Loading...
HomeMy WebLinkAboutWPO201600041 Calculations 2016-05-17PROJECT MANAGEMENT HIMPCIVIL ENGINEERING LAND PLANNING ENGINEERINGf May 17, 2016 VSMP Reviewer Albemarle County Regarding: Hillbrook Stormwater Management VSMP Amendment To Whom It May Concern, APPROVED by the Albemarle County Community Developrnen Department Date Pile a�i ono Enclosed are the calculations and details relating to stormwater treatment for the proposed development Hillbrook. The presence of rock in the approved location of the detention facility necessitated its re -location to the right-of-way. The following calculation packet shows all details updated per the as -built design of the detention facility. Pollutant removal is achieved with a combination of impervious disconnection and level 2 bioretention. All pollutant removal is applied to "D.A. A" on the VRRM, which is delineated on the post -development drainage map. The bioretention 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 bioretention. 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 significantly 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.* (Qpre * 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 Summarv: Northwest M Qmax 1.47 Cfs I Q1 1.47 cfs East (Raintree) Q1( re) 0.32 cfs Q1ost 0.13 cfs RVt re 0.042 a.f. RViost 0.016 a.f. Qto re 3.29 cfs Qjo ost 3.10 cfs If you have any questions please do not hesitate to contact me at your earliest opportunity. I may be reached at: Justin(.shimp-engineedng.com or by phone at 434-953-6116. Yours Truly, Justin Shimp, P.E. 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 HELBROOK / 1 i PRE —DEVELOPMENT SWM MAP DEVELONM�NT AR6, l / / ' t � C F.S" II -roc 110WPattl l la t l �lI I /l // � . } I �l I D.A.I c, , FSITE, I I ► D.A. 1 1 \ 1 \ \ \ \ \ I \ - -1- , `I 111. 2 ONSITBJ I I 1 1 \ \ \ \ I I I I- 5 \ O. w r I �1.856 A r 1 \ \ I I I I r -:% D.3�8 A'' I I 4110� 8 AC. 1 I - '� '„= I =9.4 MIN. ItoC-14+.8 M�N. ToC 5.I. I I I ` I \ - .a, I \0.23 CFS �� , .-f�.321 IFS I 1 1 I ► I / / / I I - Y 1-A .50 FS � I ) I AF� =D.O\ i AREA/O 17 AF E� ":, 1 1` ✓ ' I I / / 414* IMPERVIOUS Area 1 Time of Concentration � a i 1 1 I I I I 200 ft overland flow 7.7% slope 0.35 C—value 13.2 min Seelye Chart _ �K'' L/'/( 1 1 I \ I slope 1.4 fps velocity NEH Figure 15-4 < I I \ I 128 ft s. c. flow —woods 8.2% P P Y 1.4 min. 9 14.6 min. Area 2 Time of Concentration ` \ \ 1A z ) i-- ,-- �-L1 \ I \ 88 ft overland flow 10.3% slope 0.35 C—value 9.1 min Seelye Chart 223 ft swale 12 ft height 0.3 min. Kirpich Chart 9.4 min. 40 0 40 80 120 \ \ _ 17 1 s 1 Scale: 1 "=40' �y 4 D. .2 3 a 1 D.A.2 Offsite D.A.I D.A.2 Onsite Osubcat ReachLinkDrainage Diagram for Hillbrook Pre -Development Prepared by Shimp Engineering, P.C., Printed 7/1/2015 HydroCADO 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Reach Hillbrook Pre -Development Type // 24-hr lyr 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 1124-hr lyr 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 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 // 24-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 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 I�ErAlHP'D / /, ,� %, -f. c E_�e_E LOPM_�NT - _ ,� I I H I L L B R 0 0 K ' �/ '" - REQUIR- REDUCTION - B LO�IV ,/011 SITE / / W/ ems= E� CT I I I 1 POST -DEVELOPMENT SWM MAP 17 ` --- 1.41 C 1,ALLOWABLE DKlOPM TAR 1 {p j' y� J -' 1 / W W W i +lam W W W W W W W W W W W W �/ON054A+ . MON / ( M! W / � W W W W W W W W W W W W W 1 I _ N,� �l� I I I / -RV =0.01 2/A.'�P '/ /' ' I/ `� zi\ I !, � I I /lW � •Y / W W W W L W W W W W 1 W I � � / � � �Y,; 1 \ I •./�/vI W / l.�I // �((��1j�Jj W W W \W W W W � W I /W /� / � W \ W 1 I �UNDErt 1"NEI�/ - - W W\ W W W v W W W S V / I �; / �I / W / W W ` .✓ \t.229 ■ W W W I I ' 1 !( F �// fJy/ I ..."'...IIILLL l� � � W W W W .v •v 1 1 I •7 I l 11 �/ W W w W..Y W 'OF �S ATE 0�828 Ac■ rh ��• �� II ! W/ I W W y W W W \ W W W W W W W ' i I a°,:. P I r �l � I I.LI ! •4 'Yi \ \�® �� J.0 W W W 1 I 0:208-Ad. II P■ ..1 r \ ♦Ip•..� � i�/• l I 1 )jI✓I I W W _ W WI W .Y 11 I /� F]. '� �\ r i WI / I W W 1 • \ W W W 1 W� 1 I 1 � III I I / W% W W I\ (i I W W W 111Ir� W 1\\ 1 Ii W' \ W 1 \ 1 _•^. I W W I I \W � I mix- .��II I I W W W W W W W W •L �• �—/ \ 1 I I W W W W W W } I \ I&MHSG B W W f I \ W W W —..� _ �.,` W W W W "!^ W ! ` W PRESERVED IW W W w ` W / WOODS / _ W �� I • W W J{ W /W W �" W W+ s W W Wes` I ' W W / EVELOPME"T AREA / '� W 1• t11 I I \W MANAGED W r1 VI • � � / � W W Y I +Y •Y W W W / •i J 4 i� \ W �l \ W W .L W W W 1 W I W W W I / y✓ �� W � \ � � W W W W W W W W W W I I Y W W W W W W W W I _ — ` S 1� _�` W •fy 1 n�• ' \j i j. W W. I W W WI W W W I `" •k � 1 W W W W W W W W W I I — W W W W W W LAWN W W W W W W W W IMPERVIOUS SIMPLE DISCONNECTION \\ :r 1 _,,' 1 IW ,..�� W W W W W W SWM DIVIDE _~ OFFSIT '' W y W W` W W \W W W W I I REQUIRED REDUCTION: '':•'+ W� WI +Y W y W W W W �v W +Y W W W I f 0.23 CFS Qpre Ar 1 —0.08 CFS Qdev STORM DIVIDE \ 1 'T.;; { W 1 lW — \ \ S ET F�.OW / 0.15 CFS Q SIMPLE DETAIP*D\ reduction � �.182 ABC. 1 11 `' 1 W 0.2 6 AC. T TA� ,// DISCONNECTION — ,-0.1 O AC. IMO. \ 1 W\ '� \ I ToQ =11L6 N� �/ DIVIDE ` �W 1 I I Q, =I0■ 1 CFS \ \ 1 �� '� 1; I 1 I h f 40 0 40 80 120 I RV0.016dFr I !Km 0 W EL TIME OFCONCENTRA ION=5.0 MINU ES Scale: 1"=40' UNLESS OTNE SE NOTED I I 1 Energy Balance I.F. 0.8 Q pre 0.23 Cfs RV,,. 0.017 ac—ft RVde� 0.037 ac—ft Qdev 0.08 Cfs Virginia Runoff Reduction Method Worksheel Virginia Runoff Reduction Method New Development Worksheet - v2.6 -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 0.00 0.541 0.00 0.001 0.541 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 i 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) 1962 Total TP Load Reduction Achieved (lb/yr) 1 Total TN Load Reduction Achieved (lb/yr) 10.77 Adjusted Post Development TP Load (lb/yr) 0.82 Remaining Phosphorous Load Reduction (Lb/yr) Required 0.04 Drainage Area Summary D.A. A I D.A. B I D.A. C I D.A.Dj D.A. E Total Forest (acres) 0.001 0.001 0.00 0.001 0.00 0.00 Turf (acres) 0.671 0.001 0.00 0.()Ol 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 I D.A. C I D.A. D D.A. E Total TP Load Red. (lb/yr) 1.371 0.001 0.001 0.001 0.001 1.37 TN Load Red. (lb/yr) 10.771 0.001 0.001 0.001 0.001 10.77 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 I % of Total Forest (acres) 0.001 0.001 O.Col 0.001 O.00l 0.00 Turf (acres) 0.001 0.671 Oxcl 0.001 0.671 54.92 Impervious (acres) 1 0.001 0.551 0.001 0.001 0.551 45.08 BMP Selections 1 1.23i Practice Credit Area (acres) Downstream Practice 2.a. Simple Disconnection to A/B Soils (Spec #1) impervious 0.122314 6.b. acres Bioretention disconnected #2 6.b. Bioretention #2 (Spec #9) Impervious: 0.43152 Turf (Pervious): 0.674839 Total Impervious Cover Treated (acres) 0.55 Total Turf Area Treated (acres) 0.67 Total TP Load Reduction Achieved in D.A. A (lb/yr) 1.37 Total TN Load Reduction Achieved in D.A. A (lb/yr) 10.77 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 69 71 73 D.A. B CN 01 #N/A #N/A #N/A D.A. C CN 01 #N/A #N/A #N/A D.A.D CN 01 #N/A #N/A #N/A D.A. E CN 01 #N/A #N/A #N/A Summary Print Drainage Area A Drainaae Area A Land Cover (acres A soils B Soils C Soils D Soils Forest/Open Space (acres) 0.00 0.00 0.00 0.00 Managed Turf (acres) 0.00 0.67 0.00 0.00 Impervious Cover (acres) 0.00 0.55 0.00 0.00 Total Apply Runoff Reduction Practices to Reduce Treatment Volume & Pos s Land Cover Rv 0.00 0.00 0.67 0.20 0.55 0.95 Post Development Treatment Volume (cf) 2400 1.23 I,pment Load in Drainage Area A Phosphorus Untreated Volume from Remaining Load from Phosphorus Phosphorus Remaining Credit Area Upstream RR Runoff Runoff Phosphorus Upstream RR Load to Practice Removed By Phosphorus Practice I Unit I Description of Credit (Credit far-.res► Practir_.P ir_.f► Rerllictinn rgfl Vnl- lrfl Efflcienev (011Practices fibs► nhs,n Practice jIbs.j Load fibs. 2. Rooftop Disconnection 2.a. Simple Disconnection to A/B Soils (Spec 5D% runoff volume reduction #1) impervious acres disconnected for Treated area 0.50 0.12 0 211 211 0 0.00 0.26 0.13 0.13 to be Ern 6. Bioretention impervious acres draining to 6.a. Bioretention #1 or Urban Bioretention bioretention 40% runoff volume reduction 0.40 0.00 0 0 0 25 0.00 0.00 0.00 0.00 (Spec #9) turf acres draining to _ _ bioretention 40% runoff volume reduction 0.40 0.00 0 0 0 25 0.00 0.00 0.00 0.00 impervious acres draining to 6.b. Bioretention #2 (Spec #9) bioretention 80% runoff volume reduction 0.80 0.43 211 1359 340 50 0.13 0.93 0.96 0.11 - turf acres draining to 180% 1 1 1 L bioretention runoff volume reduction 0.80 0.67 j � 392 98 50 0.00 0.31 0.28 0.03 TOTAL IMPERVIOUS COVER TREATED (ac)l 0.55 TOTAL TURF AREA TREATED (ac)l 0.67 TOTAL PHOSPHORUS REMOVAL REQUIRED ON SITE (Ib/yr) 1.17 TOTAL RUNOFF REDUCTION IN D.A. A (cf) 1,962 PHOSPHORUS REMOVAL FROM RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr) 1.37 9 Offsite Undetained Inle 4 Onsite Undetained Sheet Flow ✓� I 6 Raintree Offsite Detained Detee Lion Vault Bioretention 5 \ 2 Onsite Detained D.A. A Subcat Reach on Link Hillbrook Post -Development 1yr Type 1124-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 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 = 1.46 cfs @ 11.97 hrs, Volume= 0.069 af, Depth> 0.67" 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 69 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 > 0.67" for 1yr event Inflow = 1.46 cfs @ 11.97 hrs, Volume= 0.069 of Outflow = 1.45 cfs @ 11.98 hrs, Volume= 0.069 af, Atten= 1%, Lag= 0.4 min Primary = 1.45 cfs @ 11.98 hrs, Volume= 0.069 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= 497.36' @ 11.98 hrs Surf.Area= 16 sf Storage= 20 cf Plug -Flow detention time= 0.2 min calculated for 0.069 of (100% of inflow) Center -of -Mass det. time= 0.1 min (879.7 - 879.5 ) Volume Invert Avail.Storage Storage Description #1 496.10' 108 cf 4.00'W x 4.00% x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development lyr Type i124-hrlyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 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' 13.0" 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=1.45 cfs @ 11.98 hrs HW=497.36' (Free Discharge) t1=STM 5-6 (Passes 1.45 cfs of 5.19 cfs potential flow) L2=Weir Plate Orifice (Orifice Controls 1.45 cfs @ 5.36 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=496.10' (Free Discharge) t3=STM 3-4 ( Controls 0.00 cfs) t-4=STM 4-5 ( Controls 0.00 cfs) Summary for Pond 4: Bioretention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 0.67" for 1yr event Inflow = 1.45 cfs @ 11.98 hrs, Volume= 0.069 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= 494.98' @ 24.00 hrs Surf.Area= 3,703 sf Storage= 3,005 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 #1 488.60' 908 cf Gravel Sump (Prismatic) Listed below (Recalc) 2,270 cf Overall x 40.0% Voids #2 490.85' 820 cf Bioretention Mix (Prismatic) Listed below (Recalc) 3,279 cf Overall x 25.0% Voids #3 494.10' 1,482 cf Surface Storage (Prismatic) Listed below (Recalc) 3,209 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 488.60 1,009 0 0 490.85 1,009 2,270 2,270 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 490.85 1,009 0 0 494.10 1,009 3,279 3,279 Hillbrook Post -Development 1yr Type 1124-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD09.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 4 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 494.10 1,214 0 0 495.10 1,749 1,482 1,482 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=488.60' (Free Discharge) t1=Emergency Spillway ( Controls 0.00 cfs) 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, Hillbrook Post -Development 1yr Type 1124-hr 1yr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Page 5 Summary for Pond 7: Detention On -Site Bypass is Routed through this node 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 ) 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 39.0'1. 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) t-1=Pipe 2-1 (Passes 0.32 cfs of 8.50 cfs potential flow) 12=1-yr Orifice (Orifice Controls 0.32 cfs @ 6.61 fps) 3=10-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, Hillbrook Post -Development lyr Type 1124-hrlyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 9: Mite 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: 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 10yr Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 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 Descri tion * 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 = 6.13 cfs @ 11.96 hrs, Volume= 0.275 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 * 1.229 73 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 > 2.68" for 10yr event Inflow = 6.13 cfs @ 11.96 hrs, Volume= 0.275 of Outflow = 6.13 cfs @ 11.96 hrs, Volume= 0.275 af, Atten= 0%, Lag= 0.0 min Primary = 1.95 cfs @ 11.96 hrs, Volume= 0.221 of Secondary = 4.18 cfs @ 11.96 hrs, Volume= 0.054 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 498.35' @ 11.96 hrs Surf.Area= 16 sf Storage= 36 cf Plug -Flow detention time= 0.1 min calculated for 0.275 of (100% of inflow) Center -of -Mass det. time= 0.1 min ( 830.4 - 830.3 ) Volume Invert Avail.Stora a Storage Descri tion #1 496.10' 108 cf 4.00'W x 4.00'L x 6.74'H 4'x4' Vault Storage Hillbrook Post -Development 10yr Prepared by Shimp Engineering, P.C. Type 1124-hr 10yr Rainfall=5.51" HydroCAD® 9.10 s/n 07054 @ 2011 Hydro CAD Software Solutions LLC Printed 5/17/2016 Paee 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 '/' #2 Device 1 Cc= 0.900 n= 0.011 496.00' 13.0" 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 Cc= 0.900 n= 0.011 496.10' 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=1.95 cfs @ 11.96 hrs HW=498.35' (Free Discharge) t1=STM 5-6 (Passes 1.95 cfs of 6.87 cfs potential flow) L2=Weir Plate Orifice (Orifice Controls 1.95 cfs @ 7.18 fps) Secondary OutFlow Max=4.17 cfs @ 11.96 hrs HW=498.35' (Free Discharge) t3=STM 3-4 (Inlet Controls 4.17 cfs @ 4.41 fps) -4=STM 4-5 (Passes 4.17 cfs of 7.65 cfs potential flow) Summary for Pond 4: Bioretention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 2.16" for 10yr event Inflow = 1.95 cfs @ 11.96 hrs, Volume= 0.221 of Outflow = 1.66 cfs @ 12.07 hrs, Volume= 0.151 af, Atten= 15%, Lag= 6.6 min Primary = 1.66 cfs @ 12.07 hrs, Volume= 0.151 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.04' @ 12.07 hrs Surf.Area= 3,734 sf Storage= 3,104 cf Plug -Flow detention time= 191.3 min calculated for 0.151 of (68% of inflow) Center -of -Mass det. time= 73.7 min ( 931.6 - 857.9 ) Volume Invert Avail.Stora a Storage Descri tion #1 488.60' 908 cf Gravel Sump (Prismatic) Listed below (Recalc) 2,270 cf Overall x 40.0% Voids #2 490.85' 820 cf Bioretention Mix (Prismatic) Listed below (Recalc) 3,279 cf Overall x 25.0% Voids #3 494.10' 1,482 cf Surface Storage (Prismatic) Listed below (Recalc) 3,209 cf Total Available Storage Elevation Surf.Area Inc.Store Cum -Store (feet) (sq-ft) (cubic -feet) (cubic feet) 488.60 1,009 0 0 490.85 1,009 2,270 2,270 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic feet) 490.85 1,009 0 0 494.10 1,009 3,279 3,279 Hillbrook Post -Development 10yr Type li 24-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 Hydro CAD®9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 9 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 494.10 1,214 0 0 495.10 1,749 1,482 1,482 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 PrimaryOutFlow Max=1.56 cfs @ 12.07 hrs HW=495.04' (Free Discharge) L1=Emergency Spillway (Weir Controls 1.56 cfs @ 0.50 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 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) MAO (ft/sec) (cfs) 5.0 Direct Entry, Hillbrook Post -Development 10yr Type l! 24-hr 1Oyr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 10 Summary for Pond 7: Detention On -Site Bypass is Routed through this node Inflow Area = 0.507 ac, 50.49% Impervious, Inflow Depth > 4.57" for 10yr event Inflow = 7.19 cfs @ 11.96 hrs, Volume= 0.193 of Outflow = 6.42 cfs @ 11.99 hrs, Volume= 0.193 af, Atten= 11%, Lag= 1.8 min Primary = 6.42 cfs @ 11.99 hrs, Volume= 0.193 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 493.39' @ 11.99 hrs Surf.Area= 415 sf Storage= 1,224 cf Plug -Flow detention time= 7.4 min calculated for 0.193 of (100% of inflow) Center -of -Mass det. time= 7.0 min ( 790.2 - 783.2 ) Volume Invert Avail.Stora a 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 Routinp, 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=6.41 cfs @ 11.99 hrs HW=493.38' (Free Discharge) t1=Pipe 2-1 (Passes 6.41 cfs of 10.74 cfs potential flow) L2=1-yr Orifice (Orifice Controls 0.43 cfs @ 8.73 fps) 3=10-yr Orifice (Orifice Controls 5.98 cfs @ 5.35 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, Hillbrook Post -Development 10yr Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD® 9.10 s/n 07054 @ 2011 HydroCAD Software Solutions LLC Pape 11 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 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 > 3.98" for 10yr event Inflow = 9.26 cfs @ 11.98 hrs, Volume= 0.333 of Primary = 9.26 cfs @ 11.98 hrs, Volume= 0.333 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 > 1.44" for 10yr event Inflow = 3.10 cfs @ 12.07 hrs, Volume= 0.243 of Primary = 3.10 cfs @ 12.07 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 Hillbrook Post -Development 10yr Type 1124-hr 100yr Rainfall=9.10" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Page 12 Summary for Pond 4: Bioretention Inflow Area = 1.229 ac, 0.00% Impervious, Inflow Depth > 4.05" for 100yr event Inflow = 2.48 cfs @ 11.96 hrs, Volume= 0.414 of Outflow = 2.47 cfs @ 11.97 hrs, Volume= 0.344 af, Atten= 0%, Lag= 0.4 min Primary = 2.47 cfs @ 11.97 hrs, Volume= 0.344 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 495.05' @ 11.97 hrs Surf.Area= 3,740 sf Storage= 3,122 cf Plug -Flow detention time= 123.2 min calculated for 0.344 of (83% of inflow) Center -of -Mass det. time= 44.2 min (892.8 - 848.6 ) Volume Invert Avail.Storage Storage Description #1 488.60' 908 cf Gravel Sump (Prismatic) Listed below (Recalc) 2,270 cf Overall x 40.0% Voids #2 490.85' 820 cf Bioretention Mix (Prismatic) Listed below (Recalc) 3,279 cf Overall x 25.0% Voids #3 494.10' 1,482 cf Surface Storage (Prismatic) Listed below (Recalc) 3,209 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 488.60 1,009 0 0 490.85 1,009 2,270 2,270 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 490.85 1,009 0 0 494.10 1,009 3,279 3,279 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic -feet) (cubic -feet) 494.10 1,214 0 0 495.10 1,749 1,482 1,482 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=2.24 cfs @ 11.97 hrs HW=495.05' (Free Discharge) t1=Emergency Spillway (Weir Controls 2.24 cfs @ 0.57 fps) Storm Sewer Calculations Storm Inlet Drainage Map VDOT LD-204 VDOT LD-229 VDOT LD-268 VDOT LD-347 Self -Cleaning Velocity Check e. ....... jj C\2 O ry CD cnl � w// � '— ��'� o � �/� �/��:r�� � _(� ■� ice/ ago co co I \ cd to 60 to 0 W'\ ' � I Lr 1 �,1 I I �1 � a 1 � I �i..-.�•'� r ct go- - \ zr ! \ \ \ \ — \ / 9�_ asp ._ �� �► �% \` 1, / i / / / / \\ ■ 41 ! Vm i■1 \ a'— \ \ \ \ 1 I �.�, "lam ; _I \!� \ fir► 00, ' �MSO � �► i s — — — :. � ;-4 �. � '� -h' i C� I / —lop 46 L _y 144 ,,, 00 all 40 / �r1l/ / _slfi� / 1 a\ \ \ \ �I �VI I\C5 \ \ \\ \ \\ \ o LD-204 Stormwater Inlet Computations Inlets on Grade Only Sag Inlets Only � ' ca Q � Q � c (D O N E > z N CL O p tl U > Q UI N �_ 6i VJ �QCA L a> Q >, Q O O .r ca N X X (� 0 ca _ E N 2 c fn � +' U L U +� H � t > � ca (tea N L Q tom- LLJ O Q �. (A z 5 0 O a� Q c) M (D co a 7 (D O Q U) cD o o a Cl O 2 i.) 2 o a � 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 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-3B 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 Y O O 9 p AM 0 0 o � 0 0 0 m d 0 0 0 o O y o o co 0 0 0 0 0 0 0 0 o O o 0 N C_ N O _ 0) L - a0 co M ao co M (fl O) 6i N O ?_ M M M d M M! O O r O) N N N > 0) � L O O d O O coM d a) CD C O Q U') LO LO LO N Ch r c d N .y d � In (l) O 1�2 ! Y U N C o G G c U o C 0 C 0 o u 0; O (D LO (D N 00 NI� r- Q1 O0N N (O N d m O O LO rN O 7 (f7 N L, M ` O O) d1 d Q N V7 (D O O M 00 M! M M N C C O N (6 00 d J d CD C:) C) C)M (0 N c, N p 0 0 N M O m r M-. (D w m m C;Lo 10 m coCO M O 00 OO 00 f- � r c t a a d d d d d E o> 0 o _o �va000amo 0 0 o c I o O (p (6 O r O M �O N 6 M c')o rnrnrn a)o�cocor�ti r - 0) s u1 _ co M � N (D (D O (V m c0 fo O 00 N N CO (f7 aD m M L N N N N d L6 (D 1� N C O U N r � O O a) r Oro co 00 ^ 00 O ` oo 0O r o0 h f� O [D (D (D O (.0(D (D (D (D W CO N O C C I- - O N O O r o r O o N m O V; n 0 p O 0 0 �1'i N c � ui vi Lo Lo LO (ci (n L6 (ri (D (n (D £ n F0- F E U 00 O O O M N W N a) M CO r-- ONO c co (4 0o D7 0) 7C. p O O O O O O O O O N N aQ w L W O 6i CO N O N r N (O O O O O 0 0 0 0 0 O O N O C Q7 O N Q O M 00 O LO 0 0 d N r r E (D O 0) iD Lq 0 � d (O co M O O O o O O O O O U C N O p O O N Q _ p (D O (CJ O 01 N p 00 N N d •- M M U m o O O O p 0 0 0 0 O i 0 U w C U Q O 0) O � U ,ndm Cl) N�XXX X X o m N to (O toQ O d T C O _7 N � C O O Q N F d Q 1n LO ((') d M M N �: X X X LO O 'p Z � a w �0 o_ n c c CL w m m 0 O 0 ow�ola > [V N t p LL C LL C w > M M ❑ Q QIL LL ❑ P O O i LL C (0 O O O w _ Y O z D- V- o O PL O JL O CO CO rl M M 70 rl J M M O O tp 00 C C� � O O .0 N � 05 U ❑ -J O �--i N to Q CL 7 — N L i iri y O O p � U lD O O Q O U U U) Q o o U c�v U � 0 m M O Q rV M O O Hillbrook LD-347 Hydraulic Grade Line n= 0.013 Junction Loss Outlet Water Inlet Surface Water Inlet Number 1 X2 X3 X4 1* :FTL_ _1.._ _ Elev. 2 461.28 472.76 475.66 476.98 Do 3 1 1.50 1.25 1.25 1.25 Qo 4 18.88 12.65 7.81 6.57 Lo 5 54.4 39.4 60.5 115.1 Sfo% 6 3.2327% 3.8332% 1.4628% 1.035% Hf 7 1.7586 1.5103 0.8850J 1.191 V° (8) 10.686 10.304 6.365 5.355 Ho (9) 0.4433 0.4122 0.1573 0.1113 Qj (10) 5.355 12.645 7.812 6.571 vj (11) 3.030 3.030 6.365 5.35 Qiv, (12) 16.2 38.3 49.7 35.2 Hi (13) 0.0499 0.0499 0.2202 0.1558 Angle (14) 79 49 89 3 HA Ht (15) (16) 0.0934 0.5866 0.0706 0.4373 T 0697 0.0178 0.3309 0.1113 1.3*Ht (17) 0.7625 0.5Ht (18) Final H 19 Surface Elev. 20 Rim. Elev 21 2.521 463.80 479.60 1.3906 2.901 475.66 479.80 0.4302 1.315 476.98 480.83 0.1447 0.0557 1.247 478.22 488.15 ne value el Irnet I vo used in this worksneet 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 OUS) 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 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 percent slopes B 2.4 63.3% 27C Elioak loam, 7 to 15 percent slopes B 1.0 27.7% 39D Hazel loam, 15 to 25 percent slopes B 0.3 8.9% Totals for Area of Interest 3.7 100.0% Rating Options —Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff., None Specified Tie -break Rule: Higher 19 yy S + s � f i Redington'Ln i � ! err h"• / ti Bpi. a i wrw . 1. ,I + JF t 3. C� ,e I , f � 3/3/2015 Precipitation Frequency Data Server NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, US* - Latitude: 38.0831*, Longitude:-78.4624* Elevation: 484 ft* "source: Google Maps •� �r111 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 Duration Jam' �5�t1in iL 10-min `El5-m7n," III60-m 72-h, '� 3-hr I I 6-hr 12-hr i s . In24-hr 4i[ 2{la y =3-d j 4-da y _ 7-day .j i [��ay [30-day8.53 45 day l 1 60iiay based ' 0.352 1 (0.317_Q390) 0.-5-62-71 a (0.0.885 0.703 (0.634-0.779) FO�96307 1A4 (1.27-1.65) 1.58 i (1 39 1 81) I 2.01 i (1.78-2.28) j 2 52 (2 23-2.89) . 3.01 (2.71 3.39) - 3.55 (3.19_3.97) 3.79 (3.44-4.20) i 8-4. (� (3.68 4.42) 4 67 (4 28 5.10) j 5,29 (4.88-5.74) t6635 6.95 E (6.50-7.45) 10.6 -0-111.3) 12.5 (11.8-13.2) point precipitation JI-_ JLe' 0.420 (0.379-0.466)j 0.671 0 4 0.844 (0.762-0.936),9�1.10) -1.29 , 1.46 (1.32-1.62) -� ;175 (1.54 1.99) 192 ^(1.68-2.20)� 2 43 (2.15 2.76) 3 05 (2.69 3 49 i ,!_1L 3 65 (3.28 4.10) 4.31 (3.87-4.82) ' 4,59 (4.16 5'08) 4 87 i (4.45 5 35) 5.62 (5 16-6.14)� (58_6.89) 8.29 (7.76-8.89) 10.1 (9,51-10.8� 12.6 (11199-13.3 14.7 (13.915.5) L6.1-17,9) frequency 0.492 (0.444-!. 45) 0.789 0.7 , 0998 IF(OL8��i 42 � . ,(1.64-2.01) j(L9-2,34) 2,19 (1.93-2.49) 2.40 (2.10-2.75) j 3.02 i (2.66-3.42) ! 3.80 3 34-4.35) ` � ,. 4.66 ( {4.17-5.23) _I,. 5.48 (4.91-6.12) ; } 5 83 (5.28-6.46) ; 6 18 (5 64 6.79) ; 7.02 (6 4-7.68) i 7,85 (7.23 8.50) 10.0 (9.36-10.7) 12.0 (11.2-12.7� (12.5-14.2)� 14.7 (13_9-15_6), (15.4 17.0 (17�6-19.7) Average 10 0.553 (0_498-0_613)� 0 L(O.780)I 1.12 (1.01-1.24) . ._1.80) . 2.58 (2.27-2.92) 2.81 (2,45-33.21) 3.56 i (3.12-4.02) 4 50 (3.94 5 13 ____ _� � 5 51 (4.92 6.17) j� 6.44 i (5.76-7.18) j 6.85 (6.18 7.57) 7 25 I (6.61 7 96) ; 8.18 (7`48-8.93) , 9.06 (8.32-9.80)' 11.4 (10.6-12.2) 134 16.3 17.2) 18.7 estimates recurrence J 25 0.624 (0.558-0.688)j .994 0.889-1.10) i 1.26 (1.13-1.39) i. (1.67206) 2 (2.22.74) 3.07 ! (2.69-3 47) 3.35 (2.91-3.83 4.28 (3.73 4.83) 5.47 { (4 76-6.22) � 6.77 (6.00-7.55) y 7.84 (6.95�8.72 _ ) I_( 8.33 (7.47 9.19) 8.8215 (8 00 9.67) 9.84 (8.94 10 7)� 10.8 I (9.85-71.6) 13.2 E (12.3-14.2) 15.2 (14_2-16.2) 18.3 (17.2-19.4) J 20.8 (19.6-22,0) with 90% Interval -i-- 50 0.678 (0.604_0_747) 108�(1 962-1.1 1.37 (1.22 1.51) 1 . (1.83-2.27)s�9 . A (2,49-3.08)] 3.48 (3 03-3.94) I 3.81 (3.29 4.34) 4.90 (4.24-5_53) J 6.34 I (5.46v7.20) , I, 7,55 (6.91 8.74) 9.01 7 93 10.0)J 9.56 (8.53-10.6) 10.1 (9.13 11.1) 11.2 (10^1 12.2) 12.2[13.6 (11.1.13.2) 14.7 (13,6-15.7) 16.6 (15.5_17.7) 19.8 (186-21.0) ` 22.4 (21.1-23.6) (22.5-25.3) confidence (years) 100 0.729 (0.646-0_804)j 32)'(6-0.744 0 1.47 (1.30-1.61) . (1.99-247 . (2.74-3.40) 3.91 (3`38-4.41) 4.28 (3.67 4.88) 5.56 (4.77 6.27) i 7.28 (6.19-8 26),1 9 04 (7 89 10.1) . -. _,_..__...._ 10.3 (8,98-11.4) ' 10.9 , (9.65 12.0) (10 3 12.7) i .3-1 )FL 12.7 (11.4-13 9) ( i (12.3-14 8)(13 16.1 (14,9-17.3) r 7.9 (16.7-19.1) 21.3 (19.9 22.6)J 23.9J intervals 1... 200 0.778 (0.684 0.858) AJ1.32 (1.507008 I 1.56 i 1.371.72 2.42 2.132.67) _j 9340 I (2.-3.75) 4.36 (3.74-4.92) l 4.78 i (4.07-5.44) 6.28 (5 33 7.08) i 8 32 _(6.98 9.43) �F(8.11-11.2) 10.4 (8.94-11.5) I 11,7 (10.1-13.0) l 12.4 (10.9-13.7) I 131 6 14 3 - )•-I 14 3 (12 7 15.6) J 15.2 11 7 16.5 17.6 ` (16.2-18.9) 19.3 (17.9-20.6) 22.7 (21.2-24.1) 1 25.4 (23`8-26.8) (in inches)1 500 .._.. 0.837 (0.728_0.925) (1.15 1 46 1.67 (1.45 1.84) 2.65 31 -293) 3.81 (3.31.4.21) i 498 (4.22-5.62) 5.46 (4.59-6.23) i 7.30 (6.10-824)J 9.86 12.3 (10 5 13.7) 13.7 (11�7-15 3 ` ) i 14.5 (12.6-16.0) .4-1 I i (13.4-16 8) , 16.6 (14 6 18 1) 17410dy (15.5 18.9) 19.7 (17,9-21.2) 21.0 (19.4-22.5) (22.7426.1) J 27.2 (25.4-28�8) I 1000 0.885 (0.763.0.982)I 1.39 �F �f J (1.20-1.55) 1.75 (151_1.94) 2.8330mm,1 2.44-3.14L 4.14In(1.08�13 (3.57_4.59) j 5.51 ! (4.62-6.24) ' 6.05 + (5.03-6.91) 8.20 j (6.76-9_27) i 11.2 (9.09-12.8) j 14.0 (11 7 15.5) 15.4 (13.0-17.2) 16.3 (14.0 18.0) 1 _1 I (14 9-18.9) i 18.5 (16 1-20.3) 19.2 16 9-21.0) 21.3 (19.3-23.0) 22.4(8,02-9,09) (20.5-24.0) 25.8 (23.9 27.6) j 28.5 (26.5-30.3) 11 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Backto Too PF graphical http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?fat=38.0831&lon=-78.4624&data=depth&units=english&series=pds 114