Loading...
HomeMy WebLinkAboutWPO202300020 Calculations 2023-03-24SHIMP ENGINEERING, P.C. Design Focused Engineering March 23, 2023 Engineering Review Albemarle County Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Regarding: WP02023-000XX Berkmar Flats Stormwater Management Plan Dear Reviewer, 3JA%3 AL The purpose of this project is to construct a 26-unit multi -family housing development. The total area of disturbance is 2.54 acres. Water Quantity: The stormwater management for this site will be addressed through the use of a detention pond. The pond will release runoff at rates compliant with the Energy Balance Equation. Summaries of the pre and post development flow rates at the point of analysis are shown below. Please see drainage area maps located in this packet for more detail. This site is compliant with water quantity requirements by meeting 9VAC25-870-66-B.3.a. Channel Protection: Energy Balance Equation with Run-on for POA 1 Berkmar Flats 1 Yr, 24 Hr Storm Comparison Ipw <_ Q i ere, sar ((RV i ere. sae)i(RV t eau, sae))(I.F.)+Q i ere. ac ae ((RV I P oaw)'(RV i east aadre)) LF. = 0.8 Mica LOD>_ 1 ac. I.17.-0.9 trlten LOD 5 1 ac. I.F. = LO when predev site n fidly forested PfeDev Site Fully Forested? = no I.F. = 0.8 Lhnits of Disturbance = 1.54 ac Onsite Of .site Pre Dev Area Onsite = 1.64 ac Pre Dev DA Offsite 0.80 ae Post Dev Area Onsite = 2.07 ac Post Dcv DA OffSne = 0.80 ac Q I vies site = 0.20 cis Q l eee. case = 0.12 is RVteee.see = 0.034 of RVtemomte = 0.018 of RV i eeet sae — 0.185 of RV I eostasw — 0.019 of Regalatofy Maximum Postdev 1-pi, Flow Rate Max Qipose S 0.15 ers Achieved Design Postdev 1-yr Flow Rate Design Qlpan = 0.14 cis Energy Balance Equation Compliance Check: Achieved Notes- I The asmmpuon m the calculation above is that the site equals the land-diowhing activity (LDA). The definition for'site is not clearly defi e i to the regulations. but LDAs are defined as regulated. The nester quantity entaiia are applied to the site as per the tegulaoow 2. This site diseharges to an emsmg charnel. Since postdovelopment racoH to this oudaB meets the energy balance agweon, Channel Prorccuou Requirements per 9VAC25-870-66-B.3 a are tail and charnel ptol,vt. re,wenwntt are satisfied. The point of analysis (POA 1) is located in a manmade swale prior an existing 18" culvert. The swale was modeled in Hydraulic Toolbox using field -verified conditions and the design 2-yr storm to determine that the swale is non -erosive in the post -development condition. The input parameters and a cross-section of the swale are shown below. 0 r a, w 2yr Mandmade channel Type: F�_� 3 Define... Sides lope l(Zl). 8.0 H:1V Side Slope 2(Z2): 8.0 H:1V Channel'•Wath(B): 0.0 (ft Pipe Dlameter(D). 0.0 (it) Longitudinal Slope: 0.069 RAI r Override Default Manning's Roughness: 0.0350 r Um Lining Lining Type lWoven Paper Net r Enter Flow: 0.320 (cis) * Enter Depth: 0.144 (It) Flow 0.320 cfs Depth 0.144 ft Area of now 0.166 sq fit Netted Perimeter 2.326 ft Hydraulic Radius 0.072 ft Top Width(T) Z3DB ft Froude Number 1.261 Critical Depth 0.158 ft OiticalVelocity, 1.556 fps critical Slope 0.04204 Wit critical Top'Width 2.533 ft Mae Shear Stress 0.621 IbA^2 Avg Shear Stress 0.308 IbA^2 Compositehlanningsn Equ... Lotter. Hamina's Roughness 0.0350 Cross Section Station (ft) x Concentrated runoff from this site is discharged in a manmade swale into an existing storm structure. It is assumed that the existing structure is inadequate so reduction in the 10-yr flow rate is sufficient to meet flood protection requirements set forth in 9VAC25-870-66-C.2.b. Flood Protection: Peak Flow Rate to Existing Channel for POA 1 Berkman Flats 10 Yr, 24 Fir Storm Comparison Regulatory Maximum 30-yr Flow Rate Q10pre=MAX QIOPmt = 3.62 cis Achieved Design Postdev 10-yr Flow Rate Design Qiopwt = 1.41 cis Flood Protection Compliance Check: Achieved ores: 1. Des site discharges into an exiang charnel. Du 14yr aow rate is reduced which meets th<cuergy balau<e equatim and th< Good protection counts a 9VAC25-870-66.0 Water Quality: According to the VRRM New Development Compliance Spreadsheet, a TP Load Reduction of 1.57 lb/yr is required. The nutrient treatment requirement will be met through the purchase of nutrient credits. Best Regards, Chris Marshall, EIT Shimp Engineering, P.C. Contents: Pre -Development Stormwater Management Calculations: Pre -Development Drainage Area Map Pre -Development HydroCAD Analysis Time of Concentration Calculation Time of Concentration Nomographs Post -Development Stormwater Management Calculations: Post -Development Drainage Area Map Post -Development HydroCAD Analysis Energy Balance Equation Summary LD-204 Stormwater Inlet Computations LD-229 Storm Drain Design Computations LD-268 Ditch Design Outlet Protection Calculations Stormwater Quality Calculations: VRRM Pre -Development Land Use Map VRRM Post -Development Land Use Map VRRM Re -Development Spreadsheet Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre -Development Stormwater Management Calculations: Pre -Development Drainage Area Map Pre -Development HydroCAD Analysis Time of Concentration Calculation Time of Concentration Nomographs BERKMAR FATS PREDEV DRAINAGE AREA MAP DRAINAGE AREA 1: up TOTAL AREA = 2.44 AC _°-«,_ --- HSG TYPE B _ __/-/- - ONSITE = 1.64 AC ° \\\ \� \ \\\\` I I//\�_ IMPERVIOUS = 0.10 AC MANAGED TURF = 0.08 AC WOODS = 1.46 AC I / OFFSITE = 0.80 AC IMPERVIOUS = 0.12 AC MANAGED TURF = 0.00 AC WOODS = 0.68 AC TIME OF CONCENTRATION = 18.1 MINUTES DRAINAGE AREA 50 0 50 100 1 mams� In: c ue �.'\:'&<° Scale: 1 "=50' 50 DA 1 (Or (2S) DA/ (Offsite) CA POA 1 S4 Reach X 4on Llflk Predev Predev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 2 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite) Runoff Area=1.640 ac 6.10% Impervious Runoff Depth=0.25' Tc=18.1 min UI Adjusted CN=57 Runoff=0.20 cfs 0.034 of Subcatchment2S: DA 1 (Offsite) Runoff Area=0.800 ac 15.00% Impervious Runoff Depth=0.28" Tc=18.1 min UI Adjusted CN=58 Runoff=0.12 cfs 0.018 of Link 3L: POA 1 Inflow=0.32 cfs 0.053 of Primary=0.32 cfs 0.053 of Total Runoff Area = 2.440 ac Runoff Volume = 0.053 of Average Runoff Depth = 0.26" 90.98% Pervious = 2.220 ac 9.02% Impervious = 0.220 ac Predev Predev Type // 24-hr 1-YR Rainfall=3.01" Prepared by (enter your company name here) Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Pape 3 Summary for Subcatchment 1S: DA 1 (Onsite) Runoff = 0.20 cfs @ 12.19 hrs, Volume= 0.034 af, Depth= 0.25" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 1.460 55 Woods, Good, HSG B 0.080 61 >75% Grass cover, Good, HSG B 0.100 98 Unconnected pavement, HSG B 1.640 58 Weighted Average, UI Adjusted CN = 57 1.540 93.90% Pervious Area 0.100 6.10% Impervious Area 0.100 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (f 1sec) (cfs) 18.1 Direct Entry, Subcatchment 1S: DA 1 (Onsite) Hydrograph - ■ Runoff I I I 0.2 --r-r--r-- 0 19 018 I 0.17 ---J--,--'--- 0.16 0.15 .......... 0.14 _ 0.13 --L-L--J--L--- 0.12 --`---�--; 0.11 --r-,--; 0.1 --r-r-r LL 0.09 _ 0.08 0.07 006 I _l _T 0.05 I I I I I 0.04 0.03 0.02 nn. -r -r -1 -T -r I I I I I ---,-- --; --;------- - YRe-kC 4ihr;'L.76Y 1 __T__ T__ r__r__I__T__T_ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I - __;-- --;------RMWAted=1:64aad- __I__r__T__T__r__I___I__T__r__r__r__I___I__T__r__r__I__ --'--J--J--L--L--'-- tntnafF':Deptlro- 25;"- T T V=18.�- --r--I T -I-- I-- I -- I--I--I---I-- I-- I -- I--I---I---I-- I -- I -- I --I-- ILI Ad1Mste$-0N=57 __l__T__T__r__I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I --r-r-T--I--r-T--r--r--r--I--T--T--r-_I__ I I I I I I I I I I I I Time (hours) Predev Predev Type // 24-hr 1-YR Rainfall=3.01" Prepared by (enter your company name here) Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Pane 4 Summary for Subcatchment 2S: DA 1 (Offsite) Runoff = 0.12 cfs @ 12.18 hrs, Volume= 0.018 af, Depth= 0.28" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 0.680 55 Woods, Good, HSG B 0.120 98 Unconnected pavement, HSG B 0.800 61 Weighted Average, UI Adjusted CN = 58 0.680 85.00% Pervious Area 0.120 15.00% Impervious Area 0.120 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (f /sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 1 (Offsite) Hydrograph 0.13- - --- 0.12 cfs -- -- --'-----t--*-- -- --t U.,2Xpe_'�,lL4ihr:'LiYk --rr--r--r----r-r--T--T--r--I-r-r-T--T_ r Reinfalh341"'- _--- __i__r__�_ __i__r__T__T__r__i __i__Rdn6ff'A-i@e&O-.800-ale 009 --,--- - --UfftgFgmle- _ 0.08 M __�__�__�__�__ __�__�__�__�__�___�___�__�__ _�__1 ID I v 0.07fiFDeplEh�0: 0 T_d=18.�1_ rh_ih_ ,� 0.06 i _I _J _1 _1 _L _I _I _J _1 _1 _L _I _I _1 _1 _L _I 0.06 - -- --; --;-- ---------�--;UI;A IJ_4ls ec-gN=SO- 0.03 0.02 0.01 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hove) ■ Runoff Predev Predev Type // 24-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here} Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Paoe 5 Summary for Link 3L: POA 7 Inflow Area = 2.440 ac, 9.02% Impervious, Inflow Depth = 0.26" for 1-YR event Inflow = 0.32 cfs @ 12.19 hrs, Volume= 0.053 of Primary = 0.32 cfs @ 12.19 hrs, Volume= 0.053 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link 3L: POA 1 Hydrograph ■ Inflow I I I ■ Primary 0.34 0.32 cfs o.3z - -- IiRfkoiiv rea=,2.44$'Ia 0.3 I I I I I I I I I I I I I I I I 0.28 _I I I I __-__r__r__1__4__r__1__-__ -1 -y -+ -r-~ -T -r -1 -~ -i -r -1 -~ 0.24 -1 -7 -t -r -1 -y -r -I -y 0 22 i 02 �..i 0.18 I I I 3 0 0.16 1 1 1 1 1 1 1 1 1 1 1 1 1 LL 0.14 III II I 0'12 � - __II __ __II II I1 _II1 I1 _I IIII I I I I I I I I I I I I I I I I I I I 0.1 I I I I I I I I I I I I I I I I I I I T-- 0.06, I I I I I I I I I I , 0.06 0.04 0.02 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time thous) Predev Predev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 6 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite) Runoff Area=1.640 ac 6.10% Impervious Runoff Depth=1.38" Tc=18.1 min UI Adjusted CN=57 Runoff=2.38 cfs 0.189 of Subcatchment2S: DA 1 (Offsite) Runoff Area=0.800 ac 15.00% Impervious Runoff Depth=1.45" Tc=18.1 min UI Adjusted CN=58 Runoff=1.24 cfs 0.097 of Link 3L: POA 1 Inflow=3.62 cfs 0.286 of Primary=3.62 cfs 0.286 of Total Runoff Area = 2.440 ac Runoff Volume = 0.286 of Average Runoff Depth = 1.40" 90.98% Pervious = 2.220 ac 9.02% Impervious = 0.220 ac Predev Predev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 7 Summary for Subcatchment 1S: DA 1 (Onsite) Runoff = 2.38 cfs @ 12.13 hrs, Volume= 0.189 af, Depth= 1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfall=5.50" Area (ac) CN Description 1.460 55 Woods, Good, HSG B 0.080 61 >75% Grass cover, Good, HSG B 0.100 98 Unconnected pavement, HSG B 1.640 58 Weighted Average, UI Adjusted CN = 57 1.540 93.90% Pervious Area 0.100 6.10% Impervious Area 0.100 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 1S: DA 1 (Onsite) Hydrograph 2.38 cfs Type II 24-hr 10-YR Rainfall=5.56' Runoff Area=1.640 ad Runoff Volume=0.189 of Runoff Depth=1.38" Tc=18.1 min UI Adjusted CN=57 12 14 16 18 20 22 24 26 Time (hours) ❑ Runoff Predev Predev Type 1124-hr 10-YR Rainfall=5.50" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 8 Summary for Subcatchment 2S: DA 1 (Offsite) Runoff = 1.24 cfs @ 12.12 hrs, Volume= 0.097 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfall=5.50" Area (ac) CN Description 0.680 55 Woods, Good, HSG B 0.120 98 Unconnected pavement, HSG B 0.800 61 Weighted Average, UI Adjusted CN = 58 0.680 85.00% Pervious Area 0.120 15.00% Impervious Area 0.120 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (f /sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 1 (Offsite) Hydrograph 1.24 cfs :Type I� 24-6H06Yk R'ai nfal1-5.'50 Rtrnbff Areh=0.800 ad rkOn6ff Vpltpm64.p97 elf kunoff'Depth41.4L5"' Td=18.1 tnih UN Adjpsl CAN=50 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Predev Predev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 9 Summary for Link X: POA 1 Inflow Area = 2.440 ac, 9.02% Impervious, Inflow Depth = 1.40" for 10-YR event Inflow = 3.62 cfs @ 12.12 hrs, Volume= 0.286 of Primary = 3.62 cfs @ 12.12 hrs, Volume= 0.286 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link X: POA 1 Hydrograph 4 3 f 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) ❑ Inflow ❑ Primary Predev Predev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 10 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite) Runoff Area=1.640 ac 6.10% Impervious Runoff Depth=3.74" Tc=18.1 min UI Adjusted CN=57 Runoff=7.11 cfs 0.511 of Subcatchment2S: DA 1 (Offsite) Runoff Area=0.800 ac 15.00% Impervious Runoff Depth=3.86" Tc=18.1 min UI Adjusted CN=58 Runoff=3.59 cfs 0.258 of Link 3L: POA 1 Inflow=10.70 cfs 0.769 of Primary=10.70 cfs 0.769 of Total Runoff Area = 2.440 ac Runoff Volume = 0.769 of Average Runoff Depth = 3.78" 90.98% Pervious = 2.220 ac 9.02% Impervious = 0.220 ac Predev Predev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 11 Summary for Subcatchment 1S: DA 1 (Onsite) Runoff = 7.11 cfs @ 12.11 hrs, Volume= 0.511 af, Depth= 3.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 1.460 55 Woods, Good, HSG B 0.080 61 >75% Grass cover, Good, HSG B 0.100 98 Unconnected pavement, HSG B 1.640 58 Weighted Average, UI Adjusted CN = 57 1.540 93.90% Pervious Area 0.100 6.10% Impervious Area 0.100 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 1S: DA 1 (Onsite) Hydrograph ■Runoff 7.11 cfs Type,Il 241hr,100-6Yk s Ra1nfaHx9:041-' Runoff'Are�=1.640 at 5 KOngt(Vg1Lim6=;0.$1a,1 elf RunoffMepthw&.174, LL iL T6=18.1l ih 3 U1 A,dllisted CAN=57 Time (hours) Predev Predev Type 1124-hr 100-YR Rainfall=9.01" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 12 Summary for Subcatchment 2S: DA 1 (Offsite) Runoff = 3.59 cfs @ 12.11 hrs, Volume= 0.258 af, Depth= 3.86" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 0.680 55 Woods, Good, HSG B 0.120 98 Unconnected pavement, HSG B 0.800 61 Weighted Average, UI Adjusted CN = 58 0.680 85.00% Pervious Area 0.120 15.00% Impervious Area 0.120 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (f /sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 1 (Offsite) Hydrograph ------- -- -- -- --------- -- -- -- --------- -- -- ----------- 4 I 1 1 I 1 I I I I I I I 1 I I 1 3.59 cjs I I 1 1 ■ Runolf 1 Type'1ll 24.6 pOtYF� 1 1 1 1 I1r --'�--I--,--,--7 --F--�-,--,--,--T--�--�--� --1--,-Rain#aAT9.041 - 3 1 1 1 1 1 1 1 1 1 1 1 1 RUnbff Ares=0.800 alp 1 1 1 1 1 1 �4n44� VPI�#me=0.250 elf J1ttneff l:pti�3:88�' 2, Td=18.1 tnih LL UN A1d1NSteo CAN=5$ 1 1 I I I 1 1 1 I I I 1 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I i I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Predev Predev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 13 Summary for Link X: POA 1 Inflow Area = 2.440 ac, 9.02% Impervious, Inflow Depth = 3.78" for 100-YR event Inflow = 10.70 cfs @ 12.11 hrs, Volume= 0.769 of Primary = 10.70 cfs @ 12.11 hrs, Volume= 0.769 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link X: POA 1 Hydrograph I ■ I Inflow _______-__ _r__r_ Primary Inflow Area=2.440'ac- I I I I I I I -4 -f -I -Y -Y _M1 F -♦ F -h F I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I _l__r__r _I _, _T _r _I _, _7 _r I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Berkmar Flats Time of Concentration Calculations - Predev 100 ft overland flow 2.0% slope 0.35 C-value 13.2 min Seelye Chart 402 ft s. c. flow 11.2% slope 1.7 fps velocity 3.9 min. NEH Figure 15-4 70 ft swale 4 ft height 1.0 min. Kirpich Chart 18.1 min. 35 30 Paved V a z 25 c .e 300 ct Bare r W 0 20 N 200 Sal . Poor W \ Grass s ,,Surface,,Surfacei z Z Average i- ] 0.5 1e) Grass u � L0 0 15 90 \ / 80 Dense Gross.t \ a z 0 70 \ 5.0 m a 60 / 10 W cc 50 20 a (Z N U 40 10 0 30 9 W J B 20 7 l0 6 OVERLAND FLOW TIME (Seelye Chan) Source: Data Buok for Civil Engineers. E.E. Seelye Plate 5-1 1992 TRAVEL TIME FOR CHANNEL FLOW (Kirpich Chart) N (feet) 500 Tt (min.) 200 00 100 L (f"t) I000a txe 50 p)e - 50 75000 x0ve: (1) For Dee xith nat.l ehenrei, Zi lU (2) For {axed channels, mlti Ply d 1000 n to Tt by 0.2 9 g s s00 5 rim 1 I TIME OF CONCENTRATION OF SMALL DRAINAGE BASINS Source: VDOT V-13 Plate 5-3 Post -Development Stormwater Management Calculations: Post -Development Drainage Area Map Post -Development HydroCAD Analysis Energy Balance Equation Summary LD-204 Stormwater Inlet Computations LD-229 Storm Drain Design Computations LD-268 Ditch Design Outlet Protection Calculations BERKMAR FATS POSTDEV DRAINAGE AREA MAP DRAINAGE AREA 1: r .. TOTAL AREA = 2.87 AC an HSG TYPE B L / ` m �„ —��� � - \ _ _ ONSITE — 2.07 AC I—___` IMPERVIOUS = 0_85 AC %�--- — \\\\\\ I I , ✓ -- MANAGED TURF = 1.22 AC WOODS = 0.00 AC TIME OF CONCENTRATION DRAINAGE AREA \��I_ �/ \\ (ASSUMED) = 5.0 MINUTES OFFSITE = 0.80 IMPERVIOUS = 0.12 AC _ \ MANAGED TURF = 0.00 AC WOODS = 0.68 AC TIME OF CONCENTRATION = 18.1 MINUTES - `°\�;..�°�n NOTE: POA 1 IS 1 — \ LOCATED IN THE �. MANMADE SWALE a� /``°� / II I I / \ \ \ JUST BEFORE AN /�° ab C k•r/ l \� �� / / ' / </y/ / / / / EXISTING 18„ _ _ CULVERT. OD/ J \ \ � ,r nil �• \ \ \ tm LOD oD A� HE 111.1�� \mow I = 50 C \ \ \ \ \ \ \ a,s�E �� .< � \ � \,,� > .,� � ,m•m"" i Scale: 1 "=50' 50 DA 1 1S (Onsite, eate Del POA 1 S4 Reach X 4on Llnk D5S 1 (Offsite, ntreated) Postdev Postdev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 2 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite, Treated) Runoff Area=1.890 ac 44.97% Impervious Runoff Depth=1.14" Tc=5.0 min CN=78 Runoff=3.97 cfs 0.179 of Subcatchment2S: DA 1 (Offsite, Treated) Runoff Area=0.250 ac 24.00% Impervious Runoff Depth=0.34" Tc=18.1 min UI Adjusted CN=60 Runoff=0.06 cfs 0.007 of Pond 3P: Detention Pond Peak Elev=518.80' Storage=5,187 cf Inflow=3.97 cfs 0.186 of Outflow=0.08 cfs 0.132 of Subcatchment4S: DA 1 (Onsite, Untreated) Runoff Area=0.180 ac 0.00% Impervious Runoff Depth=0.37" Tc=5.0 min CN=61 Runoff=0.09 cfs 0.006 of Subcatchment5S: DA 1 (Offsite, Untreated) Runoff Area=0.550 ac 10.91% Impervious Runoff Depth=0.25" Tc=18.1 min UI Adjusted CN=57 Runoff=0.07 cfs 0.011 of Link 6L: POA 1 Inflow=0.14 cfs 0.149 of Primary=0.14 cfs 0.149 of Total Runoff Area = 2.870 ac Runoff Volume = 0.203 of Average Runoff Depth = 0.85" 66.20% Pervious = 1.900 ac 33.80% Impervious = 0.970 ac Postdev Postdev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 3 Summary for Subcatchment 1S: DA 1 (Onsite, Treated) Runoff = 3.97 cfs @ 11.97 hrs, Volume= 0.179 af, Depth= 1.14" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 0.850 98 Paved parking, HSG B 1.040 61 >75% Grass cover, Good, HSG B 1.890 78 Weighted Average 1.040 55.03% Pervious Area 0.850 44.97% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 3- Subcatchment 1S: DA 1 (Onsite, Treated) Hydrograph Type II 24-hr 1-Yk Rainfall=3.01" Runoff Area=1.890 ad Runoff Vplume=0.179 of Runoff Depth=1.14" Tc=5.0 milk CN=78 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) ❑ Runaff Postdev Postdev Type // 24-hr 1-YR Rainfall=3.01" Prepared by (enter your company name here) Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Pane 4 Summary for Subcatchment 2S: DA 7 (Offsite, Treated) Runoff = 0.06 cfs @ 12.17 hrs, Volume= 0.007 af, Depth= 0.34" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.060 98 Unconnected pavement, HSG B 0.250 65 Weighted Average, UI Adjusted CN = 60 0.190 76.00% Pervious Area 0.060 24.00% Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 7 (Offsite, Treated) Hydrograph 1--J--1--LL---J--1--L--1----J--LL------,--1L---J--1--1-- ■Runoff 0.05 0.06 cL 0.055 Type II 24 hr;1 YP.-------J--'---------�--- 1� ICIIA005 I Reinfa ll=;3.01'� 1---------- ---------------------------------0.045 1 __.q aoI I I I I 1 1 I 10.0< T _I _1 _y,@ 0.035beptl�t:0.34�t -I -I -y0.03 , 1 1 1 1 LL4 _I _I _�0.0251 002;- ;--L -,11AO1pste4ON=64- 1 1 L L__I__ I__J0.0151 1 1 I1 1 1 I1 1 1 1 1 1 1 1 1 1 0.01 1 1 1 1 1 1 1 1 1 1 1 I I 1 1 1 I 1 1 I I I 1 1 1 I 1 1 0.005 y 10 Postdev Postdev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 5 Summary for Pond 3P: Detention Pond Inflow Area = 2.140 ac, 42.52% Impervious, Inflow Depth = 1.04" for 1-YR event Inflow = 3.97 cfs @ 11.97 hrs, Volume= 0.186 of Outflow = 0.08 cfs @ 17.16 hrs, Volume= 0.132 af, Atten= 98%, Lag= 311.4 min Primary = 0.08 cfs @ 17.16 hrs, Volume= 0.132 of Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs / 2 Peak Elev= 518.80' @ 17.16 hrs Surf.Area= 0 sf Storage= 5,187 cf Plug -Flow detention time= 641.9 min calculated for 0.132 of (71 % of inflow) Center -of -Mass det. time= 533.9 min ( 1,385.6 - 851.8 ) Volume Invert Avail.Storage Storage Description #1 517.49' 20,850 cf Custom Stage Data Listed below Elevation Inc.Store Cum.Store (feet) (cubic -feet) (cubic -feet) 517.49 0 0 517.50 15 15 518.00 1,819 1,834 520.00 8,358 10,192 522.00 10,658 20,850 Device Routing Invert Outlet Devices #1 Primary 517.00' 15.0" Round Culvert L= 27.5' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 517.00' / 514.75' S= 0.0818 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior #2 Device 1 520.50' 36.0" Horiz. Standpipe C= 0.600 Limited to weir flow at low heads #3 Device 1 518.08' 2.0" Vert. Orifice/Grate C= 0.600 #4 Device 1 519.33' 4.0" Vert. Orifice/Grate C= 0.600 #5 Primary 521.00' 10.0' long x 15.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Primary OutFlow Max=0.08 cfs @ 17.16 hrs HW=518.80' (Free Discharge) 1=Culvert (Passes 0.08 cfs of 5.06 cfs potential flow) 2=Standpipe ( Controls 0.00 cfs) 3=Orifice/Grate (Orifice Controls 0.08 cfs @ 3.85 fps) =Orifice/Grate ( Controls 0.00 cfs) S=Broad-Crested Rectangular Weir( Controls 0.00 cfs) Postdev Prepared W Postdev Type // 24-hr 1-YR Rainfall=3.01" by {enter your company name here} Printed 3/23/2023 D 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Page 6 Pond 3P: Detention Pond Hydrograph 3.9 7 C ■ Inflow - fS i--i--i- i ■Primary I'r1f OW ;Area=2 140 :at Poa;k rIOV=818.8Q,' Storage:5y187, cf JO.08fs o 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Time (hours) Pond 3P: Detention Pond Stage -Discharge Discharge (cfs) 40 42 44 46 48 ❑ Primary Postdev Postdev Type // 24-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here} Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Paoe 7 a Pond 3P: Detention Pond Stage -Area -Storage storage (cubic -feet) ❑ Storage Postdev Postdev Type // 24-hr 1-YR Rainfall=3.01" Prepared by (enter your company name here) Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Pane 8 Summary for Subcatchment 4S: DA 7 (Onsite, Untreated) Runoff = 0.09 cfs @ 11.99 hrs, Volume= 0.006 af, Depth= 0.37" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.180 61 >75% Grass cover, Good, HSG B 0.180 61 Weighted Average 0.180 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (f /ft) (f /sec) (cfs) 5.0 Direct Entry, Subcatchment 4S: DA 7 (Onsite, Untreated) Hydrograph I I I I I I I I I 1 01 -----1--, 0-_ -,-- - I- - - 9cS-_ 0.095 ------- _ ._0 ------ __ 0.09 - -_y -_-__111I 0.08$ R- Il __1LI _ 0.06 n�4fa-hlLzrL 3�yaLYf LLe - QA75 -- - -------�t_ign_OrfAea_=0.-'-fr8-.0-rr_-a- d_-_- O.OT 1 __,__,__r__ VpIt#me=O00$-i0.065 0.06 - r--r-- -- -I Dept"0477 g.055 ' r__r__I__I_n 3 0.05 LL 0.045 -----I---- -- 1 I --1---1----�--- 1 1 --I---- -- --I-----I-- -- -------I- , Tc=C :Mlh --1---1------L--1---1--------1---1-- a-U 1 1 1 1 1 1 1 1 0.04 ' --1---1--I--I--- I1� --1---1--I--I--L--I---1--I--=--I--I---1-- �----C`N�G7- 0.035 1 __L_J__J__1__. 1 1 1 1 i __I__J__1__1__L__L__I__J__1__L__L__I__J__J__ LI__ 0.03 -I 1 0.025 -I 1 0.02 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 0.015 / 1 1 1 __r_y__y__,__. 1 1 1 1 1 1 1 1 1 1 1 0.01 ' 1 1 --r--r-r--r--r 1 1 1 1 1 1 I 1 1 1 1 1 1 1 ---r__r--r-r-----r--r--r--1-----r--r--r- 22 24 26 28 30 32 34 36 38 40 42 44 46 Time (hove) ■ Runoff Postdev Postdev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 9 Summary for Subcatchment 5S: DA 1 (Offsite, Untreated) Runoff = 0.07 cfs @ 12.19 hrs, Volume= 0.011 af, Depth= 0.25" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 1-YR Rainfall=3.01" Area (ac) CN Description 0.060 98 Unconnected pavement, HSG B 0.490 55 Woods, Good, HSG B 0.550 60 Weighted Average, UI Adjusted CN = 57 0.490 89.09% Pervious Area 0.060 10.91 % Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 5S: DA 1 (Offsite, Untreated) 0.07 I 0.07 0.065 0.06 I I I I I 0.055 I I I I I 0.05 i i i I I 0.045 0.04 __I--J--1--L-- c 0.035 0.03 - -- ------ 0.025 -I -y _{ -} 0.02 0.015 I I I I I 0.01 I Hydrograph _li __'r __'i __�__ �I__'r __'r __� __i__11__li __'r __�___i__li __'r __ ■Runoff Type II �4 hll 1iYO- RainfaIM3.01--------------------- "r-- I I I I I I I I I I I I I I I I I I I I I I -- --; --Runoff Ate -0.550 at - til Volulme=10.01 I of I I I I I ------- ,--L_Runoffbe ft:425!!'__ III A/� N IyR I I I I I I I T�y�. r �i.• I I I I I I I I I I I I I UtjA01"s#eo GN5? I I I I I I I I I I I I I I I I -T -T I I l -T -r I I l -T -r -I -1 -1 -T 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Postdev Postdev Type 1124-hr 1-YR Rainfall=3.01" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 10 Summary for Link 6L: POA 1 Inflow Area = 2.870 ac, 33.80% Impervious, Inflow Depth > 0.62" for 1-YR event Inflow = 0.14 cfs @ 12.20 hrs, Volume= 0.149 of Primary = 0.14 cfs @ 12.20 hrs, Volume= 0.149 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link 6L: POA 1 Hydrograph ■ Inflw _ J_LLJ__ 1_LJJ_L__LJJ_LJJI . Primary y 0.15 0.14 I I I I I I I cfs IeI I --I ,` --TII -,II --,II --IrI -I f 0.14 nI -ry ra1, VAO ' ------*--~- F--------L-J----F----J----~----J--F----J-- 0.13 I I I I I I I I I I I I I I I I I I I I I 0.12. / I I I I I I I I I I I I I I I I I I I 0A -I -4 -♦ F I I I I -4 _♦ -F-Y -i -F -I -4 -4 -F -I -4 -F -I -4 I I I I I I I I I I I I I I 01 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0,06 / I I I I I I I I I I I I I I I I I / - I-_ I__I I __I___I__ I I I__ I__ I __I __I__ I__I __I _ I__ 0 007 I I I I I I I I I I I I I I LL , I I I I I I I I I I I I I I I I 0.06 / / -I -4 -t -F I I I I -h -I -y -t -F I -y -♦ -F -I -Y -h -I -y I I I I I I I I I I I I I 0.05 / / I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.04 1 L__JI __L1 __ _JI L1 _ 11 _ LI 0.03 , I I I 1 1 11 I 1 0.02 --r 1 ----r 11 --r--r-,--r--r-,- ----r--r-,-_ I 1 1 I 1 1 1 II I 22 24 26 28 30 32 34 36 38 40 42 44 Time (horns) Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 11 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite, Treated) Runoff Area=1.890 ac 44.97% Impervious Runoff Depth=3.14" Tc=5.0 min CN=78 Runoff=10.80 cfs 0.495 of Subcatchment2S: DA 1 (Offsite, Treated) Runoff Area=0.250 ac 24.00% Impervious Runoff Depth=1.60" Tc=18.1 min UI Adjusted CN=60 Runoff=0.44 cfs 0.033 of Pond 3P: Detention Pond Peak Elev=520.50' Storage=12,843 cf Inflow=11.00 cfs 0.528 of Outflow=0.58 cfs 0.471 of Subcatchment4S: DA 1 (Onsite, Untreated) Runoff Area=0.180 ac 0.00% Impervious Runoff Depth=1.68" Tc=5.0 min CN=61 Runoff=0.55 cfs 0.025 of Subcatchment5S: DA 1 (Offsite, Untreated) Runoff Area=0.550 ac 10.91% Impervious Runoff Depth=1.38" Tc=18.1 min UI Adjusted CN=57 Runoff=0.80 cfs 0.063 of Link 6L: POA 1 Inflow=1.41 cfs 0.559 of Primary=1.41 cfs 0.559 of Total Runoff Area = 2.870 ac Runoff Volume = 0.617 of Average Runoff Depth = 2.58" 66.20% Pervious = 1.900 ac 33.80% Impervious = 0.970 ac Postdev Postdev Type 1124-hr 10-YR Rainfall=5.50" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 12 Summary for Subcatchment 1S: DA 1 (Onsite, Treated) Runoff = 10.80 cfs @ 11.96 hrs, Volume= 0.495 af, Depth= 3.14" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfa11=5.50" Area lac) CN Descriotion 0.850 98 Paved parking, HSG B 1.040 61 >75% Grass cover, Good, HSG B 1.890 78 Weighted Average 1.040 55.03% Pervious Area 0.850 44.97% Impervious Area Tc Length 5.0 12 11 I I I I I I I I I I 10 ----------- I I I I 9 I I I I I I I I I I I I 7 I I I I 6- 4- 3- 2 I I I I I I I I I I I I I I Description Direct Entry, Subcatchment 1S: DA 1 (Onsite, Treated) I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ---- Tpe-0-24-hr 1-0.6 I I I I I I I I I I I ........ Ip I ,,�yl��pl /� I�,^/I�_ I IAI I; I I I I I I I I I I I I I I I/�I y J R n ILV�It' ne=A. 9 r rino# I'IDeptF>-r& 114"' --I I ' --' ----Tc*3:,0-lnitr- I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I iyl I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I -r -r -I -I -y -y -y _} _♦ -r -I -I -y -y _{ _} -r I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1A I I I I 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 Time (hours) ■ Runoff Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 13 Summary for Subcatchment 2S: DA 1 (Offsite, Treated) Runoff = 0.44 cfs @ 12.12 hrs, Volume= 0.033 af, Depth= 1.60" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfall=5.50" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.060 98 Unconnected pavement, HSG B 0.250 65 Weighted Average, UI Adjusted CN = 60 0.190 76.00% Pervious Area 0.060 24.00% Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 1 (Offsite, Treated) -r-r-r 0.48 0.46 --I--r--r-0.44 0.44 ------JI-----` 0.42 - - -- 'I--�--+--r 04 0.38 0.36 --r-�--�--T--r 0.34 -_L_J__J__1__L 0.32 --r-�--�--+--r 0.3 0.28 � �. 0.2fi --r-,--T--T--r 0.24 0.22 6 LL 0.2 0.16 --- ---'--' T - 0.14 --J--,--1--' 0.12 '-1 -I -T -T 0.1 J J 0.08 0.06 - - - - Hydrograph I I 5 --r--r--T--r--I-__I--T--T--T--r--I---I--T--T--r-- I-- --t-------II-- - P-Llf24-6r-J D� ye I I I I I I I I I I I I I I I I l,� Joe 0_25aad- _ _ ----T--T----r-,--,-- noff Depth -- -601- I1__L__I__ -T r I�=18.Tr1��-MIth --I-- -- -- --; --III---III---- ;Mp►d1ps*e$-q�� T r T T--i--r - -I T T 7 -r _-I--J--1--1--L--L--I--1--1--1--L--I--J--1--1--L--L- I I 1 __I__r__T__r__r__I--- I__T__r__r__r__I___i__T__r__r__I- -------------- I_I _- _T _r _r _I _y _T _T _r _I I I I 1 I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) ■ Runoff Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 14 Summary for Pond 3P: Detention Pond Inflow Area = 2.140 ac, 42.52% Impervious, Inflow Depth = 2.96" for 10-YR event Inflow = 11.00 cfs @ 11.96 hrs, Volume= 0.528 of Outflow = 0.58 cfs @ 13.06 hrs, Volume= 0.471 af, Atten= 95%, Lag= 65.7 min Primary = 0.58 cfs @ 13.06 hrs, Volume= 0.471 of Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs / 2 Peak Elev= 520.50' @ 13.06 hrs Surf.Area= 0 sf Storage= 12,843 cf Plug -Flow detention time= 459.4 min calculated for 0.471 of (89% of inflow) Center -of -Mass det. time= 404.9 min ( 1,227.4 - 822.5 ) Volume Invert Avail.Storage Storage Description #1 517.49' 20,850 cf Custom Stage Data Listed below Elevation Inc.Store Cum.Store (feet) (cubic -feet) (cubic -feet) 517.49 0 0 517.50 15 15 518.00 1,819 1,834 520.00 8,358 10,192 522.00 10,658 20,850 Device Routing Invert Outlet Devices #1 Primary 517.00' 15.0" Round Culvert L= 27.5' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 517.00' / 514.75' S= 0.0818 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior #2 Device 1 520.50' 36.0" Horiz. Standpipe C= 0.600 Limited to weir flow at low heads #3 Device 1 518.08' 2.0" Vert. Orifice/Grate C= 0.600 #4 Device 1 519.33' 4.0" Vert. Orifice/Grate C= 0.600 #5 Primary 521.00' 10.0' long x 15.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Primary OutFlow Max=0.58 cfs @ 13.06 hrs HW=520.50' (Free Discharge) 1=Culvert (Passes 0.58 cfs of 7.91 cfs potential flow) 2=Standpipe ( Controls 0.00 cfs) 3=Orifice/Grate (Orifice Controls 0.16 cfs @ 7.36 fps) =Orifice/Grate (Orifice Controls 0.42 cfs @ 4.82 fps) S=Broad-Crested Rectangular Weir( Controls 0.00 cfs) Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.501r Prepared by {enter your company name here} Printed 3/23/2023 HydroCAD® 9.10 s/n 07054 ©2010 HydroCAD Software Solutions LLC Page 15 Pond 3P: Detention Pond Hydrograph --I--1--7r--II --.-- �I--T--I---1--rr--� -1--TrI--I--17rrI--I-- ■Inow I 1_T_T_11C-1- - T-r7-1r1-- ■Primar y12„ 1lnflaw!Are0_0121:140-,a4- _ _ } IIIIIII g Cf I I I ' 3+IrII II _, -+-+-:StI oIII 84rIII 2T'III gIrIII T{YyIII , -T -r ----1 --- V I I I I I I I I, 3 6 " __I__y__T__r__I__T__T__y__y__T__r__I__y__T__r__I__y__,__r__r_y__ p " I I I I I I I I I I I I I I I I I I I I I I LL i -4 -+ I I I I I I I I I I I I I I I I I I I I I I 4- " " y -4 -i -r -I -y -+ -F -I -y -i -h -F -I I I I I I I I I I I I I I I I I I I I I I I 3 " I I I I I I I I I I I I I I I I I I I I I I I I I I I i 1 I I I I I I I I I I I I I I 21 " I 0.58 cfs W 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (hours) Pond 3P: Detention Pond Stage -Discharge Discharge (cfs) ❑ Primary Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 16 a Pond 3P: Detention Pond Stage -Area -Storage storage (cubic -feet) ❑ Storage Postdev Postdev Type 1124-hr 10-YR Rainfall=5.50" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 17 Summary for Subcatchment 4S: DA 7 (Onsite, Untreated) Runoff = 0.55 cfs @ 11.97 hrs, Volume= 0.025 af, Depth= 1.68" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfall=5.50" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.180 61 >75% Grass cover, Good, HSG B 0.180 61 Weighted Average 0.180 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (f /ft) (f /sec) (cfs) 5.0 Direct Entry, Subcatchment 4S: DA 7 (Onsite, Untreated) Hydrograph 1 1 1 0.8 -- -"IT 1-- -- -- ---------1--+-- --1-----II-- -- -- --I-- 0.55I 1 1 � � � II II _ � IT��� 1111.2#-h_r_j OiYk 0.5 IL��MiA11T� I rlr]I_a`L 1 1 rt u r lJ11 {. V- I I I I I I I I I I I I I I I I I I I I 0.4 I 1 1 I PIOOff -,VQ[[qMRFLO-02$-per .@ 0.35 noff :iDep�� po�r- v C Iy� .Iy.� yI 0 0.3 1 y 1i 1i 1 -rIC-=*JD A+ ih- LL 1 1 1 0.25 � I 1 I I I I I 1 1 1 I I 1 1 1 i� I 1 �1 1 1 1 1 1 1 1 1 1 0.2 1 1 I I 1 1 1 I I 1 1 I 1 1 I I I 1 1 1 1 1 1 1 1 1 1 1 0.15 I 1 1 1 1 1 I I I 1 1 I I 1 1 I 1 1 I I 1 0.1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 0 05 1 1 1 1 1 1 1 1 1 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (hove) ■ Runoff Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 18 Summary for Subcatchment 5S: DA 1 (Offsite, Untreated) Runoff = 0.80 cfs @ 12.13 hrs, Volume= 0.063 af, Depth= 1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 10-YR Rainfall=5.50" Area (ac) CN Description 0.060 98 Unconnected pavement, HSG B 0.490 55 Woods, Good, HSG B 0.550 60 Weighted Average, UI Adjusted CN = 57 0.490 89.09% Pervious Area 0.060 10.91 % Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 5S: DA 1 (Offsite, Untreated) I I I 0.85 D.80 08 0.75 _J 0.7 0.65 0.6 0.55 0.5 ... 0.45 3 --r-J--�-- 0 0.4 LL 0.35 0.3 ' __- _ -I 0.25 0'2 J _I _J _1 _L 0.15 --r-J----L--� 0.1 I I I I n ns Hydrograph I I I I 7--r--r--r- �__Y__i__i__iI__i__ T__ r__I__ I I I ITYl, Y�_J__1__1__L__L_ RainfaI145.5Q"r_L_J__J__�__1__L__L__ I_ I I I I I I I I I I I I I I I I I --,__;-_;-_;__I, __II--R-tee-&.550Fat- I I I I I I I I I I I I I I I I IkunofFllDeptlr1.38�' __=__L__1__L_J14��p_'IJJItL_ I I I I I I I I I I I I I I I I I I I I I I I I I I I I-�--1--r-r--r--r-�--r I - I - I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I _ - J--1--L--L--I---I--1--L--L--L --I---I--1--L--L--I-- I I I I I I I I I I I I I I I I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) ■ Runoff Postdev Postdev Type/1 24-hr 10-YR Rainfall=5.50" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 19 Summary for Link 6L: POA 1 Inflow Area = 2.870 ac, 33.80% Impervious, Inflow Depth > 2.34" for 10-YR event Inflow = 1.41 cfs @ 12.11 hrs, Volume= 0.559 of Primary = 1.41 cfs @ 12.11 hrs, Volume= 0.559 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link 6L: POA 1 Hydrograph ■ Inflow 0 Primary 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 20 Time span=0.00-48.00 hrs, dt=0.03 hrs, 1601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1 S: DA 1 (Onsite, Treated) Runoff Area=1.890 ac 44.97% Impervious Runoff Depth=6.33" Tc=5.0 min CN=78 Runoff=21.03 cfs 0.997 of Subcatchment2S: DA 1 (Offsite, Treated) Runoff Area=0.250 ac 24.00% Impervious Runoff Depth=4.11" Tc=18.1 min UI Adjusted CN=60 Runoff=1.20 cfs 0.086 of Pond 3P: Detention Pond Peak Elev=521.38' Storage=17,538 cf Inflow=21.67 cfs 1.083 of Outflow=15.32 cfs 1.024 of Subcatchment4S: DA 1 (Onsite, Untreated) Runoff Area=0.180 ac 0.00% Impervious Runoff Depth=4.23" Tc=5.0 min CN=61 Runoff=1.41 cfs 0.063 of Subcatchment5S: DA 1 (Offsite, Untreated) Runoff Area=0.550 ac 10.91% Impervious Runoff Depth=3.74" Tc=18.1 min UI Adjusted CN=57 Runoff=2.38 cfs 0.171 of Link 6L: POA 1 Inflow=18.17 cfs 1.259 of Primary=18.17 cfs 1.259 of Total Runoff Area = 2.870 ac Runoff Volume = 1.318 of Average Runoff Depth = 5.51" 66.20% Pervious = 1.900 ac 33.80% Impervious = 0.970 ac Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 21 Summary for Subcatchment IS: DA 7 (Onsite, Treated) Runoff = 21.03 cfs @ 11.96 hrs, Volume= 0.997 af, Depth= 6.33" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 0.850 98 Paved parking, HSG B 1.040 61 >75% Grass cover, Good, HSG B 1.890 78 Weighted Average 1.040 55.03% Pervious Area 0.850 44.97% Impervious Area Tc Length Description 5.0 Direct Entry, Subcatchment 1S: DA 1 (Onsite, Treated) - 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) ■ Runoff Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by (enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 22 Summary for Subcatchment 2S: DA 7 (Offsite, Treated) Runoff = 1.20 cfs @ 12.11 hrs, Volume= 0.086 af, Depth= 4.11" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 0.190 55 Woods, Good, HSG B 0.060 98 Unconnected pavement, HSG B 0.250 65 Weighted Average, UI Adjusted CN = 60 0.190 76.00% Pervious Area 0.060 24.00% Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 2S: DA 7 (Offsite, Treated) Hydrograph I i i � I I I I i i i I I I i � i I I ■Runoff 1.20 cfs type IIIII 24-6hi,,100tYk I.rr --'�--�--,--,--7 --�--�-,--,--,--T--�--�--� --�--,-Rain#aAT9.041 - RtlinbfflAres=0. ,50 ad rk4n6f(VP1L#me=0.p8$ elf kunoff l'DepthT4.I1 go I I I I Td=18.1 tinih I I UN AIId1NSl CAN=60 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD@ 9.10 s/n 07054 @ 2010 HvdroCAD Software Solutions LLC Paae 23 Summary for Pond 3P: Detention Pond Inflow Area = 2.140 ac, 42.52% Impervious, Inflow Depth = 6.07" for 100-YR event Inflow = 21.67 cfs @ 11.96 hrs, Volume= 1.083 of Outflow = 15.32 cfs @ 12.02 hrs, Volume= 1.024 af, Atten= 29%, Lag= 3.8 min Primary = 15.32 cfs @ 12.02 hrs, Volume= 1.024 of Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs / 2 Peak Elev= 521.38' @ 12.02 hrs Surf.Area= 0 sf Storage= 17,538 cf Plug -Flow detention time= 255.7 min calculated for 1.024 of (95% of inflow) Center -of -Mass det. time= 225.7 min ( 1,028.5 - 802.8 ) Volume Invert Avail.Storage Storage Description #1 517.49' 20,850 cf Custom Stage Data Listed below Elevation Inc.Store Cum.Store (feet) (cubic -feet) (cubic -feet) 517.49 0 0 517.50 15 15 518.00 1,819 1,834 520.00 8,358 10,192 522.00 10,658 20,850 Device Routing Invert Outlet Devices #1 Primary 517.00' 15.0" Round Culvert L= 27.5' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 517.00' / 514.75' S= 0.0818 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior #2 Device 1 520.50' 36.0" Horiz. Standpipe C= 0.600 Limited to weir flow at low heads #3 Device 1 518.08' 2.0" Vert. Orifice/Grate C= 0.600 #4 Device 1 519.33' 4.0" Vert. Orifice/Grate C= 0.600 #5 Primary 521.00' 10.0' long x 15.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Primary OutFlow Max=15.11 cfs @ 12.02 hrs HW=521.37' (Free Discharge) 1=Culvert (Inlet Controls 9.03 cfs @ 7.36 fps) 2=Standpipe (Passes < 25.03 cfs potential flow) 3=Orifice/Grate (Passes < 0.19 cfs potential flow) =Orifice/Grate (Passes < 0.58 cfs potential flow) S=Broad-Crested Rectangular Weir(Weir Controls 6.08 cfs @ 1.64 fps) Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01 rr Prepared by {enter your company name here} Printed 3/23/2023 Pond 3P: Detention Pond ------------------------------- — ------------- I I I _r__,__ 24 21.67 cfs L L 23 ' - -;-- ;__'__=__�_ -_==r-22 =-,-- ;-- r= iwA�14Q1;noeaa= 21 -T -Y -I -7 -T -Y_ -I_--Y___ 20 __1__L__I_ __ J__ L__L_ J__ J__ L__ L__I Il_ He 18 IV10 n '-', raf �VV'�tl= --I--y-- 15.32 cfs16 I I I I I I I I I I I I I I I I I I I 15 14 , ,' _ 13 12 3 ,' r__r_ __1__7 1__7__r__-_I__r__r__I__I__7__r__r__I__ 10 � , I __I__l__T__r_ I __l__r__I _1__l__T__r__I _1__T__r__I__1__1__r__r__I__ g__1__L__L_J__ i I I I , , -I -y -T -r "1 -T -I --I -y -T -r -I -1 -t -r -I --I -T -r -r -I 7 I I I I I I I I I I I I I I I I I I I I I 8 5 __I__I__I__I_ III II__ - _I__I__I___I__I__I __I___I___I__I__I___I I I I I 4 i -I -y -Y -h -+ _h -I -Y -y -♦ -F -I I I _� -T -h -F -I W 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (hours) Pond 3P: Detention Pond Stage -Discharge Discharge (cfs) ■ Inflow ■ Primary ❑ Primary Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01 rr Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 25 a Pond 3P: Detention Pond Stage -Area -Storage storage (cubic -feet) ❑ Storage Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 26 Summary for Subcatchment 4S: DA 1 (Onsite, Untreated) Runoff = 1.41 cfs @ 11.96 hrs, Volume= 0.063 af, Depth= 4.23" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 0.000 98 Paved parking, HSG B 0.180 61 >75% Grass cover, Good, HSG B 0.180 61 Weighted Average 0.180 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 4S: DA 1 (Onsite, Untreated) Hydrograph ❑ Runoff 1.41 cfs Type II 24-hr 100-YR Rainfall=9.01" Runoff Area=0.180 ac Runoff Volume=0.063 of Runoff Depth=4.23" Tc=5.0 milk CN=6;1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (hours) Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here) Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 27 Summary for Subcatchment 5S: DA 1 (Offsite, Untreated) Runoff = 2.38 cfs @ 12.11 hrs, Volume= 0.171 af, Depth= 3.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Type II 24-hr 100-YR Rainfall=9.01" Area (ac) CN Description 0.060 98 Unconnected pavement, HSG B 0.490 55 Woods, Good, HSG B 0.550 60 Weighted Average, UI Adjusted CN = 57 0.490 89.09% Pervious Area 0.060 10.91 % Impervious Area 0.060 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.1 Direct Entry, Subcatchment 5S: DA 1 (Offsite, Untreated) Hydrograph 2.38 cfs ❑ Runo Type II 24-hr 100-YR Rainfall=9.01" 2 Runoff Area=0.550 ac Runoff Volume=0.171 of Runoff Depth=3.74" LL Tc=18.1 mitt UI Adjusted CN=57 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) Postdev Postdev Type 1124-hr 100-YR Rainfall=9.01" Prepared by {enter your company name here} Printed 3/23/2023 HvdroCAD® 9.10 s/n 07054 ©2010 HvdroCAD Software Solutions LLC Paae 28 Summary for Link 6L: POA 1 Inflow Area = 2.870 ac, 33.80% Impervious, Inflow Depth > 5.26" for 100-YR event Inflow = 18.17 cfs @ 12.02 hrs, Volume= 1.259 of Primary = 18.17 cfs @ 12.02 hrs, Volume= 1.259 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.03 hrs Link 6L: POA 1 Hydrograph —,— �----r _ --; —;--1----}--�� --��--I--T--� --I---I-- �--� --- --I-- ❑Inflw 20 ❑Primary cfs --'--'-- 18.17 --+--'--�__'__+__+_-'--�--+--+--'--�--'--+--+--'-- 19 - ---- --��I---- ;--}- 16 __I__�__r ._4- ,__ r__ r__I__,__ r__ r__r__I_. 17' 16 ' 15 ' 14 13 I I �.' 12 1 1 I __I___r__r_ r__r_�__r__r_i _I__r__r_I__r__r__r__I__ u 11 1 1 1 1 1 1 1 1 1 10 �' 1 _ I__J__1__L_ 1 1 1 1 1 1 0 9 ' 1 LL ' - 1--J--1--L- -J--`--`-J--J--L--`--I--J--1--L- I--J--1--L--`-J-- 6 i 7 i I � _I _y _T _h 6 , 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 __I__�__r__r. _�__r__r_�__�__r__r__r_�__r__r__I__�__r__r__r__I__ 5 1 I 1 I I 1 1 1 1 1 1 1 I I 1 1 I I I 1 I I I 1 1 I I I 4 ' 3 ' 1 1 1 1 1 1 2 , Time (hours) Channel Protection: Energy Balance Equation with Run-on for POA 1 Berkmar Flats 1 Yr, 24 Hr Storm Comparison Q 1post < Q 1 Pre, site ((RV t Pre, site)/(RV 1 Post, soc))(I.F.) + Q 1 Pre, oosrte ((RV 1 Pre, ooSiW)/(RV 1 Post oosite)) I.F. = 0.8 when LOD > 1 ac, I.F.=0.9 when LOD < 1 ac, I.F. = 1.0 when predev site is fully forested PreDev Site Fully Forested? = no I.F. = 0.8 Limits of Disturbance = 2.54ac Onsite Offsite Pre Dev Area Onsite = 1.64 ac Pre Dev DA Offsite = 0.80 ac Post Dev Area Onsite = 2.07 ac Post Dev DA OftSite = 0.80 ac Q t Pre, Sac = 0.20 efs Q t Pre, otrt, = 0.12 efs RV t Pre, site = 0.034 of RV t Pre, otnte = 0.018 of RV t Post, site = 0.185 of RV t Post, onite = 0.018 of Regulatory Maximum Postdev 1-yr Flow Rate Max Qtpost < 0.15 cfs Achieved Design Postdev 1-yr Flow Rate Design Qipost = 0.14 cfs Energy Balance Equation Compliance Check: Achieved Notes: 1. The assumption in the calculation above is that the site equals the land -disturbing activity (LDA). The definition for "site" is not clearly defined in the regulations, but LDAs are defined as regulated. The water quantity criteria are applied to the site as per the regulations. 2. This site discharges to an existing channel. Since postdevelopment runoff to this outfall meets the energy balance equation, Channel Protection Requirements per 9VAC25-870-66-B.3.a are met, and channel protection requirements are satisfied. Flood Protection: Peak Flow Rate to Existing Channel for POA 1 Berkmar Flats 10 Yr, 24 Hr Storm Comparison Regulatory Maximum 10-yr Flow Rate Qropm = Max QroPost = 3.62 cfs Achieved Design Postdev 10-yr Flow Rate Design Qtopost = 1.41 cfs Flood Protection Compliance Check: Achieved ' Notes: 1. This site discharges into an existing channel. The 10-yr flow rate is reduced which meets the energy balance equation and the flood protection requirements in 9VAC25-870-66.0 Berkmar Flats LD-204 Stormwater Inlet Computations Inlets on Grade Only Sag Inlets Only g E z o q d a a m ❑ E C y E 2 W ul X E = d U u r 2 d v G m o v' w 82 ¢ rc ❑ a a O (� a r� rm ❑ a O �❑ c� o 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 (ft) (sf) (ac) (in/hQ (cFs)('f) (7) (ft) (ft) (cfs) (cfs) (ft) (ft) (ft) A2 DI-3B 8 9,030 0.21 0.90 0.19 5.2 0.96 0.00 0.96 0.015 0.02 0.05 0.02 4.55 0.11 84.9% 0.82 0.15 6.2 1.15 0.00 1.15 0.015 0.02 0.05 0.02 4.86 0.12 71.0% 0.82 0.33 Al DI-3B 8 12,937 0.30 0.90 0.27 5.2 1.38 0.15 1.53 0.015 0.02 0.05 0.02 0.14 0.5 0.27067 5.948 6.2 1.65 0.33 1.99 0.015 0.02 0.05 0.02 0.15 0.5 0.29883 7.088 Berkmar Flats LD-229 Storm Drain Design Computations To Catch. Runoff Increment Accum. Total 10yr 10-yr Up Down Pipe Invert Pipe Pipe Velocity Flow time S=From . Structure Area Ccef AC AC TOG Intensity Flow Invert Invert Length Slope Diameter Capacity Inuemenl (ac) (min) (in/hr) (cfs) Elev. Elev. (R) % (in) (cfs) (Ns) (min) 1 2 3 4 5 6 T 8 9 10 11 12 13 14 15 16 17 A2 Al 0.21 0.90 0.19 0.19 5.00 6.18 1.15 542.00 535.20 165.00 4.12% 15 3.0 6.3 0." Al AO 030 0.90 0.27 045 5.00 6.18 2.80 535.00 534.00 75.50 1.32% 15 6.1 7.4 0.17 Channel Lining Type TYPE 1 EC-2 TYPE I EC-3 Berkmar Flats Modified LD-268 Roadside and Median Ditch Design Form Side Slope Min. Max Ditch C A CA Tc 12 Q2 110 Q10 :1 L :1 R Slope Ft/Ft Slope Allowable Velocity 2-yr 10-yr Matting Type Freeboard Channel Depth Channel Width INCR I ACC Ft/Ft `Velocity "Depth 1 0.60 0.49 0.29 0.29 5.0 5.17 1.52 6.81 2.00 3 3 0.04 0.16 4.0 1.97 0.14 EC-2 TYPE 1 1.86 2.00 6 2 0.85 0.92 0.78 0.78 5.0 5.17 4.04 6.81 5.33 4 4 0.16 0.46 7.0 4.20 0.13 EC-3 TYPE 1 1.87 2.00 8.00 *2-yr Velocity calculations performed using steepest slope & 2-yr flow " 10-yr Depth calculation performed using shallowest slope & 10-yr flow Outlet Protection Calculations - Reference Nomograph 3.18-3 Pipe Outfall # La ft W ft Do in Do ft 3Do ft d50 ft d50 in Depth in AO 8 9.25 15 1.25 3.75 0.5 6 9 BO 8 9.25 15 1.25 3.75 0.5 6 9 Stormwater Quality Calculations: VRRM Pre -Development Land Use Map VRRM Post -Development Land Use Map VRRM Re -Development Spreadsheet BERKMAR FLATS PREDEV LAND USE MAP us / b iwil�yAb'�`Y°�DAY LIMITS OF DISTURBANCE = 2.54 AC \° j ' ' ^y _,--_ USG TYPE B SOILS 11 I: .cs° L ::F:;:•:•;I IMPERVIOUS = 0.10 AC � /*'•�•'•' MANAGED TURF = 0.24 AC / l 11 ��'•'�':�:•.�..•�•..;.•.•.•:•:•'••••.•:•'••:•I:�:�:n° �•I:�;:F:•:•:�':/:.• �/-�� __— Jill/ i \ \.��. :;: :��• ,� �..:,: ::;: :: I;:;:: sa: I::;:4:I ::f: :�' /: :�: _—j - �T WOODS = 2.20 AC _�i// :•�;•.`•,•;.;.::�:�;:;� � •.•.•.•..•.•.•.•;. nett•• a '•l''•/:;:/;�:C:;/;:� ��/-�`��— f�� rc i••:�•'::::::�•..::::�:•.�-:�:::::�;:;:;:�:�'�'�/'•'�'�'� �y �/ moo.• I' 1•'Y':'' _ �—� r`��s �-. \ �:�����;:�:� �����' :��: ._n� nnnnnn•I..j.;r .I•':I;••I:; I __� CAM rx �a / ,°�..,� �°„„,nab ✓ � �• : � . • • , . •/ / ' / . •�:. • � • /: : / . I I / � , 14 10 emu. / �' / •�::/: :%;:•/;.•�. 50 0 Scale: 1'=50' [DO IMPERVIOUS AREA MANAGED TURF [A WOODS 50 lop BERKMAR FLATS POSTDEV LAND USE MAP y�madl��fal��y!WSfJ�.q��� p�yy�f o, tqW-, — ;Y�C�'*f1%�.+•:L£5'"'Hdt]Ka�l�"L!i 4F(l�.l,l �w MI..RIi R���S§'+'^i�14��6':9Rai{4YatM3.f-L"8!P3s&�e'YSa,^�� w1 `!!5841 �!!�!'�Mi�A�•, ��!'1ilY+li �l1"!'1!�`!l •111M!!'l li4 r �;...'phi;./...Y.i,S.1,..1'N�.H..-,r_. "�''ey01 m,``� � �^•\ \ �� ` �� � � : • �• :�'• : ; f , ;'• ;��" �, f :�• � :fir; ;J : r I: /� / \\ off' �'�,af nom \ \\�\ \\ ���WG•�WO'"�OD // // /msiw�r�. r�`ia v4za.v / ,xm s ot,rr Pso § • 1 m�"v \ %. \ — — — / 'iv4 S • we Y4. - / = ' / \ \ \ ��..,- E%' a \v� �' \ � — � / / �iy! fib•". / / \ � orm � \\\ � aye / // / / /// /I •', ' \ = yl� [..T \ ✓ // r �Pl \ \ XSRPMEH LMPIPPE[uELW... LIMITS OF DISTURBANCE = 2.54 AC USG TYPE B SOILS IMPERVIOUS = 0.83 AC MANAGED TURF = 1.71 AC WOODS = 0.00 AC AScale: 1"=50' Ro'] IMPERVIOUS AREA MANAGED TURF 11 WOODS 50 C6Q Yginio Ruirofj RetluN'an MCMotl Re-Oevelognenr Wlplianu SpreuasM1eer - Version... Mad.eaxesmxe.m.msne'i ozma wan euPsaxm,m mesPeawmlxm proot N... . wmmarmsn ear Lnearo bpm,m Prmem xu Site Information Post -Development Project )Treatment Volume and Loads) Enter Total OisWrbetl Area (acres) j 25a Cheek: RmPwsignsveeihsu f. 2013 DrM nuns lis sra[G - '® finsi—tR] No - ------------------ ® ioble Rur6e0 ureu errtereez J Pmn.wemnPmem Lana tn.er laomsl _____ WOle oelrrol-wmuma e. 2. '.. wrgalm>�1-m.em,a- 6qux�smaarlasl nm Port-0evMopnmttlaM fn 1 aSaY roar ns 1.- wmumq n s s pmuasee�v pore v relom.n aw pm Om '.. xe�ymnnl>�1-m.eme,a— fv o-t rererea '. egam�sw.nl>sl ag '. Ya4d a Onon,K fnuYKK - Rurm. Coolfici do -- - --- na—ueel .l a6a& [stla n6ePa mI- r. . . an i ml mosue-all[ucl Al nS mana6Prrun nss nm 011 nII UodII W-,se) meia=Mel nw ninaa.uswmeml -- -- --- ..e.se.exe,pe2 .rn.eu emsrn lrree.sm.erw --- ..lowsPon —an. pxawnaxsti.s�. I.weoer w- ro ar 1.1r., I w Freova-ma,er.,e.a an M.aal oe,:oare rmnlaoexl e11 me am r nef- .�.,an xraa,a area , wa.layssl aerurt •a`Ianeal aenyee rur[mv r�.l w.gw mum ore nm waigmee v.IeM ore wp�¢eml^•II na�eer.r ex vx xw,a..ae*m 6n x 6.�een.r Irso--ysel ON nN ni.us[mrerl+�resl oS gym" bl�ab`0sa xow P.w aNnpe.by x.emcemaal aNh.u. aMw�l .I.,oe,.laa ax al a�moe�.a vx xl.a�.e. r.umx zs .n w.:xe area l+eal a�olo4 zA ieu �" t]6 IcW do. a. and Treatment Volume and Nu rielrt Loatl Treatment Volume and Nutrient Lead a a ov>e loss ren'am�ivli�ne miles n eaxila a 1. Oni6v ePy IRm glum wme ve MOkwlm.ral�o rze 6n normsv. e,.Y srels.d.rtnl� ngew.eMea a us nel_oirsay `.'m r� ss _1_ z.SK eq _ m rvrm6 a me�xe dd6 dd3 wmema 26s wnaew�lynva Irry pp .^^Oaeagn.^nlw u InhN IIb/elAr Iwnl• la/rx - rxa+nerx�... sm+ .M nu On Mrl w ru-wmrm...xn I�Nme/ya Pa+iWeeM N.m ur, zs w _. ymin.+v atl uWn wauw Que.ywn.µ.ewm.nga 035 xeu LII xetlMgMam �Ix/vN Iwro ew.a.,a.ev,.,r o.ewvo�,wwrer Post-Development Rec, uirement for Site Area i TP Loaa Reiu[rion Repuirea llb/yrl I.ST Naumann Loatls (IMormational Purposes Only) no..wemnaxwlmlllpMl 3ev sert. mcerv��l N. raze liuyr Site Results (Water Quality Compliance) Area Checks O.A.A O.A.B O.A.0 A. D.A.E ARMEM FOREST/OVEN SPACE (a[) am O.M 0.M i0.00 O.W OK. I IMPEWnMCOVERTRENTFDIa[ 0.00 O.M 0.00�M. OWOK. MANAGEDMRFARENIa[) 0.00 O.M 0.00 00.W OK. MANAGED TURF AREA TREATED (a[) am O.M 0.00 O.W OK. AREA CHECK OK OK. OK. OK. Site Treatment VOIUMe (ffa) 4.158 Runoff Reduction Volume and TP By Drainage Area O.A. A D.AD O.A. E TOTALRUNOFF REDUCNON VOLUME ACHIEVED pF) 0 0 0 LOADAVAKABLE FOR REMOVAL (b/1) 0.00 MM0 0.00 0.0.00TPID MDUCTIONAGVEVED (b/yr) 0.00 0.00 O.W am TP LOAD REMAINING (lb/yr) 0.00 0.00 O.W am NMMEN MD REDUCTION ACHIEVED (b/yr) am O.W 0.00 0.00 O.W 0.00 Total Phosphorus FINAL POST -DEVELOPMENT TP LOAD Qb/yr) 2.61 lP LOAD REDUCTION REQUIRED pb/yrl 1.57 TP WAD REDUCTIONACHIEVED (b/yr) 0.00 W LOAD REMAINING (lb/N): 2.61 REMAINING TP LOAD REDUCTION REQUIRED pb/yr): 1.57 Total Nitrogen (For Information Purposes) POST-DEVEMPMEM WAD (Ib/yr)jj 18.69 NMMEN LOAD REDUCTION ACHIEVED)Ib/yr) 0.w REMAINING POST-DEV M MEM NRRWEN LOAD)Ib/yr) 18.69 o�00000 ��00000 �00000 ®000a0 �00000 �00000 ®000a0 �00000 �00000 m00000 Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Fn Fflr," F MAPLEGEND Area of Interest (A01) 0 Area of Interest A01) Solis Soil Rating Polygons 0 A Q AID o B Q BID o C 0 CID 0 D 0 Not rated or not available Soil Rating Lines . r A ,y AID rV B ram/ B/D N C N CID i D . . Not rated or not available Soil Rating Points A Q AID O B 0 BID Hydrologic Soil Group —Albemarle County, Virginia 0 C CID D 13 Not rated or not available Water Features Streams and Canals Transportation µ� Rails N Interstate Highways �y US Routes Major Roads Local Roads Background . Aerial Photography MAP INFORMATION The soil surveys that comprise your AC I were mapped at 1:15,800. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Albemarle County, Virginia Survey Area Data: Version 16, Aug 23, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 8, 2020---Sep 23, 2020 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources Web Soil Survey 3/152023 Conservation Service National Cooperative Soil Survey Page 2 of Hydrologic Soil Group --Albemarle County, Virginia Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 27B Elioak loam, 2 to 7 B 0.3 2.8% percent slopes 27C Elioak loam, 7 to 15 B 3.5 28.7% percent slopes 34D Glenelg loam, 15 to 25 B 0.7 5.6% percent slopes 39D Hazel loam, 15 to 25 B 1.2 9.7% percent slopes 47E Philomont sandy loam, A 0.1 0.6% 25 to 45 percent slopes 65B Fairview sandy loam, 2 B 6.3 52.5% to 7 percent slopes 65C Fairview sandy loam, 7 B 0.0 0.1 % to 15 percent slopes Totals for Area of Interest 12.0 100.0% Natural Resources Web Soil Survey 3/15/2023 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group —Albemarle County, Virginia Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie -break Rule: Higher Natural Resources Web Soil Survey 3/15/2023 Conservation Service National Cooperative Soil Survey Page 4 of 4 NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* d¢r `" Latitude: 38.0888o, Longitude:-78.4783o Elevation: mlft** � 'source: ESRI Maps source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonin, 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)' Average recurrence interval (years) Duration ��� 10 26 501 100 200 500 1000 6-min (0.3117--0.389) (0.307 .419 0.465) (0.443-0.545) (04 97---0 612) (0.557---0 687) (0.03-0.6746) (0.645-0.803) (0.684-0 857) (07 28-0.925) (0.762-0 981) F-0--5611 IF 1.08 10-min (0.660.622) (0.6050.0743) (0.7110-0872) (07 94-0978) (0.8Ml.lO) (0.961--11.19) (1.02-1 28) (1.08-21336) (1.15i46) (1.20-31955) 15-min (0.020777) (0.7 00.934) (0. 984610) (1.M1.24) (1: 3-21639) (1.22-3t51) (1.30-11..61) (1.37--1.71) 1 (1.451.84) (1.511.94) 30-min (0.696107) 1 (1.051..29) 1 (1.27-1?57) 1 (1.46- .79) 1 (1.67-2606) 1 (1.83 227) 1 (1.99-2.47) 1 (2.23-2?67) 1 (2.31 2593) 1 (2.44-3.14) 60-min (1.08-1.33) (1.32-11..62) (1.64-2.01) (1.90-2.8) (2.22�-2.74) (2.483.07) (2.3--3.40) (2.993074) (3.31-a20) (3. 6-4.59) 4.35 2-hr (1.27-1.64) (1.54L99) (1.93-2.49) (2.6-2.91) (2. 83.47) (3.03436.93) (3.84.41) (3. 3-4.91) (4.225762) (4.61523) 3-hr (1.8-1.81) (1.662.19) 1 (2.09-2.75) (2.453.21) 1 (2.913.82) (3.84.33) (3.674.87) (4.065.43) (46 622) (5.02590) 6-hr (17 62.28) (2: 52.75) (2.66-3.42) (3.1114501) (3.724.82) (4.245.51) (4. 66.26) (5.32-7707) (6.09-8.23) (6. 6 9.25) 47 8.31 11.2 12-hr (223-2.89) (2. 9-9A8) (3.34-4.34) (3.94-5.12) (47 5821) (5.45--37319) (6. 8825) (6.979.41) (8. 0---11.2) (9.08- 2.8) 24hr (27 0-3.38) 3.64 (3.27009) (a. 65.22) (4.91 6015) (5. 9-7553) 7.83 (6.89-8.71) (7.87--010.0) (8.910-111A) (10.4- 3.6) (117415.5) 36 2-day (3:9-3.96) (3.6�81) (4.906710) (5.764�16) (6.94-8.69) (7.919897) (8.96-121.4) (10.1-12.9) (117--15.2) (13.0-137.1) 6.836) 3-day (3.434.19) (4: 55507) (5.276.µ) (6 (7. 69017) (8.51- 0.5) (9.63- 2.0) 1 (10.8- 3.6) (125 6.0) (13.9- 8.0) �� (3.674.41) (4.44-5.34) (56 36.78) (6.0-7.94) (7. 89965) (9.11--11.1) (10.3- 2.6) 1 (11.6-14.3) 1 (13.4- 6.7) 1 (14.9-18.9) 4. 5.61 7-0ey (4.2759) (5: 56.13) (6. 2-OZ66) (7.468.91) (8.92-- 0.7) (10.1- 2.2) (114- 3.8) (127-15.5) 1 (1475 8.1) (16.0- 0.2) 10-0ey (4.875872) (58 5687) (7. 1-8.48) (8.0-9.78) (9.83-1.6) (11.0-13.1) (12.3-14.7) (13.6-16.4) (15.4- 8.8) (16.9-20.9) ) 20-dey (64 9-744) (7.85�87) (9.34-110.7) (10.6-2.2) (12.3-14.1) (135- 5.7) (14.9-17.3) (162- 8.9) (179-21.2) (19222.9) 30-0ey (8.01 9.07) (9.6-10.7) (112- 2.7) (12.514.2) 5.2 (142- 6.1) (155-167.6) (167- 9.1) (iZ9- 0.5) (19.4- 2.5) (20.5-3.9) 46-day (10.0-111.3) (11.8- 3.3) (13.8-15.5) (15.3-137.2) (17.2-19.4) (18.6-21.0) (199722.5) (2121-24.0) (22274- 6.0) (23?8-27.5) 60-day (118-13.2) . (139- 5.5) . (16A-1179 (176 9.6) (19z6-21.9) (21212 3.6) (2243 5.2) (2327-26.7) (25.3-28.7) (26?5- 0.2) 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 NOAAAtias 14 document for more information. Back to Top PF graphical