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228 Route 28 Stormwater Report r3
__________________________________________________________________________________________ Green Seal Environmental, LLC 114 State Road, Sagamore Beach, MA 02562 | Tel: (508) 888-6034 | Fax: (508) 888-1506 | www.gseenv.com __________________________________________________________________________________________ Stormwater Management Report M Proposed A Plus Market 228 Route 28 Yarmouth, MA Applicant/Owner: A Plus Real Estate LLC 206 Barnstable Road Hyannis, MA 02601 February 2024 revised July 2024 Table of Contents PROJECT NARRATIVE Project Description Regulatory Compliance Stormwater Checklist APPENDICES Appendix A: Standard 2 Existing HydroCAD Report Existing Watersheds Appendix B: NRCS Soil Report Appendix C: Standard 2 Proposed HydroCAD Report Proposed Watersheds plan Appendix D: Standard 9 Long-term Operation & Maintenance Plan Maintenance Log Forms Appendix E: Standard 8 Construction Period Pollution Prevention Plan Appendix F: Misc. Stormwater Documentation Appendix H: Site Plan Set (Attached) PROPERTY OWNER/APPLICANT: A Plus Real Estate LLC 206n Barnstable Road Hyannis, MA 02601 1 GREEN SEAL ENVIRONMENTAL, LLC Project Description This Stormwater Report describes the improvements to the stormwater management systems located at 228 Route 28 Yarmouth MA (the Site) and documents the Site’s compliance with the Massachusetts Stormwater Standards (the Standards) and the Town of Yarmouth Stormwater Management Regulations (the Regulations). The Site is located at 228 Route 28, with frontage and access only on state Route 28 (see Figure 1). The proposed project is new construction of a retail store with apartments on a second story. The Site was previously occupied by a restaurant, whose building has been demolished, leaving a partial foundation slab, paved areas, and utilities. Stormwater controls evident include a leaching catchbasin in the paved area; no other stormwater controls were found during the survey or on record plans reviewed. The site is served by municipal water, fire protection, and is also served by an on-site sewage disposal system. This system will be used until municipal sewer becomes available. 2 GREEN SEAL ENVIRONMENTAL, LLC Existing Conditions The Existing Conditions plan included in the Site Plan Set shows the existing stormwater features on the Site. One catchbasin, which appears to be a drywell, is present in the existing paved area. No other stormwater features were evident. Two catchbasins are present in the gutter along Route 28, but they do not receive any significant runoff from the Site, as it is graded away from the back of the sidewalk. The rear portion of the site, including paved areas, is tributary to the offsite wetland to the rear (north) of the site. The front right portion of the site is tributary to the aforementioned catchbasin/drywell, and does not appear to discharge to the drainage system in the state highway. The front left portion of the site currently drains internally to a low point within the former building area. This low point appears to be due to the demolition of the building. Runoff patterns from when the building was present aren’t known. It appears likely that at least some of the runoff entered onto the state highway gutter through the existing westernmost driveway. In order to model site runoff, the Site was subdivided into several Watershed Areas, both existing and proposed, as described in Appendix A (Existing Conditions) and Appendix C (Proposed Conditions), with design points selected based on the above conditions. The models compare pre- and post- development runoff to the offsite wetland and to the state highway. According to Natural Resource Conservation Service (NRCS) mapping, included in Appendix B, the site is underlain by Carver coarse sand, 0-3 percent slopes, assigned to Hydrologic Soil Group A. Soil evaluations conducted on the Site are consistent with this mapping. 3 GREEN SEAL ENVIRONMENTAL, LLC Proposed Conditions The applicant is proposing to construct a new building and supporting parking, as noted previously. As shown on the Proposed Watersheds plan, the new site layout will include the new building, reconfigured paved area, and new landscaping. These changes will change runoff patterns on the site somewhat, while remaining similar to existing conditions. Impervious cover will increase very slightly, from 38,641 square feet to 38,803 square feet. The major change to site hydrology will be the construction of new stormwater facilities to comply with current regulations. For purposes of modeling, surface runoff from the proposed site is divided into 3 discharge locations. Landscaped portions of the rear of the site will continue to discharge to the offsite wetland. All impervious surfaces will discharge to new stormwater practices. The Project utilizes the following stormwater Best Management Practices (BMPs): Non-Structural Pretreatment Practices o Good housekeeping o Pavement sweeping Structural Pretreatment Practice o Rip rap apron/Vegetated Filter Strip Structural Treatment Practice o Exfiltrating Rain Garden o Subsurface Infiltration Infiltration Practice o Exfiltrating Rain Garden o Subsurface Infiltration The proposed facility use is not a Land Use with Higher Potential Pollutant Load (LUHPPL). Thus, the water quality structures must meet the requirement of treating the first ½ inch of runoff under the Policy. The Exfiltrating Rain Garden and Subsurface Infiltration will in fact exfiltrate the entire runoff volume of their tributary areas. Due to the permeable soils encountered, the Exfiltrating Rain Garden and Subsurface Infiltration will also mitigate peak rates of runoff, with all runoff detained and exfiltrated for all storms up to and including the 100 year storm. Larger storms will discharge into the gutter of Route 28 and not affect adjacent properties. 4 GREEN SEAL ENVIRONMENTAL, LLC Methodology Pre- and post-development stormwater analysis was completed for the 2-, 10-, and 100-year, 24-hour storm event using HydroCAD® stormwater modeling software. This stormwater modeling software was developed using TR-55 and TR-20 modeling protocol and is widely used and accepted in the engineering design practice. Since calculated values for time of concentration would be very short, a minimum value (6 minutes) is used for proposed impervious areas. The HydroCAD® report for pre- and post-development conditions along with the corresponding Watersheds) are included in Appendix A and C. Analysis of the stormwater management system’s discharge points indicate that there will be no overall increase in stormwater discharge from the site as a result of the proposed project development for the 2-, 10-, and 100-year storm events. MassDEP Stormwater Management Standards Stormwater Standards The Massachusetts Stormwater Management Policy (the Policy) established ten stormwater management standards which need to be considered for new or redevelopment projects. For redevelopment of a previously developed site, as is the case with this Project, projects must meet the stormwater management standards to the maximum extent practicable. At the very least, the stormwater system must be designed to improve existing conditions. The following section presents these ten Stormwater Standards, identifies how said standard applies to the proposed Project, and how the Project complies. Standard 1 No untreated Discharges No new stormwater conveyances (e.g. outfalls) may discharge untreated stormwater directly to or cause erosion in the wetlands or waters of the Commonwealth. No new stormwater conveyances are proposed. Standard 2 Peak Rate Stormwater management systems shall be designed so that the post- development peak discharge rates do not exceed the Existing discharge rates. Site modification have been designed to ensure that overall proposed runoff (post-development) does not exceed existing (pre-development) runoff rate to offsite. The pre and post development peak stormwater rates for each watershed have been calculated for the 2-, 10-, and 100-year rainfall events. A comparison of the off-site peak flow for the pre- and post-development conditions is presented in the table below. The table demonstrates that most runoff is retained on site, and the offsite discharge to the property to the north 5 GREEN SEAL ENVIRONMENTAL, LLC is equal or reduced under proposed conditions. Table 1 – Peak Flow Rate Comparison (cfs) 2-Year 10-Year 100-Year Pre Post Pre Post Pre Post Offsite to North 0.02 0.00 0.30 0.00 1.93 0.25 Offsite to Rt. 28 3.20* 0.00** 5.19* 0.00** 9.84 0.00** * see Node 5L for description; ** all developed site runoff infiltrated The stormwater management policy requires that post-development peak runoff rates are maintained for the 2- and 10-year storm events. In addition to meeting that requirement, the calculations indicate that the 100-year storm event will be contained on site, with no runoff onto adjacent properties. Appendix A contains the HydroCAD® reports for the existing conditions and Appendix C contains the HydroCAD® reports for post-development (proposed) conditions. Standard 3 Loss of Annual Recharge Loss of annual recharge to groundwater shall be eliminated or minimized through the use of environmentally sensitive site design, low impact development techniques, stormwater best management practices, and good operation and maintenance. MassDEP only requires recharge to the maximum extent practicable where recharge volume may cause or contribute to groundwater contamination. Pre-existing recharge is maintained and the proposed Exfiltrating Rain Garden and Subsurface Infiltration will provide additional recharge meeting the standards. Please refer to the calculation in Appendix F. Standard 4 Water Quality (TSS Removal Rates) Stormwater Management Systems shall be designed to remove 80% of the average annual post-construction load of Total Suspended Solids (TSS). The proposed stormwater management systems include structural stormwater best management practices that capture total suspended solids (TSS) from impervious surfaces. Runoff from Proposed Watershed 3 from trafficked impervious areas will be directed to the vegetated filter strip that provides TSS removal prior to entering the Exfiltrating Rain Garden. Runoff from trafficked impervious areas 6 GREEN SEAL ENVIRONMENTAL, LLC in Proposed Watershed 2 will be directed to a deep sump catchbasin connected to a Stormceptor 450i water quality inlet before being discharged into the Subsurface Infiltration system. A Long-term Operation and Maintenance (pollution prevention) plan has been prepared outlining maintenance tasks and frequency required to promote reliable operation of the proposed stormwater treatment system BMPs. The Long-Term Operations and Maintenance Plan is provided in Appendix D. Standard 5 Land Use with Higher Potential Pollutant Loads For land uses with higher potential pollutant loads, source control and pollution prevention shall be implemented in accordance with the Massachusetts Stormwater Handbook to eliminate or reduce the discharge of stormwater runoff from such land uses to the maximum extent practicable. The proposed use is NOT a LUHPPL and no special source control and pollution prevention measures are required. Standard 6 Critical Areas (Zone II Discharges) Stormwater discharges within the Zone II or Interim Wellhead Protection Area (IWPA) of a public water supply and stormwater discharges near or to any other critical area require the use of the specific source control and pollution prevention measures and the specific structural stormwater best management practices determined by the Department to be suitable for managing discharges to such areas, as provided in the Massachusetts Stormwater Handbook. This standard is not applicable to this site, as the Site is not located within a Zone II or IWPA or any other critical zone. Standard 7 Redevelopment A redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural best management practice requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. This project qualifies as a partial redevelopment project. Documentation of compliance to Standards 1, 2, 3, as well as applicable components of 4, 5, and 6 for new impervious areas are included in this report. The Project meets the Redevelopment Standards. The Project improves over existing conditions by the addition of water quality measures, infiltration, and downstream protection meeting current Stormwater Standards. 7 GREEN SEAL ENVIRONMENTAL, LLC Standard 8 Erosion and Sedimentation Control Plan A plan to control construction-related impacts including erosion, sedimentation and other pollutant sources during construction and land disturbance activities (construction period erosion, sedimentation, and pollution prevention plan) shall be developed and implemented An Erosion Control and Demolition Plan is included in the site plan set including construction details and notes. Proposed erosion and sedimentation controls include perimeter erosion controls barriers, stabilized construction entrance, stockpile management, and the stabilization of disturbed areas as well as good housekeeping measures. A written Construction Period Pollution Prevention Plan is provided in Appendix E. Standard 9 Operation and Maintenance Plan A long-term operation and maintenance plan shall be developed and implemented to ensure that stormwater management systems function as designed. The Long-Term Operation and Maintenance Plan (O&M Plan) details activities and good housekeeping practices to maintain the effectiveness of the proposed stormwater system. The O&M Plan included in Appendix D, includes the following general practices as part of the long-term operations and maintenance of the stormwater system: Street Sweeping. Street Sweeping is proposed as part of TSS removal for all paved areas and will be conducted at the required frequencies and/or with the appropriate equipment as required to meet TSS removal efficiencies. Good Housekeeping. The Site will be kept clean of litter, debris, and sediments with the establishment of regular site inspections and litter clean-ups and street sweeping. Landscaping at the site will be maintained with regular mowing, repair of erosion, removal of sedimentation, etc. Stormwater structures will be inspected and cleaned per the schedule outlined in the O&M Plan. Operational Controls. The Facility will operate in accordance with applicable permits and a Facility Operations and Maintenance Plan. Inspections. Inspection of the stormwater system will occur in accordance with the schedule outlined in the Plan. As mentioned above, protocols to address standards 8 and 9 have been included at the end of this report. Standard 10 Illicit Discharges to the Stormwater Management System All illicit discharges to the stormwater management system are prohibited. The project will be constructed in accordance with the design plans and will not create any illicit discharges to the stormwater management system. During our survey of the property we did not encounter any evidence of illicit discharges. 8 GREEN SEAL ENVIRONMENTAL, LLC Town of Yarmouth Stormwater Management Regulations Section 2.05 (1) Low Impact Development (LID) Low Impact Development techniques have been employed to the extent practicable in the design of the project: No disturbance to any Wetland Resource Area or buffer zone Minimized disturbance to existing trees and shrubs Bioretention (Exfiltrating Rain Garden) Roof runoff directly to infiltration system without crossing pavement Extensive tree plantings with some canopy over pavement The small size, single building, and operational needs of the project limit LID practices to those cited. Other Applicable Design Performance Standards Section 2.05 (3) (a) 100 year post-development stormwater volume controlled on site with no offsite discharge Section 2.05 (3) (b) Roof is shingle and membrane and not metal and can be infiltrated without pretreatment as the site is outside of a Zone 2 or IWPA Section 2.05 (5) (b) All runoff from trafficked impervious areas is directed through pretreatment into infiltration practices, eliminating any stormwater discharge of TSS, TP, and TN. Section 2.06 An Erosion and Sediment Control Plan meeting the requirements of this section is included in the Site Plan. There are no stormwater discharges from construction activities to Waters of the United States proposed. Only the remaining undeveloped area of the site remains tributary to the offsite wetland to the north. Therefore coverage under the Construction General Permit does not appear to be warranted. Should that change, a SWPPP will be submitted prior to construction. Section 2.07 An Operation and Maintenance Plan includes the requirement for annual and quinquennial certifications. Section 2.09 Final report and as-built plan will be submitted as required. swcheck • 04/01/08 Stormwater Report Checklist • Page 1 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. A Stormwater Report must be submitted with the Notice of Intent permit application to document compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for the Stormwater Report (which should provide more substantive and detailed information) but is offered here as a tool to help the applicant organize their Stormwater Management documentation for their Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, the Stormwater Report must contain the engineering computations and supporting information set forth in Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth. The Stormwater Report must include: The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see page 2) that certifies that the Stormwater Report contains all required submittals.1 This Checklist is to be used as the cover for the completed Stormwater Report. Applicant/Project Name Project Address Name of Firm and Registered Professional Engineer that prepared the Report Long-Term Pollution Prevention Plan required by Standards 4-6 Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. swcheck • 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. swcheck • 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. swcheck • 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. swcheck • 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. swcheck • 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. swcheck • 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. ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX A STANDARD 2 EXISTING HYDROCAD REPORT EXISTING WATERSHEDS PLAN 1S A 2S B 3S C 4L Offsite to North 5L Route 28 Routing Diagram for Existing - 228 R28 Prepared by Green Seal Environmental LLC, Printed 5/6/2024 HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link NOAA10 24-hr C 2-Year Rainfall=3.26"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 2HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: A Runoff = 0.02 cfs @ 13.28 hrs, Volume= 449 cf, Depth= 0.14" Routed to Link 4L : Offsite to North Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 15,339 30 Woods, Good, HSG A 13,500 39 >75% Grass cover, Good, HSG A 9,350 98 Paved parking, HSG A 38,189 50 Weighted Average 28,839 75.52% Pervious Area 9,350 24.48% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.2 30 0.0070 0.06 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 6.5 162 0.0070 0.42 Shallow Concentrated Flow, Shallow concentrated Woodland Kv= 5.0 fps 14.7 192 Total Subcatchment 1S: A Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)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 Runoff=0.02 cfs @ 13.28 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=38,189 sf Runoff Volume=449 cf Runoff Depth=0.14" Flow Length=192' Slope=0.0070 '/' Tc=14.7 min CN=50 0.02 cfs @ 13.28 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 3HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: B Runoff = 2.05 cfs @ 12.10 hrs, Volume= 4,785 cf, Depth= 2.41" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 1,370 30 Woods, Good, HSG A 962 39 >75% Grass cover, Good, HSG A 21,519 98 Paved parking, HSG A 23,851 92 Weighted Average 2,332 9.78% Pervious Area 21,519 90.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.1 50 0.0060 0.75 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.9 82 0.0060 1.57 Shallow Concentrated Flow, Shallow concentrated flow Paved Kv= 20.3 fps 2.0 132 Total Subcatchment 2S: B Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=2.05 cfs @ 12.10 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=23,851 sf Runoff Volume=4,785 cf Runoff Depth=2.41" Flow Length=132' Slope=0.0060 '/' Tc=2.0 min CN=92 2.05 cfs @ 12.10 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 4HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: C Runoff = 1.15 cfs @ 12.10 hrs, Volume= 2,398 cf, Depth= 1.45" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 12,096 68 <50% Grass cover, Poor, HSG A 7,772 98 Paved parking, HSG A 19,868 80 Weighted Average 12,096 60.88% Pervious Area 7,772 39.12% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 45 0.0100 0.90 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.3 31 0.0100 1.61 Shallow Concentrated Flow, Shallow concentrated flow Unpaved Kv= 16.1 fps 1.1 76 Total Subcatchment 3S: C Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Runoff=1.15 cfs @ 12.10 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=19,868 sf Runoff Volume=2,398 cf Runoff Depth=1.45" Flow Length=76' Slope=0.0100 '/' Tc=1.1 min CN=80 1.15 cfs @ 12.10 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 5HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 4L: Offsite to North Inflow Area = 38,189 sf, 24.48% Impervious, Inflow Depth = 0.14" for 2-Year event Inflow = 0.02 cfs @ 13.28 hrs, Volume= 449 cf Primary = 0.02 cfs @ 13.28 hrs, Volume= 449 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 4L: Offsite to North Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)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=38,189 sf Inflow=0.02 cfs @ 13.28 hrs Primary=0.02 cfs @ 13.28 hrs 0.02 cfs @ 13.28 hrs0.02 cfs @ 13.28 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 6HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 5L: Route 28 Inflow Area = 43,719 sf, 67.00% Impervious, Inflow Depth = 1.97" for 2-Year event Inflow = 3.20 cfs @ 12.10 hrs, Volume= 7,183 cf Primary = 3.20 cfs @ 12.10 hrs, Volume= 7,183 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 5L: Route 28 Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=43,719 sf Inflow=3.20 cfs @ 12.10 hrs Primary=3.20 cfs @ 12.10 hrs 3.20 cfs @ 12.10 hrs3.20 cfs @ 12.10 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 7HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: A Runoff = 0.30 cfs @ 12.28 hrs, Volume= 1,875 cf, Depth= 0.59" Routed to Link 4L : Offsite to North Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 15,339 30 Woods, Good, HSG A 13,500 39 >75% Grass cover, Good, HSG A 9,350 98 Paved parking, HSG A 38,189 50 Weighted Average 28,839 75.52% Pervious Area 9,350 24.48% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.2 30 0.0070 0.06 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 6.5 162 0.0070 0.42 Shallow Concentrated Flow, Shallow concentrated Woodland Kv= 5.0 fps 14.7 192 Total Subcatchment 1S: A Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Runoff=0.30 cfs @ 12.28 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=38,189 sf Runoff Volume=1,875 cf Runoff Depth=0.59" Flow Length=192' Slope=0.0070 '/' Tc=14.7 min CN=50 0.30 cfs @ 12.28 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 8HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: B Runoff = 3.17 cfs @ 12.10 hrs, Volume= 7,624 cf, Depth= 3.84" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 1,370 30 Woods, Good, HSG A 962 39 >75% Grass cover, Good, HSG A 21,519 98 Paved parking, HSG A 23,851 92 Weighted Average 2,332 9.78% Pervious Area 21,519 90.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.1 50 0.0060 0.75 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.9 82 0.0060 1.57 Shallow Concentrated Flow, Shallow concentrated flow Paved Kv= 20.3 fps 2.0 132 Total Subcatchment 2S: B Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Runoff=3.17 cfs @ 12.10 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=23,851 sf Runoff Volume=7,624 cf Runoff Depth=3.84" Flow Length=132' Slope=0.0060 '/' Tc=2.0 min CN=92 3.17 cfs @ 12.10 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 9HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: C Runoff = 2.04 cfs @ 12.10 hrs, Volume= 4,416 cf, Depth= 2.67" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 12,096 68 <50% Grass cover, Poor, HSG A 7,772 98 Paved parking, HSG A 19,868 80 Weighted Average 12,096 60.88% Pervious Area 7,772 39.12% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 45 0.0100 0.90 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.3 31 0.0100 1.61 Shallow Concentrated Flow, Shallow concentrated flow Unpaved Kv= 16.1 fps 1.1 76 Total Subcatchment 3S: C Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=2.04 cfs @ 12.10 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=19,868 sf Runoff Volume=4,416 cf Runoff Depth=2.67" Flow Length=76' Slope=0.0100 '/' Tc=1.1 min CN=80 2.04 cfs @ 12.10 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 10HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 4L: Offsite to North Inflow Area = 38,189 sf, 24.48% Impervious, Inflow Depth = 0.59" for 10-Year event Inflow = 0.30 cfs @ 12.28 hrs, Volume= 1,875 cf Primary = 0.30 cfs @ 12.28 hrs, Volume= 1,875 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 4L: Offsite to North Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=38,189 sf Inflow=0.30 cfs @ 12.28 hrs Primary=0.30 cfs @ 12.28 hrs 0.30 cfs @ 12.28 hrs0.30 cfs @ 12.28 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 11HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 5L: Route 28 Inflow Area = 43,719 sf, 67.00% Impervious, Inflow Depth = 3.30" for 10-Year event Inflow = 5.19 cfs @ 12.10 hrs, Volume= 12,040 cf Primary = 5.19 cfs @ 12.10 hrs, Volume= 12,040 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 5L: Route 28 Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)5 4 3 2 1 0 Inflow Area=43,719 sf Inflow=5.19 cfs @ 12.10 hrs Primary=5.19 cfs @ 12.10 hrs 5.19 cfs @ 12.10 hrs5.19 cfs @ 12.10 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 12HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: A Runoff = 1.93 cfs @ 12.24 hrs, Volume= 7,453 cf, Depth= 2.34" Routed to Link 4L : Offsite to North Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 15,339 30 Woods, Good, HSG A 13,500 39 >75% Grass cover, Good, HSG A 9,350 98 Paved parking, HSG A 38,189 50 Weighted Average 28,839 75.52% Pervious Area 9,350 24.48% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.2 30 0.0070 0.06 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 6.5 162 0.0070 0.42 Shallow Concentrated Flow, Shallow concentrated Woodland Kv= 5.0 fps 14.7 192 Total Subcatchment 1S: A Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=1.93 cfs @ 12.24 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=38,189 sf Runoff Volume=7,453 cf Runoff Depth=2.34" Flow Length=192' Slope=0.0070 '/' Tc=14.7 min CN=50 1.93 cfs @ 12.24 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 13HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: B Runoff = 5.67 cfs @ 12.10 hrs, Volume= 14,295 cf, Depth= 7.19" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 1,370 30 Woods, Good, HSG A 962 39 >75% Grass cover, Good, HSG A 21,519 98 Paved parking, HSG A 23,851 92 Weighted Average 2,332 9.78% Pervious Area 21,519 90.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.1 50 0.0060 0.75 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.9 82 0.0060 1.57 Shallow Concentrated Flow, Shallow concentrated flow Paved Kv= 20.3 fps 2.0 132 Total Subcatchment 2S: B Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Runoff=5.67 cfs @ 12.10 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=23,851 sf Runoff Volume=14,295 cf Runoff Depth=7.19" Flow Length=132' Slope=0.0060 '/' Tc=2.0 min CN=92 5.67 cfs @ 12.10 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 14HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: C Runoff = 4.18 cfs @ 12.10 hrs, Volume= 9,546 cf, Depth= 5.77" Routed to Link 5L : Route 28 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 12,096 68 <50% Grass cover, Poor, HSG A 7,772 98 Paved parking, HSG A 19,868 80 Weighted Average 12,096 60.88% Pervious Area 7,772 39.12% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 45 0.0100 0.90 Sheet Flow, Sheet flow Smooth surfaces n= 0.011 P2= 3.26" 0.3 31 0.0100 1.61 Shallow Concentrated Flow, Shallow concentrated flow Unpaved Kv= 16.1 fps 1.1 76 Total Subcatchment 3S: C Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)4 3 2 1 0 Runoff=4.18 cfs @ 12.10 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=19,868 sf Runoff Volume=9,546 cf Runoff Depth=5.77" Flow Length=76' Slope=0.0100 '/' Tc=1.1 min CN=80 4.18 cfs @ 12.10 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 15HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 4L: Offsite to North Inflow Area = 38,189 sf, 24.48% Impervious, Inflow Depth = 2.34" for 100-Year event Inflow = 1.93 cfs @ 12.24 hrs, Volume= 7,453 cf Primary = 1.93 cfs @ 12.24 hrs, Volume= 7,453 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 4L: Offsite to North Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=38,189 sf Inflow=1.93 cfs @ 12.24 hrs Primary=1.93 cfs @ 12.24 hrs 1.93 cfs @ 12.24 hrs1.93 cfs @ 12.24 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Existing - 228 R28 Printed 5/6/2024Prepared by Green Seal Environmental LLC Page 16HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Summary for Link 5L: Route 28 Inflow Area = 43,719 sf, 67.00% Impervious, Inflow Depth = 6.54" for 100-Year event Inflow = 9.84 cfs @ 12.10 hrs, Volume= 23,841 cf Primary = 9.84 cfs @ 12.10 hrs, Volume= 23,841 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 5L: Route 28 Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)11 10 9 8 7 6 5 4 3 2 1 0 Inflow Area=43,719 sf Inflow=9.84 cfs @ 12.10 hrs Primary=9.84 cfs @ 12.10 hrs 9.84 cfs @ 12.10 hrs9.84 cfs @ 12.10 hrs ROUTE 2861'±61'±148'±91'±6'±10'±111'±84'±7'±12'±192 ft @ 0.7%76 ft @ 1.0%112 ft @ 0. 6 %0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.10.10.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.10.10.10.20.20.20.20.20.10.10.00.00.00.00.00.00.00.00.10.10.20.20.30.20.20.10.10.00.00.00.00.00.00.00.00.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0ttt͘'^ Es͘KDd >͗;ϱϬϴͿϴϴϴͲϲϬϯϰϭϭϰ^dd ZK͕h/>/E'^'DKZ ,͕DϬϮϱϲϮ'Z E^ > Es/ZKED Ed>͕>>&y͗;ϱϬϴͿϴϴϴͲϭϱϬϲW ZD/d^EK͘d KDD Edd, ^ Zt/E'^Z d, WZKW ZdzK&d, ^/'E E'/E Z͕'Z E^ > Es/ZKED Ed>͕>>͘hEhd,KZ/ Z WZKhd/KE&KZEzWhZWK^ /^E/E&Z/E' D EdhWKEKWzZ/',d>t^͘s/K>dKZ^t/>> ^h: ddKWZK^ hd/KE͘/D E^/KE^Z ^/E/d ͘h^ K&d,/^W>EKE^d/dhd ^ WdE K&d ZD^EKE/d/KE^^ d&KZd,/EKDWEz/E'WZK: dKhD Edd/KE͘/d/^d, Z ^WKE^//>/dzK&d, h^ ZdKKE&/ZD/^Z WE/ ^t/d,d, E'/E ZWZ/KZdKh^ ͘ϮϮϴZKhd ϮϴzZDKhd,͕DKE^ Zs'ZKhWZt/E'd/d> ͗d ,͗ , < z͗ E'/E Z͗ d ͗^> ͗^, d͗Z s/^/KE^:KϬϮͬϮϴͬϮϰ:K>Kh^DWEKddK^> ^^/d ϭϬϰͬϭϴͬϮϰdŽǁŶŽĨzĂƌŵŽƵƚŚ^ƚĂĨĨĐŽŵŵĞŶƚƐ y/^d/E'td Z^, ^t^Ͳ Z & ZdK^, d'ͲϮͲEKd ^Θ> ' EACB20 0 20 40 8010 ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX B NRCS SOIL REPORT SOIL EVALUATIONS United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Barnstable County, Massachusetts 228 Route 28 Yarmouth MA Natural Resources Conservation Service February 28, 2024 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................8 Soil Map................................................................................................................9 Legend................................................................................................................10 Map Unit Legend................................................................................................11 Map Unit Descriptions.........................................................................................11 Barnstable County, Massachusetts.................................................................13 54A—Freetown and Swansea mucks, coastal lowland, 0 to 1 percent slopes....................................................................................................13 55A—Freetown coarse sand, 0 to 3 percent slopes, sanded surface.........14 66A—Ipswich - Pawcatuck - Matunuck complex, 0 to 2 percent slopes, very frequently flooded..........................................................................16 252A—Carver coarse sand, 0 to 3 percent slopes......................................19 252B—Carver coarse sand, 3 to 8 percent slopes......................................20 607—Water, saline......................................................................................22 References............................................................................................................24 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 9 Custom Soil Resource Report Soil Map 46119004612000461210046122004612300461240046125004611900461200046121004612200461230046124004612500395000 395100 395200 395300 395400 395500 395600 395700 395800 395900 396000 395000 395100 395200 395300 395400 395500 395600 395700 395800 395900 396000 41° 39' 28'' N 70° 15' 40'' W41° 39' 28'' N70° 14' 54'' W41° 39' 5'' N 70° 15' 40'' W41° 39' 5'' N 70° 14' 54'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 19N WGS84 0 200 400 800 1200 Feet 0 50 100 200 300 Meters Map Scale: 1:4,910 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 20, Sep 12, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 10, 2022—Jun 30, 2022 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. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 54A Freetown and Swansea mucks, coastal lowland, 0 to 1 percent slopes 6.8 5.5% 55A Freetown coarse sand, 0 to 3 percent slopes, sanded surface 12.2 9.8% 66A Ipswich - Pawcatuck - Matunuck complex, 0 to 2 percent slopes, very frequently flooded 15.1 12.2% 252A Carver coarse sand, 0 to 3 percent slopes 36.6 29.5% 252B Carver coarse sand, 3 to 8 percent slopes 40.8 33.0% 607 Water, saline 12.3 10.0% Totals for Area of Interest 123.8 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit Custom Soil Resource Report 11 descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 Barnstable County, Massachusetts 54A—Freetown and Swansea mucks, coastal lowland, 0 to 1 percent slopes Map Unit Setting National map unit symbol: 2tyqd Elevation: 0 to 250 feet Mean annual precipitation: 40 to 52 inches Mean annual air temperature: 48 to 55 degrees F Frost-free period: 190 to 250 days Farmland classification: Not prime farmland Map Unit Composition Freetown, coastal lowland, and similar soils:50 percent Swansea, coastal lowland, and similar soils:40 percent Minor components:10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Freetown, Coastal Lowland Setting Landform:Bogs, marshes, swamps Landform position (three-dimensional):Dip Down-slope shape:Concave Across-slope shape:Concave Parent material:Highly decomposed organic material Typical profile Oe - 0 to 2 inches: mucky peat Oa - 2 to 79 inches: muck Properties and qualities Slope:0 to 1 percent Surface area covered with cobbles, stones or boulders:0.0 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to high (0.14 to 14.17 in/hr) Depth to water table:About 0 to 6 inches Frequency of flooding:Rare Frequency of ponding:Frequent Available water supply, 0 to 60 inches: Very high (about 19.2 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 5w Hydrologic Soil Group: B/D Ecological site: F144AY043MA - Acidic Organic Wetlands Hydric soil rating: Yes Description of Swansea, Coastal Lowland Setting Landform:Swamps, bogs, marshes Custom Soil Resource Report 13 Landform position (three-dimensional):Dip Down-slope shape:Concave Across-slope shape:Concave Parent material:Highly decomposed organic material over loose sandy and gravelly glaciofluvial deposits Typical profile Oa - 0 to 36 inches: muck Cg - 36 to 79 inches: coarse sand Properties and qualities Slope:0 to 1 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to high (0.14 to 14.17 in/hr) Depth to water table:About 0 to 6 inches Frequency of flooding:Rare Frequency of ponding:Frequent Available water supply, 0 to 60 inches: Very high (about 17.3 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 5w Hydrologic Soil Group: B/D Ecological site: F144AY043MA - Acidic Organic Wetlands Hydric soil rating: Yes Minor Components Rainberry, coastal lowland Percent of map unit:10 percent Landform:Kettles, depressions Landform position (two-dimensional):Toeslope Landform position (three-dimensional):Tread Down-slope shape:Concave Across-slope shape:Linear Hydric soil rating: Yes 55A—Freetown coarse sand, 0 to 3 percent slopes, sanded surface Map Unit Setting National map unit symbol: 2t2qj Elevation: 0 to 180 feet Mean annual precipitation: 40 to 52 inches Mean annual air temperature: 48 to 55 degrees F Frost-free period: 190 to 250 days Farmland classification: Farmland of unique importance Custom Soil Resource Report 14 Map Unit Composition Freetown, sanded surface, and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Freetown, Sanded Surface Setting Landform:Kettles, bogs, depressions Landform position (two-dimensional):Toeslope Landform position (three-dimensional):Talf Down-slope shape:Concave Across-slope shape:Concave Parent material:Sandy human-transported material over highly decomposed organic material Typical profile ^Ap - 0 to 15 inches: coarse sand 2Oa - 15 to 79 inches: muck Properties and qualities Slope:0 to 3 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to high (0.14 to 14.17 in/hr) Depth to water table:About 0 to 6 inches Frequency of flooding:Frequent Frequency of ponding:None Available water supply, 0 to 60 inches: Very high (about 20.9 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 5w Hydrologic Soil Group: B/D Ecological site: F144AY043MA - Acidic Organic Wetlands Hydric soil rating: Yes Minor Components Swansea, sanded surface, inactive Percent of map unit:5 percent Landform:Kettles, bogs, depressions Landform position (two-dimensional):Toeslope Landform position (three-dimensional):Talf Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes Rainberry, sanded surface Percent of map unit:4 percent Landform:Kettles, depressions Landform position (two-dimensional):Toeslope Landform position (three-dimensional):Tread Down-slope shape:Concave Custom Soil Resource Report 15 Across-slope shape:Linear Hydric soil rating: Yes Udipsamments, wet substratum Percent of map unit:3 percent Landform:Dikes on bogs Landform position (two-dimensional):Footslope Landform position (three-dimensional):Tread Down-slope shape:Concave, convex Across-slope shape:Concave, linear Hydric soil rating: No Tihonet Percent of map unit:3 percent Landform position (two-dimensional):Toeslope Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: Yes 66A—Ipswich - Pawcatuck - Matunuck complex, 0 to 2 percent slopes, very frequently flooded Map Unit Setting National map unit symbol: 2tyqm Elevation: 0 to 10 feet Mean annual precipitation: 36 to 71 inches Mean annual air temperature: 39 to 55 degrees F Frost-free period: 140 to 250 days Farmland classification: Not prime farmland Map Unit Composition Ipswich and similar soils:50 percent Pawcatuck and similar soils:25 percent Matunuck and similar soils:15 percent Minor components:10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Ipswich Setting Landform:Tidal marshes Landform position (three-dimensional):Dip Down-slope shape:Linear Across-slope shape:Linear Parent material:Partially- decomposed herbaceous organic material Typical profile Oe - 0 to 42 inches: mucky peat Oa - 42 to 59 inches: muck Custom Soil Resource Report 16 Properties and qualities Slope:0 to 2 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to very high (0.14 to 99.90 in/hr) Depth to water table:About 0 inches Frequency of flooding:Very frequent Frequency of ponding:None Calcium carbonate, maximum content:5 percent Maximum salinity:Nonsaline to strongly saline (1.0 to 112.0 mmhos/cm) Sodium adsorption ratio, maximum:20.0 Available water supply, 0 to 60 inches: Very high (about 26.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8w Hydrologic Soil Group: A/D Ecological site: R144AY002CT - Tidal Salt High Marsh mesic very frequently flooded, R144AY001CT - Tidal Salt Low Marsh mesic very frequently flooded Hydric soil rating: Yes Description of Pawcatuck Setting Landform:Tidal marshes Landform position (three-dimensional):Dip Down-slope shape:Linear Across-slope shape:Linear Parent material:Partially- decomposed herbaceous organic material over sandy mineral material Typical profile Oe - 0 to 46 inches: mucky peat Cg - 46 to 60 inches: mucky sand Properties and qualities Slope:0 to 2 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to very high (0.14 to 99.90 in/hr) Depth to water table:About 0 inches Frequency of flooding:Very frequent Frequency of ponding:None Calcium carbonate, maximum content:5 percent Maximum salinity:Nonsaline to strongly saline (1.0 to 112.0 mmhos/cm) Sodium adsorption ratio, maximum:20.0 Available water supply, 0 to 60 inches: Very high (about 21.4 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8w Hydrologic Soil Group: A/D Custom Soil Resource Report 17 Ecological site: R144AY002CT - Tidal Salt High Marsh mesic very frequently flooded, R144AY001CT - Tidal Salt Low Marsh mesic very frequently flooded Hydric soil rating: Yes Description of Matunuck Setting Landform:Tidal marshes Landform position (three-dimensional):Dip Down-slope shape:Linear Across-slope shape:Linear Parent material:Partially- decomposed herbaceous organic material over glaciofluvial deposits and/or sandy marine deposits Typical profile Oe - 0 to 12 inches: mucky peat Cg - 12 to 72 inches: sand Properties and qualities Slope:0 to 2 percent Depth to restrictive feature:More than 80 inches Drainage class:Very poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):Moderately low to very high (0.14 to 99.90 in/hr) Depth to water table:About 0 inches Frequency of flooding:Very frequent Frequency of ponding:None Calcium carbonate, maximum content:5 percent Maximum salinity:Nonsaline to strongly saline (1.0 to 112.0 mmhos/cm) Sodium adsorption ratio, maximum:20.0 Available water supply, 0 to 60 inches: Moderate (about 8.2 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8w Hydrologic Soil Group: A/D Ecological site: R144AY002CT - Tidal Salt High Marsh mesic very frequently flooded, R144AY001CT - Tidal Salt Low Marsh mesic very frequently flooded Hydric soil rating: Yes Minor Components Hooksan Percent of map unit:5 percent Landform:Dunes Landform position (three-dimensional):Rise Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Succotash Percent of map unit:5 percent Landform:Spits on back-barrier flats Landform position (three-dimensional):Rise Down-slope shape:Linear Across-slope shape:Linear Custom Soil Resource Report 18 Hydric soil rating: No 252A—Carver coarse sand, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 2y07w Elevation: 0 to 990 feet Mean annual precipitation: 36 to 71 inches Mean annual air temperature: 39 to 55 degrees F Frost-free period: 140 to 240 days Farmland classification: Not prime farmland Map Unit Composition Carver, coarse sand, and similar soils:80 percent Minor components:20 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Carver, Coarse Sand Setting Landform:Moraines, outwash plains Landform position (two-dimensional):Summit, shoulder Landform position (three-dimensional):Side slope, crest, tread Down-slope shape:Convex, linear Across-slope shape:Linear Parent material:Sandy glaciofluvial deposits Typical profile Oi - 0 to 2 inches: slightly decomposed plant material Oe - 2 to 3 inches: moderately decomposed plant material A - 3 to 7 inches: coarse sand E - 7 to 10 inches: coarse sand Bw1 - 10 to 15 inches: coarse sand Bw2 - 15 to 28 inches: coarse sand BC - 28 to 32 inches: coarse sand C - 32 to 67 inches: coarse sand Properties and qualities Slope:0 to 3 percent Depth to restrictive feature:More than 80 inches Drainage class:Excessively drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat):Moderately high to very high (1.42 to 14.17 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Maximum salinity:Nonsaline (0.0 to 1.9 mmhos/cm) Custom Soil Resource Report 19 Available water supply, 0 to 60 inches: Low (about 4.3 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Ecological site: F149BY005MA - Dry Outwash Hydric soil rating: No Minor Components Deerfield Percent of map unit:10 percent Landform:Outwash plains, kame terraces, outwash deltas, outwash terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Concave Hydric soil rating: No Hinckley Percent of map unit:5 percent Landform:Moraines, eskers, kames, outwash deltas, outwash terraces, outwash plains, kame terraces Landform position (two-dimensional):Summit, shoulder, backslope, footslope, toeslope Landform position (three-dimensional):Head slope, nose slope, side slope, crest, riser, tread Down-slope shape:Convex Across-slope shape:Convex Hydric soil rating: No Merrimac Percent of map unit:3 percent Landform:Kame terraces, outwash deltas, outwash terraces Landform position (three-dimensional):Riser, tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Mashpee Percent of map unit:2 percent Landform:Depressions, drainageways, terraces Landform position (three-dimensional):Tread Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes 252B—Carver coarse sand, 3 to 8 percent slopes Map Unit Setting National map unit symbol: 2y07x Custom Soil Resource Report 20 Elevation: 0 to 240 feet Mean annual precipitation: 36 to 71 inches Mean annual air temperature: 39 to 55 degrees F Frost-free period: 140 to 240 days Farmland classification: Not prime farmland Map Unit Composition Carver, coarse sand, and similar soils:80 percent Minor components:20 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Carver, Coarse Sand Setting Landform:Moraines, outwash plains Landform position (two-dimensional):Summit, shoulder, backslope, footslope, toeslope Landform position (three-dimensional):Head slope, nose slope, side slope, crest, tread Down-slope shape:Convex, linear Across-slope shape:Linear Parent material:Sandy glaciofluvial deposits Typical profile Oi - 0 to 2 inches: slightly decomposed plant material Oe - 2 to 3 inches: moderately decomposed plant material A - 3 to 7 inches: coarse sand E - 7 to 10 inches: coarse sand Bw1 - 10 to 15 inches: coarse sand Bw2 - 15 to 28 inches: coarse sand BC - 28 to 32 inches: coarse sand C - 32 to 67 inches: coarse sand Properties and qualities Slope:3 to 8 percent Depth to restrictive feature:More than 80 inches Drainage class:Excessively drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):Moderately high to very high (1.42 to 14.17 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Maximum salinity:Nonsaline (0.0 to 1.9 mmhos/cm) Available water supply, 0 to 60 inches: Low (about 4.3 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Ecological site: F149BY005MA - Dry Outwash Hydric soil rating: No Minor Components Deerfield Percent of map unit:10 percent Custom Soil Resource Report 21 Landform:Outwash terraces, outwash plains, kame terraces, outwash deltas Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Concave Hydric soil rating: No Hinckley Percent of map unit:5 percent Landform:Moraines, eskers, kames, outwash deltas, outwash terraces, outwash plains, kame terraces Landform position (two-dimensional):Summit, shoulder, backslope, footslope, toeslope Landform position (three-dimensional):Head slope, nose slope, side slope, crest, riser, tread Down-slope shape:Convex Across-slope shape:Convex Hydric soil rating: No Merrimac Percent of map unit:3 percent Landform:Kame terraces, outwash deltas, outwash terraces Landform position (three-dimensional):Riser, tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Mashpee Percent of map unit:2 percent Landform:Depressions, drainageways, terraces Landform position (three-dimensional):Tread Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes 607—Water, saline Map Unit Setting National map unit symbol: b28j Frost-free period: 120 to 220 days Farmland classification: Not prime farmland Map Unit Composition Water, saline:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Water, Saline Typical profile - 0 to 0 inches: water Custom Soil Resource Report 22 Custom Soil Resource Report 23 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 24 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 25 ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX C STANDARD 2 PROPOSED HYDROCAD REPORT PROPOSED WATERSHEDS PLAN 1S 1 2S 2 3S 3 ROOF 4 5P Rain Garden 8P Rtank 9L Offsite to north Routing Diagram for Proposed - 228 R28 r3 Prepared by Green Seal Environmental LLC, Printed 7/3/2024 HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 2HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: 1 Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0 cf, Depth= 0.00" Routed to Link 9L : Offsite to north Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 15,292 30 Woods, Good, HSG A 15,160 39 >75% Grass cover, Good, HSG A 30,452 34 Weighted Average 30,452 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.1 30 0.0100 0.07 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 5.1 152 0.0100 0.50 Shallow Concentrated Flow, Shallow concentrated flow Woodland Kv= 5.0 fps 12.2 182 Total Subcatchment 1S: 1 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Runoff=0.00 cfs @ 0.00 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=30,452 sf Runoff Volume=0 cf Runoff Depth=0.00" Flow Length=182' Slope=0.0100 '/' Tc=12.2 min CN=34 0.00 cfs @ 0.00 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 3HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: 2 Runoff = 1.53 cfs @ 12.13 hrs, Volume= 3,835 cf, Depth= 1.66" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 7,280 39 >75% Grass cover, Good, HSG A 20,464 98 Paved parking, HSG A 27,744 83 Weighted Average 7,280 26.24% Pervious Area 20,464 73.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 2S: 2 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Runoff=1.53 cfs @ 12.13 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=27,744 sf Runoff Volume=3,835 cf Runoff Depth=1.66" Tc=6.0 min CN=83 1.53 cfs @ 12.13 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 4HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: 3 Runoff = 0.28 cfs @ 12.14 hrs, Volume= 792 cf, Depth= 0.72" Routed to Pond 5P : Rain Garden Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 6,939 39 >75% Grass cover, Good, HSG A 5,415 98 Paved parking, HSG A * 873 98 RG Water surface area 13,227 67 Weighted Average 6,939 52.46% Pervious Area 6,288 47.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 3S: 3 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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 Runoff=0.28 cfs @ 12.14 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=13,227 sf Runoff Volume=792 cf Runoff Depth=0.72" Tc=6.0 min CN=67 0.28 cfs @ 12.14 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 5HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment ROOF: 4 Runoff = 0.91 cfs @ 12.13 hrs, Volume= 2,645 cf, Depth= 3.03" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Area (sf) CN Description 10,485 98 Roofs, HSG A 10,485 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment ROOF: 4 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Runoff=0.91 cfs @ 12.13 hrs NOAA10 24-hr C 2-Year Rainfall=3.26" Runoff Area=10,485 sf Runoff Volume=2,645 cf Runoff Depth=3.03" Tc=6.0 min CN=98 0.91 cfs @ 12.13 hrs NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 6HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 5P: Rain Garden Inflow Area = 13,227 sf, 47.54% Impervious, Inflow Depth = 0.72" for 2-Year event Inflow = 0.28 cfs @ 12.14 hrs, Volume= 792 cf Outflow = 0.07 cfs @ 12.39 hrs, Volume= 792 cf, Atten= 76%, Lag= 15.0 min Discarded = 0.07 cfs @ 12.39 hrs, Volume= 792 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 11.71' @ 12.39 hrs Surf.Area= 354 sf Storage= 150 cf Plug-Flow detention time= 15.9 min calculated for 792 cf (100% of inflow) Center-of-Mass det. time= 15.9 min ( 923.6 - 907.7 ) Volume Invert Avail.Storage Storage Description #1 11.00' 1,657 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 11.00 67 0 0 12.00 471 269 269 13.00 1,132 802 1,071 13.55 1,000 586 1,657 Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.07 cfs @ 12.39 hrs HW=11.71' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.07 cfs) NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 7HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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=13,227 sf Inflow=0.28 cfs @ 12.14 hrs Discarded=0.07 cfs @ 12.39 hrs Peak Elev=11.71' Storage=150 cf 0.28 cfs @ 12.14 hrs 0.07 cfs @ 12.39 hrs Pond 5P: Rain Garden Discarded Stage-Discharge Discharge (cfs) 0.20.180.160.140.120.10.080.060.040.020Elevation (feet)13 12 11 Exfiltration NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 8HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Surface Storage Stage-Area-Storage Storage (cubic-feet) 1,6001,4001,2001,0008006004002000 Surface/Horizontal/Wetted Area (sq-ft) 1,1001,0009008007006005004003002001000 Elevation (feet)13 12 11 Custom Stage Data NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 9HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 8P: Rtank Inflow Area = 38,229 sf, 80.96% Impervious, Inflow Depth = 2.03" for 2-Year event Inflow = 2.43 cfs @ 12.13 hrs, Volume= 6,480 cf Outflow = 0.70 cfs @ 11.97 hrs, Volume= 6,480 cf, Atten= 71%, Lag= 0.0 min Discarded = 0.70 cfs @ 11.97 hrs, Volume= 6,480 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 10.21' @ 12.29 hrs Surf.Area= 3,640 sf Storage= 979 cf Plug-Flow detention time= 5.9 min calculated for 6,480 cf (100% of inflow) Center-of-Mass det. time= 5.9 min ( 816.5 - 810.6 ) Volume Invert Avail.Storage Storage Description #1 9.97' 6,000 cf Ferguson R-Tank UD 2 x 720 Inside #2 Inside= 23.6"W x 27.2"H => 4.23 sf x 1.97'L = 8.3 cf Outside= 23.6"W x 27.2"H => 4.46 sf x 1.97'L = 8.8 cf 720 Chambers in 12 Rows #2 9.80' 1,842 cf 26.00'W x 140.00'L x 3.00'H Stone 10,920 cf Overall - 6,316 cf Embedded = 4,604 cf x 40.0% Voids 7,842 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 9.80'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.70 cfs @ 11.97 hrs HW=9.83' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.70 cfs) NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 10HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=38,229 sf Inflow=2.43 cfs @ 12.13 hrs Discarded=0.70 cfs @ 11.97 hrs Peak Elev=10.21' Storage=979 cf 2.43 cfs @ 12.13 hrs 0.70 cfs @ 11.97 hrs Pond 8P: Rtank Discarded Stage-Discharge Discharge (cfs) 0.650.60.550.50.450.40.350.30.250.20.150.10.050Elevation (feet)12 11 10 Exfiltration NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 11HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Surface Storage Stage-Area-Storage Storage (cubic-feet) 7,0006,0005,0004,0003,0002,0001,0000 Surface/Horizontal/Wetted Area (sq-ft) 3,6003,4003,2003,0002,8002,6002,4002,2002,0001,8001,6001,4001,2001,0008006004002000 Elevation (feet)12 11 10 Ferguson R-Tank UD 2 Stone NOAA10 24-hr C 2-Year Rainfall=3.26"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 12HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Link 9L: Offsite to north Inflow Area = 30,452 sf, 0.00% Impervious, Inflow Depth = 0.00" for 2-Year event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 9L: Offsite to north Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=30,452 sf Inflow=0.00 cfs @ 0.00 hrs Primary=0.00 cfs @ 0.00 hrs 0.00 cfs @ 0.00 hrs0.00 cfs @ 0.00 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 13HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: 1 Runoff = 0.00 cfs @ 20.13 hrs, Volume= 92 cf, Depth= 0.04" Routed to Link 9L : Offsite to north Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 15,292 30 Woods, Good, HSG A 15,160 39 >75% Grass cover, Good, HSG A 30,452 34 Weighted Average 30,452 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.1 30 0.0100 0.07 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 5.1 152 0.0100 0.50 Shallow Concentrated Flow, Shallow concentrated flow Woodland Kv= 5.0 fps 12.2 182 Total Subcatchment 1S: 1 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)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 Runoff=0.00 cfs @ 20.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=30,452 sf Runoff Volume=92 cf Runoff Depth=0.04" Flow Length=182' Slope=0.0100 '/' Tc=12.2 min CN=34 0.00 cfs @ 20.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 14HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: 2 Runoff = 2.67 cfs @ 12.13 hrs, Volume= 6,797 cf, Depth= 2.94" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 7,280 39 >75% Grass cover, Good, HSG A 20,464 98 Paved parking, HSG A 27,744 83 Weighted Average 7,280 26.24% Pervious Area 20,464 73.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 2S: 2 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=2.67 cfs @ 12.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=27,744 sf Runoff Volume=6,797 cf Runoff Depth=2.94" Tc=6.0 min CN=83 2.67 cfs @ 12.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 15HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: 3 Runoff = 0.70 cfs @ 12.14 hrs, Volume= 1,790 cf, Depth= 1.62" Routed to Pond 5P : Rain Garden Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 6,939 39 >75% Grass cover, Good, HSG A 5,415 98 Paved parking, HSG A * 873 98 RG Water surface area 13,227 67 Weighted Average 6,939 52.46% Pervious Area 6,288 47.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 3S: 3 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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 Runoff=0.70 cfs @ 12.14 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=13,227 sf Runoff Volume=1,790 cf Runoff Depth=1.62" Tc=6.0 min CN=67 0.70 cfs @ 12.14 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 16HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment ROOF: 4 Runoff = 1.33 cfs @ 12.13 hrs, Volume= 3,935 cf, Depth= 4.50" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Area (sf) CN Description 10,485 98 Roofs, HSG A 10,485 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment ROOF: 4 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Runoff=1.33 cfs @ 12.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74" Runoff Area=10,485 sf Runoff Volume=3,935 cf Runoff Depth=4.50" Tc=6.0 min CN=98 1.33 cfs @ 12.13 hrs NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 17HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 5P: Rain Garden Inflow Area = 13,227 sf, 47.54% Impervious, Inflow Depth = 1.62" for 10-Year event Inflow = 0.70 cfs @ 12.14 hrs, Volume= 1,790 cf Outflow = 0.13 cfs @ 12.42 hrs, Volume= 1,790 cf, Atten= 81%, Lag= 17.1 min Discarded = 0.13 cfs @ 12.42 hrs, Volume= 1,790 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 12.34' @ 12.42 hrs Surf.Area= 695 sf Storage= 467 cf Plug-Flow detention time= 32.6 min calculated for 1,790 cf (100% of inflow) Center-of-Mass det. time= 32.6 min ( 910.0 - 877.4 ) Volume Invert Avail.Storage Storage Description #1 11.00' 1,657 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 11.00 67 0 0 12.00 471 269 269 13.00 1,132 802 1,071 13.55 1,000 586 1,657 Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.13 cfs @ 12.42 hrs HW=12.34' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.13 cfs) NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 18HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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=13,227 sf Inflow=0.70 cfs @ 12.14 hrs Discarded=0.13 cfs @ 12.42 hrs Peak Elev=12.34' Storage=467 cf 0.70 cfs @ 12.14 hrs 0.13 cfs @ 12.42 hrs Pond 5P: Rain Garden Discarded Stage-Discharge Discharge (cfs) 0.20.180.160.140.120.10.080.060.040.020Elevation (feet)13 12 11 Exfiltration NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 19HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Surface Storage Stage-Area-Storage Storage (cubic-feet) 1,6001,4001,2001,0008006004002000 Surface/Horizontal/Wetted Area (sq-ft) 1,1001,0009008007006005004003002001000 Elevation (feet)13 12 11 Custom Stage Data NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 20HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 8P: Rtank Inflow Area = 38,229 sf, 80.96% Impervious, Inflow Depth = 3.37" for 10-Year event Inflow = 4.00 cfs @ 12.13 hrs, Volume= 10,732 cf Outflow = 0.70 cfs @ 11.86 hrs, Volume= 10,732 cf, Atten= 83%, Lag= 0.0 min Discarded = 0.70 cfs @ 11.86 hrs, Volume= 10,732 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 10.66' @ 12.40 hrs Surf.Area= 3,640 sf Storage= 2,308 cf Plug-Flow detention time= 16.2 min calculated for 10,730 cf (100% of inflow) Center-of-Mass det. time= 16.2 min ( 815.4 - 799.2 ) Volume Invert Avail.Storage Storage Description #1 9.97' 6,000 cf Ferguson R-Tank UD 2 x 720 Inside #2 Inside= 23.6"W x 27.2"H => 4.23 sf x 1.97'L = 8.3 cf Outside= 23.6"W x 27.2"H => 4.46 sf x 1.97'L = 8.8 cf 720 Chambers in 12 Rows #2 9.80' 1,842 cf 26.00'W x 140.00'L x 3.00'H Stone 10,920 cf Overall - 6,316 cf Embedded = 4,604 cf x 40.0% Voids 7,842 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 9.80'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.70 cfs @ 11.86 hrs HW=9.83' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.70 cfs) NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 21HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)4 3 2 1 0 Inflow Area=38,229 sf Inflow=4.00 cfs @ 12.13 hrs Discarded=0.70 cfs @ 11.86 hrs Peak Elev=10.66' Storage=2,308 cf 4.00 cfs @ 12.13 hrs 0.70 cfs @ 11.86 hrs Pond 8P: Rtank Discarded Stage-Discharge Discharge (cfs) 0.650.60.550.50.450.40.350.30.250.20.150.10.050Elevation (feet)12 11 10 Exfiltration NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 22HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Surface Storage Stage-Area-Storage Storage (cubic-feet) 7,0006,0005,0004,0003,0002,0001,0000 Surface/Horizontal/Wetted Area (sq-ft) 3,6003,4003,2003,0002,8002,6002,4002,2002,0001,8001,6001,4001,2001,0008006004002000 Elevation (feet)12 11 10 Ferguson R-Tank UD 2 Stone NOAA10 24-hr C 10-Year Rainfall=4.74"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 23HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Link 9L: Offsite to north Inflow Area = 30,452 sf, 0.00% Impervious, Inflow Depth = 0.04" for 10-Year event Inflow = 0.00 cfs @ 20.13 hrs, Volume= 92 cf Primary = 0.00 cfs @ 20.13 hrs, Volume= 92 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 9L: Offsite to north Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)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=30,452 sf Inflow=0.00 cfs @ 20.13 hrs Primary=0.00 cfs @ 20.13 hrs 0.00 cfs @ 20.13 hrs0.00 cfs @ 20.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 24HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: 1 Runoff = 0.25 cfs @ 12.27 hrs, Volume= 1,952 cf, Depth= 0.77" Routed to Link 9L : Offsite to north Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 15,292 30 Woods, Good, HSG A 15,160 39 >75% Grass cover, Good, HSG A 30,452 34 Weighted Average 30,452 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.1 30 0.0100 0.07 Sheet Flow, Sheet flow Grass: Dense n= 0.240 P2= 3.26" 5.1 152 0.0100 0.50 Shallow Concentrated Flow, Shallow concentrated flow Woodland Kv= 5.0 fps 12.2 182 Total Subcatchment 1S: 1 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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 Runoff=0.25 cfs @ 12.27 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=30,452 sf Runoff Volume=1,952 cf Runoff Depth=0.77" Flow Length=182' Slope=0.0100 '/' Tc=12.2 min CN=34 0.25 cfs @ 12.27 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 25HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: 2 Runoff = 5.35 cfs @ 12.13 hrs, Volume= 14,151 cf, Depth= 6.12" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 7,280 39 >75% Grass cover, Good, HSG A 20,464 98 Paved parking, HSG A 27,744 83 Weighted Average 7,280 26.24% Pervious Area 20,464 73.76% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 2S: 2 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)5 4 3 2 1 0 Runoff=5.35 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=27,744 sf Runoff Volume=14,151 cf Runoff Depth=6.12" Tc=6.0 min CN=83 5.35 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 26HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: 3 Runoff = 1.86 cfs @ 12.13 hrs, Volume= 4,680 cf, Depth= 4.25" Routed to Pond 5P : Rain Garden Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 6,939 39 >75% Grass cover, Good, HSG A 5,415 98 Paved parking, HSG A * 873 98 RG Water surface area 13,227 67 Weighted Average 6,939 52.46% Pervious Area 6,288 47.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment 3S: 3 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=1.86 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=13,227 sf Runoff Volume=4,680 cf Runoff Depth=4.25" Tc=6.0 min CN=67 1.86 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 27HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment ROOF: 4 Runoff = 2.30 cfs @ 12.13 hrs, Volume= 6,911 cf, Depth= 7.91" Routed to Pond 8P : Rtank Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Area (sf) CN Description 10,485 98 Roofs, HSG A 10,485 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Minimum value Subcatchment ROOF: 4 Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Runoff=2.30 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15" Runoff Area=10,485 sf Runoff Volume=6,911 cf Runoff Depth=7.91" Tc=6.0 min CN=98 2.30 cfs @ 12.13 hrs NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 28HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 5P: Rain Garden Inflow Area = 13,227 sf, 47.54% Impervious, Inflow Depth = 4.25" for 100-Year event Inflow = 1.86 cfs @ 12.13 hrs, Volume= 4,680 cf Outflow = 0.22 cfs @ 14.50 hrs, Volume= 4,680 cf, Atten= 88%, Lag= 142.0 min Discarded = 0.22 cfs @ 14.50 hrs, Volume= 4,680 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 13.52' @ 12.65 hrs Surf.Area= 1,007 sf Storage= 1,629 cf Plug-Flow detention time= 72.6 min calculated for 4,680 cf (100% of inflow) Center-of-Mass det. time= 72.6 min ( 917.3 - 844.7 ) Volume Invert Avail.Storage Storage Description #1 11.00' 1,657 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 11.00 67 0 0 12.00 471 269 269 13.00 1,132 802 1,071 13.55 1,000 586 1,657 Device Routing Invert Outlet Devices #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.22 cfs @ 14.50 hrs HW=13.00' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.22 cfs) NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 29HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=13,227 sf Inflow=1.86 cfs @ 12.13 hrs Discarded=0.22 cfs @ 14.50 hrs Peak Elev=13.52' Storage=1,629 cf 1.86 cfs @ 12.13 hrs 0.22 cfs @ 14.50 hrs Pond 5P: Rain Garden Discarded Stage-Discharge Discharge (cfs) 0.20.180.160.140.120.10.080.060.040.020Elevation (feet)13 12 11 Exfiltration NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 30HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 5P: Rain Garden Surface Storage Stage-Area-Storage Storage (cubic-feet) 1,6001,4001,2001,0008006004002000 Surface/Horizontal/Wetted Area (sq-ft) 1,1001,0009008007006005004003002001000 Elevation (feet)13 12 11 Custom Stage Data NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 31HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Pond 8P: Rtank Inflow Area = 38,229 sf, 80.96% Impervious, Inflow Depth = 6.61" for 100-Year event Inflow = 7.65 cfs @ 12.13 hrs, Volume= 21,063 cf Outflow = 0.70 cfs @ 11.61 hrs, Volume= 21,063 cf, Atten= 91%, Lag= 0.0 min Discarded = 0.70 cfs @ 11.61 hrs, Volume= 21,063 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 11.96' @ 12.68 hrs Surf.Area= 3,640 sf Storage= 6,204 cf Plug-Flow detention time= 55.4 min calculated for 21,060 cf (100% of inflow) Center-of-Mass det. time= 55.4 min ( 838.4 - 783.0 ) Volume Invert Avail.Storage Storage Description #1 9.97' 6,000 cf Ferguson R-Tank UD 2 x 720 Inside #2 Inside= 23.6"W x 27.2"H => 4.23 sf x 1.97'L = 8.3 cf Outside= 23.6"W x 27.2"H => 4.46 sf x 1.97'L = 8.8 cf 720 Chambers in 12 Rows #2 9.80' 1,842 cf 26.00'W x 140.00'L x 3.00'H Stone 10,920 cf Overall - 6,316 cf Embedded = 4,604 cf x 40.0% Voids 7,842 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 9.80'8.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.70 cfs @ 11.61 hrs HW=9.83' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.70 cfs) NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 32HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Inflow Discarded Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)8 7 6 5 4 3 2 1 0 Inflow Area=38,229 sf Inflow=7.65 cfs @ 12.13 hrs Discarded=0.70 cfs @ 11.61 hrs Peak Elev=11.96' Storage=6,204 cf 7.65 cfs @ 12.13 hrs 0.70 cfs @ 11.61 hrs Pond 8P: Rtank Discarded Stage-Discharge Discharge (cfs) 0.650.60.550.50.450.40.350.30.250.20.150.10.050Elevation (feet)12 11 10 Exfiltration NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 33HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Pond 8P: Rtank Surface Storage Stage-Area-Storage Storage (cubic-feet) 7,0006,0005,0004,0003,0002,0001,0000 Surface/Horizontal/Wetted Area (sq-ft) 3,6003,4003,2003,0002,8002,6002,4002,2002,0001,8001,6001,4001,2001,0008006004002000 Elevation (feet)12 11 10 Ferguson R-Tank UD 2 Stone NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r3 Printed 7/3/2024Prepared by Green Seal Environmental LLC Page 34HydroCAD® 10.20-4b s/n 07546 © 2023 HydroCAD Software Solutions LLC Summary for Link 9L: Offsite to north Inflow Area = 30,452 sf, 0.00% Impervious, Inflow Depth = 0.77" for 100-Year event Inflow = 0.25 cfs @ 12.27 hrs, Volume= 1,952 cf Primary = 0.25 cfs @ 12.27 hrs, Volume= 1,952 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link 9L: Offsite to north Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (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=30,452 sf Inflow=0.25 cfs @ 12.27 hrs Primary=0.25 cfs @ 12.27 hrs 0.25 cfs @ 12.27 hrs0.25 cfs @ 12.27 hrs ROUTE 2861'±61'±148'±91'±6'±10'±111'±84'±7'±12'±DD DDDDDDCOCOCOCOCOCOCOCOCOCOCOttt͘'^ Es͘KDd >͗;ϱϬϴͿϴϴϴͲϲϬϯϰϭϭϰ^dd ZK͕h/>/E'^'DKZ ,͕DϬϮϱϲϮ'Z E^ > Es/ZKED Ed>͕>>&y͗;ϱϬϴͿϴϴϴͲϭϱϬϲW ZD/d^EK͘d KDD Edd, ^ Zt/E'^Z d, WZKW ZdzK&d, ^/'E E'/E Z͕'Z E^ > Es/ZKED Ed>͕>>͘hEhd,KZ/ Z WZKhd/KE&KZEzWhZWK^ /^E/E&Z/E' D EdhWKEKWzZ/',d>t^͘s/K>dKZ^t/>> ^h: ddKWZK^ hd/KE͘/D E^/KE^Z ^/E/d ͘h^ K&d,/^W>EKE^d/dhd ^ WdE K&d ZD^EKE/d/KE^^ d&KZd,/EKDWEz/E'WZK: dKhD Edd/KE͘/d/^d, Z ^WKE^//>/dzK&d, h^ ZdKKE&/ZD/^Z WE/ ^t/d,d, E'/E ZWZ/KZdKh^ ͘ϮϮϴZKhd ϮϴzZDKhd,͕DKE^ Zs'ZKhWZt/E'd/d> ͗d ,͗ , < z͗ E'/E Z͗ d ͗^> ͗^, d͗Z s/^/KE^:KϬϮͬϮϴͬϮϰ:K>Kh^DWEKddK^> ^^/d ϭϬϰͬϭϴͬϮϰdŽǁŶŽĨzĂƌŵŽƵƚŚ^ƚĂĨĨĐŽŵŵĞŶƚƐϮ ϬϲͬϭϳͬϮϰ dŽǁŶWůĂŶŶĞƌĐŽŵŵĞŶƚƐt^ͲWZ & ZdK^, d'ͲϮͲEKd ^Θ> ' EWZKWK^ td Z^, ^1324182 ft @ 1.0%20 0 20 40 8010 ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX D STANDARD 9 LONG TERM OPERATIONS & MAINTENANCE PLAN MAINTENANCE LOG FORMS LONG TERM POLLUTION PREVENTION AND OPERATION AND MAINTENANCE PLAN. 228 Route 28 Yarmouth MA Proposed A Plus Market LONG-TERM POLLUTION PREVENTION AND OPERATION AND MAINTENANCE PLAN Introduction As required by Standards 4 and 9 of the Stormwater Management Handbook and Section 2.07 of the Town of Yarmouth Stormwater Management Regulations, this Long-Term Pollution Prevention and Operation and Maintenance Plan has been developed for source control and pollution prevention at the site after construction. Maintenance Responsibility The responsibility of the Long-Term Pollution Prevention and Operation and Maintenance Plan will be that of the Owner or their heirs or assigns. Estimated budget for Stormwater Maintenance Activities: The estimated annual budget for the routine maintenance of stormwater facilities is as follows: Catch basin cleaning: $ 300.00 Stormceptor inspection/cleaning: $ 300.00 Pavement sweeping: $ 300.00 Maintenance of the Exfiltrating Rain Garden will be incorporated into the regular landscape maintenance performed regularly and the cost is included in that budget. Routine visual inspection tasks are understood to be performed by facility staff and are not included in the above estimates. Good Housekeeping Practices Trash/Litter Management The site is to be kept clean of trash and debris at all times. All generated trash and rubbish is to be deposited in covered dumpsters. Dumpsters shall be screened from view and emptied on a regular basis. Street Sweeping Street Sweeping will be provided on the property’s paved surfaces at least twice annually to mitigate potential dust. Regenerative Air sweepers are not recommended for use at this site as these blow air onto the paved surface, causing fines to rise during sweeping activities. Stormwater BMPs All stormwater BMPs are to be inspected and maintained as follows: Catch Basin. Inspect and/or clean catch basins quarterly as part of the regular inspection schedule. Remove accumulated trash and debris from the grates upon discovery. Inspect the integrity of the frames and grates and repair or replace as needed. Record sediment depth and/or the presence of floating oils during each quarterly inspection. Remove sediments two times per year at a minimum or whenever the depth of deposits in the sumps is greater than 12 inches (25% of sump) by clamshell buckets or preferably vacuum truck, as the clamshell buckets can damage the interior tee/hood. Increase inspection frequency if depth of sediment deposits regularly exceeds 12 inches. Ensure that only accumulated sediment is removed and not the underlying soil that supports the structure, if it is a drywell. Dispose of catch basin sediments in accordance with all applicable regulations and policies. In the absence of evidence of contamination, catch basin sediments can be accepted by landfills as solid waste. Some landfill operators may require testing. Contaminated water or sediments removed from catch basins should be disposed of in accordance with all applicable local, state and federal laws and regulations including M.G.L.c. 21C and 310 CMR 30.00. Drain lines. After construction, the drain line shall be inspected visually from either end after every major storm for the first few months to ensure proper functions. Presence of accumulated sand and silt would indicate more frequent maintenance of the pre-treatment devices is required. Thereafter, the drainlines shall be inspected biannually. Stormceptor. Maintenance of the Stormceptor system is performed using vacuum trucks. No entry into the unit is required for maintenance (in most cases). The need for maintenance can be determined easily by inspecting the unit from the surface. The depth of oil in the unit can be determined by inserting a dipstick in the oil inspection/cleanout port. Similarly, the depth of sediment can be measured from the surface without entry into the Stormceptor via a dipstick tube equipped with a ball valve. This tube would be inserted through the riser pipe. Maintenance should be performed once the sediment depth exceeds 8 inches for the 450i model. Although annual servicing is recommended, the frequency of maintenance may need to be increased or reduced based on local conditions (i.e. if the unit is filling up with sediment more quickly than projected, maintenance may be required semi-annually; conversely once the site has stabilized maintenance may only be required every two or three years). Oil is removed through the oil inspection/cleanout port and sediment is removed through the riser pipe. Alternatively, oil could be removed from the 24 inches (600 mm) opening if water is removed from the lower chamber to lower the oil level below the drop pipes. The following procedures should be taken when cleaning out Stormceptor: 1. Check for oil through the oil cleanout port 2. Remove any oil separately using a small portable pump 3. Decant the water from the unit to the sanitary sewer, if permitted by the local regulating authority, or into a separate containment tank 4. Remove the sludge from the bottom of the unit using the vacuum truck 5. Re-fill Stormceptor with water where required by the local jurisdiction Rain Garden. Premature failure of bio retention areas, to include rain gardens, is a significant issue caused by lack of regular maintenance. Ensuring long-term maintenance involves sustained public education and deed restrictions or covenants for privately owned cells. Bio retention areas require careful attention while plants are being established and seasonal landscaping maintenance thereafter. Inspect sediment traps and inlets to the bio-retention cells regularly for sediment build-up, structural damage, and standing water. Remove any litter and/or debris collected in rain garden or its sediment trap upon discovery. Verify the trap is level and distributing water equally. Inspect side slopes and riprap. Repair as necessary. Re-mulch void areas as needed. Inspect Vegetation. Remove any invasive species upon discovery. Annually in the spring investigate the plant mortality as periodic die off is expected. Replace dead vegetation in kind. Treat diseased vegetation as needed. Remove and replace dead vegetation twice per year (spring and fall). The shredded wood mulch will require replacement once every two years (preferably in the early spring) or when the material gets “blinded”. Replacement material shall NOT be ornamental dyed product commonly used in landscapes but rather simple shredded wood, The bio-retention soil should be replaced every 10 years. Never store plowed snow in bio retention areas. Snow Disposal and Plowing Plowed snow shall be stored on unused areas of pavement. Snowmelt from snow storage areas shall be routed through the catchbasin, Stormceptor, or vegetated filter strip for the removal of TSS and other non-water components prior to discharge. Dumping of snow into any water body, including rivers, ponds, or wetlands (including the on-site stormwater infiltration basin and rain garden) is prohibited. Snow disposed of in open water can cause water quality impacts and flooding. Training The long-term pollution prevention plan is to be implemented by the 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. Emergency Contacts The owner will be required to maintain an updated list of Emergency Contacts for the site. This list will be provided to the Yarmouth Conservation Commission. 1. Refer to the Massachusetts Stormwater Standards (current version) for recommendations regarding frequency for inspections and maintenance of specific BMP. Stormceptor® STC Operation and Maintenance Guide ENGINEERED SOLUTIONS 2 Stormceptor® Operation and Maintenance Guide Stormceptor Design Notes • Only the STC 450i is adaptable to function with a catch basin inlet and/or inline pipes. • Only the Stormceptor models STC 450i to STC 7200 may accommodate multiple inlet pipes. Inlet and outlet invert elevation differences are as follows: Maximum inlet and outlet pipe diameters: • The inlet and in-line Stormceptor units can accommodate turns to a maximum of 90 degrees. • Minimum distance from top of grade to crown is 2 feet (0.6 m) • Submerged conditions. A unit is submerged when the standing water elevation at the proposed location of the Stormceptor unit is greater than the outlet invert elevation during zero flow conditions. In these cases, please contact your local Stormceptor representative and provide the following information: • Top of grade elevation • Stormceptor inlet and outlet pipe diameters and invert elevations • Standing water elevation • Stormceptor head loss, K = 1.3 (for submerged condition, K = 4) Inlet and Outlet Pipe Invert Elevations Differences Inlet Pipe Configuration STC 450i STC 900 to STC 7200 STC 11000 to STC 16000 Single inlet pipe 3 in. (75 mm)1 in. (25 mm)3 in. (75 mm) Multiple inlet pipes 3 in. (75 mm)3 in. (75 mm)Only one inlet pipe. Inlet/Outlet Configuration Inlet Unit STC 450i In-Line Unit STC 900 to STC 7200 Series* STC 11000 to STC 16000 Straight Through 24 inch (600 mm)42 inch (1050 mm)60 inch (1500 mm) Bend (90 degrees)18 inch (450 mm)33 inch (825 mm)33 inch (825 mm) Stormceptor® Operation and Maintenance Guide 3 OPERATION AND MAINTENANCE GUIDE Table of Content 1. About Stormceptor ......................................................................................................................................................................4 2. Stormceptor Design Overview ......................................................................................................................................................4 3. Key Operation Features ................................................................................................................................................................6 4. Stormceptor Product Line .............................................................................................................................................................7 5. Sizing the Stormceptor System...................................................................................................................................................10 6. Spill Controls ..............................................................................................................................................................................12 7. Stormceptor Options ..................................................................................................................................................................14 8. Comparing Technologies ............................................................................................................................................................17 9. Testing ........................................................................................................................................................................................18 10. Installation .................................................................................................................................................................................18 11. Stormceptor Construction Sequence ..........................................................................................................................................18 12. Maintenance ..............................................................................................................................................................................19 4 Stormceptor® Operation and Maintenance Guide 1. About Stormceptor The Stormceptor® STC (Standard Treatment Cell) was developed by Imbrium™ Systems to address the growing need to remove and isolate pollution from the storm drain system before it enters the environment. The Stormceptor STC targets hydrocarbons and total suspended solids (TSS) in stormwater runoff. It improves water quality by removing contaminants through the gravitational settling of fine sediments and floatation of hydrocarbons while preventing the re-suspension or scour of previously captured pollutants. The development of the Stormceptor STC revolutionized stormwater treatment, and created an entirely new category of environmental technology. Protecting thousands of waterways around the world, the Stormceptor System has set the standard for effective stormwater treatment. 1.1. Patent Information The Stormceptor technology is protected by the following patents: • Australia Patent No. 693,164 • 693,164 • 707,133 • 729,096 • 779401 • Austrian Patent No. 289647 • Canadian Patent No 2,009,208 •2,137,942 • 2,175,277 • 2,180,305 • 2,180,383 • 2,206,338 • 2,327,768 (Pending) • China Patent No 1168439 • Denmark DK 711879 • German DE 69534021 • Indonesian Patent No 16688 • Japan Patent No 9-11476 (Pending) • Korea 10-2000-0026101 (Pending) • Malaysia Patent No PI9701737 (Pending) • New Zealand Patent No 314646 • United States Patent No 4,985,148 • 5,498,331 • 5,725,760 • 5,753,115 • 5,849,181 • 6,068,765 • 6,371,690 • Stormceptor OSR Patent Pending • Stormceptor LCS Patent Pending 2. Stormceptor Design Overview 2.1. Design Philosophy The patented Stormceptor System has been designed to focus on the environmental objective of providing long-term pollution control. The unique and innovative Stormceptor design allows for continuous positive treatment of runoff during all rainfall events, while ensuring that all captured pollutants are retained within the system, even during intense storm events. An integral part of the Stormceptor design is PCSWMM for Stormceptor - sizing software developed in conjunction with Computational Hydraulics Inc. (CHI) and internationally acclaimed expert, Dr. Bill James. Using local historical rainfall data and continuous simulation modeling, this software allows a Stormceptor unit to be designed for each individual site and the corresponding water quality objectives. By using PCSWMM for Stormceptor, the Stormceptor System can be designed to remove a wide range of particles (typically from 20 to 2,000 microns), and can also be customized to remove a specific particle size distribution (PSD). The specified PSD should accurately reflect what is in the stormwater runoff to ensure the device is achieving the desired water quality objective. Since stormwater runoff contains small particles (less than 75 microns), it is important to design a treatment system to remove smaller particles in addition to coarse particles. Stormceptor® Operation and Maintenance Guide 5 2.2. Benefits The Stormceptor System removes free oil and suspended solids from stormwater, preventing spills and non-point source pollution from entering downstream lakes and rivers. The key benefits, capabilities and applications of the Stormceptor System are as follows: • Provides continuous positive treatment during all rainfall events • Can be designed to remove over 80% of the annual sediment load • Removes a wide range of particles • Can be designed to remove a specific particle size distribution (PSD) • Captures free oil from stormwater • Prevents scouring or re-suspension of trapped pollutants • Pre-treatment to reduce maintenance costs for downstream treatment measures (ponds, swales, detention basins, filters) • Groundwater recharge protection • Spills capture and mitigation • Simple to design and specify • Designed to your local watershed conditions • Small footprint to allow for easy retrofit installations • Easy to maintain (vacuum truck) • Multiple inlets can connect to a single unit • Suitable as a bend structure • Pre-engineered for traffic loading (minimum AASHTO HS-20) • Minimal elevation drop between inlet and outlet pipes • Small head loss • Additional protection provided by an 18” (457 mm) fiberglass skirt below the top of the insert, for the containment of hydrocarbons in the event of a spill. 2.3. Environmental Benefit Freshwater resources are vital to the health and welfare of their surrounding communities. There is increasing public awareness, government regulations and corporate commitment to reducing the pollution entering our waterways. A major source of this pollution originates from stormwater runoff from urban areas. Rainfall runoff carries oils, sediment and other contaminants from roads and parking lots discharging directly into our streams, lakes and coastal waterways. The Stormceptor System is designed to isolate contaminants from getting into the natural environment. The Stormceptor technology provides protection for the environment from spills that occur at service stations and vehicle accident sites, while also removing contaminated sediment in runoff that washes from roads and parking lots. 6 Stormceptor® Operation and Maintenance Guide 3. Key Operation Features 3.1. Scour Prevention A key feature of the Stormceptor System is its patented scour prevention technology. This innovation ensures pollutants are captured and retained during all rainfall events, even extreme storms. The Stormceptor System provides continuous positive treatment for all rainfall events, including intense storms. Stormceptor slows incoming runoff, controlling and reducing velocities in the lower chamber to create a non-turbulent environment that promotes free oils and floatable debris to rise and sediment to settle. The patented scour prevention technology, the fiberglass insert, regulates flows into the lower chamber through a combination of a weir and orifice while diverting high energy flows away through the upper chamber to prevent scouring. Laboratory testing demonstrated no scouring when tested up to 125% of the unit’s operating rate, with the unit loaded to 100% sediment capacity (NJDEP, 2005). Second, the depth of the lower chamber ensures the sediment storage zone is adequately separated from the path of flow in the lower chamber to prevent scouring. 3.2. Operational Hydraulic Loading Rate Designers and regulators need to evaluate the treatment capacity and performance of manufactured stormwater treatment systems. A commonly used parameter is the “operational hydraulic loading rate” which originated as a design methodology for wastewater treatment devices. Operational hydraulic loading rate may be calculated by dividing the flow rate into a device by its settling area. This represents the critical settling velocity that is the prime determinant to quantify the influent particle size and density captured by the device. PCSWMM for Stormceptor uses a similar parameter that is calculated by dividing the hydraulic detention time in the device by the fall distance of the sediment. Where: vSC = critical settling velocity, ft/s (m/s) H = tank depth, ft (m) ØH = hydraulic detention time, ft/s (m/s) Q = volumetric flow rate, ft3/s (m3/s) AS = surface area, ft2 (m2) (Tchobanoglous, G. and Schroeder, E.D. 1987. Water Quality. Addison Wesley.) Unlike designing typical wastewater devices, stormwater systems are designed for highly variable flow rates including intense peak flows. PCSWMM for Stormceptor incorporates all of the flows into its calculations, ensuring that the operational hydraulic loading rate is considered not only for one flow rate, but for all flows including extreme events. 3.3. Double Wall Containment The Stormceptor System was conceived as a pollution identifier to assist with identifying illicit discharges. The fiberglass insert has a continuous skirt that lines the concrete barrel wall for a depth of 18 inches (457 mm) that provides double wall containment for hydrocarbons storage. This protective barrier ensures that toxic floatables do not migrate through the concrete wall into the surrounding soils. vSC = H = Q 6H AS Stormceptor® Operation and Maintenance Guide 7 4. Stormceptor Product Line 4.1. Stormceptor Models A summary of Stormceptor models and capacities are listed in Table 1. NOTE: Storage volumes may vary slightly from region to region. For detailed information, contact your local Stormceptor representative. 4.2. Inline Stormceptor The Inline Stormceptor, Figure 1, is the standard design for most stormwater treatment applications. The patented Stormceptor design allows the Inline unit to maintain continuous positive treatment of total suspended solids (TSS) year-round, regardless of flow rate. The Inline Stormceptor is composed of a precast concrete tank with a fiberglass insert situated at the invert of the storm sewer pipe, creating an upper chamber above the insert and a lower chamber below the insert. Table 1. Stormceptor Models Stormceptor Model Total Storage Volume U.S. Gal (L)Hydrocarbon Storage Capacity U.S. Gal (L)Maximum Sediment Capacity ft3 (L) STC 450i 470 (1,780)86 (330)46 (1,302) STC 900 952 (3,600)251 (950)89 (2,520) STC 1200 1,234 (4,670)251 (950)127 (3,596) STC 1800 1,833 (6,940)251 (950)207 (5,861) STC 2400 2,462 (9,320)840 (3,180)205 (5,805) STC 3600 3,715 (1,406)840 (3,180)373 (10,562) STC 4800 5,059 (1,950)909 (3,440)543 (15,376) STC 6000 6,136 (23,230)909 (3,440)687 (19,453) STC 7200 7,420 (28,090)1,059 (4,010)839 (23,757) STC 11000 11,194 (42,370)2,797 (10, 590)1,086 (30,752) STC 13000 13,348 (50,530)2,797 (10, 590)1,374 (38,907) STC 16000 15,918 (60,260)3,055 (11, 560)1,677 (47,487) 8 Stormceptor® Operation and Maintenance Guide Operation As water flows into the Stormceptor unit, it is slowed and directed to the lower chamber by a weir and drop tee. The stormwater enters the lower chamber, a non-turbulent environment, allowing free oils to rise and sediment to settle. The oil is captured underneath the fiberglass insert and shielded from exposure to the concrete walls by a fiberglass skirt. After the pollutants separate, treated water continues up a riser pipe, and exits the lower chamber on the downstream side of the weir before leaving the unit. During high flow events, the Stormceptor System’s patented scour prevention technology ensures continuous pollutant removal and prevents re-suspension of previously captured pollutants. Technical Manual 6 Figure 1. Inline Stormceptor Operation As water flows into the Stormceptor unit, it is slowed and directed to the lower chamber by a weir and drop tee. The stormwater enters the lower chamber, a non-turbulent environment, allowing free oils to rise and sediment to settle. The oil is captured underneath the fiberglass insert and shielded from exposure to the concrete walls by a fiberglass skirt. After the pollutants separate, treated water continues up a riser pipe, and exits the lower chamber on the downstream side of the weir before leaving the unit. During high flow events, the Stormceptor System’s patented scour prevention technology ensures continuous pollutant removal and prevents re-suspension of previously captured pollutants. 4.3. Inlet Stormceptor The Inlet Stormceptor System, Figure 2, was designed to provide protection for parking lots, loading bays, gas stations and other spill-prone areas. The Inlet Stormceptor is designed to remove sediment from stormwater introduced through a grated inlet, a storm sewer pipe, or both. Stormceptor® Operation and Maintenance Guide 9 4.3. Inlet Stormceptor The Inlet Stormceptor System, Figure 2, was designed to provide protection for parking lots, loading bays, gas stations and other spill-prone areas. The Inlet Stormceptor is designed to remove sediment from stormwater introduced through a grated inlet, a storm sewer pipe, or both. The Inlet Stormceptor design operates in the same manner as the Inline unit, providing continuous positive treatment, and ensuring that captured material is not re-suspended. 4.4. Series Stormceptor Designed to treat larger drainage areas, the Series Stormceptor System, Figure 3, consists of two adjacent Stormceptor models that function in parallel. This design eliminates the need for additional structures and piping to reduce installation costs. Technical Manual 7 Figure 2. Inlet Stormceptor The Inlet Stormceptor design operates in the same manner as the Inline unit, providing continuous positive treatment, and ensuring that captured material is not re-suspended. 4.4. Series Stormceptor Designed to treat larger drainage areas, the Series Stormceptor System, Figure 3, consists of two adjacent Stormceptor models that function in parallel. This design eliminates the need for additional structures and piping to reduce installation costs. 10 Stormceptor® Operation and Maintenance Guide The Series Stormceptor design operates in the same manner as the Inline unit, providing continuous positive treatment, and ensuring that captured material is not re-suspended. 5. Sizing the Stormceptor System The Stormceptor System is a versatile product that can be used for many different aspects of water quality improvement. While addressing these needs, there are conditions that the designer needs to be aware of in order to size the Stormceptor model to meet the demands of each individual site in an efficient and cost-effective manner. PCSWMM for Stormceptor is the support tool used for identifying the appropriate Stormceptor model. In order to size a unit, it is recommended the user follow the seven design steps in the program. The steps are as follows: STEP 1 – Project Details The first step prior to sizing the Stormceptor System is to clearly identify the water quality objective for the development. It is recommended that a level of annual sediment (TSS) removal be identified and defined by a particle size distribution. STEP 2 – Site Details Identify the site development by the drainage area and the level of imperviousness. It is recommended that imperviousness be calculated based on the actual area of imperviousness based on paved surfaces, sidewalks and rooftops. STEP 3 – Upstream Attenuation The Stormceptor System is designed as a water quality device and is sometimes used in conjunction with onsite water quantity control devices such as ponds or underground detention systems. When possible, a greater benefit is typically achieved when installing a Stormceptor unit upstream of a detention facility. By placing the Stormceptor unit upstream of a detention structure, a benefit of less maintenance of the detention facility is realized. Technical Manual 8 Figure 3. Series System The Series Stormceptor design operates in the same manner as the Inline unit, providing continuous positive treatment, and ensuring that captured material is not re-suspended. 5. Sizing the Stormceptor System The Stormceptor System is a versatile product that can be used for many different aspects of water quality improvement. While addressing these needs, there are conditions that the designer needs to be aware of in order to size the Stormceptor model to meet the demands of each individual site in an efficient and cost-effective manner. PCSWMM for Stormceptor is the support tool used for identifying the appropriate Stormceptor model. In order to size a unit, it is recommended the user follow the seven design steps in the program. The steps are as follows: STEP 1 – Project Details The first step prior to sizing the Stormceptor System is to clearly identify the water quality objective for the development. It is recommended that a level of annual sediment (TSS) removal be identified and defined by a particle size distribution. Stormceptor® Operation and Maintenance Guide 11 STEP 4 – Particle Size Distribution It is critical that the PSD be defined as part of the water quality objective. PSD is critical for the design of treatment system for a unit process of gravity settling and governs the size of a treatment system. A range of particle sizes has been provided and it is recommended that clays and silt-sized particles be considered in addition to sand and gravel-sized particles. Options and sample PSDs are provided in PCSWMM for Stormceptor. The default particle size distribution is the Fine Distribution, Table 2, option. If the objective is the long-term removal of 80% of the total suspended solids on a given site, the PSD should be representative of the expected sediment on the site. For example, a system designed to remove 80% of coarse particles (greater than 75 microns) would provide relatively poor removal efficiency of finer particles that may be naturally prevalent in runoff from the site. Since the small particle fraction contributes a disproportionately large amount of the total available particle surface area for pollutant adsorption, a system designed primarily for coarse particle capture will compromise water quality objectives. STEP 5 – Rainfall Records Local historical rainfall has been acquired from the U.S. National Oceanic and Atmospheric Administration, Environment Canada and regulatory agencies across North America. The rainfall data provided with PCSMM for Stormceptor provides an accurate estimation of small storm hydrology by modeling actual historical storm events including duration, intensities and peaks. STEP 6 – Summary At this point, the program may be executed to predict the level of TSS removal from the site. Once the simulation has completed, a table shall be generated identifying the TSS removal of each Stormceptor unit. STEP 7 – Sizing Summary Performance estimates of all Stormceptor units for the given site parameters will be displayed in a tabular format. The unit that meets the water quality objective, identified in Step 1, will be highlighted. Table 2. Fine Distribution Particle Size Distribution Specific Gravity 20 20%1.3 60 20%1.8 150 20%2.2 400 20%2.65 2000 20%2.65 12 Stormceptor® Operation and Maintenance Guide 5.1. PCSWMM for Stormceptor The Stormceptor System has been developed in conjunction with PCSWMM for Stormceptor as a technological solution to achieve water quality goals. Together, these two innovations model, simulate, predict and calculate the water quality objectives desired by a design engineer for TSS removal. PCSWMM for Stormceptor is a proprietary sizing program which uses site specific inputs to a computer model to simulate sediment accumulation, hydrology and long-term total suspended solids removal. The model has been calibrated to field monitoring results from Stormceptor units that have been monitored in North America. The sizing methodology can be described by three processes: 1. Determination of real time hydrology 2. Buildup and wash off of TSS from impervious land areas 3. TSS transport through the Stormceptor (settling and discharge). The use of a calibrated model is the preferred method for sizing stormwater quality structures for the following reasons: x The hydrology of the local area is properly and accurately incorporated in the sizing (distribution of flows, flow rate ranges and peaks, back-to-back storms, inter-event times) x The distribution of TSS with the hydrology is properly and accurately considered in the sizing x Particle size distribution is properly considered in the sizing x The sizing can be optimized for TSS removal x The cost benefit of alternate TSS removal criteria can be easily assessed x The program assesses the performance of all Stormceptor models. Sizing may be selected based on a specific water quality outcome or based on the Maximum Extent Practicable For more information regarding PCSWMM for Stormceptor, contact your local Stormceptor representative, or visit www.imbriumsystems.com to download a free copy of the program. 5.2. Sediment Loading Characteristics The way in which sediment is transferred to stormwater can have a considerable effect on which type of system is implemented. On typical impervious surfaces (e.g. parking lots) sediment will build over time and wash off with the next rainfall. When rainfall patterns are examined, a short intense storm will have a higher concentration of sediment than a long slow drizzle. Together with rainfall data representing the site’s typical rainfall patterns, sediment loading characteristics play a part in the correct sizing of a stormwater quality device. Typical Sites For standard site design of the Stormceptor System, PCSWMM for Stormceptor is utilized to accurately assess the unit’s performance. As an integral part of the product’s design, the program can be used to meet local requirements for total suspended solid removal. Typical installations of manufactured stormwater treatment devices would occur on areas such as paved parking lots or paved roads. These are considered “stable” surfaces which have non – erodible surfaces. Unstable Sites While standard sites consist of stable concrete or asphalt surfaces, sites such as gravel parking lots, or maintenance yards with stockpiles of sediment would be classified as “unstable”. These types of sites do not exhibit first flush characteristics, are highly erodible and exhibit atypical sediment loading characteristics and must therefore be sized more carefully. Contact your local Stormceptor representative for assistance in selecting a proper unit sized for such unstable sites. 6. Spill Controls When considering the removal of total petroleum hydrocarbons (TPH) from a storm sewer system there are two functions of the system: oil removal, and spill capture. ‘Oil Removal’ describes the capture of the minute volumes of free oil mobilized from impervious surfaces. In this instance relatively low concentrations, volumes and flow rates are considered. While the Stormceptor unit will still provide an appreciable oil removal function during higher flow events and/or with higher TPH concentrations, desired effluent limits may be exceeded under these conditions. Stormceptor® Operation and Maintenance Guide 13 Technical Manual 12 level alarm is designed to trigger at approximately 85% of the unit’s available depth level for oil capture. The feature acts as a safeguard against spills caused by exceeding the oil storage capacity of the separator and eliminates the need for manual oil level inspection. The oil level alarm installed on the Stormceptor insert is illustrated in Figure 4. Figure 4. Oil level alarm 6.2. Increased Volume Storage Capacity The Stormceptor unit may be modified to store a greater spill volume than is typically available. Under such a scenario, instead of installing a larger than required unit, modifications can be made to the recommended Stormceptor model to accommodate larger volumes. Contact your local Stormceptor representative for additional information and assistance for modifications. 7. Stormceptor Options The Stormceptor System allows flexibility to incorporate to existing and new storm drainage infrastructure. The following section identifies considerations that should be reviewed when installing the system into a drainage network. For conditions that fall outside of the recommendations in this section, please contact your local Stormceptor representative for further guidance. 7.1. Installation Depth Minimum Cover The minimum distance from the top of grade to the crown of the inlet pipe is 24 inches (600 mm). For situations that have a lower minimum distance, contact your local Stormceptor representative. 7.2. Maximum Inlet and Outlet Pipe Diameters Maximum inlet and outlet pipe diameters are illustrated in Figure 5. Contact your local Stormceptor representative for larger pipe diameters. ‘Spill Capture’ describes a manner of TPH removal more appropriate to recovery of a relatively high volume of a single phase deleterious liquid that is introduced to the storm sewer system over a relatively short duration. The two design criteria involved when considering this manner of introduction are overall volume and the specific gravity of the material. A standard Stormceptor unit will be able to capture and retain a maximum spill volume and a minimum specific gravity. For spill characteristics that fall outside these limits, unit modifications are required. Contact your local Stormceptor Representative for more information. One of the key features of the Stormceptor technology is its ability to capture and retain spills. While the standard Stormceptor System provides excellent protection for spill control, there are additional options to enhance spill protection if desired. 6.1. Oil Level Alarm The oil level alarm is an electronic monitoring system designed to trigger a visual and audible alarm when a pre-set level of oil is reached within the lower chamber. As a standard, the oil level alarm is designed to trigger at approximately 85% of the unit’s available depth level for oil capture. The feature acts as a safeguard against spills caused by exceeding the oil storage capacity of the separator and eliminates the need for manual oil level inspection. The oil level alarm installed on the Stormceptor insert is illustrated in Figure 4. 6.2. Increased Volume Storage Capacity The Stormceptor unit may be modified to store a greater spill volume than is typically available. Under such a scenario, instead of installing a larger than required unit, modifications can be made to the recommended Stormceptor model to accommodate larger volumes. Contact your local Stormceptor representative for additional information and assistance for modifications. 14 Stormceptor® Operation and Maintenance Guide 7. Stormceptor Options The Stormceptor System allows flexibility to incorporate to existing and new storm drainage infrastructure. The following section identifies considerations that should be reviewed when installing the system into a drainage network. For conditions that fall outside of the recommendations in this section, please contact your local Stormceptor representative for further guidance. 7.1. Installation Depth Minimum Cover The minimum distance from the top of grade to the crown of the inlet pipe is 24 inches (600 mm). For situations that have a lower minimum distance, contact your local Stormceptor representative. 7.2. Maximum Inlet and Outlet Pipe Diameters Maximum inlet and outlet pipe diameters are illustrated in Figure 5. Contact your local Stormceptor representative for larger pipe diameters Technical Manual 13 Figure 5. Maximum pipe diameters for straight through and bend applications *The bend should only be incorporated into the second structure (downstream structure) of the Series Stormceptor System 7.3. Bends The Stormceptor System can be used to change horizontal alignment in the storm drain network up to a maximum of 90 degrees. Figure 6 illustrates the typical bend situations of the Stormceptor System. Bends should only be applied to the second structure (downstream structure) of the Series Stormceptor System. 7.3. Bends The Stormceptor System can be used to change horizontal alignment in the storm drain network up to a maximum of 90 degrees. Figure 6 illustrates the typical bend situations of the Stormceptor System. Bends should only be applied to the second structure (downstream structure) of the Series Stormceptor System. Stormceptor® Operation and Maintenance Guide 15 Technical Manual 14 Figure 6. Maximum bend angles 7.4. Multiple Inlet Pipes The Inlet and Inline Stormceptor System can accommodate two or more inlet pipes. The maximum number of inlet pipes that can be accommodated into a Stormceptor unit is a function of the number, alignment and diameter of the pipes and its effects on the structural integrity of the precast concrete. When multiple inlet pipes are used for new developments, each inlet pipe shall have an invert elevation 3 inches (75 mm) higher than the outlet pipe invert elevation. 7.4. Multiple Inlet Pipes The Inlet and Inline Stormceptor System can accommodate two or more inlet pipes. The maximum number of inlet pipes that can be accommodated into a Stormceptor unit is a function of the number, alignment and diameter of the pipes and its effects on the structural integrity of the precast concrete. When multiple inlet pipes are used for new developments, each inlet pipe shall have an invert elevation 3 inches (75 mm) higher than the outlet pipe invert elevation. 7.5. Inlet/Outlet Pipe Invert Elevations Recommended inlet and outlet pipe invert differences are listed in Table 3. 7.6. Shallow Stormceptor In cases where there may be restrictions to the depth of burial of storm sewer systems. In this situation, for selected Stormceptor models, the lower chamber components may be increased in diameter to reduce the overall depth of excavation required. 7.7. Customized Live Load The Stormceptor system is typically designed for local highway truck loading (AASHTO HS- 20). When the project requires live loads greater than HS-20, the Stormceptor System may be customized structurally for a pre-specified live load. Contact your local Stormceptor representative for customized loading conditions. Table 3. Recommended Drops Between Inlet and Outlet Pipe Inverts Number of Inlet Pipes Inlet System In-Line System Series System 1 3 inches (75 mm)1 inch (25 mm)3 inches (75 mm) >1 3 inches (75 mm)3 inches (75 mm)Not Applicable 16 Stormceptor® Operation and Maintenance Guide 7.8. Pre-treatment The Stormceptor System may be sized to remove sediment and for spills control in conjunction with other stormwater BMPs to meet the water quality objective. For pretreatment applications, the Stormceptor System should be the first unit in a treatment train. The benefits of pre-treatment include the extension of the operational life (extension of maintenance frequency) of large stormwater management facilities, prevention of spills and lower total life- cycle maintenance cost. 7.9. Head loss The head loss through the Stormceptor System is similar to a 60 degree bend at a manhole. The K value for calculating minor losses is approximately 1.3 (minor loss = k*1.3v2/2g). However, when a Submerged modification is applied to a Stormceptor unit, the corresponding K value is 4. 7.10. Submerged The Submerged modification, Figure 7, allows the Stormceptor System to operate in submerged or partially submerged storm sewers. This configuration can be installed on all models of the Stormceptor System by modifying the fiberglass insert. A customized weir height and a secondary drop tee are added. Submerged instances are defined as standing water in the storm drain system during zero flow conditions. In these instances, the following information is necessary for the proper design and application of submerged modifications: • Stormceptor top of grade elevation • Stormceptor outlet pipe invert elevation • Standing water elevation Technical Manual 16 Submerged instances are defined as standing water in the storm drain system during zero flow conditions. In these instances, the following information is necessary for the proper design and application of submerged modifications: • Stormceptor top of grade elevation • Stormceptor outlet pipe invert elevation • Standing water elevation Figure 7. Submerged Stormceptor Stormceptor® Operation and Maintenance Guide 17 8. Comparing Technologies Designers have many choices available to achieve water quality goals in the treatment of stormwater runoff. Since many alternatives are available for use in stormwater quality treatment it is important to consider how to make an appropriate comparison between “approved alternatives”. The following is a guide to assist with the accurate comparison of differing technologies and performance claims. 8.1. Particle Size Distribution (PSD) The most sensitive parameter to the design of a stormwater quality device is the selection of the design particle size. While it is recommended that the actual particle size distribution (PSD) for sites be measured prior to sizing, alternative values for particle size should be selected to represent what is likely to occur naturally on the site. A reasonable estimate of a particle size distribution likely to be found on parking lots or other impervious surfaces should consist of a wide range of particles such as 20 microns to 2,000 microns (Ontario MOE, 1994). There is no absolute right particle size distribution or specific gravity and the user is cautioned to review the site location, characteristics, material handling practices and regulatory requirements when selecting a particle size distribution. When comparing technologies, designs using different PSDs will result in incomparable TSS removal efficiencies. The PSD of the TSS removed needs to be standard between two products to allow for an accurate comparison. 8.2. Scour Prevention In order to accurately predict the performance of a manufactured treatment device, there must be confidence that it will perform under all conditions. Since rainfall patterns cannot be predicted, stormwater quality devices placed in storm sewer systems must be able to withstand extreme events, and ensure that all pollutants previously captured are retained in the system. In order to have confidence in a system’s performance under extreme conditions, independent validation of scour prevention is essential when examining different technologies. Lack of independent verification of scour prevention should make a designer wary of accepting any product’s performance claims. 8.3. Hydraulics Full scale laboratory testing has been used to confirm the hydraulics of the Stormceptor System. Results of lab testing have been used to physically design the Stormceptor System and the sewer pipes entering and leaving the unit. Key benefits of Stormceptor are: • Low head loss (typical k value of 1.3) • Minimal inlet/outlet invert elevation drop across the structure • Use as a bend structure • Accommodates multiple inlets The adaptability of the treatment device to the storm sewer design infrastructure can affect the overall performance and cost of the site. 8.4. Hydrology Stormwater quality treatment technologies need to perform under varying climatic conditions. These can vary from long low intensity rainfall to short duration, high intensity storms. Since a treatment device is expected to perform under all these conditions, it makes sense that any system’s design should accommodate those conditions as well. Long-term continuous simulation evaluates the performance of a technology under the varying conditions expected in the climate of the subject site. Single, peak event design does not provide this information and is not equivalent to long-term simulation. Designers should request long-term simulation performance to ensure the technology can meet the long-term water quality objective. 18 Stormceptor® Operation and Maintenance Guide 9. Testing The Stormceptor System has been the most widely monitored stormwater treatment technology in the world. Performance verification and monitoring programs are completed to the strictest standards and integrity. Since its introduction in 1990, numerous independent field tests and studies detailing the effectiveness of the Stormceptor System have been completed. •Coventry University, UK – 97% removal of oil, 83% removal of sand and 73% removal of peat •National Water Research Institute, Canada, - scaled testing for the development of the Stormceptor System identifying both TSS removal and scour prevention. •New Jersey TARP Program – full scale testing of an STC 900 demonstrating 75% TSS removal of particles from 1 to 1000 microns. Scour testing completed demonstrated that the system does not scour. The New Jersey Department of Environmental Protection was followed. •City of Indianapolis – full scale testing of an STC 900 demonstrating over 80% TSS removal of particles from 50 microns to 300 microns at 130% of the unit’s operating rate. Scour testing completed demonstrated that the system does not scour. •Westwood Massachusetts (1997), demonstrated >80% TSS removal •Como Park (1997), demonstrated 76% TSS removal •Ontario MOE SWAMP Program – 57% removal of 1 to 25 micron particles •Laval Quebec – 50% removal of 1 to 25 micron particles 10.Installation The installation of the concrete Stormceptor should conform in general to state highway, or local specifications for the installation of manholes. Selected sections of a general specification that are applicable are summarized in the following sections. 10.1. Excavation Excavation for the installation of the Stormceptor should conform to state highway, or local specifications. Topsoil removed during the excavation for the Stormceptor should be stockpiled in designated areas and should not be mixed with subsoil or other materials. Topsoil stockpiles and the general site preparation for the installation of the Stormceptor should conform to state highway or local specifications. The Stormceptor should not be installed on frozen ground. Excavation should extend a minimum of 12 inches (300 mm) from the precast concrete surfaces plus an allowance for shoring and bracing where required. If the bottom of the excavation provides an unsuitable foundation additional excavation may be required. In areas with a high water table, continuous dewatering may be required to ensure that the excavation is stable and free of water. 10.2. Backfilling Backfill material should conform to state highway or local specifications. Backfill material should be placed in uniform layers not exceeding 12 inches (300mm) in depth and compacted to state highway or local specifications. 11.Stormceptor Construction Sequence The concrete Stormceptor is installed in sections in the following sequence: 1.Aggregate base 2.Base slab 3.Lower chamber sections 4.Upper chamber section with fiberglass insert 5.Connect inlet and outlet pipes 6.Assembly of fiberglass insert components (drop tee, riser pipe, oil cleanout port and orifice plate 7.Remainder of upper chamber 8.Frame and access cover The precast base should be placed level at the specified grade. The entire base should be in contact with the underlying compacted granular material. Subsequent sections, complete with joint seals, should be installed in accordance with the precast concrete manufacturer’s recommendations. Stormceptor® Operation and Maintenance Guide 19 Adjustment of the Stormceptor can be performed by lifting the upper sections free of the excavated area, re-leveling the base and re- installing the sections. Damaged sections and gaskets should be repaired or replaced as necessary. Once the Stormceptor has been constructed, any lift holes must be plugged with mortar. 12. Maintenance 12.1. Health and Safety The Stormceptor System has been designed considering safety first. It is recommended that confined space entry protocols be followed if entry to the unit is required. In addition, the fiberglass insert has the following health and safety features: • Designed to withstand the weight of personnel • A safety grate is located over the 24 inch (600 mm) riser pipe opening • Ladder rungs can be provided for entry into the unit, if required 12.2. Maintenance Procedures Maintenance of the Stormceptor system is performed using vacuum trucks. No entry into the unit is required for maintenance (in most cases). The vacuum service industry is a well- established sector of the service industry that cleans underground tanks, sewers and catch basins. Costs to clean a Stormceptor will vary based on the size of unit and transportation distances. The need for maintenance can be determined easily by inspecting the unit from the surface. The depth of oil in the unit can be determined by inserting a dipstick in the oil inspection/cleanout port. Similarly, the depth of sediment can be measured from the surface without entry into the Stormceptor via a dipstick tube equipped with a ball valve. This tube would be inserted through the riser pipe. Maintenance should be performed once the sediment depth exceeds the guideline values provided in the Table 4. Table 4. Sediment Depths Indicating Required Servicing* Particle Size Specific Gravity Model Sediment Depth inches (mm) 450i 8 (200) 900 8 (200) 1200 10 (250) 1800 15 (381) 2400 12 (300) 3600 17 (430) 4800 15 (380) 6000 18 (460) 7200 15 (381) 11000 17 (380) 13000 20 (500) 16000 17 (380) * based on 15% of the Stormceptor unit’s total storage Although annual servicing is recommended, the frequency of maintenance may need to be increased or reduced based on local conditions (i.e. if the unit is filling up with sediment more quickly than projected, maintenance may be required semi-annually; conversely once the site has stabilized maintenance may only be required every two or three years). Oil is removed through the oil inspection/cleanout port and sediment is removed through the riser pipe. Alternatively oil could be removed from the 24 inches (600 mm) opening if water is removed from the lower chamber to lower the oil level below the drop pipes. The following procedures should be taken when cleaning out Stormceptor: 1. Check for oil through the oil cleanout port 2. Remove any oil separately using a small portable pump 3. Decant the water from the unit to the sanitary sewer, if permitted by the local regulating authority, or into a separate containment tank 4. Remove the sludge from the bottom of the unit using the vacuum truck 5. Re-fill Stormceptor with water where required by the local jurisdiction 12.3. Submerged Stormceptor Careful attention should be paid to maintenance of the Submerged Stormceptor System. In cases where the storm drain system is submerged, there is a requirement to plug both the inlet and outlet pipes to economically clean out the unit. 12.4. Hydrocarbon Spills The Stormceptor is often installed in areas where the potential for spills is great. The Stormceptor System should be cleaned immediately after a spill occurs by a licensed liquid waste hauler. 12.5. Disposal Requirements for the disposal of material from the Stormceptor System are similar to that of any other stormwater Best Management Practice (BMP) where permitted. Disposal options for the sediment may range from disposal in a sanitary trunk sewer upstream of a sewage treatment plant, to disposal in a sanitary landfill site. Petroleum waste products collected in the Stormceptor (free oil/chemical/fuel spills) should be removed by a licensed waste management company. 12.6. Oil Sheens With a steady influx of water with high concentrations of oil, a sheen may be noticeable at the Stormceptor outlet. This may occur because a rainbow or sheen can be seen at very small oil concentrations (<10 mg/L). Stormceptor will remove over 98% of all free oil spills from storm sewer systems for dry weather or frequently occurring runoff events. The appearance of a sheen at the outlet with high influent oil concentrations does not mean the unit is not working to this level of removal. In addition, if the influent oil is emulsified the Stormceptor will not be able to remove it. The Stormceptor is designed for free oil removal and not emulsified conditions. 800-925-5240 www.ContechES.com SUPPORT Drawings and specifications are available at www.ContechES.com. Site-specific design support is available from our engineers. ©2020 Contech Engineered Solutions LLC, a QUIKRETE Company Contech Engineered Solutions LLC provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, stormwater, and earth stabilization products. For information, visit www.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. Stormceptor Technical Manual 05/20 ENGINEERED SOLUTIONS ANNUAL STORMWATER MAINTENANCE LOG 228 Route 28, Yarmouth MA Inspection Date: ___________ Instructions 1. Refer to attached locus plan for component identification 2. Inspect each component for visual damage and assess functionality. 3. Keep one copy of Maintenance Log and transmit (1) copy to the Yarmouth Conservation Commission EXISTING CATCH BASINS (CB) Q1 _____ Q2 _____ Q3 _____ Q4 _____ Maintenance Item Structure Comments CB-1 Does the frame or grate show any damage? Is curbing near the catchbasin intact? Are there visible floatables on water surface? Is there an apparent oil layer? What is its estimated thickness? What is the estimated depth of the sediment accumulation? Is maintenance required? ANNUAL STORMWATER MAINTENANCE LOG 228 Route 28, Yarmouth MA Inspection Date: ___________ RAIN GARDENS (RG) Q1 _____ Q2 _____ Q3 _____ Q4 _____ Maintenance Item Structure Comments RG-1 What is the sediment depth in the central bottom area? Does the rain garden or central sediment trap have any litter or debris? Are all side slopes, vegetated filter strip, and stone diaphragm intact? Does mulch/soil show evidence of sediment carryover? Is there any dead vegetation or invasive species? Is there standing water in central in the rain garden? Is maintenance required? ANNUAL STORMWATER MAINTENANCE LOG 228 Route 28, Yarmouth MA Inspection Date: ___________ STORMCEPTOR Q1 _____ Q2 _____ Q3 _____ Q4 _____ Maintenance Item Structure Comments Does the frame, cover, or insert show damage? Is floating product present in the inspection/cleanout port? If present has oil been removed per manufacturer’s procedure? Does the depth of sediment observed in the riser pipe equal to or greater than 8 inches? If >8” depth has it been removed via vacuum truck? ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX E CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN 228 Route 28, Yarmouth MA Proposed A Plus Market 1 EROSION AND SEDMENTATION CONTROL PLAN- CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN (CPPPP) Introduction As required by Standards 4 and 9 of the Stormwater Management Handbook and Section 2.06 of the Town of Yarmouth Stormwater Management Regulations, this Construction Period Pollution Prevention Plan has been developed for source control and pollution prevention at the site during construction. This project does not appear to require coverage under the National Pollutant Discharge Elimination System (NPDES) Construction General Permit (CGP). No stormwater discharges from construction activity are planned to enter into the Waters of the United States. An area that will remain undisturbed is tributary to a wetland located offsite to the north. An NPDES Stormwater Pollution Prevention Plan will be substituted for this Plan after review and permitting, if CGP coverage is required and the final project area still exceeds 1 acre. Storm events during construction represent the largest threat to pollution of natural areas. It is the contractor's responsibility to monitor local weather reports during construction and prior to scheduling earthmoving or other construction activities which will leave large disturbed areas un-stabilized. The following general controls will be implemented during construction. These controls are shown on the Erosion Control Plans. Perimeter Controls Silt fence or compost filter tubes will be used to prevent the migration of soil and silt from the work site. The erosion controls will define the limit of work in areas where they are installed and no construction activities will occur downgradient of the installed perimeter erosion controls. The locations of the perimeter erosion controls shall be verified by the engineer and/or local Town agent, if necessary. In no case is the limit of work to extend beyond the sedimentation barriers/ limit of disturbance as shown on the project plans. The contactor, or other designated employee, shall be responsible for the daily inspection and maintenance of all the perimeter controls and shall implement all necessary measures to repair and maintain this line. Erosion and sedimentation controls shall be visually inspected after every storm event. Close inspection will be made for undercutting beneath the controls. Sediment shall be collected and disposed of in a pre-approved location by the contractor as directed by the engineer. Perimeter controls shall be replaced as necessary. CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN 228 Route 28, Yarmouth MA Proposed A Plus Market 2 Vegetated buffer strips will be maintained beyond the limits of the project area to act as living sediment filters that intercept and detain stormwater runoff. Vegetation will be left wherever practicable during construction. If conditions or time of year do not allow final revegetation, wood chips or mulch shall be used to stabilize disturbed slopes. Any temporary placed mulch or wood chips will be removed and the ground surface re-seeded at the beginning of the following growing season. Soil stabilization measures including seeding will be initiated as soon as practicable on portions of the site where construction activities have temporarily or permanently ceased, but in no case more than 30 days after the construction activity has ceased. These measures may include mulching, hydroseeding, erosion control blankets, and soil roughening. Existing or proposed slopes exceeding 2H:1V shall have erosion control matting installed to stabilize the disturbed slopes during construction. In certain circumstances additional or enhanced perimeter erosion controls may be required to adequately protect the environment. This may involve installation of additional silt fence, straw bales, and/or temporary berms with stilling ponds. Soil erosion and sedimentation control measures shall be inspected either on weekly basis or every 14 days and after each rainfall event of 0.25 inches or greater during construction. Weekly inspections are recommended. Stockpiled Sediment or Soil and Staging Areas Soil may need to be stockpiled temporarily during construction. Stockpile areas will not interfere with construction equipment and will be located away from any areas of concentrated flow or pavement. The slopes of the stockpiles shall be roughened by equipment tracking and shall not exceed 2H:1V to prevent erosion. The stockpile area shall be encircled with perimeter erosion controls (compost filter tubes or straw bales, or a combination thereof). A minimum surplus of 25-feet of erosion control barrier shall be stored on site at all times. Construction Vehicle Traffic The construction site will be accessed from Woburn Street, and the existing entrances will be maintained during construction until the new driveways are established. A stabilized pad of stone will be installed at each entrance used for access to remove debris from tires as vehicles leave the work area. CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN 228 Route 28, Yarmouth MA Proposed A Plus Market 3 The construction entrance shall be inspected weekly and within 24-hours of a storm event that produces 0.25 inches of rain or more during a 24-hour period. A minimum 6-inch thick pad shall be maintained and top-dressed with washed trap rock as needed to prevent tracking or flow of sediments onto public roads. Any sediment tracked out from the work area shall be removed by sweeping, shoveling, vacuuming, or other effective methods at the end of each working day. Tracked out sediments will not be hosed into any stormwater conveyances, storm drain inlets, or waterbody/ resource areas, as it is prohibited. Trucks delivering or removing soils, materials, and/or equipment to and from the site must be cleaned of any excess soil prior to leaving the site to ensure that no significant amount of sediment is carried off-site. Debris, excess soil, and sediment shall be removed from sideboards and wheel flaps of all vehicles leaving the project site in a designated location. Every effort shall be made to adequately remove sediment and debris without the use of water. Debris and sediment dry-removed from vehicles and equipment should be cleaned and disposed of immediately to prevent further tracking. Trucks must close and lock dump body gate prior to leaving the site. Should significant amounts of sediment accumulate on surrounding roadways, it shall be removed promptly. General Housekeeping Catch basins near the construction entrance and downslope from the proposed activity, if any, shall be fitted with inlet protection consisting of fabric silt bags to trap any sediment generated from construction activities. These devices/ inserts shall be inspected regularly and cleaned or replaced when necessary. Accumulated sediment shall be collected and disposed of in a pre- approved location by the contractor as directed by the engineer. Construction dust shall be minimized by stabilized disturbed areas as quickly as possible. Dust control will be implemented as needed during demolition of existing structures, after ground disturbance has begun, and during windy conditions while ground disturbance is occurring. The contractor shall have on site or immediate access to a water truck for the duration of the project to control dust. Paved areas will be sprayed to minimize dust as needed. During construction, the site shall have a covered dumpster for the disposal of packaging and general construction debris. The site shall also have portable sanitary facilities in an amount adequate to serve the number of workers. These facilities shall be cleaned regularly, and not placed within buffer zone to a resource area. CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN 228 Route 28, Yarmouth MA Proposed A Plus Market 4 All demolition debris or impacted soils shall be promptly removed from the site and properly disposed of in accordance with all applicable laws. All trucks and containers leaving the site shall be covered. Burial of any stumps, solid debris, and/or stones or boulders on-site is prohibited unless otherwise indicated by the engineer. Any building products, paints, or fuels will be stored in appropriate containers and secured to prevent the potential for spills. These materials will be stored and handled in accordance with the requirements set forth in the site specific SWPPP. Should impacted soils be encountered, they shall be handled in accordance with applicable regulations and as directed by a Massachusetts Licensed Site Professional (LSP). Dewatering Dewatering actives will be required during construction. Any dewatering will be conducted in accordance with all applicable regulations and a dewatering plan prepared by the contractor and as approved by the Engineer and LSP. Demolition The contractor shall be responsible for promptly and properly managing all debris during the demolition of the existing pavement on site. All materials from demolition shall be legally disposed of in a manner that prevents materials from generating excessive dust and ensures minimum interference with roads, sidewalks, and streets. Site Stabilization Disturbed areas will be minimized to the maximum extent practicable. Disturbed areas where activities are complete or are temporarily inactive will be stabilized appropriately to minimize soil erosion. Stabilization measures include but are not limited to, mulching, seeding, installing erosion control matting, or tackifier. Erosion control matting shall be used on disturbed slopes greater than 2H:1V to reduce the potential for erosion and downgradient erosion. Construction Sequence 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 following general principles during the construction phase: Protect and maintain existing vegetation wherever possible Minimize the area of disturbance CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN 228 Route 28, Yarmouth MA Proposed A Plus Market 5 To the extent possible, route unpolluted flows around disturbed areas Install mitigation devices as early as possible Minimize the time disturbed areas are left unstabilized Maintain siltation control devices in proper condition The contractor should use the suggested construction sequencing as a general guide and modify the suggested methods and procedures as required to best suit seasonal, atmospheric, and site-specific physical constraints for the purpose of minimizing the environmental impact of construction: Cutting and Clearing. Install temporary erosion control (TEC) devices as required to prevent transport of sediment off-site during initial stages of construction. Demolition to Limits of Construction Phase. Install TEC devices as required to prevent sediment transport. Place perimeter erosion controls around stockpiles. Stabilize all exposed surfaces that will not be under immediate construction. Store and/or dispose of all pavement as indicated and in applicable local, State, and federal regulations. Protect existing stormwater features (catchbasins, drain manholes, piping, etc.). Report to engineer when structures are exposed for verification, and any new structures encountered. Complete initial site grading. Utilities. Install sewer connection, water and fire protection services, underground electric and telephone conduit, and natural gas service. Stormwater. Install stormwater structures as shown on site plan. Provide temporary protection against sediment entering the structures. Parking Lot Paving. Fine grade gravel base and install processed gravel to the design grades. Install curbing. Compact pavement base as work progresses. Install pavement binder course for paved parking lot and driveway. Install final top course of pavement. Stripe parking spaces as shown on approved plan. Landscaping. Fine grade landscaped areas and place loam. Install plantings, mulch, and loam and seed as applicable. Final Clean-up. Complete final landscaping and site restoration. Clean inverts of pipes and catch basins. Remove sediment and debris from rip-rap outlet areas. Remove TEC devices only after permanent vegetation and erosion control has been fully established. ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX F MISC. STORMWATER DOCUMENTATION Location:228 Route 28 Yarmouth MA Rear portion of site TSS Removal Calculation Worksheet A B C D E TSS Removal Starting TSS Amount Remaining BMP RATE LOAD*Removed (BxC)Load (C-D) 1.00 0.00 1.00 Deep sump hooded catchbasins 0.25 1.00 0.25 0.75 "Stormceptor" treatment device 0.77 0.75 0.58 0.17 Subsurface infiltration 0.80 0.17 0.14 0.03 0.00 0.00 TSS Total Removal =97% Project: A Plus Market Prepared By:JDO Reviewed by:SDC Date:2/28/2024 Location:228 Route 28 Yarmouth MA Rain Garden TSS Removal Calculation Worksheet A B C D E TSS Removal Starting TSS Amount Remaining BMP RATE LOAD*Removed (BxC)Load (C-D) 1.00 0.00 1.00 Rain Garden w/pretreatment 0.90 1.00 0.90 0.10 0.10 0.00 0.10 0.10 0.00 0.10 0.00 0.00 TSS Total Removal =90% Project: A Plus Market Prepared By:JDO Reviewed by:SDC Date:2/28/2024 WATER QUALITY VOLUME CALCULATION Project: A Plus Market Yarmouth MA Location: 228 Route 28 Yarmouth MA Water Quality Depth 1 in BMP Contributi ng Imperviou s Area Contributing Impervious Area RequiredWater Quality Volume Water Quality Volume Provided sf Ac cf cf Rain Garden 6288 0.14 524 1657 Subsurface Infiltration 30950 0.71 2579 7842 NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r1-04-17-UPDATED AREAS Printed 5/6/2024Prepared by Green Seal Environmental LLC HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Hydrograph for Pond 5P: Rain Garden Time (hours) Inflow (cfs) Storage (cubic-feet) Elevation (feet) Discarded (cfs) 0.00 0.00 0 11.00 0.00 2.00 0.00 0 11.00 0.00 4.00 0.00 0 11.00 0.00 6.00 0.00 0 11.00 0.00 8.00 0.00 0 11.01 0.00 10.00 0.02 9 11.10 0.02 12.00 0.76 431 12.29 0.13 14.00 0.08 1,305 13.21 0.21 16.00 0.05 471 12.35 0.13 18.00 0.05 151 11.71 0.07 20.00 0.04 58 11.39 0.04 22.00 0.03 27 11.23 0.03 24.00 0.02 9 11.10 0.02 26.00 0.00 0 11.00 0.00 28.00 0.00 0 11.00 0.00 30.00 0.00 0 11.00 0.00 32.00 0.00 0 11.00 0.00 34.00 0.00 0 11.00 0.00 36.00 0.00 0 11.00 0.00 38.00 0.00 0 11.00 0.00 40.00 0.00 0 11.00 0.00 42.00 0.00 0 11.00 0.00 44.00 0.00 0 11.00 0.00 46.00 0.00 0 11.00 0.00 48.00 0.00 0 11.00 0.00 50.00 0.00 0 11.00 0.00 52.00 0.00 0 11.00 0.00 54.00 0.00 0 11.00 0.00 56.00 0.00 0 11.00 0.00 58.00 0.00 0 11.00 0.00 60.00 0.00 0 11.00 0.00 62.00 0.00 0 11.00 0.00 64.00 0.00 0 11.00 0.00 66.00 0.00 0 11.00 0.00 68.00 0.00 0 11.00 0.00 70.00 0.00 0 11.00 0.00 72.00 0.00 0 11.00 0.00 NOAA10 24-hr C 100-Year Rainfall=8.15"Proposed - 228 R28 r1-04-17-UPDATED AREAS Printed 5/6/2024Prepared by Green Seal Environmental LLC HydroCAD® 10.20-4b s/n 07930 © 2023 HydroCAD Software Solutions LLC Hydrograph for Pond 8P: Rtank Time (hours) Inflow (cfs) Storage (cubic-feet) Elevation (feet) Discarded (cfs) 0.00 0.00 0 9.80 0.00 2.00 0.02 1 9.80 0.02 4.00 0.03 2 9.80 0.03 6.00 0.07 4 9.80 0.07 8.00 0.11 7 9.80 0.11 10.00 0.22 14 9.81 0.22 12.00 3.54 1,161 10.28 0.70 14.00 0.30 5,124 11.60 0.70 16.00 0.19 1,851 10.51 0.70 18.00 0.16 10 9.81 0.16 20.00 0.12 8 9.81 0.13 22.00 0.09 6 9.80 0.09 24.00 0.06 4 9.80 0.06 26.00 0.00 0 9.80 0.00 28.00 0.00 0 9.80 0.00 30.00 0.00 0 9.80 0.00 32.00 0.00 0 9.80 0.00 34.00 0.00 0 9.80 0.00 36.00 0.00 0 9.80 0.00 38.00 0.00 0 9.80 0.00 40.00 0.00 0 9.80 0.00 42.00 0.00 0 9.80 0.00 44.00 0.00 0 9.80 0.00 46.00 0.00 0 9.80 0.00 48.00 0.00 0 9.80 0.00 50.00 0.00 0 9.80 0.00 52.00 0.00 0 9.80 0.00 54.00 0.00 0 9.80 0.00 56.00 0.00 0 9.80 0.00 58.00 0.00 0 9.80 0.00 60.00 0.00 0 9.80 0.00 62.00 0.00 0 9.80 0.00 64.00 0.00 0 9.80 0.00 66.00 0.00 0 9.80 0.00 68.00 0.00 0 9.80 0.00 70.00 0.00 0 9.80 0.00 72.00 0.00 0 9.80 0.00 MOUNDSOLV G M A F A S W -T A Z . (2017) S Stormwater recharge moundiing analysis 228 Route 28 Yarmouth MA Revision 1 Solution Method Zlotnik et al. (2017) transient solution for a rectangular source (linearization method 1) Site Description Aquifer Data Property Value Horizontal hydraulic conductivity, K (ft/d)150 Specific yield, Sy 0.5 Initial saturated thickness, h0 (ft)10 Maximum allowable water-table rise, σ (ft)2 Dip, i (ft/ft)0.0001 Slope rotation from x axis, γ (°)0 Recharge Sources Property Source 1 X coordinate at center, X (ft)0 Y coordinate at center, Y (ft)0 Dimension along x* axis, L (ft)140 Dimension along y* axis, W (ft)26 Rotation from slope direction, ϕ (°)0 Recharge rate, Q (ft³/d)5306 Infiltration rate, q (ft/d)1.457692308 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 1/9 Map of recharge source. Monitoring Points Elapsed Time, t = 1 d Name x (ft)y (ft)s (ft)h (ft)z (ft) Source 1 0 0 0.6111 10.61 0 Contour plot of water-table rise. Contour plot of water-table elevation. Time Series Data Time Source 1 (d)s (ft)h (ft) 0 0 10 0.002916 0.008499 10.01 0.006561 0.01895 10.02 0.01112 0.03124 10.03 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 2/9 0.01681 0.04528 10.05 0.02393 0.06108 10.06 0.03283 0.07877 10.08 0.04395 0.09852 10.1 0.05786 0.1206 10.12 0.07524 0.1452 10.15 0.09696 0.1725 10.17 0.1241 0.203 10.2 0.1581 0.2366 10.24 0.2005 0.2735 10.27 0.2535 0.3137 10.31 0.3198 0.357 10.36 0.4027 0.4032 10.4 0.5063 0.452 10.45 0.6358 0.5031 10.5 0.7977 0.5562 10.56 1 0.6111 10.61 Time-series plot of water-table rise. Time-series plot of water-table elevation. Profile Data 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 3/9 Profile Along X* Axis for Source 1 at Elapsed Time, t = 1 d x* (ft)s (ft)h (ft)z (ft) -140 0.0454 10.03 -0.014 -134.4 0.05362 10.04 -0.01344 -128.8 0.06319 10.05 -0.01288 -123.2 0.07431 10.06 -0.01232 -117.6 0.08723 10.08 -0.01176 -112 0.1023 10.09 -0.0112 -106.4 0.1197 10.11 -0.01064 -100.8 0.1402 10.13 -0.01008 -95.2 0.1641 10.15 -0.00952 -89.6 0.1923 10.18 -0.00896 -84 0.226 10.22 -0.0084 -78.4 0.2667 10.26 -0.00784 -72.8 0.317 10.31 -0.00728 -67.2 0.3765 10.37 -0.00672 -61.6 0.4265 10.42 -0.00616 -56 0.4665 10.46 -0.0056 -50.4 0.499 10.49 -0.00504 -44.8 0.5258 10.52 -0.00448 -39.2 0.5478 10.54 -0.00392 -33.6 0.5658 10.56 -0.00336 -28 0.5803 10.58 -0.0028 -22.4 0.5917 10.59 -0.00224 -16.8 0.6003 10.6 -0.00168 -11.2 0.6063 10.61 -0.00112 -5.6 0.6099 10.61 -0.00056 0 0.6111 10.61 0 5.6 0.6099 10.61 0.00056 11.2 0.6063 10.61 0.00112 16.8 0.6003 10.6 0.00168 22.4 0.5916 10.59 0.00224 28 0.5802 10.58 0.0028 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 4/9 33.6 0.5657 10.57 0.00336 39.2 0.5477 10.55 0.00392 44.8 0.5257 10.53 0.00448 50.4 0.499 10.5 0.00504 56 0.4664 10.47 0.0056 61.6 0.4263 10.43 0.00616 67.2 0.3764 10.38 0.00672 72.8 0.3169 10.32 0.00728 78.4 0.2666 10.27 0.00784 84 0.2259 10.23 0.0084 89.6 0.1922 10.2 0.00896 95.2 0.164 10.17 0.00952 100.8 0.1401 10.15 0.01008 106.4 0.1197 10.13 0.01064 112 0.1022 10.11 0.0112 117.6 0.08716 10.1 0.01176 123.2 0.07424 10.09 0.01232 128.8 0.06313 10.08 0.01288 134.4 0.05357 10.07 0.01344 140 0.04536 10.06 0.014 The axes of Source 1 (x*, y*) are rotated 0° from the axes of mapping coordinate system (x, y) Profile of water-table rise along x* axis of Source 1. 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 5/9 Profile of water-table elevation along x* axis of Source 1. Profile Along Y* Axis for Source 1 at Elapsed Time, t = 1 d y* (ft)s (ft)h (ft)z (ft) -140 0.01987 10.02 0 -134.4 0.02387 10.02 0 -128.8 0.02858 10.03 0 -123.2 0.03408 10.03 0 -117.6 0.04048 10.04 0 -112 0.04791 10.05 0 -106.4 0.0565 10.06 0 -100.8 0.06639 10.07 0 -95.2 0.07774 10.08 0 -89.6 0.0907 10.09 0 -84 0.1055 10.11 0 -78.4 0.1222 10.12 0 -72.8 0.1412 10.14 0 -67.2 0.1626 10.16 0 -61.6 0.1866 10.19 0 -56 0.2135 10.21 0 -50.4 0.2435 10.24 0 -44.8 0.2769 10.28 0 -39.2 0.3139 10.31 0 -33.6 0.3548 10.35 0 -28 0.3998 10.4 0 -22.4 0.4491 10.45 0 -16.8 0.503 10.5 0 -11.2 0.56 10.56 0 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 6/9 -5.6 0.5983 10.6 0 0 0.6111 10.61 0 5.6 0.5983 10.6 0 11.2 0.56 10.56 0 16.8 0.503 10.5 0 22.4 0.4491 10.45 0 28 0.3998 10.4 0 33.6 0.3548 10.35 0 39.2 0.3139 10.31 0 44.8 0.2769 10.28 0 50.4 0.2435 10.24 0 56 0.2135 10.21 0 61.6 0.1866 10.19 0 67.2 0.1626 10.16 0 72.8 0.1412 10.14 0 78.4 0.1222 10.12 0 84 0.1055 10.11 0 89.6 0.0907 10.09 0 95.2 0.07774 10.08 0 100.8 0.06639 10.07 0 106.4 0.0565 10.06 0 112 0.04791 10.05 0 117.6 0.04048 10.04 0 123.2 0.03408 10.03 0 128.8 0.02858 10.03 0 134.4 0.02387 10.02 0 140 0.01987 10.02 0 The axes of Source 1 (x*, y*) are rotated 0° from the axes of mapping coordinate system (x, y) 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 7/9 Profile of water-table rise along y* axis of Source 1. Profile of water-table elevation along y* axis of Source 1. Sensitivity Data Source 1, x=0 ft, y=0 ft Parameter Water-Table Rise (ft) Multiplier K Sy h₀i 0.8 0.6962 0.6668 0.6962 0.6111 0.82 0.6864 0.6605 0.6864 0.6111 0.84 0.6769 0.6545 0.6769 0.6111 0.86 0.6678 0.6486 0.6678 0.6111 0.88 0.6589 0.6428 0.6589 0.6111 0.9 0.6503 0.6372 0.6503 0.6111 0.92 0.642 0.6317 0.642 0.6111 0.94 0.6339 0.6264 0.6339 0.6111 0.96 0.6261 0.6212 0.6261 0.6111 0.98 0.6185 0.6161 0.6185 0.6111 1 0.6111 0.6111 0.6111 0.6111 1.02 0.6039 -1E+31 0.6039 0.6111 1.04 0.5969 -1E+31 0.5969 0.6111 1.06 0.5901 -1E+31 0.5901 0.6111 1.08 0.5835 -1E+31 0.5835 0.6111 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 8/9 1.1 0.577 -1E+31 0.577 0.6111 1.12 0.5707 -1E+31 0.5707 0.6111 1.14 0.5646 -1E+31 0.5646 0.6111 1.16 0.5586 -1E+31 0.5586 0.6111 1.18 0.5528 -1E+31 0.5528 0.6111 1.2 0.5471 -1E+31 0.5471 0.6111 Sensitivity plot for water-table rise. Notation h is water-table elevation above datum¹ h₀ is aquifer saturated thickness prior to mounding i is dip of aquifer K is horizontal hydraulic conductivity L is dimension of recharge source parallel to x* axis q is infiltration rate (= Q / L·W) Q is recharge rate s is water-table rise above static water table Sy is specific yield t is time since start of recharge t₀ is time when recharge stops W is dimension of recharge source parallel to y* axis x, y are mapping Cartesian coordinate axes x*, y* are recharge source Cartesian coordinate axes z is elevation above datum¹ γ is angle between x axis and dip direction ϕ is angle between dip direction and x* axis of recharge source σ is maximum acceptable water-table rise ¹Elevation datum is the base of aquifer beneath the center of primary recharge source Report generated by MOUNDSOLV v4.0 on 06 May 2024 at 14:10:32 MOUNDSOLV (www.aqtesolv.com) Copyright © 2019-2021 HydroSOLVE, Inc. All rights reserved. 5/6/24, 2:13 PM MOUNDSOLV : Groundwater Mounding Analysis file:///C:/Users/j.oleary/Documents/1 Active files/228 Mounding r1.htm 9/9 Project Information & Location Project Name 228 Route 28 Project Number 24-01 City Yarmouth State/ Province Massachusetts Country United States of America Date 2/20/2024 Designer Information EOR Information (optional) Name Jack O'Leary Name Company Green Seal Environmental LLC Company Phone #781-206-7521 Phone # Email j.oleary@gseenv.com Email The recommended Stormceptor Model(s) which achieve or exceed the user defined water quality objective for each site within the project are listed in the below Sizing Summary table. Site Name Watershed 2 Recommended Stormceptor Model STC 450i Target TSS Removal (%)80.0 TSS Removal (%) Provided 81 PSD Fine Distribution Rainfall Station HYANNIS The recommended Stormceptor model achieves the water quality objectives based on the selected inputs, historical rainfall records and selected particle size distribution. Detailed Stormceptor Sizing Report ±Watershed 2 Stormceptor Sizing Summary Stormceptor Model % TSS Removal Provided STC 450i 81 STC 900 88 STC 1200 88 STC 1800 88 STC 2400 91 STC 3600 91 STC 4800 93 STC 6000 93 STC 7200 95 STC 11000 96 STC 13000 96 STC 16000 97 Stormwater Treatment Recommendation Detailed Sizing Report ±Page 1 of 7Stormceptor Notes Stormceptor performance estimates are based on simulations using PCSWMM for Stormceptor, which uses the EPA Rainfall and Runoff modules. Design estimates listed are only representative of specific project requirements based on total suspended solids (TSS) removal defined by the selected PSD, and based on stable site conditions only, after construction is completed. For submerged applications or sites specific to spill control, please contact your local Stormceptor representative for further design assistance. Hydrology Analysis PCSWMM for Stormceptor calculates annual hydrology with the US EPA SWMM and local continuous historical rainfall data. Performance calculations of Stormceptor are based on the average annual removal of TSS for the selected site parameters. The Stormceptor is engineered to capture sediment particles by treating the required average annual runoff volume, ensuring positive removal efficiency is maintained during each rainfall event, and preventing negative removal efficiency (scour). Smaller recurring storms account for the majority of rainfall events and average annual runoff volume, as observed in the historical rainfall data analyses presented in this section. Rainfall Station State/Province Massachusetts Total Number of Rainfall Events 1268 Rainfall Station Name HYANNIS Total Rainfall (in)531.6 Station ID #3821 Average Annual Rainfall (in)33.2 Coordinates 41°24'0"N, 70°10'47"W Total Evaporation (in)26.3 Elevation (ft)50 Total Infiltration (in)78.9 Years of Rainfall Data 14 Total Rainfall that is Runoff (in)426.4 Stormceptor The Stormceptor oil and sediment separator is sized to treat stormwater runoff by removing pollutants through gravity separation and flotation. Stormceptor¶s patented design generates positive TSS removal for each rainfall event, including large storms. Significant levels of pollutants such as heavy metals, free oils and nutrients are prevented from entering natural water resources and the re-suspension of previously captured sediment (scour) does not occur. Stormceptor provides a high level of TSS removal for small frequent storm events that represent the majority of annual rainfall volume and pollutant load. Positive treatment continues for large infrequent events, however, such events have little impact on the average annual TSS removal as they represent a small percentage of the total runoff volume and pollutant load. Design Methodology Stormceptor is sized using PCSWMM for Stormceptor, a continuous simulation model based on US EPA SWMM. The program calculates hydrology using local historical rainfall data and specified site parameters. With US EPA SWMM¶s precision, every Stormceptor unit is designed to achieve a defined water quality objective. The TSS removal data presented follows US EPA guidelines to reduce the average annual TSS load. The Stormceptor¶s unit process for TSS removal is settling. The settling model calculates TSS removal by analyzing: Site parameters Continuous historical rainfall data, including duration, distribution, peaks & inter-event dry periods Particle size distribution, and associated settling velocities (Stokes Law, corrected for drag) TSS load Detention time of the system Detailed Sizing Report ±Page 2 of 7Stormceptor Drainage Area Total Area (acres)0.66 Imperviousness %85.0 Water Quality Objective TSS Removal (%)80.0 Runoff Volume Capture (%) Oil Spill Capture Volume (Gal) Peak Conveyed Flow Rate (CFS) Water Quality Flow Rate (CFS) Design Details Stormceptor Inlet Invert Elev (ft)10.50 Stormceptor Outlet Invert Elev (ft)10.40 Stormceptor Rim Elev (ft)13.30 Normal Water Level Elevation (ft)9.80 Pipe Diameter (in)12 Pipe Material RCP - concrete Multiple Inlets (Y/N)Yes Grate Inlet (Y/N)Yes Particle Size Distribution (PSD) Removing the smallest fraction of particulates from runoff ensures the majority of pollutants, such as metals, hydrocarbons and nutrients are captured. The table below identifies the Particle Size Distribution (PSD) that was selected to define TSS removal for the Stormceptor design. Fine Distribution Particle Diameter (microns) Distribution %Specific Gravity 20.0 20.0 1.30 60.0 20.0 1.80 150.0 20.0 2.20 400.0 20.0 2.65 2000.0 20.0 2.65 Up Stream Storage Storage (ac-ft)Discharge (cfs) 0.000 0.000 Up Stream Flow Diversion Max. Flow to Stormceptor (cfs) Detailed Sizing Report ±Page 3 of 7Stormceptor Site Name Watershed 2 Site Details Drainage Area Total Area (acres)0.66 Imperviousness %85.0 Infiltration Parameters Horton¶s equation is used to estimate infiltration Max. Infiltration Rate (in/hr)2.44 Min. Infiltration Rate (in/hr)0.4 Decay Rate (1/sec)0.00055 Regeneration Rate (1/sec)0.01 Surface Characteristics Width (ft)339.00 Slope %2 Impervious Depression Storage (in)0.02 Pervious Depression Storage (in)0.2 Impervious Manning¶s n 0.015 Pervious Manning¶s n 0.25 Evaporation Daily Evaporation Rate (in/day)0.1 Dry Weather Flow Dry Weather Flow (cfs)0 Maintenance Frequency Maintenance Frequency (months) >12 Winter Months Winter Infiltration 0 TSS Loading Parameters TSS Loading Function Buildup/Wash-off Parameters Target Event Mean Conc. (EMC) mg/L Exponential Buildup Power Exponential Washoff Exponent TSS Availability Parameters Availability Constant A Availability Factor B Availability Exponent C Min. Particle Size Affected by Availability (micron) Detailed Sizing Report ±Page 4 of 7Stormceptor Cumulative Runoff Volume by Runoff Rate Runoff Rate (cfs)Runoff Volume (ft³)Volume Over (ft³)Cumulative Runoff Volume (%) 0.035 501550 526326 48.8 0.141 878158 149665 85.4 0.318 975309 52503 94.9 0.565 1008349 19461 98.1 0.883 1019943 7865 99.2 1.271 1024044 3764 99.6 1.730 1025719 2090 99.8 2.260 1026392 1416 99.9 2.860 1026933 875 99.9 3.531 1027537 272 100.0 Detailed Sizing Report ±Page 5 of 7Stormceptor Rainfall Event Analysis Rainfall Depth (in)No. of Events Percentage of Total Events (%) Total Volume (in)Percentage of Annual Volume (%) 0.25 711 56.1 71 13.4 0.50 204 16.1 74 14.0 0.75 141 11.1 88 16.5 1.00 81 6.4 72 13.5 1.25 51 4.0 57 10.7 1.50 20 1.6 28 5.2 1.75 14 1.1 23 4.3 2.00 12 0.9 22 4.2 2.25 7 0.6 15 2.8 2.50 7 0.6 17 3.2 2.75 4 0.3 11 2.0 3.00 4 0.3 12 2.2 3.25 3 0.2 9 1.8 3.50 2 0.2 7 1.3 3.75 2 0.2 7 1.3 4.00 3 0.2 12 2.2 4.25 2 0.2 8 1.6 4.50 0 0.0 0 0.0 4.75 0 0.0 0 0.0 Detailed Sizing Report ±Page 6 of 7Stormceptor For Stormceptor Specifications and Drawings Please Visit: https://www.conteches.com/technical-guides/search?filter=1WBC0O5EYX Detailed Sizing Report ±Page 7 of 7Stormceptor ENVIRONMENTAL | ENGINEERING | SURVEY | ENERGY APPENDIX H SITE PLAN SET (ATTACHED TO SUBMITTAL)