Three County Fairgrounds Stormwater Drainage Report 11-03-2010

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Three County Fairgrounds Stormwater Drainage Report 11-03-2010

  1. 1. - • Stormwater Drainage Report City of Northampton Stormwater Permit Application For: Prepared by: ~~~The~ Berkshire Design Group, Inc. 4 Allen Place, Northampton, Massachusetts 0 I060 Three County Fairgrounds Phase 1 Redevelopment Plan Northampton, MA October 1, 2010 Revised October 25,2010 Revised November 1,2010 Revised November 3,2010 Prepared for: Three County Fairgrounds 59 Fair Street Northampton, MA 01060
  2. 2. STORMWATER MANAGEMENT PERMIT Fcc: Paid Dale: Paid Pc:mulll City ofNortta.mpton DCplrlmenl of Public: Work.~ APPLICATION Approved By' _ _ _ _ __ Appro..·aJ Dati: =---,,=_~,-­ ( For IJPW 1J.Je only) 1. Project I Site Information ProjectlSiteName: :r1yV'« rM'l~ ~NJ.lMS -?L..'&.i.12Lrtle6(~~ Project Street I Location: S1' ~J~+ Assessor's Map: -- 2ff~ Parcel(s): ""2.6"( Estimated Area to be Disturbed (rr): _--7--'-'-D-'>LJJ-I.O;.."1B-""-'-'L/-=-__________ Total Area ofimpervious Surfaces: (paved, parking, decks, roofs, etc.) (rr) Existing i30,9'2- Proposed • Project Type (check one) CJ Residential Site (I unit and 1-5 Acres Disturbed) CJ Residential Site (I unit and greater than 5 Acres Disturbed) CJ Minor Residential Subdivision (I lot and disturbing I to 5 acres ofland) CJ Residential Subdivision and Other Residential such as Townhouse or Retirement Development (2 or more units in B common plan of development) CJ Commercial Subdivision I'j9..commerciaJ or Industrial Site ~c::: CJ Land Disturbance Only (No change in site use or buildings. May include reconstruction ofparking lots, roads, and driveways' utility work; and lawn and landscaping work.) 2. Applicant Information Name: ~.jc.e.. ;v.c[r)'3;7: Address: 0/1 ~ lJ 50llih ?t-.-eef-- Telephone: lfB- S8Y- '1030 E-Mail: rna; Ie h4¥bo.rj~dl~ F~: ____________________________ 4. Certification 53D. ":} I Permit Review and Inspection Fee 5700 51 ,100 5700 or SI per linear foot of roadway or common driveway (which ever is greater) 52000 or 52 per linear foot ofroadway or common driveway (which ever is greater) 52000 or 52 per linear foot ofroadway or common driveway (which ever is greater) I- 5700 per acre disturbed (maximum of55,OOO) 5100 per acre disturbed 3. Owner Information (if different from (%;ca.t) &uce.. 7h4 ~ I herby certify that the information contained herein Including all attachments Is true, accurate and complete to the best of my k.nowledge. Further, l grant the Northampton Department of Public Works and its agents permission to enter the property to review this application and make inspections during and after cL£v4 /!)8;Uo ) _ Applient;S~i~alure date R?v::e~~b~~"~· C> ~-"Bt-OLeStJ&ro;-S ~? UJ&t!J4t F Owner's sig;.ature . Date
  3. 3. 5. Application Requirements The application to the Northampton Department of Public Works (DPW) for a Stormwater Management Permit must include submission of the following: ill Completed and Signed Stormwater Management Permit Application o Non-Refundable Permit Review and Inspection Fee l/A ~Operation, Maintenance, and Inspection Agreement ~hree complete copies of the Stonnwater Management Plan and Erosion and Sediment Control Plan prepared by a professional engineer licensed by the Commonwealth of Massachusetts, and including the minimum documentation listed below (see the Northampton Stonnwater Management Ordinance (Chapter 22, Article V) for more information): :2--?-ofILS Project Documentation: (Check circles below indicating that you have provided the following minimum infonnation) A Identity all operators for the project site and the potions over which each operator has control. ci::All plans submitted have been prepared and stamped by a professional engineer licensed by the Commonwealth of Massachusetts o The applicant has certified on the drawings that all clearing, grading. drainage, construction, and development shall be conducted in strict accordance with the plan f:f Locus map ill The existing zoning, and land use at the site ~ The proposed land use C4 The location of existing and proposed easements ® The location of existing and proposed utilities -fQ The site's existing & proposed topography with contours at 2 foot intervals fQ Soils investigation (by a Certified Soil Evaluator or Certified Professional Soil Scientist) including borings or test pits, to a depth greater than 4 ft. below estimated seasonal ground water for areas where construction of infiltration practices will occur. Q Estimated seasonal high groundwater elevation (November to April) in areas to be used for storm water retention, detention, or infiltration (by a Certified Soil Evaluator or Certified Professional Soil Scientist). ~ A description & delineation of existing stonmwater conveyances. impoundments, and wetlands on or adjacent to the site or into which stom] water flows. !Q A delineation of 100-year flood plains, if applicable. ~ The existing and proposed vegetation and ground surfaces with runoff coefficient for each. S{. A drainage area map showing pre and post construction watershed boundaries, drainage area. stonm water flow paths, and receiving water. ~ A description and drawings of all components of the proposed drainage system including: I) tbe structural details for all components of the proposed drainage systems and stonm water management facilities (including size, inverts, and grade); 2) all measures for the detention, retention or infiltration of water; 3) all measures for the protection of water quality; 4) notes on drawings specitying materials to be used, construction specifications, and typicals; 5) the existing and proposed site hydrology with supporting drainage calculations (including the 1,2, 10, and 100 year NRCS design stonms); Northampton Department of Public Works Stonnwater Management Penn it Page 2
  4. 4. 6) proposed improvements including location of buildings or other structures, impervious surfaces. and drainage facilities, if applicable; 7) location, cross sections, and profiles of all potentially impacted brooks, streams, drainage swales and their method ofstabilization; and 8) proposed ownership ofdrainage system structures. l-Estimate ofthe total area expected to be disturbed by excavation, grading or other construction activities. Iii..A description and location ofall measures (i.e., Best Management Practices) that will be implemented as part of the construction activity to control pollutants in storm water discharges. A description of when each control measure will be implemented in the construction schedule, which operator is responsible for the implementation of each control measure and a maintenance and inspection schedule for each control measure during construction. 6( A description ofconstruction and waste materials expected to be stored on-site, and a description ofcontrols to reduce pollutants from these materials including storage practices to minimize exposure of the materials to storm water, and spill prevention and response. P- Timing, schedules, and sequence of development including clearinjl, strippi~g, "m rading,. I construction, final grading, and vegetative stabilization. I _ Ui1 tIL.'5>>'0 M1 ~ o:>'tT' L-Y l..lWt:~ "5'Wt" Pr; o('{ 0 6. Application Submission, Review, and Approval Procedures q)t1"*,,,"d-~ 0< 1. Application Submittal: The application to the Northampton DPW for a Stormwater Management Permit must be submitted prior to or concurrently with any land use permit application. Submission of an application should be made to the Northampton Department of Public Works, 125 Locust St., Northampton, MA 01060. For more information and copies of the Northampton Stormwater Ordinance visit the DPW web site at http://www.northamptonma.gov/dpw/Stormwater/ or contact Doug McDonald at 413-587-1582 x308 or dmcdonaldlalnohodpw.org 2. Administrative Review: The Northampton DPW will have 7 days from the receipt of the application to review the application for administrative completeness. Incomplete applications will be disapproved and returned to the applicant based on the determination that they are admirustratively incomplete. 3. Review: If the application is found to be complete, the Northampton DPW will review the application and supporting documents based on the criteria set forth in the Northampton Stonnwater Management Ordinance (Chapter 22, Article V) and will take final action within 21 days (including the 7 day administrative review period) of the receipt of a complete application unless such time is extended by agreement between the applicant and the DPW. 4. Final Action: The Northampton DPW's tinal action will be in writing and will be sent to the applicant and the appropriate City Department(s) and Board(s). Northampton Department of Public Works Stonnwater Management Pennit Page 3
  5. 5. Three County Fairgrounds • 10/08/09 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 8 2 • 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.
  6. 6. I 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 Repo~71"~¥~~5-o~i~S ~~~ date of this permit application. Registered Professional Engineer Block and Si~ature ~,. Signature and Date I oj e/zDl 0• I Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? D New development [8J Redevelopment D Mix of New Development and Redevelopment Three County Fairgrounds· 10/08109 Stormwater Report Checklist· Page 2 of 8
  7. 7. Three County Fairgrounds • 10/08/09 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): Media filtration system inlets for detention system 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.
  8. 8. Three County Fairgrounds • 10/08/09 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 Field 1 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 (to the maximum extent practicable) 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. As a redevelopment project 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.
  9. 9. Three County Fairgrounds • 10/08/09 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.
  10. 10. Three County Fairgrounds • 10/08/09 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. Per STC Sizing 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. Rated 2 on MASTEP 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) Not Applicable – Proposed project site is not expected to yield high potential pollutant loads. 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 Not Applicable – The project site does not discharge to a critical area. 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.
  11. 11. Three County Fairgrounds • 10/08/09 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.
  12. 12. Three County Fairgrounds • 10/08/09 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.
  13. 13. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 1 Table of Contents Introduction 2 Site Terrain and Soils 3 Existing Conditions 3 Proposed Conditions 5 Calculations and Design 6 MADEP Stormwater Standards 8 Summary 10 Figures Figure 1 Pre- Development Drainage Area Map Figure 2 Post Development Drainage Area Map Figure 3 USDA Soils Map Appendices Appendix A Pre- and Post Development Hydrologic Calculations Appendix B Soil Test Pit Information Appendix C TSS Removal Summary and Calculations Appendix D Standard 3 Recharge Calculations Appendix E Proposed Stormwater Management System Operation &Maintenance P Plan Appendix F Long Term Pollution Prevention Plan
  14. 14. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 2 I. Introduction The following report presents an analysis of the stormwater management system for the proposed Phase 1 redevelopment the Three County Fairgrounds, located off Route 9 in Northampton, Massachusetts which is located in the SC zoning district. Locus Map (site outlined in red) The proposed project involves the redevelopment of a portion of the site. The 15 existing horse barns and other small buildings will be demolished and 3 new barns are proposed to be constructed, along with associated roads/walking paths, landscaping, and stormwater management. The drainage areas analyzed total 56.80 acres of which approximately 16.30 acres will be disturbed by construction activities. The impervious area on site will increase by approximately 1.16 acres due to the new construction. The proposed stormwater management system will work in conjunction with the existing system. Mechanisms to reduce runoff and treat water quality include existing deep sump catch basins, new drains with sumps, subsurface detention systems, an
  15. 15. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 3 infiltration trench designed specifically for the phase 1 portion of the project, stormwater treatment chamber, and 2 existing detention ponds. Site Terrain and Soils The project site is comprised of a relatively flat terrain with the exception of the steep slope adjacent to Route 9. The site surface generally consists of grassed, gravelly, exposed dirt, and paved areas. The USDA Soil Survey of Hampshire County, Massachusetts, Central Part report classifies the site soils as (see Figure 3 for Soil Map): • (8A) Limerick Silt Loam Hydrologic Group: C Depth to Water Table: 0.0’-1.5’ • (96A) Hadley Silt Loam Hydrologic Group: B Depth to Water Table: 4.0’-6.0’ • (98A) Winooski Silt Loam Hydrologic Group: B Depth to Water Table: 1.5’-3.0’ A series of test pits were conducted on site to determine subsurface conditions. The purpose of the test pits was to evaluate the site for the existence of ledge, the ability of the site to support stormwater drainage components, and for groundwater information. In general, the test pits confirmed the USDA Soil Survey findings for the site as ground water is generally high throughout the site, and the soils consisted mostly of a silty loam. The test pit logs are attached in Appendix B. III. Existing Conditions The existing site contains 6 drainage areas (E-1 through E-6) and 3 different control points used for determining peak runoff rates, and the site has an average curve number of 74. The drainage areas and control points are shown on the Pre- Development Drainage Area Plan (see Figure 1). The following is a brief description of each drainage area:
  16. 16. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 4 E-1 E-1 is approximately 24.06 acres and contains a large area of the existing track, horse barns, other miscellaneous buildings, grassed areas, paved areas, and gravel areas. The area drains to existing catch basins which direct the stormwater to the existing detention basin at the east end of the site (shown as E-Pond1 on Figure 1). The easterly detention pond has 2 outlets: The first outlet is a 12” CMP located on the north edge of Fair Street which discharges water across the street to the property line located at the southeastern area of the site (shown as E-CP1 on Figure 1). The second outlet is a catch basin located just south of Horse Barn H & C. When the level of water in the pond exceeds elevation 117’, it overflows out of the catch basin and spills over Cross Path Road into the adjacent property (shown as E-CP3 on Figure 1) causing standing water in the spring and summer and frozen ponding in the winter. Occasionally when a large fairgrounds event is planned, the detention pond is pumped at 200gpm (0.45cfs) to an existing catch basin on the west side of the site (shown as E-Pond2 on Figure 1) in order to drain the adjacent area. It is pertinent to pump the drainage system due to the fact that the only piped outlet is at elevation 116’ on Cross Path Road. For the sake of consistency within pre and post calculations, the pump system is assumed to run full time for the duration of the storm events. This allows a similar comparison between existing conditions and the proposed site design. The pump is modeled as a pond with a base flow out of 0.45cfs which discharges to the Williams Street Brook system (shown as E-CP2 on Figure 1) which is undersized in most storms. E-2 E-2 is approximately 10.75 acres and contains a portion of the existing track, buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into existing catch basins which discharge into the westerly retention basin (E-Pond2). The detention pond discharges into the Williams Street Brook drainage system through a 12” pipe (E-CP1). E-3 E-3 is approximately 10.38 acres and contains adjacent houses, buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into existing catch basins which discharge directly into the Williams Street Brook drainage system (E-CP1). E-4 E-4 is approximately 7.52 acres and is located south of the main area and contains a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This area sheet flows overland to the southern property line (E-CP2). E-5
  17. 17. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 5 E-5 is approximately 3.41 acres and is located north of the main area and contains a portion of Ferry Road, a basketball court, and grassed areas. This area sheet flows over Ferry Road where it begins to pond until it enters the existing westerly detention basin which drains to the Williams Street Brook system (E-CP1). E-6 E-6 is approximately 0.68 acres and is located north of the main area and contains a portion of Ferry Road, abutting houses, and grassed areas. This area sheet flows toward existing catch basins where it is directed to the easterly detention basin which drains to the south eastern area of the site (E-CP2). IV. Proposed Conditions The proposed project does not alter the site significantly and it retains the general flow patterns of the existing stormwater system. The proposed site contains 6 drainage areas (P-1 through P-6) and 3 different control points used for determining peak runoff rates. The drainage areas and control points are shown on the Post-Development Drainage Area Plan (see Figure 2). The following is a brief description of each drainage area: P-1 P-1 is approximately 27.48 acres and contains the 3 new horse barns, a new restroom, new paved road/walk areas, a large area of the existing track, other miscellaneous buildings, grassed areas, paved areas, a portion of the Morgan horse rings, and gravel areas. This area of the site will contain 2 large subsurface stone detention systems which will be hydraulically connected to the easterly detention basin. Areas that drain directly to the subsurface system are directed to low spots which allow for the runoff to infiltrate through the specified soil media prior to entering the system. The area adjacent to the 3 new horse barns will drain to a new system installed under 2 new concrete pads between the barns. Each pad contains drain inlets with 2’ sumps. Before horse manure is permitted to be stockpiled on the pads, the drains inlets are replaced with covers to prohibit potential contamination of the drainage system and the horse barn roof areas are piped directly into the drain system to allow for separation of roof runoff which will increase the water quality entering the detention basin. The outlet from the new subsurface system will be outfitted with a stormwater treatment chamber designed to remove a minimum of 80% TSS for the increase in impervious area on site. The rest of the area within P-1 drains to existing catch basins or sheet flows to the existing detention basins on the east side of the site (shown as P-Pond1 on Figure 2). The detention pond has 3 outlets. The first outlet is a 12” CMP located on the north edge of Fair Street which discharges water across the street to the property (P-CP2); unlike in existing conditions, the existing low catch basin adjacent to Cross Path Road is proposed to be removed in this phase and a berm at elevation
  18. 18. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 6 117.2’ (second outlet) will be constructed to ensure the water flowing to the east is less than it was in existing conditions (P-CP3). Occasionally when a large fairgrounds event is planned, the retention pond is pumped (the site will continue to utilized the existing pump at 200gpm) to an existing catch basin (P-CP1) on the west side of the site (shown as P-Pond2 on Figure 2). In order to provide a consistent timing of pump use for existing and proposed conditions, the pump was modeled as a base flow of 0.45cfs (200gpm) directed to the Williams Street Brook drainage infrastructure and was assumed to be running at all times. With the construction of the new drainage infrastructure, an Operation and Maintenance plan is proposed that will require the pump system to run after storms to ensure the drainage system will be drained within 72 hours. It is pertinent to pump the drainage system due to the fact that the only outlet remains at Cross Path Road. An infiltration trench has been designed to catch and retain the runoff from a large part of the main road that is proposed in the middle of the site. The system consists of a long and shallow stone filled bed which will catch the runoff from a large amount of the new pavement, and allow the runoff to recharge into the ground. The system has been designed to be very shallow and has low spot at the center of the trench which will promote the runoff to infiltrate as well as serve as a monitoring system for determining the trench’s performance. P-2 P-2 is approximately 9.27 acres and contains a portion of the existing track, buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into existing catch basins which discharge into the westerly retention basin (P-Pond2). The detention pond discharges into the Williams Street Brook drainage system through a 12” pipe (P-CP1). P-3 P-3 is approximately 8.46 acres and contains adjacent houses, buildings, grassed areas, paved areas, new horse rings, and gravel areas. This area sheet flows into existing catch basins which discharge directly into the Williams Street Brook drainage system (P-CP1). P-4 P-4 is approximately 7.52 acres and is located south of the main area and contains a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This area sheet flows overland to the southern property line (P-CP2). P-5 P-5 is approximately 3.41 acres and is located north of the main area and contains a portion of Ferry Road, a basketball court, and grassed areas. This area sheet flows over Ferry Road where it begins to pond until it enters the existing westerly detention basin which drains to the Williams Street Brook system (P-CP1).
  19. 19. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 7 P-6 P-6 is approximately 0.68 acres and is located north of the main area and contains a portion of Ferry Road, abutting houses, and grassed areas. This area sheet flows toward existing catch basins where it is directed to the easterly detention basin which drains to the south eastern area of the site (P-CP2). V. Calculations and Design Drainage calculations were performed on Hydrocad Stormwater Modeling System version 8.0 using Soil Conservation Service (SCS) TR-20 methodology. The SCS method is based on rainfall observations, which were used to develop the Intensity-Duration-Frequency relationship, or IDF curve. The mass curve is a dimensionless distribution of rainfall over time, which indicates the fraction of the rainfall event that occurs at a given time within a 24-hour precipitation event. This synthetic distribution develops peak rates for storms of varying duration and intensities. The SCS distribution provides a cumulative rainfall at any point in time and allows volume dependent routing runoff calculations to occur. These calculations are included in the appendices. The watershed boundaries for calculation purposes are divided according to the proposed site grading and the natural limits of the drainage areas. The curve numbers (CNs) and times of concentration for the existing and proposed subcatchment areas are based on the soil type and the existing and proposed cover conditions at the site. The soil hydrologic group assumed for the site is noted in Figure 3. Watershed subcatchment areas, runoff coefficients and watercourse slopes are based on survey information. Calculations were performed for the 2-, 10-, and 100-year frequency storms under existing and proposed conditions. The results of the calculations are presented in Table 1 below. Appendix A presents the Hydrocad calculations. Flow Rates & Water Quantity Table 1 on the following page presents the comparison of flow rates and water quantity at both existing and proposed control points.
  20. 20. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 8 Table 1 Peak Flow and Volume Summary *Names in parentheses refer to HydroCad model and calculations. Note that the volumes are less for proposed conditions during the first 24 hours after the storm began. This is due to the large increase in storage area within the proposed detention system. However when the pump system drains the proposed basin, the volume directed to the Williams Street Brook control point (CP3) will be greater in proposed conditions. VI. MADEP Stormwater Standards Compliance The following section details how the project follows the MADEP Stormwater Management Policy’s ten stormwater management standards. Standard 1 - Untreated Stormwater No new outlets are proposed on the site and the site has added treatment capacity to the existing site through the use of infiltration trenches, deep sump basins, a large subsurface detention system with filtration inlet areas, and a stormwater treatment chamber. The existing stormwater system has been modified to treat the stormwater prior to discharging it off site. Condition & Point of Analysis Peak Flow Rate(cfs) Volume (acre-ft) Peak Flow Rate(cfs) Volume (acre-ft) Peak Flow Rate(cfs) Volume (acre-ft) Existing – Control Pt. (E-CP1)* Proposed – Control Pt. (P-CP1)* Existing – Control Pt. (E-CP2)* Proposed – Control Pt. (P-CP2)* Existing – Control Pt. (P-CP3)* Proposed – Control Pt. (P-CP3)* 2.779 0.00 0.000 0.00 0.000 35.50 2.620 0.00 0.000 1.52 0.178 35.51 33.17 7.960 7.14 2.582 16.48 4.543 29.19 7.310 7.52 2.696 18.21 4.891 2-Year Storm 10-Year Storm 100-Year Storm 3.00” 4.50” 6.50” 23.43 4.551 4.21 0.474 10.65 2.620 21.42 4.538 4.21 0.879 10.82 3.136
  21. 21. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 9 Standard 2 - Post-Development Peak Discharge Rates The stormwater system is designed so that post-development peak discharge rates are equal or less than pre-development peak discharge rates leaving the site. Although the proposed site will have an increase of impervious area, the new subsurface detention systems will provide significant storage and reduce the peak flows from existing conditions. During the 24 hour storm the volume of water discharged to the control points will be less than existing conditions due to the large storage area proposed. However because the system requires pumping to drain, the proposed basin is not fully drained after the 24 hour period shown in the peak flow/volume calculations. The remaining volume left after the storm will be drained by the pump for the next several hours (which happens in existing conditions as well). However, the peak flows will be equal to or reduced from existing conditions in the 2, 10, and 100 year storms which will improve the functionality of the site. Refer to Table 1 Peak Flow and Volume Summary and Appendix A for HydroCAD calculations. Standard 3 - Recharge to Groundwater The proposed redevelopment has been designed to provide recharge groundwater to the maximum extent practicable in proposed conditions. In the full build of the project (a mix of new and redevelopment) a large infiltration basin is proposed at the south parcel. However the connection under the roadway to this basin was proposed at this phase and shallow infiltration trench systems are proposed at the south side of the main roadway and adjacent to 2 of the new barns. These systems have been sized to accommodate and recharge the increase in impervious area and are designed to capture approximately 84.8% of the 1.16acres of increased impervious area. The basin has been designed to be very shallow which will allow it to drain down in less than 72 hours and will encourage infiltration on the smaller more common storms. Note that the infiltration trench was not included in the peak flow calculations to provide a more conservative proposed peak flow and volume estimate. Standard 4 – Water Quality The proposed redevelopment will provide increase water quality treatment of the site. The proposed detention system has been designed with multiple inlet areas which allow the runoff to infiltrate through soil media prior to entering the system which provides treatment for runoff very similar to a rain garden. The new detention systems will then discharge to a stormwater treatment chamber (STC 900) which has been sized to treat the increase in impervious area with a TSS removal rate of 81.2% (see appendix for StormCeptor sizing chart). The treatment chamber then discharges into the existing basin where any remaining solids have the opportunity to settle on the bottom.
  22. 22. Three County Fairgrounds - Phase 1 October 1, 2010 – Revised 10/25/10 & 11/1/10& 11/3/10 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 10 The site will also be implementing an improved manure management system between the horse barns. Contaminated water will not be able to enter the system as it will be block until the manure has left the vicinity of the drains Standard 5 - Higher Potential Pollutant Loads The proposed project is not expected to yield high potential pollutant loads. Standard 6 - Protection of Critical Areas The project site does not discharge to critical areas as defined in MA DEP Stormwater Policy Handbook. Standard 7 - Redevelopment Projects The proposed project is a redevelopment project and will improve the site to the maximum extent practicable by incorporating recharge and water quality measures that will function for the phase until the full build out is constructed. Standard 8 - Erosion/Sediment Control Erosion and sediment controls will be fully been incorporated into the project design to prevent erosion, control sediments, and stabilized exposed soils during construction and land disturbance. This project is covered by a NPDES Construction General Permit and a SWPPP will be submitted by the contractor prior to the start of construction. Standard 9 - Operation/Maintenance Plan An Operation and Maintenance Plan for the proposed project is included in Appendix E. It includes general controls for construction and long term maintenance of the stormwater management system. Standard 10 – Prohibition of Illicit Discharges No illicit discharges will occur as a result of this project. VII. Summary The impervious area from existing to proposed conditions will increase by approximately 1.16 acres from the construction of the 3 new barns and new paved areas. The combination of the improvements to the stormwater system on site will ensure that the redevelopment will significantly improve the existing site.
  23. 23. Three County Fairgrounds-Phase 1 October 1, 2010 Revised 11/1/10 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Figures Figures
  24. 24. "n z "l III "c 5 z "0 "n ~0 <n " _The _Berkshire =-oos;gn _ Group, Inc. 4 Allen Place Northampton, MassachuseUs 01060 (413) 582-7000 • FAX (413) 582-7005 Figure Title: / ./[§J/ n / -=/ ~ I Pre-Deve/opemen! Drainage Area Map Three County Fairgrounds j NORTHAMPTON MASSACHUSEITS Revisions: Date: Scale: 10/01/10 1"=300' Figure Number 1 I I
  25. 25. _The _Berkshire =-oos;gn _ Group, Inc. 100_........... i '1ft'a,"'F'",..-" I § I 4 Allen Place Northampton, MassachuseUs 01060 (413) 582·7000 • FAX (413) 582·7005 I • --,~- t •• / I (~, Figure Title: Post-Developement Drainage Area Map Three County Fairgrounds NORTHAMPTON MASSACHUSETTS •....:..."""'",,,,,,,,,..../'-c....~ : I : ;.....Ul..,) •••••• ..,,11111111111111 Revisions: 10125110 Date: Scale: 10/1/10 1"=300' Figure Number 2
  26. 26. _The _Berkshire =-oos;gn _ Group, Inc. 4 Allen Place Northampton, MassachuseUs 01060 (413) 582-7000 • FAX (413) 582-7005 Figure Title: Hydrologic Soils Group Map Three County Fairgrounds NORTHAMPTON MASSACHUSETTS Revisions: Date: Scale: 10/1/10 1"=300' Figure Number 3
  27. 27. Three County Fairgrounds-Phase 1 October 1, 2001 Revised 11/1/10 &11/3/10 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix A – Pre- and Post Development Hydrologic Calculations
  28. 28. E-1 Area to Easterly Basin E-2 Area To Westerly Basin E-3 Direct to Road Drainage Infrastructure E-4 Southeast Area of Site to South Property Line E-5 Area north of site (includes basketball court) E-6 Northeast of Site (Road and abutting property) P-1 Area to Easterly Basin P-2 Area To Westerly Basin P-3 Direct to Road Drainage Infrastructure P-4 Southeast Area of Site to South Property Line P-5 Area north of site (includes basketball court) P-6 Northeast of Site (Road and abutting property) E-CP1 Williams St. Brook Infrastructure E-CP2 South Property Line E-CP3 Cross Paths Road P-CP1 Williams St. Brook Infrastructure P-CP2 South Property Line P-CP3 Cross Paths Road E-Pond1 Existing East Detention Basin E-Pond2 Existing West Detention Basin E-Pump CB Existing Pump System from East Basin E-Pump. CB Existing Pump System from East Basin P-Pond 1 Existing East Detention Basin & New Trench Systems P-Pond 2 Existing West Detention Basin Drainage Diagram for Three Country Fairgrounds Phase 1- Stormwater Permit rev110310 Prepared by The Berkshire Design Group 11/3/2010 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcat Reach Pond Link
  29. 29. Revised 11/3/10 Three Country Fairgrounds Phase 1- Stormwater Permit rev110310 Page 2Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcats) 58.105 61 >75% Grass cover, Good, HSG B (E-1,E-2,E-3,E-4,E-5,E-6,P-1,P-1,P-2,P-3,P-4,P-5,P-6) 4.859 74 >75% Grass cover, Good, HSG C (E-4,E-5,P-4,P-5) 1.586 85 Existing Gravel/Stone Dust (P-1) 15.840 85 Gravel/Stone Dust (E-1,E-2,E-3,E-4,P-2,P-3,P-4) 0.968 96 Morgan Rings (stonedust) (P-3) 7.181 96 Proposed TRG Paving (P-1,P-1,P-3) 0.413 98 (P-1) 1.362 98 Basin (E-2,E-4,P-2,P-4) 0.460 98 Basins (E-1,P-1) 1.949 98 Paved parking (E-5,E-6,P-5,P-6) 0.702 98 Paved parking & roofs (P-1) 2.140 98 Road (E-4,P-4) 17.585 98 Road/Roof (E-1,E-2,E-3,P-1,P-2,P-3) 0.448 98 Roof (E-4) 113.597
  30. 30. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 3Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=1,048,195 sf Runoff Depth>0.85"Subcatchment E-1: Area to Easterly Basin Flow Length=888' Tc=17.0 min CN=73 Runoff=15.84 cfs 1.712 af Runoff Area=468,308 sf Runoff Depth>1.25"Subcatchment E-2: Area To Westerly Basin Flow Length=1,136' Tc=16.9 min CN=80 Runoff=11.10 cfs 1.116 af Runoff Area=451,921 sf Runoff Depth>0.85"Subcatchment E-3: Direct to Road Drainage Infrastructure Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=6.47 cfs 0.737 af Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment E-4: Southeast Area of Site to South Property Flow Length=750' Tc=17.3 min CN=71 Runoff=4.21 cfs 0.474 af Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment E-5: Area north of site (includes basketball c Flow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af Runoff Area=29,661 sf Runoff Depth>1.19"Subcatchment E-6: Northeast of Site (Road and abutting prop Flow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af Runoff Area=27.478 ac Runoff Depth>1.18"Subcatchment P-1: Area to Easterly Basin Flow Length=888' Tc=17.0 min CN=79 Runoff=26.74 cfs 2.711 af Runoff Area=403,083 sf Runoff Depth>1.37"Subcatchment P-2: Area To Westerly Basin Flow Length=1,136' Tc=16.9 min CN=82 Runoff=10.64 cfs 1.060 af Runoff Area=8.458 ac Runoff Depth>0.96"Subcatchment P-3: Direct to Road Drainage Infrastructure Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=75 Runoff=6.07 cfs 0.674 af Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment P-4: Southeast Area of Site to South Property Flow Length=750' Tc=17.3 min CN=71 Runoff=4.21 cfs 0.474 af Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment P-5: Area north of site (includes basketball c Flow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af Runoff Area=29,664 sf Runoff Depth>1.19"Subcatchment P-6: Northeast of Site (Road and abutting prop Flow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af Inflow=7.52 cfs 2.696 afReach E-CP1: Williams St. Brook Infrastructure Outflow=7.52 cfs 2.696 af Inflow=4.21 cfs 0.879 afReach E-CP2: South Property Line Outflow=4.21 cfs 0.879 af Inflow=0.00 cfs 0.000 afReach E-CP3: Cross Paths Road Outflow=0.00 cfs 0.000 af
  31. 31. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 4Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Inflow=7.14 cfs 2.582 afReach P-CP1: Williams St. Brook Infrastructure Outflow=7.14 cfs 2.582 af Inflow=4.21 cfs 0.474 afReach P-CP2: South Property Line Outflow=4.21 cfs 0.474 af Inflow=0.00 cfs 0.000 afReach P-CP3: Cross Paths Road Outflow=0.00 cfs 0.000 af Peak Elev=116.42' Storage=46,413 cf Inflow=16.49 cfs 1.779 afPond E-Pond1: Existing East Detention B Discarded=0.45 cfs 0.470 af Primary=0.68 cfs 0.405 af Secondary=0.00 cfs 0.000 af Outflow=1.13 cfs 0.876 af Peak Elev=117.32' Storage=27,837 cf Inflow=13.03 cfs 1.372 afPond E-Pond2: Existing West Detention B 12.0" x 55.0' Culvert Outflow=2.01 cfs 1.064 af Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump: Existing Pump System from East Basin Outflow=0.45 cfs 0.894 af Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump.: Existing Pump System from East Basin Outflow=0.45 cfs 0.894 af Peak Elev=115.73' Storage=107,696 cf Inflow=27.40 cfs 2.778 afPond P-Pond 1: Existing East Detention Discarded=0.45 cfs 0.894 af Primary=0.00 cfs 0.000 af Secondary=0.00 cfs 0.000 af Outflow=0.45 cfs 0.894 af Peak Elev=117.30' Storage=27,284 cf Inflow=12.56 cfs 1.316 afPond P-Pond 2: Existing West Detention 12.0" x 55.0' Culvert Outflow=1.95 cfs 1.014 af Total Runoff Area = 113.597 ac Runoff Volume = 9.605 af Average Runoff Depth = 1.01" 77.94% Pervious Area = 88.539 ac 22.06% Impervious Area = 25.058 ac
  32. 32. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 5Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcatchment E-1: Area to Easterly Basin Runoff = 15.84 cfs @ 12.26 hrs, Volume= 1.712 af, Depth> 0.85" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 10,000 98 Basins 574,174 61 >75% Grass cover, Good, HSG B 115,775 98 Road/Roof 348,246 85 Gravel/Stone Dust 1,048,195 73 Weighted Average 922,420 Pervious Area 125,775 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 100 0.0080 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 2.4 788 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 17.0 888 Total Subcatchment E-2: Area To Westerly Basin Runoff = 11.10 cfs @ 12.25 hrs, Volume= 1.116 af, Depth> 1.25" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 29,666 98 Basin 190,948 61 >75% Grass cover, Good, HSG B 126,576 98 Road/Roof 121,118 85 Gravel/Stone Dust 468,308 80 Weighted Average 312,066 Pervious Area 156,242 Impervious Area
  33. 33. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 6Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.3 100 0.0050 0.23 Sheet Flow, Fallow n= 0.050 P2= 3.00" 7.5 376 0.0070 0.84 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 2.1 660 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 16.9 1,136 Total Subcatchment E-3: Direct to Road Drainage Infrastructure Runoff = 6.47 cfs @ 12.30 hrs, Volume= 0.737 af, Depth> 0.85" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 292,465 61 >75% Grass cover, Good, HSG B 139,412 98 Road/Roof 20,044 85 Gravel/Stone Dust 451,921 73 Weighted Average 312,509 Pervious Area 139,412 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 19.5 100 0.0050 0.09 Sheet Flow, Cultivated: Residue>20% n= 0.170 P2= 3.00" Subcatchment E-4: Southeast Area of Site to South Property Line Runoff = 4.21 cfs @ 12.27 hrs, Volume= 0.474 af, Depth> 0.76" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 0 98 Basin 207,984 61 >75% Grass cover, Good, HSG B 36,840 98 Road 19,517 98 Roof 27,926 85 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 71 Weighted Average 271,058 Pervious Area 56,357 Impervious Area
  34. 34. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 7Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.8 100 0.0080 0.92 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 15.5 650 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 17.3 750 Total Subcatchment E-5: Area north of site (includes basketball court) Runoff = 2.15 cfs @ 12.35 hrs, Volume= 0.257 af, Depth> 0.90" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 50,138 61 >75% Grass cover, Good, HSG B 27,807 98 Paved parking 70,681 74 >75% Grass cover, Good, HSG C 148,626 74 Weighted Average 120,819 Pervious Area 27,807 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.4 100 0.0060 0.10 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 4.7 270 0.0040 0.95 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 1.3 125 0.0060 1.57 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.3 50 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 22.7 545 Total Subcatchment E-6: Northeast of Site (Road and abutting property) Runoff = 0.74 cfs @ 12.18 hrs, Volume= 0.067 af, Depth> 1.19" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 15,016 61 >75% Grass cover, Good, HSG B 14,645 98 Paved parking 29,661 79 Weighted Average 15,016 Pervious Area 14,645 Impervious Area
  35. 35. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 8Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 6.3 345 0.0020 0.91 Shallow Concentrated Flow, Paved Kv= 20.3 fps 4.3 180 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.3 625 Total Subcatchment P-1: Area to Easterly Basin Runoff = 26.74 cfs @ 12.25 hrs, Volume= 2.711 af, Depth> 1.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (ac) CN Description 0.230 98 Basins 12.908 61 >75% Grass cover, Good, HSG B 4.046 98 Road/Roof 1.586 85 Existing Gravel/Stone Dust 6.837 96 Proposed TRG Paving 0.702 98 Paved parking & roofs 0.323 96 Proposed TRG Paving 0.433 61 >75% Grass cover, Good, HSG B 0.413 98 27.478 79 Weighted Average 22.087 Pervious Area 5.391 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 100 0.0080 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 2.4 788 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 17.0 888 Total Subcatchment P-2: Area To Westerly Basin Runoff = 10.64 cfs @ 12.24 hrs, Volume= 1.060 af, Depth> 1.37" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00"
  36. 36. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 9Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Area (sf) CN Description 29,666 98 Basin 130,648 61 >75% Grass cover, Good, HSG B 117,154 98 Road/Roof 125,615 85 Gravel/Stone Dust 403,083 82 Weighted Average 256,263 Pervious Area 146,820 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.3 100 0.0050 0.23 Sheet Flow, Fallow n= 0.050 P2= 3.00" 7.5 376 0.0070 0.84 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 2.1 660 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 16.9 1,136 Total Subcatchment P-3: Direct to Road Drainage Infrastructure Runoff = 6.07 cfs @ 12.30 hrs, Volume= 0.674 af, Depth> 0.96" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (ac) CN Description 4.945 61 >75% Grass cover, Good, HSG B 2.085 98 Road/Roof 0.439 85 Gravel/Stone Dust 0.021 96 Proposed TRG Paving 0.968 96 Morgan Rings (stonedust) 8.458 75 Weighted Average 6.373 Pervious Area 2.085 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 19.5 100 0.0050 0.09 Sheet Flow, Cultivated: Residue>20% n= 0.170 P2= 3.00" Subcatchment P-4: Southeast Area of Site to South Property Line Runoff = 4.21 cfs @ 12.27 hrs, Volume= 0.474 af, Depth> 0.76" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00"
  37. 37. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 10Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Area (sf) CN Description 0 98 Basin 207,984 61 >75% Grass cover, Good, HSG B 56,357 98 Road 27,926 85 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 71 Weighted Average 271,058 Pervious Area 56,357 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.8 100 0.0080 0.92 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 15.5 650 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 17.3 750 Total Subcatchment P-5: Area north of site (includes basketball court) Runoff = 2.15 cfs @ 12.35 hrs, Volume= 0.257 af, Depth> 0.90" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 50,138 61 >75% Grass cover, Good, HSG B 27,807 98 Paved parking 70,681 74 >75% Grass cover, Good, HSG C 148,626 74 Weighted Average 120,819 Pervious Area 27,807 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.4 100 0.0060 0.10 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 4.7 270 0.0040 0.95 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 1.3 125 0.0060 1.57 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.3 50 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 22.7 545 Total
  38. 38. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 11Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcatchment P-6: Northeast of Site (Road and abutting property) Runoff = 0.74 cfs @ 12.18 hrs, Volume= 0.067 af, Depth> 1.19" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf) CN Description 15,019 61 >75% Grass cover, Good, HSG B 14,645 98 Paved parking 29,664 79 Weighted Average 15,019 Pervious Area 14,645 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 6.3 345 0.0020 0.91 Shallow Concentrated Flow, Paved Kv= 20.3 fps 4.3 180 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.3 625 Total Reach E-CP1: Williams St. Brook Infrastructure Inflow Area = 24.538 ac, Inflow Depth > 1.32" for 2 YRS event Inflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 af Outflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP2: South Property Line Inflow Area = 32.261 ac, Inflow Depth > 0.33" for 2 YRS event Inflow = 4.21 cfs @ 12.27 hrs, Volume= 0.879 af Outflow = 4.21 cfs @ 12.27 hrs, Volume= 0.879 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP3: Cross Paths Road Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
  39. 39. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 12Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Reach P-CP1: Williams St. Brook Infrastructure Inflow Area = 21.123 ac, Inflow Depth > 1.47" for 2 YRS event Inflow = 7.14 cfs @ 12.32 hrs, Volume= 2.582 af Outflow = 7.14 cfs @ 12.32 hrs, Volume= 2.582 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP2: South Property Line Inflow Area = 35.675 ac, Inflow Depth > 0.16" for 2 YRS event Inflow = 4.21 cfs @ 12.27 hrs, Volume= 0.474 af Outflow = 4.21 cfs @ 12.27 hrs, Volume= 0.474 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP3: Cross Paths Road Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Pond E-Pond1: Existing East Detention Basin Inflow Area = 24.744 ac, Inflow Depth > 0.86" for 2 YRS event Inflow = 16.49 cfs @ 12.26 hrs, Volume= 1.779 af Outflow = 1.13 cfs @ 16.24 hrs, Volume= 0.876 af, Atten= 93%, Lag= 238.7 min Discarded = 0.45 cfs @ 11.85 hrs, Volume= 0.470 af Primary = 0.68 cfs @ 16.24 hrs, Volume= 0.405 af Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.42' @ 16.24 hrs Surf.Area= 42,251 sf Storage= 46,413 cf Plug-Flow detention time= 328.8 min calculated for 0.874 af (49% of inflow) Center-of-Mass det. time= 196.4 min ( 1,072.9 - 876.5 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc)
  40. 40. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 13Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.00 6,800 0 0 113.00 7,463 7,132 7,132 114.00 8,704 8,084 15,215 115.00 10,000 9,352 24,567 116.00 11,362 10,681 35,248 117.00 85,524 48,443 83,691 118.00 272,423 178,974 262,665 118.50 407,822 170,061 432,726 Device Routing Invert Outlet Devices #1 Secondary 117.00' 100.0' 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 #2 Primary 116.00' 12.0" Vert. Invert of 12" CMP Outlet on Fair Street C= 0.600 #3 Discarded 0.00' 0.45 cfs Existing Pump (200gpm) to E-CP1 at all elevations Discarded OutFlow Max=0.45 cfs @ 11.85 hrs HW=112.07' (Free Discharge) 3=Existing Pump (200gpm) to E-CP1 (Exfiltration Controls 0.45 cfs) Primary OutFlow Max=0.68 cfs @ 16.24 hrs HW=116.42' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 0.68 cfs @ 2.20 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.00' TW=0.00' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Pond E-Pond2: Existing West Detention Basin Inflow Area = 14.163 ac, Inflow Depth > 1.16" for 2 YRS event Inflow = 13.03 cfs @ 12.26 hrs, Volume= 1.372 af Outflow = 2.01 cfs @ 13.31 hrs, Volume= 1.064 af, Atten= 85%, Lag= 63.4 min Primary = 2.01 cfs @ 13.31 hrs, Volume= 1.064 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.32' @ 13.31 hrs Surf.Area= 25,722 sf Storage= 27,837 cf Plug-Flow detention time= 220.1 min calculated for 1.064 af (78% of inflow) Center-of-Mass det. time= 135.4 min ( 994.0 - 858.6 ) Volume Invert Avail.Storage Storage Description #1 116.00' 133,406 cf Custom Stage Data (Prismatic) Listed below (Recalc)
  41. 41. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 14Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 116.00 19,210 0 0 117.00 21,276 20,243 20,243 118.00 35,033 28,155 48,398 119.00 64,989 50,011 98,409 119.50 75,000 34,997 133,406 Device Routing Invert Outlet Devices #1 Primary 116.26' 12.0" x 55.0' long Culvert CMP, projecting, no headwall, Ke= 0.900 Outlet Invert= 116.13' S= 0.0024 '/' Cc= 0.900 n= 0.011 Concrete pipe, straight & clean Primary OutFlow Max=2.01 cfs @ 13.31 hrs HW=117.32' TW=0.00' (Dynamic Tailwater) 1=Culvert (Barrel Controls 2.01 cfs @ 2.99 fps) Pond E-Pump: Existing Pump System from East Basin Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base Flow Outflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 0%, Lag= 0.0 min Primary = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.60' @ 0.00 hrs Device Routing Invert Outlet Devices #1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600 Primary OutFlow Max=0.45 cfs @ 0.00 hrs HW=116.60' TW=0.00' (Dynamic Tailwater) 1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps) Pond E-Pump.: Existing Pump System from East Basin Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base Flow Outflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 0%, Lag= 0.0 min Primary = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.60' @ 0.00 hrs Device Routing Invert Outlet Devices #1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600 Primary OutFlow Max=0.45 cfs @ 0.00 hrs HW=116.60' TW=0.00' (Dynamic Tailwater) 1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps)
  42. 42. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 15Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Pond P-Pond 1: Existing East Detention Basin & New Trench Systems Inflow Area = 28.159 ac, Inflow Depth > 1.18" for 2 YRS event Inflow = 27.40 cfs @ 12.25 hrs, Volume= 2.778 af Outflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 98%, Lag= 0.0 min Discarded = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Starting Elev= 112.84' Surf.Area= 55,135 sf Storage= 25,602 cf Peak Elev= 115.73' @ 24.00 hrs Surf.Area= 58,769 sf Storage= 107,696 cf (82,094 cf above start) Plug-Flow detention time= 490.4 min calculated for 0.306 af (11% of inflow) Center-of-Mass det. time= (not calculated: outflow precedes inflow) Volume Invert Avail.Storage Storage Description #1 112.00' 329,498 cf Surface Storage (Prismatic) Listed below (Recalc) #2 112.34' 31,003 cf Trench A (all) (Prismatic) Listed below (Recalc) 80,488 cf Overall - 2,981 cf Embedded = 77,506 cf x 40.0% Voids #3 112.34' 4,408 cf Trench C (west) (Prismatic) Listed below (Recalc) 11,021 cf Overall x 40.0% Voids #4 112.34' 5,735 cf Trench C (east) (Prismatic) Listed below (Recalc) 14,337 cf Overall x 40.0% Voids #5 112.34' 1,682 cf Trench D (north) (Prismatic) Listed below (Recalc) 4,205 cf Overall x 40.0% Voids #6 112.34' 1,682 cf Trench D (south) (Prismatic) Listed below (Recalc) 4,205 cf Overall x 40.0% Voids #7 112.84' 2,981 cf 18.0"D x 168.70'L Pipe In West Trench System x 10 Inside #2 #8 111.84' 2,138 cf 18.0"D x 121.00'L Pipe In East Trench System x 10 Inside #11 #9 111.34' 14,057 cf Trench E (west) (Prismatic) Listed below (Recalc) 35,142 cf Overall x 40.0% Voids #10 111.34' 15,494 cf Trench E (east) (Prismatic) Listed below (Recalc) 38,734 cf Overall x 40.0% Voids #11 111.34' 11,139 cf Trench B (all) (Prismatic) Listed below (Recalc) 29,985 cf Overall - 2,138 cf Embedded = 27,847 cf x 40.0% Voids 419,816 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.00 6,800 0 0 113.00 7,463 7,132 7,132 114.00 8,704 8,084 15,215 115.00 10,000 9,352 24,567 116.00 11,362 10,681 35,248 117.00 95,677 53,520 88,768 118.00 385,783 240,730 329,498
  43. 43. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 16Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.34 17,272 0 0 117.00 17,272 80,488 80,488 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.34 2,499 0 0 116.75 2,499 11,021 11,021 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.34 2,920 0 0 117.25 2,920 14,337 14,337 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.34 1,054 0 0 116.33 1,054 4,205 4,205 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.34 1,054 0 0 116.33 1,054 4,205 4,205 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 111.34 6,460 0 0 116.78 6,460 35,142 35,142 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 111.34 9,311 0 0 115.50 9,311 38,734 38,734 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 111.34 7,208 0 0 115.50 7,208 29,985 29,985 Device Routing Invert Outlet Devices #1 Primary 116.23' 12.0" Vert. Invert of 12" CMP Outlet on Fair Street C= 0.600 #2 Discarded 0.00' 0.45 cfs Existing Pump (200gpm) to P-CP1 at all elevations #3 Secondary 117.20' 550.0' long x 2.0' breadth New Berm on Cross Path Rd (117.15') 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 Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88 2.85 3.07 3.20 3.32
  44. 44. Revised 11/3/10 Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi Page 17Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.45 cfs @ 0.00 hrs HW=112.84' (Free Discharge) 2=Existing Pump (200gpm) to P-CP1 (Exfiltration Controls 0.45 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.84' TW=0.00' (Dynamic Tailwater) 1=Invert of 12" CMP Outlet on Fair Street ( Controls 0.00 cfs) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.84' TW=0.00' (Dynamic Tailwater) 3=New Berm on Cross Path Rd (117.15') ( Controls 0.00 cfs) Pond P-Pond 2: Existing West Detention Basin Inflow Area = 12.665 ac, Inflow Depth > 1.25" for 2 YRS event Inflow = 12.56 cfs @ 12.25 hrs, Volume= 1.316 af Outflow = 1.95 cfs @ 13.26 hrs, Volume= 1.014 af, Atten= 84%, Lag= 60.3 min Primary = 1.95 cfs @ 13.26 hrs, Volume= 1.014 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.30' @ 13.26 hrs Surf.Area= 25,424 sf Storage= 27,284 cf Plug-Flow detention time= 223.0 min calculated for 1.014 af (77% of inflow) Center-of-Mass det. time= 137.9 min ( 991.3 - 853.5 ) Volume Invert Avail.Storage Storage Description #1 116.00' 133,406 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 116.00 19,210 0 0 117.00 21,276 20,243 20,243 118.00 35,033 28,155 48,398 119.00 64,989 50,011 98,409 119.50 75,000 34,997 133,406 Device Routing Invert Outlet Devices #1 Primary 116.26' 12.0" x 55.0' long Culvert CMP, projecting, no headwall, Ke= 0.900 Outlet Invert= 116.13' S= 0.0024 '/' Cc= 0.900 n= 0.011 Concrete pipe, straight & clean Primary OutFlow Max=1.95 cfs @ 13.26 hrs HW=117.30' TW=0.00' (Dynamic Tailwater) 1=Culvert (Barrel Controls 1.95 cfs @ 2.97 fps)
  45. 45. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 18Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Runoff Area=1,048,195 sf Runoff Depth>1.89"Subcatchment E-1: Area to Easterly Basin Flow Length=888' Tc=17.0 min CN=73 Runoff=37.63 cfs 3.787 af Runoff Area=468,308 sf Runoff Depth>2.45"Subcatchment E-2: Area To Westerly Basin Flow Length=1,136' Tc=16.9 min CN=80 Runoff=22.27 cfs 2.198 af Runoff Area=451,921 sf Runoff Depth>1.89"Subcatchment E-3: Direct to Road Drainage Infrastructure Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=15.35 cfs 1.632 af Runoff Area=327,415 sf Runoff Depth>1.74"Subcatchment E-4: Southeast Area of Site to South Property Flow Length=750' Tc=17.3 min CN=71 Runoff=10.65 cfs 1.090 af Runoff Area=148,626 sf Runoff Depth>1.96"Subcatchment E-5: Area north of site (includes basketball c Flow Length=545' Tc=22.7 min CN=74 Runoff=4.96 cfs 0.558 af Runoff Area=29,661 sf Runoff Depth>2.37"Subcatchment E-6: Northeast of Site (Road and abutting prop Flow Length=625' Tc=12.3 min CN=79 Runoff=1.53 cfs 0.135 af Runoff Area=27.478 ac Runoff Depth>2.37"Subcatchment P-1: Area to Easterly Basin Flow Length=888' Tc=17.0 min CN=79 Runoff=54.78 cfs 5.424 af Runoff Area=403,083 sf Runoff Depth>2.63"Subcatchment P-2: Area To Westerly Basin Flow Length=1,136' Tc=16.9 min CN=82 Runoff=20.54 cfs 2.027 af Runoff Area=8.458 ac Runoff Depth>2.04"Subcatchment P-3: Direct to Road Drainage Infrastructure Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=75 Runoff=13.64 cfs 1.439 af Runoff Area=327,415 sf Runoff Depth>1.74"Subcatchment P-4: Southeast Area of Site to South Property Flow Length=750' Tc=17.3 min CN=71 Runoff=10.65 cfs 1.090 af Runoff Area=148,626 sf Runoff Depth>1.96"Subcatchment P-5: Area north of site (includes basketball c Flow Length=545' Tc=22.7 min CN=74 Runoff=4.96 cfs 0.558 af Runoff Area=29,664 sf Runoff Depth>2.37"Subcatchment P-6: Northeast of Site (Road and abutting prop Flow Length=625' Tc=12.3 min CN=79 Runoff=1.53 cfs 0.135 af Inflow=18.21 cfs 4.891 afReach E-CP1: Williams St. Brook Infrastructure Outflow=18.21 cfs 4.891 af Inflow=10.82 cfs 3.136 afReach E-CP2: South Property Line Outflow=10.82 cfs 3.136 af Inflow=1.52 cfs 0.178 afReach E-CP3: Cross Paths Road Outflow=1.52 cfs 0.178 af
  46. 46. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 19Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Inflow=16.48 cfs 4.543 afReach P-CP1: Williams St. Brook Infrastructure Outflow=16.48 cfs 4.543 af Inflow=10.65 cfs 2.620 afReach P-CP2: South Property Line Outflow=10.65 cfs 2.620 af Inflow=0.00 cfs 0.000 afReach P-CP3: Cross Paths Road Outflow=0.00 cfs 0.000 af Peak Elev=117.03' Storage=86,787 cf Inflow=38.97 cfs 3.922 afPond E-Pond1: Existing East Detention B Discarded=0.45 cfs 0.520 af Primary=2.77 cfs 2.046 af Secondary=1.52 cfs 0.178 af Outflow=4.74 cfs 2.745 af Peak Elev=118.29' Storage=59,913 cf Inflow=26.83 cfs 2.756 afPond E-Pond2: Existing West Detention B 12.0" x 55.0' Culvert Outflow=3.70 cfs 2.365 af Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump: Existing Pump System from East Basin Outflow=0.45 cfs 0.894 af Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump.: Existing Pump System from East Basin Outflow=0.45 cfs 0.894 af Peak Elev=117.01' Storage=180,119 cf Inflow=56.15 cfs 5.558 afPond P-Pond 1: Existing East Detention Discarded=0.45 cfs 0.894 af Primary=1.99 cfs 1.531 af Secondary=0.00 cfs 0.000 af Outflow=2.44 cfs 2.425 af Peak Elev=118.21' Storage=56,598 cf Inflow=25.08 cfs 2.585 afPond P-Pond 2: Existing West Detention 12.0" x 55.0' Culvert Outflow=3.60 cfs 2.209 af Total Runoff Area = 113.597 ac Runoff Volume = 20.071 af Average Runoff Depth = 2.12" 77.94% Pervious Area = 88.539 ac 22.06% Impervious Area = 25.058 ac
  47. 47. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 20Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcatchment E-1: Area to Easterly Basin Runoff = 37.63 cfs @ 12.25 hrs, Volume= 3.787 af, Depth> 1.89" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 10,000 98 Basins 574,174 61 >75% Grass cover, Good, HSG B 115,775 98 Road/Roof 348,246 85 Gravel/Stone Dust 1,048,195 73 Weighted Average 922,420 Pervious Area 125,775 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 100 0.0080 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 2.4 788 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 17.0 888 Total Subcatchment E-2: Area To Westerly Basin Runoff = 22.27 cfs @ 12.24 hrs, Volume= 2.198 af, Depth> 2.45" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 29,666 98 Basin 190,948 61 >75% Grass cover, Good, HSG B 126,576 98 Road/Roof 121,118 85 Gravel/Stone Dust 468,308 80 Weighted Average 312,066 Pervious Area 156,242 Impervious Area
  48. 48. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 21Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.3 100 0.0050 0.23 Sheet Flow, Fallow n= 0.050 P2= 3.00" 7.5 376 0.0070 0.84 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 2.1 660 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 16.9 1,136 Total Subcatchment E-3: Direct to Road Drainage Infrastructure Runoff = 15.35 cfs @ 12.28 hrs, Volume= 1.632 af, Depth> 1.89" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 292,465 61 >75% Grass cover, Good, HSG B 139,412 98 Road/Roof 20,044 85 Gravel/Stone Dust 451,921 73 Weighted Average 312,509 Pervious Area 139,412 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 19.5 100 0.0050 0.09 Sheet Flow, Cultivated: Residue>20% n= 0.170 P2= 3.00" Subcatchment E-4: Southeast Area of Site to South Property Line Runoff = 10.65 cfs @ 12.25 hrs, Volume= 1.090 af, Depth> 1.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 0 98 Basin 207,984 61 >75% Grass cover, Good, HSG B 36,840 98 Road 19,517 98 Roof 27,926 85 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 71 Weighted Average 271,058 Pervious Area 56,357 Impervious Area
  49. 49. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 22Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.8 100 0.0080 0.92 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 15.5 650 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 17.3 750 Total Subcatchment E-5: Area north of site (includes basketball court) Runoff = 4.96 cfs @ 12.33 hrs, Volume= 0.558 af, Depth> 1.96" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 50,138 61 >75% Grass cover, Good, HSG B 27,807 98 Paved parking 70,681 74 >75% Grass cover, Good, HSG C 148,626 74 Weighted Average 120,819 Pervious Area 27,807 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.4 100 0.0060 0.10 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 4.7 270 0.0040 0.95 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 1.3 125 0.0060 1.57 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.3 50 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 22.7 545 Total Subcatchment E-6: Northeast of Site (Road and abutting property) Runoff = 1.53 cfs @ 12.17 hrs, Volume= 0.135 af, Depth> 2.37" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 15,016 61 >75% Grass cover, Good, HSG B 14,645 98 Paved parking 29,661 79 Weighted Average 15,016 Pervious Area 14,645 Impervious Area
  50. 50. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 23Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 6.3 345 0.0020 0.91 Shallow Concentrated Flow, Paved Kv= 20.3 fps 4.3 180 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.3 625 Total Subcatchment P-1: Area to Easterly Basin Runoff = 54.78 cfs @ 12.24 hrs, Volume= 5.424 af, Depth> 2.37" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (ac) CN Description 0.230 98 Basins 12.908 61 >75% Grass cover, Good, HSG B 4.046 98 Road/Roof 1.586 85 Existing Gravel/Stone Dust 6.837 96 Proposed TRG Paving 0.702 98 Paved parking & roofs 0.323 96 Proposed TRG Paving 0.433 61 >75% Grass cover, Good, HSG B 0.413 98 27.478 79 Weighted Average 22.087 Pervious Area 5.391 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.6 100 0.0080 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 2.4 788 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 17.0 888 Total Subcatchment P-2: Area To Westerly Basin Runoff = 20.54 cfs @ 12.23 hrs, Volume= 2.027 af, Depth> 2.63" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50"
  51. 51. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 24Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Area (sf) CN Description 29,666 98 Basin 130,648 61 >75% Grass cover, Good, HSG B 117,154 98 Road/Roof 125,615 85 Gravel/Stone Dust 403,083 82 Weighted Average 256,263 Pervious Area 146,820 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.3 100 0.0050 0.23 Sheet Flow, Fallow n= 0.050 P2= 3.00" 7.5 376 0.0070 0.84 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 2.1 660 0.0100 5.36 4.21 Circular Channel (pipe), Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.011 Concrete pipe, straight & clean 16.9 1,136 Total Subcatchment P-3: Direct to Road Drainage Infrastructure Runoff = 13.64 cfs @ 12.28 hrs, Volume= 1.439 af, Depth> 2.04" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (ac) CN Description 4.945 61 >75% Grass cover, Good, HSG B 2.085 98 Road/Roof 0.439 85 Gravel/Stone Dust 0.021 96 Proposed TRG Paving 0.968 96 Morgan Rings (stonedust) 8.458 75 Weighted Average 6.373 Pervious Area 2.085 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 19.5 100 0.0050 0.09 Sheet Flow, Cultivated: Residue>20% n= 0.170 P2= 3.00" Subcatchment P-4: Southeast Area of Site to South Property Line Runoff = 10.65 cfs @ 12.25 hrs, Volume= 1.090 af, Depth> 1.74" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50"
  52. 52. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 25Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Area (sf) CN Description 0 98 Basin 207,984 61 >75% Grass cover, Good, HSG B 56,357 98 Road 27,926 85 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 71 Weighted Average 271,058 Pervious Area 56,357 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.8 100 0.0080 0.92 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 15.5 650 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 17.3 750 Total Subcatchment P-5: Area north of site (includes basketball court) Runoff = 4.96 cfs @ 12.33 hrs, Volume= 0.558 af, Depth> 1.96" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 50,138 61 >75% Grass cover, Good, HSG B 27,807 98 Paved parking 70,681 74 >75% Grass cover, Good, HSG C 148,626 74 Weighted Average 120,819 Pervious Area 27,807 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 16.4 100 0.0060 0.10 Sheet Flow, Grass: Short n= 0.150 P2= 3.00" 4.7 270 0.0040 0.95 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 1.3 125 0.0060 1.57 Shallow Concentrated Flow, Paved Kv= 20.3 fps 0.3 50 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 22.7 545 Total
  53. 53. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 26Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcatchment P-6: Northeast of Site (Road and abutting property) Runoff = 1.53 cfs @ 12.17 hrs, Volume= 0.135 af, Depth> 2.37" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf) CN Description 15,019 61 >75% Grass cover, Good, HSG B 14,645 98 Paved parking 29,664 79 Weighted Average 15,019 Pervious Area 14,645 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.0100 1.01 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.00" 6.3 345 0.0020 0.91 Shallow Concentrated Flow, Paved Kv= 20.3 fps 4.3 180 0.0100 0.70 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 12.3 625 Total Reach E-CP1: Williams St. Brook Infrastructure Inflow Area = 24.538 ac, Inflow Depth > 2.39" for 10 YRS event Inflow = 18.21 cfs @ 12.29 hrs, Volume= 4.891 af Outflow = 18.21 cfs @ 12.29 hrs, Volume= 4.891 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP2: South Property Line Inflow Area = 32.261 ac, Inflow Depth > 1.17" for 10 YRS event Inflow = 10.82 cfs @ 12.28 hrs, Volume= 3.136 af Outflow = 10.82 cfs @ 12.28 hrs, Volume= 3.136 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach E-CP3: Cross Paths Road Inflow = 1.52 cfs @ 13.70 hrs, Volume= 0.178 af Outflow = 1.52 cfs @ 13.70 hrs, Volume= 0.178 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
  54. 54. Revised 11/3/10 Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per Page 27Prepared by The Berkshire Design Group 11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Reach P-CP1: Williams St. Brook Infrastructure Inflow Area = 21.123 ac, Inflow Depth > 2.58" for 10 YRS event Inflow = 16.48 cfs @ 12.29 hrs, Volume= 4.543 af Outflow = 16.48 cfs @ 12.29 hrs, Volume= 4.543 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP2: South Property Line Inflow Area = 35.675 ac, Inflow Depth > 0.88" for 10 YRS event Inflow = 10.65 cfs @ 12.25 hrs, Volume= 2.620 af Outflow = 10.65 cfs @ 12.25 hrs, Volume= 2.620 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Reach P-CP3: Cross Paths Road Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Pond E-Pond1: Existing East Detention Basin Inflow Area = 24.744 ac, Inflow Depth > 1.90" for 10 YRS event Inflow = 38.97 cfs @ 12.24 hrs, Volume= 3.922 af Outflow = 4.74 cfs @ 13.70 hrs, Volume= 2.745 af, Atten= 88%, Lag= 87.5 min Discarded = 0.45 cfs @ 10.90 hrs, Volume= 0.520 af Primary = 2.77 cfs @ 13.70 hrs, Volume= 2.046 af Secondary = 1.52 cfs @ 13.70 hrs, Volume= 0.178 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.03' @ 13.70 hrs Surf.Area= 92,042 sf Storage= 86,787 cf Plug-Flow detention time= 271.3 min calculated for 2.745 af (70% of inflow) Center-of-Mass det. time= 172.5 min ( 1,025.2 - 852.7 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc)

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