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HomeMy WebLinkAboutWPO202000033 Calculations WPO VSMP 2020-06-05 June 5, 2020 County of Albemarle Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Regarding: Malloy Ford TMP 45-68A Stormwater Management Plan Dear Reviewer, The purpose of this project is to add a parking area to a site with an existing building and limited parking. Parking will be added where a portion of the existing building was removed. The total area of disturbance is 0.91 acres. Runoff from the site is analyzed at two points, labeled POA1 and POA2. Please see VSMP plan sheets C8 and C9 for the locations of these drainage areas and points of analysis. The drainage areas to points of analysis are separated into disturbed and undisturbed area, since the improvement factor is only applied to the disturbed portions continue to function as designed. Runoff to POA1 outlets to an existing stormwater pipe (labeled A1) while runoff to POA2 is released over land from the site and eventually picked up by a drop inlet down the road outside of Route 29. In both cases, the peak flow rates released at these points of analysis are less than in predevelopment conditions and conform with channel and flood protection requirements. Please see below for a summary of energy balance calculations. The first table shows 1 yr, 24 hr storm peak flow rates and runoff volume for drainage areas within the disturbed area. The improvement factor of 0.9 is applied to these values in the energy balance equation. The second table shows all values for drainage areas outside of the limits of disturbance, no improvement factor was applied to these values. The third table shows the final results, along with 10 yr, 24 hr storm peak flow rates of both pre and post development conditions. For further detail on these drainage areas and calculations, please see the HydroCAD reports included in this document. Note that time of concentration calculations are not included as all are assumed 5 minutes. Table 1. Values for DAs Within LOD - Energy Balance Equation PREDEV POSTDEV POA Q1 RV RV 1 2.39 0.115 0.102 2 0.67 0.031 0.027 Table 2. Values for DAs Outside LOD – Energy Balance Equation PREDEV POSTDEV POA Q1 RV RV 1 1.63 0.088 0.088 2 0 0 0 Table 3. Summary of Results – Energy Balance Equation & Flood Protection Table 1 Table 2 Q1 Allowable = [(Q1Pre(LOD)*RvPre(LOD)*I.F.)/RvPost(LOD)]+[(Q1Pre*RvPre)/RvPost] Or Q1 Pre, whichever is less POA Q1 ALLOWABLE (CFS) Q1 PROPOSED (CFS) Q10 PRE Q10 POST 1 4.03 3.79 7.91 7.71 2 0.69 0.61 1.62 1.53 According to the VRRM spreadsheet included in this packet, the target phosphorus load reduction is 0.01 lb/yr. Nutrient credits will be purchased to satisfy this requirement. Contents: Pre-Development Stormwater Management Calculations: Pre-Development Landuse Map Pre-Development HydroCAD Analysis Post-Development Stormwater Management Calculations: Post-Development Landuse Map Post-Development HydroCAD Analysis Stormwater Quality Calculations: VRRM Redevelopment Spreadsheet Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre-Development Stormwater Management Calculations Pre-Development Landuse Map Pre-Development HydroCAD Analysis 300306090Scale: 1"=30' 1S POA 2 DA (IN LOD) 2S POA 1 DA (IN LOD) 3S POA 1 DA (Outside LOD) 5L POA 1 6L POA 2 Drainage Diagram for Pre Dev Prepared by {enter your company name here}, Printed 6/5/2020 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Subcat Reach Pond Link PreDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 2HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=11,140 sf 50.77% Impervious Runoff Depth=1.45"Subcatchment 1S: POA 2 DA (IN LOD) Tc=5.0 min CN=83 Runoff=0.67 cfs 0.031 af Runoff Area=28,892 sf 76.44% Impervious Runoff Depth=2.08"Subcatchment 2S: POA 1 DA (IN LOD) Tc=5.0 min CN=91 Runoff=2.39 cfs 0.115 af Runoff Area=16,577 sf 100.00% Impervious Runoff Depth=2.78"Subcatchment 3S: POA 1 DA (Outside Tc=5.0 min CN=98 Runoff=1.63 cfs 0.088 af Inflow=4.03 cfs 0.203 afLink 5L: POA 1 Primary=4.03 cfs 0.203 af Inflow=0.67 cfs 0.031 afLink 6L: POA 2 Primary=0.67 cfs 0.031 af Total Runoff Area = 1.300 ac Runoff Volume = 0.234 af Average Runoff Depth = 2.16" 21.71% Pervious = 0.282 ac 78.29% Impervious = 1.017 ac PreDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 3HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: POA 2 DA (IN LOD) Runoff = 0.67 cfs @ 11.96 hrs, Volume= 0.031 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" Area (sf) CN Description 3,444 61 >75% Grass cover, Good, HSG B 2,040 80 >75% Grass cover, Good, HSG D * 0 98 Impervious, HSG B * 5,656 98 Impervious, HSG D 11,140 83 Weighted Average 5,484 49.23% Pervious Area 5,656 50.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: POA 1 DA (IN LOD) Runoff = 2.39 cfs @ 11.95 hrs, Volume= 0.115 af, Depth= 2.08" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" Area (sf) CN Description 2,544 80 >75% Grass cover, Good, HSG D 4,263 61 >75% Grass cover, Good, HSG B * 15,501 98 HSG D Imperv * 6,584 98 HSG B Imperv 28,892 91 Weighted Average 6,807 23.56% Pervious Area 22,085 76.44% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 3S: POA 1 DA (Outside LOD) Runoff = 1.63 cfs @ 11.95 hrs, Volume= 0.088 af, Depth= 2.78" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" PreDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 4HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Area (sf) CN Description 0 80 >75% Grass cover, Good, HSG D 0 61 >75% Grass cover, Good, HSG B * 6,994 98 HSG D Imperv * 9,583 98 HSG B Imperv 16,577 98 Weighted Average 16,577 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 5L: POA 1 Inflow Area = 1.044 ac, 85.03% Impervious, Inflow Depth = 2.33" for 1 yr, 24 hr event Inflow = 4.03 cfs @ 11.95 hrs, Volume= 0.203 af Primary = 4.03 cfs @ 11.95 hrs, Volume= 0.203 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Summary for Link 6L: POA 2 Inflow Area = 0.256 ac, 50.77% Impervious, Inflow Depth = 1.45" for 1 yr, 24 hr event Inflow = 0.67 cfs @ 11.96 hrs, Volume= 0.031 af Primary = 0.67 cfs @ 11.96 hrs, Volume= 0.031 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs PreDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 5HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=11,140 sf 50.77% Impervious Runoff Depth=3.63"Subcatchment 1S: POA 2 DA (IN LOD) Tc=5.0 min CN=83 Runoff=1.62 cfs 0.077 af Runoff Area=28,892 sf 76.44% Impervious Runoff Depth=4.47"Subcatchment 2S: POA 1 DA (IN LOD) Tc=5.0 min CN=91 Runoff=4.90 cfs 0.247 af Runoff Area=16,577 sf 100.00% Impervious Runoff Depth=5.26"Subcatchment 3S: POA 1 DA (Outside Tc=5.0 min CN=98 Runoff=3.01 cfs 0.167 af Inflow=7.91 cfs 0.414 afLink 5L: POA 1 Primary=7.91 cfs 0.414 af Inflow=1.62 cfs 0.077 afLink 6L: POA 2 Primary=1.62 cfs 0.077 af Total Runoff Area = 1.300 ac Runoff Volume = 0.491 af Average Runoff Depth = 4.54" 21.71% Pervious = 0.282 ac 78.29% Impervious = 1.017 ac PreDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 6HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: POA 2 DA (IN LOD) Runoff = 1.62 cfs @ 11.95 hrs, Volume= 0.077 af, Depth= 3.63" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" Area (sf) CN Description 3,444 61 >75% Grass cover, Good, HSG B 2,040 80 >75% Grass cover, Good, HSG D * 0 98 Impervious, HSG B * 5,656 98 Impervious, HSG D 11,140 83 Weighted Average 5,484 49.23% Pervious Area 5,656 50.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 2S: POA 1 DA (IN LOD) Runoff = 4.90 cfs @ 11.95 hrs, Volume= 0.247 af, Depth= 4.47" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" Area (sf) CN Description 2,544 80 >75% Grass cover, Good, HSG D 4,263 61 >75% Grass cover, Good, HSG B * 15,501 98 HSG D Imperv * 6,584 98 HSG B Imperv 28,892 91 Weighted Average 6,807 23.56% Pervious Area 22,085 76.44% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 3S: POA 1 DA (Outside LOD) Runoff = 3.01 cfs @ 11.95 hrs, Volume= 0.167 af, Depth= 5.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" PreDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Pre Dev Printed 6/5/2020Prepared by {enter your company name here} Page 7HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Area (sf) CN Description 0 80 >75% Grass cover, Good, HSG D 0 61 >75% Grass cover, Good, HSG B * 6,994 98 HSG D Imperv * 9,583 98 HSG B Imperv 16,577 98 Weighted Average 16,577 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 5L: POA 1 Inflow Area = 1.044 ac, 85.03% Impervious, Inflow Depth = 4.76" for 10 yr, 24 hr event Inflow = 7.91 cfs @ 11.95 hrs, Volume= 0.414 af Primary = 7.91 cfs @ 11.95 hrs, Volume= 0.414 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Summary for Link 6L: POA 2 Inflow Area = 0.256 ac, 50.77% Impervious, Inflow Depth = 3.63" for 10 yr, 24 hr event Inflow = 1.62 cfs @ 11.95 hrs, Volume= 0.077 af Primary = 1.62 cfs @ 11.95 hrs, Volume= 0.077 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Post-Development Stormwater Management Calculations Post-Development Landuse Map Post-Development HydroCAD Analysis 300306090Scale: 1"=30' 1S POA 1 DA (IN LOD) 5S POA 2 DA (IN LOD) 12S POA 1 DA (Outside LOD) 14S POA 2 to DA (Outside LOD) 4L POA 2 11L POA 1 Drainage Diagram for Post Dev Prepared by {enter your company name here}, Printed 6/5/2020 HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Subcat Reach Pond Link PostDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 2HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=29,104 sf 67.67% Impervious Runoff Depth=1.83"Subcatchment 1S: POA 1 DA (IN LOD) Tc=5.0 min CN=88 Runoff=2.16 cfs 0.102 af Runoff Area=10,607 sf 39.29% Impervious Runoff Depth=1.32"Subcatchment 5S: POA 2 DA (IN LOD) Tc=5.0 min CN=81 Runoff=0.58 cfs 0.027 af Runoff Area=16,577 sf 100.00% Impervious Runoff Depth=2.78"Subcatchment 12S: POA 1 DA (Outside Tc=5.0 min CN=98 Runoff=1.63 cfs 0.088 af Runoff Area=321 sf 100.00% Impervious Runoff Depth=2.78"Subcatchment 14S: POA 2 to DA (Outside Tc=5.0 min CN=98 Runoff=0.03 cfs 0.002 af Inflow=0.61 cfs 0.029 afLink 4L: POA 2 Primary=0.61 cfs 0.029 af Inflow=3.79 cfs 0.190 afLink 11L: POA 1 Primary=3.79 cfs 0.190 af Total Runoff Area = 1.300 ac Runoff Volume = 0.218 af Average Runoff Depth = 2.02" 28.00% Pervious = 0.364 ac 72.00% Impervious = 0.936 ac PostDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 3HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: POA 1 DA (IN LOD) Runoff = 2.16 cfs @ 11.96 hrs, Volume= 0.102 af, Depth= 1.83" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" Area (sf) CN Description 6,723 61 >75% Grass cover, Good, HSG B 2,687 80 >75% Grass cover, Good, HSG D * 4,119 98 IMPERV B * 15,575 98 IMPERV D 29,104 88 Weighted Average 9,410 32.33% Pervious Area 19,694 67.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 5S: POA 2 DA (IN LOD) Runoff = 0.58 cfs @ 11.96 hrs, Volume= 0.027 af, Depth= 1.32" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" Area (sf) CN Description 3,449 61 >75% Grass cover, Good, HSG B 2,990 80 >75% Grass cover, Good, HSG D * 0 98 IMPERV B * 4,168 98 IMPERV D 10,607 81 Weighted Average 6,439 60.71% Pervious Area 4,168 39.29% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 12S: POA 1 DA (Outside LOD) Runoff = 1.63 cfs @ 11.95 hrs, Volume= 0.088 af, Depth= 2.78" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" PostDev Type II 24-hr 1 yr, 24 hr Rainfall=3.01"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 4HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Area (sf) CN Description 0 61 >75% Grass cover, Good, HSG B 0 80 >75% Grass cover, Good, HSG D * 9,583 98 IMPERV B * 6,994 98 IMPERV D 16,577 98 Weighted Average 16,577 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 14S: POA 2 to DA (Outside LOD) Runoff = 0.03 cfs @ 11.95 hrs, Volume= 0.002 af, Depth= 2.78" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr, 24 hr Rainfall=3.01" Area (sf) CN Description * 321 98 321 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 4L: POA 2 Inflow Area = 0.251 ac, 41.08% Impervious, Inflow Depth = 1.36" for 1 yr, 24 hr event Inflow = 0.61 cfs @ 11.96 hrs, Volume= 0.029 af Primary = 0.61 cfs @ 11.96 hrs, Volume= 0.029 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Summary for Link 11L: POA 1 Inflow Area = 1.049 ac, 79.40% Impervious, Inflow Depth = 2.17" for 1 yr, 24 hr event Inflow = 3.79 cfs @ 11.95 hrs, Volume= 0.190 af Primary = 3.79 cfs @ 11.95 hrs, Volume= 0.190 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs PostDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 5HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Time span=0.00-48.00 hrs, dt=0.05 hrs, 961 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=29,104 sf 67.67% Impervious Runoff Depth=4.15"Subcatchment 1S: POA 1 DA (IN LOD) Tc=5.0 min CN=88 Runoff=4.70 cfs 0.231 af Runoff Area=10,607 sf 39.29% Impervious Runoff Depth=3.43"Subcatchment 5S: POA 2 DA (IN LOD) Tc=5.0 min CN=81 Runoff=1.47 cfs 0.070 af Runoff Area=16,577 sf 100.00% Impervious Runoff Depth=5.26"Subcatchment 12S: POA 1 DA (Outside Tc=5.0 min CN=98 Runoff=3.01 cfs 0.167 af Runoff Area=321 sf 100.00% Impervious Runoff Depth=5.26"Subcatchment 14S: POA 2 to DA (Outside Tc=5.0 min CN=98 Runoff=0.06 cfs 0.003 af Inflow=1.53 cfs 0.073 afLink 4L: POA 2 Primary=1.53 cfs 0.073 af Inflow=7.71 cfs 0.398 afLink 11L: POA 1 Primary=7.71 cfs 0.398 af Total Runoff Area = 1.300 ac Runoff Volume = 0.471 af Average Runoff Depth = 4.35" 28.00% Pervious = 0.364 ac 72.00% Impervious = 0.936 ac PostDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 6HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: POA 1 DA (IN LOD) Runoff = 4.70 cfs @ 11.95 hrs, Volume= 0.231 af, Depth= 4.15" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" Area (sf) CN Description 6,723 61 >75% Grass cover, Good, HSG B 2,687 80 >75% Grass cover, Good, HSG D * 4,119 98 IMPERV B * 15,575 98 IMPERV D 29,104 88 Weighted Average 9,410 32.33% Pervious Area 19,694 67.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 5S: POA 2 DA (IN LOD) Runoff = 1.47 cfs @ 11.96 hrs, Volume= 0.070 af, Depth= 3.43" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" Area (sf) CN Description 3,449 61 >75% Grass cover, Good, HSG B 2,990 80 >75% Grass cover, Good, HSG D * 0 98 IMPERV B * 4,168 98 IMPERV D 10,607 81 Weighted Average 6,439 60.71% Pervious Area 4,168 39.29% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 12S: POA 1 DA (Outside LOD) Runoff = 3.01 cfs @ 11.95 hrs, Volume= 0.167 af, Depth= 5.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" PostDev Type II 24-hr 10 yr, 24 hr Rainfall=5.50"Post Dev Printed 6/5/2020Prepared by {enter your company name here} Page 7HydroCAD® 9.10 s/n 07054 © 2011 HydroCAD Software Solutions LLC Area (sf) CN Description 0 61 >75% Grass cover, Good, HSG B 0 80 >75% Grass cover, Good, HSG D * 9,583 98 IMPERV B * 6,994 98 IMPERV D 16,577 98 Weighted Average 16,577 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 14S: POA 2 to DA (Outside LOD) Runoff = 0.06 cfs @ 11.95 hrs, Volume= 0.003 af, Depth= 5.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type II 24-hr 10 yr, 24 hr Rainfall=5.50" Area (sf) CN Description * 321 98 321 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Link 4L: POA 2 Inflow Area = 0.251 ac, 41.08% Impervious, Inflow Depth = 3.48" for 10 yr, 24 hr event Inflow = 1.53 cfs @ 11.95 hrs, Volume= 0.073 af Primary = 1.53 cfs @ 11.95 hrs, Volume= 0.073 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Summary for Link 11L: POA 1 Inflow Area = 1.049 ac, 79.40% Impervious, Inflow Depth = 4.55" for 10 yr, 24 hr event Inflow = 7.71 cfs @ 11.95 hrs, Volume= 0.398 af Primary = 7.71 cfs @ 11.95 hrs, Volume= 0.398 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Stormwater Quality Calculations VRRM Redevelopment Spreadsheet Project Name:  Date:  Linear Development Project?No Site Information Post‐Development Project (Treatment Volume and Loads) 0.91 TRUE 10%Linear project?No The site's net increase in impervious cover (acres) is: 0 ✔ Post‐Development TP Load Reduction for Site (lb/yr): 0.01 ✔ Pre‐ReDevelopment Land Cover  (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) ‐‐ undisturbed  forest/open space 0.00 Managed Turf (acres) ‐‐ disturbed, graded for  yards or other turf to be mowed/managed 0.18 0.11 0.28 Impervious Cover (acres)0.15 0.48 0.63 0.91 Post‐Development Land Cover  (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) ‐‐ undisturbed,  protected forest/open space or reforested land 0.00 Managed Turf (acres) ‐‐ disturbed, graded for  yards or other turf to be mowed/managed 0.23 0.13 0.36 Impervious Cover (acres)0.09 0.45 0.55 Area Check OK. OK. OK. OK.0.91 Constants Runoff Coefficients (Rv) Annual Rainfall (inches)43 A Soils B Soils C Soils D Soils Target Rainfall Event (inches)1.00 Forest/Open Space 0.02 0.03 0.04 0.05 Total Phosphorus (TP) EMC (mg/L)0.26 Managed Turf 0.15 0.20 0.22 0.25 Total Nitrogen (TN) EMC (mg/L)1.86 Impervious Cover 0.95 0.95 0.95 0.95 Target TP Load (lb/acre/yr)0.41 Pj (unitless correction factor)0.90 Pre‐ReDevelopment Listed Adjusted1 Forest/Open Space Cover (acres)0.00 0.00 Forest/Open Space  Cover (acres)0.00 Forest/Open Space  Cover (acres)0.00 Weighted Rv(forest)0.00 0.00 Weighted Rv(forest)0.00 Weighted Rv(forest)0.00 % Forest 0% 0%% Forest 0%% Forest 0% Managed Turf Cover (acres)0.28 0.28 Managed Turf Cover  (acres)0.36 Managed Turf Cover  (acres)0.36 Weighted Rv(turf)0.22 0.22 Weighted Rv (turf)0.22 Weighted Rv (turf)0.22 % Managed Turf 31% 31%% Managed Turf 40%% Managed Turf 40% Impervious Cover (acres)0.63 0.63 Impervious Cover (acres)0.55 ReDev. Impervious  Cover (acres)0.55 New Impervious Cover  (acres)0.00 Rv(impervious)0.95 0.95 Rv(impervious)0.95 Rv(impervious)0.95 Rv(impervious)‐‐ % Impervious 69% 69%% Impervious 60%% Impervious 60% Total Site Area (acres)0.91 0.91 Final Site Area (acres)0.91 Total ReDev. Site Area  (acres)0.91 Site Rv 0.72 0.72 Final Post Dev Site Rv 0.66 ReDev Site Rv 0.66 Pre‐ReDevelopment Treatment Volume  (acre‐ft) 0.0549 0.0549 Final Post‐Development  Treatment Volume       (acre‐ft)  0.0499 Post‐ReDevelopment  Treatment Volume      (acre‐ft)  0.0499 Post‐Development  Treatment Volume  (acre‐ft)  ‐‐ Pre‐ReDevelopment Treatment Volume  (cubic feet) 2,393 2,393 Final Post‐Development  Treatment Volume  (cubic feet)  2,174 Post‐ReDevelopment  Treatment Volume      (cubic feet)  2,174 Post‐Development  Treatment Volume (cubic  feet)  ‐‐ Pre‐ReDevelopment TP Load                (lb/yr)1.50 1.50 Final Post‐ Development TP Load  (lb/yr) 1.37 Post‐ReDevelopment  Load (TP)               (lb/yr)* 1.37 Post‐Development TP  Load (lb/yr)‐‐ Pre‐ReDevelopment TP Load per acre (lb/acre/yr)1.65 1.65 Final Post‐Development TP  Load per acre  (lb/acre/yr) 1.50 Post‐ReDevelopment TP  Load per acre  (lb/acre/yr) 1.50 0.37 Max. Reduction Required  (Below Pre‐ ReDevelopment Load) 10% TP Load Reduction  Required for  Redeveloped Area  (lb/yr) 0.01 TP Load Reduction  Required for New  Impervious Area (lb/yr) 0 0.01 Malloy Furniture 6/3/2020 LAND COVER SUMMARY -- POST DEVELOPMENTLAND COVER SUMMARY -- PRE-REDEVELOPMENT  Maximum reduction required: Enter Total Disturbed Area (acres)  →Check: Land cover areas entered correctly? Total disturbed area entered? BMP Design Specifications List: Treatment Volume and Nutrient Load Land Cover Summary‐Post (Final) 2013 Draft Stds & Specs Land Cover Summary‐Pre Land Cover Summary‐Post Post‐ReDevelopment TP Load Reduction Required (lb/yr) Post‐Development Requirement for Site Area Baseline TP Load (lb/yr) (0.41 lbs/acre/yr applied to pre‐redevelopment area excluding pervious  land proposed for new impervious cover) 1 Adjusted Land Cover Summary:  Pre ReDevelopment land cover minus pervious land cover (forest/open space or  managed turf) acreage proposed for new impervious cover.   Adjusted total acreage is consistent with Post‐ReDevelopment acreage (minus  acreage  of new impervious cover).   Column I shows load reduction requriement for new impervious cover (based on new  development load limit, 0.41 lbs/acre/year).  Post ReDev. & New Impervious Treatment Volume and Nutrient Load Land Cover Summary‐Post Post‐Development New Impervious CLEAR  ALL (Ctrl+Shift+R) data input cells constant values calculation cells final results Site Results (Water Quality Compliance) Area Checks D.A. A D.A. B D.A. C D.A. D D.A. E AREA CHECK FOREST/OPEN SPACE (ac)0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER (ac)0.00 0.00 0.00 0.00 0.00 OK. IMPERVIOUS COVER TREATED (ac)0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA (ac)0.00 0.00 0.00 0.00 0.00 OK. MANAGED TURF AREA TREATED (ac)0.00 0.00 0.00 0.00 0.00 OK. AREA CHECK  OK. OK. OK. OK. OK. Site Treatment Volume (ft3)2,174 Runoff Reduction Volume and TP By Drainage Area D.A. A D.A. B D.A. C D.A. D D.A. E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED (ft3)000000 TP LOAD AVAILABLE FOR REMOVAL  (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REDUCTION ACHIEVED  (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00 TP LOAD REMAINING  (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00 NITROGEN LOAD REDUCTION ACHIEVED  (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00 Total Phosphorus  LINEAR PROJECT: FINAL POST‐DEVELOPMENT TP LOAD (lb/yr)1.37 TP LOAD REDUCTION REQUIRED (lb/yr)0.01 TP LOAD REDUCTION ACHIEVED  (lb/yr)0.00 TP LOAD REMAINING (lb/yr):1.37 REMAINING TP LOAD REDUCTION REQUIRED (lb/yr):0.01 Total Nitrogen (For Information Purposes) POST‐DEVELOPMENT LOAD (lb/yr)9.77 NITROGEN LOAD REDUCTION ACHIEVED  (lb/yr)0.00 REMAINING POST‐DEVELOPMENT NITROGEN LOAD (lb/yr)9.77 Virginia Runoff Reduction Method WorksheetDEQ Virginia Runoff Reduction Method Re‐Development Compliance Spreadsheet  ‐ Version 3.0 BMP Design Specifications List:2013 Draft Stds & SpecsDate: 43985430.91Site Land Cover SummaryPre‐ReDevelopment Land Cover  (acres)A soils B Soils C Soils D Soils Totals% of TotalForest/Open (acres)0.00 0.00 0.00 0.00 0.00 0Managed Turf (acres)0.00 0.18 0.00 0.11 0.28 31Impervious Cover (acres)0.00 0.15 0.00 0.48 0.63 690.91 100Post‐ReDevelopment Land Cover  (acres)A soils B Soils C Soils D Soils Totals% of TotalForest/Open (acres)0.00 0.00 0.00 0.00 0.00 0Managed Turf (acres)0.00 0.23 0.00 0.13 0.36 40Impervious Cover (acres)0.00 0.09 0.00 0.45 0.55 600.91 100Site Tv and Land Cover Nutrient LoadsPost‐ReDevelopmentPost‐Development (New Impervious)Adjusted Pre‐ReDevelopmentPre‐ReDevelopment TP Load per acre(lb/acre/yr)Final Post‐Development TP Load per acre (lb/acre/yr)Post‐ReDevelopment TP Load per acre (lb/acre/yr)Site Rv0.66‐‐0.721.65 1.50 1.50Treatment Volume (ft3) 2,174‐‐2,393TP Load (lb/yr)1.37‐‐1.50Total TP Load Reduction Required (lb/yr)0.01 0Pre‐ReDevelopmentTN Load (lb/yr)10.76Final Post‐Development Load (Post‐ReDevelopment & New Impervious) 9.770.01Final Post‐Development (Post‐ReDevelopment & New Impervious)0.662,1741.37Total Disturbed Acreage: Total Rainfall (in):Site SummaryProject Title: Malloy FurnitureSummary Print Virginia Runoff Reduction Method WorksheetSite Compliance SummaryTotal Runoff Volume Reduction (ft3)  0Total TP Load Reduction Achieved (lb/yr)0.00Total TN Load Reduction Achieved (lb/yr)0.00Remaining Post Development TP Load (lb/yr)1.37Remaining TP Load Reduction (lb/yr) Required0.01Maximum % Reduction Required Below Pre‐ReDevelopment Load10%Summary Print Virginia Runoff Reduction Method WorksheetDrainage Area SummaryD.A. A D.A. BD.A. C D.A. D D.A. ETotalForest/Open (acres)0.00 0.00 0.00 0.00 0.00 0.00Managed Turf (acres)0.00 0.00 0.00 0.00 0.00 0.00Impervious Cover (acres)0.00 0.00 0.00 0.00 0.00 0.00Total Area (acres)0.00 0.00 0.00 0.00 0.00 0.00Summary Print Independent Reports Excerpt from NRCS Soils Report NOAA Precipitation Report 6 Custom Soil Resource Report Soil Map 421912042191504219180421921042192404219270421912042191504219180421921042192404219270721880 721910 721940 721970 722000 722030 722060 722090 722120 722150 721880 721910 721940 721970 722000 722030 722060 722090 722120 722150 38° 5' 38'' N 78° 28' 11'' W38° 5' 38'' N78° 28' 0'' W38° 5' 32'' N 78° 28' 11'' W38° 5' 32'' N 78° 28' 0'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS84 0 50 100 200 300 Feet 0 15 30 60 90 Meters Map Scale: 1:1,280 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI 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 13, Sep 17, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: May 20, 2019—Aug 1, 2019 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. Custom Soil Resource Report 7 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 27C Elioak loam, 7 to 15 percent slopes 1.6 43.2% 88 Udorthents, loamy, 2 to 25 percent slopes 1.5 41.1% 93D Watt channery silt loam, 15 to 25 percent slopes 0.6 15.7% Totals for Area of Interest 3.7 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or Custom Soil Resource Report 8 Albemarle County, Virginia 27C—Elioak loam, 7 to 15 percent slopes Map Unit Setting National map unit symbol: kb8z Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: Farmland of statewide importance Map Unit Composition Elioak and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Elioak Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down-slope shape: Convex Across-slope shape: Convex Parent material: Residuum weathered from mica schist Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 39 inches: silty clay H3 - 39 to 79 inches: silt loam Properties and qualities Slope: 7 to 15 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 6.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Hydric soil rating: No Custom Soil Resource Report 10 88—Udorthents, loamy, 2 to 25 percent slopes Map Unit Setting National map unit symbol: 2xxz3 Elevation: 360 to 1,540 feet Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: Not prime farmland Map Unit Composition Udorthents and similar soils: 85 percent Minor components: 5 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Udorthents Setting Landform: Interfluves Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down-slope shape: Convex Across-slope shape: Convex Parent material: Residuum weathered from granite and gneiss Properties and qualities Slope: 2 to 25 percent Depth to restrictive feature: More than 80 inches Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Minor Components Hatboro, occasionally flooded Percent of map unit: 5 percent Landform: Flood plains Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: Yes 93D—Watt channery silt loam, 15 to 25 percent slopes Map Unit Setting National map unit symbol: kbg8 Custom Soil Resource Report 11 Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: Not prime farmland Map Unit Composition Watt and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Watt Setting Landform: Hills Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope Down-slope shape: Linear Across-slope shape: Convex Parent material: Residuum weathered from graphite schist Typical profile H1 - 0 to 10 inches: channery silt loam H2 - 10 to 18 inches: very channery silt loam H3 - 18 to 28 inches: very channery silt loam H4 - 28 to 79 inches: bedrock Properties and qualities Slope: 15 to 25 percent Depth to restrictive feature: 20 to 40 inches to paralithic bedrock Natural drainage class: Somewhat excessively drained Runoff class: High Capacity of the most limiting layer to transmit water (Ksat): Very low to high (0.00 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low (about 2.4 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 6e Hydrologic Soil Group: B Hydric soil rating: No Custom Soil Resource Report 12 2/6/2020 Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=38.0944&lon=-78.4703&data=depth&units=english&series=pds 1/4 NOAA Atlas 14, Volume 2, Version 3 Location name: Charlottesville, Virginia, USA* Latitude: 38.0944°, Longitude: -78.4703° Elevation: 521.72 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF_tabular | PF_graphical | Maps_&_aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Duration Average recurrence interval (years) 1 2 5 10 25 50 100 200 500 1000 5-min 0.351 (0.317‑0.390) 0.419 (0.378‑0.465) 0.492 (0.443‑0.545) 0.553 (0.497‑0.612) 0.623 (0.557‑0.687) 0.678 (0.604‑0.747) 0.729 (0.646‑0.803) 0.778 (0.684‑0.857) 0.837 (0.728‑0.925) 0.885 (0.763‑0.982) 10-min 0.561 (0.506‑0.622) 0.670 (0.605‑0.744) 0.788 (0.710‑0.872) 0.884 (0.795‑0.978) 0.993 (0.888‑1.10) 1.08 (0.961‑1.19) 1.16 (1.03‑1.28) 1.23 (1.08‑1.36) 1.32 (1.15‑1.46) 1.39 (1.20‑1.55) 15-min 0.701 (0.632‑0.778) 0.842 (0.760‑0.935) 0.996 (0.898‑1.10) 1.12 (1.00‑1.24) 1.26 (1.13‑1.39) 1.37 (1.22‑1.51) 1.46 (1.30‑1.61) 1.56 (1.37‑1.72) 1.67 (1.45‑1.84) 1.75 (1.51‑1.94) 30-min 0.962 (0.867‑1.07) 1.16 (1.05‑1.29) 1.42 (1.27‑1.57) 1.62 (1.46‑1.79) 1.87 (1.67‑2.06) 2.06 (1.83‑2.27) 2.24 (1.99‑2.47) 2.42 (2.13‑2.67) 2.65 (2.31‑2.93) 2.83 (2.44‑3.14) 60-min 1.20 (1.08‑1.33) 1.46 (1.32‑1.62) 1.82 (1.64‑2.01) 2.11 (1.90‑2.34) 2.48 (2.22‑2.74) 2.79 (2.48‑3.07) 3.09 (2.74‑3.40) 3.40 (2.99‑3.74) 3.81 (3.31‑4.21) 4.14 (3.57‑4.59) 2-hr 1.44 (1.27‑1.64) 1.75 (1.54‑1.99) 2.19 (1.93‑2.49) 2.57 (2.27‑2.91) 3.07 (2.68‑3.47) 3.48 (3.03‑3.93) 3.91 (3.38‑4.41) 4.36 (3.74‑4.91) 4.98 (4.22‑5.62) 5.50 (4.62‑6.23) 3-hr 1.58 (1.39‑1.81) 1.91 (1.68‑2.19) 2.39 (2.10‑2.75) 2.81 (2.45‑3.21) 3.35 (2.91‑3.82) 3.81 (3.29‑4.33) 4.28 (3.67‑4.87) 4.77 (4.06‑5.44) 5.46 (4.59‑6.23) 6.05 (5.03‑6.90) 6-hr 2.01 (1.78‑2.28) 2.43 (2.15‑2.75) 3.02 (2.66‑3.42) 3.55 (3.11‑4.02) 4.27 (3.72‑4.82) 4.90 (4.24‑5.52) 5.56 (4.76‑6.26) 6.27 (5.32‑7.07) 7.29 (6.09‑8.23) 8.19 (6.75‑9.26) 12-hr 2.52 (2.23‑2.89) 3.04 (2.69‑3.48) 3.80 (3.34‑4.34) 4.49 (3.94‑5.12) 5.47 (4.75‑6.21) 6.33 (5.45‑7.19) 7.27 (6.18‑8.25) 8.31 (6.97‑9.41) 9.84 (8.10‑11.2) 11.2 (9.08‑12.8) 24-hr 3.01 (2.70‑3.38) 3.64 (3.27‑4.09) 4.65 (4.16‑5.22) 5.50 (4.91‑6.15) 6.75 (5.99‑7.54) 7.83 (6.89‑8.72) 9.02 (7.87‑10.0) 10.3 (8.91‑11.5) 12.3 (10.4‑13.6) 14.0 (11.7‑15.5) 2-day 3.55 (3.19‑3.97) 4.30 (3.87‑4.81) 5.47 (4.90‑6.10) 6.43 (5.74‑7.16) 7.82 (6.94‑8.69) 8.99 (7.92‑9.97) 10.3 (8.96‑11.4) 11.6 (10.1‑12.9) 13.6 (11.7‑15.2) 15.3 (13.0‑17.1) 3-day 3.78 (3.43‑4.19) 4.58 (4.15‑5.07) 5.81 (5.27‑6.44) 6.83 (6.17‑7.56) 8.31 (7.46‑9.17) 9.54 (8.51‑10.5) 10.9 (9.63‑12.0) 12.3 (10.8‑13.6) 14.4 (12.5‑16.0) 16.2 (13.9‑18.0) 4-day 4.01 (3.67‑4.42) 4.86 (4.44‑5.34) 6.16 (5.63‑6.78) 7.24 (6.60‑7.95) 8.80 (7.98‑9.65) 10.1 (9.11‑11.1) 11.5 (10.3‑12.6) 13.0 (11.6‑14.3) 15.2 (13.4‑16.8) 17.1 (14.9‑18.9) 7-day 4.66 (4.27‑5.09) 5.61 (5.15‑6.13) 7.01 (6.42‑7.66) 8.16 (7.46‑8.91) 9.81 (8.92‑10.7) 11.2 (10.1‑12.2) 12.7 (11.4‑13.8) 14.2 (12.7‑15.6) 16.5 (14.5‑18.1) 18.4 (16.0‑20.2) 10-day 5.29 (4.87‑5.73) 6.34 (5.85‑6.87) 7.83 (7.21‑8.48) 9.04 (8.31‑9.78) 10.7 (9.83‑11.6) 12.1 (11.0‑13.1) 13.6 (12.3‑14.7) 15.1 (13.6‑16.4) 17.3 (15.4‑18.9) 19.1 (16.9‑20.9) 20-day 6.94 (6.49‑7.44) 8.28 (7.75‑8.87) 10.00 (9.34‑10.7) 11.3 (10.6‑12.2) 13.2 (12.3‑14.1) 14.6 (13.5‑15.7) 16.1 (14.9‑17.3) 17.6 (16.2‑18.9) 19.6 (17.9‑21.2) 21.2 (19.2‑22.9) 30-day 8.51 (8.01‑9.08) 10.1 (9.50‑10.8) 11.9 (11.2‑12.7) 13.3 (12.5‑14.2) 15.2 (14.2‑16.2) 16.6 (15.5‑17.6) 17.9 (16.7‑19.1) 19.2 (17.9‑20.5) 21.0 (19.4‑22.5) 22.3 (20.5‑23.9) 45-day 10.6 (10.0‑11.3) 12.6 (11.8‑13.3) 14.7 (13.8‑15.5) 16.3 (15.3‑17.2) 18.3 (17.2‑19.4) 19.8 (18.6‑21.0) 21.2 (19.9‑22.5) 22.6 (21.1‑24.0) 24.4 (22.7‑26.0) 25.8 (23.8‑27.5) 60-day 12.5 (11.8‑13.2) 14.7 (13.9‑15.5) 16.9 (16.0‑17.9) 18.6 (17.6‑19.7) 20.8 (19.6‑21.9) 22.4 (21.1‑23.6) 23.9 (22.4‑25.2) 25.3 (23.7‑26.8) 27.1 (25.3‑28.7) 28.4 (26.5‑30.2) 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 NOAA Atlas 14 document for more information. Back to Top PF graphical