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Fairgrounds Phase 1 Stormwater Permit Report Stormwater Drainage Report ______________________________________________________________________________________ for Three County Fairgrounds Phase 1 Redevelopment Plan Northampton, MA March 18, 2010 Prepared by: 4 Allen Place, Northampton, Massachusetts 01060 Prepared for: Three County Fairgrounds 59 Fair Street Northampton, MA 01060 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 82 • Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. 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): 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. 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 predevelopment 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 – Reduction in Impervious Area = Same or greater recharge on site Soil Analysis provided. Required Recharge Volume calculation provided. Required Recharge volume reduced through use of the LID site Design Credits. Sizing the infiltration, BMPs is based on the following method: Check the method used. Static Simple Dynamic Dynamic Field1 Runoff from all impervious areas at the site discharging to the infiltration BMP. Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: Site is comprised solely of C and D soils and/or bedrock at the land surface M.G.L. c. 21E sites pursuant to 310 CMR 40.0000 Solid Waste Landfill pursuant to 310 CMR 19.000 Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. – Redevelopment project with less impervious area proposed 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. 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; 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. 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: MASTEP review The ½” or 1” Water Quality Volume or The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume. The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary BMP and proposed TSS removal rate is provided. This documentation may be in the form of the propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying performance of the proprietary BMPs. A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing that the BMPs selected are consistent with the TMDL is provided. Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) 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. 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. 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 DRAFT 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. Three County Fairgrounds -Phase 1 March 18, 2010 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 Stormwater Standards 7 Summary 9 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 Operation &Maintenance Plan Appendix D Long Term Pollution Prevention Plan Appendix E Stormwater Pollution Prevention and Erosion Control Plan Appendix F Water Quality Information Three County Fairgrounds -Phase 1 March 18, 2010 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 small portion of the site. The 15 existing horse barns and 2 other small buildings will be demolished and 3 new barns are proposed to be constructed. The drainage areas analyzed total 56.80 acres of which approximately 6.62 acres will be disturbed by construction activities. The impervious area on site will decrease by approximately 620sf due to the demolition of many of the existing buildings. The existing stormwater management system is sufficient to minimize proposed peak flows to reduce or match the existing flows off the site, recharge appropriate volumes of stormwater, and treat stormwater to the maximum extent Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 3 practicable. Mechanisms to reduce runoff and treat water quality include existing deep sump catch basins, new drains with sumps, 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: Three County Fairgrounds -Phase 1 March 18, 2010 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 to the other existing pond on the west side of the site (shown as E-Pond2 on Figure 1) in order to drain the adjacent area. The westerly basin discharges to the Williams Street Brook system (shown as ECP2 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 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 Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 5 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 patterns. The proposed site contains 6 drainage areas (P-1 through P-6) and 3 different control points used for determining peak runoff rates, and the site has an average curve number of 74 (the same as existing conditions). 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 24.06 acres and contains the 3 new horse barns, a large area of the existing track, other miscellaneous buildings, grassed areas, paved areas, and gravel areas. The 3 new horse barns will generally drain to a new drain system installed under 2 new concrete pads between the barns. Each pad contains 5 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. The drains are all designed with sumps and they are directed to a deep sump hooded catch basin which discharge to a StormCeptor 2400 unit prior to discharging to the detention basin to maximize TSS removal. 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 rest of the existing 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 2 outlets. The first outlet is a 12” CMP located on the north edge of Fair Street which discharges water across across the street to the property line located at the south eastern area of the site (shown as P-CP1 on Figure 2). The second outlet is a catch basin located just south of Horse Barn H & C (which will be removed in proposed conditions). When the level of water in the pond exceeds elevation 117’, it overflows out of the catch basin and spills over Fair Street into adjacent property (shown as P-CP3 on Figure 2) causing standing water in the spring and summer and frozen ponding in the winter. Occasionally when a large fairgrounds event is planned, the retention pond is pumped to the other existing pond on the west side of the site (shown as P-Pond2 on Figure 2) in order to drain the adjacent area. The westerly basin discharges to the Williams Street Brook system (shown as P-CP2 on Figure 2) which is undersized in most storms. P-2 P-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 (P-Pond2). Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 6 The detention pond discharges into the Williams Street Brook drainage system through a 12” pipe (P-CP1). P-3 P-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 (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). 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 Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 7 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 In the post development conditions the runoff from the proposed site will be reduced due to a reduction of impervious area. Table 1 below presents the comparison of flow rates and water quantity at both existing and proposed control points. Table 1 Peak Flow and Volume Summary *Names in parentheses refer to HydroCad model and calculations. I. I. MADEP Stormwater Standards Compliance 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)* 2.899 0.00 0.000 1.29 0.162 33.55 2.792 0.00 0.000 1.79 0.241 35.24 33.55 7.003 6.83 1.669 17.62 3.798 32.57 6.908 6.86 1.697 17.66 3.854 2-Year Storm 10-Year Storm 100-Year Storm 3.00” 4.50” 6.50” 22.81 4.596 3.85 1.024 10.21 3.237 22.72 4.590 3.85 1.091 10.37 3.256 Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 8 The following section details how the project will meet DEP Stormwater Management Policy’s ten stormwater management standards. This project is a Redevelopment Project and Volume 2 Chapter 3 of the MA DEP Stormwater handbook was utilized to ensure that the project will comply with the standards to the maximum extent practicable. Standard 1 -Untreated Stormwater The proposed redevelopment will utilize the existing stormwater management system and will not create any new discharges as the runoff from the new barns will be directed to the existing easterly detention basin. The impervious area on site will be reduced in proposed conditions and the majority of the new impervious area will be directed to 2 drain systems between the barns, which are equipped with sumps to remove potential solids the may enter the system. The roof runoff will be directly piped into the system as MA DEP recommends. In addition, measures have been taking to ensure manure from the barns does not enter the drainage system as it does in existing conditions by enforcing employees to cover the drain system prior to moving and disposing of any manure. Do to the improved water quality and reduction in impervious area, the project site will comply with Standard 1 as required for a redevelopment project Standard 2 -Post-Development Peak Discharge Rates The proposed project will have a net loss of 620sf of impervious area so the site will generate less runoff in proposed conditions. The existing stormwater system is sufficiently designed to ensure that post-development peak discharge rates are equal or less than pre-development peak discharge rates leaving the site. Refer to Table 1 Peak Flow and Volume Summary and Appendix A for HydroCAD calculations. Standard 3 -Recharge to Groundwater The proposed project will improve the recharge opportunities on site by reducing the impervious area from existing conditions as the proposed project will have a net loss of 620sf of impervious area. Redevelopment projects require that proposed sites approximate the annual recharge from the existing site. The net loss in impervious area provides the site with the equal or greater opportunity for water to infiltrate into the ground and recharge the groundwater to the maximum extent practicable as required for redevelopment projects. Standard 4 – Water Quality The proposed redevelopment will utilize the existing detention basin at the east end of the site and a series of drains located within new concrete pads between the new barns. There are 5 drains per pad and all contain a 2’ sump system which directs the stormwater to a deep sump hooded catch basin which providing additional pretreatment for the stormwater. The new catch basin will discharge to a StormCeptor 2400 unit allowing prior to entering the existing detention basin, Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 9 achieving a combined TSS removal rate of approximately 83% improving water quality to the maximum extent practicable as required for redevelopment projects. The proposed manure management system will also increase the water quality as the existing site does not have measures in place to prevent manure from entering the stormwater system and causing contamination. To ensure that the water quality on site will improve and be maintained at the proper level of performance, an operation and maintenance plan has been incorporated into the plans to ensure that the existing catch basins and detention basins are maintained in order to ensure that they will function efficiently. The reduction in impervious area will also allow the stormwater management system to function more efficiently. Based on the improvements to the existing conditions and treatment capabilities of the new and existing stormwater BMPs, the project effectively meets the standard 4 and improves existing conditions. Note that a Long Term Pollution Prevention Plan will be implemented to maintain a clean site and ensure that all BMPs are functioning to their maximum potential. See Appendix D for Long Term Pollution Prevention Plan. 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 as per the MA DEP Volume 2 Chapter 3 definition: A “Redevelopment is defined to include: Development rehabilitation, expansion and phased projects on previously developed sites, provided the redevelopment results in no net increase in impervious area”. The project has a proposed reduction in impervious area and has incorporated the redevelopment checklist as guidance for the design. Standard 8 -Erosion/Sediment Control Erosion and sediment controls have been incorporated into the project design to prevent erosion, control sediments, and stabilized exposed soils during construction and land disturbance. See Appendix E for Construction Period Pollution Prevention and Erosion Sedimentation Control. Standard 9 -Operation/Maintenance Plan An Operation and Maintenance Plan for the proposed project is included in Appendix C. It includes general controls for construction and long term maintenance of the stormwater management system. Three County Fairgrounds -Phase 1 March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 10 Standard 10 – Prohibition of Illicit Discharges No Illicit Discharge Compliance Statement is included with this report however one will be submitted prior to the discharge of any stormwater to postconstruction BMPs. VII. Summary The impervious area from existing to proposed conditions will decrease by approximately 620sf from the demolition of existing buildings and construction of the 3 new barns. The combination of the new drain systems adjacent to the barns along, the StormCeptor unit, and the existing stormwater management system improves the site stormwater system and will meet the required standards for an MA DEP Redevelopment project. Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Figures Figures Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix A – Pre-and Post Development Hydrologic Calculations 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 LineP-CP3 Cross Paths Road E-Pond1 Existing East Detention E-Pond2 Basin Existing West Detention Basin P-Pond 1 Existing East Detention Basin P-Pond 2 Existing West Detention Basin Drainage Diagram for Three Country Fairgrounds Phase 1-Active Prepared by The Berkshire Design Group 3/22/2010 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC Subcat Reach Pond Pond Link Three Country Fairgrounds Phase 1-Active Prepared by The Berkshire Design Group Page 2 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Area Listing (selected nodes) Area (acres) CN Description (subcats) 61.511 61 >75% Grass cover, Good, HSG B (E-1,E-2,E-3,E-4,E-5,E-6,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) 23.355 80 Gravel/Stone Dust (E-1,E-2,E-3,E-4,P-1,P-2,P-3,P-4) 1.362 98 Basin (E-2,E-3,E-4,P-2,P-3,P-4) 0.459 98 Basins (E-1,P-1) 1.949 98 Paved parking (E-5,E-6,P-5,P-6) 9.391 98 Road (E-1,E-2,E-3,E-4,P-1,P-2,P-3,P-4) 10.711 98 Roof (E-1,E-2,E-3,E-4,P-1,P-2,P-3,P-4) 113.596 Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 3 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Subcatchment E-1: Area to Easterly Basin Runoff Area=1,048,195 sf Runoff Depth>0.80" Flow Length=888' Tc=17.0 min CN=72 Runoff=14.69 cfs 1.613 af Subcatchment E-2: Area To Westerly Basin Runoff Area=468,308 sf Runoff Depth>1.12" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=9.89 cfs 1.007 af Subcatchment E-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>0.85" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=6.47 cfs 0.737 af Subcatchment E-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>0.71" Flow Length=750' Tc=17.3 min CN=70 Runoff=3.85 cfs 0.445 af Subcatchment E-5: Area north of site ((includes basketball c Runoff Area=148,626 sf Runoff Depth>0.90" Flow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af Subcatchment E-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>1.19" Flow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af Subcatchment P-1: Area to Easterly Basin Runoff Area=1,062,120 sf Runoff Depth>0.76" Flow Length=888' Tc=17.0 min CN=71 Runoff=13.74 cfs 1.538 af Subcatchment P-2: Area To Westerly Basin Runoff Area=454,383 sf Runoff Depth>1.12" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=9.59 cfs 0.977 af Subcatchment P-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>0.85" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=6.47 cfs 0.737 af Subcatchment P-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>0.71" Flow Length=750' Tc=17.3 min CN=70 Runoff=3.85 cfs 0.445 af Subcatchment P-5: Area north of site (includes basketball c Runoff Area=148,626 sf Runoff Depth>0.90" Flow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af Subcatchment P-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>1.19" Flow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af Reach E-CP1: Williams St. Brook Infrastructure Inflow=6.86 cfs 1.697 af Outflow=6.86 cfs 1.697 af Reach E-CP2: South Property Line Inflow=3.85 cfs 1.091 af Outflow=3.85 cfs 1.091 af Reach E-CP3: Cross Paths Road Inflow=0.00 cfs 0.000 af Outflow=0.00 cfs 0.000 af Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 4 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow=6.83 cfs 1.669 af Outflow=6.83 cfs 1.669 af Reach P-CP2: South Property Line Inflow=3.85 cfs 1.024 af Outflow=3.85 cfs 1.024 af Reach P-CP3: Cross Paths Road Inflow=0.00 cfs 0.000 af Outflow=0.00 cfs 0.000 af Pond E-Pond1: Existing East Detention B Peak Elev=116.49' Storage=49,652 cf Inflow=15.33 cfs 1.680 af Primary=0.91 cfs 0.646 af Secondary=0.00 cfs 0.000 af Outflow=0.91 cfs 0.646 af Pond E-Pond2: Existing West Detention B Peak Elev=117.23' Storage=25,436 cf Inflow=11.84 cfs 1.264 af 12.0" x 55.0' Culvert Outflow=1.76 cfs 0.960 af Pond P-Pond 1: Existing East Detention B Peak Elev=116.46' Storage=48,428 cf Inflow=14.38 cfs 1.605 af Primary=0.82 cfs 0.578 af Secondary=0.00 cfs 0.000 af Outflow=0.82 cfs 0.578 af Pond P-Pond 2: Existing West Detention Peak Elev=117.21' Storage=24,919 cf Inflow=11.54 cfs 1.234 af 12.0" x 55.0' Culvert Outflow=1.71 cfs 0.932 af Total Runoff Area = 113.596 ac Runoff Volume = 8.149 af Average Runoff Depth = 0.86" 78.99% Pervious Area = 89.724 ac 21.01% Impervious Area = 23.872 ac Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 5 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Subcatchment E-1: Area to Easterly Basin Runoff = 14.69 cfs @12.26 hrs, Volume= 1.613 af, Depth> 0.80" 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 25,182 98 Road 90,593 98 Roof 348,246 80 Gravel/Stone Dust 1,048,195 72 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 = 9.89 cfs @12.25 hrs, Volume= 1.007 af, Depth> 1.12" 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 56,968 98 Road 69,608 98 Roof 121,118 80 Gravel/Stone Dust 468,308 78 Weighted Average 312,066 Pervious Area 156,242 Impervious Area Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 6 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 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 = 3.85 cfs @12.28 hrs, Volume= 0.445 af, Depth> 0.71" 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 Weighted Average 271,058 Pervious Area 56,357 Impervious Area Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 7 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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= 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 Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 8 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 = 13.74 cfs @12.27 hrs, Volume= 1.538 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 10,000 98 Basins 601,924 61 >75% Grass cover, Good, HSG B 25,182 98 Road 98,595 98 Roof 326,419 80 Gravel/Stone Dust 1,062,120 71 Weighted Average 928,343 Pervious Area 133,777 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 = 9.59 cfs @12.25 hrs, Volume= 0.977 af, Depth> 1.12" 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 181,148 61 >75% Grass cover, Good, HSG B 56,968 98 Road 60,986 98 Roof 125,615 80 Gravel/Stone Dust 454,383 78 Weighted Average Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 9 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 306,763 Pervious Area 147,620 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 = 6.47 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 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 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 P-4: Southeast Area of Site to South Property Line Runoff = 3.85 cfs @12.28 hrs, Volume= 0.445 af, Depth> 0.71" 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" Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 10 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 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 Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 11 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 15,016 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 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 > 0.83" for 2 YRS event Inflow = 6.86 cfs @12.32 hrs, Volume= 1.697 af Outflow = 6.86 cfs @12.32 hrs, Volume= 1.697 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 > 0.41" for 2 YRS event Inflow = 3.85 cfs @12.28 hrs, Volume= 1.091 af Outflow = 3.85 cfs @12.28 hrs, Volume= 1.091 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 Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 12 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow Area = 24.218 ac, Inflow Depth > 0.83" for 2 YRS event Inflow = 6.83 cfs @12.32 hrs, Volume= 1.669 af Outflow = 6.83 cfs @12.32 hrs, Volume= 1.669 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 = 32.580 ac, Inflow Depth > 0.38" for 2 YRS event Inflow = 3.85 cfs @12.28 hrs, Volume= 1.024 af Outflow = 3.85 cfs @12.28 hrs, Volume= 1.024 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 > 0.81" for 2 YRS event Inflow = 15.33 cfs @12.26 hrs, Volume= 1.680 af Outflow = 0.91 cfs @17.12 hrs, Volume= 0.646 af, Atten= 94%, Lag= 291.7 min Primary = 0.91 cfs @17.12 hrs, Volume= 0.646 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= 116.49' @17.12 hrs Surf.Area= 47,597 sf Storage= 49,652 cf Plug-Flow detention time= 387.7 min calculated for 0.646 af (38% of inflow) Center-of-Mass det. time= 245.3 min ( 1,125.1 -879.8 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) 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 Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 13 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Primary OutFlow Max=0.91 cfs @17.12 hrs HW=116.49' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 0.91 cfs @2.38 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 > 1.07" for 2 YRS event Inflow = 11.84 cfs @12.26 hrs, Volume= 1.264 af Outflow = 1.76 cfs @13.47 hrs, Volume= 0.960 af, Atten= 85%, Lag= 72.5 min Primary = 1.76 cfs @13.47 hrs, Volume= 0.960 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.23' @13.47 hrs Surf.Area= 24,404 sf Storage= 25,436 cf Plug-Flow detention time= 225.6 min calculated for 0.960 af (76% of inflow) Center-of-Mass det. time= 136.6 min ( 1,000.8 -864.2 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=1.76 cfs @13.47 hrs HW=117.23' TW=0.00' (Dynamic Tailwater) 1=Culvert (Barrel Controls 1.76 cfs @2.89 fps) Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 14 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Pond P-Pond 1: Existing East Detention Basin Inflow Area = 25.064 ac, Inflow Depth > 0.77" for 2 YRS event Inflow = 14.38 cfs @12.26 hrs, Volume= 1.605 af Outflow = 0.82 cfs @17.46 hrs, Volume= 0.578 af, Atten= 94%, Lag= 311.9 min Primary = 0.82 cfs @17.46 hrs, Volume= 0.578 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= 116.46' @17.46 hrs Surf.Area= 45,651 sf Storage= 48,428 cf Plug-Flow detention time= 399.0 min calculated for 0.577 af (36% of inflow) Center-of-Mass det. time= 253.7 min ( 1,137.0 -883.2 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) 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 Primary OutFlow Max=0.82 cfs @17.46 hrs HW=116.46' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 0.82 cfs @2.32 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 P-Pond 2: Existing West Detention Basin Inflow Area = 13.843 ac, Inflow Depth > 1.07" for 2 YRS event Inflow = 11.54 cfs @12.26 hrs, Volume= 1.234 af Outflow = 1.71 cfs @13.49 hrs, Volume= 0.932 af, Atten= 85%, Lag= 73.9 min Primary = 1.71 cfs @13.49 hrs, Volume= 0.932 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 Three Country Fairgrounds Phase 1-Active YRS Rainfall=3.00" Prepared by The Berkshire Design Group Page 15 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Peak Elev= 117.21' @13.49 hrs Surf.Area= 24,111 sf Storage= 24,919 cf Plug-Flow detention time= 227.4 min calculated for 0.932 af (76% of inflow) Center-of-Mass det. time= 137.5 min ( 1,001.8 -864.3 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=1.71 cfs @13.49 hrs HW=117.21' TW=0.00' (Dynamic Tailwater) 1=Culvert (Barrel Controls 1.71 cfs @2.86 fps) Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 16 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Subcatchment E-1: Area to Easterly Basin Runoff Area=1,048,195 sf Runoff Depth>1.81" Flow Length=888' Tc=17.0 min CN=72 Runoff=35.96 cfs 3.637 af Subcatchment E-2: Area To Westerly Basin Runoff Area=468,308 sf Runoff Depth>2.29" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=20.70 cfs 2.047 af Subcatchment E-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>1.89" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=15.35 cfs 1.632 af Subcatchment E-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>1.67" Flow Length=750' Tc=17.3 min CN=70 Runoff=10.14 cfs 1.044 af Subcatchment E-5: Area north of site (includes basketball c Runoff Area=148,626 sf Runoff Depth>1.96" Flow Length=545' Tc=22.7 min CN=74 Runoff=4.96 cfs 0.558 af Subcatchment E-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>2.37" Flow Length=625' Tc=12.3 min CN=79 Runoff=1.53 cfs 0.135 af Subcatchment P-1: Area to Easterly Basin Runoff Area=1,062,120 sf Runoff Depth>1.74" Flow Length=888' Tc=17.0 min CN=71 Runoff=34.76 cfs 3.535 af Subcatchment P-2: Area To Westerly Basin Runoff Area=454,383 sf Runoff Depth>2.29" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=20.08 cfs 1.986 af Subcatchment P-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>1.89" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=15.35 cfs 1.632 af Subcatchment P-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>1.67" Flow Length=750' Tc=17.3 min CN=70 Runoff=10.14 cfs 1.044 af Subcatchment P-5: Area north of site (includes basketball c Runoff Area=148,626 sf Runoff Depth>1.96" 1.96" Flow Length=545' Tc=22.7 min CN=74 Runoff=4.96 cfs 0.558 af Subcatchment P-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>2.37" Flow Length=625' Tc=12.3 min CN=79 Runoff=1.53 cfs 0.135 af Reach E-CP1: Williams St. Brook Infrastructure Inflow=17.66 cfs 3.854 af Outflow=17.66 cfs 3.854 af Reach E-CP2: South Property Line Inflow=10.37 cfs 3.256 af Outflow=10.37 cfs 3.256 af Reach E-CP3: Cross Paths Road Inflow=1.79 cfs 0.241 af Outflow=1.79 cfs 0.241 af Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 17 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow=17.62 cfs 3.798 af Outflow=17.62 cfs 3.798 af Reach P-CP2: South Property Line Inflow=10.21 cfs 3.237 af Outflow=10.21 cfs 3.237 af Reach P-CP3: Cross Paths Road Inflow=1.29 cfs 0.162 af Outflow=1.29 cfs 0.162 af Pond E-Pond1: Existing East Detention B Peak Elev=117.04' Storage=87,154 cf Inflow=37.30 cfs 3.771 af Primary=2.78 cfs 2.212 af Secondary=1.79 cfs 0.241 af Outflow=4.57 cfs 2.453 af Pond E-Pond2: Existing West Detention B Peak Elev=118.19' Storage=55,628 cf Inflow=25.28 cfs 2.605 af 12.0" x 55.0' Culvert Outflow=3.57 cfs 2.222 af Pond P-Pond 1: Existing East Detention B Peak Elev=117.03' Storage=86,444 cf Inflow=36.09 cfs 3.669 af Primary=2.76 cfs 2.192 af Secondary=1.29 cfs 0.162 af Outflow=4.04 cfs 2.354 af Pond P-Pond 2: Existing West Detention Peak Elev=118.16' Storage=54,241 cf Inflow=24.67 cfs 2.544 af 12.0" x 55.0' Culvert Outflow=3.53 cfs 2.166 af Total Runoff Area = 113.596 ac Runoff Volume = 17.942 af Average Runoff Depth = 1.90" 78.99% Pervious Area = 89.724 ac 21.01% Impervious Area = 23.872 ac Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 18 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Subcatchment E-1: Area to Easterly Basin Runoff = 35.96 cfs @12.25 hrs, Volume= 3.637 af, Depth> 1.81" 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 25,182 98 Road 90,593 98 Roof 348,246 80 Gravel/Stone Dust 1,048,195 72 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 = 20.70 cfs @12.24 hrs, Volume= 2.047 af, af, Depth> 2.29" 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 56,968 98 Road 69,608 98 Roof 121,118 80 Gravel/Stone Dust 468,308 78 Weighted Average 312,066 Pervious Area 156,242 Impervious Area Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 19 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 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 = 10.14 cfs @12.26 hrs, Volume= 1.044 af, Depth> 1.67" 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 Weighted Average 271,058 Pervious Area 56,357 Impervious Area Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 20 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 21 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 = 34.76 cfs @12.25 hrs, Volume= 3.535 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 10,000 98 Basins 601,924 61 >75% Grass cover, Good, HSG B 25,182 98 Road 98,595 98 Roof 326,419 80 Gravel/Stone Dust 1,062,120 71 Weighted Average 928,343 Pervious Area 133,777 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 = 20.08 cfs @12.24 hrs, Volume= 1.986 af, Depth> 2.29" 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 181,148 61 >75% Grass cover, Good, HSG B 56,968 98 Road 60,986 98 Roof 125,615 80 Gravel/Stone Dust 454,383 78 Weighted Average Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 22 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 306,763 Pervious Area 147,620 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 = 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 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 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 P-4: Southeast Area of Site to South Property Line Runoff = 10.14 cfs @12.26 hrs, Volume= 1.044 af, Depth> 1.67" 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" Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 23 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 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 Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 24 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 15,016 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 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 > 1.88" for 10 YRS event Inflow = 17.66 cfs @12.29 hrs, Volume= 3.854 af Outflow = 17.66 cfs @12.29 hrs, Volume= 3.854 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 > 1.21" for 10 YRS event Inflow = 10.37 cfs @12.29 hrs, Volume= 3.256 af Outflow = 10.37 cfs @12.29 hrs, Volume= 3.256 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 = 1.79 cfs @13.73 hrs, Volume= 0.241 af Outflow = 1.79 cfs @13.73 hrs, Volume= 0.241 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 25 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow Area = 24.218 ac, Inflow Depth > 1.88" for 10 YRS event Inflow = 17.62 cfs @12.29 hrs, Volume= 3.798 af Outflow = 17.62 cfs @12.29 hrs, Volume= 3.798 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 = 32.580 ac, Inflow Depth > 1.19" for 10 YRS event Inflow = 10.21 cfs @12.28 hrs, Volume= 3.237 af Outflow = 10.21 cfs @12.28 hrs, Volume= 3.237 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 = 1.29 cfs @14.02 hrs, Volume= 0.162 af Outflow = 1.29 cfs @14.02 hrs, Volume= 0.162 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-E-Pond1: Existing East Detention Basin Inflow Area = 24.744 ac, Inflow Depth > 1.83" for 10 YRS event Inflow = 37.30 cfs @12.24 hrs, Volume= 3.771 af Outflow = 4.57 cfs @13.73 hrs, Volume= 2.453 af, Atten= 88%, Lag= 89.2 min Primary = 2.78 cfs @13.73 hrs, Volume= 2.212 af Secondary = 1.79 cfs @13.73 hrs, Volume= 0.241 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.04' @13.73 hrs Surf.Area= 92,784 sf Storage= 87,154 cf Plug-Flow detention time= 289.0 min calculated for 2.448 af (65% of inflow) Center-of-Mass det. time= 182.8 min ( 1,038.0 -855.3 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) 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 Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 26 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Primary OutFlow Max=2.78 cfs @13.73 hrs HW=117.04' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 2.78 cfs @3.53 fps) Secondary OutFlow Max=1.79 cfs @13.73 hrs HW=117.04' TW=0.00' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir (Weir Controls 1.79 cfs @0.46 fps) Pond E-Pond2: Existing West Detention Basin Inflow Area = 14.163 ac, Inflow Depth > 2.21" for 10 YRS event Inflow = 25.28 cfs @12.25 hrs, Volume= 2.605 af Outflow = 3.57 cfs @13.31 hrs, Volume= 2.222 af, Atten= 86%, Lag= 63.4 min Primary = 3.57 cfs @13.31 hrs, Volume= 2.222 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 118.19' @13.31 hrs Surf.Area= 40,749 sf Storage= 55,628 cf Plug-Flow detention time= 218.7 min calculated for 2.222 af (85% of inflow) Center-of-Mass det. time= 155.6 min ( 998.8 -843.3 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=3.57 cfs @13.31 hrs HW=118.19' TW=0.00' (Dynamic Tailwater) 1=Culvert (Inlet Controls 3.57 cfs @4.55 fps) Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 27 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Pond P-Pond 1: Existing East Detention Basin Inflow Area = 25.064 ac, Inflow Depth > 1.76" for 10 YRS event Inflow = 36.09 cfs @12.25 hrs, Volume= 3.669 af Outflow = 4.04 cfs @14.02 hrs, Volume= 2.354 af, Atten= 89%, Lag= 106.5 min Primary = 2.76 cfs @14.02 hrs, Volume= 2.192 af Secondary = 1.29 cfs @14.02 hrs, Volume= 0.162 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.03' @14.02 hrs Surf.Area= 91,343 sf Storage= 86,444 cf Plug-Flow detention time= 296.7 min calculated for 2.350 af (64% of inflow) Center-of-Mass det. time= 188.5 min ( 1,046.3 -857.8 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.00 6,800 0 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 Primary OutFlow Max=2.76 cfs @14.02 hrs HW=117.03' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 2.76 cfs @3.51 fps) Secondary OutFlow Max=1.28 cfs @14.02 hrs HW=117.03' TW=0.00' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir (Weir Controls 1.28 cfs @0.41 fps) Pond P-Pond 2: Existing West Detention Basin Inflow Area = 13.843 ac, Inflow Depth > 2.21" for 10 YRS event Inflow = 24.67 cfs @12.25 hrs, Volume= 2.544 af Outflow = 3.53 cfs @13.29 hrs, Volume= 2.166 af, Atten= 86%, Lag= 62.4 min Primary = 3.53 cfs @13.29 hrs, Volume= 2.166 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 Three Country Fairgrounds Phase 1-Active YRS Rainfall=4.50" Prepared by The Berkshire Design Group Page 28 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Peak Elev= 118.16' @13.29 hrs Surf.Area= 39,717 sf Storage= 54,241 cf Plug-Flow detention time= 217.7 min calculated for 2.166 af (85% of inflow) Center-of-Mass det. time= 154.0 min ( 997.4 -843.4 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=3.53 cfs @13.29 hrs HW=118.16' TW=0.00' (Dynamic Tailwater) 1=Culvert (Inlet Controls 3.53 cfs @4.49 fps) Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 29 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Subcatchment E-1: Area to Easterly Basin Runoff Area=1,048,195 sf Runoff Depth>3.40" Flow Length=888' Tc=17.0 min CN=72 Runoff=68.76 cfs 6.809 af Subcatchment E-2: Area To Westerly Basin Runoff Area=468,308 sf Runoff Depth>4.01" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=36.36 cfs 3.594 af Subcatchment E-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>3.49" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=29.00 cfs 3.021 af Subcatchment E-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>3.20" Flow Length=750' Tc=17.3 min CN=70 Runoff=20.03 cfs 2.002 af Subcatchment E-5: Area north of of site (includes basketball c Runoff Area=148,626 sf Runoff Depth>3.59" Flow Length=545' Tc=22.7 min CN=74 Runoff=9.21 cfs 1.022 af Subcatchment E-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>4.12" Flow Length=625' Tc=12.3 min CN=79 Runoff=2.66 cfs 0.234 af Subcatchment P-1: Area to Easterly Basin Runoff Area=1,062,120 sf Runoff Depth>3.30" Flow Length=888' Tc=17.0 min CN=71 Runoff=67.54 cfs 6.696 af Subcatchment P-2: Area To Westerly Basin Runoff Area=454,383 sf Runoff Depth>4.01" Flow Length=1,136' Tc=16.9 min CN=78 Runoff=35.28 cfs 3.487 af Subcatchment P-3: Direct to Road Drainage Infrastructure Runoff Area=451,921 sf Runoff Depth>3.49" Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=29.00 cfs 3.021 af Subcatchment P-4: Southeast Area of Site to South Property Runoff Area=327,415 sf Runoff Depth>3.20" Flow Length=750' Tc=17.3 min CN=70 Runoff=20.03 cfs 2.002 af Subcatchment P-5: Area north of site (includes basketball c Runoff Area=148,626 sf Runoff Depth>3.59" Flow Length=545' Tc=22.7 min CN=74 Runoff=9.21 cfs 1.022 af Subcatchment P-6: Northeast of Site (Road and abutting prop Runoff Area=29,661 sf Runoff Depth>4.12" Flow Length=625' Tc=12.3 min CN=79 Runoff=2.66 cfs 0.234 af Reach E-CP1: Williams St. Brook Infrastructure Inflow=33.55 cfs 7.003 af Outflow=33.55 cfs 7.003 af Reach E-CP2: South Property Line Inflow=22.81 cfs 4.596 af Outflow=22.81 cfs 4.596 af Reach E-CP3: Cross Paths Road Inflow=35.24 cfs 2.899 af Outflow=35.24 cfs 2.899 af Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 30 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow=32.57 cfs 6.908 af Outflow=32.57 cfs 6.908 af Reach P-CP2: South Property Line Inflow=22.72 cfs 4.590 af Outflow=22.72 cfs 4.590 af Reach P-CP3: Cross Paths Road Inflow=33.55 cfs 2.792 af Outflow=33.55 cfs 2.792 af Pond E-Pond1: Existing East Detention Peak Elev=117.28' Storage=114,710 cf Inflow=71.10 cfs 7.043 af Primary=3.34 cfs 2.594 af Secondary=35.24 cfs 2.899 af Outflow=38.58 cfs 5.493 af Pond E-Pond2: Existing West Detention B Peak Elev=180.80' Storage=98,409 cf Inflow=44.93 cfs 4.616 af 12.0" x 55.0' Culvert Outflow=23.89 cfs 3.982 af Pond P-Pond 1: Existing East Detention Peak Elev=117.27' Storage=113,549 cf Inflow=69.87 cfs 6.930 af Primary=3.32 cfs 2.588 af Secondary=33.55 cfs 2.792 af Outflow=36.87 cfs 5.380 af Pond P-Pond 2: Existing West Detention Peak Elev=136.84' Storage=98,409 cf Inflow=43.86 cfs 4.509 af 12.0" x 55.0' Culvert Outflow=13.47 cfs 3.886 af Total Runoff Area = 113.596 ac Runoff Volume = 33.145 af Average Runoff Depth = 3.50" 78.99% Pervious Area = 89.724 ac 21.01% Impervious Area = 23.872 ac Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 31 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Subcatchment E-1: Area to Easterly Basin Runoff = 68.76 cfs @12.24 hrs, Volume= 6.809 af, Depth> 3.40" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 10,000 98 Basins 574,174 61 >75% Grass cover, Good, HSG B 25,182 98 Road 90,593 98 Roof 348,246 80 Gravel/Stone Dust 1,048,195 72 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 = 36.36 cfs @12.23 hrs, Volume= 3.594 af, Depth> 4.01" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 29,666 98 Basin 190,948 61 >75% Grass cover, Good, HSG B 56,968 98 Road 69,608 98 Roof 121,118 80 Gravel/Stone Dust 468,308 78 Weighted Average 312,066 Pervious Area 156,242 Impervious Area Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 32 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 = 29.00 cfs @12.27 hrs, Volume= 3.021 af, Depth> 3.49" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 Gravel/Stone Dust 451,921 73 Weighted Average 312,509 Pervious Area 139,412 Impervious Area Tc 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 = 20.03 cfs @12.25 hrs, Volume= 2.002 af, Depth> 3.20" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 Weighted Average 271,058 Pervious Area 56,357 Impervious Area Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 33 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 = 9.21 cfs @12.32 hrs, Volume= 1.022 af, Depth> 3.59" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" 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 = 2.66 cfs @12.17 hrs, Volume= 0.234 af, Depth> 4.12" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" 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 Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 34 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 = 67.54 cfs @12.24 hrs, Volume= 6.696 af, Depth> 3.30" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 10,000 98 Basins 601,924 61 >75% Grass cover, Good, HSG B 25,182 98 Road 98,595 98 Roof 326,419 80 Gravel/Stone Dust 1,062,120 71 Weighted Average 928,343 Pervious Area 133,777 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 = 35.28 cfs @12.23 hrs, Volume= 3.487 af, Depth> 4.01" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 29,666 98 Basin 181,148 61 >75% Grass cover, Good, HSG B 56,968 98 Road 60,986 98 Roof 125,615 80 Gravel/Stone Dust 454,383 78 Weighted Average Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 35 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 306,763 Pervious Area 147,620 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 = 29.00 cfs @12.27 hrs, Volume= 3.021 af, Depth> 3.49" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf) CN Description 0 98 Basin 292,465 61 >75% Grass cover, Good, HSG B 85,542 98 Road 53,870 98 Roof 20,044 80 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 P-4: Southeast Area of Site to South Property Line Runoff = 20.03 cfs @12.25 hrs, Volume= 2.002 af, Depth> 3.20" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 36 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 80 Gravel/Stone Dust 35,148 74 >75% Grass cover, Good, HSG C 327,415 70 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 = 9.21 cfs @12.32 hrs, Volume= 1.022 af, Depth> 3.59" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" 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 Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 37 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Subcatchment P-6: Northeast of Site (Road and abutting property) Runoff = 2.66 cfs @12.17 hrs, Volume= 0.234 af, Depth> 4.12" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" 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 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 > 3.42" for 100 YRS event Inflow = 33.55 cfs @12.75 hrs, Volume= 7.003 af Outflow = 33.55 cfs @12.75 hrs, Volume= 7.003 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 > 1.71" for 100 YRS event Inflow = 22.81 cfs @12.25 hrs, Volume= 4.596 af Outflow = 22.81 cfs @12.25 hrs, Volume= 4.596 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 = 35.24 cfs @12.53 hrs, Volume= 2.899 af Outflow = 35.24 cfs @12.53 hrs, Volume= 2.899 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 38 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Reach P-CP1: Williams St. Brook Infrastructure Inflow Area = 24.218 ac, Inflow Depth > 3.42" for 100 YRS event Inflow = 32.57 cfs @12.28 hrs, Volume= 6.908 af Outflow = 32.57 cfs @12.28 hrs, Volume= 6.908 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 = 32.580 ac, Inflow Depth > 1.69" for 100 YRS event Inflow = 22.72 cfs @12.26 hrs, Volume= 4.590 af Outflow = 22.72 cfs @12.26 hrs, Volume= 4.590 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 = 33.55 cfs @12.55 hrs, Volume= 2.792 af Outflow = 33.55 cfs @12.55 hrs, Volume= 2.792 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 > 3.42" for 100 YRS event Inflow = 71.10 cfs @12.24 hrs, Volume= 7.043 af Outflow = 38.58 cfs @12.53 hrs, Volume= 5.493 af, Atten= 46%, Lag= 17.8 min Primary = 3.34 cfs @12.53 hrs, Volume= 2.594 af Secondary = 35.24 cfs @12.53 hrs, Volume= 2.899 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.28' @12.53 hrs Surf.Area= 137,511 sf Storage= 114,710 cf Plug-Flow detention time= 167.8 min calculated for 5.493 af (78% of inflow) Center-of-Mass det. time= 86.8 min ( 924.1 -837.3 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) 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 Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 39 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 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 Primary OutFlow Max=3.33 cfs @12.53 hrs HW=117.28' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 3.33 cfs @4.25 fps) Secondary OutFlow Max=35.10 cfs @12.53 hrs HW=117.28' TW=0.00' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir (Weir Controls 35.10 cfs @1.27 fps) Pond E-Pond2: Existing West Detention Basin Inflow Area = 14.163 ac, Inflow Depth > 3.91" for 100 YRS event Inflow = 44.93 cfs @12.25 hrs, Volume= 4.616 af Outflow = 23.89 cfs @12.75 hrs, Volume= 3.982 af, Atten= 47%, Lag= 30.3 min Primary = 23.89 cfs @12.75 hrs, Volume= 3.982 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 180.80' @12.75 hrs Surf.Area= 64,989 sf Storage= 98,409 cf Plug-Flow detention time= 253.1 min calculated for 3.973 af (86% of inflow) Center-of-Mass det. time= 193.9 min ( 1,021.0 -827.1 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=23.84 cfs @12.75 hrs HW=180.52' TW=0.00' (Dynamic Dynamic Tailwater) 1=Culvert (Inlet Controls 23.84 cfs @30.35 fps) Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 40 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Pond P-Pond 1: Existing East Detention Basin Inflow Area = 25.064 ac, Inflow Depth > 3.32" for 100 YRS event Inflow = 69.87 cfs @12.24 hrs, Volume= 6.930 af Outflow = 36.87 cfs @12.55 hrs, Volume= 5.380 af, Atten= 47%, Lag= 18.6 min Primary = 3.32 cfs @12.55 hrs, Volume= 2.588 af Secondary = 33.55 cfs @12.55 hrs, Volume= 2.792 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.27' @12.55 hrs Surf.Area= 135,923 sf Storage= 113,549 cf Plug-Flow detention time= 170.0 min calculated for 5.380 af (78% of inflow) Center-of-Mass det. time= 88.0 min ( 927.5 -839.5 ) Volume Invert Avail.Storage Storage Description #1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 112.00 6,800 0 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 Primary OutFlow Max=3.32 cfs @12.55 hrs HW=117.27' TW=0.00' (Dynamic Tailwater) 2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 3.32 cfs @4.22 fps) Secondary OutFlow Max=33.50 cfs @12.55 hrs HW=117.27' TW=0.00' (Dynamic Tailwater) 1=Broad-Crested Rectangular Weir (Weir Controls 33.50 cfs @1.24 fps) Pond P-Pond 2: Existing West Detention Basin Inflow Area = 13.843 ac, Inflow Depth > 3.91" for 100 YRS event Inflow = 43.86 cfs @12.25 hrs, Volume= 4.509 af Outflow = 13.47 cfs @12.81 hrs, Volume= 3.886 af, Atten= 69%, Lag= 33.7 min Primary = 13.47 cfs @12.81 hrs, Volume= 3.886 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 Three Country Fairgrounds Phase 1-Active YRS Rainfall=6.50" Prepared by The Berkshire Design Group Page 41 HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC 3/22/2010 Peak Elev= 136.84' @12.80 hrs Surf.Area= 64,989 sf Storage= 98,409 cf Plug-Flow detention time= 257.1 min calculated for 3.878 af (86% of inflow) Center-of-Mass det. time= 197.6 min ( 1,024.8 -827.2 ) Volume Invert Avail.Storage Storage Description #1 116.00' 98,409 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 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=12.76 cfs @12.81 hrs HW=135.03' TW=0.00' (Dynamic Tailwater) 1=Culvert (Inlet Controls 12.76 cfs @16.25 fps) Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 1 Date: 08/20/09 Time: 2:00 pm Weather P. Cloudy 65 F Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-37” Fill SL --------Buried asphalt, 10-20% gravel, horse shoe fragments found 37”-55” Ab Silty Loam 2.5Y3/2 ----<5% Gravel, Friable, Massive 55”-110” C1 Silty Loam 5Y4/1 5%@55” 10yr6/8 <5% Gravel, Friable, Massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: > 120” Depth to Groundwater: Standing Water in the Hole: ----Weeping from Pit Face: ----Estimated Seasonal High Ground Water: 55” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 2 Date: 08/20/09 Time: 10:48am Weather Sunny 65 F Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-19” Ap Silty Loam 2.5Y3/2 ----5% Gravel, Some sands, Firm in place, Friable in hand, Massive 19”-53” B Silty Loam 2.5Y4/4 ----<2% Gravel, Friable, Massive 53”-122” C1 Fine Sandy Loam 5Y4/4 5%@53” 5Y6/2 <2% Gravel, Friable, Massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: > 122” Depth to Groundwater: Standing Water in the Hole: 114” Weeping from Pit Face: 116” Estimated Seasonal High Ground Water: 53” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 3 Date: 08/20/09 Time: 9:45am Weather Sunny 65 F Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-16” Ap Silty Loam 2.5Y4/3 ----10% Gravel, Friable, Single grained, some sands 16”-39” B Silty Loam 2.5Y4/4 ----<2% Gravel, Friable, Massive 39”-118” C1 Silty Loam 5Y4/3 5%@52” 10YR6/8 <2% Gravel, Friable, very moist, Massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: > 118” Depth to Groundwater: Standing Water in the Hole: ----Weeping from Pit Face: ----Estimated Seasonal High Ground Water: 52” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 4 Date: 08/20/09 Time: 8:36am Weather Sunny 65 F Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-10” Ap Silty Loam 10YR3/3 ----10% Gravel, Firm, Single grained 10”-36” B Silty Loam 2.5Y4/3 ----<2% Gravel, Friable, Massive 36”-115” C1 Silty Loam 2.5Y4/4 5-10%@36” 10YR5/8 <2% Gravel, Friable, very moist, Massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: > 115” Depth to Groundwater: Standing Water in the Hole: 114” Weeping from Pit Face: 110” Estimated Seasonal High Ground Water: 36” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 5 Date: 08/20/09 Time: 12:18pm Weather Sunny 65 F Location (identify on site plan) See Plan Land Use Riding Ring Slope (%) See Plan Surface Stones n/o Vegetation Grass/stonedust Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-10” Ap Silty Loam 2.5Y3/2 ----10% Gravel, Friable, Single grained 10”-16” B Silty Loam 2.5Y4/3 ----<2% Gravel, Friable, Massive 16”-37” C1 Silty Loam 2.5Y4/4 5%@16” 7.5YR4/6 5-10% Gravel, Friable, very moist, massive, could possibly be a buried A layer 37”-88” C2 Silty Loam 5Y4/1 10%@37” 7.5YR5/6 5-10% gravel, firm in place, friable in hand, massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: > 88” Depth to Groundwater: Standing Water in the Hole: 80” Weeping from Pit Face: 70” Estimated Seasonal High Ground Water: 16” Possibly Perched Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits –NOT CONDUCTED DUE TO EXPOSED CONDUIT Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 6 Date: 08/20/09 Time: 12:00pm Weather Sunny 65 F Location (identify on site plan) See Plan Land Use Dirt road Slope (%) See Plan Surface Stones n/o Vegetation none Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Depth to Bedrock: Depth to Groundwater: Standing Water in the Hole: Weeping from Pit Face: Estimated Seasonal High Ground Water: Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 7 Date: 08/20/09 Time: 1:15pm Weather Partly Cloudy 65 F Location (identify on site plan) See Plan Land Use Inside of track Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-37” Ap Silty Loam 2.5Y4/3 ----10% Gravel, Friable, Single grained, some sands 37”-55” B Silty Loam 2.5Y4/4 ----2-5% Gravel, Friable, Massive 55”-103” C1 Silty Loam 2.5Y4/4 5%@55” 10YR5/8 <2% Gravel, Friable in hand, somewhat firm in place, Massive * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: >103 Depth to Groundwater: Standing Water in the Hole: ----Weeping from Pit Face: ----Estimated Seasonal High Ground Water: 55” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Three County Fairgrounds, Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By:Felix Harvey, Noho DPW Deep Hole Number TP 8 Date: 08/20/09 Time: 1:15pm Weather Partly Cloudy 65 F Location (identify on site plan) See Plan Land Use Lawn area Slope (%) See Plan Surface Stones n/o Vegetation Grass Landform Floodplain Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0-11” Ap Silty Loam 5YR 2.5/1 ----<5% Gravel, Friable, Single grained, some sands 11”-25” B Silty Loam 10YR 3/2 ----2-5% Gravel, Friable, Massive 25”-108” C1 Silty Loam 5Y 3/1 10%@54” 10YR6/8 <1% Gravel, Massive, very moist * MINIMUM OF 2 HOLES REQ UIRED AT E VERY PROPOS ED DISPOSAL DISPOSAL ARE A Parent Material (geologic) Alluvial Depth to Bedrock: >108” Depth to Groundwater: Standing Water in the Hole: ----Weeping from Pit Face: ----Estimated Seasonal High Ground Water: 54” Percolation Test: Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix C – Proposed Stormwater Management System Operation & Maintenance Plan Three County Fairgrounds March 18, 2009 Northampton, MA Operation & Maintenance Plan 1 Proposed Stormwater Management System Operation & Maintenance Plan During Construction The Contractor shall be responsible for inspection and maintenance during construction. At all times, siltation fabric fencing, stakes and hay bales sufficient to construct a sedimentation control barrier a minimum of 50 feet long will be stockpiled on the site in order to repair established barriers which may have been damaged or breached. An inspection of all erosion control and stormwater management systems shall be conducted by the Contractor at least once a week and during all rain storms until the completion of construction. In case of any noted breach or failure, the Contractor shall immediately make appropriate repairs to any erosion control system and notify the engineer of any problems involving stormwater management systems. A rain storm shall be defined as all or one of the following: • Any storm in which rain is predicted to last for twelve consecutive hours or more. • Any storm for which a flash flood watch or warning is issued. • Any single storm predicted to have a cumulative rainfall of greater than onehalf inch. • Any storm not meeting the previous three thresholds but which would mark a third consecutive day of measurable rainfall. The Contractor shall also inspect the erosion control and stormwater management systems at times of significant increase in surface water runoff due to rapid thawing when the risk of failure of erosion control measures is significant. In such instances as remedial action is necessary, the Contractor shall repair any and all significant deficiencies in erosion control systems within two days. The Department of Public Works shall be notified of any significant failure of stormwater management systems and erosion and sediment control measures and shall be notified of any release of pollutants to a water body (stream, brook, pond, etc.) or into a conveyance system to a water body. Three County Fairgrounds March 18, 2009 Northampton, MA Operation & Maintenance Plan 2 The Contractor shall remove the sediment from behind the fence of the sedimentation control barrier when the accumulated sediment has reached onehalf of the original installed height of the barrier. Post-Construction Stormwater Management System Owner: The Owner, Three County Fairgrounds Fair Street Northampton, MA 01060 shall own the stormwater management system. Party Responsible for Operation & Maintenance: The Owner, Three County Fairgrounds Fair Street Northampton, MA 01060 shall operate and maintain the stormwater management system. Inspection & Maintenance Schedule: 1) Street Sweeping Street and parking area sweeping shall take place twice annually. 2) Detention Basin (The following recommendations follow the MADEP Stormwater Policy guidelines.) Inspections a. Initial six months of use. Examine for stabilization and function, including determination of the duration of water standing in the basin, any sediment erosion, excessive compaction of soils, or low spots. b. Twice per year. Three County Fairgrounds March 18, 2009 Northampton, MA Operation & Maintenance Plan 3 Examine basin for the following: differential settlement, cracking, erosion, leakage, or tree growth on embankments, condition of riprap, sediment accumulation, and health of turf where applicable. Any adverse conditions noted during any inspections shall be addressed by repair or reconsideration of design components. Mowing and General Maintenance Occasional mowing (2 times per year min.) shall be performed on the side slopes and basin bottom where turf is present. Accumulated grass clippings and/or organic matter and trash and debris shall be removed. Any clogged surface areas can be loosened by deep tilling; tilled areas must be immediately revegetated. Tilling may be used in this manner for no more than two consecutive maintenance periods. Thereafter, sediment in the clogged areas shall be removed, liner material replaced, and revegetation established. Dredging/Sediment Removal Accumulated sediment shall be removed from the basin at five (5) year intervals, or as required to maintain the function of the stormwater management system as designed. During this process and until the disturbed sediment has settled, the outlet pipe shall be sealed so as to minimize the risk of conveying sediment beyond the basin. 3) Trench Systems Inspect for trench damage monthly. A minimum of twice annually, following heavy storm events and otherwise as needed perform visual inspection of all overflow inlets. Maintain visible concrete walk at all times ‘non-cleaning’ times. During barn cleaning, all inlet grates shall be replaced with a solid cover until manure and other debris has been removed. Following all events inspect for proper grading and remove all areas of collected sediment. Sediment shall also be removed following any occurrence and trench shall be restored to original conditions. 4) Hooded Catch Basin and/or Drain Manhole with Sump Oil and water separators should be inspected at least four times per year and cleaned annually or more often if required. Oil and sediments should be removed and disposed of in accordance with local, state and federal guidelines and regulations. In the case of an oil or bulk pollutant release, the system must be cleaned immediately following the spill and the proper authorities notified. Three County Fairgrounds March 18, 2009 Northampton, MA Operation & Maintenance Plan 4 5) Snow Removal & Management Plan General The stormwater management system is designed to accommodate volumes from snow melt. Since plowed snow from paved surface may contain salts, sediment, oils and various pollutants, all snow melt from vehicular areas on the site shall be routed through the drainage system or removed from the site. Principles 1. The Owner shall provide a copy of this plan and a schedule or vehicle rotation scheme to plowing contractors such that plowing may occur in an efficient manner. This may be altered based on employee schedules or severity or frequency of snow events. 2. No such snow shall be dumped or stockpiled directly into any resource area or within any area such that untreated snow melt may enter a resource area. 3. Snow removed from the site shall be disposed of such that it or its melt will have no adverse effect on other resource areas. 4. The Owner shall use alternative eco-friendly solutions throughout the site in place of standard de-icing materials. 5. The Conservation Commission and DPW shall be notified where a violation of this plan occurs. INSPECTION AND MAINTANENCE REPORT FORM Three County Fairgrounds, Northampton, MA The Berkshire Design Group, Inc. Page 1/3 I IINNSSPPEECCTTI IIOONN AANNDD MMAAI IINNTTEENNAANNCCEE RREEPPOORRTT FFOORRMM For Three County Fairgrounds – Stormwater Management System Inspection Schedule: FORM TO BE COMPLETED PER SCHEDULE PRESENTED IN OPERATION & MAINTENANCE PLAN Inspector: Date: Time: Inspector’s Qualifications: Days Since Last Rainfall: Amount of Last Rainfall (inches): Exist ing Catch Basins CB Is Surface Runoff Being Directed to Catch Basins Properly Are Sediment Traps Installed at Catch Basin Inlets Are Catch Basin Outlet Hoods Installed and Working Properly Depth of Sediment in Basin Sump Are Any Correction Measures Required Maintenance Required: To Be Performed By: On or Before: INSPECTION AND MAINTANENCE REPORT FORM Three County Fairgrounds, Northampton, MA The Berkshire Design Group, Inc. Page 2/3 STRUCTURAL CONTROLS –CON’’T Trench Systems Structure Is System Working Properly Depth of Sediment in Trench Are Any Correction Measures Required Additional Notes Sur face Stormwater Detent ion Basin (east ) Is Stormwater Entering Basin Correctly Is Stormwater Being Detained and Discharged Properly Depth of Sediment Is Erosion Stabilization Properly Installed & Maintained Is There Any Evidence of Erosion Or unintended Flow Patterns Is Mowing Required Maintenance Required: To Be Performed By: On or Before: Sur face Stormwater Detent ion Basin (west ) Is Stormwater Entering Basin Correctly Is Stormwater Being Detained and Discharged Properly Depth of Sediment Is Erosion Stabilization Properly Installed & Maintained Is There Any Evidence of Erosion Or unintended Flow Patterns Is Mowing Required Maintenance Required: To Be Performed By: On or Before: OTHER CONTROLS List Other Miscel laneous Cont rols and Observat ions Item Describe Failure/Inadequate Control Describe Recommended Remedy INSPECTION AND MAINTANENCE REPORT FORM Three County Fairgrounds, Northampton, MA The Berkshire Design Group, Inc. Page 3/3 Maintenance Required: To Be Performed By: On or Before: Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix D – Long Term Pollution Prevention Plan Three County Fairgrounds March 18, 2009 Northampton, MA Long Term Pollution Prevention Plan 1 Long Term Pollution Prevention Plan This plan was developed in compliance with the Massachusetts Department of Environmental Protection Stormwater requirements. Good Housekeeping The proposed site is designed to maintain high water quality treatment for all runoff. A general maintenance plan has been prepared and will be followed in a strict and complete manner as required. Spill Prevention Plan No hazardous materials are will be stored on site. However the following spill prevention plan will be incorporated into the Long Term Pollution Prevention Plan: • Manufacturers’ recommended methods for spill cleanup will be clearly posted and site personnel will be made aware of the procedures and the location of the information and cleanup supplies. • Materials and equipment necessary for spill cleanup will be kept in the on-site material storage area. Equipment and materials will include, but is not limited to, brooms, dust pans, mops, rags, gloves, goggles, kitty litter, sand, sawdust and plastic and metal trash containers specifically for this purpose. • All spills will be cleaned up immediately after discovery. • The spill area will be kept well ventilated and personnel will wear appropriate protective clothing to prevent injury from contact with a hazardous substance. • Spills of toxic or hazardous material will be reported, regardless of size, to the Massachusetts Department of Environmental Protection at 888-304-1133. • Should a spill occur, the spill prevention plan will be adjusted to include measures to prevent another spill and to cleanup up the spill should another occur. A description of the spill, along with the causes and cleanup measures will be included in the updated spill prevention plan. • The construction superintendent responsible for daily operation on the construction site will be the spill prevention and cleanup coordinator. The superintendent will designate at least three site personnel to receive spill prevention cleanup and training. These individuals will each become responsible for a particular phase of prevention and cleanup. The names of responsible spill personnel will be posted in the material storage area and in the on-site job trailer. Stormwater BMP Maintenance A full stormwater operation and maintenance plan has been prepared (see Appendix D of this report) in order to ensure that the system will function properly throughout the year. Landscape and Lawn Maintenance Routine mowing and associated maintenance of all landscape features will occur weekly or as needed to prevent excessive growth and debris from occurring on site. Three County Fairgrounds March 18, 2009 Northampton, MA Long Term Pollution Prevention Plan 2 Solid Waste Management Solid waste is handled on site and will comply with all requirements on a local, state, and federal level. Parking/Road Area Maintenance Street sweeping shall occur 2-4 times per year. A snow management plan has been prepared (see Appendix D) to prevent reduce impacts of dirty snow on the resource area. Training of Staff All personnel on site will be well briefed on all requirements for implementing the Long Term Pollution Prevention Plan. Emergency Contact for Implementing Long Term Pollution Prevention Plan Three County Fairgrounds Fair Street Northampton, MA 01060 Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix E -Stormwater Pollution Prevention and Erosion Control Plan Stormwater Pollution Prevention Plan _____________________________________________________________________________________ Three County Fairgrounds Redevelopment Plan -Phase 1 Northampton, Massachusetts March 18, 2010 Prepared by: 4 Allen Place, Northampton, Massachusetts 01060 Prepared For: Three County Fairgrounds 59 Fair Street Northampton, MA 01060 TABLE OF CONTENTS SITE & PROJECT DESCRIPTION ............................................................................... 1 Project Name and Location .............................................. ................................................................... 1 Applicant/Owner Name and Address: ............................................................................................... 1 Existing Zoning & Land Use & Site Area .......................................................................................... 1 Proposed Project ................................................ ................................................................................. 1 Runoff Coefficient ................................................................................................ ............................... 2 Sequence of Major Construction Activities ....................................................................................... 2 Name of Receiving Waters .................................................................................................................. 2 CONTROLS DURING CONSTRUCTION .............................................. ..................... 2 Erosion and Sediment Controls .......................................................................................................... 2 Stormwater Management .................................................................................................................... 3 Other Controls ................................................................. ................................................................... 3 Timing of Controls .............................................................................................................. ................. 4 MAINTENANCE AND INSPECTION PROCEDURES .............................................. 5 Erosion and Sediment Control Inspection and Maintenance Practices .......................... ................ 5 Non-Stormwater Discharges ............................................................................................................... 5 Inventory for Pollution Prevention Plan ............................................................................................ 5 Spill Prevention ....................................................................... ............................................................ 6 Spill Control Practices ................................................................................................................ ......... 7 CERTIFICATION OF COMPLIANCE WITH FEDERAL, STATE AND LOCAL REGULATIONS ............................................................................................................... 8 POLLUTION PREVENTION PLAN CERTIFICATION ........................................... 9 CONTRACTOR’S CERTIFICATION .......................................................................... 9 Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 1 SITE & PROJECT DESCRIPTION Project Name and Location Three County Fair Grounds Fair Street Northampton, MA 01060 Applicant/Owner Name and Address: Bruce Shallcross 59 Fair Street Northampton, MA 01060 Notification – Prior To Construction: General Contractor/Operator: City of Northampton To Be Determined Department of Public Works 30 Locust Street Northampton, MA 01060 Mr. Douglas McDonald NPDES Coordinator Phone: 413-587-1582 Existing Zoning & Land Use & Site Area The proposed project site is a 270,000 sf portion of the Three County Fairgrounds site which is located in the Special Conservancy zoning district. The existing site (within the limit of work) contains 17 buildings and gravel and stone dust areas. All of the buildings within the limit of work are proposed to be removed and disposed of prior to the construction of any new ones. The site drains into catch basins which discharge into the detention basin at the east end of the site. Proposed Project The proposed scope of Phase 1 includes the construction of 3 new barns and the 2 associated concrete depressions and drains. The proposed barns will drain into the new drains with sumps below the concrete depressions and will be connected to the easterly detention basin with an 18” HDPE pipe, allowing the site to continue functioning as it currently does. The proposed construction will generate 58,350sf of impervious area which will result in a net loss of impervious area (see attached Figure 1). The completion of Phase 1 will result in a net loss of -620sf of impervious which will slightly reduce the water quantity generated on the site. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 2 Soil disturbing activities will include: excavation and disposal of soil for grading and trenching of drain line and preparation for final seeding and planting. Runoff Coefficient The SCS overall curve number (CN) for the site will be 74 in proposed conditions Sequence of Major Construction Activities The general order of construction activities at the site will be as follows: 1. Hold preconstruction meeting at least one week prior to start of construction 6.2. Install catch basin filters at areas of disturbance 3. Demolish and dispose of existing buildings 8.4. Rough grade existing building foot print to ensure positive drainage 5. Install drainage system and pipe 14.6. Install new barn stalls 18.7. Grade and seed disturbed areas 8. Remove catch basin filters 9. Schedule post construction conference and inspection Name of Receiving Waters Runoff from this area of the site will be directed to the easterly detention basin which discharges to both the Williams Street Brook and the historic water way adjacent to Cross Path Road. CONTROLS DURING CONSTRUCTION Erosion and Sediment Controls General Sedimentation Control Practices The following general erosion and sediment controls will be utilized during construction in order to maintain local water quality: 1. Erosion control materials will be installed prior to clearing and excavation work. 2. Grading and other soil disturbance will be done so as to minimize erosion during wet seasons. 3. No clearing of natural vegetation will be required or is permitted. 4. All soil removed from the site shall be located outside of the 100-year floodplain. 5. Disturbed areas will be stabilized as soon as possible after construction. 6. Maintenance and cleaning of construction vehicles and equipment will take place in designated staging areas only. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 3 Stabilization Practices The following stabilization practices will be utilized during construction in order to maintain local water quality: 1. Temporary stabilization: temporary seeding, mulching or other suitable stabilization measures may be utilized to protect disturbed areas during prolonged construction periods. 2. Permanent stabilization: areas disturbed by construction will be permanently stabilized by seeding and mulching with seed mix. Seeded areas will be covered with straw mulch or biodegradable netting in order to protect surface until seed germination. Structural Practices The following structural erosion and sediment controls will be utilized during construction in order to maintain local water quality: 1. Catch Basin Filters: Filters consisting of silt sack and/or filter fabric fence, embedded 4-6” in the ground, will surround each existing and proposed catch basin. Filter fabric will also be installed under each inlet grate. • Filters will be placed around each catch basin prior to paving or planting. • Sediment will be removed when it reaches half of the original height of the filter. • Filter fabric under the inlet grate will be monitored and replaced as required. • Filters will be removed only after upgradient areas have been permanently stabilized. 2. Dust Control: Dust control will be maintained by sprinkler or water truck during construction to minimize sediment transport and maintain air quality at an acceptable level. Stormwater Management Stormwater in proposed conditions will mimic the flow patterns of existing conditions. Runoff from the roof will flow to a drain basin located between the barns prior to entering the existing detention basin as the east end of the site. Other Controls Waste Disposal Waste Materials: Waste materials will be collected and stored in a lidded metal dumpster rented from a licensed solid waste management company. All trash and construction debris debris will be stored in the dumpster. The dumpster will be emptied at least twice a week, or more if necessary, and disposed of in accordance with local, state and federal regulation. No construction waste materials will be buried on site. Notices stating these procedures will be Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 4 posted in the job trailer. Site personnel will be instructed in these procedures and site construction supervisor(s) will ensure that the procedures are followed. Hazardous Waste: Hazardous waste will be disposed of in the manner specified by local, state and federal regulation or by the manufacturer. Site personnel will be instructed in these procedures and site construction supervisor(s) will ensure that the procedures are followed. Sanitary Waste: Sanitary waste will be collected from portable units a minimum of three times per week by a licensed sanitary waster contractor and disposed of in accordance with local, state and federal regulation. Timing of Controls As indicated in the Sequence of major Activities, erosion control devices will be installed prior to clearing or grading of any other portions of the site. Areas where construction activity temporarily ceases for more than 21 days will be stabilized with temporary seed and mulch within 14 days of the last disturbance. Once construction activity ceases permanently in an area, that area will be stabilized with loam and seed as indicated in the plans. After the entire site is stabilized, the accumulated sediment will be removed from the catch basin filters. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 5 MAINTENANCE AND INSPECTION PROCEDURES Erosion and Sediment Control Inspection and Maintenance Practices The following inspection and maintenance practices will be utilized in this project to maintain sediment and erosion controls: • All control measures will be inspected weekly (at a minimum) and within 24 hours after any storm event of 0.5 inches or greater. • All measures will be maintained in good working order; if a repair is necessary, it will be initiated within 2 hours of report. • Contractor will stockpile on site or make available all equipment, materials (e.g. filter fabric, crushed stone, etc.) and labor necessary to make emergency erosion control improvements within 24 hours if necessary. • Temporary and permanent seeding will be inspected for bare spots, washouts and healthy growth. • A maintenance inspection report will be made after each inspection. • The site contractor will select select one or more individuals who will be responsible for inspections, maintenance and repair activities and for completing inspection and maintenance reports. • Individuals selected for inspection and maintenance responsibilities will receive training in all inspection and maintenance practices necessary for keeping the on-site erosion and sediment controls in good working order. Non-Stormwater Discharges It is expected that the following non-stormwater discharges will occur from the site during the construction period: • Uncontaminated groundwater from dewatering excavations. • Water from washing the exterior of construction vehicles. Non-stormwater discharges will be directed to stabilized surfaces or the detention basin prior to discharge. Exterior washing and rinsing of vehicles will take place more than 100 feet from wetlands or waterways. Inventory for Pollution Prevention Plan Asphalt Masonry block Cleaning solvents Metal studs Concrete Paints (enamel and latex) Detergents Petroleum-based products Fertilizers Solvents Gravel Wood Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 6 Spill Prevention All employees will be instructed regarding the following spill prevention practices. Notice of these practices will be posted in the job trailer, and the site construction supervisor will hold responsibility for ensuring that the procedures are followed. Material Management Practices The following material management practices will be used to reduce the risk of spills or other accidental exposure of materials and substances to stormwater runoff: Good Housekeeping The following good housekeeping practices will be followed on-site during the construction period: An effort will be made to store only enough product to do the job. All materials stored on-site will be stored in a neat, orderly manner in their appropriate containers and, if possible, under a roof or other enclosure. Products will be kept in their original containers with the original manufacturer’s label. Substances will will not be mixed with one another unless recommended by the manufacturer. Whenever possible, all of a product will be used up before disposing of the container. Manufacturer’s recommendations for proper used and disposal will be followed. The site superintendent will inspect daily to ensure proper use and disposal of material on-site. Hazardous Products The following practices will reduce the risks associated with hazardous materials (e.g. petroleum products, solvents, etc.): • Products will be kept in original containers unless they are not resealable. • Original labels and material safety data sheets (MSDS) will be retained; they contain important product information. • A copy of the Material Safety Data Sheet (MSDS) for each product used in construction will be kept in the job trailer. • If surplus product must be disposed of, manufacturer’ or local-and state-recommended methods for proper disposal will be followed. Product Specific Practices Petroleum Products: All on-site vehicles will be monitored for leaks and will receive regular preventative maintenance to reduce the chance of leakage. Petroleum products will be stored in tightly sealed, clearly labeled containers. Any asphalt substances used on-site will be applied according to the manufacturer’s recommendations. No vehicle refueling or maintenance will take place within 100 feet of a wetland or waterway. No petroleum-based or asphalt substances will be stored within 100 feet of a wetland or waterway. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 7 Fertilizers: Fertilizers used will be applied only in the minimum amounts recommended by the manufacturer. Once applied, fertilizer will be worked into the soil to limit exposure to stormwater. Unused fertilizer will be stored in a covered shed. The contents of any partially used bags of fertilizer will be transferred to a sealable plastic bin to avoid spills. No fertilizers will be stored within 100 feet of a wetland or waterway. Solvents, Paints and Other Hazardous Substances: All containers will be tightly sealed when not required for use. Excess material will not be discharged to the storm sewer system but will be properly disposed of according to manufacturers’ instruction or local and state regulations. No solvents, paints or other hazardous substances will be stored within 100 feet of a wetland or waterway. Concrete Trucks: Concrete trucks will not be allowed to wash out or discharge surplus concrete or drum wash water on the site. Spill Control Practices In addition to the good housekeeping and material management practices discussed in the previous sections of this plan, the following practices will be followed for spill prevention and cleanup: • Manufacturers’ recommended methods for spill cleanup will be clearly posted and site personnel will be made aware of the procedures and the location of the information and cleanup supplies. • Materials and equipment necessary for spill cleanup will be kept in the on-site material storage area. Equipment and materials will include, but is not limited to, brooms, dust pans, mops, rags, gloves, goggles, kitty litter, sand, sawdust and plastic and metal trash containers specifically for this purpose. • All spills will be cleaned up immediately after discovery. • The spill area will be kept well ventilated and personnel will wear appropriate protective clothing to prevent injury from contact with a hazardous substance. • Spills of toxic or hazardous material will be reported, regardless of size, to the Massachusetts Department of Environmental Protection at 888-304-1133. • Should a spill occur, the spill prevention plan will be adjusted to include measures to prevent another spill and to cleanup up the spill should another occur. A description of the spill, along with the causes and cleanup measures will be included in the updated spill prevention plan. • The construction superintendent responsible for daily operation on the construction site will be the spill prevention and cleanup coordinator. The superintendent will designate at least three site personnel to receive spill prevention cleanup and training. These individuals will each become responsible for a particular phase of prevention and cleanup. The names of responsible spill personnel will be posted in the material storage area and in the on-site job trailer. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 8 CERTIFICATION OF COMPLIANCE WITH FEDERAL, STATE AND LOCAL REGULATIONS This stormwater pollution prevention plan reflects State of Massachusetts requirements for stormwater management and sediment and erosion control as established by the Wetlands Protection Act (310 CMR 10.00) and by the Department of Environmental Protection Stormwater Management Policy. To ensure compliance, this plan was prepared in consultation with the following publications: Commonwealth of Massachusetts, Department of Environmental Protection. Stormwater Management Policy. November 1997. Commonwealth of Massachusetts, Department of Environmental Protection. Wetlands Protection Act Regulations: 310 CMR 10.00 for Administering M.G.L. Chapter 31, Section 40. November 1997. Commonwealth of Massachusetts, Department of Environmental Protection and Office of Coastal Zone Management. Stormwater Management, Volume One: Stormwater Policy Handbook. March 1997. Commonwealth of Massachusetts, Department of Environmental Protection and Office of Coastal Zone Management. Stormwater Management, Volume Two: Stormwater Technical Handbook. March 1997. United States Environmental Protection Agency. Storm Water Management For Construction Activities, Developing Pollution Prevention Plans And Best Management Practices, Summary Guidance. October 1992. Three County Fairgrounds DRAFT Stormwater Pollution Prevention Plan Northampton, Massachusetts March 18, 2010 9 POLLUTION PREVENTION PLAN CERTIFICATION I certify under penalty of law that this document and all attachments were prepared under my direction in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. Signed: ________________________________ CONTRACTOR’S CERTIFICATION I certify under penalty of law that I understand the terms and conditions of the general National Pollutant Discharge Elimination System (NPDES) permit that authorizes the stormwater discharges associated with industrial activity from the construction site identified as part of this certification. Signature Company Responsible For ____________________ _______________________ ____________________ _______________________ ____________________ ____________________ _______________________ ____________________ Tel: ___________________ ____________________ ____________________ _______________________ ____________________ _______________________ __________________ __ ____________________ _______________________ ____________________ Tel:____________________ ____________________ ____________________ _______________________ ____________________ __________________ _____ ____________________ ____________________ _______________________ ____________________ Tel: ___________________ ____________________ Three County Fairgrounds March 18, 2010 Northampton, Massachusetts Stormwater Drainage Report Appendix The Berkshire Design Group, Inc. Appendix Appendix F – Water Quality Information V INSTRUCTIONS: Version 1, Automated: Mar. 4, 2008 1. In BMP Column, click on Blue Cell to Activate Drop Down Menu 2. Select BMP from Drop Down Menu 3. After BMP is selected, TSS Removal and other Columns are automatically completed. Location: B C D E F TSS Removal Starting TSS Amount Remaining BMP1 Rate1 Load* Removed (C*D) Load (D-E) Deep Sump and Hooded Catch Basin 0.25 1.00 0.25 0.75 Proprietary Treatment Practice 0.77 0.75 0.58 0.17 0.00 0.17 0.00 0.17 0.00 0.17 0.00 0.17 0.00 0.17 0.00 0.17 Total TSS Removal = 83% Separate Form Needs to be Completed for Each Outlet or BMP Train Project: Three County Fairgrounds, Northampton, MA Prepared By: Brian Darnold *Equals remaining load from previous BMP (E) Date: 3/18/2010 which enters the BMP TSS Removal Calculation Worksheet Stormceptor 2400 Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed 1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept. of Environmental Protection Fact Sheet # 1 t Stormwater Technology: Stormceptor (Hydro Conduit, formerly CSR New England Pipe) Revised February 2003 Description/Definition Stormceptor is a prefabricated, underground unit that separates oils, grease, and sediment from stormwater runoff when installed with an existing or new pipe conveyance system. The unit is divided into two chambers–a treatment and a flow bypass chamber. During typical storm events, runoff is directed by the inflow weir through a drop pipe into the lower treatment chamber where sediment, oil, and grease are separated from the flow by gravity. The bypass chamber is designed to convey excess stormwater, which overtops the inflow weir, through the system without treatment. Equipment and Sizing The on-line Stormceptor units are available in eight sizes ranging from six and twelve feet in diameter with capacities of 900 to 7200 gallons. Since issuing the STEP assessment in 1998, the manufacturer has expanded the Stormceptor product line to include a storm drain inlet (STC STC 450i) and three units (Models STC 11000, STC 13000, and STC16000). These systems are not included in the STEP evaluation. Users and decision-makers may require additional field test results and new data for these new systems in order to accept performance ratings, particularly if they are higher than those reported in the STEP technology assessment and this fact sheet. Stormceptor units are available in either precast concrete or fiberglass for special applications. Concrete units are pre-engineered for HS-20 min. traffic loading at the surface. Fiberglass units can be used in areas where The Stormceptor Fact Sheet is one in a series of fact sheets for stormwater technologies and related performance evaluations, which are undertaken by the Massachusetts STrategic Envirotechnology Partnership (STEP). A summary of the STEP evaluation entitled, Technology Assessment, Stormceptor CSR New England Pipe, January 1998 is provided in this fact sheet. When a more thorough understanding of a system is required, the full Technology Assessment should be reviewed. Copies are available for downloading from the STEP Web site (www.stepsite.org/progress/reports) or by contacting the STEP Program (Phone: 617/626/1197, FAX: 617/626/1180, email: linda.benevides@state.ma.us). The information in this fact sheet is subject to future updates as additional performance information becomes available. there is a potential for oil and chemical spills. Performance/Effectiveness The system is designed to provide separation of sediment, oil, and grease from stormwater by routing runoff into a low-turbulence environment where solids settle and oils float out of solution. The system sizing is based on the drainage area, historical rainfall data, and Fact Sheet #4 Figure 1. Stormceptor operation during average flow conditions. MASSACHUSETTS STRATEGIC ENVIROTECHNOLOGY PARTNERSHIP Sedimentation Oil Rises Outflow pipe riser Outflow pipe Inflow drop pipe Inflow pipe Bypass weir the solids removal efficiency required. It is recommended that the system be used in combination with other stormwater controls to conform with the Massachusetts Stormwater Management Policy and standards. An Imperial Model STC 2000 (equivalent to the Model STC 2400) in Edmonton, Canada treats flow from a 9.8 acre commercial parking lot. This system was monitored during four storm events in 1996 and shown to have an average total suspended solids (TSS) removal efficiency of 52 percent. In designing a system to achieve a comparable removal efficiency, the relationship between system size and impervious drainage area should be considered, as detailed in Table 1 and the Technology Assessment Report. A Model STC 1200 in Westwood, Massachusetts treats flow from 0.65 acres consisting of a paved truck loading area at a manufacturing facility. The unit was monitored for six storm events in 1997, but only four events had measurable TSS influent concentrations. Of these four events, the average TSS removal efficiency efficiency was calculated to be 77 percent, which is less than the 80 percent removal targeted by the manufacturer. Based on these field monitoring results, and when the unit sizing follows the guidance in Table 1, removal efficiencies between 52 percent and 77 percent may be achieved where installations have similar rainfall and land use characteristics as those reviewed for the STEP evaluation. It is recommended that additional field research and new data be evaluated to validate performance ratings higher than those verified by STEP. Specific performance claims for oil and grease were not evaluated by STEP. However, total petroleum hydrocarbons (TPH) were analyzed during the Westwood study. Results indicated that the unit was effective in capturing oils. Technology Status The Stormceptor system provides greater solids separation and higher TSS removal efficiencies than oil and grit separators. Stormceptor systems are among the category of hydrodynamic separators, which are flowthrough devices with the capacity to settle or separate grit, oil, sediment, or other pollutants from stormwater. According to the U.S. Environmental Protection Agency, “Hydrodynamic separators are most effective where the materials to be removed from runoff are heavy particulates -which can be settled -or floatables -which can be captured, rather than solids with poor settleability or dissolved pollutants.” Although Stormceptor appears to remove sediment, grit, oil, and grease as claimed by the manufacturer, additional research is needed to determine how much sediment moves through the system untreated. The field studies evaluated for the STEP assessment predate the Stormwater Best Management Practice Demonstration Tier II Protocol (2001), which is applicable in Massachusetts and other states in the Technology Acceptance Reciprocity Partnership (TARP), to ensure quality controlled studies that can be shared among participating states. Therefore, interstate reciprocity is not available to the manufacturer, based on performance claims that were evaluated by STEP in 1998. If the TARP Protocol requirements are fulfilled in the future, the manufacturer could pursue reciprocal verification for Stormceptor systems in participating TARP states. More information on the TARP Protocol is available on the following Web site: www.dep.state.pa.us/dep/deputate/pollprev/techservices/tarp. Applications/Advantages 􀂖 Stormceptor systems identified in Table 1 should be used in combination with other BMPs to remove 80 percent of the average annual load of TSS (DEP Stormwater Policy Standard 4). Systems may be well suited for pretreatment in a mixed component system designed for stormwater recharge. 􀂖 Performance data show that Stormceptor may provide TSS removal rates in the range of 52 percent to 77 percent when sized according to Table 1. Higher TSS removal rates were achieved during low flow, low intensity storms with less than one third of an inch of runoff. Also, by reducing the impervious drainage area, Stormceptor Model Number 77% TSS removal 52% TSS removal STC 900 0.45 0.9 STC 1200 0.7 1.45 STC 1800 1.25 2.55 STC 2400 1.65 3.35 STC 3600 2.6 5.3 STC 4800 3.6 7.25 STC 6000 4.6 9.25 STC 7200 5.55 11.25 MaximumImpervious Area (acres) Table 1: Adapted from the Stormceptor sizing for TSS removal in the STEP Technology Assessment. Notes: 1) On some sites, the maximum impervious area may need to be reduced to achieve these TSS removal rates. 2) The terms “critical area sizing” (to achieve 77 percent TSS removal) and “treatment train sizing” (for 52 percent removal) are no longer used by the manufacturer, but unit sizing is still applicable. relative to the system size, the STEP Technology Assessment Report indicated that higher removal efficiencies may be achievable. However, STEP recommends collection of additional data “representing a varied set of operating conditions over a realistic maintenance cycle to verify TSS removal rates greater than 80 percent.” 􀂖 The Stormceptor system is suitable for new and retrofit applications. For retrofit applications, it should not take the place of a catch basin for the systems that have been verified. Also, for retrofit applications, it should be installed in lateral lines and not main trunk lines. 􀂖 The system is particularly well suited in constricted areas and where space is limited. 􀂖 It also is suitable for use in areas of high potential pollutant loads (DEP Stormwater Policy Standard 5), where it may be used effectively in capturing and containing oil and chemical spills. Web site: www.state.ma.us/dep/brp/stormwtr/ stormpub.htm. Considerations/Limitations 􀂖 Systems are not expected to provide significant nutrient (nitrogen and phosphorus) or fecal coliform removal. 􀂖 The systems are not recommended for use in critical areas, such as public drinking water supplies, certified vernal pools, public swimming beaches, shellfish growing areas, cold water fisheries, and some Areas of Critical Environmental Concern (ACECs), except as a pretreatment device for BMPs that have been approved by DEP for use in critical areas. The structural BMPs approved for use in critical areas are described in Standard 6 of the Stormwater Management Policy, www.state.ma.us/dep/brp/stormwtr/stormpub.htm. 􀂖 There is a limited set of useful data for predicting the relationship between treatment efficiency and loading rates. Removal efficiencies have not been demonstrated for all unit sizes. 􀂖 Further research is needed to determine how much TSS bypasses the treatment chamber during certain, higher velocity storm events which recur less frequently. 􀂖 Systems require regular maintenance to minimize the potential for washout of of the accumulated sediments. Reliability/Maintenance All BMPs require scheduled, routine maintenance to ensure that they operate as efficiently as possible. Although maintenance requirements are site specific, a general relationship between cleaning needs and depths of Table 2: The Stormceptor system clean out is based on 15 percent of the sediment storage volume in the unit. Model Number Sediment Depth (feet) STC 900 0.5 STC 1200 0.75 STC 1800 1 STC 2400 1 STC 3600 1.25 STC 4800 1 STC 6000 1.5 STC 7200 1.25 Sediment Depths Indicating Required Maintenance sediment has been established by the manufacturer. Inspection of the Stormceptor interior should be done after major storm events, particularly in the first year of operation. It is recommended that material in the treatment chamber be pumped out by a vacuum truck semiannually, or when the sediment and pollutant loads reach about 15 percent of the total storage. If the unit is used for spill containment, it should be pumped after the event is contained. Typical cleaning costs were estimated by the manufacturer in 1998 to be $250, with disposal costs averaging $300 to $500. The expected life of a system has been estimated to be 50 to 100 years. References Winkler, E.S. 1998. “Technology Assessment, Stormceptor.” University of Massachusetts, Amherst, MA. STEP Web site: www.stepsite.org/progress/reports Massachusetts Department of Environmental Protection and Office of Coastal Zone Management. 1997. “Stormwater Management Handbooks, Volumes One and Two.” Boston, MA. Handbooks Web site: www.state.ma.us/dep/brp/stormwtr/stormpub.htm. “Performance of a Proprietary Stormwater Treatment Device: The Stormceptor. The Practice of Watershed Protection: Article 120. Thomas. R. Schueler and Heather K. Holland editors. 2000. Ellicott City, MD. United States Environmental Protection Agency. “Storm Water Technology Fact Sheet Hydrodynamic Separators.” EPA 832-F-99-017. Stormceptor Web sites: www.rinkermaterials.com/stormceptor TARP Web site: www.dep.state.pa.us/dep/deputate/pollprev/techservice s/tarp.