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HomeMy WebLinkAboutWPO201700029 Calculations 2017-04-27HiMPROJECT MANAGEMENT CIVIL ENGINEERING r", LAND PLANNING ENGINEERING P: 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 Qp. 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. APPROVED by the Albemarle County Community D el gm?t Department Date <41 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 Q1 1.47 cfs East (Raintree) Qt Pre 0.32 cfs Qi(post) 0.13 cfs Qto re 3.29 cfs Qio 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(a)shimp-engineering.com or by phone at 434-227-5140 A You Truly, Lauren Gilroy Contents: Pre -Development Stormwater Management Calculations: Pre -Development Drainage Map Pre -Development HydroCAD Analysis Post -Development Stormwater Management Calculations: Post -Development Drainage Map Virginia Runoff Removal Method Reports Post -Development HydroCAD Analysis Storm Sewer Calculations: Storm Inlet Drainage Map VDOT LD-204 VDOT LD-229 VDOT LD-268 VDOT LD-347 Self -Cleaning Velocity Check Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre -Development Stormwater Management Calculations Pre -Development Drainage Map Pre -Development HydroCAD Analysis HILLBROOK PRE -DEVELOPMENT SWM MAP DEVELOPMENT AREA v. % FS! 0 - 5 ib A!�, jp� 2 ONSITEt I 10� 8 ACE 1.856 A0 PA I =9.4 MINE t0C = 14x6 MiN. RV- PEVELOPMENT AREA, AN IMPERVIOUS Area 1 Time of Concentration 200 ff overland flow 7.7% slope 0.35 C—value 13.2 min Seelye Chart -- -- 1eo o n. o. flow —woods 8.2% m"n° 1.4 /no "e|ncnr 1.* min. ws* nou� 15-4 | — � --------__ \ 146 min. Area 2 Time of Concentration IN 11 AW ua ,t overland flow /03% "/"p° oa� c—vo/uv 9.1 minse°/r° Chart uzs ,t xwo/e 12 o h°/oh+ u��—_s mm� x/,p/ch Chart — 9.4 min.| 40 O �O � \ \ \ \ O 13O 000ue: 1 =*u 4 D. .2 C3) 1 2 D.A.2 Offsite D.A.1 D.A.2 Onsite Subcat I FReach on k�kLI k Drainage Diagram for Hillbrook Pre -Development I, Prepared by Shimp Engineering, P.C., Printed 7/1/2015 HydroCAD@ 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Hillbrook Pre -Development Type 1124-hr1yr Rainfall=3. 01 " Prepared by Shimp Engineering, P.C. Printed 7/1/2015 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1: D.A.1 Runoff = 0.32 cfs @ 12.12 hrs, Volume= 0.042 af, Depth> 0.27" 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 1.856 58 Woods/grass comb., Good, HSG B 1.856 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 Direct Entry, Summary for Subcatchment 2: D.A.2 Onsite Runoff = 0.23 cfs @ 12.04 hrs, Volume= 0.017 af, Depth> 0.37" 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 0.568 61 Pasture/grassland/range, Good, HSG B 0.568 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.4 Direct Entry, Summary for Subcatchment 3: D.A.2 Offsite Runoff = 1.50 cfs @ 11.96 hrs, Volume= 0.068 af, Depth> 1.59" 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 0.182 61 Pasture/grassland/range, Good, HSG B * 0.328 98 Impervious 0.510 85 Weighted Average 0.182 35.69% Pervious Area 0.328 64.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Hillbrook Pre -Development Type ii 24-hr 1yr Rainfa11=3.01" Prepared by Shimp Engineering, P.C. Printed 7/1/2015 HydroCAD° 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 3 Summary for Link 4: D.A.2 Inflow Area = 1.078 ac, 30.43% Impervious, Inflow Depth > 0.95" for 1yr event Inflow = 1.62 cfs @ 11.97 hrs, Volume= 0.085 of Primary = 1.62 cfs @ 11.97 hrs, Volume= 0.085 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Hillbrook Pre -Development Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 7/1/2015 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 1: D.A.1 Runoff = 3.29 cfs @ 12.08 hrs, Volume= 0.225 af, Depth> 1.45" 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 1.856 58 Woods/grass comb., Good, HSG B 1.856 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 Direct Entry, Summary for Subcatchment 2: D.A.2 Onsite Runoff = 1.47 cfs @ 12.02 hrs, Volume= 0.080 af, Depth> 1.68" 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 0.568 61 Pasture/grassland/range, Good, HSG B 0.568 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.4 Direct Entry, Summary for Subcatchment 3: D.A.2 Offsite Runoff = 3.48 cfs @ 11.96 hrs, Volume= 0.163 af, Depth> 3.84" 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 0.182 61 Pasture/grassland/range, Good, HSG B * 0.328 98 Impervious 0.510 85 Weighted Average 0.182 35.69% Pervious Area 0.328 64.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Hillbrook Pre -Development Type 11 24-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 7/1/2015 HydroCAD19.10 s/n 07054 @ 2011 Hydro CAD Software Solutions LLC Page 5 Summary for Link 4: D.A.2 Inflow Area = 1.078 ac, 30.43% Impervious, Inflow Depth > 2.70" for 10yr event Inflow = 4.67 cfs @ 11.97 hrs, Volume= 0.243 of Primary = 4.67 cfs @ 11.97 hrs, Volume= 0.243 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Post -Development Stormwater Management Calculations Post -Development Drainage Map Virginia Runoff Removal Method Reports Post -Development HydroCAD Analysis u 1E'GAINED t "_ f.02cF� "I VELQPME-NT I H I L L B R 0 0 K SO -SITE / �; �', - 1: Y REQu1R RED N OW UCTION �_— S LII POST —DEVELOPMENT SWM MAP �, I 09,f69 AC: =� / / �i., W/ 1.4 C LOWABLE -%, DEELOPMENT AREA / 0154"A/. [MOM, � �.g••a \ � �B / I' yr y/I,�//J� W y y y /y y � � ,{�, y W y ,Y w w w Jy w y `I / � `(`—}_ _I J _ �—� /, \/) I 1 / j .. .�: ) I I /1 / / I / ,V y w •Y w \ y w w J, •Y y •Y y y w _—S\ I (_ '\ /'— II}. I \F L__ I / � � �-01 2-''A� ' e•o' ��'� � L/ I ��P / l � � !q/ y , ..�Y •4 y � _ _ w II y w y I y I .\ r ��I V e—� `-7 —�r\`- I ' / / ' / Iu `\ ." L /�, / ,/ / .,r �\ y /�'� \ w \w y y ,1�I ...r y •Y J" I / \ -/ \.. J '' f / / ®•� j 1 r-\ ; WI J/ I I / ./' \ �,/ \` W w / 1 y y \ "V I y w L_ __� 1 __1 t� L. 4-- ,-UNDET 1NE6 SSS_ IF� .1� �I�/jV/y �1 ` '\` { *\\ \\F •',k.- w4.229r /�)—" _40F�*TE j++(1. �I ) I l \.r /. \ \ y y ` ,4\ �`..\ W •L ,Y w y y y S,*". L I LZL— I r,.. DJ y �, 06828 AC■ F ,u I I� �lI yl `Y/ y y / y •Y y \' •� r ~. y y Y y�wr� w y W y y'' �W `✓ \ .-7, �� �� I =JJ/��// / I \\ �Vt� O ,11`` Iy y / I % , �; L �■-081.1�. \ \' / ,{� I' • (v / ! :. `.'17r1/t. )�1`t i y ` ,:�� ` \\ 1 \' ` •Y •Y ,Y rw 1 `� l�� L_ � ly�Z 1 — JN, ,f I /j, I , w •Y ,Y Jel 1'. •6. , ', y �{ l_. } . / I \ w y r `' 1 J VV i11 v v , W W I \ ,. F .. y w V• y y � y I� 1,L y � L� y y w 1 r f:. y 1 w w � y ,.,,...\\ l z i j I • j ,Y\ y ,Y \ •Y, J, W •Y w I W w II •Y',1 v�/1y,� \ �1 �� %_ � 7 �' I\ •�� I �• { r —,. 1_ � w 1, ,V w � w y ,Y y •Y w_ 1 V V y y J 1 �y w y •4 •L (f1 ` f• y y w W y y w y 1 77, i n / w v y V <:•� w YY=A• .y y y, ` L I I H S G B V I V � / PRESERVED ✓ WOODS I EVELOPME4T AREA/ �.�^ I y y •l� w y y � "� y y I I l l y •V ^ { \. I y\ y f� ,., y\ y l /�ri�.. ,s'' y w y MA NAGED w ± i. ..\� � y W\`` y � \ w w I V'•'J w/ . q' . r � 1 .f', \ �\ � •� • \ y y �` , ) y J w w y w w � r y tr�1 k; 45 •\ \\ 1.4,, \\ 1 ; � y �c� \"'—.� \ . � `.. Y w \ 4r •4 w w W y w � J" y !I , -__ —a— a � Il —'``t � , 1 __. W._.• ✓-�\\.\\ / \ � \, y .y i y y � 1 ` �~ y y �y ,y w w ,y � ,y y J, y I � y,l y y y y I, Il I / •\ t vi l � y w \ ,, w w y � y y ,„ w w y y I I — �.. —._- —^ �� •\ �. \ r \t � -.. J /+� I y y / � y , y +G ,� _ L y y y ,Y y ,Y � _ w y y w LAWN y y y IMPERVIOUS SIMPLE DISCONNECTION -.�` OFFSIT 1 1\' �`w\yw\y y y y y y 4 •Y y y y w\ y y y,y y y`y y y y 1 REQUIRED REDUCTION: SWM DIVIDE �''`'.' —0 08 C S Qde STORM DIVIDE - - DETAI14X\ j w wJ, w -- SHEET FLOW \ —` / _ SIMPLE 0.182 A`C- I `; %' ` 0.15 CFS Qredu coon 0.246 AC. TOTAL II '`` DISCONNECTION — I -0.14.0 AC. IMO. 1 r, y\ To --=1146 MIN. DIVIDE Q 1 — 0.13 CFS J � 40 0 40 80 120 -'YIIME O ONCENTRAirION=5.0 MIN ES -' Scale: 1 "=40' UNLESS OTHERISE NOTED Energy Balance I.F. 0.8 Q Pre 0.23 cfs RVPre 0.017 cc—ft RVde 0.037 ac—ft _j_ Q dev 0.08 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 B Soils C Soils D Soils Total %of Total Forest (acres) 0.001 0.541 o.00l 0.001 0.541 21.52 Turf (acres) 1 0.001 1.261 0.001 0.001 1.261 49.74 Impervious (acres) 10.001 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 (ft3) 211 Total TP Load Reduction Achieved (Ib/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 D.A. B D.A. C D.A. D I D.A. E Total Forest (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf (acres) 0.67 0.00 0.00 0.00 0.00 0.67 Impervious (acres) 0.55 0.00 0.00 0.001 0.00 0.55 1.23 Drainage Area Compliance Summary D.A. A I D.A. B I D.A. C I D.A. D D.A. E Total TP Load Red.(lb/yr) 0.131 0.001 0.001 0.001 0.001 0.13 TN Load Red. (lb/yr) 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 I B Soils I C Soils I D Soils I Total %of Total Forest (acres) 0.001 0.001 0.001 0.001 0.00 0.00 Turf (acres) 0.001 0.671 0.001 0.001 0.67 54.92 Impervious (acres) 0.001 0.551 0.001 0.001 0.551 45.08 BMP Selections i 1.23) Practice Credit Area (acres) Downstream Practice 2.a. Simple Disconnection to A/B Soils (Spec #1) impervious 0.122314 None acres 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-yearstorm Adjusted CN 10-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 of #N/A #N/A #N/A D.A.0 CN 0 #N/A #N/A #N/A D.A. D CN 0 #N/A #N/A #N/A D.A.ECN 0 #N/A #N/A #N/A Summary Print 9 ---� 10 4- 8 1 Offsite Undetained Inle 4 Onsite Undetained Sheet Flow Raintree Offsite Detained Detee tion Vault Detention (15� C2- � Onsite Detained D.A. A (Subcat', Reach on ' 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 Star -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 4.00'L x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development Type I! 24-hr 1 yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD119.10 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 '/' #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 '/' #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 '/' 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 Cc= 0.900 n= 0.011 Cc= 0.900 n= 0.011 Cc= 0.900 n= 0.011 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 4.031 = 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 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 li 24-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 Hydro CAD® 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 !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 5 Volume Invert Avail.Storage Storage Description #1 489.87' 71 cf 15.0" D x 58.0'L 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=0.32 cfs @ 12.08 hrs HW=491.98' (Free Discharge) t1=Pipe 2-1 (Passes 0.32 cfs of 8.50 cfs potential flow) 13=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 1/ 24-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 4/27/2017 HydroCAD® 9.10 s/n 070S4 © 2011 HydroCAD Software Solutions LLC Page 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.S9% 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 H 24-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 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 S7 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 II 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 4.00'L x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development Type // 24-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 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= 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=3.50 cfs @ 11.96 hrs HW=498.24' (Free Discharge) 't-1=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) L4=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 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=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 I/ 24-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 l/ 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 58.0115" 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 1 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) t-1=Pipe 2-1 (Passes 5.71 cfs of 10.35 cfs potential flow) 12=1-yr Orifice (Orifice Controls 0.41 cfs @ 8.37 fps) 3=10-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 0.054 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 = 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 Imaervious 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 Shimp 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 1/ 24-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 4.031= 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) Storm Sewer Calculations Storm Inlet Drainage Map VDOT LD-204 VDOT LD-229 VDOT LD-268 VDOT LD-347 Self -Cleaning Velocity Check r- — OEM W. MEN Lj dA Co Am MEN cc ImmI ■ ■ s II 00 U] IN Ul loo Imm MEN Ica 10 . � �l •-�-�-------r-�-�— ..a.,.,.,,, �► � �� � -.: � 1. ,�� _ 1� � / �'' �'`/ / , ,. �.%' �� � � �_ � \��� � ,,,tom .� �-� -�1! � �� '- �- � - �``.� �_ � � — �. _ �_� ems.✓ �� ����' ,r'.",'�" �.i. _ � i' / � � ``� LD-204 Stormwater Inlet Computations Inlets on Grade Only Sag Inlets Only 0) Q N Q p M N _C _ C O L > Z U) Q O Q `� U Q 0 Q_% //L� i C Q Q O .� V i C� X X /n (6 V U � C C W �y>1 Q � Q ��//�� C V) Z C U I6 U /y7 L.L Q U c /�( 0 ��( V ���(( V (c� C �'j7nj V /n(�� LL //7�� V //� (n O /��( 0 �M V "c_6 G L U Z 0 cam_ G 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) (cfs) ('/') ('/') (T) (ft) (ft) (cfs) (cfs) (ft) (ft) (ft) STR-2 DI-313 10 0.16 0.90 0.15 4.0 0.587 0.587 0.016 0.064 0.020 0.083 1.71 0.16 99.9% 0.587 0.000 STR-3 DI-313 6 0.11 0.65 0.07 4.0 0.277 0.277 0.016 0.072 0.020 0.083 1.26 0.15 100.0% 0.277 0.000 STR-3A DI-313 6 0.40 1 0.59 0.24 4.0 0.954 0.954 0.016 0.079 0.020 0.083 0.17 0.5 0.33 1.48 STR-4 DI-313 10 0.27 0.68 0.18 4.0 0.732 0.732 0.016 0.115 0.020 0.083 1.67 0.16 100.0% 0.732 0.000 STR-5A DI-313 10 0.28 0.66 0.19 4.0 0.743 0.743 0.016 0.116 0.020 0.083 1.67 0.16 100.0% 0.743 0.000 STR-X4 DI-313 8 0.35 0.54 0.19 4.0 0.759 0.759 0.016 0.047 0.020 0.083 1.69 0.16 100.0% 0.759 0.000 0 n n o n n rn rn 0 o (0 aID n E o o n o 0 0 0 r 0 o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 h C O O) T (p M M M M of M M T L) M r L, a UO r M M V' M M r CO Q1 n r rn r CIJ N O a N N a) U-) O O V O O cz M V CA e- O C0 C O a r Lo LO LO L) (n N r C Cn r V O C2 U a U C � ai v u u) � in (n (n n n (n OD m n E r 0 moo' Y 0 0 0 0 0 o 0 L(.o� 0 0 0 0 0 9 M CO O LO O nn m � O O O 0 0 N N O a) LO N V `- Lo V' N "T O 0 O N O O O (D (D M u) W r n Cl)00 Cb (o LO � O (O Qi M 6 Q 4 U) Q ((7 a C a) a C @ O O O O O O O O O O O Cl CO N co'y cm) C) CD CD C)N OJ O M n CO n r O N cc r CO CO to (O Co m O C',LO Lo M O a)+r rn rn rn m rn 00 00 00 00 n n n n co c Q O C W 'IT --I,�t a 'IT V G O � C O o 0 0 00CD o o0oo0M 3 Uo r r r r r o C r rn rn rn m rn co n r r ti m m coo coo d � N -fl ((7 CO O (o CO O N O — W n O CCj co co a) C (n N N Cn N N (O (q � t6 = 3 N N r N V (n to (n O of n N C) CC) O L L p O C - Q C N O Mn 00 N n W O N L [O (D CD M (O (o (6 M O (O (6 (o m (0 (> 'c N F N 3 N Q O O n O n g O O r N Co n O N J n 0 O O O O 7O O r r N o') O V -a c LO LO (O u) (n Lo (n (n (n (n (n Ln (n (n a) O U � F d 00 O 61 O) N M W O o 7 CO c`) (0 O O O O O O O O v U 00 a7 C7 0 r OOD O N C N a) Q Q L a0 O O M V n Un U) (n Cl) O W L, 17 N O r n n N O O C) C) C)0 0 0 0 0 C) C:)L C Q Y 0 0 (6 3 � 00 Cfl co 00 O Lo (.0 CO (D (fl u) (q O 0 0 o) O V (Ci N 10 4'7 (T n .N C1 E w V w O C U O O O O O 0 0 O O O O O U 3 O 0 K U .N � L n n 00 co n o r m co (n rn u) rn L co N N N N r r r M M U? r O U O O C. O O 0 0 O C) U iV N U Q 4) O 0 a) O a0 N L() (� (O V M Cl) N �- X X X X X O O Q O T C N � C L LO (c') V M M N r X X X X o N O LL a Z 0 ON Hillbrook LD-347 Hydraulic Grade Line n= 0.013 Junction Loss Outlet Inlet Water Water Inlet Number Surface Elev. Do QC) Lc) Sfo% Hf Vo Ho Qj Vj Qivi Hj Angle Ho Ht 1.3*Ht 0.51-It Surface Final H Elev. Rim. Elev 1 2 3 4 5 6 7 (8) (9) (10) 1 (11) (12) (13) (14) (15) (16) (17) (18) 19 20 21 X2 461.28 1.50 18.88 54.4 3.2327% 1.7586 10.686 0.4433 5.355 3.030 16.2 0.0499 79 0.0934 0.5866 0.7625 2.521 463.80 479.60 12.645 3.030 38.3 0.0499 49 0.0706 X3 472.76 1.25 12.65 39.4 3.8332% 1.5103 10.304 0.4122 7.812 6.365 49.7 0.2202 89 0.4373 1.0697 1.3906 2.901 475.66 479.80 X4 475.66 1.25 7.81 60.5 1.4628% 0.8850 6.365 0.1573 6.571 5.35 35.2 0.1558 3 0.0178 1 0.3309 1 0.4302 1 1.315 1 476.98 1 480.83 1 * 1 476.98 1.25 6.57 115.1 1.035% 1.191 5.355 0.1113 1 1 1 0.1113 1 0.1447 1 0.0557 1.247 1 478.22 1 488.15 *The value of Inlet 1 Qo used in this worksheet is from LD-229 and does not account for detention. Self -Cleaning Velocity Check Hillbrook From To Pipe (in) Slope % AC" Int (in/hr) Flow (cfs) Velocity (ft/s) 4 5 15 0.6% 0.18 2.95 0.54 3.0 5A 5 15 0.6% 0.19 2.90 0.54 3.0 5 6 15 0.5% 0.37 1.90 0.70 3.0 5A 5 15 0.6% 0.19 2.90 0.54 3.0 5 4 15 0.6% 0.19 2.95 0.55 3.0 4 3 15 11.5% 0.37 0.50 0.18 6.1 3A 3 15 2.2% 0.06 2.20 0.12 3.0 3 2 15 2.8% 0.49 0.50 0.25 4.1 2 1 15 1.5% 0.81 0.50 0.40 4.2 1 X4 15 6.2% 1.13 0.50 0.56 6.7 *From LD-229 This computation shows the minimum intensity required to achieve the self-cleaning velocityof 3.0 ft/s. Please note that the intensity for a 2-year storm with a 5.0 minute time of concentration is 5.2 in/hr. Independent Reports Excerpt from NRCS Soils Report NOAA Precipitation Report Infiltration Report N r 722570 722600 722630 722660 I I N V r�t •' $_ ski•. v .../ ,• J 1 r r. f r - 722570 722600 722630 722660 722690 3 Map Scale: 1:958 r printed on B landscape (17" x 11") sheet Meters N 0 10 20 40 60 Feet 0 45 90 180 270 A Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84 Custom Soil Resource Report Map —Hydrologic Soil Group 722690 722720 722750 rk- 722720 722750 722780 722780 722810 :� a •.•i 'a:_ -fir. b F N n 722870 722900 38` 5 0" N V 8 m a � v t" 38° 4' S4" N 722810 722840 722870 722900 3 0 N n 17 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 27B Elioak loam, 2 to 7 B 2.4 63.3% percent slopes 27C Elioak loam, 7 to 15 B 1.0 27.7% percent slopes 39D Hazel loam, 15 to 25 B 0.3 8.9% percent slopes Totals for Area of Interest 3.71 100.0% Rating Options —Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie -break Rule: Higher 19 3/3/2015 Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, US* A' Latitude: 38.0831*, Longitude:-78.4624* Elevation: 484 ft* N p * source: Google Maps # 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 DurationlAverage recurrence interval (years) ��� mm ll-i 2 �5 10 25 50 100 200 5 00 1000 ��__7__ [�ji:n]L(O.,0.352 0.420 0.492 0.553 0.624 0.678 0.729 0.778 0.837 0.885 17 0.390� (0.379 0.466 (0.444-0.545J (0.498 0.6� 13)S (0.558 0.688) (0.604 0.747)I (0.646-0.804) (0.684 0.858); (0.728 0.925) (0.763-0.98� 0.562 0.671 0.789 0.885 0.994 1.08 1.16 1.23 1.32 1.39 10-min (0.507-0.623) (0.606-0.744) (0.710-0.873)i (0.796-0.980)i (0.889-1.10) (0.962-1.19) (1.03-1.28) -Zj(1.08-1.36) 1' (1.15-1.46) (1.20-1.55) 15-min 0.703 0.844 0.998 1 F__1_.12 1.26 1.37 1.47 1.56 1.67 1.75 (0.634--_0.779)J(0.762-0.936) (0.899 1.10) (1.01-1.24) (1.13-1.39) (1.22-1.51) (1.30-1.61) (1.37-1.72) (1.45-1.84) (1.51-1.94) [��:in]F_o-9_63 1.17 1.42 1.62 1.87 j 2.06 2.24 2.42 2.65 2.83 (0.869-1.07)) (1.05-1.29) (1.28-1.57� (1.46-1.80) (1.67-2.06) (1.83-2.27) (1.99-2.47) (2.13-2.67) (2.31-2.93) (2.44-3.14) 1.20 1.46 1.82 2.11 i 2.48 2.79 3.09 3-A 3.81 4.14 60f11in (1.08-1.33) j (1.32-1.62) (1.64-2.01) (1.90-2.34) (2.22-2.74) (2.49-3.08) (2.74-3.40) (2.99-3.75) (3.31-4.21) (3.57-4.59) 2-hr 1.44 1.75 2.19 I 2.58 I 3.07F 3A8 IF 3.91 4.36 11 4.98 F 5.51 (1.271.65) (1.541.99) (1.93-249) (2.27-2.92) 11 (2.69-3.47) i (3.03-394�j (3.38-4.41) (3J4 4.92) (4.22 5.62) (462 6.24) F3-h7r 1.58 1.92 2A0 1 2581 3.35 3.81 4.28 4.78I 5.46 6. 55 (1.39 1.81) (1.68-2.20) 2.10 2.75) 2.91-3.83) (3.29-434)J 3.67-4.88) (4.07-5.44) 4.59-6.23)5.03-6.91) 6-hr 2.01 2.43 3.02 3.56 4.28 4.90 IF-5-.5-671 6.28 7.30 F 8. 00 (1.78-2.28) I (2.15-2.76) (2.66-3.42) (3.12-4.02) i (3.73-4.83) (4.24-5.53) 11 (4.77-6.27) (5.33-7.08) (6.10 8.24) (6.76-9.27) 2.52 3.05 3.80 4.50 5.47 6.34 7.28 8.32 9.86 11.2 D�r (2 23-2.89) (2.69Y3Y49j (3.34-4.35) , (3.94-5.13) (4.76 6.22) (5.46-7l20) (6.19-826) (6.98-9.43) (8.11 11.2) (9.09-12.8) 3.01 i 3.65 4 66j 5.51 6.77� 7.85 ' 9 4 10A 12.3 14.0 24-hr L(2.71-3.39) �(3.228-4.10) ' (4.17-5.23) i (4.92-6.17) (6.00-7 55) `s,j (6.91-8.74) :' (7.89-10.1) (8.94-11.5) (10.5-13.7) (11.7-15.5) L.,,._._..Y 3.55 4.31 5.48 6.44 0 7.84 9.01 16.3 11.7 13.7 15.4 2-day (3.19-3.97) (3.87-4.82) (4.91-6.12) (5.76-7.18) 11 (6.95-8.72) 11 (7.93.93-10.0) (8.98 11.4) (10.1-13.0) 11 (11.7-15.3) 11 (13.0-17.2) - 12AI 14.5685 8.33 9.56 10.93day 3.79 4.59 16.3 (3.44-4.20) 4.16-5.08) 9.19) (8.53-09.65-120) (09-13.7) (12.6-160) (4.0-18.0) 52-6..57. _17 IF 4-da (3. 84?42 (4. 55?35) (5.646.79) (6.617596) (8. 089.67) (9.1311.1) r(10.3127) (11 14.3)� (134516.8)µ (1419 8.9) 4.67 5.62 7.02 8.18 9.84 11.2 12.7 4.3 16.6 18.5 7-day (4.28-5.10) (5.16 6.14) (6.44 7.68) (7.48-8.93)1 (8.94-10.7) (10.1-12.2) (11.4 13.9) [12' .7-15.6) (14.6-18.1) (16.1-20.3)j ��10-da 5.29 6.35 7.85 9.06 10.8 12.2 13.6 15.2 17A 99.2 (4.88-5.74) 1 (5.86-6.89) (7.23-8.50) ; (8.32-9.80) (9.85-1 L6) (11.1-13.2) I (12.3-14L8) (13.7-16.5) (15.5-418.9) I (16.9-21.0) 20-da 6.95 8.29 10.0 11 A 13.2 14.7 16.1 17.6 19.7 (6.50-7.421.3 5) (7.76-8.89) (9.36-10.7) I (10.6-12.2) (12.3-14.2) (13.6-15.7) I (14.9-17.3) (16.2-18.9) (17.9-21.2) (19.3-23.0) 30-da 8.53 10.1 12.0 13.4 15.2 16.6 17.9 19.3 21.0 22.4 (8.02-9.09� (9.51_10.8) -IL(11.2 12.7) (12.5 14.2) (14.2 16.2) (15.5 17.7) (16.7 19.1) (17.9 20.6) (19.4 22.5) (20.5 24.0) 45-day 10.6 j12.6 14.7 16.3 18.3 19.8 I 21.3 22.7 24.5 25.8 (10.0-11.3) (11.9-13.3) (13.9-15.6) (15.4-17.2) (17.2-19.4) (18.6-21.0) (19.9-22.6) (21.2-24.1) (22.7-26.1) (23.9-27.6) 60{la 12.5 14.7 17.0 18.7 20 8 22.4 23.9 25A 27.2 28.5 (11.8-13.2) (13.9-15.5) (16.1-17.9) (17.6 19.7 (19.6 22.0) (21.1-23.6) (22.5-25.3) (23.8 26.8) (254-28.8) (26.5-30.3) 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 (fora 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. PF graphical http://hdsc.nws.noaa.govfhdsc/pfds/pfds_ pri ntpage.htm I?lat=38.0831 &Ion=-78.4624&data=depth&units=engl i sh&series= pds 1/4 Ir B-Z I' B-3 NONNI V 1 FROEHLING & ROBERTSON, INC. Boring Location Plan Engineering Stability Since 1881 Client: Red Dirt Developments 6181 Rockfish Gap Turnpike Project: Old Brook Road Infiltration Testing Crozet, Virginia 22932-3330 F&R Project No. 71T0015 T434.823.5154 I F 434.823.4764 Date: April, 2015 1 Scale: 1" = 50' 1 Drawing No.: 2 SINGE �& FROEHLIN[3 & F208ERTSON9 INC. Project No: 71T0015 Elevation: Client: Red Dirt Developments Project: Old Brook Road Infiltration City/State: Charlottesville, VA Total Depth: 13.0' Boring Location: See Boring Location Plan BORING LOG Boring: B-1 (1 of 1) Drilling Method: HSA Hammer Type: Automatic Date Drilled: 4/29/15 Driller: Douglas Elevation Depth p Description of Materials *Sample Sample N-Value Remarks (Classification) Blows (feet) (blows/ft) 0.4 " Surficial Organic Soil 1.0 Brown, Moist, Loose, Silty SAND (SM) 2-3-5 <<C>RESIDUUM 8 2.5 3.5 3'S Subsurface water was not Light Brown, Moist, Very Dense, Silty SAND (SM) 10-23-45 encountered during RESIDUUM 5.0 68 drilling or upon auger remvoal 6.0 6.0 Soft Weathered Rock when sampled becomes a 27-50/5 Brown, Moist, Very Dense, Silty SAND (SM), Little 100+ Gravel 7 5 SOFT WEATHERED ROCK 10-43-50/3 8.5 10.0 100+ 11.5 50/5 13.0 100+ Boring Terminated at 13 Feet Number of blows required for a 140 lb hammer drooning 30" to drive 2" O D 1 375" 1 D sampler a total of 18 inc p� in throo r in—montc The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value. SINCE c- FROEHLING ,sEl & ROBERTSON9 INC. BORING LOG Boring: B-2 (1 of 1) Project No: 71T0015 Elevation: Drilling Method: HSA Client: Red Dirt Developments Total Depth: 13.0' Hammer Type: Automatic Project: Old Brook Road Infiltration Date Drilled: 4/29/15 City/State: Charlottesville, VA Boring Location: See Boring Location Plan Driller: Douglas Description of Materials * Sample Sample N-Value Elevation Depth �De�thj blows/ft Remarks (Classification) Blows 0.4 Surficial Organic Soil 1.0 Brown, Very Moist, Loose, Clayey SAND (SC) 2-2-4 RESIDUUM 6 2.5 3.5 3'S Subsurface water was not Ligh Brown and Gray, Moist, Medium Dense to 8-14-15 encountered during Dense, Silty SAND (SM) 5 0 29 drilling or upon auger RESIDUUM remvoal 6.0 10-16-20 7.5 36 8.5 8'S Soft Weathered Rock when sampled becomes a 30-50/5 Brown, Moist, Very Dense, Silty SAND (SM) 10.0 100+ SOFT WEATHERED ROCK 11.5 50/4 13.0 13.0 100+ s Boring Terminated at 13 Feet +��.,.vo � cyun cu +`ry iv nan nnci uIUPIJ 115w w ui ivc t v.v., 1.Ji7 i.v. �.dniNiei d wLdi ul lb InCneS In Lnree b increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value. SINCE FROEHLING 1881 Project No: 71T0015 Client: Red Dirt Developments Project: Old Brook Road Infiltration City/State: Charlottesville, VA & ROBERTSON, INC. Elevation: Total Depth: 13.0' Boring Location: See Boring Location Plan BORING LOG Boring: B-3 (1 of 1) Drilling Method: HSA Hammer Type: Automatic Date Drilled: 4/29/15 Driller: Douglas Elevation Depth p Description of Materials (Classification) * Sample Blows Sample Depth feet N-Value (blows/ft)�R�emarks 0.4UBrown, Organic Soil ery Moist, Soft, Sandy LeanCLAY (CL), 1-1-31.0 vel POSSIBLE FILL 2 5 4 3.5 6.0 3.5 5.0 6.0 4 Subsurface water was not encountered during drilling or upon auger remvoal CH grown, Very Moist, Soft, Fat CLAY ( ) POSSIBLE FILL 1-2-2 Brown, Moist, Medium Dense to Loose, Silty 7-12-15 SAND (SM) RESIDUUM 7 5 27 8.5 6-8-9 10.0 17 11.5 1-4-4 13.0 8 Boring Terminated at 13 Feet - -- Number of blows reauired for a 140 lb hammer dronnincr 30 to drive 7" n n 1 37S" l n camnlar n M41 of 1 R i—hoc in rh— 9" in—.,,.,..rc The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value. W -C -I J ai M p E 0�� � OZ a Ln 0 W M L- V ma Q0 0 LL a D MA W n Ln 6 Z Z 0 N m W J > I Cu w ° o a �„ Ln °1 Q Q Q 0 0 Y O LL L_ O U Z O Y w z_ m V ++ v N L � L Y a u a 'u n r IHE III m H09 i00 00 ko N N O O C CD s L s L L L U) 0- Q C cma�a (6 C C C Lo CM O — N CO '-000 7r-NM LLmmm Z M = LO 00 Z r d ~ CO O LL _ N II N r Co N N Co > II II O O O O (/) _ C: + d Z O M r — N 0o r II LL LL L m cA U Z N LO 00 r r 0 LL r � � U r II II p O+L, ON_ II 4- O CL N N N O II � O C O > 0)L U +' Cu L N (!� " `C —_ = > O O Ln O Ln Ln Ln Ln rq N m Ln CD OLO LO (11) 43dao