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2021-10-13 SW Permit Amend Request - 60 Damon4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com BerkshireDesignGroup August 26, 2021 Revised October 13, 2021 Doug McDonald Northampton DPW 210 Main Street Northampton, MA 01060 RE: 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Doug, The purpose of this letter is to address proposed amendments to the previously approved stormwater management system at 60 Damon Road in Northampton. A previous project at this site submitted a Stormwater Drainage Report to the City of Northampton in July 2012. The project was for the ‘Connecticut River Greenway: Lane Business Park & Northampton Community Boathouse’. The proposed stormwater management system consisted of four separate treatment trains, each with their own discharge that eventually flowed to the Connecticut River. One train consisted of a rain garden, two trains consisted of proprietary Stormwater Treatment Chambers (SWTCs) discharging to level lip spreaders, and the last train consisted of deep sump catch basins flowing into an infiltration trench. After many rounds of reviews and comments, the City approved the final proposed stormwater system in the Fall of 2012. Pre-Development Conditions (October 2012) Prior to any construction, as of October 2012, runoff from the entire site sheet flowed overland to various swales and ultimately discharged into the Connecticut River. ‘Figure 1: Existing Conditions Subcatchment Plan’ from October 9, 2012, shows two drainage areas. The majority of the site was modeled as one drainage area, E- 1, from which runoff flowed directly to the control point (Connecticut River). A small portion of the site, just east of center, was modeled as another drainage area, E-2, that flowed through a swale to the control point. Conditions Post-Phase I (2018) Following the approval and issuance of relevant permits, the project was only partially constructed. In 2018, the boathouse and surrounding parking and paved drives were built, along with the relevant components of the stormwater management system. These components included the rain garden treatment train and a portion of one SWTC treatment train. ‘Figure 2: Proposed Conditions Subcatchment Plan’ shows the drainage areas that were approved in October 2012. The rain garden treatment train captures and treats stormwater runoff from the boathouse itself and the surrounding pavement area. The entirety of the designed train was constructed and is currently in use. This is drainage area P-3 in Figure 2. The partially constructed SWTC train was designed to treat runoff from two parking areas as well as roof runoff from a new building. Out of the designed areas, only one parking area was constructed and routed to the SWTC and level lip spreader. This treatment train is for drainage area P-2 in Figure 2. Neither the infiltration trench treatment train nor the other SWTC train were constructed. The areas that these trains were designed to treat remain unchanged from the original existing conditions. In Figure 2, the infiltration trench treats runoff from area P-4 and the other SWTC treats runoff from P-5. August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 2 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Proposed Phase II Amendments (Modifications) The project is proposed to be completed based on a modified site plan, requiring adjustments to the un-built portions of the proposed stormwater management system. ‘Figure 3: Modified Design Subcatchment Plan’ shows the modified drainage areas. Drainage Area P-1 The project proposes slight modifications to all drainage areas. ‘Table 1: Surrounding Site, P-1’ shows the effects of these modifications on P-1. The area added to P-1 mostly consists of grass surfaces, with the exception of the existing gravel parking area around the building in P-4 that will remain. Table 1: Surrounding Site, P-1 Original Design Area (sf)Modified Design Area (sf) Grass 93,913 Grass 121,933 Woods 648,260 Woods 648,260 Gravel 11,979 Gravel 16,460 Roof 9,670 Roof 9,670 Pavement 49,045 Pavement 49,045 Total Area 812,867 Total Area 845,368 Drainage Area P-2 The project proposes changes to the building and parking in drainage area P-2 that will be conveyed to the partially constructed SWTC (North SWTC) treatment train. ‘Table 2: North SWTC, P-2’ shows a breakdown between the original design areas and the modified design areas. Table 2: North SWTC, P-2 Original Design Area (sf)Modified Design Area (sf) Grass 6,713 Grass 1,730 Roof 10,053 Roof 13,751 Pavement 25,682 Pavement 18,179 Treated Impervious Area 35,735 Treated Impervious Area 31,930 Total Area 42,448 Total Area 33,660 As is evident, under the modified design the North SWTC treats 8,788 square-feet less than the original design. While the roof area routed to the North SWTC increases in the modified design, the pavement area decreases by a larger amount. In total, the impervious area conveyed to the North SWTC is reduced by 3,805 square-feet. Therefore, the original and approved SWTC treatment train will adequately handle the modified design. Additional stormwater treatment calculations are provided in ‘Water Quality Documents’. August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 3 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Drainage Area P-3 The project proposes minimal changes to the boathouse and surrounding parking area, since the majority of this area has already been constructed. There were some subtle modifications to the original project components submitted for this area. These changes are shown in ‘Table 3: Rain Garden, P-3’. Table 3: Rain Garden, P-3 Original Design Area (sf)Modified Design Area (sf) Grass 21,894 Grass 29,144 Roof 20,406 Roof 11,791 Pavement 28,555 Pavement 28,555 Treated Impervious Area 48,961 Treated Impervious Area 40,346 Total Area 70,855 Total Area 69,490 Drainage Area P-4 In drainage area P-4, the project proposes to modify the original building area and completely fore-go the parking lot in the original design. This is the largest adjustment to the original design from the new project. ‘Table 4: Infiltration Trench, P-4’ shows a breakdown between the original design areas and the modified design areas. Table 4: Infiltration Trench, P-4 Original Design Area (sf)Modified Design Area (sf) Grass 5,504 Grass 0 Roof 9,801 Roof 4,700 Pavement 14,877 Pavement 0 Treated Impervious Area 24,678 Treated Impervious Area 4,700 Total Area 30,182 Total Area 4,700 Under the modified design the infiltration trench receives significantly less runoff than the original design (25,482 square-feet). The reason the area is reduced so much is from the removal of the parking lot from the original design. The modified roof area is also over 3,000 square-feet less than the original design. The discrepancy in area is incorporated into area P-1 in the modified design, which is essentially existing conditions. Therefore, the original and approved infiltration trench will more than adequately handle the modified design. Additional stormwater treatment calculations are provided in ‘Water Quality Documents’. Drainage Area P-5 The project proposes slight changes to the building and road layout in drainage area P-5. The original design proposed a small building, a parking lot, and road access for the rest of the site in this area. The modified design replaces the building and parking lot with one larger building and adjusts the layout of the road access to accommodate these changes. As part of these adjustments, the catch-basins that capture and convey the stormwater runoff within this area have been relocated to continue to capture all runoff. ‘Table 5: South SWTC, P-5’ shows a breakdown between the original design areas and the modified areas. August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 4 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Table 5: South SWTC, P-5 Original Design Area (sf)Modified Design Area (sf) Grass 19,429 Grass 14,306 Roof 9,801 Roof 23,661 Pavement 35,023 Pavement 27,642 Treated Impervious Area 44,824 Treated Impervious Area 51,303 Total Area 64,253 Total Area 65,609 As is evident, both the total area and the amount of impervious area conveyed to the South SWTC increases in the modified design. The pavement area, however, decreases from the original to the modified design. The original design called for the South SWTC to be a Stormceptor 450i made by Contech. The modified design area was inputted into Contech’s Stormceptor sizing program, which calculated that the 450i (original design SWTC) will achieve 80% TSS removal. See attached ‘Brief Stormceptor Sizing Report Modified P-5’. Therefore, the original and approved SWTC will adequately handle the modified design. Additional stormwater treatment calculations are provided in ‘Water Quality Documents’. Stormwater Standards Compliance The proposed Phase II modifications will continue to meet the Massachusetts Stormwater Standards, as listed below: Standard 1: Stormwater Conveyance The modified design retains the three stormwater outlets as the original design. These outlets include two level lip spreaders and the rain garden. All of the outlets will only discharge treated stormwater and are adequately designed to prevent erosion. Standard 2: Peak Discharge The modified design will have peak discharge rates lower than pre-development conditions. ‘Table 6: Peak Discharge Comparison’ shows the peak flow and total volume of runoff to the control point (Connecticut River) for the pre-development and the modified proposed conditions. Table 6: Peak Discharge Comparison 2-YR Storm (3.0")10-YR Storm (4.5")100-YR Storm (6.5") Time of Analysis for CP (Connecticut River)Peak Flow (cfs) Total Volume (ac- ft) Peak Flow (cfs) Total Volume (ac- ft) Peak Flow (cfs) Total Volume (ac- ft) Pre-Development (Oct. 2012)9.42 1.233 26.63 3.019 54.46 5.934 Phase II (Aug. 2021)8.59 1.262 26.31 2.981 54.11 5.801 August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 5 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Standard 3: Groundwater Recharge The modified design provides more than the required groundwater recharge volume, as shown in the calculations below: Required Recharge Volume New Impervious Area = Proposed Impervious Area – Existing Impervious Area Proposed Impervious Area = 146,648 sf Existing Impervious Area = 75,181 sf New Impervious Area = 146,648 sf – 75,181 sf = 71,467 sf Target Depth Factor (HSG B Soils) = 0.35” Required Recharge Volume = (71,467 sf) x (0.35”) x (1’/12”) = 2,084 cf Capture Area Adjustment Impervious Area routed to Rain Garden + Infiltration Basin = 48,983 sf + 4,700 sf = 53,683 sf % of New Impervious Area routed to Recharge Systems = (53,683 sf) / (71,467 sf) = 75% > 65% OK Recharge Adjustment Ratio = 1 / 0.75 = 1.33 Adjusted Recharge Volume = (1.33) x (2,084 cf) = 2,775 cf Provided Recharge Volume Rain Garden Recharge Volume = 2,675 cf Infiltration Basin Recharge Volume = 2,192 cf Recharge Volume Provided = 2,675 cf + 2,192 cf = 4,867 cf > 2,775 cf OK Recharge Systems Drawdown Time Rain Garden Provided Recharge Volume = 2,675 cf Rawls Rate, K (Loamy Sand) = 2.41 inch/hour Bottom Area = 3,869 sf Drawdown Time = (2,675 cf) / (2.41 in/hour) / (3,869 sf) / (1’/12”) = 3.5 Hours < 72 Hours OK Infiltration Trench Provided Recharge Volume = 2,192 cf Rawls Rate, K (Sandy Loam) = 1.02 inch/hour Bottom Area = 1,370 sf Drawdown Time = (2,192 cf) / (1.02 in/hour) / (1,370 sf) / (1’/12”) = 19 Hours < 72 Hours OK Standard 4: Total Suspended Solids (TSS) Removal The modified design will remove at least 80% of total suspended solids (TSS) of the post-construction site layout. In the attached ‘Water Quality Documents’, TSS Removal Worksheets are provided for each drainage area/treatment train. Also found in the ‘Water Quality Documents’ are the proprietary BMP reports which show the TSS removal rate for each Stormceptor 450i. It should be noted that the infiltration basin is solely receiving roof runoff, therefore there is no pre-treatment device for that treatment train. ‘Table 7: TSS Removal by Treatment Train’ summarizes the percent TSS Removal by drainage area. August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 6 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Table 7: TSS Removal by Treatment Train Drainage Area Water Treatment BMP TSS Removal P-2 Stormceptor 450i 81% P-3 Rain Garden 90% P-4 Infiltration Basin 80% P-5 Stormceptor 450i 80% The modified design will also provide the requisite Water Quality Volume, as shown in the calculations below: Rain Garden (Area P-3) Impervious Area routed to Rain Garden = 48,983 sf Water Quality Depth = 0.5” Required Water Quality Volume = (48,983 sf) x (1’/12”) x (0.5”) = 2,041 cf Provided Water Quality Volume = 2,675 cf > 2,041 cf OK Infiltration Basin (Area P-4) Impervious Area routed to Infiltration Basin = 4,700 sf Water Quality Depth = 0.5” Required Water Quality Volume = (4,700 sf) x (1’/12”) x (0.5”) = 196 cf Provided Water Quality Volume = 2,192 cf > 196 cf OK Proprietary BMPs - Stormceptor 450i (Areas P-2 & P-5) Attached ‘Brief Stormceptor Sizing Reports’ show adequate sizing. Standard 5: Land uses with Higher Potential Pollutant Load (LUHPPL) The modified design is not expected to yield high potential pollutant loads. Standard 6: Critical Areas The project proposes four different outlets of stormwater runoff, all of which are designed to obtain a minimum average of 80% TSS removal prior to discharge. Standard 7: Redevelopment Project The existing developed site contained no stormwater management system. The proposed project includes four treatment trains that meet Standards 2 and 3, as well as the structural BMP requirements of Standards 4 and 6. Standard 5 is not applicable to this project. Standard 8: Erosion & Sediment Control Erosion and sediment controls have been incorporated into the project design to precent erosion, control sediments, and stabilized exposed soils during construction and land disturbance. The project requires a Stormwater Pollution Prevention Plan to be submitted prior to the start of the construction. August 26, 2021 Revised October 13, 2021 60 Damon Road – Marijuana Manufacturing Facility Stormwater Management Amendment Page 7 of 7 4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com Standard 9: Operation & Maintenance Plan An Operation and Maintenance (O&M) Plan was submitted with the original Stormwater Permit Application. All components of the stormwater system are the same as the original design, therefore the inspection and maintenance schedule remains unchanged. A copy of the new O&M plan is attached to this letter. Standard 10: Prohibition of Illicit Discharges An Illicit Discharge Compliance Statement is included with this letter. Conclusion The modified design of the stormwater management system continues to meet the Stormwater Standards and requirements of the original approved Stormwater Permit. Please do not hesitate to contact Liam at (413) 582-7000 or liam@berkshiredesign.com if you have any questions about the information contained in this letter. Sincerely, Berkshire Design Group, Inc. Chris Chamberland, PE 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts Stormwater Management System The Berkshire Design Group, Inc. Appendix Figures 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts Stormwater Management System The Berkshire Design Group, Inc. Appendix HydroCAD Report E-1 Existing Site E-2 Existing Site- Portion to NE Swale P-1 Proposed Site P-2 Proposed Site P-3 Proposed Site P-4 Proposed Site P-5 Proposed Site E-CP Connecticut River ES Existing Swale ES. Existing Swale P-CP Connecticut River IT Infiltration Trench LLS1 Level Spreader 1 LLS2 Level Spreader 2 RG Rain Garden WL New Low Wetland Area Routing Diagram for Smith Boathouse - Modified Design 2021.08.25 Prepared by Berkshire Design Group, Printed 10/12/2021 HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 2HydroCAD® 10.10-5a s/n 11721 © 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 YRS Type III 24-hr Default 24.00 1 3.00 2 2 10 YRS Type III 24-hr Default 24.00 1 4.50 2 3 100 YRS Type III 24-hr Default 24.00 1 6.50 2 Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 3HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 1.492 79 <50% Grass cover, Poor, HSG B (E-1, E-2) 3.739 61 >75% Grass cover, Good, HSG B (E-1, P-1, P-2, P-3, P-5) 1.274 74 >75% Grass cover, Good, HSG C (E-1, P-1) 0.378 96 Gravel (P-1) 1.664 96 Gravel Area (E-1) 4.893 98 Paved parking & roofs (E-1, P-1, P-2, P-3, P-4, P-5) 2.045 98 Paved parking, HSG B (E-1, P-1) 21.642 55 Woods, Good, HSG B (E-1, E-2, P-1) 4.500 70 Woods, Good, HSG C (E-1, P-1) 5.521 65 Woods/grass comb., Fair, HSG B (E-1, E-2, P-1) 47.148 67 TOTAL AREA Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 4HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 34.440 HSG B E-1, E-2, P-1, P-2, P-3, P-5 5.773 HSG C E-1, P-1 0.000 HSG D 6.935 Other E-1, P-1, P-2, P-3, P-4, P-5 47.148 TOTAL AREA Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 5HydroCAD® 10.10-5a s/n 11721 © 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 0.000 1.492 0.000 0.000 0.000 1.492 <50% Grass cover, Poor E-1, E-2 0.000 3.739 1.274 0.000 0.000 5.013 >75% Grass cover, Good E-1, P-1, P-2, P-3, P-5 0.000 0.000 0.000 0.000 0.378 0.378 Gravel P-1 0.000 0.000 0.000 0.000 1.664 1.664 Gravel Area E-1 0.000 2.045 0.000 0.000 0.000 2.045 Paved parking E-1, P-1 0.000 0.000 0.000 0.000 4.893 4.893 Paved parking & roofs E-1, P-1, P-2, P-3, P-4, P-5 0.000 21.642 4.500 0.000 0.000 26.142 Woods, Good E-1, E-2, P-1 0.000 5.521 0.000 0.000 0.000 5.521 Woods/grass comb., Fair E-1, E-2, P-1 0.000 34.440 5.773 0.000 6.935 47.148 TOTAL AREA Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 6HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1,013,902 sf 11.37% Impervious Runoff Depth>0.62"Subcatchment E-1: Existing Site Flow Length=1,101' Tc=21.0 min CN=68 Runoff=9.26 cfs 1.208 af Runoff Area=21,035 sf 0.00% Impervious Runoff Depth>0.63"Subcatchment E-2: Existing Site- Portion to Tc=6.0 min CN=68 Runoff=0.29 cfs 0.025 af Runoff Area=845,368 sf 6.95% Impervious Runoff Depth>0.43"Subcatchment P-1: Proposed Site Flow Length=841' Tc=17.4 min CN=63 Runoff=4.64 cfs 0.696 af Runoff Area=33,660 sf 94.86% Impervious Runoff Depth>2.55"Subcatchment P-2: Proposed Site Tc=6.0 min CN=96 Runoff=2.11 cfs 0.164 af Runoff Area=69,490 sf 58.06% Impervious Runoff Depth>1.38"Subcatchment P-3: Proposed Site Tc=6.0 min CN=82 Runoff=2.52 cfs 0.183 af Runoff Area=4,700 sf 100.00% Impervious Runoff Depth>2.77"Subcatchment P-4: Proposed Site Tc=6.0 min CN=98 Runoff=0.31 cfs 0.025 af Runoff Area=65,608 sf 78.20% Impervious Runoff Depth>1.98"Subcatchment P-5: Proposed Site Tc=6.0 min CN=90 Runoff=3.40 cfs 0.249 af Inflow=9.42 cfs 1.233 afReach E-CP: Connecticut River Outflow=9.42 cfs 1.233 af Avg. Flow Depth=0.19' Max Vel=1.82 fps Inflow=1.04 cfs 0.118 afReach ES: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=1.02 cfs 0.117 af Avg. Flow Depth=0.09' Max Vel=1.21 fps Inflow=0.29 cfs 0.025 afReach ES.: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=0.27 cfs 0.025 af Inflow=7.45 cfs 1.218 afReach P-CP: Connecticut River Outflow=7.45 cfs 1.218 af Peak Elev=142.98' Storage=1,083 cf Inflow=0.31 cfs 0.025 afPond IT: Infiltration Trench Outflow=0.00 cfs 0.000 af Peak Elev=147.11' Storage=145 cf Inflow=2.11 cfs 0.164 afPond LLS1: Level Spreader 1 Outflow=2.11 cfs 0.161 af Peak Elev=145.15' Storage=199 cf Inflow=3.40 cfs 0.249 afPond LLS2: Level Spreader 2 Outflow=3.42 cfs 0.244 af Peak Elev=141.72' Storage=2,982 cf Inflow=2.52 cfs 0.183 afPond RG: Rain Garden Outflow=1.17 cfs 0.121 af Peak Elev=137.17' Storage=379 cf Inflow=1.17 cfs 0.121 afPond WL: New Low Wetland Area Outflow=1.04 cfs 0.118 af Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 7HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Total Runoff Area = 47.148 ac Runoff Volume = 2.550 af Average Runoff Depth = 0.65" 85.28% Pervious = 40.210 ac 14.72% Impervious = 6.938 ac Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 8HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Site Runoff = 9.26 cfs @ 12.35 hrs, Volume= 1.208 af, Depth> 0.62" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 75,181 98 Paved parking & roofs * 72,493 96 Gravel Area 152,762 65 Woods/grass comb., Fair, HSG B 467,077 55 Woods, Good, HSG B 98,000 70 Woods, Good, HSG C 14,000 61 >75% Grass cover, Good, HSG B 25,000 74 >75% Grass cover, Good, HSG C 57,094 79 <50% Grass cover, Poor, HSG B 40,055 98 Paved parking, HSG B 12,240 74 >75% Grass cover, Good, HSG C 1,013,902 68 Weighted Average 898,666 88.63% Pervious Area 115,236 11.37% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Sheet flow over gravel Smooth surfaces n= 0.011 P2= 3.00" 2.5 260 0.0120 1.76 Shallow Concentrated Flow, Flow Over Gravel Unpaved Kv= 16.1 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 21.0 1,101 Total Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 9HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment E-1: Existing Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)10 9 8 7 6 5 4 3 2 1 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=1,013,902 sf Runoff Volume=1.208 af Runoff Depth>0.62" Flow Length=1,101' Tc=21.0 min CN=68 9.26 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 10HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Site- Portion to NE Swale Runoff = 0.29 cfs @ 12.11 hrs, Volume= 0.025 af, Depth> 0.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 8,829 65 Woods/grass comb., Fair, HSG B 4,300 55 Woods, Good, HSG B 7,906 79 <50% Grass cover, Poor, HSG B 21,035 68 Weighted Average 21,035 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment E-2: Existing Site- Portion to NE Swale Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=21,035 sf Runoff Volume=0.025 af Runoff Depth>0.63" Tc=6.0 min CN=68 0.29 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 11HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Site Runoff = 4.64 cfs @ 12.35 hrs, Volume= 0.696 af, Depth> 0.43" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 9,670 98 Paved parking & roofs * 16,460 96 Gravel 78,887 65 Woods/grass comb., Fair, HSG B 471,363 55 Woods, Good, HSG B 98,010 70 Woods, Good, HSG C 103,698 61 >75% Grass cover, Good, HSG B 14,985 74 >75% Grass cover, Good, HSG C 49,045 98 Paved parking, HSG B 3,250 74 >75% Grass cover, Good, HSG C 845,368 63 Weighted Average 786,653 93.05% Pervious Area 58,715 6.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.6 100 0.0400 3.00 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 17.4 841 Total Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 12HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment P-1: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=845,368 sf Runoff Volume=0.696 af Runoff Depth>0.43" Flow Length=841' Tc=17.4 min CN=63 4.64 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 13HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Site Runoff = 2.11 cfs @ 12.09 hrs, Volume= 0.164 af, Depth> 2.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 31,930 98 Paved parking & roofs 1,730 61 >75% Grass cover, Good, HSG B 33,660 96 Weighted Average 1,730 5.14% Pervious Area 31,930 94.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-2: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=33,660 sf Runoff Volume=0.164 af Runoff Depth>2.55" Tc=6.0 min CN=96 2.11 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 14HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-3: Proposed Site Runoff = 2.52 cfs @ 12.10 hrs, Volume= 0.183 af, Depth> 1.38" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 40,346 98 Paved parking & roofs 29,144 61 >75% Grass cover, Good, HSG B 69,490 82 Weighted Average 29,144 41.94% Pervious Area 40,346 58.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-3: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=69,490 sf Runoff Volume=0.183 af Runoff Depth>1.38" Tc=6.0 min CN=82 2.52 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 15HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-4: Proposed Site Runoff = 0.31 cfs @ 12.09 hrs, Volume= 0.025 af, Depth> 2.77" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 4,700 98 Paved parking & roofs 4,700 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-4: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=4,700 sf Runoff Volume=0.025 af Runoff Depth>2.77" Tc=6.0 min CN=98 0.31 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 16HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-5: Proposed Site Runoff = 3.40 cfs @ 12.09 hrs, Volume= 0.249 af, Depth> 1.98" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 51,303 98 Paved parking & roofs 14,305 61 >75% Grass cover, Good, HSG B 65,608 90 Weighted Average 14,305 21.80% Pervious Area 51,303 78.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-5: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 2 YRS Rainfall=3.00" Runoff Area=65,608 sf Runoff Volume=0.249 af Runoff Depth>1.98" Tc=6.0 min CN=90 3.40 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 17HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach E-CP: Connecticut River Inflow Area = 23.759 ac, 11.13% Impervious, Inflow Depth > 0.62" for 2 YRS event Inflow = 9.42 cfs @ 12.35 hrs, Volume= 1.233 af Outflow = 9.42 cfs @ 12.35 hrs, Volume= 1.233 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)10 9 8 7 6 5 4 3 2 1 0 Inflow Area=23.759 ac 9.42 cfs9.42 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 18HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES: Existing Swale Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 0.88" for 2 YRS event Inflow = 1.04 cfs @ 12.41 hrs, Volume= 0.118 af Outflow = 1.02 cfs @ 12.43 hrs, Volume= 0.117 af, Atten= 2%, Lag= 1.4 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 1.82 fps, Min. Travel Time= 0.7 min Avg. Velocity = 0.83 fps, Avg. Travel Time= 1.6 min Peak Storage= 44 cf @ 12.42 hrs Average Depth at Peak Storage= 0.19' , Surface Width= 3.91' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.595 ac Avg. Flow Depth=0.19' Max Vel=1.82 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 1.04 cfs1.02 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 19HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES.: Existing Swale Inflow Area = 0.483 ac, 0.00% Impervious, Inflow Depth > 0.63" for 2 YRS event Inflow = 0.29 cfs @ 12.11 hrs, Volume= 0.025 af Outflow = 0.27 cfs @ 12.15 hrs, Volume= 0.025 af, Atten= 5%, Lag= 2.3 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 1.21 fps, Min. Travel Time= 1.1 min Avg. Velocity = 0.46 fps, Avg. Travel Time= 2.8 min Peak Storage= 18 cf @ 12.12 hrs Average Depth at Peak Storage= 0.09' , Surface Width= 2.94' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES.: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.483 ac Avg. Flow Depth=0.09' Max Vel=1.21 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 0.29 cfs 0.27 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 20HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach P-CP: Connecticut River Inflow Area = 23.389 ac, 18.35% Impervious, Inflow Depth > 0.63" for 2 YRS event Inflow = 7.45 cfs @ 12.36 hrs, Volume= 1.218 af Outflow = 7.45 cfs @ 12.36 hrs, Volume= 1.218 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)8 7 6 5 4 3 2 1 0 Inflow Area=23.389 ac 7.45 cfs7.45 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 21HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond IT: Infiltration Trench Inflow Area = 0.108 ac,100.00% Impervious, Inflow Depth > 2.77" for 2 YRS event Inflow = 0.31 cfs @ 12.09 hrs, Volume= 0.025 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 142.98' @ 24.00 hrs Surf.Area= 1,370 sf Storage= 1,083 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 141.00' 2,192 cf Custom Stage Data (Prismatic) Listed below (Recalc) 5,480 cf Overall x 40.0% Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 1,370 0 0 145.00 1,370 5,480 5,480 Device Routing Invert Outlet Devices #1 Primary 147.50'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=141.00' (Free Discharge) 1=Orifice/Grate ( Controls 0.00 cfs) Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 22HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond IT: Infiltration Trench Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.108 ac Peak Elev=142.98' Storage=1,083 cf 0.31 cfs 0.00 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 23HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS1: Level Spreader 1 Inflow Area = 0.773 ac, 94.86% Impervious, Inflow Depth > 2.55" for 2 YRS event Inflow = 2.11 cfs @ 12.09 hrs, Volume= 0.164 af Outflow = 2.11 cfs @ 12.09 hrs, Volume= 0.161 af, Atten= 0%, Lag= 0.0 min Primary = 2.11 cfs @ 12.09 hrs, Volume= 0.161 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 147.11' @ 12.09 hrs Surf.Area= 230 sf Storage= 145 cf Plug-Flow detention time= 21.3 min calculated for 0.161 af (98% of inflow) Center-of-Mass det. time= 9.1 min ( 784.6 - 775.5 ) Volume Invert Avail.Storage Storage Description #1 146.00' 145 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 60 0 0 147.00 230 145 145 Device Routing Invert Outlet Devices #1 Primary 147.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=2.05 cfs @ 12.09 hrs HW=147.11' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 2.05 cfs @ 0.88 fps) Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 24HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS1: Level Spreader 1 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.773 ac Peak Elev=147.11' Storage=145 cf 2.11 cfs2.11 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 25HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS2: Level Spreader 2 Inflow Area = 1.506 ac, 78.20% Impervious, Inflow Depth > 1.98" for 2 YRS event Inflow = 3.40 cfs @ 12.09 hrs, Volume= 0.249 af Outflow = 3.42 cfs @ 12.09 hrs, Volume= 0.244 af, Atten= 0%, Lag= 0.0 min Primary = 3.42 cfs @ 12.09 hrs, Volume= 0.244 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 145.15' @ 12.09 hrs Surf.Area= 292 sf Storage= 199 cf Plug-Flow detention time= 16.6 min calculated for 0.244 af (98% of inflow) Center-of-Mass det. time= 5.9 min ( 814.8 - 808.9 ) Volume Invert Avail.Storage Storage Description #1 144.00' 199 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 144.00 105 0 0 145.00 292 199 199 Device Routing Invert Outlet Devices #1 Primary 145.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=3.34 cfs @ 12.09 hrs HW=145.15' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 3.34 cfs @ 1.03 fps) Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 26HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS2: Level Spreader 2 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=1.506 ac Peak Elev=145.15' Storage=199 cf 3.40 cfs3.42 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 27HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 1.38" for 2 YRS event Inflow = 2.52 cfs @ 12.10 hrs, Volume= 0.183 af Outflow = 1.17 cfs @ 12.32 hrs, Volume= 0.121 af, Atten= 53%, Lag= 13.2 min Primary = 1.17 cfs @ 12.32 hrs, Volume= 0.121 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 141.72' @ 12.32 hrs Surf.Area= 4,415 sf Storage= 2,982 cf Plug-Flow detention time= 175.4 min calculated for 0.121 af (66% of inflow) Center-of-Mass det. time= 71.1 min ( 909.9 - 838.8 ) Volume Invert Avail.Storage Storage Description #1 141.00' 4,248 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 3,869 0 0 142.00 4,627 4,248 4,248 Device Routing Invert Outlet Devices #1 Primary 141.65'25.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=1.15 cfs @ 12.32 hrs HW=141.72' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 1.15 cfs @ 0.67 fps) Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 28HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=1.595 ac Peak Elev=141.72' Storage=2,982 cf 2.52 cfs 1.17 cfs Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 29HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond WL: New Low Wetland Area Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 0.91" for 2 YRS event Inflow = 1.17 cfs @ 12.32 hrs, Volume= 0.121 af Outflow = 1.04 cfs @ 12.41 hrs, Volume= 0.118 af, Atten= 12%, Lag= 5.6 min Primary = 1.04 cfs @ 12.41 hrs, Volume= 0.118 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 137.17' @ 12.41 hrs Surf.Area= 2,234 sf Storage= 379 cf Plug-Flow detention time= 24.3 min calculated for 0.118 af (97% of inflow) Center-of-Mass det. time= 9.2 min ( 919.1 - 909.9 ) Volume Invert Avail.Storage Storage Description #1 136.95' 3,241 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 136.95 10 0 0 137.00 1,745 44 44 138.00 4,650 3,198 3,241 Device Routing Invert Outlet Devices #1 Primary 137.05'10.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=1.03 cfs @ 12.41 hrs HW=137.17' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 1.03 cfs @ 0.87 fps) Type III 24-hr 2 YRS Rainfall=3.00"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 30HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond WL: New Low Wetland Area Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.595 ac Peak Elev=137.17' Storage=379 cf 1.17 cfs 1.04 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 31HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1,013,902 sf 11.37% Impervious Runoff Depth>1.52"Subcatchment E-1: Existing Site Flow Length=1,101' Tc=21.0 min CN=68 Runoff=26.21 cfs 2.957 af Runoff Area=21,035 sf 0.00% Impervious Runoff Depth>1.53"Subcatchment E-2: Existing Site- Portion to Tc=6.0 min CN=68 Runoff=0.82 cfs 0.062 af Runoff Area=845,368 sf 6.95% Impervious Runoff Depth>1.20"Subcatchment P-1: Proposed Site Flow Length=841' Tc=17.4 min CN=63 Runoff=17.43 cfs 1.935 af Runoff Area=33,660 sf 94.86% Impervious Runoff Depth>4.03"Subcatchment P-2: Proposed Site Tc=6.0 min CN=96 Runoff=3.25 cfs 0.260 af Runoff Area=69,490 sf 58.06% Impervious Runoff Depth>2.63"Subcatchment P-3: Proposed Site Tc=6.0 min CN=82 Runoff=4.83 cfs 0.350 af Runoff Area=4,700 sf 100.00% Impervious Runoff Depth>4.26"Subcatchment P-4: Proposed Site Tc=6.0 min CN=98 Runoff=0.46 cfs 0.038 af Runoff Area=65,608 sf 78.20% Impervious Runoff Depth>3.39"Subcatchment P-5: Proposed Site Tc=6.0 min CN=90 Runoff=5.69 cfs 0.426 af Inflow=26.63 cfs 3.019 afReach E-CP: Connecticut River Outflow=26.63 cfs 3.019 af Avg. Flow Depth=0.39' Max Vel=2.70 fps Inflow=4.25 cfs 0.284 afReach ES: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=4.13 cfs 0.284 af Avg. Flow Depth=0.17' Max Vel=1.70 fps Inflow=0.82 cfs 0.062 afReach ES.: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=0.78 cfs 0.062 af Inflow=25.37 cfs 2.897 afReach P-CP: Connecticut River Outflow=25.37 cfs 2.897 af Peak Elev=144.05' Storage=1,669 cf Inflow=0.46 cfs 0.038 afPond IT: Infiltration Trench Outflow=0.00 cfs 0.000 af Peak Elev=147.14' Storage=145 cf Inflow=3.25 cfs 0.260 afPond LLS1: Level Spreader 1 Outflow=3.26 cfs 0.256 af Peak Elev=145.21' Storage=199 cf Inflow=5.69 cfs 0.426 afPond LLS2: Level Spreader 2 Outflow=5.73 cfs 0.421 af Peak Elev=141.82' Storage=3,436 cf Inflow=4.83 cfs 0.350 afPond RG: Rain Garden Outflow=4.52 cfs 0.288 af Peak Elev=137.35' Storage=835 cf Inflow=4.52 cfs 0.288 afPond WL: New Low Wetland Area Outflow=4.25 cfs 0.284 af Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 32HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Total Runoff Area = 47.148 ac Runoff Volume = 6.028 af Average Runoff Depth = 1.53" 85.28% Pervious = 40.210 ac 14.72% Impervious = 6.938 ac Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 33HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Site Runoff = 26.21 cfs @ 12.31 hrs, Volume= 2.957 af, Depth> 1.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 75,181 98 Paved parking & roofs * 72,493 96 Gravel Area 152,762 65 Woods/grass comb., Fair, HSG B 467,077 55 Woods, Good, HSG B 98,000 70 Woods, Good, HSG C 14,000 61 >75% Grass cover, Good, HSG B 25,000 74 >75% Grass cover, Good, HSG C 57,094 79 <50% Grass cover, Poor, HSG B 40,055 98 Paved parking, HSG B 12,240 74 >75% Grass cover, Good, HSG C 1,013,902 68 Weighted Average 898,666 88.63% Pervious Area 115,236 11.37% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Sheet flow over gravel Smooth surfaces n= 0.011 P2= 3.00" 2.5 260 0.0120 1.76 Shallow Concentrated Flow, Flow Over Gravel Unpaved Kv= 16.1 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 21.0 1,101 Total Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 34HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment E-1: Existing Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=1,013,902 sf Runoff Volume=2.957 af Runoff Depth>1.52" Flow Length=1,101' Tc=21.0 min CN=68 26.21 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 35HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Site- Portion to NE Swale Runoff = 0.82 cfs @ 12.10 hrs, Volume= 0.062 af, Depth> 1.53" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 8,829 65 Woods/grass comb., Fair, HSG B 4,300 55 Woods, Good, HSG B 7,906 79 <50% Grass cover, Poor, HSG B 21,035 68 Weighted Average 21,035 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment E-2: Existing Site- Portion to NE Swale Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=21,035 sf Runoff Volume=0.062 af Runoff Depth>1.53" Tc=6.0 min CN=68 0.82 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 36HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Site Runoff = 17.43 cfs @ 12.27 hrs, Volume= 1.935 af, Depth> 1.20" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 9,670 98 Paved parking & roofs * 16,460 96 Gravel 78,887 65 Woods/grass comb., Fair, HSG B 471,363 55 Woods, Good, HSG B 98,010 70 Woods, Good, HSG C 103,698 61 >75% Grass cover, Good, HSG B 14,985 74 >75% Grass cover, Good, HSG C 49,045 98 Paved parking, HSG B 3,250 74 >75% Grass cover, Good, HSG C 845,368 63 Weighted Average 786,653 93.05% Pervious Area 58,715 6.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.6 100 0.0400 3.00 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 17.4 841 Total Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 37HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment P-1: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=845,368 sf Runoff Volume=1.935 af Runoff Depth>1.20" Flow Length=841' Tc=17.4 min CN=63 17.43 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 38HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Site Runoff = 3.25 cfs @ 12.09 hrs, Volume= 0.260 af, Depth> 4.03" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 31,930 98 Paved parking & roofs 1,730 61 >75% Grass cover, Good, HSG B 33,660 96 Weighted Average 1,730 5.14% Pervious Area 31,930 94.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-2: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=33,660 sf Runoff Volume=0.260 af Runoff Depth>4.03" Tc=6.0 min CN=96 3.25 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 39HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-3: Proposed Site Runoff = 4.83 cfs @ 12.09 hrs, Volume= 0.350 af, Depth> 2.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 40,346 98 Paved parking & roofs 29,144 61 >75% Grass cover, Good, HSG B 69,490 82 Weighted Average 29,144 41.94% Pervious Area 40,346 58.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-3: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=69,490 sf Runoff Volume=0.350 af Runoff Depth>2.63" Tc=6.0 min CN=82 4.83 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 40HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-4: Proposed Site Runoff = 0.46 cfs @ 12.09 hrs, Volume= 0.038 af, Depth> 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 4,700 98 Paved parking & roofs 4,700 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-4: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=4,700 sf Runoff Volume=0.038 af Runoff Depth>4.26" Tc=6.0 min CN=98 0.46 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 41HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-5: Proposed Site Runoff = 5.69 cfs @ 12.09 hrs, Volume= 0.426 af, Depth> 3.39" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 51,303 98 Paved parking & roofs 14,305 61 >75% Grass cover, Good, HSG B 65,608 90 Weighted Average 14,305 21.80% Pervious Area 51,303 78.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-5: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)6 5 4 3 2 1 0 Type III 24-hr 10 YRS Rainfall=4.50" Runoff Area=65,608 sf Runoff Volume=0.426 af Runoff Depth>3.39" Tc=6.0 min CN=90 5.69 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 42HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach E-CP: Connecticut River Inflow Area = 23.759 ac, 11.13% Impervious, Inflow Depth > 1.52" for 10 YRS event Inflow = 26.63 cfs @ 12.31 hrs, Volume= 3.019 af Outflow = 26.63 cfs @ 12.31 hrs, Volume= 3.019 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Inflow Area=23.759 ac 26.63 cfs26.63 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 43HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES: Existing Swale Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 2.14" for 10 YRS event Inflow = 4.25 cfs @ 12.16 hrs, Volume= 0.284 af Outflow = 4.13 cfs @ 12.18 hrs, Volume= 0.284 af, Atten= 3%, Lag= 1.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 2.70 fps, Min. Travel Time= 0.5 min Avg. Velocity = 1.03 fps, Avg. Travel Time= 1.3 min Peak Storage= 123 cf @ 12.17 hrs Average Depth at Peak Storage= 0.39' , Surface Width= 5.93' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)4 3 2 1 0 Inflow Area=1.595 ac Avg. Flow Depth=0.39' Max Vel=2.70 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 4.25 cfs4.13 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 44HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES.: Existing Swale Inflow Area = 0.483 ac, 0.00% Impervious, Inflow Depth > 1.53" for 10 YRS event Inflow = 0.82 cfs @ 12.10 hrs, Volume= 0.062 af Outflow = 0.78 cfs @ 12.12 hrs, Volume= 0.062 af, Atten= 4%, Lag= 1.3 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 1.70 fps, Min. Travel Time= 0.8 min Avg. Velocity = 0.60 fps, Avg. Travel Time= 2.2 min Peak Storage= 38 cf @ 12.11 hrs Average Depth at Peak Storage= 0.17' , Surface Width= 3.68' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES.: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=0.483 ac Avg. Flow Depth=0.17' Max Vel=1.70 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 0.82 cfs 0.78 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 45HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach P-CP: Connecticut River Inflow Area = 23.389 ac, 18.35% Impervious, Inflow Depth > 1.49" for 10 YRS event Inflow = 25.37 cfs @ 12.22 hrs, Volume= 2.897 af Outflow = 25.37 cfs @ 12.22 hrs, Volume= 2.897 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Inflow Area=23.389 ac 25.37 cfs25.37 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 46HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond IT: Infiltration Trench Inflow Area = 0.108 ac,100.00% Impervious, Inflow Depth > 4.26" for 10 YRS event Inflow = 0.46 cfs @ 12.09 hrs, Volume= 0.038 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 144.05' @ 24.00 hrs Surf.Area= 1,370 sf Storage= 1,669 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 141.00' 2,192 cf Custom Stage Data (Prismatic) Listed below (Recalc) 5,480 cf Overall x 40.0% Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 1,370 0 0 145.00 1,370 5,480 5,480 Device Routing Invert Outlet Devices #1 Primary 147.50'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=141.00' (Free Discharge) 1=Orifice/Grate ( Controls 0.00 cfs) Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 47HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond IT: Infiltration Trench Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.108 ac Peak Elev=144.05' Storage=1,669 cf 0.46 cfs 0.00 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 48HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS1: Level Spreader 1 Inflow Area = 0.773 ac, 94.86% Impervious, Inflow Depth > 4.03" for 10 YRS event Inflow = 3.25 cfs @ 12.09 hrs, Volume= 0.260 af Outflow = 3.26 cfs @ 12.09 hrs, Volume= 0.256 af, Atten= 0%, Lag= 0.0 min Primary = 3.26 cfs @ 12.09 hrs, Volume= 0.256 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 147.14' @ 12.09 hrs Surf.Area= 230 sf Storage= 145 cf Plug-Flow detention time= 14.9 min calculated for 0.256 af (99% of inflow) Center-of-Mass det. time= 6.8 min ( 771.3 - 764.5 ) Volume Invert Avail.Storage Storage Description #1 146.00' 145 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 60 0 0 147.00 230 145 145 Device Routing Invert Outlet Devices #1 Primary 147.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=3.17 cfs @ 12.09 hrs HW=147.14' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 3.17 cfs @ 1.01 fps) Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 49HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS1: Level Spreader 1 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=0.773 ac Peak Elev=147.14' Storage=145 cf 3.25 cfs3.26 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 50HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS2: Level Spreader 2 Inflow Area = 1.506 ac, 78.20% Impervious, Inflow Depth > 3.39" for 10 YRS event Inflow = 5.69 cfs @ 12.09 hrs, Volume= 0.426 af Outflow = 5.73 cfs @ 12.09 hrs, Volume= 0.421 af, Atten= 0%, Lag= 0.1 min Primary = 5.73 cfs @ 12.09 hrs, Volume= 0.421 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 145.21' @ 12.09 hrs Surf.Area= 292 sf Storage= 199 cf Plug-Flow detention time= 10.8 min calculated for 0.421 af (99% of inflow) Center-of-Mass det. time= 4.4 min ( 798.3 - 793.9 ) Volume Invert Avail.Storage Storage Description #1 144.00' 199 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 144.00 105 0 0 145.00 292 199 199 Device Routing Invert Outlet Devices #1 Primary 145.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=5.58 cfs @ 12.09 hrs HW=145.21' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 5.58 cfs @ 1.23 fps) Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 51HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS2: Level Spreader 2 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)6 5 4 3 2 1 0 Inflow Area=1.506 ac Peak Elev=145.21' Storage=199 cf 5.69 cfs5.73 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 52HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 2.63" for 10 YRS event Inflow = 4.83 cfs @ 12.09 hrs, Volume= 0.350 af Outflow = 4.52 cfs @ 12.12 hrs, Volume= 0.288 af, Atten= 6%, Lag= 1.9 min Primary = 4.52 cfs @ 12.12 hrs, Volume= 0.288 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 141.82' @ 12.12 hrs Surf.Area= 4,492 sf Storage= 3,436 cf Plug-Flow detention time= 107.4 min calculated for 0.287 af (82% of inflow) Center-of-Mass det. time= 36.7 min ( 856.8 - 820.2 ) Volume Invert Avail.Storage Storage Description #1 141.00' 4,248 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 3,869 0 0 142.00 4,627 4,248 4,248 Device Routing Invert Outlet Devices #1 Primary 141.65'25.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=4.37 cfs @ 12.12 hrs HW=141.82' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 4.37 cfs @ 1.04 fps) Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 53HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Inflow Area=1.595 ac Peak Elev=141.82' Storage=3,436 cf 4.83 cfs 4.52 cfs Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 54HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond WL: New Low Wetland Area Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 2.17" for 10 YRS event Inflow = 4.52 cfs @ 12.12 hrs, Volume= 0.288 af Outflow = 4.25 cfs @ 12.16 hrs, Volume= 0.284 af, Atten= 6%, Lag= 2.4 min Primary = 4.25 cfs @ 12.16 hrs, Volume= 0.284 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 137.35' @ 12.16 hrs Surf.Area= 2,764 sf Storage= 835 cf Plug-Flow detention time= 12.5 min calculated for 0.284 af (99% of inflow) Center-of-Mass det. time= 4.9 min ( 861.8 - 856.8 ) Volume Invert Avail.Storage Storage Description #1 136.95' 3,241 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 136.95 10 0 0 137.00 1,745 44 44 138.00 4,650 3,198 3,241 Device Routing Invert Outlet Devices #1 Primary 137.05'10.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=4.15 cfs @ 12.16 hrs HW=137.35' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 4.15 cfs @ 1.40 fps) Type III 24-hr 10 YRS Rainfall=4.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 55HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond WL: New Low Wetland Area Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Inflow Area=1.595 ac Peak Elev=137.35' Storage=835 cf 4.52 cfs 4.25 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 56HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1,013,902 sf 11.37% Impervious Runoff Depth>3.00"Subcatchment E-1: Existing Site Flow Length=1,101' Tc=21.0 min CN=68 Runoff=53.64 cfs 5.813 af Runoff Area=21,035 sf 0.00% Impervious Runoff Depth>3.01"Subcatchment E-2: Existing Site- Portion to Tc=6.0 min CN=68 Runoff=1.66 cfs 0.121 af Runoff Area=845,368 sf 6.95% Impervious Runoff Depth>2.52"Subcatchment P-1: Proposed Site Flow Length=841' Tc=17.4 min CN=63 Runoff=39.82 cfs 4.080 af Runoff Area=33,660 sf 94.86% Impervious Runoff Depth>6.02"Subcatchment P-2: Proposed Site Tc=6.0 min CN=96 Runoff=4.76 cfs 0.388 af Runoff Area=69,490 sf 58.06% Impervious Runoff Depth>4.45"Subcatchment P-3: Proposed Site Tc=6.0 min CN=82 Runoff=8.04 cfs 0.591 af Runoff Area=4,700 sf 100.00% Impervious Runoff Depth>6.26"Subcatchment P-4: Proposed Site Tc=6.0 min CN=98 Runoff=0.67 cfs 0.056 af Runoff Area=65,608 sf 78.20% Impervious Runoff Depth>5.33"Subcatchment P-5: Proposed Site Tc=6.0 min CN=90 Runoff=8.72 cfs 0.669 af Inflow=54.46 cfs 5.934 afReach E-CP: Connecticut River Outflow=54.46 cfs 5.934 af Avg. Flow Depth=0.51' Max Vel=3.14 fps Inflow=7.26 cfs 0.524 afReach ES: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=7.16 cfs 0.524 af Avg. Flow Depth=0.25' Max Vel=2.10 fps Inflow=1.66 cfs 0.121 afReach ES.: Existing Swale n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs Outflow=1.61 cfs 0.121 af Inflow=52.58 cfs 5.659 afReach P-CP: Connecticut River Outflow=52.58 cfs 5.659 af Peak Elev=147.50' Storage=2,192 cf Inflow=0.67 cfs 0.056 afPond IT: Infiltration Trench Outflow=0.03 cfs 0.006 af Peak Elev=147.19' Storage=145 cf Inflow=4.76 cfs 0.388 afPond LLS1: Level Spreader 1 Outflow=4.77 cfs 0.384 af Peak Elev=145.28' Storage=199 cf Inflow=8.72 cfs 0.669 afPond LLS2: Level Spreader 2 Outflow=8.75 cfs 0.664 af Peak Elev=141.89' Storage=3,761 cf Inflow=8.04 cfs 0.591 afPond RG: Rain Garden Outflow=7.68 cfs 0.528 af Peak Elev=137.48' Storage=1,204 cf Inflow=7.68 cfs 0.528 afPond WL: New Low Wetland Area Outflow=7.26 cfs 0.524 af Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 57HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Total Runoff Area = 47.148 ac Runoff Volume = 11.718 af Average Runoff Depth = 2.98" 85.28% Pervious = 40.210 ac 14.72% Impervious = 6.938 ac Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 58HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Site Runoff = 53.64 cfs @ 12.30 hrs, Volume= 5.813 af, Depth> 3.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 75,181 98 Paved parking & roofs * 72,493 96 Gravel Area 152,762 65 Woods/grass comb., Fair, HSG B 467,077 55 Woods, Good, HSG B 98,000 70 Woods, Good, HSG C 14,000 61 >75% Grass cover, Good, HSG B 25,000 74 >75% Grass cover, Good, HSG C 57,094 79 <50% Grass cover, Poor, HSG B 40,055 98 Paved parking, HSG B 12,240 74 >75% Grass cover, Good, HSG C 1,013,902 68 Weighted Average 898,666 88.63% Pervious Area 115,236 11.37% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Sheet flow over gravel Smooth surfaces n= 0.011 P2= 3.00" 2.5 260 0.0120 1.76 Shallow Concentrated Flow, Flow Over Gravel Unpaved Kv= 16.1 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 21.0 1,101 Total Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 59HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment E-1: Existing Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)60 55 50 45 40 35 30 25 20 15 10 5 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=1,013,902 sf Runoff Volume=5.813 af Runoff Depth>3.00" Flow Length=1,101' Tc=21.0 min CN=68 53.64 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 60HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Site- Portion to NE Swale Runoff = 1.66 cfs @ 12.10 hrs, Volume= 0.121 af, Depth> 3.01" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 8,829 65 Woods/grass comb., Fair, HSG B 4,300 55 Woods, Good, HSG B 7,906 79 <50% Grass cover, Poor, HSG B 21,035 68 Weighted Average 21,035 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment E-2: Existing Site- Portion to NE Swale Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=21,035 sf Runoff Volume=0.121 af Runoff Depth>3.01" Tc=6.0 min CN=68 1.66 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 61HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Site Runoff = 39.82 cfs @ 12.25 hrs, Volume= 4.080 af, Depth> 2.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 9,670 98 Paved parking & roofs * 16,460 96 Gravel 78,887 65 Woods/grass comb., Fair, HSG B 471,363 55 Woods, Good, HSG B 98,010 70 Woods, Good, HSG C 103,698 61 >75% Grass cover, Good, HSG B 14,985 74 >75% Grass cover, Good, HSG C 49,045 98 Paved parking, HSG B 3,250 74 >75% Grass cover, Good, HSG C 845,368 63 Weighted Average 786,653 93.05% Pervious Area 58,715 6.95% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.6 100 0.0400 3.00 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 11.0 430 0.0170 0.65 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.8 131 0.0600 1.22 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 4.0 180 0.0230 0.76 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 17.4 841 Total Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 62HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Subcatchment P-1: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=845,368 sf Runoff Volume=4.080 af Runoff Depth>2.52" Flow Length=841' Tc=17.4 min CN=63 39.82 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 63HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Site Runoff = 4.76 cfs @ 12.09 hrs, Volume= 0.388 af, Depth> 6.02" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 31,930 98 Paved parking & roofs 1,730 61 >75% Grass cover, Good, HSG B 33,660 96 Weighted Average 1,730 5.14% Pervious Area 31,930 94.86% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-2: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=33,660 sf Runoff Volume=0.388 af Runoff Depth>6.02" Tc=6.0 min CN=96 4.76 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 64HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-3: Proposed Site Runoff = 8.04 cfs @ 12.09 hrs, Volume= 0.591 af, Depth> 4.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 40,346 98 Paved parking & roofs 29,144 61 >75% Grass cover, Good, HSG B 69,490 82 Weighted Average 29,144 41.94% Pervious Area 40,346 58.06% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-3: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)9 8 7 6 5 4 3 2 1 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=69,490 sf Runoff Volume=0.591 af Runoff Depth>4.45" Tc=6.0 min CN=82 8.04 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 65HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-4: Proposed Site Runoff = 0.67 cfs @ 12.09 hrs, Volume= 0.056 af, Depth> 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 4,700 98 Paved parking & roofs 4,700 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-4: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=4,700 sf Runoff Volume=0.056 af Runoff Depth>6.26" Tc=6.0 min CN=98 0.67 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 66HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment P-5: Proposed Site Runoff = 8.72 cfs @ 12.09 hrs, Volume= 0.669 af, Depth> 5.33" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 51,303 98 Paved parking & roofs 14,305 61 >75% Grass cover, Good, HSG B 65,608 90 Weighted Average 14,305 21.80% Pervious Area 51,303 78.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment P-5: Proposed Site Runoff Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)9 8 7 6 5 4 3 2 1 0 Type III 24-hr 100 YRS Rainfall=6.50" Runoff Area=65,608 sf Runoff Volume=0.669 af Runoff Depth>5.33" Tc=6.0 min CN=90 8.72 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 67HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach E-CP: Connecticut River Inflow Area = 23.759 ac, 11.13% Impervious, Inflow Depth > 3.00" for 100 YRS event Inflow = 54.46 cfs @ 12.30 hrs, Volume= 5.934 af Outflow = 54.46 cfs @ 12.30 hrs, Volume= 5.934 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)60 55 50 45 40 35 30 25 20 15 10 5 0 Inflow Area=23.759 ac 54.46 cfs54.46 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 68HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES: Existing Swale Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 3.94" for 100 YRS event Inflow = 7.26 cfs @ 12.15 hrs, Volume= 0.524 af Outflow = 7.16 cfs @ 12.16 hrs, Volume= 0.524 af, Atten= 1%, Lag= 0.7 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 3.14 fps, Min. Travel Time= 0.4 min Avg. Velocity = 1.22 fps, Avg. Travel Time= 1.1 min Peak Storage= 183 cf @ 12.16 hrs Average Depth at Peak Storage= 0.51' , Surface Width= 7.09' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)8 7 6 5 4 3 2 1 0 Inflow Area=1.595 ac Avg. Flow Depth=0.51' Max Vel=3.14 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 7.26 cfs7.16 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 69HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach ES.: Existing Swale Inflow Area = 0.483 ac, 0.00% Impervious, Inflow Depth > 3.01" for 100 YRS event Inflow = 1.66 cfs @ 12.10 hrs, Volume= 0.121 af Outflow = 1.61 cfs @ 12.11 hrs, Volume= 0.121 af, Atten= 3%, Lag= 1.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 2.10 fps, Min. Travel Time= 0.6 min Avg. Velocity = 0.71 fps, Avg. Travel Time= 1.8 min Peak Storage= 63 cf @ 12.10 hrs Average Depth at Peak Storage= 0.25' , Surface Width= 4.45' Bank-Full Depth= 1.00' Flow Area= 7.0 sf, Capacity= 32.33 cfs 2.00' x 1.00' deep channel, n= 0.100 Earth, dense brush, high stage Side Slope Z-value= 5.0 '/' Top Width= 12.00' Length= 79.0' Slope= 0.2025 '/' Inlet Invert= 137.00', Outlet Invert= 121.00' ‡ Reach ES.: Existing Swale Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.483 ac Avg. Flow Depth=0.25' Max Vel=2.10 fps n=0.100 L=79.0' S=0.2025 '/' Capacity=32.33 cfs 1.66 cfs1.61 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 70HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Reach P-CP: Connecticut River Inflow Area = 23.389 ac, 18.35% Impervious, Inflow Depth > 2.90" for 100 YRS event Inflow = 52.58 cfs @ 12.22 hrs, Volume= 5.659 af Outflow = 52.58 cfs @ 12.22 hrs, Volume= 5.659 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP: Connecticut River Inflow Outflow Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)55 50 45 40 35 30 25 20 15 10 5 0 Inflow Area=23.389 ac 52.58 cfs52.58 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 71HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond IT: Infiltration Trench Inflow Area = 0.108 ac,100.00% Impervious, Inflow Depth > 6.26" for 100 YRS event Inflow = 0.67 cfs @ 12.09 hrs, Volume= 0.056 af Outflow = 0.03 cfs @ 16.60 hrs, Volume= 0.006 af, Atten= 96%, Lag= 270.8 min Primary = 0.03 cfs @ 16.60 hrs, Volume= 0.006 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 147.50' @ 16.60 hrs Surf.Area= 1,370 sf Storage= 2,192 cf Plug-Flow detention time= 818.2 min calculated for 0.006 af (11% of inflow) Center-of-Mass det. time= 440.4 min ( 1,184.0 - 743.6 ) Volume Invert Avail.Storage Storage Description #1 141.00' 2,192 cf Custom Stage Data (Prismatic) Listed below (Recalc) 5,480 cf Overall x 40.0% Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 1,370 0 0 145.00 1,370 5,480 5,480 Device Routing Invert Outlet Devices #1 Primary 147.50'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.01 cfs @ 16.60 hrs HW=147.50' (Free Discharge) 1=Orifice/Grate (Weir Controls 0.01 cfs @ 0.20 fps) Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 72HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond IT: Infiltration Trench Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=0.108 ac Peak Elev=147.50' Storage=2,192 cf 0.67 cfs 0.03 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 73HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS1: Level Spreader 1 Inflow Area = 0.773 ac, 94.86% Impervious, Inflow Depth > 6.02" for 100 YRS event Inflow = 4.76 cfs @ 12.09 hrs, Volume= 0.388 af Outflow = 4.77 cfs @ 12.09 hrs, Volume= 0.384 af, Atten= 0%, Lag= 0.0 min Primary = 4.77 cfs @ 12.09 hrs, Volume= 0.384 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 147.19' @ 12.09 hrs Surf.Area= 230 sf Storage= 145 cf Plug-Flow detention time= 10.5 min calculated for 0.384 af (99% of inflow) Center-of-Mass det. time= 5.0 min ( 761.1 - 756.1 ) Volume Invert Avail.Storage Storage Description #1 146.00' 145 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 60 0 0 147.00 230 145 145 Device Routing Invert Outlet Devices #1 Primary 147.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=4.64 cfs @ 12.09 hrs HW=147.18' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 4.64 cfs @ 1.15 fps) Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 74HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS1: Level Spreader 1 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Inflow Area=0.773 ac Peak Elev=147.19' Storage=145 cf 4.76 cfs4.77 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 75HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond LLS2: Level Spreader 2 Inflow Area = 1.506 ac, 78.20% Impervious, Inflow Depth > 5.33" for 100 YRS event Inflow = 8.72 cfs @ 12.09 hrs, Volume= 0.669 af Outflow = 8.75 cfs @ 12.09 hrs, Volume= 0.664 af, Atten= 0%, Lag= 0.0 min Primary = 8.75 cfs @ 12.09 hrs, Volume= 0.664 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 145.28' @ 12.09 hrs Surf.Area= 292 sf Storage= 199 cf Plug-Flow detention time= 7.6 min calculated for 0.664 af (99% of inflow) Center-of-Mass det. time= 3.3 min ( 785.1 - 781.7 ) Volume Invert Avail.Storage Storage Description #1 144.00' 199 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 144.00 105 0 0 145.00 292 199 199 Device Routing Invert Outlet Devices #1 Primary 145.00'22.0' long x 1.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=8.52 cfs @ 12.09 hrs HW=145.27' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 8.52 cfs @ 1.41 fps) Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 76HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond LLS2: Level Spreader 2 Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)9 8 7 6 5 4 3 2 1 0 Inflow Area=1.506 ac Peak Elev=145.28' Storage=199 cf 8.72 cfs8.75 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 77HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 4.45" for 100 YRS event Inflow = 8.04 cfs @ 12.09 hrs, Volume= 0.591 af Outflow = 7.68 cfs @ 12.12 hrs, Volume= 0.528 af, Atten= 4%, Lag= 1.6 min Primary = 7.68 cfs @ 12.12 hrs, Volume= 0.528 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 141.89' @ 12.12 hrs Surf.Area= 4,546 sf Storage= 3,761 cf Plug-Flow detention time= 77.1 min calculated for 0.527 af (89% of inflow) Center-of-Mass det. time= 27.6 min ( 832.9 - 805.3 ) Volume Invert Avail.Storage Storage Description #1 141.00' 4,248 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 141.00 3,869 0 0 142.00 4,627 4,248 4,248 Device Routing Invert Outlet Devices #1 Primary 141.65'25.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=7.46 cfs @ 12.12 hrs HW=141.89' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 7.46 cfs @ 1.25 fps) Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 78HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)9 8 7 6 5 4 3 2 1 0 Inflow Area=1.595 ac Peak Elev=141.89' Storage=3,761 cf 8.04 cfs 7.68 cfs Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 79HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Summary for Pond WL: New Low Wetland Area Inflow Area = 1.595 ac, 58.06% Impervious, Inflow Depth > 3.98" for 100 YRS event Inflow = 7.68 cfs @ 12.12 hrs, Volume= 0.528 af Outflow = 7.26 cfs @ 12.15 hrs, Volume= 0.524 af, Atten= 6%, Lag= 2.2 min Primary = 7.26 cfs @ 12.15 hrs, Volume= 0.524 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 137.48' @ 12.15 hrs Surf.Area= 3,128 sf Storage= 1,204 cf Plug-Flow detention time= 8.5 min calculated for 0.523 af (99% of inflow) Center-of-Mass det. time= 3.9 min ( 836.9 - 832.9 ) Volume Invert Avail.Storage Storage Description #1 136.95' 3,241 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 136.95 10 0 0 137.00 1,745 44 44 138.00 4,650 3,198 3,241 Device Routing Invert Outlet Devices #1 Primary 137.05'10.0' long x 2.0' breadth Broad-Crested Rectangular 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32 Primary OutFlow Max=7.23 cfs @ 12.15 hrs HW=137.47' (Free Discharge) 1=Broad-Crested Rectangular Weir (Weir Controls 7.23 cfs @ 1.70 fps) Type III 24-hr 100 YRS Rainfall=6.50"Smith Boathouse - Modified Design 2021.08.25 Printed 10/12/2021Prepared by Berkshire Design Group Page 80HydroCAD® 10.10-5a s/n 11721 © 2020 HydroCAD Software Solutions LLC Pond WL: New Low Wetland Area Inflow Primary Hydrograph Time (hours) 2423222120191817161514131211109876543210Flow (cfs)8 7 6 5 4 3 2 1 0 Inflow Area=1.595 ac Peak Elev=137.48' Storage=1,204 cf 7.68 cfs 7.26 cfs 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts Stormwater Management System The Berkshire Design Group, Inc. Appendix Water Quality Documents INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location:Area P-2: CB & STC 450i B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E)TSS RemovalCalculation WorksheetDeep Sump and Hooded Catch Basin 0.25 1.00 0.25 0.75 Proprietary Treatment Practice 0.75 0.75 0.56 0.19 0.00 0.19 0.00 0.19 0.00 0.19 0.00 0.19 0.00 0.19 0.00 0.19 Total TSS Removal =81% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:60 Damon Road Prepared By:LM *Equals remaining load from previous BMP (E) Date:9/16/2021 which enters the BMP VINSTRUCTIONS:Version 1, Automated: Mar. 4, 20081. In BMP Column, click on Blue Cell to Activate Drop Down Menu2. Select BMP from Drop Down Menu3. After BMP is selected, TSS Removal and other Columns are automatically completed.Location: B C D E FTSS Removal Starting TSS Amount RemainingBMP1Rate1Load* Removed (C*D) Load (D-E)Rain Garden 0.901.00 0.90 0.100.000.10 0.00 0.100.000.10 0.00 0.100.000.10 0.00 0.100.000.10 0.00 0.10Total TSS Removal =90%Separate Form Needs to be Completed for Each Outlet or BMP TrainProject:CT River Greenway/Lane Business ParkPrepared By:BCD*Equals remaining load from previous BMP (E)Date:7/27/2012which enters the BMPTSS Removal Calculation WorksheetArea P-3: Rain Garden w/ PretreatmentNon-automated TSS Calculation Sheetmust be used if Proprietary BMP Proposed1. From MassDEP Stormwater Handbook Vol. 1Mass. Dept. of Environmental Protection INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location:Area P-4: Infiltration Trench B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E)TSS RemovalCalculation WorksheetInfiltration Trench 0.80 1.00 0.80 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 Total TSS Removal =80% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:60 Damon Road Prepared By:LM *Equals remaining load from previous BMP (E) Date:9/16/2021 which enters the BMP INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location:Area P-5: CB & STC 450i B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E)TSS RemovalCalculation WorksheetDeep Sump and Hooded Catch Basin 0.25 1.00 0.25 0.75 Proprietary Treatment Practice 0.73 0.75 0.55 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 Total TSS Removal =80% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:60 Damon Road Prepared By:LM *Equals remaining load from previous BMP (E) Date:9/16/2021 which enters the BMP Project Information & Location Project Name 60 Damon Road Project Number 39195 City Northampton State/ Province Massachusetts Country United States of America Date 8/24/2021 Designer Information EOR Information (optional) Name Liam McCann Name Company Berkshire Design Group Company Phone #978-877-8808 Phone # Email liam@berkshiredesign.com Email Brief Stormceptor Sizing Report - P-2 Site Name P-2 Target TSS Removal (%)80 TSS Removal (%) Provided 81 Recommended Stormceptor Model STC 900 Stormceptor Sizing Summary Stormceptor Model % TSS Removal Provided STC 450i 75 STC 900 81 STC 1200 81 STC 1800 82 STC 2400 84 STC 3600 85 STC 4800 88 STC 6000 88 STC 7200 90 STC 11000 92 STC 13000 93 STC 16000 94 The recommended Stormceptor Model achieves the water quality objectives based on the selected inputs, historical rainfall records and selected particle size distribution. Stormwater Treatment Recommendation The recommended Stormceptor Model(s) which achieve or exceed the user defined water quality objective for each site within the project are listed in the below Sizing Summary table. Stormceptor Brief Sizing Report ±Page 1 of 2 Notes ‡Stormceptor performance estimates are based on simulations using PCSWMM for Stormceptor, which uses the EPA Rainfall and Runoff modules. ‡Design estimates listed are only representative of specific project requirements based on total suspended solids (TSS) removal defined by the selected PSD, and based on stable site conditions only, after construction is completed. ‡For submerged applications or sites specific to spill control, please contact your local Stormceptor representative for further design assistance. Drainage Area Total Area (acres)0.77 Imperviousness %94.9 Water Quality Objective TSS Removal (%)80.0 Runoff Volume Capture (%) Oil Spill Capture Volume (Gal) Peak Conveyed Flow Rate (CFS) Water Quality Flow Rate (CFS) Rainfall Station Name KNIGHTVILLE DAM State/Province Massachusetts Station ID #3985 Years of Records 14 Latitude 42°10'12"N Longitude 72°31'12"W Up Stream Storage Storage (ac-ft)Discharge (cfs) 0.000 0.000 Particle Size Distribution (PSD) The selected PSD defines TSS removal Fine Distribution Particle Diameter (microns) Distribution % Specific Gravity 20.0 20.0 1.30 60.0 20.0 1.80 150.0 20.0 2.20 400.0 20.0 2.65 2000.0 20.0 2.65 Up Stream Flow Diversion Max. Flow to Stormceptor (cfs) Sizing Details For Stormceptor Specifications and Drawings Please Visit: https://www.conteches.com/technical-guides/search?filter=1WBC0O5EYX Stormceptor Brief Sizing Report ±Page 2 of 2 Project Information & Location Project Name 60 Damon Road Project Number 39195 City Northampton State/ Province Massachusetts Country United States of America Date 8/24/2021 Designer Information EOR Information (optional) Name Liam McCann Name Company Berkshire Design Group Company Phone #978-877-8808 Phone # Email liam@berkshiredesign.com Email Brief Stormceptor Sizing Report - Modified P-5 Site Name Modified P-5 Target TSS Removal (%)80 TSS Removal (%) Provided 82 Recommended Stormceptor Model STC 900 Stormceptor Sizing Summary Stormceptor Model % TSS Removal Provided STC 450i 73 STC 900 82 STC 1200 82 STC 1800 82 STC 2400 86 STC 3600 86 STC 4800 89 STC 6000 89 STC 7200 91 STC 11000 94 STC 13000 94 STC 16000 95 The recommended Stormceptor Model achieves the water quality objectives based on the selected inputs, historical rainfall records and selected particle size distribution. Stormwater Treatment Recommendation The recommended Stormceptor Model(s) which achieve or exceed the user defined water quality objective for each site within the project are listed in the below Sizing Summary table. Stormceptor Brief Sizing Report ±Page 1 of 2 Notes ‡Stormceptor performance estimates are based on simulations using PCSWMM for Stormceptor, which uses the EPA Rainfall and Runoff modules. ‡Design estimates listed are only representative of specific project requirements based on total suspended solids (TSS) removal defined by the selected PSD, and based on stable site conditions only, after construction is completed. ‡For submerged applications or sites specific to spill control, please contact your local Stormceptor representative for further design assistance. Drainage Area Total Area (acres)1.51 Imperviousness %78.2 Water Quality Objective TSS Removal (%)80.0 Runoff Volume Capture (%) Oil Spill Capture Volume (Gal) Peak Conveyed Flow Rate (CFS) Water Quality Flow Rate (CFS) Rainfall Station Name KNIGHTVILLE DAM State/Province Massachusetts Station ID #3985 Years of Records 14 Latitude 42°10'12"N Longitude 72°31'12"W Up Stream Storage Storage (ac-ft)Discharge (cfs) 0.000 0.000 Particle Size Distribution (PSD) The selected PSD defines TSS removal Fine Distribution Particle Diameter (microns) Distribution % Specific Gravity 20.0 20.0 1.30 60.0 20.0 1.80 150.0 20.0 2.20 400.0 20.0 2.65 2000.0 20.0 2.65 Up Stream Flow Diversion Max. Flow to Stormceptor (cfs) Sizing Details For Stormceptor Specifications and Drawings Please Visit: https://www.conteches.com/technical-guides/search?filter=1WBC0O5EYX Stormceptor Brief Sizing Report ±Page 2 of 2 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts Stormwater Management System The Berkshire Design Group, Inc. Appendix Operation & Maintenance Plan and Form 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts 1 Proposed Stormwater Management Plan System Operation & Maintenance This Operation & Maintenance Plan is an amendment to an existing Plan for ‘CT River Greenway & Lane Business Park’ dated July 27, 2012, and revised September 18, 2013. The system components, inspection, and maintenance schedule are the same as the original Plan. Ownership and responsibility for operation and maintenance remain the City of Northampton until an agreement is made between the City and the owners of 60 Damon Road. During Construction The Contractor shall be responsible for inspection and maintenance during construction. At all times, siltation fabric fencing, stakes and hay bales sufficient to construct a sedimentation control barrier a minimum of 50 feet long will be stockpiled on the site in order to repair established barriers which may have been damaged or breached. An inspection of all erosion control and stormwater management systems shall be conducted by the Contractor at least once a week and during all rain storms until the completion of construction. In case of any noted breach or failure, the Contractor shall immediately make appropriate repairs to any erosion control system and notify the engineer of any problems involving stormwater management systems. A rain storm shall be defined as all or one of the following: Any storm in which rain is predicted to last for twelve consecutive hours or more. Any storm for which a flash flood watch or warning is issued. Any single storm predicted to have a cumulative rainfall of greater than one-half inch. Any storm not meeting the previous three thresholds but which would mark a third consecutive day of measurable rainfall. The Contractor shall also inspect the erosion control and stormwater management systems at times of significant increase in surface water runoff due to rapid thawing when the risk of failure of erosion control measures is significant. In such instances as remedial action is necessary, the Contractor shall repair any and all significant deficiencies in erosion control systems within two days. The Northampton Department of Public Works shall be notified of any significant failure of stormwater management systems and erosion and sediment control measures and shall be notified of any release of pollutants to a water body (stream, brook, pond, etc.). The Contractor shall remove the sediment from behind the fence of the sedimentation control barrier when the accumulated sediment has reached one-half of the original installed height of the barrier. 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts 2 This project requires a NPDES General Permit for Stormwater Discharges from Constriction Activities. Contractor and Owner are responsible for finalizing a Stormwater Pollution Prevention Plan (SWPPP) and filing for the NDPES permit prior to the start of construction. All clearing, grading, drainage, construction, and development shall be conducted in strict accordance with the SWPPP. Post-Construction Stormwater Management System Owner: City of Northampton 210 Main Street Northampton, MA 01060 Party Responsible for Operation & Maintenance: City of Northampton 210 Main Street Northampton, MA 01060 Inspection & Maintenance Schedule: 1) Street Sweeping Street and parking area sweeping shall take place a minimum of 2 times per year. 2) Rain Garden A rain garden has been incorporated into the stormwater system to remove pollutants within the stormwater runoff. Both the pre-treatment stone diaphragm system and rain garden area should be inspected monthly for sediment build-up, litter and debris, structural damage and standing water. Inspect soil and repair eroded areas within the bioretention system monthly and re-mulch void areas as needed. Treat diseased vegetation as needed. Remove and replace dead vegetation twice per year (spring and fall). Fertilize and prune annually. Remove invasive species as needed to prevent them from spreading into the bioretention area. Replace mulch annually in the early spring. In the winter, it is important to ensure that snow is not plowed into the rain garden as this will cause the runoff to bypass the system without proper treatment. The grassed area between the paving and rain garden should be mown at a minimum of 2x a year and up to 12x a year. 3) Hooded Catch Basin and/or Drain Manhole with Sump Oil and water separators should be inspected at least four times per year and cleaned annually or more often if required. Oil and sediments should be removed and disposed of in accordance with local, state and federal guidelines and 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts 3 regulations. In the case of an oil or bulk pollutant release, the system must be cleaned immediately following the spill and the proper authorities notified. 4) Stormwater Treatment Chambers The Stormwater Treatment Chamber, of which there are 2 StormCeptor (Model # STC450) water quality structures or equal treatment chambers, shall be inspected and maintained according the manufacturer’s specifications. Rinker, the manufacturer of Stormceptor recommends that maintenance be completed on the structures at least once per year, but advises that the units be checked once every three months during the first year to determine the rate of sediment and oil accumulation and to establish an appropriate maintenance schedule. The rate at which the system collects pollutants will depend on site activities. Maintenance or cleaning shall be performed when the stored volume reaches 15% (6 inch sediment depth) of the Stormceptor capacity, when oil (hydrocarbon) has accumulated to 1 inch or greater depth, or immediately in the event of a fuel or oil spill according the manufacturer’s specifications. All material removed from the Stormceptor shall be disposed in accordance with applicable local, state, and federal guidelines and regulations. For more detail of how the StormCeptor should be maintained see the StormCeptor's Owner Manual. 5) Infiltration Trench Infiltration trenches require regular removal of accumulated sediment to maintain an optimal rate of infiltration. The Pretreatment BMP (Deep Sump Hooded Catch Basin) should be routinely inspected and cleaned as described in this document to prevent sediment from entering the infiltration system. Inspect the infiltration trench after the first several rainfall events, after all major storms, and on regularly scheduled dates every six months. After large storms the trench should be inspected for ponding water through the observation well. If ponding is occurring this may indicate that the trench requires rehabilitation. To rehabilitate a trench all accumulated sediment must be stripped from the bottom, the bottom of the trench must be scarified and tilled to induce infiltration, and all of the stone aggregate and filter fabric or media must be removed and replaced. The grass on top of the trench should be mowed seasonally to maintain a level of no higher than 4 inches. The maintenance log (attached) for the project, including inspections, repairs, replacement and disposal shall be maintained for a period of three (3) years and be made available to MassDEP and the Northampton Conservation Commission upon request. INSPECTION AND MAINTANENCE REPORT FORM The Berkshire Design Group, Inc.Page 1/3 INSPECTIO N AND MAINTEN A N CE REPO R T FORM For Stormwater Infrastructure 60 Damon Road – Marijuana Manufacturing Facility Northampton, MA Inspection Schedule: FORM TO BE COMPLETED PER SCHEDULE PRESENTED IN OPERATION & MAINTENANCE PLAN Inspector: Date:Time: Inspector’s Qualifications: Days Since Last Rainfall: Amount of Last Rainfall (inches): Catch Basins CB # or Location Is Surface Runoff Being Directed to Catch Basins Properly Are Sediment Traps Installed at Catch Basin Inlets Are Catch Basin Outlet Hoods Installed and Working Properly Depth of Sediment in Basin Sump Are Any Correction Measures Required Maintenance Required: To Be Performed By:On or Before: INSPECTION AND MAINTANENCE REPORT FORM The Berkshire Design Group, Inc.Page 2/3 Stormwater Treatment Chambers SWTC #Is Stormwater Being Retained and Discharged Properly Depth of Sediment in Sump Are Any Correction Measures Required 1 2 Maintenance Required: To Be Performed By:On or Before: Infiltration Trench Structure Is Structure Working Properly Are Any Correction Measures Required Is the Trench Drawn Down 72 Hours After Storm Infiltration Trench Maintenance Required: To Be Performed By:On or Before: Rain Garden Structure Is Structure Working Properly Depth of Sediment in Structure Debris and Sediment Type and Disposal Location Are Any Correction/Repair Measures Required Rain Garden 1 Stormwater System Maintenance Required: To Be Performed By:On or Before: INSPECTION AND MAINTANENCE REPORT FORM The Berkshire Design Group, Inc.Page 3/3 OTH ER C ONTROLS List Other Miscellaneous Controls and Observations Item Describe Failure/Inadequate Control Describe Recommended Remedy Maintenance Required: To Be Performed By:On or Before: 60 Damon Road – Marijuana Manufacturing Facility October 13, 2021 Northampton, Massachusetts Stormwater Management System The Berkshire Design Group, Inc. Appendix Illicit Discharge Statement