 of Outflow = 3.80 cfs @ 12.01 hrs, Volume= 0.153 af, Atten= 5%, Lag= 1.3 min Primary = 3.80 cfs @ 12.01 hrs, Volume= 0.153 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 492.56' @ 12.01 hrs Surf.Area= 467 sf Storage= 852 cf Plug -Flow detention time= 8.8 min calculated for 0.153 of (100% of inflow) Center -of -Mass det. time= 8.4 min ( 809.2 - 800.8 ) Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.0115" Storage S= 0.0025 7' #2 490.41' 1,470 cf 48.0" D x 39.0148" Storage S= 0.0025 T x 3 1,541 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 489.00' 15.0" Round Pipe 2-1 L= 124.2' Ke= 0.600 Inlet / Outlet Invert= 489.00' / 482.80' S= 0.0499 7' Cc= 0.900 n= 0.011 #2 Device 1 489.97' 3.0" Vert. 1-yr Orifice C= 0.600 #3 Device 1 492.00' 46.0" W x 3.5" H Vert. 10-yr Orifice C= 0.600 Primary OutFlow Max=3.79 cfs @ 12.01 hrs HW=492.55' (Free Discharge) L1=Pipe 2-1 (Passes 3.79 cfs of 9.48 cfs potential flow) 1:3=10-yr 2=1-yr Orifice (Orifice Controls 0.37 cfs @ 7.55 fps) Orifice (Orifice Controls 3.42 cfs @ 3.06 fps) Summary for Subcatchment 8: Onsite Undetained Runoff = 0.84 cfs @ 11.96 hrs, Volume= 0.038 af, Depth> 2.68" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51 " Area (ac) CN Description 0.115 61 >75% Grass cover, Good, HSG B ' 0.054 98 Impervious 0.169 73 Weighted Average 0.115 68.05% Pervious Area 0.054 31.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paae 14 Summary for Subcatchment 9: Offsite Undetained Runoff = 2.19 cfs @ 11.96 hrs, Volume= 0.102 af, Depth> 3.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description 0.120 61 >75% Grass cover, Good, HSG B 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59% Pervious Area 0.208 63.41 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area = 1.004 ac, 51.59% Impervious, Inflow Depth> 3.50" for 10yr event Inflow = 6.52 cfs @ 11.98 hrs, Volume= 0.293 of Primary = 6.52 cfs @ 11.98 hrs, Volume= 0.293 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Link 11: Flow at Open Space Inflow Area = 2.030 ac, 0.00% Impervious, Inflow Depth> 2.00" for 10yr event Inflow = 2.62 cfs @ 12.05 hrs, Volume= 0.338 of Primary = 2.62 cfs @ 12.05 hrs, Volume= 0.338 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Subcatchment 12S: Original Sheetflow Area Runoff = 1.50 cfs @ 12.05 hrs, Volume= 0.092 af, Depth> 1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description 0.246 61 >75% Grass cover, Good, HSG B 0.554 55 Woods, Good, HSG B 0.800 57 Weighted Average 0.800 100.00% Pervious Area Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-19 Type 1124-hr 10yr Rainfall=5.51 " Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 15 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 16 Time span=0.00-24.00 hrs, dt=0.01 hrs, 2401 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1: D.A. B (New Sheetflow) Runoff Area=0.240 ac 0.00% Impervious Runoff Depth>5.90" Tc=11.6 min CN=74 Runoff=2.04 cfs 0.118 of Subcatchment 2: D.A. A Runoff Area=0.990 ac 0.00% Impervious Runoff Depth>6.28" Tc=10.0 min CN=77 Runoff=9.34 cfs 0.518 of Pond 3. Vault Peak Elev=498.55' Storage=39 cf Inflow=9.34 cfs 0.518 of Primary=3.75 cfs 0.430 of Secondary=5.59 cfs 0.088 of Outflow=9.34 cfs 0.518 of Pond 4: Detention Peak EIev=495.07' Storage=4,834 cf Inflow=3.75 cfs 0.430 of Outflow=4.51 cfs 0.351 of Subcatchment 5: Onsite Detained Runoff Area=0.325 ac 35.69% Impervious Runoff Depth>5.91" Tc=5.0 min CN=74 Runoff=3.46 cfs 0.160 of Subcatchment 6: Offsite Detained Runoff Area=0.182 ac 76.92% Impervious Runoff Depth>7.76" Tc=5.0 min CN=89 Runoff=2.34 cfs 0.118 of Pond 7: Detention Peak EIev=496.59' Storage=1,541 cf Inflow=10.60 cfs 0.366 of Outflow=11.96 cfs 0.366 of Subcatchment 8: Onsite Undetained Runoff Area=0.169 ac 31.95% Impervious Runoff Depth>5.79" Tc=5.0 min CN=73 Runoff=1.77 cfs 0.082 of Subcatchment 9: Offsite Undetained Runoff Area=0.328 ac 63.41% Impervious Runoff Depth>7.15" Tc=5.0 min CN=84 Runoff=4.02 cfs 0.195 of Link 10: Inlet X4 Inflow=17.47 cfs 0.643 of Primary=17.47 cfs 0.643 of Link 11: Flow at Open Space Inflow=10.39 cfs 0.722 of Primary=10.39 cfs 0.722 of Subcatchment 12S: Original Sheetflow Area Runoff Area=0.800 ac 0.00% Impervious Runoff Depth>3.79" Tc=11.6 min CN=57 Runoff=4.41 cfs 0.253 of Total Runoff Area = 3.034 ac Runoff Volume = 1.444 of Average Runoff Depth = 5.71" 82.93% Pervious = 2.516 ac 17.07% Impervious = 0.518 ac Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 17 Summary for Subcatchment 1: D.A. B (New Sheetflow) Runoff = 2.04 cfs @ 12.03 hrs, Volume= 0.118 af, Depth> 5.90" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.240 74 Sheet Flow Adjusted CN 0.240 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 9.34 cfs @ 12.01 hrs, Volume= 0.518 af, Depth> 6.28" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.990 77 Adjusted CN 0.990 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Pond 3: Vault Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth> 6.28" for 100yr event Inflow = 9.34 cfs @ 12.01 hrs, Volume= 0.518 of Outflow = 9.34 cfs @ 12.01 hrs, Volume= 0.518 af, Atten= 0%, Lag= 0.1 min Primary = 3.75 cfs @ 12.01 hrs, Volume= 0.430 of Secondary = 5.59 cfs @ 12.01 hrs, Volume= 0.088 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 498.55' @ 12.01 hrs Surf.Area= 16 sf Storage= 39 cf Plug -Flow detention time= 0.1 min calculated for 0.518 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 804.0 - 803.9 ) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.001 x 6.74'H 4'x4' Vault Storage Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 18 Device Routing Invert Outlet Devices #1 Primary 496.00' 15.0" Round STM 5-6 L= 180.5' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 495.10' S= 0.0050 '/' Cc= 0.900 n= 0.011 #2 Device 1 496.00' 24.0" W x 3.0" H Vert. Weir Plate Orifice C= 0.600 #3 Secondary 497.45' 15.0" Round STM 3-4 L= 71.5' Ke= 0.100 Inlet / Outlet Invert= 497.45' / 490.20' S= 0.1014 '/' Cc= 0.900 n= 0.011 #4 Device 3 496.10' 15.0" Round STM 4-5 L= 16.1' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 496.10' S=-0.0062 7' Cc= 0.900 n= 0.011 Primary OutFlow Max=3.75 cfs @ 12.01 hrs HW=498.55' (Free Discharge) L1=STM 5-6 (Passes 3.75 cfs of 7.20 cfs potential flow) L2=Weir Plate Orifice (Orifice Controls 3.75 cfs @ 7.50 fps) T ndary OutFlow Max=5.58 cfs @ 12.01 hrs HW=498.55' (Free Discharge) STM 3-4 (Inlet Controls 5.58 cfs @ 4.87 fps) =STM 4-5 (Passes 5.58 cfs of 8.46 cfs potential flow) Summary for Pond 4: Detention Inflow Area = 0.990 ac, 0.00% Impervious, Inflow Depth > 5.21" for 100yr event Inflow = 3.75 cfs @ 12.01 hrs, Volume= 0.430 of Outflow = 4.51 cfs @ 12.00 hrs, Volume= 0.351 af, Atten= 0%, Lag= 0.0 min Primary = 4.51 cfs @ 12.00 hrs, Volume= 0.351 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.07' @ 12.00 hrs Surf.Area= 1,714 sf Storage= 4,834 cf Plug -Flow detention time= 163.5 min calculated for 0.351 of (82% of inflow) Center -of -Mass det. time= 82.2 min ( 903.4 - 821.2 ) Volume Invert Avail.Storage Storage Description #1 489.70' 2,936 cf Gravel (Prismatic) Listed below (Recalc) 9,256 cf Overall - 1,917 cf Embedded = 7,339 cf x 40.0% Voids #2 489.70' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf _ Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap 4,852 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.70 1,714 0 0 495.10 1,714 9,256 9,256 Device Routing Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADG 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paae 19 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 #2 Primary 489.70' 3.0" Round Culvert L= 110.0' Ke= 0.800 Inlet / Outlet Invert= 489.70' / 488.00' S= 0.0155 '/' Cc= 0.900 n= 0.015 Primary OutFlow Max=3.92 cfs @ 12.00 hrs HW=495.07' (Free Discharge) 1:1=Emergency Spillway (Weir Controls 3.74 cfs @ 0.67 fps) 2=Culvert (Barrel Controls 0.18 cfs @ 3.76 fps) Summary for Subcatchment 5: Onsite Detained Runoff = 3.46 cfs @ 11.96 hrs, Volume= 0.160 af, Depth> 5.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.116 98 Impervious 0.209 61 >75% Grass cover, Good, HSG B 0.325 74 Weighted Average 0.209 64.31 % Pervious Area 0.116 35.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6: Offsite Detained Runoff = 2.34 cfs @ 11.96 hrs, Volume= 0.118 af, Depth> 7.76" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.140 98 Impervious 0.042 61 >75% Grass cover. Good. HSG B 0.182 89 Weighted Average 0.042 23.08% Pervious Area 0.140 76.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post- Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Paoe 20 Summary for Pond 7: Detention Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 8.66" for 100yr event Inflow = 10.60 cfs @ 11.98 hrs, Volume= 0.366 of Outflow = 11.96 cfs @ 11.98 hrs, Volume= 0.366 af, Atten= 0%, Lag= 0.0 min Primary = 11.96 cfs @ 11.98 hrs, Volume= 0.366 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 496.59' @ 11.98 hrs Surf.Area= 0 sf Storage= 1,541 cf Plug -Flow detention time= 7.0 min calculated for 0.366 of (100% of inflow) Center -of -Mass det. time= 6.7 min ( 780.7 - 774.0) Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.01 15" Storage S= 0.0025 T #2 490.41' 1,470 cf 48.0" D x 39.0148" Storage S= 0.0025 7' x 3 1,541 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 489.00' 15.0" Round Pipe 2-1 L= 124.2' Ke= 0.600 Inlet / Outlet Invert= 489.00' / 482.80' S= 0.0499 '/' Cc= 0.900 n= 0.011 #2 Device 1 489.97' 3.0" Vert. 1-yr Orifice C= 0.600 #3 Device 1 492.00' 46.0" W x 3.5" H Vert. 10-yr Orifice C= 0.600 Primary OutFlow Max=11.94 cfs @ 11.98 hrs HW=496.58' (Free Discharge) L1=Pipe 2-1 (Passes 11.94 cfs of 14.61 cfs potential flow) T__3=10-yr 2=1-yr Orifice (Orifice Controls 0.60 cfs @ 12.26 fps) Orifice (Orifice Controls 11.34 cfs @ 10.14 fps) Summary for Subcatchment 8: Onsite Undetained Runoff = 1.77 cfs @ 11.96 hrs, Volume= 0.082 af, Depth> 5.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.115 61 >75% Grass cover, Good, HSG B 0.054 98 Impervious 0.169 73 Weighted Average 0.115 68.05% Pervious Area 0.054 31.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Pacae 21 Summary for Subcatchment 9: Offsite Undetained Runoff = 4.02 cfs @ 11.96 hrs, Volume= 0.195 af, Depth> 7.15" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=9.10" Area (ac) CN Description 0.120 61 >75% Grass cover, Good, HSG B 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59% Pervious Area 0.208 63.41 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area = 1.004 ac, 51.59% Impervious, Inflow Depth> 7.68" for 100yr event Inflow = 17.47 cfs @ 11.98 hrs, Volume= 0.643 of Primary = 17.47 cfs @ 11.98 hrs, Volume= 0.643 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Link 11: Flow at Open Space Inflow Area = 2.030 ac, 0.00% Impervious, Inflow Depth > 4.27" for 100yr event Inflow = 10.39 cfs @ 12.00 hrs, Volume= 0.722 of Primary = 10.39 cfs @ 12.00 hrs, Volume= 0.722 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Subcatchment 12S: Original Sheetf low Area Runoff = 4.41 cfs @ 12.04 hrs, Volume= 0.253 af, Depth> 3.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rai nfall=9.10" Area (ac) CN Description 0.246 61 >75% Grass cover, Good, HSG B 0.554 55 Woods, Good, HSG B 0.800 57 Weighted Average 0.800 100.00% Pervious Area Post-Dev 10-yr Hillbrook Post -Development Amendment As -Built 8-15-1 Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 8/26/2019 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 22 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, PROJECT MANAGEMENT SHIMt', CIVIL ENGINEERING LAND PLANNING ENGINEERING' HI'llbrook Subdivision 8-15-2019 Original SWM Calculations • Original SWM Letter • Original Post -Development SWM Map • Original VRRM Spreadsheet • Original Post -Development HydroCAD Report PROJECT MANAGEMENT SHIMV JCIVIL ENGINEERING LAND PLANNING ENGINEERINGa April 27, 2017 David James Albemarle County Department of Community Development Regarding: Hillbrook Stormwater Management VSMP Amendment Dear Mr. James, Enclosed are the calculations and details relating to stormwater treatment for the proposed development Hillbrook. Concerns regarding maintenance of the bioretention facility, specifically regarding the intrusiveness of maintenance procedures on neighboring homeowners, which would reduce the likelihood that the HOA would be timely with maintenance tasks, led to the submittal of this VSMP amendment, which calls for a retention basin with less maintenance required. Pollutant removal is achieved with a combination of impervious disconnection and offsite nutrient credit purchases. All pollutant removal is applied to "D.A. A" on the VRRM, which is delineated on the post - development drainage map. The detention is designed to be off-line, with a flow-splitter incorporated into the vault STM 5. The 1-year storm flows through the 3"x13" orifice in to the detention. STM 4 has a 15" overflow structure set just above the 1-year water surface elevation of the vault to capture the bulk of larger storm flows. On the east, the site sheet flows onto the Raintree property. As shown in the summary table below, the post -development peak flow and runoff volume are reduced for both the 1-year and 10-year storms. The values shown are computed in the HydroCAD reports. On the northwest, the site discharges to a natural channel before the 1 % point, so the energy balance equation is applied to limit the peak 1-year discharge. I. F.* (QpYe * RVpre) Qdev — RVdev QPre and RVPre are shown on the pre -development drainage map and computed in the pre -development HydroCAD report. RVdev is shown on the post -development drainage map and computed in the post - development HydroCAD report. Qdev is computed on the post -development drainage map. Q1, the design flow, is computed in the post -development HydroCAD report. A 48" detention structure limits the 1-year peak discharge to the northwest. The site discharges through existing storm sewer that is adequate to convey the 10-yr storm before reaching the natural channel, which fully contains the 10-yr flow without flooding. Flow Summary: Northwest (M) Qmax 1.47 cfs Qi 1.47 cfs East (Raintree) Qt re 0.32 cfs Qjost 0.13 cfs Q10pre 3.29 cfs Q1o(post) 3.20 cfs If you have any questions please do not hesitate to contact me at your earliest opportunity. I may be reached at: lauren@shimp-en_ in�g.com or by phone at 434-227-5140 A. Yours Truly, Lauren Gilroy //j, .,13(EAWIMSCHAFt E. i-AMWELOPMENT 1, f.oz CTS__ U HILLBROOK SET-�►I,N t "-Pl �REQUIRER REDUCTIO tH Ow POST —DEVELOPMENT SWM MAP -614�SJTE , .1 i N� -\ �"M�L 1 MtNT ARE� ,A 1 1 -Z � ji 11.411 C LLOWABLE 0.,f69(ACE DEVELOP -7 7 �0.054 At. IMP. ' •� �; `/ ;�,, W - 7 IW=0.01 2 A .7 T 7 v- v qqwr 'i A, D F4 P-UNDET4tNED 1-229, _/\R s_Kv -OFi1TE . CZ J 1Z AD V mro-ll M328 C. I P. : Y A' K 1� J_ 2 V� III V� ✓ ,Y w W ,,I. •Y J_ I J i 'Y W V W L W W i W 1 W W 0� `��'m` � • 1 7 � HSG B 7 PO v PRESERVED L7 WOODS A A I Ak DEVELOPMENT AREA! MANAGED 41111111p LAWN IMPERVIOUS SIMPLE DISCONNECTION ::-�OFFSITREQUIRED REDUCTION: SWM DIVIDE -� 0.23 CFS Q pre 0.08 CFS Qdev SWEET FLOW - STORM DIVIDE DETA11411, 0.15 CFS Qreduction SIMPLE 0.246 AC. TOTAL DISCONNECTION �.182 AC. DIVIDE -0).40 ACM IMP. ToC 11.6 MIN. Q,=0.13 CFS 40 0 40 80 120 RV=0.016 AF 'TIME OFF—CONCENTRATION=5.0 MIN ES Scale: 1"=40 UNLtS&OTHERISE NOTED u Energy Balance 1. F. 0.8 Qpre 0.23 Cfs RVpre 0.017 ac—ft RVdev 0.037 ac—ft Qdev F0.087 Cfs Virginia Runoff Reduction Method Worksheet Virginia Runoff Reduction Method New Development Worksheet - v2.8 - June 2014 Site Data Summary Total Rainfall = 43 inches Site Land Cover Summary A Soils I B Soils I C Soils I D Soils I Total I % of Total Forest (acres) 1 0.001 0.541 0.00 0.00 0.54 21.52 Turf (acres) 1 0.001 1.261 0.001 0.001 1.261 49.74 Impervious (acres) 1 0.001 0.731 0.001 0.001 0.731 28.73 1 2.531 100.001 Site Rv 0.38 Post Development Treatment Volume (ft3) 3476 Post Development TP Load (lb/yr) 2.18 Post Development TN Load (lb/yr) 15.62 Total TP Load Reduction Required (lb/yr) 1.15 Total Runoff Volume Reduction (ft') 211 Total TP Load Reduction Achieved (lb/yr) 0 Total TN Load Reduction Achieved (lb/yr) 1.89 Adjusted Post Development TP Load (lb/yr) 2.05 Remaining Phosphorous Load Reduction (Lb/yr) Required 1.02 Drainage Area Summary D.A. A I D.A. B I D.A. C I D.A. D D.A. E Total Forest (acres) 0.001 0.001 0.00 0.00 0.00 0.00 Turf (acres) 0.671 0.001 0.001 0.001 0.00 0.67 Impervious (acres) 0.551 0.001 0.001 0.001 0.00 0.55 1.23 Drainage Area Compliance Summary D.A. A I D.A. B 1 D.A. C I D.A. D I D.A. E I Total TP Load Red. (lb/yr) 0.131 0.001 0.001 0.001 0.00 0.13 TN Load Red. (lb/yr) 1 1.891 0.001 0.001 0.001 0.001 1.89 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary A Soils B Soils C Soils D Soils Total % of Total Forest (acres) 0.001 0.00 0.00 0.00 0.00 0.00 Turf(acres) 0.001 0.67 0.00 0.001 0.67 54.92 Impervious (acres) 0.001 0.55 0.00 0.001 0.55 45.08 BMP Selections 1 1.23� Practice Credit Area (acres) Downstream Practice 2.a. Simple Disconnection to A/B Soils (Spec #1) impervious 0.122314 None acres 1 disconnected Total impervious Cover Treated (acres) 0.12 Total Turf Area Treated (acres) 0.00 Total TP Load Reduction Achieved in D.A. A (lb/yr) 0.13 Total TN Load Reduction Achieved in D.A. A (lb/yr) 1.89 Summary Print Virginia Runoff Reduction Method Worksheet Channel and Flood Protection Weighted CN 1-year storm Adjusted CN 2-year storm Adjusted CN 30-year storm Adjusted CN Target Rainfall Event (in) 3.01 3.65 5.51 D.A. A CN 78 77 77 77 D.A.B CN 01 #N/A I #N/A #N/A D.A. C CN 01 #N/A I #N/A #N/A D.A. D CN 01 #N/A I #N/A #N/A D.A. E CN 01 #N/A I #N/A I #N/A Summary Print i 9 -D 10 � ` 8 1 Offsite Undetained Inle 4 Onsite Undetained Sheet Flow 11 6 --{� 7 Q- - 3 -� 4 Raintree Offsite Detained Detee tion Vault Detention 5 (:j) Onsite Detained D.A. A Subcat Reach on j Link Hillbrook Post -Development Type 1124-hr 1yr Rainfall=3. 01 " Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1: Sheet Flow Runoff = 0.13 cfs @ 12.09 hrs, Volume= 0.016 af, Depth> 0.25" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description * 0.550 55 Conservation Area * 0.246 61 Sheet Flow 0.796 57 Weighted Average 0.796 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 2.46 cfs @ 11.97 hrs, Volume= 0.110 af, Depth> 1.08" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description * 1.229 77 Adjusted CN 1.229 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 3: Vault Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 1.08" for 1yr event Inflow = 2.46 cfs @ 11.97 hrs, Volume= 0.110 of Outflow = 2.46 cfs @ 11.97 hrs, Volume= 0.110 af, Atten= 0%, Lag= 0.2 min Primary = 2.46 cfs @ 11.97 hrs, Volume= 0.110 of Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 497.17' @ 11.97 hrs Surf.Area= 16 sf Storage= 17 cf Plug -Flow detention time= 0.1 min calculated for 0.110 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 850.8 - 850.7 ) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.001 x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development Type// 24-hr lyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 3 Device Routing Invert Outlet Devices #1 Primary 496.00' 15.0" Round STM 5-6 L= 180.5' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 495.10' S= 0.0050 '/' Cc= 0.900 n= 0.011 #2 Device 1 496.00' 24.0" W x 3.0" H Vert. Weir Plate Orifice C= 0.600 #3 Secondary 497.45' 15.0" Round STM 3-4 L= 71.5' Ke= 0.100 Inlet / Outlet Invert= 497.45' / 490.20' S= 0.1014 '/' Cc= 0.900 n= 0.011 #4 Device 3 496.10' 15.0" Round STM 4-5 L= 16.1' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 496.10' S=-0.0062 '/' Cc= 0.900 n= 0.011 Primary OutFlow Max=2.46 cfs @ 11.97 hrs HW=497.17' (Free Discharge) t1=STM 5-6 (Passes 2.46 cfs of 4.30 cfs potential flow) t2=Weir Plate Orifice (Orifice Controls 2.46 cfs @ 4.91 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=496.10' (Free Discharge) t3=STM 3-4 ( Controls 0.00 cfs) L4=STM 4-5 ( Controls 0.00 cfs) Summary for Pond 4: Detention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 1.08" for 1yr event Inflow = 2.46 cfs @ 11.97 hrs, Volume= 0.110 of Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 494.38' @ 24.00 hrs Surf.Area= 1,714 sf Storage= 4,801 cf Plug -Flow detention time= (not calculated: initial storage excedes outflow) Center -of -Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 489.00' 3,415 cf Gravel (Prismatic) Listed below (Recalc) 10,455 cf Overall - 1,917 cf Embedded = 8,539 cf x 40.0% Voids #2 490.10' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap 5,332 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.00 1,714 0 0 495.10 1,714 10,455 10,455 Device Routing Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=489.00' (Free Discharge) t1=Emergency Spillway ( Controls 0.00 cfs) Hillbrook Post -Development Type I! 24-hr 1yr Rainfall=3. 01 " Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 5: Onsite Detained Runoff = 0.55 cfs @ 11.97 hrs, Volume= 0.025 af, Depth> 0.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description * 0.116 98 Impervious 0.209 61 >75% Grass cover, Good, HSG B 0.325 74 Weighted Average 0.209 64.31% Pervious Area 0.116 35.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6: Mite Detained Runoff = 0.63 cfs @ 11.96 hrs, Volume= 0.029 af, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description * 0.140 98 Impervious 0.042 61 >75% Grass cover. Good. HSG B 0.182 89 Weighted Average 0.042 23.08% Pervious Area 0.140 76.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 7: Detention Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 1.27" for 1yr event Inflow = 1.17 cfs @ 11.96 hrs, Volume= 0.054 of Outflow = 0.32 cfs @ 12.08 hrs, Volume= 0.054 af, Atten= 72%, Lag= 7.2 min Primary = 0.32 cfs @ 12.08 hrs, Volume= 0.054 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 491.98' @ 12.08 hrs Surf.Area= 454 sf Storage= 585 cf Plug -Flow detention time= 12.1 min calculated for 0.054 of (100% of inflow) Center -of -Mass det. time= 11.3 min (844.1- 832.8 ) Hillbrook Post -Development Type // 24-hr 1yr Rainfall=3. 01 " Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD119.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 5 Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.0115" Storage S= 0.0025 '/' #2 490.41' 1,470 cf 48.0" D x 39.0148" Storage S= 0.0025 '/' x 3 1,541 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 489.00' 15.0" Round Pipe 2-1 L= 124.2' Ke= 0.600 Inlet / Outlet Invert= 489.00' / 482.80' S= 0.0499 '/' Cc= 0.900 n= 0.011 #2 Device 1 489.97' 3.0" Vert. 1-yr Orifice C= 0.600 #3 Device 1 492.00' 46.0" W x 3.5" H Vert. 10-yr Orifice C= 0.600 Primary OutFlow Max=0.32 cfs @ 12.08 hrs HW=491.98' (Free Discharge) ti=Pipe 2-1 (Passes 0.32 cfs of 8.50 cfs potential flow) t3=102=1-yr Orifice (Orifice Controls 0.32 cfs @ 6.61 fps) -yr Orifice ( Controls 0.00 cfs) Summary for Subcatchment 8: Onsite Undetained Runoff = 0.27 cfs @ 11.97 hrs, Volume= 0.012 af, Depth> 0.86" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.115 61 >75% Grass cover, Good, HSG B * 0.054 98 Impervious 0.169 73 Weighted Average 0.115 68.05% Pervious Area 0.054 31.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 9: Offsite Undetained Runoff = 0.93 cfs @ 11.96 hrs, Volume= 0.042 af, Depth> 1.52" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area (ac) CN Description 0.120 61 >75% Grass cover, Good, HSG B * 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59% Pervious Area 0.208 63.41% Impervious Area Hillbrook Post -Development Type /I24-hrlyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Paee 6 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area = 1.004 ac, 51.59% Impervious, Inflow Depth > 1.28" for 1yr event Inflow = 1.47 cfs @ 11.97 hrs, Volume= 0.107 of Primary = 1.47 cfs @ 11.97 hrs, Volume= 0.107 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Link 11: Raintree Inflow Area = 2.025 ac, 0.00% Impervious, Inflow Depth > 0.10" for 1yr event Inflow = 0.13 cfs @ 12.09 hrs, Volume= 0.016 of Primary = 0.13 cfs @ 12.09 hrs, Volume= 0.016 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Hillbrook Post -Development Type /I 24-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 1: Sheet Flow Runoff = 1.49 cfs @ 12.05 hrs, Volume= 0.092 af, Depth> 1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description * 0.550 55 Conservation Area * 0.246 61 Sheet Flow 0.796 57 Weighted Average 0.796 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 6.90 cfs @ 11.96 hrs, Volume= 0.313 af, Depth> 3.05" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type 11 24-hr 10yr Rainfall=5.51" Area (ac) CN Description * 1.229 77 Adjusted CN 1.229 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 3: Vault Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 3.05" for 10yr event Inflow = 6.90 cfs @ 11.96 hrs, Volume= 0.313 of Outflow = 6.90 cfs @ 11.96 hrs, Volume= 0.312 af, Atten= 0%, Lag= 0.0 min Primary = 3.50 cfs @ 11.96 hrs, Volume= 0.277 of Secondary = 3.40 cfs @ 11.96 hrs, Volume= 0.035 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 498.24' @ 11.96 hrs Surf.Area= 16 sf Storage= 34 cf Plug -Flow detention time= 0.1 min calculated for 0.312 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 820.6 - 820.5 ) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.001 x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development Prepared by Shimp Engineering, P.C. HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Type It 24-hr 10yr Rainfall=5.51" Printed 4/27/2017 Page 8 Device Routing Invert Outlet Devices #1 Primary 496.00' 15.0" Round STM 5-6 L= 180.5' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 495.10' S= O.00SO '/' Cc= 0.900 n= 0.011 #2 Device 1 496.00' 24.0" W x 3.0" H Vert. Weir Plate Orifice C= 0.600 #3 Secondary 497.45' 15.0" Round STM 3-4 L= 71.5' Ke= 0.100 Inlet / Outlet Invert= 497.45' / 490.20' S= 0.1014 '/' Cc= 0.900 n= 0.011 #4 Device 3 496.10' 15.0" Round STM 4-5 L= 16.1' Ke= 0.100 Inlet / Outlet Invert= 496.00' / 496.10' S=-0.0062 '/' Cc= 0.900 n= 0.011 Primary OutFlow Max=3.50 cfs @ 11.96 hrs HW=498.24' (Free Discharge) t1=STM 5-6 (Passes 3.50 cfs of 6.68 cfs potential flow) t2=Weir Plate Orifice (Orifice Controls 3.50 cfs @ 7.01 fps) Secondary OutFlow Max=3.39 cfs @ 11.96 hrs HW=498.24' (Free Discharge) t3=STM 3-4 (Inlet Controls 3.39 cfs @ 4.13 fps) t4=STM 4-5 (Passes 3.39 cfs of 7.17 cfs potential flow) Summary for Pond 4: Detention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 2.71" for 10yr event Inflow = 3.50 cfs @ 11.96 hrs, Volume= 0.277 of Outflow = 1.87 cfs @ 12.09 hrs, Volume= 0.157 af, Atten= 47%, Lag= 7.9 min Primary = 1.87 cfs @ 12.09 hrs, Volume= 0.157 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.04' @ 12.09 hrs Surf.Area= 1,714 sf Storage= 5,291 cf Plug -Flow detention time= 229.8 min calculated for 0.156 of (56% of inflow) Center -of -Mass det. time= 104.3 min ( 938.0 - 833.7 ) Volume Invert Avail.Storage Storage Description #1 489.00' 3,415 cf Gravel (Prismatic) Listed below (Recalc) 10,455 cf Overall -1,917 cf Embedded = 8,539 cf x 40.0% Voids #2 490.10' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.031 = 106.5 cf Overall Size= 100.0"W x 60.0"H x 4.331 with 0.31' Overlap 5,332 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.00 1,714 0 0 495.10 1,714 10,455 10,455 Device Routine Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=1.63 cfs @ 12.09 hrs HW=495.04' (Free Discharge) t1=Emergency Spillway (Weir Controls 1.63 cfs @ 0.51 fps) Hillbrook Post -Development Type 1124-hr 1Oyr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 5: Onsite Detained Runoff = 1.67 cfs @ 11.96 hrs, Volume= 0.075 af, Depth> 2.77" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description * 0.116 98 Impervious 0.209 61 >75% Grass cover, Good, HSG B 0.325 74 Weighted Average 0.209 64.31% Pervious Area 0.116 35.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6: Offsite Detained Runoff = 1.34 cfs @ 11.96 hrs, Volume= 0.065 af, Depth> 4.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description * 0.140 98 Impervious 0.042 61 >75% Grass cover, Good, HSG B 0.182 89 Weighted Average 0.042 23.08% Pervious Area 0.140 76.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 7: Detention Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 4.14" for 10yr event Inflow = 6.41 cfs @ 11.96 hrs, Volume= 0.175 of Outflow = 5.72 cfs @ 11.99 hrs, Volume= 0.175 af, Atten= 11%, Lag= 1.6 min Primary = 5.72 cfs @ 11.99 hrs, Volume= 0.175 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 493.12' @ 11.99 hrs Surf.Area= 442 sf Storage= 1,110 cf Plug -Flow detention time= 8.0 min calculated for 0.175 of (100% of inflow) Center -of -Mass det. time= 7.6 min ( 797.8 - 790.2 ) Hillbrook Post -Development Type Il 24-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Page 10 Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.0% 15" Storage S= 0.0025 #2 490.41' 1,470 cf 48.0" D x 39.0'L 48" Storage S= 0.0025 '/' x 3 1,541 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 489.00' 15.0" Round Pipe 2-1 L= 124.2' Ke= 0.600 Inlet / Outlet Invert= 489.00' / 482.80' S= 0.0499 '/' Cc= 0.900 n= 0.011 #2 Device 1 489.97' 3.0" Vert. 1-yr Orifice C= 0.600 #3 Device 1 492.00' 46.0" W x 3.5" H Vert. 10-yr Orifice C= 0.600 Primary OutFlow Max=5.71 cfs @ 11.99 hrs HW=493.12' (Free Discharge) Ll=Pipe 2-1 (Passes S.71 cfs of 10.3S cfs potential flow) 13=102=1-yr Orifice (Orifice Controls 0.41 cfs @ 8.37 fps) -yr Orifice (Orifice Controls 5.30 cfs @ 4.74 fps) Summary for Subcatchment 8: Onsite Undetained Runoff = 0.84 cfs @ 11.96 hrs, Volume= 0.038 af, Depth> 2.68" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description 0.115 61 >75% Grass cover, Good, HSG B * 0.054 98 Impervious 0.169 73 Weighted Average 0.115 68.05% Pervious Area 0.0S4 31.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 9: Mite Undetained Runoff = 2.19 cfs @ 11.96 hrs, Volume= 0.102 af, Depth> 3.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area (ac) CN Description 0.120 61 >75% Grass cover, Good, HSG B * 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59% Pervious Area 0.208 63.41% Impervious Area Hillbrook Post -Development Type 1124-hr 10yr Rainfall=5.51" Prepared by 5himp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 11 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area = 1.004 ac, 51.59% Impervious, Inflow Depth > 3.76" for 10yr event Inflow = 8.59 cfs @ 11.98 hrs, Volume= 0.315 of Primary = 8.59 cfs @ 11.98 hrs, Volume= 0.315 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Summary for Link 11: Raintree Inflow Area = 2.025 ac, 0.00% Impervious, Inflow Depth > 1.47" for 10yr event Inflow = 3.20 cfs @ 12.09 hrs, Volume= 0.248 of Primary = 3.20 cfs @ 12.09 hrs, Volume= 0.248 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Hillbrook Post -Development Type 1124-hr 100yr Rainfall=9. 10 " Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Page 12 Summary for Pond 4: Detention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 4.92" for.100yr. event Inflow = 4.37 cfs @ 11.96 hrs, Volume= 0.504 of Outflow = 4.37 cfs @ 11.96 hrs, Volume= 0.383 af, Atten= 0%, Lag= 0.1 min Primary = 4.37 cfs @ 11.96 hrs, Volume= 0.383 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.07' @ 11.96 hrs Surf.Area= 1,714 sf Storage= 5,315 cf Plug -Flow detention time= 156.0 min calculated for 0.383 of (76% of inflow) Center -of -Mass det. time= 57.4 min ( 880.8 - 823.5 ) Volume Invert Avail.Storage Storage Description #1 489.00' 3,415 cf Gravel (Prismatic) Listed below (Recalc) 10,455 cf Overall - 1,917 cf Embedded = 8,539 cf x 40.0% Voids #2 490.10' 1,917 cf StormTech MC-4500 x 18 Inside #1 Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap 5,332 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 489.00 1,714 0 0 495.10 1,714 10,455 10,455 Device Routing Invert Outlet Devices #1 Primary 495.00' 80.0' long x 2.0' breadth Emergency Spillway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=4.11 cfs @ 11.96 hrs HW=495.07' (Free Discharge) t1=Emergency Spillway (Weir Controls 4.11 cfs @ 0.69 fps)