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WPO201500102 Calculations 2015-12-07
PROJECT MANAGEMENT SHIMP CIVIL ENGINEERING LAND PLANNING ENGINEERING December 07, 2015 id1H1' � � Max Greene GP Albemarle County Community Development U JU.' IN M. SHIMP ;- um Lie.40./45183 Regarding: Timberwood Commons Stormwater Quality and Quantity Plan '0,, ONAL Dear Mr. Greene, Enclosed are the calculations and details relating to stormwater quantity and quality. Outflows from the site are limited to assumed runoff from the pre-development site area. Pre-development cover was assumed to be woodlands and soils were assumed to occur in the same proportions as the overall Hollymead Town Center development. Excess post-development runoff is detained in an underground pipe storage facility. Water quality standards, (9VAC25-870-65), is addressed with the purchase of 1.28 lb/year of nutrient credits. In order to meet Minimum Water Quantity Standards, channel protection and flood protection needs to be addressed (9VAC25-870-33) in accordance with the following energy balance equation for natural storm water conveyance systems: QDeveloped I � .F.*(QPre-developed* RVPre-Developed)/RV Developed mai Because we assumed the site to be completely wooded, we proceeded without the improvement factor. We found the RVpre of the site by determining the longest time of concentration of the site and entering it into HydroCAD along with the pre development site conditions. The hydrograph determined that Qpre=0.38 cfs and RVpre=.034 ac-ft. In order to find RVpost,the site was divided into sub-drainage areas going to each detention pipe within the constraints of the property boundaries. These values were entered into HydroCAD RRM model, in which the runoff volumes were calculated then summed together to get RVpost =.162 ac.-ft. The next goal was to find the Qpost for the site: QDeveloped= (QPre-developed RVPre-Developed)/RVDeveloped, we determined the required Qpost= .08 cfs. In addition to detaining the pre development levels, we must provide additional detention to meet the requirements of the energy balance equation. The SWM plan exceeds that requirement as shown in the table below. Summary Table for project outflows: Pre-Development Post-Development 1-Yr Flow 0.38 cfs 0.07 cfs 10-Yr Flow 2.88 cfs .49 cfs a a Contents: a_ Pre-Development Stormwater Management Calculations: Pre-Development HydroCAD Analysis a Post-Development Stormwater Management Calculations: Post-Development Drainage Map Post-Development HydroCAD Analysis a Stormwater Quality Calculations: VDEQ RRM Spreadsheets Post-Development RRM HydroCAD Analysis Storm Inlet and Drain Computations: . Storm Inlet Drainage Area Map VDOT Drainage Manual LD-204 VDOT Drainage Manual LD-229 a Independent Reports: Excerpt from NRCS Soils Report a NOAA Precipitation Report a a a a a a a a a a Pre-Development Stormwater Management Calculations Pre-Development HydroCAD Analysis a a .a aera .a .a �.a Notes: a The pre-development area was assumed to be equal to the post-development area draining to the underground detention facility. As conditions prior to Hollymead Town Center are unknown, these calculations are based on the conservative assumptions that before development, the site was in a wooded condition with soils equivalent to those in the overall development. a a aa. atlr ai ar ar aa. a.. arr Pre- Development aa. Drainage aif a�w aar a. SUbCat Reach 'On• Drainage Diagram for Timberwood Commons Pre-Development Prepared by Shimp Engineering P.C., Printed 12/3/2015 HydroCAD?9.10 sin 07054 ?2011 HydroCAD Software Solutions LLC ar Timberwood Commons Pre-Development Type 1124-hr lyr Rainfall=2.98" Prepared by Shimp Engineering P.C. Printed 12/3/2015 HydroCAD?9.10 s/n 07054 ? 2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1: Pre-Development Drainage Runoff = 0.38 cfs @ 12.11 hrs, Volume= 0.034 af, Depth> 0.46" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type Il 24-hr 1yr Rainfall=2.98" Area (sf) CN Description 16,493 55 Woods, Good, HSG B 22,313 70 Woods, Good, HSG C 38,806 64 Weighted Average 38,806 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.0 Direct Entry, SHEET gas Timberwood Commons Pre-Development Type 1124-hr 10yr Rainfall=5.45" Prepared by Shimp Engineering P.C. Printed 12/3/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 1: Pre-Development Drainage Runoff = 2.03 cfs @ 12.09 hrs, Volume= 0.139 af, Depth> 1.87" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.45" Area (sf) CN Description 16,493 55 Woods, Good, HSG B 22,313 70 Woods, Good, HSG C 38,806 64 Weighted Average 38,806 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.0 Direct Entry, SHEET Post-Development Stormwater Management Calculations ® Post-Development Drainage Map Post-Development HydroCAD Analysis Notes: Assumed 5 minute time of concentration for all subcatchments because of the large impervious percentage. DA's 2, 3, and 4 are reduced as much as is practical. CII M OD CI •0 • • Em E. •' N — --P --I L_J - i.b • `. 1 ca ° o 00 -7 1 1 1 1 r—1 01 73 --lj 0 0 < - \ 0 CD )>\ ,\ Up —17 0 0 C:=3 CO i 0/A) , • . .• . 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L---' >< „....• ---No cf-) ,,,,- 0 0-------co (x) • ,/ • CD CO CD :- (1) 0 -71 i ____ _________ . __ __- _ _ .._ _. , ... - • -0 - 0 • ' • , ',..., ' ' • 0 U •0 0 __ . , . . - - - • - 0 . 0 • , Q 0 0 1S D.A. to et. Pipe #1 1P Deten ion Pipe : A <2S> D.A. to Det. Pipe #2 Undergroun Detention MINI JIM 1111 411111Point of Analysis Ste (Subca) Reach 'on. Drainage Diagram for Timberwood Commons Post-Development(11-2015) Prepared by Shimp Engineering P.C., Printed 12/7/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Timberwood Commons Post-Development(11-2015) Type 1124-hr 1yr Rainfall=2.98" Prepared by Shimp Engineering P.C. Printed 12/7/2015 .. HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: D.A. to Det. Pipe#1 Runoff = 0.81 cfs @ 11.96 hrs, Volume= 0.040 af, Depth> 2.43" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1 yr Rainfall=2.98" Area(sf) CN Description 3,311 98 Unconnected pavement, HSG B 326 61 >75% Grass cover, Good, HSG B 441 74 >75%Grass cover, Good, HSG C 4,479 98 Unconnected pavement, HSG C 8,557 95 Weighted Average 767 8.96% Pervious Area 7,790 91.04% Impervious Area 7,790 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: D.A. to Det. Pipe#2 Runoff = 2.62 cfs @ 11.96 hrs, Volume= 0.124 af, Depth> 2.14" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type 1124-hr 1 yr Rainfall=2.98" Area (sf) CN Description 10,295 98 Unconnected pavement, HSG B 13,928 98 Unconnected pavement, HSG C 2,561 61 >75%Grass cover, Good, HSG B 3,465 74 >75%Grass cover, Good, HSG C 30,249 92 Weighted Average 6,026 19.92% Pervious Area 24,223 80.08% Impervious Area 24,223 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 1 P: Detention Pipe Inflow Area= 0.196 ac, 91.04% Impervious, Inflow Depth > 2.43" for 1 yr event Inflow = 0.81 cfs @ 11.96 hrs, Volume= 0.040 af .. Outflow = 0.28 cfs @ 12.06 hrs, Volume= 0.040 af, Atten= 65%, Lag= 6.3 min Primary = 0.28 cfs @ 12.06 hrs, Volume= 0.040 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt=0.01 hrs Peak Elev=546.56' @ 12.06 hrs Surf.Area= 0.009 ac Storage= 0.009 af Plug-Flow detention time= 9.0 min calculated for 0.040 of (100% of inflow) Center-of-Mass det. time=8.9 min ( 787.2 - 778.3 ) S Timberwood Commons Post-Development(11-2015) Type 1124-hr 1yr Rainfall=2.98" Prepared by Shimp Engineering P.C. Printed 12/7/2015 ... HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 3 Volume Invert Avail.Storage Storage Description #1 545.00' 0.029 af 48.0" D x 100.0'L Pipe Storage S=0.0020'/' Device Routing Invert Outlet Devices #1 Primary 545.00' 15.0" Round Culvert L= 103.4' Ke= 0.400 Inlet/Outlet Invert=545.00'/535.88' S= 0.0882 7' Cc= 0.900 n= 0.013 #2 Device 1 545.00' 3.0"Vert. 1 year orifice C= 0.600 #3 Device 1 546.60' 4.0"Vert. 10 year orifice C= 0.600 #4 Primary 547.80' Custom Weir/Orifice, Cv=2.62(C=3.28) Head (feet) 0.00 0.25 0.50 0.75 1.00 1.20 �. Width (feet) 3.67 3.40 3.04 2.53 1.74 0.00 Erimary OutFlow Max=0.28 cfs @ 12.06 hrs HW=546.56' (Free Discharge) Culvert (Passes 0.28 cfs of 6.11 cfs potential flow) 2=1 year orifice (Orifice Controls 0.28 cfs @ 5.76 fps) 3=10 year orifice ( Controls 0.00 cfs) -4=Custom Weir/Orifice ( Controls 0.00 cfs) Summary for Pond 2P: Underground Detention Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 2.20" for 1yr event Inflow = 2.87 cfs @ 11.96 hrs, Volume= 0.164 of Outflow = 0.06 cfs @ 15.85 hrs, Volume= 0.045 af, Atten= 98%, Lag= 233.2 min Discarded = 0.01 cfs @ 7.98 hrs, Volume= 0.012 af �. Primary = 0.05 cfs @ 15.85 hrs, Volume= 0.033 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt=0.01 hrs Peak Elev= 534.40' @ 15.85 hrs Surf.Area= 0.085 ac Storage=0.123 af Plug-Flow detention time= 395.6 min calculated for 0.045 of (28%of inflow) Center-of-Mass det. time= 251.7 min ( 1,045.2 - 793.6) Volume Invert Avail.Storage Storage Description #1 532.03' 0.040 af 6.00'W x 186.00'L x 6.00'H Drainage Field 0.154 af Overall - 0.053 af Embedded = 0.101 of x 40.0%Voids #2 533.03' 0.053 af 48.0" D x 182.0'L Pipe Storage S=0.0020'/' Inside#1 #3 532.03' 0.051 af 25.00'W x 104.00'L x 6.00'H Drainage Field 0.358 af Overall - 0.231 af Embedded = 0.127 af x 40.0%Voids #4 533.03' 0.231 of 48.0" D x 200.0'L Pipe Storage S=0.0020'/' x 4 Inside#3 0.375 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 533.03' 15.0" Round Culvert L= 145.8' Ke= 0.400 Inlet/Outlet Invert= 533.03'/532.30' S= 0.00507' Cc= 0.900 n= 0.013 .. #2 Device 1 534.25' 4.0"Vert. 1 year orifice C= 0.600 #3 Device 1 535.25' 6.0"Vert. 10 year orifice C= 0.600 #4 Primary 536.00' 100 year orifice,Cv=2.62(C=3.28) Head (feet) 0.00 0.30 0.60 0.90 1.03 Width (feet) 3.49 3.09 2.48 1.42 0.00 #5 Discarded 532.03' 0.100 in/hr Exfiltration over Surface area Timberwood Commons Post-Development(11-2015) Type 1124-hr 1yr Rainfall=2.98" Prepared by Shimp Engineering P.C. Printed 12/7/2015 . HydroCAD?9.10 sin 07054 ?2011 HydroCAD Software Solutions LLC Page 4 iscarded OutFlow Max=0.01 cfs @ 7.98 hrs HW=532.09' (Free Discharge) Exfiltration (Exfiltration Controls 0.01 cfs) Erimary OutFlow Max=0.05 cfs @ 15.85 hrs HW=534.40' (Free Discharge) „.. Culvert (Passes 0.05 cfs of 4.49 cfs potential flow) 2_1 year orifice (Orifice Controls 0.05 cfs @ 1.33 fps) 3_10 year orifice ( Controls 0.00 cfs) —4=100 year orifice ( Controls 0.00 cfs) .. Summary for Link 3L: Point of Analysis . Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 0.45" for 1yr event Inflow = 0.05 cfs @ 15.85 hrs, Volume= 0.033 of Primary = 0.05 cfs @ 15.85 hrs, Volume= 0.033 af, Atten= 0%, Lag= 0.0 min . Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs ar .. dm mu me Am dm um M.. Timberwood Commons Post-Development(11-2015) Type 1124-hr 10yr Rainfall=5.45" Prepared by Shimp Engineering P.C. Printed 12/7/2015 ..,, HydroCAD?9.10 sin 07054 ?2011 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1S: D.A. to Det. Pipe#1 lk Runoff = 1.54 cfs @ 11.96 hrs, Volume= 0.080 af, Depth> 4.86" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs �. Type II 24-hr 10yr Rainfall=5.45" Area (sf) CN Description 3,311 98 Unconnected pavement, HSG B 326 61 >75%Grass cover, Good, HSG B 441 74 >75%Grass cover, Good, HSG C 4,479 98 Unconnected pavement, HSG C 8,557 95 Weighted Average 767 8.96% Pervious Area 7,790 91.04% Impervious Area 7,790 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: D.A. to Det. Pipe#2 Runoff = 5.27 cfs @ 11.96 hrs, Volume= 0.262 af, Depth> 4.53" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.45" Area (sf) CN Description 10,295 98 Unconnected pavement, HSG B 13,928 98 Unconnected pavement, HSG C 2,561 61 >75%Grass cover, Good, HSG B 3,465 74 >75%Grass cover, Good, HSG C 30,249 92 Weighted Average 6,026 19.92% Pervious Area 24,223 80.08% Impervious Area 24,223 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 1 P: Detention Pipe Inflow Area= 0.196 ac, 91.04% Impervious, Inflow Depth > 4.86" for 10yr event Inflow = 1.54 cfs @ 11.96 hrs, Volume= 0.080 of �. Outflow = 0.75 cfs @ 12.04 hrs, Volume= 0.080 af, Atten= 51%, Lag= 5.2 min Primary = 0.75 cfs @ 12.04 hrs, Volume= 0.080 of Routing by Stor-lnd method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 547.59'@ 12.04 hrs Surf.Area= 0.009 ac Storage= 0.019 af Plug-Flow detention time= 10.5 min calculated for 0.080 of (100%of inflow) .,, Center-of-Mass det. time= 10.3 min ( 771.1 - 760.8) Timberwood Commons Post-Development(11-2015) Type II 24-hr 10yr Rainfall=5.45" Prepared by Shimp Engineering P.C. Printed 12/7/2015 ,.. HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 6 Volume Invert Avail.Storage Storage Description ..` #1 545.00' 0.029 af 48.0" D x 100.0'L Pipe Storage S=0.0020'/' Device Routing Invert Outlet Devices #1 Primary 545.00' 15.0" Round Culvert L= 103.4' Ke=0.400 Inlet/Outlet Invert=545.00'/535.88' S= 0.0882 '/' Cc= 0.900 n= 0.013 #2 Device 1 545.00' 3.0"Vert. 1 year orifice C= 0.600 #3 Device 1 546.60' 4.0"Vert. 10 year orifice C= 0.600 #4 Primary 547.80' Custom Weir/Orifice, Cv=2.62(C=3.28) Head (feet) 0.00 0.25 0.50 0.75 1.00 1.20 ... Width (feet) 3.67 3.40 3.04 2.53 1.74 0.00 12rimary OutFlow Max=0.75 cfs @ 12.04 hrs HW=547.59' (Free Discharge) Culvert (Passes 0.75 cfs of 8.87 cfs potential flow) "" 2=1 year orifice (Orifice Controls 0.37 cfs @ 7.56 fps) 3=10 year orifice (Orifice Controls 0.38 cfs @ 4.36 fps) -4=Custom Weir/Orifice ( Controls 0.00 cfs) Summary for Pond 2P: Underground Detention Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 4.60" for 10yr event Inflow = 5.88 cfs @ 11.96 hrs, Volume= 0.341 of Outflow = 0.46 cfs @ 12.92 hrs, Volume= 0.219 af, Atten= 92%, Lag=57.3 min Discarded = 0.01 cfs @ 5.04 hrs, Volume= 0.014 af Primary = 0.45 cfs @ 12.92 hrs, Volume= 0.205 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 535.36'@ 12.92 hrs Surf.Area= 0.085 ac Storage= 0.206 of Plug-Flow detention time= 269.2 min calculated for 0.219 of (64%of inflow) Center-of-Mass det. time= 167.9 min ( 942.1 - 774.2 ) Volume Invert Avail.Storage Storage Description #1 532.03' 0.040 of 6.00'W x 186.00'L x 6.00'H Drainage Field 0.154 of Overall - 0.053 of Embedded = 0.101 af x 40.0%Voids "" #2 533.03' 0.053 af 48.0" D x 182.0'L Pipe Storage S=0.0020'P Inside#1 #3 532.03' 0.051 of 25.00'W x 104.00'L x 6.00'H Drainage Field 0.358 of Overall - 0.231 af Embedded = 0.127 of x 40.0%Voids #4 533.03' 0.231 of 48.0" D x 200.0'L Pipe Storage S=0.0020'/' x 4 Inside#3 0.375 of Total Available Storage .. Device Routing Invert Outlet Devices #1 Primary 533.03' 15.0" Round Culvert L= 145.8' Ke=0.400 Inlet/Outlet Invert=533.03'/532.30' S= 0.0050 'P Cc= 0.900 n= 0.013 m. #2 Device 1 534.25' 4.0"Vert. 1 year orifice C= 0.600 #3 Device 1 535.25' 6.0"Vert. 10 year orifice C= 0.600 #4 Primary 536.00' 100 year orifice, Cv=2.62(C=3.28) Head (feet) 0.00 0.30 0.60 0.90 1.03 .. Width (feet) 3.49 3.09 2.48 1.42 0.00 #5 Discarded 532.03' 0.100 in/hr Exfiltration over Surface area .. Timberwood Commons Post-Development(11-2015) Type 1124-hr 10yr Rainfall=5.45" Prepared by Shimp Engineering P.C. Printed 12/7/2015 .. HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 7 piscarded OutFlow Max=0.01 cfs @ 5.04 hrs HW=532.09' (Free Discharge) .. =Exfiltration (Exfiltration Controls 0.01 cfs) EPrimary OutFlow Max=0.44 cfs @ 12.92 hrs HW=535.36' (Free Discharge) q. Culvert (Passes 0.44 cfs of 6.05 cfs potential flow) 2=1 year orifice (Orifice Controls 0.41 cfs @ 4.68 fps) 3=10 year orifice (Orifice Controls 0.04 cfs @ 1.13 fps) —4=100 year orifice ( Controls 0.00 cfs) Summary for Link 3L: Point of Analysis •• Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 2.76" for 10yr event Inflow = 0.45 cfs @ 12.92 hrs, Volume= 0.205 af Primary = 0.45 cfs @ 12.92 hrs, Volume= 0.205 af, Atten= 0%, Lag= 0.0 min m` Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs .. an nws .. .. Timberwood Commons Post-Development(11-2015) Type 1124-hr 100yr Rainfall=8.92" Prepared by Shimp Engineering P.C. Printed 12/7/2015 ... HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: D.A. to Det. Pipe#1 Runoff = 2.56 cfs @ 11.96 hrs, Volume= 0.136 af, Depth> 8.31" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=8.92" Area (sf) CN Description 3,311 98 Unconnected pavement, HSG B 326 61 >75% Grass cover, Good, HSG B 441 74 >75% Grass cover, Good, HSG C 4,479 98 Unconnected pavement, HSG C "' 8,557 95 Weighted Average 767 8.96% Pervious Area 7,790 91.04% Impervious Area 7,790 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) "" 5.0 Direct Entry, Summary for Subcatchment 2S: D.A. to Det. Pipe#2 Runoff = 8.92 cfs @ 11.96 hrs, Volume= 0.460 af, Depth> 7.95" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs ffi` Type II 24-hr 100yr Rainfall=8.92" Area(sf) CN Description .. 10,295 98 Unconnected pavement, HSG B 13,928 98 Unconnected pavement, HSG C 2,561 61 >75%Grass cover, Good, HSG B 3,465 74 >75%Grass cover, Good, HSG C 30,249 92 Weighted Average 6,026 19.92% Pervious Area 24,223 80.08% Impervious Area .r 24,223 100.00% Unconnected Tc Length Slope Velocity Capacity Description .r (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 1 P: Detention Pipe Inflow Area= 0.196 ac, 91.04% Impervious, Inflow Depth > 8.31" for 100yr event Inflow = 2.56 cfs @ 11.96 hrs, Volume= 0.136 of — Outflow = 2.51 cfs @ 11.97 hrs, Volume= 0.136 af, Atten= 2%, Lag=0.9 min Primary = 2.51 cfs @ 11.97 hrs, Volume= 0.136 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt=0.01 hrs . Peak Elev= 548.07'@ 11.97 hrs Surf.Area= 0.008 ac Storage= 0.023 af Plug-Flow detention time= 9.5 min calculated for 0.136 of (100%of inflow) ,® Center-of-Mass det. time= 9.3 min ( 758.6 - 749.3 ) Timberwood Commons Post-Development(11-2015) Type 1124-hr 100yr Rainfall=8.92" Prepared by Shimp Engineering P.C. Printed 12/7/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 3 Volume Invert Avail.Storage Storage Description #1 545.00' 0.029 of 48.0" D x 100.0'L Pipe Storage S=0.0020'/' Device Routing Invert Outlet Devices #1 Primary 545.00' 15.0" Round Culvert L= 103.4' Ke=0.400 Inlet/Outlet Invert= 545.00'/535.88' S= 0.0882 '/' Cc= 0.900 n= 0.013 #2 Device 1 545.00' 3.0"Vert. 1 year orifice C= 0.600 #3 Device 1 546.60' 4.0"Vert. 10 year orifice C= 0.600 #4 Primary 547.80' Custom Weir/Orifice, Cv=2.62(C=3.28) Head (feet) 0.00 0.25 0.50 0.75 1.00 1.20 Width (feet) 3.67 3.40 3.04 2.53 1.74 0.00 primary OutFlow Max=2.51 cfs @ 11.97 hrs HW=548.07' (Free Discharge) Culvert (Passes 0.89 cfs of 9.90 cfs potential flow) 2_1 year orifice (Orifice Controls 0.41 cfs @ 8.26 fps) 3_10 year orifice (Orifice Controls 0.48 cfs @ 5.50 fps) -4=Custom Weir/Orifice (Weir Controls 1.63 cfs @ 1.71 fps) Summary for Pond 2P: Underground Detention Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 8.03" for 100yr event Inflow = 11.38 cfs @ 11.96 hrs, Volume= 0.596 of Outflow = 4.93 cfs @ 12.05 hrs, Volume= 0.468 af, Atten= 57%, Lag= 5.6 min Discarded = 0.01 cfs @ 3.28 hrs, Volume= 0.015 of Primary = 4.92 cfs @ 12.05 hrs, Volume= 0.453 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Peak Elev= 536.47' @ 12.05 hrs Surf.Area= 0.085 ac Storage= 0.299 of Plug-Flow detention time= 210.0 min calculated for 0.468 of (79%of inflow) Center-of-Mass det. time= 128.0 min ( 888.5 - 760.5 ) Volume Invert Avail.Storage Storage Description #1 532.03' 0.040 af 6.00'W x 186.00'L x 6.00'H Drainage Field 0.154 af Overall - 0.053 af Embedded = 0.101 of x 40.0% Voids #2 533.03' 0.053 of 48.0" D x 182.0'L Pipe Storage S=0.0020'/' Inside#1 #3 532.03' 0.051 of 25.00'W x 104.00'L x 6.00'H Drainage Field 0.358 of Overall - 0.231 af Embedded = 0.127 af x 40.0%Voids #4 533.03' 0.231 af 48.0" D x 200.0'L Pipe Storage S=0.0020'/' x 4 Inside#3 0.375 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 533.03' 15.0" Round Culvert L= 145.8' Ke=0.400 Inlet/Outlet Invert= 533.03'/532.30' S= 0.0050 '/' Cc= 0.900 n= 0.013 .. #2 Device 1 534.25' 4.0"Vert. 1 year orifice C= 0.600 #3 Device 1 535.25' 6.0"Vert. 10 year orifice C= 0.600 #4 Primary 536.00' 100 year orifice,Cv=2.62(C=3.28) Head (feet) 0.00 0.30 0.60 0.90 1.03 Width (feet) 3.49 3.09 2.48 1.42 0.00 #5 Discarded 532.03' 0.100 in/hr Exfiltration over Surface area Timberwood Commons Post-Development(11-2015) Type 1124-hr 100yr Rainfall=8.92" Prepared by Shimp Engineering P.C. Printed 12/7/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 4 piscarded OutFlow Max=0.01 cfs @ 3.28 hrs HW=532.09' (Free Discharge) =Exfiltration (Exfiltration Controls 0.01 cfs) EPrimary OutFlow Max=4.91 cfs @ 12.05 hrs HW=536.47' (Free Discharge) �,. =Culvert (Passes 1.53 cfs of 7.68 cfs potential flow) 2=1 year orifice (Orifice Controls 0.60 cfs @ 6.89 fps) 3=10 year orifice (Orifice Controls 0.93 cfs @ 4.73 fps) —4=100 year orifice (Weir Controls 3.37 cfs @ 2.29 fps) Summary for Link 3L: Point of Analysis Inflow Area= 0.891 ac, 82.49% Impervious, Inflow Depth > 6.10" for 100yr event Inflow = 4.92 cfs @ 12.05 hrs, Volume= 0.453 af Primary = 4.92 cfs @ 12.05 hrs, Volume= 0.453 af, Atten= 0%, Lag= 0.0 min '°` Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Stormwater Quality Calculations ar VDEQ RRM Spreadsheets Post-Development RRM HydroCAD Analysis a a air . . . S S a S .. a S ras Virginia Runoff Reduction Method New Development Worksheet--v2.8_2011Specs NM Site Data Summary Total Rainfall=43 inches row Site Land Cover Summary A Soils 8 Soils C Soils D Soils Total %of Total Forest(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf(acres) 0.00 0.10 0.14 0.00 0.24 25.00 crit Impervious(acres) 0.00 0.31 0.41 0.00 0.72 75.00 0.96 100.00 Site Rv 0.77 sae Post Development Treatment Volume(ft3) 2667 Post Development TP Load(Ib/yr) 1.68 Post Development TN Load(Ib/yr) 11.99 Total TP Load Reduction Required(Ib/yr) 1.28 art Total Runoff Volume Reduction(ft3) 0 Total TP Load Reduction Achieved(Ib/yr) 0 Total TN Load Reduction Achieved(Ib/yr) 0.00 sill Adjusted Post Development TP Load(Ib/yr) 1.68 Remaining Phosphorous Load Reduction(Lb/yr)Required 1.28 AM Drainage Area Summary D.A.A D.A.B D.A.C D.A.D D.A.E Total Forest(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf(acres) 0.00 0.00 0.00 0.00 0.00 0.00 `'r Impervious(acres) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Drainage Area Compliance Summary AM D.A.A D.A.B D.A.C D.A.D D.A.E Total TP Load Red.(Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 TN Load Red.(Ib/yr) 0.00 0.00 0.00 0.00 0.00 0.00 wr AM AM ,r• MI a aa. Channel and Flood Protection Weighted CN 1-year 2-year storm 10-year storm Adjusted CN storm aism Adjusted Adjusted CN CN Target Rainfall Event(in) 2.98 3.61 5.45 D.A.A CN 0 #N/A #N/A #N/A D.A.B CN 0 #N/A #N/A RN/A ru D.A.C CN 0 #N/A #N/A #N/A D.A.D CN 0 #N/A #N/A #N/A D.A.E CN 0 #N/A #N/A #N/A aaa am aaaa ar ari aar air aaa ar an aar aaa ar Air i . Y nr W I I Y Y Y Y ' a, OOOO Ire 1 I 1 a Q 1 a ------ 000o I 1 W I a Q O � 11 O 8 g t a i '0 � 1 Q ar SIO p CCao i 1 Q O1 01 am 1 COaa ' 1 wry m 1 Y 1 Q p O 1 i SW pQ 00 o - n ---101 8'8. IYL 1Q 1I 1 1100 rr Q 0 0 1 QQ re W W V u v ` -W .u-- • - 5110 i >i)-a'F-W W 6 Z O 1 iW Z W U a'LL a'iV 2 m 0 m C. w I 2 O s-1m 1 (07 f-0F-I JJ U 0 1 Z �01 Fe' J U p H al ' Ole 1-- >O �> O >1 a> 0 '>> K Q F W W W Q H W W Q am w p a W� K V OJ -IWI re V 3 a() LL 2 O LLQ SO2 Z 1 2 Q Z 07 /-! 'Q Ce Z 0 '8 0 � :Q Z 0 III ° ;> 1 wZ ap = C? c 7� O Ism W J O 7 u) 0 I- 7 re o � J - O O ix I UJ a 0ci) 10; a' Z ui Hwy O 1- 0 dO 0 < ZW Q 1 < 0-.a 2 /n i 0. OJ O ®"' 0 U) a DL. Z w -J 7 0 a w > U) O w = C 00 0 O a w p p Co a.. [ = a. a 0 0 0 4' ,a o'z y en J 3 V Fan _' v 0 r d • i= OF -1 W C i 11 Q O 0 w 1 i 0 Cr 2 co I a I Iz1 a a Aft Va. 1 DA 1 Detention #1 3 0 DA 2 a Detention #2 (subca) Reach 'on, Drainage Diagram for Timberwood Commons Post-Development RRM Prepared by Shimp Engineering P.C., Printed 12/3/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Timberwood Commons Post-Development RRM Type 1124-hr 1yr Rainfall=2.98" Prepared by Shimp Engineering P.C. Printed 12/3/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1: DA 1 Runoff = 0.86 cfs @ 11.96 hrs, Volume= 0.045 af, Depth> 2.75" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs �• Type II 24-hr 1 yr Rainfall=2.98" Area (sf) CN Description 3,674 98 Unconnected roofs, HSG B 4,970 98 Unconnected roofs, HSG C 8,644 98 Weighted Average 8,644 100.00% Impervious Area 8,644 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 3: DA 2 Runoff = 2.45 cfs @ 11.96 hrs, Volume= 0.117 af, Depth> 2.23" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 1 yr Rainfall=2.98" Area (sf) CN Description 9,855 98 Unconnected roofs, HSG B 1,825 61 >75% Grass cover, Good, HSG B 2,470 74 >75% Grass cover, Good, HSG C 13,333 98 Unconnected roofs, HSG C 27,483 93 Weighted Average 4,295 15.63% Pervious Area 23,188 84.37% Impervious Area 23,188 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Timberwood Commons Post-Development RRM Type 1124-hr 10yr Rainfall=5.45" Prepared by Shimp Engineering P.C. Printed 12/3/2015 HydroCAD?9.10 s/n 07054 ?2011 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 1: DA 1 Runoff = 1.59 cfs @ 11.96 hrs, Volume= 0.086 af, Depth> 5.21" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs �•• Type II 24-hr 10yr Rainfall=5.45" Area (sf) CN Description 3,674 98 Unconnected roofs, HSG B 4,970 98 Unconnected roofs, HSG C 8,644 98 Weighted Average 8,644 100.00% Impervious Area 8,644 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 3: DA 2 Runoff = 4.85 cfs @ 11.96 hrs, Volume= 0.244 af, Depth> 4.64" �• Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=5.45" Area (sf) CN Description 9,855 98 Unconnected roofs, HSG B 1,825 61 >75%Grass cover, Good, HSG B 2,470 74 >75% Grass cover, Good, HSG C 13,333 98 Unconnected roofs, HSG C 27,483 93 Weighted Average 4,295 15.63% Pervious Area saw23,188 84.37% Impervious Area 23,188 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, a Storm Inlet and Drain Computations Storm Inlet Drainage Area Map VDOT Drainage Manual LD-204 VDOT Drainage Manual LD-229 a 1 III 1 \ 1 \, ,._ AIN \ MIN PI 1 ---,„ , . 1 .,g, ,... ,-/./ \ I I 1 in I I 1 1 1 \1 \I 1 \\9 0 01 0 ,. \ Ai 1 1 (..,/,____. ,_...... 7,574:00 4-.0., >, s... ,,C .47, .,_ cri _C-C).s, /I ..: -•-• . _ . 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U Gutter X-slope Total Gutter - °) Spread 03 a) w w w 4) (O O Co N oo000v Depth at Curb N � O Wil 0') oo . 00 00 % Effice ncy 00 (000 e 0 0 iv - o -- ow Cc) Q intercepted O N W O Q) pp 0 o 0 1.v ,Q Bypassed 00000 00 - 00 • 0 0�- Midpoint Depth 03 W N Curb Height 0 0 0 in in 0n Fp' r) 0 0 0 V,)ND/H �O A W N O) C)) O) N Midpoint Spread � 0 Oa cal 0 Independent Reports Exerpt from NRCS Soils Report NOAA Precipitation Report Custom Soil Resource Report Map—Hydrologic Soil Group io am N N r 6 r 724200 724270 724340 724410 724480 724550 724620 38°7'57" x :,:: 38°7'57" AM 1,' CO 4.. CMV • ' �, f T O^ G A 1. x a • M N ,r M CM k f ' or *: <":3,� {h` {/° 1. 410. iji 4ft /• yXN -,ft(if 4.-'''' ` Yorn;, r; � t f— 'f Ak i k,• 'r orf „...$-4,' '•: alli } IN MIS r 1 ,r.4t 44 /...# *'. X Ili N �� n� �I�Y..:,•./ f 4 it {£ f. 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Custom Soil Resource Report MIN Table—Hydrologic Soil Group Hydrologic Soil Group—Summary by Map Unit—Albemarle County,Virginia(VA003) �r Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 27B Elioak loam,2 to 7 percent C 4.3 23.6% slopes 27C Elioak loam,7 to 15 percent C 1.5 8.3% slopes 28C3 Elioak clay loam,7 to 15 percent C 4.1 22.8% slopes,severely eroded e" 34D Glenelg loam, 15 to 25 percent B 7.6 42.5% slopes W Water 0.5 2.8% Totals for Area of Interest 18.0 100.0% Rating Options—Hydrologic Soil Group 4/111 Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher AIN 91111 MIN Ufa20 .... 1/11/12 Precipitation Frequency Data Server NOAA Atlas 14,Volume 2,Version 3 Location name:Virg , *iniaUS ' . ..1 Coordinates:38.1282,-78.4452 Itigt 1. I Elevation:583 ft* *source:Google Maps POINT PRECIPITATION FREQUENCY ESTIMATES .. G.M.Bonnin,D.Martin,B.Lin,T.Parzybok M.Yekia,and D.Riley NOAA,National Weather Service,Silver Spring,Maryland . PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals(in inches)1 I Average recurrence interval (years) ' Duration - f j 1 2 5 1 0 1 25 50 100 ..,1 200 500 I 1000 I -go0.417 0.490 1 0.551 : 0.621 i 0.677 , 0.729 1 0.778 0.839 0.888 1 5-mm 1 0.349 (1315-0.387) (0.377-0.462) (0.442-0.542) (0.496-0.609)1(0.556-0.685)1(0.603-0.745)1(0.645-0.802) (0.684-0357) (0.729-0.927) (0.765-0.985) 10i 0.558 0.666 0.784 0.881 IL 0.990 1.08 i 1.16 IL 1.23 1.33 I 1.40 -m n (0.504-0.618) (0.602-0.739) (0.707-0.868) (0.793-0.975)l (0.887-1.09); (0.960-1.19)i (1.02-1.27) 1 (1.08-1.36) (1.15-1.47) 1 Am 150.697 0.838 0.992 1.11 ; 1.25 1.36 ; 1.46 1 1.56 1.67 I 1.75 ! -min 1(0.629-0.773) (0.757-0.929) (0.895-1.10) (1.00-1.23) 1 (1.12-1.38) j (1.22-1.50) ' (1.30-1.61)1 (1.37-1.72) (1.45-1.85) (1.51-1.95) 30-min 0.956 1.16 1.41 1.61 ! 1.86 2.06 ' 2.24 1 2.42 2.66 I 2.84 I 1 (0.863-1.06) (1.05-1.28) (1.27-1.56) (1.45-1.79) 1 (1.67-2.05) ; (1.83-2.26) 1 (1.99-2.47) ; (2.13-2.67) (2.31-2.94)sj (2.45-3.15) AN 1 601.19 1.45 1.81 2.10 2.48 ; 2.79 ; 3.09 3.40 3.81 i 4.15 -min ' I (1.08-1.32) (1.31-1.61) (1.63-2.00) (1.89-233) ; (2.22-2.73) ; (2.48-107) ; (2.73-3A0) (2.99-3.74) (3.31-4.21) 1 (3.58-4.60) l• 1.43 1.74 2.18 2.56 ! 3.06 ; 3.47 ' 3.90 i 4.35 4.98 1 5.51 ! 2-hr (1.27-1.62) (134-1.97) (1.912A6)._(2:27-239) ; (2.68:3.44) (3.03-3.91) (3.38-4.38) 1 (3.75-4.89) (4.24-5.61) 1 ( 64-6.23) 3-h1 1.57 [ 1.90 L 2.38 r 2.79 : 3.33 3.79 ; 4.27 I 4.77 5.46 6.06 (1.38-1.79) (1.67-2.17) (2.09-2.72) (Z45-3.18) 1 (2.91-3.79) (3.29-4.31) (3.67-4.84)J (4.07-5.42) (4.61-6.22) (5.05-6.91) 6-hr 1.99 2.41 3.00 3.53 i 4.24 4.87 5.53 ; 6.24 7.26 1 8.17 (1.77-2.26) (2.13-2.74) 1 (2.64-3.40) (3.10-3.99) 1 (3.70-4.80) ; (4.21-5A9) i (4.74-6.24) 1 (5.29-7.05) J (6.07-8.22) 1 (6.73-9.26) ago ; •' I . 12-hr 2.50 3.02 3.76 L 4.45 : 5.42 : 6.28 7.21 8.25 I 1 11.2 ] (2.21-2.86)( 2.67-3.45) (3.31-4.30) (3.91-5.08) j 9.78(4.71-a16) ; (5A1-7.13) 1 ss(6.14-8.18) (6.92-9.35) (8.05-11.1)1 (9.04-12.7)j 24-hr 2.98 3.61 4.61 5.45 ' 6.69 . 7.75 i 8.92 ! 10.2 12.1 13.8 (2.67-3.36) (3.24-4.06)J (4.12-5.18) 0.86-6.11) 1 (5.92-7A8) (6.82-8.65) (7.78-9.95) ' (8 82-11 4) (10 3 13 5) (11 6 15 3) air I 2d1i 3.51 4.26 5.41 6.36 1 7.73 8.89 1 10.1 I 11.5 13.5 15.1 - ay (3.16-3.93) 1 (3.83.4,76) (4.86-6.04) (5.70-7.09) 1 (6.88-8.60) (7.85-9.87) 1 (8.88-11.3) i (9.99-12.8) (11.6-15.0) (12.8-16.9) 1 I 3.74 4.53 5.76 6.76 1 8.22 9.44 ' 10.8 [ 12.2 14.3 16.0 I 3-day p.40-4.15 )(4.11-5.03)i J5.21-6.38) (6.11-7.49) 1 (7.38-9.08) 1 (8.42-10.4) . (9.53-11.9) (10.7-13.5) (12.4-15.8) (13.8-17.8) ow ' .-.,. ........,.........-----...-............ -.. --.. -.... ---..............-----... .-.----.,---. I 397 481 6.10 7.16 8.71 ' 9A9 ' 11A I 12A 15.1 ' 1691 4-day I (3.63-4.38) (4.39-5.30) (5.57-6.72) (6.52-7.88) ; (7.89-9.57) , (9.9o) i (102-12.5) 1 J11.4-14.2) (13.2-16.6) 1 (14.7-18.7)1 7-d4.61 5.55 6.94 8.08 9.72 11.1 ; 12.5 14.1 16.3 I 18.2 I ay (4.23-5.06) (5.09-6.08) (6.35-7.61) (7.37-8.85) i (8.82-10.6) (10.0-12.1) 1 (1t2-13.7) (1Z5-15.4) (14.3-18.0)j (15.8-20.1) alel , 1 0I 5.24 6.28 7.76 8.95 i 10.6 : 12.0 ! 13.5 15.0 17.2 18.9 -d ay 1 (4.82-5.69) (5.79-6.82)j (7.13-8.42) (8.21-9.71) ! (9.72-11.5) 1 (10.9-13.0) i (12.2-14.6) 1 (115:13.3) (15.3-18.7) (16.7-20.7) 20-da 6.88 L 8.21 9.91 11.3 IL 13.1 ; 14.5 I 16.0 I 17.4 19.5 21.0 y J6.43-7.39) (7.67-8.81)_(9.25-10.6) (10.5-12.1) ; (12.1-14.0) , (13.4-15.5) 1 (14.7-17.1)i (16.0-18.8) (17.7-21.0) (19.0-22.8) vim I 30-day 8.44 10.0 11.8 13.2 IL 15.0 ; 16.4 ; 17.8 i 19.1 20.8 22.1 (7.93-9.01) (9.40-10.7) (11.1-12.6) (12.4-14:1) 1 (14.1-16.0) ; (15.3-17.5) j (16.5-18.9) (17.7-20.4) (19.2-22.3) (20.3-23.7)s. .------- I 10.5 12.5 14.6 16.1 I 18.1 ; 19.6 1 21.1 1 22.4 i 24.2 25.5 NM 1 45-clay_ (9.94-11.2) (11.7-13.2) (13.7-15A) (15.2-17.1) 1 (17.0-19.2) 1 (18.4-20.8)1 (19.7-22.3)1 (20.9-23.8) (22.5-25.8) (23.6-27.3) „.,. 60-day 12.4 14.6 16.8 18.5 I 20.6 I 22.2 1 23.7 25.1 26.9 28.2 i (11.7-13.1) (13.8-15.4) j (15.9-17.7) (17.5-19.5) 1 (19.4-21.8) L(20.9-23.4) 1 (22.2-25.0) (23.5-26.5) (25.1:28.5) (26.2-29.9) !1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(POS). on Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a i given duration and average recurrence interval)w ill 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 RV values. IPlease refer to NOAA Atlas 14 document for mare information. _____ wria Back to Too PF graphical . I I hdsc.nws.noaa.gov/hdscfpfds/pfds_printpage.html?lat=38.1282&lon=-78.44... 1/4 ....