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HomeMy WebLinkAboutStormwater Report STORMWATER MANAGEMENT REPORT Follins Pond Boat Ramp - Yarmouth, MA January 2024 Cape Cod Boat Ramp Stormwater Retrofit Project Partner: Association to Preserve Cape Cod Owner/Operator: Town of Yarmouth _SW Checklist Follins • 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. _SW Checklist Follins • 04/01/08 Stormwater Report Checklist • Page 2 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report B. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note: Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.) and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer’s Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (if included) and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature Signature and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? New development Redevelopment Mix of New Development and Redevelopment 1/15/2024 _SW Checklist Follins • 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): Underground infiltration chambers 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. _SW Checklist Follins • 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. _SW Checklist Follins • 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. _SW Checklist Follins • 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. _SW Checklist Follins • 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. _SW Checklist Follins • 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. i STORMWATER MANAGEMENT REPORT FOLLINS POND BOAT RAMP CAPE COD BOAT RAMP STORMWATER RETROFIT PROJECT YARMOUTH , MA Table of Contents STORMWATER CHECKLIST ......................................................................................................... ii EXECUTIVE SUMMARY .............................................................................................................. 1 1.0 INTRODUCTION ............................................................................................................. 2 1.1 Background.................................................................................................................. 2 1.2 Project Goals ............................................................................................................... 3 1.3 Design Methodology .................................................................................................... 3 2.0 Existing Conditions ........................................................................................................ 4 2.1 Receiving Water and Watershed .................................................................................. 5 2.2 Drainage Area .............................................................................................................. 6 2.3 Resource Areas ........................................................................................................... 6 2.4 Soils ............................................................................................................................. 7 3.0 Proposed Conditions.................................................................................................... 7 3.1 Drainage Areas ............................................................................................................ 8 3.2 Structural Stormwater Control Measures (SCMs)......................................................... 8 3.3 Retrofitting existing drainage infrastructure .................................................................. 9 3.4 Non-structural SCMs .................................................................................................... 9 4.0 Stormwater Design Components ...............................................................................10 4.1 Water Quality ..............................................................................................................10 4.2 Recharge ....................................................................................................................12 4.3 Water Quantity ............................................................................................................12 4.4 Erosion Control ...........................................................................................................13 4.5 Operation and Maintenance ........................................................................................14 4.6 Illicit Discharges ..........................................................................................................14 5.0 REFERENCES .................................................................................................................15 TABLES Table 1. Project MASMS Compliance Summary ........................................................................................... 2 Table 2. Test Pit (TP) Results ......................................................................................................................... 7 ii Table 3. Compliance with Water Quality Volume (WQV) Requirements ................................................... 10 Table 4. Compliance with Water Quality Pollutant Load Reduction Requirements ................................... 11 Table 5. Compliance with Recharge Requirements .................................................................................... 12 Table 6. Summary of Existing and Proposed Condition Peak Flow Rates and Runoff Volumes ................. 13 FIGURES Figure 1: Locus Map Figure 2: Aerial Map Figure 3: Constraints Map Figure 4: Receiving Waters Map Figure 5: Soils Map APPENDICES Appendix A: Drainage Areas Appendix B: Hydrologic/Hydraulic Model Results Appendix C: Wetland Resources Summary Memo Appendix D: Soil Test Pit Logs Appendix E: Operation and Maintenance Guide Appendix F: Pollutant Controls During Construction Appendix G: Site Plans Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 1 EXECUTIVE SUMMARY The purpose of this report is to describe existing and proposed site drainage conditions at the Follins Pond Boat Ramp, as well as measures to prevent stormwater pollution during and after construction. This project is part of a regional effort led by the Association to Preserve Cape Cod (APCC) to improve water quality at public boat ramps on Cape Cod by implementing green stormwater infrastructure (GSI) retrofits. This site is identified as a priority under the Cape Cod Water Resources Restoration Project (CCWRRP) and as such, additional input and review of the design was conducted by the Natural Resources Conservation Science (NRCS) and the Cape Cod Conservation District (CCCD). The main goal for this site is to better capture, manage and treat stormwater runoff from Follins Pond Road and Gun Rock Road prior to entering Follins Pond. Follins Pond Road and Gun Rock Road have steep existing grades and the existing drainage infrastructure (e.g., catchbasins and underground infiltration systems) cannot currently capture all of the runoff in the catchment area. While part of this project is to implement new GSI along Follins Pond Road and Gun Rock Road, the project will also improve the ability of the existing infiltration systems to capture more runoff than it currently does. The project includes the following structural and non-structural stormwater control measures (SCMs): • Deep Sump Catchbasins for Pretreatment • Infiltration Trenches to Store and Infiltrate Runoff • Underground Infiltration Chambers for Managing Large Storm Events • Pavement Regrading and Resetting & Replacing Grates of Existing Catchbasins to Capture More Runoff Since the proposed stormwater management system is a retrofit project undertaken solely to improve water quality at the site, it falls under the redevelopment category in accordance with the Massachusetts Stormwater Management Standards (MASMS 2008), as described in Massachusetts Stormwater Handbook, Volume 1 Chapter 1. As a redevelopment project, the design is required to meet the MASMS standards to the maximum extent practicable (MEP). As shown in Table 1, the proposed project meets or exceeds each standard, except the recharge, water quality, and critical areas standards, which is met to the MEP. Each of the proposed treatment SCMs (infiltration trenches) are designed to capture and treat the full one inch of runoff of their contributing drainage areas, either alone or in combination with the existing infiltration systems. Some areas of the site could not be captured due to site constraints, as Follins Pond Road and Gun Rock Road are privately- owned and require abutter approval prior to work being done in the Town-managed right-of-way. However, through the integration of underground infiltration chambers and regrading and resetting the existing catchbasin rims, the proposed design reduces peak runoff flow rates and volumes for the 2-, 10- , 25-, and 100-year storms. Overall, this project will significantly improve conditions at the Follins Pond Boat Ramp and reduce on-going impacts to Follins Pond and downstream resources. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 2 Table 1. Project MASMS Compliance Summary Minimum Standard Type Compliance Report Reference(s) 1 New Stormwater Conveyances Narrative Yes Section 3.2 2 Water Quantity Calculation Yes Section 4.3/Table 6/Appendix B 3 Recharge Calculation Yes Section 4.2/Table 5/Appendix B 4 Water Quality Calculation MEP Section 4.1/Table 3/Table 4/Appendix B 5 Land Uses with Higher Potential Pollutant Loading Narrative Not Applicable Section 2.0 6 Critical Areas Narrative MEP Section 4.1 7 Redevelopment Narrative Yes Section 4.0 8 Erosion Control Narrative Yes Section 4.4/Appendix G 9 Operation and Maintenance Narrative Yes Section 4.5/Appendix E 10 Illicit Discharges Narrative Yes Section 4.6 1.0 INTRODUCTION This report provides a summary of the stormwater management systems proposed for the Follins Pond Boat Ramp in Yarmouth, MA, a Town-operated boat ramp (Figure 1). The Yarmouth Department of Natural Resources and Department of Public Works are proposing this project in collaboration with the Association to Preserve Cape Cod (APCC) as a part of a regional effort (Cape Cod Boat Ramp Stormwater Retrofit Project) to improve water quality at public boat ramps across Cape Cod. The proposed project has been designed to retrofit existing impervious areas for water quality improvements while also managing runoff from larger storms and improving overall site conditions. This report describes the existing and proposed site conditions and the practices to be implemented to reduce stormwater discharges and pollutants during and after construction. As required for retrofit projects, the stormwater system for the project has been designed to conform to the requirements of the Massachusetts Stormwater Standards (MASMS) to the maximum extent practicable. 1.1 Background Freshwater ponds and coastal embayments across Cape Cod are significantly degraded by nutrient and bacteria impairment. Land uses, including stormwater runoff and fertilizer use, contribute on average 20% of the controllable nitrogen load within our coastal watersheds (Cape Cod Commission 208 Plan, 2015) and bacterial contamination, including cyanobacteria, regularly causes closures of beaches. In report (APCC’s 2022 State of the Waters), 90% of the coastal embayments and 39% of the freshwater ponds assessed received unacceptable water quality scores. These high nutrient loads are of concern for the environment, our coastal economy, and public health as they negatively impact habitat for fish and shellfish and can result in unsafe conditions for swimming, fishing and boating. Public boats ramps are a common source of pollution in areas of high recreational use. As such, these locations have been targeted by APCC’s regional project. This site is identified as a priority under the Cape Cod Water Resources Restoration Project (CCWRRP) and as such, additional input and review of the design was conducted by the Natural Resources Conservation Science (NRCS) and the Cape Cod Conservation District (CCCD). Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 3 As part of an EPA Southeast New England Program (SNEP) Watershed Grant, APCC and partners first identified 20 public boat ramps across 10 Cape Cod towns in need of improved stormwater management. Concept designs for each of these twenty sites were ranked based on various criteria including potential pollutant removal (i.e., load and drainage area), water quality status of the associated waterbody, construction cost and feasibility, and additional human use and resource benefits (restored shellfish and anadromous fish habitat, proximity to environmental justice communities, improved climate resiliency, opportunity for public education, etc.). With additional funding from a CZM FY23 Coastal Habitat and Water Quality Grant, 25% and 75% designs were developed for seven high- ranking priority sites, including this one at Follins Pond, which has a direct connection to Nantucket Sound via a surface water stream (Bass River). 1.2 Project Goals The purpose of this project is to improve water quality in Follins Pond and downstream waters by reducing or eliminating pollutant loads from stormwater runoff at the public boat ramp using green stormwater infrastructure (GSI) stormwater control measures (SCMs). Specifically, the project aims to maximize pollutant removal (% bacteria, nitrogen and phosphorus) and water quality volume treated. Follins Pond Road and Gun Rock Road have existing steep grades, so it is difficult to capture all the runoff into the existing drainage infrastructure (e.g., catchbasins and infiltration systems). The project will also help to direct more runoff into the existing infiltration systems to reduce overall flows to Follins Pond. Over time, we hope this work leads to a reduction in the frequency and/or length of prohibitions to shellfish farming/harvesting in the pond and downstream embayments related to bacteria contamination or cyanobacteria blooms; reduction in nutrients and associated algal blooms, including toxic cyanobacteria blooms, in the pond and downstream embayments; and improvements to the Bass River system. 1.3 Design Methodology The design was completed by the following tasks: • Preliminary field assessment of the site and contributing drainage area to identify usage, physical and environmental constraints and opportunities, and long-term operation and maintenance concerns; • Determination of drainage areas and land coverage within the project area; • Selection of structural and non-structural SCMs best suited to site conditions and project goals; • Structural SCM sizing and performance estimates (described further below); • Hydrologic/Hydraulic Modeling (described further below); • Grading and layout of site plan; • Erosion control plan development; and • Operation and maintenance (O&M) plan development. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 4 SCM Performance Estimates The proposed SCMs were selected and sized to maximize pollutant load removals. Since the waterbodies this site drains to are shellfish growing areas and have water quality impairments and are subject to TMDLs, the SCMs were chosen to maximize not only total suspended solids (TSS) removal, but total nitrogen (TN), total phosphorus (TP) and bacteria load reductions as well. MASMS was used as a reference for TSS removal estimates for infiltration trenches, but the more recently developed pollutant load removal curves (USEPA 2021 & Paradigm Environmental 2019) were used for TP, TN, and bacteria.1 Hydrologic/Hydraulic Modeling Existing and proposed conditions for the project area were modeled using HydroCAD software, which combines USDA Natural Resources Conservation Service hydrology and hydraulic techniques (commonly known as SCS TR-55 and TR-20) to generate hydrographs. Conditions were evaluated for the water quality event (storm that produces 1 inch of runoff, or a roughly 1.2-inch rain event) as well as larger storm events, including the 2-, 10-, 25- and 100-year 24-hour Type III storm events. The rainfall depths used for each storm event are the NOAA+ values (NOAA Atlas 14 90% Upper Confidence value multiplied by 0.9) (NOAA NWS, 2017). Rainfall values are included in Appendix A. 2.0 Existing Conditions The Follins Pond boat ramp is a water access point on Follins Pond. The area is intended for fishing and boating purposes only. This land use is not classified as a land use with higher potential pollutant loads (LUHPPL) and thus, is not subject to MASWMS Standard 5. The project site includes an access road (Follins Pond Road) down to a boat ramp, with parking predominantly occurring along the west side of the road (Figure 2). The existing pavement is in good condition. The Town installed a series of three infiltration systems along Follins Pond Road (see Figure below, which shows the plan for the infiltration system at the intersection of Gun Rock Road and Follins Pond Road), and double catchbasins on either side of the road to capture runoff and provide pretreatment before discharging into the infiltration system located below the road. Follins Pond Road is steep, making it challenging for the existing catchbasins to capture all of the stormwater flowing down the road. Follins Pond Road also has a flat cross slope (e.g., not crowned), so stormwater is not concentrated in a gutter line and often bypasses the existing catchbasins. Furthermore, the catchbasin rims are at the same grade as the road around it. 1 It is important to note that these curves have a crosswalk to help users determine which specific curve to reference: for infiltrating trenches and infiltration chambers, the appropriate curve is the Infiltration Trench (Soil infiltration rate = 8.27 in/hr) Performance Curve. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 5 2.1 Receiving Water and Watershed Follins Pond boat ramp discharges stormwater into Follins Pond, an estuarine pond at the headwaters of the Bass River. The pond provides habitat for shellfish growing areas. However, it is listed as impaired for total nitrogen and nutrient/eutrophication biological indicators by the most recent Massachusetts DEP 303(d) – 2018/2020 Integrated list of Waters, and APCC’s State of the Waters Report lists it as unacceptable for nutrient loading. Follins Pond is located in the Bass River Watershed, for which total maximum daily load documents (TMDLs) have been developed for nitrogen. The full list of impairments for this portion of the watershed is listed below, and a map showing these resources is included in Figure 4: • Follins Pond (MA96-114) Yarmouth, Bass River Watershed – Impaired for total nitrogen and nutrient/eutrophication biological indicators; Category 4a (TMDL completed) of the 2018/2020 Integrated List of Waters. • Kelleys Bay (MA96-113) Yarmouth, Bass River Watershed – Impaired for total nitrogen and nutrient/eutrophication biological indicators; Category 4a (TMDL completed) of the 2018/2020 Integrated List of Waters. • Dinahs Pond (MA96-112) Yarmouth, Bass River Watershed – Impaired for total nitrogen and nutrient/eutrophication biological indicators; Category 4a (TMDL completed) of the 2018/2020 Integrated List of Waters. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 6 • Bass River (MA96-118) “Grand Cove” portion, Yarmouth, Bass River Watershed – Impaired for total nitrogen and nutrient/eutrophication biological indicators; Category 4a (TMDL completed) of the 2018/2020 Integrated List of Waters. • Bass River (MA96-12) Headwaters outlet, Yarmouth, Bass River Watershed – Impaired for total nitrogen, fecal coliform, and estuarine bioassessments; Category 4a (TMDL completed) of the 2018/2020 Integrated List of Waters. 2.2 Drainage Area The boat ramp’s existing contributing drainage area is approximately 7.9 acres. This area consists of undisturbed forest, residential properties, small lawn areas, and roads. Based on existing topography and flow paths, the total drainage area was divided into four separate drainage areas: DA0 (southern area that drains to the boat ramp), DA1 (drains to infiltration system 1), DA2 (drains to infiltration system 2), and DA3 (Gun Rock Road and area north that drains to infiltration system 3). While DA1, DA2, and DA3 were delineated as the areas draining to each existing infiltration system, the existing infiltration systems are not modeled in HydroCAD. Due to the lack of crown in the road and steep slope, most stormwater bypasses the catchbasin inlets to these systems and continues down the road as surface runoff. This has been confirmed by HW and Town staff. As a conservative estimate, HW has assumed the existing systems only account for a 15% reduction in runoff. All drainage areas eventually drain to the pond at the boat ramp, modeled as Study Point 1 (SP1). See the existing conditions drainage area map and a detailed breakdown of land cover in Appendix A, as well as the existing HydroCAD model report in Appendix B. 2.3 Resource Areas HW wetland biologists delineated several resource areas at the site in January 2023. A full description of these resource areas is included in Appendix C, and their locations and associated buffers are shown on the plans in Appendix G. The wetland resource areas identified on or adjacent to the site include Salt Marsh; Coastal Bank; Land Subject to Coastal Storm Flowage (LSCSF); and the 35-foot, 50-foot, and 100- foot Buffer Zones Land Under Waterbodies and Waterways (LUW) and Banks of Land Under the Ocean, Ponds, Streams, Rivers, Lakes, or Creeks that Underlie an Anadromous/Catadromous Fish Run (“Fish Run”). The site also occurs within a Coastal Watershed Area; however, the proposed project activities do not incorporate any of the prohibited practices referenced in section 2.11(1)(b)(1-6) of the Yarmouth Wetland Regulations. While much of the vegetation at the site is native woodlands, one invasive plant(Asiatic Bittersweet) were present at or near the site but were isolated to a small area of the Coastal Bank just west of Follins Pond Road and limited in abundance. The project site at the southern end of Follins Pond Road are located within a Special Flood Hazard Area, Zone AE (1% annual chance of flooding, with base flood elevations of 9 feet) (Appendix C). Since the site discharges near a shellfish growing area, it is considered a critical area and subject to MASWMS Standard 6. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 7 2.4 Soils Soils data from the Natural Resources Conservation Service (NRCS) indicate that the soils within the drainage area are composed entirely of Carver coarse sand, at 3-35% slopes. Carver coarse sand is hydrologic soil group A (HSG), as shown in Figure 5. Three test pits (TP) were conducted at the site on January 19, 2023 to evaluate subsurface conditions and estimated seasonal high groundwater (ESHGW) based on evidence of mottling or redox. The test pits were witnessed and logged by an HW Massachusetts Title 5 Approved Soil Evaluator; results are shown in Table 2 below. Test pits were conducted just in three areas: the western part of Follins Pond Road near the boat ramp (TP-1), the intersection of Follins Pond Road and Gun Rock Road on the eastern side of Follins Pond Road (TP-2), and the curve in Gun Rock Road on the southern side of the road (TP-3). The parent material of the native soil unit, Carver Coarse Sand is sandy glaciofluvial, comprising mostly outwash plain and moraine landforms. Based on the depth of the proposed SCMs, a design infiltration rate (Rawls) of 8.27 in/hr is used. See Appendix D for soil test pit logs. No groundwater features were observed in the test pits, so ESHGW was assumed at pit bottom. Table 2. Test Pit (TP) Results Test Pit ID Surface Elevation at TP (ft) Pit Bottom Elevation (ft) ESHGW Elevation (ft) Soil Texture(s) at SCM Design Infiltration Rate (in/hr) Notes TP-1 6.9 -0.6 Below -0.6 Medium sand 8.27 ESHGW placed at pit bottom for design purposes. However, actual ESHGW is likely much lower. TP-2 34.2 27.7 Below 27.7 Medium sand 8.27 TP- 3 37.2 29.2 Below 29.2 Fine sand 8.27 3.0 Proposed Conditions The proposed project consists of the following stormwater and related site development improvements: • Regraded and resurfaced parts of Follins Pond Road, including resetting existing catchbasin rims, to better capture runoff; • Regraded and resurfaced the southern portion of Gun Rock Road to better direct runoff; • GSI including infiltration trenches and underground infiltration chambers; and • Protection of as many existing mature trees as possible. The proposed GSI system is designed to meet the following major objectives: • Capture, treat, and infiltrate at least the first one inch of runoff; and Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 8 • Reduce peak flows and runoff volumes from the site by infiltrating the 25-year storm runoff volume (chambers only). 3.1 Drainage Areas The boat ramp’s contributing drainage area under proposed conditions is very similar to existing, with a total of approximately 7.9 acres. While DA0 (to the Pond) and DA1 (existing Infiltration System 1) remained the same, DA2 and DA3 were subdivided for the proposed conditions in order to model flows to the proposed SCMs. The proposed DA2 drainage areas are DA2 (existing Infiltration System 2), DA2A (new Infiltration Trench 1), and DA2B (new Infiltration Trench 2). The proposed DA3 drainage areas are DA3 (new Infiltration Trench 3), DA3A & DA3B (existing Infiltration System 3), and DA3C (new catch basin and infiltration chambers). The model assumes that all runoff is able to enter the existing infiltration systems due to the retrofits and site improvements. The majority of the site will discharge eventually to Study Point 1 (SP1), similar to in existing conditions. See the proposed conditions drainage area map and a detailed breakdown of land cover in Appendix A, as well as the proposed HydroCAD model report in Appendix B. 3.2 Structural Stormwater Control Measures (SCMs) The proposed stormwater management includes a GSI approach to capture, treat, infiltrate, and detain runoff by using the following SCMs. There are four stormwater GSI practices proposed throughout the site - three of the practices are infiltration trenches and one is an underground infiltration chamber system. Pretreatment will be provided with deep sump catchbasins. The stormwater management systems were designed to meet Standard 1, so that no new untreated stormwater runoff will be directed to any off-site areas or resource areas. Runoff from contributing impervious areas will be treated by the proposed practices. Deep Sump Catchbasin Deep sump catchbasins have a sump for pretreatment of the runoff from the paved surfaces to allow for sediment and other debris to settle out prior to conveyance into the infiltration trenches or chamber system. Infiltration Trenches (IT) An infiltration trench is an underground practice that detains, treats, and infiltrates runoff. It is identical to a tree trench without trees. There three infiltration trenches are proposed in the right of way. The space and grade of the site only allow the addition of trees in one of the infiltration trenches (IT3). The system consists of pretreatment via deep sump catchbasin(s) with a grate, a perforated inflow pipe, the stone storage reservoir, and native plantings. Once the trench reaches capacity, the upstream structure will fill with stormwater and runoff will bypass the catch basin grates and continue down the boat ramp. The infiltration trenches have greater than 2-feet separation to ESHGW as required. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 9 Underground Infiltration Chambers (UICs) Underground infiltration chambers (UICs) include a range of proprietary, modular structures embedded in clean, crushed stone. They are installed underground, typically under parking or landscaped areas, and create large void spaces for temporary storage of stormwater, allowing it to rapidly fill during storm events and slowly infiltrate into the underlying native soil after a storm event. One UIC is proposed under Gun Rock Road. It is sized to fully retain and infiltrate runoff from the 25- year storm event for the contributing drainage areas, as requested by the Town. UIC-1 manages runoff from DA3C. Runoff from the 100-year storm will exceed the capacity of these systems, and the excess will discharge down the road to the boat ramp and be captured by a downstream existing infiltration system. UIC-1 has greater than 2-feet separation to ESHGW as required. Existing Infiltration Systems (IS) The existing infiltration systems consist of concrete galleys that provide underground temporary storage of stormwater. Like the underground infiltration chambers, the concrete galleys rapidly fill during storm events and allow stormwater to slowly infiltrate into the underlying native soil after a storm event. There are three of these existing systems, two in the lower section of Follins Pond Road and one at the Follins Pond Road/Gun Rock Road intersection. 3.3 Retrofitting existing drainage infrastructure As part of this project, improvements will be made to the existing drainage infrastructure, including: • Regrading and paving of the road to better direct stormwater towards the existing catchbasins, • Resetting the rim elevations of the existing catchbasins to lower them slightly, and • Replacing the grates with high-capacity catchbasin grates to better capture runoff directed to the catchbasins. With these improvements, more stormwater runoff will actually get to and flow into the existing catchbasins and infiltrate through the infiltration systems. 3.4 Non-structural SCMs The non-structural SCMs proposed at the site include Town management of the existing infiltration systems and street sweeping. The Town will institute a regular inspection schedule of the existing infiltration systems (and associated catchbasins) to ensure they are functioning as designed. The existing infiltration systems are included in this project’s O&M Guide (Appendix E) to ensure they are inspected, cleaned, and maintained. Leaf litter and sediment was observed on site throughout the year. Regular street sweeping will help remove leaf litter and sediment so that it does not clog the existing or proposed drainage infrastructure. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 10 4.0 Stormwater Design Components The proposed SCMs were designed to meet a variety of goals and regulatory requirements as discussed above. As a retrofit project for managing existing impervious cover, this design must specifically comply with the redevelopment standard (MASMS Standard 7) by meeting all standards to the maximum extent practicable. The project fully meets this standard, as described in detail below. 4.1 Water Quality The main purpose of this retrofit project is to improve water quality. This section describes the treatment volumes and pollutant load reductions achieved by the proposed design and how they compare to the MASMS standards. Treatment Volume Per Standard 4 of MASMS, the stormwater management system for a new development site discharging to a critical area must be sized to treat the first one inch of runoff from impervious area (IA) and remove 80% or more of the annual post-construction load of total suspended solids (TSS). As a retrofit (falls under Standard 7 – Redevelopment), the project is only required to meet this to the maximum extent practicable. However, the proposed and retrofitted existing infiltration systems are sized to treat the full one-inch water quality volume (WQV) for their contributing drainage areas where possible, and only a small portion of the site could not be captured and treated at all (DA0). The proposed HydroCAD model results showing treatment of the full water quality volume are included in Appendix B and summarized below in Table 3. Table 3. Compliance with Water Quality Volume (WQV) Requirements DA ID SCM ID IA* (ac) WQv Goal (ac- ft) WQv Provided (ac-ft)** % WQv Provided Meets Requirement? Notes DA0 NA 0.17 0.014 0.000 0% N Boat Ramp not captured for this retrofit project given space and land use DA1 IS1 0.06 0.005 0.005 100% Y DA2 IS2 0.03 0.002 0.002 100% Y DA2A IT1 0.05 0.004 0.004 100% Y DA2B IT2 0.13 0.011 0.011 100% Y DA3 IT3, IS3 0.18 0.015 0.015 100% Y Infiltration trench treats approx. 0.5-inch runoff, remaining runoff is treated in existing system DA3A IS3 0.13 0.011 0.011 100% Y DA3B IS3 0.34 0.028 0.028 100% Y DA3C C1 0.87 0.073 0.073 100% Y TOTAL SITE: 1.941 0.163 0.149 91% MEP MEP for Retrofit Projects *Impervious Area **From HydroCAD results – see Appendix B for volume “discarded” for WQv Event Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 11 Pollutant Load Reductions The infiltration trenches and chambers exceed the MASMS requirements for TSS removal and maximize removals of the other pollutants of concern. Estimated TSS, phosphorus (TP), nitrogen (TN), and bacteria removals for the proposed project are provided in Table 4. The proposed O&M Guide in Appendix E was developed to ensure that the stormwater system continues to function as it was designed into the future to maintain these levels of pollutant removal. Table 4. Compliance with Water Quality Pollutant Load Reduction Requirements DA ID SCM ID IA (ac) WQv Provided (ac-ft)* Runoff Depth Treated (in) TSS Removal (%)** TP Removal (%)*** TN Removal (%)*** Bacteria Removal (%)**** Meets Reqt? DA0 NA 0.17 0.000 0.0 0% 0% 0% 0% N DA1 IS1 0.06 0.005 1.0 80% 100% 100% 100% Y DA2 IS2 0.03 0.002 1.0 80% 100% 100% 100% Y DA2A IT1 0.05 0.004 1.0 80% 100% 100% 100% Y DA2B IT2 0.13 0.011 1.0 80% 100% 100% 100% Y DA3 IT3, IS3 0.18 0.015 1.0 80% 100% 100% 100% Y DA3A IS3 0.13 0.011 1.0 80% 100% 100% 100% Y DA3B IS3 0.34 0.028 1.0 80% 100% 100% 100% Y DA3C C1 0.87 0.073 1.0 80% 100% 100% 100% Y TOTAL SITE: 1.94 0.149 0.9 73% 91% 91% 91% Y *From HydroCAD results – see Appendix B for volume “discarded” for WQv Event **From MASMS ***From MS4 NPDES Permit Appendix F Attachment 3 (USEPA 2021) ****From Paradigm Environmental (2019) In addition, since the site is located in a critical area (near a shellfishing area and the site has soils with a rapid infiltration rate) and must meet MASMS Standard 6 pretreatment to the maximum extent practicable before infiltration. The Town conducts street sweeping twice per year as part of their Massachusetts Municipal Separate Storm Sewer System (MS4) program, which can achieve 10% removal of TSS. The deep sump catchbasins provide 25% pretreatment prior to infiltration, therefore the estimated TSS removal prior to infiltration is 33%. As this is a retrofit, the site meets this standard to the maximum extent practicable. Long-term Pollution Prevention Plan Source control is important to ensure long-term functionality of the proposed SCMs and protect downstream resources and habitat. A long-term pollution prevention plan specific to this site is provided as a part of the O&M Guide in Appendix E. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 12 4.2 Recharge Infiltrating treated runoff into the underlying native sands is one of the objectives of this project. For new development projects, the MASMS requires a specific annual “recharge” volume (Rev) based on the HSG of the soil covered by new impervious surfaces, with a higher volume required for sandy soils (HSG A) and lower for silty, clayey soils (HSG D). This project is only required to provide infiltration or recharge to the maximum extent practicable as a redevelopment project. However, the proposed and retrofitted existing SCMs actually provide more than required by Standard 3, as no new impervious area is proposed and additional recharge volume is proposed. Another requirement of Standard 3 is that infiltrating SCMs must fully drain in 72 hours. The proposed HydroCAD model results showing full recharge of the first inch of runoff by the infiltrating practices and the drawdown times (from full SCM to empty) are included in Appendix B and summarized below in Table 5. The chambers are sized for the 25-year storm and have a volume of 7,800 cf and a surface area of 1,910 sf. When completely full, the chambers will draw down in less than six hours. Table 5. Compliance with Recharge Requirements DA ID SCM ID IA (ac) Soil HSG Required Recharge Depth (in) Rev Goal (ac-ft) Rev Provided (ac-ft)* % Rev Provided Draw-down Time (hrs)** Meets Reqt? Notes DA0 NA 0.17 A 0.6 0.008 0.000 0% NA N Boat Ramp not captured for this retrofit project given space and land use DA1 IS1 0.06 A 0.6 0.003 0.005 170% 12 Y DA2 IS2 0.03 A 0.6 0.001 0.002 160% 12 Y DA2A IT1 0.05 A 0.6 0.002 0.004 173% 12 Y DA2B IT2 0.13 A 0.6 0.007 0.011 168% 12 Y I DA3 IT3, IS3 0.18 A 0.6 0.009 0.015 167% 12 Y Infiltration trench recharges approx 0.5- inch runoff, remaining runoff is recharged in existing system DA3A IS3 0.13 A 0.6 0.006 0.011 172% 12 Y DA3B IS3 0.34 A 0.6 0.017 0.028 167% 12 Y DA3C C1 0.87 A 0.6 0.044 0.073 168% 12 Y TOTAL SITE: 1.94 0.097 0.149 154% Y *From HydroCAD results – see Appendix B for volume “discarded” for WQv Event **From HydroCAD results – see Appendix B for hydrograph showing time from peak elevation to fully drained basins (WQv Event or 25-yr storm for Chambers) 4.3 Water Quantity The main goal of this project is to improve water quality and habitat, but reducing water quantity impacts during large storm events was also prioritized. Due to the lack of cross slope on Follins Pond Road (the road is not crowned), the catchbasin capacity and angle, and observations during rain events by Town of Yarmouth and HW staff, the majority of stormwater runoff is not currently being captured by the existing infiltration systems. Therefore, HW did not model the existing infiltration systems in the existing HydroCAD model. However, to model the existing conditions conservatively, HW assumed and Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 13 modeled 15% of stormwater runoff entering the existing infiltration systems. The proposed conditions model assumes that all of the runoff will enter the existing infiltration systems due to the road regrading and repaving, and the high capacity catchbasin grates. The existing and proposed HydroCAD model results for these larger storm events are included in Appendix B, and the resulting peak flows and runoff volumes are summarized below in Table 6 for both existing (EX) and proposed (PR) conditions. These results show that the proposed improvements will reduce or meet peak flows and runoff volumes for all evaluated storms, and thus, fully meet the requirements of Standard 2 of the MASWMS. Table 6. Summary of Existing and Proposed Condition Peak Flow Rates and Runoff Volumes Study Point Peak Flow, cfs Runoff Volume, acre-ft 2-yr 10-yr 25-yr 100-yr 2-yr 10-yr 25-yr 100-yr SP1 EX* 4.36 6.42 7.98 11.03 0.54 0.83 1.10 1.67 EX** 3.71 5.46 6.78 9.38 0.46 0.70 0.94 1.42 PR* 1.53 3.27 6.34 8.30 0.07 0.17 0.28 0.57 Reduction % 59% 40% 7% 11% 85% 76% 70% 60% *From HydroCAD results – see Appendix B **HydroCAD results reduced by 15% 4.4 Erosion Control Controlling erosion and sedimentation from the construction site is important to meet the overall water quality goals of this retrofit project, as well as to meet MASMS Standard 8. Given this site’s size (< 1 acre of disturbance), a NPDES Construction General Permit Stormwater Pollution Plan (SWPPP) is not required. However, planning for effective erosion and sediment controls (ESCs) was important to this project’s design, and so an ESC Plan is included in the design plans (Appendix G), along with a detailed sequence of construction activities and ESC notes. Visibility fence and/or silt socks are proposed at the limit of work to protect off-site areas and trees; silt socks are proposed along the downgradient edges of the area of disturbance. Disturbed areas will be stabilized as soon as possible to minimize erosion and sedimentation with pavement, seeding and/or erosion control blankets, if necessary. A Pollutant Controls During Construction plan is also included in Appendix F that discusses these controls in more detail. With these layered ESCs implemented throughout the site, discharge of sediment-laden runoff during construction should be minimized to the maximum extent practicable. The contractor will be required to establish these erosion controls prior to beginning any other project- related work. The ESC Plan will also establish the limit of work, beyond which the contractor will not be allowed to perform any work. It is the contractor’s responsibility to monitor and correct erosion control practices throughout the duration of the project. Erosion control measures will not be removed until the project reaches completion as directed by the project engineer or landscape architect. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 14 4.5 Operation and Maintenance Ongoing maintenance is vital for long-term success at the site. All SCMs were designed to be low- maintenance in nature. These SCMs will be operated and maintained appropriately during construction and post-construction as required on the construction drawings and O&M Guide per MASMS Standard 9 (Appendix E and G). 4.6 Illicit Discharges There will be no illicit discharges to the existing system by the proposed project per MASMS Standard 10. The Long-Term Pollution Prevention Plan in the O&M Guide (Appendix E) includes measures to prevent future illicit discharges. Stormwater Management Report Horsley Witten Group, Inc. Follins Pond Boat Ramp Stormwater Retrofit Project - Yarmouth, MA January 2024 15 5.0 REFERENCES Association to Preserve Cape Cod. 2022. State of the Waters: Cape Cod Report. Cape Cod Commission. 2015. 208 Plan – Cape Cod’s Area Wide Water Quality Management Plan Updated. Massachusetts Department of Environmental Protection (MADEP). 2008. Massachusetts Stormwater Standards Manual. MADEP. 2019. See their homepage at www.state.ma.gov/dep. MassGIS (Massachusetts Office of Geographic and Environmental Information). 2023. See their homepage at: http://www.mass.gov/mgis/. National Oceanic and Atmospheric Administration (NOAA) - National Weather Service (NWS). 2017. Point Precipitation Frequency Estimates: MA. NOAA Atlas 14, Volume 10, Version 3. https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=ma Paradigm Environmental. 2019. USEPA Memo. Tisbury MA Impervious Cover Disconnection (ICD) Project: An Integrated Stormwater Management Approach for Promoting Urban Community Sustainability and Resilience - Task 4D. Develop Planning Level GI SCM Performance Curves for Estimating Cumulative Reductions in SW-Related Indicator Bacteria. USEPA (United States Environmental Protection Agency). 2019. National Pollutant Discharge Elimination System (NPDES). See their homepage at: http://cfpub.epa.gov/NPDES/. USEPA. 2021. National Pollutant Discharge Elimination System (NPDES)-General Permits for Stormwater Discharges from Small Municipal Separate Storm Sewer Systems in Massachusetts (as modified). FIGURES !( !( Path: H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\GIS\M aps\ReportFigureMaps\FollinsPond\Locus.mxd Figure 1Locus Map !(Follins Pond Boat RampDate:8/24/2023Data Sources:Bureau of GeographicInformation (MassGIS), ESRI This map is for informational purposes andmay not be suitable for legal, engineering,or surveying purposes.0 600300 FeetI FOLLINS POND Boat Ramp Cape Cod Boat Ramp Stormwa ter Re trofit Pro jectYarmouth, MA Yarmouth Site !( G U N R O C K R O A D FOLLI NS POND ROADAUNT DORAHS LANEPath: H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\GIS\M aps\ReportFigureMaps\FollinsPond\Aerial.mxd Figure 2Aerial !(Follins Pond Boat RampDate:10/17/2023Data Sources:Bureau of GeographicInformation (MassGIS), ESRI This map is for informational purposes andmay not be suitable for legal, engineering,or surveying purposes. 0 7537.5 FeetI FOLLINS POND Boat Ramp Cape Cod Boat Ramp Stormwa ter Re trofit Pro jectYarmouth, MA Yarmouth Site Follins Pond !( G U N R O C K R O A D FOLLI NS POND ROADAUNT DORAHS LANEPath: H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\GIS\M aps\ReportFigureMaps\FollinsPond\Constraints.mxd Figure 3Constraints !(Follins Pond Boat RampShorelineOpen Water Date:10/17/2023Data Sources:Bureau of GeographicInformation (MassGIS), ESRI This map is for informational purposes andmay not be suitable for legal, engineering,or surveying purposes. 0 7537.5 FeetI FOLLINS POND Boat Ramp Cape Cod Boat Ramp Stormwa ter Re trofit Pro jectYarmouth, MA Yarmouth Site Follins Pond !(Ham blinsBrook -M A96-133Bass River- MA96-12 Flax Pond- MA96090 Miss ThachersPond - MA96258 Swan PondRiver -MA96-14 ParkersRiver -MA96-38 ParkersRiver -MA96-38 ParkersRiver -MA96-38 Long Pond- MA96180 ElbowPond- MA96077 Seine Pond- MA96-110 Swan Pond- MA96-111 Follins Pond- MA96-114 Kelleys Bay- MA96-113Dinahs Pond- MA96-112 MillPond -MA96-117 MuddyCreek -MA96-115 Weir Creek- MA96-116 Bass River- MA96-118 White Pond- MA96338 !( Path: H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\GIS\M aps\ReportFigureMaps\FollinsPond\Impaired_Waters.mxd Figure 4Impaired Waters !(Follins Pond Boat Ramp 2018/2020 Integrated List Data 4C - Impairment notcaused by a pollutant 3 - No uses assessed 4A - Impaired - TMDL iscompleted 4C - Impairment notcaused by a pollutant Town Parcels Date:8/24/2023Data Sources:Bureau of GeographicInformation (MassGIS), ESRI This map is for informational purposesand may not be suitable for legal,engineering, or surveying purposes. 0 3,5001,750 FeetI FOLLINS POND Boat Ramp Cape Cod Boat Ramp Stormwa ter Re trofit Pro jectYarmouth, MA Yarmouth Site Yarmouth Dennis !( 252 D - Ca rv e r 252 C - Ca rver 607 -Wat er,sa li ne 252 B - C arv e r 252 C - Ca rver G U N R O C K R O A D FOLLI NS POND ROADAUNT DORAHS LANEPath: H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\GIS\M aps\ReportFigureMaps\FollinsPond\Soils.mxd Figure 5Soils !(Follins Pond Boat RampHydrologic Soil Group <Null>A Date:8/24/2023Data Sources:Bureau of GeographicInformation (MassGIS), ESRI This map is for informational purposes andmay not be suitable for legal, engineering,or surveying purposes. 0 7537.5 FeetI FOLLINS POND Boat Ramp Cape Cod Boat Ramp Stormwa ter Re trofit Pro jectYarmouth, MA Yarmouth Site Follins Pond APPENDIX A – Drainage Areas •Existing and Proposed Drainage Areas Maps •Land Coverage Summaries 252CHSG APrepared For:Sheet Number:Project Number:Date:Drawn By:Design By:Checked By: last modified: 01/09/24 printed: 01/09/24 by eh C:\Users\ehoffman\AppData\Local\Temp\AcPublish_3760\22032 FOLLINS DA.dwg Plan Set: Plan Title:of122032A2Town of Yarmouth Phone: 1146 MA-28 South Yarmouth, MA (508) 398-2231 DECEMBER 2023 EWH EWH/JLV GK 0SCALE IN FEET80Horsley Witten Group, Inc. Sustainable Environmental Solutions 90 Route 6A Sandwich, MA 02563 horsleywittengroup.comDA1SP1P1STUDY POINTFOLLINS POND CAPE COD BOAT RAMP STORMWATER RETROFIT PROJECT - PERMITTING PLANS YARMOUTH, MA EXISTING DRAINAGE AREA MAPDRAINAGE AREA1.005.00SOIL BOUNDARYTIME OF CONCENTRATION FLOW PATH5' MAJOR CONTOUR1' MINOR CONTOURCARVER COARSE SAND (HSG A)LEGENDSOIL TYPESPONDWOODSROOFTOPGRASSPAVEMENTWATERDRAINAGEAREABOUNDARYIMP. AREATOTAL AREA(ACRES)252BHSG ADA2DA3DA1DA0SP1CARVER COARSE SAND (HSG A)252DHSG ACARVER COARSE SAND (HSG A)252BHSG A252CHSG A252DHSG AIS1IS2IS3252CHSG A0.672.820.170.980.060.231.053.86 252CHSG APrepared For:Sheet Number:Project Number:Date:Drawn By:Design By:Checked By: last modified: 01/15/24 printed: 01/15/24 by eh H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Drawings\FOLLINS\Misc\22032 FOLLINS DA.dwg Plan Set: Plan Title:of222032A2Town of Yarmouth Phone: 1146 MA-28 South Yarmouth, MA (508) 398-2231 0SCALE IN FEET80Horsley Witten Group, Inc. Sustainable Environmental Solutions 90 Route 6A Sandwich, MA 02563 horsleywittengroup.comDA1SP1P1STUDY POINTFOLLINS POND CAPE COD BOAT RAMP STORMWATER RETROFIT PROJECT - PERMITTING PLANS YARMOUTH, MA PROPOSED DRAINAGE AREA MAPDRAINAGE AREASOIL BOUNDARYTIME OF CONCENTRATION FLOW PATH5' MAJOR CONTOUR1' MINOR CONTOURCARVER COARSE SAND (HSG A)LEGENDSOIL TYPESPONDWOODSROOFTOPGRASSPAVEMENTWATERDRAINAGEAREABOUNDARY252BHSG ADA3BDA3DA1SP1CARVER COARSE SAND (HSG A)252DHSG ACARVER COARSE SAND (HSG A)252BHSG A252CHSG A252DHSG AIS3IS2IS1IT1C1IT3DA3CDA0DA2DA2BJANUARY 2024 EWH EWH/JLV GK252CHSG A1.005.00IMP. AREATOTAL AREA(ACRES)0.170.980.060.230.030.100.341.670.180.620.873.25IT2DA2ADA3A0.050.140.130.470.130.43 APPENDIX B – Hydrologic/Hydraulic Model Results HydroCAD® Results • Existing • Proposed Calc'd by: Checked by: Date: DA0 DA1 WQv 1.21 DA2 1-yr 3.05 DA3 2-yr 3.60 5-yr 4.51 10-yr 5.27 25-yr 6.53 100-yr 8.59 500-yr 0.00 DA0 Cover type Area, ft 2 Area, ac Note Paved 4,730 0.109 Permeable 0 0.000 Roof 2,460 0.056 Water 0 0.000 Woods 29,910 0.687 Grass 5,370 0.123 Area, ft 2 Area, ac Percent TOTAL 42,470 0.975 7,190 0.165 17 DA1 Cover type Area, ft 2 Area, ac Note Paved 2,560 0.059 Permeable 0 0.000 Roof 0 0.000 Water 0 0.000 Woods 7,610 0.175 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 10,170 0.233 2,560 0.059 25 Impervious TO INFILTRATION SYSTEM 1 Impervious 24-hr Type III (inches) TO POND TO POND TO INFILTRATION SYSTEM 3 TO INFILTRATION SYSTEM 2 TO INFILTRATION SYSTEM 1 DRAINAGE AREAS NOAA 14+ EWH 11/1/2023 CAPE COD BOAT RAMPS - FOLLINS POND YARMOUTH, MA PRE-development Drainage Conditions DA2 Cover type Area, ft 2 Area, ac Note Paved 21,750 0.499 Permeable 0 0.000 Roof 7,270 0.167 Water 0 0.000 Woods 68,330 1.569 Grass 25,410 0.583 Area, ft 2 Area, ac Percent TOTAL 122,760 2.818 29,020 0.666 24 DA3 Cover type Area, ft 2 Area, ac Note Paved 27,230 0.625 Permeable 0 0.000 Roof 18,440 0.423 Water 0 0.000 Woods 118,570 2.722 Grass 4,090 0.094 Area, ft 2 Area, ac Percent TOTAL 168,330 3.864 45,670 1.048 27 ALL Cover type Area, ft 2 Area, ac Note Paved 56,270 1.292 Permeable 0 0.000 Roof 28,170 0.056 Water 0 0.000 Woods 224,420 0.861 Grass 34,870 0.123 Area, ft 2 Area, ac Percent TOTAL 343,730 7.891 84,440 1.938 25 Impervious ALL PRE-DEVELOPMENT AREAS COMBINED Impervious TO INFILTRATION SYSTEM 2 Impervious TO INFILTRATION SYSTEM 3 Calc'd by: Checked by: Date: DA0 DA1 WQv 1.21 DA2 1-yr 3.05 DA2A 2-yr 3.60 DA2B TO TREE TRENCH 2 5-yr 4.51 DA3 10-yr 5.27 DA3A 25-yr 6.53 DA3B 100-yr 8.59 DA3C 500-yr 0.00 DA0 Cover type Area, ft 2 Area, ac Note Paved 4,730 0.109 Permeable 0 0.000 Roof 2,460 0.056 Water 0 0.000 Woods 29,910 0.687 Grass 5,370 0.123 Area, ft 2 Area, ac Percent TOTAL 42,470 0.975 7,190 0.165 17 DA1 Cover type Area, ft 2 Area, ac Note Paved 2,560 0.059 Permeable 0 0.000 Roof 0 0.000 Water 0 0.000 Woods 7,620 0.175 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 10,180 0.234 2,560 0.059 25 TO TREE TRENCH 3 (GUN ROCK) TO TREE TRENCH 3 (EAST FOLLINS) TO INFILTRATION SYSTEM 1 TO POND 24-hr Type III (inches) TO INFILTRATION SYSTEM 1 TO INFILTRATION SYSTEM 2 TO TREE TRENCH 1 EWH POST-development Drainage Conditions 1/15/2024 DRAINAGE AREAS NOAA 14+ CAPE COD BOAT RAMPS - FOLLINS POND YARMOUTH, MA Impervious TO TREE TRENCH 3 (WEST FOLLINS) Impervious TO CHAMBERS TO POND DA2 Cover type Area, ft 2 Area, ac Note Paved 740 0.017 Permeable 0 0.000 Roof 350 0.008 Water 0 0.000 Woods 3,290 0.076 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 4,380 0.101 1,090 0.025 25 DA2A Cover type Area, ft 2 Area, ac Note Paved 1,080 0.025 Permeable 0 0.000 Roof 930 0.021 Water 0 0.000 Woods 4,130 0.095 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 6,140 0.141 2,010 0.046 33 DA2B Cover type Area, ft 2 Area, ac Note Paved 5,710 0.131 Permeable 0 0.000 Roof 0 0.000 Water 0 0.000 Woods 12,670 0.291 Grass 2,200 0.051 Area, ft 2 Area, ac Percent TOTAL 20,580 0.472 5,710 0.131 28 DA3 Cover type Area, ft 2 Area, ac Note Paved 4,210 0.097 Permeable 0 0.000 Roof 3,600 0.083 Water 0 0.000 Woods 19,080 0.438 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 26,890 0.617 7,810 0.179 29 TO TREE TRENCH 1 Impervious TO TREE TRENCH 3 (GUN ROCK) Impervious TO TREE TRENCH 2 Impervious TO INFILTRATION SYSTEM 2 Impervious DA3A Cover type Area, ft 2 Area, ac Note Paved 5,580 0.128 Permeable 0 0.000 Roof 0 0.000 Water 0 0.000 Woods 13,180 0.303 Grass 0 0.000 Area, ft 2 Area, ac Percent TOTAL 18,760 0.431 5,580 0.128 30 DA3B Cover type Area, ft 2 Area, ac Note Paved 8,650 0.199 Permeable 0 0.000 Roof 5,990 0.138 Water 0 0.000 Woods 35,050 0.805 Grass 23,230 0.533 Area, ft 2 Area, ac Percent TOTAL 72,920 1.674 14,640 0.336 20 DA3C Cover type Area, ft 2 Area, ac Note Paved 23,130 0.531 Permeable 0 0.000 Roof 14,820 0.340 Water 0 0.000 Woods 99,540 2.285 Grass 3,910 0.090 Area, ft 2 Area, ac Percent TOTAL 141,400 3.246 37,950 0.871 27 ALL Cover type Area, ft 2 Area, ac Note Paved 56,390 1.295 Permeable 0 0.000 Roof 28,150 0.646 Water 0 0.000 Woods 224,470 5.153 Grass 34,710 0.797 Area, ft 2 Area, ac Percent TOTAL 343,720 7.891 84,540 1.941 25 Impervious TO TREE TRENCH 3 (EAST FOLLINS) Impervious Impervious TO TREE TRENCH 3 (WEST FOLLINS) ALL POST-DEVELOPMENT AREAS COMBINED TO CHAMBERS Impervious DA0 DA1 DA2 DA3 SP1 Follins Pond Routing Diagram for 22032 FOLLINS EX Prepared by Horsley Witten Inc, Printed 12/3/2023 HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link 22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 2HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Rainfall Events Listing Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 2yr Type III 24-hr Default 24.00 1 3.60 2 2 10yr Type III 24-hr Default 24.00 1 5.27 2 3 25yr Type III 24-hr Default 24.00 1 6.53 2 4 100yr Type III 24-hr Default 24.00 1 8.59 2 5 WQV Type III 24-hr Default 24.00 1 1.21 2 22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 3HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 0.801 39 >75% Grass cover, Good, HSG A (DA0, DA2, DA3) 1.292 98 Paved parking, HSG A (DA0, DA1, DA2, DA3) 0.647 98 Unconnected roofs, HSG A (DA0, DA2, DA3) 5.152 30 Woods, Good, HSG A (DA0, DA1, DA2, DA3) 7.891 48 TOTAL AREA 22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 4HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (acres) Soil Group Subcatchment Numbers 7.891 HSG A DA0, DA1, DA2, DA3 0.000 HSG B 0.000 HSG C 0.000 HSG D 0.000 Other 7.891 TOTAL AREA 22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 5HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Ground Covers (all nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.801 0.000 0.000 0.000 0.000 0.801 >75% Grass cover, Good DA0, DA2, DA3 1.292 0.000 0.000 0.000 0.000 1.292 Paved parking DA0, DA1, DA2, DA3 0.647 0.000 0.000 0.000 0.000 0.647 Unconnected roofs DA0, DA2, DA3 5.152 0.000 0.000 0.000 0.000 5.152 Woods, Good DA0, DA1, DA2, DA3 7.891 0.000 0.000 0.000 0.000 7.891 TOTAL AREA Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 6HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=1.00-72.00 hrs, dt=0.05 hrs, 1421 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=0.57"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.43 cfs 0.046 af Runoff Area=10,170 sf 25.17% Impervious Runoff Depth=0.85"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.17 cfs 0.016 af Runoff Area=122,760 sf 23.64% Impervious Runoff Depth=0.80"Subcatchment DA2: Flow Length=622' Tc=20.2 min CN=32/98 Runoff=1.58 cfs 0.187 af Runoff Area=168,330 sf 27.13% Impervious Runoff Depth=0.91"Subcatchment DA3: Flow Length=497' Tc=24.2 min CN=30/98 Runoff=2.31 cfs 0.294 af Inflow=4.36 cfs 0.544 afPond SP1: Follins Pond Primary=4.36 cfs 0.544 af Total Runoff Area = 7.891 ac Runoff Volume = 0.544 af Average Runoff Depth = 0.83" 75.43% Pervious = 5.952 ac 24.57% Impervious = 1.938 ac Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 7HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.43 cfs @ 12.21 hrs, Volume= 0.046 af, Depth= 0.57" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=42,470 sf Runoff Volume=0.046 af Runoff Depth=0.57" Flow Length=625' Tc=16.2 min CN=31/98 0.43 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 8HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.17 cfs @ 12.15 hrs, Volume= 0.016 af, Depth= 0.85" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,610 30 Woods, Good, HSG A 10,170 47 Weighted Average 7,610 30 74.83% Pervious Area 2,560 98 25.17% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=10,170 sf Runoff Volume=0.016 af Runoff Depth=0.85" Flow Length=235' Tc=11.5 min CN=30/98 0.17 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 9HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 1.58 cfs @ 12.26 hrs, Volume= 0.187 af, Depth= 0.80" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 21,750 98 Paved parking, HSG A 7,270 98 Unconnected roofs, HSG A 68,330 30 Woods, Good, HSG A 25,410 39 >75% Grass cover, Good, HSG A 122,760 48 Weighted Average 93,740 32 76.36% Pervious Area 29,020 98 23.64% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 2.0 155 0.0700 1.32 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 367 0.0900 6.09 Shallow Concentrated Flow, Paved Kv= 20.3 fps 20.2 622 Total Subcatchment DA2: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)1 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=122,760 sf Runoff Volume=0.187 af Runoff Depth=0.80" Flow Length=622' Tc=20.2 min CN=32/98 1.58 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 10HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 2.31 cfs @ 12.32 hrs, Volume= 0.294 af, Depth= 0.91" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 27,230 98 Paved parking, HSG A 18,440 98 Unconnected roofs, HSG A 118,570 30 Woods, Good, HSG A 4,090 39 >75% Grass cover, Good, HSG A 168,330 49 Weighted Average 122,660 30 72.87% Pervious Area 45,670 98 27.13% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 127 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 497 Total Subcatchment DA3: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)2 1 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=168,330 sf Runoff Volume=0.294 af Runoff Depth=0.91" Flow Length=497' Tc=24.2 min CN=30/98 2.31 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 11HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 7.891 ac, 24.57% Impervious, Inflow Depth = 0.83" for 2yr event Inflow = 4.36 cfs @ 12.28 hrs, Volume= 0.544 af Primary = 4.36 cfs @ 12.28 hrs, Volume= 0.544 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)4 3 2 1 0 Inflow Area=7.891 ac 4.36 cfs4.36 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 12HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=1.00-72.00 hrs, dt=0.05 hrs, 1421 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth>0.88"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.63 cfs 0.071 af Runoff Area=10,170 sf 25.17% Impervious Runoff Depth>1.28"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.25 cfs 0.025 af Runoff Area=122,760 sf 23.64% Impervious Runoff Depth>1.23"Subcatchment DA2: Flow Length=622' Tc=20.2 min CN=32/98 Runoff=2.33 cfs 0.288 af Runoff Area=168,330 sf 27.13% Impervious Runoff Depth>1.38"Subcatchment DA3: Flow Length=497' Tc=24.2 min CN=30/98 Runoff=3.40 cfs 0.443 af Inflow=6.42 cfs 0.827 afPond SP1: Follins Pond Primary=6.42 cfs 0.827 af Total Runoff Area = 7.891 ac Runoff Volume = 0.827 af Average Runoff Depth = 1.26" 75.43% Pervious = 5.952 ac 24.57% Impervious = 1.938 ac Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 13HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.63 cfs @ 12.21 hrs, Volume= 0.071 af, Depth> 0.88" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=42,470 sf Runoff Volume=0.071 af Runoff Depth>0.88" Flow Length=625' Tc=16.2 min CN=31/98 0.63 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 14HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.25 cfs @ 12.15 hrs, Volume= 0.025 af, Depth> 1.28" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,610 30 Woods, Good, HSG A 10,170 47 Weighted Average 7,610 30 74.83% Pervious Area 2,560 98 25.17% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=10,170 sf Runoff Volume=0.025 af Runoff Depth>1.28" Flow Length=235' Tc=11.5 min CN=30/98 0.25 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 15HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 2.33 cfs @ 12.26 hrs, Volume= 0.288 af, Depth> 1.23" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 21,750 98 Paved parking, HSG A 7,270 98 Unconnected roofs, HSG A 68,330 30 Woods, Good, HSG A 25,410 39 >75% Grass cover, Good, HSG A 122,760 48 Weighted Average 93,740 32 76.36% Pervious Area 29,020 98 23.64% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 2.0 155 0.0700 1.32 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 367 0.0900 6.09 Shallow Concentrated Flow, Paved Kv= 20.3 fps 20.2 622 Total Subcatchment DA2: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)2 1 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=122,760 sf Runoff Volume=0.288 af Runoff Depth>1.23" Flow Length=622' Tc=20.2 min CN=32/98 2.33 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 16HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 3.40 cfs @ 12.32 hrs, Volume= 0.443 af, Depth> 1.38" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 27,230 98 Paved parking, HSG A 18,440 98 Unconnected roofs, HSG A 118,570 30 Woods, Good, HSG A 4,090 39 >75% Grass cover, Good, HSG A 168,330 49 Weighted Average 122,660 30 72.87% Pervious Area 45,670 98 27.13% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 127 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 497 Total Subcatchment DA3: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)3 2 1 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=168,330 sf Runoff Volume=0.443 af Runoff Depth>1.38" Flow Length=497' Tc=24.2 min CN=30/98 3.40 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 17HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 7.891 ac, 24.57% Impervious, Inflow Depth > 1.26" for 10yr event Inflow = 6.42 cfs @ 12.28 hrs, Volume= 0.827 af Primary = 6.42 cfs @ 12.28 hrs, Volume= 0.827 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)7 6 5 4 3 2 1 0 Inflow Area=7.891 ac 6.42 cfs6.42 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 18HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=1.00-72.00 hrs, dt=0.05 hrs, 1421 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth>1.21"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.78 cfs 0.099 af Runoff Area=10,170 sf 25.17% Impervious Runoff Depth>1.69"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.31 cfs 0.033 af Runoff Area=122,760 sf 23.64% Impervious Runoff Depth>1.66"Subcatchment DA2: Flow Length=622' Tc=20.2 min CN=32/98 Runoff=2.89 cfs 0.389 af Runoff Area=168,330 sf 27.13% Impervious Runoff Depth>1.81"Subcatchment DA3: Flow Length=497' Tc=24.2 min CN=30/98 Runoff=4.23 cfs 0.582 af Inflow=7.98 cfs 1.102 afPond SP1: Follins Pond Primary=7.98 cfs 1.102 af Total Runoff Area = 7.891 ac Runoff Volume = 1.102 af Average Runoff Depth = 1.68" 75.43% Pervious = 5.952 ac 24.57% Impervious = 1.938 ac Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 19HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.78 cfs @ 12.21 hrs, Volume= 0.099 af, Depth> 1.21" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=42,470 sf Runoff Volume=0.099 af Runoff Depth>1.21" Flow Length=625' Tc=16.2 min CN=31/98 0.78 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 20HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.31 cfs @ 12.15 hrs, Volume= 0.033 af, Depth> 1.69" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,610 30 Woods, Good, HSG A 10,170 47 Weighted Average 7,610 30 74.83% Pervious Area 2,560 98 25.17% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=10,170 sf Runoff Volume=0.033 af Runoff Depth>1.69" Flow Length=235' Tc=11.5 min CN=30/98 0.31 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 21HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 2.89 cfs @ 12.26 hrs, Volume= 0.389 af, Depth> 1.66" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 21,750 98 Paved parking, HSG A 7,270 98 Unconnected roofs, HSG A 68,330 30 Woods, Good, HSG A 25,410 39 >75% Grass cover, Good, HSG A 122,760 48 Weighted Average 93,740 32 76.36% Pervious Area 29,020 98 23.64% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 2.0 155 0.0700 1.32 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 367 0.0900 6.09 Shallow Concentrated Flow, Paved Kv= 20.3 fps 20.2 622 Total Subcatchment DA2: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)3 2 1 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=122,760 sf Runoff Volume=0.389 af Runoff Depth>1.66" Flow Length=622' Tc=20.2 min CN=32/98 2.89 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 22HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 4.23 cfs @ 12.32 hrs, Volume= 0.582 af, Depth> 1.81" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 27,230 98 Paved parking, HSG A 18,440 98 Unconnected roofs, HSG A 118,570 30 Woods, Good, HSG A 4,090 39 >75% Grass cover, Good, HSG A 168,330 49 Weighted Average 122,660 30 72.87% Pervious Area 45,670 98 27.13% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 127 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 497 Total Subcatchment DA3: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)4 3 2 1 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=168,330 sf Runoff Volume=0.582 af Runoff Depth>1.81" Flow Length=497' Tc=24.2 min CN=30/98 4.23 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 23HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 7.891 ac, 24.57% Impervious, Inflow Depth > 1.68" for 25yr event Inflow = 7.98 cfs @ 12.28 hrs, Volume= 1.102 af Primary = 7.98 cfs @ 12.28 hrs, Volume= 1.102 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)8 7 6 5 4 3 2 1 0 Inflow Area=7.891 ac 7.98 cfs7.98 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 24HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=1.00-72.00 hrs, dt=0.05 hrs, 1421 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth>1.95"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=1.08 cfs 0.159 af Runoff Area=10,170 sf 25.17% Impervious Runoff Depth>2.52"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.42 cfs 0.049 af Runoff Area=122,760 sf 23.64% Impervious Runoff Depth>2.54"Subcatchment DA2: Flow Length=622' Tc=20.2 min CN=32/98 Runoff=4.08 cfs 0.595 af Runoff Area=168,330 sf 27.13% Impervious Runoff Depth>2.68"Subcatchment DA3: Flow Length=497' Tc=24.2 min CN=30/98 Runoff=5.68 cfs 0.862 af Inflow=11.03 cfs 1.665 afPond SP1: Follins Pond Primary=11.03 cfs 1.665 af Total Runoff Area = 7.891 ac Runoff Volume = 1.665 af Average Runoff Depth = 2.53" 75.43% Pervious = 5.952 ac 24.57% Impervious = 1.938 ac Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 25HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 1.08 cfs @ 12.23 hrs, Volume= 0.159 af, Depth> 1.95" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=42,470 sf Runoff Volume=0.159 af Runoff Depth>1.95" Flow Length=625' Tc=16.2 min CN=31/98 1.08 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 26HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.42 cfs @ 12.16 hrs, Volume= 0.049 af, Depth> 2.52" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,610 30 Woods, Good, HSG A 10,170 47 Weighted Average 7,610 30 74.83% Pervious Area 2,560 98 25.17% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=10,170 sf Runoff Volume=0.049 af Runoff Depth>2.52" Flow Length=235' Tc=11.5 min CN=30/98 0.42 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 27HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 4.08 cfs @ 12.29 hrs, Volume= 0.595 af, Depth> 2.54" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 21,750 98 Paved parking, HSG A 7,270 98 Unconnected roofs, HSG A 68,330 30 Woods, Good, HSG A 25,410 39 >75% Grass cover, Good, HSG A 122,760 48 Weighted Average 93,740 32 76.36% Pervious Area 29,020 98 23.64% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 2.0 155 0.0700 1.32 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 367 0.0900 6.09 Shallow Concentrated Flow, Paved Kv= 20.3 fps 20.2 622 Total Subcatchment DA2: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)4 3 2 1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=122,760 sf Runoff Volume=0.595 af Runoff Depth>2.54" Flow Length=622' Tc=20.2 min CN=32/98 4.08 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 28HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 5.68 cfs @ 12.33 hrs, Volume= 0.862 af, Depth> 2.68" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 27,230 98 Paved parking, HSG A 18,440 98 Unconnected roofs, HSG A 118,570 30 Woods, Good, HSG A 4,090 39 >75% Grass cover, Good, HSG A 168,330 49 Weighted Average 122,660 30 72.87% Pervious Area 45,670 98 27.13% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 127 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 497 Total Subcatchment DA3: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)6 5 4 3 2 1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=168,330 sf Runoff Volume=0.862 af Runoff Depth>2.68" Flow Length=497' Tc=24.2 min CN=30/98 5.68 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 29HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 7.891 ac, 24.57% Impervious, Inflow Depth > 2.53" for 100yr event Inflow = 11.03 cfs @ 12.30 hrs, Volume= 1.665 af Primary = 11.03 cfs @ 12.30 hrs, Volume= 1.665 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)12 11 10 9 8 7 6 5 4 3 2 1 0 Inflow Area=7.891 ac 11.03 cfs11.03 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 30HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=1.00-72.00 hrs, dt=0.05 hrs, 1421 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=0.17"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.13 cfs 0.014 af Runoff Area=10,170 sf 25.17% Impervious Runoff Depth=0.25"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.05 cfs 0.005 af Runoff Area=122,760 sf 23.64% Impervious Runoff Depth=0.24"Subcatchment DA2: Flow Length=622' Tc=20.2 min CN=32/98 Runoff=0.50 cfs 0.055 af Runoff Area=168,330 sf 27.13% Impervious Runoff Depth=0.27"Subcatchment DA3: Flow Length=497' Tc=24.2 min CN=30/98 Runoff=0.73 cfs 0.087 af Inflow=1.37 cfs 0.161 afPond SP1: Follins Pond Primary=1.37 cfs 0.161 af Total Runoff Area = 7.891 ac Runoff Volume = 0.161 af Average Runoff Depth = 0.24" 75.43% Pervious = 5.952 ac 24.57% Impervious = 1.938 ac Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 31HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.13 cfs @ 12.21 hrs, Volume= 0.014 af, Depth= 0.17" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=42,470 sf Runoff Volume=0.014 af Runoff Depth=0.17" Flow Length=625' Tc=16.2 min CN=31/98 0.13 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 32HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.05 cfs @ 12.16 hrs, Volume= 0.005 af, Depth= 0.25" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,610 30 Woods, Good, HSG A 10,170 47 Weighted Average 7,610 30 74.83% Pervious Area 2,560 98 25.17% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=10,170 sf Runoff Volume=0.005 af Runoff Depth=0.25" Flow Length=235' Tc=11.5 min CN=30/98 0.05 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 33HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.50 cfs @ 12.27 hrs, Volume= 0.055 af, Depth= 0.24" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 21,750 98 Paved parking, HSG A 7,270 98 Unconnected roofs, HSG A 68,330 30 Woods, Good, HSG A 25,410 39 >75% Grass cover, Good, HSG A 122,760 48 Weighted Average 93,740 32 76.36% Pervious Area 29,020 98 23.64% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 2.0 155 0.0700 1.32 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 367 0.0900 6.09 Shallow Concentrated Flow, Paved Kv= 20.3 fps 20.2 622 Total Subcatchment DA2: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=122,760 sf Runoff Volume=0.055 af Runoff Depth=0.24" Flow Length=622' Tc=20.2 min CN=32/98 0.50 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 34HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 0.73 cfs @ 12.32 hrs, Volume= 0.087 af, Depth= 0.27" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 27,230 98 Paved parking, HSG A 18,440 98 Unconnected roofs, HSG A 118,570 30 Woods, Good, HSG A 4,090 39 >75% Grass cover, Good, HSG A 168,330 49 Weighted Average 122,660 30 72.87% Pervious Area 45,670 98 27.13% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 127 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 497 Total Subcatchment DA3: Runoff Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=168,330 sf Runoff Volume=0.087 af Runoff Depth=0.27" Flow Length=497' Tc=24.2 min CN=30/98 0.73 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS EX Printed 12/3/2023Prepared by Horsley Witten Inc Page 35HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 7.891 ac, 24.57% Impervious, Inflow Depth = 0.24" for WQV event Inflow = 1.37 cfs @ 12.28 hrs, Volume= 0.161 af Primary = 1.37 cfs @ 12.28 hrs, Volume= 0.161 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 1.00-72.00 hrs, dt= 0.05 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 72706866646260585654525048464442403836343230282624222018161412108642Flow (cfs)1 0 Inflow Area=7.891 ac 1.37 cfs1.37 cfs DA0DA1DA2DA2ADA2B DA3 DA3A DA3B DA3C C1 CHAMBERS IS1 Infiltration System 1 IS2 Infiltration System 2 IS3 Infiltration System 3 IT1 INFILTRATION TRENCH 1 IT2 INFILTRATION TRENCH 2 IT3 INFILTRATION TRENCH 3 SP1 Follins Pond Routing Diagram for 22032 FOLLINS PR Prepared by Horsley Witten Inc, Printed 1/15/2024 HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link 22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 2HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Rainfall Events Listing (selected events) Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 2yr Type III 24-hr Default 24.00 1 3.60 2 2 10yr Type III 24-hr Default 24.00 1 5.27 2 3 25yr Type III 24-hr Default 24.00 1 6.53 2 4 100yr Type III 24-hr Default 24.00 1 8.59 2 5 WQV Type III 24-hr Default 24.00 1 1.21 2 22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 3HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (sq-ft) CN Description (subcatchment-numbers) 34,710 39 >75% Grass cover, Good, HSG A (DA0, DA2B, DA3B, DA3C) 56,390 98 Paved parking, HSG A (DA0, DA1, DA2, DA2A, DA2B, DA3, DA3A, DA3B, DA3C) 28,150 98 Unconnected roofs, HSG A (DA0, DA2, DA2A, DA3, DA3B, DA3C) 224,870 30 Woods, Good, HSG A (DA0, DA1, DA2, DA2A, DA2B, DA3, DA3A, DA3B, DA3C) 344,120 48 TOTAL AREA 22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 4HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (sq-ft) Soil Group Subcatchment Numbers 344,120 HSG A DA0, DA1, DA2, DA2A, DA2B, DA3, DA3A, DA3B, DA3C 0 HSG B 0 HSG C 0 HSG D 0 Other 344,120 TOTAL AREA 22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 5HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Ground Covers (all nodes) HSG-A (sq-ft) HSG-B (sq-ft) HSG-C (sq-ft) HSG-D (sq-ft) Other (sq-ft) Total (sq-ft) Ground Cover Sub Num 34,710 000034,710 >75% Grass cover, Good 56,390 000056,390 Paved parking 28,150 000028,150 Unconnected roofs 224,8700000224,870 Woods, Good 344,120 0000344,120 TOTAL AREA Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 6HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=0.57"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.43 cfs 2,017 cf Runoff Area=10,180 sf 25.15% Impervious Runoff Depth=0.85"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.17 cfs 718 cf Runoff Area=4,780 sf 22.80% Impervious Runoff Depth=0.77"Subcatchment DA2: Tc=5.0 min CN=30/98 Runoff=0.09 cfs 306 cf Runoff Area=6,140 sf 32.74% Impervious Runoff Depth=1.10"Subcatchment DA2A: Tc=5.0 min CN=30/98 Runoff=0.17 cfs 564 cf Runoff Area=20,580 sf 27.75% Impervious Runoff Depth=0.93"Subcatchment DA2B: Tc=5.0 min CN=31/98 Runoff=0.48 cfs 1,602 cf Runoff Area=26,890 sf 29.04% Impervious Runoff Depth=0.98"Subcatchment DA3: Tc=5.0 min CN=30/98 Runoff=0.65 cfs 2,191 cf Runoff Area=18,760 sf 29.74% Impervious Runoff Depth=1.00"Subcatchment DA3A: Flow Length=480' Tc=19.7 min CN=30/98 Runoff=0.31 cfs 1,565 cf Runoff Area=72,920 sf 20.08% Impervious Runoff Depth=0.68"Subcatchment DA3B: Flow Length=495' Tc=24.2 min CN=34/98 Runoff=0.74 cfs 4,107 cf Runoff Area=141,400 sf 26.84% Impervious Runoff Depth=0.90"Subcatchment DA3C: Flow Length=235' Tc=12.7 min CN=30/98 Runoff=2.48 cfs 10,646 cf Peak Elev=29.73' Storage=3,205 cf Inflow=2.48 cfs 10,646 cfPond C1: CHAMBERS Discarded=0.37 cfs 10,639 cf Primary=0.00 cfs 0 cf Outflow=0.37 cfs 10,639 cf Peak Elev=13.60' Storage=999 cf Inflow=1.47 cfs 2,589 cfPond IS1: Infiltration System 1 Discarded=0.06 cfs 1,667 cf Primary=1.09 cfs 922 cf Outflow=1.15 cfs 2,589 cf Peak Elev=17.00' Storage=999 cf Inflow=1.73 cfs 3,413 cfPond IS2: Infiltration System 2 Discarded=0.06 cfs 1,542 cf Primary=1.32 cfs 1,871 cf Outflow=1.38 cfs 3,413 cf Peak Elev=30.87' Storage=973 cf Inflow=1.24 cfs 6,399 cfPond IS3: Infiltration System 3 Discarded=0.06 cfs 3,584 cf Primary=1.19 cfs 2,814 cf Outflow=1.24 cfs 6,399 cf Peak Elev=20.69' Storage=134 cf Inflow=1.76 cfs 3,729 cfPond IT1: INFILTRATION TRENCH 1 Discarded=0.08 cfs 551 cf Primary=1.64 cfs 3,107 cf Outflow=1.72 cfs 3,659 cf Peak Elev=23.50' Storage=297 cf Inflow=1.63 cfs 4,416 cfPond IT2: INFILTRATION TRENCH 2 Discarded=0.04 cfs 1,046 cf Primary=1.59 cfs 3,165 cf Outflow=1.63 cfs 4,211 cf Peak Elev=34.14' Storage=341 cf Inflow=0.65 cfs 2,191 cfPond IT3: INFILTRATION TRENCH 3 Discarded=0.05 cfs 1,242 cf Primary=0.60 cfs 727 cf Outflow=0.65 cfs 1,969 cf Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 7HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Inflow=1.35 cfs 2,939 cfPond SP1: Follins Pond Primary=1.35 cfs 2,939 cf Total Runoff Area = 344,120 sf Runoff Volume = 23,715 cf Average Runoff Depth = 0.83" 75.43% Pervious = 259,580 sf 24.57% Impervious = 84,540 sf Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 8HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.43 cfs @ 12.21 hrs, Volume= 2,017 cf, Depth= 0.57" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=42,470 sf Runoff Volume=2,017 cf Runoff Depth=0.57" Flow Length=625' Tc=16.2 min CN=31/98 0.43 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 9HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.17 cfs @ 12.15 hrs, Volume= 718 cf, Depth= 0.85" Routed to Pond IS1 : Infiltration System 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,620 30 Woods, Good, HSG A 10,180 47 Weighted Average 7,620 30 74.85% Pervious Area 2,560 98 25.15% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=10,180 sf Runoff Volume=718 cf Runoff Depth=0.85" Flow Length=235' Tc=11.5 min CN=30/98 0.17 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 10HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.09 cfs @ 12.07 hrs, Volume= 306 cf, Depth= 0.77" Routed to Pond IS2 : Infiltration System 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 740 98 Paved parking, HSG A 350 98 Unconnected roofs, HSG A 3,690 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 4,780 46 Weighted Average 3,690 30 77.20% Pervious Area 1,090 98 22.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA2: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=4,780 sf Runoff Volume=306 cf Runoff Depth=0.77" Tc=5.0 min CN=30/98 0.09 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 11HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2A: Runoff = 0.17 cfs @ 12.07 hrs, Volume= 564 cf, Depth= 1.10" Routed to Pond IT1 : INFILTRATION TRENCH 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 1,080 98 Paved parking, HSG A 930 98 Unconnected roofs, HSG A 4,130 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 6,140 52 Weighted Average 4,130 30 67.26% Pervious Area 2,010 98 32.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 min direct Subcatchment DA2A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=6,140 sf Runoff Volume=564 cf Runoff Depth=1.10" Tc=5.0 min CN=30/98 0.17 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 12HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2B: Runoff = 0.48 cfs @ 12.07 hrs, Volume= 1,602 cf, Depth= 0.93" Routed to Pond IT2 : INFILTRATION TRENCH 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 5,710 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 12,670 30 Woods, Good, HSG A 2,200 39 >75% Grass cover, Good, HSG A 20,580 50 Weighted Average 14,870 31 72.25% Pervious Area 5,710 98 27.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA2B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=20,580 sf Runoff Volume=1,602 cf Runoff Depth=0.93" Tc=5.0 min CN=31/98 0.48 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 13HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 0.65 cfs @ 12.07 hrs, Volume= 2,191 cf, Depth= 0.98" Routed to Pond IT3 : INFILTRATION TRENCH 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 4,210 98 Paved parking, HSG A 3,600 98 Unconnected roofs, HSG A 19,080 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 0 98 Water Surface, HSG A 26,890 50 Weighted Average 19,080 30 70.96% Pervious Area 7,810 98 29.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA3: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=26,890 sf Runoff Volume=2,191 cf Runoff Depth=0.98" Tc=5.0 min CN=30/98 0.65 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 14HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3A: Runoff = 0.31 cfs @ 12.26 hrs, Volume= 1,565 cf, Depth= 1.00" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 5,580 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 13,180 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 18,760 50 Weighted Average 13,180 30 70.26% Pervious Area 5,580 98 29.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 1.8 155 0.0800 1.41 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.7 225 0.0800 5.74 Shallow Concentrated Flow, Paved Kv= 20.3 fps 19.7 480 Total Subcatchment DA3A: 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 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=18,760 sf Runoff Volume=1,565 cf Runoff Depth=1.00" Flow Length=480' Tc=19.7 min CN=30/98 0.31 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 15HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3B: Runoff = 0.74 cfs @ 12.32 hrs, Volume= 4,107 cf, Depth= 0.68" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 8,650 98 Paved parking, HSG A 5,990 98 Unconnected roofs, HSG A 35,050 30 Woods, Good, HSG A 23,230 39 >75% Grass cover, Good, HSG A 72,920 47 Weighted Average 58,280 34 79.92% Pervious Area 14,640 98 20.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 495 Total Subcatchment DA3B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=72,920 sf Runoff Volume=4,107 cf Runoff Depth=0.68" Flow Length=495' Tc=24.2 min CN=34/98 0.74 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 16HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3C: Runoff = 2.48 cfs @ 12.17 hrs, Volume= 10,646 cf, Depth= 0.90" Routed to Pond C1 : CHAMBERS Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2yr Rainfall=3.60" Area (sf) CN Description 23,130 98 Paved parking, HSG A 14,820 98 Unconnected roofs, HSG A 99,540 30 Woods, Good, HSG A 3,910 39 >75% Grass cover, Good, HSG A 141,400 48 Weighted Average 103,450 30 73.16% Pervious Area 37,950 98 26.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 100 0.0800 0.14 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.1 10 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 12.7 235 Total Subcatchment DA3C: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Type III 24-hr 2yr Rainfall=3.60" Runoff Area=141,400 sf Runoff Volume=10,646 cf Runoff Depth=0.90" Flow Length=235' Tc=12.7 min CN=30/98 2.48 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 17HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond C1: CHAMBERS Inflow Area = 141,400 sf, 26.84% Impervious, Inflow Depth = 0.90" for 2yr event Inflow = 2.48 cfs @ 12.17 hrs, Volume= 10,646 cf Outflow = 0.37 cfs @ 11.64 hrs, Volume= 10,639 cf, Atten= 85%, Lag= 0.0 min Discarded = 0.37 cfs @ 11.64 hrs, Volume= 10,639 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT3 : INFILTRATION TRENCH 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 29.73' @ 12.81 hrs Surf.Area= 1,912 sf Storage= 3,205 cf Plug-Flow detention time= 53.9 min calculated for 10,638 cf (100% of inflow) Center-of-Mass det. time= 53.5 min ( 813.7 - 760.2 ) Volume Invert Avail.Storage Storage Description #1B 27.25' 2,581 cf 19.17'W x 99.75'L x 6.75'H Field B 12,905 cf Overall - 5,083 cf Embedded = 7,823 cf x 33.0% Voids #2B 28.00' 5,083 cf ADS_StormTech MC-7200 +Cap x 28 Inside #1 Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap 28 Chambers in 2 Rows Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf #3 27.00' 126 cf 4.00'D x 10.00'H Vertical Cone/Cylinder -Impervious #4 36.10' 327 cf Custom Stage Data (Prismatic) Listed below (Recalc) 8,117 cf Total Available Storage Storage Group B created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.10 100 0 0 36.25 400 37 37 36.30 600 25 63 36.35 10,000 265 327 Device Routing Invert Outlet Devices #1 Discarded 27.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 36.30'20.0' long x 5.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Discarded OutFlow Max=0.37 cfs @ 11.64 hrs HW=27.25' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.37 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=27.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 18HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS - Chamber Wizard Field B Chamber Model = ADS_StormTech MC-7200 +Cap (ADS StormTech® MC-7200 with cap volume) Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf 100.0" Wide + 6.0" Spacing = 106.0" C-C Row Spacing 14 Chambers/Row x 6.59' Long +2.73' Cap Length x 2 = 97.75' Row Length +12.0" End Stone x 2 = 99.75' Base Length 2 Rows x 100.0" Wide + 6.0" Spacing x 1 + 12.0" Side Stone x 2 = 19.17' Base Width 9.0" Stone Base + 60.0" Chamber Height + 12.0" Stone Cover = 6.75' Field Height 28 Chambers x 175.9 cf + 39.5 cf Cap Volume x 2 x 2 Rows = 5,082.5 cf Chamber Storage 12,905.2 cf Field - 5,082.5 cf Chambers = 7,822.6 cf Stone x 33.0% Voids = 2,581.5 cf Stone Storage Chamber Storage + Stone Storage = 7,664.0 cf = 0.176 af Overall Storage Efficiency = 59.4% Overall System Size = 99.75' x 19.17' x 6.75' 28 Chambers 478.0 cy Field 289.7 cy Stone Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 19HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=141,400 sf Peak Elev=29.73' Storage=3,205 cf 2.48 cfs 0.37 cfs0.37 cfs 0.00 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 20HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS1: Infiltration System 1 Inflow Area = 301,650 sf, 25.64% Impervious, Inflow Depth = 0.10" for 2yr event Inflow = 1.47 cfs @ 12.23 hrs, Volume= 2,589 cf Outflow = 1.15 cfs @ 12.43 hrs, Volume= 2,589 cf, Atten= 22%, Lag= 12.3 min Discarded = 0.06 cfs @ 11.87 hrs, Volume= 1,667 cf Primary = 1.09 cfs @ 12.43 hrs, Volume= 922 cf Routed to Pond SP1 : Follins Pond Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 13.60' @ 12.42 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 90.9 min calculated for 2,589 cf (100% of inflow) Center-of-Mass det. time= 90.9 min ( 842.9 - 752.0 ) Volume Invert Avail.Storage Storage Description #1 7.60' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 9.60' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 13.60'Automatic Storage Overflow (Discharged without head) #1 Discarded 7.60'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 13.55'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.87 hrs HW=7.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.43 hrs HW=13.60' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 21HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS1: Infiltration System 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=301,650 sf Peak Elev=13.60' Storage=999 cf 1.47 cfs 1.15 cfs 0.06 cfs 1.09 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 22HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS2: Infiltration System 2 Inflow Area = 291,470 sf, 25.66% Impervious, Inflow Depth = 0.14" for 2yr event Inflow = 1.73 cfs @ 12.09 hrs, Volume= 3,413 cf Outflow = 1.38 cfs @ 12.23 hrs, Volume= 3,413 cf, Atten= 20%, Lag= 8.4 min Discarded = 0.06 cfs @ 11.88 hrs, Volume= 1,542 cf Primary = 1.32 cfs @ 12.23 hrs, Volume= 1,871 cf Routed to Pond IS1 : Infiltration System 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.00' @ 12.22 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 76.0 min calculated for 3,412 cf (100% of inflow) Center-of-Mass det. time= 76.0 min ( 821.6 - 745.6 ) Volume Invert Avail.Storage Storage Description #1 11.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 13.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 17.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 16.95'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.88 hrs HW=11.10' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.23 hrs HW=17.00' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 23HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS2: Infiltration System 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=291,470 sf Peak Elev=17.00' Storage=999 cf 1.73 cfs 1.38 cfs 0.06 cfs 1.32 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 24HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS3: Infiltration System 3 Inflow Area = 259,970 sf, 25.38% Impervious, Inflow Depth = 0.30" for 2yr event Inflow = 1.24 cfs @ 12.27 hrs, Volume= 6,399 cf Outflow = 1.24 cfs @ 12.27 hrs, Volume= 6,399 cf, Atten= 0%, Lag= 0.3 min Discarded = 0.06 cfs @ 9.26 hrs, Volume= 3,584 cf Primary = 1.19 cfs @ 12.27 hrs, Volume= 2,814 cf Routed to Pond IT2 : INFILTRATION TRENCH 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 30.87' @ 12.27 hrs Surf.Area= 288 sf Storage= 973 cf Plug-Flow detention time= 83.6 min calculated for 6,398 cf (100% of inflow) Center-of-Mass det. time= 83.6 min ( 848.7 - 765.1 ) Volume Invert Avail.Storage Storage Description #1 25.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 27.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 31.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 25.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 30.75'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 9.26 hrs HW=25.06' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=1.17 cfs @ 12.27 hrs HW=30.87' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 1.17 cfs @ 0.97 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 25HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS3: Infiltration System 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=259,970 sf Peak Elev=30.87' Storage=973 cf 1.24 cfs1.24 cfs 0.06 cfs 1.19 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 26HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT1: INFILTRATION TRENCH 1 Inflow Area = 286,690 sf, 25.71% Impervious, Inflow Depth = 0.16" for 2yr event Inflow = 1.76 cfs @ 12.08 hrs, Volume= 3,729 cf Outflow = 1.72 cfs @ 12.09 hrs, Volume= 3,659 cf, Atten= 2%, Lag= 0.6 min Discarded = 0.08 cfs @ 12.09 hrs, Volume= 551 cf Primary = 1.64 cfs @ 12.09 hrs, Volume= 3,107 cf Routed to Pond IS2 : Infiltration System 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 20.69' @ 12.09 hrs Surf.Area= 426 sf Storage= 134 cf Plug-Flow detention time= 16.1 min calculated for 3,658 cf (98% of inflow) Center-of-Mass det. time= 8.3 min ( 756.1 - 747.8 ) Volume Invert Avail.Storage Storage Description #1 16.50' 98 cf Custom Stage Data (Prismatic) Listed below (Recalc) 298 cf Overall x 33.0% Voids #2 20.00' 25 cf 4.00'D x 2.00'H Vertical Cone/Cylinder -Impervious #3 20.53' 237 cf Custom Stage Data (Prismatic) Listed below (Recalc) 361 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 16.50 85 0 0 20.00 85 298 298 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 20.53 10 0 0 21.00 1,000 237 237 Device Routing Invert Outlet Devices #1 Discarded 16.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 19.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 20.53'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.08 cfs @ 12.09 hrs HW=20.69' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) 2=Orifice/Grate (Passes 0.08 cfs of 1.13 cfs potential flow) Primary OutFlow Max=1.63 cfs @ 12.09 hrs HW=20.69' (Free Discharge) 3=Orifice/Grate (Weir Controls 1.63 cfs @ 1.30 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 27HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT1: INFILTRATION TRENCH 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=286,690 sf Peak Elev=20.69' Storage=134 cf 1.76 cfs 1.72 cfs 0.08 cfs 1.64 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 28HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT2: INFILTRATION TRENCH 2 [88] Warning: Qout>Qin may require smaller dt or Finer Routing Inflow Area = 280,550 sf, 25.55% Impervious, Inflow Depth = 0.19" for 2yr event Inflow = 1.63 cfs @ 12.08 hrs, Volume= 4,416 cf Outflow = 1.63 cfs @ 12.08 hrs, Volume= 4,211 cf, Atten= 0%, Lag= 0.0 min Discarded = 0.04 cfs @ 11.36 hrs, Volume= 1,046 cf Primary = 1.59 cfs @ 12.08 hrs, Volume= 3,165 cf Routed to Pond IT1 : INFILTRATION TRENCH 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 23.50' @ 12.08 hrs Surf.Area= 212 sf Storage= 297 cf Plug-Flow detention time= 40.5 min calculated for 4,210 cf (95% of inflow) Center-of-Mass det. time= 21.2 min ( 775.6 - 754.4 ) Volume Invert Avail.Storage Storage Description #1 19.25' 245 cf Custom Stage Data (Prismatic) Listed below (Recalc) 742 cf Overall x 33.0% Voids #2 19.35' 63 cf 4.00'D x 5.00'H Vertical Cone/Cylinder -Impervious 308 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 19.25 212 0 0 22.75 212 742 742 Device Routing Invert Outlet Devices #0 Primary 24.35'Automatic Storage Overflow (Discharged without head) #1 Discarded 19.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 21.75'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 23.35'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.04 cfs @ 11.36 hrs HW=21.90' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) 2=Orifice/Grate (Passes 0.04 cfs of 0.07 cfs potential flow) Primary OutFlow Max=1.58 cfs @ 12.08 hrs HW=23.50' (Free Discharge) 3=Broad-Crested Rectangular Weir (Weir Controls 1.58 cfs @ 1.07 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 29HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT2: INFILTRATION TRENCH 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=280,550 sf Peak Elev=23.50' Storage=297 cf 1.63 cfs1.63 cfs 0.04 cfs 1.59 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 30HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT3: INFILTRATION TRENCH 3 Inflow Area = 168,290 sf, 27.19% Impervious, Inflow Depth = 0.16" for 2yr event Inflow = 0.65 cfs @ 12.07 hrs, Volume= 2,191 cf Outflow = 0.65 cfs @ 12.07 hrs, Volume= 1,969 cf, Atten= 0%, Lag= 0.1 min Discarded = 0.05 cfs @ 11.13 hrs, Volume= 1,242 cf Primary = 0.60 cfs @ 12.07 hrs, Volume= 727 cf Routed to Pond IS3 : Infiltration System 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 34.14' @ 12.07 hrs Surf.Area= 240 sf Storage= 341 cf Plug-Flow detention time= 101.8 min calculated for 1,969 cf (90% of inflow) Center-of-Mass det. time= 51.8 min ( 804.9 - 753.1 ) Volume Invert Avail.Storage Storage Description #1 28.50' 277 cf Custom Stage Data (Prismatic) Listed below (Recalc) 840 cf Overall x 33.0% Voids #2 29.10' 101 cf 4.00'D x 8.00'H Vertical Cone/Cylinder -Impervious 378 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 28.50 240 0 0 32.00 240 840 840 Device Routing Invert Outlet Devices #0 Primary 37.10'Automatic Storage Overflow (Discharged without head) #1 Discarded 28.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 31.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 35.40'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Primary 33.70'12.0" Round Culvert L= 10.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 33.70' / 31.00' S= 0.2700 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.05 cfs @ 11.13 hrs HW=31.17' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Orifice/Grate (Passes 0.05 cfs of 0.08 cfs potential flow) Primary OutFlow Max=0.60 cfs @ 12.07 hrs HW=34.14' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) 4=Culvert (Inlet Controls 0.60 cfs @ 1.79 fps) Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 31HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT3: INFILTRATION TRENCH 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=168,290 sf Peak Elev=34.14' Storage=341 cf 0.65 cfs0.65 cfs 0.05 cfs 0.60 cfs Type III 24-hr 2yr Rainfall=3.60"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 32HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 344,120 sf, 24.57% Impervious, Inflow Depth = 0.10" for 2yr event Inflow = 1.35 cfs @ 12.43 hrs, Volume= 2,939 cf Primary = 1.35 cfs @ 12.43 hrs, Volume= 2,939 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=344,120 sf 1.35 cfs1.35 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 33HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=0.88"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.63 cfs 3,101 cf Runoff Area=10,180 sf 25.15% Impervious Runoff Depth=1.28"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.25 cfs 1,083 cf Runoff Area=4,780 sf 22.80% Impervious Runoff Depth=1.16"Subcatchment DA2: Tc=5.0 min CN=30/98 Runoff=0.13 cfs 462 cf Runoff Area=6,140 sf 32.74% Impervious Runoff Depth=1.66"Subcatchment DA2A: Tc=5.0 min CN=30/98 Runoff=0.25 cfs 848 cf Runoff Area=20,580 sf 27.75% Impervious Runoff Depth=1.42"Subcatchment DA2B: Tc=5.0 min CN=31/98 Runoff=0.70 cfs 2,431 cf Runoff Area=26,890 sf 29.04% Impervious Runoff Depth=1.47"Subcatchment DA3: Tc=5.0 min CN=30/98 Runoff=0.96 cfs 3,300 cf Runoff Area=18,760 sf 29.74% Impervious Runoff Depth=1.51"Subcatchment DA3A: Flow Length=480' Tc=19.7 min CN=30/98 Runoff=0.45 cfs 2,357 cf Runoff Area=72,920 sf 20.08% Impervious Runoff Depth=1.08"Subcatchment DA3B: Flow Length=495' Tc=24.2 min CN=34/98 Runoff=1.09 cfs 6,590 cf Runoff Area=141,400 sf 26.84% Impervious Runoff Depth=1.36"Subcatchment DA3C: Flow Length=235' Tc=12.7 min CN=30/98 Runoff=3.65 cfs 16,047 cf Peak Elev=31.49' Storage=5,641 cf Inflow=3.65 cfs 16,047 cfPond C1: CHAMBERS Discarded=0.37 cfs 16,043 cf Primary=0.00 cfs 0 cf Outflow=0.37 cfs 16,043 cf Peak Elev=13.60' Storage=999 cf Inflow=2.81 cfs 6,054 cfPond IS1: Infiltration System 1 Discarded=0.06 cfs 2,001 cf Primary=2.85 cfs 4,053 cf Outflow=2.90 cfs 6,054 cf Peak Elev=17.00' Storage=999 cf Inflow=2.64 cfs 6,887 cfPond IS2: Infiltration System 2 Discarded=0.06 cfs 1,917 cf Primary=2.58 cfs 4,971 cf Outflow=2.64 cfs 6,887 cf Peak Elev=30.91' Storage=981 cf Inflow=1.85 cfs 10,303 cfPond IS3: Infiltration System 3 Discarded=0.06 cfs 4,477 cf Primary=1.80 cfs 5,826 cf Outflow=1.85 cfs 10,303 cf Peak Elev=20.74' Storage=156 cf Inflow=2.62 cfs 7,368 cfPond IT1: INFILTRATION TRENCH 1 Discarded=0.10 cfs 873 cf Primary=2.51 cfs 6,425 cf Outflow=2.61 cfs 7,298 cf Peak Elev=23.54' Storage=298 cf Inflow=2.42 cfs 8,257 cfPond IT2: INFILTRATION TRENCH 2 Discarded=0.04 cfs 1,534 cf Primary=2.38 cfs 6,520 cf Outflow=2.42 cfs 8,054 cf Peak Elev=34.26' Storage=342 cf Inflow=0.96 cfs 3,300 cfPond IT3: INFILTRATION TRENCH 3 Discarded=0.05 cfs 1,721 cf Primary=0.91 cfs 1,356 cf Outflow=0.96 cfs 3,078 cf Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 34HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Inflow=3.17 cfs 7,154 cfPond SP1: Follins Pond Primary=3.17 cfs 7,154 cf Total Runoff Area = 344,120 sf Runoff Volume = 36,218 cf Average Runoff Depth = 1.26" 75.43% Pervious = 259,580 sf 24.57% Impervious = 84,540 sf Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 35HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.63 cfs @ 12.21 hrs, Volume= 3,101 cf, Depth= 0.88" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=42,470 sf Runoff Volume=3,101 cf Runoff Depth=0.88" Flow Length=625' Tc=16.2 min CN=31/98 0.63 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 36HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.25 cfs @ 12.15 hrs, Volume= 1,083 cf, Depth= 1.28" Routed to Pond IS1 : Infiltration System 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,620 30 Woods, Good, HSG A 10,180 47 Weighted Average 7,620 30 74.85% Pervious Area 2,560 98 25.15% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=10,180 sf Runoff Volume=1,083 cf Runoff Depth=1.28" Flow Length=235' Tc=11.5 min CN=30/98 0.25 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 37HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.13 cfs @ 12.07 hrs, Volume= 462 cf, Depth= 1.16" Routed to Pond IS2 : Infiltration System 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 740 98 Paved parking, HSG A 350 98 Unconnected roofs, HSG A 3,690 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 4,780 46 Weighted Average 3,690 30 77.20% Pervious Area 1,090 98 22.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA2: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=4,780 sf Runoff Volume=462 cf Runoff Depth=1.16" Tc=5.0 min CN=30/98 0.13 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 38HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2A: Runoff = 0.25 cfs @ 12.07 hrs, Volume= 848 cf, Depth= 1.66" Routed to Pond IT1 : INFILTRATION TRENCH 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 1,080 98 Paved parking, HSG A 930 98 Unconnected roofs, HSG A 4,130 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 6,140 52 Weighted Average 4,130 30 67.26% Pervious Area 2,010 98 32.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 min direct Subcatchment DA2A: 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 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=6,140 sf Runoff Volume=848 cf Runoff Depth=1.66" Tc=5.0 min CN=30/98 0.25 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 39HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2B: Runoff = 0.70 cfs @ 12.07 hrs, Volume= 2,431 cf, Depth= 1.42" Routed to Pond IT2 : INFILTRATION TRENCH 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 5,710 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 12,670 30 Woods, Good, HSG A 2,200 39 >75% Grass cover, Good, HSG A 20,580 50 Weighted Average 14,870 31 72.25% Pervious Area 5,710 98 27.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA2B: 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 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=20,580 sf Runoff Volume=2,431 cf Runoff Depth=1.42" Tc=5.0 min CN=31/98 0.70 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 40HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 0.96 cfs @ 12.07 hrs, Volume= 3,300 cf, Depth= 1.47" Routed to Pond IT3 : INFILTRATION TRENCH 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 4,210 98 Paved parking, HSG A 3,600 98 Unconnected roofs, HSG A 19,080 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 0 98 Water Surface, HSG A 26,890 50 Weighted Average 19,080 30 70.96% Pervious Area 7,810 98 29.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA3: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=26,890 sf Runoff Volume=3,300 cf Runoff Depth=1.47" Tc=5.0 min CN=30/98 0.96 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 41HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3A: Runoff = 0.45 cfs @ 12.26 hrs, Volume= 2,357 cf, Depth= 1.51" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 5,580 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 13,180 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 18,760 50 Weighted Average 13,180 30 70.26% Pervious Area 5,580 98 29.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 1.8 155 0.0800 1.41 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.7 225 0.0800 5.74 Shallow Concentrated Flow, Paved Kv= 20.3 fps 19.7 480 Total Subcatchment DA3A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=18,760 sf Runoff Volume=2,357 cf Runoff Depth=1.51" Flow Length=480' Tc=19.7 min CN=30/98 0.45 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 42HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3B: Runoff = 1.09 cfs @ 12.31 hrs, Volume= 6,590 cf, Depth= 1.08" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 8,650 98 Paved parking, HSG A 5,990 98 Unconnected roofs, HSG A 35,050 30 Woods, Good, HSG A 23,230 39 >75% Grass cover, Good, HSG A 72,920 47 Weighted Average 58,280 34 79.92% Pervious Area 14,640 98 20.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 495 Total Subcatchment DA3B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=72,920 sf Runoff Volume=6,590 cf Runoff Depth=1.08" Flow Length=495' Tc=24.2 min CN=34/98 1.09 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 43HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3C: Runoff = 3.65 cfs @ 12.17 hrs, Volume= 16,047 cf, Depth= 1.36" Routed to Pond C1 : CHAMBERS Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10yr Rainfall=5.27" Area (sf) CN Description 23,130 98 Paved parking, HSG A 14,820 98 Unconnected roofs, HSG A 99,540 30 Woods, Good, HSG A 3,910 39 >75% Grass cover, Good, HSG A 141,400 48 Weighted Average 103,450 30 73.16% Pervious Area 37,950 98 26.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 100 0.0800 0.14 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.1 10 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 12.7 235 Total Subcatchment DA3C: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)4 3 2 1 0 Type III 24-hr 10yr Rainfall=5.27" Runoff Area=141,400 sf Runoff Volume=16,047 cf Runoff Depth=1.36" Flow Length=235' Tc=12.7 min CN=30/98 3.65 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 44HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond C1: CHAMBERS Inflow Area = 141,400 sf, 26.84% Impervious, Inflow Depth = 1.36" for 10yr event Inflow = 3.65 cfs @ 12.17 hrs, Volume= 16,047 cf Outflow = 0.37 cfs @ 11.27 hrs, Volume= 16,043 cf, Atten= 90%, Lag= 0.0 min Discarded = 0.37 cfs @ 11.27 hrs, Volume= 16,043 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT3 : INFILTRATION TRENCH 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 31.49' @ 13.14 hrs Surf.Area= 1,912 sf Storage= 5,641 cf Plug-Flow detention time= 107.1 min calculated for 16,043 cf (100% of inflow) Center-of-Mass det. time= 106.9 min ( 864.3 - 757.4 ) Volume Invert Avail.Storage Storage Description #1B 27.25' 2,581 cf 19.17'W x 99.75'L x 6.75'H Field B 12,905 cf Overall - 5,083 cf Embedded = 7,823 cf x 33.0% Voids #2B 28.00' 5,083 cf ADS_StormTech MC-7200 +Cap x 28 Inside #1 Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap 28 Chambers in 2 Rows Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf #3 27.00' 126 cf 4.00'D x 10.00'H Vertical Cone/Cylinder -Impervious #4 36.10' 327 cf Custom Stage Data (Prismatic) Listed below (Recalc) 8,117 cf Total Available Storage Storage Group B created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.10 100 0 0 36.25 400 37 37 36.30 600 25 63 36.35 10,000 265 327 Device Routing Invert Outlet Devices #1 Discarded 27.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 36.30'20.0' long x 5.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Discarded OutFlow Max=0.37 cfs @ 11.27 hrs HW=27.25' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.37 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=27.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 45HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS - Chamber Wizard Field B Chamber Model = ADS_StormTech MC-7200 +Cap (ADS StormTech® MC-7200 with cap volume) Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf 100.0" Wide + 6.0" Spacing = 106.0" C-C Row Spacing 14 Chambers/Row x 6.59' Long +2.73' Cap Length x 2 = 97.75' Row Length +12.0" End Stone x 2 = 99.75' Base Length 2 Rows x 100.0" Wide + 6.0" Spacing x 1 + 12.0" Side Stone x 2 = 19.17' Base Width 9.0" Stone Base + 60.0" Chamber Height + 12.0" Stone Cover = 6.75' Field Height 28 Chambers x 175.9 cf + 39.5 cf Cap Volume x 2 x 2 Rows = 5,082.5 cf Chamber Storage 12,905.2 cf Field - 5,082.5 cf Chambers = 7,822.6 cf Stone x 33.0% Voids = 2,581.5 cf Stone Storage Chamber Storage + Stone Storage = 7,664.0 cf = 0.176 af Overall Storage Efficiency = 59.4% Overall System Size = 99.75' x 19.17' x 6.75' 28 Chambers 478.0 cy Field 289.7 cy Stone Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 46HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)4 3 2 1 0 Inflow Area=141,400 sf Peak Elev=31.49' Storage=5,641 cf 3.65 cfs 0.37 cfs0.37 cfs 0.00 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 47HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS1: Infiltration System 1 [88] Warning: Qout>Qin may require smaller dt or Finer Routing Inflow Area = 301,650 sf, 25.64% Impervious, Inflow Depth = 0.24" for 10yr event Inflow = 2.81 cfs @ 12.10 hrs, Volume= 6,054 cf Outflow = 2.90 cfs @ 12.14 hrs, Volume= 6,054 cf, Atten= 0%, Lag= 2.8 min Discarded = 0.06 cfs @ 11.76 hrs, Volume= 2,001 cf Primary = 2.85 cfs @ 12.14 hrs, Volume= 4,053 cf Routed to Pond SP1 : Follins Pond Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 13.60' @ 12.13 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 51.1 min calculated for 6,053 cf (100% of inflow) Center-of-Mass det. time= 51.1 min ( 799.4 - 748.3 ) Volume Invert Avail.Storage Storage Description #1 7.60' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 9.60' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 13.60'Automatic Storage Overflow (Discharged without head) #1 Discarded 7.60'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 13.55'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.76 hrs HW=7.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.14 hrs HW=13.60' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 48HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS1: Infiltration System 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=301,650 sf Peak Elev=13.60' Storage=999 cf 2.81 cfs2.90 cfs 0.06 cfs 2.85 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 49HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS2: Infiltration System 2 Inflow Area = 291,470 sf, 25.66% Impervious, Inflow Depth = 0.28" for 10yr event Inflow = 2.64 cfs @ 12.09 hrs, Volume= 6,887 cf Outflow = 2.64 cfs @ 12.09 hrs, Volume= 6,887 cf, Atten= 0%, Lag= 0.3 min Discarded = 0.06 cfs @ 11.70 hrs, Volume= 1,917 cf Primary = 2.58 cfs @ 12.09 hrs, Volume= 4,971 cf Routed to Pond IS1 : Infiltration System 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.00' @ 12.03 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 52.7 min calculated for 6,887 cf (100% of inflow) Center-of-Mass det. time= 52.7 min ( 801.3 - 748.6 ) Volume Invert Avail.Storage Storage Description #1 11.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 13.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 17.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 16.95'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.70 hrs HW=11.07' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.09 hrs HW=17.00' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 50HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS2: Infiltration System 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=291,470 sf Peak Elev=17.00' Storage=999 cf 2.64 cfs2.64 cfs 0.06 cfs 2.58 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 51HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS3: Infiltration System 3 Inflow Area = 259,970 sf, 25.38% Impervious, Inflow Depth = 0.48" for 10yr event Inflow = 1.85 cfs @ 12.27 hrs, Volume= 10,303 cf Outflow = 1.85 cfs @ 12.27 hrs, Volume= 10,303 cf, Atten= 0%, Lag= 0.3 min Discarded = 0.06 cfs @ 8.05 hrs, Volume= 4,477 cf Primary = 1.80 cfs @ 12.27 hrs, Volume= 5,826 cf Routed to Pond IT2 : INFILTRATION TRENCH 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 30.91' @ 12.27 hrs Surf.Area= 288 sf Storage= 981 cf Plug-Flow detention time= 76.1 min calculated for 10,302 cf (100% of inflow) Center-of-Mass det. time= 76.1 min ( 850.2 - 774.1 ) Volume Invert Avail.Storage Storage Description #1 25.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 27.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 31.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 25.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 30.75'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 8.05 hrs HW=25.06' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=1.77 cfs @ 12.27 hrs HW=30.91' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 1.77 cfs @ 1.12 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 52HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS3: Infiltration System 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=259,970 sf Peak Elev=30.91' Storage=981 cf 1.85 cfs1.85 cfs 0.06 cfs 1.80 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 53HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT1: INFILTRATION TRENCH 1 Inflow Area = 286,690 sf, 25.71% Impervious, Inflow Depth = 0.31" for 10yr event Inflow = 2.62 cfs @ 12.08 hrs, Volume= 7,368 cf Outflow = 2.61 cfs @ 12.09 hrs, Volume= 7,298 cf, Atten= 0%, Lag= 0.5 min Discarded = 0.10 cfs @ 12.09 hrs, Volume= 873 cf Primary = 2.51 cfs @ 12.09 hrs, Volume= 6,425 cf Routed to Pond IS2 : Infiltration System 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 20.74' @ 12.09 hrs Surf.Area= 536 sf Storage= 156 cf Plug-Flow detention time= 10.5 min calculated for 7,298 cf (99% of inflow) Center-of-Mass det. time= 5.8 min ( 756.9 - 751.2 ) Volume Invert Avail.Storage Storage Description #1 16.50' 98 cf Custom Stage Data (Prismatic) Listed below (Recalc) 298 cf Overall x 33.0% Voids #2 20.00' 25 cf 4.00'D x 2.00'H Vertical Cone/Cylinder -Impervious #3 20.53' 237 cf Custom Stage Data (Prismatic) Listed below (Recalc) 361 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 16.50 85 0 0 20.00 85 298 298 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 20.53 10 0 0 21.00 1,000 237 237 Device Routing Invert Outlet Devices #1 Discarded 16.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 19.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 20.53'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.10 cfs @ 12.09 hrs HW=20.74' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.10 cfs) 2=Orifice/Grate (Passes 0.10 cfs of 1.15 cfs potential flow) Primary OutFlow Max=2.50 cfs @ 12.09 hrs HW=20.74' (Free Discharge) 3=Orifice/Grate (Weir Controls 2.50 cfs @ 1.50 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 54HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT1: INFILTRATION TRENCH 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=286,690 sf Peak Elev=20.74' Storage=156 cf 2.62 cfs2.61 cfs 0.10 cfs 2.51 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 55HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT2: INFILTRATION TRENCH 2 Inflow Area = 280,550 sf, 25.55% Impervious, Inflow Depth = 0.35" for 10yr event Inflow = 2.42 cfs @ 12.09 hrs, Volume= 8,257 cf Outflow = 2.42 cfs @ 12.09 hrs, Volume= 8,054 cf, Atten= 0%, Lag= 0.0 min Discarded = 0.04 cfs @ 10.65 hrs, Volume= 1,534 cf Primary = 2.38 cfs @ 12.09 hrs, Volume= 6,520 cf Routed to Pond IT1 : INFILTRATION TRENCH 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 23.54' @ 12.09 hrs Surf.Area= 212 sf Storage= 298 cf Plug-Flow detention time= 27.4 min calculated for 8,053 cf (98% of inflow) Center-of-Mass det. time= 15.1 min ( 774.5 - 759.4 ) Volume Invert Avail.Storage Storage Description #1 19.25' 245 cf Custom Stage Data (Prismatic) Listed below (Recalc) 742 cf Overall x 33.0% Voids #2 19.35' 63 cf 4.00'D x 5.00'H Vertical Cone/Cylinder -Impervious 308 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 19.25 212 0 0 22.75 212 742 742 Device Routing Invert Outlet Devices #0 Primary 24.35'Automatic Storage Overflow (Discharged without head) #1 Discarded 19.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 21.75'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 23.35'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.04 cfs @ 10.65 hrs HW=21.90' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) 2=Orifice/Grate (Passes 0.04 cfs of 0.07 cfs potential flow) Primary OutFlow Max=2.36 cfs @ 12.09 hrs HW=23.54' (Free Discharge) 3=Broad-Crested Rectangular Weir (Weir Controls 2.36 cfs @ 1.23 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 56HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT2: INFILTRATION TRENCH 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=280,550 sf Peak Elev=23.54' Storage=298 cf 2.42 cfs2.42 cfs 0.04 cfs 2.38 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 57HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT3: INFILTRATION TRENCH 3 Inflow Area = 168,290 sf, 27.19% Impervious, Inflow Depth = 0.24" for 10yr event Inflow = 0.96 cfs @ 12.07 hrs, Volume= 3,300 cf Outflow = 0.96 cfs @ 12.07 hrs, Volume= 3,078 cf, Atten= 0%, Lag= 0.1 min Discarded = 0.05 cfs @ 10.18 hrs, Volume= 1,721 cf Primary = 0.91 cfs @ 12.07 hrs, Volume= 1,356 cf Routed to Pond IS3 : Infiltration System 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 34.26' @ 12.07 hrs Surf.Area= 240 sf Storage= 342 cf Plug-Flow detention time= 81.5 min calculated for 3,078 cf (93% of inflow) Center-of-Mass det. time= 43.5 min ( 793.3 - 749.8 ) Volume Invert Avail.Storage Storage Description #1 28.50' 277 cf Custom Stage Data (Prismatic) Listed below (Recalc) 840 cf Overall x 33.0% Voids #2 29.10' 101 cf 4.00'D x 8.00'H Vertical Cone/Cylinder -Impervious 378 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 28.50 240 0 0 32.00 240 840 840 Device Routing Invert Outlet Devices #0 Primary 37.10'Automatic Storage Overflow (Discharged without head) #1 Discarded 28.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 31.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 35.40'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Primary 33.70'12.0" Round Culvert L= 10.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 33.70' / 31.00' S= 0.2700 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.05 cfs @ 10.18 hrs HW=31.17' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Orifice/Grate (Passes 0.05 cfs of 0.08 cfs potential flow) Primary OutFlow Max=0.91 cfs @ 12.07 hrs HW=34.26' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) 4=Culvert (Inlet Controls 0.91 cfs @ 2.01 fps) Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 58HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT3: INFILTRATION TRENCH 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=168,290 sf Peak Elev=34.26' Storage=342 cf 0.96 cfs0.96 cfs 0.05 cfs 0.91 cfs Type III 24-hr 10yr Rainfall=5.27"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 59HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 344,120 sf, 24.57% Impervious, Inflow Depth = 0.25" for 10yr event Inflow = 3.17 cfs @ 12.14 hrs, Volume= 7,154 cf Primary = 3.17 cfs @ 12.14 hrs, Volume= 7,154 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=344,120 sf 3.17 cfs3.17 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 60HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=1.21"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.78 cfs 4,291 cf Runoff Area=10,180 sf 25.15% Impervious Runoff Depth=1.69"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.32 cfs 1,430 cf Runoff Area=4,780 sf 22.80% Impervious Runoff Depth=1.54"Subcatchment DA2: Tc=5.0 min CN=30/98 Runoff=0.17 cfs 614 cf Runoff Area=6,140 sf 32.74% Impervious Runoff Depth=2.15"Subcatchment DA2A: Tc=5.0 min CN=30/98 Runoff=0.31 cfs 1,101 cf Runoff Area=20,580 sf 27.75% Impervious Runoff Depth=1.87"Subcatchment DA2B: Tc=5.0 min CN=31/98 Runoff=0.87 cfs 3,214 cf Runoff Area=26,890 sf 29.04% Impervious Runoff Depth=1.93"Subcatchment DA3: Tc=5.0 min CN=30/98 Runoff=1.19 cfs 4,314 cf Runoff Area=18,760 sf 29.74% Impervious Runoff Depth=1.97"Subcatchment DA3A: Flow Length=480' Tc=19.7 min CN=30/98 Runoff=0.56 cfs 3,077 cf Runoff Area=72,920 sf 20.08% Impervious Runoff Depth=1.52"Subcatchment DA3B: Flow Length=495' Tc=24.2 min CN=34/98 Runoff=1.36 cfs 9,219 cf Runoff Area=141,400 sf 26.84% Impervious Runoff Depth=1.79"Subcatchment DA3C: Flow Length=235' Tc=12.7 min CN=30/98 Runoff=4.53 cfs 21,084 cf Peak Elev=36.07' Storage=7,778 cf Inflow=4.53 cfs 21,084 cfPond C1: CHAMBERS Discarded=0.38 cfs 21,085 cf Primary=0.00 cfs 0 cf Outflow=0.38 cfs 21,085 cf Peak Elev=13.60' Storage=999 cf Inflow=3.54 cfs 9,792 cfPond IS1: Infiltration System 1 Discarded=0.06 cfs 2,416 cf Primary=3.48 cfs 7,376 cf Outflow=3.54 cfs 9,792 cf Peak Elev=17.00' Storage=999 cf Inflow=3.32 cfs 10,699 cfPond IS2: Infiltration System 2 Discarded=0.06 cfs 2,337 cf Primary=3.26 cfs 8,362 cf Outflow=3.32 cfs 10,699 cf Peak Elev=30.94' Storage=986 cf Inflow=2.31 cfs 14,257 cfPond IS3: Infiltration System 3 Discarded=0.06 cfs 4,961 cf Primary=2.26 cfs 9,296 cf Outflow=2.31 cfs 14,257 cf Peak Elev=20.77' Storage=173 cf Inflow=3.29 cfs 11,374 cfPond IT1: INFILTRATION TRENCH 1 Discarded=0.12 cfs 1,218 cf Primary=3.16 cfs 10,085 cf Outflow=3.28 cfs 11,303 cf Peak Elev=23.57' Storage=298 cf Inflow=3.03 cfs 12,509 cfPond IT2: INFILTRATION TRENCH 2 Discarded=0.04 cfs 2,033 cf Primary=2.99 cfs 10,272 cf Outflow=3.03 cfs 12,306 cf Peak Elev=34.34' Storage=343 cf Inflow=1.19 cfs 4,314 cfPond IT3: INFILTRATION TRENCH 3 Discarded=0.05 cfs 2,130 cf Primary=1.14 cfs 1,962 cf Outflow=1.19 cfs 4,092 cf Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 61HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Inflow=4.09 cfs 11,667 cfPond SP1: Follins Pond Primary=4.09 cfs 11,667 cf Total Runoff Area = 344,120 sf Runoff Volume = 48,343 cf Average Runoff Depth = 1.69" 75.43% Pervious = 259,580 sf 24.57% Impervious = 84,540 sf Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 62HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.78 cfs @ 12.21 hrs, Volume= 4,291 cf, Depth= 1.21" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=42,470 sf Runoff Volume=4,291 cf Runoff Depth=1.21" Flow Length=625' Tc=16.2 min CN=31/98 0.78 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 63HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.32 cfs @ 12.15 hrs, Volume= 1,430 cf, Depth= 1.69" Routed to Pond IS1 : Infiltration System 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,620 30 Woods, Good, HSG A 10,180 47 Weighted Average 7,620 30 74.85% Pervious Area 2,560 98 25.15% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: 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 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=10,180 sf Runoff Volume=1,430 cf Runoff Depth=1.69" Flow Length=235' Tc=11.5 min CN=30/98 0.32 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 64HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.17 cfs @ 12.07 hrs, Volume= 614 cf, Depth= 1.54" Routed to Pond IS2 : Infiltration System 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 740 98 Paved parking, HSG A 350 98 Unconnected roofs, HSG A 3,690 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 4,780 46 Weighted Average 3,690 30 77.20% Pervious Area 1,090 98 22.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA2: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=4,780 sf Runoff Volume=614 cf Runoff Depth=1.54" Tc=5.0 min CN=30/98 0.17 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 65HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2A: Runoff = 0.31 cfs @ 12.07 hrs, Volume= 1,101 cf, Depth= 2.15" Routed to Pond IT1 : INFILTRATION TRENCH 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 1,080 98 Paved parking, HSG A 930 98 Unconnected roofs, HSG A 4,130 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 6,140 52 Weighted Average 4,130 30 67.26% Pervious Area 2,010 98 32.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 min direct Subcatchment DA2A: 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 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=6,140 sf Runoff Volume=1,101 cf Runoff Depth=2.15" Tc=5.0 min CN=30/98 0.31 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 66HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2B: Runoff = 0.87 cfs @ 12.07 hrs, Volume= 3,214 cf, Depth= 1.87" Routed to Pond IT2 : INFILTRATION TRENCH 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 5,710 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 12,670 30 Woods, Good, HSG A 2,200 39 >75% Grass cover, Good, HSG A 20,580 50 Weighted Average 14,870 31 72.25% Pervious Area 5,710 98 27.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA2B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=20,580 sf Runoff Volume=3,214 cf Runoff Depth=1.87" Tc=5.0 min CN=31/98 0.87 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 67HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 1.19 cfs @ 12.07 hrs, Volume= 4,314 cf, Depth= 1.93" Routed to Pond IT3 : INFILTRATION TRENCH 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 4,210 98 Paved parking, HSG A 3,600 98 Unconnected roofs, HSG A 19,080 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 0 98 Water Surface, HSG A 26,890 50 Weighted Average 19,080 30 70.96% Pervious Area 7,810 98 29.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA3: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=26,890 sf Runoff Volume=4,314 cf Runoff Depth=1.93" Tc=5.0 min CN=30/98 1.19 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 68HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3A: Runoff = 0.56 cfs @ 12.26 hrs, Volume= 3,077 cf, Depth= 1.97" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 5,580 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 13,180 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 18,760 50 Weighted Average 13,180 30 70.26% Pervious Area 5,580 98 29.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 1.8 155 0.0800 1.41 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.7 225 0.0800 5.74 Shallow Concentrated Flow, Paved Kv= 20.3 fps 19.7 480 Total Subcatchment DA3A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=18,760 sf Runoff Volume=3,077 cf Runoff Depth=1.97" Flow Length=480' Tc=19.7 min CN=30/98 0.56 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 69HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3B: Runoff = 1.36 cfs @ 12.32 hrs, Volume= 9,219 cf, Depth= 1.52" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 8,650 98 Paved parking, HSG A 5,990 98 Unconnected roofs, HSG A 35,050 30 Woods, Good, HSG A 23,230 39 >75% Grass cover, Good, HSG A 72,920 47 Weighted Average 58,280 34 79.92% Pervious Area 14,640 98 20.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 495 Total Subcatchment DA3B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=72,920 sf Runoff Volume=9,219 cf Runoff Depth=1.52" Flow Length=495' Tc=24.2 min CN=34/98 1.36 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 70HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3C: Runoff = 4.53 cfs @ 12.17 hrs, Volume= 21,084 cf, Depth= 1.79" Routed to Pond C1 : CHAMBERS Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25yr Rainfall=6.53" Area (sf) CN Description 23,130 98 Paved parking, HSG A 14,820 98 Unconnected roofs, HSG A 99,540 30 Woods, Good, HSG A 3,910 39 >75% Grass cover, Good, HSG A 141,400 48 Weighted Average 103,450 30 73.16% Pervious Area 37,950 98 26.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 100 0.0800 0.14 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.1 10 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 12.7 235 Total Subcatchment DA3C: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)5 4 3 2 1 0 Type III 24-hr 25yr Rainfall=6.53" Runoff Area=141,400 sf Runoff Volume=21,084 cf Runoff Depth=1.79" Flow Length=235' Tc=12.7 min CN=30/98 4.53 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 71HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond C1: CHAMBERS Inflow Area = 141,400 sf, 26.84% Impervious, Inflow Depth = 1.79" for 25yr event Inflow = 4.53 cfs @ 12.17 hrs, Volume= 21,084 cf Outflow = 0.38 cfs @ 13.75 hrs, Volume= 21,085 cf, Atten= 92%, Lag= 94.8 min Discarded = 0.38 cfs @ 13.75 hrs, Volume= 21,085 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT3 : INFILTRATION TRENCH 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 36.07' @ 13.75 hrs Surf.Area= 1,912 sf Storage= 7,778 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 166.0 min ( 934.4 - 768.4 ) Volume Invert Avail.Storage Storage Description #1B 27.25' 2,581 cf 19.17'W x 99.75'L x 6.75'H Field B 12,905 cf Overall - 5,083 cf Embedded = 7,823 cf x 33.0% Voids #2B 28.00' 5,083 cf ADS_StormTech MC-7200 +Cap x 28 Inside #1 Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap 28 Chambers in 2 Rows Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf #3 27.00' 126 cf 4.00'D x 10.00'H Vertical Cone/Cylinder -Impervious #4 36.10' 327 cf Custom Stage Data (Prismatic) Listed below (Recalc) 8,117 cf Total Available Storage Storage Group B created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.10 100 0 0 36.25 400 37 37 36.30 600 25 63 36.35 10,000 265 327 Device Routing Invert Outlet Devices #1 Discarded 27.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 36.30'20.0' long x 5.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Discarded OutFlow Max=0.37 cfs @ 13.75 hrs HW=36.07' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.37 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=27.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 72HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS - Chamber Wizard Field B Chamber Model = ADS_StormTech MC-7200 +Cap (ADS StormTech® MC-7200 with cap volume) Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf 100.0" Wide + 6.0" Spacing = 106.0" C-C Row Spacing 14 Chambers/Row x 6.59' Long +2.73' Cap Length x 2 = 97.75' Row Length +12.0" End Stone x 2 = 99.75' Base Length 2 Rows x 100.0" Wide + 6.0" Spacing x 1 + 12.0" Side Stone x 2 = 19.17' Base Width 9.0" Stone Base + 60.0" Chamber Height + 12.0" Stone Cover = 6.75' Field Height 28 Chambers x 175.9 cf + 39.5 cf Cap Volume x 2 x 2 Rows = 5,082.5 cf Chamber Storage 12,905.2 cf Field - 5,082.5 cf Chambers = 7,822.6 cf Stone x 33.0% Voids = 2,581.5 cf Stone Storage Chamber Storage + Stone Storage = 7,664.0 cf = 0.176 af Overall Storage Efficiency = 59.4% Overall System Size = 99.75' x 19.17' x 6.75' 28 Chambers 478.0 cy Field 289.7 cy Stone Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 73HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)5 4 3 2 1 0 Inflow Area=141,400 sf Peak Elev=36.07' Storage=7,778 cf 4.53 cfs 0.38 cfs0.38 cfs 0.00 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 74HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS1: Infiltration System 1 Inflow Area = 301,650 sf, 25.64% Impervious, Inflow Depth = 0.39" for 25yr event Inflow = 3.54 cfs @ 12.10 hrs, Volume= 9,792 cf Outflow = 3.54 cfs @ 12.10 hrs, Volume= 9,792 cf, Atten= 0%, Lag= 0.3 min Discarded = 0.06 cfs @ 11.71 hrs, Volume= 2,416 cf Primary = 3.48 cfs @ 12.10 hrs, Volume= 7,376 cf Routed to Pond SP1 : Follins Pond Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 13.60' @ 12.04 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 42.5 min calculated for 9,791 cf (100% of inflow) Center-of-Mass det. time= 42.5 min ( 800.4 - 757.9 ) Volume Invert Avail.Storage Storage Description #1 7.60' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 9.60' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 13.60'Automatic Storage Overflow (Discharged without head) #1 Discarded 7.60'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 13.55'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.71 hrs HW=7.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.10 hrs HW=13.60' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 75HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS1: Infiltration System 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=301,650 sf Peak Elev=13.60' Storage=999 cf 3.54 cfs3.54 cfs 0.06 cfs 3.48 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 76HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS2: Infiltration System 2 Inflow Area = 291,470 sf, 25.66% Impervious, Inflow Depth = 0.44" for 25yr event Inflow = 3.32 cfs @ 12.09 hrs, Volume= 10,699 cf Outflow = 3.32 cfs @ 12.09 hrs, Volume= 10,699 cf, Atten= 0%, Lag= 0.3 min Discarded = 0.06 cfs @ 11.36 hrs, Volume= 2,337 cf Primary = 3.26 cfs @ 12.09 hrs, Volume= 8,362 cf Routed to Pond IS1 : Infiltration System 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.00' @ 11.88 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 44.7 min calculated for 10,698 cf (100% of inflow) Center-of-Mass det. time= 44.7 min ( 805.6 - 760.9 ) Volume Invert Avail.Storage Storage Description #1 11.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 13.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 17.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 16.95'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.36 hrs HW=11.08' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.09 hrs HW=17.00' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 77HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS2: Infiltration System 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=291,470 sf Peak Elev=17.00' Storage=999 cf 3.32 cfs3.32 cfs 0.06 cfs 3.26 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 78HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS3: Infiltration System 3 Inflow Area = 259,970 sf, 25.38% Impervious, Inflow Depth = 0.66" for 25yr event Inflow = 2.31 cfs @ 12.27 hrs, Volume= 14,257 cf Outflow = 2.31 cfs @ 12.27 hrs, Volume= 14,257 cf, Atten= 0%, Lag= 0.2 min Discarded = 0.06 cfs @ 7.11 hrs, Volume= 4,961 cf Primary = 2.26 cfs @ 12.27 hrs, Volume= 9,296 cf Routed to Pond IT2 : INFILTRATION TRENCH 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 30.94' @ 12.27 hrs Surf.Area= 288 sf Storage= 986 cf Plug-Flow detention time= 65.8 min calculated for 14,255 cf (100% of inflow) Center-of-Mass det. time= 65.8 min ( 852.5 - 786.7 ) Volume Invert Avail.Storage Storage Description #1 25.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 27.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 31.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 25.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 30.75'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 7.11 hrs HW=25.06' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=2.25 cfs @ 12.27 hrs HW=30.94' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 2.25 cfs @ 1.21 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 79HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS3: Infiltration System 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Inflow Area=259,970 sf Peak Elev=30.94' Storage=986 cf 2.31 cfs2.31 cfs 0.06 cfs 2.26 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 80HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT1: INFILTRATION TRENCH 1 Inflow Area = 286,690 sf, 25.71% Impervious, Inflow Depth = 0.48" for 25yr event Inflow = 3.29 cfs @ 12.08 hrs, Volume= 11,374 cf Outflow = 3.28 cfs @ 12.09 hrs, Volume= 11,303 cf, Atten= 0%, Lag= 0.5 min Discarded = 0.12 cfs @ 12.09 hrs, Volume= 1,218 cf Primary = 3.16 cfs @ 12.09 hrs, Volume= 10,085 cf Routed to Pond IS2 : Infiltration System 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 20.77' @ 12.09 hrs Surf.Area= 609 sf Storage= 173 cf Plug-Flow detention time= 7.9 min calculated for 11,302 cf (99% of inflow) Center-of-Mass det. time= 4.6 min ( 768.9 - 764.3 ) Volume Invert Avail.Storage Storage Description #1 16.50' 98 cf Custom Stage Data (Prismatic) Listed below (Recalc) 298 cf Overall x 33.0% Voids #2 20.00' 25 cf 4.00'D x 2.00'H Vertical Cone/Cylinder -Impervious #3 20.53' 237 cf Custom Stage Data (Prismatic) Listed below (Recalc) 361 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 16.50 85 0 0 20.00 85 298 298 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 20.53 10 0 0 21.00 1,000 237 237 Device Routing Invert Outlet Devices #1 Discarded 16.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 19.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 20.53'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.12 cfs @ 12.09 hrs HW=20.77' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.12 cfs) 2=Orifice/Grate (Passes 0.12 cfs of 1.17 cfs potential flow) Primary OutFlow Max=3.15 cfs @ 12.09 hrs HW=20.77' (Free Discharge) 3=Orifice/Grate (Weir Controls 3.15 cfs @ 1.61 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 81HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT1: INFILTRATION TRENCH 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=286,690 sf Peak Elev=20.77' Storage=173 cf 3.29 cfs3.28 cfs 0.12 cfs 3.16 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 82HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT2: INFILTRATION TRENCH 2 Inflow Area = 280,550 sf, 25.55% Impervious, Inflow Depth = 0.54" for 25yr event Inflow = 3.03 cfs @ 12.09 hrs, Volume= 12,509 cf Outflow = 3.03 cfs @ 12.09 hrs, Volume= 12,306 cf, Atten= 0%, Lag= 0.0 min Discarded = 0.04 cfs @ 10.11 hrs, Volume= 2,033 cf Primary = 2.99 cfs @ 12.09 hrs, Volume= 10,272 cf Routed to Pond IT1 : INFILTRATION TRENCH 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 23.57' @ 12.09 hrs Surf.Area= 212 sf Storage= 298 cf Plug-Flow detention time= 21.3 min calculated for 12,304 cf (98% of inflow) Center-of-Mass det. time= 12.3 min ( 789.7 - 777.4 ) Volume Invert Avail.Storage Storage Description #1 19.25' 245 cf Custom Stage Data (Prismatic) Listed below (Recalc) 742 cf Overall x 33.0% Voids #2 19.35' 63 cf 4.00'D x 5.00'H Vertical Cone/Cylinder -Impervious 308 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 19.25 212 0 0 22.75 212 742 742 Device Routing Invert Outlet Devices #0 Primary 24.35'Automatic Storage Overflow (Discharged without head) #1 Discarded 19.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 21.75'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 23.35'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.04 cfs @ 10.11 hrs HW=21.90' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) 2=Orifice/Grate (Passes 0.04 cfs of 0.07 cfs potential flow) Primary OutFlow Max=2.97 cfs @ 12.09 hrs HW=23.57' (Free Discharge) 3=Broad-Crested Rectangular Weir (Weir Controls 2.97 cfs @ 1.33 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 83HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT2: INFILTRATION TRENCH 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=280,550 sf Peak Elev=23.57' Storage=298 cf 3.03 cfs3.03 cfs 0.04 cfs 2.99 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 84HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT3: INFILTRATION TRENCH 3 Inflow Area = 168,290 sf, 27.19% Impervious, Inflow Depth = 0.31" for 25yr event Inflow = 1.19 cfs @ 12.07 hrs, Volume= 4,314 cf Outflow = 1.19 cfs @ 12.07 hrs, Volume= 4,092 cf, Atten= 0%, Lag= 0.1 min Discarded = 0.05 cfs @ 9.39 hrs, Volume= 2,130 cf Primary = 1.14 cfs @ 12.07 hrs, Volume= 1,962 cf Routed to Pond IS3 : Infiltration System 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 34.34' @ 12.07 hrs Surf.Area= 240 sf Storage= 343 cf Plug-Flow detention time= 69.8 min calculated for 4,092 cf (95% of inflow) Center-of-Mass det. time= 39.1 min ( 798.5 - 759.4 ) Volume Invert Avail.Storage Storage Description #1 28.50' 277 cf Custom Stage Data (Prismatic) Listed below (Recalc) 840 cf Overall x 33.0% Voids #2 29.10' 101 cf 4.00'D x 8.00'H Vertical Cone/Cylinder -Impervious 378 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 28.50 240 0 0 32.00 240 840 840 Device Routing Invert Outlet Devices #0 Primary 37.10'Automatic Storage Overflow (Discharged without head) #1 Discarded 28.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 31.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 35.40'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Primary 33.70'12.0" Round Culvert L= 10.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 33.70' / 31.00' S= 0.2700 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.05 cfs @ 9.39 hrs HW=31.17' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Orifice/Grate (Passes 0.05 cfs of 0.08 cfs potential flow) Primary OutFlow Max=1.14 cfs @ 12.07 hrs HW=34.34' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) 4=Culvert (Inlet Controls 1.14 cfs @ 2.15 fps) Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 85HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT3: INFILTRATION TRENCH 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Inflow Area=168,290 sf Peak Elev=34.34' Storage=343 cf 1.19 cfs1.19 cfs 0.05 cfs 1.14 cfs Type III 24-hr 25yr Rainfall=6.53"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 86HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 344,120 sf, 24.57% Impervious, Inflow Depth = 0.41" for 25yr event Inflow = 4.09 cfs @ 12.11 hrs, Volume= 11,667 cf Primary = 4.09 cfs @ 12.11 hrs, Volume= 11,667 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)4 3 2 1 0 Inflow Area=344,120 sf 4.09 cfs4.09 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 87HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=1.95"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=1.09 cfs 6,910 cf Runoff Area=10,180 sf 25.15% Impervious Runoff Depth=2.52"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.42 cfs 2,140 cf Runoff Area=4,780 sf 22.80% Impervious Runoff Depth=2.34"Subcatchment DA2: Tc=5.0 min CN=30/98 Runoff=0.22 cfs 932 cf Runoff Area=6,140 sf 32.74% Impervious Runoff Depth=3.11"Subcatchment DA2A: Tc=5.0 min CN=30/98 Runoff=0.40 cfs 1,593 cf Runoff Area=20,580 sf 27.75% Impervious Runoff Depth=2.79"Subcatchment DA2B: Tc=5.0 min CN=31/98 Runoff=1.15 cfs 4,777 cf Runoff Area=26,890 sf 29.04% Impervious Runoff Depth=2.83"Subcatchment DA3: Tc=5.0 min CN=30/98 Runoff=1.57 cfs 6,332 cf Runoff Area=18,760 sf 29.74% Impervious Runoff Depth=2.88"Subcatchment DA3A: Flow Length=480' Tc=19.7 min CN=30/98 Runoff=0.75 cfs 4,503 cf Runoff Area=72,920 sf 20.08% Impervious Runoff Depth=2.41"Subcatchment DA3B: Flow Length=495' Tc=24.2 min CN=34/98 Runoff=2.14 cfs 14,649 cf Runoff Area=141,400 sf 26.84% Impervious Runoff Depth=2.65"Subcatchment DA3C: Flow Length=235' Tc=12.7 min CN=30/98 Runoff=6.01 cfs 31,275 cf Peak Elev=36.43' Storage=8,110 cf Inflow=6.01 cfs 31,275 cfPond C1: CHAMBERS Discarded=2.28 cfs 29,955 cf Primary=2.23 cfs 1,321 cf Outflow=4.51 cfs 31,276 cf Peak Elev=13.60' Storage=999 cf Inflow=5.46 cfs 20,118 cfPond IS1: Infiltration System 1 Discarded=0.06 cfs 2,982 cf Primary=5.39 cfs 17,136 cf Outflow=5.45 cfs 20,118 cf Peak Elev=17.00' Storage=999 cf Inflow=5.32 cfs 21,178 cfPond IS2: Infiltration System 2 Discarded=0.06 cfs 3,200 cf Primary=5.22 cfs 17,978 cf Outflow=5.27 cfs 21,178 cf Peak Elev=31.00' Storage=999 cf Inflow=5.37 cfs 23,916 cfPond IS3: Infiltration System 3 Discarded=0.06 cfs 5,244 cf Primary=5.09 cfs 18,672 cf Outflow=5.14 cfs 23,916 cf Peak Elev=20.87' Storage=236 cf Inflow=5.63 cfs 22,269 cfPond IT1: INFILTRATION TRENCH 1 Discarded=0.16 cfs 1,953 cf Primary=5.24 cfs 20,246 cf Outflow=5.40 cfs 22,199 cf Peak Elev=23.68' Storage=299 cf Inflow=5.53 cfs 23,449 cfPond IT2: INFILTRATION TRENCH 2 Discarded=0.04 cfs 2,567 cf Primary=5.48 cfs 20,676 cf Outflow=5.53 cfs 23,243 cf Peak Elev=34.91' Storage=350 cf Inflow=2.82 cfs 7,653 cfPond IT3: INFILTRATION TRENCH 3 Discarded=0.05 cfs 2,668 cf Primary=2.53 cfs 4,763 cf Outflow=2.58 cfs 7,431 cf Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 88HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Inflow=6.27 cfs 24,046 cfPond SP1: Follins Pond Primary=6.27 cfs 24,046 cf Total Runoff Area = 344,120 sf Runoff Volume = 73,112 cf Average Runoff Depth = 2.55" 75.43% Pervious = 259,580 sf 24.57% Impervious = 84,540 sf Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 89HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 1.09 cfs @ 12.22 hrs, Volume= 6,910 cf, Depth= 1.95" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=42,470 sf Runoff Volume=6,910 cf Runoff Depth=1.95" Flow Length=625' Tc=16.2 min CN=31/98 1.09 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 90HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.42 cfs @ 12.15 hrs, Volume= 2,140 cf, Depth= 2.52" Routed to Pond IS1 : Infiltration System 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,620 30 Woods, Good, HSG A 10,180 47 Weighted Average 7,620 30 74.85% Pervious Area 2,560 98 25.15% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=10,180 sf Runoff Volume=2,140 cf Runoff Depth=2.52" Flow Length=235' Tc=11.5 min CN=30/98 0.42 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 91HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.22 cfs @ 12.07 hrs, Volume= 932 cf, Depth= 2.34" Routed to Pond IS2 : Infiltration System 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 740 98 Paved parking, HSG A 350 98 Unconnected roofs, HSG A 3,690 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 4,780 46 Weighted Average 3,690 30 77.20% Pervious Area 1,090 98 22.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA2: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.24 0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=4,780 sf Runoff Volume=932 cf Runoff Depth=2.34" Tc=5.0 min CN=30/98 0.22 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 92HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2A: Runoff = 0.40 cfs @ 12.07 hrs, Volume= 1,593 cf, Depth= 3.11" Routed to Pond IT1 : INFILTRATION TRENCH 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 1,080 98 Paved parking, HSG A 930 98 Unconnected roofs, HSG A 4,130 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 6,140 52 Weighted Average 4,130 30 67.26% Pervious Area 2,010 98 32.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 min direct Subcatchment DA2A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=6,140 sf Runoff Volume=1,593 cf Runoff Depth=3.11" Tc=5.0 min CN=30/98 0.40 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 93HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2B: Runoff = 1.15 cfs @ 12.07 hrs, Volume= 4,777 cf, Depth= 2.79" Routed to Pond IT2 : INFILTRATION TRENCH 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 5,710 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 12,670 30 Woods, Good, HSG A 2,200 39 >75% Grass cover, Good, HSG A 20,580 50 Weighted Average 14,870 31 72.25% Pervious Area 5,710 98 27.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA2B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=20,580 sf Runoff Volume=4,777 cf Runoff Depth=2.79" Tc=5.0 min CN=31/98 1.15 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 94HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 1.57 cfs @ 12.07 hrs, Volume= 6,332 cf, Depth= 2.83" Routed to Pond IT3 : INFILTRATION TRENCH 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 4,210 98 Paved parking, HSG A 3,600 98 Unconnected roofs, HSG A 19,080 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 0 98 Water Surface, HSG A 26,890 50 Weighted Average 19,080 30 70.96% Pervious Area 7,810 98 29.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA3: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=26,890 sf Runoff Volume=6,332 cf Runoff Depth=2.83" Tc=5.0 min CN=30/98 1.57 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 95HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3A: Runoff = 0.75 cfs @ 12.26 hrs, Volume= 4,503 cf, Depth= 2.88" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 5,580 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 13,180 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 18,760 50 Weighted Average 13,180 30 70.26% Pervious Area 5,580 98 29.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 1.8 155 0.0800 1.41 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.7 225 0.0800 5.74 Shallow Concentrated Flow, Paved Kv= 20.3 fps 19.7 480 Total Subcatchment DA3A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=18,760 sf Runoff Volume=4,503 cf Runoff Depth=2.88" Flow Length=480' Tc=19.7 min CN=30/98 0.75 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 96HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3B: Runoff = 2.14 cfs @ 12.35 hrs, Volume= 14,649 cf, Depth= 2.41" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 8,650 98 Paved parking, HSG A 5,990 98 Unconnected roofs, HSG A 35,050 30 Woods, Good, HSG A 23,230 39 >75% Grass cover, Good, HSG A 72,920 47 Weighted Average 58,280 34 79.92% Pervious Area 14,640 98 20.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 495 Total Subcatchment DA3B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)2 1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=72,920 sf Runoff Volume=14,649 cf Runoff Depth=2.41" Flow Length=495' Tc=24.2 min CN=34/98 2.14 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 97HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3C: Runoff = 6.01 cfs @ 12.17 hrs, Volume= 31,275 cf, Depth= 2.65" Routed to Pond C1 : CHAMBERS Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100yr Rainfall=8.59" Area (sf) CN Description 23,130 98 Paved parking, HSG A 14,820 98 Unconnected roofs, HSG A 99,540 30 Woods, Good, HSG A 3,910 39 >75% Grass cover, Good, HSG A 141,400 48 Weighted Average 103,450 30 73.16% Pervious Area 37,950 98 26.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 100 0.0800 0.14 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.1 10 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 12.7 235 Total Subcatchment DA3C: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Type III 24-hr 100yr Rainfall=8.59" Runoff Area=141,400 sf Runoff Volume=31,275 cf Runoff Depth=2.65" Flow Length=235' Tc=12.7 min CN=30/98 6.01 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 98HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond C1: CHAMBERS Inflow Area = 141,400 sf, 26.84% Impervious, Inflow Depth = 2.65" for 100yr event Inflow = 6.01 cfs @ 12.17 hrs, Volume= 31,275 cf Outflow = 4.51 cfs @ 12.35 hrs, Volume= 31,276 cf, Atten= 25%, Lag= 10.8 min Discarded = 2.28 cfs @ 12.34 hrs, Volume= 29,955 cf Primary = 2.23 cfs @ 12.35 hrs, Volume= 1,321 cf Routed to Pond IT3 : INFILTRATION TRENCH 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 36.43' @ 12.35 hrs Surf.Area= 11,912 sf Storage= 8,110 cf Plug-Flow detention time= 150.8 min calculated for 31,272 cf (100% of inflow) Center-of-Mass det. time= 150.8 min ( 933.0 - 782.2 ) Volume Invert Avail.Storage Storage Description #1B 27.25' 2,581 cf 19.17'W x 99.75'L x 6.75'H Field B 12,905 cf Overall - 5,083 cf Embedded = 7,823 cf x 33.0% Voids #2B 28.00' 5,083 cf ADS_StormTech MC-7200 +Cap x 28 Inside #1 Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap 28 Chambers in 2 Rows Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf #3 27.00' 126 cf 4.00'D x 10.00'H Vertical Cone/Cylinder -Impervious #4 36.10' 327 cf Custom Stage Data (Prismatic) Listed below (Recalc) 8,117 cf Total Available Storage Storage Group B created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.10 100 0 0 36.25 400 37 37 36.30 600 25 63 36.35 10,000 265 327 Device Routing Invert Outlet Devices #1 Discarded 27.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 36.30'20.0' long x 5.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Discarded OutFlow Max=2.28 cfs @ 12.34 hrs HW=36.36' (Free Discharge) 1=Exfiltration (Exfiltration Controls 2.28 cfs) Primary OutFlow Max=2.03 cfs @ 12.35 hrs HW=36.42' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 2.03 cfs @ 0.82 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 99HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS - Chamber Wizard Field B Chamber Model = ADS_StormTech MC-7200 +Cap (ADS StormTech® MC-7200 with cap volume) Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf 100.0" Wide + 6.0" Spacing = 106.0" C-C Row Spacing 14 Chambers/Row x 6.59' Long +2.73' Cap Length x 2 = 97.75' Row Length +12.0" End Stone x 2 = 99.75' Base Length 2 Rows x 100.0" Wide + 6.0" Spacing x 1 + 12.0" Side Stone x 2 = 19.17' Base Width 9.0" Stone Base + 60.0" Chamber Height + 12.0" Stone Cover = 6.75' Field Height 28 Chambers x 175.9 cf + 39.5 cf Cap Volume x 2 x 2 Rows = 5,082.5 cf Chamber Storage 12,905.2 cf Field - 5,082.5 cf Chambers = 7,822.6 cf Stone x 33.0% Voids = 2,581.5 cf Stone Storage Chamber Storage + Stone Storage = 7,664.0 cf = 0.176 af Overall Storage Efficiency = 59.4% Overall System Size = 99.75' x 19.17' x 6.75' 28 Chambers 478.0 cy Field 289.7 cy Stone Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 100HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Inflow Area=141,400 sf Peak Elev=36.43' Storage=8,110 cf 6.01 cfs 4.51 cfs 2.28 cfs2.23 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 101HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS1: Infiltration System 1 Inflow Area = 301,650 sf, 25.64% Impervious, Inflow Depth = 0.80" for 100yr event Inflow = 5.46 cfs @ 12.38 hrs, Volume= 20,118 cf Outflow = 5.45 cfs @ 12.38 hrs, Volume= 20,118 cf, Atten= 0%, Lag= 0.4 min Discarded = 0.06 cfs @ 11.51 hrs, Volume= 2,982 cf Primary = 5.39 cfs @ 12.38 hrs, Volume= 17,136 cf Routed to Pond SP1 : Follins Pond Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 13.60' @ 11.84 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 28.4 min calculated for 20,115 cf (100% of inflow) Center-of-Mass det. time= 28.4 min ( 802.3 - 773.9 ) Volume Invert Avail.Storage Storage Description #1 7.60' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 9.60' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 13.60'Automatic Storage Overflow (Discharged without head) #1 Discarded 7.60'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 13.55'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.51 hrs HW=7.73' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.38 hrs HW=13.60' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 102HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS1: Infiltration System 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Inflow Area=301,650 sf Peak Elev=13.60' Storage=999 cf 5.46 cfs5.45 cfs 0.06 cfs 5.39 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 103HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS2: Infiltration System 2 Inflow Area = 291,470 sf, 25.66% Impervious, Inflow Depth = 0.87" for 100yr event Inflow = 5.32 cfs @ 12.37 hrs, Volume= 21,178 cf Outflow = 5.27 cfs @ 12.38 hrs, Volume= 21,178 cf, Atten= 1%, Lag= 0.4 min Discarded = 0.06 cfs @ 10.53 hrs, Volume= 3,200 cf Primary = 5.22 cfs @ 12.38 hrs, Volume= 17,978 cf Routed to Pond IS1 : Infiltration System 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.00' @ 11.51 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 34.3 min calculated for 21,178 cf (100% of inflow) Center-of-Mass det. time= 34.3 min ( 816.8 - 782.5 ) Volume Invert Avail.Storage Storage Description #1 11.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 13.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 17.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 16.95'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 10.53 hrs HW=11.09' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.31 cfs @ 12.38 hrs HW=17.00' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.31 cfs @ 0.63 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 104HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS2: Infiltration System 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)5 4 3 2 1 0 Inflow Area=291,470 sf Peak Elev=17.00' Storage=999 cf 5.32 cfs 5.27 cfs 0.06 cfs 5.22 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 105HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS3: Infiltration System 3 Inflow Area = 259,970 sf, 25.38% Impervious, Inflow Depth = 1.10" for 100yr event Inflow = 5.37 cfs @ 12.35 hrs, Volume= 23,916 cf Outflow = 5.14 cfs @ 12.36 hrs, Volume= 23,916 cf, Atten= 4%, Lag= 0.5 min Discarded = 0.06 cfs @ 5.73 hrs, Volume= 5,244 cf Primary = 5.09 cfs @ 12.36 hrs, Volume= 18,672 cf Routed to Pond IT2 : INFILTRATION TRENCH 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 31.00' @ 12.33 hrs Surf.Area= 288 sf Storage= 999 cf Plug-Flow detention time= 42.3 min calculated for 23,916 cf (100% of inflow) Center-of-Mass det. time= 42.3 min ( 839.3 - 797.0 ) Volume Invert Avail.Storage Storage Description #1 25.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 27.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 31.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 25.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 30.75'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 5.73 hrs HW=25.06' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=3.54 cfs @ 12.36 hrs HW=31.00' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 3.54 cfs @ 1.41 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 106HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS3: Infiltration System 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Inflow Area=259,970 sf Peak Elev=31.00' Storage=999 cf 5.37 cfs 5.14 cfs 0.06 cfs 5.09 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 107HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT1: INFILTRATION TRENCH 1 Inflow Area = 286,690 sf, 25.71% Impervious, Inflow Depth = 0.93" for 100yr event Inflow = 5.63 cfs @ 12.36 hrs, Volume= 22,269 cf Outflow = 5.40 cfs @ 12.37 hrs, Volume= 22,199 cf, Atten= 4%, Lag= 0.6 min Discarded = 0.16 cfs @ 12.37 hrs, Volume= 1,953 cf Primary = 5.24 cfs @ 12.37 hrs, Volume= 20,246 cf Routed to Pond IS2 : Infiltration System 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 20.87' @ 12.37 hrs Surf.Area= 815 sf Storage= 236 cf Plug-Flow detention time= 5.2 min calculated for 22,196 cf (100% of inflow) Center-of-Mass det. time= 3.3 min ( 791.7 - 788.4 ) Volume Invert Avail.Storage Storage Description #1 16.50' 98 cf Custom Stage Data (Prismatic) Listed below (Recalc) 298 cf Overall x 33.0% Voids #2 20.00' 25 cf 4.00'D x 2.00'H Vertical Cone/Cylinder -Impervious #3 20.53' 237 cf Custom Stage Data (Prismatic) Listed below (Recalc) 361 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 16.50 85 0 0 20.00 85 298 298 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 20.53 10 0 0 21.00 1,000 237 237 Device Routing Invert Outlet Devices #1 Discarded 16.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 19.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 20.53'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.16 cfs @ 12.37 hrs HW=20.87' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.16 cfs) 2=Orifice/Grate (Passes 0.16 cfs of 1.20 cfs potential flow) Primary OutFlow Max=5.21 cfs @ 12.37 hrs HW=20.87' (Free Discharge) 3=Orifice/Grate (Weir Controls 5.21 cfs @ 1.91 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 108HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT1: INFILTRATION TRENCH 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Inflow Area=286,690 sf Peak Elev=20.87' Storage=236 cf 5.63 cfs 5.40 cfs 0.16 cfs 5.24 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 109HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT2: INFILTRATION TRENCH 2 Inflow Area = 280,550 sf, 25.55% Impervious, Inflow Depth = 1.00" for 100yr event Inflow = 5.53 cfs @ 12.36 hrs, Volume= 23,449 cf Outflow = 5.53 cfs @ 12.36 hrs, Volume= 23,243 cf, Atten= 0%, Lag= 0.0 min Discarded = 0.04 cfs @ 9.12 hrs, Volume= 2,567 cf Primary = 5.48 cfs @ 12.36 hrs, Volume= 20,676 cf Routed to Pond IT1 : INFILTRATION TRENCH 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 23.68' @ 12.36 hrs Surf.Area= 212 sf Storage= 299 cf Plug-Flow detention time= 13.8 min calculated for 23,243 cf (99% of inflow) Center-of-Mass det. time= 8.4 min ( 808.4 - 800.0 ) Volume Invert Avail.Storage Storage Description #1 19.25' 245 cf Custom Stage Data (Prismatic) Listed below (Recalc) 742 cf Overall x 33.0% Voids #2 19.35' 63 cf 4.00'D x 5.00'H Vertical Cone/Cylinder -Impervious 308 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 19.25 212 0 0 22.75 212 742 742 Device Routing Invert Outlet Devices #0 Primary 24.35'Automatic Storage Overflow (Discharged without head) #1 Discarded 19.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 21.75'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 23.35'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.04 cfs @ 9.12 hrs HW=21.90' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) 2=Orifice/Grate (Passes 0.04 cfs of 0.07 cfs potential flow) Primary OutFlow Max=5.45 cfs @ 12.36 hrs HW=23.68' (Free Discharge) 3=Broad-Crested Rectangular Weir (Weir Controls 5.45 cfs @ 1.65 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 110HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT2: INFILTRATION TRENCH 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)6 5 4 3 2 1 0 Inflow Area=280,550 sf Peak Elev=23.68' Storage=299 cf 5.53 cfs5.53 cfs 0.04 cfs 5.48 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 111HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT3: INFILTRATION TRENCH 3 Inflow Area = 168,290 sf, 27.19% Impervious, Inflow Depth = 0.55" for 100yr event Inflow = 2.82 cfs @ 12.35 hrs, Volume= 7,653 cf Outflow = 2.58 cfs @ 12.35 hrs, Volume= 7,431 cf, Atten= 8%, Lag= 0.1 min Discarded = 0.05 cfs @ 8.55 hrs, Volume= 2,668 cf Primary = 2.53 cfs @ 12.35 hrs, Volume= 4,763 cf Routed to Pond IS3 : Infiltration System 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 34.91' @ 12.35 hrs Surf.Area= 240 sf Storage= 350 cf Plug-Flow detention time= 44.2 min calculated for 7,431 cf (97% of inflow) Center-of-Mass det. time= 26.4 min ( 796.4 - 770.0 ) Volume Invert Avail.Storage Storage Description #1 28.50' 277 cf Custom Stage Data (Prismatic) Listed below (Recalc) 840 cf Overall x 33.0% Voids #2 29.10' 101 cf 4.00'D x 8.00'H Vertical Cone/Cylinder -Impervious 378 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 28.50 240 0 0 32.00 240 840 840 Device Routing Invert Outlet Devices #0 Primary 37.10'Automatic Storage Overflow (Discharged without head) #1 Discarded 28.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 31.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 35.40'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Primary 33.70'12.0" Round Culvert L= 10.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 33.70' / 31.00' S= 0.2700 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.05 cfs @ 8.55 hrs HW=31.17' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Orifice/Grate (Passes 0.05 cfs of 0.08 cfs potential flow) Primary OutFlow Max=2.38 cfs @ 12.35 hrs HW=34.84' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) 4=Culvert (Inlet Controls 2.38 cfs @ 3.03 fps) Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 112HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT3: INFILTRATION TRENCH 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)3 2 1 0 Inflow Area=168,290 sf Peak Elev=34.91' Storage=350 cf 2.82 cfs 2.58 cfs 0.05 cfs 2.53 cfs Type III 24-hr 100yr Rainfall=8.59"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 113HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 344,120 sf, 24.57% Impervious, Inflow Depth = 0.84" for 100yr event Inflow = 6.27 cfs @ 12.38 hrs, Volume= 24,046 cf Primary = 6.27 cfs @ 12.38 hrs, Volume= 24,046 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)7 6 5 4 3 2 1 0 Inflow Area=344,120 sf 6.27 cfs6.27 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 114HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=42,470 sf 16.93% Impervious Runoff Depth=0.17"Subcatchment DA0: Flow Length=625' Tc=16.2 min CN=31/98 Runoff=0.14 cfs 596 cf Runoff Area=10,180 sf 25.15% Impervious Runoff Depth=0.25"Subcatchment DA1: Flow Length=235' Tc=11.5 min CN=30/98 Runoff=0.05 cfs 212 cf Runoff Area=4,780 sf 22.80% Impervious Runoff Depth=0.23"Subcatchment DA2: Tc=5.0 min CN=30/98 Runoff=0.03 cfs 90 cf Runoff Area=6,140 sf 32.74% Impervious Runoff Depth=0.33"Subcatchment DA2A: Tc=5.0 min CN=30/98 Runoff=0.05 cfs 167 cf Runoff Area=20,580 sf 27.75% Impervious Runoff Depth=0.28"Subcatchment DA2B: Tc=5.0 min CN=31/98 Runoff=0.15 cfs 474 cf Runoff Area=26,890 sf 29.04% Impervious Runoff Depth=0.29"Subcatchment DA3: Tc=5.0 min CN=30/98 Runoff=0.21 cfs 648 cf Runoff Area=18,760 sf 29.74% Impervious Runoff Depth=0.30"Subcatchment DA3A: Flow Length=480' Tc=19.7 min CN=30/98 Runoff=0.10 cfs 463 cf Runoff Area=72,920 sf 20.08% Impervious Runoff Depth=0.20"Subcatchment DA3B: Flow Length=495' Tc=24.2 min CN=34/98 Runoff=0.23 cfs 1,214 cf Runoff Area=141,400 sf 26.84% Impervious Runoff Depth=0.27"Subcatchment DA3C: Flow Length=235' Tc=12.7 min CN=30/98 Runoff=0.78 cfs 3,148 cf Peak Elev=27.77' Storage=341 cf Inflow=0.78 cfs 3,148 cfPond C1: CHAMBERS Discarded=0.37 cfs 3,149 cf Primary=0.00 cfs 0 cf Outflow=0.37 cfs 3,149 cf Peak Elev=7.66' Storage=5 cf Inflow=0.05 cfs 212 cfPond IS1: Infiltration System 1 Discarded=0.05 cfs 212 cf Primary=0.00 cfs 0 cf Outflow=0.05 cfs 212 cf Peak Elev=11.03' Storage=3 cf Inflow=0.03 cfs 90 cfPond IS2: Infiltration System 2 Discarded=0.03 cfs 90 cf Primary=0.00 cfs 0 cf Outflow=0.03 cfs 90 cf Peak Elev=28.83' Storage=560 cf Inflow=0.33 cfs 1,677 cfPond IS3: Infiltration System 3 Discarded=0.06 cfs 1,677 cf Primary=0.00 cfs 0 cf Outflow=0.06 cfs 1,677 cf Peak Elev=19.46' Storage=83 cf Inflow=0.05 cfs 167 cfPond IT1: INFILTRATION TRENCH 1 Discarded=0.02 cfs 97 cf Primary=0.00 cfs 0 cf Outflow=0.02 cfs 97 cf Peak Elev=22.23' Storage=244 cf Inflow=0.15 cfs 474 cfPond IT2: INFILTRATION TRENCH 2 Discarded=0.04 cfs 269 cf Primary=0.00 cfs 0 cf Outflow=0.04 cfs 269 cf Peak Elev=33.43' Storage=332 cf Inflow=0.21 cfs 648 cfPond IT3: INFILTRATION TRENCH 3 Discarded=0.05 cfs 426 cf Primary=0.00 cfs 0 cf Outflow=0.05 cfs 426 cf Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 115HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Inflow=0.14 cfs 596 cfPond SP1: Follins Pond Primary=0.14 cfs 596 cf Total Runoff Area = 344,120 sf Runoff Volume = 7,013 cf Average Runoff Depth = 0.24" 75.43% Pervious = 259,580 sf 24.57% Impervious = 84,540 sf Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 116HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA0: Runoff = 0.14 cfs @ 12.22 hrs, Volume= 596 cf, Depth= 0.17" Routed to Pond SP1 : Follins Pond Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 4,730 98 Paved parking, HSG A 2,460 98 Unconnected roofs, HSG A 29,910 30 Woods, Good, HSG A 5,370 39 >75% Grass cover, Good, HSG A 42,470 43 Weighted Average 35,280 31 83.07% Pervious Area 7,190 98 16.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0900 0.15 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 5.0 470 0.1000 1.58 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 16.2 625 Total Subcatchment DA0: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=42,470 sf Runoff Volume=596 cf Runoff Depth=0.17" Flow Length=625' Tc=16.2 min CN=31/98 0.14 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 117HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA1: Runoff = 0.05 cfs @ 12.15 hrs, Volume= 212 cf, Depth= 0.25" Routed to Pond IS1 : Infiltration System 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 2,560 98 Paved parking, HSG A 7,620 30 Woods, Good, HSG A 10,180 47 Weighted Average 7,620 30 74.85% Pervious Area 2,560 98 25.15% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.6 100 0.1000 0.16 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.8 80 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.1 55 0.1100 6.73 Shallow Concentrated Flow, Paved Kv= 20.3 fps 11.5 235 Total Subcatchment DA1: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=10,180 sf Runoff Volume=212 cf Runoff Depth=0.25" Flow Length=235' Tc=11.5 min CN=30/98 0.05 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 118HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2: Runoff = 0.03 cfs @ 12.07 hrs, Volume= 90 cf, Depth= 0.23" Routed to Pond IS2 : Infiltration System 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 740 98 Paved parking, HSG A 350 98 Unconnected roofs, HSG A 3,690 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 4,780 46 Weighted Average 3,690 30 77.20% Pervious Area 1,090 98 22.80% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA2: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=4,780 sf Runoff Volume=90 cf Runoff Depth=0.23" Tc=5.0 min CN=30/98 0.03 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 119HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2A: Runoff = 0.05 cfs @ 12.07 hrs, Volume= 167 cf, Depth= 0.33" Routed to Pond IT1 : INFILTRATION TRENCH 1 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 1,080 98 Paved parking, HSG A 930 98 Unconnected roofs, HSG A 4,130 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 6,140 52 Weighted Average 4,130 30 67.26% Pervious Area 2,010 98 32.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 min direct Subcatchment DA2A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=6,140 sf Runoff Volume=167 cf Runoff Depth=0.33" Tc=5.0 min CN=30/98 0.05 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 120HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA2B: Runoff = 0.15 cfs @ 12.07 hrs, Volume= 474 cf, Depth= 0.28" Routed to Pond IT2 : INFILTRATION TRENCH 2 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 5,710 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 12,670 30 Woods, Good, HSG A 2,200 39 >75% Grass cover, Good, HSG A 20,580 50 Weighted Average 14,870 31 72.25% Pervious Area 5,710 98 27.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA2B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=20,580 sf Runoff Volume=474 cf Runoff Depth=0.28" Tc=5.0 min CN=31/98 0.15 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 121HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3: Runoff = 0.21 cfs @ 12.07 hrs, Volume= 648 cf, Depth= 0.29" Routed to Pond IT3 : INFILTRATION TRENCH 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 4,210 98 Paved parking, HSG A 3,600 98 Unconnected roofs, HSG A 19,080 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 0 98 Water Surface, HSG A 26,890 50 Weighted Average 19,080 30 70.96% Pervious Area 7,810 98 29.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 5 MIN DIRECT Subcatchment DA3: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=26,890 sf Runoff Volume=648 cf Runoff Depth=0.29" Tc=5.0 min CN=30/98 0.21 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 122HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3A: Runoff = 0.10 cfs @ 12.26 hrs, Volume= 463 cf, Depth= 0.30" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 5,580 98 Paved parking, HSG A 0 98 Unconnected roofs, HSG A 13,180 30 Woods, Good, HSG A 0 39 >75% Grass cover, Good, HSG A 18,760 50 Weighted Average 13,180 30 70.26% Pervious Area 5,580 98 29.74% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.2 100 0.0300 0.10 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 1.8 155 0.0800 1.41 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.7 225 0.0800 5.74 Shallow Concentrated Flow, Paved Kv= 20.3 fps 19.7 480 Total Subcatchment DA3A: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=18,760 sf Runoff Volume=463 cf Runoff Depth=0.30" Flow Length=480' Tc=19.7 min CN=30/98 0.10 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 123HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3B: Runoff = 0.23 cfs @ 12.32 hrs, Volume= 1,214 cf, Depth= 0.20" Routed to Pond IS3 : Infiltration System 3 Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 8,650 98 Paved parking, HSG A 5,990 98 Unconnected roofs, HSG A 35,050 30 Woods, Good, HSG A 23,230 39 >75% Grass cover, Good, HSG A 72,920 47 Weighted Average 58,280 34 79.92% Pervious Area 14,640 98 20.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 20.2 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 3.0 270 0.0900 1.50 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 24.2 495 Total Subcatchment DA3B: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.26 0.25 0.24 0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=72,920 sf Runoff Volume=1,214 cf Runoff Depth=0.20" Flow Length=495' Tc=24.2 min CN=34/98 0.23 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 124HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment DA3C: Runoff = 0.78 cfs @ 12.17 hrs, Volume= 3,148 cf, Depth= 0.27" Routed to Pond C1 : CHAMBERS Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr WQV Rainfall=1.21" Area (sf) CN Description 23,130 98 Paved parking, HSG A 14,820 98 Unconnected roofs, HSG A 99,540 30 Woods, Good, HSG A 3,910 39 >75% Grass cover, Good, HSG A 141,400 48 Weighted Average 103,450 30 73.16% Pervious Area 37,950 98 26.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.6 100 0.0800 0.14 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.60" 0.1 10 0.1200 1.73 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.0 125 0.0100 2.03 Shallow Concentrated Flow, Paved Kv= 20.3 fps 12.7 235 Total Subcatchment DA3C: Runoff Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr WQV Rainfall=1.21" Runoff Area=141,400 sf Runoff Volume=3,148 cf Runoff Depth=0.27" Flow Length=235' Tc=12.7 min CN=30/98 0.78 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 125HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond C1: CHAMBERS Inflow Area = 141,400 sf, 26.84% Impervious, Inflow Depth = 0.27" for WQV event Inflow = 0.78 cfs @ 12.17 hrs, Volume= 3,148 cf Outflow = 0.37 cfs @ 11.99 hrs, Volume= 3,149 cf, Atten= 53%, Lag= 0.0 min Discarded = 0.37 cfs @ 11.99 hrs, Volume= 3,149 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT3 : INFILTRATION TRENCH 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 27.77' @ 12.44 hrs Surf.Area= 1,912 sf Storage= 341 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 4.1 min ( 792.0 - 788.0 ) Volume Invert Avail.Storage Storage Description #1B 27.25' 2,581 cf 19.17'W x 99.75'L x 6.75'H Field B 12,905 cf Overall - 5,083 cf Embedded = 7,823 cf x 33.0% Voids #2B 28.00' 5,083 cf ADS_StormTech MC-7200 +Cap x 28 Inside #1 Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap 28 Chambers in 2 Rows Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf #3 27.00' 126 cf 4.00'D x 10.00'H Vertical Cone/Cylinder -Impervious #4 36.10' 327 cf Custom Stage Data (Prismatic) Listed below (Recalc) 8,117 cf Total Available Storage Storage Group B created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.10 100 0 0 36.25 400 37 37 36.30 600 25 63 36.35 10,000 265 327 Device Routing Invert Outlet Devices #1 Discarded 27.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 36.30'20.0' long x 5.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Discarded OutFlow Max=0.37 cfs @ 11.99 hrs HW=27.25' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.37 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=27.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 126HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS - Chamber Wizard Field B Chamber Model = ADS_StormTech MC-7200 +Cap (ADS StormTech® MC-7200 with cap volume) Effective Size= 91.2"W x 60.0"H => 26.68 sf x 6.59'L = 175.9 cf Overall Size= 100.0"W x 60.0"H x 6.95'L with 0.36' Overlap Cap Storage= 39.5 cf x 2 x 2 rows = 158.0 cf 100.0" Wide + 6.0" Spacing = 106.0" C-C Row Spacing 14 Chambers/Row x 6.59' Long +2.73' Cap Length x 2 = 97.75' Row Length +12.0" End Stone x 2 = 99.75' Base Length 2 Rows x 100.0" Wide + 6.0" Spacing x 1 + 12.0" Side Stone x 2 = 19.17' Base Width 9.0" Stone Base + 60.0" Chamber Height + 12.0" Stone Cover = 6.75' Field Height 28 Chambers x 175.9 cf + 39.5 cf Cap Volume x 2 x 2 Rows = 5,082.5 cf Chamber Storage 12,905.2 cf Field - 5,082.5 cf Chambers = 7,822.6 cf Stone x 33.0% Voids = 2,581.5 cf Stone Storage Chamber Storage + Stone Storage = 7,664.0 cf = 0.176 af Overall Storage Efficiency = 59.4% Overall System Size = 99.75' x 19.17' x 6.75' 28 Chambers 478.0 cy Field 289.7 cy Stone Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 127HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond C1: CHAMBERS Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=141,400 sf Peak Elev=27.77' Storage=341 cf 0.78 cfs 0.37 cfs0.37 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 128HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS1: Infiltration System 1 Inflow Area = 301,650 sf, 25.64% Impervious, Inflow Depth = 0.01" for WQV event Inflow = 0.05 cfs @ 12.15 hrs, Volume= 212 cf Outflow = 0.05 cfs @ 12.18 hrs, Volume= 212 cf, Atten= 3%, Lag= 1.7 min Discarded = 0.05 cfs @ 12.18 hrs, Volume= 212 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond SP1 : Follins Pond Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 7.66' @ 12.18 hrs Surf.Area= 288 sf Storage= 5 cf Plug-Flow detention time= 1.7 min calculated for 212 cf (100% of inflow) Center-of-Mass det. time= 1.7 min ( 788.6 - 786.9 ) Volume Invert Avail.Storage Storage Description #1 7.60' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 9.60' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 13.60'Automatic Storage Overflow (Discharged without head) #1 Discarded 7.60'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 13.55'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 12.18 hrs HW=7.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=7.60' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 129HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS1: Infiltration System 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=301,650 sf Peak Elev=7.66' Storage=5 cf 0.05 cfs 0.05 cfs0.05 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 130HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS2: Infiltration System 2 Inflow Area = 291,470 sf, 25.66% Impervious, Inflow Depth = 0.00" for WQV event Inflow = 0.03 cfs @ 12.07 hrs, Volume= 90 cf Outflow = 0.03 cfs @ 12.10 hrs, Volume= 90 cf, Atten= 5%, Lag= 1.6 min Discarded = 0.03 cfs @ 12.10 hrs, Volume= 90 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IS1 : Infiltration System 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 11.03' @ 12.10 hrs Surf.Area= 288 sf Storage= 3 cf Plug-Flow detention time= 1.7 min calculated for 90 cf (100% of inflow) Center-of-Mass det. time= 1.7 min ( 782.5 - 780.8 ) Volume Invert Avail.Storage Storage Description #1 11.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 13.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 17.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 11.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 16.95'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 12.10 hrs HW=11.03' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=11.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 131HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS2: Infiltration System 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Inflow Area=291,470 sf Peak Elev=11.03' Storage=3 cf 0.03 cfs 0.03 cfs0.03 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 132HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IS3: Infiltration System 3 Inflow Area = 259,970 sf, 25.38% Impervious, Inflow Depth = 0.08" for WQV event Inflow = 0.33 cfs @ 12.29 hrs, Volume= 1,677 cf Outflow = 0.06 cfs @ 11.75 hrs, Volume= 1,677 cf, Atten= 83%, Lag= 0.0 min Discarded = 0.06 cfs @ 11.75 hrs, Volume= 1,677 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT2 : INFILTRATION TRENCH 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 28.83' @ 13.14 hrs Surf.Area= 288 sf Storage= 560 cf Plug-Flow detention time= 71.2 min calculated for 1,677 cf (100% of inflow) Center-of-Mass det. time= 71.2 min ( 868.7 - 797.5 ) Volume Invert Avail.Storage Storage Description #1 25.00' 359 cf 12.00'W x 24.00'L x 6.00'H Prismatoid 1,728 cf Overall - 640 cf Embedded = 1,088 cf x 33.0% Voids #2 27.00' 640 cf 8.00'W x 20.00'L x 4.00'H Prismatoid Inside #1 999 cf Total Available Storage Device Routing Invert Outlet Devices #0 Primary 31.00'Automatic Storage Overflow (Discharged without head) #1 Discarded 25.00'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Primary 30.75'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.06 cfs @ 11.75 hrs HW=25.06' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=25.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 133HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IS3: Infiltration System 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=259,970 sf Peak Elev=28.83' Storage=560 cf 0.33 cfs 0.06 cfs0.06 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 134HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT1: INFILTRATION TRENCH 1 Inflow Area = 286,690 sf, 25.71% Impervious, Inflow Depth = 0.01" for WQV event Inflow = 0.05 cfs @ 12.07 hrs, Volume= 167 cf Outflow = 0.02 cfs @ 12.10 hrs, Volume= 97 cf, Atten= 69%, Lag= 1.7 min Discarded = 0.02 cfs @ 12.10 hrs, Volume= 97 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IS2 : Infiltration System 2 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 19.46' @ 12.37 hrs Surf.Area= 85 sf Storage= 83 cf Plug-Flow detention time= 204.3 min calculated for 97 cf (58% of inflow) Center-of-Mass det. time= 98.7 min ( 879.5 - 780.8 ) Volume Invert Avail.Storage Storage Description #1 16.50' 98 cf Custom Stage Data (Prismatic) Listed below (Recalc) 298 cf Overall x 33.0% Voids #2 20.00' 25 cf 4.00'D x 2.00'H Vertical Cone/Cylinder -Impervious #3 20.53' 237 cf Custom Stage Data (Prismatic) Listed below (Recalc) 361 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 16.50 85 0 0 20.00 85 298 298 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 20.53 10 0 0 21.00 1,000 237 237 Device Routing Invert Outlet Devices #1 Discarded 16.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 19.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 20.53'24.0" x 24.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.02 cfs @ 12.10 hrs HW=19.11' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) 2=Orifice/Grate (Passes 0.02 cfs of 0.04 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=16.50' (Free Discharge) 3=Orifice/Grate ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 135HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT1: INFILTRATION TRENCH 1 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=286,690 sf Peak Elev=19.46' Storage=83 cf 0.05 cfs 0.02 cfs0.02 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 136HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT2: INFILTRATION TRENCH 2 Inflow Area = 280,550 sf, 25.55% Impervious, Inflow Depth = 0.02" for WQV event Inflow = 0.15 cfs @ 12.07 hrs, Volume= 474 cf Outflow = 0.04 cfs @ 12.13 hrs, Volume= 269 cf, Atten= 73%, Lag= 3.5 min Discarded = 0.04 cfs @ 12.13 hrs, Volume= 269 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IT1 : INFILTRATION TRENCH 1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 22.23' @ 12.41 hrs Surf.Area= 212 sf Storage= 244 cf Plug-Flow detention time= 211.9 min calculated for 269 cf (57% of inflow) Center-of-Mass det. time= 104.9 min ( 885.8 - 780.8 ) Volume Invert Avail.Storage Storage Description #1 19.25' 245 cf Custom Stage Data (Prismatic) Listed below (Recalc) 742 cf Overall x 33.0% Voids #2 19.35' 63 cf 4.00'D x 5.00'H Vertical Cone/Cylinder -Impervious 308 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 19.25 212 0 0 22.75 212 742 742 Device Routing Invert Outlet Devices #0 Primary 24.35'Automatic Storage Overflow (Discharged without head) #1 Discarded 19.25'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 21.75'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 23.35'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 Discarded OutFlow Max=0.04 cfs @ 12.13 hrs HW=21.93' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) 2=Orifice/Grate (Passes 0.04 cfs of 0.09 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=19.25' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 137HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT2: INFILTRATION TRENCH 2 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=280,550 sf Peak Elev=22.23' Storage=244 cf 0.15 cfs 0.04 cfs0.04 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 138HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond IT3: INFILTRATION TRENCH 3 Inflow Area = 168,290 sf, 27.19% Impervious, Inflow Depth = 0.05" for WQV event Inflow = 0.21 cfs @ 12.07 hrs, Volume= 648 cf Outflow = 0.05 cfs @ 12.04 hrs, Volume= 426 cf, Atten= 78%, Lag= 0.0 min Discarded = 0.05 cfs @ 12.04 hrs, Volume= 426 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Pond IS3 : Infiltration System 3 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 33.43' @ 12.46 hrs Surf.Area= 240 sf Storage= 332 cf Plug-Flow detention time= 188.9 min calculated for 426 cf (66% of inflow) Center-of-Mass det. time= 91.7 min ( 872.6 - 780.8 ) Volume Invert Avail.Storage Storage Description #1 28.50' 277 cf Custom Stage Data (Prismatic) Listed below (Recalc) 840 cf Overall x 33.0% Voids #2 29.10' 101 cf 4.00'D x 8.00'H Vertical Cone/Cylinder -Impervious 378 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 28.50 240 0 0 32.00 240 840 840 Device Routing Invert Outlet Devices #0 Primary 37.10'Automatic Storage Overflow (Discharged without head) #1 Discarded 28.50'8.270 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Device 1 31.00'6.0" Vert. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Primary 35.40'10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Primary 33.70'12.0" Round Culvert L= 10.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 33.70' / 31.00' S= 0.2700 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.05 cfs @ 12.04 hrs HW=31.20' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Orifice/Grate (Passes 0.05 cfs of 0.11 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=28.50' (Free Discharge) 3=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) 4=Culvert ( Controls 0.00 cfs) Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 139HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Pond IT3: INFILTRATION TRENCH 3 Inflow Outflow Discarded Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=168,290 sf Peak Elev=33.43' Storage=332 cf 0.21 cfs 0.05 cfs0.05 cfs 0.00 cfs Type III 24-hr WQV Rainfall=1.21"22032 FOLLINS PR Printed 1/15/2024Prepared by Horsley Witten Inc Page 140HydroCAD® 10.20-3c s/n 01445 © 2023 HydroCAD Software Solutions LLC Summary for Pond SP1: Follins Pond [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 344,120 sf, 24.57% Impervious, Inflow Depth = 0.02" for WQV event Inflow = 0.14 cfs @ 12.22 hrs, Volume= 596 cf Primary = 0.14 cfs @ 12.22 hrs, Volume= 596 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Pond SP1: Follins Pond Inflow Primary Hydrograph Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420Flow (cfs)0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=344,120 sf 0.14 cfs0.14 cfs APPENDIX C – Wetland Resources Summary Memo MEMORANDUM To: Jordan Mora, APCC From: Ben Wollman, Wetland Scientist Date: April 24, 2023 Re: Wetland Resources – Follins Pond Road Boat Ramp Stormwater Retrofit Site, Yarmouth, MA HW has prepared the following memo and site figures to document the wetland resource areas at the referenced site and to provide regulatory context for future work. General Site Description The project site has proposed elements located at the southern end of Follins Pond Road, as well as on Gun Rock Road, adjacent to the properties at 22 and 26 Gun Rock Road in Yarmouth, Massachusetts, and is focused on stormwater management improvements in both of these locations. FEMA Designation According to the FEMA National Flood Hazard Map (Community Panel No. 25001C0579J, effective July 16, 2014), the portion of the site located at the southern end of Follins Pond Road is located within a Special Flood Hazard Area, Zone AE (1% annual chance of flooding, with base flood elevations of 9 feet) (Figure 1). State-listed Rare Species Habitat and Open Space According to the most recent version of the Massachusetts Natural Heritage Atlas (15th Edition, August 1, 2021), there are no areas of Estimated Habitat of Rare Wildlife and Certified Vernal Pools or Priority Habitat of Rare Species located at the site, as designated by the Massachusetts Natural Heritage and Endangered Species Program (NHESP). Wetland Resource Areas The site supports coastal wetland resource areas, as defined under the Massachusetts Wetlands Protection Act (M.G.L. Ch. 131 § 40) and the Town of Yarmouth Wetlands Protection By-law (Chapter 143) and their respective regulations. Horsley Witten Group, Inc. (HW) wetland biologists identified and delineated these resource areas during a site visit on January 10, 2023. Jurisdictional areas identified on or adjacent to the site include Salt Marsh; Coastal Bank; Land Subject to Coastal Storm Flowage (LSCSF); and the 35-foot, 50-foot, and 100-foot Buffer Zones to Salt Marsh and Coastal Bank. Additional resource areas present adjacent to the site include Jordan Mora, APCC April 24, 2023 Page 2 of 6 H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Wetland Memos\Yarmouth (Follins Pond Rd)\230424_YA-BR1_FollinsPond_wetlandsmemo_Final_22032A.docx Figure 1. Excerpt from Federal Emergency Management Agency (FEMA) FIRMette for the subject site. Land Under Waterbodies and Waterways (LUW) and Banks of Land Under the Ocean, Ponds, Streams, Rivers, Lakes, or Creeks that Underlie an Anadromous/Catadromous Fish Run (“Fish Run”). The site also occurs within a Coastal Watershed Area; however, the proposed project activities do not incorporate any of the prohibited practices referenced in section 2.11(1)(b)(1-6) of the Yarmouth Wetland Regulations. HW followed wetland resource area identification and on- site delineation procedure guidelines described in the Massachusetts Department of Environmental Protection (MassDEP) handbook, entitled Delineating Bordering Vegetated Wetlands Under the Massachusetts Wetlands Protection Act (March, 1995), Massachusetts Wetlands Protection Act (M.G.L. Ch. 131 § 40), and its implementing Regulations (310 CMR 10.00), and the Town of Yarmouth Wetlands Protection By-law (Chapter 143) and associated Town of Yarmouth Wetland Protection Regulations. Additionally, State Coastal Bank determinations were made following the DEP Program Policy 92-1: Coastal Banks (March 1992). Prior to conducting field delineations, HW reviewed existing source data, including USGS Geological Survey 7.5 minute topographic maps, Massachusetts Department of Environmental Protection (MassDEP) wetlands source data available through the Massachusetts Geographic Information System (MassGIS), USDA Natural Resources Conservation Service (NRCS) soils survey, U.S. Fish and Wildlife Service National Wetland Inventory (NWI) maps, and other source data to identify the presence of jurisdictional wetlands and waters of the United States within the site. This information was used to compile base mapping to assist in the understanding of the hydrologic variables, soils conditions, and vegetation communities (where applicable). A brief description of the regulatory definitions and the observed resources areas is provided below. Jordan Mora, APCC April 24, 2023 Page 3 of 6 H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Wetland Memos\Yarmouth (Follins Pond Rd)\230424_YA-BR1_FollinsPond_wetlandsmemo_Final_22032A.docx Salt Marsh Salt Marsh is defined at 310 CMR 10.32(2) as “a coastal wetland that extends landward up to the highest high tide line, that is, the highest spring tide of the year, and is characterized by plants that are well adapted to or prefer living in, saline soils. Dominant plants within salt marshes are salt meadow cord grass (Spartina patens) and/or saltmarsh cordgrass (Spartina alterniflora). A salt marsh may contain tidal creeks, ditches and pools.” The Town of Yarmouth Wetland Protection Regulations defines Salt Marsh similarly. The site supports Salt Marsh areas to the east and west sides of the boat ramp at the end of Follins Pond Road. To the west of the boat ramp the Salt Marsh vegetation is relatively dense and continuous within the tidal zone, extending up to the base of the Coastal Bank where the slope then rises steeply to the north and the vegetation transitions to upland species. To the east of the boat ramp the Salt Marsh vegetation covers most of the land surface within the tidal zone, but the area is more of a mosaic of coverage types, with patches of Coastal Beach areas present between sections of the Salt Marsh, which is comprised of a mix of sand and pebble material. This mosaic of coverage types also extends landward to the base of the Coastal Bank, where there is a similar steep slope rising to the north. Common species observed in the Salt Marsh at the site include smooth cordgrass (Spartina alterniflora), saltmarsh rush (Juncus gerardii), maritime marsh-elder (Iva frutescens), and eastern false willow (Baccharis halimifolia). HW delineated the landward boundary of the Salt Marsh with a series of consecutively numbered blue flagging stations labeled SM 1 – SM 4 (west of the boat ramp) and SM 5 – SM 10 (east of the boat ramp). Photo 1. View of the Salt Marsh to the west of the boat ramp. Jordan Mora, APCC April 24, 2023 Page 4 of 6 H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Wetland Memos\Yarmouth (Follins Pond Rd)\230424_YA-BR1_FollinsPond_wetlandsmemo_Final_22032A.docx Photo 2. View of the Salt Marsh to the east of the boat ramp. Coastal Bank Coastal Bank is defined at 310 CMR 10.30(2) as “the seaward face or side of any elevated landform, other than a coastal dune, which lies at the landward edge of a coastal beach, land subject to tidal action, or other wetland.” Coastal Bank is defined by at 2.05(2) of the Yarmouth Wetland Protection Regulations as “the seaward face or side of any elevated landform, other than a coastal dune, which lies at the landward edge of a coastal beach, land subject to tidal action or storm flowage, or other wetland. Any minor discontinuity of the slope notwithstanding, the top of the bank shall be the first significant break in slope that occurs above the relevant 100 year flood plain elevation.” Coastal Bank is present at the site along the east and west sides of southern end of Follins Pond Road, at the 36 Follins Pond Road and 53 Aunt Dorahs Lane properties, respectively. The Coastal Bank on both sides of the road is primarily vegetated with native trees, with some sections along the western bank containing a mix of native and non-native vines. Near the top of the eastern Coastal Bank there is a stone wall and landscape beds associated with the 36 Follins Pond Road residence. Additionally, there is a set of wooden stairs that traverse the bank at the 36 Follins Pond Road property, to provide water access to the residents, and there appears to be a maintained view corridor in line with the dwelling in the vicinity of the stairway. The area landward of the Coastal Bank on the west side of the road remains relatively naturally vegetated at the western side of the 53 Aunt Dorahs property, with similar species to those growing on the face of the Coastal Banks; however, there is also an apparent view corridor in line with the dwelling, where vegetation is actively being maintained. The two most common species observed along the Coastal Banks include pitch pine (Pinus rigida) and black oak (Quercus velutina), with additional smaller quantities of species noted that include white pine (Pinus strobus), poison ivy (Toxicodendron radicans), roundleaf greenbrier (Smilax rotundifolia), Virginia creeper (Parthenocissus quinquefolia), and Asiatic bittersweet (Celastrus orbiculatus). Jordan Mora, APCC April 24, 2023 Page 5 of 6 H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Wetland Memos\Yarmouth (Follins Pond Rd)\230424_YA-BR1_FollinsPond_wetlandsmemo_Final_22032A.docx To determine the State regulatory limits of the Coastal Bank, HW established transects along the face of the Coastal Bank (with white flagging stations) on both sides of Follins Pond Road in accordance with the DEP Program Policy 92-1. Transect 1 (T1) is located on the east side of the road and Transect 2 (T2) is located on the west side of the road. Both Transect 1 and Transect 2 conform to Figure 2 of DEP’s Program Policy 92-1. To determine the local regulatory limits of the Coastal Bank, HW established a series of consecutively numbered white flagging stations along the landward boundary of the Coastal Banks where the first significant break in slope occurred. The flagging stations were labeled TOCB 1 – TOCB 5 (west side of the road) and TOCB 6 – TOCB 9 (east side of the road). Photo 3. View of the Coastal Bank present along the east side of Follins Pond Road. Jordan Mora, APCC April 24, 2023 Page 6 of 6 H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Wetland Memos\Yarmouth (Follins Pond Rd)\230424_YA-BR1_FollinsPond_wetlandsmemo_Final_22032A.docx Photo 4. View of the Coastal Bank present along the west side of Follins Pond Road. Land Subject to Coastal Storm Flowage Land Subject to Coastal Storm Flowage is defined at 310 CMR 10.04 as “land subject to any inundation caused by coastal storms up to and including that caused by the 100-year storm, surge of record or storm of record, which ever is greater.” The project site elements at the southern end of Follins Pond Road are located within a Special Flood Hazard Area, Zone AE (1% annual chance of flooding, with base flood elevations of 9 feet) (see Figure 1 above). Invasive Species Invasive plants (as defined by the Massachusetts Invasive Plant Advisory Group) were present at or near the site but were isolated to a small area of the Coastal Bank just west of Follins Pond Road and limited in abundance. Asiatic bittersweet was the only invasive species noted to be present in this location. The Massachusetts Invasive Plant Advisory Group identifies invasive plant species as “non-native species that have spread into native or minimally managed plant systems in Massachusetts,” and which “cause economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems.” For future planning purposes, the Town may wish to develop a management plan for reducing or eliminating these plants at this site to allow for the establishment of naturally vegetated protective buffers to the wetland resource areas. If you have any questions regarding our findings, or if HW may be of further assistance, please do not hesitate to contact me directly at bwollman@horsleywitten.com or at (508) 833-6600. APPENDIX D – Soil Test Pit Logs Depth standing water in hole (after 1 hour)Form 11 - Soil Suitability Assessment for On-Site Sewage DisposalC. On-Site ReviewCommonwealth of MassachusettsYarmouthCity/Town of VegetationSlope (%)Latitude Longitude41°42'36.8"N 70°11'12.3"WDeep Observation Hole Number:1 2/20/238-10%FewOtherDepthOtherWetlands 20 (salt marsh)feetfeetfeetfeet feetfeetIf Yes:If Yes: Depth weeping from pitSoil Consistence (Moist)Soil StructureRedoximorphic FeaturesCoarse Fragments % by VolumeCobbles/StonesColorPercent GravelDepth (in)Soil Horizon/ LayerSoil Texture (USDA)Soil Matrix: Color-Moist (Munsell)14-22 Bw MS 7.5 YR 6/8 - - - - --5 - GR VFR0-14 A MS 10 YR 3/2 - -48-90 C2 MS 10 YR 8/2 -SG L22-48 C1 MS 10 YR 6/2 - - --- - SG L-- SG LSoil LogAdditional Notes:Moist soil at 90" but not wet. Stopped at 90" due to cave inDrinking Water WellDrainage Way1. Land Use:Description of Location:2. Soil Parent Material:(e.g. woodland, agricultural field, vacant lot, etc.)-9:00 am 40F, rainingWeatherTimeDateHole #3. Distances From:4. Unsuitable Materials Present:5. Groundwater Observed:Open Water BodyProperty Line~50~5Sandy Glaciofluvial depositsOutwash plainLandformFootslopePosition on Landscape (SU, SH, BS, FS, TS)Road ShoulderWest side of Follins Pond RoadSurface Stones (e.g. cobbles, stones, boulders, etc.)NoneYesNoDisturbed SoilFill MaterialWeathered/Fractured RockBedrockYesNo Depth standing water in hole (after 1 hour)Additional Notes:Stopped at 78" due to cave inSG L48-78 C MS 10 YR 8/2 - - - - ---- - SG L----22-48 Bw MS 10 YR 6/4 -SG L14-22 HTM Dense Grade - - - -4-14 HTM MS 10 yr 6/2 - - - - ---5 - GR VFRDepth ColorPercent Gravel Cobbles/Stones0-4 A MS 10 YR 3/2 -Soil LogDepth (in)Soil Horizon/ LayerSoil Texture (USDA)Soil Matrix: Color-Moist (Munsell)Redoximorphic FeaturesCoarse Fragments % by VolumeSoil StructureSoil Consistence (Moist)Otherfeet feet feet4. Unsuitable Materials Present:If Yes:5. Groundwater Observed:If Yes: Depth weeping from pit>100 ftfeet feet feetProperty Line ~5 Drinking Water Well Other3. Distances From: Open Water Body >100 ft Drainage Way Wetlands2. Soil Parent Material:Sandy Glaciofluvial depositsOutwash plain BackslopeLandform Position on Landscape (SU, SH, BS, FS, TS)(e.g. woodland, agricultural field, vacant lot, etc.) Vegetation Surface Stones (e.g. cobbles, stones, boulders, etc.) Slope (%)Description of Location: Southeast corner of intersection of Follins Pond Road/Gun Rock RoadLongitude1. Land Use: Road Shoulder Grass, mulch Few 8-10%Deep Observation Hole Number:Hole # Date Time WeatherLatitude2 2/20/23 8:30 a 40F, raining41°42'40.2"N 70°11'13.3"WCommonwealth of MassachusettsCity/Town of YarmouthForm 11 - Soil Suitability Assessment for On-Site Sewage DisposalC. On-Site ReviewYesNoDisturbed SoilFill MaterialWeathered/Fractured RockBedrockYesNo Depth standing water in hole (after 1 hour)Additional Notes:--5 5 SG L55 SG L56-96 C2 FS 2.5 YR 7/3 -SG L10-56 C1 MS 10 YR 5/6 - - -4-10 Bw MLS 10 YR 3/4 - - - 5 -------Depth ColorPercent Gravel Cobbles/Stones0-4 Pavement - - -Soil LogDepth (in)Soil Horizon/ LayerSoil Texture (USDA)Soil Matrix: Color-Moist (Munsell)Redoximorphic FeaturesCoarse Fragments % by VolumeSoil StructureSoil Consistence (Moist)Otherfeet feet feet4. Unsuitable Materials Present:If Yes:5. Groundwater Observed:If Yes: Depth weeping from pit>100 ftfeet feet feetProperty Line 5-10 ft Drinking Water Well Other3. Distances From: Open Water Body >100 ft Drainage Way Wetlands2. Soil Parent Material:Sandy Glaciofluvial depositsOutwash plain BackslopeLandform Position on Landscape (SU, SH, BS, FS, TS)(e.g. woodland, agricultural field, vacant lot, etc.) Vegetation Surface Stones (e.g. cobbles, stones, boulders, etc.) Slope (%)Description of Location: Southeast corner of bend in Gun Rock RoadLongitude1. Land Use: Road None None (paved) 1-3%Deep Observation Hole Number:Hole # Date Time WeatherLatitude3 2/20/23 1 PM 40F, cloudy41°42'40.2"N 70°11'10.4"WCommonwealth of MassachusettsCity/Town of YarmouthForm 11 - Soil Suitability Assessment for On-Site Sewage DisposalC. On-Site ReviewYesNoDisturbed SoilFill MaterialWeathered/Fractured RockBedrockYesNo APPENDIX E – Operation and Maintenance Guide Stormwater O&M Guide 1 January 2024 Follins Pond Boat Ramp – Yarmouth, MA Stormwater Operations & Maintenance Guide Follins Pond Boat Ramp Table of Contents 1. INTRODUCTION ......................................................................................................................... 2 2. RESPONSIBLE PARTIES AND BUDGET ........................................................................................ 3 3. GREEN STORMWATER INFRASTRUCTURE ................................................................................ 4 3.1. How Does Green Infrastructure Work? .......................................................................................... 4 3.2. What is required for Maintenance? ............................................................................................... 4 3.3. What practices are used at this site? ............................................................................................. 5 4. STRUCTURAL COMPONENTS: INFILTRATION TRENCH .............................................................. 6 5. STRUCTURAL COMPONENTS: STORMTECH INFILTRATION CHAMBERS ................................... 8 6. PLANTINGS ................................................................................................................................ 9 6.1. Plantings ......................................................................................................................................... 9 7. GENERAL SITE MAINTENANCE ............................................................................................... 18 8. LONG-TERM POLLUTION PREVENTION MEASURES ............................................................... 19 APPENDICES A. Inspection Checklists B. Overall Stormwater Control Measures Locations Plan C. Stormtech Owner’s Manual D. Planting Plan E. Operation and Maintenance of Existing Infiltration Systems Stormwater O&M Guide 2 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 1. INTRODUCTION This document provides a general description along with the operation and maintenance requirements for the Follins Pond Boat Ramp Stormwater Retrofit project at Follins Pond Road and Gun Rock Road. The responsible parties are required to inspect and maintain all measures as outlined in this maintenance guide throughout the year. Site maintenance is divided into three categories as outlined below. 1. Green Stormwater Infrastructure • Structural Components • Structural Maintenance Schedule • Planting • Landscape Maintenance Schedule • Weed Guide 2. General Site Maintenance • Trash & Debris • Pet Waste • Pavement Sweeping • Contributing Drainage Areas • Snow Removal • De-icing 3. Long-Term Pollution Prevention Measures Stormwater O&M Guide 3 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 2. RESPONSIBLE PARTIES AND BUDGET The Follins Pond Boat Ramp is a Town-owned and operated boat ramp. The Town will provide staff, volunteers as possible, and funding for the long-term O&M at the site. The estimated average annual O&M budget for the proposed system is shown below: • Infiltration Trench (3): $3,000 ($1,000/trench) • Infiltration Chambers (1): $1,500 ($1,500/chamber system) Owner contact information is provided below: Owner: Town of Yarmouth Contact: Department of Public Works Amanda Lima, Town Engineer 74 Town Brook Road West Yarmouth, MA 02673 508-398-2231 Contact: Division of Natural Resources Bill Bonnetti 424 Route 28 West Yarmouth, MA 02673 508-760-4800 Owner - Signature: Date: Owner - Signature: Date: Stormwater O&M Guide 4 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 3. GREEN STORMWATER INFRASTRUCTURE 3.1. How Does Green Infrastructure Work? Green Stormwater Infrastructure (GSI) is a nature-based approach to stormwater treatment and management. These stormwater practices or “treatment areas” are designed to mimic nature and use the natural filtration properties of soil and plants to remove pollutants from stormwater runoff prior to discharging to the municipal drainage system or waterbodies. GSI relies on the following basic steps to function properly. Structural components of the practices facilitate the functioning of the steps. If one of these steps, or components, does not work properly, the entire system can be compromised and the GSI practice itself could be contributing to maintenance problems. This can lead to landscape nuisances, more frequent maintenance, and costly repairs/improvement. The steps are: 1. Collect (Inlets) 2. Move Water (Conveyance) if needed, can come after capturing sediment 3. Capture Sediment (Pretreatment) 4. Treat and Manage (Filter, Infiltrate or Store) 5. Overflow (Structures and Spillways) 3.2. What is required for Maintenance? As these are nature-based systems that rely on plant upkeep, the maintenance for GSI typically falls under landscape and general site maintenance services. Proper operation and maintenance (O&M) are vital to its long-term viability. Regularly scheduled maintenance can prevent system failures due to sediment build-up, damage, or deterioration. The maintenance requirements outlined in this guide are critical to ensure proper treatment, maintain storage capacity and preserve the visual integrity. General maintenance includes the following: 1. Removing sediment from the pretreatment practices used to capture sediment. 2. Maintaining the proper drainage function and pollutant removal capacity of the systems. 3. Maintaining healthy native trees, plants, and vegetative cover as well as the removal of unwanted weeds and invasive species. It is recommended that all practices be maintained regularly as part of the routine landscape maintenance or at a minimum four times per year and after major rain events: • Early Spring: during spring cleanup • Summer: during lawn mowing and other routine site maintenance • Early Fall: when leaves begin to fall • Late Fall/Early Winter: after all the leaves have fallen during leaf removal • After major storm events: 2” of rain or greater. Stormwater O&M Guide 5 January 2024 Follins Pond Boat Ramp – Yarmouth, MA The following sections describe the general function and landscape maintenance of each practice on the site. Included in the appendices is a specific Inspection Report for the site (Appendix A) along with a plan showing the location of the items to be inspected and maintained (Appendix B). 3.3. What practices are used at this site? The following practices are present at this site: a. Infiltration Trench: Infiltration Trenches are used for temporary underground storage of stormwater in a stone reservoir, allowing it to infiltrate into the underlying native soil. b. Stormwater Underground Infiltration Chambers (UICs): UICs include a range of proprietary, modular structures embedded in clean, crushed stone. They are installed underground, typically under parking or landscaped areas, and create large void spaces for temporary storage of stormwater, allowing it to infiltrate into the underlying native soil. The maintenance for the green infrastructure is divided into two categories: a. The Structural Components that make up the basic steps of a functioning system. b. The Plantings that are the landscape and filtration element. Each category is further described in the sections below. In addition, maintenance of the existing infiltration systems is important for the overall function of the stormwater management at this site. The Town previously received the Operations and Maintenance Plan for the existing infiltration systems along Follins Pond Road, prepared by Norfolk Ram Group, LLC., which is provided in Appendix E of this report. Stormwater O&M Guide 6 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 4. STRUCTURAL COMPONENTS: INFILTRATION TRENCH 1. Collect: Stormwater runoff is collected along the road gutter via overland flow through a water quality unit inlet. 2. Capture Sediment: The water quality unit with catch basin grate captures sediment, trash, and debris. 3. Move Water: Stormwater runoff flows through the 8” perforated underdrain pipe which discharges to the stone reservoir. 4. Infiltrate: Stormwater is infiltrated into the subsoils. 5. Overflow: During larger rain events, once the stone reservoir and water quality unit have reached capacity, runoff will continue down the boat ramp. 1 4 2 4 3 5 Stormwater O&M Guide 7 January 2024 Follins Pond Boat Ramp – Yarmouth, MA MAINTENANCE SCHEDULE: INFILTRATION TRENCH A site inspection of the infiltration trench components shall be conducted at least twice a year in the Spring and Fall, and after major storm events (2” of rain or greater). Debris and trash should be removed monthly (between April and November) and sediment removal should occur during the two site inspections and during the monthly debris and trash inspections as needed. See the calendar below and the Inspection Report in Appendix A for more information. Infiltration Trench General Maintenance Schedule Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Task Frequency & Time of the Year Site Inspection X X Debris & Trash Removal X X X X X X X X Sediment Removal X x x x x x x X should also be completed after major storm events X required inspection x as needed • After rain event look for: o If standing water does not drain after 48 hours. See Inspection Report for action items. See Plantings section for information on plantings maintenance of the infiltration basin. Use the plantings maintenance calendar to combine maintenance efforts. Stormwater O&M Guide 8 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 5. STRUCTURAL COMPONENTS: STORMTECH INFILTRATION CHAMBERS See Appendix C for the Stormtech Owner’s Manual. Stormwater O&M Guide 9 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 6. PLANTINGS 6.1. Plantings The planting design for the site consists of three landscape maintenance areas. The “mow” area which consists of turf, the “no mow” areas. The plantings maintenance checklist is included in Appendix A, and the full planting plan is available in Appendix D. “Mow” Areas No “Mow” Area Stormwater O&M Guide 10 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: “MOW” AREAS MAINTENANCE There is an area of the site that is allowed to be maintained as “mowed” lawn as necessary. Landscape maintenance of “mowed” lawn areas includes the following: Seeding Loam and reseed bare spots with a seed mix that matches existing species. Mowing/Weed Whacking Cut only 1/3 of vegetation. Do not mow during drought periods or when excessively wet. Depending on height of grasses and the time of year, grass cuttings/stalks may need to be raked and removed from site. Watering Allowing the lawn areas to “brown” is desired. Water only during drought conditions or during reseeding establishment period. Fertilizing No fertilizer shall be used. Weeding Weeding should be limited to invasive and weedy species (see section 3.6 Weed Identification below and the Weed Guide at https://web.uri.edu/riss/files/In-the-Weeds.pdf). Non-chemical methods (hand pulling and hoeing) are required; chemical herbicides should be avoided. Properly remove and dispose of all invasive species off site as to prevent colonization elsewhere, this includes disposal on land beyond the project area. Monitoring During the establishment period, walk the mow areas monthly during the first year to look for invasive species, bare spots and identify potential pest or disease problems. Properly remove and dispose of all invasive species as to prevent colonization elsewhere, this includes disposal on land beyond the project area. Debris & Trash Remove and properly dispose litter from all areas prior to mowing. Stormwater O&M Guide 11 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: NO “MOW” AREA MAINTENANCE (INFILTRATION TRENCHES) By design, plants in no “mow” areas are meant to flourish throughout the growing season, leaving dry standing stalks during the dormant months. Plants do not require fertilizers or watering (except during drought or establishment period). Frequent mowing would eliminate selected species, may promote the growth of undesirable plants, and require additional maintenance and watering. It is recommended that herbaceous materials in this area be cut back no more than one time per year and only as necessary. Remove and replace vegetation as necessary, using the appropriate species as shown on the Planting Plan. The best time to plant is in early to mid-fall or early to mid-spring. Specific maintenance activities of the “no mow” area include: Seeding Loam and reseed bare spots with the specified seed mix as shown on the Planting Plan. Cutting Back Cut herbaceous materials with shears a maximum of once a year in early spring. Otherwise, allow herbaceous materials to grow to their natural heights (12” to 36”) to maintain a natural appearance. Do NOT cut area lower than 6” – maintain sporadic wooden stakes on site at 6” height to provide visual cues during cutting. Depending on height of grasses and the time of year, grass cuttings/stalks may need to be raked and removed from site so as not to clog drainage. Use a leaf blower as needed to assist in clean-up. Mulching Replenish mulched areas once per year to maintain a minimum mulch depth of 3”. Use locally sourced double-shredded wood or bark mulch free of weed seed and dyes. Pruning Prune trees and shrubs to remove deadwood and low hanging branches. Watering Water only during drought conditions or during reseeding establishment period. Fertilizing No fertilizer shall be used. Weeding Weeding should be limited to invasive and weedy species (see section on Weed Identification below and the Weed Guide at https://web.uri.edu/riss/files/In-the-Weeds.pdf). Non-chemical methods (hand pulling and hoeing) are required; chemical herbicides should be avoided. Properly remove and dispose off site all invasive species as to prevent colonization elsewhere; this includes disposal on land beyond the project area. Monitoring During the establishment period, walk the “no mow” areas monthly without the intent to cut, but to look for invasive species, bare spots and identify potential pest or disease problems. Debris & Trash Remove and properly dispose of litter from all areas. Stormwater O&M Guide 12 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: REPLACEMENTS The plants that thrive in infiltration trenches are typically quite drought tolerant due to the filter profile having a top layer of planting soil and sandy soil media below. They need to be able to withstand periods of inundation after storm events; however, when it doesn’t rain, there will be less water held naturally in the sand than in other soil types for the plants to use, so they need to tolerate dry periods as well. Specifying plants native to the area increases the ecosystem benefits by helping to support native wildlife like pollinators. If replacements are needed, use the planting plan as a guide (see Appendix D). However, if all the plants of a certain species have not done well in the infiltration trenches or other locations on the site, do not replace with that same species. Rather, replant with one or more of the other species that has thrived under the conditions or have a plant professional choose a different species based on current photos of the site. Site specific considerations for plants in infiltration trenches should be: • Preferably native and pollinator-friendly • Drought tolerant • Tolerant of inundation for 24 hours • Salt and wind tolerant • A mix of different types of plants that will create a resilient plant community: cold & warm season grasses, perennials, groundcovers in all areas. Stormwater O&M Guide 13 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: MAINTENANCE SCHEDULE By design, plants in the infiltration trenches are meant to help uptake nutrients from the stormwater and flourish throughout the growing season. The plants do not require fertilizers or mulch, and, after establishment, only need water during periods of drought. Remove and replace vegetation as necessary, using the appropriate species as discussed in the no-mow section above. Weeding and monitoring for invasive species should occur quarterly during the growing season. An annual spring “clean up” includes cutting last season’s growth of the perennials and pruning as needed. See the calendar below, the Plantings Maintenance Checklist in Appendix A, the Weed Identification section, and the Weed Identification Guide at https://web.uri.edu/riss/files/In-the-Weeds.pdf for more information. Infiltration Trenches Landscape Maintenance Schedule Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Task Frequency & Time of the Year Cutting/Mulching X Mowing x X x x x x x x X x x Weeding X X X X Monitoring X X X X Watering x x x x Seeding x x x x Plant Replacement x x x x “Mow” Areas No “Mow” Areas All areas X required x as needed • Trash and debris are removed during monthly structural component inspections but can also be completed during landscape maintenance visits for weeding and monitoring. Stormwater O&M Guide 14 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: WEED IDENTIFICATION Yellow Toadflax (Linaris vulgaris) Redroot Pigweed- (Amaranthus retroflexus) Smartweed (Polygonum lapathifolium) Dandelion (Taraxacum officinale) Stormwater O&M Guide 15 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: WEED IDENTIFICATION Fireweed (Erechtites hieracifolia) Spotted Spurge (Euphorbia maculata) Crabgrass (Digitaria ischaemum) Crabgrass with seedheads Ragweed (Ambrosia artemisiifolia) Japanese Knotweed (Polygonum cuspidatum) Stormwater O&M Guide 16 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: WEED IDENTIFICATION Ragweed (Ambrosia artemisiifolia) Oriental Bittersweet (Celastrus orbiculatus) Green Foxtail (Setaria viridis) Norway Maple Tree Seedling (Acer platanoides) Stormwater O&M Guide 17 January 2024 Follins Pond Boat Ramp – Yarmouth, MA PLANTINGS: WEED IDENTIFICATION Catalpa Tree Seedling (Catalpa speciosa) Purple Loosestrife (Lythrum salicaria) Field Bindweed (Convolvulus arvensis) Black Swallow-wort (Cynanchum louisea) Stormwater O&M Guide 18 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 7. GENERAL SITE MAINTENANCE General site maintenance includes the following requirements: Trash & Debris Remove and properly dispose of all trash and debris. Pet Waste Visitors to the site are encouraged to pick up after their pets. Remove and properly dispose of all pet waste left behind. Pet waste should be picked up and disposed of properly to reduce bacteria and nutrient levels in stormwater. Pavement Sweeping Paved roadways should be mechanically swept, at a minimum of once per year in early spring, to remove accumulated sand and sediment debris. There is a lot of leaf litter at this site, so it is recommended to remove leaf litter a few times during the fall months. Snow Removal Due to the potential for plant damage, snow piling and or removal is NOT recommended in the infiltration trenches. De-Icing When de-icing compounds are necessary for areas draining to the green stormwater infrastructure, the least harmful chemicals should be used. Excessive salting should be avoided. Use of large amounts of sand should also be avoided, since it may obstruct the conveyance system. Ice removal is NOT permitted in the infiltration trenches. Stormwater O&M Guide 19 January 2024 Follins Pond Boat Ramp – Yarmouth, MA 8. LONG-TERM POLLUTION PREVENTION MEASURES Long-term pollution prevention measures implemented at the site reduce pollutants in stormwater discharges. The following precautions will be employed on an on-going basis. Spill Prevention & Control Measures To minimize the risk of spills or other accidental exposure of materials and substances to stormwater runoff, the following material management is to be used when working on site. • Any materials stored on-site will be stored in a neat, orderly manner in their appropriate containers. • Products will be kept in their original containers with the original manufacturer’s label. • Substances will not be mixed with one another unless recommended by the manufacturer. • Manufacturers’ recommendations for proper use and disposal will be followed. • The contractor’s supervisor will be issued this Guide to ensure proper use and disposal of materials. Materials or substances listed below may be present on-site for maintenance and care should be taken to avoid spills: o Petroleum Based Products The following product-specific measures will be followed on-site: • Petroleum Products - All on-site vehicles will be monitored for leaks and receive preventative maintenance to reduce the chance of leakage. • Grass Clipping, Leaf Litter and Plant Debris – are to be removed from the property and not disposed on site. APPENDIX A – Inspection Checklists • Infiltration Trenches • Underground Infiltration Chambers • Landscaping Operation and Maintenance Checklist  Follins Pond Boat Ramp  1 Date:  Time:  Inspector:  Maintenance Item Description Maintenance (Y/N) 1, 2 & 3. Catch Basins Debris Cleanout Remove all trash, leaf litter and debris from the catch basins, inlet flumes, and forebays. Sediment/Organic Debris Removal Check for clogging and sediment accumulation that impacts inflow and outflow. Remove and properly dispose of when sediment is >3” in forebays. Remove/cut any vegetation that sprouts through voids in stone, pavement, or pavers. Erosion Check for areas of erosion (gullies, animal burrowing, or overtopping), particularly near check dam weirs, perimeter, and guard rail posts. Repair as necessary and return to design grades. Actions to be taken: 4 & 5. Infiltration Trenches and Underground Infiltration Chambers Debris Cleanout Remove trash and debris from the surface. Erosion Signs of erosion gullies, animal burrowing, or overtopping are observed. Repair as necessary. Sediment/Organic Debris Removal Remove sediment accumulation and properly dispose when accumulation is greater than or equal to 3 inches.* Water Draining properly Check for leaf litter, debris, and sediment accumulation in overflow structures that impact inflow to underground infiltration features. If accumulation present, schedule cleaning. Check for sediment accumulation and/or standing water that indicates clogging in the infiltration trench. If sediment or standing water is observed in the trench for more than 48 hours after a storm event, clean out infiltration trench. Check for sediment accumulation and/or standing water that indicates clogging in the chambers. If sediment or standing water is observed in chambers (use inspection ports) for more than 48 hours after a storm event, clean out chambers per manufacturer’s instructions in Appendix C.* Actions to be taken: Operation and Maintenance Checklist  Follins Pond Boat Ramp  2 General Site Maintenance Debris Removal Remove trash from perimeter areas. Pet Waste Removal Remove any pet waste from perimeter areas. Pavement Sweeping Sweep road minimum once a year after spring thaw. Contributing drainage area Confirm that contributing drainage area stabilized – stabilize as necessary. Snow Removal Ensure snow piles do no block inlet structures and are not placed in the green stormwater infrastructure. De-Icing If needed on road, use de-icing compounds with the least harmful chemicals. Avoid excessive salting or large amounts of sand. Actions to be taken:   *Sediment shall be disposed of offsite in a pre-approved location. Plantings Maintenance Checklist  Follins Pond Boat Ramp  1 Location: Date: Inspector: Task Description Complete (Y/N) Cutting  Cut with shears once a year in the early spring.  Do not cut lower than 6”.  Blow out leaves and cuttings for easy removal.  Remove cuttings so the bioretention area does not clog. Mowing  Mow twice a year or more frequently as needed with a mulching mower or weed whacker depending on the frequency of cutting.  Bag clippings as needed and dispose of off site.  Maintain a cutting height of 3” or greater.  Leave the grass taller in the warmer months.  Trim edges when necessary. Weeding  Weeding should be limited to invasive and exotic species, which can overwhelm the desired plant community.*  Non-chemical methods including hand pulling and hoeing are recommended.  Chemical herbicides are not allowed. Monitoring  Look for potential invasive species and identify potential disease. Remove and dispose of all invasive species.* (see weeding) Watering  During establishment or drought conditions, plants should be watered a minimum of once every seven to ten days. Seeding  Loam and re-seed bare spots with the specified seed mix as shown on the Planting Plan. Plant Replacement  Replace/replant diseases, unhealthy or dead plans to maintain a healthy plant community Fertilizing NONE Mulch NONE Actions to be taken: *Invasive species shall be disposed of offsite in a pre-approved location. “Mowed” Areas No “Mow” Areas (Bioretention Areas) All areas APPENDIX B – Overall SCM Locations G G G G G G G G G G G G G G G G G GGGGGGGGGGG GGGGGGGGGGGGGGGGGGGGGGGG G G G G G GDD DWVHYDWVGVGVRIM: 33.33'RIM: 32.65'RIM: 34.80'RIM: 34.39'RIM: 32.63'RIM: 36.28'TIMBER WALLS26 GUN ROCK ROADN/FVALENTIRIM: 35.38'RIM: 35.13'RIM: 36.21'DDDDDPROTECT WATER ANDGAS LINE DURINGCONSTRUCTION12" HDPEL=21 S=1.18%MATCHLINE (SHEET 1)MATCHLINE (SHEET 2)INFILTRATION TRENCH 370' (L) x 4.5' (W)TOP OF STONE: 32.00'DISTRIBUTION PIPE: 31.00'BOT. OF STONE: 29.00'BOT. OF PEA GRAVEL: 28.50'STORAGE VOLUME: 840 CF ±6" PERF. HDPEL=47 S=0.00%0+000+501+00 CB 301RIM:35.08'12" INV OUT WITH HOOD (E):32.50'12" HDPEL=17 S=1.32%3035282931323334363738390+000+501+001+502+002 + 5 0 2+80ABANDON EXISTINGCATCHBASIN IN PLACEUNDERGROUND RECHARGE CHAMBERS (URC-1)SIZED FOR 25-YEARS STORMTOP OF STONE: 34.00'TOP OF CHAMBER: 33.00'BOT.OF CHAMBER: 28.00'BOT.OF STONE: 27.25'STORAGE VOLUME: 6,100 CF±CONVERT EXISTING MH TOCATCHBASIN & RESET FRAMERIM: 35.09'EXISTING 12" INV IN (APPROX): 31.0'EXISTING 12" INV OUT: UNKNOWNPROPOSED 12" INV IN: 32.25'6" HDPEL=16 S=0.00%LIMIT OF REPAVING20.0'19.0'R25.0'CB 401RIM:36.13'12" INV OUT (W):31.90'DMH 400RIM:36.44'WEIR: 33.50'12" INV IN (E):31.60'12" INV IN (E):31.60'24" INV OUT (W):28.19'24" INV OUT (S):29.92'6" HDPEL=10 S=0.00%INSPECTIONPORT (TYP)LIMIT OF WORKCOFOLLINS POND ROAD ALIGNMENTGUN ROCK ROAD ALIGNMENT36.8036.8836.2133.6832.2931.5935.6429.3835.3636.4136.3536.72BB:36.53TB:36.78BB:36.30TB:36.5536.6736.4736.4736.7136.8436.35BB:36.47TB:36.7236.40BB:36.30TB:36.55BB:36.11TB:36.36BB:35.97TB:36.2236.4936.6236.25APPROXIMATE OUTLINE OFEXISTING INFILTRATION SYSTEM #3APPROXIMATE STORAGE VOLUME:1,000 CF±COCOREPLACE EXISTING DCB GRATES WITH HIGHCAPACITY ANGLED GRATE (2)RESET RIM WITH LOCALIZED PAVED DIPEAST RIM: 35.30'WEST RIM: 35.25'EXISTING 12" INV IN (APPROX): 32.4'EXISTING 12" INV OUT (APPROX): 32.8'PROPOSED 6" INV OUT WITH HOOD:31.00'36RESTORE GRADE OVERTRENCH TO MATCHEXISTING GROUNDCOISOLATOR ROWMANIFOLD12" STUBGUN ROCK ROADFOLLINS POND ROADR30.0'BB:36.58TB:36.83BB:36.33TB:36.58CB 402RIM:36.11'12" INV OUT (W):31.85'12" HDPEL=18 S=1.11%REMOVE ANDRESET MAILBOX3824" HDPEL=8 S=0.00%36.4636.5536.69BB:36.15TB:36.4036.3036.4136.4536.5036.2936.3437REMOVE ANDRESET MAILBOXRIM: 32.92'RIM: 33.67'RIM: 33.57'RIM: 32.84'APPROXIMATE LOCATION OF EXISTING DRAIN PIPE (TYP.)0"34.2TP-2DATE:JANUARY 19, 2023HTM10YR 6/2MEDIUM SANDHTMDENSE GRADE78"22"14"4"33.933.032.327.748"30.2Bw10YR 6/4MEDIUM SANDA10YR 3/2MEDIUM SANDC10YR 8/2MEDIUM SANDCAVE IN @ 78"NO GROUNDWATERFEATURES OBSERVED0"37.2TP-3Bw10YR 3/4MEDIUM LOAMYSANDC110YR 5/6MEDIUM SAND96"10"4"36.936.429.2PAVEMENT56"32.5C22.5YR 7/3FINE SANDNO GROUNDWATERFEATURES OBSERVEDPERFORMED BY:E HOFFMAN HORSLEY WITTEN GROUP, INC.DATE:JANUARY 19, 2023SOIL TEST PIT DATA41022032Aoflast modified: 01/15/24 printed: 01/15/24 by eh H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Drawings\FOLLINS\22032 FOLLINS ST.dwg (in feet)GRAPHIC SCALE01051020401 INCH = 10 FEET4C -Checked By:Designed By:Date:Drawn By: Sustainable Environmental Solutions www.horsleywitten.com 90 Route 6A Sandwich, MA 02563 508-833-6600 voice 508-833-3150 fax Horsley Witten Group, Inc.Revisions Appr.Rev.Date By Description 1 2 3 4 5 6 7 JANUARY 2024 EWH EWH GK SITE AND GRADING PLAN (1) FOLLINS POND CAPE COD BOAT RAMP STORMWATER RETROFIT PROJECT - PERMITTING PLANS YARMOUTH, MA Survey Provided By:Sheet Number:Project Number:Registration:Prepared For:Plan Set: Plan Title:Sheet :Horsley Witten Group, Inc. 90 Route 6A Sandwich, MA 02563 Phone: (508) 833-6600 Fax: (508) 833-3150 Dated: January 25, 2023 Town of Yarmouth 1146 MA-28 South Yarmouth, MA Phone: (508) 398-2231 Fax: ---- MANHOLE COVER OR CATCH BASIN FRAME & GRATE ADJUSTMENTNOT TO SCALENOTES:1.ANY REPLACEMENT STRUCTURES (FRAME & COVERS AND/OR FRAME & GRATE) TO BE DESIGNED FOR HS-20LOADING.2.REPLACEMENT STRUCTURES TO CONFORM TO MASSACHUSETTS STANDARDS WITH DIMENSIONS TO SUIT.(LEBARON FOUNDRY, NEENAH CASTINGS, OR APPR. EQUIVALENT).3.ALL STRUCTURES TO BE SET IN FULL MORTAR BED FLUSH WITH THE BINDER COURSE OF PAVEMENT.ADJUST TO GRADE WITH CLAY BRICK AND MORTAR (2 BRICK COURSES TYPICALLY, 5 BRICK COURSESMAXIMUM) OR PRECAST CONCRETE RISER.4.RIM TO BE FLUSH WITH TOP COAT AND ALL MORTAR TO BE COMPLETELY COVERED WITH A LAYER OF TOPCOAT PER THE DETAILS.EXISTINGOPENING8" WIDE FULLBED OF MORTARSTRUCTURE (FRAME & COVERAND/OR FRAME & GRATE) TO SUITRAISE OR LOWER RIM FLUSH TOPROPOSED FINISH PAVEMENT GRADEBACKFILL & COMPACTPER PAVEMENT DETAILSEXCAVATE TO A SOLIDBASE PRIOR TO SETTINGBRICK OR MORTARMORTAR FLUSH WITHBINDER COURSE OFPAVEMENTPAVEMENTPATCH ASNECESSARY(SEE DETAILS)NOTES:1.ALL SECTIONS WILL BE DESIGNED FOR H-20 LOADING.2.PROVIDE "V" KNOCKOUTS FOR PIPES WITH 2" MAXIMUMCLEARANCE TO OUTSIDE OF PIPE. MORTAR ALL PIPECONNECTIONS.3.JOINT SEALANT BETWEEN PRECAST SECTIONS WILL BEPREFORMED BUTYL RUBBER.4.CATCH BASIN FRAME & GRATE WILL BE SET IN FULL 1-0"WIDE MORTAR BED. ADJUST TO GRADE WITH PRECASTCONCRETE RISER OR BRICK.5.DO NOT PLACE MORTAR BED AROUND STRUCTUREUNTIL IT IS AT THE REQUIRED FINISH ELEVATION &ALIGNMENT.6.FRAME & COVER TO CONFORM TO MASSACHUSETTSSTANDARDS HEAVY DUTY (EAST JORDAN, NEENAH, ORAPPROVED EQUIVALENT).7.HDPE PIPE HOOD WILL BE 90° BEND FASTENED TO PIPEWITH SEALANT. BEND TO HAVE 1" PURGE HOLE DRILLEDINTO TOP OF ELBOW.8.HOOD WILL BE "THE ELIMINATOR" OIL & FLOATINGDEBRIS TRAP (MANUFACTURED BY GROUND WATERRESCUE, INC., QUINCY, MA., TEL. 617-773-1128 ON THEWEB @ WWW.KLEANSTREAM.COM) OR APPROVEDEQUIVALENT.9.CONCRETE PIPE HOOD WILL BE "SNOUT" OR APPROVEDEQUIVALENT.ALTERNATE ECCENTRIC CONEALTERNATE TOP SLABPRECAST CONCRETE CATCH BASIN (CB) WITH HOODNOT TO SCALE4'-0"Ø MIN.8" MIN.1'-0"Ø VARIES1'-0"MIN.6" MIN.2'-0" MIN.1'-0" COLLAR2'-0" SQ.OPENING4'-0"Ø MIN.SUMP(4'-0" MIN.)TOP SLABCONCENTRICCONE SECTION(SEE ALTERNATE)RISER AS REQ'DSECTION(S)MONOLITHICBASE SECTIONIN GRASS1'-0"6" MIN.FINISH GRADEOUTLET PIPESEE NOTE #2.APPROVEDCOMPACTEDSUBGRADEHOOD (SEENOTE #7)SEE NOTE #3.3/4"WASHEDSTONESEE NOTES #4 & 52'-0" SQ.OPENINGSUMP ELEV.34" COMPACTEDCRUSHED STONEINVERTNOTES:1.INSTALL DRAIN PIPE & FITTINGS IN STRICTACCORDANCE WITH THE INSTALLATIONRECOMMENDATIONS OF THE PIPE FITTINGMANUFACTURER. SUCH INSTRUCTIONS INCLUDEBUT ARE NOT LIMITED TO CUTTING, SOLVENTCEMENTING & PRIMING, JOINTS, CONNECTIONS,TRANSITIONS & ALLOWANCE FOR THERMALEXPANSION.2.FOUNDATION: WHERE THE TRENCH BOTTOM ISUNSTABLE, THE CONTRACTOR WILL EXCAVATETO A DEPTH REQUIRED BY THE ENGINEER &REPLACE WITH A SUITABLE COMPACTED GRAVELMATERIAL OR AS AN ALTERNATIVE & AT THEDISCRETION OF THE ENGINEER. THE TRENCHBOTTOM MAY BE STABILIZED USING A WOVENGEOTEXTILE FABRIC.3.BEDDING, HAUNCHING & INITIAL BACKFILL:SUITABLE MATERIAL WILL CONSIST OF CLEAN,HARD, PARTICLES OF GRAVEL MEETING THEFOLLOWING:SIEVE SIZEPERCENT PASSING3/4"85-95# 45-15# 80-34.BEDDING: UNLESS OTHERWISE APPROVED BYENGINEER, MATERIAL WILL BE INSTALLED ASREQUIRED IN ASTM D2321, LATEST EDITION.UNLESS OTHERWISE SPECIFIED BY THEENGINEER, MINIMUM BEDDING THICKNESS WILLBE 4" FOR 4" - 2'-0" PIPE, 6" FOR 2'-6" - 3'-6 PIPE", &1'-0" FOR 4'-0" & LARGER PIPE.5.FINAL BACKFILL: COMPACTED NATIVE GRAVEL OR FLOWABLE FILL.6.GENERAL BACKFILLING: (INCLUDING DISTURBEDAREAS SURROUNDING TRENCHES) WILL BEPLACED & COMPACTED IN 1'-0" MAXIMUMVERTICAL LIFTS. CONTRACTOR WILL ACHIEVE95% COMPACTION FOR THE BEDDING UNLESSOTHERWISE APPROVED BY THE ENGINEER.7.TRENCH WIDTH: UNLESS OTHERWISE SPECIFIEDBY THE ENGINEER, MINIMUM TRENCH WIDTHSWILL BE AS FOLLOWS:PAVED AREALANDSCAPED AREADRAINAGE PIPE TRENCHNOT TO SCALEMIN. PIPECOVER 30"REMOVE PAVEMENT WITHNEAT SAWCUT LINESMATCH EX. PAVEMENT& SUB-BASE WHERENECESSARYNOMINAL Ø8"10"1'-0"1'-3">1'-6"MIN. RECOMMENDEDTRENCH WIDTH2'-6"3'-0"3'-0"3'-6"5'-0"FOUNDATIONUNDISTURBED EARTHSURFACE MATERIAL PER PLANSDRAINAGE PIPEMIN. TRENCH WIDTHBEDDING MATERIALHAUNCHING TOSPRINGLINE OF PIPEINITIAL BACKFILL6" - 1'-0" ABOVETOP OF PIPEFINALBACKFILLVARIESPERMITTING SET ONLYNOT FOR CONSTRUCTIONECCENTRICCONE SECTIONSEE ALTERNATETO SLABNOTES:1.ALL SECTIONS WILL BE DESIGNED FOR H-20 LOADING.2.COPOLYMER MANHOLE STEPS WILL BE INSTALLED AT 1'-0" O.C. FOR THE FULL DEPTH OF THE STRUCTURE.3.PROVIDE "V" KNOCKOUTS FOR PIPES WITH 2" MAXIMUM CLEARANCE TO OUTSIDE OF PIPE. MORTAR ALLPIPE CONNECTIONS.4.JOINT SEALANT BETWEEN PRECAST SECTIONS WILL BE PREFORMED BUTYL RUBBER.5.DRAIN MANHOLE FRAME & COVER WILL BE SET IN FULL 1'-0" MORTAR BED. ADJUST TO GRADE WITHPRECAST CONCRETE RISER OR BRICK.6.DO NOT PLACE MORTAR BED AROUND STRUCTURE UNTIL IT IS AT THE REQUIRED FINISH ELEVATION &ALIGNMENT.7.FRAME & COVER TO CONFORM TO MASSACHUSETTS STANDARDS HEAVY DUTY (EAST JORDAN, NEENAH,OR APPROVED EQUIVALENT).4'-0"Ø MIN.8" MIN.2'-0"ØACCESS1'-0"8"2'-0"ØACCESS8"1'-0"MIN.6" MIN.PRECAST DRAIN MANHOLE (DMH)NOT TO SCALEALTERNATE TOP SLABIN GRASSCOMPACTED SUBGRADE34" COMPACTEDCRUSHED STONESEE NOTE #3Ø VARIESSEE NOTE #4SEE NOTES#5 & 6.FINISH GRADESTEPS (SEENOTE #2)RISERSECTION ASREQUIREDMONOLITHICBASE SECTION4'-0"Ø MIN.SLOPESLOPE G G G G G G G G G G G G G G G G G G G G G GGDDDDWVHYDGVWVRIM: 15.67'RIM: 15.59'RIM: 15.52'RIM: 15.45'RIM: 14.16'RIM: 13.55'RIM: 13.31'RIM: 13.98'RIM: 19.10'RIM: 19.03'RIM: 19.03'RIM: 18.91'TIMBER WALLCOBBLESTONE STRIPSHEDCOASTAL BANK 50' BUFFER ZONECOASTAL BANK 100' BUFFER ZONECOASTAL BANK 35' UNDISTURBED VEGETATIVE BUFFERCOASTAL BANK 50' BUFFER ZONE32 FOLLINS POND RDN/FGOERING32 GUN ROCK ROADN/FCOLLINSRIM (APPROX): 17.82'RIM (APPROX): 17.14'RIM (APPROX): 18.26'RIM (APPROX): 17.55'RIM (APPROX): 16.99'DDDDDDDDDRIVEWAYDRIVEWAYRIM: 15.09'RELOCATE SIGNCOORDINATE WITH OWNERLIMIT OF WORKFOLLINS POND ROADREPLACE EXISTING DCB GRATES WITH HIGH CAPACITYANGLED GRATE (4)RESET RIM WITH LOCALIZED PAVED DIPREPLACE EXISTING DCB GRATES WITH HIGHCAPACITY ANGLED GRATE (4)RESET RIM WITH LOCALIZED PAVED DIPAPPROXIMATE OUTLINE OF EXISTINGINFILTRATION SYSTEM #2APPROXIMATE STORAGE VOLUME: 1,000 CF±APPROXIMATE OUTLINE OF EXISTING INFILTRATION SYSTEM #1APPROXIMATE STORAGE VOLUME: 1,000 CF±MATCHLINE (SHEET 1)MATCHLINE (SHEET 2)INFILTRATION TRENCH 128' (L) x 8.5' (W)TOP OF STONE: 20.00'DISTRIBUTION PIPE: 19.00'BOT.OF STONE: 17.00'BOT.OF PEA GRAVEL: 16.50'STORAGE VOLUME: 300 CF ±1+502+002+503+003+40 1520251213141617181921222324262728LIMIT OF REPAVINGMATCH EXISTING GRADECB 101RIM:20.53'12" INV IN (W):17.75'6" INV OUT (E):19.00'CB 102RIM:20.53'12" INV OUT (E):18.00'12" HDPEL=16 S=1.25%6" PERF. HDPEL=22 S=0.00%CB 201RIM:23.35'12" INV IN (W):20.50'6" INV OUT (E):21.75'CB 202RIM:23.35'12" INV OUT (E):20.75'12" HDPEL=16 S=1.25%6" PERF. HDPEL=20 S=0.00%INFILTRATION TRENCH 225' (L) x 8.5' (W)TOP OF STONE: 22.75'DISTRIBUTION PIPE: 21.75'BOT.OF STONE: 19.50'BOT.OF PEA GRAVEL: 19.25'STORAGE VOLUME: 740 CF±24.8326.35FOLLINS POND ROAD ALIGNMENTCOCORIM: 13.37'RIM: 13.35'RIM: 14.04'RIM: 14.03'RIM: 14.82'RIM: 15.36'RIM: 15.40'RIM: 15.44'RIM: 15.48'RIM: 17.05'RIM: 17.59'RIM: 17.33'RIM: 17.99'RIM: 18.27'RIM: 19.09'RIM: 19.17'RIM: 19.24'RIM: 19.16'15.4015.4419.1319.20Revisions Appr.Rev.Date By Description 1 2 3 4 5 6 7 JANUARY 2024 EWH EWH GK SITE AND GRADING PLAN (2) FOLLINS POND CAPE COD BOAT RAMP STORMWATER RETROFIT PROJECT - PERMITTING PLANS YARMOUTH, MA Survey Provided By:Sheet Number:Project Number:Registration:Prepared For:Plan Set: Plan Title:Sheet :Horsley Witten Group, Inc. 90 Route 6A Sandwich, MA 02563 Phone: (508) 833-6600 Fax: (508) 833-3150 Dated: January 25, 2023 Town of Yarmouth 1146 MA-28 South Yarmouth, MA Phone: (508) 398-2231 Fax: ----51022032Aoflast modified: 01/15/24 printed: 01/15/24 by eh H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Drawings\FOLLINS\22032 FOLLINS ST.dwg(in feet)GRAPHIC SCALE01051020401 INCH = 10 FEET5C -Checked By:Designed By:Date:Drawn By: Sustainable Environmental Solutions www.horsleywitten.com 90 Route 6A Sandwich, MA 02563 508-833-6600 voice 508-833-3150 fax Horsley Witten Group, Inc. 5 18"DRAINAGE STRUCTURE FRAME & COVER/GRATENOT TO SCALENOTES:1.FRAME & COVER TO CONFORM TO MASSDOT (EASTJORDAN, NEENAH OR APPROVED EQUIVALENT).2.ALL H20 LOADING.3.MINIMUM FRAME WEIGHT:4" FLANGE 295 LBS3" FLANGE 265 LBS4.MATERIAL-CAST IRON.5.MINIMUM GRATE WEIGHT: 200LBS.6.SEE CATCH BASIN & MANHOLE DETAILS FOR INSTALLATION.2'-0"3" MIN.4" TYP.7/8"2"1'-9 34"2 18"3"2'-0"2"2'-0"2'-0"1" LIFT HOLE2'-0"114"1 12" MIN.1"DRAIN3"GRATE PLANSOLID COVER PLANSECTION A-ASECTION A-ASOLIDCOVERMANHOLEFRAMEAAAGUTTER LINE1 14"2 12"ACLPERMITTING SET ONLYNOT FOR CONSTRUCTIONINFILTRATION TRENCH PLAN VIEWNOT TO SCALEA'ASEE PLANS3' (TYP.)2' (TYP.)8" PERFORATEDSDR-35 PVC PIPECLEANOUTSEE DETAILBIT. BERMSEEPLANSCATCHBASINLOAM AND SEED.SEE PLANTING PLAN6 "3'6"VARIESINFILTRATION TRENCH CROSS SECTION A-A'NOT TO SCALEINVERT PERFORATED PIPEBOTTOM OF PEA GRAVELBOTTOM OF 34" WASHED CRUSHED STONETOP OF 34" WASHED CRUSHED STONEBIT. BERMDEEP SUMPCATCHBASIN8" SDR-35 PERFORATED PVC PIPE. 8"PERFORATED SDR-35 PVC PIPE3 ROWS SET AT 4-8-12 O'CLOCK (120° APART)34" WASHED CRUSHED STONE38" WASHED PEA GRAVELNON-WOVEN GEOTEXTILEOR EQUAL ON TOP & SIDESOF STONESEE PLANSCLEAN FILL4" LOAM AND SEEDSEE PLANTING PLANLEVEL, STABLE SUBGRADESCARIFIED TO 3" DEPTH.DO NOT COMPACT.1'LOAMY SAND1'(MIN.)CLEANOUT (CO)NOT TO SCALE1'34" WASHEDCRUSHED STONE8" PERFORATEDPVC PIPE38" WASHEDPEA GRAVEL45° ELBOW ADAPTER FOR8" PVC UNDERDRAIN PIPECAST IRON CLEANOUTCOVERVARIES6" PVC THREADEDCAP6" DIA. PVC PIPE8" TO 6" DIA.PVCREDUCERCLEANFILL4" LOAM ANDSEEDLOAMY SAND APPENDIX C –Underground Infiltration Chambers • Sample Manufacturer’s O&M Manual Isolator® Row Plus O&M Manual 2 Looking down the Isolator Row PLUS from the manhole opening, ADS PLUS Fabric is shown between the chamber and stone base. StormTech Isolator Row PLUS with Overflow Structure (not to scale) The Isolator® Row Plus Introduction An important component of any Stormwater Pollution Prevention Plan is inspection and maintenance. The StormTech Isolator Row Plus is a technique to inexpensively enhance Total Suspended Solids (TSS), Total Phosphorus (TP), Total Petroluem Hydrocarbons (TPH) and Total Nitrogen (TN) removal with easy access for inspection and maintenance. The Isolator Row Plus The Isolator Row Plus is a row of StormTech chambers, either SC-160, SC-310, SC-310-3, SC-740, DC-780, MC-3500, MC-4500 or MC-7200 models, are lined with filter fabric and connected to a closely located manhole for easy access. The fabric lined chambers provide for sediment settling and filtration as stormwater rises in the Isolator Row Plus and passes through the filter fabric. The open bottom chambers allow stormwater to flow both vertically out of the chambers. Sediments are captured in the Isolator Row Plus protecting the adjacent stone and chambers storage areas from sediment accumulation. ADS Isolator Row and Plus fabric are placed between the stone and the Isolator Row Plus chambers. The woven geotextile provides a media for stormwater filtration, a durable surface for maintenance, prevents scour of the underlying stone and remains intact during high pressure jetting. The Isolator Row Plus is designed to capture the “first flush” runoff and offers the versatility to be sized on a volume basis or a flow-rate basis. An upstream manhole provides access to the Isolator Row Plus and includes a high/low concept such that stormwater flow rates or volumes that exceed the capacity of the Isolator Row Plus bypass through a manifold to the other chambers. This is achieved with an elevated bypass manifold or a high-flow weir. This creates a differential between the Isolator Row Plus row of chambers and the manifold to the rest of the system, thus allowing for settlement time in the Isolator Row Plus. After Stormwater flows through the Isolator Row Plus and into the rest of the chamber system it is either exfiltrated into the soils below or passed at a controlled rate through an outlet manifold and outlet control structure. The Isolator Row Plus FlampTM is a flared end ramp apparatus attached to the inlet pipe on the inside of the chamber end cap. The FLAMP provides a smooth transition from pipe invert to fabric bottom. It is configured to improve chamber function performance by enhancing outflow of solid debris that would otherwise collect at the chamber's end, or more difficult to remove and require confined space entry into the chamber area. It also serves to improve the fluid and solid flow into the access pipe during maintenance and cleaning and to guide cleaning and inspection equipment back into the inlet pipe when complete. The Isolator Row Plus may be part of a treatment train system. The treatment train design and pretreatment device selection by the design engineer is often driven by regulatory requirements. Whether pretreatment is used or not, StormTech recommend using the Isolator Row Plus to minimize maintenance requirements and maintenance costs. Note: See the StormTech Design Manual for detailed information on designing inlets for a StormTech system, including the Isolator Row Plus. 3 Inspection The frequency of inspection and maintenance varies by location. A routine inspection schedule needs to be established for each individual location based upon site specific variables. The type of land use (i.e. industrial, commercial, residential), anticipated pollutant load, percent imperviousness, climate, etc. all play a critical role in determining the actual frequency of inspection and maintenance practices. At a minimum, StormTech recommends annual inspections. Initially, the Isolator Row Plus should be inspected every 6 months for the first year of operation. For subsequent years, the inspection should be adjusted based upon previous observation of sediment deposition. The Isolator Row Plus incorporates a combination of standard manhole(s) and strategically located inspection ports (as needed). The inspection ports allow for easy access to the system from the surface, eliminating the need to perform a confined space entry for inspection purposes. If upon visual inspection it is found that sediment has accumulated, a stadia rod should be inserted to determine the depth of sediment. When the average depth of sediment exceeds 3 inches throughout the length of the Isolator Row Plus, clean-out should be performed. Maintenance The Isolator Row Plus was designed to reduce the cost of periodic maintenance. By “isolating” sediments to just one row, costs are dramatically reduced by eliminating the need to clean out each row of the entire storage bed. If inspection indicates the potential need for maintenance, access is provided via a manhole(s) located on the end(s) of the row for cleanout. If entry into the manhole is required, please follow local and OSHA rules for a confined space entry. Maintenance is accomplished with the JetVac process. The JetVac process utilizes a high pressure water nozzle to propel itself down the Isolator Row Plus while scouring and suspending sediments. As the nozzle is retrieved, the captured pollutants are flushed back into the manhole for vacuuming. Most sewer and pipe maintenance companies have vacuum/JetVac combination vehicles. Selection of an appropriate JetVac nozzle will improve maintenance efficiency. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable. Rear facing jets with an effective spread of at least 45” are best. StormTech recommends a maximum nozzle pressure of 2000 psi be utilized during cleaning. JetVac reels can vary in length. For ease of maintenance, ADS recommends Isolator Row Plus lengths up to 200' (61 m). The JetVac process shall only be performed on StormTech Isolator Row Plus that have ADS Plus Fabric (as specified by StormTech) over their angular base stone. Isolator Row Plus Inspection/Maintenance SHEET OFDATE:PROJECT #:DRAWN:CHECKED:THIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THEULTIMATE RESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.4640 TRUEMAN BLVDHILLIARD, OH 430261 16/15/2023N/AHAKHAKISOLATOR ROW DETAILSC-SERIES COMBINED ISOLATOR ROW PLUS DETAILSDATEDRWNCHKDDESCRIPTIONINSPECTION & MAINTENANCE STEP 1)INSPECT ISOLATOR ROW PLUS FOR SEDIMENT A.INSPECTION PORTS (IF PRESENT) A.1.REMOVE/OPEN LID ON NYLOPLAST INLINE DRAIN A.2.REMOVE AND CLEAN FLEXSTORM FILTER IF INSTALLED A.3.USING A FLASHLIGHT AND STADIA ROD, MEASURE DEPTH OF SEDIMENT AND RECORD ON MAINTENANCE LOG A.4.LOWER A CAMERA INTO ISOLATOR ROW PLUS FOR VISUAL INSPECTION OF SEDIMENT LEVELS (OPTIONAL) A.5.IF SEDIMENT IS AT, OR ABOVE, 3" (80 mm) PROCEED TO STEP 2. IF NOT, PROCEED TO STEP 3. B.ALL ISOLATOR PLUS ROWS B.1.REMOVE COVER FROM STRUCTURE AT UPSTREAM END OF ISOLATOR ROW PLUS B.2.USING A FLASHLIGHT, INSPECT DOWN THE ISOLATOR ROW PLUS THROUGH OUTLET PIPE i)MIRRORS ON POLES OR CAMERAS MAY BE USED TO AVOID A CONFINED SPACE ENTRY ii)FOLLOW OSHA REGULATIONS FOR CONFINED SPACE ENTRY IF ENTERING MANHOLE B.3.IF SEDIMENT IS AT, OR ABOVE, 3" (80 mm) PROCEED TO STEP 2. IF NOT, PROCEED TO STEP 3. STEP 2)CLEAN OUT ISOLATOR ROW PLUS USING THE JETVAC PROCESS A.A FIXED CULVERT CLEANING NOZZLE WITH REAR FACING SPREAD OF 45" (1.1 m) OR MORE IS PREFERRED B.APPLY MULTIPLE PASSES OF JETVAC UNTIL BACKFLUSH WATER IS CLEAN C.VACUUM STRUCTURE SUMP AS REQUIRED STEP 3)REPLACE ALL COVERS, GRATES, FILTERS, AND LIDS; RECORD OBSERVATIONS AND ACTIONS. STEP 4)INSPECT AND CLEAN BASINS AND MANHOLES UPSTREAM OF THE STORMTECH SYSTEM. NOTES 1.INSPECT EVERY 6 MONTHS DURING THE FIRST YEAR OF OPERATION. ADJUST THE INSPECTION INTERVAL BASED ON PREVIOUS OBSERVATIONS OF SEDIMENT ACCUMULATION AND HIGH WATER ELEVATIONS. 2.CONDUCT JETTING AND VACTORING ANNUALLY OR WHEN INSPECTION SHOWS THAT MAINTENANCE IS NECESSARY. SUMP DEPTH TBD BY SITE DESIGN ENGINEER (24" [600 mm] MIN RECOMMENDED) ONE LAYER OF ADSPLUS125 WOVEN GEOTEXTILE BETWEEN FOUNDATION STONE AND CHAMBERS 5' (1.5 m) MIN WIDE CONTINUOUS FABRIC WITHOUT SEAMS DC-780 CHAMBER DC-780/SC-740 END CAP DC-780 ISOLATOR ROW PLUS DETAIL NTS OPTIONAL INSPECTION PORTSTORMTECH HIGHLY RECOMMENDS FLEXSTORM INSERTS IN ANY UPSTREAM STRUCTURES WITH OPEN GRATES ELEVATED BYPASS MANIFOLD 24" (600 mm) HDPE ACCESS PIPE REQUIRED USE EZ END CAP PART #: SC740ECEZ CATCH BASIN OR MANHOLE NOTE: INSPECTION PORTS MAY BE CONNECTED THROUGH ANY CHAMBER CORRUGATION CREST. STORMTECH CHAMBER CONCRETE COLLAR PAVEMENT 12" (300 mm) MIN WIDTH CONCRETE SLAB 6" (150 mm) MIN THICKNESS 4" PVC INSPECTION PORT DETAIL (SC SERIES CHAMBER) NTS 8" NYLOPLAST INSPECTION PORT BODY (PART# 2708AG4IPKIT) OR TRAFFIC RATED BOX W/SOLID LOCKING COVER CONCRETE COLLAR NOT REQUIRED FOR UNPAVED APPLICATIONS 4" (100 mm) SDR 35 PIPE 4" (100 mm) INSERTA TEE TO BE CENTERED ON CORRUGATION CREST StormTechChamber System888-892-2694 | WWW.STORMTECH.COM®SUMP DEPTH TBD BY SITE DESIGN ENGINEER (24" [600 mm] MIN RECOMMENDED) CATCH BASIN OR MANHOLE SC-740 ISOLATOR ROW PLUS DETAIL NTS SC-740 END CAP OPTIONAL INSPECTION PORTSC-740 CHAMBERSTORMTECH HIGHLY RECOMMENDS FLEXSTORM INSERTS IN ANY UPSTREAM STRUCTURES WITH OPEN GRATES ONE LAYER OF ADSPLUS125 WOVEN GEOTEXTILE BETWEEN FOUNDATION STONE AND CHAMBERS 5' (1.5 m) MIN WIDE CONTINUOUS FABRIC WITHOUT SEAMS ELEVATED BYPASS MANIFOLD 24" (600 mm) HDPE ACCESS PIPE REQUIRED USE EZ END CAP PART #: SC740ECEZ INSTALL FLAMP ON 24" (600 mm) ACCESS PIPE PART#: SC74024RAMP SUMP DEPTH TBD BY SITE DESIGN ENGINEER (24" [600 mm] MIN RECOMMENDED) CATCH BASIN OR MANHOLE SC-310 ISOLATOR ROW PLUS DETAIL NTS OPTIONAL INSPECTION PORT SC-310 END CAP SC-310 CHAMBERSTORMTECH HIGHLY RECOMMENDS FLEXSTORM INSERTS IN ANY UPSTREAM STRUCTURES WITH OPEN GRATES ONE LAYER OF ADSPLUS125 WOVEN GEOTEXTILE BETWEEN FOUNDATION STONE AND CHAMBERS 4' (1.2 m) MIN WIDE CONTINUOUS FABRIC WITHOUT SEAMS ELEVATED BYPASS MANIFOLD 12" (300 mm) HDPE ACCESS PIPE REQUIRED USE EZ END CAP PART #: SC310ECEZ INSTALL FLAMP ON 12" (300 mm) ACCESS PIPE PART#: SC31012RAMP SUMP DEPTH TBD BY SITE DESIGN ENGINEER (24" [600 mm] MIN RECOMMENDED) SC-160LP ISOLATOR ROW PLUS DETAIL NTS CATCH BASIN OR MANHOLE STORMTECH HIGHLY RECOMMENDS FLEXSTORM INSERTS IN ANY UPSTREAM STRUCTURES WITH OPEN GRATES SC-160LP CHAMBER 8" (200 mm) HDPE ACCESS PIPE REQUIRED USE 8" OPEN END CAP PART #: SC160IEPP08 OPTIONAL INSPECTION PORT SC-160LP END CAP ONE LAYER OF ADSPLUS125 WOVEN GEOTEXTILE BETWEEN FOUNDATION STONE AND CHAMBERS 4' (1.2 m) MIN WIDE CONTINUOUS FABRIC WITHOUT SEAMS WEIR WEIR HEIGHT TBD BY SITE DESIGN ENGINEER StormTech Isolator Row PLUS (not to scale) Isolator Row Plus Step By Step Maintenance Procedures Step 1 Inspect Isolator Row Plus for sediment. A) Inspection ports (if present) i. Remove lid from floor box frame ii. Remove cap from inspection riser iii. Using a flashlight and stadia rod,measure depth of sediment and record results on maintenance log. iv. If sediment is at or above 3 inch depth, proceed to Step 2. If not, proceed to Step 3. B) All Isolator Row Plus i. Remove cover from manhole at upstream end of Isolator Row Plus ii. Using a flashlight, inspect down Isolator Row Plus through outlet pipe 1. Mirrors on poles or cameras may be used to avoid a confined space entry 2. Follow OSHA regulations for confined space entry if entering manhole iii. If sediment is at or above the lower row of sidewall holes (approximately 3 inches), proceed to Step 2. If not, proceed to Step 3. Step 2 Clean out Isolator Row Plus using the JetVac process. A) A fixed floor cleaning nozzle with rear facing nozzle spread of 45 inches or more is preferable B) Apply multiple passes of JetVac until backflush water is clean C) Vacuum manhole sump as required Step 3 Replace all caps, lids and covers, record observations and actions. Step 4 Inspect & clean catch basins and manholes upstream of the StormTech system. ADS “Terms and Conditions of Sale” are available on the ADS website, www.ads-pipe.com The ADS logo and the Green Stripe are registered trademarks of Advanced Drainage Systems, Inc. StormTech® and the Isolator® Row Plus are registered trademarks of StormTech, Inc. © 2023 Advanced Drainage Systems, Inc. #11081 6/23 CS  )( Sample Maintenance Log Date Stadia Rod Readings Sediment Depth (1)–(2) Observations/Actions InspectorFixed point to chamber bottom (1) Fixed point to top of sediment (2) 3/15/11 6.3 ft none New installation. Fixed point is CI frame at grade DJM 9/24/11 6.2 0.1 ft Some grit felt SM 6/20/13 5.8 0.5 ft Mucky feel, debris visible in manhole and in Isolator Row PLUS, maintenance due NV 7/7/13 6.3 ft 0 System jetted and vacuumed DJM adspipe.com 800-821-6710 APPENDIX D –Planting Plan PERENNIAL SHRUB SEED MIX #1 SEED MIX #2 DECIDUOUS TREE KEY D D D WVHYD WV GV GV D MATCHLINE (SHEET 1) MATCHLINE (SHEET 2) 30 35 28 29 31 32 33 34 36 37 38 39 36 GUN ROCK ROADFOLLINS POND ROAD38 37 AUV 24 AG 3 SEED MIX #1 2,500 SF± SEED MIX #2 750 SF± INFILTRATION TRENCH 8 1022032Aof last modified: 01/15/24 printed: 01/15/24 by meH:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Drawings\FOLLINS\22032 FOLLINS LA.dwg8C -Checked By:Designed By:Date:Drawn By:Sustainable Environmental Solutionswww.horsleywitten.com90 Route 6ASandwich, MA 02563508-833-6600 voice508-833-3150 faxHorsley Witten Group, Inc.RevisionsAppr.Rev.DateByDescription1234567JANUARY 2024ME/KJKME/KJKHLCFOLLINS PONDCAPE COD BOAT RAMP STORMWATERRETROFIT PROJECT - PERMITTING PLANSYARMOUTH, MASurvey Provided By:Sheet Number: Project Number: Registration:Prepared For:Plan Set:Plan Title:Sheet : PLANTING PLAN (1)(in feet) GRAPHIC SCALE 010 5 10 20 40 1 INCH = 10 FEET PERMITTING SET ONLY NOT FOR CONSTRUCTION D D D D WV HY D GV WV COASTAL BANK 50' BUFFER ZONE COASTAL BANK 100' BUFFER ZONE COASTAL BANK 35' UNDISTURBED VEGETATIVE BUFFER COASTAL BANK 50' BUFFER ZONEFOLLINS POND ROADMATCHLINE (SHEET 1) MATCHLINE (SHEET 2) 15 20 25 12 13 14 16 17 18 19 21 22 23 24 26 27 28 PJM 11 AQC 28 MULCH 475 SF± INFILTRATION TRENCH INFILTRATION TRENCH MP 10 SEED MIX 1 1,550 SF±RevisionsAppr.Rev.DateByDescription1234567JANUARY 2024ME/KJKME/KJKHLCPLANTING PLAN (2)FOLLINS PONDCAPE COD BOAT RAMP STORMWATERRETROFIT PROJECT - PERMITTING PLANSYARMOUTH, MASurvey Provided By:Sheet Number: Project Number: Registration:Prepared For:Plan Set:Plan Title:Sheet : 9 1022032Aof last modified: 01/15/24 printed: 01/15/24 by meH:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Drawings\FOLLINS\22032 FOLLINS LA.dwg9C -Checked By:Designed By:Date:Drawn By:Sustainable Environmental Solutionswww.horsleywitten.com90 Route 6ASandwich, MA 02563508-833-6600 voice508-833-3150 faxHorsley Witten Group, Inc. (in feet) GRAPHIC SCALE 010 5 10 20 40 1 INCH = 10 FEET PERMITTING SET ONLY NOT FOR CONSTRUCTION APPENDIX E –O&M Plan for Existing Infiltration Systems Stormwater Improvements September 18, 2007 For the Town of Yarmouth Page 1 of 3 Operations & Maintenance Plan Norfolk Ram Group, LLC H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Stormwater Reports\Yarmouth-FollinsPond\Appendices\O&M Guide\Appendices\AppE_O&M '07.doc www.norfolkram.com Operations and Maintenance Plan 1.0 Introduction The Town of Yarmouth (Town) has implemented a program to reduce the impact of Non-Point Source Pollution Discharge on the Bass River Watershed. The treatment and reduction of stormwater discharges from residential streets discharging into Bass River/Follins Pond have been identified as priorities for improving water quality in the Watershed. The stormwater system components utilized in the CPR projects consist of deep sump catch basins, manholes, pipes, and leaching chambers. 2.0 Purpose This Operations & Maintenance Plan (O&M Plan) provides a mechanism for the consistent inspection and maintenance of stormwater system components installed during the course of the CPR projects. Included in this O&M Plan is a description of the stormwater system components, the location of each component, an inspection schedule for each stormwater system component, and forms to be utilized to document the inspection and maintenance of each stormwater system component. 3.0 Stormwater System Descriptions and Locations 3.1 Description There are numerous stormwater systems located in the Bass River/Follins Pond watershed. See as-built plans in Appendix B. 3.2 Locations This plan can be amended by listing new locations below and adding the as-built plans to O&M Binder referenced in Section 6. Follins Pond Road (3 systems) – installed 2006 Longview Drive (2 systems) – installed 2007 Wing Avenue (1 system) – installed 2007 4.0 Inspection Frequency, Safety, and Schedule 4.1 Inspection Frequency: A complete and thorough inspection of the systems using the inspection and maintenance forms provided will be performed once a month during the first six (6) months and then on an annual basis (once in the spring) and after major rain Stormwater Improvements September 18, 2007 For the Town of Yarmouth Page 2 of 3 Operations & Maintenance Plan Norfolk Ram Group, LLC H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Stormwater Reports\Yarmouth-FollinsPond\Appendices\O&M Guide\Appendices\AppE_O&M '07.doc www.norfolkram.com events (approximately 2.0 inches of rain). See Section 5.0 Implementation and Maintenance Procedures for a description of the inspection activities. 4.2 Inspection Safety: The inspector performing the inspections on the drainage structures will have the proper safety equipment (heavy duty gloves, steel-toed boots, hard hat, and first aid kits, etc.) and training before conducting any inspections. If the drainage structures reveal any safety problems the site activities may need to be modified to reduce or eliminate the safety risk. All inspections will be in accordance with the Town of Yarmouth’s DPW safety program. This program is reviewed annually by the DPW for compliance with State and Federal requirements. 4.3 Maintenance: • All maintenance work will be done in accordance with Town of Yarmouth’s DPW safety program. 5.0 Implementation and Maintenance Procedures The Yarmouth Department of Public Works (DPW) is responsible for inspecting and maintaining the stormwater system components. Inspections and maintenance will be funded in the DPW’s annual operating budget. The following list of inspections and maintenance will be performed on the required schedule. All sediment, debris, and hydrocarbons that are removed during the maintenance of the stormwater system components will be properly handled and disposed. 5.1 Catch Basins/Manholes: Inspections will be performed once during the spring. It is important to remove the sediment that has accumulated during the winter months before the spring precipitation. 5.2 Drainage Pipes: Inspections will be performed along with the catch basins yearly checks. Drainage pipes will be checked for clogs and cleaned as needed. 5.3 Leaching Chambers: For the first six (6) months inspections will be performed once a month. As long as everything is working properly, the inspection frequency can be decreased to once a year, in early spring. The leaching facility will be inspected after the first several Stormwater Improvements September 18, 2007 For the Town of Yarmouth Page 3 of 3 Operations & Maintenance Plan Norfolk Ram Group, LLC H:\Projects\2022\22032 CC Boat Ramp SW Retrofits\Reports\Stormwater Reports\Yarmouth-FollinsPond\Appendices\O&M Guide\Appendices\AppE_O&M '07.doc www.norfolkram.com storms and after major storms (approximately 2-inches). The inlet and outlet pipe will be inspected for clogging of sediment leaves, and debris. During the inspection the inspector will look for signs of ponding of water inside of the chambers after 24 hours or several days after a rain event. If water is present it may be a sign that the bottom of the trench is clogged. In the event that the ponding of the system is evident, the system will be pumped and an investigation program developed to identify the source of the pondng and remedial activities. 5.4 Street Sweeping: Street sweeping will be performed monthly during construction and then annually in the early spring using a conventional mechanical sweeper or a newer vacuum-type sweeper. 6.0 Inspections and Record Keeping An inspection form will be filled out each and every time an inspection and/or maintenance work is performed. A record of the date of sediment removal and the quantity removed will be part of the record. A three-ring loose leaf binder will be kept at the Town’s Highway Division / Department of Public Works Office located on Buck Island Road in West Yarmouth that contains all of the completed inspections forms and/or photos and related material. This binder will be maintained for a minimum of three years, include photo documentation of the inspections, and will be available for review by the Massachusetts Office of Coastal Zone Management. A review of all Operation & Maintenance actions will take place annually to ensure that these Stormwater BMP’s are being taken care of in the manner illustrated in this Operation & Maintenance plan. APPENDIX F – Pollutant Controls During Construction   Pollutant Controls During Construction 1 December 2023  Follins Pond Boat Ramp – Yarmouth, MA     POLLUTANT CONTROLS DURING CONSTRUCTION  1.1 Structural Practices  The following are the structural practices that will be implemented as part of the construction activity.   Visibility Fence/Sediment Silt Sock Barrier will be installed prior to commencement of  construction. The visibility fence will keep construction equipment within the limit of work, and  the silt sock will be used on the downgradient portions of the limit of work to allow water to  flow through it while keeping sediment on site. The Town will be informed upon their  installation so that they may inspect these barriers prior to construction. Portions of these  barriers will be replaced and/or repaired as necessary.  Barriers will be installed parallel to land  slope at the perimeter of the work site, as shown on the Plans.  Details are provided in the Plans.       Silt Sacks (or approved equivalent) will be installed at existing and proposed inlet and overflow  structures to prevent sedimentation during construction. The silt sack will be emptied/replaced  and disposed of off‐site if damage is observed.   Slope Stabilization will occur immediately upon obtaining final grades as shown on the project  site plans.  Areas that fail to stabilize will be re‐graded to final grade and stabilized as necessary.   Amount of land disturbed will be minimized to reduce potential for erosion and sedimentation.   Stabilization measures shall be initiated within 14 days following the end of construction at each  portion of the site and as soon as practicable.    The entire stormwater management system including pipe, structures, infiltration trenches, and  underground infiltration chambers will be inspected upon completion of construction. Sediment will be  removed from all elements of the stormwater management system.  All control measures must be  installed and maintained in accordance with manufacturer’s specifications, good engineering practices,  and in accordance with this report (every seven calenpdar days and after storm events).  If inspections  show that a control has failed or been installed incorrectly, the Operator must replace or modify it  within 24 hours.    1.2 Stabilization Practices  The amount of land disturbed during construction will be minimized to reduce the potential for erosion  and sedimentation. Prompt surface stabilization will be provided to control erosion in areas where  disturbances cannot be avoided during construction.  Stabilization measures shall be initiated within 14  days following the end of construction at each portion of the site.  Exceptions to this requirement are  allowable when snow cover prevents the initiation of stabilization within 14 days, in which case such  measures shall be undertaken as soon as possible.      Pollutant Controls During Construction 2 December 2023  Follins Pond Boat Ramp – Yarmouth, MA     Stabilization measures that will be, or may be, used during construction are described below:   Temporary Seeding – Temporary seeding of disturbed surfaces with fast‐growing grasses  (annual rye) to provide greater resistance to stormwater runoff and/or wind erosion for areas  where construction has temporarily ceased.   Permanent Seeding – Permanent seeding of surfaces with vegetation, including but not limited  to grass, trees, bushes, and shrubs, to stabilize the soil.  Establishing a permanent and  sustainable ground cover at a site stabilizes the soil while reducing the sediment content in  runoff.   Permanent Planting –establish all planting as required at the completion of the project.   Erosion Control Blankets ‐  install erosion control blankets along all slopes greater than 3:1.   Mulching – materials, including but not limited to hay, grass, woodchips, straw, and gravel will  be placed on the soil surface to cover and hold in place disturbed soils.    Temporary seeding or other soil stabilization measures will be provided where construction activities  have ceased at the site. Topsoil stockpiles will be temporarily seeded or covered to prevent erosion and  will be surrounded with silt fence or silt sock. When the site’s final grade has been established,  permanent vegetation will be planted on the disturbed areas. The vegetation will consist of grass,  shrubs, bushes, and trees in the locations indicated on the plans.    1.3 Other Types of Controls  Additional controls/practices will be undertaken to reduce pollution in stormwater runoff flows which  include, but are not limited to, control of off‐site mud tracking from construction site, dust suppression,  proper sanitary waste disposal, earthwork procedures timed and conducted in manners aimed to  minimize erosion and sedimentation, snow removal plans, proper management of waste materials,  proper management of hazardous waste, proper material stockpiling, and spill prevention and control  measures.   Dust Suppression – Water sprays shall be used to control dust during extended dry periods  during construction.   Earthwork – The exposure of disturbed surfaces to stormwater and potential stormwater  erosion will be minimized by well‐organized earthwork procedures.  Stabilization procedures  shall be undertaken in accordance with this report.  Grubbing during wet seasons will be  avoided if feasible.     Snow Removal Plan – Plowed snow collected from the roadway and parking areas will be  deposited onto free draining, pervious surfaces, away from the sites drainage conveyance  structures to maximize infiltration.      Pollutant Controls During Construction 3 December 2023  Follins Pond Boat Ramp – Yarmouth, MA      Waste Materials – Dumpsters rented from a licensed solid waste management company will be  used to store solid waste and debris that cannot be recycled, reused or salvaged.  The  dumpsters will meet all local and state solid waste management regulations.  Dumpsters will be  covered when refuse is not being directly deposited or withdrawn from them.  Potentially  hazardous wastes will be separated from normal wastes, including segregation of storage areas  and proper labeling of containers.  Removal of all waste from the site will be performed by  licensed contractors in accordance with applicable regulatory requirements and disposed of at  either local or regional approved facilities.  Waste materials will not be buried on‐site.  All site  personnel will be instructed regarding the correct procedures for waste disposal.  Notices  stating these procedures will be posted at the site.  Solvents and flushing materials used during  construction and pre‐operational cleaning will be provided, handled, managed, and removed by  the contractor for appropriate off‐site disposal.     Hazardous Waste Materials – Any disposal of hazardous materials will be completed using the  required paperwork.  Copies will be provided to the Engineer and to the city.   Spill Prevention and Control Measures – To minimize the risk of spills or other accidental  exposure of materials and substances to stormwater runoff, the following material management  practices will be used throughout the project:  o An effort will be made to store only enough products required to do the job.  o All materials stored on‐site will be stored in a neat, orderly manner in their appropriate  containers and, if possible, under a roof or other enclosure.  o Products will be kept in their original containers with the original manufacturer’s label.  o Substances will not be mixed with one another unless recommended by the manufacturer.  o Whenever possible, the maximum amount of a product will be used before disposing of the  container.   o Manufacturers’ recommendations for proper use and disposal will be followed.  o The site superintendent will conduct daily inspections to ensure proper use and disposal of  materials.   To reduce the risk associated with hazardous materials used on the site, the following practices  will be used:   Products will be kept in original containers unless they are not resealable.   Original labels and material safety data sheets will be retained and kept on‐site; they  contain important product information.    Pollutant Controls During Construction 4 December 2023  Follins Pond Boat Ramp – Yarmouth, MA      If surplus product must be disposed of, manufacturers’ or local and state recommended  methods for proper disposal will be followed.   Materials List ‐ Materials or substances listed below are expected to be present on‐site during  construction:  ‐ Concrete ‐ Fertilizers  ‐ Asphalt   ‐ Petroleum Based Products  ‐ Paints (enamel and latex) ‐ Cleaning Solvents  ‐ Metal Studs ‐ Wood  ‐ Concrete   ‐ Tar  ‐ Sealants   ‐ Adhesives  The following product‐specific practices will be followed on‐site:  Petroleum Products ‐ All on‐site vehicles will be monitored for leaks and receive  preventative maintenance to reduce the chance of leakage.  Petroleum products will be  stored in tightly sealed containers which area clearly labeled.  Any asphalt substances  used on‐site will be applied according to the manufacturers’ recommendations.  Paints – All containers will be tightly sealed and stored indoors when not required for  use.  Excess paint will not be discharged to the storm sewer system but will be properly  disposed of according to the manufacturers’ instructions or state and local regulations.  Concrete Trucks – Concrete trucks will not be allowed to wash out or discharge surplus  concrete or drum wash water on the site.  In addition to the good housekeeping and material management practices discussed in the previous  sections of this plan, the following practices will be followed for spill prevention and cleanup:   Manufacturers’ recommended methods for spill cleanup will be clearly posted, and site  personnel will be made aware of the procedures and location of the information and cleanup  supplies.   Materials and equipment necessary for spill cleanup will be kept in the material storage area on‐ site.  Equipment and materials will include, but not be limited to, brooms, dust pans, mops, rags,  gloves, goggles, speedi‐dry, sand, sawdust, and plastic and metal trash containers specifically for  this purpose.   All spills will be cleaned up immediately after discovery.  Spills large enough to reach the storm  water system will be reported to the National Response Center at 1‐800‐424‐8802.    Pollutant Controls During Construction 5 December 2023  Follins Pond Boat Ramp – Yarmouth, MA      The spill area will be kept well ventilated and personnel will wear appropriate protective  clothing to prevent injury from contact with a hazardous substance.   Spills of toxic or hazardous material will be reported to the appropriate state or local  government agency, regardless of the size.     The site superintendent responsible for the day‐to‐day site operations will be the spill  prevention and clean‐up coordinator.  He will designate at least three other site personnel who  will receive spill prevention and cleanup training.  These individuals will each become  responsible for a particular phase of prevention and cleanup.  The names of responsible spill  personnel will be posted in the material storage area and in the on‐site office trailer.    APPENDIX G – Site Plans