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WPO201600041 Plan - VSMP Minor Amendment 2016-06-29 (3)
1 PROJECT MANAGEMT SHIMP ' CIVIL ENGINEERINENG LAND PLANNING ENGINEERING v May 17, 2016 VSMP Reviewer Albemarle County APPROVED by the Albemarle County Regarding: Hillbrook Community Developmen Department Stormwater Management Date e, VSMP Amendment File N'10 r ,BO To Whom It May Concern, -k "I - 1— I"' U1h°v?-01 cO003? 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. 1.F.* (Qpre * Rhpre) Qdev — RUdev 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. Qi, the design flow, is computed in the post-development HydroCAD report. A 48"detention structure limits the 1-year peak discharge to the northwest. The site discharges through existing storm sewer that is adequate to convey the 10-yr storm before reaching the natural channel, which fully contains the 10-yr flow without flooding. Flow Summary: Northwest(X4) Qmax 1.47 cfs Qi 1.47 cfs East(Raintree) Q1(pre) 0.32 cfs Q1(post) 0.13 cfs RV1(pre) 0.042 a.f. RV1(post) 0.016 a.f. Q1o(pre) 3.29 cfs Q1o(post) 3.10 cfs If you have any questions please do not hesitate to contact me at your earliest opportunity. I may be reached at: Justinshimp-enqineerinq.com or by phone at 434-953-6116. Yours Truly, Justin Shimp, P.E. Tg 0 Q U JU M. --I P Y Lic,�do_��83 SSIONAL (5 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 / / / / / / '/l// u �� I I I PRE—DEVELOPMENT SWM MAP / / // // // // / a;' // // ///�/, , --0,/ L \ \ 1 I DINELOPM NT ARE \ / �I 1 i 1 i / / .is. --17 1 I/I I I I/I I A _ - -- - _ ___ \ �2 �� // / i /l 111/l�/ J \ \ II I I I 1 1 I 1 I � / /// / //�/,/// / // \\ \ i I I \ \ \ \ i , � I lll, l ; , \ I 1 I \ 1 I I / / 1iI /// / \ \ I \ \ \ \ \ 1 ///I /i;it;/ ��� CF,� `\ \- \ I I\ \ 1 \ 1 -1- I I ,�,0 �, � / 1 _7 / //// // / 1 \ \ \ \ I \ \ \ I I , /� 1 1< `T i //// /,//// // ' \ \ \\ \\ I \ -roc Towpath�\ )i \ I I / I I .K. m I 1 //// // ///r , \ , --4} ----1— 1 \ I I I 1 - , I /, // I/// , \ \ \ 1 / r 1 \ \ \ \ I I I I // // //,/,7 I 1 K , "\ \ \ I iiiiii. L 1 , \ \ I i,/ i i i I I ' �II _} 4/ 1\ \ \\ \ \ \ 1 I 1 1 I1 11111111 I (/ 11 I ` \ \ \ \ \ I I I ` II ' � I I I 1 \ \ \ \\ \ \ \ \ \ \ I I \ I " I \�/ I/ ' ii II , 1 \ \ \ \ \ \ 1 I ID.A. 2 ; FSITE 1 _Li I I \ \ \ \ \ \ \ \ \ \ \ I \ 0.510 ' I i � . : AO:SITE% i (D.A. 1 1 \ 1 \\ \ \\ \ \ I \ I I \ _I. ' ,► I�� I h .856 A�. 1 \ \ \ \ \\ \ \1 I \ I h I ' C1418 MN. \ \ \ \ ► \'� 94MIN \ I1 / \ ToC 5.0 1 . I _ \ \ \ 1 I 1 % ---� .-.. ' ,� I 1 �0.23 CFS , `\ , -0.321 IFS I 1 \ 1 I I , // / 1 l -0.0� AFI • I / ./ / / / / ® R;''t\_ _ ( 1 I-0. 17 AF / I Rt\ / AREA / 1 /1 I \ I , j)EVELOPMEMT 1 / l / / i , 1 \ � I\I \ � , / , i 1 / , I , / , i / f.-i \ \• \\ \ 1 / \ \'I; \ \ / / / / IMPERVIOUS =1i, I \ \ /\ ( I :.\ `: \ \ _ \ w^� ` 1\ j \ I \ \ Area 1 Time of Concentration I \( slope Seelye Chart 1 7 , I I \ \\ 200 ft overland flow 7 7% P 0.35 C—value 13 2 min Y 1 ` 7� 1 \ \ I 128 ft s c flow—woods 8 2% slope 1 4 fps velocity 1 4 min. NEH Figure 15-4 _ \ \ � 1\ \ I \ 1 \ \ \ 1 14 6 min � ` \ k. `_` \� \ _t ` \ 1 Area 2 Time of Concentration \\ \ \\ .' ` ) \ — — \--- — ---- --- — —� —� _ _ 1 ` \ I I 88 ft overland flow 10 3% slope 0 35 C—value 9.1 min Seelye Chart \ \\ \ •: \\ \\ r--- -- _ \\ ` \ I I / 223 ft swale 12 ft height 0 3 mm Kirpich Chart \ \ ;\ \ I I / / 9 4 min \ \ \ \ \ \ \ \ 1 I \ \ \ \\ \\ \ \ , \ 1 II I / / 40 - - - 0 40 80 120 \ \ `; % \ I I \ I i L - - - - \ \ \ \ t 1 \ Scale: 1"=40' \ `, \\ \ , 1 1 I / /1' I ...-----\,____ D/\2 _ _,. 111 1 D.A.2 Offsite D.A. 1 D.A.2 Onsite (Subca) Reach 'on. It Drainage Diagram for Hilibrook Pre-Development Prepared by Shimp Engineering, P.C., Printed 7/1/2015 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Hil!brook 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 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 lyr 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, Hil!brook 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 af 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 Hil!brook 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, Hil!brook Pre-Development Type II 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 l0yr event Inflow = 4.67 cfs @ 11.97 hrs, Volume= 0.243 af 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 . , - _ _____ • �,� / / / /� / %/ .. / ,PEAK-BIS- - GE'- - = - - - - - - - I I U 6E I.N / / / :c 1 ./ '/ , -1'. c - - E!DEVELOPMENT ; - - - - I I H L L 3 0 0 K i/O11� SITE / // - EQUIRED REDUCTION S LOW POST—DEVELOPMENT SWM MAP i/ • � 0 f S Cl ' , ! �/1L' Wl��ill��� 1.4 C ALLOWABLE I D�VELOPM T AREA I0 ` \ I // � ,/ 1 w' ```777 1 I � .J .7y .Y /.Y_� W W .Y W W y I I I I , ■0� A ■ ��■/ �•* // / : , W �/J/ /y J• W •L •Y �Y \ �L W I, W W W W * * 0 zox 0 * I / � i W W Nk W� W Y // jit • ® \W W \WY WL0-; /w / 4/it' W N - h //Li /1, , - _1 WW \ *\WD.A'` \ . W W ° ° #to!S - V I I /I 11 4//it/ WW \ * ■W , � , - t \ . , I/ / I WW � W .yW . 0-.328 4C. ,i -- /i tihriiii,//* z ' , rl I l4/Tr \ \\ . �1 0 I� ��► a W . ' Agi'mD:2r08,Ad■ I P. ( �/ 11 / /W _ 4.I 4, 4, 1 '\ — -alk \ ** \ 7zAvx * * 0 0 1 1 , __ ) -t' s"" lliiii* i . IW W. . . , 1r * W W W W Iii *\ A \\ZeX 0 0 * I 1 0100-17--_ , ' tau I \\,I ``� �-- .y 16 WI' - W:',./.4 4/% W W W%it - I W '\W W W\W W\ I 7At I I 1 W W / '" Z ice _ : 1 N. W W .y .y W .L \ 1 1 fi I W \t I' I ,�I J� .YI W Y W W I \ W\ `. 01-v- I I \ W W IW W .__ 1" " ' ll \� \W W0 ll I 1 W WI W 1 W W I I _ /'- �-- W .r W W. W ��- W `\ \ \ \ I i I \ \ _WWWW4. 1 ~• � • YWWWWW I - JW W W W Aid I 11 I . 1 I I I ••, N y WW .y W II W �� W * I I I \` / I II ' /:4 - • - 1 / I .Y W I W W \ ' ij -0. j: ii: : 3\ \ IJ��,,��A� ��i / I// .Y W W I I .Vy0 II 1I l� i Wt PRESERVED t \ + JeX 0 0 01 0 / WOODS YeX ',i'‘V \_,j(i\, W ' ' W /� W W W II W �� • I �, i ! : * W 1EVELOPMEMT AREA / /1 __1‘ if / W W {I / / \ \ / W J1 •Y W _ W 1 / W W I I r '7 \ \ .. W • I W W W I I,� / - MANAGED * W W W W W W W • W W 1� WY .y)frW .YY �Y W W * •h`\ \ \ T W / I� W W W I W r W I / Energy Balance LAWN W W W W W W \4J �C .Y J W .. .Y W .L W W W ' .Y I I.F. 0.8 i v :-:,/ \ I. \\ W W W .Y W IL .Y W W W , W 4 I W � W -_- � WyW � WWWW xWi � W IW � Wx*, W/ ' Qpre 0.23 cfs IMPERVIOUS 1 `��71- \\___, _ - \ \ 4 - W W W W W I W I W W I I / _ ( RVpre0.017ac-ft- \ WWWW W WWWIW\JWWW W •' W W W I \ I I RVdev 0.037 ac-ft SIMPLE _ / // 7` -� W W ,, W W4 W W W W W .\ y W W W I I I DISCONNECTION __ W/S y W W .1' ,1 W - .L .Y W W .Y W Qdev 0.08 cfs — — /i - OFFS IT \ \ \ \W � �© W W W _ I W W W\ W W \W W W W I I REQUIRED REDUCTION: SWM DIVIDE I= M NM \ 1 \ W\ W .y WY W W W W W W .Y W\ I 0.23 CFS Qpre — — ' DETAIIED\ \ \ . IW) W W , - - _ _ _ _ -� - \ $ ET F�OW/ / -0.08 CFS Qdev STORM DIVIDE \ � 182 AC.\ \ 1 \1 \ W _ — J \ 0.15 CFS reduction SIMPLE ■ \ \ \ W W O \ \\ 0.246 AC. T TA, / DISCONNECTION - -0.1 0 AC. IM I. \ \ I To =1116 NI, -j DIVIDE W \ / \ \\ \ \ - \ I I Q�=0.1 CFS I/ 40 _ 0 40 80 120 \ \ \ \ \ \ _- \ \ I I RV 0.0164F � \ 1 \\ \ \ ` ‘ � \ \ DIME OF�L`�NCENTRA ION=5.0 MIN ES Scale: 1"-40' \ I \ \ \ \ 4. \ UNLESS OTHEFRISE NOTED t I I /1' I \ I Virginia Runoff Reduction Method Worksheet Virginia Runoff Reduction Method New Development Worksheet-v2.8-June 2014 Site Data Summary Total Rainfall= 43 inches Site Land Cover Summary A Soils B Soils C Soils D Soils Total %of Total Forest(acres) 0.00 0.54 0.00 0.00 0.54 21 52 Turf(acres) 0 00 1.26 0.00 0.00 1.26 49.74 • Impervious(acres) 0.00 0.73 0.00 0.00 0.73 28 73 2 53 100.00 Site Rv 0 38 Post Development Treatment Volume(ft3) 3476 Post Development TP Load(Ib/yr) 2 18 Post Development TN Load(lb/yr) 15.62 Total TP Load Reduction Required(Ib/yr) 1 15 Total Runoff Volume Reduction(ft3) 1962 Total TP Load Reduction Achieved(Ib/yr) 1 Total TN Load Reduction Achieved(Ib/yr) 10.77 Adjusted Post Development TP Load(Ib/yr) 0 82 Remaining Phosphorous Load Reduction(Lb/yr)Required 0 Drainage Area Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total Forest(acres) 0 00 0.00 0 00 0 00 0 00 0.00 Turf(acres) 0.67 0.00 0.00 0.00 0.00 0.67 Impervious(acres) 0 55 0 00 0 00 0 00 0 00 0.55 1 23 Drainage Area Compliance Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total TP Load Red.(Ib/yr) 1.37 0.00 0.00 0.00 0.00 1.37 TN Load Red.(Ib/yr) 10 77 0.00 0.00 0 00 0 00 10 77 Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary A Soils B Soils C Soils D Soils Total %of Total Forest(acres) 0.00 0.00 0 00 0 00 0.00 0.00 Turf(acres) 0.00 0 67 0.00 0.00 0.67 54.92 Impervious(acres) 0.00 0.55 0.00 0.00 0.55 45.08 1.23 BMP Selections 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 2-year storm 10-year storm Adjusted CN storm Adjusted Adjusted CN CN Target Rainfall Event(in) 3 01 3.65 5 51 D.A.A CN 78 69 71 73 D A.B CN 0 UN/A UN/A UN/A D.A.C CN 0 #N/A #N/A UN/A D.A.D CN 0 UN/A UN/A UN/A D.A.E CN 0 UN/A UN/A UN/A Summary Print Drainage Area A Drainage Area A Land Cover (acres) A soils B Soils C Soils D Soils Totals Land Cover Rv Forest/Open Space(acres) 0.00 0 00 0.00 0.00 0.00 0.00 Managed Turf(acres) 0 00 0.67 0.00 0.00 0.67 0.20 _Impervious Cover(acres) 0.00 0.55 0.00 0.00 0.55 0.95 Post Development Treatment Volume(cf) 2400 Total 1.23 Apply Runoff Reduction Practices to Reduce Treatment Volume & Post-Development 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 Unit Descri.tion of Credit Credit acres Practice cf Reduction cf Volume cf Efficienc % Practices lbs lbs. Practice lbs. Load lbs. Downstream Treatment to be Em.lo ed i 2. Rooftop Disconnection 2.a.Simple Disconnection to A/B Soils(Spec 50%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 Er 13ort.non 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 MO 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 0.43 211 340 50 0.13 0.93 0.96 0.11 turf acres draining to bioretention 80%runoff volume reduction 0.80 0.67 0 392 98 50 0.00 0.31 0.28 0.03 TOTAL IMPERVIOUS COVER TREATED(ac) 0.55 TOTAL TURF AREA TREATED(ac) 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(Ib/yr) 1.37 , 9 --E> 10 4 8 1 Offsite Undetained Inle 4 Onsite Undetained Sheet Flow 6 D 4 Raintree Offsite Detained Dettion Vault Bioretention 5 2 Onsite Detained D.A. A (Subca Reach 'on. Drainage Diagram for Hillbrook Post-Development lyr I Iti Prepared by Shimp Engineering, P.C., Printed 5/17/2016 HydroCAD®9 10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Hillbrook Post-Development lyr Type 1124-hr lyr 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 lyr 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 lyr event Inflow = 1.46 cfs @ 11.97 hrs, Volume= 0.069 af 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 af Secondary= 0.00 cfs @ 0.00 hrs, Volume= 0.000 af 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 af(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'L x 6.74'H 4'x4'Vault Storage Hillbrook Post-Development lyr 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 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) t2=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) t4=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 af 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 af 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 lyr Type 1124-hr lyr Rainfall=3.01" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD®9.10 sin 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: Offsite Detained Runoff = 0.63 cfs @ 11.96 hrs, Volume= 0.029 af, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS,Time Span=0.00-24.00 hrs,dt=0.01 hrs Type II 24-hr lyr 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, Hil!brook Post-Development lyr Type 1124-hr lyr 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 lyr event Inflow = 1.17 cfs @ 11.96 hrs, Volume= 0.054 af 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 af 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 af(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'L 15"Storage S=0.0025'I' #2 490.41' 1,470 cf 48.0" D x 39.0'L 48"Storage S=0.0025'I' 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) t2=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, Hil!brook Post-Development 1yr Type 1124-hr lyr 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: Offsite Undetained Runoff = 0.93 cfs @ 11.96 hrs, Volume= 0.042 af, Depth> 1.52" Runoff by SCS TR-20 method, UH=SCS,Time Span=0.00-24.00 hrs,dt=0.01 hrs Type II 24-hr 1yr Rainfall=3.01" Area(ac) CN Description 0.120 61 >75%Grass cover,Good, HSG B * 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59%Pervious Area 0.208 63.41%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area= 1.004 ac, 51.59%Impervious, Inflow Depth> 1.28" for 1yr event Inflow = 1.47 cfs @ 11.97 hrs, Volume= 0.107 af 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 af 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 sin 07054 ©2011 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 1: Sheet Flow Runoff = 1.49 cfs @ 12.05 hrs, Volume= 0.092 af, Depth> 1.38" Runoff by SCS TR-20 method, UH=SCS,Time Span=0.00-24.00 hrs,dt=0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area(ac) CN Description * 0.550 55 Conservation Area * 0.246 61 Sheet Flow 0.796 57 Weighted Average 0.796 100.00%Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 Direct Entry, Summary for Subcatchment 2: D.A. A Runoff = 6.13 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 af 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 af Secondary= 4.18 cfs @ 11.96 hrs, Volume= 0.054 af 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 af(100%of inflow) Center-of-Mass det.time=0.1 min(830.4-830.3) 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 10yr Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD®9.10 sin 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' 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=1.95 cfs @ 11.96 hrs HW=498.35' (Free Discharge) t1=STM 5-6 (Passes 1.95 cfs of 6.87 cfs potential flow) t2=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) L4=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 af 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 af 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 af(68%of inflow) Center-of-Mass det.time=73.7 min(931.6-857.9 ) 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 10yr Type 1124-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD®9.10 sin 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 Primary OutFlow Max=1.56 cfs @ 12.07 hrs HW=495.04' (Free Discharge) t1=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) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Hillbrook Post-Development l0yr 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 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 l0yr event Inflow = 7.19 cfs @ 11.96 hrs, Volume= 0.193 af 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 af(100%of inflow) Center-of-Mass det.time=7.0 min(790.2-783.2) 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'I' 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 Veil. 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) E2=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 l0yr 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 ll 24-hr 10yr Rainfall=5.51" Prepared by Shimp Engineering, P.C. Printed 5/17/2016 HydroCAD*9.10 sin 07054 ©2011 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 9: Offsite Undetained Runoff = 2.19 cfs @ 11.96 hrs, Volume= 0.102 af, Depth> 3.74" Runoff by SCS TR-20 method, UH=SCS,Time Span=0.00-24.00 hrs,dt=0.01 hrs Type II 24-hr 10yr Rainfall=5.51" Area(ac) CN Description 0.120 61 >75%Grass cover,Good, HSG B * 0.208 98 Impervious 0.328 84 Weighted Average 0.120 36.59%Pervious Area 0.208 63.41% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 10: Inlet X4 Inflow Area= 1.004 ac, 51.59%Impervious, Inflow Depth> 3.98" for 10yr event Inflow = 9.26 cfs @ 11.98 hrs, Volume= 0.333 af 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 l0yr event Inflow = 3.10 cfs @ 12.07 hrs, Volume= 0.243 af 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 Hil!brook Post-Development 10yr Type 1124-hr IOOyr 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 af 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 af 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 af(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 I / // /I I / \ /) ( 1 \II--\-? \. H LL3 � 00 < /' /'//// , \ // ri; `\ STORM SEWER MAP /' (' j / 1 / 1 1 I ter' t I I \ \ \ 1 / I 1 \ IMPERVIOUS / #111:111 / ,._ _Z '><.___., \ l ila \ \ / \ Vitilt: 1011� I / / / / ( / (___ ___ _.-- -\ -.. . _/ \ 1 \ 1 1 I I1 I l \ , ,/ N\ \ 1 \ \\ 1 / / \ 1 \ / I I I `I \ \ \\ 1 ISli M X2A ,LEA; 1� r 1 , ` \ \\ _ ► \ \\ ' 1 .55)11 «J��i'�i_ `� _� I / \, ` -> A-- \\ ` 1 / r�. 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' ---` -\ 1 / - 1 ..-- Ape , 10.10 1 /16. \ tat 1 I I t c 4 \ / 0.196�c..1 _I _ . - N \\\ `1 �\..4\\�\ • D`a I I / 2 \ 1 /- -9.59c\\ \ \\\ �\ \ O. t8'1\ A C.•\ 1\ III ( / / / - / - - \\ \ \ \\ \AC1 1 \ \ I 1 / 7 _ _ \ \ \ \ 0.6 \ \ I 1 1 , / i / ,' �/ \ \ \ \ \\ \\\ \ \ I I \ \\ \ / I I \\ \ / \ \ \ \ \ \ \ / /..\N ",.. _Ili I \ \ / 80 0 80 160 240/ �� 11 \ \ \ / / \ j�j7 \ \ \ ) / - - - - i i 1 \ \ \ // / // / \ ---( cale 1 '=80' 7 ; -1cn -1 � � � Structure 73 (!,, — Number Dywiv D o 0 CJ o GI (1,., 6.) � w Ni Inlet Type OD W CO CO W Co °0000) o- w Curb Opening OO0000 -- O iv iv . ; ; - Catchment Area ci CO J O O 000000 cn a, o, cn o, �0 cn Runoff Coef - rnCOCOcno 000000 N o _, rnCA co cc) co A J 01 NC 000000 acoIntensity cn 3 0 0 0 0 0 0 Ni in 2^ c0 Q Catchment Er.cn � CoCTJCO Cl) CO 0.) N A J J <D n Q carryover -a ET A) 0 0 0 0 0 0 . 0 cn -▪ w cn J co (4 , Q Total C0 CON 000000 O 0 0 0 0 0 ,�, Mannings N 0) rn rn 0) rn CD O O O o 0 0 o o 0) 0) Gutter Slope 01 (0 Ni .A 0 o 0 o 0 0 io 0 0 0 o O v Pave X-slope 0 0 0 0 0 0 000000 O 0 0 06 0 Gutter X-slope co co co co co co — cn P w CO w CO w CO Total Gutter Cy) Cy) Cy) iv rn Spread cOJJ � O 0 0 0 0 , Depth at Curb rncorn cn0) 5 in 0 0- 0 0 0 0 0 0 0 •• 0 % Efficency 0 0 0 0 0 O 00 0 � cn O O 00 00 al 4, w J co W Q intercepted (0 0) N J J C O O CC -.0 0 0 0 o N o Q Bypassed 0 0 0 0 0 " Midpoint Depth N Curb Height ncni Ca 0 0 0," D/H -'0 V, Midpoint Spread LD-229 Storm Drain Design Computations Hillbrook From To Point Catch Runoff Inc Accum Tot Tot Tot Up Dn Pipe Inv Pipe Pipe Velocity Flow time Point A Coef AC AC Tc Int Flow Inv Inv Len S Dim Cap Inc (ac) (min) (in/hr) (cfs) El El (ft) % (in) (cfs) (ft/s) (min) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 4 5 0.27 0.68 0.18 0.18 5.00 6.81 1.25 496.10 496.00 16.1 0.6% 15 5.9 3.8 0.07 5A 5 0.28 0.66 0.19 0.19 5 00 6.81 1.26 496.10 496.00 16.4 0.6% 15 5.9 3.8 0.07 5 6 0.37 5.07 6.79 2.50 495.10 496.00 180.6 0.5% 15 5.4 4.3 0.70 5A 5 0.28 0.66 0.19 0.19 5.00 6.81 1.26 496.10 496.00 16.4 0.6% 15 5.9 3.8 0 07 5 4 0.19 5.07 6.79 1.26 496.10 496.00 16.1 0.6% 15 5.9 3.8 0.07 4 3 0.27 0.68 0.18 0.37 5.14 6.77 2.50 497.40 489.20 71.5 11.5% 15 26 13 0.09 3A 3 0.40 0.59 0.24 0.24 5.00 6.81 1.62 490.60 489.80 36.2 2.2% 15 11 6.5 0.09 3 2 0.11 0.65 0.07 0.68 5.09 6 78 4.59 483 10 483.00 8.54 2.8% 15 13 9.6 0.01 2 1 0.16 0.90 0.15 0.82 5.11 6.78 5.58 485.40 485.30 6.8 1.5% 15 9.4 7.9 0.01 1 X4 0.16 0.90 0.15 0.97 5.12 6.78 6.57 482.80 475.70 115.1 6.2% 15 19 14 0.14 X4 X3 0.35 0.54 0.19 1.16 5.26 6.74 7.81 475.50 473.89 60.5 2.7% 15 11 9.5 0.11 X3 X2 1.39 0.52 0 73 1.89 5.37 6.71 12.65 473.89 471.76 39.4 4.7% 15 11 13 0.05 X2A X2 1.55 0.51 0.79 0.79 5.00 6.81 5.35 473.89 471.12 89.2 3.1% 18 19 9.1 0.16 X2 X1 0.19 0.79 0.15 2.82 5.42 6.69 18.88 470.56 460.08 54.4 19.3% 18 46 25 0.04 Note:To fully provide for the split flow,this worksheet has been completed for two scenarios in the first, all flow from inlets 4 and 5A goes to the back of the site,and in the second,it goes to the front. Detention is not accounted for in this computation. Hil!brook Modified LD-268 Roadside and Median Ditch Design Form MIN MAX Earth Protective Lining DITCH C A Tc 110 Q1 p — CA :1 _:1 SLOPE SLOPE ALLOW. n=.03 n=.05 n=.015 INCR ACC L R Ft/Ft Ft/Ft VEL. VEL.* Qn VEL* DEP Qn DEP 1 0.5 0.23 0.12 0.12 10.6 5.51 0.64 3 3 0.06 0.06 3 0.03 2.06 0.32 2 0.5 0.30 0.15 0.15 10.0 5.62 0.86 3 3 0.02 0.10 3 0.04 2.10 0.33 *Velocity calculations performed using average slope for this application Hillbrook LD-347 Hydraulic Grade Line n= 0.013 Junction Loss Outlet Inlet Water Water Surface ° VoH Q V Q V H Angle Ho Ht 1.3*Ht 0.5Ht Surface Inlet Number Elev. Do Qo Lo St°/° Hf 9 Final H Elev. Rim. Elev (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (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 0.3309 0.4302 1 315 476.98 480.83 1* 476.98 1.25 6.57 115.1 1.035% 1.191 5.355 0.1113 0.1113 0.1447 0.0557 1.247 478.22 488.15 *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 Slope AC* Int Flow Velocity (in) % (in/hr) (cfs) (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 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 3.7 100.0% Rating Options—Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff. None Specified Tie-break Rule: Higher 19 Custom Soil Resource Report Map-Hydrologic Soil Group N N -223."4" 722630 722660 722690 722720 722750 722780 722810 722840 722870 722900 ilk.I. '5 " 1 •• •* • - - , ' . . * 38 0 N• • ' - - l ‘ t r , pifr.V "64. , % •. . .. . . . . 4 .. . . . 3,, i• .. 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Meters fe, N 0 10 20 40 60 Feet A °Map ornyaction4:5Web Meroator9°Corner coordnabas.WGS8418°FrIge lxs:LJIM Zone 17N WGS8427° 3/3/2015 Precipitation Frequency Data Server ,,,go, NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, US* r nUHA • Latitude: 38.0831°, Longitude: -78.4624° Wrol Elevation:484 ft* d, *source Google Maps •` POINT PRECIPITATION FREQUENCY ESTIMATES G M Bonnie,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 Duration Average recurrence interval (years) 1 2 5 10 25 50 100 200 500 1000 5-min 0.352 0A20 0A92 0.553 0.624 0.678 0.729 0.778 0.837 0.885 (0.317-0.390) (0 379-0 466) (0.444-0.545) (0.498-0.613) (0.558-0 688) (0.604-0.747) (0.646-0.804) (0.684-0.858) (0.728-0.925) (0.763-0.982) 10-min 0.562 0.671 l 0.789 0.885 0.994 1.08 1.16 1.23 1.32 1.39 (0.507-0.623) (0.606-0 744) (0.710-0.873) (0.796-0.980) (0 889-1 10) (0.962-1.19) (1.03-1.28) (1.08-1.36) (1.15-1.46) (1.20-1.55) 15-min0.703 0.844 0.998 1.12 1.26 1.37 1A7 1.56 1.67 1.75 (0.634-0.779) (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) 30{nin 0.963 1.17 1.42 1.62 1.87 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) 60-min 1.20 1A6 1.82 2.11 2A8 I 2.79 3.09 3A0 3.81 4.14 (1 08-1.33) (1.32-1.62) (1.64-2.01) (1.90-2.34) (2.22-2.74)j (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 2.58 3.07 3.48 3.91 4.36 4.98 5.51 (1 27-1.65) (1.54-1.99) (1 93-2 49) (2.27-2.92) (2.69-3.47) (3.03-3.94) (3.38-4.41) (3.74-4.92) (4.22-5.62) (4.62-6.24) 3-hr 1.58 1.92 2A0 2.81 3.35 3.81 4.28 4.78 5A6 6.05 (1.39-1.81) (1.68-2.20) (2 10-2.75) (2.45-3.21) (2.91-3.83) I (3.29-4 34)... (3 67-4.88) (4.07-5.44) (4.59-6.23) (5.03-6.91) 6-hr 2.01 2A3 3.02 3.56 4.28 4.90 5.56 628 7.30 820 (1.78-2.28) (2 15-2 76) (2.66-3.42) (3.12-4.02) (3 73-4.83) (4.24-5.53) (4.77-6.27) (5.33-7.08) (6.10-8 24) (6.76-9.27) 12-hr 2.52 3.05 3.80 4.50 5A7 6.34 728 8.32 9.86 112 (2.23-2.89) (2 69-3.49) (3.34-4.35) (3.94-5 13) (4.76-6.22) (5.46-7.20) (6.19-8 26)) (6 98-9.43) (8.11-11.2) (9.09-12.8) 24-hr 3.01 3.65 4.66 5.51 8.77 I 7.85 9.04 10.4 12.3 14.0 (2.71.3.39) (3.28-4.10) (4.17-5.23) (4.92-6.17) (6.00-7.55) (6.91-8.74)J (7.89-10.1) (8.94-11.5) (10.5-13.7) (11.7-15.5) 2-day3.55 4.31 5A8 6A4 7.84 9.01 10.3 11.7 13.7 15.4 (3.19-3.97) (3.87-4.82) (4.91-6.12) (5.76-7.18) (6.95-8 72) I (7.93-10.0) (8.98-11.4) (10 1-13.0) _(11.7-15.3) [(13.0-17.2) 3-day 3.79 4.59 5.83 6.85 8.33 9.56 10.9 12A 14.5 16.3 (3.44-4 20) (4.16-5.08) (5.28-6.46) (6.18-7.57) I (7.47-9.19) I (8.53-10.6) (9.65-12.0) (10 9-13.7) (12.6-16.0) (14.0-18.0) 4.02 4.87 6.18 725 8.82 10.1 11.5 13.1 15.3 172 4-day (3.68-4.42) (4.45-5.35) (5.64-6.79) (6.61-7.96) (8.00-9.67) (9.13-11.1) (10.3-12.7) (11.6-14.3) (13.4-16.8) (14.9-18.9) 4.67 5.62 7.02 8.18 9.84 112 12.7 14.3 16.6 18.5 7-day (4.28-5.10) (5 16-6.14) (6.44-7 68) (7.48-8.93) (8.94-10.7) (10 1-12.2) (11 4-13.9) (12.7-15.6) (14.6-18.1) (16.1-20.3) 10-day 6.35 7.85 9.06 10.8 122 13.6 152 17A 19.2 (4.88-5.74) (5.86-6 89) (7 23-8.50) (8.32-9.80) (9.85-11 6) (11 1-13 2) (12.3-14.8) (13 7-16 5) (15.5-18.9) (16.9-21.0) "-day 6.95 829 10.0 11 A 132 14.7 16.1 17.6 19.7 21.3 (6.50-7.45) (7.76-8.89) (9.36-10.7) (10.6-12.2) (12.3-14 2) (13.6-15.7) (14.9-17.3) (16.2-18.9) (17.9-21.2) (19.3-23.0) 30�ay 8.53 10.1 12.0 , 13A 152 16.6 17.9 19.3 21.0 22A (8.02-9.09) (9.51-10.8) (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 12.6 14.7 16.3 18.3 19.8 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) 12.5 14.7 17.0 18.7 20.8 22A 23.9 25A 272 28.5 60-day (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) (25.4-28 8) (26.5-30.3) 1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS) Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Too PF graphical http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_pr i ntpage.htm I?I at=38.0831&I on=-78.4624&data=depth&uni is=engl i s h&series=pits 1/4 RECEIVED 1O3 - 2016 CU1vIMUNITY DEVELOPMENT