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HomeMy WebLinkAbout4850 Great Island Plaza Stormwater Report 349 Main Street West Yarmouth, MA 02673 The picture can't be displayed. STORMWATER REPORT GREAT ISLAND PLAZA LLC MAIN STREET (ROUTE 28) & WINSLOW GRAY ROAD WEST YARMOUTH, MA 02673 JULY 2020 Owner/Applicant: GREAT ISLAND PLAZA LLC c/o Tatra Building Company, Inc. 1268 Route 28 South Yarmouth, MA 02664 BSC Job Number: 50350.01 Stormwater Report Great Island Plaza LLC West Yarmouth, MA TABLE OF CONTENTS 1.0 PROJECT INFORMATION 1.01 PROJECT DESCRIPTION 1.02 PRE-DEVELOPMENT CONDITIONS 1.03 POST-DEVELOPMENT CONDITIONS 2.0 DRAINAGE SUMMARY 2.01 STORMWATER STANDARD 1 – NEW STORMWATER CONVEYANCES 2.02 STORMWATER STANDARD 2 – STORMWATER RUNOFF RATES 2.03 STORMWATER STANDARD 3 – GROUNDWATER RECHARGE 2.04 STORMWATER STANDARD 4 – TSS REMOVAL 2.05 STORMWATER STANDARD 5 – LUHPPL 2.06 STORMWATER STANDARD 6 – CRITICAL AREAS 2.07 STORMWATER STANDARD 7 – REDEVELOPMENT PROJECTS 2.08 STORMWATER STANDARD 8 – SEDIMENTATION & EROSION CONTROL PLAN 2.09 STORMWATER STANDARD 9 – LONG TERM O&M PLAN 2.10 STORMWATER STANDARD 10 – ILLICIT DISCHARGES 2.11 CONCLUSIONS 3.0 MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION CHECKLIST FOR STORMWATER REPORT 4.0 CONSTRUCTION PERIOD POLLUTION PREVENTION AND EROSION AND SEDIMENTATION CONTROL 5.0 LONG-TERM POLLUTION PREVENTION & OPERATION AND MAINTENANCE PLAN 6.0 HYDROLOGY CALCULATIONS 6.01 EXISTING WATERSHED PLAN 6.02 EXISTING HYDROLOGY CALCULATIONS (HYDROCAD™ PRINTOUTS) 6.03 PROPOSED WATERSHED PLAN 6.04 PROPOSED HYDROLOGY CALCULATIONS (HYDROCAD™ PRINTOUTS) 7.0 ADDITIONAL DRAINAGE CALCULATIONS 7.01 TSS REMOVAL CALCULATIONS 7.02 GROUNDWATER RECHARGE VOLUME CALCULATIONS 7.03 WATER QUALITY VOLUME CALCULATIONS APPENDICES APPENDIX A – USGS LOCUS MAP APPENDIX B – FEMA MAP APPENDIX C – WEB SOIL SURVEY APPENDIX D – SOIL TEST PIT LOGS Stormwater Report Great Island Plaza LLC West Yarmouth, MA SECTION 1.0 PROJECT INFORMATION Stormwater Report Great Island Plaza LLC West Yarmouth, MA 1.01 PROJECT DESCRIPTION Great Island Plaza LLC (Applicant) is seeking to redevelop an existing mixed-use site at the properties identified as 590, 600 & 602 Main Street (Route 28) and 12 Winslow Gray Road in West Yarmouth, Massachusetts. The total site area is 2.04± acres. The project is bordered by undeveloped land to the north, undeveloped residential land and an existing commercial property to the east, Route 28 to the south and Winslow Gray Road to the west. The location is shown on the USGS map in appendix A. The Project involves the demolition of one building and partial demolition of another building. In addition to the demolition, one new commercial building will be constructed, and three new additions will be incorporated the primary structure. New utility services will be provided for all buildings, and the project will also require substantial re-grading, stormwater management improvements, the creation of new driveways and parking areas and landscaping. The Project has been designed to comply with the Department of Environmental Protection’s Stormwater Management Standards and the Town of Yarmouth Zoning Bylaws. 1.02 PRE-DEVELOPMENT CONDITIONS The majority of the site is relatively flat. However, the eastern portion of the site contains moderate (0-5%) slopes. Stormwater runoff generally flows from the center of the site outward. All runoff currently flows offsite. The pre- development HydroCAD model has been developed with three (3) subcatchment areas. Subcatchment 1S is located in the northwest corner of the property. Stormwater runoff form this area flows offsite toward Winslow Gray Road. Subcatchment 2S is located in the southwest corner of the property. Stormwater runoff form this area flows toward the intersection of Route 28 and Winslow Gray Road, generally in a westerly direction. The remaining and largest area of the site is Subcatchment 3S, which represents eastern portions of the site. Stormwater runoff from this area flows offsite in toward the commercial property at 606 & 610 Route 28. NRCS Web Soil Survey identifies the soils underlying the site as Map Unit 252A Carver coarse sand, 0 to 3 percent slopes. Based on Web Soil Survey, these soils are excessively drained and belong to Hydrologic Soil Group A. 1.03 POST-DEVELOPMENT CONDITIONS The proposed stormwater management system has been designed to meet or exceed the provisions of the Massachusetts Department of Environmental Protection (MassDEP) Stormwater Management Standards for new construction. The site has been designed in such a manner that the post-development drainage patterns will mirror those of the pre- development condition. Site drainage will be collected and managed onsite. Stormwater runoff from impervious areas will be treated and infiltrated onsite. Stormwater runoff from much of the outer perimeter of the property will continue to drain offsite, as it does in the pre-development condition. However, the areas of the site that drain offsite are greatly reduced from that of the pre-development scenario. As a result of this, the peak rate of stormwater runoff has been significantly reduced for all design storms, at each of the design points (Summary Nodes 1R, 2R & 3R). Stormwater runoff will be recharged into the ground through the implementation of BMPs including a bioretention area (rain garden) and four (4) subsurface infiltration systems, consisting of Cultec R-330XLHD leaching chambers installed within a bed of crushed stone. Stormwater runoff throughout the site will be collected in deep-sump & hooded catch basins and routed to the various BMPs via stormdrains and drain manholes. Stormwater runoff from the impervious portions of the site will be pre- treated to achieve a minimum TSS removal rate of 44% (due to the presence of rapidly draining soils), and ultimately treated to a minimum TSS removal rate of 80%. Pretreatment will be accomplished through the use of three (3) water quality treatment units and one (1) sediment forebay. Following pre-treatment, stormwater will be conveyed to one of the aforementioned BMPs, where it will be treated and then recharged to the ground. Stormwater Report Great Island Plaza LLC West Yarmouth, MA Specifics of the project’s compliance with the MassDEP Stormwater Management Standards are discussed in detail in the following sections. Stormwater Report Great Island Plaza LLC West Yarmouth, MA SECTION 2.0 DRAINAGE SUMMARY Stormwater Report Great Island Plaza LLC West Yarmouth, MA 2.01 Stormwater Standard 1 – New Stormwater Conveyances Per MassDEP Stormwater Management Standard #1, no new outfalls may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. There are no known stormwater outfalls in this development and no new outfalls are proposed. 2.02 Stormwater Standard 2 – Stormwater Runoff Rates Watershed modeling was performed using HydroCAD Stormwater Modeling Software version 10.0, a computer aided design program that combines SCS runoff methodology with standard hydraulic calculations. A model of the site’s hydrology was developed for both pre- and post-development conditions to assess the effects of the proposed development on the resource areas to the northwest of the site. The stormwater management systems for the project has been designed such that the post-development conditions do not increase the peak runoff rates for the 2-year, 10-year, 25-year and 100-year, 24-hour storm events, as detailed in the table below. Peak Flow Discharge Rates Node 1R – Offsite Flow to Winslow Gray Road (West) Storm Event Pre-Development Peak Discharge Rate (cfs) Post-Development Peak Discharge Rate (cfs) Change in Peak Discharge Rate (cfs) 2-Year 0 0 0 10-Year 0.05 0 -0.05 25-Year 0.14 0.01 -0.13 100-Year 0.34 0.02 -0.32 Node 2R – Offsite Flow to Intersection (Southwest) Storm Event Pre-Development Peak Discharge Rate (cfs) Post-Development Peak Discharge Rate (cfs) Change in Peak Discharge Rate (cfs) 2-Year 0.96 0.12 -0.84 10-Year 1.52 0.27 -1.25 25-Year 1.96 0.40 -1.56 100-Year 2.65 0.61 -2.04 Stormwater Report Great Island Plaza LLC West Yarmouth, MA Node 3R – Offsite Flow to East Storm Event Pre-Development Peak Discharge Rate (cfs) Post-Development Peak Discharge Rate (cfs) Change in Peak Discharge Rate (cfs) 2-Year 1.13 0.53 -0.60 10-Year 2.31 0.86 -1.45 25-Year 3.31 1.11 -2.20 100-Year 4.98 1.51 -3.47 2.03 Stormwater Standard 3 – Groundwater Recharge The ground water recharge is estimated based on the Massachusetts Stormwater Management Standard #3, as follows: Rv = F x impervious area Rv= Required Recharge Volume, expressed in Ft3, cubic yards, or acre-feet F= Target Depth Factor associated with each Hydrologic Soil Group Impervious Area= pavement and rooftop area on site Table 1.2 Recharge Target Depth by Hydrologic Soil Group NRCS HYDROLOGIC SOIL TYPE APPROX. SOIL TEXTURE TARGET DEPTH FACTOR (F) A sand 0.60-inch B loam 0.35-inch C silty loam 0.25-inch D clay 0.10-inch The Natural Resources Conservation Service (NRCS) has classified the soils underlying the project site as a combination of soil groups 51 (2%) and 103C (98%). Based on the location and resulting data from test pits, the site is modeled as Hydraulic Group C. Soil type 51, Swansea Muck, is associated with the areas directly adjacent to Stop River at the bottom of the slope. Due to the hilly nature of the site, the standing water elevation of Stop River is more than 20 feet in elevation below the bottom of the proposed drainage system, so groundwater is not a limiting factor in the stormwater drainage design. To determine the recharge volume provided in the recharge system, the Static Method was used as described in the DEP’s Massachusetts Stormwater Handbook, Volume 3. A drawdown calculation was performed in accordance with the DEP’s Massachusetts Stormwater Handbook, Volume 3, to verify that the proposed recharge systems would drain completely within 72-hours. This drawdown calculation along with calculations to determine the recharge required are provided in Section 7.0 of this report. 2.04 Stormwater Standard 4 – TSS Removal As a re-development, the project stormwater management system will achieve a TSS removal greater than 80%. The proposed stormwater management system has been designed to provide treatment of runoff in order to reduce suspended solids prior to discharge off-site through the implementation of the following best management practices: Stormwater Report Great Island Plaza LLC West Yarmouth, MA  Deep Sump Hooded Catch Basins (Pre-treatment)  Hydro International water quality units (or approved equal) (Pre-treatment)  Underground Stormwater Infiltration Systems (Cultec R-330XLHD) (80% TSS removal)  Bio-Retention Area (90% TSS removal) The water quality volume is defined as the runoff volume requiring TSS Removal for the site and is equal to 1-inch of runoff over the total impervious area of the post-development site. The required water quality volume required for the project is calculated below based on the post-development impervious area: 𝑊𝑄𝑉= 1.0 𝑖𝑛 𝑥 1 𝑓𝑡 12 𝑖𝑛𝑥 1.475 𝑎𝑐 𝑥 43,560 𝑓𝑡ଶ = 𝟓,𝟑𝟓𝟒 𝒇𝒕𝟑 The infiltration systems have been sized to treat the required water quality volume. 2.05 Stormwater Standard 5 – Land Uses with Higher Potential Pollutant Loads The Project is not a land use with higher potential pollutant loads, therefore this Standard does not apply. 2.06 Stormwater Standard 6 – Stormwater Discharges to a Critical Area The project is not subject to Standard 6. There are no discharges to any Critical Area, as defined by the Massachusetts Stormwater Handbook. 2.07 Stormwater Standard 7 – Redevelopment Projects This project is a redevelopment, but is designed to fully comply with the MassDEP Stormwater Management Standards. 2.08 Stormwater Standard 8 – Sedimentation and Erosion Control Plan Erosion and sedimentation controls are shown on the Project Site Plan set (page 6 of 7). Additionally, a Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan is included in Section 4.0 of this Report. 2.09 Stormwater Standard 9 – Long Term Operation and Maintenance Plan A Long-Term Operation and Maintenance Plan is included in Section 5.0 of this Report. 2.10 Stormwater Standard 10 – Illicit Discharges There are no known illicit discharges on the project site and none are proposed. A signed, illicit discharge compliance statement will be submitted prior to the start of construction. 2.11 Conclusion The Project has been designed to meet the applicable provisions of the Stormwater Management Standards. The proposed BMPs will serve to attenuate peak runoff rates, provide treatment to stormwater prior to discharge, and promote recharge to groundwater. The project will protect adjacent properties and will meet the requirements of the MassDEP Stormwater Management Standards. ∴ Water Quality Volume = 5,354 cubic feet Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. SECTION 3.0 MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION CHECKLIST FOR STORMWATER REPORT Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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 Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Section 3.0 - Mass DEP Stormwater Checklist.docx • 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. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. SECTION 4.0 CONSTRUCTION PERIOD POLLUTION PREVENTION AND EROSION AND SEDIMENTATION CONTROL PLAN Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.0 CONSTRUCTION PERIOD POLLUTION PREVENTION AND EROSION AND SEDIMENTATION CONTROL PLAN This Section specifies requirements and suggestions for implementation of a Stormwater Pollution Prevention Plan (SWPPP) for the proposed photovoltaic system located at 0 Scenic Highway, Bourne, Massachusetts. The SWPPP shall be provided and maintained on-site by the Contractor(s) during all construction activities. The SWPPP shall be updated as required to reflect changes to construction activity. The stormwater pollution prevention measures contained in the SWPPP shall be at least the minimum required by Local Regulations. The Contractor shall provide additional measures to prevent pollution from stormwater discharges in compliance with the National Pollution Discharge Elimination System (NPDES) Phase II permit requirements and all other local, state and federal requirements. The SWPPP shall include provisions for, but not be limited to, the following: 1. Construction Trailers 2. Lay-down Areas 3. Equipment Storage Areas 4. Stockpile Areas 5. Disturbed Areas The Contractor shall NOT begin construction without submitting evidence that a NPDES Notice of Intent (NOI) governing the discharge of stormwater from the construction site for the entire construction period has been filed at least fourteen (14) days prior to construction. It is the Contractor's responsibility to complete and file the NOI, unless otherwise determined by the project team. The cost of any fines, construction delays and remedial actions resulting from the Contractor's failure to comply with all provisions of local regulations and Federal NPDES permit requirements shall be paid for by the Contractor at no additional cost to the Owner. As a requirement of the EPA’s NPDES permitting program, each Contractor and Subcontractor responsible for implementing and maintaining stormwater Best Management Practices shall execute a Contractor's Certification form. Erosion and Sedimentation Control The Contractor shall be solely responsible for erosion and sedimentation control at the site. The Contractor shall utilize a system of operations and all necessary erosion and sedimentation control measures, even if not specified herein or elsewhere, to minimize erosion damage at the site to prevent the migration of sediment into environmentally sensitive areas. Environmentally sensitive areas include all wetland resource areas within, and downstream of, the site, and those areas of the site that are not being altered. Erosion and sedimentation control shall be in accordance with this Section, the design drawings, and the following:  “National Pollutant Discharge Elimination System General Permit for Discharges from Construction Activities (EPA Construction General Permit February 16, 2017).  Massachusetts Stormwater Management Policy Handbook issued by the Massachusetts Department of Environmental Protection, January 2008.  Massachusetts Erosion and Sediment Control Guidelines for Urban and Suburban Areas, A Guide for Planners, Designers and Municipal Officials, March 1997. The BMP's presented herein should be used as a guide for erosion and sedimentation control and are not Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. intended to be considered specifications for construction. The most important BMP is maintaining a rapid construction process, resulting in prompt stabilization of surfaces, thereby reducing erosion potential. Given the primacy of rapid construction, these guidelines have been designed to allow construction to progress with essentially no hindrance by the erosion control methods prescribed. These guidelines have also been designed with sufficient flexibility to allow the Contractor to modify the suggested methods as required to suit seasonal, atmospheric, and site-specific physical constraints. Another important BMP is the prevention of concentrated water flow. Sheet flow does not have the erosive potential of a concentrated rivulet. These guidelines recommend construction methods that allow localized erosion control and a system of construction, which inhibits the development of shallow concentrated flow. These BMP's shall be maintained throughout the construction process. CONTACT INFORMATION AND RESPONSIBLE PARTIES The following is a list of all project-associated parties: Owner Great Island Plaza LLC C/O Tatra Building Company 1268 Route 28 South Yarmouth, MA 02664 Contractor To be determined Environmental Consultant BSC Group, Inc. 349 Route 28, Unit D West Yarmouth, MA 02673 Contact: Brian G. Yergatian, P.E., LEED AP Phone: (617) 896–4590 Email: byergatian@bscgroup.com Qualified SWPPP Inspectors To Be Determined 4.1 Procedural Conditions of the Construction General Permit (CGP) The following list outlines the stormwater responsibilities for all construction operators working on the Project. The operators below agree through a cooperative agreement to abide by the following conditions throughout the duration of the construction project, effective the date of signature of the required SWPPP. These conditions apply to all operators on the project site. The project is subject to EPA’s NPDES General Permit through the CGP. The goal of this permit is to prevent the discharge of pollutants associated with construction activity from entering the existing and proposed storm drain system or surface waters. All contractors/operators involved in clearing, grading and excavation construction activities must sign the appropriate certification statement required, which will remain with the SWPPP. The owner must also sign a certification, which is to remain with the SWPPP in accordance with the signatory requirements of the SWPPP. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. Once the SWPPP is finalized, a signed copy, plus supporting documents, must be held at the project site during construction. A copy must remain available to EPA, State and Local agencies, and other interested parties during normal business hours. The following items associated with this SWPPP must be posted in a prominent place at the construction site until final stabilization has been achieved:  The completed/submitted NOI form  Location where the public can view the SWPPP during normal business hours  A copy of the signed/submitted NOI, permit number issued by the EPA and a copy of the current CGP. Project specific SWPPP documents are not submitted to the US EPA unless the agency specifically requests a copy for review. SWPPP documents requested by a permitting authority, the permitee(s) will submit it in a timely manner. EPA inspectors will be allowed free and unrestricted access to the project site and all related documentation and records kept under the conditions of the permit. The permitee is expected to keep all BMP’s and Stormwater controls operating correctly and maintained regularly. Any additions to the project which will significantly change the anticipated discharges of pollutants, must be reported to the EPA. The EPA should also be notified in advance of any anticipated events of noncompliance. The permitee must also orally inform the EPA of any discharge, which may endanger health or the environment within 24 hours, with a written report following within 5 days. In maintaining the SWPPP, all records and supporting documents will be compiled together in an orderly fashion. Inspection reports and amendments to the SWPPP must remain with the document. Federal regulations require permitee(s) to keep their Project Specific SWPPP and all reports and documents for at least three (3) years after the project is complete. 4.2 Project Description and Intended Construction Sequence The site is currently an existing sand and gravel pit. The proposed activities will include the following major components:  Demolition / partial demolition of two existing buildings on site, three building additions, and one new building  Site grading, stormwater management facilities, and new utility services  New driveway areas, parking areas, and landscaping areas The proposed site development will disturb 1.98± acres. Soil disturbing activities will include site demolition, clearing and grubbing, installing stabilized construction exits, installation of erosion and sedimentation controls, grading, stormwater management systems, utilities, building foundations, construction of site driveways and preparation for final landscaping. Please refer to Table 1 for the projects anticipated construction timetable. A description of BMP’s associated with project timetable and construction-phasing elements is provided in this Erosion and Sediment Control Plan. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. Table 1 – Anticipated Construction Timetable Construction Phasing Activity Anticipated Timetable Demolition, Grubbing and Stripping of Limits of Construction Phase To be determined Rough Site Grading and Site Utilities To be determined Utility Plan Construction To be determined Landscaping To be determined 4.3 Potential Sources of Pollution Any project site activities that have the potential to add pollutants to runoff are subject to the requirements of the SWPPP. Listed below are a description of potential sources of pollution from both sedimentation to Stormwater runoff, and pollutants from sources other than sedimentation. Table 2 – Potential Sources of Sediment to Stormwater Runoff Table 3 – Potential Pollutants and Sources, other than Sediment to Stormwater Runoff Potential Source Activities/Comments Staging Areas and Construction Vehicles Vehicle refueling, minor equipment maintenance, sanitary facilities and hazardous waste storage Materials Storage Area General building materials, solvents, adhesives, paving materials, paints, aggregates, trash, etc. Construction Activities Construction, paving, curb/gutter installation, concrete pouring/mortar/stucco 4.4 Erosion and Sedimentation Control Best Management Practices The project site is characterized by primarily pervious surface. All construction activities will implement Best Management Practices (BMP’s) in order to minimize overall site disturbance and impacts to the sites natural features. Please refer to the following sections for a detailed description of site specific BMP’s. In addition, an Erosion and Sedimentation Control Plan is provided in the Site Plans. 4.5 Timetable and Construction Phasing Potential Source Activities/Comments Construction Site Entrance and Site Vehicles Vehicles leaving the site can track soils onto public roadways. Site Vehicles can readily transport exposed soils throughout the site and off-site areas. Grading Operations Exposed soils have the potential for erosion and discharge of sediment to off-site areas. Material Excavation, Relocation, and Stockpiling Stockpiling of materials during excavation and relocation of soils can contribute to erosion and sedimentation. In addition, fugitive dust from stockpiled material, vehicle transport and site grading can be deposited in wetlands and waterway. Landscaping Operations Landscaping operations specifically associated with exposed soils can contribute to erosion and sedimentation. Hydro seeding, if not properly applied, can runoff to adjacent wetlands and waterways. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. This section provides the Owner and Contractor with a suggested order of construction that shall minimize erosion and the transport of sediments. The individual objectives of the construction techniques described herein shall be considered an integral component of the project design intent of each project phase. The construction sequence is not intended to prescribe definitive construction methods and should not be interpreted as a construction specification document. However, the Contractor shall follow the general construction phase principles provided below:  Protect and maintain existing vegetation wherever possible.  Minimize the area of disturbance.  To the extent possible, route unpolluted flows around disturbed areas.  Install mitigation devices as early as possible.  Minimize the time disturbed areas are left un-stabilized.  Maintain siltation control devices in proper condition.  The contractor should use the suggested sequence and techniques as a general guide and modify the suggested methods and procedures as required to best suit seasonal, atmospheric, and site specific physical constraints for minimizing the environmental impact of construction. Demolition, Grubbing and Stripping of Limits of Construction Phase  Install Temporary Erosion Control (TEC) devices as required to prevent sediment transport into resource areas.  Place a ring of silt socks and/or haybales around stockpiles.  Stabilize all exposed surfaces that will not be under immediate construction.  Store and/or dispose all pavement and building demolition debris as indicated in accordance with all applicable local, state, and federal regulations. Driveway Area Sub-Base Construction  Install temporary culverts and diversion ditches and additional TEC devices as required by individual construction area constraints to direct potential runoff toward detention areas designated for the current construction phase.  Compact gravel as work progresses to control erosion potential.  Apply water to control air suspension of dust.  Avoid creating an erosive condition due to over-watering.  Install piped utility systems as required as work progresses, keeping all inlets sealed until all downstream drainage system components are functional. Binder Construction  Fine grade gravel base and install processed gravel to the design grades.  Compact pavement base as work progresses.  Install pavement binder coat starting from the downhill end of the site and work toward the top. Finish Paving  Repair and stabilize damaged side slopes.  Clean inverts of drainage structures.  Install final top coat of pavement. Final Clean-up  Clean inverts of culverts and catch basins.  Remove sediment and debris from rip-rap outlet areas. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed.  Remove TEC devices only after permanent vegetation and erosion control has been fully established. 4.6 Site Stabilization Grubbing Stripping and Grading  Erosion control devices shall be in place as shown on the design plans before grading commences.  Stripping shall be done in a manner, which will not concentrate runoff. If precipitation is expected, earthen berms shall be constructed around the area being stripped, with a silt sock, silt fence or haybale dike situated in an arc at the low point of the berm.  If intense precipitation is anticipated, silt socks, haybales, dikes and /or silt fences shall be used as required to prevent erosion and sediment transport. The materials required shall be stored on site at all time.  If water is required for soil compaction, it shall be added in a uniform manner that does not allow excess water to flow off the area being compacted.  Dust shall be held at a minimum by sprinkling exposed soil with an appropriate amount of water. Maintenance of Disturbed Surfaces  Runoff shall be diverted from disturbed side slopes in both cut and fill.  Mulching may be used for temporary stabilization.  Silt sock, haybale or silt fences shall be set where required to trap products of erosion and shall be maintained on a continuing basis during the construction process. Loaming and Seeding  Loam shall not be placed unless it is to be seeded directly thereafter.  All disturbed areas shall have a minimum of 4” of loam placed before seeded and mulched.  Consideration shall be given to hydro-mulching, especially on slopes in excess of 3 to 1.  Loamed and seeded slopes shall be protected from washout by mulching or other acceptable slope protection until vegetation begins to grow. Stormwater Collection System Installation  The Stormwater drainage system shall be installed from the downstream end up and in a manner which will not allow runoff from disturbed areas to enter pipes.  Excavation for the drainage system shall not be left open when rainfall is expected overnight. If left open under other circumstances, pipe ends shall be closed by a staked board or by an equivalent method.  All catch basin openings shall be covered by a silt bag between the grate and the frame or protected from sediment by silt fence surrounding the catch basin grate. Completion of Paved Areas  During the placement of sub-base and pavement, the entrance to the Stormwater drainage systems shall be sealed when rain is expected. When these entrances are closed, consideration must be given to the direction of run-off and measures shall be undertaken to minimize erosion and to provide for the collection of sediment.  In some situations, it may be necessary to keep catch basins open.  Appropriate arrangements shall be made downstream to remove all sediment deposition. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. Stabilization of Surfaces  Stabilization of surfaces includes the placement of pavement, rip-rap, wood bark mulch and the establishment of vegetated surfaces.  Upon completion of construction, all surfaces shall be stabilized even though it is apparent that future construction efforts will cause their disturbance.  Vegetated cover shall be established during the proper growing season and shall be enhanced by soil adjustment for proper pH, nutrients and moisture content.  Surfaces that are disturbed by erosion processes or vandalism shall be stabilized as soon as possible.  Areas where construction activities have permanently or temporarily ceased shall be stabilized within 14 days from the last construction activity, except when construction activity will resume within 21 days (e.g., the total time period that construction activity is temporarily ceased is less than 21 days).  Hydro-mulching of grass surfaces is recommended, especially if seeding of the surfaces is required outside the normal growing season.  Hay mulch is an effective method of temporarily stabilizing surfaces, but only if it is properly secured by branches, weighted snow fences or weighted chicken wire. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.7 Temporary Structural Erosion Control Measures Temporary erosion control measures serve to minimize construction-associated impacts to undisturbed areas. Please refer to the following sections for a description of temporary erosion control measures implemented as part of the project and this sample SWPPP. 4.7.1 Staked Straw Wattles and/or Silt Fencing The siltation barriers will demarcate the limit of work, form a work envelope and provide additional assurance that construction equipment will not enter the undisturbed portions of the site. All barriers will remain in place until disturbed areas are stabilized. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.7.2 Temporary Stormwater Diversion Swale A temporary diversion swale is an effective practice for temporarily diverting stormwater flows and to reduce stormwater runoff velocities during storm events. The swale channel can be installed before infrastructure construction begins at the site, or as needed throughout the construction process. The diversion swale should be routinely compacted or seeded to minimize the amount of exposed soil. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.7.3 Dewatering Basins Dewatering may be required during stormwater system, foundation construction and utility installation. Should the need for dewatering arise, groundwater will be pumped directly into a temporary settling basin, which will act as a sediment trap during construction. All temporary settling basins will be located within close proximity of daily work activities. Prior to discharge, all groundwater will be treated by means of the settling basin or acceptable substitute. Discharges from sediment basins will be free of visible floating, suspended and settleable solids that would impair the functions of a wetland or degrade the chemical composition of the wetland resource area receiving ground or surface water flows and will be to the combined system. 4.7.4 Material Stockpiling Locations Piping and trench excavate associated with the subsurface utility work will be contained with a single row of silt socks and/or haybales. 4.8 Permanent Structural Erosion Control Measures Permanent erosion control measures serve to minimize post-construction impacts to undisturbed areas. Please refer to the following sections for a description of permanent erosion control measures implemented as part of the project and this SWPPP. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.9 Good Housekeeping Best Management Practices 4.9.1 Material Handling and Waste Management Solid waste generation during the construction period will be primarily construction debris. The debris will include scrap lumber (used forming and shoring pallets and other shipping containers), waste packaging materials (plastic sheeting and cardboard), scrap cable and wire, roll-off containers (or dumpsters) and will be removed by a contract hauler to a properly licensed landfill. The roll-off containers will be covered with a properly secured tarp before the hauler exits the site. In addition to construction debris, the construction work force will generate some amount of household-type wastes (food packing, soft drink containers, and other paper). Trash containers for these wastes will be located around the site and will be emptied regularly to prevent wind-blown litter. This waste will also be removed by a contract hauler. All hazardous waste material such as oil filters, petroleum products, paint and equipment maintenance fluids will be stored in structurally sound and sealed shipping containers in the hazardous-materials storage area and segregated from other non-waste materials. Secondary containment will be provided for all materials in the hazardous materials storage area and will consist of commercially available spill pallets. Additionally, all hazardous materials will be disposed of in accordance with federal, state and municipal regulations. Two temporary sanitary facilities (portable toilets) will be provided at the site in the combined staging area. The toilets will be away from a concentrated flow path and traffic flow and will have collection pans underneath as secondary treatment. All sanitary waste will be collected from an approved party at a minimum of three times per week. 4.9.2 Building Material Staging Areas Construction equipment and maintenance materials will be stored at the combined staging area and materials storage areas. Silt fence will be installed around the perimeter to designate the staging and materials storage area. A watertight shipping container will be used to store hand tools, small parts and other construction materials. Non-hazardous building materials such as packaging material (wood, plastic and glass) and construction scrap material (brick, wood, steel, metal scraps, and pine cuttings) will be stored in a separate covered storage facility adjacent to other stored materials. All hazardous-waste materials such as oil filters, petroleum products, paint and equipment maintenance fluids will be stored in structurally sound and sealed containers under cover within the hazardous materials storage area. Large items such as framing materials and stockpiled lumber will be stored in the open storage area. Such materials will be elevated on wood blocks to minimize contact with runoff. The combined storage areas are expected to remain clean, well-organized and equipped with ample cleaning supplies as appropriate for the materials being stored. Perimeter controls such as containment structures, covers and liners will be repaired or replaced as necessary to maintain proper function. 4.9.3 Designated Washout Areas Designated temporary, below-ground concrete washout areas will be constructed, as required, to minimize the pollution potential associated with concrete, paint, stucco, mixers etc. Signs will, if required, be posted marking the location of the washout area to ensure that concrete equipment operators use the proper facility. Concrete pours will not be conducted during or before an anticipated precipitation event. All excess concrete and concrete washout slurries from the concrete mixer trucks and chutes will be discharged to the washout area or hauled off-site for disposal. Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed. 4.9.4 Equipment/Vehicle Maintenance and Fueling Areas Several types of vehicles and equipment will be used on-site throughout the project including graders, scrapers, excavators, loaders, paving equipment, rollers, trucks and trailers, backhoes and forklifts. All major equipment/vehicle fueling and maintenance will be performed off-site. A small, 20-gallon pickup bed fuel tank will be kept on-site in the combined staging area. When vehicle fueling must occur on-site, the fueling activity will occur in the staging area. Only minor equipment maintenance will occur on-site. All equipment fluids generated from maintenance activities will be disposed of into designated drums stored on spill pallets. Absorbent, spill-cleanup materials and spill kits will be available at the combined staging and materials storage area. Drip pans will be placed under all equipment receiving maintenance and vehicles and equipment parked overnight. 4.9.5 Equipment/Vehicle Wash down Area All equipment and vehicle washing will be performed off-site. 4.9.6 Spill Prevention Plan A spill containment kit will be kept on-site in the Contractor’s trailer and/or the designated staging area throughout the duration of construction. Should there be an accidental release of petroleum product into a resource area, the appropriate agencies will be immediately notified. 4.9.7 Inspections Maintenance of existing and proposed BMP’s to address stormwater management facilities during construction is an on-going process. The purpose of the inspections is to observe all sources of stormwater or non-stormwater discharge as identified in the SWPPP as well as the status of the receiving waters and fulfill the requirements of the Order of Conditions. The following sections describe the appropriate inspection measures to adequately implement the project’s SWPPP. A blank inspection form is provided at the end of this section. Completed inspection forms are to be maintained on site. Inspection Personnel The owner’s appointed representative will be responsible for performing regular inspections of erosion controls and ordering repairs as necessary. Inspection Frequency Inspections will be performed by qualified personnel once every 7 days and within 24-hours after a storm event of greater than one-quarter inch, in accordance with the CGP. The inspections must be documented on the inspection form provided at the end of this section, and completed forms will be provided to the on- site supervisor and maintained at the Owner’s office throughout the entire duration of construction. Inspection Reporting Each inspection report will summarize the scope of the inspection, name(s) and qualifications of personnel making the inspection, and major observations relating to the implementation of the SWPPP, including compliance and non-compliance items. Completed inspection reports will remain with the completed SWPPP on site. 4.9.8 Amendment Requirements The final SWPPP is intended to be a working document that is utilized regularly on the construction site, and provides guidance to the Contractor. It must reflect changes made to the originally proposed plan and will be updated to include project specific activities and ensure that they are in compliance with the NPDES General Permit and state and local laws and regulations. It should be amended whenever there is a change in design, construction, operation or maintenance that affects discharge of pollutants. The following items should be addressed should an amendment to the SWPPP occur: Stormwater Report Great Island Plaza LLC West Yarmouth, MA The picture can't be displayed.  Dates of certain construction activities such as major grading activities, clearing and initiation of and completion of stabilization measures should be recorded.  Future amendments to the SWPPP will be recorded as required. As this SWPPP is amended, all amendments will be kept on site and made part of the SWPPP.  Upon completion of site stabilization (completed as designed and/or 70% background vegetative cover), it can be documented and marked on the plans. Inspections are no longer required at this time.  Inspections often identify areas not included in the original SWPPP, which will require the SWPPP to be amended. These updates should be made within seven days of being recognized by the inspector. 4.10 SWPPP Inspection and Maintenance Report The following form is an example to be used for SWPPP Inspection Reporting. Stormwater Report Great Island Plaza LLC West Yarmouth, MA Stormwater Construction Site Inspection and Maintenance Report TO BE COMPLETED AT LEAST EVERY 7 DAYS AND WITHIN 24 HOURS OF A STORM EVENT OF AT LEAST 0.25 INCHES. AFTER SITE STABILIZATION, TO BE COMPLETED AT LEAST ONCE PER MONTH FOR THREE YEARS OR UNTIL A NOTICE OF TERMINATION IS FILED (IF APPLICABLE). General Information Project Name Great Island Plaza NPDES Tracking No. (if applicable) Location 590, 600 & 602 Route 28, 12 Winslow Gray Rd, West Yarmouth, MA 02673 Date of Inspection Start/End Time Inspector’s Name(s) Inspector’s Title(s) Inspector’s Contact Information Inspector’s Qualifications Describe present phase of construction Type of Inspection:  Regular  Pre-storm event  During storm event  Post-storm event Weather Information Has there been a storm event since the last inspection? Yes No If yes, provide: Storm Start Date & Time: Storm Duration (hrs): Approximate Amount of Precipitation (in): Weather at time of this inspection?  Clear Cloudy  Rain  Sleet  Fog  Snowing  High Winds  Other: Temperature: Have any discharges occurred since the last inspection? Yes No If yes, describe: Are there any discharges at the time of inspection? Yes No If yes, describe: Stormwater Report Great Island Plaza LLC West Yarmouth, MA Site-specific BMPs  Number the structural and non-structural BMPs identified in your SWPPP on your site map and list them below (add as many BMPs as necessary). Carry a copy of the numbered site map with you during your inspections. This list will ensure that you are inspecting all required BMPs at your site.  Describe corrective actions initiated, date completed, and note the person that completed the work in the Corrective Action Log. BMP BMP Installed? BMP Maintenance Required? Corrective Action Needed and Notes Action required by whom and when 1 Catch Basin Protection Yes No Yes No 2 Haybale & Silt Fencing Yes No Yes No 3 Straw Wattles Yes No Yes No 4 Construction Entrance Yes No Yes No 5 Sediment Basins Yes No Yes No 6 Dewatering Pit Yes No Yes No Stormwater Report Great Island Plaza LLC West Yarmouth, MA Overall Site Issues Below are some general site issues that should be assessed during inspections. Customize this list as needed for conditions at your site. BMP/activity Implemented? Maintenance Required? Corrective Action Needed and Notes Action required by whom and when 1 Are all slopes and disturbed areas not actively being worked properly stabilized? Yes No Yes No 2 Are natural resource areas (e.g., streams, wetlands, mature trees, etc.) protected with barriers or similar BMPs? Yes No Yes No 3 Are perimeter controls and sediment barriers adequately installed (keyed into substrate) and maintained? Yes No Yes No 4 Are discharge points and receiving waters free of any sediment deposits? Yes No Yes No 5 Are storm drain inlets properly protected? Yes No Yes No 6 Is the construction exit preventing sediment from being tracked into the street? Yes No Yes No 7 Is trash/litter from work areas collected and placed in covered dumpsters? Yes No Yes No 8 Are washout facilities (e.g., paint, stucco, concrete) available, clearly marked, and maintained? Yes No Yes No 9 Are vehicle and equipment fueling, cleaning, and maintenance areas free of spills, leaks, or any other deleterious material? Yes No Yes No Vehicle Maintenance not allowed on site 10 Are materials that are potential stormwater contaminants stored inside or under cover? Yes No Yes No Stormwater Report Great Island Plaza LLC West Yarmouth, MA Non-Compliance Describe any incidents of non-compliance not described above: CERTIFICATION STATEMENT “I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.” Print name and title: . (Qualified Person Performing the Inspection) Signature:_____________________________________________________ Date: . Print name and title: __________________________________________________________________________ (Contractor/Operator) Signature:______________________________________________________ Date: 11 Are non-stormwater discharges (e.g., wash water, dewatering) properly controlled? Yes No Yes No 12 (Other) Yes No Yes No Stormwater Report Great Island Plaza LLC West Yarmouth, MA SECTION 5.0 LONG-TERM POLLUTION PREVENTION & OPERATION AND MAINTENANCE PLAN Stormwater Report Great Island Plaza LLC West Yarmouth, MA 5.0 LONG-TERM POLLUTION PREVENTION & OPERATION AND MAINTENANCE PLAN As required by Standard #4 of the Stormwater Management Policy, this Long-Term Pollution Prevention Plan has been developed for source control and pollution prevention at the site after construction. MAINTENANCE RESPONSIBILITY Ensuring that the provisions of the Long-Term Pollution Prevention Plan are followed will be the responsibility of The Applicant. GOOD HOUSEKEEPING PRACTICES The site to be kept clean of trash and debris at all times. Trash, junk, etc. is not to be left outside. VEHICLE WASHING CONTROLS The following BMP’s, or equivalent measures, methods or practices are required if you are engaged in vehicle washing and/or steam cleaning: It is allowable to rinse down the body or a vehicle, including the bed of a truck, with just water without doing any wash water control BMP’s. If you wash (with mild detergents) on an area that infiltrates water, such as gravel, grass, or loose soil, it is acceptable to let the wash water infiltrate as long as you only wash the body of vehicles. However, if you wash on a paved area and use detergents or other cleansers, or if you wash/rinse the engine compartment or the underside of vehicles, you must take the vehicles to a commercial vehicle wash. REQUIREMENTS FOR ROUTINE INSPECTIONS AND MAINTENANCE OF STORMWATER BMPS All stormwater BMPs are to be inspected and maintain as follows; Straw Wattles, Silt Fence, and other temporary measures The temporary erosion control measures will be installed up gradient of any area where any disturbance or alteration might otherwise allow for erosion or sedimentation. They will be regularly inspected to ensure that they are functioning adequately. Additional supplies of these temporary measures will be stockpiled on site for any immediate needs or routine replacement. Deep Sump Hooded Catch Basins Regular maintenance is essential. Catch basins remain effective at removing pollutants only if they are cleaned out frequently. Inspect or clean basins at least four times per year and at the end of the foliage and snow removal seasons. Sediments must also be removed four times per year or whenever the depth of the deposits in the catch basin sump is greater than or equal to one half the depth from the bottom of the invert to the lowest pipe in the basin. Water Quality Treatment Units The water quality treatment structures require periodic inspection and cleaning to maintain operation and function. Owners should have these units inspected on a semi-annual basis and after periods of intense precipitation. Inspections Stormwater Report Great Island Plaza LLC West Yarmouth, MA can be done by using clear Plexiglas tube (“sludge judge”) to extract a water column sample. When sediment accumulation reaches 15% of storage capacity, cleaning of the unit is required. The water quality structures must and will be checked and cleaned immediately after petroleum spills, contact appropriate regulatory agencies. Maintenance of these units should be done by a vacuum truck that will remove the water, sediment debris, floating hydrocarbons and other materials in unit. Proper cleaning and disposal of the removed materials and liquid must be followed. Subsurface Infiltration Systems Maintenance is required for the proper operation of the underground precast infiltration systems. Infiltration systems are prone to failure due to clogging if upstream water quality units are not maintained. The use of pre-treatment BMPs will minimize failure and maintenance requirements. After construction, the infiltration system should be inspected after every major storm for the first few months to ensure proper stabilization. Water levels in the access ports should be recorded over several days to check the drainage of the systems. It is recommended that a log book be maintained showing the depth of water in the systems at each observation in order to determine the rate at which the system dewaters after runoff producing storm events. Once the performance characteristics of the system have been verified, the monitoring schedule can be reduced to annual basis, unless the performance data suggests that a more frequent schedule is required. Preventative maintenance of the systems should be performed at least twice a year, and sediment should be removed from any and all pretreatment and collection structures. Sediment should be removed when deposits approach within six inches of the invert heights of connecting pipes, or in sumped inlet structures. The system is designed with access covers such that a vacuum truck tube can be used to remove sediment. Bio-Retention Area Bio-retention areas require routine maintenance to ensure that the system functions well as a stormwater BMP and maintains an aesthetic element. A landscaping contractor working elsewhere on the site can complete maintenance tasks in many cases. Systems require careful attention while plants are being established and seasonal landscaping thereafter. Proper selection of plant species and support during establishment of vegetation should minimize – if not eliminate – the need for fertilizers and pesticides. Bio-retention areas should be inspected on a semi-annual basis and after major storm events. The system should be inspected monthly for erosion. Eroded areas shall be repaired by reseeding or mulching as necessary. Vegetated areas should be properly maintained and mowed to a height of 2-inches. Accumulated litter and debris should be periodically removed to ensure that the storage areas will function properly. Outlet structures should be inspected periodically and after every storm to ensure that the outlet is functioning properly. Paved surfaces directed to the bio-retention area should be cleaned periodically to remove litter, debris, and vehicle generated residues and other non-point source pollutants to provide increased pollution control. Vegetation should be inspected twice per year, at the beginning and end of the growing season. Dead and diseased vegetation should be removed and replaced. Weeds and invasive species should be removed and woody vegetation should be pruned as necessary. Pre-treatment devices, inflow locations, and overflows should be inspected annually to ensure proper functioning. Any sediment build-up should be removed. Stormwater Report Great Island Plaza LLC West Yarmouth, MA PROVISIONS FOR MAINTENANCE OF LAWNS, GARDENS AND OTHER LANDSCAPE AREAS Suggested Maintenance Operations A. Trees and Shrubs Disease and Pest Management - Prevention of disease or infestation is the first step of Pest Management. A plant that is in overall good health is far less susceptible to disease. Good general landscape maintenance can reduce problems from disease. Inspections of plant materials for signs of disease or infestation are to be performed monthly by the Landscape Maintenance Contractor’s Certified Arborist. This is a critical step for early diagnosis. Trees and Shrubs that have been diagnosed to have a plant disease or an infestation of insect pests are to be treated promptly with an appropriate material by a licensed applicator. Fertilization - Trees and shrubs live outside their natural environment and should be given proper care to maintain health and vigor. Fertilizing trees and shrubs provides the plants with nutrients needed to resist insect attack, to resist drought and to grow thicker foliage. Fertilizing of new and old trees may be done in one of three ways, in either the early spring or the late fall.  Systemic Injection of new and existing trees on trees 2 inches or greater in diameter. You must be licensed to apply this method.  Soil Injection – a liquid fertilizer with a product such as Arbor Green or Rapid Grow injected into the soil under the drip zone of a tree or shrub. Material must be used according to manufacturers’ specifications to be effective. Outside contracting is recommended.  Punch Bar Method – a dry fertilizer such as 10-10-10, may be used by punched holes in the drip zone of the tree 12-18” deep, two feet apart around the circumference, to the edge of the drip line. Three pounds of fertilizer should be used per diameter inch for trees with trunks six inches or more in diameter.  Fertilizer of shrubs – use a fertilizer such as 10-10-10, broadcast over the planting area according to the manufacturers’ rate and water in.  All fertilization must be noted on daily maintenance log. Watering - Trees and Shrubs will need supplemental watering to remain in vigorous health. All new plants need to be watered once a week in cool weather, twice a week during warm weather, and up to three times in a week during periods of extreme heat and drought. Trees and shrubs should be watered in such a manner as to totally saturate the soil in the root zone area. Over-watering or constant saturation of the soil must be avoided as this could lead to root rot and other disease problems. The use of a soil moisture meter can help you monitor the soil’s water intake. Plant Replacement - Unhealthy plants that may cause widespread infestation of other nearby plants shall be immediately removed from the site. Any vegetation removed from the site must be recorded and submitted with the daily maintenance log. The area shall be treated to prevent further infestation. The plant shall then be replaced with a healthy specimen of the same species and size. This work shall have a pre-established budget allowance for the year. A spring inspection of all plant materials shall be performed to identify those plant materials that are not in vigorously healthy condition. Unhealthy plant materials shall be evaluated. If the problem is determined to be minor the plant material shall be given appropriate restorative care in accordance with this maintenance guideline until it is restored to a vigorously healthy condition. Unhealthy plant materials that do not respond to restorative care or are determined to be beyond saving shall be replaced with a healthy specimen of the same species and size. In the case of the necessity of replacing extremely large plant materials the Landscape Architect shall determine the size of the replacement plant. Pruning - Proper pruning is the selective removal of branches without changing the plant’s natural appearance, or habit of growth. All tree pruning is to be performed by a licensed Arborist. All branches that are dead, broken, scared or crossing should be removed. All cuts should be made at the collar and not cut flush with the base. Pruning on the site shall be done for the following purposes; Stormwater Report Great Island Plaza LLC West Yarmouth, MA  To maintain or reduce the size of a tree or shrub  To remove dead, diseased or damaged branches  To rejuvenate old shrubs and encourage new growth  To stimulate future flower and fruit development  To maximize the visibility of twig color  To prevent damage and reduce hazards to people and properties All shrubs are recommended to be pruned on an annual basis to prevent the shrub from becoming overgrown and eliminate the need for drastic pruning. There are several types of pruning for deciduous shrubs. Hand snips should be used to maintain a more natural look or hand shears can be used for a more formal appearance. Winter Protection - All trees and shrubs are to be watered, fertilized, and mulched before the first frost. All stakes should be checked and ties adjusted. Damaged branches should be pruned. Broadleaf and Coniferous Evergreen plant materials are to be sprayed with an anti-desiccant product to prevent winter burn. The application shall be repeated during a suitable mid-winter thaw. Shrubs located in areas likely to be piled with snow during snow removal (but not designated as Snow Storage Areas) shall be marked by six-foot high poles with bright green banner flags. Stockpiles of snow are not to be located in these areas due to potential damage to the plant materials from both the weight of the snow and the snow melting chemicals. At the fall landscape maintenance conference parameters will be discussed between the Landscape Maintenance Contractor and the snow removal contractor to assure minimal damage and loss of landscape amenities during the winter season. Seasonal Clean Up - A thorough spring cleanup is to be performed. This includes the removal and replacement of dead or unhealthy plant materials and the cleanup of plant debris and any general debris that has accumulated over the winter season. Mulch is to be lightly raked to clean debris from the surface without removing any mulch. Twigs and debris are to be removed from the planting beds throughout the growing season. Mulching - Planting beds shall be mulched with a treated shredded hardwood mulch free from dirt, debris, and insects. A sample of this mulch shall be given to the Owner for approval prior to installation. Maintain a 2-3” maximum depth and keep free of weeds either by hand weeding or by the use of a pre-emergent weed control such as Treflan or Serfian. Seasonal re-mulching shall occur as necessary in the spring and the fall to maintain this minimum depth. When new mulch is added to the planting bed it shall be spread to create a total depth of no more than three inches. Edges should be maintained in a cleanly edged fashion. Mulch shall not be placed directly against the trunk of any tree or shrub. B. Groundcover and Perennials Disease and Pest Management – Pesticides and herbicides should be applied only as problems occur, with the proper chemical applied only by a trained professional or in the case of pesticide, a Certified Pesticide Applicator. Plants should be monitored weekly and treated accordingly. Fertilizer – The health of the plants can be maintained or improved, and their growth encouraged by an application of complete fertilizer. Apply a fertilizer such as 4-12-4 as growth becomes apparent and before mulching. Apply to all groundcover and perennial planting areas by hand and avoid letting the fertilizer come in contact with the foliage, or use a liquid fertilizer and apply by soaking the soil. Apply according to the manufacturers’ specifications. Fertilization shall stop at the end of July. Water – Groundcovers and Perennials will need supplemental watering in order to become established, healthy plants. All new plants need to be watered once a week in cool weather, twice a week during warm weather, and up to three times in a week during periods of extreme heat and drought. Until established, groundcovers and perennials should be watered in such a manner as to totally saturate the soil in the root zone area, to a depth of 6 inches. Once established, Stormwater Report Great Island Plaza LLC West Yarmouth, MA perennials shall continue to be watered as necessary to maintain them in a vigorous healthy condition. Over-watering or constant saturation of the soil must be avoided as this could lead to root rot and other disease problems. The use of a soil moisture meter can help you monitor the soil’s water intake. On-site water shall be furnished by the Owner. Hose and other watering equipment shall be furnished by the Landscape Maintenance Contractor. Replacement – Any unhealthy plant/s that may cause widespread infestation of other nearby plants shall be immediately removed from the site. Any vegetation removed from the site must be recorded and submitted with the landscape maintenance log. The area shall be treated to prevent further infestation. The plant/s shall then be replaced with healthy specimen/s of the same species and size. Old Forge shall have a pre-established budget allowance for this type of replacement, each year. Plant material that is damaged as a result of other landscape maintenance activities, such as mowing, shall be replaced with healthy specimens of the same species and size, at no additional cost to the owner. Deadheading – Perennials shall be checked on a weekly basis and dead-headed once flowers have faded or as necessary based on plant type and duration of flower. Spent flowers can be pinched off with the thumb and forefinger. Continue to remove all faded flowers until Fall. All associated debris shall be removed from site daily. Staking – Upright-growing perennials need support especially when in flower. Use of bamboo stakes, galvanized wire hoops or mesh may be necessary for their support. Supports should be put in place before they have become too difficult to handle. The supports should not be taller than the mature height of the perennial plant. Division of Perennials – Two or three-year-old perennials are easily divided in the spring if more plants are needed. To divide, cut out the entire section of plant to be divided, including roots. The larger divisions (those with three or more shoots), can be set out immediately in their permanent location, where they can be expected to bloom the same season. Smaller divisions are best planted in an out-of-the-way planting bed until the following autumn or spring, when they can be moved to their permanent location. Weeding – All planting beds should be kept weed-free. Weed either by hand or with a pre-emergent herbicide such as Treflen used according to manufacturers’ specifications. Manual weeding is to be used in combination with the use of spot applications of herbicides. Both live and dead weeds are to be pulled and removed from the site. All herbicide applications shall be documented in the Landscape Maintenance Log. The actual product label or the manufacturer’s product specification sheet for the specific product shall also be included in the Log. Only personnel with appropriate applicator licenses shall supervise and/or perform the application of pesticide products requiring a license. Winterizing – Perennial gardens should be cleaned-up when growth ceases in the fall. Remove foliage of plants that normally die down to the ground. Divide and replant over-grown clumps. C. Lawn Areas - Turf Systems Mowing – Proper mowing is an integral part of any good turf maintenance program. Without it, the finest in fertilization, watering and other vital maintenance practices would be completely ineffective. Proper mowing will help control dicot weeds; help the turf survive during periods of extreme heat, and gain strength and vigor to resist disease and other infestations. Mowing height – The proper mowing height will vary somewhat according to the type of grass. The most common type of seed & sod lawns contains a mixture of bluegrass, fine fescue and perennial rye, which should be mowed at 2-3 inches. Stormwater Report Great Island Plaza LLC West Yarmouth, MA Mowing frequency – The basic rule of thumb for mowing frequency is to never remove more than 1/3 of the grass blade in one mowing. Example: if you want to mow your turf at 2 inches, you should cut it when it reaches 3 inches. Removing more than ½ of the grass plant at a time can put the plant into shock, thus making it more susceptible to stress disease and weed infestation. Mowing frequency will vary with the growing season and should be set by the plant height and not a set date. It will often be necessary to mow twice a week during periods of surge growth to help maintain plant health and color. Mowing should be cut back during periods of stress. Grass clippings should be removed whenever they are thick enough to layer the turf. The return of clippings to the soil actually adds nutrients and helps retain moisture. Heavily clumped grass clippings are a sign of infrequent mowing, calling for an adjustment in the mowing schedule. When mowing any area, try to alternate mowing patterns. This tends to keep grass blades more erect and assures an even cut. A dull mower will cause color loss due to tearing of the turf plant, and since mowing will ultimately determine the appearance of any turf area there is an absolute necessity for a clean sharp cut. Weed & Pest Control and Fertilizing- In order to maintain turf grass health, vigor color, and nutrients, fertilizer must be added to the soil. Recommendations for fertilization of lawn areas are as follows; fertilize at the rate of one (1) pound of nitrogen per thousand square feet, per year is optimum. Fertilizer should be a balanced slow release, sulfur coated type fertilizer. Weed Control - All turf areas will require some weed control, for both weed grasses and dicot weeds. Weeds should be treated at the appropriate time and with a material labeled for the target weed. Please refer to the fertilizer weed and pest schedule for timing. Pest Control - All turf areas will require some pest control. Pests should be treated at the appropriate time with a material labeled for the target pest. Please refer to the fertilizer, weed and pest schedule for timing. Lime - A common cause for an unhealthy lawn is acidic soil. When the PH is below the neutral range (between 6-7) vital plant nutrients become fixed in the soil and cannot be absorbed by the grass plant. Lime corrects an acid soil condition, supplies calcium for plant growth and improves air and water circulation. Limestone applied at the rate of 50 lbs. per thousand square feet will adjust the soil PH one point over a period of 6-9 months. D. Fertilizer, Weed & Pest Control Schedule – Turf Systems Spring - Fertilize one (1) pound of nitrogen per 1,000 square feet (April) Pre-emergent weed grass control Broadleaf weed control Late Spring - Fertilize one (1) pound of nitrogen per 1,000 square feet (June) Pre-emergent weed grass control Broadleaf weed control Insect Control (if needed) *Summer - Fertilize one (1) pound of nitrogen per 1,000 square feet (August) Broadleaf weed control (if needed) Insect Control (if needed) Fall - Fertilize one (1) pound of nitrogen per 1,000 square feet (September) *Omit if area is not to be irrigated Lawn Maintenance Task Schedule Stormwater Report Great Island Plaza LLC West Yarmouth, MA MARCH (Weather permitting)  Clean up winter debris, sand, leaves, trash etc.  Re-edge mulch beds, maintain at 2-3” maximum.  Fertilize plants  Aerate and thatch turf (conditions permitting) APRIL  Reseed or sod all areas needing attention.  Fertilize and weed control  Lime  Start mowing when grass reaches 2-1/2”, mow to 2” MAY  Mow turf to 2-2-1/2”  Weed as necessary.  Check for disease and pest problems in both turf and plants. JUNE  Mow turf to 2-1/2” – 3”  Fertilize and weed control.  Weed  Check for disease and pest problems in both turf and plants, treat as necessary. PROVISIONS FOR SOLID WASTE MANAGEMENT (SITE TRASH) Trash will be placed in on-site dumpsters and the Owner will make provisions for its regular and timely removal. SNOW DISPOSAL AND PLOWING PLANS The purpose of the snow and snowmelt management plan is to provide guidelines regarding snow disposal site selection, site preparation and maintenance that are acceptable to the Department of Environmental Protection. For the areas that require snow removal, snow storage onsite will largely be accomplished by using pervious areas along the shoulder of the roadway and development as windrowed by plows.  Avoid dumping of snow into any water body, including rivers, ponds, or wetlands. In addition to water quality impacts and flooding, snow disposed of in open water can cause navigational hazards when it freezes into ice blocks.  Avoid disposing of snow on top of storm drain catch basins or in stormwater basins. Snow combined with sand and debris may block a storm drainage system, causing localized flooding. A high volume of sand, sediment, and litter released from melting snow also may be quickly transported through the system into surface water.  In significant storm events, the melting or off-site trucking of snow may be implemented. These activities shall be conducted in accordance with all local, state and federal regulations. WINTER ROAD SALT AND/OR SAND USE AND STORAGE RESTRICTIONS The applicant will be responsible for sanding and salting the site. No storage on site. STREET SWEEPING SCHEDULES Stormwater Report Great Island Plaza LLC West Yarmouth, MA There are three types of sweepers: Mechanical, Regenerative Air, and Vacuum Filter. 1) Mechanical: Mechanical sweepers use brooms or rotary brushes to scour the pavement. 2) Regenerative Air: These sweepers blow air onto the road or parking lot surface, causing fines to rise where they are vacuumed. 3) Vacuum filter: These sweepers remove fines along roads. Two general types of vacuum filter sweepers are available - wet and dry. The dry type uses a broom in combination with the vacuum. The wet type uses water for dust suppression Regardless of the type chosen, the efficiency of street sweeping is increased when sweepers are operated in tandem. This project has not included street sweeping as part of the TSS removal calculations. However, it is recommended that street sweeping of the parking areas occur four times a year, including once after the spring snow melt. Reuse and Disposal of Street Sweepings Once removed from paved surfaces, the sweepings must be handled and disposed of properly. Mass DEP’s Bureau of Waste Prevention has issued a written policy regarding the reuse and disposal of street sweepings. These sweepings are regulated as a solid waste, and can be used in three ways:  In one of the ways already approved by Mass DEP (e.g., daily cover in a landfill, additive to compost, fill in a public way)  If approved under a Beneficial Use Determination  Disposed in a landfill TRAINING OF STAFF OR PERSONNEL INVOLVED WITH IMPLEMENTING LONG-TERM POLLUTION PREVENTION PLAN The Long-Term Pollution Prevention Plan is to be implemented by property owner of the site. Trained and, if required, licensed Professionals are to be hired by the owner as applicable to implement the Long-Term Pollution Prevention Plan. LIST OF EMERGENCY CONTACTS FOR IMPLEMENTING LONG-TERM POLLUTION PREVENTION PLAN The applicant will be required to implement the Long-Term Pollution Prevention Plan and will create and maintain a list of emergency contacts. Stormwater Report Great Island Plaza LLC West Yarmouth, MA POST CONSTRUCTION PHASE INSPECTION SCHEDULE AND EVALUATION CHECKLIST Inspection Date Inspector BMP Inspected Inspection Frequency Requirements Comments Recommendation Follow-up Inspection Required (yes/no) Catch Basins Four times a year Water Quality Units Four times a year Infiltration Systems Twice a year Bio-Retention Area Twice a year 1. Refer to the Massachusetts Stormwater Handbook Volume Two: Stormwater Technical Handbook (February 2008) for recommendations regarding frequency for inspections and maintenance of specific BMP’s 2. Inspections to be conducted by a qualified professional such as an environmental scientist or civil engineer. 3. Limited or no use of sodium chloride salts, fertilizers or pesticides recommended. 4. Other Notes: (Include deviations from Conservation Commission Approvals, Planning Board Approvals and Approved Plans) Stormwater Report Great Island Plaza LLC West Yarmouth, MA SECTION 6.0 HYDROLOGY CALCULATIONS Stormwater Report Great Island Plaza LLC West Yarmouth, MA 6.01 EXISTING WATERSHED PLAN Stormwater Report Great Island Plaza LLC West Yarmouth, MA 6.02 EXISTING HYDROLOGY CALCULATIONS (HYDROCAD™ PRINTOUTS) 1S Subcatchment Area 1 2S Subcatchment Area 2 3S Subcatchment Area 3 1R Area off-site - Northwest 2R Area off-site - Southwest 3R Area off-site - East Routing Diagram for 5035001-Pre Prepared by BSC Group, Printed 7/7/2020 HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Subcat Reach Pond Link Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 2HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=11,584 sf 12.31% Impervious Runoff Depth=0.12"Subcatchment 1S: Subcatchment Area 1 Tc=6.0 min CN=46 Runoff=0.00 cfs 0.003 af Runoff Area=20,781 sf 62.10% Impervious Runoff Depth=1.72"Subcatchment 2S: Subcatchment Area 2 Tc=6.0 min CN=80 Runoff=0.96 cfs 0.068 af Runoff Area=56,653 sf 39.49% Impervious Runoff Depth=0.86"Subcatchment 3S: Subcatchment Area 3 Tc=6.0 min CN=66 Runoff=1.13 cfs 0.093 af Inflow=0.00 cfs 0.003 afReach 1R: Area off-site - Northwest Outflow=0.00 cfs 0.003 af Inflow=0.96 cfs 0.068 afReach 2R: Area off-site - Southwest Outflow=0.96 cfs 0.068 af Inflow=1.13 cfs 0.093 afReach 3R: Area off-site - East Outflow=1.13 cfs 0.093 af Total Runoff Area = 2.044 ac Runoff Volume = 0.164 af Average Runoff Depth = 0.96" 58.77% Pervious = 1.201 ac 41.23% Impervious = 0.843 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 3HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Subcatchment Area 1 Runoff = 0.00 cfs @ 13.66 hrs, Volume= 0.003 af, Depth= 0.12" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 1,426 98 Roofs, HSG A 10,158 39 >75% Grass cover, Good, HSG A 11,584 46 Weighted Average 10,158 87.69% Pervious Area 1,426 12.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Subcatchment Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.005 0.005 0.005 0.004 0.004 0.004 0.004 0.004 0.003 0.003 0.003 0.003 0.003 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.000 0.000 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=11,584 sf Runoff Volume=0.003 af Runoff Depth=0.12" Tc=6.0 min CN=46 0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 4HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Subcatchment Area 2 Runoff = 0.96 cfs @ 12.09 hrs, Volume= 0.068 af, Depth= 1.72" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 7,661 98 Paved parking, HSG A 1,471 96 Gravel surface, HSG A 227 98 Unconnected pavement, HSG A 5,018 98 Roofs, HSG A 6,404 39 >75% Grass cover, Good, HSG A 20,781 80 Weighted Average 7,875 37.90% Pervious Area 12,906 62.10% Impervious Area 227 1.76% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Subcatchment Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=20,781 sf Runoff Volume=0.068 af Runoff Depth=1.72" Tc=6.0 min CN=80 0.96 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 5HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Subcatchment Area 3 Runoff = 1.13 cfs @ 12.10 hrs, Volume= 0.093 af, Depth= 0.86" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 14,823 98 Paved parking, HSG A 3,806 96 Gravel surface, HSG A 1,868 98 Unconnected pavement, HSG A 5,683 98 Roofs, HSG A 30,473 39 >75% Grass cover, Good, HSG A 56,653 66 Weighted Average 34,279 60.51% Pervious Area 22,374 39.49% Impervious Area 1,868 8.35% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Subcatchment Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=56,653 sf Runoff Volume=0.093 af Runoff Depth=0.86" Tc=6.0 min CN=66 1.13 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 6HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.266 ac, 12.31% Impervious, Inflow Depth = 0.12" for 2-year event Inflow = 0.00 cfs @ 13.66 hrs, Volume= 0.003 af Outflow = 0.00 cfs @ 13.66 hrs, Volume= 0.003 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.005 0.005 0.005 0.004 0.004 0.004 0.004 0.004 0.003 0.003 0.003 0.003 0.003 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.000 0.000 0 Inflow Area=0.266 ac 0.00 cfs0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 7HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.477 ac, 62.10% Impervious, Inflow Depth = 1.72" for 2-year event Inflow = 0.96 cfs @ 12.09 hrs, Volume= 0.068 af Outflow = 0.96 cfs @ 12.09 hrs, Volume= 0.068 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.477 ac 0.96 cfs0.96 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 8HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 1.301 ac, 39.49% Impervious, Inflow Depth = 0.86" for 2-year event Inflow = 1.13 cfs @ 12.10 hrs, Volume= 0.093 af Outflow = 1.13 cfs @ 12.10 hrs, Volume= 0.093 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.301 ac 1.13 cfs1.13 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 9HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=11,584 sf 12.31% Impervious Runoff Depth=0.42"Subcatchment 1S: Subcatchment Area 1 Tc=6.0 min CN=46 Runoff=0.05 cfs 0.009 af Runoff Area=20,781 sf 62.10% Impervious Runoff Depth=2.72"Subcatchment 2S: Subcatchment Area 2 Tc=6.0 min CN=80 Runoff=1.52 cfs 0.108 af Runoff Area=56,653 sf 39.49% Impervious Runoff Depth=1.59"Subcatchment 3S: Subcatchment Area 3 Tc=6.0 min CN=66 Runoff=2.31 cfs 0.173 af Inflow=0.05 cfs 0.009 afReach 1R: Area off-site - Northwest Outflow=0.05 cfs 0.009 af Inflow=1.52 cfs 0.108 afReach 2R: Area off-site - Southwest Outflow=1.52 cfs 0.108 af Inflow=2.31 cfs 0.173 afReach 3R: Area off-site - East Outflow=2.31 cfs 0.173 af Total Runoff Area = 2.044 ac Runoff Volume = 0.290 af Average Runoff Depth = 1.70" 58.77% Pervious = 1.201 ac 41.23% Impervious = 0.843 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 10HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Subcatchment Area 1 Runoff = 0.05 cfs @ 12.30 hrs, Volume= 0.009 af, Depth= 0.42" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 1,426 98 Roofs, HSG A 10,158 39 >75% Grass cover, Good, HSG A 11,584 46 Weighted Average 10,158 87.69% Pervious Area 1,426 12.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Subcatchment Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 10-year Rainfall=4.80" Runoff Area=11,584 sf Runoff Volume=0.009 af Runoff Depth=0.42" Tc=6.0 min CN=46 0.05 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 11HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Subcatchment Area 2 Runoff = 1.52 cfs @ 12.09 hrs, Volume= 0.108 af, Depth= 2.72" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 7,661 98 Paved parking, HSG A 1,471 96 Gravel surface, HSG A 227 98 Unconnected pavement, HSG A 5,018 98 Roofs, HSG A 6,404 39 >75% Grass cover, Good, HSG A 20,781 80 Weighted Average 7,875 37.90% Pervious Area 12,906 62.10% Impervious Area 227 1.76% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Subcatchment Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=20,781 sf Runoff Volume=0.108 af Runoff Depth=2.72" Tc=6.0 min CN=80 1.52 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 12HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Subcatchment Area 3 Runoff = 2.31 cfs @ 12.10 hrs, Volume= 0.173 af, Depth= 1.59" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 14,823 98 Paved parking, HSG A 3,806 96 Gravel surface, HSG A 1,868 98 Unconnected pavement, HSG A 5,683 98 Roofs, HSG A 30,473 39 >75% Grass cover, Good, HSG A 56,653 66 Weighted Average 34,279 60.51% Pervious Area 22,374 39.49% Impervious Area 1,868 8.35% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Subcatchment Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=56,653 sf Runoff Volume=0.173 af Runoff Depth=1.59" Tc=6.0 min CN=66 2.31 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 13HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.266 ac, 12.31% Impervious, Inflow Depth = 0.42" for 10-year event Inflow = 0.05 cfs @ 12.30 hrs, Volume= 0.009 af Outflow = 0.05 cfs @ 12.30 hrs, Volume= 0.009 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=0.266 ac 0.05 cfs0.05 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 14HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.477 ac, 62.10% Impervious, Inflow Depth = 2.72" for 10-year event Inflow = 1.52 cfs @ 12.09 hrs, Volume= 0.108 af Outflow = 1.52 cfs @ 12.09 hrs, Volume= 0.108 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.477 ac 1.52 cfs1.52 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 15HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 1.301 ac, 39.49% Impervious, Inflow Depth = 1.59" for 10-year event Inflow = 2.31 cfs @ 12.10 hrs, Volume= 0.173 af Outflow = 2.31 cfs @ 12.10 hrs, Volume= 0.173 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=1.301 ac 2.31 cfs2.31 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 16HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=11,584 sf 12.31% Impervious Runoff Depth=0.74"Subcatchment 1S: Subcatchment Area 1 Tc=6.0 min CN=46 Runoff=0.14 cfs 0.017 af Runoff Area=20,781 sf 62.10% Impervious Runoff Depth=3.51"Subcatchment 2S: Subcatchment Area 2 Tc=6.0 min CN=80 Runoff=1.96 cfs 0.140 af Runoff Area=56,653 sf 39.49% Impervious Runoff Depth=2.22"Subcatchment 3S: Subcatchment Area 3 Tc=6.0 min CN=66 Runoff=3.31 cfs 0.241 af Inflow=0.14 cfs 0.017 afReach 1R: Area off-site - Northwest Outflow=0.14 cfs 0.017 af Inflow=1.96 cfs 0.140 afReach 2R: Area off-site - Southwest Outflow=1.96 cfs 0.140 af Inflow=3.31 cfs 0.241 afReach 3R: Area off-site - East Outflow=3.31 cfs 0.241 af Total Runoff Area = 2.044 ac Runoff Volume = 0.397 af Average Runoff Depth = 2.33" 58.77% Pervious = 1.201 ac 41.23% Impervious = 0.843 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 17HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Subcatchment Area 1 Runoff = 0.14 cfs @ 12.13 hrs, Volume= 0.017 af, Depth= 0.74" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 1,426 98 Roofs, HSG A 10,158 39 >75% Grass cover, Good, HSG A 11,584 46 Weighted Average 10,158 87.69% Pervious Area 1,426 12.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Subcatchment Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 25-year Rainfall=5.70" Runoff Area=11,584 sf Runoff Volume=0.017 af Runoff Depth=0.74" Tc=6.0 min CN=46 0.14 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 18HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Subcatchment Area 2 Runoff = 1.96 cfs @ 12.09 hrs, Volume= 0.140 af, Depth= 3.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 7,661 98 Paved parking, HSG A 1,471 96 Gravel surface, HSG A 227 98 Unconnected pavement, HSG A 5,018 98 Roofs, HSG A 6,404 39 >75% Grass cover, Good, HSG A 20,781 80 Weighted Average 7,875 37.90% Pervious Area 12,906 62.10% Impervious Area 227 1.76% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Subcatchment Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=20,781 sf Runoff Volume=0.140 af Runoff Depth=3.51" Tc=6.0 min CN=80 1.96 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 19HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Subcatchment Area 3 Runoff = 3.31 cfs @ 12.09 hrs, Volume= 0.241 af, Depth= 2.22" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 14,823 98 Paved parking, HSG A 3,806 96 Gravel surface, HSG A 1,868 98 Unconnected pavement, HSG A 5,683 98 Roofs, HSG A 30,473 39 >75% Grass cover, Good, HSG A 56,653 66 Weighted Average 34,279 60.51% Pervious Area 22,374 39.49% Impervious Area 1,868 8.35% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Subcatchment Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=56,653 sf Runoff Volume=0.241 af Runoff Depth=2.22" Tc=6.0 min CN=66 3.31 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 20HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.266 ac, 12.31% Impervious, Inflow Depth = 0.74" for 25-year event Inflow = 0.14 cfs @ 12.13 hrs, Volume= 0.017 af Outflow = 0.14 cfs @ 12.13 hrs, Volume= 0.017 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 Inflow Area=0.266 ac 0.14 cfs0.14 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 21HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.477 ac, 62.10% Impervious, Inflow Depth = 3.51" for 25-year event Inflow = 1.96 cfs @ 12.09 hrs, Volume= 0.140 af Outflow = 1.96 cfs @ 12.09 hrs, Volume= 0.140 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.477 ac 1.96 cfs1.96 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 22HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 1.301 ac, 39.49% Impervious, Inflow Depth = 2.22" for 25-year event Inflow = 3.31 cfs @ 12.09 hrs, Volume= 0.241 af Outflow = 3.31 cfs @ 12.09 hrs, Volume= 0.241 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=1.301 ac 3.31 cfs3.31 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 23HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=11,584 sf 12.31% Impervious Runoff Depth=1.37"Subcatchment 1S: Subcatchment Area 1 Tc=6.0 min CN=46 Runoff=0.34 cfs 0.030 af Runoff Area=20,781 sf 62.10% Impervious Runoff Depth=4.79"Subcatchment 2S: Subcatchment Area 2 Tc=6.0 min CN=80 Runoff=2.65 cfs 0.190 af Runoff Area=56,653 sf 39.49% Impervious Runoff Depth=3.28"Subcatchment 3S: Subcatchment Area 3 Tc=6.0 min CN=66 Runoff=4.98 cfs 0.356 af Inflow=0.34 cfs 0.030 afReach 1R: Area off-site - Northwest Outflow=0.34 cfs 0.030 af Inflow=2.65 cfs 0.190 afReach 2R: Area off-site - Southwest Outflow=2.65 cfs 0.190 af Inflow=4.98 cfs 0.356 afReach 3R: Area off-site - East Outflow=4.98 cfs 0.356 af Total Runoff Area = 2.044 ac Runoff Volume = 0.576 af Average Runoff Depth = 3.39" 58.77% Pervious = 1.201 ac 41.23% Impervious = 0.843 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 24HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Subcatchment Area 1 Runoff = 0.34 cfs @ 12.11 hrs, Volume= 0.030 af, Depth= 1.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 1,426 98 Roofs, HSG A 10,158 39 >75% Grass cover, Good, HSG A 11,584 46 Weighted Average 10,158 87.69% Pervious Area 1,426 12.31% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Subcatchment Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=11,584 sf Runoff Volume=0.030 af Runoff Depth=1.37" Tc=6.0 min CN=46 0.34 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 25HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Subcatchment Area 2 Runoff = 2.65 cfs @ 12.09 hrs, Volume= 0.190 af, Depth= 4.79" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 7,661 98 Paved parking, HSG A 1,471 96 Gravel surface, HSG A 227 98 Unconnected pavement, HSG A 5,018 98 Roofs, HSG A 6,404 39 >75% Grass cover, Good, HSG A 20,781 80 Weighted Average 7,875 37.90% Pervious Area 12,906 62.10% Impervious Area 227 1.76% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Subcatchment Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=20,781 sf Runoff Volume=0.190 af Runoff Depth=4.79" Tc=6.0 min CN=80 2.65 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 26HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Subcatchment Area 3 Runoff = 4.98 cfs @ 12.09 hrs, Volume= 0.356 af, Depth= 3.28" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 14,823 98 Paved parking, HSG A 3,806 96 Gravel surface, HSG A 1,868 98 Unconnected pavement, HSG A 5,683 98 Roofs, HSG A 30,473 39 >75% Grass cover, Good, HSG A 56,653 66 Weighted Average 34,279 60.51% Pervious Area 22,374 39.49% Impervious Area 1,868 8.35% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Subcatchment Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=56,653 sf Runoff Volume=0.356 af Runoff Depth=3.28" Tc=6.0 min CN=66 4.98 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 27HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.266 ac, 12.31% Impervious, Inflow Depth = 1.37" for 100-year event Inflow = 0.34 cfs @ 12.11 hrs, Volume= 0.030 af Outflow = 0.34 cfs @ 12.11 hrs, Volume= 0.030 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.266 ac 0.34 cfs0.34 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 28HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.477 ac, 62.10% Impervious, Inflow Depth = 4.79" for 100-year event Inflow = 2.65 cfs @ 12.09 hrs, Volume= 0.190 af Outflow = 2.65 cfs @ 12.09 hrs, Volume= 0.190 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.477 ac 2.65 cfs2.65 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Pre Printed 7/7/2020Prepared by BSC Group Page 29HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 1.301 ac, 39.49% Impervious, Inflow Depth = 3.28" for 100-year event Inflow = 4.98 cfs @ 12.09 hrs, Volume= 0.356 af Outflow = 4.98 cfs @ 12.09 hrs, Volume= 0.356 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)5 4 3 2 1 0 Inflow Area=1.301 ac 4.98 cfs4.98 cfs Stormwater Report Great Island Plaza LLC West Yarmouth, MA 6.03 PROPOSED WATERSHED PLAN Stormwater Report Great Island Plaza LLC West Yarmouth, MA 6.04 PROPOSED HYDROLOGY CALCULATIONS (HYDROCAD™ PRINTOUTS) 1S Area 1 2S Area 2 3S Area 3 4S Area 4 5S Area 5 6S Areaa 6 7S Area 7 8S Area 8 9S Area 9 10S Post Office 1R Area off-site - Northwest 2R Area off-site - Southwest 3R Area off-site - East 1P Infiltration System #1 2P Infiltration System #2 3P Infiltration System #3 4P Infiltration System #4 5P Drywell RG Rain Garden Routing Diagram for 5035001-Post Prepared by BSC Group, Printed 7/7/2020 HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Subcat Reach Pond Link Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 2HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=18,860 sf 73.65% Impervious Runoff Depth=1.87"Subcatchment 1S: Area 1 Tc=6.0 min CN=82 Runoff=0.95 cfs 0.067 af Runoff Area=12,953 sf 94.80% Impervious Runoff Depth=3.04"Subcatchment 2S: Area 2 Tc=6.0 min CN=95 Runoff=0.99 cfs 0.075 af Runoff Area=6,468 sf 95.41% Impervious Runoff Depth=3.04"Subcatchment 3S: Area 3 Tc=6.0 min CN=95 Runoff=0.50 cfs 0.038 af Runoff Area=6,407 sf 91.21% Impervious Runoff Depth=2.83"Subcatchment 4S: Area 4 Tc=6.0 min CN=93 Runoff=0.47 cfs 0.035 af Runoff Area=9,313 sf 35.54% Impervious Runoff Depth=0.58"Subcatchment 5S: Area 5 Tc=6.0 min CN=60 Runoff=0.10 cfs 0.010 af Runoff Area=12,473 sf 78.89% Impervious Runoff Depth=2.19"Subcatchment 6S: Areaa 6 Tc=6.0 min CN=86 Runoff=0.73 cfs 0.052 af Runoff Area=1,469 sf 5.58% Impervious Runoff Depth=0.03"Subcatchment 7S: Area 7 Tc=6.0 min UI Adjusted CN=41 Runoff=0.00 cfs 0.000 af Runoff Area=7,408 sf 41.74% Impervious Runoff Depth=0.76"Subcatchment 8S: Area 8 Tc=6.0 min CN=64 Runoff=0.12 cfs 0.011 af Runoff Area=12,120 sf 67.51% Impervious Runoff Depth=1.64"Subcatchment 9S: Area 9 Tc=6.0 min CN=79 Runoff=0.53 cfs 0.038 af Runoff Area=1,548 sf 100.00% Impervious Runoff Depth=3.37"Subcatchment 10S: Post Office Tc=6.0 min CN=98 Runoff=0.12 cfs 0.010 af Inflow=0.00 cfs 0.000 afReach 1R: Area off-site - Northwest Outflow=0.00 cfs 0.000 af Inflow=0.12 cfs 0.011 afReach 2R: Area off-site - Southwest Outflow=0.12 cfs 0.011 af Inflow=0.53 cfs 0.038 afReach 3R: Area off-site - East Outflow=0.53 cfs 0.038 af Peak Elev=12.00' Storage=0.014 af Inflow=1.09 cfs 0.086 afPond 1P: Infiltration System #1 Outflow=0.31 cfs 0.086 af Peak Elev=12.15' Storage=841 cf Inflow=1.49 cfs 0.074 afPond 2P: Infiltration System #2 Outflow=0.42 cfs 0.075 af Peak Elev=13.26' Storage=0.007 af Inflow=0.50 cfs 0.038 afPond 3P: Infiltration System #3 Outflow=0.13 cfs 0.038 af Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 3HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Peak Elev=14.04' Storage=0.008 af Inflow=0.47 cfs 0.035 afPond 4P: Infiltration System #4 Outflow=0.11 cfs 0.035 af Peak Elev=11.76' Storage=0.001 af Inflow=0.12 cfs 0.010 afPond 5P: Drywell Outflow=0.04 cfs 0.010 af Peak Elev=15.95' Storage=363 cf Inflow=0.95 cfs 0.067 afPond RG: Rain Garden Discarded=0.10 cfs 0.045 af Primary=0.79 cfs 0.022 af Outflow=0.89 cfs 0.067 af Total Runoff Area = 2.044 ac Runoff Volume = 0.336 af Average Runoff Depth = 1.97" 27.84% Pervious = 0.569 ac 72.16% Impervious = 1.475 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 4HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Area 1 Runoff = 0.95 cfs @ 12.09 hrs, Volume= 0.067 af, Depth= 1.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 13,045 98 Paved parking, HSG A 4,970 39 >75% Grass cover, Good, HSG A 845 98 Water Surface, HSG A 18,860 82 Weighted Average 4,970 26.35% Pervious Area 13,890 73.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=18,860 sf Runoff Volume=0.067 af Runoff Depth=1.87" Tc=6.0 min CN=82 0.95 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 5HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Area 2 Runoff = 0.99 cfs @ 12.08 hrs, Volume= 0.075 af, Depth= 3.04" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 12,280 98 Paved parking, HSG A 673 39 >75% Grass cover, Good, HSG A 12,953 95 Weighted Average 673 5.20% Pervious Area 12,280 94.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=12,953 sf Runoff Volume=0.075 af Runoff Depth=3.04" Tc=6.0 min CN=95 0.99 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 6HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Area 3 Runoff = 0.50 cfs @ 12.08 hrs, Volume= 0.038 af, Depth= 3.04" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 6,171 98 Unconnected pavement, HSG A 297 39 >75% Grass cover, Good, HSG A 6,468 95 Weighted Average 297 4.59% Pervious Area 6,171 95.41% Impervious Area 6,171 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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-year Rainfall=3.60" Runoff Area=6,468 sf Runoff Volume=0.038 af Runoff Depth=3.04" Tc=6.0 min CN=95 0.50 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 7HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Area 4 Runoff = 0.47 cfs @ 12.08 hrs, Volume= 0.035 af, Depth= 2.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 5,844 98 Unconnected pavement, HSG A 563 39 >75% Grass cover, Good, HSG A 6,407 93 Weighted Average 563 8.79% Pervious Area 5,844 91.21% Impervious Area 5,844 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Area 4 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.52 0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=6,407 sf Runoff Volume=0.035 af Runoff Depth=2.83" Tc=6.0 min CN=93 0.47 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 8HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Area 5 Runoff = 0.10 cfs @ 12.11 hrs, Volume= 0.010 af, Depth= 0.58" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 3,310 98 Unconnected pavement, HSG A 6,003 39 >75% Grass cover, Good, HSG A 9,313 60 Weighted Average 6,003 64.46% Pervious Area 3,310 35.54% Impervious Area 3,310 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Area 5 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.11 0.105 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 2-year Rainfall=3.60" Runoff Area=9,313 sf Runoff Volume=0.010 af Runoff Depth=0.58" Tc=6.0 min CN=60 0.10 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 9HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Areaa 6 Runoff = 0.73 cfs @ 12.09 hrs, Volume= 0.052 af, Depth= 2.19" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 9,840 98 Unconnected pavement, HSG A 2,633 39 >75% Grass cover, Good, HSG A 12,473 86 Weighted Average 2,633 21.11% Pervious Area 9,840 78.89% Impervious Area 9,840 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 6S: Areaa 6 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 2-year Rainfall=3.60" Runoff Area=12,473 sf Runoff Volume=0.052 af Runoff Depth=2.19" Tc=6.0 min CN=86 0.73 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 10HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: Area 7 Runoff = 0.00 cfs @ 16.70 hrs, Volume= 0.000 af, Depth= 0.03" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Adj Description 82 98 Unconnected pavement, HSG A 1,387 39 >75% Grass cover, Good, HSG A 1,469 42 41 Weighted Average, UI Adjusted 1,387 94.42% Pervious Area 82 5.58% Impervious Area 82 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 7S: Area 7 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.000 0.000 0.000 0.000 0.000 0.000 0 0 0 0 0 0 0 0 0 0 Type III 24-hr 2-year Rainfall=3.60" Runoff Area=1,469 sf Runoff Volume=0.000 af Runoff Depth=0.03" Tc=6.0 min UI Adjusted CN=41 0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 11HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Area 8 Runoff = 0.12 cfs @ 12.10 hrs, Volume= 0.011 af, Depth= 0.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 3,092 98 Unconnected pavement, HSG A 4,316 39 >75% Grass cover, Good, HSG A 7,408 64 Weighted Average 4,316 58.26% Pervious Area 3,092 41.74% Impervious Area 3,092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 8S: Area 8 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 2-year Rainfall=3.60" Runoff Area=7,408 sf Runoff Volume=0.011 af Runoff Depth=0.76" Tc=6.0 min CN=64 0.12 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 12HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: Area 9 Runoff = 0.53 cfs @ 12.09 hrs, Volume= 0.038 af, Depth= 1.64" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 8,182 98 Unconnected pavement, HSG A 3,938 39 >75% Grass cover, Good, HSG A 12,120 79 Weighted Average 3,938 32.49% Pervious Area 8,182 67.51% Impervious Area 8,182 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 9S: Area 9 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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-year Rainfall=3.60" Runoff Area=12,120 sf Runoff Volume=0.038 af Runoff Depth=1.64" Tc=6.0 min CN=79 0.53 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 13HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 10S: Post Office Runoff = 0.12 cfs @ 12.08 hrs, Volume= 0.010 af, Depth= 3.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 2-year Rainfall=3.60" Area (sf) CN Description 1,548 98 Roofs, HSG A 1,548 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Post Office Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 2-year Rainfall=3.60" Runoff Area=1,548 sf Runoff Volume=0.010 af Runoff Depth=3.37" Tc=6.0 min CN=98 0.12 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 14HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.034 ac, 5.58% Impervious, Inflow Depth = 0.03" for 2-year event Inflow = 0.00 cfs @ 16.70 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 16.70 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.000 0.000 0.000 0.000 0.000 0.000 0 0 0 0 0 0 0 0 0 0 Inflow Area=0.034 ac 0.00 cfs0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 15HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.170 ac, 41.74% Impervious, Inflow Depth = 0.76" for 2-year event Inflow = 0.12 cfs @ 12.10 hrs, Volume= 0.011 af Outflow = 0.12 cfs @ 12.10 hrs, Volume= 0.011 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 Inflow Area=0.170 ac 0.12 cfs0.12 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 16HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.278 ac, 67.51% Impervious, Inflow Depth = 1.64" for 2-year event Inflow = 0.53 cfs @ 12.09 hrs, Volume= 0.038 af Outflow = 0.53 cfs @ 12.09 hrs, Volume= 0.038 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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=0.278 ac 0.53 cfs0.53 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 17HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 1P: Infiltration System #1 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=535) Inflow Area = 0.511 ac, 70.02% Impervious, Inflow Depth = 2.01" for 2-year event Inflow = 1.09 cfs @ 12.09 hrs, Volume= 0.086 af Outflow = 0.31 cfs @ 12.44 hrs, Volume= 0.086 af, Atten= 71%, Lag= 21.2 min Discarded = 0.31 cfs @ 12.44 hrs, Volume= 0.086 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.00' @ 12.44 hrs Surf.Area= 0.035 ac Storage= 0.014 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 8.9 min ( 801.7 - 792.8 ) Volume Invert Avail.Storage Storage Description #1A 11.25' 0.030 af 25.67'W x 59.50'L x 3.54'H Field A 0.124 af Overall - 0.049 af Embedded = 0.075 af x 40.0% Voids #2A 11.75' 0.049 af Cultec R-330XLHD x 40 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 0.079 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.25'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.31 cfs @ 12.44 hrs HW=12.00' (Free Discharge) 1=Exfiltration ( Controls 0.31 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 18HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 8 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 57.50' Row Length +12.0" End Stone x 2 = 59.50' Base Length 5 Rows x 52.0" Wide + 6.0" Spacing x 4 + 12.0" Side Stone x 2 = 25.67' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 40 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 5 Rows = 2,142.2 cf Chamber Storage 5,408.7 cf Field - 2,142.2 cf Chambers = 3,266.6 cf Stone x 40.0% Voids = 1,306.6 cf Stone Storage Chamber Storage + Stone Storage = 3,448.8 cf = 0.079 af Overall Storage Efficiency = 63.8% Overall System Size = 59.50' x 25.67' x 3.54' 40 Chambers 200.3 cy Field 121.0 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 19HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.511 ac Peak Elev=12.00' Storage=0.014 af 1.09 cfs 0.31 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 20HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 2P: Infiltration System #2 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=538) Inflow Area = 0.719 ac, 75.73% Impervious, Inflow Depth = 1.24" for 2-year event Inflow = 1.49 cfs @ 12.10 hrs, Volume= 0.074 af Outflow = 0.42 cfs @ 12.46 hrs, Volume= 0.075 af, Atten= 72%, Lag= 21.2 min Discarded = 0.42 cfs @ 12.46 hrs, Volume= 0.075 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.15' @ 12.46 hrs Surf.Area= 2,028 sf Storage= 841 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 12.6 min ( 805.7 - 793.1 ) Volume Invert Avail.Storage Storage Description #1A 11.40' 1,720 cf 30.50'W x 66.50'L x 3.54'H Field A 7,183 cf Overall - 2,884 cf Embedded = 4,300 cf x 40.0% Voids #2A 11.90' 2,884 cf Cultec R-330XLHD x 54 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 4,603 cf Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.40'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.42 cfs @ 12.46 hrs HW=12.15' (Free Discharge) 1=Exfiltration ( Controls 0.42 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 21HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 9 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 64.50' Row Length +12.0" End Stone x 2 = 66.50' Base Length 6 Rows x 52.0" Wide + 6.0" Spacing x 5 + 12.0" Side Stone x 2 = 30.50' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 54 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 6 Rows = 2,883.5 cf Chamber Storage 7,183.4 cf Field - 2,883.5 cf Chambers = 4,299.8 cf Stone x 40.0% Voids = 1,719.9 cf Stone Storage Chamber Storage + Stone Storage = 4,603.5 cf = 0.106 af Overall Storage Efficiency = 64.1% Overall System Size = 66.50' x 30.50' x 3.54' 54 Chambers 266.1 cy Field 159.3 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 22HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.719 ac Peak Elev=12.15' Storage=841 cf 1.49 cfs 0.42 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 23HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 3P: Infiltration System #3 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=524) Inflow Area = 0.148 ac, 95.41% Impervious, Inflow Depth = 3.04" for 2-year event Inflow = 0.50 cfs @ 12.08 hrs, Volume= 0.038 af Outflow = 0.13 cfs @ 12.45 hrs, Volume= 0.038 af, Atten= 74%, Lag= 22.0 min Discarded = 0.13 cfs @ 12.45 hrs, Volume= 0.038 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 13.26' @ 12.45 hrs Surf.Area= 0.014 ac Storage= 0.007 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 12.1 min ( 789.5 - 777.4 ) Volume Invert Avail.Storage Storage Description #1A 12.37' 0.013 af 16.00'W x 38.50'L x 3.54'H Field A 0.050 af Overall - 0.019 af Embedded = 0.031 af x 40.0% Voids #2A 12.87' 0.019 af Cultec R-330XLHD x 15 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.031 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.37'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.13 cfs @ 12.45 hrs HW=13.26' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 24HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 5 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 36.50' Row Length +12.0" End Stone x 2 = 38.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 15 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 815.9 cf Chamber Storage 2,181.7 cf Field - 815.9 cf Chambers = 1,365.8 cf Stone x 40.0% Voids = 546.3 cf Stone Storage Chamber Storage + Stone Storage = 1,362.2 cf = 0.031 af Overall Storage Efficiency = 62.4% Overall System Size = 38.50' x 16.00' x 3.54' 15 Chambers 80.8 cy Field 50.6 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 25HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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=0.148 ac Peak Elev=13.26' Storage=0.007 af 0.50 cfs 0.13 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 26HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 4P: Infiltration System #4 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=504) Inflow Area = 0.147 ac, 91.21% Impervious, Inflow Depth = 2.83" for 2-year event Inflow = 0.47 cfs @ 12.08 hrs, Volume= 0.035 af Outflow = 0.11 cfs @ 12.49 hrs, Volume= 0.035 af, Atten= 78%, Lag= 24.3 min Discarded = 0.11 cfs @ 12.49 hrs, Volume= 0.035 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 14.04' @ 12.49 hrs Surf.Area= 0.012 ac Storage= 0.008 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 17.1 min ( 805.7 - 788.7 ) Volume Invert Avail.Storage Storage Description #1A 12.95' 0.010 af 16.00'W x 31.50'L x 3.54'H Field A 0.041 af Overall - 0.015 af Embedded = 0.026 af x 40.0% Voids #2A 13.45' 0.015 af Cultec R-330XLHD x 12 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.025 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.95'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.11 cfs @ 12.49 hrs HW=14.04' (Free Discharge) 1=Exfiltration ( Controls 0.11 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 27HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 4 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 29.50' Row Length +12.0" End Stone x 2 = 31.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 12 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 659.4 cf Chamber Storage 1,785.0 cf Field - 659.4 cf Chambers = 1,125.6 cf Stone x 40.0% Voids = 450.2 cf Stone Storage Chamber Storage + Stone Storage = 1,109.6 cf = 0.025 af Overall Storage Efficiency = 62.2% Overall System Size = 31.50' x 16.00' x 3.54' 12 Chambers 66.1 cy Field 41.7 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 28HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.52 0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.147 ac Peak Elev=14.04' Storage=0.008 af 0.47 cfs 0.11 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 29HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 5P: Drywell [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=550) Inflow Area = 0.036 ac,100.00% Impervious, Inflow Depth = 3.37" for 2-year event Inflow = 0.12 cfs @ 12.08 hrs, Volume= 0.010 af Outflow = 0.04 cfs @ 12.36 hrs, Volume= 0.010 af, Atten= 67%, Lag= 16.8 min Discarded = 0.04 cfs @ 12.36 hrs, Volume= 0.010 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 11.76' @ 12.36 hrs Surf.Area= 0.005 ac Storage= 0.001 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 6.1 min ( 760.1 - 754.0 ) Volume Invert Avail.Storage Storage Description #1 11.00' 0.008 af 10.00'W x 20.00'L x 5.67'H Prismatoid 0.026 af Overall - 0.005 af Embedded = 0.021 af x 40.0% Voids #2 12.00' 0.005 af 6.00'D x 3.58'H Vertical Cone/Cylinder x 2 Inside #1 0.005 af Overall - 3.0" Wall Thickness = 0.005 af 0.013 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.04 cfs @ 12.36 hrs HW=11.76' (Free Discharge) 1=Exfiltration ( Controls 0.04 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 30HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 5P: Drywell Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 Inflow Area=0.036 ac Peak Elev=11.76' Storage=0.001 af 0.12 cfs 0.04 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 31HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 0.433 ac, 73.65% Impervious, Inflow Depth = 1.87" for 2-year event Inflow = 0.95 cfs @ 12.09 hrs, Volume= 0.067 af Outflow = 0.89 cfs @ 12.12 hrs, Volume= 0.067 af, Atten= 6%, Lag= 1.7 min Discarded = 0.10 cfs @ 12.12 hrs, Volume= 0.045 af Primary = 0.79 cfs @ 12.12 hrs, Volume= 0.022 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 15.95' @ 12.12 hrs Surf.Area= 520 sf Storage= 363 cf Plug-Flow detention time= 27.3 min calculated for 0.067 af (100% of inflow) Center-of-Mass det. time= 27.3 min ( 858.0 - 830.7 ) Volume Invert Avail.Storage Storage Description #1 14.00' 752 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 14.00 2 10.9 0 0 2 15.00 157 71.4 59 59 400 16.00 546 134.3 332 391 1,435 16.50 915 200.6 361 752 3,204 Device Routing Invert Outlet Devices #1 Discarded 14.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' #2 Device 3 15.70'2.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Primary 13.15'12.0" Round Culvert L= 25.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet / Outlet Invert= 13.15' / 12.90' S= 0.0100 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.10 cfs @ 12.12 hrs HW=15.95' (Free Discharge) 1=Exfiltration ( Controls 0.10 cfs) Primary OutFlow Max=0.79 cfs @ 12.12 hrs HW=15.95' TW=11.86' (Dynamic Tailwater) 3=Culvert (Passes 0.79 cfs of 5.73 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 0.79 cfs @ 1.63 fps) Great Island Plaza, West Yarmouth, MA Type III 24-hr 2-year Rainfall=3.60"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 32HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Outflow Discarded Primary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.433 ac Peak Elev=15.95' Storage=363 cf 0.95 cfs 0.89 cfs 0.10 cfs 0.79 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 33HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=18,860 sf 73.65% Impervious Runoff Depth=2.90"Subcatchment 1S: Area 1 Tc=6.0 min CN=82 Runoff=1.47 cfs 0.105 af Runoff Area=12,953 sf 94.80% Impervious Runoff Depth=4.22"Subcatchment 2S: Area 2 Tc=6.0 min CN=95 Runoff=1.35 cfs 0.105 af Runoff Area=6,468 sf 95.41% Impervious Runoff Depth=4.22"Subcatchment 3S: Area 3 Tc=6.0 min CN=95 Runoff=0.68 cfs 0.052 af Runoff Area=6,407 sf 91.21% Impervious Runoff Depth=4.00"Subcatchment 4S: Area 4 Tc=6.0 min CN=93 Runoff=0.65 cfs 0.049 af Runoff Area=9,313 sf 35.54% Impervious Runoff Depth=1.19"Subcatchment 5S: Area 5 Tc=6.0 min CN=60 Runoff=0.26 cfs 0.021 af Runoff Area=12,473 sf 78.89% Impervious Runoff Depth=3.28"Subcatchment 6S: Areaa 6 Tc=6.0 min CN=86 Runoff=1.09 cfs 0.078 af Runoff Area=1,469 sf 5.58% Impervious Runoff Depth=0.23"Subcatchment 7S: Area 7 Tc=6.0 min UI Adjusted CN=41 Runoff=0.00 cfs 0.001 af Runoff Area=7,408 sf 41.74% Impervious Runoff Depth=1.45"Subcatchment 8S: Area 8 Tc=6.0 min CN=64 Runoff=0.27 cfs 0.021 af Runoff Area=12,120 sf 67.51% Impervious Runoff Depth=2.63"Subcatchment 9S: Area 9 Tc=6.0 min CN=79 Runoff=0.86 cfs 0.061 af Runoff Area=1,548 sf 100.00% Impervious Runoff Depth=4.56"Subcatchment 10S: Post Office Tc=6.0 min CN=98 Runoff=0.17 cfs 0.014 af Inflow=0.00 cfs 0.001 afReach 1R: Area off-site - Northwest Outflow=0.00 cfs 0.001 af Inflow=0.27 cfs 0.021 afReach 2R: Area off-site - Southwest Outflow=0.27 cfs 0.021 af Inflow=0.86 cfs 0.061 afReach 3R: Area off-site - East Outflow=0.86 cfs 0.061 af Peak Elev=12.52' Storage=0.030 af Inflow=1.61 cfs 0.126 afPond 1P: Infiltration System #1 Outflow=0.33 cfs 0.126 af Peak Elev=12.80' Storage=1,933 cf Inflow=2.34 cfs 0.124 afPond 2P: Infiltration System #2 Outflow=0.44 cfs 0.124 af Peak Elev=13.75' Storage=0.013 af Inflow=0.68 cfs 0.052 afPond 3P: Infiltration System #3 Outflow=0.13 cfs 0.052 af Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 34HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Peak Elev=14.67' Storage=0.014 af Inflow=0.65 cfs 0.049 afPond 4P: Infiltration System #4 Outflow=0.11 cfs 0.049 af Peak Elev=12.28' Storage=0.003 af Inflow=0.17 cfs 0.014 afPond 5P: Drywell Outflow=0.04 cfs 0.014 af Peak Elev=16.05' Storage=416 cf Inflow=1.47 cfs 0.105 afPond RG: Rain Garden Discarded=0.12 cfs 0.059 af Primary=1.28 cfs 0.045 af Outflow=1.40 cfs 0.105 af Total Runoff Area = 2.044 ac Runoff Volume = 0.506 af Average Runoff Depth = 2.97" 27.84% Pervious = 0.569 ac 72.16% Impervious = 1.475 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 35HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Area 1 Runoff = 1.47 cfs @ 12.09 hrs, Volume= 0.105 af, Depth= 2.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 13,045 98 Paved parking, HSG A 4,970 39 >75% Grass cover, Good, HSG A 845 98 Water Surface, HSG A 18,860 82 Weighted Average 4,970 26.35% Pervious Area 13,890 73.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=18,860 sf Runoff Volume=0.105 af Runoff Depth=2.90" Tc=6.0 min CN=82 1.47 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 36HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Area 2 Runoff = 1.35 cfs @ 12.08 hrs, Volume= 0.105 af, Depth= 4.22" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 12,280 98 Paved parking, HSG A 673 39 >75% Grass cover, Good, HSG A 12,953 95 Weighted Average 673 5.20% Pervious Area 12,280 94.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=12,953 sf Runoff Volume=0.105 af Runoff Depth=4.22" Tc=6.0 min CN=95 1.35 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 37HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Area 3 Runoff = 0.68 cfs @ 12.08 hrs, Volume= 0.052 af, Depth= 4.22" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 6,171 98 Unconnected pavement, HSG A 297 39 >75% Grass cover, Good, HSG A 6,468 95 Weighted Average 297 4.59% Pervious Area 6,171 95.41% Impervious Area 6,171 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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 10-year Rainfall=4.80" Runoff Area=6,468 sf Runoff Volume=0.052 af Runoff Depth=4.22" Tc=6.0 min CN=95 0.68 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 38HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Area 4 Runoff = 0.65 cfs @ 12.08 hrs, Volume= 0.049 af, Depth= 4.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 5,844 98 Unconnected pavement, HSG A 563 39 >75% Grass cover, Good, HSG A 6,407 93 Weighted Average 563 8.79% Pervious Area 5,844 91.21% Impervious Area 5,844 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Area 4 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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-year Rainfall=4.80" Runoff Area=6,407 sf Runoff Volume=0.049 af Runoff Depth=4.00" Tc=6.0 min CN=93 0.65 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 39HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Area 5 Runoff = 0.26 cfs @ 12.10 hrs, Volume= 0.021 af, Depth= 1.19" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 3,310 98 Unconnected pavement, HSG A 6,003 39 >75% Grass cover, Good, HSG A 9,313 60 Weighted Average 6,003 64.46% Pervious Area 3,310 35.54% Impervious Area 3,310 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Area 5 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=9,313 sf Runoff Volume=0.021 af Runoff Depth=1.19" Tc=6.0 min CN=60 0.26 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 40HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Areaa 6 Runoff = 1.09 cfs @ 12.09 hrs, Volume= 0.078 af, Depth= 3.28" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 9,840 98 Unconnected pavement, HSG A 2,633 39 >75% Grass cover, Good, HSG A 12,473 86 Weighted Average 2,633 21.11% Pervious Area 9,840 78.89% Impervious Area 9,840 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 6S: Areaa 6 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=12,473 sf Runoff Volume=0.078 af Runoff Depth=3.28" Tc=6.0 min CN=86 1.09 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 41HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: Area 7 Runoff = 0.00 cfs @ 12.44 hrs, Volume= 0.001 af, Depth= 0.23" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Adj Description 82 98 Unconnected pavement, HSG A 1,387 39 >75% Grass cover, Good, HSG A 1,469 42 41 Weighted Average, UI Adjusted 1,387 94.42% Pervious Area 82 5.58% Impervious Area 82 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 7S: Area 7 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=1,469 sf Runoff Volume=0.001 af Runoff Depth=0.23" Tc=6.0 min UI Adjusted CN=41 0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 42HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Area 8 Runoff = 0.27 cfs @ 12.10 hrs, Volume= 0.021 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 3,092 98 Unconnected pavement, HSG A 4,316 39 >75% Grass cover, Good, HSG A 7,408 64 Weighted Average 4,316 58.26% Pervious Area 3,092 41.74% Impervious Area 3,092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 8S: Area 8 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10-year Rainfall=4.80" Runoff Area=7,408 sf Runoff Volume=0.021 af Runoff Depth=1.45" Tc=6.0 min CN=64 0.27 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 43HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: Area 9 Runoff = 0.86 cfs @ 12.09 hrs, Volume= 0.061 af, Depth= 2.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 8,182 98 Unconnected pavement, HSG A 3,938 39 >75% Grass cover, Good, HSG A 12,120 79 Weighted Average 3,938 32.49% Pervious Area 8,182 67.51% Impervious Area 8,182 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 9S: Area 9 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.95 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-year Rainfall=4.80" Runoff Area=12,120 sf Runoff Volume=0.061 af Runoff Depth=2.63" Tc=6.0 min CN=79 0.86 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 44HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 10S: Post Office Runoff = 0.17 cfs @ 12.08 hrs, Volume= 0.014 af, Depth= 4.56" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 10-year Rainfall=4.80" Area (sf) CN Description 1,548 98 Roofs, HSG A 1,548 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Post Office Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 10-year Rainfall=4.80" Runoff Area=1,548 sf Runoff Volume=0.014 af Runoff Depth=4.56" Tc=6.0 min CN=98 0.17 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 45HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.034 ac, 5.58% Impervious, Inflow Depth = 0.23" for 10-year event Inflow = 0.00 cfs @ 12.44 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 12.44 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0 0 Inflow Area=0.034 ac 0.00 cfs0.00 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 46HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.170 ac, 41.74% Impervious, Inflow Depth = 1.45" for 10-year event Inflow = 0.27 cfs @ 12.10 hrs, Volume= 0.021 af Outflow = 0.27 cfs @ 12.10 hrs, Volume= 0.021 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.170 ac 0.27 cfs0.27 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 47HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.278 ac, 67.51% Impervious, Inflow Depth = 2.63" for 10-year event Inflow = 0.86 cfs @ 12.09 hrs, Volume= 0.061 af Outflow = 0.86 cfs @ 12.09 hrs, Volume= 0.061 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.95 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=0.278 ac 0.86 cfs0.86 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 48HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 1P: Infiltration System #1 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=482) Inflow Area = 0.511 ac, 70.02% Impervious, Inflow Depth = 2.95" for 10-year event Inflow = 1.61 cfs @ 12.09 hrs, Volume= 0.126 af Outflow = 0.33 cfs @ 12.52 hrs, Volume= 0.126 af, Atten= 80%, Lag= 26.2 min Discarded = 0.33 cfs @ 12.52 hrs, Volume= 0.126 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.52' @ 12.52 hrs Surf.Area= 0.035 ac Storage= 0.030 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 21.2 min ( 808.8 - 787.7 ) Volume Invert Avail.Storage Storage Description #1A 11.25' 0.030 af 25.67'W x 59.50'L x 3.54'H Field A 0.124 af Overall - 0.049 af Embedded = 0.075 af x 40.0% Voids #2A 11.75' 0.049 af Cultec R-330XLHD x 40 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 0.079 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.25'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.33 cfs @ 12.52 hrs HW=12.52' (Free Discharge) 1=Exfiltration ( Controls 0.33 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 49HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 8 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 57.50' Row Length +12.0" End Stone x 2 = 59.50' Base Length 5 Rows x 52.0" Wide + 6.0" Spacing x 4 + 12.0" Side Stone x 2 = 25.67' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 40 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 5 Rows = 2,142.2 cf Chamber Storage 5,408.7 cf Field - 2,142.2 cf Chambers = 3,266.6 cf Stone x 40.0% Voids = 1,306.6 cf Stone Storage Chamber Storage + Stone Storage = 3,448.8 cf = 0.079 af Overall Storage Efficiency = 63.8% Overall System Size = 59.50' x 25.67' x 3.54' 40 Chambers 200.3 cy Field 121.0 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 50HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.511 ac Peak Elev=12.52' Storage=0.030 af 1.61 cfs 0.33 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 51HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 2P: Infiltration System #2 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=485) Inflow Area = 0.719 ac, 75.73% Impervious, Inflow Depth = 2.06" for 10-year event Inflow = 2.34 cfs @ 12.10 hrs, Volume= 0.124 af Outflow = 0.44 cfs @ 12.54 hrs, Volume= 0.124 af, Atten= 81%, Lag= 26.5 min Discarded = 0.44 cfs @ 12.54 hrs, Volume= 0.124 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.80' @ 12.54 hrs Surf.Area= 2,028 sf Storage= 1,933 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 31.1 min ( 812.0 - 781.0 ) Volume Invert Avail.Storage Storage Description #1A 11.40' 1,720 cf 30.50'W x 66.50'L x 3.54'H Field A 7,183 cf Overall - 2,884 cf Embedded = 4,300 cf x 40.0% Voids #2A 11.90' 2,884 cf Cultec R-330XLHD x 54 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 4,603 cf Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.40'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.44 cfs @ 12.54 hrs HW=12.80' (Free Discharge) 1=Exfiltration ( Controls 0.44 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 52HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 9 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 64.50' Row Length +12.0" End Stone x 2 = 66.50' Base Length 6 Rows x 52.0" Wide + 6.0" Spacing x 5 + 12.0" Side Stone x 2 = 30.50' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 54 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 6 Rows = 2,883.5 cf Chamber Storage 7,183.4 cf Field - 2,883.5 cf Chambers = 4,299.8 cf Stone x 40.0% Voids = 1,719.9 cf Stone Storage Chamber Storage + Stone Storage = 4,603.5 cf = 0.106 af Overall Storage Efficiency = 64.1% Overall System Size = 66.50' x 30.50' x 3.54' 54 Chambers 266.1 cy Field 159.3 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 53HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.719 ac Peak Elev=12.80' Storage=1,933 cf 2.34 cfs 0.44 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 54HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 3P: Infiltration System #3 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=480) Inflow Area = 0.148 ac, 95.41% Impervious, Inflow Depth = 4.22" for 10-year event Inflow = 0.68 cfs @ 12.08 hrs, Volume= 0.052 af Outflow = 0.13 cfs @ 12.51 hrs, Volume= 0.052 af, Atten= 80%, Lag= 25.8 min Discarded = 0.13 cfs @ 12.51 hrs, Volume= 0.052 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 13.75' @ 12.51 hrs Surf.Area= 0.014 ac Storage= 0.013 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 22.6 min ( 792.0 - 769.3 ) Volume Invert Avail.Storage Storage Description #1A 12.37' 0.013 af 16.00'W x 38.50'L x 3.54'H Field A 0.050 af Overall - 0.019 af Embedded = 0.031 af x 40.0% Voids #2A 12.87' 0.019 af Cultec R-330XLHD x 15 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.031 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.37'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.13 cfs @ 12.51 hrs HW=13.75' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 55HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 5 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 36.50' Row Length +12.0" End Stone x 2 = 38.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 15 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 815.9 cf Chamber Storage 2,181.7 cf Field - 815.9 cf Chambers = 1,365.8 cf Stone x 40.0% Voids = 546.3 cf Stone Storage Chamber Storage + Stone Storage = 1,362.2 cf = 0.031 af Overall Storage Efficiency = 62.4% Overall System Size = 38.50' x 16.00' x 3.54' 15 Chambers 80.8 cy Field 50.6 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 56HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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=0.148 ac Peak Elev=13.75' Storage=0.013 af 0.68 cfs 0.13 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 57HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 4P: Infiltration System #4 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=448) Inflow Area = 0.147 ac, 91.21% Impervious, Inflow Depth = 4.00" for 10-year event Inflow = 0.65 cfs @ 12.08 hrs, Volume= 0.049 af Outflow = 0.11 cfs @ 12.55 hrs, Volume= 0.049 af, Atten= 83%, Lag= 27.7 min Discarded = 0.11 cfs @ 12.55 hrs, Volume= 0.049 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 14.67' @ 12.55 hrs Surf.Area= 0.012 ac Storage= 0.014 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 31.6 min ( 811.1 - 779.5 ) Volume Invert Avail.Storage Storage Description #1A 12.95' 0.010 af 16.00'W x 31.50'L x 3.54'H Field A 0.041 af Overall - 0.015 af Embedded = 0.026 af x 40.0% Voids #2A 13.45' 0.015 af Cultec R-330XLHD x 12 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.025 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.95'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.11 cfs @ 12.55 hrs HW=14.67' (Free Discharge) 1=Exfiltration ( Controls 0.11 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 58HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 4 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 29.50' Row Length +12.0" End Stone x 2 = 31.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 12 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 659.4 cf Chamber Storage 1,785.0 cf Field - 659.4 cf Chambers = 1,125.6 cf Stone x 40.0% Voids = 450.2 cf Stone Storage Chamber Storage + Stone Storage = 1,109.6 cf = 0.025 af Overall Storage Efficiency = 62.2% Overall System Size = 31.50' x 16.00' x 3.54' 12 Chambers 66.1 cy Field 41.7 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 59HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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=0.147 ac Peak Elev=14.67' Storage=0.014 af 0.65 cfs 0.11 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 60HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 5P: Drywell [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=522) Inflow Area = 0.036 ac,100.00% Impervious, Inflow Depth = 4.56" for 10-year event Inflow = 0.17 cfs @ 12.08 hrs, Volume= 0.014 af Outflow = 0.04 cfs @ 12.44 hrs, Volume= 0.014 af, Atten= 74%, Lag= 21.5 min Discarded = 0.04 cfs @ 12.44 hrs, Volume= 0.014 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.28' @ 12.44 hrs Surf.Area= 0.005 ac Storage= 0.003 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 11.7 min ( 760.4 - 748.7 ) Volume Invert Avail.Storage Storage Description #1 11.00' 0.008 af 10.00'W x 20.00'L x 5.67'H Prismatoid 0.026 af Overall - 0.005 af Embedded = 0.021 af x 40.0% Voids #2 12.00' 0.005 af 6.00'D x 3.58'H Vertical Cone/Cylinder x 2 Inside #1 0.005 af Overall - 3.0" Wall Thickness = 0.005 af 0.013 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.04 cfs @ 12.44 hrs HW=12.28' (Free Discharge) 1=Exfiltration ( Controls 0.04 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 61HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 5P: Drywell Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 Inflow Area=0.036 ac Peak Elev=12.28' Storage=0.003 af 0.17 cfs 0.04 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 62HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 0.433 ac, 73.65% Impervious, Inflow Depth = 2.90" for 10-year event Inflow = 1.47 cfs @ 12.09 hrs, Volume= 0.105 af Outflow = 1.40 cfs @ 12.11 hrs, Volume= 0.105 af, Atten= 5%, Lag= 1.6 min Discarded = 0.12 cfs @ 12.11 hrs, Volume= 0.059 af Primary = 1.28 cfs @ 12.11 hrs, Volume= 0.045 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 16.05' @ 12.11 hrs Surf.Area= 575 sf Storage= 416 cf Plug-Flow detention time= 24.5 min calculated for 0.105 af (100% of inflow) Center-of-Mass det. time= 24.5 min ( 842.5 - 818.0 ) Volume Invert Avail.Storage Storage Description #1 14.00' 752 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 14.00 2 10.9 0 0 2 15.00 157 71.4 59 59 400 16.00 546 134.3 332 391 1,435 16.50 915 200.6 361 752 3,204 Device Routing Invert Outlet Devices #1 Discarded 14.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' #2 Device 3 15.70'2.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Primary 13.15'12.0" Round Culvert L= 25.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet / Outlet Invert= 13.15' / 12.90' S= 0.0100 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.12 cfs @ 12.11 hrs HW=16.04' (Free Discharge) 1=Exfiltration ( Controls 0.12 cfs) Primary OutFlow Max=1.28 cfs @ 12.11 hrs HW=16.04' TW=12.19' (Dynamic Tailwater) 3=Culvert (Passes 1.28 cfs of 5.85 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 1.28 cfs @ 1.92 fps) Great Island Plaza, West Yarmouth, MA Type III 24-hr 10-year Rainfall=4.80"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 63HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Outflow Discarded Primary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.433 ac Peak Elev=16.05' Storage=416 cf 1.47 cfs 1.40 cfs 0.12 cfs 1.28 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 64HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=18,860 sf 73.65% Impervious Runoff Depth=3.71"Subcatchment 1S: Area 1 Tc=6.0 min CN=82 Runoff=1.87 cfs 0.134 af Runoff Area=12,953 sf 94.80% Impervious Runoff Depth=5.11"Subcatchment 2S: Area 2 Tc=6.0 min CN=95 Runoff=1.62 cfs 0.127 af Runoff Area=6,468 sf 95.41% Impervious Runoff Depth=5.11"Subcatchment 3S: Area 3 Tc=6.0 min CN=95 Runoff=0.81 cfs 0.063 af Runoff Area=6,407 sf 91.21% Impervious Runoff Depth=4.89"Subcatchment 4S: Area 4 Tc=6.0 min CN=93 Runoff=0.79 cfs 0.060 af Runoff Area=9,313 sf 35.54% Impervious Runoff Depth=1.73"Subcatchment 5S: Area 5 Tc=6.0 min CN=60 Runoff=0.40 cfs 0.031 af Runoff Area=12,473 sf 78.89% Impervious Runoff Depth=4.12"Subcatchment 6S: Areaa 6 Tc=6.0 min CN=86 Runoff=1.36 cfs 0.098 af Runoff Area=1,469 sf 5.58% Impervious Runoff Depth=0.46"Subcatchment 7S: Area 7 Tc=6.0 min UI Adjusted CN=41 Runoff=0.01 cfs 0.001 af Runoff Area=7,408 sf 41.74% Impervious Runoff Depth=2.05"Subcatchment 8S: Area 8 Tc=6.0 min CN=64 Runoff=0.40 cfs 0.029 af Runoff Area=12,120 sf 67.51% Impervious Runoff Depth=3.41"Subcatchment 9S: Area 9 Tc=6.0 min CN=79 Runoff=1.11 cfs 0.079 af Runoff Area=1,548 sf 100.00% Impervious Runoff Depth=5.46"Subcatchment 10S: Post Office Tc=6.0 min CN=98 Runoff=0.20 cfs 0.016 af Inflow=0.01 cfs 0.001 afReach 1R: Area off-site - Northwest Outflow=0.01 cfs 0.001 af Inflow=0.40 cfs 0.029 afReach 2R: Area off-site - Southwest Outflow=0.40 cfs 0.029 af Inflow=1.11 cfs 0.079 afReach 3R: Area off-site - East Outflow=1.11 cfs 0.079 af Peak Elev=12.97' Storage=0.042 af Inflow=2.02 cfs 0.158 afPond 1P: Infiltration System #1 Outflow=0.34 cfs 0.158 af Peak Elev=13.36' Storage=2,834 cf Inflow=2.97 cfs 0.163 afPond 2P: Infiltration System #2 Outflow=0.46 cfs 0.164 af Peak Elev=14.13' Storage=0.017 af Inflow=0.81 cfs 0.063 afPond 3P: Infiltration System #3 Outflow=0.14 cfs 0.063 af Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 65HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Peak Elev=15.18' Storage=0.018 af Inflow=0.79 cfs 0.060 afPond 4P: Infiltration System #4 Outflow=0.11 cfs 0.060 af Peak Elev=12.64' Storage=0.003 af Inflow=0.20 cfs 0.016 afPond 5P: Drywell Outflow=0.04 cfs 0.016 af Peak Elev=16.11' Storage=456 cf Inflow=1.87 cfs 0.134 afPond RG: Rain Garden Discarded=0.12 cfs 0.069 af Primary=1.66 cfs 0.065 af Outflow=1.78 cfs 0.134 af Total Runoff Area = 2.044 ac Runoff Volume = 0.639 af Average Runoff Depth = 3.75" 27.84% Pervious = 0.569 ac 72.16% Impervious = 1.475 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 66HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Area 1 Runoff = 1.87 cfs @ 12.09 hrs, Volume= 0.134 af, Depth= 3.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 13,045 98 Paved parking, HSG A 4,970 39 >75% Grass cover, Good, HSG A 845 98 Water Surface, HSG A 18,860 82 Weighted Average 4,970 26.35% Pervious Area 13,890 73.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=18,860 sf Runoff Volume=0.134 af Runoff Depth=3.71" Tc=6.0 min CN=82 1.87 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 67HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Area 2 Runoff = 1.62 cfs @ 12.08 hrs, Volume= 0.127 af, Depth= 5.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 12,280 98 Paved parking, HSG A 673 39 >75% Grass cover, Good, HSG A 12,953 95 Weighted Average 673 5.20% Pervious Area 12,280 94.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=12,953 sf Runoff Volume=0.127 af Runoff Depth=5.11" Tc=6.0 min CN=95 1.62 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 68HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Area 3 Runoff = 0.81 cfs @ 12.08 hrs, Volume= 0.063 af, Depth= 5.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 6,171 98 Unconnected pavement, HSG A 297 39 >75% Grass cover, Good, HSG A 6,468 95 Weighted Average 297 4.59% Pervious Area 6,171 95.41% Impervious Area 6,171 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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 25-year Rainfall=5.70" Runoff Area=6,468 sf Runoff Volume=0.063 af Runoff Depth=5.11" Tc=6.0 min CN=95 0.81 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 69HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Area 4 Runoff = 0.79 cfs @ 12.08 hrs, Volume= 0.060 af, Depth= 4.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 5,844 98 Unconnected pavement, HSG A 563 39 >75% Grass cover, Good, HSG A 6,407 93 Weighted Average 563 8.79% Pervious Area 5,844 91.21% Impervious Area 5,844 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Area 4 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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 25-year Rainfall=5.70" Runoff Area=6,407 sf Runoff Volume=0.060 af Runoff Depth=4.89" Tc=6.0 min CN=93 0.79 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 70HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Area 5 Runoff = 0.40 cfs @ 12.10 hrs, Volume= 0.031 af, Depth= 1.73" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 3,310 98 Unconnected pavement, HSG A 6,003 39 >75% Grass cover, Good, HSG A 9,313 60 Weighted Average 6,003 64.46% Pervious Area 3,310 35.54% Impervious Area 3,310 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Area 5 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=9,313 sf Runoff Volume=0.031 af Runoff Depth=1.73" Tc=6.0 min CN=60 0.40 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 71HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Areaa 6 Runoff = 1.36 cfs @ 12.09 hrs, Volume= 0.098 af, Depth= 4.12" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 9,840 98 Unconnected pavement, HSG A 2,633 39 >75% Grass cover, Good, HSG A 12,473 86 Weighted Average 2,633 21.11% Pervious Area 9,840 78.89% Impervious Area 9,840 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 6S: Areaa 6 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=12,473 sf Runoff Volume=0.098 af Runoff Depth=4.12" Tc=6.0 min CN=86 1.36 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 72HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: Area 7 Runoff = 0.01 cfs @ 12.33 hrs, Volume= 0.001 af, Depth= 0.46" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Adj Description 82 98 Unconnected pavement, HSG A 1,387 39 >75% Grass cover, Good, HSG A 1,469 42 41 Weighted Average, UI Adjusted 1,387 94.42% Pervious Area 82 5.58% Impervious Area 82 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 7S: Area 7 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.007 0.007 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 25-year Rainfall=5.70" Runoff Area=1,469 sf Runoff Volume=0.001 af Runoff Depth=0.46" Tc=6.0 min UI Adjusted CN=41 0.01 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 73HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Area 8 Runoff = 0.40 cfs @ 12.09 hrs, Volume= 0.029 af, Depth= 2.05" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 3,092 98 Unconnected pavement, HSG A 4,316 39 >75% Grass cover, Good, HSG A 7,408 64 Weighted Average 4,316 58.26% Pervious Area 3,092 41.74% Impervious Area 3,092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 8S: Area 8 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=7,408 sf Runoff Volume=0.029 af Runoff Depth=2.05" Tc=6.0 min CN=64 0.40 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 74HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: Area 9 Runoff = 1.11 cfs @ 12.09 hrs, Volume= 0.079 af, Depth= 3.41" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 8,182 98 Unconnected pavement, HSG A 3,938 39 >75% Grass cover, Good, HSG A 12,120 79 Weighted Average 3,938 32.49% Pervious Area 8,182 67.51% Impervious Area 8,182 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 9S: Area 9 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 25-year Rainfall=5.70" Runoff Area=12,120 sf Runoff Volume=0.079 af Runoff Depth=3.41" Tc=6.0 min CN=79 1.11 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 75HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 10S: Post Office Runoff = 0.20 cfs @ 12.08 hrs, Volume= 0.016 af, Depth= 5.46" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 25-year Rainfall=5.70" Area (sf) CN Description 1,548 98 Roofs, HSG A 1,548 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Post Office Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.22 0.21 0.2 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 25-year Rainfall=5.70" Runoff Area=1,548 sf Runoff Volume=0.016 af Runoff Depth=5.46" Tc=6.0 min CN=98 0.20 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 76HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.034 ac, 5.58% Impervious, Inflow Depth = 0.46" for 25-year event Inflow = 0.01 cfs @ 12.33 hrs, Volume= 0.001 af Outflow = 0.01 cfs @ 12.33 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.007 0.007 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 Inflow Area=0.034 ac 0.01 cfs0.01 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 77HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.170 ac, 41.74% Impervious, Inflow Depth = 2.05" for 25-year event Inflow = 0.40 cfs @ 12.09 hrs, Volume= 0.029 af Outflow = 0.40 cfs @ 12.09 hrs, Volume= 0.029 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.170 ac 0.40 cfs0.40 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 78HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.278 ac, 67.51% Impervious, Inflow Depth = 3.41" for 25-year event Inflow = 1.11 cfs @ 12.09 hrs, Volume= 0.079 af Outflow = 1.11 cfs @ 12.09 hrs, Volume= 0.079 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.278 ac 1.11 cfs1.11 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 79HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 1P: Infiltration System #1 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=439) Inflow Area = 0.511 ac, 70.02% Impervious, Inflow Depth = 3.70" for 25-year event Inflow = 2.02 cfs @ 12.09 hrs, Volume= 0.158 af Outflow = 0.34 cfs @ 12.56 hrs, Volume= 0.158 af, Atten= 83%, Lag= 28.5 min Discarded = 0.34 cfs @ 12.56 hrs, Volume= 0.158 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.97' @ 12.56 hrs Surf.Area= 0.035 ac Storage= 0.042 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 32.5 min ( 817.2 - 784.7 ) Volume Invert Avail.Storage Storage Description #1A 11.25' 0.030 af 25.67'W x 59.50'L x 3.54'H Field A 0.124 af Overall - 0.049 af Embedded = 0.075 af x 40.0% Voids #2A 11.75' 0.049 af Cultec R-330XLHD x 40 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 0.079 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.25'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.34 cfs @ 12.56 hrs HW=12.97' (Free Discharge) 1=Exfiltration ( Controls 0.34 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 80HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 8 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 57.50' Row Length +12.0" End Stone x 2 = 59.50' Base Length 5 Rows x 52.0" Wide + 6.0" Spacing x 4 + 12.0" Side Stone x 2 = 25.67' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 40 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 5 Rows = 2,142.2 cf Chamber Storage 5,408.7 cf Field - 2,142.2 cf Chambers = 3,266.6 cf Stone x 40.0% Voids = 1,306.6 cf Stone Storage Chamber Storage + Stone Storage = 3,448.8 cf = 0.079 af Overall Storage Efficiency = 63.8% Overall System Size = 59.50' x 25.67' x 3.54' 40 Chambers 200.3 cy Field 121.0 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 81HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.511 ac Peak Elev=12.97' Storage=0.042 af 2.02 cfs 0.34 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 82HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 2P: Infiltration System #2 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=441) Inflow Area = 0.719 ac, 75.73% Impervious, Inflow Depth = 2.73" for 25-year event Inflow = 2.97 cfs @ 12.10 hrs, Volume= 0.163 af Outflow = 0.46 cfs @ 12.58 hrs, Volume= 0.164 af, Atten= 84%, Lag= 28.8 min Discarded = 0.46 cfs @ 12.58 hrs, Volume= 0.164 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 13.36' @ 12.58 hrs Surf.Area= 2,028 sf Storage= 2,834 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 46.7 min ( 822.5 - 775.9 ) Volume Invert Avail.Storage Storage Description #1A 11.40' 1,720 cf 30.50'W x 66.50'L x 3.54'H Field A 7,183 cf Overall - 2,884 cf Embedded = 4,300 cf x 40.0% Voids #2A 11.90' 2,884 cf Cultec R-330XLHD x 54 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 4,603 cf Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.40'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.46 cfs @ 12.58 hrs HW=13.36' (Free Discharge) 1=Exfiltration ( Controls 0.46 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 83HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 9 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 64.50' Row Length +12.0" End Stone x 2 = 66.50' Base Length 6 Rows x 52.0" Wide + 6.0" Spacing x 5 + 12.0" Side Stone x 2 = 30.50' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 54 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 6 Rows = 2,883.5 cf Chamber Storage 7,183.4 cf Field - 2,883.5 cf Chambers = 4,299.8 cf Stone x 40.0% Voids = 1,719.9 cf Stone Storage Chamber Storage + Stone Storage = 4,603.5 cf = 0.106 af Overall Storage Efficiency = 64.1% Overall System Size = 66.50' x 30.50' x 3.54' 54 Chambers 266.1 cy Field 159.3 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 84HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=0.719 ac Peak Elev=13.36' Storage=2,834 cf 2.97 cfs 0.46 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 85HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 3P: Infiltration System #3 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=445) Inflow Area = 0.148 ac, 95.41% Impervious, Inflow Depth = 5.11" for 25-year event Inflow = 0.81 cfs @ 12.08 hrs, Volume= 0.063 af Outflow = 0.14 cfs @ 12.54 hrs, Volume= 0.063 af, Atten= 83%, Lag= 27.7 min Discarded = 0.14 cfs @ 12.54 hrs, Volume= 0.063 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 14.13' @ 12.54 hrs Surf.Area= 0.014 ac Storage= 0.017 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 31.4 min ( 796.3 - 764.9 ) Volume Invert Avail.Storage Storage Description #1A 12.37' 0.013 af 16.00'W x 38.50'L x 3.54'H Field A 0.050 af Overall - 0.019 af Embedded = 0.031 af x 40.0% Voids #2A 12.87' 0.019 af Cultec R-330XLHD x 15 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.031 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.37'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.14 cfs @ 12.54 hrs HW=14.13' (Free Discharge) 1=Exfiltration ( Controls 0.14 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 86HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 5 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 36.50' Row Length +12.0" End Stone x 2 = 38.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 15 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 815.9 cf Chamber Storage 2,181.7 cf Field - 815.9 cf Chambers = 1,365.8 cf Stone x 40.0% Voids = 546.3 cf Stone Storage Chamber Storage + Stone Storage = 1,362.2 cf = 0.031 af Overall Storage Efficiency = 62.4% Overall System Size = 38.50' x 16.00' x 3.54' 15 Chambers 80.8 cy Field 50.6 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 87HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (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=0.148 ac Peak Elev=14.13' Storage=0.017 af 0.81 cfs 0.14 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 88HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 4P: Infiltration System #4 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=406) Inflow Area = 0.147 ac, 91.21% Impervious, Inflow Depth = 4.89" for 25-year event Inflow = 0.79 cfs @ 12.08 hrs, Volume= 0.060 af Outflow = 0.11 cfs @ 12.58 hrs, Volume= 0.060 af, Atten= 85%, Lag= 29.7 min Discarded = 0.11 cfs @ 12.58 hrs, Volume= 0.060 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 15.18' @ 12.58 hrs Surf.Area= 0.012 ac Storage= 0.018 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 43.1 min ( 817.6 - 774.4 ) Volume Invert Avail.Storage Storage Description #1A 12.95' 0.010 af 16.00'W x 31.50'L x 3.54'H Field A 0.041 af Overall - 0.015 af Embedded = 0.026 af x 40.0% Voids #2A 13.45' 0.015 af Cultec R-330XLHD x 12 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.025 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.95'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.11 cfs @ 12.58 hrs HW=15.18' (Free Discharge) 1=Exfiltration ( Controls 0.11 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 89HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 4 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 29.50' Row Length +12.0" End Stone x 2 = 31.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 12 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 659.4 cf Chamber Storage 1,785.0 cf Field - 659.4 cf Chambers = 1,125.6 cf Stone x 40.0% Voids = 450.2 cf Stone Storage Chamber Storage + Stone Storage = 1,109.6 cf = 0.025 af Overall Storage Efficiency = 62.2% Overall System Size = 31.50' x 16.00' x 3.54' 12 Chambers 66.1 cy Field 41.7 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 90HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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=0.147 ac Peak Elev=15.18' Storage=0.018 af 0.79 cfs 0.11 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 91HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 5P: Drywell [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=501) Inflow Area = 0.036 ac,100.00% Impervious, Inflow Depth = 5.46" for 25-year event Inflow = 0.20 cfs @ 12.08 hrs, Volume= 0.016 af Outflow = 0.04 cfs @ 12.48 hrs, Volume= 0.016 af, Atten= 78%, Lag= 23.8 min Discarded = 0.04 cfs @ 12.48 hrs, Volume= 0.016 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 12.64' @ 12.48 hrs Surf.Area= 0.005 ac Storage= 0.003 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 16.5 min ( 762.4 - 745.9 ) Volume Invert Avail.Storage Storage Description #1 11.00' 0.008 af 10.00'W x 20.00'L x 5.67'H Prismatoid 0.026 af Overall - 0.005 af Embedded = 0.021 af x 40.0% Voids #2 12.00' 0.005 af 6.00'D x 3.58'H Vertical Cone/Cylinder x 2 Inside #1 0.005 af Overall - 3.0" Wall Thickness = 0.005 af 0.013 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.04 cfs @ 12.48 hrs HW=12.64' (Free Discharge) 1=Exfiltration ( Controls 0.04 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 92HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 5P: Drywell Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.22 0.21 0.2 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 Inflow Area=0.036 ac Peak Elev=12.64' Storage=0.003 af 0.20 cfs 0.04 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 93HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 0.433 ac, 73.65% Impervious, Inflow Depth = 3.71" for 25-year event Inflow = 1.87 cfs @ 12.09 hrs, Volume= 0.134 af Outflow = 1.78 cfs @ 12.11 hrs, Volume= 0.134 af, Atten= 5%, Lag= 1.6 min Discarded = 0.12 cfs @ 12.11 hrs, Volume= 0.069 af Primary = 1.66 cfs @ 12.11 hrs, Volume= 0.065 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 16.11' @ 12.11 hrs Surf.Area= 620 sf Storage= 456 cf Plug-Flow detention time= 22.9 min calculated for 0.134 af (100% of inflow) Center-of-Mass det. time= 22.9 min ( 833.9 - 811.0 ) Volume Invert Avail.Storage Storage Description #1 14.00' 752 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 14.00 2 10.9 0 0 2 15.00 157 71.4 59 59 400 16.00 546 134.3 332 391 1,435 16.50 915 200.6 361 752 3,204 Device Routing Invert Outlet Devices #1 Discarded 14.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' #2 Device 3 15.70'2.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Primary 13.15'12.0" Round Culvert L= 25.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet / Outlet Invert= 13.15' / 12.90' S= 0.0100 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.12 cfs @ 12.11 hrs HW=16.11' (Free Discharge) 1=Exfiltration ( Controls 0.12 cfs) Primary OutFlow Max=1.65 cfs @ 12.11 hrs HW=16.11' TW=12.46' (Dynamic Tailwater) 3=Culvert (Passes 1.65 cfs of 5.93 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 1.65 cfs @ 2.10 fps) Great Island Plaza, West Yarmouth, MA Type III 24-hr 25-year Rainfall=5.70"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 94HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Outflow Discarded Primary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.433 ac Peak Elev=16.11' Storage=456 cf 1.87 cfs 1.78 cfs 0.12 cfs 1.66 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 95HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Time span=0.00-36.00 hrs, dt=0.01 hrs, 3601 points x 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=18,860 sf 73.65% Impervious Runoff Depth=5.01"Subcatchment 1S: Area 1 Tc=6.0 min CN=82 Runoff=2.50 cfs 0.181 af Runoff Area=12,953 sf 94.80% Impervious Runoff Depth=6.51"Subcatchment 2S: Area 2 Tc=6.0 min CN=95 Runoff=2.04 cfs 0.161 af Runoff Area=6,468 sf 95.41% Impervious Runoff Depth=6.51"Subcatchment 3S: Area 3 Tc=6.0 min CN=95 Runoff=1.02 cfs 0.080 af Runoff Area=6,407 sf 91.21% Impervious Runoff Depth=6.27"Subcatchment 4S: Area 4 Tc=6.0 min CN=93 Runoff=0.99 cfs 0.077 af Runoff Area=9,313 sf 35.54% Impervious Runoff Depth=2.67"Subcatchment 5S: Area 5 Tc=6.0 min CN=60 Runoff=0.65 cfs 0.048 af Runoff Area=12,473 sf 78.89% Impervious Runoff Depth=5.46"Subcatchment 6S: Areaa 6 Tc=6.0 min CN=86 Runoff=1.77 cfs 0.130 af Runoff Area=1,469 sf 5.58% Impervious Runoff Depth=0.96"Subcatchment 7S: Area 7 Tc=6.0 min UI Adjusted CN=41 Runoff=0.02 cfs 0.003 af Runoff Area=7,408 sf 41.74% Impervious Runoff Depth=3.08"Subcatchment 8S: Area 8 Tc=6.0 min CN=64 Runoff=0.61 cfs 0.044 af Runoff Area=12,120 sf 67.51% Impervious Runoff Depth=4.68"Subcatchment 9S: Area 9 Tc=6.0 min CN=79 Runoff=1.51 cfs 0.108 af Runoff Area=1,548 sf 100.00% Impervious Runoff Depth=6.86"Subcatchment 10S: Post Office Tc=6.0 min CN=98 Runoff=0.25 cfs 0.020 af Inflow=0.02 cfs 0.003 afReach 1R: Area off-site - Northwest Outflow=0.02 cfs 0.003 af Inflow=0.61 cfs 0.044 afReach 2R: Area off-site - Southwest Outflow=0.61 cfs 0.044 af Inflow=1.51 cfs 0.108 afReach 3R: Area off-site - East Outflow=1.51 cfs 0.108 af Peak Elev=13.82' Storage=0.064 af Inflow=2.69 cfs 0.209 afPond 1P: Infiltration System #1 Outflow=0.37 cfs 0.209 af Peak Elev=14.54' Storage=4,274 cf Inflow=3.96 cfs 0.229 afPond 2P: Infiltration System #2 Outflow=0.51 cfs 0.229 af Peak Elev=14.80' Storage=0.024 af Inflow=1.02 cfs 0.080 afPond 3P: Infiltration System #3 Outflow=0.14 cfs 0.080 af Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 96HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Peak Elev=16.36' Storage=0.025 af Inflow=0.99 cfs 0.077 afPond 4P: Infiltration System #4 Outflow=0.12 cfs 0.077 af Peak Elev=13.24' Storage=0.005 af Inflow=0.25 cfs 0.020 afPond 5P: Drywell Outflow=0.05 cfs 0.020 af Peak Elev=16.21' Storage=518 cf Inflow=2.50 cfs 0.181 afPond RG: Rain Garden Discarded=0.14 cfs 0.082 af Primary=2.24 cfs 0.099 af Outflow=2.38 cfs 0.181 af Total Runoff Area = 2.044 ac Runoff Volume = 0.852 af Average Runoff Depth = 5.00" 27.84% Pervious = 0.569 ac 72.16% Impervious = 1.475 ac Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 97HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Area 1 Runoff = 2.50 cfs @ 12.09 hrs, Volume= 0.181 af, Depth= 5.01" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 13,045 98 Paved parking, HSG A 4,970 39 >75% Grass cover, Good, HSG A 845 98 Water Surface, HSG A 18,860 82 Weighted Average 4,970 26.35% Pervious Area 13,890 73.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 1S: Area 1 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=18,860 sf Runoff Volume=0.181 af Runoff Depth=5.01" Tc=6.0 min CN=82 2.50 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 98HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: Area 2 Runoff = 2.04 cfs @ 12.08 hrs, Volume= 0.161 af, Depth= 6.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 12,280 98 Paved parking, HSG A 673 39 >75% Grass cover, Good, HSG A 12,953 95 Weighted Average 673 5.20% Pervious Area 12,280 94.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Area 2 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=12,953 sf Runoff Volume=0.161 af Runoff Depth=6.51" Tc=6.0 min CN=95 2.04 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 99HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Area 3 Runoff = 1.02 cfs @ 12.08 hrs, Volume= 0.080 af, Depth= 6.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 6,171 98 Unconnected pavement, HSG A 297 39 >75% Grass cover, Good, HSG A 6,468 95 Weighted Average 297 4.59% Pervious Area 6,171 95.41% Impervious Area 6,171 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: Area 3 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=6,468 sf Runoff Volume=0.080 af Runoff Depth=6.51" Tc=6.0 min CN=95 1.02 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 100HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Area 4 Runoff = 0.99 cfs @ 12.08 hrs, Volume= 0.077 af, Depth= 6.27" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 5,844 98 Unconnected pavement, HSG A 563 39 >75% Grass cover, Good, HSG A 6,407 93 Weighted Average 563 8.79% Pervious Area 5,844 91.21% Impervious Area 5,844 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 4S: Area 4 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=6,407 sf Runoff Volume=0.077 af Runoff Depth=6.27" Tc=6.0 min CN=93 0.99 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 101HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Area 5 Runoff = 0.65 cfs @ 12.09 hrs, Volume= 0.048 af, Depth= 2.67" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 3,310 98 Unconnected pavement, HSG A 6,003 39 >75% Grass cover, Good, HSG A 9,313 60 Weighted Average 6,003 64.46% Pervious Area 3,310 35.54% Impervious Area 3,310 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: Area 5 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=9,313 sf Runoff Volume=0.048 af Runoff Depth=2.67" Tc=6.0 min CN=60 0.65 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 102HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Areaa 6 Runoff = 1.77 cfs @ 12.09 hrs, Volume= 0.130 af, Depth= 5.46" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 9,840 98 Unconnected pavement, HSG A 2,633 39 >75% Grass cover, Good, HSG A 12,473 86 Weighted Average 2,633 21.11% Pervious Area 9,840 78.89% Impervious Area 9,840 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 6S: Areaa 6 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=12,473 sf Runoff Volume=0.130 af Runoff Depth=5.46" Tc=6.0 min CN=86 1.77 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 103HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: Area 7 Runoff = 0.02 cfs @ 12.12 hrs, Volume= 0.003 af, Depth= 0.96" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Adj Description 82 98 Unconnected pavement, HSG A 1,387 39 >75% Grass cover, Good, HSG A 1,469 42 41 Weighted Average, UI Adjusted 1,387 94.42% Pervious Area 82 5.58% Impervious Area 82 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 7S: Area 7 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.025 0.024 0.023 0.022 0.021 0.02 0.019 0.018 0.017 0.016 0.015 0.014 0.013 0.012 0.011 0.01 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=1,469 sf Runoff Volume=0.003 af Runoff Depth=0.96" Tc=6.0 min UI Adjusted CN=41 0.02 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 104HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Area 8 Runoff = 0.61 cfs @ 12.09 hrs, Volume= 0.044 af, Depth= 3.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 3,092 98 Unconnected pavement, HSG A 4,316 39 >75% Grass cover, Good, HSG A 7,408 64 Weighted Average 4,316 58.26% Pervious Area 3,092 41.74% Impervious Area 3,092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 8S: Area 8 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=7,408 sf Runoff Volume=0.044 af Runoff Depth=3.08" Tc=6.0 min CN=64 0.61 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 105HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: Area 9 Runoff = 1.51 cfs @ 12.09 hrs, Volume= 0.108 af, Depth= 4.68" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 8,182 98 Unconnected pavement, HSG A 3,938 39 >75% Grass cover, Good, HSG A 12,120 79 Weighted Average 3,938 32.49% Pervious Area 8,182 67.51% Impervious Area 8,182 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 9S: Area 9 Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=12,120 sf Runoff Volume=0.108 af Runoff Depth=4.68" Tc=6.0 min CN=79 1.51 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 106HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 10S: Post Office Runoff = 0.25 cfs @ 12.08 hrs, Volume= 0.020 af, Depth= 6.86" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type III 24-hr 100-year Rainfall=7.10" Area (sf) CN Description 1,548 98 Roofs, HSG A 1,548 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 10S: Post Office Runoff Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 100-year Rainfall=7.10" Runoff Area=1,548 sf Runoff Volume=0.020 af Runoff Depth=6.86" Tc=6.0 min CN=98 0.25 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 107HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 1R: Area off-site - Northwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.034 ac, 5.58% Impervious, Inflow Depth = 0.96" for 100-year event Inflow = 0.02 cfs @ 12.12 hrs, Volume= 0.003 af Outflow = 0.02 cfs @ 12.12 hrs, Volume= 0.003 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 1R: Area off-site - Northwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.025 0.024 0.023 0.022 0.021 0.02 0.019 0.018 0.017 0.016 0.015 0.014 0.013 0.012 0.011 0.01 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0 Inflow Area=0.034 ac 0.02 cfs0.02 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 108HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 2R: Area off-site - Southwest [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.170 ac, 41.74% Impervious, Inflow Depth = 3.08" for 100-year event Inflow = 0.61 cfs @ 12.09 hrs, Volume= 0.044 af Outflow = 0.61 cfs @ 12.09 hrs, Volume= 0.044 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 2R: Area off-site - Southwest Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)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=0.170 ac 0.61 cfs0.61 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 109HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Reach 3R: Area off-site - East [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 0.278 ac, 67.51% Impervious, Inflow Depth = 4.68" for 100-year event Inflow = 1.51 cfs @ 12.09 hrs, Volume= 0.108 af Outflow = 1.51 cfs @ 12.09 hrs, Volume= 0.108 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Reach 3R: Area off-site - East Inflow Outflow Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.278 ac 1.51 cfs1.51 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 110HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 1P: Infiltration System #1 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=371) Inflow Area = 0.511 ac, 70.02% Impervious, Inflow Depth = 4.90" for 100-year event Inflow = 2.69 cfs @ 12.09 hrs, Volume= 0.209 af Outflow = 0.37 cfs @ 12.63 hrs, Volume= 0.209 af, Atten= 86%, Lag= 32.4 min Discarded = 0.37 cfs @ 12.63 hrs, Volume= 0.209 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 13.82' @ 12.63 hrs Surf.Area= 0.035 ac Storage= 0.064 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 52.0 min ( 832.9 - 780.9 ) Volume Invert Avail.Storage Storage Description #1A 11.25' 0.030 af 25.67'W x 59.50'L x 3.54'H Field A 0.124 af Overall - 0.049 af Embedded = 0.075 af x 40.0% Voids #2A 11.75' 0.049 af Cultec R-330XLHD x 40 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 0.079 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.25'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.37 cfs @ 12.63 hrs HW=13.82' (Free Discharge) 1=Exfiltration ( Controls 0.37 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 111HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 5 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 8 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 57.50' Row Length +12.0" End Stone x 2 = 59.50' Base Length 5 Rows x 52.0" Wide + 6.0" Spacing x 4 + 12.0" Side Stone x 2 = 25.67' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 40 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 5 Rows = 2,142.2 cf Chamber Storage 5,408.7 cf Field - 2,142.2 cf Chambers = 3,266.6 cf Stone x 40.0% Voids = 1,306.6 cf Stone Storage Chamber Storage + Stone Storage = 3,448.8 cf = 0.079 af Overall Storage Efficiency = 63.8% Overall System Size = 59.50' x 25.67' x 3.54' 40 Chambers 200.3 cy Field 121.0 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 112HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 1P: Infiltration System #1 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)3 2 1 0 Inflow Area=0.511 ac Peak Elev=13.82' Storage=0.064 af 2.69 cfs 0.37 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 113HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 2P: Infiltration System #2 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=377) Inflow Area = 0.719 ac, 75.73% Impervious, Inflow Depth = 3.82" for 100-year event Inflow = 3.96 cfs @ 12.10 hrs, Volume= 0.229 af Outflow = 0.51 cfs @ 12.64 hrs, Volume= 0.229 af, Atten= 87%, Lag= 32.2 min Discarded = 0.51 cfs @ 12.64 hrs, Volume= 0.229 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 14.54' @ 12.64 hrs Surf.Area= 2,028 sf Storage= 4,274 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 69.9 min ( 840.5 - 770.6 ) Volume Invert Avail.Storage Storage Description #1A 11.40' 1,720 cf 30.50'W x 66.50'L x 3.54'H Field A 7,183 cf Overall - 2,884 cf Embedded = 4,300 cf x 40.0% Voids #2A 11.90' 2,884 cf Cultec R-330XLHD x 54 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 4,603 cf Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 11.40'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.51 cfs @ 12.64 hrs HW=14.54' (Free Discharge) 1=Exfiltration ( Controls 0.51 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 114HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 6 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 9 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 64.50' Row Length +12.0" End Stone x 2 = 66.50' Base Length 6 Rows x 52.0" Wide + 6.0" Spacing x 5 + 12.0" Side Stone x 2 = 30.50' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 54 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 6 Rows = 2,883.5 cf Chamber Storage 7,183.4 cf Field - 2,883.5 cf Chambers = 4,299.8 cf Stone x 40.0% Voids = 1,719.9 cf Stone Storage Chamber Storage + Stone Storage = 4,603.5 cf = 0.106 af Overall Storage Efficiency = 64.1% Overall System Size = 66.50' x 30.50' x 3.54' 54 Chambers 266.1 cy Field 159.3 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 115HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 2P: Infiltration System #2 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)4 3 2 1 0 Inflow Area=0.719 ac Peak Elev=14.54' Storage=4,274 cf 3.96 cfs 0.51 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 116HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 3P: Infiltration System #3 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=393) Inflow Area = 0.148 ac, 95.41% Impervious, Inflow Depth = 6.51" for 100-year event Inflow = 1.02 cfs @ 12.08 hrs, Volume= 0.080 af Outflow = 0.14 cfs @ 12.58 hrs, Volume= 0.080 af, Atten= 86%, Lag= 30.1 min Discarded = 0.14 cfs @ 12.58 hrs, Volume= 0.080 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 14.80' @ 12.58 hrs Surf.Area= 0.014 ac Storage= 0.024 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 45.4 min ( 805.1 - 759.7 ) Volume Invert Avail.Storage Storage Description #1A 12.37' 0.013 af 16.00'W x 38.50'L x 3.54'H Field A 0.050 af Overall - 0.019 af Embedded = 0.031 af x 40.0% Voids #2A 12.87' 0.019 af Cultec R-330XLHD x 15 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.031 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.37'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.14 cfs @ 12.58 hrs HW=14.80' (Free Discharge) 1=Exfiltration ( Controls 0.14 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 117HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 5 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 36.50' Row Length +12.0" End Stone x 2 = 38.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 15 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 815.9 cf Chamber Storage 2,181.7 cf Field - 815.9 cf Chambers = 1,365.8 cf Stone x 40.0% Voids = 546.3 cf Stone Storage Chamber Storage + Stone Storage = 1,362.2 cf = 0.031 af Overall Storage Efficiency = 62.4% Overall System Size = 38.50' x 16.00' x 3.54' 15 Chambers 80.8 cy Field 50.6 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 118HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 3P: Infiltration System #3 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.148 ac Peak Elev=14.80' Storage=0.024 af 1.02 cfs 0.14 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 119HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 4P: Infiltration System #4 [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=344) Inflow Area = 0.147 ac, 91.21% Impervious, Inflow Depth = 6.27" for 100-year event Inflow = 0.99 cfs @ 12.08 hrs, Volume= 0.077 af Outflow = 0.12 cfs @ 12.63 hrs, Volume= 0.077 af, Atten= 88%, Lag= 33.0 min Discarded = 0.12 cfs @ 12.63 hrs, Volume= 0.077 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 16.36' @ 12.63 hrs Surf.Area= 0.012 ac Storage= 0.025 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 61.1 min ( 829.5 - 768.4 ) Volume Invert Avail.Storage Storage Description #1A 12.95' 0.010 af 16.00'W x 31.50'L x 3.54'H Field A 0.041 af Overall - 0.015 af Embedded = 0.026 af x 40.0% Voids #2A 13.45' 0.015 af Cultec R-330XLHD x 12 Inside #1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 0.025 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 12.95'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.12 cfs @ 12.63 hrs HW=16.36' (Free Discharge) 1=Exfiltration ( Controls 0.12 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 120HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 - Chamber Wizard Field A Chamber Model = Cultec R-330XLHD (Cultec Recharger® 330XLHD) Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 3 rows 52.0" Wide + 6.0" Spacing = 58.0" C-C Row Spacing 4 Chambers/Row x 7.00' Long +1.50' Row Adjustment = 29.50' Row Length +12.0" End Stone x 2 = 31.50' Base Length 3 Rows x 52.0" Wide + 6.0" Spacing x 2 + 12.0" Side Stone x 2 = 16.00' Base Width 6.0" Base + 30.5" Chamber Height + 6.0" Cover = 3.54' Field Height 12 Chambers x 52.2 cf +1.50' Row Adjustment x 7.45 sf x 3 Rows = 659.4 cf Chamber Storage 1,785.0 cf Field - 659.4 cf Chambers = 1,125.6 cf Stone x 40.0% Voids = 450.2 cf Stone Storage Chamber Storage + Stone Storage = 1,109.6 cf = 0.025 af Overall Storage Efficiency = 62.2% Overall System Size = 31.50' x 16.00' x 3.54' 12 Chambers 66.1 cy Field 41.7 cy Stone Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 121HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 4P: Infiltration System #4 Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=0.147 ac Peak Elev=16.36' Storage=0.025 af 0.99 cfs 0.12 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 122HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond 5P: Drywell [87] Warning: Oscillations may require smaller dt or Finer Routing (severity=466) Inflow Area = 0.036 ac,100.00% Impervious, Inflow Depth = 6.86" for 100-year event Inflow = 0.25 cfs @ 12.08 hrs, Volume= 0.020 af Outflow = 0.05 cfs @ 12.52 hrs, Volume= 0.020 af, Atten= 81%, Lag= 26.1 min Discarded = 0.05 cfs @ 12.52 hrs, Volume= 0.020 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 13.24' @ 12.52 hrs Surf.Area= 0.005 ac Storage= 0.005 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 24.5 min ( 767.3 - 742.8 ) Volume Invert Avail.Storage Storage Description #1 11.00' 0.008 af 10.00'W x 20.00'L x 5.67'H Prismatoid 0.026 af Overall - 0.005 af Embedded = 0.021 af x 40.0% Voids #2 12.00' 0.005 af 6.00'D x 3.58'H Vertical Cone/Cylinder x 2 Inside #1 0.005 af Overall - 3.0" Wall Thickness = 0.005 af 0.013 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' Discarded OutFlow Max=0.05 cfs @ 12.52 hrs HW=13.24' (Free Discharge) 1=Exfiltration ( Controls 0.05 cfs) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 123HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond 5P: Drywell Inflow Discarded Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.036 ac Peak Elev=13.24' Storage=0.005 af 0.25 cfs 0.05 cfs Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 124HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Summary for Pond RG: Rain Garden Inflow Area = 0.433 ac, 73.65% Impervious, Inflow Depth = 5.01" for 100-year event Inflow = 2.50 cfs @ 12.09 hrs, Volume= 0.181 af Outflow = 2.38 cfs @ 12.11 hrs, Volume= 0.181 af, Atten= 5%, Lag= 1.6 min Discarded = 0.14 cfs @ 12.11 hrs, Volume= 0.082 af Primary = 2.24 cfs @ 12.11 hrs, Volume= 0.099 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 16.21' @ 12.11 hrs Surf.Area= 687 sf Storage= 518 cf Plug-Flow detention time= 20.9 min calculated for 0.181 af (100% of inflow) Center-of-Mass det. time= 21.0 min ( 823.5 - 802.5 ) Volume Invert Avail.Storage Storage Description #1 14.00' 752 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 14.00 2 10.9 0 0 2 15.00 157 71.4 59 59 400 16.00 546 134.3 332 391 1,435 16.50 915 200.6 361 752 3,204 Device Routing Invert Outlet Devices #1 Discarded 14.00'8.270 in/hr Exfiltration over Horizontal area Conductivity to Groundwater Elevation = 1.00' #2 Device 3 15.70'2.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Primary 13.15'12.0" Round Culvert L= 25.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet / Outlet Invert= 13.15' / 12.90' S= 0.0100 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.14 cfs @ 12.11 hrs HW=16.21' (Free Discharge) 1=Exfiltration ( Controls 0.14 cfs) Primary OutFlow Max=2.24 cfs @ 12.11 hrs HW=16.21' TW=12.91' (Dynamic Tailwater) 3=Culvert (Passes 2.24 cfs of 6.05 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 2.24 cfs @ 2.33 fps) Great Island Plaza, West Yarmouth, MA Type III 24-hr 100-year Rainfall=7.10"5035001-Post Printed 7/7/2020Prepared by BSC Group Page 125HydroCAD® 10.00-22 s/n 00904 © 2018 HydroCAD Software Solutions LLC Pond RG: Rain Garden Inflow Outflow Discarded Primary Hydrograph Time (hours) 3635343332313029282726252423222120191817161514131211109876543210Flow (cfs)2 1 0 Inflow Area=0.433 ac Peak Elev=16.21' Storage=518 cf 2.50 cfs 2.38 cfs 0.14 cfs 2.24 cfs Stormwater Report Great Island Plaza LLC West Yarmouth, MA SECTION 7.0 ADDITIONAL DRAINAGE CALCULATIONS Stormwater Report Great Island Plaza LLC West Yarmouth, MA 7.01 TSS REMOVAL CALCULATIONS TSS Removal Calculation Worksheet Location: West Yarmouth, MA Project: Great Island Plaza Prepared By: T. MacDonald Date: 7/7/20 Subcatchment Areas 1S Total Impervious Area, Acres= 0.319 A BCDE BMP TSS Removal Rate Starting TSS Load* Amount Removed (BxC) Remaining Load (C-D) Rain Garden 0.9 1.00 0.9 0.10 Subsurface Chambers 0.8 0.10 0.08 0.02 TSS Removal =0.98 Subcatchment Areas 2S, 3S, 4S, 5S, 6S Total Impervious Area, Acres= 0.860 ABCDE BMP TSS Removal Starting TSS Amount Remaining Load Deep Sump Hooded Catch Basins 0.25 1.00 0.25 0.75 Water Quality Unit 0.8 0.75 0.60 0.15 Subsurface Chambers 0.8 0.15 0.12 0.03 TSS Removal = 0.97 Subcatchment Areas 7S, 8S, and 9S Total Impervious Area, Acres= 0.261 A `CDE BMP TSS Removal Rate Starting TSS Load* Amount Removed (BxC) Remaining Load (C-D) None 0.0 1.00 0.0 1.00 TSS Removal = 0.00 Subcatchment Area 10S Total Impervious Area, Acres= 0.036 A `CDE BMP TSS Removal Rate Starting TSS Load* Amount Removed (BxC) Remaining Load (C-D) Drywell 0.8 1.00 0.80 0.20 TSS Removal = 0.80 WEIGHTED AVERAGE Total Site TSS Removal= Total Site TSS Removal = 0.80 *Equals remaining load from previous BMP (E) [(0.319*0.98)+(0.860*0.97)+(0.261*0)+(0.036*0.80)] (0.319+0.860+0.261+0.036) Prj\2290800\Design\Drainage\TSS-REMOVAL Weighted Ave.xls 7/8/2020 8:50 AM Stormwater Report Great Island Plaza LLC West Yarmouth, MA 7.02 GROUNDWATER RECHARGE VOLUME CALCULATIONS Stormwater Report Great Island Plaza LLC West Yarmouth, MA Required Recharge Volume Rv = F x Impervious Area Where: Rv = Recharge Volume F=Target Depth Factor associated with each Hydrologic Soil Group (F=0.60-inch for Soil Type A) Impervious Area = Proposed Pavement area on-site 𝑅𝑣=൬ 0.60 𝑖𝑛 12 𝑖𝑛/𝑓𝑡൰ (1.475 𝑎𝑐)൬43,560 𝑠𝑓 𝑎𝑐൰ = 3,213 𝑐𝑓 Rv = 3,213 cf (required recharge volume) Structural Storage Provided: o Infiltration Basin = 11,258 cubic feet provided. Refer to the HydroCAD calculations for more information. Drawdown Time The following formula must be used to demonstrate that each proposed infiltration BMP will drain within 72 hours: Time drawdown = Rv (K)(Bottom Area) Rv = Storage Volume (Required Recharge Volume) K = Saturated Hydraulic Conductivity For “Static” and “Simple Dynamic” Methods, use Rawls Rate Bottom Area = Bottom Area of Recharge Structure Infiltration System #1 Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(1,527 ft2) Time drawdown = 3.05 hours Stormwater Report Great Island Plaza LLC West Yarmouth, MA Rain Garden #1 Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(915 ft2) Time drawdown = 5.10 hours Infiltration System #2 Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(2,028 ft2) Time drawdown = 2.30 hours Infiltration System #3 Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(616 ft2) Time drawdown = 7.57 hours Infiltration System #4 Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(504 ft2) Time drawdown = 9.25 hours Drywell Time drawdown = 3,213 ft3 (8.270 in/hr)(1 ft/12 in)(200 ft2) Time drawdown = 23.31 hours Stormwater Report Great Island Plaza LLC West Yarmouth, MA 7.03 WATER QUALITY VOLUME CALCULATIONS Stormwater Report Great Island Plaza LLC West Yarmouth, MA Water Quality Volume Calculation VWQ = (DWQ/12 inches/foot) * (AIMP square feet) VWQ = Required Water Quality Volume (in cubic feet) DWQ = Water Quality Depth: 1.0-inch used (1-inch for rapid infiltration rates, greater than 2.4 inches per hour & 0.5-inch for other areas) AIMP = Total Impervious Area (in acres) used for driveways, parking, etc. Infiltration Basin #1 AIMP = 1.475 ac VWQ = (1 inch/12 inches/foot) * (1.475 ac x 43,560 square feet/ac) VWQ = 5,354 cubic feet (required volume), provided volume = 11,258 cubic feet (refer to HydroCAD Stormwater Report Great Island Plaza LLC West Yarmouth, MA APPENDIX A USGS LOCUS MAP Stormwater Report Great Island Plaza LLC West Yarmouth, MA APPENDIX B FEMA MAP USGS The National Map: Orthoimagery. Data refreshed April 2020 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 7/8/2020 at 10:36 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 70°14'7"W 41°39'15"N 70°13'30"W 41°38'48"N Stormwater Report Great Island Plaza LLC West Yarmouth, MA APPENDIX C WEB SOIL SURVEY Soil Map—Barnstable County, Massachusetts (GREAT ISLAND PLAZA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/30/2020 Page 1 of 34611600461162046116404611660461168046117004611720461160046116204611640461166046116804611700397510397530397550397570397590397610397630397650397670397690 397510 397530 397550 397570 397590 397610 397630 397650 397670 397690 41° 39' 2'' N 70° 13' 51'' W41° 39' 2'' N70° 13' 42'' W41° 38' 58'' N 70° 13' 51'' W41° 38' 58'' N 70° 13' 42'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 19N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:880 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:25,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Barnstable County, Massachusetts Survey Area Data: Version 16, Sep 12, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 10, 2018—Nov 17, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Barnstable County, Massachusetts (GREAT ISLAND PLAZA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/30/2020 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 252A Carver coarse sand, 0 to 3 percent slopes 2.2 100.0% Totals for Area of Interest 2.2 100.0% Soil Map—Barnstable County, Massachusetts GREAT ISLAND PLAZA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/30/2020 Page 3 of 3 Stormwater Report Great Island Plaza LLC West Yarmouth, MA APPENDIX D SOIL TEST PIT LOGS Title V - Form 11.doc • rev. 3/15/18 Form 11 – Soil Suitability Assessment for On-Site Sewage Disposal • Page 2 of 5 Commonwealth of Massachusetts City/Town of Yarmouth Form 11 - Soil Suitability Assessment for On-Site Sewage Disposal C. On-Site Review (minimum of two holes required at every proposed primary and reserve disposal area) Deep Observation Hole Number: TP-1 Hole # 6/9/20 Date 3 PM Time 80 Sun Weather Latitude Longitude:1. Land Use Open field (e.g., woodland, agricultural field, vacant lot, etc.) Grass Vegetation Some surface stones Surface Stones (e.g., cobbles, stones, boulders, etc.) 0-5% Slope (%) Description of Location: 2. Soil Parent Material: sandy glaciofluvial deposits outwash plains Landform SH Position on Landscape (SU, SH, BS, FS, TS) 3. Distances from: Open Water Body N/A feet Drainage Way N/A feet Wetlands N/A feet Property Line >25 feet Drinking Water Well N/A feet Other feet 4. Unsuitable Materials Present: Yes No If Yes: Disturbed Soil Fill Material Weathered/Fractured Rock Bedrock 5. Groundwater Observed: Yes No If yes: Depth Weeping from Pit Depth Standing Water in Hole Soil Log Depth (in) Soil Horizon /Layer Soil Texture (USDA Soil Matrix: Color-Moist (Munsell) Redoximorphic Features Coarse Fragments % by Volume Soil StructureSoil Consistence (Moist) Other Depth Color PercentGravel Cobbles & Stones0-8 A LS 10YR 4/2 - - - - - granular friable - 8-30 B LS 10YR 6/8 - - - - - granular friale 30-120 C FS 2.5Y 6/3 - - - 1 - SG LOOSE Additional Notes: No GW observed Title V - Form 11.doc • rev. 3/15/18 Form 11 – Soil Suitability Assessment for On-Site Sewage Disposal • Page 3 of 5 Commonwealth of Massachusetts City/Town of Yarmouth Form 11 - Soil Suitability Assessment for On-Site Sewage Disposal C. On-Site Review (minimum of two holes required at every proposed primary and reserve disposal area) Deep Observation Hole Number: TP-2 Hole # 6/9/20 Date 3:30 PM Time 80 Sun Weather Latitude Longitude: 1. Land Use: Open Field (e.g., woodland, agricultural field, vacant lot, etc.) Grass Vegetation Some surface stones Surface Stones (e.g., cobbles, stones, boulders, etc.) 0-5% Slope (%) Description of Location: 2. Soil Parent Material: sandy glaciofluvial deposits outwash plains Landform SH Position on Landscape (SU, SH, BS, FS, TS) 3. Distances from: Open Water Body N/A feet Drainage Way N/A feet Wetlands N/A feet Property Line >25 feetDrinking Water Well N/A feet Other feet4. Unsuitable Materials Present: Yes No If Yes: Disturbed Soil Fill Material Weathered/Fractured Rock Bedrock5. Groundwater Observed: Yes No If yes:Depth Weeping from PitDepth Standing Water in HoleSoil LogDepth (in) Soil Horizon /Layer Soil Texture (USDA) Soil Matrix: Color-Moist (Munsell) Redoximorphic Features Coarse Fragments % by Volume Soil Structure Soil Consistence (Moist) Other Depth Color PercentGravel Cobbles & Stones 0-10 A LS 10YR 4/2 - - - - - granular friable 10-28 B LS 10YR 6/8 - -- - - - granular friable 28-120 C FS 2.5Y 6/3 - - - 1 - SG Loose Additional Notes: No GW observed