three county fairgrounds stormwater permit application

8/8/2019 Three County Fairgrounds Stormwater Permit Application

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Storm waterDrainage ReportCity of Northampton Stormwater Permit Application

For:

Prepared by:~ ~ ~ T h e BerkshireDesignGroup, Inc.4 Allen Place, Northampton, Massachusetts 0 I060

Three County FairgroundsPhase 1 Redevelopment PlanNorthampton, MA

October 1, 2010Revised October 25,2010Revised November 1,2010Revised November 3,2010

Prepared for:Three County Fairgrounds

59 Fair StreetNorthampton, MA 01060


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STORMWATER MANAGEMENTPERMIT Fcc: PaidDale: Paid

Pc:mulllCity ofNortta.mptonDCplrlmenl of Public: W o r k . ~

APPLICATION Approved By ' _____Appro . aJ Dati: - - - , , = _ ~( For IJPW 1J.Je only)1. Project I Site Information

ProjectlSiteName: : r 1 y V ' r M ' l \ ~ ~ N J \ . l M S - ? L . . ' & . i . 1 2 L r t l e \ 6 ( ~ ~ Project Street I Location: S1' ~ J ~ + Assessor's Map: -- 2 f f ~ Parcel(s): ""2.6"(Estimated Area to be Disturbed (rr): _--7\--'-'-D-'>LJJ-I.O;.."1B-""-'-\'L/-=-_________Total Area ofimpervious Surfaces:(paved, parking, decks, roofs, etc.) (rr)

Existingi30,9'2- Proposed

Project Type (check one)CJ Residential Site (I unit and 1-5 Acres Disturbed)CJ Residential Site (I unit and greater than 5 Acres Disturbed)CJ Minor Residential Subdivision (I lot and disturbing I to 5acres ofland)CJ Residential Subdivision and Other Residential such asTownhouse or Retirement Development (2 or more units in B

common plan of development)CJ Commercial SubdivisionI j9..commerciaJ or Industrial Site ~ c : : : CJ Land Disturbance Only (No change in s ite use or buildings .May include reconstruction of parking lots, roads, anddriveways' utility work; and lawn and landscaping work.)

2. Applicant InformationName: ~ . j c . e . . ;\v.\\c r)'3;7:Address: 0/1 lJ 50llih ?t-.-eef-Telephone: lfB- S8Y- '1030E-Mail: rna; Ie h 4 b o . r j ~ d l ~ F ~ : ____________________________

4. Certification

53D. "\:} IPermit Review and Inspection Fee570051 , 1005700 or SI per linear foot of roadway orcommon driveway (which ever is greater)52000 or 52 per linear foot of roadway orcommon driveway (which ever is greater)52000 or 52 per linear foot of roadway orcommon driveway (which ever is greater)

I- 5700 per acre disturbed (maximum of55,OOO)5100 per acre disturbed

3. Owner Information(if different from (%;ca . t )&uce.. 7h4

I herby certify that the information contained herein Including all attachments Is true, accurate and completeto the best of my k.nowledge. Further, l grant the Northampton Department of Public Works and its agentspermission to enter the propert y to review this application and make inspections during and aftercL v4 /!)8;Uo) _ Applient;S ~ i ~ a l u r e dateR ? v : : e ~ ~ b ~ ~ " ~ \ C> " B t - O L e S t J &ro;-S

UJ&t!J4t FOwner's sig;.ature . Date


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5. Application RequirementsTh e application to the Northampton Department of Public Works (DPW) fo r a StormwaterManagement Permit must include submission of the following:

ill Completed and Signed Stormwater Management Permit Applicationo Non-Refundable Permit Review and Inspection Fee \l/A~ O p e r a t i o n , Maintenance, and Inspection Agreement~ h r e e complete copies of the Stonnwater Management Plan an d Erosion an d Sediment

Control Plan prepared by a professional engineer licensed by the Commonwealth ofMassachusetts, and including th e minimum documentation listed below (see th eNorthampton Stonnwater Management Ordinance (Chapter 22 , Article V) for moreinformation): :2--?-ofILSProject Documentation:(Check circles below indicating that you have provided the following minimum infonnation)

A Identity all operators for the project site and the potions over which each operator has control.ci::All plans submitted have been prepared and stamped by a professional engineer licensed bythe Commonwealth of Massachusettso The applicant has certified on the drawings that all clearing, grading. drainage, construction ,and development shall be conducted in strict accordance with the planf:f Locus mapi l l The existing zoning, and land use at the siteThe proposed land useC4 The location of existing and proposed easements The location of existing and proposed utilities

-fQ The site ' s existing & proposed topography with contours at 2 foot intervalsfQ Soils investigation (by a Certified Soil Evaluator or Certified Professional Soil Scientist)including borings or test pits, to a depth greater than 4 ft. below estimated seasonal ground

water for areas where construction of infiltration practices will occur.Q Estimated seasonal high groundwater elevation (November to April) in areas to be used forstorm water retention, detention, or infiltration (by a Certified Soil Evaluator or CertifiedProfessional Soil Scientist).A description & delineation of existing stonmwater conveyances. impoundments, andwetlands on or adjacent to the site or into which stom] water flows.

!Q A delineation of 100-year flood plains, if applicable.The existing and proposed vegetation and ground surfaces with runoff coefficient for each.S{. A drainage area map showing pre and post construction watershed boundaries, drainage area.stonm water flow paths, and receiving water.A description and drawings of all components of the proposed drainage system including:I) tbe structural details for all components of the proposed drainage systems and stonm

water management facilities (including size, inverts , and grade);2) all measures for the detention , retention or infiltration of water;3) all measures for the protection of water quality;4) notes on drawings specitying materials to be used, construction specifications, and

typicals;5) the existing and proposed site hydrology with supporting drainage calculations (includingthe 1,2, 10 , and 100 year NRCS design stonms) ;Northampton Department of Public WorksStonnwater Management Penn it

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6) proposed improvements including location of buildings or other structures, impervioussurfaces. and drainage facilities, if applicable;7) location, cross sections, and profiles of all potentially impacted brooks, streams, drainageswales and their method of stabilization; and8) proposed ownership of drainage system structures.\l- Estimate ofthe total area expected to be disturbed by excavation , grading or otherconstruction activities.Iii.. A description and location of all measures (i.e., Best Management Practices) that will beimplemented as part of the construction activity to control pollutants in storm waterdischarges. A description of when each control measure will be implemented in theconstruction schedule, which operator is responsible for the implementation of each controlmeasure and a maintenance and inspection schedule for each control measure duringconstruction.6( A description of construction and waste materials expected to be stored on-site, and adescription of controls to reduce pollutants from these materials including storage practices tominimize exposure of the materials to storm water, and spill prevention and response .P- Timing, schedules, and sequence of development including clearinjl, s t r i p p i ~ g , "m rading,. Iconstruction, final grading, and vegetative stabilization. I _ Ui 1\ tIL. 5>\>'0 M1 \o:>'tT\'\

L-Y l . . l W t : ~ "5'Wt" P ; o('{ 06. Application Submission, Review, and Approval Procedures q ) t 1 " * , , , " d - ~ 0


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Three County Fairgrounds 10/08/09 Stormwater Report Checklist Page 1 of 8

Massachusetts Department of Environmental ProtectionBureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

A. Introduction

Important: Whenfilling out forms

on the computer,use only the tabkey to move yourcursor - do notuse the returnkey.

A Stormwater Report must be submitted with the Notice of Intent permit application to documentcompliance 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 offeredhere as a tool to help the applicant organize their Stormwater Management documentation for theirReport 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 inVolume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared andcertified 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 (seepage 2) that certifies that the Stormwater Report contains all required submittals.

1This 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 requiredby Standard 8

2

Operation and Maintenance Plan required by Standard 9

In addition to all plans and supporting information, the Stormwater Report must include a brief narrativedescribing stormwater management practices, including environmentally sensitive site design and LIDtechniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans arerequired 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 sitewhere infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas forboth 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 ofthe Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. Thesoils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of theMassachusetts Stormwater Handbook.

To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater ReportChecklist by checking the box to indicate that the specified information has been included in theStormwater Report. If any of the information specified in the checklist has not been submitted, theapplicant must provide an explanation. The completed Stormwater Report Checklist and Certificationmust be submitted with the Stormwater Report.

1The 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 tothe 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 inthe Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves theproject and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Planbefore commencing any land disturbance activity on the site.


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Massachusetts Department of Environmental ProtectionBureau of Resource Protection - Wetlands ProgramChecklist for Stormwater ReportB. Stormwater Checklist and CertificationThe following checklist is intended to serve as a guide for applicants as to the elements that ordinarilyneed to be addressed in a complete Stormwater Report. The checklist is also intended to provideconservation commissions and other reviewing authorities with a summary of the components necessaryfor a comprehensive Stormwater Report that addresses the ten Stormwater Standards.Note: Because stormwater requirements vary from project to project, it is possible that a completeStormwater Report may not include information on some of the subjects specified in the Checklist. If it isdetermined that a specific item does not apply to the project under review , please note that the item is. notapplicable (N .A.) and provide the reasons for that determination.A complete checklist must include the Certification set forth below signed by the Registered ProfessionalEngineer who prepared the Stormwater Report.Registered Professional Engineer's CertificationI have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term PollutionPrevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Longterm Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (ifincluded) and the plans showing the stormwater management system, and have determined that theyhave been prepared in accordance with the requirements of the Stormwater Management Standards asfurther elaborated by the Massachusetts Stormwater Handbook. I have also determined that theinformation presented in the Stormwater Checklist is accurate and that the information presented in theStormwater R e p o ~ 7 1 " ~ ~ ~ 5 \ - ~ ~ ~ date of this permit application.Registered Professional Engineer Block and a t u r e

. Signature and DateIoj e/zDl 0 I

ChecklistProject Type: Is the application for new development, redevelopment, or a mix of new andredevelopment?D New development[8J RedevelopmentD Mix of New Development and Redevelopment

Three County Fairgrounds 10 /08109 Stormwater Report Checkl ist Page 2 of 8


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Checklist (continued)

LID Measures: Stormwater Standards require LID measures to be considered. Document whatenvironmentally sensitive design and LID Techniques were considered during the planning and design of

the project:

No disturbance to any Wetland Resource Areas

Site Design Practices (e.g. clustered development, reduced frontage setbacks)

Reduced Impervious Area (Redevelopment Only)

Minimizing disturbance to existing trees and shrubs

LID Site Design Credit Requested:

Credit 1

Credit 2

Credit 3

Use of country drainage versus curb and gutter conveyance and pipe

Bioretention Cells (includes Rain Gardens)

Constructed Stormwater Wetlands (includes Gravel Wetlands designs)

Treebox Filter

Water Quality Swale

Grass Channel

Green Roof

Other (describe):Media filtration system inlets for detention system

Standard 1: No New Untreated Discharges

No new untreated discharges

Outlets have been designed so there is no erosion or scour to wetlands and waters of theCommonwealth

Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included.


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Standard 2: Peak Rate Attenuation

Standard 2 waiver requested because the project is located in land subject to coastal storm flowageand stormwater discharge is to a wetland subject to coastal flooding.

Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hourstorm.

Calculations provided to show that post-development peak discharge rates do not exceed pre-development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-siteflooding increases during the 100-year 24-hour storm, calculations are also provided to show thatpost-development peak discharge rates do not exceed pre-development rates for the 100-year 24-hour storm.

Standard 3: Recharge

Soil Analysis provided.

Required Recharge Volume calculation provided.

Required Recharge volume reduced through use of the LID site Design Credits.

Sizing the infiltration, BMPs is based on the following method: Check the method used.

Static Simple Dynamic Dynamic Field1

Runoff from all impervious areas at the site discharging to the infiltration BMP.

Runoff from all impervious areas at the site is notdischarging to the infiltration BMP and calculationsare provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient togenerate the required recharge volume (to the maximum extent practicable)

Recharge BMPs have been sized to infiltrate the Required Recharge Volume

Recharge BMPs have been sized to infiltrate the Required Recharge Volume onlyto the maximumextent 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 extentpracticable. As a redevelopment project

Calculations showing that the infiltration BMPs will drain in 72 hours are provided.

Property includes a M.G.L. c. 21E site or a solid waste landfill and a mounding analysis is included.

180% TSS removal is required prior to discharge to inf iltration BMP if Dynamic Field method is used.


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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 moundinganalysis is provided.

Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetlandresource areas.

Standard 4: Water Quality

The Long-Term Pollution Prevention Plan typically includes the following:

Good housekeeping practices;

Provisions for storing materials and waste products inside or under cover;

Vehicle washing controls;

Requirements for routine inspections and maintenance of stormwater BMPs; Spill prevention and response plans;

Provisions for maintenance of lawns, gardens, and other landscaped areas;

Requirements for storage and use of fertilizers, herbicides, and pesticides;

Pet waste management provisions;

Provisions for operation and management of septic systems;

Provisions for solid waste management;

Snow disposal and plowing plans relative to Wetland Resource Areas;

Winter Road Salt and/or Sand Use and Storage restrictions;

Street sweeping schedules;

Provisions for prevention of illicit discharges to the stormwater management system;

Documentation that Stormwater BMPs are designed to provide for shutdown and containment in theevent 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 anattachment to the Wetlands Notice of Intent.

Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule forcalculating 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, ifapplicable, the 44% TSS removal pretreatment requirement, are provided.


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Standard 4: Water Quality (continued)

The BMP is sized (and calculations provided) based on:

The or 1 Water Quality Volume or

The equivalent flow rate associated with the Water Quality Volume and documentation isprovided showing that the BMP treats the required water quality volume. Per STC Sizing

The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietaryBMP and proposed TSS removal rate is provided. This documentation may be in the form of thepropriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbookand submitting copies of the TARP Report, STEP Report, and/or other third party studies verifyingperformance of the proprietary BMPs. Rated 2 on MASTEP

A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showingthat 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 PollutionPrevention 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 priortothe discharge of stormwater to the post-construction stormwater BMPs.

The NPDES Multi-Sector General Permit does notcover the land use.

LUHPPLs are located at the site and industry specific source control and pollution preventionmeasures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snowmelt and runoff, and been included in the long term Pollution Prevention Plan.

All exposure has been eliminated.

All exposure has notbeen 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 andgrease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oilgrit 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 MassDEPhas approved for stormwater discharges to or near that particular class of critical area.

Critical areas and BMPs are identified in the Stormwater Report.


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Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximumextent practicable

The project is subject to the Stormwater Management Standards only to the maximum ExtentPracticable as a:

Limited Project

Small Residential Projects: 5-9 single family houses or 5-9 units in a multi-family developmentprovided 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 developmentwith a discharge to a critical area

Marina and/or boatyard provided the hull painting, service and maintenance areas are protectedfrom 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 anexplanation 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 toimprove existing conditions is provided in the Stormwater Report. The redevelopment checklist foundin Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document thatthe proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatmentand 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 thefollowing 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 containingthe information set forth above has been included in the Stormwater Report.


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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 whyit is not possible to submit the Construction Period Pollution Prevention and Erosion andSedimentation Control Plan with the application. A Construction Period Pollution Prevention andErosion and Sedimentation Control has notbeen included in the Stormwater Report but will besubmitted beforeland disturbance begins.

The project is notcovered by a NPDES Construction General Permit.

The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in theStormwater 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 andincludes 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 notthe owner of the parcel where the BMP is located and the StormwaterReport includes the following submissions:

A copy of the legal instrument (deed, homeowners association, utility trust or other legal entity)that establishes the terms of and legal responsibility for the operation and maintenance of theproject site stormwater BMPs;

A plan and easement deed that allows site access for the legal entity to operate and maintainBMP 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 tothe discharge ofany stormwater to post-construction BMPs.


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Three County Fairgrounds - Phase 1 October 1, 2010 Revised 10/25/10 & 11/1/10& 11/3/10

Northampton, Massachusetts Stormwater Drainage Report

The Berkshire Design Group, Inc. Page 1

Table of Contents

Introduction 2

Site Terrain and Soils 3

Existing Conditions 3

Proposed Conditions 5

Calculations and Design 6

MADEP Stormwater Standards 8

Summary 10

Figures

Figure 1 Pre- Development Drainage Area Map

Figure 2 Post Development Drainage Area Map

Figure 3 USDA Soils Map

Appendices

Appendix A Pre- and Post Development Hydrologic Calculations

Appendix B Soil Test Pit Information

Appendix C TSS Removal Summary and Calculations

Appendix D Standard 3 Recharge Calculations

Appendix E Proposed Stormwater Management System Operation &Maintenance

P Plan

Appendix F Long Term Pollution Prevention Plan


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infiltration trench designed specifically for the phase 1 portion of the project,

stormwater treatment chamber, and 2 existing detention ponds.

Site Terrain and Soils

The project site is comprised of a relatively flat terrain with the exception of thesteep 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 LoamHydrologic Group: C

Depth to Water Table: 0.0-1.5

(96A) Hadley Silt LoamHydrologic Group: B


(98A) Winooski Silt LoamHydrologic Group: B


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 ConditionsThe 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:


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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 gravelareas. The area drains to existing catch basins which direct the stormwater to the

existing detention basin at the east end of the site (shown as E-Pond1 on Figure

1). The easterly detention pond has 2 outlets: The first outlet is a 12 CMP

located on the north edge of Fair Street which discharges water across the street to

the property line located at the southeastern area of the site (shown as E-CP1 on

Figure 1). The second outlet is a catch basin located just south of Horse Barn H &

C. When the level of water in the pond exceeds elevation 117, it overflows out

of the catch basin and spills over Cross Path Road into the adjacent property

(shown as E-CP3 on Figure 1) causing standing water in the spring and summer

and frozen ponding in the winter. Occasionally when a large fairgrounds event is

planned, the detention pond is pumped at 200gpm (0.45cfs) to an existing catch

basin on the west side of the site (shown as E-Pond2 on Figure 1) in order to drain

the adjacent area. It is pertinent to pump the drainage system due to the fact that

the only piped outlet is at elevation 116 on Cross Path Road. For the sake of

consistency within pre and post calculations, the pump system is assumed to run

full time for the duration of the storm events. This allows a similar comparison

between existing conditions and the proposed site design. The pump is modeled

as a pond with a base flow out of 0.45cfs which discharges to the Williams Street

Brook system (shown as E-CP2 on Figure 1) which is undersized in most storms.

E-2

E-2 is approximately 10.75 acres and contains a portion of the existing track,buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into

existing catch basins which discharge into the westerly retention basin (E-Pond2).

The detention pond discharges into the Williams Street Brook drainage system

through a 12 pipe (E-CP1).

E-3

E-3 is approximately 10.38 acres and contains adjacent houses, buildings, grassed

areas, paved areas, and gravel areas. This area sheet flows into existing catch

basins which discharge directly into the Williams Street Brook drainage system

(E-CP1).

E-4

E-4 is approximately 7.52 acres and is located south of the main area and contains

a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This

area sheet flows overland to the southern property line (E-CP2).

E-5


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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-6E-6 is approximately 0.68 acres and is located north of the main area and contains

a portion of Ferry Road, abutting houses, and grassed areas. This area sheet flows

toward existing catch basins where it is directed to the easterly detention basin

which drains to the south eastern area of the site (E-CP2).

IV. Proposed Conditions

The proposed project does not alter the site significantly and it retains the general

flow patterns of the existing stormwater system. The proposed site contains 6

drainage areas (P-1 through P-6) and 3 different control points used fordetermining peak runoff rates. The drainage areas and control points are shown

on the Post-Development Drainage Area Plan (see Figure 2). The following is a

brief description of each drainage area:

P-1

P-1 is approximately 27.48 acres and contains the 3 new horse barns, a new

restroom, new paved road/walk areas, a large area of the existing track, other

miscellaneous buildings, grassed areas, paved areas, a portion of the Morgan

horse rings, and gravel areas. This area of the site will contain 2 large subsurface

stone detention systems which will be hydraulically connected to the easterly

detention basin. Areas that drain directly to the subsurface system are directed tolow spots which allow for the runoff to infiltrate through the specified soil media

prior to entering the system. The area adjacent to the 3 new horse barns will drain

to a new system installed under 2 new concrete pads between the barns. Each pad

contains drain inlets with 2 sumps. Before horse manure is permitted to be

stockpiled on the pads, the drains inlets are replaced with covers to prohibit

potential contamination of the drainage system and the horse barn roof areas are

piped directly into the drain system to allow for separation of roof runoff which

will increase the water quality entering the detention basin. The outlet from the

new subsurface system will be outfitted with a stormwater treatment chamber

designed to remove a minimum of 80% TSS for the increase in impervious area

on site.

The rest of the area within P-1 drains to existing catch basins or sheet flows to the

existing detention basins on the east side of the site (shown as P-Pond1 on Figure

2). The detention pond has 3 outlets. The first outlet is a 12 CMP located on the

north edge of Fair Street which discharges water across the street to the property

(P-CP2); unlike in existing conditions, the existing low catch basin adjacent to

Cross Path Road is proposed to be removed in this phase and a berm at elevation


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117.2 (second outlet) will be constructed to ensure the water flowing to the east

is less than it was in existing conditions (P-CP3). Occasionally when a large

fairgrounds event is planned, the retention pond is pumped (the site will continue

to utilized the existing pump at 200gpm) to an existing catch basin (P-CP1) on the

west side of the site (shown as P-Pond2 on Figure 2). In order to provide a

consistent timing of pump use for existing and proposed conditions, the pump wasmodeled as a base flow of 0.45cfs (200gpm) directed to the Williams Street Brook

drainage infrastructure and was assumed to be running at all times. With the

construction of the new drainage infrastructure, an Operation and Maintenance

plan is proposed that will require the pump system to run after storms to ensure

the drainage system will be drained within 72 hours. It is pertinent to pump the

drainage system due to the fact that the only outlet remains at Cross Path Road.

An infiltration trench has been designed to catch and retain the runoff from a large

part of the main road that is proposed in the middle of the site. The system

consists of a long and shallow stone filled bed which will catch the runoff from a

large amount of the new pavement, and allow the runoff to recharge into the

ground. The system has been designed to be very shallow and has low spot at the

center of the trench which will promote the runoff to infiltrate as well as serve as a

monitoring system for determining the trenchs performance.

P-2

P-2 is approximately 9.27 acres and contains a portion of the existing track,

buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into

existing catch basins which discharge into the westerly retention basin (P-Pond2).

The detention pond discharges into the Williams Street Brook drainage system

through a 12 pipe (P-CP1).

P-3P-3 is approximately 8.46 acres and contains adjacent houses, buildings, grassed

areas, paved areas, new horse rings, and gravel areas. This area sheet flows into

existing catch basins which discharge directly into the Williams Street Brook

drainage system (P-CP1).

P-4

P-4 is approximately 7.52 acres and is located south of the main area and contains

a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This

area sheet flows overland to the southern property line (P-CP2).

P-5

P-5 is approximately 3.41 acres and is located north of the main area and contains

a portion of Ferry Road, a basketball court, and grassed areas. This area sheet

flows over Ferry Road where it begins to pond until it enters the existing westerly

detention basin which drains to the Williams Street Brook system (P-CP1).


19/99




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 intime and allows volume dependent routing runoff calculations to occur. These

calculations are included in the appendices.

The watershed boundaries for calculation purposes are divided according to the

proposed site grading and the natural limits of the drainage areas. The curve

numbers (CNs) and times of concentration for the existing and proposed

subcatchment areas are based on the soil type and the existing and proposed cover

conditions at the site. The soil hydrologic group assumed for the site is noted in

Figure 3. Watershed subcatchment areas, runoff coefficients and watercourse

slopes are based on survey information.

Calculations were performed for the 2-, 10-, and 100-year frequency storms under

existing and proposed conditions. The results of the calculations are presented in

Table 1 below. Appendix A presents the Hydrocad calculations.

Flow Rates & Water Quantity

Table 1 on the following page presents the comparison of flow rates and water

quantity at both existing and proposed control points.


20/99




Table 1 Peak Flow and Volume

Summary

*Names in parentheses refer to HydroCad model and calculations.

Note that the volumes are less for proposed conditions during the first 24 hoursafter the storm began. This is due to the large increase in storage area within the

proposed detention system. However when the pump system drains the proposed

basin, the volume directed to the Williams Street Brook control point (CP3) will

be greater in proposed conditions.

VI. MADEP Stormwater Standards Compliance

The following section details how the project follows the MADEP Stormwater

Management Policys ten stormwater management standards.

Standard 1 - Untreated StormwaterNo new outlets are proposed on the site and the site has added treatment capacity

to the existing site through the use of infiltration trenches, deep sump basins, a

large subsurface detention system with filtration inlet areas, and a stormwater

treatment chamber. The existing stormwater system has been modified to treat the

stormwater prior to discharging it off site.

Condition

& Point of

Analysis

Peak Flow

Rate(cfs)

Volume

(acre-ft)

Peak Flow

Rate(cfs)

Volume

(acre-ft)

Peak Flow

Rate(cfs)

Volume

(acre-ft)

Existing

Control Pt.

(E-CP1)*

Proposed

Control Pt.

(P-CP1)*

Existing

Control Pt.

(E-CP2)*

Proposed

Control Pt.

(P-CP2)*

Existing

Control Pt.

(P-CP3)*

Proposed

Control Pt.

(P-CP3)*

2.779

0.00 0.000 0.00 0.000 35.50 2.620

0.00 0.000 1.52 0.178 35.51

33.17 7.960

7.14 2.582 16.48 4.543 29.19 7.310

7.52 2.696 18.21 4.891

2-Year Storm 10-Year Storm 100-Year Storm

3.00 4.50 6.50

23.43 4.551

4.21 0.474 10.65 2.620 21.42 4.538

4.21 0.879 10.82 3.136


21/99




Standard 2 - Post-Development Peak Discharge Rates

The stormwater system is designed so that post-development peak discharge rates

are equal or less than pre-development peak discharge rates leaving the site.

Although the proposed site will have an increase of impervious area, the new

subsurface detention systems will provide significant storage and reduce the peak

flows from existing conditions. During the 24 hour storm the volume of waterdischarged to the control points will be less than existing conditions due to the

large storage area proposed. However because the system requires pumping to

drain, the proposed basin is not fully drained after the 24 hour period shown in the

peak flow/volume calculations. The remaining volume left after the storm will be

drained by the pump for the next several hours (which happens in existing

conditions as well). However, the peak flows will be equal to or reduced from

existing conditions in the 2, 10, and 100 year storms which will improve the

functionality of the site. Refer to Table 1 Peak Flow and Volume Summary and

Appendix A for HydroCAD calculations.

Standard 3 - Recharge to GroundwaterThe proposed redevelopment has been designed to provide recharge groundwater

to the maximum extent practicable in proposed conditions. In the full build of the

project (a mix of new and redevelopment) a large infiltration basin is proposed at

the south parcel. However the connection under the roadway to this basin was

proposed at this phase and shallow infiltration trench systems are proposed at the

south side of the main roadway and adjacent to 2 of the new barns. These systems

have been sized to accommodate and recharge the increase in impervious area and

are designed to capture approximately 84.8% of the 1.16acres of increased

impervious area. The basin has been designed to be very shallow which will

allow it to drain down in less than 72 hours and will encourage infiltration on the

smaller more common storms.

Note that the infiltration trench was not included in the peak flow calculations to

provide a more conservative proposed peak flow and volume estimate.

Standard 4 Water Quality

The proposed redevelopment will provide increase water quality treatment of the

site. The proposed detention system has been designed with multiple inlet areas

which allow the runoff to infiltrate through soil media prior to entering the system

which provides treatment for runoff very similar to a rain garden. The new

detention systems will then discharge to a stormwater treatment chamber (STC

900) which has been sized to treat the increase in impervious area with a TSSremoval rate of 81.2% (see appendix for StormCeptor sizing chart). The

treatment chamber then discharges into the existing basin where any remaining

solids have the opportunity to settle on the bottom.


22/99




The site will also be implementing an improved manure management system

between the horse barns. Contaminated water will not be able to enter the system

as it will be block until the manure has left the vicinity of the drains

Standard 5 - Higher Potential Pollutant Loads

The proposed project is not expected to yield high potential pollutant loads.

Standard 6 - Protection of Critical Areas

The project site does not discharge to critical areas as defined in MA DEP

Stormwater Policy Handbook.

Standard 7 - Redevelopment Projects

The proposed project is a redevelopment project and will improve the site to the

maximum extent practicable by incorporating recharge and water quality measures

that will function for the phase until the full build out is constructed.

Standard 8 - Erosion/Sediment ControlErosion and sediment controls will be fully been incorporated into the project

design to prevent erosion, control sediments, and stabilized exposed soils during

construction and land disturbance. This project is covered by a NPDES

Construction General Permit and a SWPPP will be submitted by the contractor

prior to the start of construction.

Standard 9 - Operation/Maintenance Plan

An Operation and Maintenance Plan for the proposed project is included in

Appendix E. It includes general controls for construction and long term

maintenance of the stormwater management system.

Standard 10 Prohibition of Illicit Discharges

No illicit discharges will occur as a result of this project.

VII. Summary

The impervious area from existing to proposed conditions will increase by

approximately 1.16 acres from the construction of the 3 new barns and new paved

areas. The combination of the improvements to the stormwater system on site will

ensure that the redevelopment will significantly improve the existing site.


23/99

Three County Fairgrounds-Phase 1 October 1, 2010Revised 11/1/10

Northampton, Massachusetts Stormwater Drainage Report Appendix

The Berkshire Design Group, Inc. Figures

Figures


24/99

"z"lIII"5z""0


25/99

_The_Be rksh i r e=-oos ;gn_ Group, Inc.

100_........... i'1ft'a,"'F'"\, .-"

I I

4 Allen Place Northampton, MassachuseUs 01060(413) 5827000 FAX (413) 5827005

I

--,~ t /

I

Figure Title:Post-Developement Drainage Area MapThree County Fairgrounds

NORTHAMPTON MASSACHUSETTS

....:.." "'",,,,,,,,,..../'-c ...: I :;. ...U l . )

..,\,\11111111111111

Revisions:10125110

Date: Scale:10/1/10 1"=300'

Figure Number

2


26/99

_The_Be rksh i r e=-oos;gn_ Group, Inc.4 Allen Place Northampton, MassachuseUs 01060(413) 582-7000 FAX (413) 582-7005

Figure Title: Hydrologic Soils Group MapThree County Fairgrounds

NORTHAMPTON MASSACHUSETTS

Revisions:

Date: Scale:10/1/10 1"=300'

Figure Number

3


27/99

Three County Fairgrounds-Phase 1 October 1, 2001Revised 11/1/10 &11/3/10

Northampton, Massachusetts Stormwater Drainage Report Appendix

The Berkshire Design Group, Inc. Appendix

Appendix A Pre- and Post Development

Hydrologic Calculations


28/99

E-1

Area to Easterly BasinE-2

Area To W esterly Basin

E-3

Direct to Road DrainageInfrastructure

E-4

Southeast Area of Siteto South Property Line

E-5

Area north of site(includes basketball

court)

E-6

Northeast of Site (Roadand abutting property)

P-1

Area to Easterly Basin

P-2

Area To W esterly Basin

P-3

Direct to Road DrainageInfrastructure

P-4

Southeast Area of Siteto South Property Line

P-5

Area north of site(includes basketball

court)

P-6

Northeast of Site (Roadand abutting property)

E-CP1

Williams St. BrookInfrastructure

E-CP2

South Property Line

E-CP3

Cross Paths Road

P-CP1

Williams St. BrookInfrastructure

P-CP2

South Property Line

P-CP3

Cross Paths Road

E-Pond1

Existing East DetentionBasin

E-Pond2

Existing West DetentionBasin

E-Pump

CB

Existing Pump Systemfrom East Basin

E-Pump.

CB

Existing Pump Systemfrom East Basin

P-Pond1

Existing East DetentionBasin & New Trench

Systems

P-Pond2

Existing West DetentionBasin

Drainage Diagram for Three Country Fairgrounds Phase 1- Stormwater Permit rev110310

Prepared by The Berkshire Design Group 11/3/2010HydroCAD 8.00 s/n 000752 2006 HydroCAD Software Solutions LLC

Subcat Reach Pond Link


29/99

Revised 11/3/10

Three Country Fairgrounds Phase 1- Stormwater Permit rev110310Page 2Prepared by The Berkshire Design Group

11/3/2010HydroCAD 8.00 s/n 000752 2006 HydroCAD Software Solutions LLC

Area Listing (selected nodes)

Area (acres) CN Description (subcats)

58.105 61 >75% Grass cover, Good, HSG B (E-1,E-2,E-3,E-4,E-5,E-6,P-1,P-1,P-2,P-3,P-4,P-5,P

4.859 74 >75% Grass cover, Good, HSG C (E-4,E-5,P-4,P-5)

1.586 85 Existing Gravel/Stone Dust (P-1)

15.840 85 Gravel/Stone Dust (E-1,E-2,E-3,E-4,P-2,P-3,P-4)

0.968 96 Morgan Rings (stonedust) (P-3)

7.181 96 Proposed TRG Paving (P-1,P-1,P-3)

0.413 98 (P-1)

1.362 98 Basin (E-2,E-4,P-2,P-4)

0.460 98 Basins (E-1,P-1)

1.949 98 Paved parking (E-5,E-6,P-5,P-6)

0.702 98 Paved parking & roofs (P-1)

2.140 98 Road (E-4,P-4)

17.585 98 Road/Roof (E-1,E-2,E-3,P-1,P-2,P-3)

0.448 98 Roof (E-4)

113.597


30/99

Revised 11/3/10Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi

Page 3Prepared by The Berkshire Design Group11/3/2010HydroCAD 8.00 s/n 000752 2006 HydroCAD Software Solutions LLC

Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 pointsRunoff by SCS TR-20 method, UH=SCS

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method

Runoff Area=1,048,195 sf Runoff Depth>0.85"Subcatchment E-1: Area to Easterly BasinFlow Length=888' Tc=17.0 min CN=73 Runoff=15.84 cfs 1.712 af

Runoff Area=468,308 sf Runoff Depth>1.25"Subcatchment E-2: Area To Westerly BasinFlow Length=1,136' Tc=16.9 min CN=80 Runoff=11.10 cfs 1.116 af

Runoff Area=451,921 sf Runoff Depth>0.85"Subcatchment E-3: Direct to Road Drainage InfrastructureFlow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=6.47 cfs 0.737 af

Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment E-4: Southeast Area of Site to South Property

Flow Length=750' Tc=17.3 min CN=71 Runoff=4.21 cfs 0.474 af

Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment E-5: Area north of site (includes basketball cFlow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af

Runoff Area=29,661 sf Runoff Depth>1.19"Subcatchment E-6: Northeast of Site (Road and abutting propFlow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af

Runoff Area=27.478 ac Runoff Depth>1.18"Subcatchment P-1: Area to Easterly BasinFlow Length=888' Tc=17.0 min CN=79 Runoff=26.74 cfs 2.711 af

Runoff Area=403,083 sf Runoff Depth>1.37"Subcatchment P-2: Area To Westerly BasinFlow Length=1,136' Tc=16.9 min CN=82 Runoff=10.64 cfs 1.060 af

Runoff Area=8.458 ac Runoff Depth>0.96"Subcatchment P-3: Direct to Road Drainage InfrastructureFlow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=75 Runoff=6.07 cfs 0.674 af

Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment P-4: Southeast Area of Site to South PropertyFlow Length=750' Tc=17.3 min CN=71 Runoff=4.21 cfs 0.474 af

Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment P-5: Area north of site (includes basketball cFlow Length=545' Tc=22.7 min CN=74 Runoff=2.15 cfs 0.257 af

Runoff Area=29,664 sf Runoff Depth>1.19"Subcatchment P-6: Northeast of Site (Road and abutting propFlow Length=625' Tc=12.3 min CN=79 Runoff=0.74 cfs 0.067 af

Inflow=7.52 cfs 2.696 afReach E-CP1: Williams St. Brook InfrastructureOutflow=7.52 cfs 2.696 af

Inflow=4.21 cfs 0.879 afReach E-CP2: South Property LineOutflow=4.21 cfs 0.879 af

Inflow=0.00 cfs 0.000 afReach E-CP3: Cross Paths RoadOutflow=0.00 cfs 0.000 af


31/99



Inflow=7.14 cfs 2.582 afReach P-CP1: Williams St. Brook InfrastructureOutflow=7.14 cfs 2.582 af

Inflow=4.21 cfs 0.474 afReach P-CP2: South Property LineOutflow=4.21 cfs 0.474 af

Inflow=0.00 cfs 0.000 afReach P-CP3: Cross Paths RoadOutflow=0.00 cfs 0.000 af

Peak Elev=116.42' Storage=46,413 cf Inflow=16.49 cfs 1.779 afPond E-Pond1: Existing East Detention BDiscarded=0.45 cfs 0.470 af Primary=0.68 cfs 0.405 af Secondary=0.00 cfs 0.000 af Outflow=1.13 cfs 0.876 af

Peak Elev=117.32' Storage=27,837 cf Inflow=13.03 cfs 1.372 afPond E-Pond2: Existing West Detention B12.0" x 55.0' Culvert Outflow=2.01 cfs 1.064 af

Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump: Existing Pump System from East BasinOutflow=0.45 cfs 0.894 af

Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump.: Existing Pump System from East BasinOutflow=0.45 cfs 0.894 af

Peak Elev=115.73' Storage=107,696 cf Inflow=27.40 cfs 2.778 afPond P-Pond 1: Existing East DetentionDiscarded=0.45 cfs 0.894 af Primary=0.00 cfs 0.000 af Secondary=0.00 cfs 0.000 af Outflow=0.45 cfs 0.894 af

Peak Elev=117.30' Storage=27,284 cf Inflow=12.56 cfs 1.316 afPond P-Pond 2: Existing West Detention12.0" x 55.0' Culvert Outflow=1.95 cfs 1.014 af

Total Runoff Area = 113.597 ac Runoff Volume = 9.605 af Average Runoff Depth = 1.01"77.94% Pervious Area = 88.539 ac 22.06% Impervious Area = 25.058 ac


32/99



Subcatchment E-1: Area to Easterly Basin

Runoff = 15.84 cfs @ 12.26 hrs, Volume= 1.712 af, Depth> 0.85"

Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrsType III 24-hr 2 YRS Rainfall=3.00"

Area (sf) CN Description

10,000 98 Basins574,174 61 >75% Grass cover, Good, HSG B115,775 98 Road/Roof348,246 85 Gravel/Stone Dust

1,048,195 73 Weighted Average922,420 Pervious Area125,775 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




29,666 98 Basin190,948 61 >75% Grass cover, Good, HSG B126,576 98 Road/Roof121,118 85 Gravel/Stone Dust

468,308 80 Weighted Average312,066 Pervious Area

156,242 Impervious Area


33/99




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 fps2.1 660 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




292,465 61 >75% Grass cover, Good, HSG B139,412 98 Road/Roof20,044 85 Gravel/Stone Dust

451,921 73 Weighted Average312,509 Pervious Area139,412 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




0 98 Basin207,984 61 >75% Grass cover, Good, HSG B36,840 98 Road19,517 98 Roof27,926 85 Gravel/Stone Dust35,148 74 >75% Grass cover, Good, HSG C



34/99




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)




50,138 61 >75% Grass cover, Good, HSG B27,807 98 Paved parking70,681 74 >75% Grass cover, Good, HSG C




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


22.7 545 Total

Subcatchment E-6: Northeast of Site (Road and abutting property)




15,016 61 >75% Grass cover, Good, HSG B14,645 98 Paved parking



35/99




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 fps4.3 180 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



Area (ac) CN Description

0.230 98 Basins12.908 61 >75% Grass cover, Good, HSG B4.046 98 Road/Roof1.586 85 Existing Gravel/Stone Dust6.837 96 Proposed TRG Paving0.702 98 Paved parking & roofs0.323 96 Proposed TRG Paving0.433 61 >75% Grass cover, Good, HSG B0.413 98

27.478 79 Weighted Average22.087 Pervious Area5.391 Impervious Area




17.0 888 Total

Subcatchment P-2: Area To Westerly Basin




36/99




29,666 98 Basin

130,648 61 >75% Grass cover, Good, HSG B117,154 98 Road/Roof125,615 85 Gravel/Stone Dust



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


16.9 1,136 Total

Subcatchment P-3: Direct to Road Drainage Infrastructure



Area (ac) CN Description4.945 61 >75% Grass cover, Good, HSG B2.085 98 Road/Roof0.439 85 Gravel/Stone Dust0.021 96 Proposed TRG Paving0.968 96 Morgan Rings (stonedust)

8.458 75 Weighted Average6.373 Pervious Area2.085 Impervious Area


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




37/99




0 98 Basin

207,984 61 >75% Grass cover, Good, HSG B56,357 98 Road27,926 85 Gravel/Stone Dust35,148 74 >75% Grass cover, Good, HSG C



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 fps17.3 750 Total

Subcatchment P-5: Area north of site (includes basketball court)




50,138 61 >75% Grass cover, Good, HSG B

27,807 98 Paved parking70,681 74 >75% Grass cover, Good, HSG C




4.7 270 0.0040 0.95 Shallow Concentrated Flow,Grassed Waterway Kv= 15.0 fps



22.7 545 Total


38/99



Subcatchment P-6: Northeast of Site (Road and abutting property)




15,019 61 >75% Grass cover, Good, HSG B14,645 98 Paved parking



1.7 100 0.0100 1.01 Sheet Flow,Smooth surfaces n= 0.011 P2= 3.00"


4.3 180 0.0100 0.70 Shallow Concentrated Flow,Short Grass Pasture Kv= 7.0 fps

12.3 625 Total

Reach E-CP1: Williams St. Brook Infrastructure

Inflow Area = 24.538 ac, Inflow Depth > 1.32" for 2 YRS eventInflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 afOutflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 af, Atten= 0%, Lag= 0.0 min

Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs

Reach E-CP2: South Property Line



Reach E-CP3: Cross Paths Road

Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 afOutflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min



39/99



Reach P-CP1: Williams St. Brook Infrastructure



Reach P-CP2: South Property Line



Reach P-CP3: Cross Paths Road

Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 afOutflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min


Pond E-Pond1: Existing East Detention Basin

Inflow Area = 24.744 ac, Inflow Depth > 0.86" for 2 YRS event

Inflow = 16.49 cfs @ 12.26 hrs, Volume= 1.779 afOutflow = 1.13 cfs @ 16.24 hrs, Volume= 0.876 af, Atten= 93%, Lag= 238.7 minDiscarded = 0.45 cfs @ 11.85 hrs, Volume= 0.470 afPrimary = 0.68 cfs @ 16.24 hrs, Volume= 0.405 afSecondary = 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 hrsPeak Elev= 116.42' @ 16.24 hrs Surf.Area= 42,251 sf Storage= 46,413 cf

Plug-Flow detention time= 328.8 min calculated for 0.874 af (49% of inflow)Center-of-Mass det. time= 196.4 min ( 1,072.9 - 876.5 )

Volume Invert Avail.Storage Storage Description

#1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc)


40/99



Elevation Surf.Area Inc.Store Cum.Store(feet) (sq-ft) (cubic-feet) (cubic-feet)

112.00 6,800 0 0113.00 7,463 7,132 7,132114.00 8,704 8,084 15,215115.00 10,000 9,352 24,567116.00 11,362 10,681 35,248117.00 85,524 48,443 83,691118.00 272,423 178,974 262,665118.50 407,822 170,061 432,726

Device Routing Invert Outlet Devices

#1 Secondary 117.00' 100.0' long x 5.0' breadth Broad-Crested Rectangular WeirHead (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.002.50 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 2.652.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88

#2 Primary 116.00' 12.0" Vert. Invert of 12" CMP Outlet on Fair Street C= 0.600#3 Discarded 0.00' 0.45 cfs Existing Pump (200gpm) to E-CP1 at all elevations

Discarded OutFlow Max=0.45 cfs @ 11.85 hrs HW=112.07' (Free Discharge)3=Existing Pump (200gpm) to E-CP1 (Exfiltration Controls 0.45 cfs)

Primary OutFlow Max=0.68 cfs @ 16.24 hrs HW=116.42' TW=0.00' (Dynamic Tailwater)2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 0.68 cfs @ 2.20 fps)

Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.00' TW=0.00' (Dynamic Tailwater)1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)

Pond E-Pond2: Existing West Detention Basin

Inflow Area = 14.163 ac, Inflow Depth > 1.16" for 2 YRS eventInflow = 13.03 cfs @ 12.26 hrs, Volume= 1.372 afOutflow = 2.01 cfs @ 13.31 hrs, Volume= 1.064 af, Atten= 85%, Lag= 63.4 minPrimary = 2.01 cfs @ 13.31 hrs, Volume= 1.064 af


Plug-Flow detention time= 220.1 min calculated for 1.064 af (78% of inflow)

Center-of-Mass det. time= 135.4 min ( 994.0 - 858.6 )




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116.00 19,210 0 0117.00 21,276 20,243 20,243118.00 35,033 28,155 48,398119.00 64,989 50,011 98,409119.50 75,000 34,997 133,406


#1 Primary 116.26' 12.0" x 55.0' long Culvert CMP, projecting, no headwall, Ke= 0.900Outlet Invert= 116.13' S= 0.0024 '/' Cc= 0.900n= 0.011 Concrete pipe, straight & clean

Primary OutFlow Max=2.01 cfs @ 13.31 hrs HW=117.32' TW=0.00' (Dynamic Tailwater)1=Culvert (Barrel Controls 2.01 cfs @ 2.99 fps)

Pond E-Pump: Existing Pump System from East Basin

Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base FlowOutflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 0%, Lag= 0.0 minPrimary = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af

Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrsPeak Elev= 116.60' @ 0.00 hrs


#1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600

Primary OutFlow Max=0.45 cfs @ 0.00 hrs HW=116.60' TW=0.00' (Dynamic Tailwater)1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps)

Pond E-Pump.: Existing Pump System from East Basin

Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base FlowOutflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 0%, Lag= 0.0 minPrimary = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af

Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrsPeak Elev= 116.60' @ 0.00 hrs


#1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600

Primary OutFlow Max=0.45 cfs @ 0.00 hrs HW=116.60' TW=0.00' (Dynamic Tailwater)1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps)


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Pond P-Pond 1: Existing East Detention Basin & New Trench Systems

Inflow Area = 28.159 ac, Inflow Depth > 1.18" for 2 YRS eventInflow = 27.40 cfs @ 12.25 hrs, Volume= 2.778 afOutflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Atten= 98%, Lag= 0.0 minDiscarded = 0.45 cfs @ 0.00 hrs, Volume= 0.894 afPrimary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 afSecondary = 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 hrsStarting Elev= 112.84' Surf.Area= 55,135 sf Storage= 25,602 cfPeak Elev= 115.73' @ 24.00 hrs Surf.Area= 58,769 sf Storage= 107,696 cf (82,094 cf above start)

Plug-Flow detention time= 490.4 min calculated for 0.306 af (11% of inflow)Center-of-Mass det. time= (not calculated: outflow precedes inflow)


#1 112.00' 329,498 cf Surface Storage (Prismatic) Listed below (Recalc)#2 112.34' 31,003 cf Trench A (all) (Prismatic) Listed below (Recalc)

80,488 cf Overall - 2,981 cf Embedded = 77,506 cf x 40.0% Voids#3 112.34' 4,408 cf Trench C (west) (Prismatic) Listed below (Recalc)

11,021 cf Overall x 40.0% Voids#4 112.34' 5,735 cf Trench C (east) (Prismatic) Listed below (Recalc)

14,337 cf Overall x 40.0% Voids#5 112.34' 1,682 cf Trench D (north) (Prismatic) Listed below (Recalc)

4,205 cf Overall x 40.0% Voids#6 112.34' 1,682 cf Trench D (south) (Prismatic) Listed below (Recalc)

4,205 cf Overall x 40.0% Voids#7 112.84' 2,981 cf 18.0"D x 168.70'L Pipe In West Trench System x 10 Inside #2#8 111.84' 2,138 cf 18.0"D x 121.00'L Pipe In East Trench System x 10 Inside #11#9 111.34' 14,057 cf Trench E (west) (Prismatic) Listed below (Recalc)

35,142 cf Overall x 40.0% Voids#10 111.34' 15,494 cf Trench E (east) (Prismatic) Listed below (Recalc)

38,734 cf Overall x 40.0% Voids#11 111.34' 11,139 cf Trench B (all) (Prismatic) Listed below (Recalc)

29,985 cf Overall - 2,138 cf Embedded = 27,847 cf x 40.0% Voids

419,816 cf Total Available Storage


112.00 6,800 0 0113.00 7,463 7,132 7,132114.00 8,704 8,084 15,215115.00 10,000 9,352 24,567116.00 11,362 10,681 35,248117.00 95,677 53,520 88,768118.00 385,783 240,730 329,498


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112.34 17,272 0 0117.00 17,272 80,488 80,488


112.34 2,499 0 0116.75 2,499 11,021 11,021


112.34 2,920 0 0117.25 2,920 14,337 14,337


112.34 1,054 0 0116.33 1,054 4,205 4,205


112.34 1,054 0 0116.33 1,054 4,205 4,205


111.34 6,460 0 0116.78 6,460 35,142 35,142


111.34 9,311 0 0115.50 9,311 38,734 38,734


111.34 7,208 0 0115.50 7,208 29,985 29,985


#1 Primary 116.23' 12.0" Vert. Invert of 12" CMP Outlet on Fair Street C= 0.600#2 Discarded 0.00' 0.45 cfs Existing Pump (200gpm) to P-CP1 at all elevations#3 Secondary 117.20' 550.0' long x 2.0' breadth New Berm on Cross Path Rd (117.15')

Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.002.50 3.00 3.50Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.882.85 3.07 3.20 3.32


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Discarded OutFlow Max=0.45 cfs @ 0.00 hrs HW=112.84' (Free Discharge)

2=Existing Pump (200gpm) to P-CP1 (Exfiltration Controls 0.45 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.84' TW=0.00' (Dynamic Tailwater)1=Invert of 12" CMP Outlet on Fair Street ( Controls 0.00 cfs)

Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.84' TW=0.00' (Dynamic Tailwater)3=New Berm on Cross Path Rd (117.15') ( Controls 0.00 cfs)

Pond P-Pond 2: Existing West Detention Basin


Primary = 1.95 cfs @ 13.26 hrs, Volume= 1.014 af


Plug-Flow detention time= 223.0 min calculated for 1.014 af (77% of inflow)Center-of-Mass det. time= 137.9 min ( 991.3 - 853.5 )



Elevation Surf.Area Inc.Store Cum.Store

(feet) (sq-ft) (cubic-feet) (cubic-feet)116.00 19,210 0 0117.00 21,276 20,243 20,243118.00 35,033 28,155 48,398119.00 64,989 50,011 98,409119.50 75,000 34,997 133,406


#1 Primary 116.26' 12.0" x 55.0' long Culvert CMP, projecting, no headwall, Ke= 0.900Outlet Invert= 116.13' S= 0.0024 '/' Cc= 0.900n= 0.011 Concrete pipe, straight & clean

Primary OutFlow Max=1.95 cfs @ 13.26 hrs HW=117.30' TW=0.00' (Dynamic Tailwater)

1=Culvert (Barrel Controls 1.95 cfs @ 2.97 fps)


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Revised 11/3/10Type III 24-hr 10 YRS Rainfall=4.50"Three Country Fairgrounds Phase 1- Stormwater Per


Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 pointsRunoff by SCS TR-20 method, UH=SCS

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method

Runoff Area=1,048,195 sf Runoff Depth>1.89"Subcatchment E-1: Area to Easterly BasinFlow Length=888' Tc=17.0 min CN=73 Runoff=37.63 cfs 3.787 af

Runoff Area=468,308 sf Runoff Depth>2.45"Subcatchment E-2: Area To Westerly BasinFlow Length=1,136' Tc=16.9 min CN=80 Runoff=22.27 cfs 2.198 af

Runoff Area=451,921 sf Runoff Depth>1.89"Subcatchment E-3: Direct to Road Drainage InfrastructureFlow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=15.35 cfs 1.632 af

Runoff Area=327,415 sf Runoff Depth>1.74"Subcatchment E-4: Southeast Area of Site to South Property

Flow Length=750' Tc=17.3 min CN=71 Runoff=10.65 cfs 1.090 af

Runoff Area=148,626 sf Runoff Depth>1.96"Subcatchment E-5: Area north of site (includes basketball cFlow Length=545' Tc=22.7 min CN=74 Runoff=4.96 cfs 0.558 af

Runoff Area=29,661 sf Runoff Depth>2.37"Subcatchment E-6: Northeast of Site (Road and abutting propFlow Length=625' Tc=12.3 min CN=79 Runoff=1.53 cfs 0.135 af

Runoff Area=27.478 ac Runoff Depth>2.37"Subcatchment P-1: Area to Easterly BasinFlow Length=888' Tc=17.0 min CN=79 Runoff=54.78 cfs 5.424 af

Runoff Area

three county fairgrounds stormwater permit application

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