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HomeMy WebLinkAboutWPO201900010 Calculations 2019-11-07 Property of Bella Signature Homes, LLC ALBEMARLE COUNTY, VIRGINIA SITE DEVELOPMENT PLAN DESIGN CALCULATIONS & NARRATIVE AUGUST 15, 2019 e site TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Clint Shifflett, PE Timmons Group 608 Preston Ave Suite 200 Charlottesville,VA 22903 434.962.4337 ,`�1 ALT H�p pot '16'*- CLINT W. :Cid SfLETT • y� • 4 Liic.N 571 APPROVED by the Albemarlee�Department Community ev lop Date I File � ��� Table of Contents Section Title 1 Project Narrative 2 LD 229—Storm Sewer Design Computations 3 LD 204—Storm Inlet Design Computations 4 Virginia Runoff Reduction Method Worksheet Summary 5 Pre-Developed HydroCAD Calculations 6 Post-Developed HydroCAD Calculations Project Narrative: This project consists of the construction of approximately 1,000 LF of road, along with drain fields, driveways and homes over 5 subdivided residential lots. The total limits of disturbance consist of 6.36 acres including clearing and grading for individual lots. The site consists of 0.99 acres of proposed impervious area. Water Quality: The entire parcel area of 18.28 acres was analyzed. In the pre-development condition, there is 0.02 acre of impervious cover within the limits of disturbance, and the remaining 18.24 acres of woods. In the proposed condition there will be 10.54 acres of grass cover, 0.99 acres of impervious cover and 6.75 acres of preserved woods within a proposed conservation easement. Utilizing the preserved woods on site satisfies the required phosphorous removal Per the Virginia Runoff Reduction Spreadsheet. Water Quantity: The site generally drains towards the southeast corner of the property. A dry pond facility, SWM-1, is proposed to detain and release runoff such that the resulting runoff from the site meets the 1 year 24-hour storm requirements of the energy balance equation. Additionally, the 10 year 24-hour storm is being detained to reduce the pre- developed 10 year 24-hour storm to meet flood protection requirements. See Sheet C7.1 for Water Quantity Summary. LD-229 PROJECT: Earlysville Road Subdivision Designed by: CG STORM SEWER DESIGN COMPUTATIONS LOCATION: Earlysville Road COUNTY: Charlottesville Checked by: STORM FREQUENCY 10 NOAA STATION: UNITS ENGLISH DRAIN. RUNOFF CA TOTAL RAIN RUNOFF INVERT ELEVATIONS LENGTH SLOPE SIZE SHAPE Number Capacity Friction NORMAL FLOW FLOW PIPE FROM POINT TO POINT AREA COEFF. INCRE- ACCUM- INLET FALL Lateral Total Q UPPER LOWER of Pipe (Dia.Or of Pipes Slope Depth of Area of Hm Vn En TIME NO. REFERENCE STA. REFERENCE STA. "A" "C" MENT ULATED TIME END END Span/Rise) Flow,do Flow,An REMARKS Acre Minutes In/Hr CFS CFS Ft. Ft./Ft. In. CFS Ft./Ft. Ft. SqFt Ft. Ft/Sec Ft. Sec. (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) 201 202 200 0.18 0.64 0.12 0.12 5.00 6.54 0.00 0.75 534.73 528.70 105.70 0.05705 18 Circular 1 25.09 0.00010 0.18 0.12 0.11 6.35 0.81 16.64 401 402 400 0.00 0.00 0.00 5.00 0.00 0.00 28.69 550.89 544.66 138.50 0.04498 18 Circular 1 24.14 0.06630 1.50 1.77 0.38 16.24 5.59 8.53 Pressure Flow N � N NUMBER 0 m m O TYPE r m N 0 I o LENGTH(FT;M) N IA o ? o m o Z 0 STATION 1l G� m H 0 P DRAINAGE AREA o (AC;HA) 0 C 0 CA 0 o £CA N cn cn I(IN/HR;mm/HR) o '0 o Q INCR.(CFS;CMS) Oco c m c) Qc CARRYOVER 0 0 (CFS:CMS) 0 QT GUTTER FLOW in 00 (CFS;CMS) S GUTTER SLOPE o (FT/FT;M/M) 0 Sx CROSS SLOPE (FT/FT:M/M) fn cr n N T(SPREAD)(FT;M) <. —i c o W(GUTTER WIDTH) 0 (FT;M) W/T Sw(GUTTER SLOPE) (FT/FT:M/M) -I n 0 Sw/Sx Eo(App.9C-8) C a S'w 0 Z Sc Cl) COMPUTED LENGTH Lr(FT;M) L,SPECIFIED N LENGTH(FT;M) 0) v L/LT m N 0 mZ om E(App.9C-18) C� o Q INTERCEPTED 0 oo (CFS;CMS)or d/h QbCARRYOVER (CFS;CMS) Depth at Curb(IN; MM) Allowable Ponding Depth d(FT;M) Height of Curb Opening h(FT;M) -- - cn C d/n 5 Z ym to 0 0 is Depth at Inlet(IN; MM) r N (n m S 2 T SPREAD r@ SAG m (FT;M) 0 D3 to b7 m 0 CFD C. ro C) cwi N Tl '�1 t REMARKS c° • DEO Virginia Runoff Reduction Method New Development Compliance Spreadsheet•Version 3.0 1:20s t BMP Standards aM Specifications 01013 Draft IMP Standards aM Specifications Project Name Property of Della Signature Homes,LLC CLEAR ALL data rest cells Date: 7/13E1019 constant slues Nfifl y r quorum,,st 2013 Draft Stds a Specs aYau4don cells hral results Site Information Post-Development Project(Treatment Volume and Loads) Land Cover(acres) •Soils I BSoils CSoits DSORs tows Forest/Oa.soar.taunt undaturbed. gratened lornt(ooen soda.or reform.land 6.75 6J5 Managed Tod arrnl ...nee, 10.54 vac sor other turf to.mawee(moaere l0.st In...ou.Corer lam) 099 099 fe,e,r/ow•sPna.o,.n.murrxPuo-neem daanreanae wnn the a r.. 18 3e Runoff CmHicien s(Ra) Annual it f I males a soils CSaes DSpils IIEv n n M1 restlOeen StoweB003 00a 0.05 rusuPIcMumt11 Managed Tun 015 0Z0 0.20 0.25 Total Nltra en TN EMC m L meervous Carer 095 095 095 095 Post-Development Requirement for Site Area •• TP LOAD REDUCTION NOT REQUIRED t AND COVER SUMMARY--POST DEVELOPMENT Land Cover Somme T.eatm n v.I m nd Nutn.nt Lod • Vo forest/OmSpace Cover(acres) 6.35 Treatmentla<re tt)lume 0.2309 Managed Turf Corer lanes) 10.5a 5301 Weighted Pr(turf) 0.20 %Maaged Tart SI% Imper0ous Cover(warn) 0 99 M(impervious) 0.95 %Impent,. 5°% Site Results(Water Quality Compliance) Area Checks D a A 0 ft 8 0 4 C 0•0 .Pt E AI.ONO, .2.PI/rel...0000.1 Uri. ,rre 000 0 CO 000 OE. PAIKOMOUS COY.J. 000 000 0 00 000 0 DO . .-- PAPPEntiki TAM ilia*Teln; o co 000 0 00 000 0 00 OK ._ . U.A.Of 0 Tett An.LLAL 000 000 0 00 000 000 OK WOVE.1.P.WI TIVI.J.i) .a' 0 CO 000 0.0 .0 ea Ana cm«._ _OK OK. ma ret ca. • -• r• f Site Treatment Votumeite)MEM • . •• f• • Ruipnipduction Volume anp May prpinape Area, . _ 0 A A 0•0 OA S 0 4 0 0,.E I OKAL . 0 . ......L.1.24"Y.1.2.1•PV`1,1?in .._ ._ ir WAD AVAILARII f011 1.10.1.DIV. .00 OM OM 000 000 ,...................1110.1.212,Aping.,(113/20..._ 0.00 „,... 0.00 AM 0 00 000 000 r•LOM ei.laineW(OHO 000 000 000 0 00 000 000 211111261“.1411Q VOOJIMArincra ty.br) ore I 0 DO I MOD I 000 I 000 I 0.00 Total Phosphorus i' • PitalagnIASkiiSakitali Tr LAS014/n,.11112MIN . • • • V LetAJAMPPeriailklailoJeaio IllerIMI • • • TAR Ai eliCiVtainittiii.Mir ailtrill= 0 0 0 t. i' R Lcie2 Si afakenuOtina irii , •Ir------- .-1-------------r-......f•--— YhIPIPLP4 if WIPPitial*P lifloliii_o Mira.-__i'A__:*__. • • . ._I"`..''R,PuiiinS C0010A1IT9.00.PCCIPAL*t--—_-a- ......................IrerMkrr_ntitsil P_ii9il's9' MU eeduattanit lioeonktel . A a • a INPinilkieftli ttePO9PIAPIPOP1 110411, . .. . PIMPIPO telrinealetalitialelaiMPLUI•D*000 -• f f• a • • • • • • • ,, ., , . . Virginia Runoff Reduction Method Worksheet DEQ Virginia Runoff Reduction Method New Development Compliance Spreadsheet -Version 3.0 BMP Design Specifications List: 2013 Draft Stds&Specs Site Summary Project Title:Property of Bella Signature Homes,LLC Date:43509 Total Rainfall=43 inches Site Land Cover Summary A soils B Soils C Soils D Soils Totals %of Total Forest/Open(acres) 0.00 6.75 0.00 0.00 6.75 37 Managed Turf(acres) 0.00 10.54 0.00 0.00 10.54 58 Impervious Cover(acres) 0.00 0.99 0.00 0.00 0.99 5 18.28 100 Site Tv and Land Cover Nutrient Loads Site Rv 0.18 Treatment Volume(ft3) 11,801 TP Load(Ib/yr) 7.41 TN Load(Ib/yr) 53.04 Total TP Load Reduction Required(Ih/yr) -0.08 ** TP LOAD REDUCTION NOT REQUIRED Site Compliance Summary Total Runoff Volume Reduction(ft3) 0 Total TP Load Reduction Achieved(Ib/yr) 0.00 Total TN Load Reduction Achieved(Ib/yr) 0.00 Remaining Post Development TP Load (Ib/yr) 7.41 Remaining TP Load Reduction(lb/yr) 0.00 **TARGET TP REDUCTION EXCEEDED BY 0.08 LB/YEAR"" Required Summary Print Virginia Runoff Reduction Method Worksheet Drainage Area Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total Forest/Open(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Impervious Cover(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Total Area(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Drainage Area Compliance Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total TP Load Reduced(Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 TN Load Reduced(Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 Summary Print Virginia Runoff Reduction Method Worksheet Runoff Volume and CN Calculations 1-year storm 2-year storm 10-year storm Target Rainfall Event(in) 0.00 0.00 0.00 Drainage Areas RV&CN Drainage Area A Drainage Area B Drainage Area C Drainage Area D Drainage Area E CN 0 0 0 0 0 RR(ft3) 0 0 0 0 0 RV wo RR(ws-in) 0.00 0.00 0.00 0.00 0.00 1-year return period RV w RR(ws-in) 0.00 0.00 0.00 0.00 0.00 CN adjusted 0 0 0 0 0 RV wo RR(ws-in) 0.00 0.00 0.00 0.00 0.00 2-year return period RV w RR(ws-in) 0.00 0.00 0.00 0.00 0.00 CN adjusted 0 0 0 0 0 RV wo RR(ws-in) 0.00 0.00 0.00 0.00 0.00 10-year return period RV w RR(ws-in) 0.00 0.00 0.00 0.00 0.00 CS adjusted 0 0 0 0 0 Summary Pont 2S 1S Pre-Dev 1 -ON Pre-Dev 1 -0 8L Pre-Dev Combined Subcat Reach 'on. Link Routing Diagram for EarlysvilleSubdv_PrePost Prepared by Timmons Group, Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 2 Area Listing (selected nodes) Area CN Description (acres) (subcatchment-numbers) 0.860 98 Impervious (1 S, 2S) 7.250 70 Managed Turf (1S) 1.810 63 Wooded (1S, 2S) 9.920 71 TOTAL AREA 9 EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 3 Soil Listing (selected nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 0.000 HSG B 0.000 HSG C 0.000 HSG D 9.920 Other 1 S, 2S 9.920 TOTAL AREA f EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 4 Ground Covers (selected nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.000 0.000 0.000 0.860 0.860 Impervious 1S, 2S 0.000 0.000 0.000 0.000 7.250 7.250 Managed Turf 1 S 0.000 0.000 0.000 0.000 1.810 1.810 Wooded 1 S, 2S 0.000 0.000 0.000 0.000 9.920 9.920 TOTAL AREA EarlysvilleSubdv_PrePost Type II 24-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 5 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: Pre-Dev 1-0 Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>0.76" Flow Length=410' Tc=15.9 min CN=73 Runoff=8.13 cfs 0.518 af Subcatchment2S: Pre-Dev 1-ON Runoff Area=1.730 ac 1.16% Impervious Runoff Depth>0.37" Flow Length=340' Tc=13.3 min CN=63 Runoff=0.72 cfs 0.053 af Link 8L: Pre-Dev Combined Inflow=8.85 cfs 0.571 af Primary=8.85 cfs 0.571 af Total Runoff Area = 9.920 ac Runoff Volume = 0.571 af Average Runoff Depth = 0.69" 91.33% Pervious =9.060 ac 8.67% Impervious = 0.860 ac EarlysvilleSubdv_PrePost Type 1124-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Palle 6 Summary for Subcatchment 1S: Pre-Dev 1-0 Runoff = 8.13 cfs @ 12.10 hrs, Volume= 0.518 af, Depth> 0.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-Year Rainfall=2.99" Area (ac) CN Description * 0.840 98 Impervious * 7.250 70 Managed Turf * 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 1S: Pre-Dev 1-0 Hydrograph 9 •Runoff 18.13 cfs I 8- Type II 24-hr 7_ 1-Year Rainfall=2.99" Runoff Area=8.190 ac 6- Runoff Volume=0.518 af 5- Runoff Depth>0.76" LL 4- Flow Length=410' Tc=15.9 min CN=73 2- 0 , . 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type 1124-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: Pre-Dev 1-ON Runoff = 0.72 cfs @ 12.09 hrs, Volume= 0.053 af, Depth> 0.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-Year Rainfall=2.99" Area (ac) CN Description 0.020 98 Impervious 1.710 63 Wooded 1.730 63 Weighted Average 1.710 98.84% Pervious Area 0.020 1.16% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.62" 2.7 240 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 13.3 340 Total Subcatchment 2S: Pre-Dev 1-ON Hydrograph 0.8 p Runoff 0.75= 10.72 cfs I 0.7i Type II 24-hr 0.65= 1-Year Rainfall=2.99" 0.6 U.55 Runoff Area=1.730 ac 0.5i Runoff Volume=0.053 af 0.45= Runoff Depth>0.37" 0.4= 2 0.35_ Flow Length=340' 0.3= Tc=13.3 min 0.252: CN=63 0.2j 0.15= 0.1. 0.05 0` 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 1-YearRainfa11=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 8 Summary for Link 8L: Pre-Dev Combined Inflow Area = 9.920 ac, 8.67% Impervious, Inflow Depth > 0.69" for 1-Year event Inflow = 8.85 cfs @ 12.10 hrs, Volume= 0.571 af Primary = 8.85 cfs @ 12.10 hrs, Volume= 0.571 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 8L: Pre-Dev Combined Hydrograph / ■Inflow [8 85 cfs 0 Primary 9 [8.85cfs Inflow Area=9.920 ac 8 7 6 5 LL 4 3 2 1- 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type ll 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 9 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentlS: Pre-Dev 1-0 Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>1.14" Flow Length=410' Tc=15.9 min CN=73 Runoff=12.50 cfs 0.776 af Subcatchment2S: Pre-Dev 1-ON Runoff Area=1.730 ac 1.16% Impervious Runoff Depth>0.63" Flow Length=340' Tc=13.3 min CN=63 Runoff=1.42 cfs 0.091 af Link 8L: Pre-Dev Combined Inflow=13.91 cfs 0.866 af Primary=13.91 cfs 0.866 af Total Runoff Area = 9.920 ac Runoff Volume= 0.866 af Average Runoff Depth = 1.05" 91.33% Pervious = 9.060 ac 8.67% Impervious = 0.860 ac EarlysvilleSubdv_PrePost Type II 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 1S: Pre-Dev 1-0 Runoff = 12.50 cfs @ 12.09 hrs, Volume= 0.776 af, Depth> 1.14" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2-Year Rainfall=3.62" Area (ac) CN Description * 0.840 98 Impervious * 7.250 70 Managed Turf * 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 1S: Pre-Dev 1-0 Hydrograph ■Runoff 13- 1 12.50 cfs I ,2 Type II 24-hr 2-Year Rainfall=3.62" Runoff Area=8.190 ac Runoff Volume=0.776 af " Runoff Depth>1.14" ' 6_ Flow Length=410' 5- Tc=15.9 min CN=73 3- 2- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type ll 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 2S: Pre-Dev 1-ON Runoff = 1.42 cfs @ 12.08 hrs, Volume= 0.091 af, Depth> 0.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2-Year Rainfall=3.62" Area (ac) CN Description * 0.020 98 Impervious * 1.710 63 Wooded 1.730 63 Weighted Average 1.710 98.84% Pervious Area 0.020 1.16% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.62" 2.7 240 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 13.3 340 Total Subcatchment 2S: Pre-Dev 1-ON Hydrograph l •Runoff 1 1.42 cfs Type II 24-hr 2-Year Rainfall=3.62" Runoff Area=1.730 ac t. Runoff Volume=0.091 af Runoff Depth>0.63" LL Flow Length=340' Tc=13.3 min CN=63 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type 11 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 12 Summary for Link 8L: Pre-Dev Combined Inflow Area = 9.920 ac, 8.67% Impervious, Inflow Depth > 1.05" for 2-Year event Inflow = 13.91 cfs @ 12.09 hrs, Volume= 0.866 af Primary = 13.91 cfs @ 12.09 hrs, Volume= 0.866 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 8L: Pre-Dev Combined Hydrograph �■InflowPrimary 15- 113.91 Ns ■ 14- I1391cfsInflow Area=9.920 ac 13- 12 11- 10 9: 111111 v 82 7- u. - 3 i 04. 6- 5 4_ 3a 2- 1 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 sin 08663 ©2017 HydroCAD Software Solutions LLC Page 13 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentlS: Pre-Dev 1-0 Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>2.42" Flow Length=410' Tc=15.9 min CN=73 Runoff=27.00 cfs 1.654 af Subcatchment2S: Pre-Dev 1-ON Runoff Area=1.730 ac 1.16% Impervious Runoff Depth>1.63" Flow Length=340' Tc=13.3 min CN=63 Runoff=4.12 cfs 0.235 af Link 8L: Pre-Dev Combined Inflow=31.02 cfs 1.889 af Primary=31.02 cfs 1.889 af Total Runoff Area = 9.920 ac Runoff Volume = 1.889 af Average Runoff Depth = 2.28" 91.33% Pervious =9.060 ac 8.67% Impervious = 0.860 ac EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 14 Summary for Subcatchment 1S: Pre-Dev 1-0 Runoff = 27.00 cfs @ 12.08 hrs, Volume= 1.654 af, Depth> 2.42" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-Year Rainfall=5.46" Area (ac) CN Description * 0.840 98 Impervious • 7.250 70 Managed Turf • 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 1S: Pre-Dev 1-0 Hydrograph 30-/ ©Runoff 28- 127.00 cfs I 26- Type II 24-hr 24 10-Year Rainfall=5.46" 22- 20= Runoff Area=8.190 ac 18_ Runoff Volume=1.654 af 16- Runoff Depth>2.42" O 14: Flow Length=410' 12 Tc=15.9 min CN=73 6- 4 2: 5 6 7 8 9 10 11 12 13 14 15 16T 17 18 19 20 Time (hours) ti EarlysvilleSubdv_PrePost Type 1124-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment 2S: Pre-Dev 1-ON Runoff = 4.12 cfs @ 12.06 hrs, Volume= 0.235 af, Depth> 1.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-Year Rainfall=5.46" Area (ac) CN Description * 0.020 98 Impervious * 1.710 63 Wooded 1.730 63 Weighted Average 1.710 98.84% Pervious Area 0.020 1.16% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.62" 2.7 240 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 13.3 340 Total Subcatchment 2S: Pre-Dev 1-ON Hydrograph 7 O Runoff 1 4.12 ds I 4- Type II 24-hr 10-Year Rainfall=5.46" Runoff Area=1.730 ac 3-Runoff Volume=0.235 af Runoff Depth>1.63" u. 2- Flow Length=340' Tc=13.3 min CN=63 1- 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type ll 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 16 Summary for Link 8L: Pre-Dev Combined Inflow Area = 9.920 ac, 8.67% Impervious, Inflow Depth > 2.28" for 10-Year event Inflow = 31.02 cfs @ 12.08 hrs, Volume= 1.889 af Primary = 31.02 cfs @ 12.08 hrs, Volume= 1.889 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Link 8L: Pre-Dev Combined Hydrograph / Inflow ` 34: I3102as I 0 Primary 32: I31.02cfs Inflow Area=9.920 ac 30H 28 26 24 22 ^ 20 18 0 16 LL 14 12 0 0 8 4 0 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 3S (4S Post-Dev 1 O-D Post-Dev 1 ON-D (OFFSITE DETAINED) 11 P (ONSITE DETAINED) SWM 1 (Dry Pond) (Subca) Reach 'on. Link Routing Diagram for EarlysvilleSubdv_PrePost Prepared by Timmons Group, Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 2 Area Listing (selected nodes) Area CN Description (acres) (subcatchment-numbers) 1.170 98 Impervious (3S, 4S) 8.650 70 Managed Turf (3S,4S) 0.100 63 Wooded (3S) 9.920 73 TOTAL AREA EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 3 Soil Listing (selected nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 0.000 HSG B 0.000 HSG C 0.000 HSG D 9.920 Other 3S, 4S 9.920 TOTAL AREA EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 4 Ground Covers (selected nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.000 0.000 0.000 1.170 1.170 Impervious 3S, 4S 0.000 0.000 0.000 0.000 8.650 8.650 Managed Turf 3S, 4S 0.000 0.000 0.000 0.000 0.100 0.100 Wooded 3S 0.000 0.000 0.000 0.000 9.920 9.920 TOTAL AREA EarlysvilleSubdv_PrePost Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 5 Pipe Listing (selected nodes) Line# Node In-Invert Out-Invert Length Slope n Diam/Width Height Inside-Fill Number (feet) (feet) (feet) (ft/ft) (inches) (inches) (inches) 1 11 P 550.89 544.66 138.5 0.0450 0.013 18.0 0.0 0.0 EarlysvilleSubdv_PrePost Type II 24-hr 1-YearRainfa11=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 6 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment3S: Post-Dev 1 O-D Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>0.76" Flow Length=410' Tc=15.9 min CN=73 Runoff=8.13 cfs 0.518 af Subcatchment4S: Post-Dev 1 ON-D Runoff Area=1.730 ac 19.08% Impervious Runoff Depth>0.86" Flow Length=340' Tc=8.9 min CN=75 Runoff=2.55 cfs 0.124 af Pond 11P: SWM 1 (Dry Pond) Peak Elev=553.98' Storage=5,036 cf Inflow=10.01 cfs 0.642 af Outflow=8.32 cfs 0.624 af Total Runoff Area = 9.920 ac Runoff Volume = 0.642 af Average Runoff Depth = 0.78" 88.21% Pervious = 8.750 ac 11.79% Impervious = 1.170 ac EarlysvilleSubdv_PrePost Type II 24-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Pace 7 Summary for Subcatchment 3S: Post-Dev 1 O-D (OFFSITE DETAINED) Runoff = 8.13 cfs @ 12.10 hrs, Volume= 0.518 af, Depth> 0.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-Year Rainfall=2.99" Area (ac) CN Description * 0.840 98 Impervious * 7.250 70 Managed Turf * 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 3S: Post-Dev 1O-D (OFFSITE DETAINED) Hydrograph 9/ O Runoff` 1813cfs I 8- Type II 24-hr 7_ 1-Year Rainfall=2.99" Runoff Area=8.190 ac 6- Runoff Volume=0.518 af 5- Runoff Depth>0.76" LL 4- Flow Length=410' Tc=15.9 min 3- CN=73 2- 1 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 4S: Post-Dev 1ON-D (ONSITE DETAINED) Runoff = 2.55 cfs @ 12.01 hrs, Volume= 0.124 af, Depth> 0.86" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1-Year Rainfall=2.99" Area (ac) CN Description * 0.330 98 Impervious * 1.400 70 Managed Turf 1.730 75 Weighted Average 1.400 80.92% Pervious Area 0.330 19.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 100 0.1000 0.24 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 1.9 240 0.0900 2.10 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 8.9 340 Total Subcatchment 4S: Post-Dev 1ON-D (ONSITE DETAINED) Hydrograph ®Runoff 12.55 cfs I Type II 24-hr 1-Year Rainfall=2.99" 2 Runoff Area=1.730 ac Runoff =0.124 of RunoffVolume Depth>0.86" Flow Length=340' Tc=8.9 min CN=75 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 9 Summary for Pond 11 P: SWM 1 (Dry Pond) Inflow Area = 9.920 ac, 11.79% Impervious, Inflow Depth > 0.78" for 1-Year event Inflow = 10.01 cfs @ 12.07 hrs, Volume= 0.642 af Outflow = 8.32 cfs @ 12.16 hrs, Volume= 0.624 af, Atten= 17%, Lag= 5.6 min Primary = 8.32 cfs @ 12.16 hrs, Volume= 0.624 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 553.98'@ 12.17 hrs Surf.Area= 4,774 sf Storage= 5,036 cf Plug-Flow detention time=24.6 min calculated for 0.622 af(97% of inflow) Center-of-Mass det. time= 14.4 min ( 834.0 - 819.6 ) Volume Invert Avail.Storage Storage Description #1 552.75' 24,900 cf Custom Stage Data (Prismatic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 552.75 3,500 0 0 553.00 3,700 900 900 554.00 4,800 4,250 5,150 556.00 7,100 11,900 17,050 557.00 8,600 7,850 24,900 Device Routing Invert Outlet Devices #1 Primary 550.89' 18.0" Round Culvert L= 138.5' CPP, end-section conforming to fill, Ke= 0.500 Inlet/ Outlet Invert= 550.89'/544.66' S= 0.0450'/' Cc= 0.900 n= 0.013, Flow Area= 1.77 sf #2 Device 1 552.75' 18.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 553.83' 52.2" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 555.33' 30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=8.03 cfs @ 12.16 hrs HW=553.97' (Free Discharge) -1=Culvert (Passes 8.03 cfs of 12.98 cfs potential flow) AL2=Orifice/Grate (Orifice Controls 5.77 cfs @ 3.76 fps) 3=Orifice/Grate (Weir Controls 2.27 cfs @ 1.21 fps) -4=Sharp-Crested Rectangular Weir( Controls 0.00 cfs) EarlysvilleSubdv_PrePost Type II 24-hr 1-Year Rainfall=2.99" Prepared by Timmons Group Printed 8/14/2019 HydroCADO 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 10 Pond 11 P: SWM 1 (Dry Pond) Hydrograph / •Inflow 117 110.01 cfs i O Primary 102 Inflow Area=9.920 ac 1832cfs Peak Elev=553.98' 8: Storage=5,036 cf u 6- LL53 10 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type ll 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD®10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 11 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment3S: Post-Dev 1 O-D Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>1.14" Flow Length=410' Tc=15.9 min CN=73 Runoff=12.50 cfs 0.776 af Subcatchment4S: Post-Dev 1 ON-D Runoff Area=1.730 ac 19.08% Impervious Runoff Depth>1.26" Flow Length=340' Tc=8.9 min CN=75 Runoff=3.77 cfs 0.182 af Pond 11P: SWM 1 (Dry Pond) Peak Elev=554.17' Storage=5,989 cf Inflow=15.34 cfs 0.957 af Outflow=13.61 cfs 0.936 af Total Runoff Area = 9.920 ac Runoff Volume = 0.957 af Average Runoff Depth = 1.16" 88.21% Pervious = 8.750 ac 11.79% Impervious = 1.170 ac EarlysvilleSubdv_PrePost Type II 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment 3S: Post-Dev 10-D (OFFSITE DETAINED) Runoff = 12.50 cfs @ 12.09 hrs, Volume= 0.776 af, Depth> 1.14" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2-Year Rainfall=3.62" Area (ac) CN Description * 0.840 98 Impervious * 7.250 70 Managed Turf * 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 3S: Post-Dev 10-D (OFFSITE DETAINED) Hydrograph ■Runoff 13 112.50 chs I 12- Type II 24-hr 2-Year Rainfall=3.62" 107 Runoff Area=8.190 ac 97 Runoff Volume=0.776 af 8-. Runoff Depth>1.14" 3 7_ LL 6- Flow Length=410' 5 Tc=15.9 min CN=73 37 2- 1 0 5 6 7 8 9 10 11 12 '13' 14 .15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 sin 08663 ©2017 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 4S: Post-Dev 1ON-D (ONSITE DETAINED) Runoff = 3.77 cfs @ 12.01 hrs, Volume= 0.182 af, Depth> 1.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 2-Year Rainfall=3.62" Area (ac) CN Description * 0.330 98 Impervious * 1.400 70 Managed Turf 1.730 75 Weighted Average 1.400 80.92% Pervious Area 0.330 19.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 100 0.1000 0.24 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 1.9 240 0.0900 2.10 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 8.9 340 Total Subcatchment 4S: Post-Dev 1 ON-D (ONSITE DETAINED) Hydrograph 0 Runoff 4 I377cfs I Type II 24-hr 2-Year Rainfall=3.62" 3 Runoff Area=1 .730 ac Runoff Volume=0.182 af Runoff Depth>1.26" 2101 Flow Length=340' Tc=8.9 min / CN=75 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 14 Summary for Pond 11 P: SWM 1 (Dry Pond) Inflow Area = 9.920 ac, 11.79% Impervious, Inflow Depth > 1.16" for 2-Year event Inflow = 15.34 cfs @ 12.07 hrs, Volume= 0.957 af Outflow = 13.61 cfs @ 12.13 hrs, Volume= 0.936 af, Atten= 11%, Lag= 3.6 min Primary = 13.61 cfs @ 12.13 hrs, Volume= 0.936 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 554.17'@ 12.13 hrs Surf.Area= 4,997 sf Storage= 5,989 cf Plug-Flow detention time=20.2 min calculated for 0.936 af(98% of inflow) Center-of-Mass det. time= 11.9 min ( 823.0 - 811.1 ) Volume Invert Avail.Storage Storage Description #1 552.75' 24,900 cf Custom Stage Data (Prismatic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 552.75 3,500 0 0 553.00 3,700 900 900 554.00 4,800 4,250 5,150 556.00 7,100 11,900 17,050 557.00 8,600 7,850 24,900 Device Routing Invert Outlet Devices #1 Primary 550.89' 18.0" Round Culvert L= 138.5' CPP, end-section conforming to fill, Ke= 0.500 Inlet/Outlet Invert= 550.89'/544.66' S= 0.0450'/' Cc= 0.900 n= 0.013, Flow Area= 1.77 sf #2 Device 1 552.75' 18.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 553.83' 52.2" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 555.33' 30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=13.51 cfs @ 12.13 hrs HW=554.16' (Free Discharge) -1=Culvert (Inlet Controls 13.51 cfs @ 7.65 fps) -2=Orifice/Grate (Passes < 6.98 cfs potential flow) 3=Orifice/Grate (Passes < 8.54 cfs potential flow) -4=Sharp-Crested Rectangular Weir( Controls 0.00 cfs) EarlysvilleSubdv_PrePost Type II 24-hr 2-Year Rainfall=3.62" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 15 Pond 11 P: SWM 1 (Dry Pond) Hydrograph 17 / ■Inflow II 115.34 cts I •Primary 16- Inflow Area=9.920 ac 15H 14- [1361crs Peak Elev=554.17' 13H 12H, ii Storage=5,989 cf 11_ N 10 2. 9 0 8= LL 7 I 5- / 4- oO. 3- 2 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 16 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment3S: Post-Dev 1 O-D Runoff Area=8.190 ac 10.26% Impervious Runoff Depth>2.42" Flow Length=410' Tc=15.9 min CN=73 Runoff=27.00 cfs 1.654 af Subcatchment4S: Post-Dev 1 ON-D Runoff Area=1.730 ac 19.08% Impervious Runoff Depth>2.60" Flow Length=340' Tc=8.9 min CN=75 Runoff=7.73 cfs 0.375 of Pond 11 P: SWM 1 (Dry Pond) Peak Elev=555.57' Storage=14,128 cf Inflow=32.98 cfs 2.030 af Outflow=28.69 cfs 2.001 of Total Runoff Area = 9.920 ac Runoff Volume = 2.030 af Average Runoff Depth = 2.46" 88.21% Pervious= 8.750 ac 11.79% Impervious = 1.170 ac EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 17 Summary for Subcatchment 3S: Post-Dev 1 O-D (OFFSITE DETAINED) Runoff = 27.00 cfs @ 12.08 hrs, Volume= 1.654 af, Depth> 2.42" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-Year Rainfall=5.46" Area (ac) CN Description * 0.840 98 Impervious * 7.250 70 Managed Turf * 0.100 63 Wooded 8.190 73 Weighted Average 7.350 89.74% Pervious Area 0.840 10.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 13.4 100 0.0200 0.12 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 2.5 310 0.0850 2.04 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 15.9 410 Total Subcatchment 3S: Post-Dev 1O-D (OFFSITE DETAINED) Hydrograph 307/ ■Runoff 28= 127.00 ds 26= Type II 24-hr 241 10-Year Rainfall=5.46" 22- Runoff Area=8.190 ac 20= 18_ Runoff Volume=1.654 af 16 Runoff Depth>2.42" 14- Flow Length=410' 12- Tc=15.9 min 10-, CN=73 6= 4- 2= 0- , . .. . . 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type 1124-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 18 Summary for Subcatchment 4S: Post-Dev 1 ON-D (ONSITE DETAINED) Runoff = 7.73 cfs @ 12.00 hrs, Volume= 0.375 af, Depth> 2.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-Year Rainfall=5.46" Area (ac) CN Description * 0.330 98 Impervious * 1.400 70 Managed Turf 1.730 75 Weighted Average 1.400 80.92% Pervious Area 0.330 19.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 100 0.1000 0.24 Sheet Flow, Grass: Dense n= 0.240 P2= 3.62" 1.9 240 0.0900 2.10 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 8.9 340 Total Subcatchment 4S: Post-Dev ION-D (ONSITE DETAINED) Hydrograph ®Runoff 8— 1773cfs I Type II 24-hr 7- 10-Year Rainfall=5.46" 6- Runoff Area=1.730 ac Runoff Volume=0.375 af 0 5- Runoff Depth>2.60" 42 Flow Length=340' 3- Tc=8.9 m i n CN=75 2- 1- 0 � ' �. .. . r . , . . . 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 20 Time (hours) EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 19 Summary for Pond 11 P: SWM 1 (Dry Pond) Inflow Area = 9.920 ac, 11.79% Impervious, Inflow Depth > 2.46" for 10-Year event Inflow = 32.98 cfs @ 12.06 hrs, Volume= 2.030 af Outflow = 28.69 cfs @ 12.15 hrs, Volume= 2.001 af, Atten= 13%, Lag= 5.4 min Primary = 28.69 cfs @ 12.15 hrs, Volume= 2.001 af Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 555.57'@ 12.15 hrs Surf.Area= 6,610 sf Storage= 14,128 cf Plug-Flow detention time=16.4 min calculated for 2.001 af(99% of inflow) Center-of-Mass det. time= 10.8 min ( 806.4 - 795.6 ) Volume Invert Avail.Storage Storage Description #1 552.75' 24,900 cf Custom Stage Data (Prismatic)Listed below(Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 552.75 3,500 0 0 553.00 3,700 900 900 554.00 4,800 4,250 5,150 556.00 7,100 11,900 17,050 557.00 8,600 7,850 24,900 Device Routing Invert Outlet Devices #1 Primary 550.89' 18.0" Round Culvert L= 138.5' CPP, end-section conforming to fill, Ke= 0.500 Inlet/Outlet Invert= 550.89'/544.66' S= 0.0450'/' Cc= 0.900 n= 0.013, Flow Area= 1.77 sf #2 Device 1 552.75' 18.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 553.83' 52.2" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #4 Primary 555.33' 30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=28.58 cfs @ 12.15 hrs HW=555.57' (Free Discharge) 1=Culvert (Inlet Controls 16.87 cfs @ 9.55 fps) '2=Orifice/Grate (Passes < 12.25 cfs potential flow) 3=Orifice/Grate (Passes < 94.47 cfs potential flow) -4=Sharp-Crested Rectangular Weir(Weir Controls 11.71 cfs @ 1.61 fps) EarlysvilleSubdv_PrePost Type II 24-hr 10-Year Rainfall=5.46" Prepared by Timmons Group Printed 8/14/2019 HydroCAD® 10.00-20 s/n 08663 ©2017 HydroCAD Software Solutions LLC Page 20 Pond 11 P: SWM 1 (Dry Pond) Hydrograph / a Inflow } 36= I32.98cis I ❑Primary 34. Inflow Area=9.920 ac 32= 30 I28.69cfs Peak EIev=555.57' 28- 26 Storage=14,128 cf 24= l 22 20- 18= LL 16= 14- it, 12- 10- 8= 6- 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) RECEIVED AU6 1 5 2019 COMMUNITY DEVELOPMENT