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HomeMy WebLinkAbout0.1 Drainage Report (Rev 7-15-2025)STORMWATER REPORT & MAINTENANCE PLAN FOR PROPOSED GASOLINE FILLING STATION WITH WITH CONVENINCE STORE AND DRIVE-THRU AND A 4-UNIT RESIDENTIAL BUILDING AT 1272, 1276 & 1282 ROUTE 28 SOUTH YARMOUTH, MA 02664 PREPARED FOR: EKATERINA & FAMILY, LLC 1282 ROUTE 28 SOUTH YARMOUTH, MA 02664 savoncc@gmail.com (508) 258-8201 PREPARED BY: CHOUBAH ENGINEERING GROUP, P.C. CONSULTING PROFESSIONAL ENGINEERS 112 STATE ROAD (RTE.6) N. DARMOUTH, MA 02747 CEG # 20-586 April 2, 2025 Revised July 14, 2025 Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 2 TABLE OF CONTENTS Description Page Cover Page 1 Table of Contents 2 Project Description 3-5 Pre-Development Conditions 6 Post-Development Conditions 7-8 Summary 9 Stormwater Management Standards 10-12 Supporting Documents Appendix “A” Existing Watershed Data (2yr -10yr – 100yr Storm Events) Appendix “B” Proposed Watershed Data (2yr -10yr – 100yr Storm Events) Appendix “C” Water Quality Volume & TSS Calculations, Total Phosphorous (TP) & Total Nitrogen (TN) removal rates calculations Appendix “D” Stormwater Check List Appendix “E” Soil Data Appendix “F” Fuel & Stormwater Management Operation & Maintenance Plan Appendix “G” Existing and Proposed Watershed Plans Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 3 PROJECT DESCRIPTION The property comprises three lots, 1272 Route 28 which has a small commercial building and measures 11,936 SF, 1276 Route 28 which has 5 cottages and measures 21,780 SF and 1282 Route 28 which has a gas station and measures 16,117 SF). The area of the combined lots is approximately 49,833 square feet (1.14 acres). All properties are located in the B-2 Business District. It is bound to the north by residential properties, to the south by Route 28 and to the east and west by existing commercial businesses. Currently there are seven buildings on the property, an 820 square-foot steel canopy over two dispensing pumps, an 1,800 square foot convenience store and 5 residential cottages with associated paved parking. Access to the site is via four existing driveways from Route 28. Currently most of the site runoff drains to Route 28 without any treatment (refer to Existing Conditions Plan). The canopy structure as well as some of the cottages are existing non-conforming structures and do not meet the current required front and rear setbacks. Existing canopy is 2 feet from the front property line where 30 feet is required and some cottages are 10 feet from the rear property line where 20 feet is required. In addition, the property does not meet the required 20-foot front and rear landscape setbacks. Most of the front landscape setback is completely covered with impervious surfaces and driveways and there are some undefined landscape within the rear 20- foot landscape buffer. The owner of the properties would like to redevelop the property and demolish all existing buildings on site and construct a gasoline filling station with four fueling dispensers, overhead steel canopy, two double walled fiberglass fuel storage tanks and a 3,890 square-foot building with convenience store and a drive thru and a separate two-story building with 4 residential units (total of 3,755 SF) along the southeast corner of the property. The proposed canopy would be placed 41 feet from the front property line (existing is 2 feet) and proposed building would be 47 feet in compliance with the 20-foot rear setback (existing is 10 Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 4 feet). Site improvements would also include a new stormwater collection system, new septic system, new utilities, landscape, and lighting. The new building design including drainage, utilities and landscape improvements to the site are substantially more attractive and architecturally pleasing than the existing one and would enhance the neighborhood. Presently all runoff generated from impervious and developed areas on site sheet flows untreated in a southerly and northwesterly directions and drains to Route 28 storm drain collection system and to adjacent properties to the north and west. With the proposed site improvements all runoff generated from paved surfaces, landscaped and roof areas will be collected by a closed drainage system, treated, and discharged to an on-site infiltration system designed to accommodate the 100-year storm in compliance with the MASSDEP and the Town of Yarmouth stormwater regulations. Runoff from site to adjacent properties and to Route 28 will be eliminated as a result of the site redevelopment. The project includes provisions that will provide infiltration/groundwater recharge. Stormwater runoff from the project parking areas will be collected by a Precast Concrete Stormceptor Unit and deep sump catch basin then directed to the subsurface infiltration systems designed to completely infiltrate stormwater runoff generated from a 100-year Type III storm event. Stormwater runoff generated from roof surfaces will be collected by a closed pipe conveyance system and also directed to a subsurface infiltration facility designed to completely infiltrate stormwater runoff generated from a 100-year Type III storm event. The subsurface infiltration facility will provide recharge to groundwater, improve water quality, and provide attenuation of peak flows. This design consideration will ensure that the maximum recharge will occur. A new septic system in compliance with MASSDEP Title V would be constructed on site. Access will be improved by reducing curb openings and providing additional landscape buffer within the front landscape setback an increase of approximately 80% over existing conditions. Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 5 An erosion barrier consisting of staked silt sock with a siltation fence will be placed around the entire proposed limits of construction as shown on the site preparation and demolition plan prior to construction. In addition, a tracking gravel pad will be installed prior to construction at the site for dust control. The contractor will be responsible for maintaining the erosion barrier and gravel pad during the entire construction period. Erosion control devices will be removed after construction is completed and all disturbed areas are restored to pre-existing conditions. Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 6 PRE-DEVELOPMENT CONDITIONS (Existing runoff to adjacent properties to the north and west Runoff generated from this Existing Watershed (EW1) including paved parking, roofs, and undeveloped gravel surfaces sheet flows in northerly and westerly directions to adjacent properties without any treatment. (Existing runoff to Route 28: Runoff generated from Existing Watershed (EW2) includes paved parking, roofs, and undeveloped gravel surfaces sheet flows in a southwesterly direction and drains to Route 28 Stormwater Collection System without any treatment. TOTAL EXISTING SUMMARY (EW1 + EW2) Rainfall Event Existing Runoff to Adjacent properties Existing Runoff to Route 28 2-year 0.64 cfs 1.58 cfs 10-year 1.22 cfs 2.31 cfs 100-year 2.54 cfs 3.77 cfs Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 7 POST-DEVELOPMENT CONDITIONS (Proposed runoff to the onsite infiltration systems): With proposed site improvements all runoff generated from the site will be collected by a closed drainage system and treated before discharge to on-site infiltration systems to meet the standards of the Massachusetts Stormwater Management Policy and the Town of Yarmouth for water quality and flood control and does not increase the discharge rate of runoff from existing conditions. Runoff from the landscaped areas along the northerly, easterly and westerly sides of the property is directed to depressed areas along the property lines designed to infiltrate in place into the soils without any treatment similar to the existing conditions. The four proposed watershed areas are described as follows: PW10 is the watershed area of the runoff generated from the building roof areas (convenience store) and paved areas around the building and the paved parking along the northwesterly corner of the property. This runoff is collected by a closed drainage system, treated and discharged to infiltration system #1 sized to accommodate the 100yr storm event as shown on the grading and drainage plans. PW20 is the watershed area of the runoff generated from the fueling area. This runoff is collected by a closed drainage system, treated and discharged to infiltration system #2 sized to accommodate the 100yr storm event as shown on the grading and drainage plans. PW30 is the watershed area of the runoff generated from the canopy roof area and the residential building roof area and its associated parking along the northeasterly corner of the property. This runoff is collected by a closed drainage system, treated and discharged to infiltration system #3 sized to accommodate the 100yr storm event as shown on the grading and drainage plans. PW40 is the watershed area of the runoff generated from the northerly, easterly and westerly sides of the property. With the proposed grading this runoff is directed to depressed swales along Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 8 the property lines designed to infiltrate in place into the soils without any treatment similar to the existing conditions as shown on the grading and drainage plans. TOTAL PROPOSED RUNOFF SUMMARY (PW10)+(PW20)+(PW30)+(PW40) Rainfall Event from PW10 from PW20 from PW30 from PW40 2-year 0 cfs 0 cfs 0 cfs 0 cfs 10-year 0 cfs 0 cfs 0 cfs 0 cfs 100-year 0 cfs 0 cfs 0 cfs 0 cfs As this table indicates no increases in peak stormwater discharges during each of the design rainfall events are anticipated due to the proposed improvements. The proposed site impervious surface including the building roof areas will be collected and directed toward an onsite subsurface infiltration systems sized to accommodate the 100yr storm event. No runoff from the project area will discharge into the adjacent Streets or properties. Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 9 SUMMARY Based on the HydroCAD analysis for the 2, 10 and 100 year storm events, no runoff from the project area will discharge into the adjacent properties or Route 28. The implementation of new water quality BMPs to a site that currently has none, will improve and treat stormwater runoff prior to discharge to the onsite infiltration system. Based on these findings, no adverse drainage impacts to adjacent or downstream properties will be precipitated by the project. Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 10 STORMWATER MANAGEMENT STANDARDS The proposed stormwater management system is designed to meet the standards of the Massachusetts Stormwater Management Policy and the Town of Yarmouth for water quality and flood control and does not increase the discharge rate of runoff from existing conditions. Stormwater runoff rates were calculated utilizing HydroCAD, a computer aided design program that utilizes the NRCS SCS TR-20 method. The rainfalls amounts for each storm event were taken from http://precip.eas.cornell.edu/ and are as follows: 24-Hour Type III Rainfall Amount (inches) 2-YEAR 10-YEAR 100-YEAR 3.2 4.4 6.9 The following is a brief explanation of how the stormwater management standards set forth in the Massachusetts Stormwater Policy Handbook is met by the proposed design. Standard 1: No New Untreated Discharges No untreated stormwater runoff from the proposed parking facility will be discharged off-site. Runoff from the constructed paved areas will be discharged to deep sump catch basins equipped with oil water separators, then to a water quality inlet (Stormceptor) prior to discharge into a subsurface infiltration systems. Standard 2: Post-Development Peak Discharge Rates Attenuation of the post development peak discharge rates to the pre development levels for the 2yr through 100 year 24-hour type III storm events have been met. Refer to Appendix A & B for HydroCAD calculations. Standard 3: Groundwater Recharge (Rev) The project site is located on a plot designated with a NRCS Hydrologic Soils Group (HSG) “A” type soils. The prescribed recharge factor for HSG Type “A” soils is 0.60. The proposed impervious area to be recharged is 23,900 sq.ft., which requires a Rev of 1,992 ft3. The project design incorporates subsurface infiltration basins that will collect runoff from the proposed, impervious surface, building roof area and the fuel pump canopy. The implementation of the Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 11 subsurface infiltration basins will provide treatment to runoff before groundwater recharge to a location that currently has none. Standard 4: Water Quality (WQv) & TSS Removal Stormwater runoff from the proposed project area will be treated prior to discharge through an accepted Best Management Practice (BMP) listed in the Massachusetts Stormwater Policy Handbook. The Best Management Practices (BMPs) include: Sweeping of paved areas, deep sump catch basins equipped with “snout” oil/water separator, subsurface infiltration basins and water quality structures (STORMCEPTOR). The TSS removal rate for this site will be 92.50% exceeding the requirement. Water quality volumes were calculated based on 1” of runoff. Refer to Appendix C for WQv & WQ Flow Calculations & TSS Removal Calculations. Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs) The project is a redevelopment of an existing commercial with paved parking with no stormwater collection or treatment. Runoff generated from the new parking facility will be directed through a treatment train that includes routing through a water quality structure (STORMCEPTOR) prior to connecting into the subsurface infiltration basins. Standard 6: Critical Areas The project site is not located within a Mass DEP Critical Area. Water quality structures (Deep Sump Catch Basin with Oil/Water separator and Stormceptor) will be installed to treat stormwater runoff prior to entering the proposed subsurface infiltration basin. Water quality volumes were calculated based on 1” of runoff. Standard 7: Redevelopments The project is a redevelopment of an existing property. The standards of the Massachusetts Stormwater Policy Handbook have been met. Stormwater Calculations 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 12 Standard 8: Construction Period Pollution Prevention and Erosion and Sediment Control: Erosion and sediment controls have been incorporated into the project design to prevent erosion, control sediments, and stabilize exposed soils during construction and land disturbance. Please refer to attached Site Preparation and Demolition and Erosion Control Plan, Site Details Plan, and General Notes for procedures to be implemented during the construction phase of this project. Standard 9: Operation and Maintenance Plan Please refer to the attached “Fuel & Stormwater System Operation and Maintenance Plan” (Appendix F) Standard 10: Illicit Discharges to Drainage system Illicit discharges to the drainage system from the site are prohibited. The Owner of records of the property would comply with local, state, and federal regulations regarding discharges to stormwater drainage system. The owner is responsible for the inspection and maintenance of the stormwater and infiltration system. Responsible Party Information Jay Imad EKATERINA & FAMILY, LLC 1282 Route 28 Yarmouth, MA 02664 (508) 258-8201 savoncc@gmail.com $33(1',;³$´ (;,67,1*:$7(56+(''$7$ \U±\U±\U±\U±\U67250(9(176 EW1 Existing Runoff to Adjacent Properties EW2 Existing Runoff to Route 28 Routing Diagram for Yarmouth Gas Station, Existing Runoff (EW1-EW2) Prepared by Choubah Enginnering Group, P.C., Printed 4/24/2025 HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 2 Year Storm Rainfall=3.34"Yarmouth Gas Station, Existing Runoff (EW1-EW Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 2HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=24,200 sf 18.93% Impervious Runoff Depth=1.13"Subcatchment EW1: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 Runoff=0.70 cfs 0.052 af Runoff Area=25,633 sf 79.98% Impervious Runoff Depth=2.48"Subcatchment EW2: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 Runoff=1.66 cfs 0.122 af Type III 24-hr 2 Year Storm Rainfall=3.34"Yarmouth Gas Station, Existing Runoff (EW1-EW Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 3HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff = 0.70 cfs @ 12.10 hrs, Volume= 0.052 af, Depth= 1.13" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Year Storm Rainfall=3.34" Area (sf) CN Description 1,504 98 Paved parking, HSG A 3,077 98 Roofs, HSG A 19,619 68 <50% Grass cover, Poor, HSG A 24,200 74 Weighted Average 19,619 81.07% Pervious Area 4,581 18.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0100 1.61 Shallow Concentrated Flow, grass Unpaved Kv= 16.1 fps 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.1 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (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 2 Year Storm Rainfall=3.34" Runoff Area=24,200 sf Runoff Volume=0.052 af Runoff Depth=1.13" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 0.70 cfs Type III 24-hr 2 Year Storm Rainfall=3.34"Yarmouth Gas Station, Existing Runoff (EW1-EW Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 4HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW2: Existing Runoff to Route 28 Runoff = 1.66 cfs @ 12.09 hrs, Volume= 0.122 af, Depth= 2.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Year Storm Rainfall=3.34" Area (sf) CN Description 4,028 98 Roofs, HSG A 16,473 98 Paved parking, HSG A 5,132 68 <50% Grass cover, Poor, HSG A 25,633 92 Weighted Average 5,132 20.02% Pervious Area 20,501 79.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.92 Sheet Flow, grass Smooth surfaces n= 0.011 P2= 3.30" 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.5 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW2: Existing Runoff to Route 28 Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2 Year Storm Rainfall=3.34" Runoff Area=25,633 sf Runoff Volume=0.122 af Runoff Depth=2.48" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 1.66 cfs Type III 24-hr 10 Year Storm Rainfall=4.86"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 5HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=24,200 sf 18.93% Impervious Runoff Depth=2.25"Subcatchment EW1: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 Runoff=1.45 cfs 0.104 af Runoff Area=25,633 sf 79.98% Impervious Runoff Depth=3.95"Subcatchment EW2: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 Runoff=2.58 cfs 0.194 af Type III 24-hr 10 Year Storm Rainfall=4.86"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 6HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff = 1.45 cfs @ 12.09 hrs, Volume= 0.104 af, Depth= 2.25" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Year Storm Rainfall=4.86" Area (sf) CN Description 1,504 98 Paved parking, HSG A 3,077 98 Roofs, HSG A 19,619 68 <50% Grass cover, Poor, HSG A 24,200 74 Weighted Average 19,619 81.07% Pervious Area 4,581 18.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0100 1.61 Shallow Concentrated Flow, grass Unpaved Kv= 16.1 fps 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.1 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10 Year Storm Rainfall=4.86" Runoff Area=24,200 sf Runoff Volume=0.104 af Runoff Depth=2.25" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 1.45 cfs Type III 24-hr 10 Year Storm Rainfall=4.86"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 7HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW2: Existing Runoff to Route 28 Runoff = 2.58 cfs @ 12.09 hrs, Volume= 0.194 af, Depth= 3.95" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Year Storm Rainfall=4.86" Area (sf) CN Description 4,028 98 Roofs, HSG A 16,473 98 Paved parking, HSG A 5,132 68 <50% Grass cover, Poor, HSG A 25,633 92 Weighted Average 5,132 20.02% Pervious Area 20,501 79.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.92 Sheet Flow, grass Smooth surfaces n= 0.011 P2= 3.30" 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.5 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW2: Existing Runoff to Route 28 Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 10 Year Storm Rainfall=4.86" Runoff Area=25,633 sf Runoff Volume=0.194 af Runoff Depth=3.95" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 2.58 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 8HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=24,200 sf 18.93% Impervious Runoff Depth=3.03"Subcatchment EW1: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 Runoff=1.96 cfs 0.140 af Runoff Area=25,633 sf 79.98% Impervious Runoff Depth=4.88"Subcatchment EW2: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 Runoff=3.15 cfs 0.239 af Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 9HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff = 1.96 cfs @ 12.09 hrs, Volume= 0.140 af, Depth= 3.03" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 1,504 98 Paved parking, HSG A 3,077 98 Roofs, HSG A 19,619 68 <50% Grass cover, Poor, HSG A 24,200 74 Weighted Average 19,619 81.07% Pervious Area 4,581 18.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0100 1.61 Shallow Concentrated Flow, grass Unpaved Kv= 16.1 fps 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.1 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=24,200 sf Runoff Volume=0.140 af Runoff Depth=3.03" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 1.96 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 10HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW2: Existing Runoff to Route 28 Runoff = 3.15 cfs @ 12.09 hrs, Volume= 0.239 af, Depth= 4.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 4,028 98 Roofs, HSG A 16,473 98 Paved parking, HSG A 5,132 68 <50% Grass cover, Poor, HSG A 25,633 92 Weighted Average 5,132 20.02% Pervious Area 20,501 79.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.92 Sheet Flow, grass Smooth surfaces n= 0.011 P2= 3.30" 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.5 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW2: Existing Runoff to Route 28 Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=25,633 sf Runoff Volume=0.239 af Runoff Depth=4.88" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 3.15 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 11HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=24,200 sf 18.93% Impervious Runoff Depth=3.64"Subcatchment EW1: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 Runoff=2.36 cfs 0.168 af Runoff Area=25,633 sf 79.98% Impervious Runoff Depth=5.59"Subcatchment EW2: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 Runoff=3.57 cfs 0.274 af Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 12HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff = 2.36 cfs @ 12.09 hrs, Volume= 0.168 af, Depth= 3.64" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 1,504 98 Paved parking, HSG A 3,077 98 Roofs, HSG A 19,619 68 <50% Grass cover, Poor, HSG A 24,200 74 Weighted Average 19,619 81.07% Pervious Area 4,581 18.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0100 1.61 Shallow Concentrated Flow, grass Unpaved Kv= 16.1 fps 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.1 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=24,200 sf Runoff Volume=0.168 af Runoff Depth=3.64" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 2.36 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Gas Station, Existing Runoff (EW1-EW2 Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 13HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW2: Existing Runoff to Route 28 Runoff = 3.57 cfs @ 12.09 hrs, Volume= 0.274 af, Depth= 5.59" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 4,028 98 Roofs, HSG A 16,473 98 Paved parking, HSG A 5,132 68 <50% Grass cover, Poor, HSG A 25,633 92 Weighted Average 5,132 20.02% Pervious Area 20,501 79.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.92 Sheet Flow, grass Smooth surfaces n= 0.011 P2= 3.30" 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.5 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW2: Existing Runoff to Route 28 Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)4 3 2 1 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=25,633 sf Runoff Volume=0.274 af Runoff Depth=5.59" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 3.57 cfs Type III 24-hr 100 Year Storm Rainfall=7.27"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 14HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=24,200 sf 18.93% Impervious Runoff Depth=4.28"Subcatchment EW1: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 Runoff=2.77 cfs 0.198 af Runoff Area=25,633 sf 79.98% Impervious Runoff Depth=6.32"Subcatchment EW2: Existing Runoff to Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 Runoff=4.01 cfs 0.310 af Type III 24-hr 100 Year Storm Rainfall=7.27"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 15HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff = 2.77 cfs @ 12.09 hrs, Volume= 0.198 af, Depth= 4.28" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Year Storm Rainfall=7.27" Area (sf) CN Description 1,504 98 Paved parking, HSG A 3,077 98 Roofs, HSG A 19,619 68 <50% Grass cover, Poor, HSG A 24,200 74 Weighted Average 19,619 81.07% Pervious Area 4,581 18.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0100 1.61 Shallow Concentrated Flow, grass Unpaved Kv= 16.1 fps 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.1 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW1: Existing Runoff to Adjacent Properties Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 100 Year Storm Rainfall=7.27" Runoff Area=24,200 sf Runoff Volume=0.198 af Runoff Depth=4.28" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=74 2.77 cfs Type III 24-hr 100 Year Storm Rainfall=7.27"Yarmouth Gas Station, Existing Runoff (EW1-E Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 16HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment EW2: Existing Runoff to Route 28 Runoff = 4.01 cfs @ 12.08 hrs, Volume= 0.310 af, Depth= 6.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Year Storm Rainfall=7.27" Area (sf) CN Description 4,028 98 Roofs, HSG A 16,473 98 Paved parking, HSG A 5,132 68 <50% Grass cover, Poor, HSG A 25,633 92 Weighted Average 5,132 20.02% Pervious Area 20,501 79.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.92 Sheet Flow, grass Smooth surfaces n= 0.011 P2= 3.30" 1.6 100 0.0100 1.06 Sheet Flow, paved Smooth surfaces n= 0.011 P2= 3.30" 2.5 150 Total, Increased to minimum Tc = 6.0 min Subcatchment EW2: Existing Runoff to Route 28 Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)4 3 2 1 0 Type III 24-hr 100 Year Storm Rainfall=7.27" Runoff Area=25,633 sf Runoff Volume=0.310 af Runoff Depth=6.32" Flow Length=150' Slope=0.0100 '/' Tc=6.0 min CN=92 4.01 cfs $33(1',;³%´ 352326(':$7(56+(''$7$ \U±\U±\U±\U±\U67250(9(176 PW10 Proposed Runoff to Infiltration System DP1 DP1 Routing Diagram for Yarmouth Proposed Runoff (PW10) Prepared by Choubah Enginnering Group, P.C., Printed 7/16/2025 HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 2HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=7,951 sf 91.99% Impervious Runoff Depth=2.58"Subcatchment PW10: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=0.53 cfs 0.039 af Peak Elev=21.05' Storage=0.008 af Inflow=0.53 cfs 0.039 afPond DP1: DP1 Outflow=0.16 cfs 0.039 af Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 3HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW10: Proposed Runoff to Infiltration System Runoff = 0.53 cfs @ 12.09 hrs, Volume= 0.039 af, Depth= 2.58" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Yr Storm Rainfall=3.34" Area (sf) CN Description 1,040 98 Roofs, HSG A 6,274 98 Paved parking, HSG A 637 39 >75% Grass cover, Good, HSG A 7,951 93 Weighted Average 637 8.01% Pervious Area 7,314 91.99% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW10: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)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 2 Yr Storm Rainfall=3.34" Runoff Area=7,951 sf Runoff Volume=0.039 af Runoff Depth=2.58" Flow Length=200' Tc=6.0 min CN=93 0.53 cfs Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 4HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP1: DP1 Inflow Area = 0.183 ac, 91.99% Impervious, Inflow Depth = 2.58" for 2 Yr Storm event Inflow = 0.53 cfs @ 12.09 hrs, Volume= 0.039 af Outflow = 0.16 cfs @ 12.03 hrs, Volume= 0.039 af, Atten= 69%, Lag= 0.0 min Primary = 0.16 cfs @ 12.03 hrs, Volume= 0.039 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 21.05' @ 12.41 hrs Surf.Area= 0.019 ac Storage= 0.008 af Plug-Flow detention time= 11.9 min calculated for 0.039 af (100% of inflow) Center-of-Mass det. time= 11.9 min ( 803.1 - 791.2 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.013 af ADS_StormTech SC-740 +Cap x 12 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 12 Chambers in 3 Rows #2 20.15' 0.019 af 22.00'W x 24.00'L x 3.50'H Prismatoid 0.042 af Overall x 45.0% Voids 0.032 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.16 cfs @ 12.03 hrs HW=20.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 5HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP1: DP1 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)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=0.183 ac Peak Elev=21.05' Storage=0.008 af 0.53 cfs 0.16 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 6HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=7,951 sf 91.99% Impervious Runoff Depth=4.06"Subcatchment PW10: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=0.81 cfs 0.062 af Peak Elev=21.75' Storage=0.016 af Inflow=0.81 cfs 0.062 afPond DP1: DP1 Outflow=0.16 cfs 0.062 af Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 7HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW10: Proposed Runoff to Infiltration System Runoff = 0.81 cfs @ 12.09 hrs, Volume= 0.062 af, Depth= 4.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Yr Storm Rainfall=4.86" Area (sf) CN Description 1,040 98 Roofs, HSG A 6,274 98 Paved parking, HSG A 637 39 >75% Grass cover, Good, HSG A 7,951 93 Weighted Average 637 8.01% Pervious Area 7,314 91.99% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW10: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (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 Yr Storm Rainfall=4.86" Runoff Area=7,951 sf Runoff Volume=0.062 af Runoff Depth=4.06" Flow Length=200' Tc=6.0 min CN=93 0.81 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 8HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP1: DP1 Inflow Area = 0.183 ac, 91.99% Impervious, Inflow Depth = 4.06" for 10 Yr Storm event Inflow = 0.81 cfs @ 12.09 hrs, Volume= 0.062 af Outflow = 0.16 cfs @ 11.91 hrs, Volume= 0.062 af, Atten= 80%, Lag= 0.0 min Primary = 0.16 cfs @ 11.91 hrs, Volume= 0.062 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 21.75' @ 12.51 hrs Surf.Area= 0.018 ac Storage= 0.016 af Plug-Flow detention time= 25.2 min calculated for 0.062 af (100% of inflow) Center-of-Mass det. time= 25.2 min ( 804.3 - 779.1 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.013 af ADS_StormTech SC-740 +Cap x 12 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 12 Chambers in 3 Rows #2 20.15' 0.019 af 22.00'W x 24.00'L x 3.50'H Prismatoid 0.042 af Overall x 45.0% Voids 0.032 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.16 cfs @ 11.91 hrs HW=20.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 9HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP1: DP1 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (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=0.183 ac Peak Elev=21.75' Storage=0.016 af 0.81 cfs 0.16 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 10HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=7,951 sf 91.99% Impervious Runoff Depth=5.00"Subcatchment PW10: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=0.99 cfs 0.076 af Peak Elev=22.28' Storage=0.022 af Inflow=0.99 cfs 0.076 afPond DP1: DP1 Outflow=0.16 cfs 0.076 af Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 11HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW10: Proposed Runoff to Infiltration System Runoff = 0.99 cfs @ 12.08 hrs, Volume= 0.076 af, Depth= 5.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 1,040 98 Roofs, HSG A 6,274 98 Paved parking, HSG A 637 39 >75% Grass cover, Good, HSG A 7,951 93 Weighted Average 637 8.01% Pervious Area 7,314 91.99% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW10: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=7,951 sf Runoff Volume=0.076 af Runoff Depth=5.00" Flow Length=200' Tc=6.0 min CN=93 0.99 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 12HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP1: DP1 Inflow Area = 0.183 ac, 91.99% Impervious, Inflow Depth = 5.00" for 25 Yr Storm event Inflow = 0.99 cfs @ 12.08 hrs, Volume= 0.076 af Outflow = 0.16 cfs @ 11.85 hrs, Volume= 0.076 af, Atten= 84%, Lag= 0.0 min Primary = 0.16 cfs @ 11.85 hrs, Volume= 0.076 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.28' @ 12.55 hrs Surf.Area= 0.017 ac Storage= 0.022 af Plug-Flow detention time= 35.5 min calculated for 0.076 af (100% of inflow) Center-of-Mass det. time= 35.5 min ( 809.4 - 773.9 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.013 af ADS_StormTech SC-740 +Cap x 12 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 12 Chambers in 3 Rows #2 20.15' 0.019 af 22.00'W x 24.00'L x 3.50'H Prismatoid 0.042 af Overall x 45.0% Voids 0.032 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.16 cfs @ 11.85 hrs HW=20.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 13HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP1: DP1 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.183 ac Peak Elev=22.28' Storage=0.022 af 0.99 cfs 0.16 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 14HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=7,951 sf 91.99% Impervious Runoff Depth=5.71"Subcatchment PW10: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=1.12 cfs 0.087 af Peak Elev=22.77' Storage=0.027 af Inflow=1.12 cfs 0.087 afPond DP1: DP1 Outflow=0.16 cfs 0.087 af Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 15HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW10: Proposed Runoff to Infiltration System Runoff = 1.12 cfs @ 12.08 hrs, Volume= 0.087 af, Depth= 5.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 1,040 98 Roofs, HSG A 6,274 98 Paved parking, HSG A 637 39 >75% Grass cover, Good, HSG A 7,951 93 Weighted Average 637 8.01% Pervious Area 7,314 91.99% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW10: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=7,951 sf Runoff Volume=0.087 af Runoff Depth=5.71" Flow Length=200' Tc=6.0 min CN=93 1.12 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 16HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP1: DP1 Inflow Area = 0.183 ac, 91.99% Impervious, Inflow Depth = 5.71" for 50 Yr Storm event Inflow = 1.12 cfs @ 12.08 hrs, Volume= 0.087 af Outflow = 0.16 cfs @ 11.82 hrs, Volume= 0.087 af, Atten= 86%, Lag= 0.0 min Primary = 0.16 cfs @ 11.82 hrs, Volume= 0.087 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.77' @ 12.58 hrs Surf.Area= 0.015 ac Storage= 0.027 af Plug-Flow detention time= 44.8 min calculated for 0.087 af (100% of inflow) Center-of-Mass det. time= 44.7 min ( 815.4 - 770.7 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.013 af ADS_StormTech SC-740 +Cap x 12 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 12 Chambers in 3 Rows #2 20.15' 0.019 af 22.00'W x 24.00'L x 3.50'H Prismatoid 0.042 af Overall x 45.0% Voids 0.032 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.16 cfs @ 11.82 hrs HW=20.69' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 17HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP1: DP1 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.183 ac Peak Elev=22.77' Storage=0.027 af 1.12 cfs 0.16 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 18HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=7,951 sf 91.99% Impervious Runoff Depth=6.44"Subcatchment PW10: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=1.26 cfs 0.098 af Peak Elev=23.57' Storage=0.031 af Inflow=1.26 cfs 0.098 afPond DP1: DP1 Outflow=0.16 cfs 0.098 af Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 19HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW10: Proposed Runoff to Infiltration System Runoff = 1.26 cfs @ 12.08 hrs, Volume= 0.098 af, Depth= 6.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Yr Storm Rainfall=7.27" Area (sf) CN Description 1,040 98 Roofs, HSG A 6,274 98 Paved parking, HSG A 637 39 >75% Grass cover, Good, HSG A 7,951 93 Weighted Average 637 8.01% Pervious Area 7,314 91.99% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW10: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100 Yr Storm Rainfall=7.27" Runoff Area=7,951 sf Runoff Volume=0.098 af Runoff Depth=6.44" Flow Length=200' Tc=6.0 min CN=93 1.26 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 20HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP1: DP1 Inflow Area = 0.183 ac, 91.99% Impervious, Inflow Depth = 6.44" for 100 Yr Storm event Inflow = 1.26 cfs @ 12.08 hrs, Volume= 0.098 af Outflow = 0.16 cfs @ 11.76 hrs, Volume= 0.098 af, Atten= 87%, Lag= 0.0 min Primary = 0.16 cfs @ 11.76 hrs, Volume= 0.098 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 23.57' @ 12.62 hrs Surf.Area= 0.012 ac Storage= 0.031 af Plug-Flow detention time= 54.7 min calculated for 0.098 af (100% of inflow) Center-of-Mass det. time= 54.7 min ( 822.5 - 767.8 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.013 af ADS_StormTech SC-740 +Cap x 12 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 12 Chambers in 3 Rows #2 20.15' 0.019 af 22.00'W x 24.00'L x 3.50'H Prismatoid 0.042 af Overall x 45.0% Voids 0.032 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.16 cfs @ 11.76 hrs HW=20.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW10) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 21HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP1: DP1 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.183 ac Peak Elev=23.57' Storage=0.031 af 1.26 cfs 0.16 cfs PW20 Proposed Runoff to Infiltration System DP2 DP2 Routing Diagram for Yarmouth Proposed Runoff (PW20) Prepared by Choubah Enginnering Group, P.C., Printed 7/16/2025 HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 2HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=16,130 sf 92.24% Impervious Runoff Depth=2.58"Subcatchment PW20: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=1.08 cfs 0.080 af Peak Elev=21.02' Storage=0.016 af Inflow=1.08 cfs 0.080 afPond DP2: DP2 Outflow=0.34 cfs 0.080 af Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 3HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW20: Proposed Runoff to Infiltration System Runoff = 1.08 cfs @ 12.09 hrs, Volume= 0.080 af, Depth= 2.58" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Yr Storm Rainfall=3.34" Area (sf) CN Description 5,300 98 Roofs, HSG A 9,578 98 Paved parking, HSG A 1,252 39 >75% Grass cover, Good, HSG A 16,130 93 Weighted Average 1,252 7.76% Pervious Area 14,878 92.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW20: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2 Yr Storm Rainfall=3.34" Runoff Area=16,130 sf Runoff Volume=0.080 af Runoff Depth=2.58" Flow Length=200' Tc=6.0 min CN=93 1.08 cfs Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 4HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP2: DP2 Inflow Area = 0.370 ac, 92.24% Impervious, Inflow Depth = 2.58" for 2 Yr Storm event Inflow = 1.08 cfs @ 12.09 hrs, Volume= 0.080 af Outflow = 0.34 cfs @ 12.06 hrs, Volume= 0.080 af, Atten= 68%, Lag= 0.0 min Primary = 0.34 cfs @ 12.06 hrs, Volume= 0.080 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 21.02' @ 12.39 hrs Surf.Area= 0.040 ac Storage= 0.016 af Plug-Flow detention time= 11.3 min calculated for 0.080 af (100% of inflow) Center-of-Mass det. time= 11.3 min ( 802.5 - 791.2 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.026 af ADS_StormTech SC-740 +Cap x 25 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 25 Chambers in 5 Rows #2 20.15' 0.040 af 28.00'W x 40.00'L x 3.50'H Prismatoid 0.090 af Overall x 45.0% Voids 0.067 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.34 cfs @ 12.06 hrs HW=20.71' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.34 cfs) Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 5HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP2: DP2 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.370 ac Peak Elev=21.02' Storage=0.016 af 1.08 cfs 0.34 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 6HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=16,130 sf 92.24% Impervious Runoff Depth=4.06"Subcatchment PW20: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=1.65 cfs 0.125 af Peak Elev=21.68' Storage=0.032 af Inflow=1.65 cfs 0.125 afPond DP2: DP2 Outflow=0.34 cfs 0.125 af Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 7HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW20: Proposed Runoff to Infiltration System Runoff = 1.65 cfs @ 12.09 hrs, Volume= 0.125 af, Depth= 4.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Yr Storm Rainfall=4.86" Area (sf) CN Description 5,300 98 Roofs, HSG A 9,578 98 Paved parking, HSG A 1,252 39 >75% Grass cover, Good, HSG A 16,130 93 Weighted Average 1,252 7.76% Pervious Area 14,878 92.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW20: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10 Yr Storm Rainfall=4.86" Runoff Area=16,130 sf Runoff Volume=0.125 af Runoff Depth=4.06" Flow Length=200' Tc=6.0 min CN=93 1.65 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 8HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP2: DP2 Inflow Area = 0.370 ac, 92.24% Impervious, Inflow Depth = 4.06" for 10 Yr Storm event Inflow = 1.65 cfs @ 12.09 hrs, Volume= 0.125 af Outflow = 0.34 cfs @ 11.94 hrs, Volume= 0.125 af, Atten= 79%, Lag= 0.0 min Primary = 0.34 cfs @ 11.94 hrs, Volume= 0.125 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 21.68' @ 12.51 hrs Surf.Area= 0.039 ac Storage= 0.032 af Plug-Flow detention time= 23.6 min calculated for 0.125 af (100% of inflow) Center-of-Mass det. time= 23.6 min ( 802.7 - 779.1 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.026 af ADS_StormTech SC-740 +Cap x 25 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 25 Chambers in 5 Rows #2 20.15' 0.040 af 28.00'W x 40.00'L x 3.50'H Prismatoid 0.090 af Overall x 45.0% Voids 0.067 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.34 cfs @ 11.94 hrs HW=20.68' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.34 cfs) Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 9HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP2: DP2 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.370 ac Peak Elev=21.68' Storage=0.032 af 1.65 cfs 0.34 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 10HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=16,130 sf 92.24% Impervious Runoff Depth=5.00"Subcatchment PW20: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=2.01 cfs 0.154 af Peak Elev=22.16' Storage=0.044 af Inflow=2.01 cfs 0.154 afPond DP2: DP2 Outflow=0.34 cfs 0.154 af Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 11HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW20: Proposed Runoff to Infiltration System Runoff = 2.01 cfs @ 12.08 hrs, Volume= 0.154 af, Depth= 5.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 5,300 98 Roofs, HSG A 9,578 98 Paved parking, HSG A 1,252 39 >75% Grass cover, Good, HSG A 16,130 93 Weighted Average 1,252 7.76% Pervious Area 14,878 92.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW20: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=16,130 sf Runoff Volume=0.154 af Runoff Depth=5.00" Flow Length=200' Tc=6.0 min CN=93 2.01 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 12HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP2: DP2 Inflow Area = 0.370 ac, 92.24% Impervious, Inflow Depth = 5.00" for 25 Yr Storm event Inflow = 2.01 cfs @ 12.08 hrs, Volume= 0.154 af Outflow = 0.34 cfs @ 11.88 hrs, Volume= 0.154 af, Atten= 83%, Lag= 0.0 min Primary = 0.34 cfs @ 11.88 hrs, Volume= 0.154 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.16' @ 12.55 hrs Surf.Area= 0.036 ac Storage= 0.044 af Plug-Flow detention time= 33.1 min calculated for 0.154 af (100% of inflow) Center-of-Mass det. time= 33.1 min ( 807.0 - 773.9 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.026 af ADS_StormTech SC-740 +Cap x 25 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 25 Chambers in 5 Rows #2 20.15' 0.040 af 28.00'W x 40.00'L x 3.50'H Prismatoid 0.090 af Overall x 45.0% Voids 0.067 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.34 cfs @ 11.88 hrs HW=20.69' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.34 cfs) Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 13HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP2: DP2 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.370 ac Peak Elev=22.16' Storage=0.044 af 2.01 cfs 0.34 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 14HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=16,130 sf 92.24% Impervious Runoff Depth=5.71"Subcatchment PW20: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=2.27 cfs 0.176 af Peak Elev=22.60' Storage=0.053 af Inflow=2.27 cfs 0.176 afPond DP2: DP2 Outflow=0.34 cfs 0.176 af Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 15HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW20: Proposed Runoff to Infiltration System Runoff = 2.27 cfs @ 12.08 hrs, Volume= 0.176 af, Depth= 5.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 5,300 98 Roofs, HSG A 9,578 98 Paved parking, HSG A 1,252 39 >75% Grass cover, Good, HSG A 16,130 93 Weighted Average 1,252 7.76% Pervious Area 14,878 92.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW20: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=16,130 sf Runoff Volume=0.176 af Runoff Depth=5.71" Flow Length=200' Tc=6.0 min CN=93 2.27 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 16HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP2: DP2 Inflow Area = 0.370 ac, 92.24% Impervious, Inflow Depth = 5.71" for 50 Yr Storm event Inflow = 2.27 cfs @ 12.08 hrs, Volume= 0.176 af Outflow = 0.34 cfs @ 11.82 hrs, Volume= 0.176 af, Atten= 85%, Lag= 0.0 min Primary = 0.34 cfs @ 11.82 hrs, Volume= 0.176 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.60' @ 12.58 hrs Surf.Area= 0.033 ac Storage= 0.053 af Plug-Flow detention time= 41.5 min calculated for 0.176 af (100% of inflow) Center-of-Mass det. time= 41.4 min ( 812.1 - 770.7 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.026 af ADS_StormTech SC-740 +Cap x 25 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 25 Chambers in 5 Rows #2 20.15' 0.040 af 28.00'W x 40.00'L x 3.50'H Prismatoid 0.090 af Overall x 45.0% Voids 0.067 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.34 cfs @ 11.82 hrs HW=20.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.34 cfs) Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 17HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP2: DP2 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.370 ac Peak Elev=22.60' Storage=0.053 af 2.27 cfs 0.34 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 18HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=16,130 sf 92.24% Impervious Runoff Depth=6.44"Subcatchment PW20: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=93 Runoff=2.55 cfs 0.199 af Peak Elev=23.28' Storage=0.063 af Inflow=2.55 cfs 0.199 afPond DP2: DP2 Outflow=0.34 cfs 0.199 af Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 19HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW20: Proposed Runoff to Infiltration System Runoff = 2.55 cfs @ 12.08 hrs, Volume= 0.199 af, Depth= 6.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Yr Storm Rainfall=7.27" Area (sf) CN Description 5,300 98 Roofs, HSG A 9,578 98 Paved parking, HSG A 1,252 39 >75% Grass cover, Good, HSG A 16,130 93 Weighted Average 1,252 7.76% Pervious Area 14,878 92.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW20: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 100 Yr Storm Rainfall=7.27" Runoff Area=16,130 sf Runoff Volume=0.199 af Runoff Depth=6.44" Flow Length=200' Tc=6.0 min CN=93 2.55 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 20HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP2: DP2 Inflow Area = 0.370 ac, 92.24% Impervious, Inflow Depth = 6.44" for 100 Yr Storm event Inflow = 2.55 cfs @ 12.08 hrs, Volume= 0.199 af Outflow = 0.34 cfs @ 11.79 hrs, Volume= 0.199 af, Atten= 87%, Lag= 0.0 min Primary = 0.34 cfs @ 11.79 hrs, Volume= 0.199 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 23.28' @ 12.61 hrs Surf.Area= 0.026 ac Storage= 0.063 af Plug-Flow detention time= 51.2 min calculated for 0.198 af (100% of inflow) Center-of-Mass det. time= 51.1 min ( 818.9 - 767.8 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.026 af ADS_StormTech SC-740 +Cap x 25 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 25 Chambers in 5 Rows #2 20.15' 0.040 af 28.00'W x 40.00'L x 3.50'H Prismatoid 0.090 af Overall x 45.0% Voids 0.067 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.34 cfs @ 11.79 hrs HW=20.68' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.34 cfs) Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW20) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 21HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP2: DP2 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.370 ac Peak Elev=23.28' Storage=0.063 af 2.55 cfs 0.34 cfs PW30 Proposed Runoff to Infiltration System DP3 DP3 Routing Diagram for Yarmouth Proposed Runoff (PW30) Prepared by Choubah Enginnering Group, P.C., Printed 7/16/2025 HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 2HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=11,658 sf 84.98% Impervious Runoff Depth=2.21"Subcatchment PW30: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=89 Runoff=0.68 cfs 0.049 af Peak Elev=20.94' Storage=0.009 af Inflow=0.68 cfs 0.049 afPond DP3: DP3 Outflow=0.24 cfs 0.049 af Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 3HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW30: Proposed Runoff to Infiltration System Runoff = 0.68 cfs @ 12.09 hrs, Volume= 0.049 af, Depth= 2.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Yr Storm Rainfall=3.34" Area (sf) CN Description 1,932 98 Roofs, HSG A 7,975 98 Paved parking, HSG A 1,751 39 >75% Grass cover, Good, HSG A 11,658 89 Weighted Average 1,751 15.02% Pervious Area 9,907 84.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW30: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (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 2 Yr Storm Rainfall=3.34" Runoff Area=11,658 sf Runoff Volume=0.049 af Runoff Depth=2.21" Flow Length=200' Tc=6.0 min CN=89 0.68 cfs Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 4HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP3: DP3 Inflow Area = 0.268 ac, 84.98% Impervious, Inflow Depth = 2.21" for 2 Yr Storm event Inflow = 0.68 cfs @ 12.09 hrs, Volume= 0.049 af Outflow = 0.24 cfs @ 12.06 hrs, Volume= 0.049 af, Atten= 65%, Lag= 0.0 min Primary = 0.24 cfs @ 12.06 hrs, Volume= 0.049 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 20.94' @ 12.38 hrs Surf.Area= 0.028 ac Storage= 0.009 af Plug-Flow detention time= 9.0 min calculated for 0.049 af (100% of inflow) Center-of-Mass det. time= 9.0 min ( 818.4 - 809.4 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.017 af ADS_StormTech SC-740 +Cap x 16 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 16 Chambers in 4 Rows #2 20.15' 0.026 af 24.00'W x 34.00'L x 3.50'H Prismatoid 0.066 af Overall x 40.0% Voids 0.043 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.24 cfs @ 12.06 hrs HW=20.65' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 5HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP3: DP3 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (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=0.268 ac Peak Elev=20.94' Storage=0.009 af 0.68 cfs 0.24 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 6HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=11,658 sf 84.98% Impervious Runoff Depth=3.64"Subcatchment PW30: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=89 Runoff=1.10 cfs 0.081 af Peak Elev=21.67' Storage=0.021 af Inflow=1.10 cfs 0.081 afPond DP3: DP3 Outflow=0.24 cfs 0.081 af Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 7HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW30: Proposed Runoff to Infiltration System Runoff = 1.10 cfs @ 12.09 hrs, Volume= 0.081 af, Depth= 3.64" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Yr Storm Rainfall=4.86" Area (sf) CN Description 1,932 98 Roofs, HSG A 7,975 98 Paved parking, HSG A 1,751 39 >75% Grass cover, Good, HSG A 11,658 89 Weighted Average 1,751 15.02% Pervious Area 9,907 84.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW30: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10 Yr Storm Rainfall=4.86" Runoff Area=11,658 sf Runoff Volume=0.081 af Runoff Depth=3.64" Flow Length=200' Tc=6.0 min CN=89 1.10 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 8HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP3: DP3 Inflow Area = 0.268 ac, 84.98% Impervious, Inflow Depth = 3.64" for 10 Yr Storm event Inflow = 1.10 cfs @ 12.09 hrs, Volume= 0.081 af Outflow = 0.24 cfs @ 11.94 hrs, Volume= 0.081 af, Atten= 79%, Lag= 0.0 min Primary = 0.24 cfs @ 11.94 hrs, Volume= 0.081 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 21.67' @ 12.50 hrs Surf.Area= 0.027 ac Storage= 0.021 af Plug-Flow detention time= 22.0 min calculated for 0.081 af (100% of inflow) Center-of-Mass det. time= 22.0 min ( 817.4 - 795.4 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.017 af ADS_StormTech SC-740 +Cap x 16 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 16 Chambers in 4 Rows #2 20.15' 0.026 af 24.00'W x 34.00'L x 3.50'H Prismatoid 0.066 af Overall x 40.0% Voids 0.043 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.24 cfs @ 11.94 hrs HW=20.65' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 9HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP3: DP3 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.268 ac Peak Elev=21.67' Storage=0.021 af 1.10 cfs 0.24 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 10HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=11,658 sf 84.98% Impervious Runoff Depth=4.55"Subcatchment PW30: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=89 Runoff=1.37 cfs 0.102 af Peak Elev=22.22' Storage=0.029 af Inflow=1.37 cfs 0.102 afPond DP3: DP3 Outflow=0.24 cfs 0.102 af Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 11HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW30: Proposed Runoff to Infiltration System Runoff = 1.37 cfs @ 12.09 hrs, Volume= 0.102 af, Depth= 4.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 1,932 98 Roofs, HSG A 7,975 98 Paved parking, HSG A 1,751 39 >75% Grass cover, Good, HSG A 11,658 89 Weighted Average 1,751 15.02% Pervious Area 9,907 84.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW30: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=11,658 sf Runoff Volume=0.102 af Runoff Depth=4.55" Flow Length=200' Tc=6.0 min CN=89 1.37 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 12HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP3: DP3 Inflow Area = 0.268 ac, 84.98% Impervious, Inflow Depth = 4.55" for 25 Yr Storm event Inflow = 1.37 cfs @ 12.09 hrs, Volume= 0.102 af Outflow = 0.24 cfs @ 11.88 hrs, Volume= 0.102 af, Atten= 83%, Lag= 0.0 min Primary = 0.24 cfs @ 11.88 hrs, Volume= 0.102 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.22' @ 12.55 hrs Surf.Area= 0.025 ac Storage= 0.029 af Plug-Flow detention time= 32.4 min calculated for 0.102 af (100% of inflow) Center-of-Mass det. time= 32.4 min ( 821.6 - 789.3 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.017 af ADS_StormTech SC-740 +Cap x 16 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 16 Chambers in 4 Rows #2 20.15' 0.026 af 24.00'W x 34.00'L x 3.50'H Prismatoid 0.066 af Overall x 40.0% Voids 0.043 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.24 cfs @ 11.88 hrs HW=20.67' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 13HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP3: DP3 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.268 ac Peak Elev=22.22' Storage=0.029 af 1.37 cfs 0.24 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 14HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=11,658 sf 84.98% Impervious Runoff Depth=5.25"Subcatchment PW30: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=89 Runoff=1.56 cfs 0.117 af Peak Elev=22.74' Storage=0.036 af Inflow=1.56 cfs 0.117 afPond DP3: DP3 Outflow=0.24 cfs 0.117 af Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 15HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW30: Proposed Runoff to Infiltration System Runoff = 1.56 cfs @ 12.09 hrs, Volume= 0.117 af, Depth= 5.25" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 1,932 98 Roofs, HSG A 7,975 98 Paved parking, HSG A 1,751 39 >75% Grass cover, Good, HSG A 11,658 89 Weighted Average 1,751 15.02% Pervious Area 9,907 84.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW30: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=11,658 sf Runoff Volume=0.117 af Runoff Depth=5.25" Flow Length=200' Tc=6.0 min CN=89 1.56 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 16HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP3: DP3 Inflow Area = 0.268 ac, 84.98% Impervious, Inflow Depth = 5.25" for 50 Yr Storm event Inflow = 1.56 cfs @ 12.09 hrs, Volume= 0.117 af Outflow = 0.24 cfs @ 11.85 hrs, Volume= 0.117 af, Atten= 85%, Lag= 0.0 min Primary = 0.24 cfs @ 11.85 hrs, Volume= 0.117 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 22.74' @ 12.58 hrs Surf.Area= 0.023 ac Storage= 0.036 af Plug-Flow detention time= 41.4 min calculated for 0.117 af (100% of inflow) Center-of-Mass det. time= 41.3 min ( 826.8 - 785.4 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.017 af ADS_StormTech SC-740 +Cap x 16 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 16 Chambers in 4 Rows #2 20.15' 0.026 af 24.00'W x 34.00'L x 3.50'H Prismatoid 0.066 af Overall x 40.0% Voids 0.043 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.24 cfs @ 11.85 hrs HW=20.69' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 17HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP3: DP3 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.268 ac Peak Elev=22.74' Storage=0.036 af 1.56 cfs 0.24 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 18HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=11,658 sf 84.98% Impervious Runoff Depth=5.97"Subcatchment PW30: Proposed Runoff to Flow Length=200' Tc=6.0 min CN=89 Runoff=1.77 cfs 0.133 af Peak Elev=23.57' Storage=0.042 af Inflow=1.77 cfs 0.133 afPond DP3: DP3 Outflow=0.24 cfs 0.133 af Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 19HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW30: Proposed Runoff to Infiltration System Runoff = 1.77 cfs @ 12.09 hrs, Volume= 0.133 af, Depth= 5.97" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Yr Storm Rainfall=7.27" Area (sf) CN Description 1,932 98 Roofs, HSG A 7,975 98 Paved parking, HSG A 1,751 39 >75% Grass cover, Good, HSG A 11,658 89 Weighted Average 1,751 15.02% Pervious Area 9,907 84.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.2 100 1.0000 6.68 Sheet Flow, Paved Parking Smooth surfaces n= 0.011 P2= 3.30" 0.3 100 0.0100 6.55 5.15 Pipe Channel, 12" HDPE 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.009 PVC, smooth interior 0.5 200 Total, Increased to minimum Tc = 6.0 min Subcatchment PW30: Proposed Runoff to Infiltration System Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100 Yr Storm Rainfall=7.27" Runoff Area=11,658 sf Runoff Volume=0.133 af Runoff Depth=5.97" Flow Length=200' Tc=6.0 min CN=89 1.77 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 20HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Pond DP3: DP3 Inflow Area = 0.268 ac, 84.98% Impervious, Inflow Depth = 5.97" for 100 Yr Storm event Inflow = 1.77 cfs @ 12.09 hrs, Volume= 0.133 af Outflow = 0.24 cfs @ 11.79 hrs, Volume= 0.133 af, Atten= 87%, Lag= 0.0 min Primary = 0.24 cfs @ 11.79 hrs, Volume= 0.133 af Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Peak Elev= 23.57' @ 12.61 hrs Surf.Area= 0.019 ac Storage= 0.042 af Plug-Flow detention time= 51.2 min calculated for 0.133 af (100% of inflow) Center-of-Mass det. time= 51.2 min ( 833.2 - 782.0 ) Volume Invert Avail.Storage Storage Description #1 20.65' 0.017 af ADS_StormTech SC-740 +Cap x 16 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 16 Chambers in 4 Rows #2 20.15' 0.026 af 24.00'W x 34.00'L x 3.50'H Prismatoid 0.066 af Overall x 40.0% Voids 0.043 af Total Available Storage Device Routing Invert Outlet Devices #1 Primary 20.15'8.270 in/hr Exfiltration over Horizontal area Primary OutFlow Max=0.24 cfs @ 11.79 hrs HW=20.65' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW30) Printed 7/16/2025Prepared by Choubah Enginnering Group, P.C. Page 21HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Pond DP3: DP3 Inflow Primary Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.268 ac Peak Elev=23.57' Storage=0.042 af 1.77 cfs 0.24 cfs PW40 Perimeter Landscape Routing Diagram for Yarmouth Proposed Runoff (PW40) Prepared by Choubah Enginnering Group, P.C., Printed 4/24/2025 HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 2HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=14,094 sf 0.00% Impervious Runoff Depth=0.00"Subcatchment PW40: Perimeter Landscape Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 Runoff=0.00 cfs 0.000 af Type III 24-hr 2 Yr Storm Rainfall=3.34"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 3HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW40: Perimeter Landscape Runoff = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 2 Yr Storm Rainfall=3.34" Area (sf) CN Description 14,094 39 >75% Grass cover, Good, HSG A 14,094 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.5 20 0.0100 0.09 Sheet Flow, Landscape Grass: Short n= 0.150 P2= 3.30" 3.5 20 Total, Increased to minimum Tc = 6.0 min Subcatchment PW40: Perimeter Landscape Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0 0 0 0 0 Type III 24-hr 2 Yr Storm Rainfall=3.34" Runoff Area=14,094 sf Runoff Volume=0.000 af Runoff Depth=0.00" Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 0.00 cfs Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 4HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=14,094 sf 0.00% Impervious Runoff Depth=0.17"Subcatchment PW40: Perimeter Landscape Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 Runoff=0.01 cfs 0.005 af Type III 24-hr 10 Yr Storm Rainfall=4.86"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 5HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW40: Perimeter Landscape Runoff = 0.01 cfs @ 12.51 hrs, Volume= 0.005 af, Depth= 0.17" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 10 Yr Storm Rainfall=4.86" Area (sf) CN Description 14,094 39 >75% Grass cover, Good, HSG A 14,094 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.5 20 0.0100 0.09 Sheet Flow, Landscape Grass: Short n= 0.150 P2= 3.30" 3.5 20 Total, Increased to minimum Tc = 6.0 min Subcatchment PW40: Perimeter Landscape Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)0.009 0.008 0.007 0.007 0.006 0.006 0.005 0.005 0.004 0.004 0.003 0.003 0.002 0.002 0.001 0.001 0.000 0 Type III 24-hr 10 Yr Storm Rainfall=4.86" Runoff Area=14,094 sf Runoff Volume=0.005 af Runoff Depth=0.17" Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 0.01 cfs Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 6HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=14,094 sf 0.00% Impervious Runoff Depth=0.39"Subcatchment PW40: Perimeter Landscape Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 Runoff=0.05 cfs 0.011 af Type III 24-hr 25 Yr Storm Rainfall=5.81"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 7HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW40: Perimeter Landscape Runoff = 0.05 cfs @ 12.36 hrs, Volume= 0.011 af, Depth= 0.39" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 25 Yr Storm Rainfall=5.81" Area (sf) CN Description 14,094 39 >75% Grass cover, Good, HSG A 14,094 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.5 20 0.0100 0.09 Sheet Flow, Landscape Grass: Short n= 0.150 P2= 3.30" 3.5 20 Total, Increased to minimum Tc = 6.0 min Subcatchment PW40: Perimeter Landscape Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)0.052 0.05 0.048 0.046 0.044 0.042 0.04 0.038 0.036 0.034 0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Type III 24-hr 25 Yr Storm Rainfall=5.81" Runoff Area=14,094 sf Runoff Volume=0.011 af Runoff Depth=0.39" Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 0.05 cfs Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 8HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=14,094 sf 0.00% Impervious Runoff Depth=0.61"Subcatchment PW40: Perimeter Landscape Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 Runoff=0.09 cfs 0.016 af Type III 24-hr 50 Yr Storm Rainfall=6.53"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 9HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW40: Perimeter Landscape Runoff = 0.09 cfs @ 12.29 hrs, Volume= 0.016 af, Depth= 0.61" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 50 Yr Storm Rainfall=6.53" Area (sf) CN Description 14,094 39 >75% Grass cover, Good, HSG A 14,094 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.5 20 0.0100 0.09 Sheet Flow, Landscape Grass: Short n= 0.150 P2= 3.30" 3.5 20 Total, Increased to minimum Tc = 6.0 min Subcatchment PW40: Perimeter Landscape Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr 50 Yr Storm Rainfall=6.53" Runoff Area=14,094 sf Runoff Volume=0.016 af Runoff Depth=0.61" Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 0.09 cfs Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 10HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Time span=0.00-30.00 hrs, dt=0.03 hrs, 1001 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=14,094 sf 0.00% Impervious Runoff Depth=0.87"Subcatchment PW40: Perimeter Landscape Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 Runoff=0.17 cfs 0.023 af Type III 24-hr 100 Yr Storm Rainfall=7.27"Yarmouth Proposed Runoff (PW40) Printed 4/24/2025Prepared by Choubah Enginnering Group, P.C. Page 11HydroCAD® 10.00-26 s/n 09957 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment PW40: Perimeter Landscape Runoff = 0.17 cfs @ 12.14 hrs, Volume= 0.023 af, Depth= 0.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.03 hrs Type III 24-hr 100 Yr Storm Rainfall=7.27" Area (sf) CN Description 14,094 39 >75% Grass cover, Good, HSG A 14,094 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.5 20 0.0100 0.09 Sheet Flow, Landscape Grass: Short n= 0.150 P2= 3.30" 3.5 20 Total, Increased to minimum Tc = 6.0 min Subcatchment PW40: Perimeter Landscape Runoff Hydrograph Time (hours) 3029282726252423222120191817161514131211109876543210Flow (cfs)0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 100 Yr Storm Rainfall=7.27" Runoff Area=14,094 sf Runoff Volume=0.023 af Runoff Depth=0.87" Flow Length=20' Slope=0.0100 '/' Tc=6.0 min CN=39 0.17 cfs APPENDIX “C” WATER QUALITY VOLUME & TSS CALCULATIONS, TOTAL PHOSPHOROUS (TP) & TOTAL NITROGEN (TN) REMOVAL RATES CALCULATIONS 1.0" Water Quality Flow Calculations Sheet1 of 1 Project: 1272, 1276 & 1282 Route 28 Location: South Yarmouth,MA Calc By:HC Date: 04/02/2025 Chk.By:HC Date: 04/02/2025 TOTAL SITE Water Quality Flow (CFS) = 0.66 THREE STORMCEPTORS STC-450i WILL BE UTILIZED TO MEET WATER STANDARDS AND PROVIDE PRETREATMENT PRIOR TO ENTERING INFILTRATION BASINS Water quality measures will be achieved thru the use of STORMCEPTOR Hydrodynamic Separators sized in accordance with MassDEP Standard Method to Convert Required Water Quality Volume to a Discharge Rate for Sizing Flow Based Manufactured Proprietary Stormwater Treatment Practices Q 1 = (qu)(A)(WQV) qu = the unit peak discharge, in csm/in. (Determined by using Table in Figure 4) A = impervious surface drainage area (in square miles) WQV = water quality volume in watershed inches (1.0-inches in this case) Tc = (6 minutes) /(60 minutes/hr) = 0.1 hours 1 acre = 0.0015625 mi 2 PW20 Water Quality FlowQ=(qu)(A)(WQV) Tc = (6 minutes) /(60 minutes/hr) = 0.1 Impervious Area (Ac.)= 0.22 Impervious Area (mi2 ) = 0.00035 WQV (in) = 1.0 qu = 774 Q (cfs)= 0.27 PW30 Water Quality FlowQ=(qu)(A)(WQV) Tc = (6 minutes) /(60 minutes/hr) = 0.1 Impervious Area (Ac.)= 0.18 Impervious Area (mi2 ) = 0.00028 WQV (in) = 1.0 qu = 774 Q (cfs)= 0.22 PW10 Water Quality FlowQ=(qu)(A)(WQV) Tc = (6 minutes) /(60 minutes/hr) = 0.1 Impervious Area (Ac.)= 0.14 Impervious Area (mi2 ) = 0.00023 WQV (in) = 1.0 qu = 774 Q (cfs)= 0.18 1.0" Water Quality Volume Calculations Sheet 1 of 1 Proje ct: 1272, 1276 & 1282 Route 28 Location: South Yarmouth, MA Calc. By: HC Date: 04/02/2025 Chk. By: HC Date: 04/02/2025 Water quality measures will be achieved thru the use of Stormceptor Hydrodynamic Separator sized in accordance with MassDEP Standard Method to Convert Required Water Quality Volume to a Discharge Rate for Sizing Flow Based Manufactured Proprietary Stormwater Treatment Practices See attached modified CN and Water Quality Flow Calculations Water Quality Volume (WQV), PW10 Total Contributing Area (ft2) =(Impervious Area 7,314 s.f. ) (WQV) (ft 3 ) = Contributing Impervious Area (ft 2 ) x 1.0"x 1 ft/12 in Impervious Area (ft 2 ) = 7,314 (WQV) (ft 3 ) = 610 Water Quality Volume (WQV), PW20 Total Contributing Area (ft2) =(Impervious Area 15,012 s.f.)   (WQV) (ft3) = Contributing Impervious Area (ft 2 ) x 1.0"x 1 ft/12 in Impervious Area (ft 2 ) = 15,012 (WQV) (ft3) = 1,251 Water Quality Volume (WQV), PW30 Total Contributing Area (ft2) =(Impervious Area 9,914 s.f.)   (WQV) (ft3) = Contributing Impervious Area (ft 2 ) x 1.0"x 1 ft/12 in Impervious Area (ft 2 ) = 9,914 (WQV) (ft 3) = 826 Total Phosphorous and Total Nitrogen Removal Rates Calculations Total Phosphorus Load and Total Nitrogen load reduction target = 100% (same calculations for each) Contributing Impervious Drainage area (IA) in acres Performance Curve for Infiltration rate of 8.27 in/hr. (Figure 3-8) SCM type is infiltration SCM-Volume IA-in for a P target = 100% is 2 in. SCM-Volume is converted to cubic feet using formula: SCM-Volume in cubic feet = IA (ACRES) x SCM-Volume (IA-in.) x 3,630 cubic-feet/acre-in Proposed Watershed (PW10) impervious area = 1,040 sf (roof) + 6,274 sf (pavement) = 7,314 sf/43,560 sf/acre = 0.17 acres SCM-Volume in cubic feet = 0.17 Acre x 2 in. x 3,630 cubic-feet/acre-in = 1,234 cubic feet Required volume for 100% removal = 1,234 cubic feet Provided storage volume by Infiltration System #1 = 0.032 ac-ft x 43,560 = 1,394 cubic feet (larger than 1,234 required) Proposed Watershed (PW20) impervious area = 5,300 sf (roof) + 9,578 sf (pavement) = 14,878 sf/43,560 sf/acre = 0.34 acres SCM-Volume in cubic feet = 0.34 Acre x 2 in. x 3,630 cubic-feet/acre-in = 2,468 cubic feet Required volume for 100% removal = 2,468 cubic feet Provided storage volume by Infiltration System #2 = 0.067 ac-ft x 43,560 = 2,919 cubic feet (larger than 2,468 required) Proposed Watershed (PW20) impervious area = 1,932 sf (roof) + 7,975 sf (pavement) = 9,907 sf/43,560 sf/acre = 0.23 acres SCM-Volume in cubic feet = 0.26 Acre x 2 in. x 3,630 cubic-feet/acre-in = 1,670 cubic feet Required volume for 100% removal = 1,670 cubic feet Provided storage volume by Infiltration System #3 = 0.043 ac-ft x 43,560 = 1,873 cubic feet (almost same as 1,670 required) TSS REMOVAL (* Per DEP Technical Guidance Manual) Project 1272, 1276 & 1282 Route 28 Engineer Choubah Engineering Group, P.C. Location Yarmouth, MA Date 07/15/2025 Contributing to Subsurface Infiltration Systems A B C D E F BMP TSS Removal Rate* Starting TSS Load Amount Removed (BXC) Cumulative Removed (D1 To D2) Amount Remaining (C-D) 1 Deep Sump Catch Basins & Manholes with Oil/Water Separator 25% 100 25.00 25.00 75.00 2 STORMCEPTOR Oil/water separator Structures 50% 75.00 37.50 62.50 37.50 3 Subsurface Infiltration System 80% 37.50 30.00 92.50 7.50 www.rinkerstormceptor.com Phone: (413) 562-3647 Environmentally Engineered Stormwater Solutions... that exceed your client’s needs! Stormwater Treatment Made Simple! Dirty water enters the unit Inlet Vortex draws pollutants into the lower chamber Optimized for hydraulic efficiency, pollutant capture and retention Large pollutant storage volume reduces maintenance frequency Design Flexibility Easy to inspect and maintain Clean water enters the environment Spill protection limits liability Proven Performance TSS & Oil Removal Scour Prevention Small Footprint „„ Stormceptor® is an underground stormwater quality treatment device that is unparalleled in its effectiveness for pollutant capture and retention. With thousands of systems operating worldwide, Stormceptor delivers protection every day in every storm. With patented technology, optimal treatment occurs by allowing free oil to rise and sediment to settle. The Stormceptor design prohibits scour and release of previously captured pollutants, ensuring superior treatment and protection during even the most extreme storm events. Stormceptor is very easy to design and provides flexibility under varying site constraints such as tight right-of-ways, zero lot lines and retrofit projects. Design flexibility allows for a cost-effective approach to stormwater treatment. Stormceptor has proven performance backed by the longest record of lab and field verification in the industry. Tested Performance „Fine particle capture „Prevents scour or release „95%+ Oil removal 1 Depth Below Pipe Inlet Invert to the Bottom of Base Slab, and Maximum Sediment Capacity can vary to accommodate specific site designs and pollutant loads. Depths can vary to accommodate special designs or site conditions. Contact your local representative for assistance. 2 Water Quality Flow Rate (Q) is based on 80% annual average TSS removal of the OK110 particle size distribution. 3 Peak Conveyance Flow Rate is based upon ideal velocity of 3 feet per second and outlet pipe diameters of 18-inch, 36-inch, and 54-inch diameters. 4 Hydrocarbon & Sediment capacities can be modified to accommodate specific site design requirements, contact your local representative for assistance. Massachusetts – Water Quality (Q) Flow Rate www.rinkerstormceptor.com Manufacturing Plant: Westfield, MA Phone: (413) 562-3647 11-22-13-R13-802 MDEPwww.stormceptor.com Stormceptor STC Model Inside Diameter Typical Depth Below Inlet Pipe Invert 1 Water Quality Flow Rate Q 2 Peak Conveyance Flow Rate 3 Hydrocarbon Capacity 4 Maximum Sediment Capacity 4 (ft) (in) (cfs) (cfs) (Gallons) (ft 3) STC 450i 4 68 0.40 5.5 86 46 STC 900 6 63 0.89 22 251 89 STC 2400 8 104 1.58 22 840 205 STC 4800 10 140 2.47 22 909 543 STC 7200 12 148 3.56 22 1,059 839 STC 11000 2 x 10 142 4.94 48 2,792 1,086 STC 16000 2 x 12 148 7.12 48 3,055 1,677 10 StormTech SC-740 Chamber StormTech SC-740 Chamber (not to scale) :849,7ऺ";0.4ȑ.,?4:9> "4E0ऺ஫Cऺ&ऺCऺ஬ 85.4” x 51.0” x 30.0” (2,170 x 1,295 x 762 mm) Chamber Storage 45.9 ft 3 (1.30 m 3) Min. Installed Storage* 74.9 ft 3 (2.12 m 3) Weight 74.0 lbs (33.6 kg) *Assumes 6” (150 mm) stone above, below and between chambers and 40% stone porosity. #30ऺ49>?,770/ऺ.3,8-0=ऺ>D>?08ऺ>3,77ऺ;=:A4/0ऺ?30ऺ7:,/ऺ1,.?:=>ऺ>;0.4ȑ0/ऺ49ऺ?30ऺ,,>3?:ऺ7=1/ऺ-=4/20ऺ/0>429ऺ>;0.4ȑ.,?4:9>ऺ>0.?4:9ऺழவறழவऺ1:=ऺ earth and live loads, with consideration for impact and multiple vehicle presences. 18" (450 mm) MIN* 8' (2.4 m) MAX 51" (1295 mm) 6" (150 mm) MIN 6" (150 mm) MIN 12" (300 mm) TYP 30" (760 mm) DEPTH OF STONE TO BE DETERMINED BY SITE DESIGN ENGINEER 6" (150 mm) MIN 12" (300 mm) MIN SITE DESIGN ENGINEER IS RESPONSIBLE FOR THE ENSURING THE REQUIRED BEARING CAPACITY OF SUBGRADE SOILS PAVEMENT LAYER (DESIGNED BY SITE DESIGN ENGINEER) CHAMBERS SHALL BE BE DESIGNED IN ACCORDANCE WITH ASTM F2787 "STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC CORRUGATED WALL STORMWATER COLLECTION CHAMBERS". GRANULAR WELL-GRADED SOIL/AGGREGATE MIXTURES, <35% FINES, COMPACT IN 6" (150 mm) MAX LIFTS TO 95% PROCTOR DENSITY. SEE THE TABLE OF ACCEPTABLE FILL MATERIALS. ADS GEOSYTHETICS 601T NON-WO GEOTEXTILE ALL AROUND CLEAN, CRUS ANGULAR EMBEDMENT ST CHAMBERS SHALL MEET THE REQUIREMENTS FOR ASTM F2418 POLYPROPLENE (PP) CHAMBERS OR ASTM F2922 POLYETHYLENE (PE) CHAMBERS EMBEDMENT STONE SHALL BE A CLEAN, CRUSHED AND ANGULAR STONE WITH AN AASHTO M43 DESIGNATION BETWEEN #3 AND #57 PERIMETER STO EXCAVATION W (CAN BE SLOPED OR VERTICAL) SC-740 END CAP *MINIMUM COVER TO BOTTOM OF FLEXIBLE PAVEMENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR, INCREASE COVER TO 24" (600 mm). Designed to meet the most stringent industry performance standards for superior structural integrity while providing designers with a cost-effective method to save valuable land and protect water resources. The StormTech >D>?08ऺ4>ऺ/0>4290/ऺ;=48,=47Dऺ?:ऺ-0ऺ@>0/ऺ@9/0=ऺ;,=6492ऺ7:?>யऺ?3@>ऺ8,C484E492ऺ7,9/ऺ@>,20ऺ1:=ऺ;=4A,?0ऺ஫.:880=.4,7஬ऺ and public applications. StormTech chambers can also be used in conjunction with Green Infrastructure, thus enhancing the performance and extending the service life of these practices. Shipping 30 chambers/pallet 60 end caps/pallet 12 pallets/truck 11 Note: Add 1.13 ft3 (0.032 m3) of storage for each additional inch (25 mm) of stone foundation. Depth of Water in System in. (mm) Cumulative Chamber Storage ft3 (m 3) Total System Cumulative Storage ft3 (m 3) 42 (1067) 45.90 (1.300) 74.90 (2.121) 41 (1041) 45.90 (1.300) 73.77 (2.089) 40 (1016) 45.90 (1.300) 72.64 (2.057) 39 (991) 45.90 (1.300) 71.52 (2.025) 38 (965) 45.90 (1.300) 70.39 (1.993) 37 (940) 45.90 (1.300) 69.26 (1.961) 36 (914) 45.90 (1.300) 68.14 (1.929) 35 (889) 45.85 (1.298) 66.98 (1.897) 34 (864) 45.69 (1.294) 65.75 (1.862) 33 (838) 45.41 (1.286) 64.46 (1.825) 32 (813) 44.81 (1.269) 62.97 (1.783) 31 (787) 44.01 (1.246) w61.36 (1.737) 30 (762) 43.06 (1.219) 59.66 (1.689) 29 (737) 41.98 (1.189) 57.89 (1.639) 28 (711) 40.80 (1.155) 56.05 (1.587) 27 (686) 39.54 (1.120) 54.17 (1.534) 26 (660) 38.18 (1.081) 52.23 (1.479) 25 (635) 36.74 (1.040) 50.23 (1.422) 24 (610) 35.22 (0.977) 48.19 (1.365) 23 (584) 33.64 (0.953) 46.11 (1.306) 22 (559) 31.99 (0.906) 44.00 (1.246) 21 (533) 30.29 (0.858) 1.85 (1.185) 20 (508) 28.54 (0.808) 39.67 (1.123) 19 (483) 26.74 (0.757) 37.47 (1.061) 18 (457) 24.89 (0.705) 35.23 (0.997) 17 (432) 23.00 (0.651) 32.96 (0.939) 16 (406) 21.06 (0.596) 30.68 (0.869) 15 (381) 19.09 (0.541) 28.36 (0.803) 14 (356) 17.08 (0.484) 26.03 (0.737) 13 (330) 15.04 (0.426) 23.68 (0.670) 12 (305) 12.97 (0.367) 21.31 (0.608) 11 (279) 10.87 (0.309) 18.92 (0.535) 10 (254) 8.74 (0.247) 16.51 (0.468) 9 (229) 6.58 (0.186) 14.09 (0.399) 8 (203) 4.41 (0.125) 11.66 (0.330) 7 (178) 2.21 (0.063) 9.21 (0.264) 6 (152) 0 (0) 6.76 (0.191) 5 (127) 0 (0) 5.63 (0.160) 4 (102) 0 (0) 4.51 (0.128) 3 (76) 0 (0) 3.38 (0.096) 2 (51) 0 (0) 2.25 (0.064) 1 (25) 0 (0) 1.13 (0.032) Stone Foundation Stone Cover TONS (yds3)Stone Foundation Depth 61216 SC-740 3.8 (2.8) 4.6 (3.3) 5.5 (3.9) KILOGRAMS (m3) 150 mm 300 mm 450 mm SC-740 3,450 (2.1) 4,170 (2.5) 4,490 (3.0) Note: Assumes 6” (150 mm) of stone above and between chambers. Amount of Stone Per Chamber yd3 (m 3)Stone Foundation Depth 6 (150) 12 (300) 18 (450) SC-740 5.5 (4.2) 6.2 (4.7) 6.8 (5.2) Note: Assumes 6” (150 mm) of row separation and 18” (450 mm) of cover. The volume of excavation will vary as depth of cover increases. Volume Excavation Per Chamber ft3 (m 3) Bare Chamber Storage ft3 (m 3) Chamber and Stone Foundation Depth in. (mm) 6 (150) 12 (300) 18 (450) SC-740 45.9 (1.3) 74.9 (2.1) 81.7 (2.3) 88.4 (2.5) Storage Volume Per Chamber Note: Assumes 6” (150 mm) stone above chambers, 6” (150 mm) row spacing and 40% stone porosity. SC-740 Cumulative Storage Volumes per chamber Assumes 40% Stone Porosity. Calculations are Based Upon a 6” (150 mm) Stone Base Under Chambers. APPENDIX “D” Stormwater Checklist swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 1 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. A Stormwater Report must be submitted with the Notice of Intent permit application to document compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for the Stormwater Report (which should provide more substantive and detailed information) but is offered here as a tool to help the applicant organize their Stormwater Management documentation for their Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, the Stormwater Report must contain the engineering computations and supporting information set forth in Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth. The Stormwater Report must include:  The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see page 2) that certifies that the Stormwater Report contains all required submittals.1 This Checklist is to be used as the cover for the completed Stormwater Report.  Applicant/Project Name  Project Address  Name of Firm and Registered Professional Engineer that prepared the Report  Long-Term Pollution Prevention Plan required by Standards 4-6  Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82  Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 2 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report B. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note: Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.) and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer’s Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (if included) and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature Signature and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? New development Redevelopment Mix of New Development and Redevelopment 04/01/2025 X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 3 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) LID Measures: Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project: No disturbance to any Wetland Resource Areas Site Design Practices (e.g. clustered development, reduced frontage setbacks) Reduced Impervious Area (Redevelopment Only) Minimizing disturbance to existing trees and shrubs LID Site Design Credit Requested: Credit 1 Credit 2 Credit 3 Use of “country drainage” versus curb and gutter conveyance and pipe Bioretention Cells (includes Rain Gardens) Constructed Stormwater Wetlands (includes Gravel Wetlands designs) Treebox Filter Water Quality Swale Grass Channel Green Roof Other (describe): Standard 1: No New Untreated Discharges No new untreated discharges Outlets have been designed so there is no erosion or scour to wetlands and waters of the Commonwealth Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included. X X X Infiltration of roof runoff and Stormceptor BMP X X X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 4 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 2: Peak Rate Attenuation Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm. Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm. Standard 3: Recharge Soil Analysis provided. Required Recharge Volume calculation provided. Required Recharge volume reduced through use of the LID site Design Credits. Sizing the infiltration, BMPs is based on the following method: Check the method used. Static Simple Dynamic Dynamic Field1 Runoff from all impervious areas at the site discharging to the infiltration BMP. Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: Site is comprised solely of C and D soils and/or bedrock at the land surface M.G.L. c. 21E sites pursuant to 310 CMR 40.0000 Solid Waste Landfill pursuant to 310 CMR 19.000 Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. Calculations showing that the infiltration BMPs will drain in 72 hours are provided. Property includes a M.G.L. c. 21E site or a solid waste landfill and a mounding analysis is included. 1 80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. X X X X X X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 5 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 3: Recharge (continued) The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas. Standard 4: Water Quality The Long-Term Pollution Prevention Plan typically includes the following: Good housekeeping practices; Provisions for storing materials and waste products inside or under cover; Vehicle washing controls; Requirements for routine inspections and maintenance of stormwater BMPs; Spill prevention and response plans; Provisions for maintenance of lawns, gardens, and other landscaped areas; Requirements for storage and use of fertilizers, herbicides, and pesticides; Pet waste management provisions; Provisions for operation and management of septic systems; Provisions for solid waste management; Snow disposal and plowing plans relative to Wetland Resource Areas; Winter Road Salt and/or Sand Use and Storage restrictions; Street sweeping schedules; Provisions for prevention of illicit discharges to the stormwater management system; Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL; Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan; List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge: is within the Zone II or Interim Wellhead Protection Area is near or to other critical areas is within soils with a rapid infiltration rate (greater than 2.4 inches per hour) involves runoff from land uses with higher potential pollutant loads. The Required Water Quality Volume is reduced through use of the LID site Design Credits. Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided. X X X X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 6 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) The BMP is sized (and calculations provided) based on: The ½” or 1” Water Quality Volume or The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume. The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary BMP and proposed TSS removal rate is provided. This documentation may be in the form of the propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying performance of the proprietary BMPs. A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing that the BMPs selected are consistent with the TMDL is provided. Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution Prevention Plan (SWPPP) has been included with the Stormwater Report. The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior to the discharge of stormwater to the post-construction stormwater BMPs. The NPDES Multi-Sector General Permit does not cover the land use. LUHPPLs are located at the site and industry specific source control and pollution prevention measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow melt and runoff, and been included in the long term Pollution Prevention Plan. All exposure has been eliminated. All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list. The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil grit separator, a filtering bioretention area, a sand filter or equivalent. Standard 6: Critical Areas The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP has approved for stormwater discharges to or near that particular class of critical area. Critical areas and BMPs are identified in the Stormwater Report. X X X X X X X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 7 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum extent practicable The project is subject to the Stormwater Management Standards only to the maximum Extent Practicable as a: Limited Project Small Residential Projects: 5-9 single family houses or 5-9 units in a multi-family development provided there is no discharge that may potentially affect a critical area. Small Residential Projects: 2-4 single family houses or 2-4 units in a multi-family development with a discharge to a critical area Marina and/or boatyard provided the hull painting, service and maintenance areas are protected from exposure to rain, snow, snow melt and runoff Bike Path and/or Foot Path Redevelopment Project Redevelopment portion of mix of new and redevelopment. Certain standards are not fully met (Standard No. 1, 8, 9, and 10 must always be fully met) and an explanation of why these standards are not met is contained in the Stormwater Report. The project involves redevelopment and a description of all measures that have been taken to improve existing conditions is provided in the Stormwater Report. The redevelopment checklist found in Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document that the proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatment and structural BMP requirements of Standards 4-6 to the maximum extent practicable and (b) improves existing conditions. Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan must include the following information: Narrative; Construction Period Operation and Maintenance Plan; Names of Persons or Entity Responsible for Plan Compliance; Construction Period Pollution Prevention Measures; Erosion and Sedimentation Control Plan Drawings; Detail drawings and specifications for erosion control BMPs, including sizing calculations; Vegetation Planning; Site Development Plan; Construction Sequencing Plan; Sequencing of Erosion and Sedimentation Controls; Operation and Maintenance of Erosion and Sedimentation Controls; Inspection Schedule; Maintenance Schedule; Inspection and Maintenance Log Form. A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan containing the information set forth above has been included in the Stormwater Report. X X swcheck.doc • 04/01/08 Stormwater Report Checklist • Page 8 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control (continued) The project is highly complex and information is included in the Stormwater Report that explains why it is not possible to submit the Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and Erosion and Sedimentation Control has not been included in the Stormwater Report but will be submitted before land disturbance begins. The project is not covered by a NPDES Construction General Permit. The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the Stormwater Report. The project is covered by a NPDES Construction General Permit but no SWPPP been submitted. The SWPPP will be submitted BEFORE land disturbance begins. Standard 9: Operation and Maintenance Plan The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and includes the following information: Name of the stormwater management system owners; Party responsible for operation and maintenance; Schedule for implementation of routine and non-routine maintenance tasks; Plan showing the location of all stormwater BMPs maintenance access areas; Description and delineation of public safety features; Estimated operation and maintenance budget; and Operation and Maintenance Log Form. The responsible party is not the owner of the parcel where the BMP is located and the Stormwater Report includes the following submissions: A copy of the legal instrument (deed, homeowner’s association, utility trust or other legal entity) that establishes the terms of and legal responsibility for the operation and maintenance of the project site stormwater BMPs; A plan and easement deed that allows site access for the legal entity to operate and maintain BMP functions. Standard 10: Prohibition of Illicit Discharges The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges; An Illicit Discharge Compliance Statement is attached; NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of any stormwater to post-construction BMPs. X X X X X X X X APPENDIX “E” Soil Data APPENDIX “F” Fuel & Stormwater Management Operation & Maintenance Plan 1 FUEL & STORMWATER MANAGEMENT OPERATION & MAINTENANCE PLAN FOR PROPOSED GASOLINE FILLING STATION WTH CONVENIENCE STORE AND DRIVE-THRU AND A 4-UNIT RESIDENTIAL BUILDING AT 1272, 1276 & 1282 ROUTE 28 SOUTH YARMOUTH, MA 02664 PREPARED FOR: EKATERINA & FAMILY, LLC 1282 ROUTE 28 SOUTH YARMOUTH, MA 02664 savoncc@gmail.com (508) 258-8201 PREPARED BY: CHOUBAH ENGINEERING GROUP, P.C. CONSULTING PROFESSIONAL ENGINEERS 112 STATE ROAD (RTE.6) N. DARMOUTH, MA 02747 CEG # 20-586 April 2, 2025 Revised July 14, 2025 2 Fuel & Stormwater Management Operation & Maintenance Plan For 1272, 1276 & 1282 Route 28 South Yarmouth, MA 02664 Introduction The following Operations and maintenance plan has been prepared for the proposed gasoline filling station, and residential building at 1272, 1276 & 1282 Route 28 in Yarmouth Massachusetts. The purpose of this plan is to provide guidance and procedures for proper stormwater management for the project during and post construction. During construction, an erosion barrier consisting of staked silt sock with a siltation fence will be placed along the proposed limits of construction as shown on the site plan prior to construction. Gravel tracking pads will be placed at the entrance driveways in compliance with the Town of Yarmouth erosion control ordinance. The contractor will be responsible for maintaining the erosion barriers and pads during the entire construction period. Erosion control devices will be removed after construction is completed and all disturbed areas are restored and accepted. Routine Site Maintenance Parking lot maintenance in the form of sweeping with high efficiency vacuum sweeper shall be conducted on a monthly average with sweeping scheduled primarily in spring and fall. Sweeping provides important non-point source pollution control. When practical and as weather permits, accumulated sediments should be swept and removed on an as needed basis during the month of January through March. Preventive Measures Spill Prevention and Response Plan The tenant/operator of the facility shall train all maintenance personnel and truck drivers in the proper handling and cleanup of spilled Hazardous Substances or Oil. No spilled Hazardous Substances or Oil shall be allowed to come in contact with stormwater discharges. In case of any spill the emergency shut-off valve at the stormwater discharge pipe located in the parking lot should be closed to prevent any spill of hazardous materials reaching the on-site infiltration 3 system. All personnel should be trained to easily locate and shut off the 12” emergency shut-off valve. If such contact occurs, the stormwater discharge shall be contained on site until appropriate measures in compliance with state and federal regulations are taken to dispose such contaminated stormwater. It shall be the responsibilities of the tenant/operator to train all personnel in spill prevention and cleanup procedures. In order to prevent or minimize the potential for a spill of Hazardous Substances or Oil to come into contact with stormwater, the following steps shall be implemented: 12” emergency shut-off valve should be turned off to closed position. A spill control and containment kit (containing for example, absorbent materials, acid neutralizing powder, brooms, dust pans, mops, rags, gloves, goggles and eye wear protection, plastic, and metal trash containers, etc.) shall be readily available. Any spill of fuel on site shall be reported by the Operator of the facility to the Massachusetts Department of Environmental protection MASSDEP and local fire department in compliance with all applicable local and state fire and environmental regulations. Manufacture’s recommendations for spill cleanup shall be known and maintenance personnel shall be trained regarding these procedures and the location of the information and cleanup supplies. It is the responsibility of the tenant/operator to ensure that all hazardous waste discovered or generated at the site are disposed of by a licensed hazardous materials disposal company. In the event of a spill of hazardous substances the responsible parties shall take all necessary measures to contain and abate the spill and to prevent the discharge of the hazardous substance or oil to stormwater system or off-site. Any spill that occurs shall be documented on a spill report form that is enclosed in this document. There should be no washing of vehicles on site. There should be no storage or disposal of toxic materials on site. There should be no discharges of non-stormwater to the stormwater system. Snow Storage: Snow is being stored on site within paved surfaces to prevent the transfer of oil and petroleum base products to the ground via infiltration. With the proposed site grading snow melt from snow storage area is collected by two catch basins equipped with deep sumps and then 4 directed to a proprietary stormwater BMP structure for pre-treatment of runoff prior to discharge to on–site infiltration system. The stormwater system is designed to achieve 92.5% TSS (Total Suspended Solids) removal rates in compliance with the Massachusetts Department of Environmental Protection Guidelines. Stormwater: runoff collected from fueling pad and paved surfaces on site will be conveyed to two catch basins equipped with deep sumps and directed to a BMP structure equipped with an oil/water separator for pre-treatment. Fueling Area: fueling pads are designed to control spills and to treat collected stormwater and/or wastewater to required levels. The concrete containment pad around the fueling island is sloped toward catch basins with deep sumps and is directed to a BMP structure with an oil/water separator. The fueling pad will be constructed using impervious concrete materials to prevent the transfer of oil or petroleum base products to the ground via infiltration. The transfer of fuel from the delivery tank trucks to the fuel storage tank will be conducted in impervious contained and ensured areas so that appropriate overflow protection is used. BMPs for Auto Fueling Facilities (Gas stations) Description of Pollutant Sources: A fueling station is a facility dedicated to the transfer of fuels from a stationary pumping station to mobile vehicles or equipment. It includes above- or under- ground fuel storage facilities. In addition to general service gas stations, fueling may also occur at 24-hour convenience stores, construction sites, warehouses, car washes, manufacturing establishments, port facilities, and businesses with fleet vehicles. Typically, stormwater contamination at fueling stations is caused by leaks/spills of fuels, lube oils, radiator coolants, and vehicle washwater. Pollutant Control Approach: Construct new or substantially remodeled fueling stations on an impervious concrete pad under a roof to keep out rainfall and stormwater run-on. Use a treatment BMP such as an oil grit separator, sand filter or equivalent for contaminated stormwater and wastewaters in the fueling containment area. 5 Applicable Operational BMPs:  Prepare an emergency spill response and cleanup plan and have designated trained person(s) available either on-site or on call at all times to promptly and properly implement that plan and immediately cleanup all spills. Keep suitable cleanup materials, such as dry adsorbent materials, on-site to allow prompt cleanup of a spill.  Train employees on the proper use of fuel dispensers. Post “No Topping Off” signs (topping off gas tanks causes spillage and vents gas fumes to the air). Make sure that the automatic shutoff on the fuel nozzle is functioning properly.  The person conducting the fuel transfer must be present at the fueling pump during fuel transfer, particularly at unattended or self-serve stations.  Keep drained oil filters in a suitable container or drum. Drums should be closed on an impervious pad with adequate containment.  For more information about when you need to report a spill to MassDEP and how quickly you need to report it (in many instances a spill must be reported within 2 hours), go to this MassDEP web page: http://mass.gov/dep/cleanup/dealin01.htm Maintenance of Fences and landscape As part of the parking lot maintenance the owner of the facility shall conduct at least a yearly inspection at the end of each winter and plowing season to ensure all existing fences and landscape are in good working conditions. The owner shall replace broken fences and dead trees or shrubs as needed to maintain a functional buffer from the adjacent properties. Maintenance of Stromwater management Devices Catch Basins/Drainage Manholes All Structures will be inspected four times per year. Structures will be cleaned twice a year or whenever the depth of deposits is greater than or equal to one half the depth from the bottom of the invert of the lowest pipe in the basin and at the end of the foliage and snow removal seasons. All Structures will be cleaned using a vacuum truck to remove trapped sediment and water/oil from the deep sumps. Material or fluid removed during cleanings will be disposed in accordance with all federal, state, and local regulations. 6 STORMCEPTOR STORMCEPTOR shall be inspected in accordance with the manufacturer requirements and after major storm events. Structures will be cleaned twice a year by removing oil, grease, and sediments. Material or fluid removed during cleanings shall be disposed of in accordance with all federal, state, and local regulations. STORMCEPTOR Maintenance A proprietary separator, (“STORMCEPTOR”) will be inspected in accordance with the manufacturer requirements, but no less than twice a year following installation, and no less than once a year thereafter.  Units should be inspected post construction, prior to being put into service.  Inspect every six months for the first year to determine the oil and sediment accumulation rate.  In subsequent years, inspections can be based on first-year observations or local requirements.  Cleaning is required once the sediment depth reaches 15% of storage capacity, (generally taking one year or longer). Local regulations for maintenance frequency may vary.  Inspect the unit immediately after an oil, fuel, or chemical spill.  A licensed waste management company should remove oil and sediment and dispose responsibly. Sediment and other trapped pollutants will be removed and the structures will be cleaned at the frequency specified by the manufacturer. Cleaning of the units will be conducted using the method specified by the manufacturer. Underground Infiltration System Maintenance Infiltration systems will be aggressively maintained on a regular schedule. Units will be inspected every six months. For the first year of installation infiltration units shall be checked and inspected after every major storm event (2 year return frequency). Inlet pipes will be checked monthly to determine if they are clogged and accumulated sediment, trash, debris, leaves, and vegetation will be removed. If infiltration system fails to fully dewater within 72 7 hours of a storm event, then the responsible party (facility Owner/Operator) shall retain a qualified professional engineer to assess the cause of failure of the system and develop recommendations for corrective action. Corrective action must be implemented immediately to restore system function. Restrictions on the application of fertilizers, including: Fertilizer shall not be applied during or immediately prior to heavy rainfall, such as but not limited to thunderstorms, hurricanes, or northeastern storms, or when the soil is saturated due to intense or extended rainfall; Fertilizer shall not be applied between November 12 and the following March 31; Fertilizer shall not be applied, spilled, or deposited on impervious surfaces or in a manner that allows it to enter into storm drains; Fertilizer shall not be applied within 100 feet of any surface water or within the Zone I of a public drinking water well; Fertilizer containing phosphorus shall not be applied unless a soil test taken not more than three years before the proposed fertilizer application indicates that additional phosphorus is needed for growth of that turf, or unless establishing new turf or reestablishing or repairing turf after substantial damage or land disturbance; A single application of fertilizer that contains nitrogen shall not exceed 1.0 pound of nitrogen per 1,000 square feet, shall consist of at least 20% slow-release nitrogen (SRN) fertilizer (NOTE: This represents the minimum percentage: use of higher SRN content is generally preferable, especially on sandy root zones, during stress and pre-stress periods, and when there are fewer annual applications of nitrogen made to a lawn) and the annual rate shall not exceed 3.2 pounds of actual nitrogen per thousand square feet. Single applications shall be done at intervals of no less than four weeks until the annual maximum is reached; Grass clippings, leaves, or any other vegetative debris shall not be deposited into or within 50 feet of water bodies, retention and detention areas, drainage ditches or stormwater drains, or onto impervious surfaces, such as, but not limited to, roadways and sidewalks, except during scheduled clean-up programs; and On Site Maintenance An updated Inspection and Maintenance Log listing individual BMP’s, including the sweeping program, the inspection and maintenance requirements and the dates performed should be kept on site for a minimum of 3 years, on an ongoing basis. 8 BMP’S Maintenance Log Date Inspector Ownership and Responsibility The proposed gasoline filling station is under the ownership of EKATERINA & FAMILY, LLC who will be responsible for complying with all Environmental Permits. During construction of the facility and the stormwater management system the Contractor will be responsible for all day to day operation and maintenance of all stormwater control systems. After construction is completed, of EKATERINA & FAMILY, LLC will take over all maintenance requirements for the stormwater control system in compliance with this Operation & Maintenance Plan. Responsible Party Contact Information Jay Imad EKATERINA & FAMILY, LLC 1282 Route 28 Yarmouth, MA 02664 (508) 258-8201 savoncc@gmail.com Preliminary Stormwater O&M Maintenance Budget Inspection and Maintenance = $500.00 x 4 times per year = $2,000.00 APPENDIX “G” Existing & Proposed Watershed Plans KRONREYBURN REYBURN ALIBRIOEWS-1AREA=0.56 ACAVG. CN=74Tc=6.0 min.EWS-2AREA=0.59 ACAVG. CN=92Tc=6.0 min.R O U T E 28 S T A T E H I G H W A YSheet Number: 1 OF 2Sheet Title:Project Number: 20-586Drawn By: CMSDesigned By: CMSScale: AS SHOWNChecked By: HCRevisions112 STATE ROAD (ROUTE 6), No. DARTMOUTH, MA 02747TEL:(508) 858-5040 FAX:(508) 858-5041www.choubahgroup.comConsulting Professional EngineersChoubah Engineering Group, p.c.Issue Date: 04/02/2025DateNo.DescriptionPROJECT:PROPOSED GASOLINE FILLINGSTATION WITH ASSOCIATEDCONVENIENCE STORE & DRIVETHRU AND A 4 UNITRESIDENTIAL BUILDING AT1272, 1276 & 1282 ROUTE 28SOUTH YARMOUTH, MAPREPARED FOR:EKATERINA & FAMILY,LLC1282 ROUTE 28SOUTH YARMOUTH, MA07/15/20251Addressed Peer Review CommentsEXISTING WATERSHEDPLAN01"=20' SCALE IN FEET80402010LOCUS MAPNOT TO SCALEN REYBURN REYBURN ALIBRIOLOADING ZONER O U T E 28 S T A T E H I G H W A YPW-40AREA=0.32 ACAVG. CN=39Tc=6.0 min.PW-10AREA=0.18 ACAVG. CN=93Tc=6.0 min.PW-30AREA=0.28 ACAVG. CN=89Tc=6.0 min.PW-20AREA=0.37 ACAVG. CN=93Tc=6.0 min.Sheet Number: 2 OF 2Sheet Title:Project Number: 20-586Drawn By: CMSDesigned By: CMSScale: AS SHOWNChecked By: HCRevisions112 STATE ROAD (ROUTE 6), No. DARTMOUTH, MA 02747TEL:(508) 858-5040 FAX:(508) 858-5041www.choubahgroup.comConsulting Professional EngineersChoubah Engineering Group, p.c.Issue Date: 04/02/2025DateNo.DescriptionPROJECT:PROPOSED GASOLINE FILLINGSTATION WITH ASSOCIATEDCONVENIENCE STORE & DRIVETHRU AND A 4 UNITRESIDENTIAL BUILDING AT1272, 1276 & 1282 ROUTE 28SOUTH YARMOUTH, MAPREPARED FOR:EKATERINA & FAMILY,LLC1282 ROUTE 28SOUTH YARMOUTH, MA07/15/20251Addressed Peer Review CommentsPROPOSED WATERSHEDPLAN01"=20' SCALE IN FEETLOCUS MAPNOT TO SCALEN10204080