CDM Northampton Stormwater System Assessment and Plan 2012-05 Vol 1

Stormwater and Flood Control System Assessment and Utility Plan

Northampton, Massachusetts Department of Public Works

Volume I Final Report

May 2012

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Table of Contents

Executive Summary

Section 1 ‐ Introduction 1.1 Introduction ................................................................................................... 1‐1

1.2 Federal Stormwater Management Regulations – Historical Overview ............. 1‐5

1.3 Federal Stormwater Management Regulations – Pending Changes ................ 1‐5

1.4 Flood Control – Regulatory Mandates ............................................................ 1‐7

1.5 Infrastructure Funding ................................................................................... 1‐8

1.6 Project Summary ........................................................................................... 1‐8

1.7 Scope of Work ............................................................................................... 1‐9

Section 2 ‐ Existing Conditions and Alternatives Analyses 2.1 Introduction ................................................................................................... 2‐1

2.2 Stormwater Drainage and Flood Control System Overview ............................. 2‐1

2.2.1 Field Inspection Approach .................................................................. 2‐4

2.2.2 Drainage Analysis Approach ............................................................... 2‐4

2.3 Flooding Problems ......................................................................................... 2‐5

2.3.1 Bridge Street/Meadows Area ............................................................. 2‐5

2.3.1.1 Site Inspection and Area Description ..................................... 2‐5

2.3.1.2 Existing Conditions Hydraulic Model ..................................... 2‐8

2.3.1.3 Preliminary Review of Alternatives ....................................... 2‐8

2.3.2 Elm Street Brook/Florence Area ......................................................... 2‐9

2.3.2.1 Site Inspection and Area Description ..................................... 2‐9

2.3.2.2 Existing Conditions Hydraulic Model ................................... 2‐11

2.3.2.3 Preliminary Review of Alternatives ..................................... 2‐12

2.3.3 King Street/Market Street/Downtown Area ..................................... 2‐13

2.3.3.1 Site Inspection and Area Description ................................... 2‐13



2.3.4 Austin Circle/Ryan Road Area ........................................................... 2‐16

2.3.4.1 Site Inspection and Area Description ................................... 2‐16



2.4 Flood Control Systems .................................................................................. 2‐20

2.4.1 East Levee Description ...................................................................... 2‐20

2.4.2 West Levee Description .................................................................... 2‐20

2.4.3 East and West Levee Inspection ........................................................ 2‐21

2.4.4 East/West Levee Recommended Improvements ............................... 2‐22

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2.4.5 Northampton Flood Control Pumping Station – Hockanum Road –

Inspection ........................................................................................ 2‐24

2.4.5.1 Recommended Improvements ............................................ 2‐25

2.4.6 West Street Stormwater Pumping Station ‐ Inspection ...................... 2‐26

2.4.6.1 Recommended Improvements ............................................ 2‐27

2.5 River Erosion ................................................................................................ 2‐27

2.5.1 River Road – Mill River ..................................................................... 2‐27

2.5.2 Federal Street Flood Wall ................................................................. 2‐28

2.5.3 Roberts Meadow Brook Channel ...................................................... 2‐28

2.6 Current Operational Cost and Funding Levels ............................................... 2‐28

2.6.1 Regulatory Compliance ..................................................................... 2‐28

2.6.2 Stormwater Drainage Operations Staffing ........................................ 2‐28

2.6.3 Flood Control Operations Staffing ..................................................... 2‐29

Section 3 ‐ Capital Improvements Plan and Operational Budget Requirements 3.1 Introduction ................................................................................................... 3‐1

3.2 Summary of Recommended Plan .................................................................... 3‐1

3.2.1 Street Improvement Projects .............................................................. 3‐1

3.2.2 Municipal Green Infrastructure/Building Project Retrofit/Capital

Allowance .......................................................................................... 3‐5

3.2.3 Bridge Street/Meadows Area ............................................................. 3‐5

3.2.4 Elm Street Brook/Florence Area ......................................................... 3‐6

3.2.5 King Street/Market Street Area .......................................................... 3‐6

3.2.6 Austin Circle/Ryan Road Area ............................................................. 3‐7

3.2.7 Flood Control/Pumping Station Improvements ................................... 3‐7

3.2.8 Levee Improvements .......................................................................... 3‐7

3.2.9 River Erosion Improvements ............................................................... 3‐7

3.3 Future Operational Cost Projections ............................................................... 3‐8

3.4 Estimated Costs and Preliminary Schedule ..................................................... 3‐8

3.5 Project Prioritization .................................................................................... 3‐15

Section 4 ‐ Environmental Permitting 4.1 Introduction ................................................................................................... 4‐1

4.2 Description of Applicable Permits ................................................................... 4‐2

4.2.1 Federal Permits/Approvals ................................................................. 4‐2

4.2.1.1 Clean Water Act, Section 404 ................................................ 4‐2

4.2.1.2 Federal Endangered Species Act of 1973 ................................ 4‐3

4.2.1.3 National Pollutant Discharge Elimination System (NPDES) –

Construction General Permit ................................................. 4‐3

4.2.2 State Permits/Approvals .................................................................... 4‐3

4.2.2.1 Certificate from the Executive Office of Environmental Affairs

(MEPA Approval) .................................................................. 4‐3

4.2.2.2 Massachusetts Wetlands Protection Act (M.G.L. c131, s.40; 310

CMR 10.00) ........................................................................... 4‐4

4.2.2.3 Massachusetts Rivers Potection Act (Ch. 258 of the Acts of

1996; 310 CMR 10.58) ........................................................... 4‐4

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4.2.2.4 401 Water Quality Certification Program (314 CMR 9.00) ...... 4‐4

4.2.2.5 Massachusetts Endangered Species Act (M.G.L. c.131A; 321

CMR 10.00) ........................................................................... 4‐5

4.2.2.6 Waterways Licensing Program (M.G.L. Chapter 91; 310 CMR

9.00) ..................................................................................... 4‐5

4.2.2.7 Environmental Results Program (310 CMR 7.26 [42:43]) ........ 4‐5

4.2.3 Local Permits/Approvals ..................................................................... 4‐5

5.2.3.1 Wetlands Protection Act and City Ordinance ......................... 4‐5

4.3 Conclusion ..................................................................................................... 4‐6

Section 5 – Stormwater and Flood Control Utility 5.1 Introduction ................................................................................................... 5‐1

5.1.1 Objectives ......................................................................................... 5‐1

5.1.2 Stormwater Utilities in Other Communities ........................................ 5‐1

5.1.3 Methodology ..................................................................................... 5‐4

5.1.4 Key Findings ....................................................................................... 5‐4

5.2 Stormwater and Flood Control Utility Implementation Considerations ........... 5‐5

5.2.1 Stormwater and Flood Control Utility Background .............................. 5‐5

5.2.2 Structural Considerations ................................................................... 5‐6

5.2.3 Public Education and Involvement ...................................................... 5‐7

5.2.4 Management and Budgeting .............................................................. 5‐7

5.2.4.1 Budgeting ............................................................................. 5‐8

5.2.4.2 Billing ................................................................................... 5‐8

5.2.5 Funding Options ................................................................................. 5‐8

5.2.6 Stormwater Credits .......................................................................... 5‐10

5.3 Project Revenue Requirement ...................................................................... 5‐11

5.3.1 General Assumptions ....................................................................... 5‐11

5.3.2 Operations and Maintenance Expenses ............................................ 5‐12

5.3.2.1 Incremental O&M ............................................................... 5‐12

5.3.2.2 Allocated O&M ................................................................... 5‐13

5.3.3 Debt Service Expenses ...................................................................... 5‐13

5.3.4 Revenue Requirement ...................................................................... 5‐14

5.4 Parcel Analysis and Equivalent Residential Unit Calculation .......................... 5‐15

5.4.1 Impervious Area ............................................................................... 5‐15

5.4.2 Equivalent Residential Unit Calculation............................................. 5‐17

5.4.3 Estimated Total Billing Units ............................................................. 5‐18

5.5 Calculation of Stormwater and Flood Control Fee ......................................... 5‐18

5.6 Recommendations ....................................................................................... 5‐20

Appendices

Appendix A – Field Inspection Memoranda and Photographs

Appendix B – Drainage Analysis

Appendix C – Pipe Capacity Analysis

Appendix D – Detailed Debt Service Schedule

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Executive Summary

Drainage and flood control systems, while often taken for granted, are critical to the economic

wellbeing of any community, as these systems are vital to the protection of property and the safety

of individuals that reside within the community. In recent years, the deteriorating condition of

drainage and flood control infrastructure across the country has been well documented and, in

combination with extreme weather events, has resulted in several dramatic flooding events that have

created enormous economic disruption and damage to personal and public property.

Like Northampton, many communities across the country have aging infrastructure that is in urgent

need of refurbishment or replacement, followed by periodic maintenance. In many instances,

infrastructure constructed decades ago has now exceeded its useful life and/or is now operating

beyond its intended capacity due to the impact of continued development and increased impervious

area within urban areas and upstream watersheds. Additionally, new regulatory mandates place

further burden on communities to monitor and control both the quantity and quality of stormwater

discharged to ponds, streams and rivers, resulting in new capital and ongoing maintenance

requirements.

While the challenges are daunting, many communities are taking steps to address these challenges in

a thoughtful, systematic manner. Fundamental to this effort is the need to evaluate existing drainage

and flood control systems, identify weaknesses and deficiencies in these systems, and develop a

technically sound, cost‐effective plan to address these deficiencies. However, in the past, such plans

often lacked a sustainable source of funds to finance the implementation of needed improvements.

Accordingly, progressive communities such as Northampton are considering a critical new component

to their stormwater management plan – the implementation of a new stormwater fee that is fair and

equitable, and provides a reliable, dedicated source of revenue to fund needed improvements to

drainage and flood control systems. This new fee would be administered by a newly formed

Stormwater and Flood Control Utility and, as with other utilities, the stormwater fee would be based

directly on the cost of service provided. The process undertaken by Northampton to evaluate such a

fee and the results of the evaluation are described in this Stormwater and Flood Control System

Assessment and Utility Plan.

Existing Infrastructure Condition

The City of Northampton owns and is responsible for the operation and maintenance of

approximately 3,750 catch basins and inlets and approximately 108 miles of drainage that lead to

more than 280 outfalls. A large percentage of these drain lines are over 100 years old and require

replacement because of their deteriorated condition, the need for additional stormwater conveyance

capacity, or both.

Executive Summary

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Additionally, the City owns and is responsible for the operation and maintenance of a flood control system that

was constructed by the Army Corp of Engineers (USACE) in 1940 to provide protection against flooding from the

Connecticut and Mill Rivers. This system requires significant refurbishment, as levees and retaining walls that

protect the downtown area from high river waters need maintenance to ensure their structural integrity, and

the 70‐year old flood control pumping station that diverts floodwater through the levee under flood conditions

requires replacement.

The City faces many serious challenges in restoring and maintaining fully functional drainage and flood control

systems, including:

Replacement and refurbishment of older drainage and flood control infrastructure that no longer fulfills

its intended purpose

Upgrades of the existing drainage system to serve areas of the City that now experience flooding

Compliance with new EPA regulations governing stormwater management that will mandate a wide

range of system improvements and monitoring of stormwater quality and quantity

Compliance with USACE requirements that will require the City to repair and certify that existing flood

control systems meet USACE standards.

All of the above represent real and significant costs to the City that must be addressed to avoid the risk of non‐

compliance or, worse, the risk of serious damage to public and private property and the associated financial and

quality of life impacts on Northampton residents, business owners, and visitors.

Financial Need Assessment

To develop realistic estimates of the level of funding required to address drainage system and flood control

needs, preliminary engineering was performed and a recommended plan developed to address representative

known drainage system deficiencies in the following areas of the City:

Bridge Street / Meadows Area

Elm Street Brook / Florence Area

King Street / Market Street Area

Austin Circle / Ryan Road Area

Additionally, recommendations were developed to address needed flood control system improvements,

including repairs to levees, replacement of the West Street Stormwater Pumping Station with a portable pump,

and replacement of the Northampton Flood Control Pumping Station with a new facility. Allowances were also

made for compliance with new EPA permit requirements, river erosion improvements, general drainage

infrastructure improvements, and gradual implementation of green stormwater management practices (which

are strongly encouraged by new regulations).

These prioritized recommendations form the basis of a $95.6 million program of capital improvements to be

implemented over a 20‐year period, as shown in Table ES‐1. In the initial five years of the program, it is

estimated that an expenditure of approximately $33.1 million is required to implement high priority projects,

including drainage improvements in the Bridge Street / Meadows area and Elm Street Brook/Florence area,

River Road floodwall improvements, Roberts Meadows Brook channel improvements, levee improvements and

certification, West Street Stormwater Pumping Station improvements, and replacement of the Flood Control

Pumping Station (note that replacement of the Flood Control Pumping Station represents about $17.4 million of

the required expenditure – the largest single item in the recommended improvements program).

Executive Summary

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2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031

Bridge Street/Meadows Phase 1 Improvements $441,000 $5,072,000

River Road Floodwall Improvements $155,000 $1,453,000

Roberts Meadow Brook Channel Improvements $43,680 $502,320

Federal Street Retaining Wall Improvements $120,000 $1,380,000

Elm Street Brook/Florence Area Phase 1 Improvements $516,000 $5,939,000

King Street/Market Street Area Phase 1 and 2 Improvements $911,000 $5,160,000 $5,315,000

Levee Certification $275,000 $275,000

Levee Capital Improvements $280,000 $275,000 $56,000 $647,000

Flood Control Pumping Station Upgrades $1,391,000 $15,998,000

West Street Portable Pumps $46,000 $533,000

Austin Circle/Ryan Road Area Phase 2 Improvements $327,000 $3,757,000

Bridge Street/Meadows Area Phase 3 Improvements $448,000 $5,156,000

Elm Street Brook/Florence Area Phase 3 Improvements $1,033,000 $5,850,000 $6,025,000


EPA MS4 Permit Requirements Allowance $250,000 $250,000 $250,000 $250,000 $250,000

Annual Allowance for Drainage Infrastructure $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000

Municipal Green Design/Construction Allowance $258,000 $265,000 $273,000 $281,000 $290,000 $299,000 $307,000 $317,000 $326,000 $336,000 $346,000 $356,000 $367,000 $378,000 $389,000 $401,000 $413,000 $426,000 $438,000 $452,000

Total Costs per Year $1,761,680 $3,961,320 $6,151,000 $3,115,000 $18,087,000 $7,769,000 $7,347,000 $6,132,000 $1,153,000 $4,593,000 $1,294,000 $7,045,000 $6,717,000 $7,546,000 $4,532,000 $4,653,000 $913,000 $926,000 $938,000 $952,000

Grand Total $95,586,000

Planning/Operations

Design

Construction

YearProject Description

Table ES.1

Summary Project Cost Schedule

Executive Summary

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This 20‐year program of capital improvements forms the basis for evaluation of a stormwater fee, with capital

costs annualized on the assumption that projects will be financed through the issuance of 20‐year bonds. By

completing preliminary engineering and developing capital cost estimates for specific priority projects (as

opposed to allowances for generic projects), the City can have greater confidence that the stormwater fee

estimates developed as part of this study are realistic and reflect the current infrastructure investment needs of

the City.

Basis of a Northampton Stormwater and Flood Control Utility

While there are a relatively small number of stormwater utilities in New England and across the country, interest

in such utilities has grown dramatically in recent years as communities have recognized the need for a reliable,

dedicated source of revenue to fund needed improvements to drainage and flood control infrastructure. While

the details of specific utilities can vary, the underlying premise of all stormwater utilities is that costs for

drainage and stormwater improvements should be shared equitably, with the amount of impervious area

associated with a particular parcel serving as a proxy for the contribution of stormwater generated by that

particular parcel (parcels with more impervious area generate more stormwater and therefore place a greater

burden on drainage and flood control systems). Because there is a direct and proven relationship between

impervious area and the rate and volume of stormwater generated, allocation of stormwater‐related costs

based on impervious area is more equitable than traditional methods of cost allocation, such as allocation based

on water consumption or property values.

Essentially, there are three steps to determining a defensible stormwater fee:

1. Step 1: Estimate the revenue requirements for the Stormwater and Flood Control Utility. The annual

revenue requirements for the utility are based on annualized capital program requirements (debt service),

system operation, and system maintenance costs. Estimates of annualized debt service for a Northampton

utility have been developed based on the capital program previously discussed, as well as requirements for

system operation and maintenance based on analysis of current system expenditures and estimates of

increased expenditures required to comply with new permit requirements. The results of these analyses

are shown in Table ES‐2 and Figure ES‐1, and show an initial annual revenue requirement of approximately

$1.5 million growing to approximately $3.9 million over a five‐year period.

2. Step 2: Assess the City’s impervious area and use it to develop an ERU‐type billing system. It is

recommended that an Equivalent Residential Unit (ERU) system be used as the basis of the stormwater fee.

Under an ERU system, residential units are assigned one billing unit per dwelling unit, a duplex is assigned

two billing units, and a three‐family home is assigned three billing units. Additionally, larger residential and

non‐residential parcels are assigned billing units based on the amount of impervious area for a specific

parcel relative to the impervious area associated with an equivalent residential unit. The amount of

impervious area for a given ERU is determined using the City’s Geographic Information System (GIS)

database, which allows for calculation of a typical ERU based on analysis of impervious area at residential

parcels across the city. For Northampton, one ERU is estimated to be 2,671 square feet.

3. Step 3: Calculate a rate per equivalent unit and the impact on typical rate payers. Based on the annual

revenue required (Step 1) and the impervious area identified within the City (Step 2), a rate for each ERU is

determined. For Northampton, a stormwater rate of $66.63 per ERU has been estimated for FY2012, with

the impact on various types of properties summarized in Table ES‐3. So, if implemented, a single‐family

home will pay an annual stormwater fee of $66.63, with larger residential and commercial properties paying

proportionally higher fees based on the ERU system.

Executive Summary

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Table ES‐2 Revenue Requirement

2011 2012 2013 2014 2015 2016

O&M $1,470,232 $1,567,960 $1,615,279 $1,664,031 $1,714,261 $1,766,013

Existing Debt Service $48,340 $54,644 $41,944 $38,684 $37,484 $35,474

Anticipated Debt Service $0 $69,850 $316,548 $789,821 $1,337,643 $2,048,693

Revenue Requirement $1,518,572 $1,692,454 $1,973,771 $2,492,536 $3,089,388 $3,850,180

Figure ES‐1 Revenue Requirement (thousands)

Table ES‐3 Proposed Equivalent Residential Unit Stormwater Fee Schedule, FY 2012

Classification Billing Units ERU Rate per ERU

Single‐Family 1 1.00 $66.63

Two‐Family 2 2.00 $133.26

Three‐Family 3 3.00 $199.90

Classification Impervious

Area ERU Rate per ERU

Large Residential 10,821 4.05 $269.95

Commercial/Industrial with 1,000 square feet of IA 1,000 0.37 $24.95


Commercial/Industrial with 100,000 square feet of IA 100,000 37.44 $2,494.58

$‐

$500

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$1,500

$2,000

$2,500

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$4,500

2011 2012 2013 2014 2015 2016

O&M Existing Debt Service Anticipated Debt Service

Executive Summary

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Policy Considerations for a Stormwater and Flood Control Utility

In addition to financial considerations and rate equity, a number of policy issues should be considered as part of

the implementation of a stormwater and flood control utility. These considerations include:

Public Education: A critical component of any implementation plan is a public education program that will

explain to both residents and the business community the need for investment in stormwater and flood control

infrastructure and the benefits of raising this revenue through a stormwater fee as opposed to alternate cost

allocation metrics such as water consumption or property valuation. Examples of public education activities

include distribution of press releases that describe the role and purpose of the stormwater and flood control

utility, incorporating the basics of stormwater management into school curriculum, and holding public meetings

to discuss the new utility.

Stormwater Credits: To help alleviate the immediate impact of a stormwater fee on customers with large

impervious areas and/or encourage practices that reduce the magnitude of stormwater discharges, the City may

consider a program of stormwater credits that can serve to reduce the overall stormwater fee paid by certain

property owners. Stormwater credits may be provided when a property owner has put in place stormwater

controls that provide relief beyond what may have been required as a condition of property development.

Examples of practices where stormwater credits may be applied include the construction of detention ponds or

green rooftops, the conservation of natural areas in new development, and the application of low income

credits for residential customers with financial hardship. In addition to stormwater treatment practices, some

utilities and municipalities also provide credit related to stormwater education, as well as for stormwater

systems that are separate from the municipal system, but have been required to comply with MS4 permitting

requirements. While stormwater credits can provide benefits in terms of equity and “good practice” incentives, it

is recommended that the City develop clear guidelines for such credits prior to full implementation of the

stormwater utility so that the public understands the rules for such credits prior to receiving an initial

stormwater fee assessment.

Summary

Implementation of a Stormwater and Flood Control Utility will provide the City with a dedicated means of

funding for needed investment in stormwater and flood control infrastructure. The methodology described in

this evaluation seeks to align the cost of providing stormwater and flood control protection with the cost burden

imposed by individual customers on stormwater and flood protection systems, and thereby provides an

equitable allocation of these necessary costs. Additionally, the direct relationship between the quantity of

stormwater generated by a particular parcel (using impervious area as a proxy) and the stormwater fee applied

to a parcel directly encourages customers and new developers to find ways to minimize stormwater impacts.

These behavioral incentives will help the City achieve compliance with new stormwater management

regulations that encourage green design practices and a reduction in the volume of stormwater generated.

As a result of this evaluation, the City has a defensible basis for estimating the magnitude of such a stormwater

fee. This estimate is not based on generic or hypothetical costs, but on preliminary engineering used to develop

site‐specific cost estimates to address several of the more serious deficiencies to the City’s drainage and flood

control systems. Based on this analysis, it is recommended that, for Fiscal Year 2012, the City adopt a

stormwater charge of $66.63 based on an ERU with an impervious area of 2,671 sq. ft. As the City begins to

undertake specific stormwater‐related capital improvements, this stormwater fee can be adjusted by the City to

fund infrastructure priorities. Such a fee will allow the City to undertake a reasonable program of needed capital

Executive Summary

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improvements, provide needed maintenance of existing assets, and maintain compliance with increasingly

stringent stormwater management regulations.

The ability of a Stormwater and Flood Control Utility to address the real and serious issues of stormwater

management and flood control in a careful, considered manner with costs allocated fairly and rationally will

benefit the residents and businesses of Northampton for decades to come. It will provide security against the

disruption and economic damage that can result from the failure of aging infrastructure that has exceeded its

useful life and/or is operating beyond its intended capacity.

1‐1 106678‐80349‐03‐11.docx

Section 1 ‐ Introduction

1.1 Introduction The City of Northampton’s (City) storm drainage system includes about 3,750 catch basins and inlets

and approximately 108 miles of drainage pipes that lead to more than 280 outfalls (Figure 1.1). A

large percentage of the drain lines are over 100 years old. These systems are in need of replacement

and many areas of the City require improved drainage infrastructure.

The City adopted the Sustainable Northampton Comprehensive Plan (Sustainable Plan) on December

19, 2007. The plan outlined many sustainability goals including Goal IC‐3 – Upgrade the City’s Aging

Stormwater Management System. The objectives of this goal include:

1. Develop and implement a plan to maintain, repair, replace, and improve aging infrastructure

throughout the City.

2. Include “low impact” and National Pollution Discharge Elimination System drainage

improvements concurrently with any pavement management program or project.

3. Invest in stormwater management improvements.

4. Make certain that investments in stormwater are distributed by comparable infrastructure

needs.

The strategy and actions outlined for accomplishing these objectives are as follows: “Complete an

engineering assessment on the ability to meet present and future stormwater management

requirements. Include low impact and green design considerations in the assessment. Create a long‐

term priority improvement plan.”

The City is provided flood protection from the Connecticut and Mill Rivers via a flood control system

that was constructed in 1940 by the Army Corps of Engineers (USACE). Another goal in the

Sustainable Plan is Goal EEC‐7 Develop Strategies to Protect the City from the Impacts of Natural

Hazards. The need to cost‐effectively maintain the City’s flood control facilities is in keeping with the

goals of the Sustainability Plan.

This study presents an approach to meet the goals of the Sustainable Plan. It describes the types of

stormwater and flood control improvements that the City requires and also presents the framework

to implement a new Stormwater and Flood Control Utility. If adopted by the City, this new Utility

would establish an Enterprise Fund to manage a comprehensive program that will provide funding for

capital projects and the annual operation and maintenance of the City’s stormwater system and flood

control systems.

The City faces challenges on many levels related to management of its stormwater management and

flood control systems. Briefly, these challenges include:

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0 2,000 4,000Feet

\\Camgissvr1\Projects\M_Billings\Northampton\mxd\Figure2_1.mxd JD 11/21/11

Northampton Flood Control Pumping Station

City ofNorthampton

Stormwater and FloodControl SystemAssessment and

Utility Plan

Figure 1.1City-Wide Drainageand Flood Control

System Map

LegendTown Boundary

Stormwater Pumping Station

Stormwater Pipe < 12"

Stormwater Pipe 12" to 24"

Stormwater Pipe > 24" to 82"

Levee

Drainage Areas

Parcel Boundary

Streams

Lakes and Rivers

DEP Wetlands

Wetlands (MassGIS)

Basemap: PlanimetricsSources: City of Northampton and MassGISCoordinate System: NAD83 Mass. State PlaneMainland FIPS 2001 (feet)

Section 1 Introduction

1‐3 106678‐80349‐03‐11

Aging Stormwater Infrastructure ‐ Much of the City’s

stormwater infrastructure is over 100 years old and in

need of repair or replacement. Photo 1.1 is a

photograph of a 2010 drain failure on Florence Road.

New Stormwater Infrastructure is Needed ‐ Where the

need for new stormwater systems have been

identified, no source of funding exists to construct

needed improvements. Photo 1.2 a photograph of

flooding in the Austin Circle and Ryan Road area.

Aging Flood Control Infrastructure ‐ The City has an extensive flood control pumping system and levee

system that was built in the 1940’s by the USACE after

the historic floods of 1936 and 1938. This important

infrastructure protects much of the downtown area

from flooding by the Connecticut River and the Mill

River. Important components of this system need

capital improvements or replacement. Photo 1.3 a

photograph of flooding downtown in 1936 and Photo

1.4 is a photograph of the West Street flood wall that

was erected in August 2011 prior to Hurricane Irene.

River Erosion ‐ The City is blessed with scenic brooks and rivers. However, the Mill River and other brooks

cause streambank erosion that threatens both private

and public property if not controlled. There is no

funding available for erosion control projects that are

important to protect private and public property from

damage. Photo 1.5 is a photograph showing the

dilapidated condition of the Mill River retaining wall.

New Stormwater Regulatory Mandates – Revised U.S.

Environmental Protection Agency (EPA) regulations

governing stormwater management (National

Pollutant Discharge Elimination System or NPDES)

regulations are anticipated to be released in the next

few months. These regulations will include new

mandates such as additional maintenance activities,

outfall monitoring requirements, as well as stormwater

retrofit capital projects. Photo 1.6 is a photograph of a

small diameter outfall off Ward Avenue and Photo 1.7 is a photograph of a large‐diameter outfall off

Hampton Avenue.

Photo 1.1 Florence Road Drain Failure

Photo 1.2 Austin Circle/Ryan Road

Photo 1.3 1936 Flood


1‐4 106678‐80349‐03‐11

New Flood Control Regulatory Mandates ‐ The USACE is

requiring a complete engineering assessment and upgrade of

the City’s flood control system. In addition, the Federal

Emergency Management Agency (FEMA) is also in the process

of updating Flood Insurance Rate Maps (FIRM) in several

Massachusetts Counties. As part of map updating, FEMA will

require that the City certify that the flood control systems meet

USACE standards. The FIRM mapping update for Hampshire

County is not yet scheduled but is expected in the near term.

Photo 1.8 is a photograph of the Connecticut River levee in

August 2011.

Inadequate Funding ‐ Currently, the City provides very little funding on an annual basis for stormwater and

flood control‐related work. In the last decade or more the capital funding amount has typically been under

$100,000 per year, with funding for capital projects zeroed out of the budget three years ago. Current

funding is from the General Budget where City‐wide demands are great. A new source of sustainable

funding is needed to meet the needs described above.

Photo 1.4 West Street Flood Wall

Photo 1.5 Mill River Retaining Wall Photo 1.6 Ward Avenue Outfall

Photo 1.7 Hampton Avenue Outfall Photo 1.8 Connecticut River Levee


1‐5 106678‐80349‐03‐11

1.2 Federal Stormwater Management Regulations – Historical Overview

The City’s storm drain discharges are subject to the NPDES Stormwater Phase II Municipal Separate Storm Sewer

System (MS4) General Permit.

Since 2003, the City has complied with the EPA’s NPDES Stormwater Phase II permit for smaller communities

with municipal separate storm sewer systems. The NPDES Stormwater Permit regulates discharges from

Northampton’s municipal storm system and mandates steps the City must take to control the quantity and

quality of water discharged from the storm drain system. Over the first five years of the NPDES Stormwater

Permit coverage, the City met the EPA’s requirements to implement a stormwater management program that

included the following six minimum controls: Public Education, Public Involvement, Illicit Discharge Detection

and Elimination, Construction Site Stormwater Runoff Control, Post Construction Stormwater Management,

Good Housekeeping and Pollution Prevention.

In June of 2004 the Northampton City Council approved both the Illicit Connections and Discharges to the

Municipal Storm Drain System Ordinance and the Erosion and Sediment Control and Post‐Construction

Stormwater Management Ordinance. Since that time the main focus of the Northampton Stormwater

Management Program has been the implementation of the Stormwater Management Permit program. Between

June 2004 and August 2011 the Northampton Department of Public Works (DPW) issued a total of 61

Stormwater Management Permits for development projects disturbing over one Acre. The fees collected are

directly dependent on the number and size of development projects each year. A revolving fund was established

that was intended to fund the implementation of the Stormwater Management Program. However, the revenue

from the stormwater permit fees proved to be inadequate to consistently pay for the cost of maintaining

compliance with the City’s NPDES Stormwater MS4 Permit. In 2006 the revolving fund was ended and

stormwater permit fees are now deposited directly in the City’s General Fund.

The stormwater system is operated and maintained on a limited budget funded through the City’s General Fund.

The budget is used for emergency repairs of the system, catch basin cleaning and repair, engineering, new

connection permits, and compliance with the NPDES permit. Over the past 25 years the City has performed

repairs on the stormwater system on an emergency basis only. Other than catch basin cleaning, no routine

inspection, maintenance, and repair takes place, and each year the system condition continues to deteriorate.

In March 2011 the City completed the eighth year of implementation of the Stormwater Management Program

as required by the EPA. The program has been implemented with the smallest budget possible to keep the City

in compliance. The ability to comply with regulatory requirements is a function of consistent funding needed for

staffing and equipment costs needed to properly operate and maintain the municipal storm drain system,

including activities such as street sweeping and catch basin cleaning. Looking ahead, the City’s NPDES

Stormwater permit compliance costs will likely increase four to five‐fold when the new EPA regulations are

instituted.

1.3 Federal Stormwater Management Regulations – Pending Changes

In December 2010 the EPA issued a Draft of proposed changes to the Massachusetts Interstate, Merrimack, and

South Coastal Small MS4 General Permit (Draft Permit) for public comments. Information about this Draft Permit

can be found on the EPA website (www.epa.gov/region1/npdes/stormwater/mimsc_sms4.html) It is projected


1‐6 106678‐80349‐03‐11

that the final permit changes will be issued by early 2012. The proposed changes to this MS4 permit include

many new and costly obligations for the City. A small sample of the new requirements is discussed below.

Data Requirements: The Draft Permit requires the gathering, and in some cases mapping, of an enormous

quantity of data. Much of this information is required in the first two years in order to perform the analyses

required to meet the permit milestones. Even though Northampton has a well‐established Geographic

Information System (GIS) system, the data compilation and analysis alone could consume the better part of the

five‐year permit cycle. The individual data requirements by themselves may be feasible to obtain, but

collectively they present a considerable effort involving personnel with a high level of knowledge and skill.

Proposed Outfall Sampling: The new permit requires sampling 25 percent of the drainage outfalls each year

during both dry and wet weather. The City of Northampton has about 287 stormwater outfalls. The sampling of

this many outfalls is costly and would require either City staff time, or hiring a consultant to complete the

sampling. New sampling equipment and analytical costs will also be incurred to comply with this new

requirement.

Illicit Discharge Detection and Elimination (IDDE) Program: The discharge of sanitary sewage and other

pollutants through stormwater systems is prohibited and any illicit connections found through sampling need to

be corrected within 30 days. In some cases the connections are the responsibility of private land‐owners to fix

and in other cases the City may be responsible for constructing the improvement and the associated repair cost.

Nitrogen Reduction Requirements: Since the City is located within the Connecticut River basin and thus

ultimately discharges to Long Island Sound, a 10 percent reduction in nitrogen is proposed to meet water quality

standards. Given the level of attention Northampton has paid to our stormwater sampling and mitigation

program to date, we are concerned that even the best efforts may result in failure to comply, and we are

concerned about the associated consequences if additional appropriate Best Management Practices (BMPs)

cannot be implemented in a timely and cost‐effective manner. The types and cost of BMPs is expected to be

significant.

BMPs ‐ Constructed Retrofits: The Draft Permit requires that the City complete an inventory and priority ranking

of City‐owned property and infrastructure (including public right of ways) that may have the potential to be

retrofitted with BMPs designed to reduce the frequency, volume, and peak intensity of stormwater discharges.

By year 3 of the permit, EPA requires that some BMP retrofit projects be completed. The inventory and priority

for the entire City is a large undertaking. The design, permitting, and construction of BMP retrofits will be time

consuming and costly.

Public Education and Outreach: The Draft Permit includes the production and distribution of eight public

education notices, in addition to several ordinances and programs intended to teach the public how to minimize

their impacts on stormwater quality.

Catch Basin Inspection and Cleaning: The Draft permit requires inspection and cleaning of every catch basin

such that no sump is more than 50 percent full. This may require cleaning catch basins more often than one per

year. Currently, the City cleans catch basins annually.

Floor Drain Inspections: The draft permit requires Identifying and determining the outlet of every floor drain in

every municipal building within one year of the effective date of the permit. In older cities like Northampton,

plumbing plans are not available for many municipal buildings, and dye testing would be required to understand

the plumbing configuration and outlet location of every floor drain. Again, additional City staff time or the use of

contractors would be needed to comply with this requirement.


1‐7 106678‐80349‐03‐11

There are many other costly requirements to comply with this new permit. The costs to maintain compliance

with the Draft permit may require spending nearly three times the current budget or approximately $250,000

per year for the City of Northampton.

1.4 Flood Control – Regulatory Mandates The City is provided flood protection from the Connecticut and Mill Rivers via a flood control system that was

constructed in 1940 by the USACE. The City is responsible for maintaining flood control infrastructure. The levees

(or dikes) and pumping stations along both rivers protect the City from flooding in critical low lying elevations.

The flood control system for the City consists of two main parts. An earthen levee about a mile in length on the

eastern part of the City provides protection against high water from the Connecticut River. In addition, an

earthen levee and concrete flood wall about a half mile in length in conjunction with the Mill River diversion

canal provides protection against flash floods on the Mill River and backwater from the Connecticut River via the

Ox Bow. The City maintains a flood control pumping station located at the wastewater treatment plant on

Hockanum Road. Wastewater treatment plant staff operates the pumping stations while the entire DPW is

engaged in the maintenance and operation of the flood control levees and Mill River diversion channel. A

smaller pumping station is located on West Street adjacent to the Mill River.

The USACE issued inspection reports dated August 26, 2011 for the Mill River Flood Control System and for the

Connecticut River Flood Control System. These reports included a long list of required improvements that must

be completed by September 2012. Generally, these improvements were related to removal of trees and

vegetation, establishing new turf on levee systems, video inspections of toe drain systems, and related work.

The completion of this work is beyond the means of the DPW staff. Bidding of the completion of this work is

needed, in order to have a contractor complete the improvements. Currently, there is no funding source to

complete this work other than the General Fund budget.

Also, in a meeting at the USACE office in Concord, Massachusetts on August 26, 2011, the City was informed that

notification will be sent in the next few months that significant engineering studies must be completed by the

City for all flood system components. These engineering studies will be required to include:

Preparation of topographic surveys to determine elevations and freeboard allowances;

Geotechnical borings;

Hydraulic and hydrologic analyses;

Seepage and slope stability analyses of dikes; stability analyses of floodwalls; settlement analyses for dikes,

pumping stations, and floodwalls; and seismic assessment for flood control structures; and

Inspections of all penetrations through the levees.

The USACE had preliminarily indicated that these studies will be required to be completed within two years of

receiving written notification of this requirement. The City anticipates receiving this notification by the end of

2011, resulting in an estimated deadline of the end of 2013 for completion of this work. These studies are

expected to cost hundreds of thousands of dollars to perform. Other Cities along the Connecticut River such as

Chicopee, Springfield and Hartford have completed these studies and found that millions of dollars of levee and

flood control pumping station improvements were required.

In addition to the USACE requirements, FEMA is in the process of updating Flood Insurance Rate Maps (FIRM)

across Massachusetts, with Hampshire County maps scheduled for updating in 2012 or later. As part of the FIRM

updates, FEMA will require the City to certify that flood control systems, including levees, meet current USACE


1‐8 106678‐80349‐03‐11

standards. This certification process includes engineering assessment similar to the above‐listed studies and

associated flood control capital improvements. The certification process has cost other Massachusetts

communities millions of dollars. If the City flood control system is not certified, the properties currently

protected by this system would no longer be protected. Property owners in the flood zone that have federally

backed mortgages would then be required to purchase expensive flood insurance.

1.5 Infrastructure Funding The use of the General Fund to pay for stormwater infrastructure is nearly universal in Massachusetts, but in

most cases the General Fund is insufficient to meet all of the needs of aging and inadequate infrastructure, nor is

there funding to meet the increasingly stringent regulations. There is inadequate funding to meet the

stormwater, flood control and stream erosion project needs in the City. Very limited funding for this

infrastructure has been provided through the City’s General Fund. The financial resources of the City to fund

infrastructure through the General Fund appears to be very limited, where General Fund resources are used for

all City operations such as schools, Fire and Police Departments. Monies from the General Fund have been

unable to keep pace with the requirements to maintain and/or replace existing infrastructure or construct new

infrastructure in locations where the need is great.

Since tax exempt properties, such as colleges, state and federal properties do not pay property taxes, they do

not contribute to the General Fund. Many tax exempt properties have large expanses of impervious area that

generate significant stormwater flows. The costs associated with the City managing this stormwater is paid by

tax payers. Stormwater utilities have been established in other communities on an equitable fee for service

basis where fees are determined based on usage (amount of impervious area is one alternative for determining

fees).

Many Cities and Towns have implemented, or are in the process of evaluating the formation of new utilities for

the management of stormwater and related infrastructure. Locally in western Massachusetts, Chicopee and

Westfield have implemented a stormwater utility. The charging of user fees for stormwater management is

authorized under state law (MGL c.83 s.16). The implementation of a stormwater utility is an equitable means to

provide the stable revenue source needed to manage stormwater infrastructure and to meet the ever expanding

regulatory state and federal mandates. Also, shifting infrastructure costs to a utility fee basis provides some

relief to the General Fund budget by removing stormwater‐related costs from that budget.

1.6 Project Summary This project consists of two parts. The first part of the study involved identifying drainage, river erosion and

flood control improvements projects. Preliminary cost estimates were prepared for these projects and

summarized in a 20‐year capital improvements plan. The second part of the study considered establishing a

stormwater and flood control utility and the various approaches used successfully by other communities. The

20‐year capital improvements plan and projected operational costs were used to evaluate various utility rate

structures.

The drainage projects that were evaluated included areas that are flood‐prone or are known to have stormwater

capacity issues. These drainage projects are considered representative of projects that may be needed across

the City. The projects analyzed include:

King Street/Market Street/Downtown Area;

Bridge Street/Meadows Area;


1‐9 106678‐80349‐03‐11

Elm Street Brook Area (Florence Area); and

Ryan Road/Austin Circle Area.

River erosion projects considered are known problem areas where various grant funding has been sought for

repairs. The projects include:

River Road Retaining Wall/Floodwall improvements (Mill River);

Roberts Meadow Brook channel improvements and erosion repair; and

Federal Street retaining wall repair (Mill River).

Flood Control projects were selected based on an engineering inspection of these City flood control systems.

The projects included:

Flood Control pumping station replacement; and

Levee system evaluations and improvements.

The recommended plan focuses on improvements to alleviate existing flooding and river erosion problems in

these representative areas. Flood control projects are also identified and included. The study presents a

preliminary 20‐year capital improvement plan. In addition, future operations and maintenance costs were

estimated as needed to comply with the Draft EPA MS4 Stormwater Permit. The capital improvements plan and

operating costs were used in the evaluation of various stormwater utility options.

1.7 Scope of Work Specific tasks completed for this study include:

1. Inventory and assessment of existing stormwater drainage infrastructure, including stream erosion projects.

Work included field inspections and hydraulic modeling of sample problem areas identified by the City.

2. Inventory and assessment of existing flood control infrastructure including pumping stations and levee

systems.

3. Review and accounting of current operational budgets for drainage and flood control operations.

4. Determination of a 20‐year Capital Improvement Plan for stormwater drainage, river erosion and flood

control projects.

5. Determination of future budget allocations needed to meet regulatory mandates.

6. Evaluation of a new Stormwater and Flood Control Utility, including revenue requirements, rate structure

options, rate modifiers, discounts and exemptions, billing options, and implementation steps.

2‐1

106678‐80349 03 11

Section 2 ‐ Existing Conditions and Alternatives Analyses

2.1 Introduction This section provides an assessment of the existing conditions for representative areas of the

stormwater drainage system, areas currently experiencing river erosion (Figure 2.1) and the flood

control system. This section also discusses the Department of Public Works’ current operational cost

and funding levels to manage the City’s stormwater drainage and flood control operations. For the

stormwater drainage system, a summary of modeling results and alternatives analyses for four flood‐

prone areas selected by the City as being representative of the types of projects that would require

funding is provided. For the flood control system, recommendations to address deficiencies in the

levee system and pumping stations are provided.

2.2 Stormwater Drainage and Flood Control System Overview

Figure 1.1 in Section 1 is a map of the Northampton drainage and flood control systems, including the

West Street stormwater pumping station, Northampton Flood Control Pumping Station and levees.

Overall, the drainage system includes approximately 108 miles of drain pipe, ranging in diameter

from 4 to 82 inches. There are approximately 3,750 catch basins and more than 280 outfalls

discharging to rivers, brooks, wetlands, and ponds. At many locations, the City stormwater was

initially managed through a combined sewer overflow (CSO) system, with only one pipe (combined

sewer) collecting sanitary sewer flow and stormwater runoff, instead of two separate pipes (sewers

and drains). During wet weather, combined sewer flow that exceeded the capacity of the system

would overflow to rivers and streams around the City. As the City performed sewer separation, many

of the original combined sewers were converted into storm drains and new sewers were constructed

to collect sanitary flow separately. As a result, many of the drains are smaller than 12 inches in

diameter (the recommended minimum drain size to reduce clogging problems, highlighted in red on

Figure 1.1). Also, a significant portion of the stormwater drainage system, consisting of turn‐of‐the‐

century vitrified clay, iron, stone and brick pipe, and asbestos cement pipe from the 1950s, is aging,

deteriorating, lacking hydraulic capacity, and may need to be replaced. A review of the stormwater

drainage system within the King Street/Market Street, Bridge Street/Meadows, and Elm Street

Brook/Florence areas indicates that nearly 47 percent of the pipes (approximately 6.1 miles) are

made of vitrified clay, iron, stone, brick, or asbestos cement. The large percentage of clay pipe, stone

and brick pipe is an indication of the age of this infrastructure. Table 2.1 provides the breakdown of

pipe lengths by material for these areas.

ELM STREET

WIL L

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WILLIAMSBURG

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SOUTHHADLEY

HOLYOKE

HATFIELD

Ryan Road/Austin Circle Area

Elm Street Brook Area

King Street/Market Street/Downtown Area

Bridge Street/Meadows Area

Federal StreetRetaining Wall Repair

River Road Retaining Wall/Floodwall Improvements

Roberts Meadow BrookChannel Improvements

and Erosion Repair

A1

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A2

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A4

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PRINCE STREET

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Day B

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Bro ok

P INE BRO O K

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Barrett St B

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Br ook

Br

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RO

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City ofNorthampton

Stormwater and FloodControl SystemAssessment and

Utility Plan

Figure 2.1RepresentativeProject Areas

Legend

Town Boundary

Parcel Boundary

Streams

DEP Wetlands

Wetlands (MassGIS)

Lakes and Rivers

Section 2 Existing Conditions

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106678‐80349‐03‐11

Table 2.1

Summary of Pipe Material in Four Study Areas

Pipe Type Total Feet Total Miles % Total

Concrete 35,943 6.81 53%

Vitrified Clay (VC) 24,055 4.55 35%

Iron 1,017 0.19 1.5%

Stone 1,870 0.35 2.7%

Brick 1,890 0.36 2.8%

Asbestos Cement (AC) 3,238 0.61 4.8%

Polyvinyl Chloride (PVC) 78 0.01 0.1%

Total 68,090 12.87 100%

The City has not assessed the City’s drainage system in a comprehensive way since 1971. Portions of the

drainage system have been inspected since that time. For example, in July 1981, Almer Huntley Jr. & Associates

performed an inspection of the Market Street Brook system in the King Street area, presenting the results in the

report North Industrial Park Drainage Study (“Almer Huntley report”). The Market Street Brook system

discharges into the Historic Mill River bed, downstream of Hockanum Road. The report documented the

condition of this 1800s‐vintage system from the outfall to its beginning upstream of North Street. Inspections

revealed that the Market Street Brook system is a composite of various pipe diameters, shapes, and materials, at

times going under existing buildings and through private property. One of the earliest sections is located in the

vicinity of Holyoke Street. Constructed in 1846, it is mostly a 5‐t by 6‐ft brick box with a brick arch roof and

wooden plank floor. Between Holyoke and Bridge Streets, the drainage system is comprised mostly of a stone or

brick box with a brick arch roof and wooden plank floor. Even though this section was constructed between

1846 and 1893, it was found to be in good overall condition. However, from Bridge Street to the beginning of

this system upstream of North Street, the pipes were found to be in overall poor condition. Constructed mostly

in the mid‐ to late 1800s, the pipe varies between a double brick ring and a stone box with a brick arch. The

inspection found sections of the brick ring out of round, longitudinal cracking, and missing bricks and stones.

This system has not been inspected since 1981.

The levee flood control system was constructed by the U.S. Army Corps of Engineers (USACE) as part of the

Comprehensive Plan for Control of Flood in the Connecticut River Basin. Construction of the flood protection

system was started in December 1938 and completed in June 1941. The levee flood control system consists of

two levees, as shown on Figure 2.1: the eastern part of the system (East Levee) includes an earth embankment

about one mile long with three concrete flood walls that provides flood protection against rising waters of the

Connecticut River, and the western part (West Levee) includes earth embankment segments and a concrete

flood wall designed to protect against rising waters and flash floods from the Mill River and backwater from a

diversion canal linked to the Connecticut River. As part of this project, a diversion dike, consisting of an earthen

embankment with a core of selected impervious material, was constructed just downstream from the West

Street Bridge at the Smith College power plant. It diverts the Mill River from the diversion dike through the

former Hulberts Pond to the Connecticut River Oxbow Lake via an 11,000‐foot‐long diversion canal. The

purpose of diverting the Mill River was to eliminate flooding in the City’s downtown area. Existing closed

drainage systems in the King Street/Market Street area currently discharge to the original Mill River bed,

referred to as the “Historic Mill River” in this report.


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106678‐80349‐03‐11

2.2.1 Field Inspection Approach

As discussed in Section 1, the City Department of Public Works (DPW) identified the following areas within the

City as being indicative of the types of projects that will require funding:

King Street/Market Street area

Bridge Street/Meadows area

Elm Street Brook/Florence area

Ryan Road area

These projects illustrate the scale and cost of typical capital projects. There are similar capital projects needed

across the City.

Camp Dresser & McKee Inc. (CDM) conducted field inspections of these areas to assess the current condition of

the drainage systems. This was accomplished by physically walking the system and inspecting selected

structures, land use types, topography, verifying Geographic Information System (GIS) mapping, and noting

defects or other conditions that should be considered during hydrologic modeling. Highlights of the field

inspections are provided here in the following sections; Appendix A provides detailed field inspection

memoranda and photographs.

2.2.2 Drainage Analysis Approach

CDM performed drainage analyses of these four flood‐prone and critical drainage areas under existing and

future build‐out conditions to examine the drainage systems’ capacities and size new drains if needed. The

drainage analyses determined peak rates of runoff during 2‐, 10‐, 25‐, and 100‐year 24‐hour storm events using

the U.S. Army Corps of Engineers HEC‐HMS Flood Hydrograph Package, version 3.5. This computer model

simulates runoff and routing of stormwater flows through the watersheds, and is based on the Soil Conservation

Service (SCS) Method. CDM used spreadsheets based on Manning’s Equation and the Orifice Equation (allowing

system surcharging to within one foot of the manhole cover) to evaluate the capacity of selected closed

drainage systems to control peak rates of runoff during a 10‐year 24‐hour storm under future build‐out

conditions. Chapter 290, Section 52 of the City Code requires that closed drainage systems be designed for a

minimum 10‐year storm event. Open channels and culverts serving major drainage areas, as well as stormwater

detention/retention basins, where flooding would produce property damage or a safety hazard, are designed to

control peak rates of runoff during a minimum 25‐year 24‐hour storm, and if possible, a 100‐year 24‐hour storm.

Precipitation data for standard storms used in the models were taken from Cornell University “Atlas of

Precipitation Extremes for the Northeastern United States and Southeastern Canada” (September 1993). The

estimated precipitation depths during the 2‐, 10‐, 25‐, and 100‐year 24‐hour storms are 3.11, 4.38, 5.37, and

7.35 inches, respectively. Compared to rainfall depths in Technical Paper No. 40 (“Rainfall Frequency Atlas of

the United States”), the rainfall depths from the Cornell University study are higher for storms greater than a 10‐

year 24‐hour storm, and provide a more conservative evaluation and design of existing and proposed

stormwater management facilities, as well as a factor of safety for potential climate change.

CDM delineated sub‐drainage areas within each study area using topographic and existing drainage system

information taken from the City’s Geographic Information System (GIS) mapping. The GIS mapping was also

used to determine the land use, hydrologic soil group (HSG), and impervious area within each sub‐drainage area.

Curve numbers (CNs) were assigned to each land use based on the HSG to develop a weighted CN for each sub‐

drainage area.


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106678‐80349‐03‐11

To determine future build‐out conditions, CDM consulted with the Director of the Northampton Office of

Planning and Development to determine which sub‐drainage areas are likely to undergo development in the

future. Curve numbers in the HEC‐HMS computer model were adjusted to reflect future build‐out conditions.

Runoff velocities for estimating time of concentration (Tc) were based on the “SCS National Engineering

Handbook, Figure 15.2 – Velocities for Upland Method of estimating Tc.” A minimum Tc of 10 minutes was used

for all sub‐drainage areas less than 1 acre, while a minimum Tc of 15 minutes was used for all sub‐drainage areas

greater than 1 acre. CDM used Muskingum routing to account for attenuation of peak flows within drainage

areas.

2.3 Flooding Problems As discussed in Section 1, the DPW identified four drainage areas that are prone to significant flooding and/or

are in critical areas (Figure 1.1). For each study area, CDM performed a field inspection of the drainage system,

developed an existing conditions HEC‐HMS computer model, and developed potential alternatives to relieve

flooding. This section provides a summary of this effort. In Appendix B, Tables B.1 through B.4 present the HEC‐

HMS modeling results under existing conditions for the four study areas. Similarly, Tables B.5 through B.8

present the HEC‐HMS modeling results under future build‐out conditions.

CDM also performed pipe capacity analyses for existing and future build‐out pipe conditions for major drain lines

and for streets known to have flooding problems in the King Street/Market Street area, Bridge Street/Meadows

area, and Elm Street Brook/Florence areas. Tables in Appendix C provide the existing and future build‐out pipe

capacity analyses. The pipe capacity analysis evaluated the adequacy of the pipes for peak rates of runoff during

a 10‐year 24‐hour storm event. A Manning’s n‐value of 0.013 was used for all proposed reinforced concrete

pipes. Pipes that have inadequate hydraulic capacity and are recommended for improvements are highlighted

in the Tables in Appendix C. In some cases, some pipes that are shown to not have sufficient capacity are not

recommended for improvements and justification is provided in the table. This section of the report describes

the major drain lines that need to be improved, but additional smaller lines are presented in this appendix. All

pipes less than 12‐inch in diameter are also highlighted and recommended for replacement with a minimum 12‐

inch diameter pipe. Upgrading of these pipes is not as critical as other recommended drainage system

improvements and should be targeted for the later phases of the Capital Improvement Plan.

2.3.1 Bridge Street/Meadows Area

2.3.1.1 Site Inspection and Area Description

Area Description

The Bridge Street/Meadows area is currently served by two separate drainage systems. Portions of the area are

located in the Connecticut River floodplain on the eastern side of the City and upstream portions lie at higher

elevations west and north of the floodplain. The drainage system is shown on Figure 2.2. The open drainage

channel along Cross Path Road down to the levee in the vicinity of Eastern Avenue, and the cross‐country closed

drainage system parallel to Bridge Street are prone to flooding.

On the west side of Bridge Street, the Day Avenue Brook drainage area is connected to a low‐lying drain line that

runs through residential backyards between Day Avenue and Marshall Street and flows in a northeasterly

direction across Damon Road discharging to the Connecticut River through the 42‐inch MassDOT outfall. This

outfall recently collapsed on a river bank that washed out. The large industrial area northwest of these

neighborhoods also discharges to this outfall, and is a potential area for managing stormwater on‐site with Best

Management Practices (BMPs), such as rain gardens, permeable pavement and street planters. MassDOT is

currently preparing drawings to repair the collapsed outfall.

CONNECTICUT RIVER

MILL RIVER

LL RIVER

Northampton Flood ControlPumping Station

West StreetStormwater

Pumping Station

Approximate Wetland Boundary Estimated by City

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\\Camgissvr1\Projects\M_Billings\Northampton\mxd\KingSt_WilliamSt_DrainageArea_Map.mxd JD 11/21/2011

Legend

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350 0 350 700175

Feet


Drain Pipe

Drain Lateral

Culvert

Drainage Channel

Detention/Retention Basin

Stormwater Pumping StationDrainage Area Boundary

Drain Manhole

Catch Basin/Inlet

Stormwater Outfall

Area Prone to Flooding

King Street Brook Drainage Area ID

Williams Street Brook Drainage Area ID

City of NorthamptonStormwater and Flood Control System

Assessment and Utility PlanFigure 2.2

King Street/Market Street andBridge Street/Meadows Drainage Areas

Contour

Parcel Boundary

Building

DEP Wetlands

Wetlands (MassGIS)

Levee


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106678‐80349‐03‐11

The second drainage system in this area is the Williams Street Brook drainage system which includes developed

areas along and west of Bridge Street, Pomeroy Terrace, and Williams Street, as well as less developed areas

east of Bridge Street in the Connecticut River floodplain. The Williams Street Brook drain line flows south and

discharges to the Historic Mill River. The floodplain area has experienced repetitive flooding particularly in the

following areas: Sheldon Field and Parking Lot, the Three County Fairgrounds, Old Ferry Road, Cross Path Road,

Fair Street, and the undeveloped area to the south of Fair Street particularly to the west of Cross Path Road and

along the alignment of the Williams Street Brook drainage pipe. This flooding has caused local roads to become

impassible in moderate storms and caused icing problems in the winter in this low‐lying floodplain. The drainage

system passes through the East Levee (described below) and includes a valve structure with the purpose of

preventing flood waters from passing through the dike. The valve is shut only when the Connecticut River has

reached a level of 115 feet at the gauging station at the Northampton Flood Control Pumping Station, a rare

occurrence which results in a the system being temporarily out of service. A large redevelopment of the Three

County Fairgrounds is planned in the near future; thus, upgrades to existing drainage infrastructure to improve

the drainage systems in this area are needed in concert with this project’s completion.

Field Inspection

On Tuesday November 30, 2010, CDM conducted a field survey of the

Bridge Street/Meadows area drainage system.

The Williams Street Brook system’s outfall is located in the east bank of

the Historic Mill River near the wastewater treatment plant entrance. The

24‐inch concrete pipe was about 30 percent filled in with silt and

sediment. It was also observed that the Historic Mill River itself was highly

silted.

Upstream, the main trunk line of the drainage system runs cross country

between Williams Street and Valley Street. There is also a branch of 15‐

and 12‐inch drains on Williams Street, which combines with the main

trunk line on Hockanum Road. There was no sign of recent street flooding in this area.

In the wooded wetland area in the flood plain adjacent to the East Levee, several inlets to the stormwater

system were found, along with a network of drainage ditches. These shallow ditches convey stormwater from

upstream field areas during high water events. The inlets to the stormwater system in this area act as relief for

the drain during peak flows and also allow flooded areas to drain after rain events have subsided.

There is a collapsed 42‐inch diameter Massachusetts Department of Transportation (MassDOT) outfall at the

Connecticut River near Damon Road that is connected to drains in the nearby industrial park and residential

areas. The outfall area has fallen into significant disrepair and includes pipes other than the 42‐inch drain.

Severe bank erosion at the outfall site has sloughed off soil about 50 feet back from the original bank of the

river. Approximately 50 yards upstream, a manhole adjacent to Damon Road was inspected and found to be in

excellent condition.

Lastly the flood plain area around the Three County Fairgrounds was inspected, including Fair Street, Old Ferry

Road, and Cross Path Road and assessed for the potential location for stormwater management facilities.

Photo 2.1 Williams Street Brook Outfall


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106678‐80349‐03‐11

2.3.1.2 Existing Conditions Hydraulic Model

The Bridge Street/Meadows area watershed is approximately 185 acres and is a mixture of industrial, dense

urban residential, and special conservancy districts. This area includes the Three County Fairgrounds and

agricultural land. Figure 2.2 shows the sub‐drainage area delineations (identified by numbers) and drainage

systems for the Bridge Street/Meadows area.

The Bridge Street/Meadows area closed drainage system consists of two main lines, one flowing south and the

other flowing north. The dividing line between the south and north systems is at Lincoln Avenue. The south‐

flowing drain line (Williams Street Brook) ranges in size from 12 to 24 inches in diameter. It originates on Bridge

Street (Route 9) and becomes a cross‐country system at the Three County Fairgrounds at Old Ferry Road. It

traverses through residential and agricultural land and goes through the East Levee before discharging to the

Historic Mill River. The north‐flowing drain line (Day Avenue Brook) ranges in size from 12 to 42 inches in

diameter. It originates at Lincoln Avenue and travels cross‐country through an old streambed until the

intersection of Marshall and Crosby Streets. At the intersection of Crosby Street and the Norwottuck Rail Trail,

the drain line converges with a drain line from the industrial park, and then crosses under Interstate Route 91,

discharging to the Connecticut River at Damon Road via the MassDOT 42‐inch diameter collapsed pipe

The peak rates of runoff during 2‐, 10‐, 25‐, and 100‐year 24‐hour storm events for each sub‐drainage area can

be found on Table B.1 in Appendix B. The pipe capacity analysis for existing conditions found that several pipes

are under capacity, as shown on the tables in Appendix C. The results of the pipe capacity analysis are discussed

in greater depth in the following section.

2.3.1.3 Preliminary Review of Alternatives

To address flooding that occurs in the floodplain area between Bridge Street and Route I‐91, including the

Fairground area, CDM considered three alternatives.

1. Create a flood storage area upstream of the East Levee near Pomeroy Terrace. This area currently floods

when the 24‐inch system is above capacity. Preliminary modeling indicates that the proposed flood storage

area would have a surface area of approximately three acres and a 25‐year storm maximum stage depth of

3.5 feet. However, this alternative was eliminated from consideration because a field investigation of the

area by Northampton staff indicates that the proposed flood storage area location is a wetland, as shown on

Figure 3.1. CDM has received permission from permitting agencies in Massachusetts in the past to enhance

the flood storage capabilities of wetlands as a measure to protect properties from extreme flooding;

however, the Massachusetts Department of Environmental Protection prefers that this not be done.

Stormwater detention/retention basins are generally designed to protect wetland areas, not to use them as

basins.

2. Collect stormwater runoff from sub‐drainage areas 2 and 4 and route the flows north through the existing

cross‐country drainage system to the existing MassDOT 42‐inch diameter pipe that discharges to the

Connecticut River. The additional flow to the north‐flowing drainage system from areas 2 and 4 is 40 cfs.

The pipe capacity analysis under existing conditions indicates that the 42‐inch diameter pipe is undersized

and needs to be a 66‐inch diameter pipe. Similarly, the cross‐country pipes from Lincoln Avenue to Marshall

Street are undersized under existing conditions and need to be replaced with a 18‐inch to 36‐inch diameter

drains. Construction of this replacement drainage system would require obtaining easements from all the

private property owners abutting the pipe. CDM also considered directing the flows from areas 2 and 4 to

Bridge Street. However, Bridge Street is a busy state road (Route 9), whose ground elevation is nearly 10

feet higher than the ground elevation of the cross‐country pipe. Thus, because of the differences in the

ground elevations, it would be difficult to convey flows to the existing 42‐inch diameter pipe via gravity

flow.


2‐9

106678‐80349‐03‐11

3. Redirect flows from the Three County Fairgrounds, and sub‐drainage areas 1, 2, and 3 to Old Ferry Road,

through the airport, to the Connecticut River in order to address the flooding in the floodplain area. An

alternative alignment is directing flows to Old Ferry Road, then to Cross Path Road, discharging at the

Connecticut River. The total flow collected is 90 cfs and requires a 48‐inch diameter pipe. The pipe

alignment from Old Ferry Road to Cross Path Road remains on all public roads, avoiding the need for

easements at the airport, but it is longer than the pipe alignment through the airport. Both alignments

create a new discharge to the Connecticut River. Despite the logistical and permitting considerations

associated with this alternative, it achieves the objective of reducing the flooding to the agricultural land

adjacent to Pomeroy Terrace, while still continuing to provide flows to the existing wetland located adjacent

to the levee.

As previously stated, the pipe capacity analysis indicates that the existing MassDOT 42‐inch diameter pipe that

discharges to the Connecticut River needs to be upsized to a 66‐inch diameter pipe. Calculations indicate that

the 48‐inch diameter pipe serving the industrial area just upstream of this pipe should be upsized to a 60‐inch

diameter pipe. Similar to the commercial area upstream of Church Street in the King Street area, there are

opportunities in this industrial area to install on‐site stormwater BMPs to reduce peak stormwater discharges.

CDM recommends that the property owners in the industrial park manage stormwater on‐site with BMPs to

reduce flows instead of upsizing the existing 48‐inch diameter pipe. CDM does recommend that the MassDOT

upsize the existing 42‐inch diameter outfall to a 66‐inch diameter pipe when they repair the pipe in the near

future. Repairing the existing 42‐inch diameter pipe and using the existing parallel 24‐inch diameter pipe does

not provide sufficient capacity to convey the calculated flows.

The pipe capacity analysis indicates that other sections of the Bridge Street/Meadows area drainage systems

need to be upsized to convey future build‐out flows. In sub‐drainage area 12, the existing 12‐to 18‐inch

diameter cross‐country system needs to be replaced with 18‐ to 36‐inch diameter pipes. However, given that

this system is located in a former streambed, obtaining sufficient cover for those pipes may be difficult. Twin

pipes or alternative box culvert or oval pipe systems may need to be used here. In sub‐drainage area 9 the

existing system in Williams Street needs to be replaced with 18‐ to 24‐inch diameter pipes. The 24‐inch

diameter pipe at the downstream end of the Williams Street Brook needs to be upsized to a 42‐inch diameter

pipe from the outfall at the Historic Mill River to just upstream of Hockunam Road and then upsized to a 30‐inch

diameter pipe to just upstream of Montview Avenue. See Section 3.2.3 for a discussion of the recommended

plan and preliminary cost estimate.

2.3.2 Elm Street Brook/Florence Area


Area Description

The Elm Street Brook watershed includes a mixture of rural/lightly developed land and moderate density

development including: a large portion of the Florence downtown area, residential areas, Cooley Dickinson

Hospital, Northampton High School (NHS), and Smith Vocational and Agricultural High School. The brook enters

a closed drainage system at the MassDOT property on Locust Street and at the Northampton High School and

ultimately discharges to the Mill River. Flooding currently occurs at the intersection of Elm Street, Milton Street

and Riverside Drive, along and south of Elm Street west of this intersection, Nutting Avenue, and at the

intersection of Milton Street and Ormond Drive. The flooding causes these roads to become impassable at

times. The drainage system is shown on Figure 2.3.

MILL RIVER

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\\camgissvr1\Projects\M_Billings\Northampton\mxd\ElmSt_DrainageArea_Map.mxd SCC July 2011

91

91

Drain Pipe

Drain Lateral

Culvert

Drainage Channel


LegendDrainage Area Boundary


Drain Manhole

Catch Basin/Inlet

Stormwater Outfall



Assessment and Utility Plan

Figure 2.3Elm Street Brook/Florence Drainage Areas

Contour

Parcel Boundary

Building

DEP Wetlands

Wetlands (MassGIS) 350 0 350 700175

Feet



2‐11

106678‐80349‐03‐11

Field Inspection

On Wednesday, December 22, 2010 CDM conducted a field survey of the Elm Street Brook drainage system.

The stormwater retention pond located adjacent to Federal Street, south of the Northampton High School

athletic fields, is fed by a 36‐inch high density polyethylene (HDPE) drain pipe originating on Elm Street. The

retention pond was found to need some routine maintenance to remove some of the vegetation in the pond.

Elm Street Brook (Brook) crosses underneath Federal Street and empties into the Mill River through a channel

that is about 10 feet wide and 4 to 5 feet deep. The box culvert under Federal Street is in poor condition.

Headwalls on both sides show advanced degradation; the concrete has chipped away to expose a significant

amount of rebar.

At the intersection of Elm and Milton Streets the Brook is conveyed via 36‐inch and 48‐inch culverts under Elm

Street and the high school grounds, re‐emerging south of the track. No blockages were present during the time

of inspection, however some large branches were found in the downstream manhole near the high school

parking lot.

Upstream of the 36‐inch and 48‐inch culverts, Elm Street Brook flows along the northern side of Elm Street. The

stream is well established and is migrating very close to Elm Street, exposing existing gas lines. Upstream of this

section, the brook veers off away from Elm Street towards the Smith Vocational and Agricultural High School’s

land. This area was assessed for the potential location of a stormwater management basin.

The Brook crosses under Route 9 through a culvert and meanders upstream through an area that is generally

heavily wooded and undeveloped.


The Elm Street Brook area watershed is approximately 690

acres and is primarily a moderately dense residential area with

small areas of industrial and business development, as well as a

special conservancy district. The

watershed also includes the Smith Vocational and Agricultural

High School, Cooley Dickenson Hospital and NHS. Sub‐drainage

area delineations and drainage systems are shown on Figure

2.3.

The drainage system for the Elm Street Brook area watershed

consists of an extensive network of closed pipes and open

channels, as shown on Figure 2.3. Most of the sub‐drainage areas (totaling approximately 535 acres) drain to an

open channel located along the north side of Elm Street. This channel crosses under Elm Street in 36‐ and 48‐

inch diameter culverts at NHS. The 36‐inch culvert conveys flows to a detention basin on school property, which

outlets under Federal Street to a channel that discharges to the Mill River. The 48‐inch culvert under the playing

fields daylights into an open channel on school property that flows under Federal Street, discharging to the same

channel as the outlet from the detention basin.



are under capacity, as shown on the tables in Appendix C. The results of the pipe capacity analysis are discussed


Photo 2.2 Elm Street Brook


2‐12

106678‐80349‐03‐11


Flooding at Elm Street near Nutting Avenue is the primary flooding issue in this drainage area. CDM considered

three alternatives to alleviate flooding in these areas.

1. Construct flood storage area just downstream of the dirt road on the Smith Vocational and Agricultural High

School property. The drainage area tributary to the flood storage area is very large – 478 acres. Preliminary

modeling indicates that the surface area of the flood storage area would need to be correspondingly large,

32 acres, with a four‐foot design flow depth, to have a significant effect on reducing downstream flows. A

flood storage area of this size is not feasible at this site.

2. Eliminate the 18‐inch pipe discharge to Elm Street Brook at the intersection of South Main Street and Elm

Street, and upsize the existing pipe in Federal Street to convey an additional 32 cfs. The pipe capacity

analysis under future build‐out conditions for this alternative indicates that the existing 18‐inch diameter

pipe at the discharge point to the Mill River needs to be upsized to a 54‐inch diameter pipe. This alternative

was eliminated because approximately 2,600 feet of pipe in Federal Street needs to be upsized and will not

provide relief of the localized flooding along Elm Street.

3. Modify the Elm Street Brook channel to provide relief at the location of flooding. Analysis of the Elm Street

Brook channel adjacent to Elm Street indicates that its capacity at its narrowest point is approximately 90

cfs. The narrowest section of the channel is closest to the street and results in flooding of Elm Street when

it overtops. The 10‐year storm peak rate of runoff entering the channel at this location is 270 cfs. The

channel is an environmental resource area that permitting agencies will want to preserve. Any

improvements to enlarge the channel to convey more flow must preserve the channels natural path and

characteristics. An alternative to enlarging the brook is to install a 7‐foot by 4‐foot box culvert in Elm Street

to convey brook overflows to Milton Street. A weir structure installed in the channel can redirect the

overflows into this culvert. The existing drainage system in Elm Street will tie into this system. The existing

12‐ inch diameter pipe in Milton Street will be replaced with a 48‐inch diameter pipe from Elm Street to

Federal Street. The box culvert will tie directly into this pipe and any surcharging will back up into the Elm

Street Brook channel and flow into the existing 36‐ and 48‐inch culverts that cross under Elm Street. In

Federal Street, the existing 18‐inch diameter pipe will be upsized to a 48‐inch pipe and convey flows west to

a new discharge point.

A new 72‐inch diameter pipe will be constructed from Federal Street and go through a parking lot,

discharging upstream of existing wetlands adjacent to the Mill River. A new discharge point to the Mill River

protects the existing channel and abutters between Federal Street and the Mill River from flooding. The

proposed discharge pipe size is 72 inches to accommodate future flows from Federal Street as part of

needed future upgrades to the drainage system. Installing a new pipe at Milton Street provides relief at the

source of flooding near NHS and will also reduce flows to the detention basin at the high school. Milton

Street is scheduled for full‐depth reconstruction, making it more practical to install a new pipe in Milton

Street and in a shorter section of Federal Street, rather than constructing nearly 2,600 feet of new pipe in

Federal Street.

The pipe capacity analysis for the major drain lines in the Elm Street Brook area indicates that several pipes need

to be enlarged to accommodate 10‐year 24‐hour peak rates of runoff. In Federal Street, from Warner Street to

the proposed new 72‐inch diameter discharge point, it is recommended the existing system be replaced with

new pipes ranging in diameter from 24 to 48 inches. In addition, in Federal Street, from Vernon Street to the

existing outfall to the Mill River, the existing 10‐inch diameter pipe needs to be upsized to a 36‐inch diameter

pipe. Within sub‐drainage area F, from High Street to Straw Avenue, the existing drainage system should be


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replaced with a new system with diameters ranging from 12 to 36 inches. See Section 3.2.4 for a discussion of

the recommended plan and preliminary cost estimate.

2.3.3 King Street/Market Street/Downtown Area


Area Description

The two main trunk lines in the King Street system (i.e., King Street and Market Street Brook systems) have an

interconnection at Main Street (Rte. 9) underneath the railroad bridge. This interconnection was inspected by

CDM and City staff. It was confirmed that the old culvert (carrying sanitary and storm flows) located in the

Fitzwilly’s Pub parking lot was abandoned and a new diversion structure constructed in Main Street. The King

Street main trunk line enters the diversion structure as a 66‐inch pipe and exits the structure as a 60‐ inch pipe.

A 36‐inch relief pipe in the diversion structure connects to the Market Street Brook system.

The downtown King Street area has two main drain lines. The King Street drain line conveys stormwater runoff

from the highly developed commercial area along Route 5 (King Street) and discharges to the Historic Mill River

bed. The Market Street Brook drain line (discussed above) originates along the existing abandoned railroad bed

in the vicinity of North Street, between Woodmont Road and Highland Avenue, and it discharges to the Historic

Mill River bed. The two drainage systems are connected to each other through a diversion structure located on

Main Street. These drainage systems are shown on Figure 2.2. The section of Main Street under the railroad

bridge and State Street from just north of Main Street to Summer Street are prone to localized flooding.

Field Inspection

On Tuesday December 7, 2010 CDM conducted a field survey of the King

Street area drainage system.

There are two drainage systems, both of which discharge to the Historic

Mill River bed: a 60‐inch circular concrete pipe located under the

railroad bridge off Hockanum Road, and a 66‐inch circular concrete pipe

located behind the condominiums on Randolph Place near the bikeway.

The river bed has significant sediment accumulation in areas; however,

the outfalls had less than 20 percent sediment at the end of the pipes

and look to be in good condition.

The field crew met with DPW staff to discuss some specific areas

where localized flooding had occurred in a recent storm. These areas

were the North Street underpass between Market and King Streets,

condominiums on Gothic Street, and State Street at Stoddard Street.

On North Street, two catch basins at the low point of the underpass

directly connect to the old Market Street Brook culvert and flooding

may be due to the need for more frequent catch basin maintenance or

additional grate.

Photo 2.4 60‐in Outfall at Hockanum Road

Photo 2.3 66‐in Outfall at Randolph Place


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Stoddard Street is experiencing flooding from backwater coming from the wetland behind Stop & Shop. Heavy

beaver activity has caused water to pool upstream of the wetlands sediment trap and migrate through

homeowners’ yards into the street along the side of the bikeway.

State Street had been observed with large puddles during high‐intensity downpours.


The King Street area watershed is approximately 397 acres and is a mixture of industrial, business and urban

residential districts. Business and residential development is dense, and includes sections of downtown

Northampton. The highly impervious business district is generally centered along King Street. This drainage

area also includes portions of the Smith College campus. Sub‐drainage area delineations and the King Street

area drainage systems are shown on Figure 2.2. The King Street/Market Street area sub‐systems are identified

by letters and the Bridge Street/Meadows area sub‐systems are identified by numbers on this figure.

The King Street closed drainage system consists of two main lines, with the overall drainage area nearly equally

divided between the two systems. The King Street drain line ranges in size from 12 inches to 66 inches in

diameter. It follows King Street to Merrick Lane, and then travels down Strong Avenue, Pearl Street and

Pleasant Street before discharging to the Historic Mill River bed.

The Market Street Brook drain line originates along the existing abandoned railroad bed in the vicinity of North

Street, between Woodmont Road and Highland Avenue. It generally follows the railroad bed to Hockanum

Road, before discharging to the Historic Mill River bed. It begins as a 36‐inch diameter pipe and then gradually

increases in size through a varying series of circular, box and arch pipes. The approximate maximum equivalent

diameter in the system is 82 inches. Upstream of the Market Street Brook closed drainage system, there is a

series of open channels that conveys stormwater runoff from the industrial park to the Market Street Brook

system. Additionally, there is a private 12‐inch closed drainage system that originates from a rear section of

retail businesses along King Street, which also ties into the upstream end of the Market Street Brook system. At

the intersection of Main Street and Strong Avenue, there is a diversion structure in the King Street system that

diverts flows to the Market Street system via a 36‐inch diameter pipe.



are undercapacity, as shown on the tables in Appendix C. The results of the pipe capacity analysis are discussed



Within the King Street area, Church Street is currently prone to localized flooding. The pipe capacity analysis

indicates that the existing 21‐inch diameter pipe in this street cannot adequately convey flows under existing

and future build‐out conditions during a 10‐year 24‐hour storm event. A 36‐inch diameter pipe along the entire

street length is needed to relieve flooding on Church Street.

Upstream of Church Street, the King Street system is slightly undersized for a 10‐year 24‐hour design storm

(there is an existing 30‐inch drain and a 36‐inch drain is needed). There are opportunities on largely impervious

commercial properties in this area to manage stormwater on‐site with Best Management Practices (BMPs), such

as bioretention street planters, rain gardens, green roofs and porous pavement. A recommended alternative to

upsizing the pipe from 30 to 36 inches is to install these types of BMPs to reduce rates and volumes of

stormwater runoff to the drainage system in this section of King Street. If the proposed stormwater utility

program described in Section 5 is adopted, property owners can be provided the option of receiving credit and


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reducing the cost of their utility bills for installing BMPs that reduce stormwater runoff and improve the water

quality of receiving waters.

Downstream of Church Street, it is recommended that the King Street system be upsized to a 48‐inch diameter

pipe at Church Street and gradually increased to a 72‐inch diameter pipe at Trumbull Road. These pipes were

sized assuming that BMPs are not installed in the upstream retail properties.

In State Street near Trumbull Road, the pipe capacity analysis indicates that a 36‐inch diameter pipe is needed to

alleviate flooding that currently occurs near Trumbull Road. Upstream of the 36‐inch diameter pipe, it is

recommended the existing 10‐inch lateral system that ties into State Street be upsized to 12‐ to 24‐inch

diameter pipes. In sub‐drainage area M (see Figure 3.1), it is recommended the existing 12‐inch diameter

system be replaced with a new system that ranges from 12 to 18 inches in diameter. The existing 24‐ to 36‐inch

diameter pipe in Trumbull Road should be replaced with a new system that ranges from 48 to 54 inches in

diameter.

Downstream of Trumbull Road to the diversion manhole, the pipe capacity analysis indicates that the existing

48‐ to 66‐inch diameter pipe in King Street needs to be upsized to a 78‐inch diameter pipe. The pipes

downstream of the diversion manhole are adequate to convey flows and do not need to be upsized.

In general, the Market Street Brook system has nearly sufficient capacity to convey flows associated with the 10‐

year 24‐hour storm event to the Historic Mill River bed; however, upstream of Bridge Street, the pipes are in

poor structural condition, which may contribute to flooding problems. Upstream of North Street, the pipe

capacity analysis indicates that the 48 inch diameter equivalent system described in Section 2 is adequate to

convey flows. However, the 1981 North Industrial Park Drainage Study prepared by Almer Huntley (“Almer

Huntley report”) on this system noted that the overall condition of this section of pipe is poor. Between Bridge

Street and North Street, Almer Huntley was not able to inspect the pipe because the manholes were not

accessible. They did inspect the pipe just downstream of North Street and just upstream of Bridge Street, and

found the condition to be poor. In these areas, the Almer Huntley report documented longitudinal cracks and

missing bricks and stones. Between North Street and Bridge Street, the average equivalent pipe diameter is 44

inches and CDM’s pipe capacity analysis indicates that a 48‐inch diameter pipe is needed to adequately convey

flows. Thus, given the poor condition of the existing system and the lack of sufficient capacity in some sections

of the system, CDM recommends replacing the 44‐ and 48‐inch diameter equivalent pipes with a 48‐inch

diameter pipe. Repairing and upsizing this section of pipe will reduce the localized flooding that currently occurs

at North Street.

Downstream of Bridge Street, Almer Huntley found the existing Market Street Brook system to be in good

condition. However, an inspection is recommended to confirm the current condition. The pipe continues to be

a composite of pipe diameters, shapes and materials, such as a brick box with a brick arch roof and a wooden

plank floor. CDM’s pipe capacity analysis indicates that from Bridge Street to the outfall at the Historic Mill River

bed the Market Street Brook system has the capacity to convey future build‐out flows and, thus, it is not

recommended that this section of pipe be upsized.

The drainage system associated with Market Street currently ties into the Market Street Brook system at Bridge

Street. The system begins as a 12‐inch diameter pipe near Walnut Street and gradually increases to a 24‐inch

diameter pipe at Bridge Street. The pipe capacity analysis indicates that the drainage system in Market Street is

insufficient to convey flows during a 10‐year 24‐hour storm. It is recommended that the system be replaced

with a 24‐inch diameter pipe beginning at Walnut Street and gradually increased to a 48‐inch diameter pipe

towards Bridge Street.


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Photo 2.5 Swale behind Austin Circle

Sub‐drainage area D shown on Figure 3.1 is currently served by a private 12‐inch diameter drainage line that

connects into the Market Street Brook drainage system. The feasibility of re‐routing this drainage line to the

King Street system was considered in the future build‐out analysis. Modeling indicates that redirecting flows

from sub‐drainage area D from the Market Street Brook system to the King Street system would have a minor

effect on either system. For the 10‐year 24‐hour storm event, it accounts for only 3 and 4 percent (6 to 8 cfs) of

the total flows to the King Street and Market Street Brook systems, respectively. Thus, if one or both systems

are enlarged, the drainage system from sub‐drainage area D could be conveyed in either system.

Overall, the King Street/Market Street business district is highly impervious and is likely to see extensive

redevelopment over the next 10 to 20 years. This is a potential area for incorporating green infrastructure/Best

Management Practices (BMPs), such as green roofs, porous pavement and bioretention systems in the form of

street planters and rain gardens, during redevelopment. In areas where soils are not conducive for infiltration

(i.e., clay) these BMPs can still provide stormwater treatment prior to discharge to the storm drain system via an

underdrain system. See Section 3.2.5 for a discussion of the recommended plan and preliminary cost estimate.

2.3.4 Austin Circle/Ryan Road Area


On Wednesday, December 22, 2010 CDM conducted a field survey

of the Ryan Road area. Between Austin Circle and the elementary

school on Ryan Road, there is a drainage ditch that periodically

overtops and floods into the backyards and basements of residents

living on Austin Circle. This flat ditch receives storm flows from

Ryan Road school, Ryan Road, and the area north of Ryan Road, in

the vicinity of the Matthew Drive area. Further downstream in the

channel, the build‐up of sediment is occurring at the culvert

crossings at Brierwood Drive and Acrebrook Drive. These sections

of channel are in need of sediment removal.

Matthew Drive is also affected by drainage problems. The top of the

hill above Matthew Drive has a perched pond that at the time of

inspection had no freeboard and was discharging to a seasonal

streambed which flows down the hill, through a resident’s yard,

onto the street and into a catch basin.

The culverts under Brierwood Drive and Acrebrook Drive show

evidence of significant sediment build‐up resulting from ponding

and slow flow velocities through this area. The drainage system is

shown on Figure 2.4. The drainage ditch between Austin Circle

and the elementary school, as well as the low‐lying grassed area

along Ryan Road on the school property, are prone to flooding.


The Ryan Road area watershed is approximately 121 acres and is a medium density residential area. Most of the

area north of Ryan Road is wooded and undeveloped land, with the exception of one housing subdivision and a

shooting range. This wooded area contains a small natural pond that overflows down the hill, causing erosion

on a property at the corner of Matthew Drive and Gregory Lane. The Ryan Road Elementary School is located

within this drainage area. Sub‐drainage delineations and drainage systems are shown on Figure 2.4.

A1

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OVERLOOK DRIVE

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\\camgissvr1\Projects\M_Billings\Northampton\mxd\RyanRoad_DrainageArea_Map.mxd JD 11/21/2011

Drain Pipe

Drain Lateral

Culvert

Drainage Channel


LegendDrainage Area Boundary


Drain Manhole

Catch Basin/Inlet

Stormwater Outfall


91

91



Figure 2.4Austin Circle/Ryan Road

Drainage Areas

Contour

Parcel Boundary

Building

DEP Wetlands

Wetlands (Delineated by City)

Wetlands (MassGIS) Basemap: PlanimetricsSources: City of Northampton and MassGISCoordinate System: NAD83 Mass. State PlaneMainland FIPS 2001 (feet)

150 0 150 30075

Feet


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Approximately 45 acres of the area north of Ryan Road are routed through the two detention basins associated

with the housing subdivision. The remaining northern area sheet flows to Ryan Road. Stormwater runoff from

the area north of Ryan Road and from the elementary school building and parking lots is collected in a 15‐inch

diameter pipe that crosses the elementary school property and discharges upward through a grate that is

adjacent to an open channel that runs through the backyards of residences on Austin Circle. Most of the

remaining drainage area sheet flows directly to this channel. Local street drainage associated with Brierwood

and Acrebrook Drives discharges directly into 36‐inch diameter culverts located under these streets.


be found on Table B.4 in Appendix B.


Three alternatives were considered for Ryan Road to address the drainage ditch that periodically overtops and

floods into the backyards and basements of residents living on Austin Circle.

1. Install a new street drainage system that intercepts the existing 15‐inch diameter pipe that crosses Ryan

Road with a 30‐inch diameter relief pipe in Ryan Road. This system would convey flow to Brierwood Drive

and then down Brierwood Drive, discharging just upstream of the 36‐inch diameter culvert in Brierwood

Drive. A variation of this alternative is intercepting the 15‐inch diameter pipe with a 30‐inch diameter relief

pipe and crossing diagonally across the elementary school’s athletic fields, discharging just upstream of the

36‐inch culvert. This alternative conveys flows from the drainage area north of Ryan Road. It increases the

peak flow at the culvert from 21 to 37 cfs, causing an increase in the hydraulic grade line at the culvert by

approximately one foot. The 36‐inch diameter culvert would need to be increased in size to lower the grade

line, which would increase peak rates of runoff to downstream properties.

2. Upsize the 15‐inch diameter pipe across the elementary school property to a 30‐inch diameter pipe to

convey runoff from a 25‐year storm event, and provide channel improvements in the channel adjacent to

Austin Circle. The improved conveyance of flow through the 30‐inch pipe will result in a downstream

increase in the hydraulic grade line at the Brierwood Drive culvert. Thus, this alternative and the first

alternative do not effectively address the flooding problems that residents of the Austin Circle currently

experience. The Brierwood Drive culvert acts as a control and the headwater backs up into the channel, a

condition the first two alternatives will exacerbate because of the increased flows to the culvert.

3. Create a flood storage area just upstream of the Brierwood Drive culvert and use the culvert as the outlet

control for the flood storage area. With a surface area of approximately 1.3 acres, the flood storage area

has a total depth of four feet (25‐year storm maximum stage plus one foot of freeboard). A 24‐inch

diameter pipe will intercept the 15‐inch diameter pipe at Ryan Road and convey runoff from the drainage

area north of Ryan Road diagonally across the athletic fields to the flood storage area. The 15‐inch diameter

pipe will continue to convey runoff from the elementary school to the existing channel, which will discharge

into the flood storage area. This alternative lowers the hydraulic grade line by approximately 0.8 feet,

resulting in less water backing up into the channel. It also reduces flows downstream of the culvert by 13

cfs during a 2‐ year 24‐hour storm event. The City performed a wetlands survey along the drainage ditch in

September 2011. The wetlands survey indicates that there are bordering vegetated wetlands along the

alignment of the ditch. The flood storage area has been located to not impact these wetland areas.

4. This alternative is a variation of Alternative #3. Because of the high degree of imperviousness of the school

and the short time of concentration, the runoff from the school was calculated to be 19 cfs for the 25‐year

storm. The existing 15‐inch diameter pipe would convey this flow to the channel. However, a channel to

convey a flow of this magnitude would have a top width of approximately 26 feet. Thus, instead of installing


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a 24‐inch diameter pipe from Ryan Road across the athletic fields to the flood storage area, the 15‐inch pipe

through the school property would be upsized to a 30‐inch pipe to collect and convey flows from the

drainage area north of Ryan Road and from the elementary school, and then turn easterly at the

southeastern corner of the elementary school, crossing the fields, to the flood storage area. This option

significantly reduces the flow to the channel to approximately 10 cfs. The channel would have a total depth

of 3 ft and a top width of 21 ft.

For all four alternatives, channel improvements are recommended to improve conveyance of flows. Currently,

the channel between the Brierwood Drive culvert and Acrebrook Drive culvert is not well‐defined and it is

recommended that a better defined channel be created. The channel along Austin Circle needs to be cleaned to

remove brush and other debris. It is noted that theses channels are on private property, have no easements to

the City and were created by the developer for these subdivisions. See Section 3.2.6 for a discussion of the

recommended plan and preliminary cost estimate.

2.4 Flood Control Systems 2.4.1 East Levee Description

The East Levee flood control system is an earthen fill levee and three concrete flood walls, with a total length of

approximately 4,950 feet and a maximum height of approximately 23 feet. The width of the crest is about 10

feet with an 8‐foot‐wide gravel surface and grass‐covered edges. The crest of the levee was constructed at an

elevation of about El. 131.6 to El. 131.3 NAVD88.

As shown on Figure 2.1, the earth embankment starts at the intersection of Pomeroy Terrace and Hancock

Street, continues southeasterly and crosses Ventures Field Road. Beyond the Ventures Field Road crossing, the

embankment bends and the alignment extends southwesterly and crosses Hockanum Road and meets the

Northampton Flood Control Pumping Station at the Old Mill River. From the pumping station, the earth

embankment bends and crosses the Boston & Maine railroad tracks and then Route 5. Concrete retaining

walls/abutments are constructed at the railroad crossing and the highway crossing and function as stop‐log

structures during a potential flood event. Stop‐logs are stored in corrugated metal storage houses constructed

next to the crossings. The earth embankment extends westerly beyond Route 5 approximately 500 feet where

the embankment is in contact with the natural earth high ground.

Design and record drawings show that the core of the embankment is constructed with a random soil material.

The embankment material river‐side of the core is an impervious clay‐like blanket material, and a sandy pervious

material is shown land‐side of the core. Based on the record plans, most of the river‐side slope of the levee was

presented as a 2.5 horizontal: 1 vertical (2.5H:1V) slope, and a 3H:1V slope at the segment between Ventures

Field Road and Hockanum Road. Most of the land‐side slope of the levee was shown to be a 2H:1V slope, and a

3H:1V slope at the segment between Ventures Field Road and Hockanum Road.

A toe drain system consisting of 8‐inch to 15‐inch porous concrete pipe in gravel bedding filter trenches exists

below grade along most of the embankment toe of slope. Intermittent manholes are installed to service the toe

drain system. The toe drain system collects the seepage water through the levee fill and discharges to the

stormwater collection system.

2.4.2 West Levee Description

The West Levee flood control system consists of earthen fill levee segments and a concrete flood wall, with a

total length of approximately 2,300 feet. Based on the record plans, the crest of the levee segments is shown to

be generally 10 feet wide and grass‐covered. The crest of the levee segment north of West Street was


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constructed at elevations ranging from El. 145.5 to El. 144.8 ft NAVD88. The crest of the levee segment south of

the bridge of the former railroad crossing was constructed at an elevation of about El. 139.1 NAVD88. The

embankment is approximately 16 feet high.

The system begins at high ground near Paradise Pond just northeast of the Paradise Pond Dam, and adjacent to

College Lane on the property of Smith College (Figure 2.1). The embankment extends southerly, parallel with the

east bank of the Mill River for about 1,100 feet to the crossing at West Street. A concrete “T” flood wall extends

southerly from West Street to the current bike path bridge crossing, formerly the New York, New Haven &

Hartford Railroad. The concrete flood wall is about 450 feet long and contacts the stone abutment of the bridge

of the former railroad. Most of the length of the wall is about 10 feet above ground surface with a top elevation

of about El. 140 NAVD88. The top of the wall and stop‐log structure at the West Street south curb is about El.

145.3 NAVD88 to match the elevation of the levee and stop‐log retaining wall at the north curb. A concrete flood

wall and an earth embankment with slight curvature extend from the former railroad crossing abutment in a

southerly direction about 900 feet to the natural earth abutment and high ground at Hebert Avenue. This last

earth embankment segment serves as a dam, which permitted the Mill River to be diverted into the Diversion

Canal.

Based on the record drawings, the river‐side slope of the northerly levee segment is shown as a 2.5H:1V slope.

The levee segment south of the flood wall was built with a 3H:1V slope to the end at Hebert Avenue. The slope

surface is protected with a one‐foot layer of hand‐placed riprap. Most of the land‐side slope of the levee is

shown to be a 2H:1V slope.

A toe drain system consisting of 8‐inch to 10‐inch porous concrete pipe in filtered trenches exists below grade

along most of the embankment toe of slope. Intermittent manholes are installed to service the toe drain system.

The construction of the Northampton Flood Control Pumping Station at the East Levee involved the diversion of

the Mill River, which originally flowed through the City. Flows originating from the upstream Mill River were

diverted into the new diversion canal, which begins at the southern portion of the West Levee and directs flow

to the old Connecticut River Ox Bow, currently called Ox Bow Lake. The diversion route made it necessary to

close Grove Street and to build a new bridge with a drop structure where the canal crosses South Street.

Downstream of the drop structure, the canal bottom is about 35 feet wide, with 3H: 1V side‐slopes. The bottom

and side slopes are lined with stone riprap. The canal extends about 8,000 feet beyond the end of the drop

structure to the discharge point at Ox Bow Lake.

2.4.3 East and West Levee Inspection

On December 22, 2010, CDM, accompanied by a representative from the City, performed a general visual

inspection of the levee system. A separate, more detailed inspection and evaluation of the levee system is

currently being performed by others for the USACE.

In general, the levee systems were found to be in very good condition. Only isolated areas were noted to have

deficiencies that would usually be corrected with normal maintenance practices. In general, the deficiencies

included:

1. A few trees and thick brush growing near the toe of the river‐side slopes of the levee and at the river‐side

face of the concrete flood wall at isolated areas;

2. Ruts, small depressions on the crest of the earth embankments;

3. The grass on the crest of the earth embankments worn by foot traffic exposing bare soil to potential

erosion;


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4. Isolated area of missing riprap on the slope of the diversion channel near the end of the West Levee; and

5. Potential clogging of the toe drain system as reported by recent USACE inspection.

Recently, the USACE has inspected the levees on two separate occasions: September 18, 2009 and on December

10, 2010/January 14, 2011.

The 2009 inspection found the levees to be in a “Minimally Acceptable” condition, meaning that no deficiencies

were identified that would prevent the system from performing as intended during a flood event. The report

noted deficiencies that included:

1. Heavy vegetation, including large bushes, trees, and tall grass, growing on and along the toe of slope of the

levees;

2. Heavy vegetation, including trees, growing in the riprap channel banks of the diversion canal;

3. Sections of the levee crown and slope with little to no sod cover due to pedestrian traffic;

4. Areas of riprap along the levee toe have been displaced;

5. Animal burrows on the crown and slope of the levee;

6. Vegetation and sediment in the intake pond at the pump station.

Similarly, the 2010/2011 inspection found the levees to be in a “Minimally Acceptable” condition. The report

noted the same deficiencies as those found during the 2009 inspection. The inspection also found some spalling

occurring on the concrete flood walls. The USACE has required that deficiencies be repaired by January 2013 or

2014, depending on the item.

2.4.4 East/West Levee Recommended Improvements

Based on the visual inspection of the East and West Levees performed by CDM, we recommend the following

activities that improve the overall conditions of the levees, but do not alter the current design.

Cut and clear trees and thick brush on the levee and at least 15 feet beyond the abutments and at the toe

of the levee. This is the current (new) USACE requirements. The removal of the trees greater than four

inches in diameter and any planned excavation of roots should be designed by a qualified levee/dam

engineer. Holes should be filled with low‐permeability fill on the river‐side slope and compacted fill on

the land‐side slope.

Remove burrowing animals and backfill holes with compacted fill. Alternatively, flowable fill could be

used to fill the hole. The material may have to be rodded to force the mix further into the hole. After the

mix is installed, the upper 6 in. +/‐ of the hole should be backfilled with soil and seeded to promote grass

growth

Repair areas of sparse vegetation and small depressions on the crest and land‐side slope by establishing a

healthy stand of grass to prevent future erosion. Continue to monitor for new bare spots, and maintain

grass since the crest of the levee system is used for hiking/walking by the public.

Potential clogging of the toe drain system at the land‐side toe of the embankments should be

investigated, and sediment should be removed from the toe drain pipe and manholes.


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Remove the salt shed located against the land‐side face of the concrete flood wall of the west levee

system at the physical plant property of Smith College.

Update the Operation and Maintenance Manual to include inspection schedules, annual training, and

operational and maintenance procedures required to ensure satisfactory operation of the levee system

to reduce the potential for deterioration to the facility.

When flood control levee system accreditation is required, follow the general guidelines outlined in the

memo in Appendix A in accordance with CFR 65.10.

These recommendations will require design by a professional engineer, application for applicable permits, and

construction by a contractor experienced in levee repair. CDM also recommends the following activities be

undertaken on a regular or yearly basis.

Regular maintenance activities should be performed at least twice a year or as conditions warrant from

the Spring to Fall seasons to control and limit growth of vegetation on the levee and the banks of the

diversion canal.

Monitor areas for dislodged riprap, and replace riprap stones to protect exposed embankment soils.

Annual training to responsible staff for erection of flood control stop log structures.

The 2009 and 2010/2011 inspections made similar recommendations for repairing the levees.

Excess vegetation should be removed and vegetative growth controlled in the long term with a

maintenance program.

Sod should be reestablished on the bare areas of the levee crown and maintained.

Animal borrows should be excavated and backfilled, and an animal control program established.

Areas of missing riprap should be replaced with new riprap.

The toe drain system should be inspected by remote camera every five years.

The intake pond at the pump station should be cleared of vegetation.

In addition, the 2010/2011 USACE Report identified several system data gaps that will require extensive

engineering to be completed by January 2014. The most notable system data gaps include:

Recent topographic survey information and comparison to the design height/available freeboard;

Hydraulic and hydrologic analyses of the entire flood control system;

Seepage and slope stability analyses for the dikes, floodwalls and diversion canal;

Settlement analyses for the dike, pumping station, and floodwalls;

Confirmation with additional test boring that the “artificial fill” was removed down to the moderately

impervious formation prior to constructing the dike near Smith College; and

Pipe inspection reports for all pipes that pass through or under the flood control system.


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For flood control projects to be recognized by FEMA on the NFIP maps, adequate evidence must be provided

showing the flood control system provides reasonable assurance that protection from the base flood exists in

accordance with CFR 65.10. The accreditation process with respect to the stability of the earthen embankment

levees and flood walls includes:

A topographic survey of the system to confirm system geometry and the 3‐foot freeboard requirement ;

A subsurface exploration program to evaluate the composition and in‐situ strength of embankment and

foundation materials;

Evaluating erosion protection from currents and/or wave action;

Embankment and foundation stability and seepage analyses of the earthen embankments in accordance

with USACE EM‐1110‐2‐1913, Design and Construction of Levees;

Stability and seepage analyses of the flood walls in accordance with the USACE Phase II Interim Guidance

for Evaluating Existing I‐Walls, dated October 25, 2006; and

Settlement evaluations to assess the potential and magnitude of loss of freeboard.

Several of the system data gaps that have been identified by the USACE are consistent with the data

requirements (shown above) for the accreditation process. Data gap analyses to be completed for the USACE

should also include all scope items that are needed for FEMA accreditation.

2.4.5 Northampton Flood Control Pumping Station – Hockanum Road – Inspection

The Northampton Flood Control Pumping Station was constructed in 1940 by the USACE as part of the

Northampton Flood Control System in conjunction with the Connecticut River Flood Control Project. It is located

on the Old Mill River approximately 1.4 miles upstream of the

confluence with the Connecticut River, and provides flood

protection for a major portion of the City, including the downtown

business district. Stormwater flow during normal river level is by

gravity. The primary function of the pumping station is to pump

stormwater through the levee when the Connecticut River is in

flood stage. The pumping station is currently manually operated

by DPW employees.

The pumping station is a brick building constructed between two

earth embankments of the levee with interconnecting concrete

counterfort flood walls. It houses four pumps: three 48‐inch

propeller pumps that can pump a total of 150,000 gpm, two

powered by gasoline engines and one powered by diesel engine;

and a single 16‐inch Worthington trash pump that is designed to pass up to 6‐inch diameter solids, powered by

an electric motor. When flood stage is reached, stormwater is diverted from the gravity flow chamber to the

pumping chambers using two electrically operated sluice gates. While in operation, the pump inlet chambers

are protected from large debris by two trash racks located upstream of the inlet sluice gate. The pumping

station includes a gasoline fueled emergency standby generator if the main power feeder fails. The standby

generator is sized to provide power for the 16‐inch pump, valve operators and lighting.

Photo 2.6 Northampton Flood Control Pumping Station


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CDM accompanied Northampton staff on field inspections of the Northampton Flood Control and Stormwater

Pumping Stations.

Interviews with DPW staff and inspection of the Northampton Flood Control Pumping Station revealed that

there are only minor imminent mechanical problems with the pumping equipment and the drives. The major

issue at the station is that it is manually operated, and it must be monitored continuously when operating or

when operation may be expected to commence. Other deficiencies noted during the inspection include:

1. Influent Screen Area: Access for a portable mechanical device to reach and clean the upstream face of the

influent screens is poor because of the configuration of the screen structure. In addition, raising and

lowering of the existing screens is a manual operation, and is potentially dangerous to City workers. The

screens are left lowered in place throughout times of the year when the station may need to operate. This

causes debris to be collected, even when pumps are not operating.

2. Sluice Gates: The City workers are concerned that the operators for the main sluice gates may not work

reliably in electric mode. If they fail to work, opening the gates manually will be a lengthy operation for City

workers.

3. Standby Generator: Because of safety concerns, gasoline‐powered standby generators are no longer used;

they are typically fueled by diesel, natural gas, or propane. In addition, current codes no longer allow

standby generators to be cooled by municipal water supplies because of reliability concerns. The City

currently uses its water supply to cool the generator, which could fail during a flooding situation.

In general, the pumping station is over 70 years old and at this advanced age, the City runs the increased risk

that the pumping station will not operate reliably under flood conditions. In addition, because of the age of the

pumping station, the availability of repair parts is questionable. The City runs the risk of having significant

downtime at the pumping station, while the City searches for, or possibly fabricates, repair parts. Thus, CDM

recommends the City take a proactive approach to improve the reliability of the pumping station by

implementing the recommended improvements described in the following section.

2.4.5.1 Recommended Improvements

If the City opts to keep the existing facility and only repair/replace the deficiencies identified during the

inspection to potentially save money, CDM recommends the following activities in order of importance.

1. Replace both of the electric motor‐operated sluice gate operators because of the concerns over their

current reliability.

2. Rework the influent screen area.

a. The existing screens with their hazardous manual operators should be removed.

b. Install a mechanically‐cleaned screen because the screens need to be cleaned frequently during station

operation. The screens should be coarse type, with 3‐to 4‐inch clear openings. Screen width is 8 feet.

c. For reliability, a bypass manually cleaned screen should be provided in case the mechanically cleaned

screen experiences operational problems.

d. The screen area should also be made easily accessible to catch basin cleaning type equipment so that

objects too large for the mechanically cleaned screen can be removed.


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e. Modification of the influent screen structure will require demolition of the existing screen structure and

construction of a new structure.

3. Replace the existing gasoline‐engine‐driven standby generator. The generator should be replaced with a

radiator‐cooled diesel‐engine‐driven generator capable of running all building systems (lights, heat, gate

operators, sump pump, etc.) plus the electric motor‐driven pump. We do not recommend a natural gas

engine because the engine needs to be physically larger than a diesel engine in order to get the required

horsepower, and is therefore more expensive. Also, in a flooding situation, the supply of natural gas may be

cut off, leaving the station inoperable.

4. Replace the existing electric‐motor‐driven pump. Because of its advanced age, it may not operate reliably in

the future. Thus, it should be replaced with a new pump that has the same capacity of the existing 50

horsepower pump.

5. Because of their age, replace the three existing stormwater pumps, including their engine drives and right‐

angle gear drives in‐ kind, with three new diesel‐engine‐driven pumps. Similar to the generator, the

replacement engine drives must be radiator cooled with unit mounted radiators. This will require major

revisions to the ventilation and air handling systems in the building to obtain adequate ventilation air and

exhaust the heated air outdoors.

6. In conjunction with replacement of the pumps, the existing pump discharge piping, isolation valves, and

outlet flap valves should be replaced because the pipe will need to be reworked to align with replacement

pumps.

7. Existing electrical, lighting, and ventilation systems should be replaced because of the age of these systems.

8. Upgrade the pumping station building to meet current accessibility and egress requirements. Implementing

the recommendations listed above, such as replacement of the ventilation system, will result in

modifications to the physical structure of the building. These changes to the building will trigger compliance

with current building codes for accessibility and egress.

9. Assuming the preceding recommendations are implemented, new monitoring and automated control

systems should be provided to allow the station to operate automatically with minimal supervision to

reduce personnel costs for pumping station operation. This task will require replacement or upgrade of

existing level monitors on the Connecticut River side of the dike, as well as in the influent channel and pump

wells. A Supervisory Control and Data Acquisition (SCADA) type panel should be provided to coordinate

monitoring with control of the pumps.

Alternatively, based on a field evaluation of the Northampton Flood Control Pumping Station, CDM recommends

replacing the existing pumping station with an entirely new facility. The new facility will replace the engine‐

driven pumps and standby generator in‐kind with three new diesel engines, right angle gear drives, stormwater

pumps, and one standby generator. Because the pump engines are the only source of power for operation of the

pumps, they will be evaluated as continuous duty application, requiring a high degree of emissions control (EPA

Tier 4). The design of the new facility will need to take into account the potential for increased flows to the

pumping station due to the recommended upgrades in the upstream drainage systems. The cost estimate

provided in this report assumes a new facility.

2.4.6 West Street Stormwater Pumping Station– Inspection

The West Street Stormwater Pumping Station is located on the Mill River, adjacent to the West Street river

crossing. Similar to the Northampton Flood Control Pumping Station, its primary function is to divert


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Photo 2.7 West Street Pumping Station

stormwater that collects behind the levee and flood wall through the levee when the Mill River is in flood stage.

The manually‐operated West Street Stormwater Pumping Station serves a 14.6‐acre area inside the levee that is

a low point for collection of stormwater runoff.

The pumping station is an on‐grade structure, with exterior dimensions of approximately 12 by 9 feet. The

building houses one engine‐driven self‐priming type pump. The pumping station was built after the flood of

1955 in 1957.

The pump is connected to the West Street stormwater collection system by a 6‐inch steel suction pipe that rises

just outside the building from a manhole. The self‐priming pump is a 6‐inch Rex Chainbelt. No rating data plate

could be identified, but its capacity is likely to be approximately 800 to 1,000 gpm. The pump is driven by a

spark‐ignited engine power unit (assembled by Hanlon Waters) fueled by propane. The propane fuel tank is a

300‐lb propane bottle located outside the station.

CDM accompanied Northampton staff on a field inspection of the West Street pumping station.

No obvious deficiencies at the West Street Pumping Station were

observed during the inspection. However, the future reliability of

the pumping station is questionable because it is rarely used.

Near the pumping station, two stormwater collection system

outlets were observed. They discharge into the river, one higher

than the other, and both were built into the retaining wall along

the river bank. Both have cast iron flap valves, which appear to

open freely. The lower of the two flap valves appears to be new,

and uses a resilient seat. However, the seat appears to have

swollen to the point that the flap cannot close onto its seat. The flap

cannot be forced manually to full closure, resulting in flooding of the

stormwater collection system tributary to this flap gate when the river elevation is high. Thus, the leakage may

fully negate the capacity of the pumping station.

Similar to the Northampton Flood Control Pumping Station, this pumping station is manually operated. When

the station must be operated, an operator must be on‐site at all times. Because the pumping station is not

automated, determination of the need to operate the pumping station is dependent upon visual observations of

flooding in the storm system on West Street.

2.4.6.1 Recommended Improvements

The West Street Stormwater Pumping Station does not have the capacity to discharge adequate flow to prevent

flooding of the West Street drainage area. Assuming that utility power is not available during flooding

conditions, a pump at this location should be engine‐driven. Instead of installing a permanent pump at this

location, CDM recommends the City purchase a portable diesel‐engine driven pump with capacity of

approximately 6,000 gpm, which can be brought to the site and set up temporarily for flood control.

2.5 River Erosion 2.5.1 River Road – Mill River

The proposed River Road Retaining Wall/Floodwall improvements are located in the Leeds Village section of

Northampton (see Figure 2.1 and Photo 1.5). Flows from the Mill River have scoured and undercut significant

sections of the wall, and surface runoff has compromised the integrity of the upper portions of the wall. In


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Photo 2.8 Federal Street Flood Wall

Photo 2.9 Roberts Meadow Brook Channel

addition, the Williamsburg sanitary sewer interceptor is located within River Road and is in danger of collapsing

due to river erosion. The City is proposing to remove the existing stone masonry wall and replace it with a cast‐

in‐place concrete retaining wall that will protect the road and sewer from the 100‐year flood event.

2.5.2 Federal Street Flood Wall

The Federal Street retaining wall improvements are proposed along

the Mill River in the vicinity of Vernon Street and Ward Avenue (see

Figure 2.1 and Photo 2.8). The purpose of this project is to protect a

30‐inch sewer interceptor. Erosion is occurring along the sharp bank

angle, which is leading to the exposure of the interceptor.

2.5.3 Roberts Meadow Brook Channel

The Roberts Meadow Brook channel is located between the Lower

Roberts Meadow Reservoir Dam and Reservoir Road in Leeds (see Figure 2.1

and Photo 2.9). The channel is comprised primarily of dry masonry sidewalls

and a naturalized boulder and cobble bottom. High flow events

have resulted in significant erosion of the channel sidewalls, which is

threatening the dwellings and driveways of adjacent private

properties. The City has proposed to extend the floodwall upstream

from the Reservoir Road bridge to the critical area in the channel.

The new floodwall would be a cast‐in‐place concrete retaining wall

with sufficient height to protect adjacent properties from the 100‐

year flood event.

2.6 Current Operational Cost and Funding Levels 2.6.1 Regulatory Compliance

The City is currently complying with all requirements of the 2003 NPDES Phase II permit. The City maintains a

public education and participation program, which includes educational brochures, stormwater education in the

high school, availability of rain barrels, storm drain labeling, outfall monitoring by volunteer groups, household

hazardous waste collection days, and community cleanups. The storm drain maps, with outfalls, have been put

into a Geographic Information System (GIS) and are continuously updated. In 2004, the City approved both the

Illicit Connections and Discharges to the Municipal Storm Drain System Ordinance and the Erosion and Sediment

Control and Post‐Construction Stormwater Management Ordinance. These ordinances are currently enforced.

The City’s street sweeping program sweeps all wards once per year and all streets in the downtown business

district every week from mid‐April to June. The City’s 3,750 catch basins are cleaned once per year, generating

20 tons of debris. In total, the City has spent in excess of $l00,000 annually on implementing the requirements

of this permit.

2.6.2 Stormwater Drainage Operations Staffing

Operation and maintenance activities associated with stormwater drainage operations fall mainly under the

Streets Division and the Sewer/Drain Division. Currently, funds to pay the compensation for sewer and drain

staff are allocated 2/3 from the sewer Enterprise Fund and 1/3 from the General Fund. Compensation for


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overtime is split 50 percent between the enterprise and General Funds. Storm drain materials and equipment‐

related costs are funded through the General Fund.

Generally, the current staffing is as follows:

Streets Division: Three staff spend about half‐time on street sweeping operations.

Sewer/Drain Division: Nine staff provide maintenance activities on the City sewer and drain systems, including

television inspections of drains, cleaning catch basins with a clamshell or vactor truck and infrastructure repairs.

Vehicle Maintenance: One vehicle maintenance staff person is assigned to vehicle maintenance on sweepers

and drain‐related equipment.

Regulatory Compliance: Currently, one part‐time planner is mainly responsible for compliance with the NPDES

Phase II permit. He is assisted by the GIS Coordinator, when compliance requires GIS mapping. Other

engineering and scientist staff may provide technical support as needed. The part‐time planner is funded

through the General Fund. Other technical staff are funded through various Enterprise Funds and the General

Fund.

2.6.3 Flood Control Operations Staffing

Flood control activities are paid for through the General Fund. Labor associated with flood control activities is

paid for through the Sewer Enterprise Fund for straight time and the General Fund for overtime. Staffing for

flood control activities are assigned to the Wastewater Treatment Division. Typically, the staff includes two to

three flood control technicians plus one supervisor. During flooding situations, staff from other departments

participate in flood control activities as needed, such as erecting the West Street flood wall.

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106678‐80349‐03‐11

Section 3 ‐ Capital Improvements Plan and Operational Budget Requirements

3.1 Introduction This section summarizes the recommended drainage system and flood control improvements plan,

including construction phasing, additional television inspection needs for final design, cost estimates

and schedules. It also includes the following proposed river erosion control projects: River Road

floodwall improvements, Roberts Meadow Brook channel improvements, and Federal Street

retaining wall improvements.

The recommended drainage system improvements have been phased as follows:

Phase 1 and 2 projects – needed to address high priority flooding problems or other issues,

such as pipe collapses; and

Phase 3 and 4 projects – are in areas with less flooding problems, designed to provide capacity

to control 10‐year 24‐hour storm peak rates of runoff.

3.2 Summary of Recommended Plan Figures 3.1 through 3.3 illustrate the recommended plans for each of the project areas. These maps

also provide locations of City‐owned property where there are opportunities for the City to install

stormwater Best Management Practices (BMPs)/green design facilities to reduce stormwater runoff

to drainage systems, improve the water quality of receiving waters and comply with the upcoming

new Environmental Protection Agency (EPA) Municipal Separate Storm System (MS4) permit.

3.2.1 Street Improvement Projects

The DPW maintains a conditional assessment database of all city streets pavement. This pavement

condition database is updated yearly. The purpose of the database is to determine the priority listing

for street work ranging from crack sealing, to asphalt mill and overlay, to full depth reconstruction.

Funding for roadway repair projects is primarily provided by the state under the Chapter 90 program.

Chapter 90 funding provides for the cost of asphalt resurfacing. The construction funding for new

sewer lines that may be needed as part of a street reconstruction project is provided through the

City’s Sewer Enterprise Fund. If new water lines are required, the funding is provided by the Water

Enterprise Fund. Historically, the City has funded drainage improvements through the General Fund,

as determined by the City Council through the capital improvements process. Because of the lack of

available monies in the General Fund, funding for storm drain construction has been extremely

limited. The DPW reports that a $62,000 budget line item for storm drain construction was removed

from the budget in 2010 as part of a DPW budget cut. If a street is identified as a high priority and in

need of reconstruction, and funding is not available for construction of a new drainage system, that

street is removed from the priority paving list. A good example of this funding dilemma is Milton

Street, a street that is desperately in need of reconstruction, but is on hold because of the lack of

funding to install a new drainage system.

Alignment #2New 48" RCP Drain

Alignment #1New 48" RCP Drain

CONNECTICUT RIVER

MILL RIVER

CONNECTICUT RIVERManage StormwaterOn-Site with BMPs

Manage StormwaterOn-Site with BMPs

Northampton Flood ControlPumping Station

West StreetStormwater

Pumping Station

Phase 2 Northampton FloodControl Pumping Station

Phase 1 and 2Levee Improvements

Phase 1 and 2Levee Improvements

Phase 2 Portable StormwaterPumping Station

66"

Nelson/Nygaard Design Charrette Area

Approximate Wetland Boundary Estimated by City

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AVENUE

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STREET WALNUT

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STRE

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AVENUE

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AVENUE

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AVENUE

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STREET

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AVENUE

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\\camgissvr1\Projects\M_Billings\Northampton\mxd\KingSt_WilliamSt_Recommendations.mxd JD 11/21/2011

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Assessment and Utility PlanFigure 3.1

King Street/Market Street and Bridge Street/Meadows Areas Recommended Plan

Proposed DrainageSystem Improvements

( )Existing Pipe Diameter

Proposed Pipe Diameter24"10"

9’ x 5’ Box

Legend

Drain Manhole

Catch Basin/Inlet

Stormwater Outfall


Contour

Drain Lateral

Culvert

Drainage Channel


Drain Pipe

Parcel Boundary

Building

DEP Wetlands

Wetlands (MassGIS)

City of Northampton Property

LeveeDrainage Area Boundary


Manage Stormwater On-Sitewith BMPs

400 0 400 800200

Feet


Phase 2Phase 3Phase 4

Phase 1

New 48" RCP Drain

New 72" RCP Drain

MILL RIVER

Manage StormwaterOn-Site with BMPs

New 7’x4’ Box Drain

NU

TTIN

G A

VE

NU

E

147

Federal Street Retaining Wall Improvements

Weir Structure

10’’

8’’

15’’

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BARDWELL STREET

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STREET

KIMBALL STREET

DRYADS GREEN

SANDERSON AVENUE

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GLEASON ROAD

MAIN STREET FLORENCE

CO

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PARADISE

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LAUR

EL RIDGE DRIVE

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FORBES A

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HAROLD STREET

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E DRIV

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MANDELLE ROAD

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TON

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DENNISTON PLACE

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P IN E BROO K

Broughtons

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PINE BROOK

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\\camgissvr1\Projects\M_Billings\Northampton\mxd\ElmSt_Recommendations.mxd SCC July 2011

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Legend

350 0 350 700175

Feet




Figure 3.2Elm Street Brook/Florence Area

Recommended Plan


Phase I

10"

24"Phase 3 ( )

Existing Pipe Diameter

Proposed Pipe Diameter

Drainage Area Boundary


Drain Manhole

Catch Basin/Inlet

Stormwater Outfall


Parcel Boundary

Building

DEP Wetlands

Wetlands (MassGIS)


ContourDrain Pipe

Drain Lateral

Culvert

Drainage Channel


New 30" RCP Drain

ChannelImprovements

ChannelImprovements

Flood Storage AreaNew 30" RCP Drain

Plug and AbandonExisting Pipe

12’’

10’’

48’’

12’’

18’’

12’’

12’’

8’’

12’’

12’’

15’’

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442

383

295

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BIRCH HILL ROAD

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SUMMERFIELD STREET

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GOLDEN DRIVE

GOLDEN DRIVE

AUS

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AUSTIN CIRCLE

\\camgissvr1\Projects\M_Billings\Northampton\mxd\RyanRoad_Recommendations.mxd JD 11/21/2011



Figure 3.3Austin Circle/Ryan Road

Area Recommended Plan

Legend

91

91

Drainage Area Boundary


Drain Manhole

Catch Basin/Inlet

Stormwater Outfall

Flood Storage Area


Phase 2

Drain Pipe

Drain Lateral

Culvert

Drainage Channel



150 0 150 30075

Feet


Contour

Parcel Boundary

Building

DEP Wetlands

Wetlands (MassGIS)


Wetlands (Delineated by City)

Section 3 Capital Improvements Plan and Operational Budget Requirements

3‐5

106678‐80349‐03‐11

In the future reestablishing an annual budget amount for new drain system construction would allow the DPW

to better prioritize street reconstruction projects because complete funding would be available for paving and

all street utilities. The annual budget would need to be significantly greater than previous budgets in order to

maintain the city stormwater system. This funding would result in an improvement in the management of city

streets and related utilities.

Based on conversations with the City, an annual budget of $500,000 is suggested for construction of new storm

drains or replacement of old drains as part of street improvement projects. This is comparable to the annual

amount budgeted by the City for water line and sewer line improvements.

3.2.2 Municipal Green Infrastructure/Building Project Retrofit/ Capital Allowance

The proposed NPDES permit contains requirements for “Good House Keeping and Pollution Prevention for

Permittee Owned Operations.” The section of the proposed permit has wide ranging requirements that will

involve one‐time capital expenditures and annual maintenance requirements beyond what is currently done.

These requirements include small and large obligations. The following provides some information about the

capital requirements, while the operational requirements are discussed in Section 3.3:

Parks and Open Space: Where waterfowl may congregate and feeding by the public occurs, the City is required

to install educational signage about the threat posed to receiving waters. Pet waste requirements include

preparation and distribution of educational flyers, signage, provision of pet waste bags, and disposal receptacles.

Buildings and Facilities: An inventory of all floor drains in City‐owned buildings must be prepared and all floor

drain connections that are connected to the drain system must be disconnected and piped to the sewer system.

Given the age of many City buildings, many floor drains may not be properly connected to the sewer. The design

and construction of new connections from floor drains to the sewer system will be required.

Vehicles and Equipment: City vehicles with fluid leaks must be stored indoors or in a contained area until

repaired and all vehicle washing must be discharged to the sewer system. Construction of improvements to

DPW facilities and other city facilities may be needed to meet this requirement.

City property and rights of way – retrofits: The draft permit requires the city to construct BMPs on City property

and within right of ways for City streets. These BMPS are to be designed to reduce the frequency, volume, and

peak intensity of stormwater discharges, as well as to reduce pollutant loadings into the drainage system and

receiving waters. The costs associated with these capital projects could be considerable given that the

construction of detention basins, water quality swales, rain gardens, permeable pavement and other capital

intensive BMPs would be required.

Based on conversations with the City, an annual budget of $200,000 is suggested for green infrastructure and

other retrofit construction. This budget is escalated with time in Table 3.6.

3.2.3 Bridge Street/Meadows Area

The recommended Phase 1 Bridge Street/Meadows area drainage improvements (Figure 3.1) consist of

approximately 5,500 feet of new drainage pipe ranging from 48‐ to 66‐inches in diameter. These improvements

include the 48‐inch diameter drain from the Three County Fairgrounds to the Connecticut River and the 66‐inch

diameter Massachusetts Department of Transportation (MassDOT) drain replacement at Damon Road. On‐site

management of stormwater with BMPs is recommended in the industrial area, instead of increasing pipe sizes in


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that area. Phase 3 improvements consist of 7,500 feet of new drainage pipe, ranging from 12‐to‐42‐inches in

diameter. The preliminary project cost estimate for these improvements is $11,117,000. See Table 3.1 for a

breakdown of these costs.

3.2.4 Elm Street Brook/Florence Area

The recommended Phase 1 Elm Street Brook area drainage improvements (Figure 3.2) consist of approximately

1,900 feet of new 48‐inch diameter drainage pipe and 1,600 feet of 7‐ by 4‐foot box culvert. The recommended

Phase 3 Elm Street Brook area drainage improvements (Figure 3.2) consist of approximately 15,000 feet of new

drainage pipe ranging from 12‐ to 72‐inches in diameter. The Smith Vocational and Agricultural High School is

located on a City‐owned parcel and on‐site management of stormwater with BMPs is recommended at this

location. The total estimated cost for drainage improvements in this area is $19,364,000. See Table 3.2 for a

breakdown of costs and phasing.

3.2.5 King Street/Market Street Area

The recommended Phases 1 and 2 King Street area drainage improvements (Figure 3.1) consist of approximately

5,400 feet of new drainage pipe ranging from 36‐ to 78‐inches in diameter, and 560 feet of 9‐foot by 5‐foot box

culvert in the Historic Mill River. Drainage pipe improvements include replacement of pipes in the Market Street

Brook system from North Street to Bridge Street, and replacement of pipes in King Street. Television inspections

of the drains in the Market Street Brook system upstream of Main Street should be performed during the final

design of improvements in this area to determine the condition of this system and whether it needs to be

replaced.

The recommended Phases 3 and 4 King Street area drainage improvements (Figure 3.1) consist of approximately

7,200 feet of new drainage pipe ranging from 12‐ to 60‐inches in diameter. On‐site management of stormwater

with BMPs is recommended in the retail area along upper King Street instead of increasing pipe sizes in that

area. These BMPs could be required during the planning board approval process or as part of the City’s

stormwater permit program.

On March 14‐16, 2011 Nelson\Nygaard conducted a three‐day design charrette with the City to address bicycle

and pedestrian access, while maintaining levels of vehicle throughput, for portions of King and Main Streets.

The charrette identified the need to reduce King and Main Streets from a four‐lane cross‐section to a two‐lane

cross‐section (also known as a “road diet”) to improve pedestrian and bicycle safety, while also creating several

opportunities for new public spaces.

The road diet also provides several opportunities for the installation of stormwater BMPs on Main and King

Streets. On Main Street, the Nelson/Nygaard study recommended using the additional space to widen sidewalks

to allow outdoor dining, street trees and other vegetation. Opportunities for BMPs on Main Street include

permeable pavers on the sidewalks for infiltration and street planters and bioretention gardens to collect and

treat stormwater runoff from the street. On lower King Street, the study recommended center left‐turn lanes

with vegetated medians. These vegetated medians could be designed as bioretention areas or street planters to

collect and treat stormwater.

On upper King Street, in addition to center left‐turn lanes, the study recommended one‐way cycletracks

constructed at‐grade with the sidewalks, but separated from the sidewalk by a 10‐foot‐wide vegetated strip.

Opportunities for green infrastructure include permeable pavers for the sidewalks, porous pavement for the

cycletracks, bioretention areas in the vegetated strip, and street planters in the vegetated median. All of these

stormwater BMPs will reduce peak runoff to the King Street drainage system and provide treatment of


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stormwater, improving receiving water quality. It is recommended that pipe capacity improvement design for

the King Street drainage system occur concurrently with modifications to King and Main Streets because

detailed hydrologic/hydraulic analyses associated with the proposed stormwater BMPs may indicate that pipe

sizes smaller than those shown on the recommended plan (Figure 3.1) may be feasible. . The total estimated

cost for drainage improvements in this area is $19,424,000. See Table 3.3 for a breakdown of costs and phasing.

3.2.6 Austin Circle/Ryan Road Area

The recommended Phase 2 Austin Circle/Ryan Road area drainage improvements (Figure 3.3) consist of

approximately 1,300 feet of new 30‐inch diameter drainage pipe, a 1.3‐acre flood storage area, and 1,500 feet of

channel improvements. The total estimated cost for drainage improvements in this area is $4,084,000. See

Table 3.4 for a breakdown of costs.

3.2.7 Flood Control Pumping Station Improvements

Recommendations for the Northampton Flood Control Pumping Station and the West Street stormwater

pumping station are discussed in Sections 2.3.5.1 and 2.3.6.1. For the Northampton Flood Control Pumping

Station, the cost estimate is based on a complete new facility. For the West Street Pumping Station, it is

recommended that the City purchase a portable diesel‐engine‐driven pump with capacity on the order of 6,000

gpm, instead of installing a permanent pump at this location. Pumping station improvements are scheduled for

Phase 2. The total estimated cost for the Flood Control Pumping Station improvements is $23,653,000. See

Table 3.5 for a breakdown of costs and phasing.

3.2.8 Levee Improvements

As discussed in Section 2.3.4, the levee improvements mandated by USACE include repairing areas with ruts,

small depressions, sparse vegetation, and missing riprap, and removing trees and thick brush on the levee and at

least 15 feet beyond the abutments and at the toe of the levee. Regular maintenance activities are also

recommended at least twice a year, or as conditions warrant, to control and limit growth of vegetation on the

levee and the banks of the diversion canal. The USACE has also mandated an engineering evaluation of the

levees to assess data gaps. Levee improvements must be completed by January 2013 or 2014, depending on the

item, as discussed in Section 2.

3.2.9 River Erosion Improvements

The proposed River Road Retaining Wall/Floodwall Improvements are located in the Leeds Village section of

Northampton (See Figure 1.1). Flows from the Mill River have scoured and undercut significant sections of the

wall, and surface runoff has compromised the integrity of the upper portions of the wall. In addition, the

Williamsburg sanitary sewer interceptor is located within River Road and is in danger of collapsing due to river

erosion. The City is proposing to remove the existing stone masonry wall and replace it with a cast‐in‐place

concrete retaining wall that will protect the road and sewer from the 100‐year flood event. This project is

scheduled for Phase 1.

The Roberts Meadow Brook channel is located between the Lower Roberts Meadow Reservoir Dam and

Reservoir Road in Leeds (see Figure 1.1). The channel is comprised primarily of dry masonry sidewalls and a

naturalized boulder and cobble bottom. High flow events have resulted in significant erosion of the channel

sidewalls, which is threatening the dwellings and driveways of adjacent private properties. The City has

proposed to extend the floodwall upstream from the Reservoir Road bridge to the critical area in the channel.

The new floodwall would be a cast‐in‐place concrete retaining wall with sufficient height to protect adjacent

properties from the 100‐year flood event. This project will be performed during Phase 1.


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The third project improves the Federal Street retaining wall along the Mill River, as shown in Figure 3.2. The

purpose of this project is to protect a 30‐inch sewer interceptor. Erosion is occurring along the sharp bank

angle, which is leading to the exposure of the interceptor. This project will be performed during Phase 2.

3.3 Future Operational Cost Projections Additional operational staff, equipment and funding will be needed to address the maintenance and

replacement needs of the City’s aging drainage infrastructure and to comply with the new requirements of the

pending changes to the NPDES Phase II permit. The proposed NPDES permit has many requirements that will

require both operational and technical staff, as well as new equipment needs. Some of these requirements are

discussed below.

Data Requirements: The Draft NPDES Permit requires the gathering, and in some cases mapping, of an

enormous quantity of data. Much of this information is required in the first two years after permit issuance in

order to perform the analyses required to meet the permit milestones. Northampton has a well‐established

Geographic Information System (GIS), but a significant amount of professional staff time will be required for the

data compilation and analysis.

Proposed Outfall Sampling: The new permit requires sampling 25 percent of each community’s outfalls each

year during both dry and wet weather. The City of Northampton has almost 300 stormwater outfalls that

discharge to various brooks, streams, and rivers, resulting in the need to sample about 75 outfalls two times per

year. These sampling events will require DPW staff labor and sampling equipment to accomplish, as well as

possible laboratory testing fees.

Nitrogen Reduction Requirements and Best Management Practices (BMPs): The Draft NPDES Permit requires

the use of both structural and non‐structural BMPs to ensure water quality standards will be met. The draft

NPDES permit requires a 10 percent reduction in the amount of nitrogen discharged in stormwater. This will be

required since the City is located within the Connecticut River basin and thus ultimately discharges to Long

Island Sound. The construction of many BMPs within the City stormwater system will be required to reduce the

amount of nitrogen discharged. These types of BMPs are stormwater retrofit construction projects that will

require capital funding to accomplish.

Public Education and Outreach: The Draft Permit includes the production and distribution of eight public

education notices, in addition to several ordinances and programs intended to teach the public how to minimize

their impacts on stormwater quality. Professional DPW staff will be required to manage the requirements of the

public education and outreach program.

Catch Basin Inspection and Cleaning: The draft permit requires street sweeping twice per year (spring and fall)

and a catch basin cleaning frequency that ensures that no catch basin will be more than 50 percent full of debris.

Currently, most City streets are swept once per year and only certain catch basins are cleaned on a regular basis.

The City has over 150 miles of paved streets and over 3,750 catch basins. Additional DPW staff and equipment

will be required to meet these new regulatory requirements.

3.4 Estimated Costs and Preliminary Schedule Tables 3.1 through 3.5 present the estimated project costs and projected schedules for construction of the

recommended drainage and flood control facilities. Table 3.6 summarizes the total project costs for the 20‐year

plan.


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Project costs include estimated construction costs, a 25 percent construction contingency, engineering and

implementation costs. The need for land acquisition and easements was not determined and those costs are

not included. Estimated mid‐points of construction used in the cost estimates vary for each project and are

provided in Tables 3.1 through 3.5.

Table 3.1

Bridge Street/Meadows Area Drainage Improvements Preliminary Project Cost Estimate

Location/Description Pipe

Size (in) Quantity Unit

Unit Cost Depth 0 to 8 ft

Construction Cost

Phase 1

New Drains 48 4,700 lf $670 $3,149,000

66 770 lf $950 MassDOT Project

Headwalls and Riprap Pads (42‐ to 84‐in pipe)

1 ea $80,000 $80,000

Subtotal 5,470 lf $3,229,000

Construction Contingencies (25%) $807,250

Total Construction Cost (April 2011 ENR 9027) $4,036,250

Construction Cost at Mid‐Point of Phase 1 Construction* $4,410,519

Engineering and Implementation Costs (25 %) $1,102,630

Phase 1 Opinion of Probable Project Costs (Rounded) $5,513,000

Phase 3

New Drains 12 3,650 lf $255 $930,750

18 1,225 lf $330 $404,250

24 500 lf $370 $185,000

30 1,300 lf $400 $520,000

36 350 lf $470 $164,500

42 490 lf $635 $311,150

Subtotal 7,515 lf $2,515,650






Total Opinion of Probable Project Costs (Rounded) $11,117,000

Notes:

Land acquisition/easement costs not included

Costs are April 2011 dollars (ENR 9027)

*Phase 1: Apr '11 to Apr'14, 3% per year; Phase 3: Apr '11 to Apr '23, 3% per year


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Table 3.2

Elm Street Brook/Florence Area Drainage Improvements Preliminary Project Cost Estimate

Location/Description Pipe Size

(in) Quantity Unit


Construction Cost

Phase 1

New Drains 48 1,860 lf $670 $1,246,200

New Box Culvert 7‐ft x 4‐ft 1,645 lf $1,200 $1,974,000

Headwalls and Riprap Pads (42‐ to 84‐in pipe)

3 ea $80,000 $240,000

Subtotal 3,505 lf $3,460,200




Engineering and Implementation Costs (25 percent) $1,291,144


Phase 3

New Drains 12 8,000 lf $255 $2,040,000

18 1,750 lf $330 $577,500

24 1,580 lf $370 $584,600

36 1,200 lf $470 $564,000

48 1,860 lf $670 $1,246,200

72 530 lf $1,000 $530,000

Subtotal 14,920 lf $5,542,300

Construction Contingencies (25%) $1,385,575






Notes: Land acquisition/easement costs not included Costs are April 2011 dollars (ENR 9027) * Phase 1: Apr '11 to Apr '17, 3% per year; Phase 3 Apr '11 to Apr '24/'25, 3% per year


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Table 3.3

King Street/Market Street Area Drainage Improvements Preliminary Project Cost Estimate

Location/Description Pipe Size

(in) Quantity Unit Unit Cost Depth 0 to 8 ft

Construction Cost

Phases 1 and 2

New Drains 36 320 lf $470 $150,400

48 2,800 lf $670 $1,876,000

66 420 lf $950 $399,000

72 400 lf $1,000 $400,000

78 1,480 lf $1,300 $1,924,000

New Box Culvert 9‐ft x 5‐ft 560 lf $1,800 $1,008,000

Subtotal 5,981 lf $5,837,400



Construction Cost at Mid‐Point of Phase 1/2 Construction* $9,108,690


Phase 1/2 Opinion of Probable Project Costs (Rounded) $11,386,000

Phases 3 and 4

New Drains 12 1,500 lf $255 $382,500

18 950 lf $330 $313,500

24 2,000 lf $370 $740,000

36 1,360 lf $470 $639,200

54 800 lf $740 $592,000

60 630 lf $930 $585,900

Subtotal 7,240 lf $3,253,100



Construction Cost at Mid‐Point of Phase 3/4 Construction* $6,430,309


Phase 3/4 Opinion of Probable Project Costs (Rounded) $8,038,000


Notes:



*Phase 1/2: Apr '11 to Apr'18/'19, 3% per year; Phase 3/4: Apr '11 to Apr '26/'27, 3% per year


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Table 3.4

Austin Circle/Ryan Road Area Drainage Improvements Preliminary Project Cost Estimate

Location/Description Pipe

Size (in) Quantity Unit


Construction Cost

Phase 2

New Drains 30 1,300 lf $400 $520,000

Headwalls and Riprap Pads (up to 36‐in pipe)

4 ea $25,000 $100,000

Flood Storage Area 1.3 acre $500,000 $650,000

Channel Improvements 1,500 lf $450 $675,000

Subtotal 2,800 lf $1,945,000




Engineering and Implementation Costs (25 percent) $816,800

Opinion of Probable Project Costs (Rounded) $4,084,000

Notes:



*Phase 2: Apr '11 to Apr '21, 3% per year


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Table 3.5

Flood Control System Improvements Preliminary Project Cost Estimate

Description of Capital Improvement Construction Costs

Phase 1

Levee Capital Improvements $436,000

Levee Certification Allowance $445,000

Subtotal $881,000

Construction Contingencies (25 percent)

Capital Improvements Only $109,000

Total Construction Cost $990,000

Construction Cost at Mid‐Point of Construction* $1,019,700


Phase 2

Levee Capital Improvements Allowance $500,000

Flood Control Pumping Station Upgrades $12,000,000

West Street Portable Pumps $400,000

Subtotal $12,900,000


Total Construction Cost (April 2011 ENR 9207 ) $16,125,000

Construction Cost at Mid‐Point of Construction** $18,106,000


Phase 1 Opinion of Probable Costs (Rounded) $22,633,000

Opinion of Probable Project Costs (Rounded) $23,653,000

Notes:


Costs are April 2011 dollars (ENR 9207 Estimated)

*Mar '12 3% per year

**April 2011 to April 2012 to Apr '18 (levee improvements), '15 (stormwater P.S.),'16 (West St P.S.)

Section 3 Capital Improvement Plan and Operational Budget

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2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031

Bridge Street/Meadows Phase 1 Improvements $441,000 $5,072,000

River Road Floodwall Improvements $155,000 $1,453,000

Roberts Meadow Brook Channel Improvements $43,680 $502,320

Federal Street Retaining Wall Improvements $120,000 $1,380,000

Elm Street Brook/Florence Area Phase 1 Improvements $516,000 $5,939,000


Levee Certification $275,000 $275,000

Levee Capital Improvements $280,000 $275,000 $56,000 $647,000

Flood Control Pumping Station Upgrades $1,391,000 $15,998,000

West Street Portable Pumps $46,000 $533,000

Austin Circle/Ryan Road Area Phase 2 Improvements $327,000 $3,757,000

Bridge Street/Meadows Area Phase 3 Improvements $448,000 $5,156,000

Elm Street Brook/Florence Area Phase 3 Improvements $1,033,000 $5,850,000 $6,025,000


EPA MS4 Permit Requirements Allowance $250,000 $250,000 $250,000 $250,000 $250,000

Annual Allowance for Drainage Infrastructure $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000 $500,000

Municipal Green Design/Construction Allowance $258,000 $265,000 $273,000 $281,000 $290,000 $299,000 $307,000 $317,000 $326,000 $336,000 $346,000 $356,000 $367,000 $378,000 $389,000 $401,000 $413,000 $426,000 $438,000 $452,000

Total Costs per Year $1,761,680 $3,961,320 $6,151,000 $3,115,000 $18,087,000 $7,769,000 $7,347,000 $6,132,000 $1,153,000 $4,593,000 $1,294,000 $7,045,000 $6,717,000 $7,546,000 $4,532,000 $4,653,000 $913,000 $926,000 $938,000 $952,000

Grand Total $95,586,000

Planning/Operations

Design

Construction

YearProject Description

Table 3.6

Summary Project Cost Schedule

Section 3 Capital Improvement Plan and Budget Operational Requirements

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3.5 Project Prioritization Construction phasing of the recommended drainage and flood control improvements will depend upon the

City’s availability of funding to implement these improvements. Twenty‐year bonds will likely be issued to

accomplish the projects. Section 5 uses the costs summarized in Section 3.4 above, assuming issuance of 20‐

year bonds, to evaluate creation of a Stormwater and Flood Control Utility to fund the recommended

stormwater and flood control improvement projects, as well as annual maintenance of drainage infrastructure

and permitting requirements.

The highest priorities are flood control, street improvements, the Bridge Street/Meadows area, which includes

the Fairgrounds, and the Elm Street Brook area where chronic flooding limits access to the area around

Northampton High School. As discussed above, the recommended drainage system improvements consist of

two types of projects:

Phase 1 and 2 projects – needed to address high priority flooding problems or other issues, such as pipe

collapses

Phase 3 and 4 projects ‐ designed to provide capacity to control 10‐year 24‐hour storm peak rates of runoff in

areas with less significant flooding problems

Table 3.7 provides a preliminary prioritization ranking system for the drainage and flood control projects that

can be used by the City for future stormwater and flood control system asset management using the City’s

VUEworks program. The prioritization ranking system includes a list of key qualitative (non‐cost) and

quantitative (cost) assessment criteria used to screen each project. Each project is rated based on key

assessment criteria, and the criteria is assigned weighting factors to account for varying degrees of importance.

It is recommended that the matrix be re‐evaluated every few years to determine whether it would be more

beneficial to re‐order project priorities.

Section 3 Capital Improvement Plan and Budget Operational Requirements

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106678‐80349‐03‐11

Table 3.7 Stormwater Capital Improvement Projects – Prioritization Ranking Summary

5.0% 10.0% 2.5% 10.0% 15.0% 22.5% 25.0% 10.0%

Watershed Improvement Nature of Problem Sys

tem

Des

ign

Cap

acity

(ye

ar)

Cos

t (E

ngin

eerin

g D

esig

n,

Per

mitt

ing

&

Con

stru

ctio

n)

Pro

ject

aff

ects

pa

rcel

s in

F

EM

A

flood

plai

n

Acr

es I

mpa

cted

Fac

ility

C

apac

ity

Env

ironm

enta

l Q

ualit

y

Acc

ess

&

Eas

emen

ts

Con

nect

ion

to

City

-Pla

nned

P

roje

cts

Con

stru

ctab

ility

Roa

dway

s/P

rop

erty

Flo

oded

To

tal C

ost

Sco

re

Bridge Street/Meadows Area48" drain from 3C Fairgrounds to Connecticut River, 66" drain replacement at Damon Road. (Phase 1) Flooding at Fairgrounds and lower Williams Street 10

$5,513,000YES 5 4 0 4 5 4 5 3 4.250

Elm Street Brook/Florence AreaInstall weir structure and box drain in Elm Street, new drain in Milton and Federal Streets, and new outfall from Federal Street to Mill River. (Phase 1)

Flooding along Elm Street, particularly at the intersection of Milton Street. 10

$6,085,000NO 4 4 0 4 4 3 5 3 3.825

King Street/Market Street Area

48" drain in Market Street Brook from North Street to Bridge Street, 36" drain in Market Street, 66" to 78" drain in King Street from North Street to Main Street, 9' x 5' box culvert in Old Mill River. (Phase 1 and 2)

Drainage systems do not accommodate 10-year storm

10

$11,386,000

NO 4 3 0 3 4 2 3 5 3.100

Austin Circle/Ryan Road AreaCreation of a Flood Storage Area, installation of 24" drain, and improvements to existing channel.

Flooding along existing channel25

$3,225,000No 2 4 5 3 0 3 5 2 3.050

Bridge Street/Meadows AreaUpsize all pipes <12" to 12" pipes, upsize cross-country drainage system near Coolidge Avenue, upsize pipes in Pomeroy Terrace, upsize pipes in Williams Street. (Phase 3)

Drainage systems do not accommodate 10-year storm10

$6,456,000No 3 5 0 2 1 1 5 3 2.775

Elm Street Brook/Florence Area

Upsize all pipes <12" to 12" pipes, upsize pipes in Federal Street, North Elm Street, Locust Street, Stitson Avenue, High Street, Straw Avenue, Fox Farms Road, Bridge Road, Strawberry Hill Street, and Chestnut Street. (Phase 3)

Drainage systems do not accommodate 10-year storm

10

$12,908,000

No 3 4 0 4 1 3 2 5 2.775

King Street/Market Street AreaUpsize all pipes <12" to 12" pies, upsize pipes in Upper King Street, Walnut Street, State Street, Trumbull Avenue and Church Street. (Phase 3 and 4)

Drainage systems do not accommodate 10-year storm10

$8,038,000No 3 2 0 4 2 2 3 4 2.650

LEGEND: Ranking Based on Quantifiable Data

Notes:(1) Costs that occur annually - MS4 permitting, drainage infrastructure, and municipal green design projects - are not included in this table.(2) Capital projects that are subject to a FEMA grant - River Road floodwall improvements, Roberts Meadow Brook channel improvements and Federal Street retaining wall improvements - are not included in this table.(3) Levee accreditation not included because subject to FEMA scheduling.

Project Affects Parcels in FEMA Floodplain

4‐1 10678‐80349

Section 4 – Environmental Permitting

4.1 Introduction Section 3 presented the recommended plans for the King Street/Market Street Area, Bridge

Street/Meadows Area, Elm Street Brook/Florence Area, Austin Circle/Ryan Road area drainage areas,

to be designed, permitted and constructed in four phases, as well as the Northampton flood control

system and river erosion recommended improvements.

These anticipated projects can proceed as standalone projects. Hence each phase of the work in

each watershed and the flood control improvements will be designed, permitted and built separately.

Following are the anticipated environmental permits and approvals for each watershed for Phases 1

through 4, and for the flood control and river erosion improvements:

Location

Federal Approvals

State Approvals Local

Approvals

USACE Permit

NPDES Permit

MEPA Water Quality

Certification

CH. 91 License

Order of Conditions

Phase 1 and 2


X X X X

Bridge Street/Meadows Area

X X X X X X


X X X X X

Austin Circle/Ryan Road Area

X X X X X

Phase 3 and 4


X X X X

Bridge Street/ Meadows Area

X X X X


X X X X

Flood Control Projects X X X X

River Erosion Projects X X X X

Section 4 Environmental Permitting

4‐2 10678‐80349

In addition, the new pump engines and emergency standby generator for the replacement Flood Control

Pumping Station will need to obtain Installation Compliance Certification as part of the MassDEP Environmental

Results Program.

During preliminary design the proposed improvements will be evaluated to determine what permits and

approvals are needed and a strategy to effectively navigate the approval process will be prepared. A “permitting

plan” will be incorporated into the preliminary design report for each project.

4.2 Description of Applicable Permits There are a number of federal, state and local permits required to implement the drainage improvements.

Because city drainage systems are linked to, or incorporate water courses and wetlands, e.g. Elm Street Brook

and the Connecticut River, permits and approvals will be required to work in or adjacent to these resources.

The following identifies federal, state and local permits/approvals required to work in or adjacent to regulated

natural resources.

4.2.1 Federal Permits/Approvals

4.2.1.1 Clean Water Act, Section 404

Section 404 of the Clean Water Act (CWA) regulates the discharge of dredged or fill materials into the Waters of

the U.S., including adjacent wetlands. Any discharge of dredged or fill material into Waters of the U.S. and/or

adjacent wetlands to prosecute drainage improvements, will require approval from the U.S. Army Corps of

Engineers (USACE) in accordance with Section 404 of the CWA.

In Massachusetts, the USACE issued a General Permit (GP) to streamline the permitting process. The GP

establishes three categories of review: Category I involves a pre‐discharge notification but no formal review by

the USACE provided all applicable GP conditions are met; Category II activities require screening by the USACE

for compliance with GP conditions; and, an Individual Permit is required for large‐scale projects (e.g., those

altering more than 1 acre of vegetated wetland or landfill bank) which do not meet the terms and general

conditions of the GP based on concerns for the aquatic environment or for other factor of the public interest.

Section 10 of the Rivers and Harbors Act

Section 10 of the Rivers and Harbors Act of 1899 (Section 10) requires approval from the USACE to place fill or

construct structures in Navigable Waters. Note, the Massachusetts GP was issued pursuant to Section 404 of the

CWA and Section 10 of the Rivers and Harbors Act of 1899. Therefore, review for work subject to Section 10 is

the same as described above for Section 404 of the CWA.

Executive Order 11988 (E.O. 11988), Protection of Floodplains

E.O. 11988 directs that federal actions (i.e. federal funding or approvals) occurring within floodplains must be

performed so as to avoid adverse impact to the floodplain, and to minimize potential harm and to restore and

preserve the natural and beneficial values of the floodplain.

This requirement is addressed by the USACE concurrent with their review pursuant to CWA Section 404,

described above. Floodplain associated with the Connecticut River will be altered during construction, including

excavation and refill. Preliminary design calculations have indicated that there will be no net loss of floodplain

storage capacity. This will be confirmed during future design work.


4‐3 10678‐80349

Executive Order 11990 (E.O. 11990), Protection of Wetlands

E.O. 11990 directs that federal actions (i.e. federal funding or approvals) occurring within a federal jurisdictional

wetland must be performed so as to minimize the destruction, loss, or degradation of wetlands. This

requirement is addressed by the USACE concurrent with their review pursuant to Section 404 of the CWA

described above.

4.2.1.2 Federal Endangered Species Act of 1973

Section 10 of the Endangered Species Act (ESA) is designed to regulate a wide range of activities affecting plants

and animals designated as Endangered or Threatened, and the habitats upon which they depend. With some

exceptions, the ESA prohibits activities affecting these protected species and their habitats unless authorized by

a permit from the U.S. Fish and Wildlife Service (USFWS) or the National Marine Fisheries Service (NMFS).

Permitted activities are designed to be consistent with the conservation of the protected species.

The ESA makes it unlawful to import or export; deliver, receive, carry, transport, or ship in interstate or foreign

commerce in the course of a commercial activity; sell or offer for sale in interstate or foreign commerce; take

(includes harm, harass, pursue, hunt, shoot, wound, kill, trap, capture, or collect any wildlife within the United

States); take on the high seas; possess, ship, deliver, carry, transport, sell, or receive unlawfully taken wildlife;

remove and reduce to possession any plant from areas under Federal jurisdiction; maliciously damage or destroy

an endangered plant on areas under Federal jurisdiction; and, remove, cut, dig up, or damage or destroy any

endangered plant in knowing violation of any State law or regulation or in the course of a violation of a State

criminal trespass law. These prohibitions apply to live or dead animals or plants, their progeny (seeds in the case

of plants), and parts or products derived from them.

Section 7 of the ESA requires Federal agencies to consult with the USFWS to ensure that actions they fund,

authorize, permit, or otherwise carry out will not jeopardize the continued existence of any listed species or

adversely modify designated critical habitats.

The presence or absence of federally protected species will be determined during preliminary design.

4.2.1.3 National Pollutant Discharge Elimination System (NPDES) – Construction General Permit

The NPDES Construction General Permit (CGP) authorizes stormwater discharges from construction activities

that result in a total land disturbance of equal to or greater than one acre, where those discharges enter Waters

of the United States or a municipal separate storm sewer system (MS4) leading to Waters of the United States

subject to the conditions set forth in this permit. The proposed drainage and flood improvement projects will

alter more than 1 acre of land and stormwater will be discharged to the Waters of the U.S.; therefore,

compliance with the CGP is required.

Pursuant to the requirements of the CGP, the project proponent, or designee, will prepare a Storm Water

Pollution Prevention Pollution Plan (SWPPP) to document stormwater control measures during the construction

periods for the projects. Following completion of the SWPPP, the proponent or designee will complete and

submit to EPA a Notice of Intent to discharge stormwater.

4.2.2 State Permits/Approvals

4.2.2.1 Certificate from the Executive Office of Environmental Affairs (MEPA Approval)

The Massachusetts Environmental Policy Act (MEPA) requires the review and evaluation of certain large‐scale

projects to describe the environmental impact and requires that permit granting agencies identify feasible


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measures to mitigate potential environmental damage. The MEPA Regulations (301 CMR 11.00) establish

thresholds, a procedure, and time line for a two‐tiered review process, which generally proceeds as follows: the

project proponent submits an Environmental Notification Form (ENF) to the Secretary of Environmental Affairs

(Secretary). A twenty day public comment period follows during which time the Secretary receives comments

from the public and agencies, and holds a site visit and consultation session. Up to ten days following the close

of the comment period, the Secretary issues a Certificate stating whether an Environmental Impact Report (EIR)

is needed and what the scope of the EIR should include, if required. If no EIR is needed the state permitting

agencies can issue the required permits and the project can go forward. Please note, MEPA approval is not

required before an Order of Conditions is issued by a local Conservation Commission. If an EIR is required, it is

prepared by the proponent and submitted to the Secretary. The EIR is reviewed and commented on at both

Draft and Final stages by the public, state agencies, the Secretary, and the MEPA Unit. After completion of

review the Secretary issues a Certificate approving the project.

Approximate time required to file an ENF is about two to four weeks. The approximate agency review time is

five weeks (including the public comment period). Approximate time to complete the EIR process is dependent

upon the time needed to prepare the EIRs, but it is normally completed in twelve to twenty four months.

4.2.2.2 Massachusetts Wetlands Protection Act (M.G.L. c.131, s.40; 310 CMR 10.00)

The Massachusetts Wetlands Protection Act (MWPA) regulates alteration of state‐ defined wetland resource

areas and the Massachusetts Wetlands Protection Regulations (310 CMR 10.00) identify wetland resource areas

subject to protection and present the regulations for work in these wetland resource areas. Although a state

law, the MWPA is administered at the local level by the municipal Conservation Commission. Areas known to be

subject to protection at this time, based on Mass GIS datasource and City investigations, are shown on the

recommended plan figures, and along the Connecticut, Mill and Old Mill Rivers.

A Notice of Intent (NOI) will be prepared and submitted to the Northampton Conservation Commission for

activities within areas subject to protection under the Massachusetts Wetlands Protection Act.

4.2.2.3 Massachusetts Rivers Protection Act (Ch. 258 of the Acts of 1996; 310 CMR 10.58)

The Rivers Protection Act protects perennial rivers, streams, brooks, etc., in the Commonwealth and is enacted

through Section 10.58 of the Massachusetts Wetlands Protection Regulations. It establishes a 200‐foot wide

Riverfront Area that extends horizontally on both sides of perennial waterways. In certain urban areas, the

Riverfront Area is only 25 feet wide. The Connecticut, Mill and Old Mill Rivers are perennial rivers and have an

associated 200‐foot wide Riverfront Area.

Because the Rivers Protection Act is administered through the Wetlands Protection Regulations, the NOIs for the

projects, described above, will address compliance with the Rivers Protection Act.

4.2.2.4 401 Water Quality Certification Program (314 CMR 9.00)

Section 401 of the Clean Water Act requires that states certify that federal actions will not prevent the

attainment of state water quality criteria. The proposed projects will involve work in the Connecticut, Mill and

Old Mill Rivers and associated wetlands, thereby requiring a permit from the USACE per Section 404 of the Clean

Water Act. Consequently, a Water Quality Certification is required from the MassDEP per 314 CMR 9.00. For

minor impact projects [projects that alter less than 5,000 square feet of federal and state jurisdictional wetlands

and/or involve dredging less than 100 cubic yards of material and receive an Order of Conditions (wetlands

permit) per the Massachusetts Wetlands Protection Act] no individual Water Quality Certification is needed. For

projects that exceed those thresholds, an Individual Water Quality Certification is needed from the MassDEP.


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Massachusetts Stormwater Regulations: Recent revisions to 314 CMR 9.00 establish stormwater standards as a

regulatory requirement. These standards were developed to regulate the quantity (flow) and quality of

stormwater runoff from project sites. The proposed drainage and flood control improvements will require

stormwater runoff control features and will need to comply with the standards to the maximum extent

practicable. These provisions are reviewed by the Conservation Commission pursuant to the WPA and MassDEP

via WQC application review.

4.2.2.5 Massachusetts Endangered Species Act (M.G.L c.131A; 321 CMR 10.00)

The Massachusetts Endangered Species Act (MESA) prohibits the "take" of any rare plant or animal species listed

as Endangered, Threatened, or of Special Concern by the Massachusetts Division of Fisheries & Wildlife (MDFW).

"Take" is defined in the Act as to harass, harm, pursue, hunt, shoot, hound, kill, trap, capture, collect, process,

disrupt the nesting, breeding, feeding or migratory activity of an animal or to collect, pick, kill, transplant, cut or

process a plant. Drainage improvements are located with estimated habitats and will involve work in the

Connecticut, Mill and Historic Mill Rivers, which are also mapped as habitat for protected aquatic species.

When projects involve MESA review and also require approval pursuant to the Massachusetts Wetlands

Protection Act, MESA review can be initiated by submitting the NOI (wetland permit application) to MDFW.

Through this joint review, the MDFW will determine whether a Take Permit is needed.

4.2.2.6 Waterways Licensing Program (M.G.L. Chapter 91; 310 CMR 9.00)

The Waterways Licensing Program was formally established in 1866 with the passage of M.G.L. Chapter 91.

Chapter 91 jurisdiction extends to the mean high water mark of tidal water bodies and the ordinary high water

mark of non‐tidal water bodies, and also includes "filled tidelands.” A Waterways License will be required for

placement of fill or structures below ordinary high water line, of the Connecticut, Mill and Historic Mill Rivers.

4.2.2.7 Environmental Results Program (310 CMR 7.26[42:43])

Under the Environmental Results Program (ERP), operators of new engines and new emergency engines are

required to certify to MassDEP that they are complying with the environmental protection requirements that

apply to the new engines. Operators complete the Installation Compliance Certification Form, which has three

sections. The first section identifies the facility and contact information. The second part is a series of questions

about whether the facility is following applicable environmental requirements. The last part is the certification

statement. The certification needs to be completed within 60 days of starting operation.

4.2.3 Local Permits/Approvals

4.2.3.1 Wetlands Protection Act and City Ordinance

The Massachusetts Wetlands Protection Act and Regulations were established to protect wetland resource areas

because of the valuable functions wetlands provide such as: protection of public and private water supply;

protection of groundwater supply; flood control; storm damage prevention; prevention of pollution; protection

of land containing shellfish; protection of fisheries; and protection of wildlife habitat. Authorization is required

from the municipal Conservation Commission for any work in and adjacent to protected wetland resource areas

as described above.

In addition to the state law, the City adopted a wetlands protection ordinance to augment wetland protection.

The work subject to the ordinance will be addressed in a single joint application (NOI) to address both state and

local requirements.

Please note, additional local approvals may be required by local Zoning Board of Appeals for work with the

floodplain, Planning Board Review, and authorization to connect to municipal drainage systems. Since this


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project is currently in the conceptual design stage, evaluation of these permitting requirements is beyond the

scope of this document. These issues will be evaluated in their entirety as needed.

4.3 Conclusion The proposed drainage improvement, flood relief and river erosion improvement projects will require work in

regulated resources, e.g. rivers and wetlands, and thus meeting applicable statutory and regulatory

requirements is a critical project component during the preliminary design phase. A program‐specific permitting

plan will be developed to identify anticipated project impacts to regulated resources; permit thresholds;

required permits; suggested measures to mitigate anticipated impacts; and a strategy and schedule to apply for

environmental permits and approvals.

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Section 5 ‐ Stormwater and Flood Control Utility

5.1 Introduction Below is a summary of the drivers and main objectives of this section, a brief overview of the

approach and methodology used in developing this report and a summary of the key findings.

5.1.1 Objectives

The City of Northampton (the “City” or “Northampton”) has actively begun to evaluate the funding

needs to maintain the City’s flood control and stormwater infrastructure. As part of this evaluation,

the City requested that Camp Dresser & McKee Inc. (CDM) assess the option of implementing a

stormwater and flood control utility by developing a financial framework and stormwater fee that

could be used to recover costs incurred by the utility. To provide the City with an understanding of

how Stormwater and Flood Control Utility fees are structured, we have developed the following

information:

A planning level budget for the Stormwater and Flood Control Utility, which includes stormwater‐

related expenses currently funded through the sewer rate and General Fund, as well as

anticipated capital improvements.

An analysis of Geographic Information System (GIS) data and application of a standard industry

methodology to determine the City’s equivalent residential unit (ERU) based on impervious area.

A financial model that combines budgetary data with GIS/ERU data to develop a stormwater fee

and assess its impact on typical customers.

A discussion on some of the important policy considerations that are important to take into

account when developing a Stormwater and Flood Control Utility and the associated fees.

The remainder of this section will present the results of this evaluation.

5.1.2 Stormwater Utilities in Other Communities

In order to provide the City with a basis of comparison for stormwater and flood control utility

implementation practices, CDM developed a comparison table which provides information on

population, organizational structure, staffing needs, budget/funding activities funded by the utility

and rates/fees. The table has two sections. The first section of the table reviews stormwater utilities

in New England. The second section reviews stormwater utilities across the country. This

comparison has been compiled using information from the EPA, planning commissions and CDM

client experience. The following is a list of sources and follow up documents that can be used to gain

additional detail on stormwater utility implementation:

Section 5 Stormwater and Flood Control Utility

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Table 5.1

Stormwater Utilities in Other Communities

New England Comparisons

Municipality Population Organizational Structure Staffing Needs Budget/Funding Activities Funded Rates/Fees

Newton, MA 85,000

Stormwater Management Program within DPW

Full‐time engineer and four laborers

$1.149 million (2011)

Operations: stormwater engineer, pollution prevention, water quality sampling, corrective actions, personnel training, public education and outreach.

Capital improvements: drainage improvements, sediment removal, culvert replacement and pump station rehab.

Originally, annual uniform rate: $25 residential and $150 commercial. Recently switched to ERU charge of $25 per unit annually, through water and sewer bills.

Reading, MA 25,000 Enterprise Fund

3 ½ equivalent laborers allocated to utility, 10% of DPW director, 10% of business supervisor and 10% of health administrator. 25% of accounting/finance clerk.

$540,350 (2007)

Operations: street sweeping, vacuum truck rental, materials and supplies, consulting fees and staffing.

Capital improvements: GIS mapping, drainage improvements, river restoration, street sweeper, vacuum truck and dump truck.

ERU charge of $39.84 annually, billed through water and sewer bills.

South Burlington, VT 16,000 Stormwater Management Department, DPW

4 DPW laborers/engineers and 10% city planner.

$1.250 million (2007 estimate)

Operations: legal services, consulting fees, water quality monitoring, permitting, equipment and maintenance.

Capital improvements: upgrades to culverts, retention ponds, drainage and catch basins, GIS services and infrastructure maintenance.

ERU charge of $54 annually, through the water district.

Lewiston, ME 42,000 Enterprise Fund N/A $2.2 million (2011 estimate)

Operations: billing and collections, street sweeping, catch basin cleaning, drainage repairs and general O&M.

Capital improvements: GIS Mapping, pipe renewal and replacement, stormwater infrastructure maintenance.

ERU charge of $40 for single‐family and $60 for duplex, annually. All other customers, $40 base rate and .045 cents per sq. feet of impervious area above 2,900 sq. feet.

Chicopee, MA 55,000 Stormwater Utility Bureau, DPW N/A N/A N/A ERU charge of $100

Westfield, MA 41,000 Stormwater Utility, Special Revenue Fund

Operations: labor, catch basin cleaning, street sweeping, illicit discharge detection and elimination, stormwater control device monitoring and inspection, water quality programs and monitoring, billing and administrative costs.

Capital improvements: engineering, design, financing and construction costs for new facilities or improvement of existing facilities.

$20 flat fee for residential and impervious area‐based fee for non‐residential: $0.045 per square foot impervious surface, with a $100 minimum and $640 maximum


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Table 5.1 (con’t)

Stormwater Utilities in Other Communities

United States Comparisons

Municipality Population Organizational Structure Staffing Needs Budget/Funding Activities Funded Rates/Fees

Lancaster, PA 500,000 Enterprise Fund (planning level) N/A $1.832 million (2011 estimate)

Operations: public education and outreach, illicit discharge detection and elimination, construction site runoff control, street sweeping, catch basin cleaning, GIS mapping and stormwater management staff training.

Capital Improvements: N/A

ERU charge of $16.53 (planning stages)

Bellevue, WA 117,000 Part of Utilities Department

45 to 50 full time equivalent employees

$10 million (2004)

Gross Area and Intensity of Development, $120 annually

Charlotte/Mecklenburg County, NC

1,500,000 County Utility with inter‐governmental agreements

105 full time equivalent employees

$85 million

Flat rate for single‐family residential with ERU basis for other customer classes. Rates vary by location.

Tulsa, OH 392,000 Part of Public Works

$12‐$14 million (2002)

Impervious area/ERU basis $42 annually.

Louisville/Jefferson County Metropolitan Service District, KY

Part of Sewer District

600 full time equivalent employees (includes sewer)

$26.7 million (2006)

Flat rate for single‐family residential. Impervious area/ERU basis for other2. $56.40 annually.

Sarasota County, FL 340,000 County Utility 120 employees $20 million (2005) Assessments vary by geographic location.

Griffin, GA 25,000 City Department, with shared DPW Director

15 full time staff $1.2 million (2000)

Operations: personnel and benefits, contracted services, supplies, debt service

ERU charge of $35.40 annually.

Union, OH 6,400

Program within DPW

7 hourly employees $75,000 Operations: storm drain maintenance, catch basin cleaning

Flat Fee System (Impervious area was too complex for a small community)

Annual Cost:

Residential: $36

Commercial: $72

Industrial: $108

Fort Collins, CO 109,000

Program within the Utility Department

25 full time equivalent staff, some staffed are shared and some exclusive to the stormwater program

$7.2 million (2000)

Operations: storm drain maintenance and repair, water quality improvement, new construction development reviews, floodplain management and design of relevant capital projects.

Each parcel is charged a basin fee rate, which varies by geographic location and takes into account on‐site detention reduction factor and a runoff coefficient for each parcel

The runoff coefficient uses a formula that takes into account the percentages of impervious area, pervious area and semi‐pervious area on a per parcel basis

Valparaiso, IN 25,000 Department of Stormwater Managment

No full time employees, only reimburses City staff for labor on stormwater related business

$520,000 (2000) Operations: collection, disposal and drainage of stormwater.

ERU of $36, with multiplier for impervious area, which is broken into 6 ranges, the largest of which charges $1,152 annually for impervious area > 160,000 sq. feet


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1. Assessment of Stormwater Financing in New England, Charles River Watershed Authority, March 30, 2007.

2. Guidance for Municipal Stormwater Funding, National Association of Flood and Stormwater Management

Agencies, January, 2006.

3. How to Create a Stormwater Utility, Pioneer Valley Planning Commission, November 13, 1998.

4. Stormwaterfinance.urbancenter.iupui.edu, Center for Urban Policy and the Environment.

5. Utility Stormwater Survey, Black & Veatch, 2010.

6. South Burlington Stormwater Utility, Stormwater Credit Fee Manual, Hoyle, Tanner & Associate, Inc.s and

AMC Earth & Removal, Inc., February, 2006.

5.1.3 Methodology

To develop the analysis of a separate Stormwater and Flood Control Utility, stormwater‐related costs currently

being funded through the General Fund and Sewer Utility were identified through discussions with the City.

Based on these discussions, the portion of General Fund and Sewer Utility costs attributable to stormwater were

allocated to the Stormwater and Flood Control Utility. Having combined these costs with anticipated capital

improvements outlined in Section 3, CDM developed revenue requirement projections for the Stormwater and

Flood Control Utility and paired our financial projections with impervious area parcel data to determine a rate

per “ERU”.

The results of this analysis are compiled in this report, the goal of which is to provide the City with the necessary

information to make an informed decision on how it could implement a Stormwater and Flood Control Utility in

order to equitably recover the costs of collecting and treating stormwater through a separate rate. Given this

objective, we focused on three sequential tasks in our analysis, which are as follows:

1. Estimated Stormwater and Flood Control Utility revenue requirements

2. Assessed the City’s impervious surface area and used it to develop an ERU‐type billing system

3. Calculated a rate per equivalent unit and summarized the impact the rate would have on typical customers

This analysis uses FY 2011 as the base year for the projections. The City would not anticipate implementing the

Stormwater and Flood Control Utility within the remainder of the fiscal year. However, it is shown as a basis for

the projections to indicate how the rate would be calculated under the most current expense period.

5.1.4 Key Findings

Should the City choose to implement a stormwater utility, CDM recommends using an ERU fee, which we believe

will most appropriately distribute the costs of the stormwater system. This is an equitable approach that

depends on impervious area, but simplifies the billing system and GIS data requirements needed for

implementation. Under the ERU system, residential units would be assigned one billing unit per dwelling unit,

up to a three‐family unit. Therefore, a single‐family would be assigned one billing unit; a duplex, two billing

units; and a three‐family, three billing units. Larger residential units (i.e. more than three units) and non‐

residential parcels would be assigned billing units based on the amount of parcel impervious area to the

equivalent residential unit amount which CDM has estimated for purposes of this analysis to be 2,671 square

feet (full calculation is shown in Table 5.8). This approach equitably allocates the costs of the system, since

customers with more impervious area create a greater burden on the system and thus should be responsible for

more of the costs.


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The resulting stormwater fee from an ERU approach is shown in Table 5.2.

Table 5.2

Proposed FY 2012 Equivalent Residential Unit Stormwater Fee Schedule


Single‐family 1 1.00 $66.63

2‐Family 2 2.00 $133.26

3‐Family 3 3.00 $199.90




Commercial/Industrial with 1,000 sq. feet of IA 1,000 0.37 $24.95

Commercial/Industrial with 10,000 sq. feet of IA 10,000 3.74 $249.46

Commercial/Industrial with 100,000 sq. feet of IA 100,000 37.44 $2,494.58

A common concern about the implementation of a stormwater and flood control fee is the impact to

commercial and industrial customers, which typically have a higher proportion of impervious area than small

residential customers. Additionally, in some cases, commercial users who do not discharge significant levels of

wastewater may have a significant level of impervious surface area. The shifting cost burden can be difficult for

businesses to appropriately budget for. If the City is concerned about the effect of stormwater and flood control

fees on certain customer classes, there are certain measures that can be taken to mitigate their impact, such as

stormwater management credits, phased implementation, or continuing to recover a portion of stormwater and

flood control costs through the General Fund.

5.2 Stormwater and Flood Control Utility Implementation Considerations

Despite increasing state‐wide interest in Stormwater and Flood Control Utility creation as a means to effectively

manage permit requirements and equitably distribute the cost of stormwater impacts, the concept is still

relatively new to the world of flood control and pollution management. Implementing stormwater utilities is a

significant undertaking and, unfortunately, the lack of existing utilities serves to limit the number of examples

that can be used in assessing best practices. Given those limitations, this section combines information from

existing utilities, planning documents and CDM’s experience in helping clients to establish stormwater utilities, in

order to assist the City in its evaluation of creating a new utility.

5.2.1 Stormwater and Flood Control Utility Background

The establishment of stormwater utilities is a concept that has achieved growing popularity in the United States

since the mid‐1970s. The fundamental basis for the Stormwater and Flood Control Utility is that as the amount

of impervious area increases on a parcel, the amount of runoff from that parcel increases proportionately.

Therefore, the amount a parcel owner is charged is related to its impervious area. The impervious area charge is

an equitable funding mechanism, since charges assessed to each parcel of land are based upon usage of the

drainage system..


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The average impervious area per dwelling unit for residential land use categories is typically designated as the

“base unit” for the utility fee structure. The base unit represents the impervious area discharge potential of the

average residential dwelling and its associated lot. It can be based upon all residential development (including

multi‐family), on single‐family residential development only, or a combination to encompass smaller residential

developments. For this analysis, the average impervious area of the base unit is calculated by summing the

impervious area for smaller residential parcels (defined as structures less than four units) and dividing by the

total number of dwelling units within those structures. This basic unit is referred to as an equivalent residential

unit (ERU).

Under this approach, large residential properties (greater than three units), and non‐residential parcels are billed

based on the amount of impervious area on the parcel relative to the ERU amount. For example, if a commercial

parcel has four times as much impervious area as the base ERU unit, the commercial site would be billed four

times the residential flat fee.

During the initial history of stormwater utilities, it was relatively expensive to develop the necessary parcel

information to determine billing units and assign billing units to specific parcels. It frequently required hand

measuring parcels and conducting samples of residential parcels to estimate the ERU. However, as GIS

technology has improved, the costs of developing and implementing utilities have declined. Many municipalities

now include impervious area as a layer within their GIS and it is possible to determine, with a high level of

accuracy, the impervious cover on each parcel.

Due to the declining costs and increasing ease with which impervious area can be mapped, some utilities now

bill customers individually based on the actual amount of impervious area on the parcel regardless of whether

the property is residential or non‐residential. The result is that each parcel or customer’s fee is based on its

impact on the municipal system making the stormwater charge more consistent with other utility charges (i.e.,

water, sewer, electric). The main obstacle to this approach is developing the detailed GIS impervious area maps,

which despite technological advancements, still requires a significant effort, specifically in instances of “open

polygons”. A common example of this is a driveway, which GIS applications have difficulty delineating, relative

to something like a roof, which is a closed polygon.

5.2.2 Structural Considerations

The first step towards creating a Stormwater and Flood Control Utility is generally drafting appropriate language

as part of an ordinance. The City Council would typically approve the ordinance to establish the utility. Some

general guidelines to consider include:

Citing the existing legal authority to establish the Stormwater and Flood Control Utility

Showing evidence of the need to create the Stormwater and Flood Control Utility, and the processes

required for its creation

Creating the utility in a way that ensures consistency with local, state, and federal guidelines

The ordinance should explicitly define the role and purpose of the utility, as well as the utility’s ability to charge

and collect fees. It should further establish the process by which the stormwater fees and charges are set,

including the methodology behind the calculation and any potential exclusions for parcels such as undeveloped

land or municipal properties. The ordinance should also detail any credits that are available and the process by

which a resident could appeal a charge. We suggest the City begin reviewing existing stormwater ordinances in

other communities, as well as the City’s Sewer Utility ordinance, as a basis for its own stormwater ordinance.


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5.2.3 Public Education and Involvement

The City should consider developing a public education program designed to educate the community on the

reasons behind creating a Stormwater and Flood Control Utility, highlighting the negative impacts of stormwater

pollution. Public support for the utility may make it easier to implement the fees and charges necessary to fund

the utility. Educating the public on the basics and the impact of pollutants in stormwater may also have the

effect of creating a change in behavior and encouraging better stormwater management practices from

residents and businesses.

The City should identify the amount available to allocate towards public education and outreach, and formulate

activities it believes will be most effective for public consumption. Examples of activities include distributing

flyers or press releases outlining the role and purpose of the Stormwater and Flood Control Utility, incorporating

the basics of stormwater into school curriculum, and/or hosting public events. As a planning level estimate,

CDM has included a $20,000 line item for public education into its incremental budget in the revenue

requirement subsection.

In defining the steps for public education and acceptance for the creation of a Stormwater and Flood Control

Utility, it is important to define the message the City wants to convey to the public, and the means by which to

convey it in an effective manner. Generally, before the creation of the utility, the focus of public outreach is to

describe the utility and its general functions and to justify the need for a separate stormwater fee. For the City,

the message would most likely highlight the environmental and health impacts of stormwater pollutants and

requirements to remain in compliance with permit guidelines.

A common method to facilitate public education is through the distribution of flyers and educational packets,

incorporating stormwater information into school curricula, public hearings or press releases, inserts that

accompany water and sewer bills outlining the need for a Stormwater and Flood Control Utility, and/ a

dedicated website with stormwater education. Given that the City has decided to establish the utility as a

standalone enterprise utility, establishing a separate page on the City website dedicated to the Stormwater and

Flood Control Utility may be useful, with information on why the utility is being established, and a justification

for the stormwater and flood control fee. The site could also contain links to various web resources that

facilitate public education on the topic. See the website for the South Burlington, VT stormwater utility that

provides detailed information about their utility (sburlstormwater.com).

In conjunction with educating the public on the need for the new Stormwater and Flood Control Utility and fee,

it could also be useful to highlight behaviors that would encourage stormwater pollution prevention. Part of the

education process for the acceptance of the utility creation will include showing the public the negative impacts

of stormwater pollution, consistent with the EPA NPDES Phase II requirements, so the City may consider using

that opportunity to provide the public with ways they can help reduce stormwater pollution. It would be useful

to continue this sort of public outreach on an ongoing basis after the creation of the Stormwater and Flood

Control Utility and the implementation and acceptance of the fee.

5.2.4 Management and Budgeting

Another key aspect to creating a Stormwater and Flood Control Utility is determining how the utility is to be

managed. A new Stormwater and Flood Control Utility would operate as a stand‐alone enterprise utility, which

means that the utility would have its own separate budget with line item expenses, and the stormwater charges

would be set annually to directly offset these expenses.


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5.2.4.1 Budgeting

The City worked with CDM to identify the staffing and budgetary needs to operate the Stormwater and Flood

Control Utility. In order to develop planning level estimates, CDM worked with the City to allocate stormwater‐

related expenses from the General Fund and Sewer Utility. In addition to this, CDM developed incremental

Stormwater and Flood Control Utility costs. These are operation and maintenance (O&M) costs that will be

required to operate the City’s Stormwater and Flood Control Utility and meet permit requirements.

CDM also provided the Stormwater and Flood Control Utility with a capital improvements plan (CIP), which is

included in revenue requirement projections and must be considered in the budgeting process. In addition to

the CDM‐prepared CIP, the City may need to consider making some additional capital outlays, such as additional

street sweepers and maintenance vehicles, as it moves forward with its Stormwater and Flood Control Utility

implementation. As the City gains a better understanding of the operating costs and capital needs for the

Stormwater and Flood Control Utility, these estimates will need to be adjusted to more accurately reflect the

true cost of service.

5.2.4.2 Billing

The City will need to establish an appropriate and functioning billing system in order to ensure billing accuracy

for the stormwater fee. A common practice is to include the stormwater charge as part of an already existing

municipal bill (e.g. water and sewer). It is generally assumed that the municipality would have a master file of

accounts through some computerized billing program, so the most reasonable way to incorporate the charge is

to populate the master file with the relevant information pertaining to the stormwater charge.

A potential issue with the implementation of this rate structure that the City would need to consider is land

areas not connected to other municipal utilities. One example of this is parcels that have private wells and

septic systems. Another example is vacant parcels, which do not have utility services. The City has over 2.7

million square feet of undevelopable impervious land area, and another 4.2 million square feet in impervious

area with unknown classification. If the City were to include the stormwater charge as part of another utility bill

and incorporate the same customer listing, it would omit the vacant land.

An alternative approach to billing would be to include the stormwater fee as part of the property tax bill. All

taxable property listings would be accounted for, so a property would not need to have municipal utility service

in order to be included for the fee. However, this approach creates a similar but separate issue – the exclusion

of tax‐exempt properties. Exempt (municipal, colleges, etc.) impervious area totals around 16.2 million square

feet, and would not appear on the tax rolls or receive a property tax bill. The City will need to assess the billing

issues associated with the new stormwater fee and determine the appropriate course of action.

A third approach would be to conduct stand‐alone utility billing. However, CDM recommends against this

practice, as it would be redundant with current services and would add an additional layer of administrative

costs to the utility. For this reason, a stand‐alone billing approach is rarely used by stormwater utilities.

5.2.5 Funding Options

There are a variety of rate/fee mechanisms for recovering Stormwater and Flood Control Utility revenue

requirements. As we have developed this report, based on discussions with the City, we have taken an ERU

approach. We have included this section on funding options for the purpose of providing the City alternative

approaches to the one proposed in the report, as well as providing an understanding of why the ERU was used

as the cost recovery method in this report.


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In large part, rate/fee setting principles focus on the equity of cost recovery. Equity refers to setting rates at a

level that generates adequate revenue to fund revenue requirements, while also aligning to recover the actual

cost of service to operate and maintain the system.

Some of the general methodologies for stormwater rate and fee setting utilized by other communities include:

uniform charges based on property type, rates based solely on impervious area, a combination of impervious

and gross area, impervious area and percent of impervious area, gross property area and intensity of

development, and runoff factors. In addition to the various rates and fees, the City may also choose to recover

stormwater costs through the General Fund, which is largely what it does at present. A brief analysis of these

types of rate and fee structures follows.

Uniform charge/flat fee based on property type ‐ Each property is defined as either residential or non‐

residential, and charged a uniform fee based on customer class. This structure has the benefit of being easy to

understand and easy to implement, as it only requires analysis of property data with a residential or non‐

residential designation for each property. The main shortcoming is that it does not necessarily match the rate

with a property’s impact on the stormwater system. For example, a small retail store with a total of 1,000

square feet would be paying the same non‐residential uniform charge as a large commercial building with a

property size of 100,000 square feet. Recently, the City of Newton, MA switched from this rate structure to an

ERU‐based structure for its stormwater system to more closely match the rates with a customer’s burden to the

system.

Rates based solely on impervious area ‐ This is a common approach for stormwater utilities, as it is simple to

understand, easy to calculate and readily justifiable to the public. The underlying principal of an impervious area

fee is that the more impervious area a property has, the larger the impact it has on the stormwater system.

Thus, it should have a proportional charge to its impact on the system. This structure is used with a calculated

charge per ERU for small residential customers based on the average impervious area for that class category.

Larger residential and commercial customers are charged based on actual impervious area as a multiple of the

rate per ERU. This is the rate structure we recommend for the City, and the detailed calculations and description

of this structure are in Section 5.4 of this report.

Rates based on impervious area and gross area ‐ Impervious area and gross area are both included in this

methodology based on the logic that all land area has some impact on the stormwater system. Setting the

stormwater fee involves allocating either a percent distribution between impervious area and gross area, or a

detailed cost of service that allocates costs to one or the other. A benefit of this rate structure is the implicit

decision to charge underdeveloped land, which expands the base for distributing the costs among the

community residents. One deterrent to implementing this approach is equitably determining the allocation

factors used and effectively educating customers on the methodology.

Impervious area and percentage of impervious cover ‐ Users are charged a rate per 100 square feet, which is

defined by the percentage of impervious area to gross area on a property. The rates are generally set as

increasing in a percentage range (e.g. 0‐15%, 15‐20%, etc.), with the idea being that the more impervious area

on a property, the greater the burden. This rate structure is currently used by the City of Denver, CO.

Gross area and intensity of development ‐ An intensity of development factor is assigned to properties to

estimate the amount of impervious area per parcel. The calculation can be as simple as taking a parcel’s gross

area and multiplying it by the factor. Cincinnati, OH, for example, assigns a factor of zero to undeveloped land

up to a factor of 0.85 for commercial customers. A potential benefit of this structure is employed by Bellevue,

WA, in which a small rate is assessed to undeveloped properties, allowing for some cost recovery from


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undeveloped lands. The justification follows the same logic as the impervious and gross area rate structure – all

land contributes to the stormwater system, and so should be assessed some charge.

Runoff factor ‐ This structure aims to apply a set of factors to parcels generally in land use categories in order to

account for the amount of stormwater estimated during a storm event. It is similar to the intensity of

development factor, however it is usually considered a better gauge of the amount of actual stormwater by land

use type, but more difficult to describe and justify to the public.

5.2.6 Stormwater Credits

The impact to customers with large amounts of impervious area can often be significant, relative to their current

costs incurred through General Fund taxation. While a stormwater fee is the most equitable means for

recovering stormwater costs, relative to charging for the behavior and conditions that create stormwater runoff,

in some cases, it may be considered over burdensome to certain users in the system. There are several methods

that can be used to help control costs for these users, including phasing in stormwater fees, or providing users

with stormwater credits. This subsection focuses on the latter of the three alternatives.

As discussed in Sections 2 and 3, credits or exemptions can be used to incentivize certain practices or to provide

relief from utility fees based on specific types of land uses. Stormwater utilities typically provide credits in two

circumstances. The first is when a property owner has put in place stormwater controls that provide relief

beyond what may have been required as a condition of property development. The second is for properties that

can demonstrate that they have mitigated their impact on the municipal stormwater infrastructure through

improved stormwater treatment practices, whether it is a reduction in quantity or improvement in water quality

of stormwater runoff.

Some examples of practices where stormwater credits may be applied are:

Detention ponds

Stream buffers and filters

Green rooftops

Conservation of natural areas in new development

Reforestation

Low income credits for residential customers proving financial hardship

In addition to stormwater treatment practices, some utilities and municipalities also provide credit related to

stormwater education, as well as for stormwater systems that are separate from the municipal system, but have

been required to comply with MS4 permitting requirements.

In order to implement a stormwater credit system, it is necessary to develop a well‐defined set of guidelines and

procedures to govern them. The City must define the types of credits they can offer and the specific criteria for

meeting the credit requirements. Some examples of specific criteria that may be necessary to develop are

determining a minimum contiguous area for conservation areas, determining the minimum distance for a buffer

zone, setting a maximum gradient for filters and buffers and determining the maximum amount of fee reduction

for a given credit.

It is also necessary to support the credit program through a permitting process that requires application,

certification and follow‐up inspections to ensure the credit continues to be maintained and valid. Relative to


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the application process it is necessary to develop the appropriate paperwork and maintain administrative staff

to manage the process. For certification and inspection, the City must also maintain staff that is capable of

evaluating the structural and environmental aspects of stormwater controls. Should the City seek to develop a

stormwater credit program, there are numerous examples and guidelines present to help guide this process.

In Section 3, CDM identified locations in the recommended plan where retail, commercial and industrial

businesses should implement on‐site stormwater BMPs to reduce flows to the drainage system. These

businesses have a significant amount of impervious area and will pay comparatively higher fees; thus, to reduce

their burden, they would benefit from a stormwater credit program such as the one discussed in this section.

5.3 Projected Revenue Requirement The purpose of this section is to project the revenue requirement for the City’s hypothetical stormwater utility.

In general, the revenue requirement is calculated by adding operations and maintenance expenses, existing and

anticipated debt service, cash funded capital expenditures, and netting miscellaneous revenue. Since the

stormwater utility would have no miscellaneous revenue associated with it, the revenue requirement is simply

the total of the allocated O&M expense and debt service on stormwater capital.

The City identified both direct and indirect operating expense items that were applicable to operating the

stormwater system.

5.3.1 General Assumptions

In order to project the stormwater expenses, a set of assumptions were used in this analysis. CDM believes the

assumptions to be reasonable and prudent for the purposes of the analysis. Key assumptions are as follows:

Projections are based on the City’s FY 2011 Revised Budget and FY 2012 Department Request;

Operations and maintenance costs are inflated at 3.0 percent annually. This includes personnel and

overtime expenses;

Energy‐related costs are inflated at 5.0 percent annually;

The entirety of the operating expenses currently covered in the General Fund related to flood control would be allocated to the stormwater utility;

General operations and maintenance expenses currently covered in the General Fund related to storm

drains would be allocated to the stormwater utility. One‐third of the personnel costs would be covered by

the stormwater utility, with the exception of overtime which is split 50/50;

Since no indirect cost allocation currently exists for the stormwater utility, the allocation schedule is

assumed to follow the schedule currently used for the sewer fund. The major exception is indirect costs for

PILOT, which have been excluded from the allocation to the stormwater utility.

Capital outlays are not assumed to be funded as part of the stormwater utility;

The City currently has $250,000 in authorized borrowing not yet spent. It is assumed that this amount will

be bonded as General Obligation (GO) debt for stormwater‐related projects in FY 2012;

The capital projects in the proposed CIP are inflated to the mid‐point of construction, and are assumed to be

financed through GO bonds (i.e. no cash funded capital projects);


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GO debt is assumed issued at a rate of 5.5 percent with an amortization period of 20 years. Cost of issuance

is assumed to be 1 percent;

Stormwater utility personnel are assumed to have a fully loaded salary, including benefits, of $50,000

annually;

Municipal Separate Storm Sewer System (MS4) permit compliance staff at the stormwater utility are

assumed to have a fully loaded salary, including benefits, of $60,000; and

Rental rates for stormwater utility vehicles have been calculated based on the 10‐year amortization period

for the cost of the vehicle, plus a 10 percent markup for mileage costs.

5.3.2 Operations and Maintenance Expenses

O&M expenses for the Stormwater and Flood Control Utility have been broken into two categories. The first is

incremental O&M costs, which are new costs that will be incurred by the utility to meet MS4 compliance costs.

The second category is the cost allocations presently incurred by the City that are being transferred to the

Stormwater and Flood Control Utility.

5.3.2.1 Incremental O&M

Incremental expenses have been determined based on discussions with the City and best estimates for

stormwater implementation costs. Incremental costs included in the analysis are as shown in Table 5.3.

Monitoring and MS4 compliance staff have been included based on estimates from CDM. Per discussions with

the City, two O&M staff have been included for catch basin cleaning, street sweeping and vactor operations, a

billing clerk has been added to handle additional billing administrative responsibilities and an expense line item

has been added for public outreach. Additional equipment, including a street sweeper, part‐time use of a vactor

truck and a vehicle for catch basin cleaning, have been included to support these O&M activities. A $20,000

increase in energy expenses has also been assumed to support these activities.

Table 5.3

Projected Incremental O&M

2011 2012 2013 2014 2015 2016

Monitoring $100,000 $103,000 $106,090 $109,273 $112,551 $115,927

MS4 Staff $60,000 $61,800 $63,654 $65,564 $67,531 $69,556

O&M Staff $100,000 $103,000 $106,090 $109,273 $112,551 $115,927

O&M Vehicle $2,877 $2,963 $3,052 $3,144 $3,238 $3,335

Vactor Truck $19,927 $20,525 $21,141 $21,775 $22,428 $23,101

Street Sweeper $29,891 $30,788 $31,711 $32,663 $33,643 $34,652

Billing Clerk $50,000 $51,500 $53,045 $54,636 $56,275 $57,964

Public Education $20,000 $20,600 $21,218 $21,855 $22,510 $23,185

Energy Costs $20,000 $20,600 $21,218 $21,855 $22,510 $23,185

Total $402,695 $414,776 $427,219 $440,036 $453,237 $466,834


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5.3.2.2 Allocated O&M

The stormwater operating expenses have been separated into five categories: Overtime, Flood Control, Storm

Drains Personnel, Storm Drains O&M, and Indirect Costs. The detailed allocation factors from both the General

Fund and the indirect cost schedule are listed in the General Assumptions (Section 5.3.1). It should be noted

that within this allocation are the salaries of key staff members, including engineering, administrative services

and key management personnel.

Table 5.4 summarizes the operating expense allocation for each category, and the total eligible for cost recovery

through the stormwater and flood control fee. These amounts do not include capital outlay. Of total O&M

expenses, incremental expenses account for slightly less than 30 percent of total O&M.

Table 5.4

Stormwater O&M and Capital Outlay by Category, FY 2011 ‐ FY 2016

2011 2012 2013 2014 2015 2016

Existing Budget Allocations

Overtime $23,000 $23,000 $23,690 $24,401 $25,133 $25,887

Flood Control $32,625 $32,625 $33,884 $35,194 $36,559 $37,980

Storm Drains Personnel $109,397 $109,639 $112,928 $116,316 $119,805 $123,399

Storm Drains O&M $54,050 $54,050 $55,672 $57,342 $59,062 $60,834

Indirect Costs $848,465 $933,870 $961,886 $990,743 $1,020,465 $1,051,079

Total Allocated O&M $1,067,537 $1,153,184 $1,188,059 $1,223,995 $1,261,024 $1,299,178

Incremental O&M $402,695 $414,776 $427,219 $440,036 $453,237 $466,834

Total Allocated O&M Expenses $1,470,232 $1,567,960 $1,615,279 $1,664,031 $1,714,261 $1,766,013

5.3.3 Debt Service Expenses

Table 5.5 summarizes the debt service for the Stormwater and Flood Control Utility. The existing debt service is

associated with the $310,000 GO bond issue in FY 2007 related to Ridgewood Terrace Reconstruction, and the

$100,000 GO debt issue in FY 2011 pertaining to drainage projects. The City has $250,000 in authorized

borrowing remaining on the most recent drainage improvement spending, which for the purposes of this

exercise is assumed to be bonded in FY 2012 for general drainage system improvements and included in the

anticipated debt service. Anticipated debt service also includes the proposed CIP, $95.6M in capital spending on

the stormwater system over the next 20 years. For the purposes of these projections, no cash funded capital

projects assumed.


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Table 5.5

Debt Service

2011 2012 2013 2014 2015 2016



Total Annual Debt Service $48,340 $124,494 $358,492 $828,505 $1,375,127 $2,084,167

5.3.4 Revenue Requirement

Table 5.6 shows the anticipated revenue requirement for the Stormwater and Flood Control Utility through FY

2016.

Table 5.6

Revenue Requirement

2011 2012 2013 2014 2015 2016

O&M $1,470,232 $1,567,960 $1,615,279 $1,664,031 $1,714,261 $1,766,013




Figure 5.1

Revenue Requirement (thousands)

$‐

$500

$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

$4,000

$4,500

2011 2012 2013 2014 2015 2016

O&M Existing Debt Service Anticipated Debt Service


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5.4 Parcel Analysis and Equivalent Residential Unit Calculation 5.4.1 Impervious Area

In determining a stormwater and flood control fee, it is necessary to separate out impervious area data for the

City by land use characteristics. In undertaking this task, CDM used existing GIS information made available by

Mass GIS to generate a sorted list of impervious area by land use. The intent of this analysis is to understand the

impervious area characteristics in the City and in turn the financial impact of assessing impervious area‐based

stormwater and flood control rates on a permanent basis.

In conducting its analysis, CDM sorted available GIS data into four main categories: Residential,

Commercial/Industrial, Tax Exempt, and Other (which includes categories such as agricultural, forestation and

recreational). The summary of this data is shown in Table 5.7 and displayed graphically in Figure 5.2.

Table 5.7

Total Impervious Area and Parcel Count by Classification

Customer Classification Impervious Area (square feet)

Residential 28,595,854

Commercial/Industrial 21,336,871

Tax Exempt 16,191,191

Other 1,641,422

Total Impervious Area 67,765,338


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Figure 5.2

Total Impervious Area and Parcel Count by Classification


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5.4.2 Equivalent Residential Unit Calculation

In order to assess the potential impact of incorporating a stormwater fee with an ERU structure, it was necessary

to determine the impervious area per equivalent residential unit (ERU). The base ERU for this analysis is defined

as the average impervious area per ERU for small residential structures up through three‐family units.

Determining average impervious area per ERU required matching the residential categories within the

Massachusetts Department of Revenue land use codes with estimates on dwelling units. Based on data

provided by the City, Northampton contains 9,600 units defined as either single‐family, two‐family, or three‐

family (Table 5.8). Based on the total number of residential accounts, the average impervious area per unit is

approximately 2,671 square feet for small residential customers.

Table 5.8

Distribution of Dwelling Units, Impervious Area and ERU Calculation

ERU Calculation

Impervious Area (sq. ft. thousands)

Single‐Family1 21,315

Two‐Family 3,551

Three‐Family + 829

Total 25,696

Number of Units (thousands)

Single‐Family1 7.3

Two‐Family 1.8

Three‐Family + 0.5

Total 9.6

Number of Units (thousands)

Total Impervious Area 25,696

Total Units 9.6

Equivalent Residential Unit (sq. ft.) 2,671

1 Includes condominiums and mobile homes

The next step in developing a stormwater fee is to determine the number of ERUs in each of the remaining

customer classes. This includes: commercial/industrial, tax exempt, large residential and other customers. This

data was compiled by totaling the amount of impervious area within each category and dividing it by the

average amount of impervious area per small residential dwelling unit (i.e. the ERU). Table 5.9 below reflects

the calculations determining the dwelling units for the other customer classes.


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Table 5.9

Number of Billing Units by Customer Classification (Non‐Residential)

Non‐Residential Customers Area Square Feet Impervious

(Total)

Number of Equivalent Residential Units

(thousands)

Commercial/Industrial 21,336,871 8.0

Tax Exempt 16,191,191 6.1

Large Residential3 2,900,131 1.1

Other 1,641,422 0.6

3Large residential is defined as apartments with 4 dwelling units or more.

5.4.3 Estimated Total Billing Units

Adding the large residential and non‐residential equivalent residential units to the number of small residential

units provides a total residential equivalent for billing units. Table 5.10 summarizes the total equivalent

residential billing units by customer type.

Table 5.10

Billing Units by Customer Type

Customer Class Billing units (thousands)

Small Residential 9.6

Large Residential 1.1

Commercial/Industrial 8.0

Tax Exempt 6.1

Other 0.6

Total 25.4

5.5 Calculation of Stormwater and Flood Control Fee This section evaluates the impact of funding the City‘s Stormwater and Flood Control Utility. A stormwater fee

recovers the costs associated with stormwater management, based on the amount of impervious area contained

on each parcel. The fundamental basis for this approach is that there is a direct relationship between impervious

area and stormwater runoff (i.e. the more impervious area there is on a parcel, the greater the amount of runoff

from that parcel). Therefore, the amount a parcel is charged using a stormwater and flood control fee is related

to the quantity of impervious area. A significant benefit of this approach is that it equitably distributes

stormwater costs, in the sense that parcel owners are charged proportionally, relative to their cost imposed on

the system.

Prior to the availability and use of GIS, the ability to maintain a database of parcel and impervious area was

cumbersome and costly. Due to this implementation barrier, the trade‐off of more equitably distributing

stormwater related costs has typically been outweighed by its complexity, even though these costs are closely


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tied to impervious area. However, with the advent of GIS technology, the process of implementing a

stormwater fee has become significantly less burdensome and is no longer cost prohibitive.

Furthermore, a stormwater and flood control fee provides the benefit of more equitably distributing the costs

associated with stormwater management and flood control. This in turn has a significant benefit, in that by

aligning the means with which stormwater treatment costs are recovered with the characteristics of customers

that create the service requirement, it provides incentive for customers to improve stormwater management

practices.

Having shown the calculations for developing the ERU in the previous section, the following subsections will

provide the basis for the stormwater fee calculation and the financial impact.

Given projected revenue requirements and ERUs, CDM developed a stormwater fee which would be assessed to

customers based on impervious surface area. In order to illustrate the impact of the fee, a set of representative

customer classes has been developed. These customer classes are hypothetical and have been created to

provide means by which the City can measure the impact across customer classes. The representative customer

types examined are as follows:

Single‐family residence;

Two‐family residence;

Three‐family residence;

20‐unit apartment (Large Residential);

Commercial property with 1,000 square feet of impervious area;

Commercial property with 10,000 square feet of impervious area; and

Commercial property with 100,000 square feet of impervious area.

The base rate per ERU is calculated by dividing the annual revenue requirement by the total calculated ERUs of

25,400. The necessary revenue to fully fund the baseline Stormwater and Flood Control Utility shown in Table

5.11 is $1.692 million in FY 2012. Dividing the projected revenue requirement by the total number of ERUs

would yield a rate of $66.63 per ERU for FY 2012.

Table 5.11

Projected Annual ERU Charge

2011 2012 2013 2014 2015 2016


Residential Charge per ERU $59.79 $66.63 $77.71 $98.13 $121.63 $151.58

Using the ERU system, parcels with larger amounts of impervious area are charged proportionally higher costs to

offset their cost burden on the system. For example, a commercial customer with 100,000 square feet of

impervious area would be charged approximately $2,495 in order to account for the cost of stormwater that the

parcel contributes to the system. The impact of these rates on the various customer classes is shown in Table

5.12.


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Table 5.12

Comparison of Impacts for Standard Customer Types, FY 2012


Single‐Family 1 1.00 $66.63

Two‐Family 2 2.00 $133.26

Three‐Family 3 3.00 $199.90






Commercial/Industrial with 100,000 square feet of IA 100,000 37.44 $2,494.58

Table 5.13 summarizes the total revenue expected from general customer classes for FY 2011. It can be seen

that the revenues generated by customer class are directly proportional to the billing units, and in turn the

impervious area of each customer class.

Table 5.13

Expected Revenue per Customer Class, FY 2012

Classification Billing units (thousands) Approximate Revenue

Small Residential 9.6 $639,668

Large Residential 1.1 $73,295

Commercial/Industrial 8 $533,056

Tax Exempt 6.1 $406,456

Other 0.6 $39,979

Total 25.4 $1,692,454

5.6 Recommendations As the City evaluates the option of developing a Stormwater and Flood Control Utility, and as a means for

meeting revenue requirements, it will need to consider not only the impact of its chosen cost recovery

mechanism, but also issues related to equity and behavioral incentives. Relative to the equity of its stormwater

and flood control rate structure, the City should seek to align its cost of serving customers as closely as possible

with the charge assessed to those customers. Using this criterion, a stormwater and flood control fee will

accurately reflect the likely cost burden imposed by individual customers as stormwater runoff is closely tied to

impervious area. Relative to behavioral incentives, a stormwater and flood control fee based on impervious area

creates a price signal for stormwater customers as to the cost associated with stormwater runoff and flood

control. This directly encourages customers and new developers to find ways to minimize stormwater impacts.


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Should the City choose to move forward with implementing a stormwater and flood control fee, given its current

stormwater‐related costs, anticipated capital costs and the City’s geographic characteristics, we have projected

the City’s current stormwater charge for FY 2012to be $66.63. Given the anticipated growth in the stormwater

charge over time, should the City be interested in mitigating the impact of the stormwater and flood control fee

on customers with high impervious area, it can seek to either maintain a portion of the stormwater costs on

sewer rates or implement a stormwater credit program.

Documents

CDM Northampton Stormwater System Assessment and Plan 2012-05 Vol 1