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Stormwater Control Report - Perrotta Revised April'17
X00 ENVIRONMENTAL DESIGN PARTNERSHIP, LLP STORMWATER CONTROL REPORT PROPOSED SINGLE FAMILY HOME FOR FRANK PERROTTA TOWN OF QUEENSBURY, NEW YORK Prepared For: Frank Perrotta Prepared By: THE ENVIRONMENTAL DESIGN PARTNERSHIP 900 Route 146 Clifton Park, NY 12065 Date: December 2016 (Revised April 2017) 900 Route 146, Clifton Park, New York 12065 phone (518)371-7621 - fax(518)371-9540 ama 0 1. INTRODUCTION: The applicant is proposing the development of an existing 5.52+/- acre parcel located along the western side of Assembly Point Road in the Town of Queensbury, New York. The proposed development shall consist of access from Knox Road through an existing driveway and access easement, construction of a new driveway, and construction of a single family dwelling. The area of proposed disturbance is on the order of 26,245 square feet which exceeds the 15,000 square foot disturbance threshold and is therefore defined as a Major Project by Chapter 147 of the Queensbury Town Code. The objective of this report is to describe the proposed stormwater facilities to be constructed as part of the proposed development and confirm their adequacy for compliance with Chapter 147 of the Queensbury Town Code. 2. TECHNICAL REFERENCE Applied Microcomputer Systems' program Hydrocad was used to model the detailed characteristics of the watershed and hydraulics of the stormwater management facilities. Hydrocad employs The United States Department of Agriculture's Soil Conservation Service (SCS) Technical Release 20 (TR-20). TR-20 is the benchmark hydraulic method for computation of storm volumes and peak runoff. It is in full compliance with the methodologies specified in Town Stormwater Management Regulations. Full results are included for the 10 and 25 year, 24 hour design storm events 3. EXISTING CONDITIONS: The existing site consists of wooded and brush areas with the topography of the land in the area of the proposed development generally ranging between 3% and 20% and sloping east toward Assembly Point Road. The USDA Natural Resources Conservation Service Soil Survey indicates the soils on the site to be Charlton fine sandy loam and Massena fine sandy loam. The Soil Survey identifies the Charlton soil series as well-drained and classified as Hydrologic Soil Group (HSG) "B". The Soil Survey identifies Massena soil series as poorly drained and classified as HSG "C". Test pits were performed by The Environmental Design Partnership at the site in December 2016 and April 2017 and found a fine sandy loam with cobbles and an increased presence of silt with depth. Mottling was noted at 5 to 6 feet indicating the presence of a perched water table. The soils observed are consistent with NRCS soil survey records. 2 900 Route 146, Clifton Park, New York 12065 phone (518)371-7621 - fax(518)371-9540 amo" 0 A hydraulic model of the existing site was prepared using the Hydrocad program. One subcatchment was used to represent the existing drainage characteristics, see figure 2. The existing parameters of topography, vegetation, slope and soil type are all incorporated into the predevelopment hydraulic model. The results for the existing condition model are summarized later in this report and have been included in Appendix A. 4. POSTDEVELOPMENT Development of the property will consist of constructing the single family home and new driveway to the limits of the western property line and access easement. Stormwater management practices have been designed to attenuate and provide infiltration capacity of the stormwater runoff from the proposed impervious surfaces on the site. The proposed stormwater management shall consist of one (1) shallow grass swale spanning the width of the lot proposed for development. The shallow grass swale was designed to collect and provide infiltration capacity of stormwater runoff from the proposed driveway, dwelling and upgradient disturbed areas. The shallow grass swale has been sized accordingly to provide attenuation of stormwater runoff for storms up to and including the 25-year design storm. Overflows from the shallow grass swales will be directed to the east, down the existing vegetated slope. The post-development conditions were modeled using the HydroCAD program. Three (3) subcatchments were used to represent the proposed site drainage characteristics (Figure 3). A curve number (CN) of 61 was used for all grassed areas, a CN of 98 was used for all impervious areas, a CN of 65 was used for all existing wooded areas, and a CN of 56 was used for all existing brush areas. The results of the post-development modeling have been summarized in the following subsections and included in Appendix B. 4.1. Town of Queensbury Stormwater Regulations The proposed project will consist of greater than 15,000 square feet of disturbance and therefore, in accordance with Chapter 147 of the Town Code, is considered a major project. The proposed stormwater management system has been designed per the requirements in the Queensbury Town Code which mandates that the pre-development runoff volume for the 10-year storm must be maintained post development and that the pre-development peak rate of runoff must not be increased for the 25-year storm post development. Since the residential project will not disturb greater than 5 acres the stormwater management system does not require compliance with the NYSDEC Stormwater Management Design Manual. The following tables summarize the stormwater modeling results. 3 900 Route 146, Clifton Park, New York 12065 phone (518)371-7621 - fax(518)371-9540 amo" 0 Table 1: 10-Year Storm Runoff Volume Storm Event Predevelopment Runoff Post-Development Runoff Volume (ac-ft) Volume (ac-ft) 10-Year, 3.5" 0.124 0.086 Table 2: 25-Year Storm Runoff Rate Storm Event Predevelopment Runoff Post-Development Runoff Rate(cfs) Rate (cfs) 25-Year, 4.2" 2.93 1.61 5. SUMMARY Due to the proposed development of the project site there is the need to provide stormwater management. In order to attenuate and provide infiltration capacity from the increased site runoff, shallow grass swales have been designed. The stormwater management for the proposed site was has been designed in accordance with Chapter 147 of the Queensbury Town Code. Upon proper construction and maintenance of the storm facilities detailed on the plans, the proposed construction will have no significant adverse impacts on downstream properties and water bodies. Prepared by: Reviewed by: Kristopher LaPan, E.I.T. Dennis MacElroy, P.E. The Environmental Design Partnership The Environmental Design Partnership 4 900 Route 146, Clifton Park, New York 12065 phone (518)371-7621 - fax(518)371-9540 ama 0 REFERENCES: HydroCAD version 8.50, Applied Microcomputer Systems, Chocura,New Hampshire. Rawls, W.J., Brakensiek, D.L., and Saxton,K. E., 1982. "Estimation of Soil Properties", Transactions of the American Society of Agricultural Engineers, Vol. 25,No. J, pp. 1316-1320. S.C.S., 1982. "TR-20 Project Formulation-Hydrology, Technical Release No. 20",U.S. Department of Agriculture, Soil Conservation Service, Hydrology Unit Division of Engineering. Town of Lake George, July 2003."Chaper 175-21, Erosion, sedimentation and stormwater runoff control", Code of the Town of Lake George. United States Department of Agruculture ,N.R.C.S. Web Soil Survey, http://websoilsurvey.nres.usda.gov/app/Web Soil Survey.aspx 5 900 Route 146, Clifton Park, New York 12065 phone (518)371-7621 - fax(518)371-9540 Map Hybrid Ema�ery R A > �r eY:- a i .w t Jap SITE LOCATION rt 4 _ Long; -73.6839 Lat; 43.4375 Position of Cu rsor 0 0.2 0.4mi Figure 1: Site Location Appendix A Predevelopment Stormwater Modeling Results sk) A DESIGN POINT Subcat Reach on Link Drainage Diagram for PREDEVELOPMENT_PERROTTA Prepared by The Environmental Design Partnership, LLP, Printed 4/17/2017 HydroCAD®8.50 s/n 000476 ©2007 Hydro CAD Software Solutions LLC PREDEVELOPM ENT_PERROTTA Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.875 56 Brush, Fair, HSG B (1 S) 0.094 65 Woods/grass comb., Fair, HSG B (1 S) 0.897 76 Woods/grass comb., Fair, HSG C (1 S) 1.866 TOTAL AREA PREDEVELOPM ENT_PERROTTA Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Goup Numbers 0.000 HSG A 0.969 HSG B is 0.897 HSG C is 0.000 HSG D 0.000 Other 1.866 TOTAL AREA PREDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 4 Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 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: - Runoff Area=81,280 sf 0.00% Imperious Runoff Depth=0.80" Flow Length=250' Tc=13.0 min CN=66 Runoff=1.83 cfs 0.124 of Link A: DESIGN POINT Inflow=1.83 cfs 0.124 of Primary=1.83 cfs 0.124 of Total Runoff Area = 1.866 ac Runoff Volume = 0.124 of Average Runoff Depth = 0.80" 100.00% Pervious = 1.866 ac 0.00% Impervious = 0.000 ac PREDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1S: - Runoff = 1.83 cfs @ 12.07 hrs, Volume= 0.124 af, Depth= 0.80" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=3.50" Area (so CN Description 4,100 65 Woods/grass comb., Fair, HSG B 38,100 56 Brush, Fair, HSG B 39,080 76 Woods/grass comb., Fair, HSG C 81,280 66 Weighted Average 81,280 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.9 65 0.0450 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 1.1 185 0.1500 2.71 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.0 250 Total Summary for Link A: DESIGN POINT Inflow Area = 1.866 ac, 0.00% Impervious, Inflow Depth = 0.80" for 10 YEAR event Inflow = 1.83 cfs @ 12.07 hrs, Volume= 0.124 of Primary = 1.83 cfs @ 12.07 hrs, Volume= 0.124 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs PREDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 6 Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: - Runoff Area=81,280sf 0.00% Imperious Runoff Depth=1.21" Flow Length=250' Tc=13.0 min CN=66 Runoff=2.93 cfs 0.188 of Link A: DESIGN POINT Inflow=2.93 cfs 0.188 of Primary=2.93 cfs 0.188 of Total Runoff Area = 1.866 ac Runoff Volume = 0.188 of Average Runoff Depth = 1.21" 100.00% Pervious = 1.866 ac 0.00% Impervious = 0.000 ac PREDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 1S: - Runoff = 2.93 cfs @ 12.06 hrs, Volume= 0.188 af, Depth= 1.21" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 25 YEAR Rainfall=4.20" Area (so CN Description 4,100 65 Woods/grass comb., Fair, HSG B 38,100 56 Brush, Fair, HSG B 39,080 76 Woods/grass comb., Fair, HSG C 81,280 66 Weighted Average 81,280 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.9 65 0.0450 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 1.1 185 0.1500 2.71 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.0 250 Total Summary for Link A: DESIGN POINT Inflow Area = 1.866 ac, 0.00% Impervious, Inflow Depth = 1.21" for 25 YEAR event Inflow = 2.93 cfs @ 12.06 hrs, Volume= 0.188 of Primary = 2.93 cfs @ 12.06 hrs, Volume= 0.188 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Appendix B Post-development Stormwater Modeling Results 1S 30S 5P SHALLOW GRASS SWALE #1 A (2S DESIGN POINT Subcat Reach on Link Drainage Diagram for POSTDEVELOPMENT_PERROTTA Prepared by The Environmental Design Partnership, LLP, Printed 4/17/2017 HydroCAD®8.50 s/n 000476 ©2007 Hydro CAD Software Solutions LLC POSTDEVELOPMENT_PERROTTA Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.164 56 Brush, Fair, HSG B (1 S,3S) 0.605 61 >75% Grass cover, Good, HSG B (1S,2S) 0.098 65 Woods/grass comb., Fair, HSG B (1 S,2S) 0.766 76 Woods/grass comb., Fair, HSG C (3S) 0.224 98 Paved parking & roofs (1 S,2S) 1.856 TOTAL AREA POSTDEVELOPMENT_PERROTTA Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Goup Numbers 0.000 HSG A 0.866 HSG B 1 S, 2S, 3S 0.766 HSG C 3S 0.000 HSG D 0.224 Other 1 S, 2S 1.856 TOTAL AREA POSTDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 4 Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: - Runoff Area=25,279 sf 15.48% Imperious Runoff Depth=0.85" Flow Length=255' Tc=12.5 min CN=67 Runoff=0.63 cfs 0.041 of Subcatchment2S: - Runoff Area=17,375 sf 33.55% Imperious Runoff Depth=1.24" Flow Length=185' Tc=13.4 min CN=74 Runoff=0.66 cfs 0.041 of Subcatchment3S: - Runoff Area=38,195 sf 0.00% Imperious Runoff Depth=1.18" Flow Length=260' Tc=19.4 min CN=73 Runoff=1.11 cfs 0.086 of Pond 5P: SHALLOW GRASS SWALE#1 Peak Elev=388.70' Storage=1,435 cf Inflow=1.28 cfs 0.082 of Discarded=0.11 cfs 0.082 of Primary=0.00 cfs 0.000 of Outflow=0.11 cfs 0.082 of Link A: DESIGN POINT Inflow=1.11 cfs 0.086 of Primary=1.11 cfs 0.086 of Total Runoff Area = 1.856 ac Runoff Volume = 0.169 of Average Runoff Depth = 1.09" 87.95% Pervious = 1.632 ac 12.05% Impervious = 0.224 ac POSTDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1S: - Runoff = 0.63 cfs @ 12.06 hrs, Volume= 0.041 af, Depth= 0.85" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=3.50" Area (so CN Description 2,250 65 Woods/grass comb., Fair, HSG B 3,914 98 Paved parking & roofs 2,300 56 Brush, Fair, HSG B 16,815 61 >75% Grass cover, Good, HSG B 25,279 67 Weighted Average 21,365 Pervious Area 3,914 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.4 45 0.0300 0.07 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 2.1 210 0.0550 1.64 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.5 255 Total Summary for Subcatchment 2S: - Runoff = 0.66 cfs @ 12.06 hrs, Volume= 0.041 af, Depth= 1.24" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=3.50" Area (so CN Description 5,830 98 Paved parking & roofs 2,005 65 Woods/grass comb., Fair, HSG B 9,540 61 >75% Grass cover, Good, HSG B 17,375 74 Weighted Average 11,545 Pervious Area 5,830 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.2 45 0.0200 0.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 1.2 140 0.0750 1.92 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.4 185 Total POSTDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 3S: - Runoff = 1.11 cfs @ 12.13 hrs, Volume= 0.086 af, Depth= 1.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=3.50" Area (so CN Description 33,370 76 Woods/grass comb., Fair, HSG C 4,825 56 Brush, Fair, HSG B 38,195 73 Weighted Average 38,195 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.5 100 0.0350 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 0.9 160 0.1660 2.85 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 19.4 260 Total Summary for Pond 5P: SHALLOW GRASS SWALE #1 Inflow Area = 0.979 ac, 22.84% Impervious, Inflow Depth = 1.01" for 10 YEAR event Inflow = 1.28 cfs @ 12.06 hrs, Volume= 0.082 of Outflow = 0.11 cfs @ 13.17 hrs, Volume= 0.082 af, Atten= 91%, Lag= 66.4 min Discarded = 0.11 cfs @ 13.17 hrs, Volume= 0.082 of Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Peak Elev= 388.70' @ 13.17 hrs Surf.Area= 2,394 sf Storage= 1,435 cf Plug-Flow detention time= 132.2 min calculated for 0.082 of(100% of inflow) Center-of-Mass det. time= 132.1 min ( 1,003.4 - 871.3 ) Volume Invert Avail.Storage Storage Description #1 388.00' 3,720 cf Custom Stage Data (Irregular)Listed below (Recalc) #2 388.00' 152 cf 5.00'W x 19.00'L x 4.00'H STONE AREA-Impervious 380 cf Overall x 40.0% Voids 3,872 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 388.00 1,670 420.0 0 0 1,670 389.50 3,390 460.0 3,720 3,720 4,548 Device Routing Invert Outlet Devices #1 Primary 389.00' 10.0' long x 5.0' breadth OVERFLOW WEIR Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 POSTDEVELOPMENT_PERROTTA Type 11 24-hr 10 YEAR Rainfall=3.50" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 7 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 #2 Discarded 388.00' 2.000 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.11 cfs @ 13.17 hrs HW=388.70' (Free Discharge) L2=Exfiltration (Exfiltration Controls 0.11 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=388.00' (Free Discharge) t--1=OVERFLOW WEIR ( Controls 0.00 cfs) Summary for Link A: DESIGN POINT Inflow Area = 1.856 ac, 12.05% Impervious, Inflow Depth = 0.56" for 10 YEAR event Inflow = 1.11 cfs @ 12.13 hrs, Volume= 0.086 of Primary = 1.11 cfs @ 12.13 hrs, Volume= 0.086 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs POSTDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 8 Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: - Runoff Area=25,279 sf 15.48% Imperious Runoff Depth=1.27" Flow Length=255' Tc=12.5 min CN=67 Runoff=0.99 cfs 0.061 of Subcatchment2S: - Runoff Area=17,375 sf 33.55% Imperious Runoff Depth=1.74" Flow Length=185' Tc=13.4 min CN=74 Runoff=0.94 cfs 0.058 of Subcatchment3S: - Runoff Area=38,195 sf 0.00% Imperious Runoff Depth=1.67" Flow Length=260' Tc=19.4 min CN=73 Runoff=1.61 cfs 0.122 of Pond 5P: SHALLOW GRASS SWALE#1 Peak Elev=389.01' Storage=2,262 cf Inflow=1.92 cfs 0.119 of Discarded=0.13 cfs 0.116 of Primary=0.06 cfs 0.003 of Outflow=0.19 cfs 0.119 of Link A: DESIGN POINT Inflow=1.61 cfs 0.125 of Primary=1.61 cfs 0.125 of Total Runoff Area = 1.856 ac Runoff Volume = 0.242 of Average Runoff Depth = 1.56" 87.95% Pervious = 1.632 ac 12.05% Impervious = 0.224 ac POSTDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 1S: - Runoff = 0.99 cfs @ 12.06 hrs, Volume= 0.061 af, Depth= 1.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 25 YEAR Rainfall=4.20" Area (so CN Description 2,250 65 Woods/grass comb., Fair, HSG B 3,914 98 Paved parking & roofs 2,300 56 Brush, Fair, HSG B 16,815 61 >75% Grass cover, Good, HSG B 25,279 67 Weighted Average 21,365 Pervious Area 3,914 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.4 45 0.0300 0.07 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 2.1 210 0.0550 1.64 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.5 255 Total Summary for Subcatchment 2S: - Runoff = 0.94 cfs @ 12.06 hrs, Volume= 0.058 af, Depth= 1.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 25 YEAR Rainfall=4.20" Area (so CN Description 5,830 98 Paved parking & roofs 2,005 65 Woods/grass comb., Fair, HSG B 9,540 61 >75% Grass cover, Good, HSG B 17,375 74 Weighted Average 11,545 Pervious Area 5,830 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.2 45 0.0200 0.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 1.2 140 0.0750 1.92 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.4 185 Total POSTDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 3S: - Runoff = 1.61 cfs @ 12.13 hrs, Volume= 0.122 af, Depth= 1.67" Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Type II 24-hr 25 YEAR Rainfall=4.20" Area (so CN Description 33,370 76 Woods/grass comb., Fair, HSG C 4,825 56 Brush, Fair, HSG B 38,195 73 Weighted Average 38,195 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 18.5 100 0.0350 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.75" 0.9 160 0.1660 2.85 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 19.4 260 Total Summary for Pond 5P: SHALLOW GRASS SWALE #1 Inflow Area = 0.979 ac, 22.84% Impervious, Inflow Depth = 1.46" for 25 YEAR event Inflow = 1.92 cfs @ 12.06 hrs, Volume= 0.119 of Outflow = 0.19 cfs @ 12.86 hrs, Volume= 0.119 af, Atten= 90%, Lag= 48.3 min Discarded = 0.13 cfs @ 12.86 hrs, Volume= 0.116 of Primary = 0.06 cfs @ 12.86 hrs, Volume= 0.003 of Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs Peak Elev= 389.01' @ 12.86 hrs Surf.Area= 2,766 sf Storage= 2,262 cf Plug-Flow detention time= 192.2 min calculated for 0.119 of(100% of inflow) Center-of-Mass det. time= 192.0 min ( 1,051.8 - 859.8 ) Volume Invert Avail.Storage Storage Description #1 388.00' 3,720 cf Custom Stage Data (Irregular)Listed below (Recalc) #2 388.00' 152 cf 5.00'W x 19.00'L x 4.00'H STONE AREA-Impervious 380 cf Overall x 40.0% Voids 3,872 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 388.00 1,670 420.0 0 0 1,670 389.50 3,390 460.0 3,720 3,720 4,548 Device Routing Invert Outlet Devices #1 Primary 389.00' 10.0' long x 5.0' breadth OVERFLOW WEIR Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 POSTDEVELOPMENT_PERROTTA Type 11 24-hr 25 YEAR Rainfall=4.20" Prepared by The Environmental Design Partnership, LLP Printed 4/17/2017 HydroCAD®8.50 s/n 000476 @2007 HydroCAD Software Solutions LLC Page 11 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 #2 Discarded 388.00' 2.000 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.13 cfs @ 12.86 hrs HW=389.01' (Free Discharge) L2=Exfiltration (Exfiltration Controls 0.13 cfs) Primary OutFlow Max=0.03 cfs @ 12.86 hrs HW=389.01' (Free Discharge) t--1=OVERFLOW WEIR (Weir Controls 0.03 cfs @ 0.27 fps) Summary for Link A: DESIGN POINT Inflow Area = 1.856 ac, 12.05% Impervious, Inflow Depth = 0.81" for 25 YEAR event Inflow = 1.61 cfs @ 12.13 hrs, Volume= 0.125 of Primary = 1.61 cfs @ 12.13 hrs, Volume= 0.125 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs