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Stormwater Management Report - 268 Stevens St
DiPrete Engineering Stormwater Management Report Stevens Street Multi-Family Located in Hyannis, MA Applicant: Housing Assistance Corporation of Cape Cod 11-29-2023 Revised: 3-15-2024 Stevens Street Mutli-Family Table of Contents Executive Summary MADEP Checklist for Stormwater Report 1.0 Project Description 1 2.0 Site Conditions 1 2.1 Soils 1 2.2 Existing Site Conditions 2 2.3 Post Site Conditions 3 2.4 Stormwater Design Alternatives Analysis 4 3.0 Minimum Standards 6 3.1 Standard 1: No New Untreated Discharges 6 3.2 Standard 2: Peak Rate Attenuation 6 3.3 Standard 3: Recharge 13 3.4 Standard 4: Water Quality 16 3.5 Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs)18 3.6 Standard 6: Critical Areas 18 3.7 Standard 7: Redevelopments 18 3.8 Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control 18 3.9 Standard 9: Operation and Maintenance Plan 18 3.10 Standard 10: Prohibition of Illicit Discharges 18 Appendix A 19 A2.1 Soil Evaluations 20 A3.2.1 HydroCAD Node Diagram 27 A3.2.2 HydroCAD 2-Year Storm Analysis 32 A3.2.3 HydroCAD 10-Year Storm Analysis 36 A3.2.4 HydroCAD 25-Year Storm Analysis 40 A3.2.5 HydroCAD 100-Year Storm Analysis 44 A3.3 Water Quality Storm Analysis 70 A3.4 TSS Removal Calculation Worksheets 74 A3.5 Stormcrete Specifications 78 Appendix B Massachusetts Small MS4 General Permit – Appendix F Attachment 3 91 Appendix C Mounding Calculations 92 Appendix D USGS Bedrock Topography of West Cape Cod 95 Watershed Maps 97 Stevens Street Mutli-Family Executive Summary On behalf of the Client, we are submitting drainage calculations for the proposed development at 268 Stevens Street. The site is located at the intersection of Stevens and North Street on Assessors’ Plat 308 Lot 17. Currently the site exists today as a vacant lot with sections of pavement and dirt piles from a previously demolished collision center or vehicle maintenance building. Based on aerial imaging, it is presumed that the development was demolished sometime between 2016 and 2017. For the purpose of our analysis, the demolished development of the collision center and vehicle maintenance, has been considered as the pre-development condition. Based on the oldest available aerial imaging from 1990, the development has existed for over 25 years with its stormwater practices ultimately discharging stormwater runoff to the town’s drainage network. The intent behind this is to provide accurate pre-existing conditions of the site with its stormwater systems as it provided some stormwater treatment practices prior to discharging into the town’s drainage network. The current vacant condition would represent silted and failed systems which provide no peak attenuation in the town’s drainage system. Making these assumptions ultimately results in a conservative approach as the pre-development peak flows and volumes to the existing drainage network are reduced and establishes the maximum peak and volumes that need to be met in post-development. The client proposes to construct a new four-story multi-family building with associated access drives, parking, stormwater systems and utilities. It’s important to note that this project is classified as a redevelopment project as defined by MADEP/ the Massachusetts Stormwater Management Standards (MASWMS) Standard 7. As such, the stormwater design is considered to have made all reasonable efforts to meet the applicable standards and regulations to the maximum extent practical, including the Town of Barnstable and the MASWMS. The post-development condition, will reduce overall pavement surface from pre to post, remove the Land Use of Higher Potential Pollution Loads (LUHPPL) from the vehicle maintenance use to a residential use, and provide enhanced stormwater pretreatment and treatment systems with stormwater peak mitigation. In post development conditions, there is an overall impervious area of 53,710 sf. The impervious area consists of 35,398 sf of pavement surface and 18,312 sf of building area. In pre development conditions, the impervious area consists of 42,050 sf of pavement surface and 8,828 sf of building area. This results in an overall reduction of pavement surface area of approximately 15.8% from pre to post condition. The post development stormwater will be treated for water quality using Best Management Practices (BMPs). The Site has been designed to meet the Massachusetts Stormwater Management Standards (MASWMS) and the Town of Barnstable Code Regulations. Site constraints that were considered in the stormwater design are detailed in the Stormwater Design Alternatives Analysis (2.4) section of this report. To treat and mitigate post development flows on site, runoff collection and infiltration systems (Stormcrete), an Underground Infiltration System (Stormtech Chambers), an Aboveground Infiltration Pond, Sediment Forebay and leaching catch basins are utilized. The treatment train will remove TSS (total suspended solids) in accordance with the MASWMS. The infiltration systems are designed to Stevens Street Mutli-Family control runoff for the 2 through 25-year storm events. These will remove 80% or more of TSS generated by the proposed parking areas. The project is considered a redevelopment site. Note that due to the overall reduction in pavement area, this redevelopment will automatically result in a decrease in stormwater runoff for all design storm events. Furthermore, the proposed BMP treatment chain for the new building area has been designed to fully infiltrate all storm events up to and including the 100-year storm without bypass, which will further improve existing conditions. This report details how the proposed BMP’s will provide water quality treatment for stormwater runoff and no net increase in stormwater runoff from pre development to post development conditions. The proposed BMPs will meet the Massachusetts Stormwater Management Standards (MASWMS) and the Town of Barnstable Code Regulations. Pre development Conditions versus Post Development Conditions are summarized below: Pre Development vs. Post Development Mitigated Design Point 1: (DP-1) – Mitchells Way Conditions – Peak Flow 2-Year 10-Year 25-Year 100-Year Pre Dev Summation 1.61 3.17 5.20 8.12 Post Dev Summation 0.07 0.22 0.40 0.84 Net Change -1.54 -2.95 -4.80 -7.28 All flows in cubic feet per second (cfs) Design Point 2: (DP-2) – Stevens Street Conditions – Peak Flow 2-Year 10-Year 25-Year 100-Year Pre Dev Summation 0.08 0.82 2.04 2.71 Post Dev Summation 0.08 0.14 0.20 0.32 Net Change 0.00 -0.68 -1.84 -2.39 All flows in cubic feet per second (cfs) 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 1 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. A Stormwater Report must be submitted with the Notice of Intent permit application to document compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for the Stormwater Report (which should provide more substantive and detailed information) but is offered here as a tool to help the applicant organize their Stormwater Management documentation for their Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, the Stormwater Report must contain the engineering computations and supporting information set forth in Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth. The Stormwater Report must include: The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see page 2) that certifies that the Stormwater Report contains all required submittals.1 This Checklist is to be used as the cover for the completed Stormwater Report. Applicant/Project Name Project Address Name of Firm and Registered Professional Engineer that prepared the Report Long-Term Pollution Prevention Plan required by Standards 4-6 Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 2 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report B. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note: Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.) and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer’s Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (if included) and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature Signature and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? New development Redevelopment Mix of New Development and Redevelopment 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 3 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) LID Measures:Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project: No disturbance to any Wetland Resource Areas Site Design Practices (e.g. clustered development, reduced frontage setbacks) Reduced Impervious Area (Redevelopment Only) Minimizing disturbance to existing trees and shrubs LID Site Design Credit Requested: Credit 1 Credit 2 Credit 3 Use of “country drainage” versus curb and gutter conveyance and pipe Bioretention Cells (includes Rain Gardens) Constructed Stormwater Wetlands (includes Gravel Wetlands designs) Treebox Filter Water Quality Swale Grass Channel Green Roof Other (describe): Standard 1: No New Untreated Discharges No new untreated discharges Outlets have been designed so there is no erosion or scour to wetlands and waters of the Commonwealth Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 4 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 2: Peak Rate Attenuation Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm. Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm. Standard 3: Recharge Soil Analysis provided. Required Recharge Volume calculation provided. Required Recharge volume reduced through use of the LID site Design Credits. Sizing the infiltration, BMPs is based on the following method: Check the method used. Static Simple Dynamic Dynamic Field1 Runoff from all impervious areas at the site discharging to the infiltration BMP. Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: Site is comprised solely of C and D soils and/or bedrock at the land surface M.G.L. c. 21E sites pursuant to 310 CMR 40.0000 Solid Waste Landfill pursuant to 310 CMR 19.000 Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. Calculations showing that the infiltration BMPs will drain in 72 hours are provided. Property includes a M.G.L. c. 21E site or a solid waste landfill and a mounding analysis is included. 1 80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 5 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 3: Recharge (continued) The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas. Standard 4: Water Quality The Long-Term Pollution Prevention Plan typically includes the following: Good housekeeping practices; Provisions for storing materials and waste products inside or under cover; Vehicle washing controls; Requirements for routine inspections and maintenance of stormwater BMPs; Spill prevention and response plans; Provisions for maintenance of lawns, gardens, and other landscaped areas; Requirements for storage and use of fertilizers, herbicides, and pesticides; Pet waste management provisions; Provisions for operation and management of septic systems; Provisions for solid waste management; Snow disposal and plowing plans relative to Wetland Resource Areas; Winter Road Salt and/or Sand Use and Storage restrictions; Street sweeping schedules; Provisions for prevention of illicit discharges to the stormwater management system; Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL; Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan; List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge: is within the Zone II or Interim Wellhead Protection Area is near or to other critical areas is within soils with a rapid infiltration rate (greater than 2.4 inches per hour) involves runoff from land uses with higher potential pollutant loads. The Required Water Quality Volume is reduced through use of the LID site Design Credits. Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 6 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) The BMP is sized (and calculations provided) based on: The ½” or 1” Water Quality Volume or The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume. The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary BMP and proposed TSS removal rate is provided. This documentation may be in the form of the propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying performance of the proprietary BMPs. A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing that the BMPs selected are consistent with the TMDL is provided. Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution Prevention Plan (SWPPP) has been included with the Stormwater Report. The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior to the discharge of stormwater to the post-construction stormwater BMPs. The NPDES Multi-Sector General Permit does not cover the land use. LUHPPLs are located at the site and industry specific source control and pollution prevention measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow melt and runoff, and been included in the long term Pollution Prevention Plan. All exposure has been eliminated. All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list. The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil grit separator, a filtering bioretention area, a sand filter or equivalent. Standard 6: Critical Areas The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP has approved for stormwater discharges to or near that particular class of critical area. Critical areas and BMPs are identified in the Stormwater Report. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 7 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum extent practicable The project is subject to the Stormwater Management Standards only to the maximum Extent Practicable as a: Limited Project Small Residential Projects: 5-9 single family houses or 5-9 units in a multi-family development provided there is no discharge that may potentially affect a critical area. Small Residential Projects: 2-4 single family houses or 2-4 units in a multi-family development with a discharge to a critical area Marina and/or boatyard provided the hull painting, service and maintenance areas are protected from exposure to rain, snow, snow melt and runoff Bike Path and/or Foot Path Redevelopment Project Redevelopment portion of mix of new and redevelopment. Certain standards are not fully met (Standard No. 1, 8, 9, and 10 must always be fully met) and an explanation of why these standards are not met is contained in the Stormwater Report. The project involves redevelopment and a description of all measures that have been taken to improve existing conditions is provided in the Stormwater Report. The redevelopment checklist found in Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document that the proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatment and structural BMP requirements of Standards 4-6 to the maximum extent practicable and (b) improves existing conditions. Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan must include the following information: Narrative; Construction Period Operation and Maintenance Plan; Names of Persons or Entity Responsible for Plan Compliance; Construction Period Pollution Prevention Measures; Erosion and Sedimentation Control Plan Drawings; Detail drawings and specifications for erosion control BMPs, including sizing calculations; Vegetation Planning; Site Development Plan; Construction Sequencing Plan; Sequencing of Erosion and Sedimentation Controls; Operation and Maintenance of Erosion and Sedimentation Controls; Inspection Schedule; Maintenance Schedule; Inspection and Maintenance Log Form. A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan containing the information set forth above has been included in the Stormwater Report. 3300-001-CK-STWR-MA-DEP.doc • 04/01/08 Stormwater Report Checklist • Page 8 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control (continued) The project is highly complex and information is included in the Stormwater Report that explains why it is not possible to submit the Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and Erosion and Sedimentation Control has not been included in the Stormwater Report but will be submitted before land disturbance begins. The project is not covered by a NPDES Construction General Permit. The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the Stormwater Report. The project is covered by a NPDES Construction General Permit but no SWPPP been submitted. The SWPPP will be submitted BEFORE land disturbance begins. Standard 9: Operation and Maintenance Plan The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and includes the following information: Name of the stormwater management system owners; Party responsible for operation and maintenance; Schedule for implementation of routine and non-routine maintenance tasks; Plan showing the location of all stormwater BMPs maintenance access areas; Description and delineation of public safety features; Estimated operation and maintenance budget; and Operation and Maintenance Log Form. The responsible party is not the owner of the parcel where the BMP is located and the Stormwater Report includes the following submissions: A copy of the legal instrument (deed, homeowner’s association, utility trust or other legal entity) that establishes the terms of and legal responsibility for the operation and maintenance of the project site stormwater BMPs; A plan and easement deed that allows site access for the legal entity to operate and maintain BMP functions. Standard 10: Prohibition of Illicit Discharges The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges; An Illicit Discharge Compliance Statement is attached; NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of any stormwater to post-construction BMPs. Stevens Street Mutli-Family 1.0 Project Description The purpose of this report is to specify a Storm Water Management System for the proposed development at 268 Stevens Street in Hyannis, MA. A Stormwater System Operations and Maintenance Plan (O&M) has been prepared by DiPrete Engineering as a separate document. The proposed development is located on Assessor’s Map 308, Lot 17 and the intersection of Stevens Street and North Street. The site totals 1.49 acres and is located in the Stewarts Creek (MA96-94) watershed. The sites stormwater trajectory flows from the site to the town’s drainage network, then discharging to Aunt Betty’s Pond prior to ultimately reaching Stewarts Creek. The proposed development will include one 4-story multi-family building with associated access drives, parking, drainage and utilities. The site will be serviced by public water and sewer. Stormwater treatment and mitigation will be provided by utilizing Best Management Practices (BMPs) as established by the Massachusetts Stormwater Handbook. BMPs will consist of one Underground Infiltration System for roof runoff, 5 runoff collection and infiltration systems (Stormcrete), an aboveground infiltration pond with a sediment forebay, and 5 leaching catch basins for site stormwater treatment. Site constraints that were considered in the stormwater design are detailed in the Stormwater Design Alternatives Analysis (2.4) section of this report. The system has been designed to meet the MADEP Stormwater Handbook, otherwise known as the Massachusetts Stormwater Management Standards (MASWMS), and the Town of Barnstable Code Regulations. The project is considered a redevelopment site. Note that due to the overall reduction in pavement area, this redevelopment will automatically result in a decrease in stormwater runoff for all design storm events. Furthermore, the proposed BMP treatment chain for the new building area has been designed to fully infiltrate all storm events up to and including the 100-year storm without bypass, which will further improve existing conditions. 2.0 Site Conditions 2.1 SOILS There are the following soil types within the analyzed area of the Site as mapped by the NRCS USDA Soil Conservation service: Soil Symbol Description Hydrologic Group 252B Carver coarse sand, 3 to 8 percent slopes A 602B Urban land, 0 to 8 percent slopes Hydrologic Group A has been used for modeling the site. Site specific soil evaluations can be found in Appendix A2.1. 1 Stevens Street Mutli-Family 2.2 EXISTING SITE CONDITIONS The site is located at the intersection of Stevens Street and North Street. Access to the site comes from Stevens Street that borders the East side of the site and Mitchell’s Way that borders the Southwest side of the site. Neighboring the site is a residential and commercial development to the North and a Church and residential development to the West. Currently the site exists today as vacant lot with sections of pavement and dirt piles from a previously demolished Collision Center or vehicle maintenance building. Based on aerial imaging, it is presumed that the development was demolished sometime between 2016 and 2017. For the purpose of our analysis, the demolished development of the collision center and vehicle maintenance, has been considered as the predevelopment condition. Surface Lidar showing the collision center and vehicle maintenance was used for pre-development. Based on the oldest available aerial imaging from 1990, the development has existed for over 25 years with its stormwater practices ultimately discharging stormwater runoff to the town’s drainage network. The intent behind this is to provide accurate pre-existing conditions of the site with its stormwater systems as it provided some stormwater treatment practices prior to discharging into the town’s drainage network. The current vacant condition would represent silted and failed systems which provide no peak attenuation in the town’s drainage system. Making these assumptions ultimately results in a conservative approach as the pre-development peak flows and volumes to the existing drainage network is reduced and establishes the maximum peak and volumes that need to be met in post-development. The predevelopment condition consists of one building with associated asphalt parking. The total impervious area of 50,878 sf consists of 42,050 sf of pavement surface and 8,828 sf of building roof area. Stormwater runoff from the Eastern half of the site flows overland into an onsite leaching catch basin where it is infiltrated. Overflow from the leaching catch basin ultimately discharges to the town’s existing drainage network in Stevens Street. A section of the Southern half of the site travels via overland flow to another onsite leaching catch basin located in the south. Overflow from this leaching catch basin ultimately discharges to Mitchell’s Way. Stormwater runoff from the Western half of the site travels uncontrolled via overland flow undetained and untreated, offsite to Mitchell’s Way. Field investigations confirmed that the existing driveway and parking abutting the Northern property line flows into an existing catch basin located at the South end of the driveway, which does not discharge to the site. The site is located in the Stewarts Creek (MA96-94) watershed. The sites stormwater trajectory flows from the site to the town’s drainage network, then discharging to Aunt Betty’s Pond prior to ultimately reaching Stewarts Creek. Design Point 1 (DP-1) represents Mitchell’s Way. Design Point 2 (DP-2) represents the existing drainage network in Stevens Street. 2 Stevens Street Mutli-Family 2.3 POST SITE CONDITIONS To minimize impacts to all surrounding properties, existing drainage patterns have been identified and will be maintained or improved in post development conditions. The redevelopment removes the LUHPPL use and proposes a residential development reducing environmental impacts and concerns. In post development conditions, there is an overall impervious area of 53,710 sf. The impervious area consists of 35,398 sf of pavement surface and 18,312 sf of building area resulting in an overall reduction of pavement surface area of 15.8% from pre to post condition. Though there is an increase in building area, all building roof area will be collected and infiltrated up to the 100-year storm in post development condition. The proposed drainage analysis uses stormwater management systems to control and treat runoff from the proposed development. The following BMP’s are proposed and have been designed to include the following elements: Underground Infiltration System Leaching Catch Basins with 2’ sumps for TSS removal Runoff collection and infiltration systems (Stormcrete) Infiltration Pond Sediment Forebay o Pretreatment of impervious areas. o 2.0’ forebay depth with 3:1 grassed slopes. The above elements will used to meet the MASWMS. The proposed roof runoff will be collected and infiltrated via an underground chamber system consisting of Stormtech chambers which include treatment and infiltration up to the 100-year storm event. An emergency overflow manhole with a weir has been provided for storms higher than the 100 year storm event. Parking surface areas and associated drive aisles are collected via runoff collection and infiltration systems (Stormcrete) which provide treatment, recharge and infiltration up to the 100-year storm event. The access driveways are collected and infiltrated via onsite leaching catch basins with 2’ sumps providing pretreatment, recharge and infiltration up to the 25-year storm event. An infiltration pond is also provided at the southern access driveway to collect and infiltrate stormwater up to the 100-year storm event. The project is considered a redevelopment site. Note that due to the overall reduction in pavement area, this redevelopment will automatically result in a decrease in stormwater runoff for all design storm events. Furthermore, the proposed BMP treatment chain for the new building area has been designed to fully infiltrate all storm events up to and including the 100-year storm without bypass, which will further improve existing conditions. 3 Stevens Street Mutli-Family 2.4 Stormwater Design Alternatives Analysis An essential aspect of the design process is to assess a site's constraints and develop a site design, including stormwater management, that integrates seamlessly with the surroundings and ensures the site's practicality for construction. Several constraints influenced the stormwater design for this particular site: The Downtown Village District zoning regulations require buildings to front on the streets they are located and there a requirement for minimum building frontage. This drove the building placement to be in the southeastern corner of the site at the intersection of Stevens Street and North Street. The site's topography slopes from a high point in the northwestern corner to the southeastern corner, resulting in an approximately eight feet elevation change across the site. The seasonal high groundwater table on the site is higher than expected for Cape Cod, ranging from about 4' to 7' across the site. These constraints necessitated locating the proposed building at the low point of the site, which contradicts the typical site design approach, where stormwater practices are usually placed at the lowest point. At first, the design team looked at more “traditional” stormwater practices for the site. For a denser site with such as this, where the space for surface stormwater treatment areas is limited, collection systems discharging to underground infiltration systems may be a typical design approach. We did a schematic design for this approach and quickly discovered this type of system would require the site to be raised significantly above existing grade. For a traditional system of catch basins, to pipes to an underground infiltration system, the cross section of the proposed system typically relates to finished grade being approximately a minimum of 11’ above the seasonal high groundwater table. On this site, this would translate to a first-floor building elevation of approximately 32 with the majority of the parking field being around elevation 30 to 31. This would translate to 6’ to 11’ of fill, or 20,000 +/- cy, of fill to be brought into the site. This would also put the first floor of the building about 10’ above the adjacent street and make the driveway connections problematic and potentially infeasible from a grading and slope standpoint. This type of stormwater approach would in short make the project infeasible. Realizing the need to limit the required distance above the seasonal high groundwater table, porous pavement options presented themselves as the natural solution to a site with such constraints and were therefore explored. Since porous pavement has no need for catch basins and other drainage structures, requirements for cover over pipes or underground chambers, and the flexibility to locate porous pavement, this would serve to construct the site at the lowest elevation possible, meeting the intent of the zoning regulations and allowing the building to be sited harmoniously with the adjacent streets. When looking at porous pavement options, a concern with traditional porous asphalt is durability. In higher use parking lots such as a residential use, the constant pulling in and out of cars can cause the aggregate in porous asphalt to loosen and the surface to degrade over time. Due to this concern, in parking lots such as these, porous concrete options are favorable to porous asphalt. Stormcrete, a prefabricated porous concrete panel which has been used with great success in New England for over 15 years, was then identified as the ideal option for the surface. In addition to providing enhanced durability, Stormcrete also allows for reduced and easier maintenance than traditional porous pavement. Stormcrete is also premanufactured offsite, so it is manufactured to higher standards than traditional porous pavement due to it being made in a controlled environment. Stormcrete panels can 4 Stevens Street Mutli-Family be easily vacuumed clean, but Stormcrete's clear advantage is that individual panels can also be easily removed and cleaned or replaced if they become clogged, something that cannot be done with traditional porous asphalt pavements. From a grading standpoint, because of the lack of structures, pipes and chambers, the cross section for this option was approximately 5’ less than the traditional approach described above. This all but eliminates the excessive fill requirement that would otherwise render this site undevelopable. In addition to being a cost and transportation and disruption savings, this also allowed the building to be located where it has been proposed, at only 3’ above street level. This allows for much better pedestrian and vehicular access to the site, not to mention aesthetics and spatial compatibility with the surrounding areas. After this alternatives analysis, Stormcrete was chosen to be proposed as the ideal stormwater approach for this site. 5 Stevens Street Mutli-Family 3.0 Minimum Standards The site has been designed to meet the MASWMS to the maximum extent practicable. For the proposed development, stormwater management best practices have been selected and designed to fully comply with all applicable Standards of the MASSWMS on most of the site, rather than “maximum extent practicable”. This includes pretreatment, recharge, water quality treatment, and infiltration of stormwater from larger storm events up to and including the 100-year storm. The remaining areas and due to the steep slopes and grade change in the driveways, will not provide pretreatment and will be collected, treated and infiltrated up to the 25-year storm via onsite leaching catch basins with sumps. The following sections primarily analyze the proposed treatment chain for the new development. 3.1 Minimum Standard 1: No New Untreated Discharges There are no new untreated discharges from the proposed development. 3.2 Minimum Standard 2: Peak Rate Attenuation 3.2.1 Method of Analysis USDA Soil Conservation Service Method as defined by Technical Release No. 20 (TR-20) determines Stormwater runoff rate and volume. Type III rainfall distribution is utilized. Time of concentration is determined using Technical Release No 55 (TR-55) methodology, through the computer program HydroCAD ver. 10 by HydroCAD Software Solutions LLC. Infiltration rates have been determined based on onsite soil evaluations. The Frimpter Cape Cod Method was used to estimate the groundwater levels. The soil evaluations were used to develop a texture class. Infiltration rates are based on Rawl’s Rates. See table 2.3.3 of the Massachusetts Stormwater Handbook. Double Ring Infiltrometer Tests (ASTM D3385-03) were performed to determine the infiltration rate at the C soil horizon, refer to Appendix A2.1. The infiltrometer test, IT 23-1, showed an approximate infiltration rate of 63 in/hr. This indicates the existing onsite soils within the C horizon have an infiltration rate in excess of 63 in/hr, so in accordance with the MASWMS Volume 3, Standard 3 (Stormwater Recharge), an infiltration rate equal to half the measured rate (31.5 in/hr) was used in the analysis for the underground infiltration system and the porous pavement (Stormcrete). A second infiltrometer test, IT 23-2, showed an approximate infiltration rate of 94.8 in/hr. For the purpose of this project, a more conservative route was taken in using the rate equal to half the measured rate of 63 in/hr from IT 23-1 (31.5 in/hr). The drainage system has been designed to mitigate all stormwater flows for the 2 through 25-year storm events. 6 Stevens Street Mutli-Family Drainage Network Design Parameters: A. PIPES All drainage pipes are HDPE or equivalent unless otherwise noted. Manning's coefficient = 0.012 for HDPE Pipe Diameters & lengths as specified. The 100-year design storm is utilized for the drainage pipe design and overland flow design to ensure that the drainage system contains and channels water to the BMP areas as shown on the plans. The rational method has been used for the closed drainage system. B. STRUCTURES Manholes – Pre-cast concrete with inverts as specified. Leaching catch basins – Pre-cast concrete with 2’ sumps for TSS removal 7 Stevens Street Mutli-Family 3.2.2 Design Storm Analysis of 2-year, 10-year, 25-year and 100-year frequency storms are included. The following 24-hour rainfall intensities are obtained from the Cornell Extreme Precipitation in New York & New England (http://precip.eas.cornell.edu/). Note: For design storms where the Hydrology Handbook for Conservation Commissioners (Table F-1) lists a higher intensity than the Cornell data, that intensity has been adopted in lieu of the Cornell figure. Barnstable County. 2 year =3.60 inches 10 year =4.81 inches 25 year =5.99 inches 100 year=8.35 inches 3.2.3 Design Point Breakdown The site is analyzed as 2 watershed areas. In the pre-development stage, there are 4 sub-catchments. In the post development stage, there are 13 sub-catchments. A description of each watershed and associated sub-catchments are summarized as follows, for cover types see color watershed maps located in back of this report. Numbers in parentheses ( ) indicate the HydroCAD Node Number. Design Point-1 (DP-1:Mitchell’s Way): DP-1: Mitchell’s Way represents Mitchell’s Way road. In pre-development conditions there are two sub-catchments tributary to DP-1: Mitchell’s Way (13). Pre-10 (10) contains the western half of the site as well as a majority of the roof from the existing building. Stormwater from the roof is collected in downspouts that outlet to the western parking pavement which flows overland to DP-1 (13). Stormwater from the western half of the site travels via overland flow to DP-1 (13). Pre-11 (11) contains the southern section of the site and a section of offsite grass and pavement that flows via overland flow into Leaching Catch Basin 2 (12) at the southern edge of the property where it is infiltrated to the maximum extent practicable. Any overflow from Leaching Catch Basin 2 (12) travels via overland flow to DP-1 (13). In post development conditions there are 13 sub-catchments tributary to DP-1: Mitchell’s Way (101). Post-100 (100) consists of stormwater runoff along the Southern edge of the property that travels via overland flow to DP-1 (13). Post-102 (102) consists of stormwater runoff along the Western edge of the property that travels via overland flow to DP-1 (13). Post-204 collects stormwater runoff along the western edge of the site where stormwater flows via overland flow into porous pavement [Stormcrete (205)] where it is treated and infiltrated for the 2 through 100 year storm events. 8 Stevens Street Mutli-Family Post-206 collects stormwater runoff at the center of the site where stormwater flows via overland flow into porous pavement [Stormcrete (207)] where it is treated and infiltrated for the 2 through 100 year storm events. Post-208 collects stormwater runoff at the Northwestern corner of the site where stormwater flows via overland flow into porous pavement [Stormcrete (209)] where it is treated and infiltrated for the 2 through 100 year storm events. Post-210 collects stormwater runoff at the center of the site where stormwater flows via overland flow into porous pavement [Stormcrete (211)] where it is treated and infiltrated for the 2 through 100 year storm events. Post-212 collects onsite and offsite stormwater runoff at the Northern edge of the property where stormwater flows via overland flow into porous pavement [Stormcrete (213)] where it is treated and infiltrated for the 2 through 100 year storm events. Post-214 (214) collects stormwater runoff from the Southwestern corner of the site where stormwater flows via overland flow into a leaching catch basin [Leaching CB 15 (215)] where it is infiltrated to the maximum extent practicable. Any overflow from the leaching catch basin would ultimately travel overland to DP-1 (101). Post-216 (216) consists of stormwater runoff from the Southwestern corner of the site where stormwater flows via overland flow into a leaching catch basin [Leaching CB 17 (217)] where it is infiltrated to the maximum extent practicable. Any overflow from the leaching catch basin would ultimately travel overland to DP-1 (101). Post-218 (218) consists of stormwater runoff from the Southwestern corner of the site where stormwater flows via overland flow into a leaching catch basin [Leaching CB 19 (219)] where it is infiltrated to the maximum extent practicable. Any overflow from the leaching catch basin would ultimately travel overland to DP-1 (101). Post-220 (220) consists of stormwater runoff from the Southwestern corner of the site where stormwater flows via overland flow into a leaching catch basin [Leaching CB 21 (221)] where it is infiltrated to the maximum extent practicable. Any overflow from the leaching catch basin would ultimately travel overland to DP-1 (101). Post-222 collects stormwater runoff at the Southwestern corner of the site where stormwater flows via overland flow into the Sediment Forebay (223) where it is treated and infiltrated for the 2 through 100 year storm events. Post-224 consists of uncontrolled stormwater runoff at the Southwestern corner of the site that flows directly to the Infiltration Pond (225) where it is treated and infiltrated for the 2 through 100 year storm events. 9 Stevens Street Mutli-Family All runoff collection and infiltration systems (Stormcrete) have been designed to hold storm events greater than the 100 year storm event. Emergency overflow drainage has been added to ensure that in the unlikely event of all systems fail, that stormwater would still reach the stone reservoir for infiltration. If all infiltration systems and emergency overflows were to fail, stormwater runoff would ultimately flow to the proposed sediment forebay (223) and infiltration pond (225) before outlet to Mitchell’s Way. Below is a summary of the hydrologic parameters for the pre and post development sub-catchments in Design Point-1. Area (acres)CN Tc (min) Pre-10 0.991 79 9.2 Pre-11 0.251 82 6.0 Post-100 0.187 56 6.0 Post-102 0.041 60 6.0 Post-204 0.065 89 6.0 Post-206 0.162 85 6.0 Post-208 0.202 84 6.0 Post-210 0.151 82 6.0 Post-212 0.321 72 6.0 Post-214 0.009 84 6.0 Post-216 0.002 96 6.0 Post-218 0.010 87 6.0 Post-220 0.008 90 6.0 Post-222 0.079 73 6.0 Post-224 0.024 39 6.0 Design Point-2 (DP-2: Stevens Street): DP-2: Stevens Street represents the existing drainage network located in Stevens Street. In pre-development conditions there is two sub-catchment tributary to DP-2: Stevens Street (22). Pre-20 (20) contains the eastern half of the site as well as a small section of the roof from the existing building. Stormwater from the roof is collected in a downspout that outlets to the eastern parking pavement which travels via overland flow into Leaching Catch Basin 1 (21) where it is infiltrated to the maximum extent practicable. Any overflow from Leaching Catch Basin 1 (21) travels via overland flow to DP-2(22). In pre-development conditions, there is one sub-catchment that is presumably collected and infiltrated onsite based on survey data obtained. Pre-30 (30) consists of a small depression at the northeastern side of the existing building. 10 Stevens Street Mutli-Family In post development conditions there are 4 sub-catchments tributary to DP-2: Stevens Street (201). Post-200 (200) collects stormwater runoff from the Eastern edge of the property where stormwater flows via overland flow offsite to DP-2 (201). Post-202 consists of roof runoff from the proposed building. Stormwater runoff from the roof will be collected via and intern roof drainage network that will discharge to the Underground Infiltration System (203) where it is infiltrated for the 2 through 100 year storm events. If the Underground Infiltration System were to fail, stormwater would ultimately outlet via the emergency overflow to Stevens Street. Post-300 (300) consists of stormwater runoff at the northeastern corner of the site where stormwater travels via overland flow offsite to DP-2 (201). Post-301 (301) consists of stormwater runoff from the Northeastern corner of the site where stormwater flows via overland flow into a leaching catch basin [Leaching CB 30 302)] where it is infiltrated to the maximum extent practicable. Any overflow from the leaching catch basin would ultimately travel overland to DP-2 (201). Below is a summary of the hydrologic parameters for the pre and post development sub-catchments in Design Point-2. Area (acres)CN Tc (min) Pre-20 0.477 73 9.5 Pre-30 0.036 98 6.0 Post-200 0.030 63 6.0 Post-202 0.420 98 6.0 Post-300 0.024 88 6.0 Post-301 0.019 84 6.0 3.2.4 Outlet Protection There are no existing or proposed discharge outlets, therefore outlet protection is not required. 3.2.5 Standard 2 Conclusion The project is considered a redevelopment site. Note that due to the overall reduction in pavement area, this redevelopment will automatically result in a decrease in stormwater runoff for all design storm events. Furthermore, the proposed BMP treatment chain for the new building area has been designed to fully infiltrate all storm events up to and including the 100-year storm without bypass, which will further improve existing conditions. See HydroCAD printouts in Appendix A. The tables below present a summary of the predevelopment flows vs. the mitigated post development flows. 11 Stevens Street Mutli-Family Pre Development vs. Post Development Mitigated Design Point 1: (DP-1) – Mitchells Way Conditions – Peak Flow 2-Year 10-Year 25-Year 100-Year Pre Dev Summation 1.61 3.17 5.20 8.12 Post Dev Summation 0.07 0.22 0.40 0.84 Net Change -1.54 -2.95 -4.80 -7.28 All flows in cubic feet per second (cfs) Design Point 2: (DP-2) – Stevens Street Conditions – Peak Flow 2-Year 10-Year 25-Year 100-Year Pre Dev Summation 0.08 0.82 2.04 2.71 Post Dev Summation 0.08 0.14 0.20 0.32 Net Change 0.00 -0.68 -1.84 -2.39 All flows in cubic feet per second (cfs) As shown above, there will be no increase in stormwater runoff following the proposed construction during the 2 through 100 year storm events. The stormwater system has been designed to provide appropriate peak rate attenuation for all storm events. 12 Stevens Street Mutli-Family 3.3 Minimum Standard 3: Recharge Recharge is analyzed per watershed based on impervious area coverage in accordance with Standard 3. Groundwater recharge is determined from the following equation: Rv=F*impervious area Where:Rv=Required Recharge Volume (ac-ft) F= Target Depth Factor based on Hydrologic Soil Group Recharge (see table below) I=Impervious Area (acres) HSG Target Depth Factor (F) (inch) A 0.60 B 0.35 C 0.25 D 0.10 Due to the presence of Hydraulic Group A soils, the Target Depth Factor for this project is 0.60 inches for the Recharge Volume. Given that: For each treatment system, one practice is being used to meet both Standards 3 & 4 This site is required to meet the 1” rule for Water Quality Volume (see following section) The Water Quality Volume (1”) is larger than the Recharge Volume for this project, therefore the infiltration BMPs have been sized and designed based on the Water Quality Volume (1”). Recharge requirements will be met through the use of porous pavement, underground infiltration system, and leaching catch basins. Recharge has been analyzed using the Dynamic Field Method per the Massachusetts Stormwater Handbook Volume 3 Chapter 1. The table below summarizes the required Recharge Volume for each BMP, and the design data to be used in the analysis: BMP HSG F I (Acres) Rv Required (ac-ft) Infiltrometer Test Log In-situ saturated hydraulic conductivity rate (in/hr) Exfiltration Rate to be Used (in/hr) System A (213) A 1.0 0.182 0.015 IT 23-1 63 31.5 System B (209) A 1.0 0.154 0.013 IT 23-1 63 31.5 System C (211) A 1.0 0.109 0.009 IT 23-1 63 31.5 13 Stevens Street Mutli-Family System D(207) A 1.0 0.127 0.011 IT 23-1 63 31.5 System E (205) A 1.0 0.055 0.005 IT 23-1 63 31.5 UIS (203) A 1.0 0.420 0.035 IT 23-1 63 31.5 Leaching CB 15 A 1.0 0.007 0.001 IT 23-1 63 31.5 Leaching CB 17 A 1.0 0.002 0.000 IT 23-1 63 31.5 Leaching CB 19 A 1.0 0.008 0.001 IT 23-1 63 31.5 Leaching CB 21 A 1.0 0.007 0.001 IT 23-1 63 31.5 Leaching CB 30 A 1.0 0.015 0.001 IT 23-1 63 31.5 Sediment Forebay A 1.0 0.045 0.004 IT 23-1 63 31.5 Infiltration Pond A 1.0 0.045 0.004 IT 23-1 63 31.5 A hydrocad model was created for each applicable BMP system using contributing impervious area (only) and calibrating the rainfall data to produce a runoff volume equal to the Required Recharge (Rv) volume per the table above, during the peak 12 hours of the storm. Exfiltration was set to apply to “horizontal area only”. As shown in the reported results, all stormwater is recharged without exiting the runoff collection and infiltration systems (Stormcrete), the underground infiltration system and the leaching catch basins. See Appendix 3.3 for all HydroCAD results. Drawdown All infiltration BMPs are required to drain down the required recharge volume completely within 72 hours, using the following formula: ))((AreaBottomK RvTimedrawdown Where: Rv = Required Storage Volume K = in-situ saturated hydraulic conductivity for “Dynamic Field” Method, use 50% of the in-situ saturated hydraulic conductivity (infiltrometer test). 14 Stevens Street Mutli-Family Bottom Area = Bottom Area of Recharge Structure The table below summarizes the drawdown results for each BMP: BMP Rv (cu-ft) K (in/hr) Bottom Area (sf) Drawdown (hr) System A 653 31.5 1,700 0.01 System B 566 31.5 1,440 0.01 System C 392 31.5 1,000 0.01 System D 479 31.5 1,120 0.01 System E 218 31.5 540 0.01 UIS 1,525 31.5 1,447 0.03 Leaching CB 15 44 31.5 28 0.10 Leaching CB 17 0 31.5 28 0.00 Leaching CB 19 44 31.5 28 0.10 Leaching CB 21 44 31.5 28 0.10 Leaching CB 30 44 31.5 28 0.10 Sediment Forebay 174 31.5 25 0.22 Infiltration Pond 174 31.5 182 0.03 15 Stevens Street Mutli-Family 3.4 Minimum Standard 4: Water Quality Note that standard 4 is only required to be met to the maximum extent practicable. The proposed treatment train has been designed to meet or exceed water quality requirements per Standard 4. The stormwater management system is required to provide a minimum of 80% TSS removal per Standard 4. See Appendix A3.4 for TSS Removal Calculation Worksheets. For water quality volume requirements, per the Massachusetts Stormwater Handbook: The required water quality volume equals 1.0 inch of runoff times the total impervious area of the post development project site for a discharge – From a land use with a higher potential pollutant load Within an area with a rapid infiltration rate (greater than 2.4 inches per hour) Within a Zone II or Interim Wellhead Protection Area Near or to the following critical areas: o Outstanding Resource Waters o Special Resource Waters o Bathing beaches o Shellfish growing areas o Cold-water fisheries For all other discharges the required water quality volume equals 0.5 inches of runoff times the total impervious area of the post development site. Since this site includes rapid infiltration rates it needs to meet the 1.0 inch rule. For each treatment system, one practice is being used to meet both Standards 3 &4. Therefore the BMPs have been sized for the larger of the Recharge/ Water Quality Volume. See Section 3.3 for more details. The stormwater management system is also required to provide a minimum of 80% TSS removal per Standard 4. The stormwater management system is typically required to provide a minimum of 80% TSS removal per Standard 4, however since 100% of the impervious area is roof runoff for the Underground Infiltration System (203), pre treatment is not required and is exempt from the TSS removal calculations. See Appendix 3.4 for TSS removal worksheet. 16 Stevens Street Mutli-Family 3.4.2 TMDL The proposed development site ultimately discharges stormwater to Aunt Betty’s Pond which ultimately discharges to Stewarts Creek (Segment ID MA96-94), which has the following impairments according to the EPA Waterbody Report dated 2022: -Shellfish Harvesting (bacteria) The proposed BMPs fully infiltrate the water quality storm. Stormwater treatment in the form of groundwater recharge is widely recognized as a BMP that reduces bacteria by 90-100%1,2,3; 1.Massachusetts Department of Environmental Protection Massachusetts Stormwater Handbook, February 2008 2.New York State Department of Environmental Conservation New York State Stormwater Management Design Manual, October 2001, January 2015 3.Rhode Island Department of Environmental Management Rhode Island Stormwater Design and Installations Manual, December 2010 Since the impairments listed above do not include nitrogen, infiltration of the entire water quality storm will significantly reduce pollutants, thereby providing a net benefit to the waterbody(s) downstream. 17 Stevens Street Mutli-Family 3.5 Minimum Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs) The proposed development site is not considered a LUHPPL. Note that the predevelopment is a vehicle maintenance use considered a LUHPPPL which is being removed in post development. 3.6 Minimum Standard 6: Critical Areas The site is not located within a critical resource area. 3.7 Minimum Standard 7: Redevelopments The site is classified as a redevelopment site and has been designed, modeled and analyzed accordingly per the MASWMS. 3.8 Minimum Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control See the plan set and Stormwater Pollution Prevention Plan (SWPPP) for this development prepared by DiPrete Engineering. 3.9 Minimum Standard 9: Operation and Maintenance Plan See the Stormwater System Operations and Maintenance Plan prepared by DiPrete Engineering. 3.10 Minimum Standard 10: Prohibition of Illicit Discharges There are no existing or proposed illicit discharges on site. 18 Stevens Street Mutli-Family Appendix A 19 Stevens Street Mutli-Family A2.1 Soil Evaluations 20 DiPrete Engineering Massachusetts Soil Evaluation Form DE Project Number ___________________________ Property Owner: _____________________________________________________________________________________________________________ Property Location: ____________________________________________________________________________________________________________ Date of Test Hole: ____________________________________________________________________________________________________________ Soil Evaluator: _____________________________________________________ License Number: _________________________________________ Weather: ___________________________________________________________________________________ Time: _________________________ Coarse Fragment % by Vol. Soil Colors - Moist (Munsell) Re-Dox TH____ Horizon Depth Gravel Cobbles & Stones Matrix Re-Dox Features Depth, Percent Soil Texture (USDA) Soil Structure Other Re-Dox TH____ Horizon Depth Matrix Re-Dox Features TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ Comments:_______________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ Page 1 of 1 OtherDepth, Percent Soil Colors - Moist (Munsell) Coarse Fragment % by Vol. Cobbles & Stones Gravel Soil Texture (USDA) Soil Consistence (Moist) Soil Structure Soil Consistence (Moist) 21 DiPrete Engineering Massachusetts Soil Evaluation Form DE Project Number ___________________________ Property Owner: _____________________________________________________________________________________________________________ Property Location: ____________________________________________________________________________________________________________ Date of Test Hole: ____________________________________________________________________________________________________________ Soil Evaluator: _____________________________________________________ License Number: _________________________________________ Weather: ___________________________________________________________________________________ Time: _________________________ Coarse Fragment % by Vol. Soil Colors - Moist (Munsell) Re-Dox TH____ Horizon Depth Gravel Cobbles & Stones Matrix Re-Dox Features Depth, Percent Soil Texture (USDA) Soil Structure Other Re-Dox TH____ Horizon Depth Matrix Re-Dox Features TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ Comments:_______________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ Page 1 of 1 OtherDepth, Percent Soil Colors - Moist (Munsell) Coarse Fragment % by Vol. Cobbles & Stones Gravel Soil Texture (USDA) Soil Consistence (Moist) Soil Structure Soil Consistence (Moist) 22 DiPrete Engineering Massachusetts Soil Evaluation Form DE Project Number ___________________________ Property Owner: _____________________________________________________________________________________________________________ Property Location: ____________________________________________________________________________________________________________ Date of Test Hole: ____________________________________________________________________________________________________________ Soil Evaluator: _____________________________________________________ License Number: _________________________________________ Weather: ___________________________________________________________________________________ Time: _________________________ Coarse Fragment % by Vol. Soil Colors - Moist (Munsell) Re-Dox TH____ Horizon Depth Gravel Cobbles & Stones Matrix Re-Dox Features Depth, Percent Soil Texture (USDA) Soil Structure Other Re-Dox TH____ Horizon Depth Matrix Re-Dox Features TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ Comments:_______________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ Page 1 of 1 OtherDepth, Percent Soil Colors - Moist (Munsell) Coarse Fragment % by Vol. Cobbles & Stones Gravel Soil Texture (USDA) Soil Consistence (Moist) Soil Structure Soil Consistence (Moist) 23 DiPrete Engineering Massachusetts Soil Evaluation Form DE Project Number ___________________________ Property Owner: _____________________________________________________________________________________________________________ Property Location: ____________________________________________________________________________________________________________ Date of Test Hole: ____________________________________________________________________________________________________________ Soil Evaluator: _____________________________________________________ License Number: _________________________________________ Weather: ___________________________________________________________________________________ Time: _________________________ Coarse Fragment % by Vol. Soil Colors - Moist (Munsell) Re-Dox TH____ Horizon Depth Gravel Cobbles & Stones Matrix Re-Dox Features Depth, Percent Soil Texture (USDA) Soil Structure Other Re-Dox TH____ Horizon Depth Matrix Re-Dox Features TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ TH _______ Fill Depth ______________ Total Depth __________ Impervious/Limiting Layer Depth __________ GW Seepage Depth __________ SHWT __________ Comments:_______________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________________________ Page 1 of 1 OtherDepth, Percent Soil Colors - Moist (Munsell) Coarse Fragment % by Vol. Cobbles & Stones Gravel Soil Texture (USDA) Soil Consistence (Moist) Soil Structure Soil Consistence (Moist) 24 Double Ring Infiltrometer Field Data Sheet Project Name:Date:Diameter H2O depth Test Location:Inner Ring Water Source: Field Personnel: Ring Depth (in.): Inner: Outer: Depth to WT: Presoak Data *Reading interval determined based on water level drop during presoak period Liquid Time Elapsed Temp HR:MIN Time in. Δ in. in Δ in. (F) START END START END START END START END START END START END START END START END START END START END START END START END START END START END START END 2 3 4 5 6 13 14 15 Inner Ring 7 8 9 10 11 12 1 Outer Ring Flow Reading Start Time End Time Starting Water Level/Ending Water Level Outer Ring Remarks Trial #Weather Cond., etc 6/22/23 ` Infiltration rate: 1.05"/min = 63"/hour Test conducted at 48" in C horizon, sand texture 25 Double Ring Infiltrometer Field Data Sheet Project Name:Date:Diameter H2O depth Test Location:Inner Ring Water Source: Field Personnel: Ring Depth (in.): Inner: Outer: Depth to WT: Presoak Data *Reading interval determined based on water level drop during presoak period Liquid Time Elapsed Temp HR:MIN Time in. Δ in. in Δ in. (F) START END START END START END START END START END START END START END START END START END START END START END START END START END START END START END 2 3 4 5 6 13 14 15 Inner Ring 7 8 9 10 11 12 1 Outer Ring Flow Reading Start Time End Time Starting Water Level/Ending Water Level Outer Ring Remarks Trial #Weather Cond., etc 6/22/23 Infiltration rate: 1.58"/min = 94.8"/hour Test conducted at 48" in C horizon, sand texture 26 Stevens Street Mutli-Family A3.2.1 HydroCAD Node Diagram 27 10 Pre-10 11 Pre-11 12 Leaching Catch Basin 2 13 DP-1: Mitchell's Way 20 Pre-20 21 Leaching Catch Basin 1 22 DP-2: Stevens Street 30 Pre-30 Routing Diagram for 3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering, Printed 11/29/2023 HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link 28 3300-001-ALLS-EHCD-INHS Printed 11/29/2023Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 0.540 39 >75% Grass cover, Good, HSG A (10, 11, 20) 0.919 98 Impervious, HSG A (10, 11, 20, 30) 0.046 98 Offsite Impervious, HSG A (10, 11, 20) 0.203 98 Roofs, HSG A (10, 20) 0.047 30 Woods, Good, HSG A (10) 1.754 78 TOTAL AREA 29 100 Post-100 101 DP-1: Mitchells Way 102 Subcat 102 200 Post-200 201 DP-2: Stevens Street 202 Subcat 202 203 UIS (SC-310) 204 Post-204 205 System E (Dumpster) 206 Post-206 207 System D (Island South) 208 Post-208 209 System B (West) 210 Subcat 210 211 System C (Center Island) 212 Post-212 213 System A (North) 214 Post-214 215 Leaching CB 15 216 Post-216 217 Leaching CB 17 218 Post-218 219 Leaching CB 19 220 Post-220 221 Leaching CB 21 222 Subcat 222 223 Sediment Forebay 224 Subcat 224 225 Infiltration Pond 300 Post-300 301 Post-301 302 Leaching CB 30 Routing Diagram for 3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link 30 3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 0.522 39 >75% Grass cover, Good, HSG A (100, 102, 200, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 300, 301) 0.772 98 Impervious, HSG A (100, 200, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 300, 301) 0.040 98 Offsite Impervious, HSG A (100, 102, 200, 300) 0.420 98 Roofs, HSG A (202) 0.000 30 Woods, Good, HSG A (102) 1.755 80 TOTAL AREA 31 Stevens Street Mutli-Family A3.2.2 HydroCAD 2-Year Storm Analysis 32 Type III 24-hr 2-Year Rainfall=3.40"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.991 ac 67.79% Impervious Runoff Depth=1.49"Subcatchment 10: Pre-10 Flow Length=321' Tc=9.2 min CN=79 Runoff=1.53 cfs 0.123 af Runoff Area=0.251 ac 72.52% Impervious Runoff Depth=1.70"Subcatchment 11: Pre-11 Tc=6.0 min CN=82 Runoff=0.50 cfs 0.036 af Peak Elev=20.75' Storage=191 cf Inflow=0.50 cfs 0.036 afPond 12: Leaching Catch Basin 2 Discarded=0.18 cfs 0.033 af Primary=0.11 cfs 0.003 af Outflow=0.29 cfs 0.036 af Inflow=1.61 cfs 0.125 afLink 13: DP-1: Mitchell's Way Primary=1.61 cfs 0.125 af Runoff Area=0.477 ac 58.40% Impervious Runoff Depth=1.11"Subcatchment 20: Pre-20 Flow Length=289' Tc=9.5 min CN=73 Runoff=0.52 cfs 0.044 af Peak Elev=20.93' Storage=309 cf Inflow=0.52 cfs 0.044 afPond 21: Leaching Catch Basin 1 Discarded=0.18 cfs 0.043 af Primary=0.08 cfs 0.002 af Outflow=0.26 cfs 0.044 af Inflow=0.08 cfs 0.002 afLink 22: DP-2: Stevens Street Primary=0.08 cfs 0.002 af Runoff Area=0.036 ac 100.00% Impervious Runoff Depth=3.17"Subcatchment 30: Pre-30 Tc=6.0 min CN=98 Runoff=0.12 cfs 0.009 af 33 Type III 24-hr 2-Year Rainfall=3.60"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.187 ac 28.70% Impervious Runoff Depth=0.42"Subcatchment 100: Post-100 Tc=6.0 min CN=56 Runoff=0.05 cfs 0.006 af Inflow=0.07 cfs 0.008 afLink 101: DP-1: Mitchells Way Primary=0.07 cfs 0.008 af Runoff Area=0.041 ac 36.14% Impervious Runoff Depth=0.58"Subcatchment 102: Subcat 102 Tc=6.0 min CN=60 Runoff=0.02 cfs 0.002 af Runoff Area=0.030 ac 40.84% Impervious Runoff Depth=0.71"Subcatchment 200: Post-200 Tc=6.0 min CN=63 Runoff=0.02 cfs 0.002 af Inflow=0.09 cfs 0.007 afLink 201: DP-2: Stevens Street Primary=0.09 cfs 0.007 af Runoff Area=0.420 ac 100.00% Impervious Runoff Depth=3.37"Subcatchment 202: Subcat 202 Tc=6.0 min CN=98 Runoff=1.47 cfs 0.118 af Peak Elev=20.01' Storage=0.003 af Inflow=1.47 cfs 0.118 afPond 203: UIS (SC-310) Discarded=1.05 cfs 0.118 af Secondary=0.00 cfs 0.000 af Outflow=1.05 cfs 0.118 af Runoff Area=0.065 ac 85.47% Impervious Runoff Depth=2.45"Subcatchment 204: Post-204 Tc=6.0 min CN=89 Runoff=0.18 cfs 0.013 af Peak Elev=21.38' Storage=1 cf Inflow=0.18 cfs 0.013 afPond 205: System E (Dumpster) Outflow=0.18 cfs 0.013 af Runoff Area=0.162 ac 78.37% Impervious Runoff Depth=2.10"Subcatchment 206: Post-206 Tc=6.0 min CN=85 Runoff=0.40 cfs 0.028 af Peak Elev=21.78' Storage=2 cf Inflow=0.40 cfs 0.028 afPond 207: System D (Island South) Outflow=0.40 cfs 0.028 af Runoff Area=0.202 ac 76.24% Impervious Runoff Depth=2.02"Subcatchment 208: Post-208 Tc=6.0 min CN=84 Runoff=0.48 cfs 0.034 af Peak Elev=21.84' Storage=3 cf Inflow=0.48 cfs 0.034 afPond 209: System B (West) Outflow=0.48 cfs 0.034 af Runoff Area=0.151 ac 72.09% Impervious Runoff Depth=1.87"Subcatchment 210: Subcat 210 Tc=6.0 min CN=82 Runoff=0.33 cfs 0.023 af Peak Elev=21.82' Storage=2 cf Inflow=0.33 cfs 0.023 afPond 211: System C (Center Island) Outflow=0.33 cfs 0.023 af Runoff Area=0.321 ac 56.69% Impervious Runoff Depth=1.19"Subcatchment 212: Post-212 Tc=6.0 min CN=72 Runoff=0.43 cfs 0.032 af 34 Type III 24-hr 2-Year Rainfall=3.60"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Peak Elev=22.20' Storage=2 cf Inflow=0.43 cfs 0.032 afPond 213: System A (North) Outflow=0.43 cfs 0.032 af Runoff Area=0.009 ac 76.56% Impervious Runoff Depth=2.02"Subcatchment 214: Post-214 Tc=6.0 min CN=84 Runoff=0.02 cfs 0.002 af Peak Elev=17.69' Storage=0 cf Inflow=0.02 cfs 0.002 afPond 215: Leaching CB 15 Discarded=0.02 cfs 0.002 af Primary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.002 af Runoff Area=0.002 ac 96.08% Impervious Runoff Depth=3.14"Subcatchment 216: Post-216 Tc=6.0 min CN=96 Runoff=0.01 cfs 0.000 af Peak Elev=18.40' Storage=0 cf Inflow=0.01 cfs 0.000 afPond 217: Leaching CB 17 Discarded=0.01 cfs 0.000 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.000 af Runoff Area=0.010 ac 81.35% Impervious Runoff Depth=2.27"Subcatchment 218: Post-218 Tc=6.0 min CN=87 Runoff=0.03 cfs 0.002 af Peak Elev=17.02' Storage=0 cf Inflow=0.03 cfs 0.002 afPond 219: Leaching CB 19 Discarded=0.03 cfs 0.002 af Primary=0.00 cfs 0.000 af Outflow=0.03 cfs 0.002 af Runoff Area=0.008 ac 86.41% Impervious Runoff Depth=2.54"Subcatchment 220: Post-220 Tc=6.0 min CN=90 Runoff=0.02 cfs 0.002 af Peak Elev=17.68' Storage=2 cf Inflow=0.02 cfs 0.002 afPond 221: Leaching CB 21 Discarded=0.02 cfs 0.002 af Primary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.002 af Runoff Area=0.079 ac 57.60% Impervious Runoff Depth=1.25"Subcatchment 222: Subcat 222 Tc=6.0 min CN=73 Runoff=0.11 cfs 0.008 af Peak Elev=19.54' Storage=280 cf Inflow=0.11 cfs 0.008 afPond 223: Sediment Forebay Primary=0.11 cfs 0.008 af Secondary=0.00 cfs 0.000 af Outflow=0.11 cfs 0.008 af Runoff Area=0.024 ac 0.00% Impervious Runoff Depth=0.01"Subcatchment 224: Subcat 224 Tc=6.0 min CN=39 Runoff=0.00 cfs 0.000 af Peak Elev=17.37' Storage=76 cf Inflow=0.11 cfs 0.008 afPond 225: Infiltration Pond Outflow=0.03 cfs 0.008 af Runoff Area=0.024 ac 82.32% Impervious Runoff Depth=2.36"Subcatchment 300: Post-300 Tc=6.0 min CN=88 Runoff=0.07 cfs 0.005 af Runoff Area=0.019 ac 76.11% Impervious Runoff Depth=2.02"Subcatchment 301: Post-301 Tc=6.0 min CN=84 Runoff=0.05 cfs 0.003 af Peak Elev=19.87' Storage=2 cf Inflow=0.05 cfs 0.003 afPond 302: Leaching CB 30 Discarded=0.04 cfs 0.003 af Primary=0.00 cfs 0.000 af Outflow=0.04 cfs 0.003 af 35 Stevens Street Mutli-Family A3.2.3 HydroCAD 10-Year Storm Analysis 36 Type III 24-hr 10-Year Rainfall=4.99"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.991 ac 67.79% Impervious Runoff Depth=2.79"Subcatchment 10: Pre-10 Flow Length=321' Tc=9.2 min CN=79 Runoff=2.91 cfs 0.231 af Runoff Area=0.251 ac 72.52% Impervious Runoff Depth=3.07"Subcatchment 11: Pre-11 Tc=6.0 min CN=82 Runoff=0.90 cfs 0.064 af Peak Elev=20.81' Storage=408 cf Inflow=0.90 cfs 0.064 afPond 12: Leaching Catch Basin 2 Discarded=0.18 cfs 0.051 af Primary=0.35 cfs 0.013 af Outflow=0.53 cfs 0.064 af Inflow=3.17 cfs 0.243 afLink 13: DP-1: Mitchell's Way Primary=3.17 cfs 0.243 af Runoff Area=0.477 ac 58.40% Impervious Runoff Depth=2.27"Subcatchment 20: Pre-20 Flow Length=289' Tc=9.5 min CN=73 Runoff=1.12 cfs 0.090 af Peak Elev=21.02' Storage=515 cf Inflow=1.12 cfs 0.090 afPond 21: Leaching Catch Basin 1 Discarded=0.18 cfs 0.069 af Primary=0.82 cfs 0.022 af Outflow=1.00 cfs 0.090 af Inflow=0.82 cfs 0.022 afLink 22: DP-2: Stevens Street Primary=0.82 cfs 0.022 af Runoff Area=0.036 ac 100.00% Impervious Runoff Depth=4.75"Subcatchment 30: Pre-30 Tc=6.0 min CN=98 Runoff=0.17 cfs 0.014 af 37 Type III 24-hr 10-Year Rainfall=4.81"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.187 ac 28.70% Impervious Runoff Depth=0.95"Subcatchment 100: Post-100 Tc=6.0 min CN=56 Runoff=0.17 cfs 0.015 af Inflow=0.22 cfs 0.019 afLink 101: DP-1: Mitchells Way Primary=0.22 cfs 0.019 af Runoff Area=0.041 ac 36.14% Impervious Runoff Depth=1.19"Subcatchment 102: Subcat 102 Tc=6.0 min CN=60 Runoff=0.05 cfs 0.004 af Runoff Area=0.030 ac 40.84% Impervious Runoff Depth=1.39"Subcatchment 200: Post-200 Tc=6.0 min CN=63 Runoff=0.05 cfs 0.003 af Inflow=0.14 cfs 0.010 afLink 201: DP-2: Stevens Street Primary=0.14 cfs 0.010 af Runoff Area=0.420 ac 100.00% Impervious Runoff Depth=4.57"Subcatchment 202: Subcat 202 Tc=6.0 min CN=98 Runoff=1.98 cfs 0.160 af Peak Elev=20.39' Storage=0.010 af Inflow=1.98 cfs 0.160 afPond 203: UIS (SC-310) Discarded=1.05 cfs 0.160 af Secondary=0.00 cfs 0.000 af Outflow=1.05 cfs 0.160 af Runoff Area=0.065 ac 85.47% Impervious Runoff Depth=3.59"Subcatchment 204: Post-204 Tc=6.0 min CN=89 Runoff=0.27 cfs 0.019 af Peak Elev=21.39' Storage=1 cf Inflow=0.27 cfs 0.019 afPond 205: System E (Dumpster) Outflow=0.27 cfs 0.019 af Runoff Area=0.162 ac 78.37% Impervious Runoff Depth=3.19"Subcatchment 206: Post-206 Tc=6.0 min CN=85 Runoff=0.60 cfs 0.043 af Peak Elev=21.79' Storage=3 cf Inflow=0.60 cfs 0.043 afPond 207: System D (Island South) Outflow=0.60 cfs 0.043 af Runoff Area=0.202 ac 76.24% Impervious Runoff Depth=3.10"Subcatchment 208: Post-208 Tc=6.0 min CN=84 Runoff=0.73 cfs 0.052 af Peak Elev=21.85' Storage=4 cf Inflow=0.73 cfs 0.052 afPond 209: System B (West) Outflow=0.73 cfs 0.052 af Runoff Area=0.151 ac 72.09% Impervious Runoff Depth=2.91"Subcatchment 210: Subcat 210 Tc=6.0 min CN=82 Runoff=0.51 cfs 0.037 af Peak Elev=21.83' Storage=3 cf Inflow=0.51 cfs 0.037 afPond 211: System C (Center Island) Outflow=0.51 cfs 0.037 af Runoff Area=0.321 ac 56.69% Impervious Runoff Depth=2.05"Subcatchment 212: Post-212 Tc=6.0 min CN=72 Runoff=0.76 cfs 0.055 af 38 Type III 24-hr 10-Year Rainfall=4.81"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Peak Elev=22.21' Storage=4 cf Inflow=0.76 cfs 0.055 afPond 213: System A (North) Outflow=0.76 cfs 0.055 af Runoff Area=0.009 ac 76.56% Impervious Runoff Depth=3.10"Subcatchment 214: Post-214 Tc=6.0 min CN=84 Runoff=0.03 cfs 0.002 af Peak Elev=17.69' Storage=0 cf Inflow=0.03 cfs 0.002 afPond 215: Leaching CB 15 Discarded=0.03 cfs 0.002 af Primary=0.00 cfs 0.000 af Outflow=0.03 cfs 0.002 af Runoff Area=0.002 ac 96.08% Impervious Runoff Depth=4.34"Subcatchment 216: Post-216 Tc=6.0 min CN=96 Runoff=0.01 cfs 0.001 af Peak Elev=18.40' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 217: Leaching CB 17 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.010 ac 81.35% Impervious Runoff Depth=3.39"Subcatchment 218: Post-218 Tc=6.0 min CN=87 Runoff=0.04 cfs 0.003 af Peak Elev=17.02' Storage=0 cf Inflow=0.04 cfs 0.003 afPond 219: Leaching CB 19 Discarded=0.04 cfs 0.003 af Primary=0.00 cfs 0.000 af Outflow=0.04 cfs 0.003 af Runoff Area=0.008 ac 86.41% Impervious Runoff Depth=3.69"Subcatchment 220: Post-220 Tc=6.0 min CN=90 Runoff=0.04 cfs 0.003 af Peak Elev=17.80' Storage=7 cf Inflow=0.04 cfs 0.003 afPond 221: Leaching CB 21 Discarded=0.02 cfs 0.003 af Primary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.003 af Runoff Area=0.079 ac 57.60% Impervious Runoff Depth=2.13"Subcatchment 222: Subcat 222 Tc=6.0 min CN=73 Runoff=0.19 cfs 0.014 af Peak Elev=19.56' Storage=285 cf Inflow=0.19 cfs 0.014 afPond 223: Sediment Forebay Primary=0.19 cfs 0.014 af Secondary=0.00 cfs 0.000 af Outflow=0.19 cfs 0.014 af Runoff Area=0.024 ac 0.00% Impervious Runoff Depth=0.16"Subcatchment 224: Subcat 224 Tc=6.0 min CN=39 Runoff=0.00 cfs 0.000 af Peak Elev=18.43' Storage=191 cf Inflow=0.19 cfs 0.014 afPond 225: Infiltration Pond Outflow=0.03 cfs 0.014 af Runoff Area=0.024 ac 82.32% Impervious Runoff Depth=3.49"Subcatchment 300: Post-300 Tc=6.0 min CN=88 Runoff=0.10 cfs 0.007 af Runoff Area=0.019 ac 76.11% Impervious Runoff Depth=3.10"Subcatchment 301: Post-301 Tc=6.0 min CN=84 Runoff=0.07 cfs 0.005 af Peak Elev=20.09' Storage=10 cf Inflow=0.07 cfs 0.005 afPond 302: Leaching CB 30 Discarded=0.05 cfs 0.005 af Primary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.005 af 39 Stevens Street Mutli-Family A3.2.4 HydroCAD 25-Year Storm Analysis 40 Type III 24-hr 25-Year Rainfall=6.24"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.991 ac 67.79% Impervious Runoff Depth=3.89"Subcatchment 10: Pre-10 Flow Length=321' Tc=9.2 min CN=79 Runoff=4.05 cfs 0.322 af Runoff Area=0.251 ac 72.52% Impervious Runoff Depth=4.21"Subcatchment 11: Pre-11 Tc=6.0 min CN=82 Runoff=1.23 cfs 0.088 af Peak Elev=20.96' Storage=408 cf Inflow=1.23 cfs 0.088 afPond 12: Leaching Catch Basin 2 Discarded=0.18 cfs 0.065 af Primary=1.28 cfs 0.023 af Outflow=1.46 cfs 0.088 af Inflow=5.20 cfs 0.345 afLink 13: DP-1: Mitchell's Way Primary=5.20 cfs 0.345 af Runoff Area=0.477 ac 58.40% Impervious Runoff Depth=3.29"Subcatchment 20: Pre-20 Flow Length=289' Tc=9.5 min CN=73 Runoff=1.63 cfs 0.131 af Peak Elev=21.12' Storage=515 cf Inflow=1.63 cfs 0.131 afPond 21: Leaching Catch Basin 1 Discarded=0.18 cfs 0.088 af Primary=2.04 cfs 0.043 af Outflow=2.23 cfs 0.131 af Inflow=2.04 cfs 0.043 afLink 22: DP-2: Stevens Street Primary=2.04 cfs 0.043 af Runoff Area=0.036 ac 100.00% Impervious Runoff Depth=6.00"Subcatchment 30: Pre-30 Tc=6.0 min CN=98 Runoff=0.22 cfs 0.018 af 41 Type III 24-hr 25-Year Rainfall=5.99"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.187 ac 28.70% Impervious Runoff Depth=1.59"Subcatchment 100: Post-100 Tc=6.0 min CN=56 Runoff=0.31 cfs 0.025 af Inflow=0.40 cfs 0.031 afLink 101: DP-1: Mitchells Way Primary=0.40 cfs 0.031 af Runoff Area=0.041 ac 36.14% Impervious Runoff Depth=1.92"Subcatchment 102: Subcat 102 Tc=6.0 min CN=60 Runoff=0.09 cfs 0.006 af Runoff Area=0.030 ac 40.84% Impervious Runoff Depth=2.17"Subcatchment 200: Post-200 Tc=6.0 min CN=63 Runoff=0.07 cfs 0.005 af Inflow=0.20 cfs 0.015 afLink 201: DP-2: Stevens Street Primary=0.20 cfs 0.015 af Runoff Area=0.420 ac 100.00% Impervious Runoff Depth=5.75"Subcatchment 202: Subcat 202 Tc=6.0 min CN=98 Runoff=2.47 cfs 0.201 af Peak Elev=20.72' Storage=0.018 af Inflow=2.47 cfs 0.201 afPond 203: UIS (SC-310) Discarded=1.05 cfs 0.201 af Secondary=0.00 cfs 0.000 af Outflow=1.05 cfs 0.201 af Runoff Area=0.065 ac 85.47% Impervious Runoff Depth=4.73"Subcatchment 204: Post-204 Tc=6.0 min CN=89 Runoff=0.35 cfs 0.026 af Peak Elev=21.39' Storage=2 cf Inflow=0.35 cfs 0.026 afPond 205: System E (Dumpster) Outflow=0.35 cfs 0.026 af Runoff Area=0.162 ac 78.37% Impervious Runoff Depth=4.29"Subcatchment 206: Post-206 Tc=6.0 min CN=85 Runoff=0.80 cfs 0.058 af Peak Elev=21.79' Storage=4 cf Inflow=0.80 cfs 0.058 afPond 207: System D (Island South) Outflow=0.80 cfs 0.058 af Runoff Area=0.202 ac 76.24% Impervious Runoff Depth=4.19"Subcatchment 208: Post-208 Tc=6.0 min CN=84 Runoff=0.98 cfs 0.071 af Peak Elev=21.85' Storage=5 cf Inflow=0.98 cfs 0.071 afPond 209: System B (West) Outflow=0.98 cfs 0.071 af Runoff Area=0.151 ac 72.09% Impervious Runoff Depth=3.98"Subcatchment 210: Subcat 210 Tc=6.0 min CN=82 Runoff=0.70 cfs 0.050 af Peak Elev=21.83' Storage=4 cf Inflow=0.70 cfs 0.050 afPond 211: System C (Center Island) Outflow=0.70 cfs 0.050 af Runoff Area=0.321 ac 56.69% Impervious Runoff Depth=2.99"Subcatchment 212: Post-212 Tc=6.0 min CN=72 Runoff=1.12 cfs 0.080 af 42 Type III 24-hr 25-Year Rainfall=5.99"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Peak Elev=22.21' Storage=6 cf Inflow=1.12 cfs 0.080 afPond 213: System A (North) Outflow=1.12 cfs 0.080 af Runoff Area=0.009 ac 76.56% Impervious Runoff Depth=4.19"Subcatchment 214: Post-214 Tc=6.0 min CN=84 Runoff=0.04 cfs 0.003 af Peak Elev=17.71' Storage=1 cf Inflow=0.04 cfs 0.003 afPond 215: Leaching CB 15 Discarded=0.04 cfs 0.003 af Primary=0.00 cfs 0.000 af Outflow=0.04 cfs 0.003 af Runoff Area=0.002 ac 96.08% Impervious Runoff Depth=5.52"Subcatchment 216: Post-216 Tc=6.0 min CN=96 Runoff=0.01 cfs 0.001 af Peak Elev=18.40' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 217: Leaching CB 17 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.010 ac 81.35% Impervious Runoff Depth=4.51"Subcatchment 218: Post-218 Tc=6.0 min CN=87 Runoff=0.05 cfs 0.004 af Peak Elev=17.08' Storage=3 cf Inflow=0.05 cfs 0.004 afPond 219: Leaching CB 19 Discarded=0.04 cfs 0.004 af Primary=0.00 cfs 0.000 af Outflow=0.04 cfs 0.004 af Runoff Area=0.008 ac 86.41% Impervious Runoff Depth=4.84"Subcatchment 220: Post-220 Tc=6.0 min CN=90 Runoff=0.05 cfs 0.003 af Peak Elev=17.95' Storage=12 cf Inflow=0.05 cfs 0.003 afPond 221: Leaching CB 21 Discarded=0.02 cfs 0.003 af Primary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.003 af Runoff Area=0.079 ac 57.60% Impervious Runoff Depth=3.08"Subcatchment 222: Subcat 222 Tc=6.0 min CN=73 Runoff=0.28 cfs 0.020 af Peak Elev=19.57' Storage=290 cf Inflow=0.28 cfs 0.020 afPond 223: Sediment Forebay Primary=0.28 cfs 0.020 af Secondary=0.00 cfs 0.000 af Outflow=0.28 cfs 0.020 af Runoff Area=0.024 ac 0.00% Impervious Runoff Depth=0.44"Subcatchment 224: Subcat 224 Tc=6.0 min CN=39 Runoff=0.00 cfs 0.001 af Peak Elev=18.95' Storage=342 cf Inflow=0.28 cfs 0.021 afPond 225: Infiltration Pond Outflow=0.03 cfs 0.021 af Runoff Area=0.024 ac 82.32% Impervious Runoff Depth=4.62"Subcatchment 300: Post-300 Tc=6.0 min CN=88 Runoff=0.13 cfs 0.009 af Runoff Area=0.019 ac 76.11% Impervious Runoff Depth=4.19"Subcatchment 301: Post-301 Tc=6.0 min CN=84 Runoff=0.09 cfs 0.007 af Peak Elev=20.37' Storage=21 cf Inflow=0.09 cfs 0.007 afPond 302: Leaching CB 30 Discarded=0.06 cfs 0.007 af Primary=0.00 cfs 0.000 af Outflow=0.06 cfs 0.007 af 43 Stevens Street Mutli-Family A3.2.5 HydroCAD 100-Year Storm Analysis 44 Type III 24-hr 100-Year Rainfall=8.76"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.991 ac 67.79% Impervious Runoff Depth=6.22"Subcatchment 10: Pre-10 Flow Length=321' Tc=9.2 min CN=79 Runoff=6.38 cfs 0.514 af Runoff Area=0.251 ac 72.52% Impervious Runoff Depth=6.58"Subcatchment 11: Pre-11 Tc=6.0 min CN=82 Runoff=1.88 cfs 0.138 af Peak Elev=21.04' Storage=408 cf Inflow=1.88 cfs 0.138 afPond 12: Leaching Catch Basin 2 Discarded=0.18 cfs 0.090 af Primary=1.91 cfs 0.047 af Outflow=2.10 cfs 0.138 af Inflow=8.12 cfs 0.561 afLink 13: DP-1: Mitchell's Way Primary=8.12 cfs 0.561 af Runoff Area=0.477 ac 58.40% Impervious Runoff Depth=5.49"Subcatchment 20: Pre-20 Flow Length=289' Tc=9.5 min CN=73 Runoff=2.72 cfs 0.218 af Peak Elev=21.17' Storage=515 cf Inflow=2.72 cfs 0.218 afPond 21: Leaching Catch Basin 1 Discarded=0.18 cfs 0.125 af Primary=2.71 cfs 0.094 af Outflow=2.89 cfs 0.218 af Inflow=2.71 cfs 0.094 afLink 22: DP-2: Stevens Street Primary=2.71 cfs 0.094 af Runoff Area=0.036 ac 100.00% Impervious Runoff Depth=8.52"Subcatchment 30: Pre-30 Tc=6.0 min CN=98 Runoff=0.31 cfs 0.025 af 45 Type III 24-hr 100-Year Rainfall=8.76"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 10: Pre-10 Runoff =6.38 cfs @ 12.13 hrs, Volume=0.514 af, Depth= 6.22" Routed to Link 13 : DP-1: Mitchell's Way Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.76" Area (ac) CN Description 0.272 39 >75% Grass cover, Good, HSG A 0.480 98 Impervious, HSG A 0.015 98 Offsite Impervious, HSG A 0.177 98 Roofs, HSG A 0.047 30 Woods, Good, HSG A 0.991 79 Weighted Average 0.319 38 32.21% Pervious Area 0.672 98 67.79% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 7.9 91 0.0670 0.19 Sheet Flow, A Grass: Dense n= 0.240 P2= 3.40" 0.3 46 0.0240 2.49 Shallow Concentrated Flow, B Unpaved Kv= 16.1 fps 1.0 184 0.0240 3.14 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 9.2 321 Total Summary for Subcatchment 11: Pre-11 Runoff =1.88 cfs @ 12.09 hrs, Volume=0.138 af, Depth= 6.58" Routed to Pond 12 : Leaching Catch Basin 2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.76" Area (ac) CN Description 0.069 39 >75% Grass cover, Good, HSG A 0.156 98 Impervious, HSG A 0.026 98 Offsite Impervious, HSG A 0.251 82 Weighted Average 0.069 39 27.48% Pervious Area 0.182 98 72.52% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 46 Type III 24-hr 100-Year Rainfall=8.76"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Pond 12: Leaching Catch Basin 2 Inflow Area =0.251 ac, 72.52% Impervious, Inflow Depth = 6.58" for 100-Year event Inflow =1.88 cfs @ 12.09 hrs, Volume=0.138 af Outflow =2.10 cfs @ 12.08 hrs, Volume=0.138 af, Atten= 0%, Lag= 0.0 min Discarded =0.18 cfs @ 11.64 hrs, Volume=0.090 af Primary =1.91 cfs @ 12.08 hrs, Volume=0.047 af Routed to Link 13 : DP-1: Mitchell's Way Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 21.04' @ 12.08 hrs Surf.Area= 38 sf Storage= 408 cf Plug-Flow detention time= 5.8 min calculated for 0.138 af (100% of inflow) Center-of-Mass det. time= 5.8 min ( 800.7 - 794.9 ) Volume Invert Avail.Storage Storage Description #1 14.00'50 cf 4.00'D x 4.00'H Leaching CB Inside #3 79 cf Overall - 6.0" Wall Thickness = 50 cf #2 18.00'33 cf 4.00'D x 2.60'H Vertical Cone/Cylinder -Impervious #3 14.00'30 cf 7.00'D x 4.00'H Stone Around Leaching CB 154 cf Overall - 79 cf Embedded = 75 cf x 40.0% Voids #4 20.60'295 cf Pavement Ponding Area (Conic) Listed below (Recalc) -Impervious 408 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(cubic-feet)(cubic-feet)(sq-ft) 20.60 4 0 0 4 20.70 356 13 13 356 20.80 6,555 281 295 6,555 Device Routing Invert Outlet Devices #1 Discarded 14.00'63.000 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.70'4.0' 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=0.18 cfs @ 11.64 hrs HW=18.20' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.18 cfs) Primary OutFlow Max=1.91 cfs @ 12.08 hrs HW=21.04' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir (Weir Controls 1.91 cfs @ 1.42 fps) Summary for Link 13: DP-1: Mitchell's Way Inflow Area =1.242 ac, 68.75% Impervious, Inflow Depth = 5.42" for 100-Year event Inflow =8.12 cfs @ 12.12 hrs, Volume=0.561 af Primary =8.12 cfs @ 12.12 hrs, Volume=0.561 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs 47 Type III 24-hr 100-Year Rainfall=8.76"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 20: Pre-20 Runoff =2.72 cfs @ 12.13 hrs, Volume=0.218 af, Depth= 5.49" Routed to Pond 21 : Leaching Catch Basin 1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.76" Area (ac) CN Description 0.198 39 >75% Grass cover, Good, HSG A 0.248 98 Impervious, HSG A 0.005 98 Offsite Impervious, HSG A 0.025 98 Roofs, HSG A 0.477 73 Weighted Average 0.198 39 41.60% Pervious Area 0.279 98 58.40% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 8.1 105 0.0840 0.22 Sheet Flow, A Grass: Dense n= 0.240 P2= 3.40" 1.4 184 0.0124 2.26 Shallow Concentrated Flow, B Paved Kv= 20.3 fps 9.5 289 Total Summary for Pond 21: Leaching Catch Basin 1 Inflow Area =0.477 ac, 58.40% Impervious, Inflow Depth = 5.49" for 100-Year event Inflow =2.72 cfs @ 12.13 hrs, Volume=0.218 af Outflow =2.89 cfs @ 12.14 hrs, Volume=0.218 af, Atten= 0%, Lag= 0.5 min Discarded =0.18 cfs @ 11.45 hrs, Volume=0.125 af Primary =2.71 cfs @ 12.14 hrs, Volume=0.094 af Routed to Link 22 : DP-2: Stevens Street Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 21.17' @ 12.14 hrs Surf.Area= 38 sf Storage= 515 cf Plug-Flow detention time= 8.5 min calculated for 0.218 af (100% of inflow) Center-of-Mass det. time= 8.5 min ( 826.5 - 817.9 ) Volume Invert Avail.Storage Storage Description #1 14.00'50 cf 4.00'D x 4.00'H Leaching CB Inside #3 79 cf Overall - 6.0" Wall Thickness = 50 cf #2 18.00'33 cf 4.00'D x 2.60'H Top Vert Cone -Impervious #3 14.00'30 cf 7.00'D x 4.00'H Stone around Leaching CB 154 cf Overall - 79 cf Embedded = 75 cf x 40.0% Voids #4 20.60'401 cf Pavement Ponding Area (Conic) Listed below (Recalc) -Impervious 515 cf Total Available Storage 48 Type III 24-hr 100-Year Rainfall=8.76"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(cubic-feet)(cubic-feet)(sq-ft) 20.60 4 0 0 4 20.70 72 3 3 72 20.80 593 29 32 593 20.90 1,797 114 146 1,797 21.00 3,391 255 401 3,391 Device Routing Invert Outlet Devices #1 Discarded 14.00'63.000 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.90'8.2' 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=0.18 cfs @ 11.45 hrs HW=18.07' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.18 cfs) Primary OutFlow Max=2.70 cfs @ 12.14 hrs HW=21.17' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir (Weir Controls 2.70 cfs @ 1.23 fps) Summary for Link 22: DP-2: Stevens Street Inflow Area =0.477 ac, 58.40% Impervious, Inflow Depth = 2.36" for 100-Year event Inflow =2.71 cfs @ 12.14 hrs, Volume=0.094 af Primary =2.71 cfs @ 12.14 hrs, Volume=0.094 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Summary for Subcatchment 30: Pre-30 Runoff =0.31 cfs @ 12.08 hrs, Volume=0.025 af, Depth= 8.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.76" Area (ac) CN Description 0.036 98 Impervious, HSG A 0.036 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 49 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.187 ac 28.70% Impervious Runoff Depth=3.14"Subcatchment 100: Post-100 Tc=6.0 min CN=56 Runoff=0.67 cfs 0.049 af Inflow=0.84 cfs 0.061 afLink 101: DP-1: Mitchells Way Primary=0.84 cfs 0.061 af Runoff Area=0.041 ac 36.14% Impervious Runoff Depth=3.60"Subcatchment 102: Subcat 102 Tc=6.0 min CN=60 Runoff=0.17 cfs 0.012 af Runoff Area=0.030 ac 40.84% Impervious Runoff Depth=3.95"Subcatchment 200: Post-200 Tc=6.0 min CN=63 Runoff=0.14 cfs 0.010 af Inflow=0.32 cfs 0.024 afLink 201: DP-2: Stevens Street Primary=0.32 cfs 0.024 af Runoff Area=0.420 ac 100.00% Impervious Runoff Depth=8.11"Subcatchment 202: Subcat 202 Tc=6.0 min CN=98 Runoff=3.45 cfs 0.284 af Peak Elev=22.03' Storage=0.041 af Inflow=3.45 cfs 0.284 afPond 203: UIS (SC-310) Discarded=1.05 cfs 0.284 af Secondary=0.00 cfs 0.000 af Outflow=1.05 cfs 0.284 af Runoff Area=0.065 ac 85.47% Impervious Runoff Depth=7.03"Subcatchment 204: Post-204 Tc=6.0 min CN=89 Runoff=0.50 cfs 0.038 af Peak Elev=21.53' Storage=31 cf Inflow=0.50 cfs 0.038 afPond 205: System E (Dumpster) Outflow=0.39 cfs 0.038 af Runoff Area=0.162 ac 78.37% Impervious Runoff Depth=6.55"Subcatchment 206: Post-206 Tc=6.0 min CN=85 Runoff=1.20 cfs 0.089 af Peak Elev=22.08' Storage=134 cf Inflow=1.20 cfs 0.089 afPond 207: System D (Island South) Outflow=0.82 cfs 0.089 af Runoff Area=0.202 ac 76.24% Impervious Runoff Depth=6.43"Subcatchment 208: Post-208 Tc=6.0 min CN=84 Runoff=1.47 cfs 0.108 af Peak Elev=22.09' Storage=142 cf Inflow=1.47 cfs 0.108 afPond 209: System B (West) Outflow=1.05 cfs 0.108 af Runoff Area=0.151 ac 72.09% Impervious Runoff Depth=6.19"Subcatchment 210: Subcat 210 Tc=6.0 min CN=82 Runoff=1.07 cfs 0.078 af Peak Elev=22.12' Storage=120 cf Inflow=1.07 cfs 0.078 afPond 211: System C (Center Island) Outflow=0.73 cfs 0.078 af Runoff Area=0.321 ac 56.69% Impervious Runoff Depth=5.00"Subcatchment 212: Post-212 Tc=6.0 min CN=72 Runoff=1.88 cfs 0.134 af 50 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Peak Elev=22.55' Storage=237 cf Inflow=1.88 cfs 0.134 afPond 213: System A (North) Outflow=1.24 cfs 0.134 af Runoff Area=0.009 ac 76.56% Impervious Runoff Depth=6.43"Subcatchment 214: Post-214 Tc=6.0 min CN=84 Runoff=0.07 cfs 0.005 af Peak Elev=17.90' Storage=9 cf Inflow=0.07 cfs 0.005 afPond 215: Leaching CB 15 Discarded=0.05 cfs 0.005 af Primary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.005 af Runoff Area=0.002 ac 96.08% Impervious Runoff Depth=7.87"Subcatchment 216: Post-216 Tc=6.0 min CN=96 Runoff=0.01 cfs 0.001 af Peak Elev=18.40' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 217: Leaching CB 17 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.010 ac 81.35% Impervious Runoff Depth=6.79"Subcatchment 218: Post-218 Tc=6.0 min CN=87 Runoff=0.07 cfs 0.005 af Peak Elev=17.32' Storage=12 cf Inflow=0.07 cfs 0.005 afPond 219: Leaching CB 19 Discarded=0.05 cfs 0.005 af Primary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.005 af Runoff Area=0.008 ac 86.41% Impervious Runoff Depth=7.15"Subcatchment 220: Post-220 Tc=6.0 min CN=90 Runoff=0.07 cfs 0.005 af Peak Elev=18.28' Storage=25 cf Inflow=0.07 cfs 0.005 afPond 221: Leaching CB 21 Discarded=0.03 cfs 0.005 af Primary=0.00 cfs 0.000 af Outflow=0.03 cfs 0.005 af Runoff Area=0.079 ac 57.60% Impervious Runoff Depth=5.12"Subcatchment 222: Subcat 222 Tc=6.0 min CN=73 Runoff=0.47 cfs 0.034 af Peak Elev=19.76' Storage=347 cf Inflow=0.47 cfs 0.034 afPond 223: Sediment Forebay Primary=0.47 cfs 0.034 af Secondary=0.00 cfs 0.000 af Outflow=0.47 cfs 0.034 af Runoff Area=0.024 ac 0.00% Impervious Runoff Depth=1.31"Subcatchment 224: Subcat 224 Tc=6.0 min CN=39 Runoff=0.03 cfs 0.003 af Peak Elev=19.76' Storage=674 cf Inflow=0.49 cfs 0.036 afPond 225: Infiltration Pond Outflow=0.03 cfs 0.036 af Runoff Area=0.024 ac 82.32% Impervious Runoff Depth=6.91"Subcatchment 300: Post-300 Tc=6.0 min CN=88 Runoff=0.18 cfs 0.014 af Runoff Area=0.019 ac 76.11% Impervious Runoff Depth=6.43"Subcatchment 301: Post-301 Tc=6.0 min CN=84 Runoff=0.14 cfs 0.010 af Peak Elev=21.02' Storage=46 cf Inflow=0.14 cfs 0.010 afPond 302: Leaching CB 30 Discarded=0.08 cfs 0.010 af Primary=0.00 cfs 0.000 af Outflow=0.08 cfs 0.010 af 51 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 100: Post-100 Runoff =0.67 cfs @ 12.09 hrs, Volume=0.049 af, Depth= 3.14" Routed to Link 101 : DP-1: Mitchells Way Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.133 39 >75% Grass cover, Good, HSG A 0.035 98 Impervious, HSG A 0.018 98 Offsite Impervious, HSG A 0.187 56 Weighted Average 0.133 39 71.30% Pervious Area 0.054 98 28.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Link 101: DP-1: Mitchells Way Inflow Area =0.256 ac, 35.91% Impervious, Inflow Depth = 2.86" for 100-Year event Inflow =0.84 cfs @ 12.09 hrs, Volume=0.061 af Primary =0.84 cfs @ 12.09 hrs, Volume=0.061 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Summary for Subcatchment 102: Subcat 102 Runoff =0.17 cfs @ 12.09 hrs, Volume=0.012 af, Depth= 3.60" Routed to Link 101 : DP-1: Mitchells Way Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.025 39 >75% Grass cover, Good, HSG A 0.015 98 Offsite Impervious, HSG A 0.000 30 Woods, Good, HSG A 0.041 60 Weighted Average 0.026 39 63.86% Pervious Area 0.015 98 36.14% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 52 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Subcatchment 200: Post-200 Runoff =0.14 cfs @ 12.09 hrs, Volume=0.010 af, Depth= 3.95" Routed to Link 201 : DP-2: Stevens Street Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.018 39 >75% Grass cover, Good, HSG A 0.008 98 Impervious, HSG A 0.005 98 Offsite Impervious, HSG A 0.030 63 Weighted Average 0.018 39 59.16% Pervious Area 0.012 98 40.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Link 201: DP-2: Stevens Street Inflow Area =0.074 ac, 63.73% Impervious, Inflow Depth = 3.87" for 100-Year event Inflow =0.32 cfs @ 12.09 hrs, Volume=0.024 af Primary =0.32 cfs @ 12.09 hrs, Volume=0.024 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Summary for Subcatchment 202: Subcat 202 Runoff =3.45 cfs @ 12.08 hrs, Volume=0.284 af, Depth= 8.11" Routed to Pond 203 : UIS (SC-310) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.420 98 Roofs, HSG A 0.420 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 53 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Pond 203: UIS (SC-310) Inflow Area =0.420 ac,100.00% Impervious, Inflow Depth = 8.11" for 100-Year event Inflow =3.45 cfs @ 12.08 hrs, Volume=0.284 af Outflow =1.05 cfs @ 11.84 hrs, Volume=0.284 af, Atten= 69%, Lag= 0.0 min Discarded =1.05 cfs @ 11.84 hrs, Volume=0.284 af Secondary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Pond 302 : Leaching CB 30 Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 22.03' @ 12.39 hrs Surf.Area= 0.033 ac Storage= 0.041 af Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 6.7 min ( 747.4 - 740.7 ) Volume Invert Avail.Storage Storage Description #1A 19.77'0.024 af 21.50'W x 67.28'L x 2.33'H Field A 0.077 af Overall - 0.018 af Embedded = 0.059 af x 40.0% Voids #2A 20.27'0.018 af ADS_StormTech SC-310 +Cap x 54 Inside #1 Effective Size= 28.9"W x 16.0"H => 2.07 sf x 7.12'L = 14.7 cf Overall Size= 34.0"W x 16.0"H x 7.56'L with 0.44' Overlap 54 Chambers in 6 Rows 0.042 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Discarded 19.77'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' #2 Secondary 22.10'4.0' 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=1.05 cfs @ 11.84 hrs HW=19.80' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.05 cfs) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=19.77' TW=19.82' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Subcatchment 204: Post-204 Runoff =0.50 cfs @ 12.08 hrs, Volume=0.038 af, Depth= 7.03" Routed to Pond 205 : System E (Dumpster) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" 54 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Area (ac) CN Description 0.009 39 >75% Grass cover, Good, HSG A 0.055 98 Impervious, HSG A 0.065 89 Weighted Average 0.009 39 14.53% Pervious Area 0.055 98 85.47% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 205: System E (Dumpster) Inflow Area =0.065 ac, 85.47% Impervious, Inflow Depth = 7.03" for 100-Year event Inflow =0.50 cfs @ 12.08 hrs, Volume=0.038 af Outflow =0.39 cfs @ 12.04 hrs, Volume=0.038 af, Atten= 22%, Lag= 0.0 min Discarded =0.39 cfs @ 12.04 hrs, Volume=0.038 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 21.53' @ 12.15 hrs Surf.Area= 540 sf Storage= 31 cf Plug-Flow detention time= 0.2 min calculated for 0.038 af (100% of inflow) Center-of-Mass det. time= 0.2 min ( 778.0 - 777.8 ) Volume Invert Avail.Storage Storage Description #1 22.22'54 cf 6" Stormcrete Slab (Prismatic) Listed below (Recalc) -Impervious 270 cf Overall x 20.0% Voids #2 22.05'37 cf 2" Leveling Course (No. 8 Stone) (Prismatic) Listed below (Recalc) -Impervious 92 cf Overall x 40.0% Voids #3 21.38'145 cf 8"Reservoir (No. 57 Stone) (Prismatic) Listed below (Recalc) 362 cf Overall x 40.0% Voids 235 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.22 540 0 0 22.72 540 270 270 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.05 540 0 0 22.22 540 92 92 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 21.38 540 0 0 22.05 540 362 362 Device Routing Invert Outlet Devices #1 Discarded 21.38'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' 55 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.39 cfs @ 12.04 hrs HW=21.39' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.39 cfs) Summary for Subcatchment 206: Post-206 Runoff =1.20 cfs @ 12.08 hrs, Volume=0.089 af, Depth= 6.55" Routed to Pond 207 : System D (Island South) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.035 39 >75% Grass cover, Good, HSG A 0.127 98 Impervious, HSG A 0.162 85 Weighted Average 0.035 39 21.63% Pervious Area 0.127 98 78.37% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 207: System D (Island South) Inflow Area =0.162 ac, 78.37% Impervious, Inflow Depth = 6.55" for 100-Year event Inflow =1.20 cfs @ 12.08 hrs, Volume=0.089 af Outflow =0.82 cfs @ 12.03 hrs, Volume=0.089 af, Atten= 32%, Lag= 0.0 min Discarded =0.82 cfs @ 12.03 hrs, Volume=0.089 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 22.08' @ 12.17 hrs Surf.Area= 1,120 sf Storage= 134 cf Plug-Flow detention time= 0.5 min calculated for 0.089 af (100% of inflow) Center-of-Mass det. time= 0.5 min ( 789.5 - 789.0 ) Volume Invert Avail.Storage Storage Description #1 22.62'112 cf 6" Stormcrete Slab (Prismatic) Listed below (Recalc) -Impervious 560 cf Overall x 20.0% Voids #2 22.45'76 cf 2" Leveling Course (No. 8 Stone) (Prismatic) Listed below (Recalc) -Impervious 190 cf Overall x 40.0% Voids #3 21.78'300 cf 8"Reservoir (No. 57 Stone) (Prismatic) Listed below (Recalc) 750 cf Overall x 40.0% Voids 488 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.62 1,120 0 0 23.12 1,120 560 560 56 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.45 1,120 0 0 22.62 1,120 190 190 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 21.78 1,120 0 0 22.45 1,120 750 750 Device Routing Invert Outlet Devices #1 Discarded 21.78'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' Discarded OutFlow Max=0.82 cfs @ 12.03 hrs HW=21.80' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.82 cfs) Summary for Subcatchment 208: Post-208 Runoff =1.47 cfs @ 12.09 hrs, Volume=0.108 af, Depth= 6.43" Routed to Pond 209 : System B (West) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.048 39 >75% Grass cover, Good, HSG A 0.154 98 Impervious, HSG A 0.202 84 Weighted Average 0.048 39 23.76% Pervious Area 0.154 98 76.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 209: System B (West) Inflow Area =0.202 ac, 76.24% Impervious, Inflow Depth = 6.43" for 100-Year event Inflow =1.47 cfs @ 12.09 hrs, Volume=0.108 af Outflow =1.05 cfs @ 12.04 hrs, Volume=0.108 af, Atten= 29%, Lag= 0.0 min Discarded =1.05 cfs @ 12.04 hrs, Volume=0.108 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 22.09' @ 12.16 hrs Surf.Area= 1,440 sf Storage= 142 cf Plug-Flow detention time= 0.4 min calculated for 0.108 af (100% of inflow) Center-of-Mass det. time= 0.4 min ( 792.0 - 791.6 ) 57 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 23.01'144 cf 6" Stormcrete Slab (Prismatic) Listed below (Recalc) -Impervious 720 cf Overall x 20.0% Voids #2 22.84'98 cf 2" Leveling Course (No. 8 Stone) (Prismatic) Listed below (Recalc) -Impervious 245 cf Overall x 40.0% Voids #3 21.84'576 cf 12"Reservoir (No. 57 Stone) (Prismatic) Listed below (Recalc) 1,440 cf Overall x 40.0% Voids 818 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 23.01 1,440 0 0 23.51 1,440 720 720 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.84 1,440 0 0 23.01 1,440 245 245 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 21.84 1,440 0 0 22.84 1,440 1,440 1,440 Device Routing Invert Outlet Devices #1 Discarded 21.84'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' Discarded OutFlow Max=1.05 cfs @ 12.04 hrs HW=21.86' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.05 cfs) Summary for Subcatchment 210: Subcat 210 Runoff =1.07 cfs @ 12.09 hrs, Volume=0.078 af, Depth= 6.19" Routed to Pond 211 : System C (Center Island) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.042 39 >75% Grass cover, Good, HSG A 0.109 98 Impervious, HSG A 0.151 82 Weighted Average 0.042 39 27.91% Pervious Area 0.109 98 72.09% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 58 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Pond 211: System C (Center Island) Inflow Area =0.151 ac, 72.09% Impervious, Inflow Depth = 6.19" for 100-Year event Inflow =1.07 cfs @ 12.09 hrs, Volume=0.078 af Outflow =0.73 cfs @ 12.03 hrs, Volume=0.078 af, Atten= 32%, Lag= 0.0 min Discarded =0.73 cfs @ 12.03 hrs, Volume=0.078 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 22.12' @ 12.17 hrs Surf.Area= 1,000 sf Storage= 120 cf Plug-Flow detention time= 0.5 min calculated for 0.078 af (100% of inflow) Center-of-Mass det. time= 0.5 min ( 797.0 - 796.6 ) Volume Invert Avail.Storage Storage Description #1 22.66'100 cf 6" Stormcrete Slab (Prismatic) Listed below (Recalc) -Impervious 500 cf Overall x 20.0% Voids #2 22.49'68 cf 2" Leveling Course (No. 8 Stone) (Prismatic) Listed below (Recalc) -Impervious 170 cf Overall x 40.0% Voids #3 21.82'268 cf 8"Reservoir (No. 57 Stone) (Prismatic) Listed below (Recalc) 670 cf Overall x 40.0% Voids 436 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.66 1,000 0 0 23.16 1,000 500 500 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.49 1,000 0 0 22.66 1,000 170 170 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 21.82 1,000 0 0 22.49 1,000 670 670 Device Routing Invert Outlet Devices #1 Discarded 21.82'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' Discarded OutFlow Max=0.73 cfs @ 12.03 hrs HW=21.84' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.73 cfs) Summary for Subcatchment 212: Post-212 Runoff =1.88 cfs @ 12.09 hrs, Volume=0.134 af, Depth= 5.00" Routed to Pond 213 : System A (North) Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" 59 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Area (ac) CN Description 0.139 39 >75% Grass cover, Good, HSG A 0.182 98 Impervious, HSG A 0.321 72 Weighted Average 0.139 39 43.31% Pervious Area 0.182 98 56.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 213: System A (North) Inflow Area =0.321 ac, 56.69% Impervious, Inflow Depth = 5.00" for 100-Year event Inflow =1.88 cfs @ 12.09 hrs, Volume=0.134 af Outflow =1.24 cfs @ 12.03 hrs, Volume=0.134 af, Atten= 34%, Lag= 0.0 min Discarded =1.24 cfs @ 12.03 hrs, Volume=0.134 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 22.55' @ 12.18 hrs Surf.Area= 1,700 sf Storage= 237 cf Plug-Flow detention time= 0.6 min calculated for 0.134 af (100% of inflow) Center-of-Mass det. time= 0.6 min ( 819.3 - 818.8 ) Volume Invert Avail.Storage Storage Description #1 23.04'170 cf 6" Stormcrete Slab (Prismatic) Listed below (Recalc) -Impervious 850 cf Overall x 20.0% Voids #2 22.87'116 cf 2" Leveling Course (No. 8 Stone) (Prismatic) Listed below (Recalc) -Impervious 289 cf Overall x 40.0% Voids #3 22.20'456 cf 8" Reservoir (No. 57 Stone) (Prismatic) Listed below (Recalc) 1,139 cf Overall x 40.0% Voids 741 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 23.04 1,700 0 0 23.54 1,700 850 850 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.87 1,700 0 0 23.04 1,700 289 289 Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 22.20 1,700 0 0 22.87 1,700 1,139 1,139 Device Routing Invert Outlet Devices #1 Discarded 22.20'31.500 in/hr Exfiltration over Surface area Phase-In= 0.01' 60 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Discarded OutFlow Max=1.24 cfs @ 12.03 hrs HW=22.22' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.24 cfs) Summary for Subcatchment 214: Post-214 Runoff =0.07 cfs @ 12.09 hrs, Volume=0.005 af, Depth= 6.43" Routed to Pond 215 : Leaching CB 15 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.002 39 >75% Grass cover, Good, HSG A 0.007 98 Impervious, HSG A 0.009 84 Weighted Average 0.002 39 23.44% Pervious Area 0.007 98 76.56% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 215: Leaching CB 15 Inflow Area =0.009 ac, 76.56% Impervious, Inflow Depth = 6.43" for 100-Year event Inflow =0.07 cfs @ 12.09 hrs, Volume=0.005 af Outflow =0.05 cfs @ 12.16 hrs, Volume=0.005 af, Atten= 29%, Lag= 4.7 min Discarded =0.05 cfs @ 12.16 hrs, Volume=0.005 af Primary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 101 : DP-1: Mitchells Way Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.90' @ 12.16 hrs Surf.Area= 53 sf Storage= 9 cf Plug-Flow detention time= 0.6 min calculated for 0.005 af (100% of inflow) Center-of-Mass det. time= 0.6 min ( 792.2 - 791.6 ) Volume Invert Avail.Storage Storage Description #1 17.68'71 cf 6.00'D x 2.50'H Leaching CB #2 17.68'25 cf Stone Around Leaching CB (Irregular) Listed below (Recalc) 63 cf Overall x 40.0% Voids 96 cf Total Available Storage Elevation Surf.Area Perim.Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft) 17.68 25 28.3 0 0 25 20.18 25 28.3 63 63 96 61 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Discarded 17.68'31.500 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.48'4.50" x 4.00" Horiz. Orifice/Grate X 4.00 columns X 4 rows C= 0.600 in 24.00" x 24.00" Grate (50% open area) Limited to weir flow at low heads Discarded OutFlow Max=0.05 cfs @ 12.16 hrs HW=17.90' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=17.68' TW=0.00' (Dynamic Tailwater) 2=Orifice/Grate ( Controls 0.00 cfs) Summary for Subcatchment 216: Post-216 Runoff =0.01 cfs @ 12.08 hrs, Volume=0.001 af, Depth= 7.87" Routed to Pond 217 : Leaching CB 17 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.000 39 >75% Grass cover, Good, HSG A 0.002 98 Impervious, HSG A 0.002 96 Weighted Average 0.000 39 3.92% Pervious Area 0.002 98 96.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 217: Leaching CB 17 Inflow Area =0.002 ac, 96.08% Impervious, Inflow Depth = 7.87" for 100-Year event Inflow =0.01 cfs @ 12.08 hrs, Volume=0.001 af Outflow =0.01 cfs @ 12.09 hrs, Volume=0.001 af, Atten= 0%, Lag= 0.2 min Discarded =0.01 cfs @ 12.09 hrs, Volume=0.001 af Primary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 101 : DP-1: Mitchells Way Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 18.40' @ 12.09 hrs Surf.Area= 53 sf Storage= 0 cf Plug-Flow detention time= 0.2 min calculated for 0.001 af (100% of inflow) Center-of-Mass det. time= 0.2 min ( 751.7 - 751.5 ) 62 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 18.40'71 cf 6.00'D x 2.50'H Leaching CB #2 18.40'25 cf Stone around Leaching CB (Irregular) Listed below (Recalc) 63 cf Overall x 40.0% Voids 96 cf Total Available Storage Elevation Surf.Area Perim.Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft) 18.40 25 28.3 0 0 25 20.90 25 28.3 63 63 96 Device Routing Invert Outlet Devices #1 Discarded 18.40'31.500 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.59'4.50" x 4.00" Horiz. Orifice/Grate X 4.00 columns X 4 rows C= 0.600 in 24.00" x 24.00" Grate (50% open area) Limited to weir flow at low heads Discarded OutFlow Max=0.01 cfs @ 12.09 hrs HW=18.40' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=18.40' TW=0.00' (Dynamic Tailwater) 2=Orifice/Grate ( Controls 0.00 cfs) Summary for Subcatchment 218: Post-218 Runoff =0.07 cfs @ 12.08 hrs, Volume=0.005 af, Depth= 6.79" Routed to Pond 219 : Leaching CB 19 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.002 39 >75% Grass cover, Good, HSG A 0.008 98 Impervious, HSG A 0.010 87 Weighted Average 0.002 39 18.65% Pervious Area 0.008 98 81.35% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 219: Leaching CB 19 Inflow Area =0.010 ac, 81.35% Impervious, Inflow Depth = 6.79" for 100-Year event Inflow =0.07 cfs @ 12.08 hrs, Volume=0.005 af Outflow =0.05 cfs @ 12.17 hrs, Volume=0.005 af, Atten= 33%, Lag= 5.1 min Discarded =0.05 cfs @ 12.17 hrs, Volume=0.005 af Primary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 101 : DP-1: Mitchells Way 63 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 17.32' @ 12.17 hrs Surf.Area= 53 sf Storage= 12 cf Plug-Flow detention time= 0.8 min calculated for 0.005 af (100% of inflow) Center-of-Mass det. time= 0.8 min ( 784.4 - 783.6 ) Volume Invert Avail.Storage Storage Description #1 17.01'71 cf 6.00'D x 2.50'H Leaching CB #2 17.01'25 cf Stone around Leaching CB (Irregular) Listed below (Recalc) 63 cf Overall x 40.0% Voids 96 cf Total Available Storage Elevation Surf.Area Perim.Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft) 17.01 25 28.3 0 0 25 19.51 25 28.3 63 63 96 Device Routing Invert Outlet Devices #1 Discarded 17.01'31.500 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.00'4.50" x 4.00" Horiz. Orifice/Grate X 4.00 columns X 4 rows C= 0.600 in 24.00" x 24.00" Grate (50% open area) Limited to weir flow at low heads Discarded OutFlow Max=0.05 cfs @ 12.17 hrs HW=17.32' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=17.01' TW=0.00' (Dynamic Tailwater) 2=Orifice/Grate ( Controls 0.00 cfs) Summary for Subcatchment 220: Post-220 Runoff =0.07 cfs @ 12.08 hrs, Volume=0.005 af, Depth= 7.15" Routed to Pond 221 : Leaching CB 21 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.001 39 >75% Grass cover, Good, HSG A 0.007 98 Impervious, HSG A 0.008 90 Weighted Average 0.001 39 13.59% Pervious Area 0.007 98 86.41% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, 64 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Summary for Pond 221: Leaching CB 21 Inflow Area =0.008 ac, 86.41% Impervious, Inflow Depth = 7.15" for 100-Year event Inflow =0.07 cfs @ 12.08 hrs, Volume=0.005 af Outflow =0.03 cfs @ 12.24 hrs, Volume=0.005 af, Atten= 52%, Lag= 9.1 min Discarded =0.03 cfs @ 12.24 hrs, Volume=0.005 af Primary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 101 : DP-1: Mitchells Way Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 18.28' @ 12.24 hrs Surf.Area= 25 sf Storage= 25 cf Plug-Flow detention time= 3.9 min calculated for 0.005 af (100% of inflow) Center-of-Mass det. time= 3.9 min ( 778.5 - 774.7 ) Volume Invert Avail.Storage Storage Description #1 17.63'71 cf 6.00'D x 2.50'H Leaching CB -Impervious #2 17.63'25 cf Stone Around LCB (Irregular) Listed below (Recalc) 63 cf Overall x 40.0% Voids 96 cf Total Available Storage Elevation Surf.Area Perim.Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft) 17.63 25 28.3 0 0 25 20.13 25 28.3 63 63 96 Device Routing Invert Outlet Devices #1 Discarded 17.63'31.500 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 20.10'4.50" x 4.00" Horiz. Orifice/Grate X 4.00 columns X 4 rows C= 0.600 in 24.00" x 24.00" Grate (50% open area) Limited to weir flow at low heads Discarded OutFlow Max=0.03 cfs @ 12.24 hrs HW=18.28' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=17.63' TW=0.00' (Dynamic Tailwater) 2=Orifice/Grate ( Controls 0.00 cfs) Summary for Subcatchment 222: Subcat 222 Runoff =0.47 cfs @ 12.09 hrs, Volume=0.034 af, Depth= 5.12" Routed to Pond 223 : Sediment Forebay Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" 65 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Area (ac) CN Description 0.033 39 >75% Grass cover, Good, HSG A 0.045 98 Impervious, HSG A 0.079 73 Weighted Average 0.033 39 42.40% Pervious Area 0.045 98 57.60% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 223: Sediment Forebay Inflow Area =0.079 ac, 57.60% Impervious, Inflow Depth = 5.12" for 100-Year event Inflow =0.47 cfs @ 12.09 hrs, Volume=0.034 af Outflow =0.47 cfs @ 12.10 hrs, Volume=0.034 af, Atten= 1%, Lag= 0.7 min Primary =0.47 cfs @ 12.10 hrs, Volume=0.034 af Routed to Pond 225 : Infiltration Pond Secondary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 101 : DP-1: Mitchells Way Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Starting Elev= 19.50' Surf.Area= 266 sf Storage= 270 cf Peak Elev= 19.76' @ 14.79 hrs Surf.Area= 320 sf Storage= 347 cf (77 cf above start) Plug-Flow detention time= 128.2 min calculated for 0.027 af (82% of inflow) Center-of-Mass det. time= 16.5 min ( 833.2 - 816.7 ) Volume Invert Avail.Storage Storage Description #1 17.50'999 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 17.50 25 0 0 18.00 64 22 22 19.50 266 248 270 20.50 471 369 638 21.00 970 360 999 Device Routing Invert Outlet Devices #1 Primary 19.50'5.0' 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 #2 Secondary 20.00'5.0' 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 66 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Primary OutFlow Max=0.47 cfs @ 12.10 hrs HW=19.60' TW=18.74' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir (Weir Controls 0.47 cfs @ 0.90 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=19.50' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Subcatchment 224: Subcat 224 Runoff =0.03 cfs @ 12.12 hrs, Volume=0.003 af, Depth= 1.31" Routed to Pond 225 : Infiltration Pond Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.024 39 >75% Grass cover, Good, HSG A 0.024 39 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 225: Infiltration Pond Inflow Area =0.103 ac, 44.19% Impervious, Inflow Depth = 4.23" for 100-Year event Inflow =0.49 cfs @ 12.10 hrs, Volume=0.036 af Outflow =0.03 cfs @ 11.42 hrs, Volume=0.036 af, Atten= 95%, Lag= 0.0 min Discarded =0.03 cfs @ 11.42 hrs, Volume=0.036 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 19.76' @ 14.78 hrs Surf.Area= 138 sf Storage= 674 cf Plug-Flow detention time= 260.7 min calculated for 0.036 af (100% of inflow) Center-of-Mass det. time= 260.7 min ( 1,099.2 - 838.5 ) Volume Invert Avail.Storage Storage Description #1 18.00'1,376 cf Ponding Storage (Prismatic) Listed below (Recalc) -Impervious #2 16.00'110 cf Sand/Loam (Prismatic) Listed below (Recalc) 276 cf Overall x 40.0% Voids 1,487 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 18.00 138 0 0 18.50 254 98 98 19.00 341 149 247 19.50 439 195 442 20.00 535 244 685 20.50 638 293 979 21.00 953 398 1,376 67 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 16.00 138 0 0 18.00 138 276 276 Device Routing Invert Outlet Devices #1 Discarded 16.00'8.270 in/hr Exfiltration Outlet over Surface area Phase-In= 0.01' Discarded OutFlow Max=0.03 cfs @ 11.42 hrs HW=16.05' (Free Discharge) 1=Exfiltration Outlet (Exfiltration Controls 0.03 cfs) Summary for Subcatchment 300: Post-300 Runoff =0.18 cfs @ 12.08 hrs, Volume=0.014 af, Depth= 6.91" Routed to Link 201 : DP-2: Stevens Street Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.004 39 >75% Grass cover, Good, HSG A 0.018 98 Impervious, HSG A 0.002 98 Offsite Impervious, HSG A 0.024 88 Weighted Average 0.004 39 17.68% Pervious Area 0.020 98 82.32% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Subcatchment 301: Post-301 Runoff =0.14 cfs @ 12.09 hrs, Volume=0.010 af, Depth= 6.43" Routed to Pond 302 : Leaching CB 30 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-Year Rainfall=8.35" Area (ac) CN Description 0.005 39 >75% Grass cover, Good, HSG A 0.015 98 Impervious, HSG A 0.019 84 Weighted Average 0.005 39 23.89% Pervious Area 0.015 98 76.11% Impervious Area 68 Type III 24-hr 100-Year Rainfall=8.35"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet)(ft/ft) (ft/sec)(cfs) 6.0 Direct Entry, Summary for Pond 302: Leaching CB 30 Inflow Area =0.019 ac, 76.11% Impervious, Inflow Depth = 6.43" for 100-Year event Inflow =0.14 cfs @ 12.09 hrs, Volume=0.010 af Outflow =0.08 cfs @ 12.20 hrs, Volume=0.010 af, Atten= 44%, Lag= 7.0 min Discarded =0.08 cfs @ 12.20 hrs, Volume=0.010 af Primary =0.00 cfs @ 0.00 hrs, Volume=0.000 af Routed to Link 201 : DP-2: Stevens Street Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 21.02' @ 12.20 hrs Surf.Area= 53 sf Storage= 46 cf Plug-Flow detention time= 2.8 min calculated for 0.010 af (100% of inflow) Center-of-Mass det. time= 2.8 min ( 794.4 - 791.6 ) Volume Invert Avail.Storage Storage Description #1 19.82'85 cf 6.00'D x 3.00'H Leaching CB #2 19.82'30 cf Area around Leaching CB (Irregular) Listed below (Recalc) 75 cf Overall x 40.0% Voids 115 cf Total Available Storage Elevation Surf.Area Perim.Inc.Store Cum.Store Wet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft) 19.82 25 28.3 0 0 25 22.82 25 28.3 75 75 110 Device Routing Invert Outlet Devices #1 Discarded 19.82'31.500 in/hr Exfiltration over Wetted area Phase-In= 0.01' #2 Primary 22.82'4.50" x 4.00" Horiz. Orifice/Grate X 4.00 columns X 4 rows C= 0.600 in 24.00" x 24.00" Grate (50% open area) Limited to weir flow at low heads Discarded OutFlow Max=0.08 cfs @ 12.20 hrs HW=21.02' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=19.82' TW=0.00' (Dynamic Tailwater) 2=Orifice/Grate ( Controls 0.00 cfs) 69 Stevens Street Mutli-Family A3.3 Water Quality Storm Analysis 70 Type III 24-hr WQ Storm Rainfall=1.20"3300-001-ALLS-EHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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 Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.991 ac 67.79% Impervious Runoff Depth=0.67"Subcatchment 10: Pre-10 Flow Length=321' Tc=9.2 min CN=38/98 Runoff=0.66 cfs 0.055 af Runoff Area=0.251 ac 72.52% Impervious Runoff Depth=0.71"Subcatchment 11: Pre-11 Tc=6.0 min CN=39/98 Runoff=0.20 cfs 0.015 af Peak Elev=16.46' Storage=49 cf Inflow=0.20 cfs 0.015 afPond 12: Leaching Catch Basin 2 Discarded=0.13 cfs 0.015 af Primary=0.00 cfs 0.000 af Outflow=0.13 cfs 0.015 af Inflow=0.66 cfs 0.055 afLink 13: DP-1: Mitchell's Way Primary=0.66 cfs 0.055 af Runoff Area=0.477 ac 58.40% Impervious Runoff Depth=0.58"Subcatchment 20: Pre-20 Flow Length=289' Tc=9.5 min CN=39/98 Runoff=0.27 cfs 0.023 af Peak Elev=18.64' Storage=89 cf Inflow=0.27 cfs 0.023 afPond 21: Leaching Catch Basin 1 Discarded=0.18 cfs 0.023 af Primary=0.00 cfs 0.000 af Outflow=0.18 cfs 0.023 af Inflow=0.00 cfs 0.000 afLink 22: DP-2: Stevens Street Primary=0.00 cfs 0.000 af Runoff Area=0.036 ac 100.00% Impervious Runoff Depth=0.99"Subcatchment 30: Pre-30 Tc=6.0 min CN=0/98 Runoff=0.04 cfs 0.003 af 71 Type III 24-hr WQ Storm Rainfall=1.20"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 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 Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=0.187 ac 28.70% Impervious Runoff Depth=0.28"Subcatchment 100: Post-100 Tc=6.0 min CN=39/98 Runoff=0.06 cfs 0.004 af Inflow=0.07 cfs 0.006 afLink 101: DP-1: Mitchells Way Primary=0.07 cfs 0.006 af Runoff Area=0.041 ac 36.14% Impervious Runoff Depth=0.36"Subcatchment 102: Subcat 102 Tc=6.0 min CN=39/98 Runoff=0.02 cfs 0.001 af Runoff Area=0.030 ac 40.84% Impervious Runoff Depth=0.40"Subcatchment 200: Post-200 Tc=6.0 min CN=39/98 Runoff=0.01 cfs 0.001 af Inflow=0.04 cfs 0.003 afLink 201: DP-2: Stevens Street Primary=0.04 cfs 0.003 af Runoff Area=0.420 ac 100.00% Impervious Runoff Depth=0.99"Subcatchment 202: Subcat 202 Tc=6.0 min CN=0/98 Runoff=0.46 cfs 0.035 af Peak Elev=19.77' Storage=0.000 af Inflow=0.46 cfs 0.035 afPond 203: UIS (SC-310) Discarded=0.46 cfs 0.035 af Secondary=0.00 cfs 0.000 af Outflow=0.46 cfs 0.035 af Runoff Area=0.065 ac 85.47% Impervious Runoff Depth=0.84"Subcatchment 204: Post-204 Tc=6.0 min CN=39/98 Runoff=0.06 cfs 0.005 af Peak Elev=21.38' Storage=0 cf Inflow=0.06 cfs 0.005 afPond 205: System E (Dumpster) Outflow=0.06 cfs 0.005 af Runoff Area=0.162 ac 78.37% Impervious Runoff Depth=0.77"Subcatchment 206: Post-206 Tc=6.0 min CN=39/98 Runoff=0.14 cfs 0.010 af Peak Elev=21.78' Storage=1 cf Inflow=0.14 cfs 0.010 afPond 207: System D (Island South) Outflow=0.14 cfs 0.010 af Runoff Area=0.202 ac 76.24% Impervious Runoff Depth=0.75"Subcatchment 208: Post-208 Tc=6.0 min CN=39/98 Runoff=0.17 cfs 0.013 af Peak Elev=21.84' Storage=1 cf Inflow=0.17 cfs 0.013 afPond 209: System B (West) Outflow=0.17 cfs 0.013 af Runoff Area=0.151 ac 72.09% Impervious Runoff Depth=0.71"Subcatchment 210: Subcat 210 Tc=6.0 min CN=39/98 Runoff=0.12 cfs 0.009 af Peak Elev=21.82' Storage=1 cf Inflow=0.12 cfs 0.009 afPond 211: System C (Center Island) Outflow=0.12 cfs 0.009 af Runoff Area=0.321 ac 56.69% Impervious Runoff Depth=0.56"Subcatchment 212: Post-212 Tc=6.0 min CN=39/98 Runoff=0.20 cfs 0.015 af 72 Type III 24-hr WQ Storm Rainfall=1.20"3300-001-ALLS-PHCD-INHS Prepared by DiPrete Engineering HydroCAD® 10.20-3c s/n 01125 © 2023 HydroCAD Software Solutions LLC Peak Elev=22.20' Storage=1 cf Inflow=0.20 cfs 0.015 afPond 213: System A (North) Outflow=0.20 cfs 0.015 af Runoff Area=0.009 ac 76.56% Impervious Runoff Depth=0.75"Subcatchment 214: Post-214 Tc=6.0 min CN=39/98 Runoff=0.01 cfs 0.001 af Peak Elev=17.68' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 215: Leaching CB 15 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.002 ac 96.08% Impervious Runoff Depth=0.95"Subcatchment 216: Post-216 Tc=6.0 min CN=39/98 Runoff=0.00 cfs 0.000 af Peak Elev=18.40' Storage=0 cf Inflow=0.00 cfs 0.000 afPond 217: Leaching CB 17 Discarded=0.00 cfs 0.000 af Primary=0.00 cfs 0.000 af Outflow=0.00 cfs 0.000 af Runoff Area=0.010 ac 81.35% Impervious Runoff Depth=0.80"Subcatchment 218: Post-218 Tc=6.0 min CN=39/98 Runoff=0.01 cfs 0.001 af Peak Elev=17.01' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 219: Leaching CB 19 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.008 ac 86.41% Impervious Runoff Depth=0.85"Subcatchment 220: Post-220 Tc=6.0 min CN=39/98 Runoff=0.01 cfs 0.001 af Peak Elev=17.63' Storage=0 cf Inflow=0.01 cfs 0.001 afPond 221: Leaching CB 21 Discarded=0.01 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.001 af Runoff Area=0.079 ac 57.60% Impervious Runoff Depth=0.57"Subcatchment 222: Subcat 222 Tc=6.0 min CN=39/98 Runoff=0.05 cfs 0.004 af Peak Elev=19.52' Storage=276 cf Inflow=0.05 cfs 0.004 afPond 223: Sediment Forebay Primary=0.05 cfs 0.004 af Secondary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.004 af Runoff Area=0.024 ac 0.00% Impervious Runoff Depth=0.00"Subcatchment 224: Subcat 224 Tc=6.0 min CN=39/0 Runoff=0.00 cfs 0.000 af Peak Elev=16.19' Storage=11 cf Inflow=0.05 cfs 0.004 afPond 225: Infiltration Pond Outflow=0.03 cfs 0.004 af Runoff Area=0.024 ac 82.32% Impervious Runoff Depth=0.81"Subcatchment 300: Post-300 Tc=6.0 min CN=39/98 Runoff=0.02 cfs 0.002 af Runoff Area=0.019 ac 76.11% Impervious Runoff Depth=0.75"Subcatchment 301: Post-301 Tc=6.0 min CN=39/98 Runoff=0.02 cfs 0.001 af Peak Elev=19.82' Storage=0 cf Inflow=0.02 cfs 0.001 afPond 302: Leaching CB 30 Discarded=0.02 cfs 0.001 af Primary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.001 af 73 Stevens Street Mutli-Family A3.4 TSS Removal Calculations Worksheets 74 V INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location: B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E) Subsurface Infiltration Structure 0.80 1.00 0.80 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 Total TSS Removal =80% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:3300-001 Prepared By:JMF *Equals remaining load from previous BMP (E) Date:11/29/2023 which enters the BMPTSS RemovalCalculation WorksheetHyannis, MA - Runoff Collection & Infiltration systems Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept. of Environmental Protection 75 V INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location: B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E) Leaching Catch Basin 0.80 1.00 0.80 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 0.00 0.20 Total TSS Removal =80% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:3300-001 Prepared By:JMF *Equals remaining load from previous BMP (E) Date:11/29/2023 which enters the BMPTSS RemovalCalculation WorksheetHyannis, MA - Leaching Catch Basins Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept. of Environmental Protection 76 V INSTRUCTIONS:Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location: B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load*Removed (C*D)Load (D-E) Sediment Forebay 0.25 1.00 0.25 0.75 Infiltration Basin 0.80 0.75 0.60 0.15 0.00 0.15 0.00 0.15 0.00 0.15 0.00 0.15 0.00 0.15 0.00 0.15 Total TSS Removal =85% Separate Form Needs to be Completed for Each Outlet or BMP Train Project:3300-001 Prepared By:JMF *Equals remaining load from previous BMP (E) Date:3/14/2024 which enters the BMPTSS RemovalCalculation WorksheetHyannis, MA - Infiltration Pond Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept. of Environmental Protection 77 Stevens Street Mutli-Family A3.5 Stormcrete Specifications 78 Stormcrete® Modular Precast Porous Concrete Stormwater System Handling and Installation Manual 1. Recommended Equipment In addition to the typical earthmoving, materials handling and grading equipment, the following hand tools should also be available – 2 or 4-way chains, cables or straps rated to lift the slabs – refer to Table 2 for the number of lifting points and the slab weights Cordless impact wrench or ratchet wrench with 3/4” socket for installing and removing lifting swivel bolts Lifting swivels supplied by manufacturer Rakes and shovels for levelling screed stone 1.25” minimum diameter screed rails 2”x4” or other material to use as a screed Plastic plugs and slab spacers supplied by manufacturer. Backpack blower to keep slabs surface clean during and after installation. Diamond Bladed Masonry Cutoff Saw (6” cutting depth min. – typically requires a minimum 16” diameter blade – check saw specifications). 6579 2 2. Offloading and Storage Prior to offloading a delivery truck the slabs on the truck shall be carefully inspected for any damage. Any observed damage shall be immediately reported to the delivery driver and the quantity and type of damage shall be noted on the delivery ticket. Offloading should be performed by a trained and experienced equipment operator. Due to the unique structural properties of porous concrete, extra care should be taken when handling the slabs. A forklift or similar equipment should be used when offloading Stormcrete® slabs. It is recommended that the equipment be fitted with forks. Chains, cables or slings should never be wrapped around slabs for offloading or installation. Slabs should be offloaded evenly from both sides of the truck to ensure that the trailer does not become unstable. Slabs delivered on pallets should be offloaded as shipped. Slabs delivered on dunnage must be picked from the highest level of dunnage. Never pick up slabs with more than one layer of dunnage. (Please see Table 1 for Stormcrete® slab sizes, shipping configurations and corresponding weights). Table 1 Stored slabs must be placed on a level or nearly level stable surface. In dusty environments slabs should be covered to prevent dust and debris from settling on slab surfaces. Slab Size Number of slabs per pallet/dunnage Number of slabs per stack Approx. Slab Weight (lbs.) Approx. Lift Weight (lbs.) 5’ x 4’ x 6” 3 9 1290 3870 5’ x 2’ x 6” 6 9 645 3870 4’ x 2.5’ x 6” 6 9 645 3870 6680 3 Allow approximately 1 s.f. of storage area for every 3 s.f. of Stormcrete® Slabs purchased. When stacking or restacking slabs 4” by 4” timbers should be placed parallel to one another and located directly beneath imbedded lifting points. Do not place timbers in the middle of the slabs or on the ends. Timbers should be at a minimum 1” thicker than the fork thickness. Place timbers between each double stack of slabs (see image below). Lower slabs evenly such that the slab comes into contact with both timbers simultaneously. To prevent edge damage, slabs should be set flat on timbers so that one edge does not contact timbers while opposite edge is supported by forks. 3. Sub-Base Preparation Reservoir Layer Placement: Reservoir layer shall not be placed and/or compact in rain or snow, or on saturated or frozen subgrade. In all cases reservoir stone shall be placed and compacted against rigid lateral boundaries, i.e., in situ, undisturbed native soils, fill materials compacted to 98% Standard Proctor density or concrete curb and headers. Compaction of reservoir stone against any flexible boundaries shall not be permitted. 6781 4 Although the approved plans shall govern over installation details and specifica- tions, the following instructions are provided by the manufacturer as minimum guidelines: Reservoir stone layer shall be constructed per approved drawings using ¾” or AASHTO No. 57 crushed angular stone. The stone must be washed and free of fines. Compact reservoir storage layer in maximum 12” lifts, with a minimum of two complete coverages, one pass each in mutually perpendicular directions, with a 3 to 5 ton smooth, single or double drum roller operated in vibratory mode. Following vibratory compaction, repeat two complete coverage’s, one pass each in mutually perpendicular directions, with the roller operated in static mode. Continue static rolling until there is no visible movement, weaving or deflection in the surface of the storage reservoir layer. For small areas inaccessible by large rollers follow the above directions using a walk-behind plate compactor. Repeat two complete coverages in each direction. The surface tolerance of the compacted storage reservoir layer shall be +/- 3/4 in. under a 10 ft. straightedge. Where specified on the design plans, place geotextile on prepared subgrade side slopes and extend a maximum of 1 foot under the bottom of the storage reservoir. Do not place geotextile under other areas of infiltrating system unless specified on the approved plans. Secure in place to prevent disturbance from vehicles and/or worker foot traffic. 6882 5 Screeding Layer Placement It is critical that the crushed stone leveling course surface be SCREEDED flat so that the slabs are fully supported with no bridging or mounding be- neath. Crushed stone base shall not be placed and/or screeded in rain or snow, or on saturated or frozen subbase. Screeding layer shall be placed per approved drawings using 3/8” crushed angular stone or No. 8 Stone. The stone must be washed and free of fines. Place and spread the stone evenly over the reservoir course to a thickness of +/- 2”. Level the surface of crushed stone (screeding is strongly recommended). Screed using a minimum 1.25” diameter rigid screed rail placed adjacent or below the slab location with the top of the rails set at the screeding level. Do not compact or disturb leveled screeding layer (if screed rails are placed in panel locations, carefully remove them to prevent disturbance to the leveling base layer). The uniformity of the leveling (base) layer determines the differential settlement between precast porous concrete paving slabs. The slab installation contractor should not correct deficiencies in the leveling layer by shimming with additional stone rather the slabs should be lifted out and the entire area should be re-leveled. 6983 6 4. Setting Stormcrete® Porous Concrete Slabs Recommended Lifting Hardware Slabs shall only be lifted and placed using supplied hoist ring swivels. 2 or 4-way chains, wire rope or nylon straps rated for the lift weight shall be used per the manufacturer’s recommendations to lift slabs – do not exceed minimum recommended angle for lifting chains. Swivels shall be securely bolted snug to the slab. Check to ensure that the bolt extends the full depth of the lifting socket. To avoid damage to the surface do not over-tightened bolts. (An electric impact wrench with a 3/4” socket is the most efficient way to attach and remove the swivels). Individual slabs should only be lifted by equipment that is rated for the slab weights shown in the adjacent table: Chains, cables or slings should never be wrapped around slabs for placement under any circumstances. Slab Dimension (ft) Max Slab Weight (lbs.) Lifting Points 5’ x 4’ x 6” 1290 4 5’ x 2’ x 6” 645 2 4’ x 2.5’ x 6” 645 2 7084 7 Placing Slabs Precast porous concrete slabs shall not be placed in heavy rain or snow, or on saturated or frozen base. Because the units are precast in a controlled environment, they are delivered to the site pre-cured which allows them to be parked or driven on immediately after placement. They may also be placed year-round, in almost any type of weather or temperature conditions. WARNING! – ENSURE THAT PLASTIC SPACER THAT ARE USED TO SEPARATE SLABS IN A STACK ARE REMOVED FROM THE BOTTOM OF ALL SLABS BEFORE SLAB PLACEMENT. Whenever possible place slabs in a staggered pattern(s) as shown below or as depicted on approved drawings. On gutter applications a string line shall be used to ensure that the curbing is straight enough to allow for proper placement of the slabs. If the existing curbing does not follow a straight alignment then the slabs should follow the alignment of a string line placed mostly parallel to the curb and ½” away from the point that is furthest toward the roadway to allow for a minimum ½” joint. . 7185 8 Guide units into place by hand, being careful not to pinch fingers. Horizontal adjustments can be made with wood wedges, levers, and rubber mallets as needed (If pry bars are used they should never come into direct contact with the top corner of the slab). Adjacent slabs shall be separated from each other by the placement of two 3/8” thick High-Density Polyethylene spacers (Part No. 18SP) supplied by the manufacturer. Spacer shall be trimmed to the right height to fit and adhered to previously placed slab with a construction adhesive such as Liquid Nails Heavy Duty Construction Adhesive or approved equal. Care should be taken to place adjacent slabs at same elevation (i.e. level to each other). Slab surfaces shall not deviate by more than 1/8” vertically and horizontally from one to the next. Placed Slabs should maintain consistent 1/8” joint widths and horizontal and vertical alignments should be continuously straightened as necessary as paving proceeds. Joints between adjacent rows of panels shall be staggered when possible. Keep slabs covered until all adjacent areas are stabilized to prevent dust and debris from reducing porosity of slabs. A backpack blower should be employed throughout the installation process to keep slab surfaces clean. Place erosion and sediment control barriers to prevent eroding areas from draining onto slabs. Whenever possible set slabs with equipment positioned next to slab area and not on previously installed slabs. When it is necessary to position equipment on slabs during setting use only light machines equipped with either rubber tires or rubber tracks. 7286 9 Immediately after the Stormcrete® system has been placed; use provided ½” nylon caps (Part No. 12NC) to fill imbedded lifting points. Care should be taken to make sure the plastic caps are flush with the surface; do not press caps down into the imbedded lifting points. Keep equipment off unrestrained paving slabs and subgrade material. Report any damage immediately to the project design professional. Cutting When required, cut slabs with a diamond bladed masonry saw with a plunge depth of 6” minimum. If field adjustments are required, slabs should be cut as indicated on the approved drawings. Cut slabs shall be no narrower than 18” and cutting shall occur so that a minimum of two embedded lifters remain for safe lifting and setting. Cutting should be performed away from sub-base material and other slabs. Do not cut slabs while in a stack or on top of another slab. Cover adjacent areas of slab being cut to prevent dust and debris from entering into the porous concrete. Slab layouts shall be planned to minimize or eliminate locations where utility structures intersect with slab joints. Whole and half slabs shall be used in combination with cast in place collars to surround utilities. 7387 10 Grade Breaks Stormcrete® slabs should be placed on a level sub-base. If grade breaks are present, ensure that they occur at an open joint. If a grade break does not occur at an open joint cut the slab to create an open joint at the break. If cutting is required reference the cutting section above. Edge Restraints NEVER place fluid material (asphalt, concrete, soil, etc.) directly up against the Stormcrete® slabs. Fluid materials shall be separated from Stormcrete® slabs by the use of a ½” preformed expansion joint material conforming to ASTM D1751 Standard Specification for Preformed Expansion Joint Filler for Concrete Paving and Structural Construction Install edge restraints per approved drawings and manufacturer’s recommendations at the indicated locations and elevations. Anchor edge restraints directly to finished leveling layer in accordance with the manufacturer’s requirements. The use of loose stone as a filler material adjacent to slabs should be avoided in favor of expansion joint material conforming to ASTM D1751 Standard Specification for Preformed Expansion Joint Filler for Concrete Paving and Structural Construction (preferred). When placing Stormcrete® Precast Porous Concrete slabs against existing concrete structures where it is not possible to pre-install ½” expansion joint material joints may be filled with No.8 clean washed gravel beneath closed cell foam backer rod and a maximum depth of ½” of elastomeric sealant such as Expansion Joint Material Shown 7488 11 Sikasil 728 RCS Limestone joint filler or approved equal. In all cases the use of a preformed expansion joint material conforming to ASTM D1751 Standard Specification for Preformed Expansion Joint Filler for Concrete Paving and Structural Construction is preferred. 5. SLAB PROTECTION & FINAL INSPECTION After work in the section is complete, the contractor shall be responsible for protecting the precast porous paving slab system from damage and/or contamination from mud, dirt, grass cuttings and accumulation of foliage and debris through the duration of construction. This should include a regular vacuum sweeping schedule. It is important that you do not attempt to wash the construction area clean. This will result in lose debris draining into the slabs/stone. Any slabs cracked or damaged during installation shall be replaced with new ones at the installers cost. Reset slabs not in conformance with specified installation tolerances. Check for and remove any accumulation of sediment or debris observed. This can be done by manually sweeping, vacuum sweepers, and in some cases, back pack blowers. Check final surface elevations of set slabs for conformance to design drawings. Slab surfaces shall not deviate by more than 1/8” vertically from one to the next and to adjacent surfaces. The surface elevation of set slabs shall be flush with manholes or the top of utility structures. 7589 12 6. STORMCRETE® PRECAST POROUS CONCRETE INSTALLATION TRAINING PROGRAM Installation contractors are strongly encouraged to participate in the Stormcrete® Precast Porous Concrete Installation Training Program. This program ensures that Installers are properly trained in the installation of Stormcrete® products. Installers successfully completing the Training Program shall receive a certificate valid for 2 years and shall be responsible for reviewing the Handling and Installation Manual and Training Program Test Questions (with correct answers) with Laborers under their employ. 7690 Stevens Street Mutli-Family Appendix B – Massachusetts Small MS4 General Permit – Appendix F Attachment 3 Full permit available here: https://www3.epa.gov/region1/npdes/stormwater/ma/2016fpd/appendix-f-2016-ma-sms4-gp.pdf 91 Stevens Street Mutli-Family Appendix C – Mounding Calculations DiPrete Engineering has prepared groundwater mounding calculations for the proposed Underground Infiltration System and the 5 Stormcrete systems. DiPrete Engineering has calculated the groundwater mounding using the USGS Hantush Calculator. The calculator is available online at http://pubs.usgs.gov/sir/2010/5102/. The calculator provided by the USGS requires several variables: R – Recharge infiltration rate (feet/day): Recharge rate is the vertical conductivity (Kv) of the soil. The vertical conductivity was determined based on the infiltrometer tests performed. The infiltrometer test, IT 23-1, showed an approximate infiltration rate of 63 in/hr. This indicates the existing onsite soils within the C horizon have an infiltration rate in excess of 63 in/hr, so in accordance with the MASWMS Volume 3, Standard 3 (Stormwater Recharge), an infiltration rate equal to half the measured rate (31.5 in/hr) was used in the analysis for the underground infiltration system and the porous pavement (Stormcrete). A value of 31.5 in/hr or 63 ft/day has been used for these calculations. Sy – Specific Yield: Specific Yield is specific to the parent material through which the infiltration occurs. Onsite soil evaluations classified the soils as sand. A value for Sy has been obtained from Table 4.3 of Hydrology and Hydraulic Systems by Ram S. Gupta: 92 Stevens Street Mutli-Family K – Hydraulic conductivity, Kh (feet/day): Mounding calculations require the hydraulic conductivity (Kh) value of the soils. According to USGS SIR 2010-5102, Vertical Conductivity is approximately 1/10 of horizontal conductivity. The vertical conductivity was determined based on the infiltrometer tests performed. The vertical conductivity is 31.5 in/hr, which equates to a horizontal conductivity of 63 in/hr or 630 ft/day. x & y – ½ of the basin length: The x and y variables represent the length and width of the system. BMP Total Length (feet) Total Width (feet) ½ Length (feet) ½ Width (feet) UIS (203)67.28 21.50 33.64 10.75 System A (213) 170.0 10.0 85.0 5.0 System B (209) 90.0 16.0 45.0 8.0 System C (211) 62.50 16.0 31.25 8.0 System D (207) 80.0 14.0 40.0 7.0 System E (205) 45.0 12.0 22.50 6.0 t – Duration of infiltration period in (days): The time of infiltration is calculated from volume infiltrated dived by the square footage of the pond and the infiltration rate (Kv). BMP Volume Infiltrated (af) Pond Infiltrating Surface Area (sf) Infiltration Rate (ft/day) T (days) UIS (203)0.272 1,446.52 630 0.013 System A (213)0.138 1,700 630 0.006 System B (209)0.108 1,440 630 0.005 System C (211)0.077 1,000 630 0.005 System D (207)0.087 1,120 630 0.005 System E (205)0.045 540 630 0.006 hi(0) – initial thickness of saturated zone (feet): The initial thickness of the saturated zone is the depth from the water table to the impervious limiting layer. Test holes performed did not encounter ledge. The lowest test hole on site (TH 23-2) has a total depth of 8ft without encountering ledge. Assuming ledge at the bottom of test hole depth for TH 23-2 would set the ledge at a minimum of approximately 4.2ft below the groundwater table. With this assumption used in all mounding calculations, there is no mounding on any stormwater system through the 100 year storm event. According to Figure 8 of the USGS document “Bedrock Topography of Western Cape cod, Massachusetts, Based on Bedrock Altitudes from Geologic Borings and analysis of ambient Seismic Noise by the Horizontal-to-Vertical Spectral- Ration Method” the approximate depth to basement surface is 100 meters or 328 feet. The USGS document can be found at the link below as well as Appendix D: 93 Stevens Street Mutli-Family https://pubs.usgs.gov/sim/3233/plates_pdfs/fairchild_ARCH_E_01-04-13_print.pdf Conclusion: BMP System Bottom System Top 100-Year Mound height (ft) 100-Year Mound Elevation UIS (203)19.77 22.10 1.928 137.45 System A (213)22.20 23.54 0.729 20.489 System B (209)21.84 23.51 0.856 20.496 System C (211)21.82 23.16 0.856 19.686 System D (207)21.78 23.12 0.798 19.228 System E (205)21.38 22.72 0.817 19.847 The mounding height is obtained from the USGS Hantush Calculator. The mound elevation is determined by adding the mound height to the average seasonal high groundwater for each respective storm system. The mounding calculations for the systems show that for all storm events up to the 100 year storm, the mound is below bottom of the Underground Infiltration System and the porous pavement areas (Stormcrete). This means that all systems will function as designed for the majority off all storm events. 94 Stevens Street Mutli-Family Appendix D – USGS Bedrock Topography of Western Cape cod, Massachusetts, Based on Bedrock Altitudes from Geologic Borings and analysis of ambient Seismic Noise by the Horizontal-to-Vertical Spectral- Ration Method 95 96 Stevens Street Mutli-Family Watershed Maps 97 WV GV WV WV UP 55-10 UP 55-9 21.3 21.3 21.5 22.1 22.4 22.7 23.2 D D D D D 20.6 21.5 21.8 21.7 21.7 21.8 21.0 22.1 22.1 21.6 21.3 20.6 20.7 21.8 21.6 21.9 22.3 22.0 21.6 23.2 22.7 21.8 21.5 22.1 21.1 21.8 22.1 21.1 22.4 23.7 24.2 25.4 24.9 23.2 23.1 23.0 22.3 UP 428-1 22.422.9 22.3 22.8 21.6 21.4 21.9 21.2 20.7 21.6 UP 428-2 UP 45A 20.3 19.9 20.520.3 19.8 GV 20.5 20.4 21.0 21.6 22.6 UP 45-30 22.0 21.6 20.8 WV WV 21.4 20.3 GV 18.1 19.6 19.3 20.0 21.5 21.0 21.9 21.520.5 21.2 UPXXXX G GGGGG DDDDDD D DDDDDDDD DDDD DOHWOHWOHWOHWOHWOHWOHWOHWOH W OH W OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHW OHWOHWOHWOHWOHWOHWOHWOHWOHWGGGGGGGGGG G GGGGGG G G G GGGGGGGGG G GG G G G G G G GGGGGGGGGGG SSSSSWWWWW a a 23 2016 SEV DTH 23-4 GWT= 47" PT IT 23-1 SEV DTH 23-2 GWT= 59" SEV DTH 23-1 GWT= 59" SEV DTH 23-8 GWT= 76" SEV DTH 23-6 GWT= 50" SEV DTH 23-7 GWT= 76" SEV DTH 23-5 GWT= 76" PT IT 23-2 W19.1 23.4 31.6 22.8 20.5 24.5 30.6 0 10' 20' 40' SCALE: 1"=20' A B37.5 DiPrete EngineeringTwo Stafford Court Cranston, RI 02920tel 401-943-1000 fax 401-464-6006 www.diprete-eng.comZ:\DEMAIN\PROJECTS\3300-001 STEVENS STREET 268\AUTOCAD DRAWINGS\3300-001-WAMP.DWG Plotted: 11/29/2023DE JOB NO: XXXX-XXX COPYRIGHT 2023 BY DIPRETE ENGINEERING ASSOCIATES, INC.ProLeEt 6Ktle32.5 LEGEND LEGEND WOODS - A SOILS WOODS - B SOILS WOODS - C SOILS GRASS - A SOILS GRASS - B SOILS GRASS - C SOILS GRAVEL - A SOILS GRAVEL - B SOILS GRAVEL - C SOILS IMPERVIOUS WOODS - D SOILS GRASS - D SOILS GRAVEL - D SOILS BRUSH - A SOILS BRUSH - B SOILS BRUSH - C SOILS BRUSH - D SOILS WATER tc line with elevations subcatchment area soil boundary reach 10 10 10 10 10 Pre-Development Watershed MapSUBCATCHMENT DRAINAGE POND/BIO RETENTION/SAND FILTER/INFILTRATING SWALE DRAINAGE STRUCTURE/POND WITH INSIGNIFICANT STORAGE REACH/SWALE DESIGN POINT 20 10 22 13 A A B C B 11 21 12 30 98 VANWV GV WV WV UP 55-10 UP 55-9 21.3 21.3 21.5 22.1 22.4 22.7 23.2 D D D D D 20.6 21.5 21.8 21.7 21.7 21.8 21.0 22.1 22.1 21.6 21.3 20.6 20.7 21.8 21.6 21.9 22.3 22.0 21.6 23.2 22.7 21.8 21.5 22.1 21.1 21.8 22.1 21.1 22.4 23.7 24.2 25.4 24.9 23.2 23.1 23.0 22.3 UP 428-1 22.422.9 22.3 22.8 21.6 21.4 21.9 21.2 20.7 21.6 UP 428-2 UP 45A 20.3 19.9 20.520.3 19.8 GV 20.5 20.4 21.0 21.6 22.6 UP 45-30 22.0 21.6 20.8 WV WV 21.4 20.3 GV 18.1 19.6 19.3 20.0 21.5 21.0 21.9 21.520.5 21.2 UPXXXX G GGGGG DDDDDD D DDDDDDDD DDDD DOHWOHWOHWOHWOHWOHWOHWO H W OH W OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHW OHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHWOHW OHWOHWOHWOHWOHWOHWOHWOHWOHWGGGGGGGGGG G GGGGGG G G G GGGGGGGGG G GG G G G G G G GGGGGGGGGGG SSSSSWWWWW 31 32 2827 2726 2528 27 23 21 19 18 17 19202 1 22 23 2425 26 27 2 8 2 9 3 0 313030 31 32 29251 9 2 1 232426 2 7 28222 0 18 3130 2928 2722 21 2223242526 21 2221 21 22 19 20 18 18 19 20 20 21 21 20 22222321212 121 212223 25 26 2728 26 23 24 a a2424252324 24 242322 21 20 19 20 252223242 226 22 21 SEV DTH 23-4 GWT= 47" PT IT 23-1 SEV DTH 23-2 GWT= 59" SEV DTH 23-1 GWT= 59" SEV DTH 23-8 GWT= 76" SEV DTH 23-6 GWT= 50" SEV DTH 23-7 GWT= 76" SEV DTH 23-5 GWT= 76" PT IT 23-2 WWW0 10' 20' 40' SCALE: 1"=20' LEGEND A LEGEND B37.5 DiPrete EngineeringTwo Stafford Court Cranston, RI 02920tel 401-943-1000 fax 401-464-6006 www.diprete-eng.comZ:\DEMAIN\PROJECTS\3300-001 STEVENS STREET 268\AUTOCAD DRAWINGS\3300-001-WAMP.DWG Plotted: 3/14/2024DE JOB NO: XXXX-XXX COPYRIGHT 2024 BY DIPRETE ENGINEERING ASSOCIATES, INC.ProLeEt 6KtleWOODS - A SOILS WOODS - B SOILS WOODS - C SOILS GRASS - A SOILS GRASS - B SOILS GRASS - C SOILS GRAVEL - A SOILS GRAVEL - B SOILS GRAVEL - C SOILS IMPERVIOUS WOODS - D SOILS GRASS - D SOILS GRAVEL - D SOILS BRUSH - A SOILS BRUSH - B SOILS BRUSH - C SOILS BRUSH - D SOILS WATER 32.5 TC LINE WITH ELEVATIONS SUBCATCHMENT AREA SOIL BOUNDARY SUBCATCHMENT DRAINAGE POND/BIO RETENTION/SAND FILTER/INFILTRATING SWALE DRAINAGE STRUCTURE/POND WITH INSIGNIFICANT STORAGE REACH/SWALE DESIGN POINT REACH 100 100 100 100 100 Post-Development Watershed Map201 101 202 200 100 204 206 210 212 301 208 207 205 209 211 213 203 214 216 218 220 300 217 221 219 215 302 223 225 224 222 102 99