Three County Fairgrounds Stormwater Drainage Report 11-03-2010

-
•
Stormwater
Drainage Report
City of Northampton Stormwater Permit Application
For:
Prepared by:
~~~The~ Berkshire
Design
Group, Inc.
4 Allen Place, Northampton, Massachusetts 0 I060
Three County Fairgrounds
Phase 1 Redevelopment Plan
Northampton, MA
October 1, 2010
Revised October 25,2010
Revised November 1,2010
Revised November 3,2010
Prepared for:
59 Fair Street
Northampton, MA 01060

STORMWATER MANAGEMENT
PERMIT
Fcc: Paid
Dale: Paid
Pc:mulll
City ofNortta.mpton
DCplrlmenl of Public: Work.~
APPLICATION Approved By' _ _ _ _ __
Appro..·aJ Dati: =---,,=_~,-
( For IJPW 1J.Je only)
1. Project I Site Information
ProjectlSiteName: :r1yV'« rM'l~ ~NJ.lMS -?L..'&.i.12Lrtle6(~~
Project Street I Location: S1' ~J~+
Assessor's Map: -- 2ff~ Parcel(s): ""2.6"(
Estimated Area to be Disturbed (rr): _--7--'-'-D-'>LJJ-I.O;.."1B-""-'-'L/-=-__________
Total Area ofimpervious Surfaces:
(paved, parking, decks, roofs, etc.) (rr)
Existing
i30,9'2-
Proposed
•
Project Type (check one)
CJ Residential Site (I unit and 1-5 Acres Disturbed)
CJ Residential Site (I unit and greater than 5 Acres Disturbed)
CJ Minor Residential Subdivision (I lot and disturbing I to 5
acres ofland)
CJ Residential Subdivision and Other Residential such as
Townhouse or Retirement Development (2 or more units in B
common plan of development)
CJ Commercial Subdivision
I'j9..commerciaJ or Industrial Site ~c:::
CJ Land Disturbance Only (No change in site use or buildings.
May include reconstruction ofparking lots, roads, and
driveways' utility work; and lawn and landscaping work.)
2. Applicant Information
Name: ~.jc.e.. ;v.c[r)'3;7:
Address: 0/1 ~ lJ 50llih ?t-.-eef--
Telephone: lfB- S8Y- '1030
E-Mail: rna; Ie h4¥bo.rj~dl~
F~: ____________________________
4. Certification
53D. ":} I
Permit Review and Inspection Fee
5700
51 ,100
5700 or SI per linear foot of roadway or
common driveway (which ever is greater)
52000 or 52 per linear foot ofroadway or
52000 or 52 per linear foot ofroadway or
I- 5700 per acre disturbed (maximum of55,OOO)
5100 per acre disturbed
3. Owner Information
(if different from (%;ca.t)
&uce.. 7h4 ~
I herby certify that the information contained herein Including all attachments Is true, accurate and complete
to the best of my k.nowledge. Further, l grant the Northampton Department of Public Works and its agents
permission to enter the property to review this application and make inspections during and after
cL£v4 /!)8;Uo
) _ Applient;S~i~alure date
R?v::e~~b~~"~· C> ~-"Bt-OLeStJ&ro;-S
~? UJ&t!J4t F
Owner's sig;.ature . Date

5. Application Requirements
The application to the Northampton Department of Public Works (DPW) for a Stormwater
Management Permit must include submission of the following:
ill Completed and Signed Stormwater Management Permit Application
o Non-Refundable Permit Review and Inspection Fee l/A
~Operation, Maintenance, and Inspection Agreement
~hree complete copies of the Stonnwater Management Plan and Erosion and Sediment
Control Plan prepared by a professional engineer licensed by the Commonwealth of
Massachusetts, and including the minimum documentation listed below (see the
Northampton Stonnwater Management Ordinance (Chapter 22, Article V) for more
information): :2--?-ofILS
Project Documentation:
(Check circles below indicating that you have provided the following minimum infonnation)
A Identity all operators for the project site and the potions over which each operator has control.
ci::All plans submitted have been prepared and stamped by a professional engineer licensed by
the Commonwealth of Massachusetts
o The applicant has certified on the drawings that all clearing, grading. drainage, construction,
and development shall be conducted in strict accordance with the plan
f:f Locus map
ill The existing zoning, and land use at the site
~ The proposed land use
C4 The location of existing and proposed easements
® The location of existing and proposed utilities
-fQ The site's existing & proposed topography with contours at 2 foot intervals
fQ Soils investigation (by a Certified Soil Evaluator or Certified Professional Soil Scientist)
including borings or test pits, to a depth greater than 4 ft. below estimated seasonal ground
water for areas where construction of infiltration practices will occur.
Q Estimated seasonal high groundwater elevation (November to April) in areas to be used for
storm water retention, detention, or infiltration (by a Certified Soil Evaluator or Certified
Professional Soil Scientist).
~ A description & delineation of existing stonmwater conveyances. impoundments, and
wetlands on or adjacent to the site or into which stom] water flows.
!Q A delineation of 100-year flood plains, if applicable.
~ The existing and proposed vegetation and ground surfaces with runoff coefficient for each.
S{. A drainage area map showing pre and post construction watershed boundaries, drainage area.
stonm water flow paths, and receiving water.
~ A description and drawings of all components of the proposed drainage system including:
I) tbe structural details for all components of the proposed drainage systems and stonm
water management facilities (including size, inverts, and grade);
2) all measures for the detention, retention or infiltration of water;
3) all measures for the protection of water quality;
4) notes on drawings specitying materials to be used, construction specifications, and
typicals;
5) the existing and proposed site hydrology with supporting drainage calculations (including
the 1,2, 10, and 100 year NRCS design stonms);
Northampton Department of Public Works
Stonnwater Management Penn it
Page 2

6) proposed improvements including location of buildings or other structures, impervious
surfaces. and drainage facilities, if applicable;
7) location, cross sections, and profiles of all potentially impacted brooks, streams, drainage
swales and their method ofstabilization; and
8) proposed ownership ofdrainage system structures.
l-Estimate ofthe total area expected to be disturbed by excavation, grading or other
construction activities.
Iii..A description and location ofall measures (i.e., Best Management Practices) that will be
implemented as part of the construction activity to control pollutants in storm water
discharges. A description of when each control measure will be implemented in the
construction schedule, which operator is responsible for the implementation of each control
measure and a maintenance and inspection schedule for each control measure during
construction.
6( A description ofconstruction and waste materials expected to be stored on-site, and a
description ofcontrols to reduce pollutants from these materials including storage practices to
minimize exposure of the materials to storm water, and spill prevention and response.
P- Timing, schedules, and sequence of development including clearinjl, strippi~g, "m rading,. I
construction, final grading, and vegetative stabilization. I _ Ui1 tIL.'5>>'0 M1 ~ o:>'tT'
L-Y l..lWt:~ "5'Wt" Pr; o('{ 0
6. Application Submission, Review, and Approval Procedures q)t1"*,,,"d-~ 0<
1. Application Submittal: The application to the Northampton DPW for a Stormwater
Management Permit must be submitted prior to or concurrently with any land use
permit application. Submission of an application should be made to the Northampton
Department of Public Works, 125 Locust St., Northampton, MA 01060. For more
information and copies of the Northampton Stormwater Ordinance visit the DPW
web site at http://www.northamptonma.gov/dpw/Stormwater/ or contact Doug McDonald
at 413-587-1582 x308 or dmcdonaldlalnohodpw.org
2. Administrative Review: The Northampton DPW will have 7 days from the receipt of
the application to review the application for administrative completeness. Incomplete
applications will be disapproved and returned to the applicant based on the
determination that they are admirustratively incomplete.
3. Review: If the application is found to be complete, the Northampton DPW will
review the application and supporting documents based on the criteria set forth in the
Northampton Stonnwater Management Ordinance (Chapter 22, Article V) and will
take final action within 21 days (including the 7 day administrative review period) of
the receipt of a complete application unless such time is extended by agreement
between the applicant and the DPW.
4. Final Action: The Northampton DPW's tinal action will be in writing and will be
sent to the applicant and the appropriate City Department(s) and Board(s).
Northampton Department of Public Works
Stonnwater Management Pennit
Page 3

Three County Fairgrounds • 10/08/09 Stormwater Report Checklist • Page 1 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
A. Introduction
Important: When
filling out forms
on the computer,
use only the tab
key to move your
cursor - do not
use the return
key.
A Stormwater Report must be submitted with the Notice of Intent permit application to document
compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for
the Stormwater Report (which should provide more substantive and detailed information) but is offered
here as a tool to help the applicant organize their Stormwater Management documentation for their
Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist,
the Stormwater Report must contain the engineering computations and supporting information set forth in
Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and
certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth.
The Stormwater Report must include:
• The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see
page 2) that certifies that the Stormwater Report contains all required submittals.
1
This Checklist
is to be used as the cover for the completed Stormwater Report.
• Applicant/Project Name
• Project Address
• Name of Firm and Registered Professional Engineer that prepared the Report
• Long-Term Pollution Prevention Plan required by Standards 4-6
• Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required
by Standard 8
2
• Operation and Maintenance Plan required by Standard 9
In addition to all plans and supporting information, the Stormwater Report must include a brief narrative
describing stormwater management practices, including environmentally sensitive site design and LID
techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are
required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types,
critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site
where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for
both existing and proposed conditions at a scale that enables verification of supporting calculations.
As noted in the Checklist, the Stormwater Management Report shall document compliance with each of
the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The
soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the
Massachusetts Stormwater Handbook.
To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report
Checklist by checking the box to indicate that the specified information has been included in the
Stormwater Report. If any of the information specified in the checklist has not been submitted, the
applicant must provide an explanation. The completed Stormwater Report Checklist and Certification
must be submitted with the Stormwater Report.
1
The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in
the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to
the post-construction best management practices.
2
For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in
the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the
project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan
before commencing any land disturbance activity on the site.

I
B. Stormwater Checklist and Certification
The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily
need to be addressed in a complete Stormwater Report. The checklist is also intended to provide
conservation commissions and other reviewing authorities with a summary of the components necessary
for a comprehensive Stormwater Report that addresses the ten Stormwater Standards.
Note: Because stormwater requirements vary from project to project, it is possible that a complete
Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is
determined that a specific item does not apply to the project under review, please note that the item is.not
applicable (N.A.) and provide the reasons for that determination.
A complete checklist must include the Certification set forth below signed by the Registered Professional
Engineer who prepared the Stormwater Report.
Registered Professional Engineer's Certification
I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution
Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long-
term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (if
included) and the plans showing the stormwater management system, and have determined that they
have been prepared in accordance with the requirements of the Stormwater Management Standards as
further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the
information presented in the Stormwater Checklist is accurate and that the information presented in the
Stormwater Repo~71"~¥~~5-o~i~S ~~~ date of this permit application.
Registered Professional Engineer Block and Si~ature
~,. Signature and Date
I oj e/zDl 0• I
Checklist
Project Type: Is the application for new development, redevelopment, or a mix of new and
redevelopment?
D New development
[8J Redevelopment
D Mix of New Development and Redevelopment
Three County Fairgrounds· 10/08109 Stormwater Report Checklist· Page 2 of 8

Checklist (continued)
LID Measures: Stormwater Standards require LID measures to be considered. Document what
environmentally sensitive design and LID Techniques were considered during the planning and design of
the project:
No disturbance to any Wetland Resource Areas
Site Design Practices (e.g. clustered development, reduced frontage setbacks)
Reduced Impervious Area (Redevelopment Only)
Minimizing disturbance to existing trees and shrubs
LID Site Design Credit Requested:
Credit 1
Credit 2
Credit 3
Use of “country drainage” versus curb and gutter conveyance and pipe
Bioretention Cells (includes Rain Gardens)
Constructed Stormwater Wetlands (includes Gravel Wetlands designs)
Treebox Filter
Water Quality Swale
Grass Channel
Green Roof
Other (describe):
Media filtration system inlets for detention system
Standard 1: No New Untreated Discharges
No new untreated discharges
Outlets have been designed so there is no erosion or scour to wetlands and waters of the
Commonwealth
Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included.

Standard 2: Peak Rate Attenuation
Standard 2 waiver requested because the project is located in land subject to coastal storm flowage
and stormwater discharge is to a wetland subject to coastal flooding.
Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour
storm.
Calculations provided to show that post-development peak discharge rates do not exceed pre-
development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site
flooding increases during the 100-year 24-hour storm, calculations are also provided to show that
post-development peak discharge rates do not exceed pre-development rates for the 100-year 24-
hour storm.
Standard 3: Recharge
Soil Analysis provided.
Required Recharge Volume calculation provided.
Required Recharge volume reduced through use of the LID site Design Credits.
Sizing the infiltration, BMPs is based on the following method: Check the method used.
Static Simple Dynamic Dynamic Field
1
Runoff from all impervious areas at the site discharging to the infiltration BMP.
Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations
are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to
generate the required recharge volume (to the maximum extent practicable)
Recharge BMPs have been sized to infiltrate the Required Recharge Volume
Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum
extent practicable for the following reason:
Site is comprised solely of C and D soils and/or bedrock at the land surface
M.G.L. c. 21E sites pursuant to 310 CMR 40.0000
Solid Waste Landfill pursuant to 310 CMR 19.000
Project is otherwise subject to Stormwater Management Standards only to the maximum extent
practicable. As a redevelopment project
Calculations showing that the infiltration BMPs will drain in 72 hours are provided.
Property includes a M.G.L. c. 21E site or a solid waste landfill and a mounding analysis is included.
1
80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used.

Standard 3: Recharge (continued)
The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10-
year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding
analysis is provided.
Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland
resource areas.
Standard 4: Water Quality
The Long-Term Pollution Prevention Plan typically includes the following:
• Good housekeeping practices;
• Provisions for storing materials and waste products inside or under cover;
• Vehicle washing controls;
• Requirements for routine inspections and maintenance of stormwater BMPs;
• Spill prevention and response plans;
• Provisions for maintenance of lawns, gardens, and other landscaped areas;
• Requirements for storage and use of fertilizers, herbicides, and pesticides;
• Pet waste management provisions;
• Provisions for operation and management of septic systems;
• Provisions for solid waste management;
• Snow disposal and plowing plans relative to Wetland Resource Areas;
• Winter Road Salt and/or Sand Use and Storage restrictions;
• Street sweeping schedules;
• Provisions for prevention of illicit discharges to the stormwater management system;
• Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the
event of a spill or discharges to or near critical areas or from LUHPPL;
• Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan;
• List of Emergency contacts for implementing Long-Term Pollution Prevention Plan.
A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an
attachment to the Wetlands Notice of Intent.
Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for
calculating the water quality volume are included, and discharge:
is within the Zone II or Interim Wellhead Protection Area
is near or to other critical areas
is within soils with a rapid infiltration rate (greater than 2.4 inches per hour)
involves runoff from land uses with higher potential pollutant loads.
The Required Water Quality Volume is reduced through use of the LID site Design Credits.
Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if
applicable, the 44% TSS removal pretreatment requirement, are provided.

Standard 4: Water Quality (continued)
The BMP is sized (and calculations provided) based on:
The ½” or 1” Water Quality Volume or
The equivalent flow rate associated with the Water Quality Volume and documentation is
provided showing that the BMP treats the required water quality volume. Per STC Sizing
The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary
BMP and proposed TSS removal rate is provided. This documentation may be in the form of the
propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook
and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying
performance of the proprietary BMPs. Rated 2 on MASTEP
A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing
that the BMPs selected are consistent with the TMDL is provided.
Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) Not Applicable –
Proposed project site is not expected to yield high potential pollutant loads.
The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution
Prevention Plan (SWPPP) has been included with the Stormwater Report.
The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior
to the discharge of stormwater to the post-construction stormwater BMPs.
The NPDES Multi-Sector General Permit does not cover the land use.
LUHPPLs are located at the site and industry specific source control and pollution prevention
measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow
melt and runoff, and been included in the long term Pollution Prevention Plan.
All exposure has been eliminated.
All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list.
The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and
grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil
grit separator, a filtering bioretention area, a sand filter or equivalent.
Standard 6: Critical Areas Not Applicable – The project site does not discharge to a critical area.
The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP
has approved for stormwater discharges to or near that particular class of critical area.
Critical areas and BMPs are identified in the Stormwater Report.

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.

Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control
(continued)
The project is highly complex and information is included in the Stormwater Report that explains why
it is not possible to submit the Construction Period Pollution Prevention and Erosion and
Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and
Erosion and Sedimentation Control has not been included in the Stormwater Report but will be
submitted before land disturbance begins.
The project is not covered by a NPDES Construction General Permit.
The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the
Stormwater Report.
The project is covered by a NPDES Construction General Permit but no SWPPP been submitted.
The SWPPP will be submitted BEFORE land disturbance begins.
Standard 9: Operation and Maintenance Plan
The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and
includes the following information:
Name of the stormwater management system owners;
Party responsible for operation and maintenance;
Schedule for implementation of routine and non-routine maintenance tasks;
Plan showing the location of all stormwater BMPs maintenance access areas;
Description and delineation of public safety features;
Estimated operation and maintenance budget; and
Operation and Maintenance Log Form.
The responsible party is not the owner of the parcel where the BMP is located and the Stormwater
Report includes the following submissions:
A copy of the legal instrument (deed, homeowner’s association, utility trust or other legal entity)
that establishes the terms of and legal responsibility for the operation and maintenance of the
project site stormwater BMPs;
A plan and easement deed that allows site access for the legal entity to operate and maintain
BMP functions.
Standard 10: Prohibition of Illicit Discharges
The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges;
An Illicit Discharge Compliance Statement is attached;
NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of
any stormwater to post-construction BMPs.

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

I. Introduction
The following report presents an analysis of the stormwater management system
for the proposed Phase 1 redevelopment the Three County Fairgrounds, located
off Route 9 in Northampton, Massachusetts which is located in the SC zoning
district.
Locus Map (site outlined in red)
The proposed project involves the redevelopment of a portion of the site. The 15
existing horse barns and other small buildings will be demolished and 3 new barns
are proposed to be constructed, along with associated roads/walking paths,
landscaping, and stormwater management.
The drainage areas analyzed total 56.80 acres of which approximately 16.30 acres
will be disturbed by construction activities. The impervious area on site will
increase by approximately 1.16 acres due to the new construction. The proposed
stormwater management system will work in conjunction with the existing
system. Mechanisms to reduce runoff and treat water quality include existing
deep sump catch basins, new drains with sumps, subsurface detention systems, an

infiltration trench designed specifically for the phase 1 portion of the project,
stormwater treatment chamber, and 2 existing detention ponds.
Site Terrain and Soils
The project site is comprised of a relatively flat terrain with the exception of the
steep slope adjacent to Route 9. The site surface generally consists of grassed,
gravelly, exposed dirt, and paved areas.
The USDA Soil Survey of Hampshire County, Massachusetts, Central Part report
classifies the site soils as (see Figure 3 for Soil Map):
• (8A) Limerick Silt Loam
Hydrologic Group: C
Depth to Water Table: 0.0’-1.5’
• (96A) Hadley Silt Loam
Hydrologic Group: B
• (98A) Winooski Silt Loam
Hydrologic 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 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:

E-1
E-1 is approximately 24.06 acres and contains a large area of the existing track,
horse barns, other miscellaneous buildings, grassed areas, paved areas, and gravel
areas. The area drains to existing catch basins which direct the stormwater to the
existing detention basin at the east end of the site (shown as E-Pond1 on Figure
1). The easterly detention pond has 2 outlets: The first outlet is a 12” CMP
located on the north edge of Fair Street which discharges water across the street to
the property line located at the southeastern area of the site (shown as E-CP1 on
Figure 1). The second outlet is a catch basin located just south of Horse Barn H &
C. When the level of water in the pond exceeds elevation 117’, it overflows out
of the catch basin and spills over Cross Path Road into the adjacent property
(shown as E-CP3 on Figure 1) causing standing water in the spring and summer
and frozen ponding in the winter. Occasionally when a large fairgrounds event is
planned, the detention pond is pumped at 200gpm (0.45cfs) to an existing catch
basin on the west side of the site (shown as E-Pond2 on Figure 1) in order to drain
the adjacent area. It is pertinent to pump the drainage system due to the fact that
the only piped outlet is at elevation 116’ on Cross Path Road. For the sake of
consistency within pre and post calculations, the pump system is assumed to run
full time for the duration of the storm events. This allows a similar comparison
between existing conditions and the proposed site design. The pump is modeled
as a pond with a base flow out of 0.45cfs which discharges to the Williams Street
Brook system (shown as E-CP2 on Figure 1) which is undersized in most storms.
E-2
E-2 is approximately 10.75 acres and contains a portion of the existing track,
buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into
existing catch basins which discharge into the westerly retention basin (E-Pond2).
The detention pond discharges into the Williams Street Brook drainage system
through a 12” pipe (E-CP1).
E-3
E-3 is approximately 10.38 acres and contains adjacent houses, buildings, grassed
areas, paved areas, and gravel areas. This area sheet flows into existing catch
basins which discharge directly into the Williams Street Brook drainage system
(E-CP1).
E-4
E-4 is approximately 7.52 acres and is located south of the main area and contains
a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This
area sheet flows overland to the southern property line (E-CP2).
E-5

E-5 is approximately 3.41 acres and is located north of the main area and contains
a portion of Ferry Road, a basketball court, and grassed areas. This area sheet
flows over Ferry Road where it begins to pond until it enters the existing westerly
detention basin which drains to the Williams Street Brook system (E-CP1).
E-6
E-6 is approximately 0.68 acres and is located north of the main area and contains
a portion of Ferry Road, abutting houses, and grassed areas. This area sheet flows
toward existing catch basins where it is directed to the easterly detention basin
which drains to the south eastern area of the site (E-CP2).
IV. Proposed Conditions
The proposed project does not alter the site significantly and it retains the general
flow patterns of the existing stormwater system. The proposed site contains 6
drainage areas (P-1 through P-6) and 3 different control points used for
determining peak runoff rates. The drainage areas and control points are shown
on the Post-Development Drainage Area Plan (see Figure 2). The following is a
brief description of each drainage area:
P-1
P-1 is approximately 27.48 acres and contains the 3 new horse barns, a new
restroom, new paved road/walk areas, a large area of the existing track, other
miscellaneous buildings, grassed areas, paved areas, a portion of the Morgan
horse rings, and gravel areas. This area of the site will contain 2 large subsurface
stone detention systems which will be hydraulically connected to the easterly
detention basin. Areas that drain directly to the subsurface system are directed to
low spots which allow for the runoff to infiltrate through the specified soil media
prior to entering the system. The area adjacent to the 3 new horse barns will drain
to a new system installed under 2 new concrete pads between the barns. Each pad
contains drain inlets with 2’ sumps. Before horse manure is permitted to be
stockpiled on the pads, the drains inlets are replaced with covers to prohibit
potential contamination of the drainage system and the horse barn roof areas are
piped directly into the drain system to allow for separation of roof runoff which
will increase the water quality entering the detention basin. The outlet from the
new subsurface system will be outfitted with a stormwater treatment chamber
designed to remove a minimum of 80% TSS for the increase in impervious area
on site.
The rest of the area within P-1 drains to existing catch basins or sheet flows to the
existing detention basins on the east side of the site (shown as P-Pond1 on Figure
2). The detention pond has 3 outlets. The first outlet is a 12” CMP located on the
north edge of Fair Street which discharges water across the street to the property
(P-CP2); unlike in existing conditions, the existing low catch basin adjacent to
Cross Path Road is proposed to be removed in this phase and a berm at elevation

117.2’ (second outlet) will be constructed to ensure the water flowing to the east
is less than it was in existing conditions (P-CP3). Occasionally when a large
fairgrounds event is planned, the retention pond is pumped (the site will continue
to utilized the existing pump at 200gpm) to an existing catch basin (P-CP1) on the
west side of the site (shown as P-Pond2 on Figure 2). In order to provide a
consistent timing of pump use for existing and proposed conditions, the pump was
modeled as a base flow of 0.45cfs (200gpm) directed to the Williams Street Brook
drainage infrastructure and was assumed to be running at all times. With the
construction of the new drainage infrastructure, an Operation and Maintenance
plan is proposed that will require the pump system to run after storms to ensure
the drainage system will be drained within 72 hours. It is pertinent to pump the
drainage system due to the fact that the only outlet remains at Cross Path Road.
An infiltration trench has been designed to catch and retain the runoff from a large
part of the main road that is proposed in the middle of the site. The system
consists of a long and shallow stone filled bed which will catch the runoff from a
large amount of the new pavement, and allow the runoff to recharge into the
ground. The system has been designed to be very shallow and has low spot at the
center of the trench which will promote the runoff to infiltrate as well as serve as a
monitoring system for determining the trench’s performance.
P-2
P-2 is approximately 9.27 acres and contains a portion of the existing track,
buildings, grassed areas, paved areas, and gravel areas. This area sheet flows into
existing catch basins which discharge into the westerly retention basin (P-Pond2).
The detention pond discharges into the Williams Street Brook drainage system
through a 12” pipe (P-CP1).
P-3
P-3 is approximately 8.46 acres and contains adjacent houses, buildings, grassed
areas, paved areas, new horse rings, and gravel areas. This area sheet flows into
existing catch basins which discharge directly into the Williams Street Brook
drainage system (P-CP1).
P-4
P-4 is approximately 7.52 acres and is located south of the main area and contains
a portion of Fair Street, existing buildings, grassed areas, and gravel areas. This
area sheet flows overland to the southern property line (P-CP2).
P-5
P-5 is approximately 3.41 acres and is located north of the main area and contains
a portion of Ferry Road, a basketball court, and grassed areas. This area sheet
flows over Ferry Road where it begins to pond until it enters the existing westerly
detention basin which drains to the Williams Street Brook system (P-CP1).

P-6
P-6 is approximately 0.68 acres and is located north of the main area and contains
a portion of Ferry Road, abutting houses, and grassed areas. This area sheet flows
toward existing catch basins where it is directed to the easterly detention basin
which drains to the south eastern area of the site (P-CP2).
V. Calculations and Design
Drainage calculations were performed on Hydrocad Stormwater Modeling System
version 8.0 using Soil Conservation Service (SCS) TR-20 methodology. The SCS
method is based on rainfall observations, which were used to develop the
Intensity-Duration-Frequency relationship, or IDF curve. The mass curve is a
dimensionless distribution of rainfall over time, which indicates the fraction of the
rainfall event that occurs at a given time within a 24-hour precipitation event. This
synthetic distribution develops peak rates for storms of varying duration and
intensities. The SCS distribution provides a cumulative rainfall at any point in
time and allows volume dependent routing runoff calculations to occur. These
calculations are included in the appendices.
The watershed boundaries for calculation purposes are divided according to the
proposed site grading and the natural limits of the drainage areas. The curve
numbers (CNs) and times of concentration for the existing and proposed
subcatchment areas are based on the soil type and the existing and proposed cover
conditions at the site. The soil hydrologic group assumed for the site is noted in
Figure 3. Watershed subcatchment areas, runoff coefficients and watercourse
slopes are based on survey information.
Calculations were performed for the 2-, 10-, and 100-year frequency storms under
existing and proposed conditions. The results of the calculations are presented in
Table 1 below. Appendix A presents the Hydrocad calculations.
Flow Rates & Water Quantity
Table 1 on the following page presents the comparison of flow rates and water
quantity at both existing and proposed control points.

Table 1 Peak Flow and Volume
Summary
*Names in parentheses refer to HydroCad model and calculations.
Note that the volumes are less for proposed conditions during the first 24 hours
after the storm began. This is due to the large increase in storage area within the
proposed detention system. However when the pump system drains the proposed
basin, the volume directed to the Williams Street Brook control point (CP3) will
be greater in proposed conditions.
VI. MADEP Stormwater Standards Compliance
The following section details how the project follows the MADEP Stormwater
Management Policy’s ten stormwater management standards.
Standard 1 - Untreated Stormwater
No new outlets are proposed on the site and the site has added treatment capacity
to the existing site through the use of infiltration trenches, deep sump basins, a
large subsurface detention system with filtration inlet areas, and a stormwater
treatment chamber. The existing stormwater system has been modified to treat the
stormwater prior to discharging it off site.
Condition
& Point of
Analysis
Peak Flow
Rate(cfs)
Volume
(acre-ft)
Peak Flow
Rate(cfs)
Volume
(acre-ft)
Peak Flow
Rate(cfs)
Volume
(acre-ft)
Existing –
Control Pt.
(E-CP1)*
Proposed –
Control Pt.
(P-CP1)*
Existing –
Control Pt.
(E-CP2)*
Proposed –
Control Pt.
(P-CP2)*
Existing –
Control Pt.
(P-CP3)*
Proposed –
Control Pt.
(P-CP3)*
2.779
0.00 0.000 0.00 0.000 35.50 2.620
0.00 0.000 1.52 0.178 35.51
33.17 7.960
7.14 2.582 16.48 4.543 29.19 7.310
7.52 2.696 18.21 4.891
2-Year Storm 10-Year Storm 100-Year Storm
3.00” 4.50” 6.50”
23.43 4.551
4.21 0.474 10.65 2.620 21.42 4.538
4.21 0.879 10.82 3.136

Standard 2 - Post-Development Peak Discharge Rates
The stormwater system is designed so that post-development peak discharge rates
are equal or less than pre-development peak discharge rates leaving the site.
Although the proposed site will have an increase of impervious area, the new
subsurface detention systems will provide significant storage and reduce the peak
flows from existing conditions. During the 24 hour storm the volume of water
discharged to the control points will be less than existing conditions due to the
large storage area proposed. However because the system requires pumping to
drain, the proposed basin is not fully drained after the 24 hour period shown in the
peak flow/volume calculations. The remaining volume left after the storm will be
drained by the pump for the next several hours (which happens in existing
conditions as well). However, the peak flows will be equal to or reduced from
existing conditions in the 2, 10, and 100 year storms which will improve the
functionality of the site. Refer to Table 1 Peak Flow and Volume Summary and
Appendix A for HydroCAD calculations.
Standard 3 - Recharge to Groundwater
The proposed redevelopment has been designed to provide recharge groundwater
to the maximum extent practicable in proposed conditions. In the full build of the
project (a mix of new and redevelopment) a large infiltration basin is proposed at
the south parcel. However the connection under the roadway to this basin was
proposed at this phase and shallow infiltration trench systems are proposed at the
south side of the main roadway and adjacent to 2 of the new barns. These systems
have been sized to accommodate and recharge the increase in impervious area and
are designed to capture approximately 84.8% of the 1.16acres of increased
impervious area. The basin has been designed to be very shallow which will
allow it to drain down in less than 72 hours and will encourage infiltration on the
smaller more common storms.
Note that the infiltration trench was not included in the peak flow calculations to
provide a more conservative proposed peak flow and volume estimate.
Standard 4 – Water Quality
The proposed redevelopment will provide increase water quality treatment of the
site. The proposed detention system has been designed with multiple inlet areas
which allow the runoff to infiltrate through soil media prior to entering the system
which provides treatment for runoff very similar to a rain garden. The new
detention systems will then discharge to a stormwater treatment chamber (STC
900) which has been sized to treat the increase in impervious area with a TSS
removal rate of 81.2% (see appendix for StormCeptor sizing chart). The
treatment chamber then discharges into the existing basin where any remaining
solids have the opportunity to settle on the bottom.

The site will also be implementing an improved manure management system
between the horse barns. Contaminated water will not be able to enter the system
as it will be block until the manure has left the vicinity of the drains
Standard 5 - Higher Potential Pollutant Loads
The proposed project is not expected to yield high potential pollutant loads.
Standard 6 - Protection of Critical Areas
The project site does not discharge to critical areas as defined in MA DEP
Stormwater Policy Handbook.
Standard 7 - Redevelopment Projects
The proposed project is a redevelopment project and will improve the site to the
maximum extent practicable by incorporating recharge and water quality measures
that will function for the phase until the full build out is constructed.
Standard 8 - Erosion/Sediment Control
Erosion and sediment controls will be fully been incorporated into the project
design to prevent erosion, control sediments, and stabilized exposed soils during
construction and land disturbance. This project is covered by a NPDES
Construction General Permit and a SWPPP will be submitted by the contractor
prior to the start of construction.
Standard 9 - Operation/Maintenance Plan
An Operation and Maintenance Plan for the proposed project is included in
Appendix E. It includes general controls for construction and long term
maintenance of the stormwater management system.
Standard 10 – Prohibition of Illicit Discharges
No illicit discharges will occur as a result of this project.
VII. Summary
The impervious area from existing to proposed conditions will increase by
approximately 1.16 acres from the construction of the 3 new barns and new paved
areas. The combination of the improvements to the stormwater system on site will
ensure that the redevelopment will significantly improve the existing site.

Three County Fairgrounds-Phase 1 October 1, 2010 Revised 11/1/10
Northampton, Massachusetts Stormwater Drainage Report Appendix
The Berkshire Design Group, Inc. Figures
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Three County Fairgrounds-Phase 1 October 1, 2001 Revised 11/1/10 &11/3/10
Northampton, Massachusetts Stormwater Drainage Report Appendix
The Berkshire Design Group, Inc. Appendix
Appendix A – Pre- and Post Development
Hydrologic Calculations

E-1
Area to Easterly Basin
E-2
Area To Westerly Basin
E-3
Direct to Road Drainage
Infrastructure
E-4
Southeast Area of Site
to South Property Line
E-5
Area north of site
(includes basketball
court)
E-6
Northeast of Site (Road
and abutting property)
P-1
Area to Easterly Basin
P-2
Area To Westerly Basin
P-3
Direct to Road Drainage
Infrastructure
P-4
Southeast Area of Site
to South Property Line
P-5
Area north of site
(includes basketball
court)
P-6
Northeast of Site (Road
and abutting property)
E-CP1
Williams St. Brook
Infrastructure
E-CP2
South Property Line
E-CP3
Cross Paths Road
P-CP1
Williams St. Brook
Infrastructure
P-CP2
South Property Line
P-CP3
Cross Paths Road
E-Pond1
Existing East Detention
Basin
E-Pond2
Existing West Detention
Basin
E-Pump
CB
Existing Pump System
from East Basin
E-Pump.
CB
Existing Pump System
from East Basin
P-Pond 1
Existing East Detention
Basin & New Trench
Systems
P-Pond 2
Existing West Detention
Basin
Drainage Diagram for Three Country Fairgrounds Phase 1- Stormwater Permit rev110310
Prepared by The Berkshire Design Group 11/3/2010
HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC
Subcat Reach Pond Link

Revised 11/3/10
Three Country Fairgrounds Phase 1- Stormwater Permit rev110310
Page 2Prepared by The Berkshire Design Group
11/3/2010HydroCAD® 8.00 s/n 000752 © 2006 HydroCAD Software Solutions LLC
Area Listing (selected nodes)
Area (acres) CN Description (subcats)
58.105 61 >75% Grass cover, Good, HSG B (E-1,E-2,E-3,E-4,E-5,E-6,P-1,P-1,P-2,P-3,P-4,P-5,P-6)
4.859 74 >75% Grass cover, Good, HSG C (E-4,E-5,P-4,P-5)
1.586 85 Existing Gravel/Stone Dust (P-1)
15.840 85 Gravel/Stone Dust (E-1,E-2,E-3,E-4,P-2,P-3,P-4)
0.968 96 Morgan Rings (stonedust) (P-3)
7.181 96 Proposed TRG Paving (P-1,P-1,P-3)
0.413 98 (P-1)
1.362 98 Basin (E-2,E-4,P-2,P-4)
0.460 98 Basins (E-1,P-1)
1.949 98 Paved parking (E-5,E-6,P-5,P-6)
0.702 98 Paved parking & roofs (P-1)
2.140 98 Road (E-4,P-4)
17.585 98 Road/Roof (E-1,E-2,E-3,P-1,P-2,P-3)
0.448 98 Roof (E-4)
113.597

Revised 11/3/10
Type III 24-hr 2 YRS Rainfall=3.00"Three Country Fairgrounds Phase 1- Stormwater Permi
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=1,048,195 sf Runoff Depth>0.85"Subcatchment E-1: Area to Easterly Basin
Flow Length=888' Tc=17.0 min CN=73 Runoff=15.84 cfs 1.712 af
Runoff Area=468,308 sf Runoff Depth>1.25"Subcatchment E-2: Area To Westerly Basin
Flow Length=1,136' Tc=16.9 min CN=80 Runoff=11.10 cfs 1.116 af
Runoff Area=451,921 sf Runoff Depth>0.85"Subcatchment E-3: Direct to Road Drainage Infrastructure
Flow Length=100' Slope=0.0050 '/' Tc=19.5 min CN=73 Runoff=6.47 cfs 0.737 af
Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment E-4: Southeast Area of Site to South Property
Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment E-5: Area north of site (includes basketball c
Runoff Area=29,661 sf Runoff Depth>1.19"Subcatchment E-6: Northeast of Site (Road and abutting prop
Runoff Area=27.478 ac Runoff Depth>1.18"Subcatchment P-1: Area to Easterly Basin
Runoff Area=403,083 sf Runoff Depth>1.37"Subcatchment P-2: Area To Westerly Basin
Runoff Area=8.458 ac Runoff Depth>0.96"Subcatchment P-3: Direct to Road Drainage Infrastructure
Runoff Area=327,415 sf Runoff Depth>0.76"Subcatchment P-4: Southeast Area of Site to South Property
Runoff Area=148,626 sf Runoff Depth>0.90"Subcatchment P-5: Area north of site (includes basketball c
Runoff Area=29,664 sf Runoff Depth>1.19"Subcatchment P-6: Northeast of Site (Road and abutting prop
Inflow=7.52 cfs 2.696 afReach E-CP1: Williams St. Brook Infrastructure
Outflow=7.52 cfs 2.696 af
Inflow=4.21 cfs 0.879 afReach E-CP2: South Property Line
Inflow=0.00 cfs 0.000 afReach E-CP3: Cross Paths Road

Revised 11/3/10
Inflow=7.14 cfs 2.582 afReach P-CP1: Williams St. Brook Infrastructure
Inflow=4.21 cfs 0.474 afReach P-CP2: South Property Line
Inflow=0.00 cfs 0.000 afReach P-CP3: Cross Paths Road
Peak Elev=116.42' Storage=46,413 cf Inflow=16.49 cfs 1.779 afPond E-Pond1: Existing East Detention B
Discarded=0.45 cfs 0.470 af Primary=0.68 cfs 0.405 af Secondary=0.00 cfs 0.000 af Outflow=1.13 cfs 0.876 af
Peak Elev=117.32' Storage=27,837 cf Inflow=13.03 cfs 1.372 afPond E-Pond2: Existing West Detention B
12.0" x 55.0' Culvert Outflow=2.01 cfs 1.064 af
Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump: Existing Pump System from East Basin
Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump.: Existing Pump System from East Basin
Peak Elev=115.73' Storage=107,696 cf Inflow=27.40 cfs 2.778 afPond P-Pond 1: Existing East Detention
Peak Elev=117.30' Storage=27,284 cf Inflow=12.56 cfs 1.316 afPond P-Pond 2: Existing West Detention
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

Revised 11/3/10
Subcatchment E-1: Area to Easterly Basin
Runoff = 15.84 cfs @ 12.26 hrs, Volume= 1.712 af, Depth> 0.85"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type III 24-hr 2 YRS Rainfall=3.00"
Area (sf) CN Description
10,000 98 Basins
574,174 61 >75% Grass cover, Good, HSG B
115,775 98 Road/Roof
348,246 85 Gravel/Stone Dust
1,048,195 73 Weighted Average
922,420 Pervious Area
125,775 Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.6 100 0.0080 0.11 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
2.4 788 0.0100 5.36 4.21 Circular Channel (pipe),
Diam= 12.0" Area= 0.8 sf Perim= 3.1' r= 0.25'
n= 0.011 Concrete pipe, straight & clean
17.0 888 Total
Subcatchment E-2: Area To Westerly Basin
29,666 98 Basin
468,308 80 Weighted Average

Revised 11/3/10
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 E-3: Direct to Road Drainage Infrastructure
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 Basin
36,840 98 Road
19,517 98 Roof
35,148 74 >75% Grass cover, Good, HSG C

Revised 11/3/10
1.8 100 0.0080 0.92 Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.00"
Short Grass Pasture Kv= 7.0 fps
17.3 750 Total
Subcatchment E-5: Area north of site (includes basketball court)
27,807 98 Paved parking
16.4 100 0.0060 0.10 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
Grassed Waterway Kv= 15.0 fps
Paved Kv= 20.3 fps
Paved Kv= 20.3 fps
22.7 545 Total
Subcatchment E-6: Northeast of Site (Road and abutting property)

Revised 11/3/10
1.7 100 0.0100 1.01 Sheet Flow,
Paved Kv= 20.3 fps
12.3 625 Total
Subcatchment P-1: Area to Easterly Basin
Area (ac) CN Description
0.230 98 Basins
12.908 61 >75% Grass cover, Good, HSG B
4.046 98 Road/Roof
1.586 85 Existing Gravel/Stone Dust
6.837 96 Proposed TRG Paving
0.702 98 Paved parking & roofs
0.413 98
27.478 79 Weighted Average
22.087 Pervious Area
5.391 Impervious Area
14.6 100 0.0080 0.11 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
17.0 888 Total
Subcatchment P-2: Area To Westerly Basin

Revised 11/3/10
29,666 98 Basin
7.3 100 0.0050 0.23 Sheet Flow,
Fallow n= 0.050 P2= 3.00"
16.9 1,136 Total
Subcatchment P-3: Direct to Road Drainage Infrastructure
2.085 98 Road/Roof
0.439 85 Gravel/Stone Dust
0.968 96 Morgan Rings (stonedust)
6.373 Pervious Area
19.5 100 0.0050 0.09 Sheet Flow,
Subcatchment P-4: Southeast Area of Site to South Property Line

Revised 11/3/10
0 98 Basin
56,357 98 Road
1.8 100 0.0080 0.92 Sheet Flow,
17.3 750 Total
Subcatchment P-5: Area north of site (includes basketball court)
16.4 100 0.0060 0.10 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
Paved Kv= 20.3 fps
Paved Kv= 20.3 fps
22.7 545 Total

Revised 11/3/10
Subcatchment P-6: Northeast of Site (Road and abutting property)
1.7 100 0.0100 1.01 Sheet Flow,
Paved Kv= 20.3 fps
12.3 625 Total
Reach E-CP1: Williams St. Brook Infrastructure
Inflow Area = 24.538 ac, Inflow Depth > 1.32" for 2 YRS event
Inflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 af
Outflow = 7.52 cfs @ 12.33 hrs, Volume= 2.696 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Reach E-CP2: South Property Line
Reach E-CP3: Cross Paths Road

Revised 11/3/10
Reach P-CP1: Williams St. Brook Infrastructure
Reach P-CP2: South Property Line
Reach P-CP3: Cross Paths Road
Pond E-Pond1: Existing East Detention Basin
Discarded = 0.45 cfs @ 11.85 hrs, Volume= 0.470 af
Primary = 0.68 cfs @ 16.24 hrs, Volume= 0.405 af
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Peak Elev= 116.42' @ 16.24 hrs Surf.Area= 42,251 sf Storage= 46,413 cf
Plug-Flow detention time= 328.8 min calculated for 0.874 af (49% of inflow)
Center-of-Mass det. time= 196.4 min ( 1,072.9 - 876.5 )
Volume Invert Avail.Storage Storage Description
#1 112.00' 432,726 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Revised 11/3/10
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
112.00 6,800 0 0
113.00 7,463 7,132 7,132
114.00 8,704 8,084 15,215
115.00 10,000 9,352 24,567
116.00 11,362 10,681 35,248
117.00 85,524 48,443 83,691
118.00 272,423 178,974 262,665
118.50 407,822 170,061 432,726
Device Routing Invert Outlet Devices
#1 Secondary 117.00' 100.0' long x 5.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
2.50 3.00 3.50 4.00 4.50 5.00 5.50
Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65
2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88
#2 Primary 116.00' 12.0" Vert. Invert of 12" CMP Outlet on Fair Street C= 0.600
#3 Discarded 0.00' 0.45 cfs Existing Pump (200gpm) to E-CP1 at all elevations
Discarded OutFlow Max=0.45 cfs @ 11.85 hrs HW=112.07' (Free Discharge)
3=Existing Pump (200gpm) to E-CP1 (Exfiltration Controls 0.45 cfs)
Primary OutFlow Max=0.68 cfs @ 16.24 hrs HW=116.42' TW=0.00' (Dynamic Tailwater)
2=Invert of 12" CMP Outlet on Fair Street (Orifice Controls 0.68 cfs @ 2.20 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=112.00' TW=0.00' (Dynamic Tailwater)
1=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Pond E-Pond2: Existing West Detention Basin
Center-of-Mass det. time= 135.4 min ( 994.0 - 858.6 )

Revised 11/3/10
116.00 19,210 0 0
117.00 21,276 20,243 20,243
118.00 35,033 28,155 48,398
119.00 64,989 50,011 98,409
119.50 75,000 34,997 133,406
#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
1=Culvert (Barrel Controls 2.01 cfs @ 2.99 fps)
Pond E-Pump: Existing Pump System from East Basin
Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base Flow
Peak Elev= 116.60' @ 0.00 hrs
#1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600
1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps)
Pond E-Pump.: Existing Pump System from East Basin
Inflow = 0.45 cfs @ 0.00 hrs, Volume= 0.894 af, Incl. 0.45 cfs Base Flow
Peak Elev= 116.60' @ 0.00 hrs
#1 Primary 116.13' 6.0" Vert. 6" Force Main C= 0.600
1=6" Force Main (Orifice Controls 0.45 cfs @ 2.34 fps)

Revised 11/3/10
Pond P-Pond 1: Existing East Detention Basin & New Trench Systems
Starting Elev= 112.84' Surf.Area= 55,135 sf Storage= 25,602 cf
Peak Elev= 115.73' @ 24.00 hrs Surf.Area= 58,769 sf Storage= 107,696 cf (82,094 cf above start)
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)
#5 112.34' 1,682 cf Trench D (north) (Prismatic) Listed below (Recalc)
#6 112.34' 1,682 cf Trench D (south) (Prismatic) Listed below (Recalc)
#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)
#10 111.34' 15,494 cf Trench E (east) (Prismatic) Listed below (Recalc)
#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 0
113.00 7,463 7,132 7,132
114.00 8,704 8,084 15,215
115.00 10,000 9,352 24,567
116.00 11,362 10,681 35,248
117.00 95,677 53,520 88,768
118.00 385,783 240,730 329,498

Revised 11/3/10
112.34 17,272 0 0
117.00 17,272 80,488 80,488
112.34 2,499 0 0
116.75 2,499 11,021 11,021
112.34 2,920 0 0
117.25 2,920 14,337 14,337
112.34 1,054 0 0
116.33 1,054 4,205 4,205
112.34 1,054 0 0
116.33 1,054 4,205 4,205
111.34 6,460 0 0
116.78 6,460 35,142 35,142
111.34 9,311 0 0
115.50 9,311 38,734 38,734
111.34 7,208 0 0
115.50 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 2.00
2.50 3.00 3.50
Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88
2.85 3.07 3.20 3.32

Revised 11/3/10
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)
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
Center-of-Mass det. time= 137.9 min ( 991.3 - 853.5 )
116.00 19,210 0 0
117.00 21,276 20,243 20,243
118.00 35,033 28,155 48,398
119.00 64,989 50,011 98,409
119.50 75,000 34,997 133,406
#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
1=Culvert (Barrel Controls 1.95 cfs @ 2.97 fps)

Revised 11/3/10
Type 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 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Runoff Area=1,048,195 sf Runoff Depth>1.89"Subcatchment E-1: Area to Easterly Basin
Runoff Area=468,308 sf Runoff Depth>2.45"Subcatchment E-2: Area To Westerly Basin
Runoff Area=451,921 sf Runoff Depth>1.89"Subcatchment E-3: Direct to Road Drainage Infrastructure
Runoff Area=327,415 sf Runoff Depth>1.74"Subcatchment E-4: Southeast Area of Site to South Property
Runoff Area=148,626 sf Runoff Depth>1.96"Subcatchment E-5: Area north of site (includes basketball c
Runoff Area=29,661 sf Runoff Depth>2.37"Subcatchment E-6: Northeast of Site (Road and abutting prop
Runoff Area=27.478 ac Runoff Depth>2.37"Subcatchment P-1: Area to Easterly Basin
Runoff Area=403,083 sf Runoff Depth>2.63"Subcatchment P-2: Area To Westerly Basin
Runoff Area=8.458 ac Runoff Depth>2.04"Subcatchment P-3: Direct to Road Drainage Infrastructure
Runoff Area=327,415 sf Runoff Depth>1.74"Subcatchment P-4: Southeast Area of Site to South Property
Runoff Area=148,626 sf Runoff Depth>1.96"Subcatchment P-5: Area north of site (includes basketball c
Runoff Area=29,664 sf Runoff Depth>2.37"Subcatchment P-6: Northeast of Site (Road and abutting prop
Inflow=18.21 cfs 4.891 afReach E-CP1: Williams St. Brook Infrastructure
Inflow=10.82 cfs 3.136 afReach E-CP2: South Property Line
Inflow=1.52 cfs 0.178 afReach E-CP3: Cross Paths Road

Revised 11/3/10
Inflow=16.48 cfs 4.543 afReach P-CP1: Williams St. Brook Infrastructure
Inflow=10.65 cfs 2.620 afReach P-CP2: South Property Line
Inflow=0.00 cfs 0.000 afReach P-CP3: Cross Paths Road
Peak Elev=117.03' Storage=86,787 cf Inflow=38.97 cfs 3.922 afPond E-Pond1: Existing East Detention B
Peak Elev=118.29' Storage=59,913 cf Inflow=26.83 cfs 2.756 afPond E-Pond2: Existing West Detention B
Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump: Existing Pump System from East Basin
Peak Elev=116.60' Inflow=0.45 cfs 0.894 afPond E-Pump.: Existing Pump System from East Basin
Peak Elev=117.01' Storage=180,119 cf Inflow=56.15 cfs 5.558 afPond P-Pond 1: Existing East Detention
Peak Elev=118.21' Storage=56,598 cf Inflow=25.08 cfs 2.585 afPond P-Pond 2: Existing West Detention
Total Runoff Area = 113.597 ac Runoff Volume = 20.071 af Average Runoff Depth = 2.12"
77.94% Pervious Area = 88.539 ac 22.06% Impervious Area = 25.058 ac

Revised 11/3/10
Subcatchment E-1: Area to Easterly Basin
10,000 98 Basins
1,048,195 73 Weighted Average
14.6 100 0.0080 0.11 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
17.0 888 Total
Subcatchment E-2: Area To Westerly Basin
29,666 98 Basin

Revised 11/3/10
7.3 100 0.0050 0.23 Sheet Flow,
Fallow n= 0.050 P2= 3.00"
16.9 1,136 Total
Subcatchment E-3: Direct to Road Drainage Infrastructure
19.5 100 0.0050 0.09 Sheet Flow,
Subcatchment E-4: Southeast Area of Site to South Property Line
0 98 Basin
36,840 98 Road
19,517 98 Roof

Revised 11/3/10
1.8 100 0.0080 0.92 Sheet Flow,
17.3 750 Total
Subcatchment E-5: Area north of site (includes basketball court)
16.4 100 0.0060 0.10 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
Paved Kv= 20.3 fps
Paved Kv= 20.3 fps
22.7 545 Total
Subcatchment E-6: Northeast of Site (Road and abutting property)

Revised 11/3/10
1.7 100 0.0100 1.01 Sheet Flow,
Paved Kv= 20.3 fps
12.3 625 Total
Subcatchment P-1: Area to Easterly Basin
0.230 98 Basins
4.046 98 Road/Roof
1.586 85 Existing Gravel/Stone Dust
0.702 98 Paved parking & roofs
0.413 98
22.087 Pervious Area
14.6 100 0.0080 0.11 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
17.0 888 Total
Subcatchment P-2: Area To Westerly Basin

Revised 11/3/10
29,666 98 Basin
7.3 100 0.0050 0.23 Sheet Flow,
Fallow n= 0.050 P2= 3.00"
16.9 1,136 Total
Subcatchment P-3: Direct to Road Drainage Infrastructure
2.085 98 Road/Roof
0.439 85 Gravel/Stone Dust
0.968 96 Morgan Rings (stonedust)
6.373 Pervious Area
19.5 100 0.0050 0.09 Sheet Flow,
Subcatchment P-4: Southeast Area of Site to South Property Line

Revised 11/3/10
0 98 Basin
56,357 98 Road
1.8 100 0.0080 0.92 Sheet Flow,
17.3 750 Total
Subcatchment P-5: Area north of site (includes basketball court)
16.4 100 0.0060 0.10 Sheet Flow,
Grass: Short n= 0.150 P2= 3.00"
Paved Kv= 20.3 fps
Paved Kv= 20.3 fps
22.7 545 Total

Revised 11/3/10
Subcatchment P-6: Northeast of Site (Road and abutting property)
1.7 100 0.0100 1.01 Sheet Flow,
Paved Kv= 20.3 fps
12.3 625 Total
Reach E-CP1: Williams St. Brook Infrastructure
Reach E-CP2: South Property Line
Reach E-CP3: Cross Paths Road

Revised 11/3/10
Reach P-CP1: Williams St. Brook Infrastructure
Reach P-CP2: South Property Line
Reach P-CP3: Cross Paths Road
Pond E-Pond1: Existing East Detention Basin
Center-of-Mass det. time= 172.5 min ( 1,025.2 - 852.7 )

Three County Fairgrounds Stormwater Drainage Report 11-03-2010

Three County Fairgrounds Stormwater Drainage Report 11-03-2010

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Three County Fairgrounds Stormwater Drainage Report 11-03-2010