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HomeMy WebLinkAboutStormwater Rep John U. Faulise, Jr., L.S. Demian A. Sorrentino, AICP, C.S.S. David C. McKay, P.E. Gerald J. Stefon, L.S. Jacob S. Faulise, E.I.T. Boundaries LLC 179 Pachaug River Drive P.O. Box 184 Griswold, CT 06351 T 860.376.2006 | F 860.376.5899 www.boundariesllc.net STORMWATER ANALYSIS PROPOSED WORKFORCE HOUSING 902 GRASSY HILL ROAD MONTVILLE, CONNECTICUT Introduction The following analysis was completed to demonstrate that the proposed development will not exceed the capacity of the downstream municipal stormwater management system and to demonstrate compliance with the Town of Montville’s Municipal Separate Storm Sewer System (MS4) permit requirements. The proposed development consists of the construction of a three-unit residential building to be used as workforce housing as well as supporting infrastructure. The building will be served by an on-site well and subsurface sewage disposal system. The subject parcel is approximately 0.47 acres. Approximately 0.41 acres will be disturbed as a result of the proposed development. Stormwater Analysis Stormwater runoff from the proposed development will be collected using curbs and gutters along the low side of the driveway. The gutters are directed to a riprap scour hole that drains to the existing vegetated swale along the property frontage. The swale will continue to carry runoff from the contributing areas to the downgradient 15-inch diameter RCP culvert that crosses Grassy Hill Road to the forested area to the northwest. Post-development stormwater runoff patterns match pre-development patterns, i.e. runoff is collected in the vegetated swale and discharged through the 15-inch diameter RCP culvert. According to the Natural Resources Conservation Service (NRCS) Web Soil Survey the soils in the project area consist of Hinckley loamy sand, 3 to 15% slopes; Agawam fine sandy loam, 3 to 8% slopes; and Timakwa and Natchaug soils, 0 to 2% slopes. Hinckley soils are classified as Hydrologic Soil Group A. Agawam soils are classified as Hydrologic Soil Group B. Timakwa and Natchaug soils are classified as Page 2 Hydrologic Soil Group B/D (modeled as Hydrologic Soil Group D to provide conservative results). The NRCS Web Soil Survey Soils Map is attached to this memorandum. Post-development conditions hydrographs were estimated using the hydrologic modeling program HydroCAD. The methodology selected was NRCS TR-20. Times of concentration were estimated using multiple segment flow paths as described in the NRCS TR-55 manual. The Type III 24-hour storm was analyzed under antecedent moisture condition two (2). Rainfall totals are as reported by the NOAA Precipitation Frequency Data Server for the project site. Post-development conditions peak runoff rates were analyzed at the existing 15-inch RCP culvert. Reported peak flow rates and water surface elevations are summarized below in Table 1. Detailed modeling results are attached to this memorandum. Table 1 Peak Runoff Rates Design Storm Event Total Peak Runoff Rate – Pond 2P (CFS) Peak Water Surface Elevation at 15-inch Culvert – Pond 2P (FT) 2-Year 1.7 129.44 10-Year 3.5 129.79 25-Year 4.7 130.05 50-Year 5.6 130.32 100-Year 6.6 130.67 The road surface elevation in the vicinity of the proposed development is 132.3 and higher. The existing 15-inch RCP culvert has the capacity to pass the modeled storm events while still maintaining greater than 1-foot (1.6 feet) of freeboard between the edge of pavement and water surface elevation during the 100- year storm event after completion of the proposed development. The Manning’s capacities of both the vegetated swale and the 15-inch RCP culvert were also calculated to confirm that there is adequate hydraulic capacity for the modeled storm events. Per Manning’s equation the 15-inch RCP culvert has capacity of 10.4 CFS when flowing full and the triangular vegetated swale has a capacity of 71.3 CFS when flowing full. Given the peak runoff rate of 6.6 CFS during the modeled 100-year storm event, the stormwater components have adequate capacity for runoff generated from the proposed development and contributing areas. The stormwater discharge to the vegetated swale will be protected from erosion by a rip rap scour hole. The modified rip rap scour hole is sized in accordance with the recommendations of the CT DEEP Soil Erosion and Sedimentation Control Guidelines and the CT DOT Drainage Manual. Table 2 Scour Protection Sizing Stormwater Discharge 100-year Discharge Velocity (FPS) Proposed Surface Treatment Typical Allowable Velocity (FPS) Pavement Leak-Off 6.1 Modified Rip Rap 0-8 (Per DOT Drainage Manual Table 11.11) Page 3 Regulatory Compliance The proposed development has been designed to comply with the requirements of local and state regulations. The Town of Montville’s Stormwater Management Plan and MS4 Permit requires the treatment of stormwater runoff from proposed developments both during construction and post- construction. Section 4, Construction Site Stormwater Runoff Control, of the Town’s Stormwater Management Plan states that “This minimum control measure outlines procedures for minimizing polluted stormwater runoff from activities that disturb one or more acres of land.” Similarly, Section 5, Post-Construction Stormwater Management in New Development or Redevelopment, states that “This minimum control measure outlines Montville’s program to address stormwater runoff from new or redevelopment projects that disturbs one or more acres of land.” Both of these thresholds are consistent with the Environmental Protection Agency’s Stormwater Phase II Final Rule fact sheets regarding the Construction Site Runoff Control Minimum Control Measure and Post-Construction Runoff Control Minimum Control Measure. Although the proposed development will result in the disturbance of less than one half acre of land, the project does include stormwater treatment measures to the maximum extent practicable given the small size of the property and required separating distances between wells, septic systems (both on the property and on adjacent properties) and stormwater management features. The following measures will be implemented during construction to prevent pollution due to stormwater runoff: Anti-tracking pad at the construction exit; Perimeter sediment fence barrier; and Stone check dam in the vegetated swale at the property line. These measures will remain in place until paving has been completed and vegetation has been established. Post-construction stormwater treatment measures include the following: A stone check dam at the discharge of the rip rap scour hole; and Disconnection of impervious areas through the use of the vegetated swale for stormwater runoff. The stone check dam, in conjunction with the rip rap scour hole, will aid in the collection of sediment from the runoff prior to draining the vegetated swale. The vegetated swale will function as a grass drainage channel, a secondary stormwater treatment practice described in the CT DEEP Stormwater Quality Manual. All runoff from the proposed development will flow through the above measures. Summary The proposed development will not exceed the capacity of the downstream stormwater features and provides treatment of stormwater runoff to the maximum extent practicable. Attachments Stormwater Analysis Figure NRCS Soils Map HydroCAD Modeling Results Manning’s Flow Rate Calculations Stormwater Analysis Figure ~~Grassy Hill R oad ~H SG A HSG A HSG B/D HSG B /DHSG B /DHSG B Stormwater AnalysisProposed Workforce Housing902 Grassy Hill Road, Montville, CTGRAPHIC SCALE NRCS Web Soil Survey Soils Map HydroCAD Modeling Results 1S DA 1 2PCB 15" RC Culvert Routing Diagram for Culvert Size CheckPrepared by {enter your company name here}, Printed 10/20/2020 HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 2HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Rainfall Events Listing (selected events) Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 2-Year Type III 24-hr Default 24.00 1 3.45 2 2 10-Year Type III 24-hr Default 24.00 1 5.14 2 3 25-Year Type III 24-hr Default 24.00 1 6.19 2 4 50-Year Type III 24-hr Default 24.00 1 6.98 2 5 100-Year Type III 24-hr Default 24.00 1 7.82 2 Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 3HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 0.419 39 >75% Grass cover, Good, HSG A (1S) 0.054 61 >75% Grass cover, Good, HSG B (1S) 0.093 80 >75% Grass cover, Good, HSG D (1S) 0.680 98 Unconnected pavement, HSG A (1S) 1.246 75 TOTAL AREA Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 4HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (acres) Soil Group Subcatchment Numbers 1.099 HSG A 1S 0.054 HSG B 1S 0.000 HSG C 0.093 HSG D 1S 0.000 Other 1.246 TOTAL AREA Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 5HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Ground Covers (all nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.419 0.054 0.000 0.093 0.000 0.566 >75% Grass cover, Good 1S 0.680 0.000 0.000 0.000 0.000 0.680 Unconnected pavement 1S 1.099 0.054 0.000 0.093 0.000 1.246 TOTAL AREA Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 6HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Pipe Listing (all nodes) Line# Node Number In-Invert (feet) Out-Invert (feet) Length (feet) Slope (ft/ft) n Width (inches) Diam/Height (inches) Inside-Fill (inches) 1 2P 128.81 127.80 38.2 0.0264 0.013 0.0 15.0 0.0 Type III 24-hr 2-Year Rainfall=3.45"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 7HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=54,290 sf 54.56% Impervious Runoff Depth=1.27"Subcatchment 1S: DA 1 Flow Length=266' Tc=7.9 min CN=75 Runoff=1.7 cfs 0.132 af Peak Elev=129.44' Inflow=1.7 cfs 0.132 afPond 2P: 15" RC Culvert 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' Outflow=1.7 cfs 0.132 af Total Runoff Area = 1.246 ac Runoff Volume = 0.132 af Average Runoff Depth = 1.27" 45.44% Pervious = 0.566 ac 54.56% Impervious = 0.680 ac Type III 24-hr 2-Year Rainfall=3.45"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 8HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: DA 1 Runoff = 1.7 cfs @ 12.12 hrs, Volume= 0.132 af, Depth= 1.27" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24-hr 2-Year Rainfall=3.45" Area (sf) CN Description 19,976 98 Unconnected pavement, HSG A 4,060 80 >75% Grass cover, Good, HSG D 2,338 61 >75% Grass cover, Good, HSG B 18,269 39 >75% Grass cover, Good, HSG A 9,647 98 Unconnected pavement, HSG A 54,290 75 Weighted Average 24,667 45.44% Pervious Area 29,623 54.56% Impervious Area 29,623 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 50 0.0220 0.16 Sheet Flow, Sheet Grass Grass: Short n= 0.150 P2= 3.45" 0.5 35 0.0290 1.19 Shallow Concentrated Flow, Shallow Grass 1 Short Grass Pasture Kv= 7.0 fps 0.2 52 0.0396 4.04 Shallow Concentrated Flow, Shallow Pavement Paved Kv= 20.3 fps 2.0 129 0.0247 1.10 Shallow Concentrated Flow, Shallow Grass 2 Short Grass Pasture Kv= 7.0 fps 7.9 266 Total Type III 24-hr 2-Year Rainfall=3.45"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 9HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcatchment 1S: DA 1 Runoff Hydrograph Time (hours)3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2-Year Rainfall=3.45" Runoff Area=54,290 sf Runoff Volume=0.132 af Runoff Depth=1.27" Flow Length=266' Tc=7.9 min CN=75 1.7 cfs Type III 24-hr 2-Year Rainfall=3.45"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 10HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Pond 2P: 15" RC Culvert Inflow Area = 1.246 ac, 54.56% Impervious, Inflow Depth = 1.27" for 2-Year event Inflow = 1.7 cfs @ 12.12 hrs, Volume= 0.132 af Outflow = 1.7 cfs @ 12.12 hrs, Volume= 0.132 af, Atten= 0%, Lag= 0.0 min Primary = 1.7 cfs @ 12.12 hrs, Volume= 0.132 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 129.44' @ 12.12 hrs Flood Elev= 132.00' Device Routing Invert Outlet Devices #1 Primary 128.81'15.0" Round 15" RCP L= 38.2' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 128.81' / 127.80' S= 0.0264 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Primary OutFlow Max=1.6 cfs @ 12.12 hrs HW=129.42' (Free Discharge) 1=15" RCP (Inlet Controls 1.6 cfs @ 2.67 fps) Pond 2P: 15" RC Culvert InflowPrimary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.246 ac Peak Elev=129.44' 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' 1.7 cfs1.7 cfs Type III 24-hr 10-Year Rainfall=5.14"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 11HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=54,290 sf 54.56% Impervious Runoff Depth=2.56"Subcatchment 1S: DA 1 Flow Length=266' Tc=7.9 min CN=75 Runoff=3.5 cfs 0.266 af Peak Elev=129.79' Inflow=3.5 cfs 0.266 afPond 2P: 15" RC Culvert 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' Outflow=3.5 cfs 0.266 af Total Runoff Area = 1.246 ac Runoff Volume = 0.266 af Average Runoff Depth = 2.56" 45.44% Pervious = 0.566 ac 54.56% Impervious = 0.680 ac Type III 24-hr 10-Year Rainfall=5.14"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 12HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: DA 1 Runoff = 3.5 cfs @ 12.12 hrs, Volume= 0.266 af, Depth= 2.56" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24-hr 10-Year Rainfall=5.14" Area (sf) CN Description 19,976 98 Unconnected pavement, HSG A 4,060 80 >75% Grass cover, Good, HSG D 2,338 61 >75% Grass cover, Good, HSG B 18,269 39 >75% Grass cover, Good, HSG A 9,647 98 Unconnected pavement, HSG A 54,290 75 Weighted Average 24,667 45.44% Pervious Area 29,623 54.56% Impervious Area 29,623 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 50 0.0220 0.16 Sheet Flow, Sheet Grass Grass: Short n= 0.150 P2= 3.45" 0.5 35 0.0290 1.19 Shallow Concentrated Flow, Shallow Grass 1 Short Grass Pasture Kv= 7.0 fps 0.2 52 0.0396 4.04 Shallow Concentrated Flow, Shallow Pavement Paved Kv= 20.3 fps 2.0 129 0.0247 1.10 Shallow Concentrated Flow, Shallow Grass 2 Short Grass Pasture Kv= 7.0 fps 7.9 266 Total Type III 24-hr 10-Year Rainfall=5.14"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 13HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcatchment 1S: DA 1 Runoff Hydrograph Time (hours)3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 10-Year Rainfall=5.14" Runoff Area=54,290 sf Runoff Volume=0.266 af Runoff Depth=2.56" Flow Length=266' Tc=7.9 min CN=75 3.5 cfs Type III 24-hr 10-Year Rainfall=5.14"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 14HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Pond 2P: 15" RC Culvert Inflow Area = 1.246 ac, 54.56% Impervious, Inflow Depth = 2.56" for 10-Year event Inflow = 3.5 cfs @ 12.12 hrs, Volume= 0.266 af Outflow = 3.5 cfs @ 12.12 hrs, Volume= 0.266 af, Atten= 0%, Lag= 0.0 min Primary = 3.5 cfs @ 12.12 hrs, Volume= 0.266 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 129.79' @ 12.12 hrs Flood Elev= 132.00' Device Routing Invert Outlet Devices #1 Primary 128.81'15.0" Round 15" RCP L= 38.2' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 128.81' / 127.80' S= 0.0264 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Primary OutFlow Max=3.4 cfs @ 12.12 hrs HW=129.77' (Free Discharge) 1=15" RCP (Inlet Controls 3.4 cfs @ 3.33 fps) Pond 2P: 15" RC Culvert InflowPrimary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=1.246 ac Peak Elev=129.79' 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' 3.5 cfs3.5 cfs Type III 24-hr 25-Year Rainfall=6.19"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 15HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=54,290 sf 54.56% Impervious Runoff Depth=3.44"Subcatchment 1S: DA 1 Flow Length=266' Tc=7.9 min CN=75 Runoff=4.7 cfs 0.358 af Peak Elev=130.05' Inflow=4.7 cfs 0.358 afPond 2P: 15" RC Culvert 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' Outflow=4.7 cfs 0.358 af Total Runoff Area = 1.246 ac Runoff Volume = 0.358 af Average Runoff Depth = 3.44" 45.44% Pervious = 0.566 ac 54.56% Impervious = 0.680 ac Type III 24-hr 25-Year Rainfall=6.19"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 16HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: DA 1 Runoff = 4.7 cfs @ 12.11 hrs, Volume= 0.358 af, Depth= 3.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24-hr 25-Year Rainfall=6.19" Area (sf) CN Description 19,976 98 Unconnected pavement, HSG A 4,060 80 >75% Grass cover, Good, HSG D 2,338 61 >75% Grass cover, Good, HSG B 18,269 39 >75% Grass cover, Good, HSG A 9,647 98 Unconnected pavement, HSG A 54,290 75 Weighted Average 24,667 45.44% Pervious Area 29,623 54.56% Impervious Area 29,623 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 50 0.0220 0.16 Sheet Flow, Sheet Grass Grass: Short n= 0.150 P2= 3.45" 0.5 35 0.0290 1.19 Shallow Concentrated Flow, Shallow Grass 1 Short Grass Pasture Kv= 7.0 fps 0.2 52 0.0396 4.04 Shallow Concentrated Flow, Shallow Pavement Paved Kv= 20.3 fps 2.0 129 0.0247 1.10 Shallow Concentrated Flow, Shallow Grass 2 Short Grass Pasture Kv= 7.0 fps 7.9 266 Total Type III 24-hr 25-Year Rainfall=6.19"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 17HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcatchment 1S: DA 1 Runoff Hydrograph Time (hours)3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Type III 24-hr 25-Year Rainfall=6.19" Runoff Area=54,290 sf Runoff Volume=0.358 af Runoff Depth=3.44" Flow Length=266' Tc=7.9 min CN=75 4.7 cfs Type III 24-hr 25-Year Rainfall=6.19"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 18HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Pond 2P: 15" RC Culvert Inflow Area = 1.246 ac, 54.56% Impervious, Inflow Depth = 3.44" for 25-Year event Inflow = 4.7 cfs @ 12.11 hrs, Volume= 0.358 af Outflow = 4.7 cfs @ 12.11 hrs, Volume= 0.358 af, Atten= 0%, Lag= 0.0 min Primary = 4.7 cfs @ 12.11 hrs, Volume= 0.358 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 130.05' @ 12.11 hrs Flood Elev= 132.00' Device Routing Invert Outlet Devices #1 Primary 128.81'15.0" Round 15" RCP L= 38.2' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 128.81' / 127.80' S= 0.0264 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Primary OutFlow Max=4.5 cfs @ 12.11 hrs HW=130.02' (Free Discharge) 1=15" RCP (Inlet Controls 4.5 cfs @ 3.74 fps) Pond 2P: 15" RC Culvert InflowPrimary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Inflow Area=1.246 ac Peak Elev=130.05' 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' 4.7 cfs4.7 cfs Type III 24-hr 50-Year Rainfall=6.98"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 19HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=54,290 sf 54.56% Impervious Runoff Depth=4.13"Subcatchment 1S: DA 1 Flow Length=266' Tc=7.9 min CN=75 Runoff=5.6 cfs 0.429 af Peak Elev=130.32' Inflow=5.6 cfs 0.429 afPond 2P: 15" RC Culvert 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' Outflow=5.6 cfs 0.429 af Total Runoff Area = 1.246 ac Runoff Volume = 0.429 af Average Runoff Depth = 4.13" 45.44% Pervious = 0.566 ac 54.56% Impervious = 0.680 ac Type III 24-hr 50-Year Rainfall=6.98"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 20HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: DA 1 Runoff = 5.6 cfs @ 12.11 hrs, Volume= 0.429 af, Depth= 4.13" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24-hr 50-Year Rainfall=6.98" Area (sf) CN Description 19,976 98 Unconnected pavement, HSG A 4,060 80 >75% Grass cover, Good, HSG D 2,338 61 >75% Grass cover, Good, HSG B 18,269 39 >75% Grass cover, Good, HSG A 9,647 98 Unconnected pavement, HSG A 54,290 75 Weighted Average 24,667 45.44% Pervious Area 29,623 54.56% Impervious Area 29,623 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 50 0.0220 0.16 Sheet Flow, Sheet Grass Grass: Short n= 0.150 P2= 3.45" 0.5 35 0.0290 1.19 Shallow Concentrated Flow, Shallow Grass 1 Short Grass Pasture Kv= 7.0 fps 0.2 52 0.0396 4.04 Shallow Concentrated Flow, Shallow Pavement Paved Kv= 20.3 fps 2.0 129 0.0247 1.10 Shallow Concentrated Flow, Shallow Grass 2 Short Grass Pasture Kv= 7.0 fps 7.9 266 Total Type III 24-hr 50-Year Rainfall=6.98"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 21HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcatchment 1S: DA 1 Runoff Hydrograph Time (hours)3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)6 5 4 3 2 1 0 Type III 24-hr 50-Year Rainfall=6.98" Runoff Area=54,290 sf Runoff Volume=0.429 af Runoff Depth=4.13" Flow Length=266' Tc=7.9 min CN=75 5.6 cfs Type III 24-hr 50-Year Rainfall=6.98"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 22HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Pond 2P: 15" RC Culvert Inflow Area = 1.246 ac, 54.56% Impervious, Inflow Depth = 4.13" for 50-Year event Inflow = 5.6 cfs @ 12.11 hrs, Volume= 0.429 af Outflow = 5.6 cfs @ 12.11 hrs, Volume= 0.429 af, Atten= 0%, Lag= 0.0 min Primary = 5.6 cfs @ 12.11 hrs, Volume= 0.429 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 130.32' @ 12.11 hrs Flood Elev= 132.00' Device Routing Invert Outlet Devices #1 Primary 128.81'15.0" Round 15" RCP L= 38.2' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 128.81' / 127.80' S= 0.0264 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Primary OutFlow Max=5.4 cfs @ 12.11 hrs HW=130.28' (Free Discharge) 1=15" RCP (Inlet Controls 5.4 cfs @ 4.43 fps) Pond 2P: 15" RC Culvert InflowPrimary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)6 5 4 3 2 1 0 Inflow Area=1.246 ac Peak Elev=130.32' 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' 5.6 cfs5.6 cfs Type III 24-hr 100-Year Rainfall=7.82"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 23HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=54,290 sf 54.56% Impervious Runoff Depth=4.88"Subcatchment 1S: DA 1 Flow Length=266' Tc=7.9 min CN=75 Runoff=6.6 cfs 0.507 af Peak Elev=130.67' Inflow=6.6 cfs 0.507 afPond 2P: 15" RC Culvert 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' Outflow=6.6 cfs 0.507 af Total Runoff Area = 1.246 ac Runoff Volume = 0.507 af Average Runoff Depth = 4.88" 45.44% Pervious = 0.566 ac 54.56% Impervious = 0.680 ac Type III 24-hr 100-Year Rainfall=7.82"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 24HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: DA 1 Runoff = 6.6 cfs @ 12.11 hrs, Volume= 0.507 af, Depth= 4.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24-hr 100-Year Rainfall=7.82" Area (sf) CN Description 19,976 98 Unconnected pavement, HSG A 4,060 80 >75% Grass cover, Good, HSG D 2,338 61 >75% Grass cover, Good, HSG B 18,269 39 >75% Grass cover, Good, HSG A 9,647 98 Unconnected pavement, HSG A 54,290 75 Weighted Average 24,667 45.44% Pervious Area 29,623 54.56% Impervious Area 29,623 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 50 0.0220 0.16 Sheet Flow, Sheet Grass Grass: Short n= 0.150 P2= 3.45" 0.5 35 0.0290 1.19 Shallow Concentrated Flow, Shallow Grass 1 Short Grass Pasture Kv= 7.0 fps 0.2 52 0.0396 4.04 Shallow Concentrated Flow, Shallow Pavement Paved Kv= 20.3 fps 2.0 129 0.0247 1.10 Shallow Concentrated Flow, Shallow Grass 2 Short Grass Pasture Kv= 7.0 fps 7.9 266 Total Type III 24-hr 100-Year Rainfall=7.82"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 25HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Subcatchment 1S: DA 1 Runoff Hydrograph Time (hours)3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)7 6 5 4 3 2 1 0 Type III 24-hr 100-Year Rainfall=7.82" Runoff Area=54,290 sf Runoff Volume=0.507 af Runoff Depth=4.88" Flow Length=266' Tc=7.9 min CN=75 6.6 cfs Type III 24-hr 100-Year Rainfall=7.82"Culvert Size Check Printed 10/20/2020Prepared by {enter your company name here} Page 26HydroCAD® 10.10-4b s/n 04031 © 2020 HydroCAD Software Solutions LLC Summary for Pond 2P: 15" RC Culvert Inflow Area = 1.246 ac, 54.56% Impervious, Inflow Depth = 4.88" for 100-Year event Inflow = 6.6 cfs @ 12.11 hrs, Volume= 0.507 af Outflow = 6.6 cfs @ 12.11 hrs, Volume= 0.507 af, Atten= 0%, Lag= 0.0 min Primary = 6.6 cfs @ 12.11 hrs, Volume= 0.507 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs / 2 Peak Elev= 130.67' @ 12.11 hrs Flood Elev= 132.00' Device Routing Invert Outlet Devices #1 Primary 128.81'15.0" Round 15" RCP L= 38.2' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 128.81' / 127.80' S= 0.0264 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.23 sf Primary OutFlow Max=6.4 cfs @ 12.11 hrs HW=130.61' (Free Discharge) 1=15" RCP (Inlet Controls 6.4 cfs @ 5.23 fps) Pond 2P: 15" RC Culvert InflowPrimary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)7 6 5 4 3 2 1 0 Inflow Area=1.246 ac Peak Elev=130.67' 15.0" Round Culvert n=0.013 L=38.2' S=0.0264 '/' 6.6 cfs6.6 cfs Manning’s Flow Rate Calculation 15 inch RCP Culvert Inputs: Pipe Diameter,d 15.0000 in Manning Roughness,n 0.0130 Pressure slope (possibly equal to pipe slope),S 0.0260 slope Percent of (or ratio to)full depth (100%or 1 if flowing full) 1.0000 fraction Results: Flow,Q 10.4155 ft^3/s Velocity,v 8.4873 ft/s Velocity head,hv 1.1195 ft Flow Area,A 1.2272 ft^2 Wetted Perimeter,P 3.9270 ft Hydraulic Radius 0.3125 ft Top Width,T 0.0000 ft Froude Number,F 0.00 Shear Stress (tractive force),2.0288 psf Manning Formula Uniform Pipe Flow at Given Slope and Depth Version 2.0 (20 June 2017) HawsEDC Calculators Manning’s Flow Rate Calculation Vegetated Swale Enter values in yellow cells only. Channel Cross-Sectional Shape - Click on choice below:Triangular Manning roughness, n =0.027 Channel Bottom Slope, S =0.016000 ft/ft Cross-Sect. Area, A =14.400ft2 Depth of flow, y =1.20 ft Wetted Perimeter, P =24.12 ft Side Slope (H:V = z:1), Z = 10.00 Hydraulic Radius, R =0.60 ft Not Used for Triang. ChannelCalculation of Discharge and Average Velocity Using the Manning Equation for Uniform Open Channel Flow - U.S. UnitsCHANNEL SHAPEInput InformationPreliminary CalculationsINPUT INFORectangularTrapezoidalTriangular Discharge thru channel, Q =71.27cfs expressed in gpm, Q =31,986gpm Average Velocity, V =4.95ft/sec References and Equations For discussion of the Manning Equation for uniform open channel flow calculations, see:Equations Used for These Calculationsthe Manning equation: Q = (1.49/n)(A)(R2/3)(S1/2)Average velocity: V = Q/AHydraulic Radius: R = A/P (A = cross-sectional area; P = wetted perimeter)Rectangular channel: A = by and P = b + 2y (b = bottom width; y = depth of flow)Triangular Channel: A = zy2 and P = 2[y2(1 + z2)]1/2 (y = depth of flow; z = side slope (H:V = z:1)Trapezoidal Channel: A = by + zy2 and P = b + 2y(1+z2)1/2 (y = depth of flow; b = bottom width; z = side slope (H:V = z:1) Mark's Standard Handbook for Mechanical Engineers, 11th Ed..3.3.16 Open-Channel Flow Standard Handbook for Civil Engineers, 21.6.4 Manning Equation for Open Channels Hydraulic Design Handbook, 3.4 Uniform Flow Perry's Chemical Engineers' Handbook, 8th Ed, 6.1.4 Incompressible Flow in Pipes and Channels RESULTSDischarge and Velocity Manning’s Flow Rate Calculation Paved Leak Off Enter values in yellow cells only. Channel Cross-Sectional Shape - Click on choice below:Rectangular Manning roughness, n =0.013 Channel Bottom Slope, S =0.050000 ft/ft Cross-Sect. Area, A =1.080ft2 Depth of flow, y =0.12 ft Wetted Perimeter, P =9.24 ft Not Used for Rect.Channel Hydraulic Radius, R =0.12 ft Bottom width, b = 9.00 ftCalculation of Discharge and Average Velocity Using the Manning Equation for Uniform Open Channel Flow - U.S. UnitsCHANNEL SHAPEInput InformationPreliminary CalculationsINPUT INFORectangularTrapezoidalTriangular Discharge thru channel, Q =6.62cfs expressed in gpm, Q =2,970gpm Average Velocity, V =6.13ft/sec References and Equations For discussion of the Manning Equation for uniform open channel flow calculations, see:Equations Used for These Calculationsthe Manning equation: Q = (1.49/n)(A)(R2/3)(S1/2)Average velocity: V = Q/AHydraulic Radius: R = A/P (A = cross-sectional area; P = wetted perimeter)Rectangular channel: A = by and P = b + 2y (b = bottom width; y = depth of flow)Triangular Channel: A = zy2 and P = 2[y2(1 + z2)]1/2 (y = depth of flow; z = side slope (H:V = z:1)Trapezoidal Channel: A = by + zy2 and P = b + 2y(1+z2)1/2 (y = depth of flow; b = bottom width; z = side slope (H:V = z:1) Mark's Standard Handbook for Mechanical Engineers, 11th Ed..3.3.16 Open-Channel Flow Standard Handbook for Civil Engineers, 21.6.4 Manning Equation for Open Channels Hydraulic Design Handbook, 3.4 Uniform Flow Perry's Chemical Engineers' Handbook, 8th Ed, 6.1.4 Incompressible Flow in Pipes and Channels RESULTSDischarge and Velocity