«>EPA
United States
Environmental Protection
Agency
United States
Environmental Protection
Agency
Office of Water (4203)
Washington, DC 20460
www.epa.gov/npdes/cso
EPA-833-R-09-001
April 2011
Green Long-Term Control Plan-EZ Template:
A Planning Tool for Combined Sewer Overflow
Control in Small Communities
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Disclaimer
The U.S. Environmental Protection Agency (EPA) has designed Green LTCP-EZ Template as a tool to
help small combined sewer overflow (CSO) communities develop their long-term CSO control plans under
the 1994 CSO Control Policy. EPA is not mandating the use of Green LTCP-EZ or the use of the
Presumption Approach under the 1994 CSO Control Policy. This document is not itself a regulation or
legally enforceable, but rather provides a path towards compliance with requirements of the 1994 CSO Control
Policy in accordance with section 402(q) of the Clean Water Act. Communities, small or otherwise, might
find the tool useful and should consult with their permitting authorities to determine whether it is
appropriate for them to use all or some portions of the Green LTCP-EZ Template.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Contents
Acronyms and Abbreviations v
Background 1
What is the Green LTCP-EZ Template and what is its purpose? 1
What is the relationship between the Green LTCP-EZ and the CSO Control Policy? 1
Who should use the Green LTCP-EZ Template? 2
What approach is used in the Green LTCP-EZ Template? 2
How is financial capability assessed? 4
Summary 4
Rationale for Using Green Infrastructure for CSO Controls 5
What is Green Infrastructure? 5
Why use Green Infrastructure to manage wet weather? 5
Checklist of Materials Recommended for Completing Green LTCP-EZ 7
General Instructions: Green LTCP-EZ Template 11
Instructions: Form Green LTCP-EZ 13
General Information 13
Nine Minimum Controls 13
Sensitive Areas 14
Water Quality Considerations 15
System Characterization 16
Public Participation 17
CSO Volume 19
Evaluation of CSO Controls 19
Financial Capability 19
Recommended CSO Control Plan 20
Instructions: Schedule 4 - CSO Volume 22
Introduction 22
Design Storm for Small Communities 22
The Rational Method 23
Calculation of CSO Volume 23
Summary 24
Sub-Sewershed Area 25
Runoff 25
Dry-Weather Flow within the CSS 26
Peak Wet-Weather Flow 26
Overflow 26
Diversion 27
Conveyance 27
Treatment 28
CSO Volume 29
Instructions: Schedule 5A - CSO Runoff Control (Green Infrastructure Runoff Controls) 30
Runoff Reduction via On-site Runoff Retention Standard or Goal 30
Runoff Reduction via Specific Green Infrastructure Practices 31
Recalculating CSO Volume 31
Impervious Area 32
Retention Standard or Goal 32
Runoff Reduction 32
Green Roofs 32
Bioretention 34
Vegetated Swales 35
Permeable Pavement 36
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Rain Barrels and Cisterns 37
Cumulative Runoff Reduction Check 37
Runoff Recalculation 38
Peak Wet-Weather Flow 38
Revised Overflow 38
Revised Diversion 39
Revised Conveyance 39
Treatment 39
CSO Volume Recalculation 40
Instructions: Schedule SB - CSO Network and WWTP Control 41
Conveyance and Treatment at the WWTP 41
Sewer Separation 41
Off-Line Storage 41
Cost of CSO Control 42
Summary 42
Conveyance and Treatment at the WWTP 43
Sewer Separation 43
Off-Line Storage 44
Summary of Controls and Costs 44
Instructions: Schedule 6 - CSO Financial Capability 45
Phase I Residential Indicator 46
Current Costs 46
Projected Costs (Current Dollars) 46
Cost Per Household 47
Median Household Income (MHI) 47
Residential Indicator 48
Phase II Permittee Financial Capability Indicators 48
Debt Indicators 49
Overall Net Debt 50
Socioeconomic Indicators 50
Unemployment Rate 51
Median Household Income 51
Financial Management Indicators 51
Property Tax and Collection Rate 52
Matrix Score: Analyzing Permittee Financial Capability Indicators 52
References 55
Glossary of Terms 56
Appendix A. One-Hour, 3-Month Rainfall Intensities, Schedule 4 - CSO Volume A-1
Appendix B. Hydraulic Calculations within Green LTCP-EZ, Schedule 4 - CSO Volume, and
Schedules 5A and SB - CSO Control B-1
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A and SB - CSO
Control C-1
Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information
for Schedule 5A - CSO Runoff Control D-1
IV
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Acronyms and Abbreviations
AF Annualization Factor
CFR Code of Federal Regulations
CPH Costs per Household
CPI Consumer Price Index
CSO Combined Sewer Overflow
CSS Combined Sewer System
DO Dissolved Oxygen
DMR Discharge Monitoring Report
DWF Dry-Weather Flow
EPA U.S. Environmental Protection Agency
FWS U.S. Fish and Wildlife Service
G.O. General Obligation
I/I Inflow/Infiltration
IR Interest Rate
LTCP Long-term Control Plan
MG Million Gallons
MGD Million Gallons per Day
MHI Median Household Income
MPV Market Property Value
NOAA National Oceanic and Atmospheric Administration
NMC Nine Minimum Controls
NMFS National Marine Fisheries Service
NPDES National Pollutant Discharge Elimination System
O&M Operation and Maintenance
POTW Publicly Owned Treatment Works
TMDL Total Maximum Daily Load
TSS Total Suspended Solids
WQS Water Quality Standards
WWT Wastewater Treatment
WWTP Wastewater Treatment Plant
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Background
What is the Green LTCP-EZ Template and what is its purpose?
The Combined Sewer Overflow (CSO) Green Long-Term Control Plan (LTCP) Template for Small
Communities (termed the Green LTCP-EZ Template) is a planning tool for small communities that are
required to develop an LTCP to address CSOs. The Green LTCP-EZ Template provides a framework for
organizing and completing an LTCP that builds on existing controls, including the use of both green and
conventional gray infrastructures to assist in the the elimination or control of CSOs in accordance with the
federal Clean Water Act (CWA). Use of the Green LTCP-EZ Template and completion of the forms and
schedules associated with the Green LTCP-EZ Template can help produce a Draft LTCP.
In May 2007, U.S. EPA developed a planning tool (LTCP-EZ) for small CSO communities to design long-
term CSO control plans using the conventional gray CSO controls. The original LTCP-EZ Template is available
at www.epa.gov/npdes/cso. The Green LTCP-EZ Template is an updated version of the original, in that it adds
several "green" infrastructure practices such as green roofs, vegetated swales, bioretention basins, pervious
pavements, rain barrels, in conjunction with conventional gray CSO control to develop a CSO long-term control plan.
The Green LTCP-EZ can be used for communities who want to assess the potential for green infrastructure
controls. For communities who do not wish to assess the potential for green infrastructure, the oroginal LTCP-EZ
Template can still be used.
Properly planned green practices naturally manages stormwater, improves water quality and control CSOs by
keeping water out of the collection systems. The Green LTCP-EZ Template consists of FORM GREEN LTCP-EZ
and related schedules and instructions. It provides a starting place and a framework for small communities to
organize and analyze basic information that is central to effective CSO control planning. Specifically, FORM GREEN
LTCP-EZ and Schedules 1 - NINE MINIMUM CONTROLS, 2 - MAP, and 3 - PUBLIC PARTICIPATION, allow
organization of some of the basic information required to comply with the 1994 CSO Control Policy.1
Schedule 4 - CSO VOLUME provides a process for assessing CSO control needs under the presumption
approach of the CSO Control Policy. It allows the permittee or other user (the term permittee will be used throughout
this document, but the term should be interpreted to include any users of the Green LTCP-EZ Template) to estimate
a target volume of combined sewage that needs to be stored, treated, or eliminated. Schedules 5A and 5B- CSO
RUNOFF, NETWORK AND WWTP CONTROLS enable the permittee to evaluate the ability of a number of widely used
green infrastructure runoff controls and pipe network CSO controls to meet the reduction target. Finally, Schedule 6 -
CSO FINANCIAL CAPABILITY provides a U.S. Environmental Protection Agency (EPA) financial capability analysis to
determine the community's financial capabilities. Permittees are free to use FORM GREEN LTCP-EZ and as many
schedules as needed to meet their local needs and requirements. FORM GREEN LTCP-EZ and its schedules are
available in hard copy format or as computer-based spreadsheets.
This publication provides background information on the CSO Control Policy and explains the data and
information requirements, technical assessments, and calculations that are addressed in the Green
LTCP-EZ Template and are necessary for its application.
What is the relationship between the Green LTCP-EZ and the CSO Control Policy?
CWA section 402(q) and the CSO Control Policy (EPA 1994) require permittees with combined sewer
systems (CSSs) that have CSOs to undertake a process to accurately characterize their sewer systems,
demonstrate implementation of the nine minimum controls (NMCs), and develop an LTCP. EPA
recognizes that resource constraints make it difficult for small communities to prepare a detailed LTCP.
Section I.D of the CSO Control Policy states,
1 Combined Sewer Overflow (CSO) Control Policy, 59 Fed. Reg. 18688-18698 (April 19, 1994) (EPA 1994).
Pursuant to section 402(q) of the Clean Water Act (CWA), permits, orders and decrees issued under the CWA for
discharges from municipal combined storm and sanitary sewer systems "shall conform" to the CSO Control Policy.
1
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
The scope of the long-term CSO control plan, including the characterization, monitoring and
modeling, and evaluation of alternatives portions of the Policy may be difficult for some small
CSSs. At the discretion of the NPDES Authority, jurisdictions with populations under 75,000 may
not need to complete all of the formal steps outlined in Section II.C. of this Policy, but should be
required through their permits or other enforceable mechanisms to comply with the nine minimum
control (II.B), public participation (II.C.2), and sensitive areas (II.C.3) portions of this Policy. In
addition, the permittee may propose to implement any of the criteria contained in this Policy for
evaluation of alternatives described in II.C.4. Following approval of the proposed plan, such
jurisdictions should construct the control projects and propose a monitoring program sufficient to
determine whether WQS are attained and designated use are protected.
EPA developed the Green LTCP-EZ Template, in part, because it recognizes that expectations for the
scope of the LTCP for small communities might be different than for larger communities. However, the
Green LTCP-EZ Template does not replace the statutory and regulatory requirements applicable to
CSOs; those requirements continue to apply to the communities using this template. Nor does its use
ensure that a community using the Green LTCP-EZ Template will necessarily be deemed to be in
compliance with those requirements. EPA hopes, however, that use of the Green LTCP-EZ Template will
facilitate compliance by small communities with those legal requirements and simplify the process of
developing an LTCP.
IMPORTANT NOTE: Each permittee should discuss use of the Green LTCP-EZ Template and coordinate
with the appropriate regulatory authority or with their permit writer and come to an agreement with the
permitting authority on whether use of the Green LTCP-EZ Template or components thereof is acceptable
for the community.
Who should use the Green LTCP-EZ Template?
The Green LTCP-EZ Template is designed as a planning tool for use by small communities that have not
developed LTCPs and have limited resources to invest in CSO planning. It is intended to help small
communities develop an LTCP that will build on NMC implementation and lead to additional elimination
and reduction of CSOs where needed. CSO communities using the Green LTCP-EZ Template should
recognize that this planning tool is for use in facility-level planning. Use of the Green LTCP-EZ Template
should be based on a solid understanding of local conditions that cause CSOs. CSO communities should
familiarize themselves with all the technical analyses required by the Green LTCP-EZ planning process.
CSO communities should obtain the assistance of qualified technical professionals (e.g. engineers and
hydraulic experts) to help complete analyses if they are unable to complete the Green LTCP-EZ
Template on their own. More detailed design studies will be required for construction of new facilities.
Even though the Green LTCP-EZ Template is particularly well suited for small CSO communities that have relatively
uncomplicated CSSs, it might be useful for large CSO communities with populations of greater than 75,000.
Large CSO communities and small CSO communities that have many CSO outfalls and complex systems might need
to take a more sophisticated approach to LTCP development, and this should be evaluated by consultation with regulators
as discussed above.
The Green LTCP-EZ Template is intended to provide a very simple assessment of CSO control needs. As
such, it might reduce the effort and costs associated with CSO control development. However, because of its simple
nature, the Green LTCP-EZ Template might not evaluate a full range of potential CSO control approaches. Permittees
electing to follow the approach provided by the Green LTCP-EZ template remain subject to all requirements of the CWA
and EPA's 1994 CSO Control Policy.
What approach is used in the Green LTCP-EZ Template?
Schedule 4 - CSO VOLUME and Schedules 5A and 5B - CSO CONTROL use the "presumption
approach" described in the CSO Control Policy to quantify the volume of combined sewage that needs to
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
be stored, treated, or eliminated. The CSO Control Policy describes two alternative approaches available
to communities to establish that their LTCPs are adequate to meet the water quality-based requirements
of the CWA: the presumption approach and the demonstration approach (Policy Section II.C.4.a.) The
presumption approach sets forth criteria that, when met, are presumed to provide an adequate level of
control to meet the water quality-based requirements:
... would be presumed to provide an adequate level of contralto meet water quality-based
requirements of the CWA , provided the permitting authority determines that such presumption is
reasonable in light of data and analysis conducted in the characterization, monitoring, and
modeling of the system and the consideration of sensitive areas described above (in Section
II.C.4.a). These criteria are provided because data and modeling of wet weather events often do
not give a clear picture of the level of CSO controls necessary to protect WQS.
Selected criterion under the presumption approach used in the Green LTCP-EZ Template
Under the presumption approach set forth in the CSO Control Policy, a community may select from one of
three sets of criteria that it must meet upon LTCP implementation (see CSO Control Policy Section
II.C.4.a.i-iii). Calculations in some parts of the Green LTCP-EZ Template (specifically, Schedule 4) use
the first criterion in section II.CAa.i., as follows:
No more than an average of four overflow events per year, provided that the permitting authority
may allow up to two additional overflow events per year. For the purpose of this criterion, an
overflow event is one or more overflows from a CSS as the result of a precipitation event that does
not receive the minimum treatment specified below.
The minimum treatment specified with respect to the criterion in Section II.CAa.i. of the CSO Control
Policy is defined as follows:
Primary clarification (Removal of floatable and settleable solids may be achieved by any combination
of treatment technologies or methods that are shown to be equivalent to primary clarification);
Solids and floatable disposal; and
Disinfection of effluent, if necessary, to meet WQS, protect designated uses, and protect human
health, including removal of harmful disinfection chemical residuals, where necessary.
This criterion is used because it allows quantification with simple procedures and a standardized format. It
should be noted that a permittee could choose to use one of the other two criteria under the presumption
approach, or the demonstration approach. Conversely, permittees may still use the other parts of the
Green LTCP-EZ Template to help complete their LTCP even if they choose not to use Schedule 4 of the
Green LTCP-EZ Template.
Calculations within Schedule 4 - CSO VOLUME and Schedules 5A and 5B - CSO
CONTROL
EPA advises permittees to consider implementing a limited rainfall and flow monitoring program. Simple regression
analyses (e.g., rainfall vs. flow response) can be used to refine the Green LTCP-EZ Template output and increase
confidence in sizing the controls generated using the Green LTCP-EZ Template. For examples of this approach to
rainfall response characterization, the permittee should refer to Combined Sewer Overflows Guidance for Monitoring
and Modeling (EPA 1999).
Schedules 4 and 5 use design storm conditions to assess the degree of CSO control required to meet the
average of four overflow events per year criterion. Design storms are critical rainfall conditions that occur
with a predictable frequency. They are used with simple calculations to quantify the volume of combined
sewage to be stored, treated, or eliminated to meet the criterion of no more than four overflows per year,
on average. The design storm is explained in further detail in the instructions for Schedule 4 - CSO
VOLUME.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
The Green LTCP-EZ Template also provides permittees with simple methods to assess the costs and
effectiveness of a variety of CSO control alternatives in Schedules 5A and 5B - CSO CONTROL.
All CSO communities are obligated to meet the requirements of the CWA and the CSO Policy, but use of
the presumption approach and the use of Schedules 4 and 5 is only one way to comply, and may not be
appropriate for every community. Some states have specific requirements that are inconsistent with
Schedules 4 and 5. Use of the Green LTCP-EZ Template does not preclude permitting authorities
from requesting clarification or requiring additional information. Permittees should consult with the
appropriate regulatory authority to determine whether or not the presumption approach and its
interpretation under Schedules 4 and 5 are appropriate for their local circumstances.
How is financial capability assessed?
The CSO Financial Capability Assessment Approach outlined in EPA's Combined Sewer Overflows
Guidance for Financial Capability Assessment and Schedule Development (EPA 1997) is used to assess
financial capability and is contained in Schedule 6 - CSO FINANCIAL CAPABILITY.
Summary
The Green LTCP-EZ Template is an optional CSO control planning tool to assist small communities in assembling
and organizing the information required in an LTCP. FORM GREEN LTCP-EZ and Schedules 1 (Nine Minimum
Controls), 2 (Map) and 3 (Public Participation) allow organization of some of the basic elements to comply
with the CSO policy. Schedule 4 - CSO VOLUME allows the permittee to estimate a target volume of
combined sewage that needs to be stored, treated, or eliminated. Schedules 5A and 5B - CSO
CONTROL enable the permittee to evaluate the ability of a number of widely used green infrastructure
runoff controls and pipe network CSO controls to meet the reduction target. Schedule 6 - CSO
FINANCIAL CAPABILITY provides an EPA financial capability analysis to assess the CSO community's
financial capabilities. FORM GREEN LTCP-EZ and its schedules are available in hard copy format or as
computer-based spreadsheets.
The CSO Control Policy and all of EPA's CSO guidance documents can be found at the following
link:http://cfpub.epa.gov/npd es/home.cfm?program_id=5.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Rationale for Using Green Infrastructure for CSO Controls
What is Green Infrastructure?
Green infrastructure is the interconnected network of open spaces and natural areas, such as greenways,
wetlands, parks, forest preserves and native plant vegetation, that naturally manages stormwater,
reduces flooding risk and improves water quality (Center for Neighborhood Technology.2008). Green
infrastructure can cost less to install and maintain when compared to traditional forms of infrastructure.
Green infrastructure projects also foster community cohesiveness by engaging all residents in the
planning, planting and maintenance of the sites.
Why use Green Infrastructure to manage wet weather?
The main drivers for using green infrastructure is an approach to wet weather management is that it may
be more cost-effective than conventional gray infrastructure, and provides sustainable, and environmentally
friendly means of controlling wet weather discharges. Green Infrastructure management approaches and
technologies infiltrate, evapotranspire, capture and reuse stormwater to maintain or restore the approximate
hydrology that existed before development.
At the largest scale, the preservation and restoration of natural landscape features (such as forests,
floodplains and wetlands) are critical components of green stormwater infrastructure. By protecting these
ecologically sensitive areas, communities can improve water quality while providing wildlife habitat and
opportunities for outdoor recreation.
On a smaller scale, green infrastructure practices include rain gardens, porous pavements, green roofs,
infiltration planters, trees and tree boxes, and rainwater harvesting for non-potable uses such as toilet
flushing and landscape irrigation, all of which help to manage stormwater runoff and improve water quality.
Why Use Green Infrastructure to Reduce CSO Events?
The natural retention and infiltration capabilities of plants and soils used in green infrastructure practices
limits the frequency of combined sewer overflow events by reducing runoff volumes and by reducing and
delaying the effects of stormwater discharges on the CSS.
CSO Control Policy
The CSO Control Policy contains four fundamental principles to ensure that CSO controls are cost-
effective and meet environmental objectives:
Providing clear levels of control that would be presumed to meet appropriate health and
environmental objectives
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Providing sufficient flexibility to municipalities, especially financially disadvantaged communities,
to consider the site-specific nature of CSOs and to determine the most cost-effective means of
reducing pollutants and meeting CWA objectives and requirements
Allowing a phased approach to implementation of CSO controls considering a community's
financial capability
Review and revision, as appropriate, of water quality standards and their implementation
procedures when developing CSO control plans to reflect the site-specific wet weather impacts of
CSOs
Green infrastructure practices support implementation of the nine minimum controls and long
term control plans by reducing runoff to
Maximize use of the collection system for storage
Maximize flow to the POTW for treatment
Minimizing and/or reducing the peaking factor
Support pollution prevention
Support proper operation and regular maintenance
Green infrastructure practices use vegetation and soils in urban and suburban areas to manage and treat
precipitation naturally rather than collecting it in pipes. Thus, by preserving natural systems and using
engineered systems such as green roofs, rain gardens, and vegetated swales, green infrastructure
mimics natural functions. Green infrastructure also includes approaches that capture and re-use
stormwater and provides the following benefits:
Create peak and baseload capacity via conservation
Effective for both new development and retrofit applications
Adapt, (re)naturalize built landscape to absorb, treat and hold water
Restore, recycle and extend natural and built regional infrastructure
Performance can be measured and valued in volume left in natural drainage
Drainage, flood control and pollution prevention moves upstream from treatment plant to
distributed sites closer to water's origins
Provides broad range of economic, social and ecological benefits (triple bottom line)
Highly effective for stormwater runoff reduction and pollutant removal
Saves money compared to conventional infrastructure
Delivers multiple community benefits along with stormwater management
Benefits of using Green Infrastructure
Cleaner water
Stable hydrology/baseflow maintenance
Reduced flooding
Cleaner air
Reduced urban temperatures
Climate change mitigation and adaptation
Jobs creation
Water supply
Energy savings
Community benefits (recreation, public health, crime prevention)
Cost savings
Habitat protection
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Checklist of Materials Recommended for Completing Green LTCP-EZ
Note: This checklist is for use with the instructions beginning on page 13. The NPDES permit and information from various departments within the
local utility or state and/or federal government will be essential sources of much of the information needed. These sources, relevant engineering
studies and facility plans for the sewer system and WWTP and the web sites listed below will generally be the information sources necessary to
complete the template.
Item and Line Number on Form
Community and system information (Form LTCP-EZ, Lines 1 & 2)
CSS area (Form LTCP-EZ, Line 3a)
Number of outfalls (Form LTCP-EZ, Line 3b)
WWTP capacity (Form LTCP-EZ, Lines 4a & 4b) for both primary
and secondary treatment units
Average dry weather WWTP Flow (Form LTCP-EZ, Line 4c)
Nine Minimum Controls (Form LTCP-EZ, Line 5)
Sensitive Areas (Form LTCP-EZ, Lines 6a - 6b)
Maps of impacted sensitive areas downstream of CSOs
Water quality data from sensitive area locations
Water Quality (Form LTCP-EZ, Lines 6c - 6d; 7)
Pollutants of concern in CSO discharges
Water quality standards in receiving water
Impairments in receiving water(s)
Determination of whether CSO discharges are contributing to
impairment of receiving water
System Characterization - general location map (Form LTCP-EZ,
Line 8)
CSO outfall number (Form LTCP-EZ, Line 9a)
Narrative description (Form LTCP-EZ, Line 9b)
Most Likely
Information Source
Facility or system
owner/operator
NPDES permit,
engineering studies or
local utility/government
«
"
«
«
Local FWS, NMFS, or
State or Tribal Heritage
Center
NPDES authority or
engineering studies
Engineering studies or
local utility/government
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Actual Source Used/Comments
Threatened or Endangered Species or their habitat at:
http://ecos.fws.gov/tess public/StartTESS.do
http://www.nmfs.noaa.gov/
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Item and Line Number on Form
Latitude/longitude (Form LTCP-EZ, Line 9c)
Receiving water (Form LTCP-EZ, Line 9d)
Sub-sewershed area (Form LTCP-EZ, Lines 10a)
Sub-sewershed principal land use (Form LTCP-EZ, Lines 10b)
Type of CSO hydraulic control structure (e.g., weir or diversion)
(Form LTCP-EZ, Line 11 a)
CSO hydraulic control capacity (Form LTCP-EZ, Line 1 1 b)
Name of downstream interceptor or pipe receiving diversion (Form
LTCP-EZ, Line 1 1c)
Public Participation (Form LTCP-EZ, Line 12)
Information on CSO controls planned for installation (Form LTCP-
EZ, Lines 16a-16d)
Number and type
Financing plan
Proposed installation schedule
Unit costs of unit processes or CSO controls
Schedule 4 Information
Sub-sewershed delineations for individual CSO outfalls
Capacities of hydraulic control structures, interceptors, and
wastewater treatment processes
Peak rate of sewage from non-CSO areas (Schedule 4 - CSO
Volume, Line 22)
Peak rate of sewage from satellite communities (Schedule 4 - CSO
Volume, Line 23)
Number of households in service area
Satellite areas (Schedule 4 - CSO Volume, Line 31)
Most Likely
Information Source
"
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«
"
"
"
"
Local utility/government
Engineering studies or
local utility/government
"
«
"
"
"
"
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Actual Source Used/Comments
This item is also used in Schedule 4 (CSO Volume)
This item is also used in Schedule 4 (CSO Volume)
This item is also used in Schedule 4 (CSO Volume) and
Schedule 5A (CSO Runoff Control)
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Item and Line Number on Form
Information on how the CSS responds to rainfall
Modeling data
Monitoring data
Pump station records
Data required for Schedule 5A - CSO Control, Green
Infrastructure Runoff Controls)
Percent impervious area by sewershed
Retention standard or goal
Percent of area to be redeveloped over planning horizon
Quantity of green infrastructure to be implemented
Green roofs - number of installations and average area
Bioretention - number of installations and average area
managed by an installation
Vegetated swales - acreage/area of installations and
average area managed by an installation
Permeable pavement - area to be installed
Rain barrels/cisterns - number of installations and average
volume of the barrel/cistern
Local green infrastructure unit costs
Percentage of installations that will be financed by the public
Financial Capability Information
(Data required for Schedule 6 - CSO Capability)
Annual budgeted O&M expenses (excluding depreciation) of
wastewater operations
Annual debt service on wastewater treatment debts
Most Likely
Information Source
Engineering studies or
local government
"
NPDES authority or local
government
Local government;
specific plan
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Local utility/government
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Actual Source Used/Comments
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Item and Line Number on Form
Projected annual O&M expenses for new wastewater projects
Projected debt costs of new wastewater projects
Median household income for the service area*
National median household income
Date of most recent general obligation (GO) bond, bond rating,
indication of whether insurance was required on the bond, and
name of credit agency
Direct net debt (GO bonds excluding double-barreled bonds - GO
debt outstanding that is supported by the property in the permittee's
service area)
Debt of overlapping entities (proportionate share of multi-
jurisdictional debt)
Full market property value (MPV)
Unemployment rate for permittee's service area
Unemployment rate for permittee's county**
Average national unemployment rate
Property tax revenues
Property taxes levied
Property tax revenue collection rate
Most Likely
Information Source
"
«
US Census Bureau and
local utility/government
US Census Bureau
Local utility/government
"
Local government
US Dept. of Labor
Statistics and local
utility/government
US Dept. of Labor
Statistics
"
Local government
"
«
Actual Source Used/Comments
http://quickfacts.census.gov/qfd/index.html
http://www.census.qov/
http://quickfacts.census.qov/qfd/states/00000.html
http://data.bls.gov/pdq/quervtool.isp?survev=la
http://data.bls.qov/pdq/querytool.isp?survev=la
http://www.bls.qov/
*To obtain median household income for the service area, from Census Bureau url, click on desired state and then select appropriate county. Note that approximations may be
required to account for differences in county and service area boundaries.
**To obtain county unemployment data from the url provided, select (1) state; (2) select area type of "counties or equivalent"; and (3) select the county or equivalent jurisdiction of
interest. Data are provided for the past 10 years and include annual averages.
FWS = U.S. Fish and Wildlife Service; NMFS = NOAA National Marine Fisheries Service (NOAA = National Oceanic and Atmospheric Administration)
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
General Instructions: Green LTCP-EZ Template
FORM GREEN LTCP-EZ encompasses all the information that most small CSO communities need to
develop a draft LTCP. This includes characterizing the CSS, documenting NMC implementation,
documenting public participation, identifying and prioritizing sensitive areas where present, and evaluating
CSO control alternatives and financial capability.
The Green LTCP-EZ Template includes a form (Form Green
LTCP-EZ) and schedules for organizing the following
information:
General information about the CSS, the wastewater
treatment plant (WWTP) and the community served
NMC implementation activities (Schedule 1 - NMC)
Sensitive area considerations
Water quality considerations
System characterization, including a map of the CSS
(Schedule 2 - MAP)
Using the Electronic Forms for the
Green LTCP-EZ Template
The electronic version of the Green LTCP-
EZ Template forms have cells that link data
in one worksheet to other worksheets.
Therefore, it is important that you work on
the worksheets in order and fill in all the
pertinent information. If you are filling in the
Green LTCP-EZ Template forms by hand,
you will have to copy the information from
one form into the other.
Public participation activities (Schedule 3 - PUBLIC PARTICIPATION)
CSO volume that needs to be controlled (Schedule 4 - CSO VOLUME)
Evaluation of green infrastructure runoff controls (Schedule 5A- CSO RUNOFF CONTROL)
Evaluation of pipe network CSO controls (Schedule 5B - CSO NETWORK and WWTP CONTROL)
Financial capability analysis (Schedule 6 - CSO FINANCIAL CAPABILITY)
Recommended CSO Control Plan, including financing plan and implementation schedule
Permittees intending to use the Green LTCP-EZ Template
should assemble the following information:
The NPDES permit.
General information about the CSS and the WWTP
including sub-sewershed delineations for individual CSO
outfalls and the capacities of hydraulic control structures,
interceptors, and wastewater treatment (WWT)
processes.
Relevant engineering studies and facility plans for the
sewer system and WWTP if available.
Maps for sewer system.
General demographic information for the community.
General financial information for the community.
A summary of historical actions and current programs that represent implementation of the NMCs. The
NMC are controls that can reduce CSOs and their effects on receiving waters, do not require
significant engineering studies or major construction, and can be implemented in a relatively short
period (e.g., less than approximately two years).
Information on water quality conditions in local waterbodies that receive CSO discharges.
Guidance from EPA
EPA has developed the Combined Sewer
Overflows Guidance for Long-Term Control
Plan (EPA 1995a) to help municipalities
develop an LTCP that includes technology-
based and water quality-based control
measures that are technically feasible,
financially capable, and consistent with the
CSO Control Policy. The guidance is
available at:
(http://www.epa.gov/npdes/pubs/owm0272.
pdf)
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Once complete, the Green LTCP-EZ Template (FORM GREEN LTCP-EZ with accompanying schedules)
can serve as a draft LTCP for a small community. All the schedules provided in the Green LTCP-EZ
Template might not be appropriate for every permittee. It might not be necessary to use all the schedules
provided in this template to complete a draft LTCP. In addition, permittees can attach the relevant
documentation to FORM GREEN LTCP-EZ in a format other than the schedules provided in the Green
LTCP-EZ Template.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Instructions:
Form Green
LTCP-EZ
General Information
Line 1 - Community
Information. Enter the
community name, National
Pollutant Discharge Elimination
System (NPDES) permit
number, owner/operator, facility
name, mailing address,
telephone number, fax number,
email address, and the date.
Line 2 - System Type. Identify
the type of system for which this
LTCP is being developed:
NPDES permit for a CSS
with a WWTP or
NPDES permit for a CSS
without a WWTP
Line 3a - CSS. Enter the total
area served by the CSS in
acres.
Line 3b - Enter the number of
permitted CSO outfalls.
Line 4 - WWTP. Enter the
following information for WWTP
capacity in million gallons per
day (MGD).
Line 4a - Primary treatment
capacity in MGD.
Line 4b - Secondary
treatment capacity in MGD.
Line 4c - Average dry-
weather flow in MGD. Dry-
weather flow is the base
sanitary flow delivered to a
CSS in periods without
rainfall orsnowmelt. It
represents the sum of flows
from homes, industry,
commercial activities, and
infiltration. Dry-weather flow
is usually measured at the
WWTP and recorded on a
Discharge Monitoring Report
(DMR).
For the purposes of the
calculation in the Green LTCP-
EZ Template, base sanitary flow
is assumed to be constant.
There is no need to adjust
entries for diurnal or seasonal
variation.
Nine Minimum Controls
The CSO Control Policy
(Section II.B.) sets out NMCs
that are technology-based
controls that communities are
expected to use to address
CSO problems, without
undertaking extensive
engineering studies or
significant construction costs,
before long-term measures are
taken. Permittees with CSSs
experiencing CSOs should have
implemented the NMCs with
appropriate documentation by
January 1, 1997.The NMCs are
NMC 1. Proper operations
and regular maintenance
programs for the CSS and
CSO outfalls.
NMC 2. Maximum use of the
CSS for storage.
NMC 3. Review and
modification of pretreatment
requirements to ensure CSO
effects are minimized.
NMC 4. Maximizing flow to
the publicly owned treatment
works (POTW) for treatment.
NMC 5. Prohibition of CSOs
during dry weather.
NMC 6. Control of solid and
floatable materials in CSOs.
NMC 7. Pollution prevention
NMC 8. Public notification to
ensure that the public
receives adequate
notification of CSO
occurrences and CSO
impacts.
NMC 9. Monitoring to
effectively characterize CSO
impacts and the efficacy of
CSO controls.
Line 5 - NMC. Permittees can
attach previously submitted
documentation on NMC
implementation, or they can use
Schedule 1 - NMC to document
NMC activities. Please check
the appropriate box on Line 5 to
indicate how documentation of
NMC implementation is
provided.
If Schedule 1 - NMC is used,
please document the activities
taken to implement the NMC.
Documentation should include
information that demonstrates
The alternatives considered
for each minimum control
The actions selected and the
reasons for their selection
The selected actions already
implemented
A schedule showing
additional steps to be taken
The effectiveness of the
minimum controls in
reducing/eliminating water
quality impacts (in reducing
the volume, frequency, and
impact of CSOs)
If no activities have been
undertaken fora particular
NMC, leave the description
blank. For examples of NMC
activities and for further
guidance on NMC
documentation, see Combined
Sewer Overflows Guidance for
Nine Minimum Controls (EPA
1995b) for examples of NMC
activities and for further
13
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
guidance on NMC
documentation.
Sensitive Areas
Permittees are expected to give
the highest priority to controlling
CSOs in sensitive areas (CSO
Control Policy Section II.C.3).
Permittees should identify all
sensitive waterbodies and the
CSO outfalls that discharge to
them. Identifying sensitive areas
can direct the selection of CSO
control alternatives. In
accordance with the CSO
Control Policy, the LTCP should
give the highest priority to the
prohibition of new or
significantly increased overflows
(whether treated or untreated) to
designated sensitive areas.
Sensitive areas, as identified in
the CSO Control Policy, include
the following:
Outstanding National
Resource Waters. These
are waters that have been
designated by some (but not
all) states, "[w]here high
quality waters constitute an
outstanding National
resource, such as waters of
National Parks, State parks
and wildlife refuges, and
waters of exceptional
recreational or ecological
significance, that water
quality shall be maintained
and protected" (Title 40 of
the Code of Federal
Regulations [CFR]
122.12(a)(3)). Tier III Waters
and Class A Waters are
sometimes designated
Outstanding National
Resource Waters. State
water quality standards
authorities are the best
source of information on the
presence of identified
Outstanding National
Resource Waters.
National Marine
Sanctuaries. The National
Oceanic and Atmospheric
Administration (NOAA) is the
trustee for the nation's
system of marine protected
areas, to conserve, protect,
and enhance their
biodiversity, ecological
integrity and cultural legacy.
Information on the location of
National Marine Sanctuaries
are at
http://sanctuaries.noaa.gov/.
Waters with Threatened or
Endangered Species and
their Habitat. Information on
threatened and endangered
species can be identified by
contacting the Fish and
Wildlife Service (FWS),
NOAA Fisheries, or state or
tribal heritage center or by
checking resources such as
the FWS Web site at
http://www.fws.gov/
endangered/wildlife.html. If
species are listed in the area,
contact the appropriate local
agency to determine if the
listed species could be
affected or if any critical
habitat areas have been
designated in waterbodies
that receive CSO discharges.
Waters with Primary
Contact Recreation: State
water quality standards
authorities are the best
source of information on the
location of waters designated
for primary contact
recreation.
Public Drinking Water
Intakes or their Designated
Protection Areas. State
water quality standards and
water supply authorities are
the best source of
information on the location of
public drinking water intakes
or their designated protection
areas. EPA's Report to
CongressImpacts and
Control of CSOs and SSOs
identifies 59 CSO outfalls in
seven states within one mile
upstream of a drinking water
intake (USEPA 2004).
Shellfish Beds. Shellfish
harvesting can be a
designated use of a
waterbody. State water
quality standards authorities
are a good source of
information on the location of
waterbodies that are
protected for shellfish
harvesting. In addition, the
National Shellfish Register of
Classified Estuarine Waters
provides a detailed analysis
of the shellfish growing areas
in coastal waters of the
United States. Information on
the location of shellfish beds
is at http://gcmd.nasa.gov/
records/GCMD NOS00039.
html.
To determine if sensitive areas
are present in the area of the
CSO, contact the appropriate
state and federal agencies. EPA
recommends that the permittee
attach to the Green LTCP-EZ
Template forms all
documentation of research
regarding sensitive areas or
contacts with agencies providing
that information (including
research on agency Web sites).
In addition, EPA encourages the
permittee to attach maps or
other materials that provide
backup information regarding
the evaluation of sensitive
areas.
Line 6a - Indicate if sensitive
areas are present. Answer Yes
or No. If sensitive areas are
present, proceed to Line 6b and
answer questions 6b, 6c, and
6d. Also provide an explanation
of how the determination was
made that sensitive areas are
present. If sensitive areas are
not present, proceed to Line 7. If
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
sensitive areas are not present,
provide an explanation of how
the determination was made.
Line 6b - Enter the type(s) of
sensitive areas present (e.g.,
public beach, drinking water
intake) for each CSO receiving
water.
Line 6c - List the permitted
CSO outfall(s) that could be
affecting the sensitive areas.
Add detail on impacts where
available (e.g., CSO outfall is
within a sensitive area, beach
closures have occurred due to
overflows.).
Line 6d - Are sensitive areas
affected by CSO discharges?
Answer Yes or No. If sensitive
areas are present but not
affected by CSO discharges,
provide documentation on how
the determination was made
and proceed to Line 7.
More detailed study
might be necessary if
sensitive areas are
present and are affected by
CSO discharges. Under such
circumstances, use of the
presumption approach in the
Green LTCP-EZ Template might
not be appropriate. The
permittee should contact the
permitting authority for further
instructions on use of the Green
LTCP-EZ Template and the
presumption approach.
Water Quality
Considerations
The main impetus for
implementing CSO controls is
attainment of water quality
standards, including designated
uses. Permittees are expected
to be knowledgeable about
water quality conditions in local
waterbodies that receive CSO
discharges. At a minimum,
permittees should check to see
if the local waterbodies have
been assessed under the 305(b)
program by the state water
quality standards agency as
being good, threatened or
impaired.
Waters designated as impaired
are included on a state's 303(d)
list. A total maximum daily load
(TMDL) is required for each
pollutant causing impairment.
EPA's Report to Congress -
Impacts and Control of CSOs
and SSOs (EPA 2004) identifies
the three causes of reported
303(d) impairment most likely to
be associated with CSOs:
Pathogens
Organic enrichment leading
to low dissolved oxygen
Sediment and siltation
Some states identify sources of
impairment, and the activities or
conditions that generate the
pollutants causing impairment
(e.g., WWTPs or agricultural
runoff). CSOs are tracked as a
source of impairment in some
but not all CSO states.
If local waterbodies receiving
CSO discharges are impaired,
permittees should check with
the permitting authority to
determine whether the
pollutants associated with CSOs
are cited as a cause of
impairment or if CSOs are listed
as a source of impairment. In
addition, permittees should
check with the permitting
authority to see if a TMDL study
is scheduled for local
waterbodies to determine the
allocation of pollutant loads,
including pollutant loads in CSO
discharges.
The 305(b) water quality
assessment information is at
http://www.epa.qov/waters/305b
/index.html. Note that not all
waters are assessed under
state programs.
A national summary on the
status of the TMDL program in
each state is at
http://www.epa.gov/owow/
tmdl/. Note that not all waters
are listed.
Line 7a - Indicate if local
waterbodies are listed by the
permitting authority as impaired.
Answer Yes or No. If No, the
permittee may continue to
LineS.
Line 7b - Indicate the causes or
sources of impairment for each
impaired waterbody.
Line 7c - Indicate if a TMDL
has been scheduled to
determine the allocation of
pollutant loads. Answer Yes or
No. If yes, provide the date.
If the identified
waterbodies have been
assessed as threatened or
impaired under the 305(b)
program, and if CSOs are cited
as a source of impairment or if
the pollutants found in CSOs
are listed as a cause of
impairment, CSOs likely cause
or contribute to a recognized
water quality problem. Under
such circumstances, permittees
should check with the permitting
authority to confirm that use of
the Green LTCP-EZ Template
or the presumption approach is
appropriate.
If the waterbodies are not
designated by the permitting
authority as impaired or if the
waterbody is impaired but the
CSO discharges are not viewed
as a cause of the impairment,
the permittee may continue with
the Green LTCP-EZ Template.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
System Characterization
CSO control planning involves
considering the site-specific
nature of CSOs. The amount of
combined sewage flow that can
be conveyed to the VWVTP in a
CSS depends on a combination
of regulator capacity, interceptor
capacity, pump station capacity,
and VWVTP capacity. The Green
LTCP-EZ Template uses the
term CSO hydraulic control
capacity as a generic reference
to these types of flow controls.
In any system, one or more of
the CSO hydraulic control
capacities might be the limiting
factor. If the community has not
previously carried out an
analysis of the peak capacity of
each portion of its CSS, EPA
strongly suggests that the
determination of each CSO
hydraulic control capacity be
carried out by individual(s)
experienced in such hydraulic
analyses. EPA also cautions
communities against evaluating
CSO regulator capacity without
considering interceptor capacity
as well, because the nominal
capacity of a given CSO
regulator could exceed that of
its receiving interceptor under
the same peak wet-weather
conditions.
To develop an adequate control
plan, the permittee needs to
have a thorough understanding
of the following:
The extent of the CSS and
the number of CSO outfalls
The interconnectivity of the
system
The response of the CSS to
rainfall
The water quality
characteristics of the CSOs
The water quality impacts
that result from CSOs
Of those, the first three
considerations are the most
important for small communities.
Communities using the Green
LTCP-EZ Template are
encouraged to obtain at least
limited rainfall and system flow
data to allow the runoff
response calculated by the
Green LTCP-EZ approach to be
checked against actual system
flow data.
Line 8 is used to indicate that a
map has been attached to the
Green LTCP-EZ Template.
Lines 9-11 provide more specific
information about the CSS.
Information on Lines 9 through
11 is organized by CSO outfall
and sub-sewershed.
Line 8 - General Location.
Please check the box on Line 8
to indicate that Schedule 2 -
MAP is attached to FORM
GREEN LTCP-EZ. Schedule 2 -
MAP should include a map or
sketch of the CSS that shows
the following:
Boundaries of the CSS
service area and, if different,
total area served by the
sewer system
CSO outfall locations
Boundaries of individual sub-
sewersheds within the CSS
that drain to a CSO outfall
Location of major hydraulic
control points such as CSO
regulators (weirs, diversion
structures, and such) and
pump stations
Location of major sewer
interceptors (show as
pathways to the VWVTP)
VWVTP, if present
Waterbodies
Delineation of the boundaries of
the CSS and individual sub-
sewersheds is very important.
Delineation is most often done
by hand with sewer maps, street
maps, contours, and the
location of key hydraulic control
points such as regulators and
sewer interceptors. The
measurement of CSS and sub-
sewershed area is also very
important. Area can be
measured directly with
geographic information systems
(CIS), computer aided design
systems, or it can be measured
by hand by overlaying graph
paper and counting squares of
known dimension in the CSS or
sub-sewershed boundary.
Line 9 - CSO Information. Use
one column in Line 9 for each
CSO outfall in the CSS (e.g.,
CSO A, CSO B). Space is
provided for up to four CSO
outfalls in FORM GREEN
LTCP-EZ. Add additional
columns if needed. See the
example for Line 9.
Line 9a - Permitted CSO
number. Enter an identifying
number for each CSO outfall.
Line 9b - Description of
location. Enter a narrative
description of the location for
each CSO outfall.
Line 9c -
Latitude/Longitude. Enter
the latitude and longitude for
each CSO outfall, where
available.
Line 9d - Receiving water.
Enter the name of the
receiving water for each
CSO outfall.
Line 10 - CSS Information.
Most (though not all) CSOs
have a defined service area,
and surface runoff in this area
enters the CSS. For the purpose
of the Green LTCP-EZ
Template, sub-sewershed area
is used to describe the defined
16
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
service area for each CSO in a
CSS.
Use one column in Line 10 to
describe the following
information for each sub-
sewershed area in the CSS.
Space is provided for up to four
sub-sewersheds. Add additional
columns if needed. See the
example for Line 10.
Line 10a - Sub-sewershed
area. Enter the area (in
acres) for the contributing
sub-sewershed. Note 1: the
sum of sub-sewershed areas
in CSS should be consistent
with Line 3a. Note 2: this
information is also used in
Schedule 4 - CSO
VOLUME.
Line 10b - Principal land
use. Enter the principal land
use for the sub-sewershed
(i.e., business - downtown,
residential-single family) See
Table 1 in Schedule 4- CSO
VOLUME.
Line 11 - CSO Hydraulic
Control Capacity. The amount
of combined sewage that can be
conveyed to the WWTP in a
CSS depends on a combination
of regulator, interceptor, pump
station, and WWTP capacity.
The volume and rate of
combined sewage that can be
conveyed in a CSS depends on
dry-weather flows and these
capacities. In any system, one
or more of the capacities could
be the limiting factor.
The CSO hydraulic control
capacity defines the amount of
combined sewage that is
diverted to the interceptor.
Interceptors are large sewer
pipes that convey dry-weather
flow and a portion of the wet
weather-generated combined
sewage flow to WWTPs.
The CSO hydraulic control
capacity of passive structures
such as weirs and orifices can
be calculated or estimated as
long as drawings are available
and the dimensions of the
structures are known. The use
of standard weir or orifice
equations is recommended if
they are appropriate for the
structures that are present. As a
general rule, the diversion rate
is often three to five times
greater than dry-weather flow.
Permittees should consult a
standard hydraulics handbook
or a professional engineer
Example: Line 9 - CSO Information
a. Permitted CSO
number
b. Description of
location
c. Latitude/Longitude
d. Receiving Water
9a
9b
9c
9d
001
Foot of King
Street
374637N
870653W
Green River
002
Near Main
Street
374634N
870632W
Green River
003
Near Water
Street
374634N
870633W
Green River
Example: Line 10 - CSS Information
a. Sub-sewershed
area (acres)
b. Principal land use
10a
10b
CSO 001
105
Medium-
Density
Residential
CSO 002
85
High-
Density
Residential
CSO 003
112
Mixed Use
familiar with the design and
operation of regulators if the
CSO hydraulic control capacity
is unknown and the permittee is
unable to determine regulator
capacity with the resources
available.
Use one column in Line 11 to
describe the following
information for each CSO and
sub-sewershed. See the
example for Line 11.
Line 11a - Type of CSO
hydraulic control. Enter the
type of hydraulic control used
for this CSO, e.g., weir.
Line 11 b - CSO hydraulic
control capacity. Enter the
capacity in MGD of the CSO
hydraulic control. Note: this
information is also used in
Schedule 4-CSO VOLUME
and Schedule 5A-CSO
RUNOFF CONTROL.
Line 11c - Name of
interceptor or downstream
pipe. Enter the name of the
interceptor that receives the
diverted flow.
Public Participation
The CSO Control Policy states,
"in developing its long-term
CSO control plan, the permittee
will employ a public
participation process that
actively involves the affected
public in the decision-making to
select the long-term CSO
controls" (II.C.2). Given the
potential for significant
expenditures of public funds for
CSO control, public support is
key to CSO program success.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Public participation can be
viewed as interaction
between the permittee (the
utility or municipality), the
general public, and other
stakeholders. Stakeholders
include civic groups,
environmental interests, and
users of the receiving
waters. The general public
and stakeholders need to be
informed about the
existence of CSOs and the
plan for CSO abatement and
control. Informing the public
about potential CSO control
alternatives is one part of
the public participation process.
Public meetings are typically
used for describing and
explaining alternatives.
Technical solutions should be
presented simply and concisely
and understandable to diverse
groups. The discussion should
include background on the
project, description of proposed
facilities/projects, the level of
control to be achieved,
temporary and permanent
impacts, potential mitigation
measures, and cost and
financial information.
Presentations to the public
should explain the benefits of
CSO control. A key objective of
the public education process is
to build support for increases in
user charges and taxes that
might be required to finance
CSO control projects.
The extent of the public
participation program generally
depends on the amount of
resources available and the size
of the CSO community. Public
participation is typically
accomplished through one or
more activities, such as the
following:
Use of Schedules
The Green LTCP-EZ Template provides an organizational framework for collecting
and presenting information and analysis that is essential for a draft LTCP. Once
complete, FORM GREEN LTCP-EZ (with accompanying schedules) can serve as a
draft LTCP for a small community under appropriate circumstances. Each of the
following three sections on CSO Volume, Evaluation of CSO Controls, and CSO
Financial Capability include schedules with calculation procedures that are
potentially valuable for small communities. However, although the types of
information used in, and generated by, such schedules is necessary for a draft
LTCP, use of the schedules is optional. Permittees with extremely simple systems,
permittees that have already completed an evaluation of CSO controls, and
permittees that have previously conducted separate analyses could choose not to
use the schedules. Under those circumstances, documentation of the evaluation of
CSO control alternatives and selection of the recommended CSO Control Plan
could be provided in another format.
CSO /Awareness:
Placing informational and
warning signs at CSO
outfalls
Media advisories for CSO
events
Public Education:
Media coverage
Newsletters/Information
booklet
Educational inserts to water
and sewer bills
Direct mailers
CSO project Web sites
Public Involvement:
Public meetings
Funding task force
Local river committee
Community leader
involvement
General public telephone
survey
Focus groups
Successful public participation
occurs when the discussion of
CSO control has involved
ratepayers and users of CSO-
affected waterbodies.
For more information on public
participation activities, see
Combined Sewer Overflows
Guidance for Long-Term Control
P/an(EPA1995a).
Examples of public participation
can also be viewed at the
following CSO project Web
sites:
City of Lansing, Michigan.
(http://www.cityoflansingmi.c
om/pubserv/cso/the_cso_sto
ry.jsp)
City of Manchester, New
Hampshire.
(http://www.manchesternh.go
v/Web
site/Departments/Environme
ntalProtection/tabid/254/Defa
ult.aspx)
City of St. Joseph, Missouri.
(http://www.ci.st-
joseph.mo.us/publicworks/wp
c cso.cfm')
City of Wilmington,
Delaware.
(http://www.wilmingtoncso.co
m/CSO home.htm)
Line 12 - Public Participation.
Please check the box on Line
12 to indicate that Schedule 3 -
PUBLIC PARTICIPATION is
attached to FORM LTCP-EZ.
Use Schedule 3 - PUBLIC
PARTICIPATION to document
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
public participation activities
undertaken (or planned) to
involve the public and
stakeholders in the decision
process to evaluate and select
CSO controls.
CSO Volume
The Green LTCP-EZ Template
applies the presumption
approach described in the CSO
Control Policy. The Green
LTCP-EZ Template uses a
design storm approach to
identify the volume of combined
sewage that needs to be stored,
treated, or eliminated to reduce
CSOs to no more than an
average of four overflow events
per year. In accordance with the
presumption approach
described in the CSO Control
Policy, a program meeting that
criterion is conditionally
presumed to provide an
adequate level of control to
meet water quality-based
requirements, provided that the
permitting authority determines
the presumption is reasonable,
according to the data and
analysis provided in the LTCP.
Use of other criteria under the
presumption approach is valid
but needs to be documented
separately
(not in Schedule 4 - CSO
VOLUME).
Line 13 - CSO Volume. Check
the appropriate box on Line 13
to indicate whether Schedule 4
- CSO VOLUME or separate
documentation is attached to
FORM GREEN LTCP-EZ.
Schedule 4 - CSO VOLUME is
used to quantify the volume of
combined sewage that needs to
be stored, treated, or
eliminated. This is called the
CSO volume throughout the
Green LTCP-EZ Template.
Specific instructions for
completion of Schedule 4 -
CSO VOLUME are provided.
Evaluation of CSO
Controls
LTCPs should contain site-
specific, cost-effective CSO
controls. Small communities are
expected to evaluate a simple
mix of land management and
pipe network controls to assess
their ability to provide cost-
effective CSO control. The
Green LTCP-EZ Template
considers the volume of
combined sewage calculated in
Schedule 4 - CSO VOLUME
that needs to be stored, treated,
or eliminated when evaluating
alternatives for CSO controls.
Schedule 5 - CSO CONTROL
has two parts that enable an
evaluation of CSO control
alternatives for the CSO volume
calculated in Schedule 4 - CSO
VOLUME. Schedule 5A
evaluates the runoff reduction
that could be achieved with
certain green infrastructure
runoff controls. Schedule 5B
evaluates potential pipe network
CSO controls. Specific
instructions for completion of
Example: Line 11 - Pi
a. Type of CSO
hydraulic control
b. CSO hydraulic
control capacity (MGD)
c. Name of interceptor
or downstream pipe
pe Ca
11a
11b
11c
pacity and Flow Information
CSO 001
Weir
1.5
South Street
Interceptor
CSO 002
Weir
1.5
South Street
Interceptor
CSO 003
Pump
station
3.0
Central
Force Main
both parts of Schedule 5 - CSO
CONTROL are provided. Note
that both parts of Schedule 5 -
CSO CONTROL can be used
iteratively to identify the most
promising CSO control plan with
respect to CSO volume
reduction and cost.
Line 14 - CSO Controls.
Check the appropriate box on
Line 14 to indicate whether
Schedules 5A and 5B - CSO
CONTROL or separate
documentation are attached to
FORM GREEN LTCP-EZ.
Financial Capability
The CSO Control Policy
recognizes the need to address
the relative importance of
environmental and financial
issues when developing an
implementation schedule for
CSO controls. The ability of
small communities to fund CSO
control influences the
implementation schedule.
Schedule 6 - CSO FINANCIAL
CAPABILITY provides an
assessment of financial
capability in a two-step process.
Step One involves
determination of a residential
indicator to assess the ability of
the resident and the community
to finance CSO controls. Step
Two involves determining a
permittee's financial indicator to
assess the financial capability of
the permittee to fund and
implement CSO controls.
Information from both Step One
and Step Two is used to
determine financial capability.
Line 15 - Financial Capability.
Permittees are encouraged to
assess their financial capability
to fund the LTCP. Check the
box in Line 15 if Schedule 6 -
CSO FINANCIAL CAPABILITY
is attached to FORM GREEN
LTCP-EZ and enter the
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
appropriate financial capability
burden in Line 15a. Otherwise,
proceed to Line 16.
Line 15a - Financial
Capability Burden. Enter the
appropriate financial capability
burden (low, medium, or high)
from Schedule 6 - CSO
FINANCIAL CAPABILITY.
Recommended CSO
Control Plan
The Green LTCP-EZ Template
guides permittees through a
series of analyses and
evaluations that form the basis
of a draft LTCP for small
communities. The
recommended CSO controls
need to be summarized so that
the permitting authority and
other interested parties can
review them. Line 16 is used for
this purpose.
Line 16 - Recommended CSO
Control Plan. Documentation of
the evaluation of CSO control
alternatives is required (CSO
Control Policy Section M.C.4.).
Permittees that have used
Schedules 5A or 5B - CSO
CONTROL to select CSO
controls should bring the
information from Schedules 5A
and/or 5B - CSO CONTROL
forward to Line 16 in FORM
GREEN LTCP-EZ. Permittees
who have completed their own
evaluation of CSO alternatives
(that is, permittees that did not
use Schedules 5A or 5B - CSO
CONTROL) need to summarize
the selected CSO control on
Line16 and attach the
appropriate documentation.
Line 16a - Provide a summary
of the CSO controls selected.
This information can come from
the controls selected on
Schedules 5A or 5B - CSO
CONTROL, or from other
analyses. Section 3.3.5,
Identification of Control
Alternatives, of EPA's
Combined Sewer Overflows
Guidance for Long-Term Control
Plan document, lists the various
source controls, collection
system controls, and storage
and treatment technologies that
might be viable. This document
also discusses preliminary
sizing considerations,
cost/performance
considerations, preliminary
siting issues, and preliminary
operating strategies, all of which
should be discussed on Line
16a of the Green LTCP-EZ
Template.
Line 16b - Provide a summary
of the cost of CSO controls
selected. Project costs include
capital, annual operation and
maintenance (O&M), and life
cycle costs. Capital costs should
include construction costs,
engineering costs for design
and services during
construction, legal and
administrative costs, and
typically a contingency. Annual
O&M costs reflect the annual
costs for labor, utilities,
chemicals, spare parts, and
other supplies required to
operate and maintain the
facilities proposed as part of the
project. Life-cycle costs refer to
the total capital and O&M costs
projected to be incurred over the
design life of the project.
At the facilities planning level,
cost curves are usually
acceptable for estimating capital
and O&M costs. When used,
cost curves should be indexed
to account for inflation, using an
index such as the Engineering
News-Record Cost Correction
Index.
Line 16c - Provide a
description of how the CSO
controls selected will be
financed. Discuss self-financing
including fees, bonds, and
grants.
Section 4.3, Financing Plan, of
Combined Sewer Overflows
Guidance for Long-Term Control
Plan (EPA 1995a), states that
the LTCP should identify a
specific capital and annual cost
funding approach. EPA's
guidance on funding options
presents a detailed description
of financing options and their
benefits and limitations, as well
as case studies on different
approaches municipalities took
to fund CSO control projects. It
also includes a summary of
capital funding options,
including bonds, loans, grants,
and privatization, as well as
annual funding options for O&M
costs for CSO controls, annual
loan payments, debt service on
bonds, and reserves for future
equipment replacement.
Line 16d - Describe the
proposed implementation
schedule for the CSO controls
selected. The implementation
schedule describes the planned
timeline for accomplishing all
the program activities and
construction projects contained
in the LTCP. Section 4.5.1.5 of
Combined Sewer Overflow
Guidance for Permit Writers
(EPA 1995c) summarizes
criteria that should be used in
developing acceptable
implementation schedules,
including the following:
Phased construction
schedules should consider
first eliminating CSOs to
sensitive areas and use
impairment.
Phased schedules should
also include an analysis of
financial capability (see
Schedule 6 - CSO
FINANCIAL CAPABILITY).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
The permittee should
evaluate financing options
and data, including grant and
loan availability, previous
and current sewer user fees
and rate structures, and
other viable funding
mechanisms and sources of
funding.
The schedule should include
milestones for all major
implementation activities,
including environmental
reviews, siting of facilities,
site acquisition, and
permitting.
The implementation
schedule is often negotiated
with the permitting authority,
and incorporating the
information listed above in
the schedule provides a
good starting point for
schedule negotiations.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Instructions: Schedule 4 - CSO Volume
Introduction
Understanding the response of the CSS to rainfall is critical for evaluating the magnitude of CSOs and
control needs. Small CSO communities do not typically have the resources to conduct the detailed
monitoring and modeling necessary to make this determination easily. Schedule 4 - CSO VOLUME of the
Green LTCP-EZ Template provides a simple, conservative means for assessing CSO control needs. The
technical approach contained in Schedule 4 - CSO VOLUME builds on the general information and CSS
characteristics provided in FORM GREEN LTCP-EZ. It rests on a simple interpretation of the presumption
approach described in the CSO Control Policy. Under the presumption approach, a CSO community
controlling CSOs to no more than an average of four overflow events per year is presumed to have an
adequate level of control to meet water quality standards.
The volume of combined sewage that needs to be treated, stored, or eliminated is calculated in Schedule
4 - CSO VOLUME. This is called the CSO volume. CSO volume is calculated with a design storm,
application of the Rational Method (described below) to determine generated runoff, and use of an
empirical equation to estimate excess combined sewage and conveyance within the CSS. Once
construction of controls is completed, it is expected that compliance monitoring will be used to assess the
ability of the controls to reduce CSO frequency to meet the average of four overflow events per year
criterion.
Design Storm for Small Communities
Calculating the volume of runoff and combined sewage that occurs due to design storm conditions is the
basis for determining what controls are needed to limit the occurrence of CSOs to an average of four
overflow events per year. The Green LTCP-EZ Template uses two design storm values, each of which
represents a rainfall intensity that, on average, occurs four times per year. These are
The statistically derived one-hour, 3-month rainfall. This design storm represents a peak flow
condition. It is reasonably intense, delivers a fairly large volume of rainfall across the CSS, and
washes off the first flush. In addition, the one-hour, 3-month rainfall facilitates a simple runoff
calculation in the Rational Method. The LTCP must provide control to eliminate the occurrence of
CSOs for hourly rainfall up to this intensity.
The statistically derived 24-hour, 3-month rainfall. This design storm complements the one-hour, 3-
month rainfall in the Green LTCP-EZ Template. The longer 24-hour storm delivers a larger volume of
rainfall with the same 3-month return interval. The LTCP must provide control to eliminate the
occurrence of CSOs for rainfall up to this amount over a 24-hour period.
Using both of these design storms in conjunction with one another ensures that CSO control needs are
quantified on the basis of both rainfall intensity and rainfall volume associated with the return frequency of
four times per year.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
The Rational Method
The Rational Method is a standard engineering calculation that is widely used to compute peak flows and
runoff volume in small urban watersheds. The Rational Method with a design storm approach is used in
the Green LTCP-EZ Template to quantify the amount of runoff volume (the CSO volume) that needs to be
controlled for each CSO outfall and contributing sub-sewershed area. The Rational Method equation is
given as follows:
Q = kdA
where
Q = runoff (MGD)
k= conversion factor (acre-inches/hour to MGD)
C = runoff coefficient (based on land use)
;'= rainfall intensity (in/hr)
A = sub-sewershed area (acres)
The Rational Method is applied twice in the Green LTCP-EZ Template: once to determine the peak runoff
rate associated with the one-hour, 3-month rainfall, and once to determine the total volume of runoff
associated with the 24-hour, 3-month rainfall. When applied properly, the Rational Method is inherently
conservative.
Calculation of CSO Volume
CSO volume is calculated in sub-sewersheds at individual CSO hydraulic controls (i.e., weir, orifice) and
at the WWTP. The procedures used to calculate CSO volume are documented in Appendix B. The
following operations are central to the calculations:
The average dry-weather flow rate of sanitary sewage is added to runoff to create a peak hourly flow
rate and is used to calculate a total volume of flow over the 24-hour period.
The ratio of the CSO hydraulic control capacity to the peak flow rate based on the one-hour, 3-month
rainfall determines the fraction of overflow within sub-sewersheds. (Note: Identifying realistic hydraulic
control capacities is an important part of the Green LTCP-EZ Template. Permittees might need to seek
assistance from qualified professionals to successfully complete this part of the Template. In addition,
it is important that interceptor capacity limitations be taken into account when identifying regulator
capacities.)
The overflow fraction is applied to the total volume of flow associated with the 24-hour, 3-month rainfall
to quantify the volume of excess combined sewage at CSO hydraulic controls. This is the CSO volume
at the CSO hydraulic control.
Diversions to the WWTP at CSO hydraulic controls are governed by an empirical relationship based
on the ratio of the CSO hydraulic control capacity to the peak flow rate and conveyance. The
diversions to the WWTP at CSO hydraulic controls are a component of the peak sewage conveyed to
the WWTP.
The ratio of primary capacity to peak sewage conveyed to the WWTP determines the fraction of
combined sewage untreated at the WWTP. This is the CSO volume at the WWTP.
The Schedule 4 - CSO VOLUME results identify the CSO volume, which is the volume of excess
combined sewage that needs to be stored, treated, or eliminated to comply with the presumption
approach. The results of the calculations, the excess CSO volumes, are linked to Schedules 5A and 5B -
CSO CONTROL where green infrastructure or pipe network control alternatives are evaluated at the sub-
sewershed level or at the WWTP.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Summary
The Green LTCP-EZ Template is designed to provide a very simple assessment of CSO control needs.
Before entering data into the Green LTCP-EZ Template, permittees should collect good information on
the characteristics of the CSS, including reliable information on CSO hydraulic control capacities.
Permitting authorities and permittees in cooperation with local authorities need to work closely or provide
incentive for a maintenance agreement for green controls in the privately owned properties so that
expected and designed results of green CSO controls can be achieved.
Additional detail and documentation on the approach used to identify overflow, diversion and WWTP
overflow fractions are provided in Appendix B.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Sub-Sewershed Area
This section characterizes the
contributing area of each CSO
sub-sewershed area, the
predominant land use, and a
runoff coefficient. These values
are critical inputs to the runoff
calculation developed in this
schedule (the Rational Method).
Schedule 4 - CSO VOLUME is
set up to accommodate up to
foursub-sewersheds. Additional
columns can be added to the
schedule as needed if there are
more than four CSO sub-
sewersheds. The number of
sub-sewersheds evaluated on
this schedule needs to
correspond to the system
characterization information
included under Form GREEN
LTCP-EZ and the map on
Schedule 2 - MAP.
Line 1 - Sub-sewershed area
(acres). Enter the area in acres
for each sub-sewershed in the
CSS (Line 10a on FORM
GREEN LTCP-EZ. If you are
using the electronic version of
the form, this value will have
been filled in automatically). Add
additional columns if needed.
Line 2 - Principal land use.
Enter the principal land use for
each sub-sewershed area (Line
10b on FORM GREEN LTCP-
EZ. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 3 - Sub-sewershed
runoff coefficient. Enter the
runoff coefficient that is most
appropriate for the sub-
sewershed on Line 3. Runoff
coefficients represent land use,
soil type, design storm, and
slope conditions. The range of
runoff coefficients associated
with different types of land use
is presented in Table 1. Use the
lower end of the range for flat
slopes or permeable, sandy
soils. Use the higher end of the
range for steep slopes or
impermeable soils such as clay
or firmly packed soils. The
higher end of the range can also
be used to add an additional
factor of safety into the
calculation.
The runoff coefficient selected
should be representative of the
entire sub-sewershed.
Permittees should consider the
distribution of land use in the
sub-sewershed and develop a
weighted runoff coefficient if
necessary. For example, a sub-
sewershed that is half
residential single family (C =
0.40) and half light industrial (C
= 0.65) would have a composite
runoff coefficient of C = 0.525
[(0.40 + 0.65)72].
At a minimum, the runoff
coefficient should be equivalent
to the percent imperviousness
for the sub-sewershed as a
decimal fraction. The percent
imperviousness is the fraction of
each sub-sewershed area that
is covered by impervious
surfaces (such as pavement,
rooftops, and sidewalks) that is
directly connected to the CSS
through catch basins, area
drains or roof leaders.
Runoff
Line 4 Design storm rainfall.
The one-hour, 3-month rainfall
intensity (inches per hour) is the
design storm used in the Green
LTCP-EZ Template to estimate
peak runoff rate. The 24-hour,
3-month rainfall is used to
estimate total volume of runoff
generated over a 24-hour
period.
Recommended one-hour, 3-
month rainfall values by state
and county are provided in
Appendix A. These values are
based on research and products
provided by the Illinois State
Water Survey and Midwest
Climate Center (1992). Values
for the midwestern states are
very specific. Values for other
states in the Northeast have
been approximated on the basis
of procedures developed by the
Midwest Climate Center. A
statistically derived
multiplication factor of 2.1 is
used to convert these one-hour,
3-month design rainfall
conditions into the 24-hour, 3-
month rainfall conditions.
Table 1. Runoff coefficients for the rational formula
Type of area (principal land use)
Business - downtown
Business - Neighborhood
Residential - Single family
Residential - Multi units, detached
Residential - Multi units, attached
Residential - Suburban
Residential -Apartments
Industrial - Light
Industrial - Heavy
Parks, cemeteries
Playgrounds
Railroad yard
Unimproved
Runoff coefficient (C)
0.70-0.95
0.50-0.70
0.30-0.50
0.40-0.75
0.60-0.75
0.25-0.40
0.50-0.70
0.50-0.80
0.60-0.90
0.10-0.25
0.20-0.35
0.20-0.35
0.10-0.30
Source: ASCE 2006
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Site-specific rainfall values or
other design storm intensities
can be used to assess the
response of the
CSS to rainfall. However, use of
different rainfall periods could
require a separate analysis
outside of Schedule 4-CSO
VOLUME.
Enter the one-hour design storm
rainfall intensity in inches for
each sub-sewershed on Line 4.
(Note: this information is also
used in Schedules 5A and 5B-
CSO CONTROL).
Line 5 - Calculated runoff
rate. Multiply Line 1 by Line 3
and then multiply this product by
Line 4 for each sub-sewershed
area and enter the result (acre-
inches per hour) on Line 5.
Line 6 - Peak runoff rate in
MGD. Multiply Line 5 by the
conversion factor (k) of 0.6517
and enter the result for each
sub-sewershed area on Line 6.
This is the one-hour design
storm runoff in MGD.
Dry-Weather Flow within
the CSS
Line 7 - Dry-weather flow rate
(MGD). Enter the average dry-
weather flow rate as a rate in
MGD for each sub-sewershed
on Line 7. If dry-weather flow is
unknown on a sub-sewershed
basis, develop an estimate
supported by (1) direct
measurement of dry-weather
flow based on the average of a
series of observations made at
different times of the day; or (2)
allocating the dry-weather flow
reported on the DMR for the
WWTP for the entire sewer
service area. Using the
allocation estimation approach
should take into consideration
characteristics of each sub-
sewershed that influence the
rate of dry-weather flow
including population,
employment, and infiltration if
known. The sum of dry-weather
flow from the CSS plus the dry-
weather flow from non-CSO
areas and satellite communities,
if present, should equal the dry-
weather flow at the WWTP.
Peak Wet-Weather Flow
Line 8 - Peak flow rate (MGD).
The peak flow rate is the sum of
the peak runoff rate and dry-
weather flow in MGD. Add Lines
6 and 7 and enter the sum for
each sub-sewershed area on
Line 8.
Overflow
Line 9 - CSO hydraulic
control capacity (MGD). CSO
hydraulic control capacity is the
maximum flow that the sub-
sewershed area sewer can
deliver to the interceptor sewer.
Enter the CSO hydraulic control
capacity in MGD for each CSO
sub-sewershed area on Line 9
(Line 11b on FORM GREEN
LTCP-EZ. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 10 - Ratio of CSO
hydraulic control capacity to
peak flow rate. Enter 1.0 on
Line 10 if Line 9 is greater than
Line 8. Otherwise, divide Line 9
by Line 8 and enter the quotient
(result) on Line 10.
Line 11- Overflow fraction of
combined sewage. This is the
overflow fraction of combined
sewage within the sub-
sewershed. It is based on the
ratio of CSO hydraulic control
capacity to peak flow rate. Take
the square of (1 minus the value
on Line 10) and enter it on Line
11. For example, if the ratio of
CSO hydraulic control capacity
to peak flow rate on Line 10 is
0.15, the overflow fraction is
(1 -0.15)2, or 0.7225.
Line 12 - 24-hour rainfall.
Multiply Line 4 by 2.1 to obtain
the 24-hour design rainfall and
enter the product on Line 12.
Line 13 - Volume of runoff
(MG). The volume of runoff for
the 24-hour rainfall is obtained
by multiplying Line 1 by Line 3
and Line 12 and converting to
MG by applying the conversion
factor 0.02715. Enter the
product on Line 13.
Line 14 - Volume of dry-
weather flow (MG). This is the
total dry-weather flow in MG for
the 24-hour design rainfall
period. It is calculated by
multiplying the dry-weather flow
rate in MGD on line 7 by 24
hours. Enter this value on Line
14.
Line 15 - Total volume of flow
(MG). This is the total volume of
flow in MG within each sub-
sewershed for the 24-hour
design rainfall period. Add Lines
13 and 14 and enter the sum on
Line 15.
Line 16 - Volume of excess
combined sewage at
individual CSO hydraulic
controls during 24-hour
rainfall period. This is also the
CSO volume at the CSO
hydraulic control and is the
combined sewage that exceeds
the diversion capacity
determined by the CSO
hydraulic control in each sub-
sewershed. Multiply Line 11 by
Line 15 and enter the product
on Line 16.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Diversion
Line 17 - Diversion fraction of
combined sewage. This is the
fraction of runoff within each
subsewershed that is collected
and diverted to the WWTP over
the 24-hour design storm
period. The diversion fraction is
based on the ratio of CSO
hydraulic control capacity to
peak flow rate and conveyance.
Determine the diversion fraction
of combined sewage from Line
10 using Table 2, and enter on
Line 17.
Line 18 - Volume of runoff
diverted to WWTP. This is the
volume of runoff within each
sub-sewershed that is collected
and diverted to the WWTP over
the 24-hour design storm
period. Multiply Line 13 by Line
17 and enter the product on
Line 18.
Line 19 - Total volume of
combined sewage conveyed
to WWTP during 24-hour
rainfall period (MG). Add Lines
14 and 18 and enter the sum on
Line 19.
Conveyance
Line 20 - Peak rate of
collected combined sewage
diverted to the WWTP within
sub-sewersheds. Identify the
smaller of Line 8 and Line 9 in
each sub-sewershed and enter
the peak rate in MGD on Line
20.
Line 21 - Peak rate of
combined sewage conveyed
to WWTP (MGD). This peak
rate represents the sum of the
peak rates of collected
combined sewage diverted to
the WWTP from individual sub-
sewersheds in MGD. Add up
sub-sewershed values on Line
20 and enter on Line 21.
Table 2. Diversion Fraction of Combined Sewage from 24-
Hour Storm
Ratio of CSO hydraulic control
capacity to peak flow rate
0.01 to 0.02
0.02 to 0.03
0.03 to 0.04
0.04 to 0.05
0.05 to 0.06
0.06 to 0.07
0.07 to 0.08
0.08 to 0.09
0.09 to 0.10
0.10to0.12
0.12to0.14
0.14to0.16
0.16to0.18
0.1 8 to 0.20
0.20 to 0.24
0.24 to 0.28
0.28 to 0.32
0.32 to 0.36
0.36 to 0.40
0.41 to 0.50
0.51 to 0.60
0.61 to 0.70
0.71 to 0.80
0.81 to 0.90
0.91 to 1.0
Diversion fraction
0.04
0.06
0.09
0.11
0.14
0.16
0.19
0.21
0.24
0.28
0.33
0.38
0.42
0.47
0.54
0.62
0.68
0.72
0.76
0.81
0.87
0.91
0.95
0.98
0.99
Line 22 - Peak rate of sewage
from non-CSO areas (MGD).
Non-CSO areas can be affected
by wet weather conditions due
to Inflow/Infiltration (I/I). The
degree to which the peak rate of
sewage in non-CSO areas is
higher than the average dry-
weather flow rate depends on
site-specific conditions. Direct
measurement of the peak rate
of sewage during wet weather is
the best approach for
determining this rate. Estimation
based on flow measured at the
WWTP and local knowledge of
the distribution of flow in the
service area provides another
approach. Peaking factors can
also be used to adjust the
average dry-weather flow
upward. Newer tight sewer
systems might have peaking
factors between 1.0 and 1.5.
Older, leakier systems might
have peaking factors between
1.5 and 3.0, or even higher.
Enter on Line 22 the peak rate
of sewage conveyed to the
WWTP from non-CSO areas in
the community (in MGD).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 23 - Peak rate of sewage
from satellite communities
(MGD). Satellite communities
can be affected by wet weather
conditions due to I/I. The degree
to which the peak rate of
sewage in satellite communities
is higher than the average dry-
weather flow rate depends on
site-specific conditions. Direct
measurement of the peak rate
of sewage during wet weather is
the best approach for
determining this rate. Estimation
based on flow measured at the
WWTP and local knowledge of
the distribution of flow in the
service area provides another
approach. Peaking factors can
also be used to adjust the
average dry-weather flow
upward. Newer tight sewer
systems might have peaking
factors between 1.0 and 1.5.
Older, leakier systems might
have peaking factors between
1.5 and 3.0, or even higher. The
maximum rate of flow from
capacity agreements can also
be used and might be more
appropriate than measurements
or estimates. Enter on Line 23
the peak rate of sewage
conveyed to the WWTP from
satellite communities (in MGD).
Line 24 - Peak rate of sewage
conveyed to the WWTP
(MGD). This is the peak rate of
sewage flow in MGD received at
the WWTP from the CSS and
adjacent non-CSO areas in the
community and satellite
communities. Add Lines 21, 22
and 23 and enter the sum on
Line 24.
Treatment
Line 25 - Primary treatment
capacity (MGD). Enter the
primary treatment capacity in
MGD on Line 25 (Line 4a on
FORM GREEN LTCP-EZ. If you
are using the electronic version
of the form, this value will have
been filled in automatically).
Using primary treatment
capacity for CSO control is a
viable option where approval of
the regulatory agency has been
obtained. The CSO Control
Policy indicates that combined
sewer flows remaining after
implementing the NMCs and
within the criteria under the
presumption approach at a
minimum should receive the
following:
Primary clarification (removal
of floatables and settleable
solids can be achieved by
any combination of treatment
technologies or methods that
are shown to be equivalent
to primary clarification)
Solids and floatables
disposal
Disinfection of effluent, if
necessary, to meet WQS,
protect designated uses and
protect human health,
including removal of harmful
disinfection residuals, where
necessary
The Combined Sewer Overflows
Guidance for Long-Term Control
Plan document, Section 3.3.3.5,
Maximum Utilization of POTW
Capacity and CSO-Related
Bypass (EPA 1995a),
addresses the specific case
where existing primary
treatment capacity exceeds
secondary treatment capacity.
For such cases, the CSO
Control Policy states that at the
request of the municipality, EPA
may allow an NPDES permit "to
approve a CSO-related bypass
of the secondary treatment
portion of the POTW treatment
plant for CSOs in certain
identified circumstances"
(II.C.7). Under that provision,
flows to the POTW within the
capacity of primary treatment
facilities but in excess of the
capacity of secondary treatment
facilities may be diverted around
the secondary facilities provided
that "all wet weather flows
passing the headworks of the
POTW treatment plant will
receive at least primary
clarification and solids and
floatables removal and disposal,
and disinfection, where
necessary, and any other
treatment that can be
reasonably provided" (II.C.7). In
addition, the CSO-related
bypass should not cause
exceedance of water quality
standards.
Line 26 - Ratio of primary
treatment capacity to peak
rate of sewage conveyed to
WWTP. Enter 1.0 on Line 26 if
Line 25 is greater than Line 24.
Otherwise, divide Line 25 by
Line 24 and enter the quotient
(result) on Line 26.
Line 27 -Fraction of
combined sewage untreated
at WWTP. This is the fraction of
sewage delivered to the WWTP
during the 24-hour rainfall
period that does not receive
primary treatment. It is based on
the ratio of primary treatment
capacity to peak rate of sewage
conveyed to the WWTP. Take
the square of (1 minus the value
on Line 26) and enter it on Line
27. For example, if the ratio of
primary treatment capacity to
peak rate of sewage conveyed
to the WWTP on Line 26 is 0.80,
the overflow fraction is (1 -
0.80)2, or 0.04.
Line 28 - Sum of combined
sewage conveyed to WWTP
during 24-hour rainfall period
(MG). Add up the sub-
sewershed values in MG on
Line 19 and enter the sum on
Line 28.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 29 - Dry-weather flow
from the non-CSO area
(MGD). Enter the dry-weather
flow rate from the non-CSO
area in MGD on Line 29. If dry-
weather flow for the non-CSO
area is unknown, develop an
estimate supported by (1) direct
measurement of dry-weather
flow based on the average of a
series of observations made at
different times of the day; or (2)
allocating the dry-weather flow
reported on the DMR for the
WWTP for the entire sewer
service area.
Line 30- Volume of sewage
from non-CSO areas during
24-hour rainfall period (MG).
The volume of sewage from
non-CSO areas during the 24-
hour rainfall period is likely to be
higher than the average dry-
weather flow rate (Line 29)
because of I/I but less than the
peak rate of sewage (Line 22).
Typical daily wet-weather
volumes should be used if
measurements are available.
Alternatively, an estimate based
on the peak rate of sewage
(Line 22) and the dry-weather
flow rate (Line 29) can be used.
Under that approach, it is
assumed that flow to the WWTP
from the non-CSO area over the
course of the 24-hour rainfall
period has a triangular shape.
The volume is calculated by
adding one-half the difference
between Line 22 and 29 and
adding the value to the dry-
weather flow rate. Subtract Line
29 from Line 22, divide by 2,
add the remainder to Line 29,
and enter this value as a volume
in MG on Line 30.
Line 31 - Dry-weather flow
from the satellite
communities (MGD). Enter the
dry-weather flow rate from the
satellite communities in MGD on
Line 29. If dry-weather flow for
the satellite communities is
unknown, develop an estimate
supported by (1) direct
measurement of dry-weather
flow based on the average of a
series of observations made at
different times of the day; or (2)
allocating the dry-weather flow
reported on the DMR for the
WWTP for the entire sewer
service area.
Line 32- Volume of sewage
from satellite communities
during 24-hour rainfall period
(MG). The volume of sewage
from satellite communities
during the 24-hour rainfall
period is likely to be higher than
the average dry-weather flow
rate (Line 31) because of I/I, but
less than the peak rate of
sewage (Line 23). Typical daily
wet-weather volumes should be
used if measurements are
available. Alternatively, an
estimate based on the peak rate
of sewage (Line 23) and the dry-
weather flow rate (Line 31) can
be used. Under that approach, it
is assumed that flow to the
WWTP from the satellite
communities over the course of
the 24-hour rainfall period has a
triangular shape. The volume is
calculated by adding one-half
the difference between Line 23
and 31 and adding the value to
the dry-weather flow rate.
Subtract Line 31 from Line 23,
divide by 2, add the remainder
to Line 31, and enter this value
as a volume in MG on Line 32.
Line 33 - Total volume of
sewage during 24-hour
rainfall event (MG). Add Lines
28, 30 and 32 and enter the
volume in MG on Line 33.
Line 34 - Volume of combined
sewage untreated at WWTP
(MG). This is also the CSO
volume at the WWTP. Enter 0.0
on Line 34 if Line 25 is greater
than Line 24. Otherwise,
multiply Line 31 by Line 27 and
enter the volume in MG on Line
34.
CSO Volume
The CSO volume that needs to
be stored, treated or eliminated
is calculated in SCHEDULE 4-
CSO Volume. The CSO
volumes are identified within
individual sub-sewersheds at
CSO hydraulic controls and at
the WWTP.
Line 35 - Volume of combined
sewage overflows at CSO
outfalls (MG). This represents
the volume of excess combined
sewage in MG that is
discharged at CSO outfalls.
Sum all sub-sewershed volumes
in MG on Line 16 and enter the
value on Line 35.
Line 36 - Volume of combined
sewage overflow at WWTP
(MG). This represents the
volume of excess combined
sewage in MG that is collected
and conveyed to the WWTP that
does not receive at least
primary treatment. Enter the
value on Line 34 on Line 36.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Instructions: Schedule 5A - CSO Runoff Control
(Green Infrastructure Runoff Controls)
The calculation in Schedule 4 - CSO VOLUME quantifies the volume of combined sewage generated by
a storm that occurs no more than four times per year (once every 3 months). That is the volume of
combined sewage that needs to be stored, treated, or eliminated under the presumption approach so that
there is no more than an average of four overflow events per year. The calculation leads the permittee to
identify the rate and volume of combined sewage conveyed to the WWTP. It also identifies the rate and
volume of combined sewage at sub-sewershed outfalls governed by CSO hydraulic controls. The
permittee is expected to develop a simple LTCP based on CSS characterization, the hydraulic response
of the CSS to precipitation established in Schedule 4 - CSO VOLUME, information presented on CSO
controls, and an understanding of local conditions and circumstances. Schedules 5A and 5B - CSO
CONTROL provide a simple approach to organize and evaluate control needs, performance, and costs.
Small communities can use this schedule iteratively to identify the mix of CSO controls needed.
The calculations in Schedule 5A - CSO RUNOFF CONTROL quantify the volume of stormwater that can
be eliminated before collection by using green infrastructure techniques. Green infrastructure practices
are those that use or mimic natural processes to infiltrate, evapotranspire (i.e., return water to the
atmosphere either through evaporation or through uptake by plants), or store (e.g., through rain barrels
and cisterns) stormwater or runoff on or near the site where it is generated. Such practices reduce
stormwater runoff, which in turn minimizes the frequency, duration and volume of CSOs. This schedule is
intended to (1) help the permittee quantify the stormwater runoff reduction that could be achieved through
green infrastructure practices, given a set runoff retention standard or goal, and (2) help the permittee
evaluate the feasibility of the runoff retention standard or goal by estimating the number of green
infrastructure runoff controls that would be required to meet the runoff retention standard or goal.
Runoff Reduction via On-site Runoff Retention Standard or Goal
To determine how much runoff reduction a permittee can expect from incorporating green infrastructure
practices, Schedule 5A uses a runoff retention standard or goal that can be associated with managed,
directly connected impervious areas (see the definition to the right). Many municipalities are beginning to
mandate on-site runoff retention standards
(e.g., retain first one-inch of rainfall) for all new | Definition of directly connected impervious areas
development or redevelopment that exceeds a
certain size. If a specific codified runoff
retention standard does not exist, the
permittee could use a runoff retention goal sewer conveVance sVstem with°ut ^t flowing over a
f. ... ... ... , .. . pervious area. For exampe, a street with a curb and gutter,
that the permittee will enforce or otherwise where mnoff f|QWS jnto apcateh basjn and subsequent^ into
encourage landowners to meet. Assuming
that this runoff retention standard or goal is
met within a planning horizon, the following
formula can be used to calculate the runoff
reduction volume achieved through
implementation:
V=kAPRv
Directly connected impervious areas are those impervious
areas that are connected hydraulically to the combined
the combined sewer system, is considered a directly
connected impervious area. A rooftop that drains directly to
this same street would also be considered directly
connected. An example of a non-directly connected
impervious area would be a parking lot where runoff flows
through a grassy pervious area, and most of the water
infiltrates into the ground. Schedule 5A considers only the
management of directly connected impervious areas,
because those are the impervious areas that are the most
w e significant contributors of runoff to the combined sewer
system.
V= runoff reduction volume (gallons
or million gallons [MG])
k = unit conversion factor
A = area of directly connected impervious surface managed (acres)
P= depth of retention standard or goal (inches)
Rv = volumetric runoff coefficient (default is 0.95)
30
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Runoff Reduction via Specific Green Infrastructure Practices
To aid in planning, Schedule 5A also provides for the estimation of the number of green infrastructure
practices that could be used to meet the runoff reduction standard or goal (note that the schedule
estimates the number of practices that will be required to achieve the goal/standard, but it does not
assess the capacity of the landscape to accommodate those practices). This part of the schedule serves
as a quality control measure to assess the feasibility of the runoff retention standard or goal. While the
true evaluation of volumetric reductions achieved by using different green infrastructure practices will be
highly dependent on local conditions and sizing and design considerations, Green LTCP-EZ uses a
simplified approach that includes using practice specific volumetric reduction rates to provide an estimate
of the volumetric reductions that can be achieved through implementation of green practices. Before
making a final selection on the approach to control overflows, the permittee needs to ensure that the
green infrastructure practices are suitable for the landscapes. The volume of runoff reduction achieved for
each practice category will be calculated using a variation of the following equation:
V=kAP24RR
where
V= runoff reduction volume (gallons or million gallons [MG])
k = unit conversion factor
A = area of impervious surface managed (acres)
P24 = depth of 24-hour design storm rainfall (inches) (from Schedule 4)
RR = average volumetric reduction rates (per practice)
Five general green infrastructure runoff controls are considered in this schedule. They are as follows:
Green Roofs
Bioretention
Vegetated Swales
Permeable Pavement
Rain Barrels and Cisterns
Use of more than one green infrastructure practice type is common. The calculations in Schedule 5A can
be used iteratively to identify the most appropriate mix of green infrastructure practices with respect to
CSO reduction and cost. CSO communities are welcome to consider using other green infrastructure
runoff controls outside the controls described above to reduce runoff. Appropriate analyses of other
controls and their associated runoff reduction should be attached and submitted along with the other
Green LTCP-EZ schedules and forms that the permittee has used to develop the LTCP.
Recalculating CSO Volume
Schedule 5A also includes a recalculation of the CSO volume determined in Schedule 4. The green
infrastructure practices are runoff-reduction techniques that affect the peak flow rate and runoff volume
from each sewershed, which in turn affects the overflow fraction, the diversion fraction, and the ultimate
CSO volume requiring controls. Therefore, it is necessary to recalculate the peak flow rate and determine
a new CSO volume for evaluation with Schedule 5B. The recalculation of the CSO volume in Schedule
5A follows the same procedure outlined in Schedule 4.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Impervious Area
This section is used to quantify
the area of directly connected
impervious surface (such as
pavement, rooftops, and
sidewalks) within each sub-
sewershed that contributes
runoff to the CSS. The directly
connected impervious area can
be measured directly using CIS
data or aerial photos. If the data
are not readily available, the
percentage of directly
connected impervious surface in
a subsewershed can be
estimated on the basis of the
principal land uses previously
identified for each sub-
sewershed in Schedule 4.
Line 1 - Sub-sewershed area
(acres). Enter the sub-
sewershed area for each sub-
sewershed on Line 1 (Line 10a
on Form GREEN LTCP-EZ. If
you are using the electronic
version of the form, this value
will have been filled in
automatically.)
Line 2 - Fraction of directly
connected impervious area
within sub-sewershed. Enter
the fraction of directly connected
impervious area within each
sub-sewershed on Line 2.
Line 3 - Directly connected
impervious area (acres) within
sub-sewershed. Multiply the
sub-sewershed area on Line 1
by the fraction of directly
connected impervious area
within the sub-sewershed on
Line 2 and enter the product on
lineS.
Retention Standard or Goal
Many municipalities are
beginning to mandate or
encourage on-site runoff
retention standards or goals
(e.g., retain first one-inch of
rainfall) for development or
redevelopment that exceeds a
certain size. In many cases,
green infrastructure practices or
controls are directed to be the
first management options
considered. In this section, the
permittee needs to supply the
runoff retention standard or
goal, as well as an estimate of
the percentage of area in the
sub-sewershed that will be
redeveloped within the planning
horizon.
Line 4 - Fraction of sub-
sewershed to be redeveloped
over planning horizon.
Estimate the fraction of the sub-
sewershed that is expected to
be redeveloped over a planning
horizon. This estimate should be
based on municipal planning
exercises or other long-range
forecasts. For purposes of this
calculation, the planning horizon
should not exceed 25 years. If
no redevelopment forecasts are
available, the permittee can use
a default redevelopment fraction
of 0.30 (30 percent) over a 25-
year planning period. Note that
this calculation should consider
only redevelopment. New
development on previously
undeveloped or greenfield areas
should not be included in the
fraction.
Line 5 - Directly connected
impervious area (acres)
managed. Multiply the directly
connected impervious area
(acres) within the sub-
sewershed on Line 3 by the
fraction of sub-sewershed to be
redeveloped over the planning
horizon on Line 4 and enter the
product on line 5.
Line 6 - Depth of rainfall
retention standard or goal
(inches). Enter a depth that
represents the quantity of
precipitation that is expected or
required to be retained
(i.e., infiltrated, stored, or
evapotranspired) on-site with
green infrastructure runoff
controls. This depth cannot be
greater than the 24-hour,
3-month rainfall previously
calculated. Typical retention
standards will likely be between
0.5 and 1.5 inches.
Runoff Reduction
The impervious area calculation
and the retention standard or
goal are used together to
determine the associated runoff
reduction.
Line 7 - Runoff retained from
managed directly connected
impervious area (acre-in).
Multiply the directly connected
impervious area (acres)
managed on Line 5 by the depth
of retention standard (inches) on
Line 6. Multiply this product by
0.95, which is the runoff
coefficient for impervious
surfaces.
Line 8 - Runoff reduction
volume (MG). To convert acre-
inches to million gallons (MG),
multiply the retained runoff from
managed impervious area on
Line 7 by 0.02715.
Green Roofs
Green roofs (also known as
vegetated roofs, eco-roofs, or
living roofs) are rooftop
stormwater management
practices that typically consist of
drought-resistant vegetation, a
soil or growing medium, a
drainage layer, and a waterproof
membrane. Green roofs have
been shown to retain a portion
of incident rainfall within the
growing medium. The amount of
rainfall stored in a green roof
depends on a number of site
specific factors, including the
roof slope and the type and
depth of the growing medium.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Local zoning and building codes
should be consulted for any
guidance on green roof
specifications.
Line 9 - 24-hour rainfall
(inches) Enter the 24-hour
rainfall (inches) on Line 9 (Line
12 on Schedule 4: CSOVOL. If
you are using the electronic
version of the form, this value
will have been filled in
automatically).
Line 10 - Number of existing
buildings with green roofs
expected to be installed.
Enter the number of existing
directly connected buildings
on which green roofs are
expected to be installed over
the previously established
planning horizon.
Line 11- Average roof
area (sq ft) of buildings
with green roofs expected
to be installed. The roof
area of buildings can vary
significantly. Residential
roofs tend to be smaller than
commercial and industrial
rooftops. Urban residential
rooftops are often smaller
than suburban residential
rooftops. An actual estimate
of rooftop sizes can
sometimes be estimated
from CIS or from aerial
photos. Note that some
rooftops, like those with
steep slopes, might not be
as amenable to green roof
installation. In addition, the
permittee might also wish to
consider that green roofs are
often not installed over the
entire building roof area.
Rooftop space can also be
required for HVAC equipment,
access structures, or patios,
causing such areas to be
unavailable for green roof
applications. Given all those
considerations, enter a value
that is characteristic of the
potential green roof area of
buildings in the sub-
sewershed(s).
Line 12 - Average green roof
runoff reduction rate. The
runoff reduction potential of a
green roof depends on a
number of site-specific factors,
including the roof slope and the
type and depth of the growing
medium. On the basis of a
qualitative understanding of the
types of green roofs to be
installed in the sub-sewershed,
select a runoff reduction rate
with green roofs expected to be
installed (Line 10) by the
average roof area of buildings
with green roofs expected to be
installed (Line 11) by the
average green roof reduction
rate (Line 12). Multiply this
product by 0.5922 (this factor
includes the unit conversion to
gallons, as well as the
impervious area runoff
coefficient of 0.95).
Line 14 - Green roof runoff
reduction volume (MG). Divide
the runoff to the CSS eliminated
Table 3. Average green infrastructure practice runoff reduction rate
Practice
Green Roofs
Bioretention
Facilities
Vegetated
Swales
Permeable
Pavement
Rain Barrels
and Cisterns
Average
runoff
reduction
rate
0.45-0.60
0.40-0.80
0.40-0.60
0.45-0.75
0.10*-0.40
General guidance on selection of runoff
reduction rate
When to select low-
end values
Sloped roofs
predominate
Poorly draining soils
predominate
Typical design uses
underdrains
Poorly draining soils
predominate
Poorly draining soils
predominate
Typical design uses
underdrains
Residential rain
barrels (50-1 50 gal)
predominate
When to select
high-end values
Flat roofs
predominate
Well draining soils
predominate
Typical design does
not use underdrains
Well draining soils
predominate
Well draining soils
predominate
Typical design does
not use underdrains
Larger capacity rain
tanks and cisterns
(1,000 -10,000 gal)
predominate
Sources: *MWCOG 2001; all others Schueler2008
from Table 3 and enter it on
Line 12. The permittee can use
a runoff reduction rate that is
higher than those listed in Table
3 only if it is appropriately
documented.
Line 13 - Runoff to CSS
eliminated due to green roof
installation. Multiply the 24-
hour rainfall (Line 9) by the
number of existing buildings
because of green roof
installation (Line 13) by
1,000,000 to convert from
gallons to MG.
Line 15 - Unit cost per square
foot for green roof
installation. Unit costs for
green roof installations can vary
significantly. Enter a cost that
reflects local conditions.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 16 - Fraction of publicly
owned or subsidized
buildings with green roofs.
Determine the number of
publicly owned buildings that will
be retrofitted with a green roof
and add to it any privately
owned buildings for which green
roofs are expected to be
partially or wholly subsidized
with public funds. For private
installations, count only the
portion of the total green roof
installation cost that is publicly
funded (i.e., if a public subsidy
pays for 10 percent of a typical
installation, count only 10
percent of that installation). The
permittee might also need to
consider the incentive cost to
install green roof in the public
property and any related cost for
future maintenance.
Line 17 - Estimated public
cost of cumulative green roof
installation. Some of the costs
of green roofs will be borne by
private entities and will not be
borne by the permittee. To
determine the cost to the
permittee, multiply the number
of existing buildings with green
roofs expected to be installed
(Line 10) by the average roof
area (sq ft) of buildings with
green roofs expected to be
installed (Line 11) by unit cost
per square foot for green roof
installation (Line 15) by fraction
of publicly owned or subsidized
buildings with green roofs (Line
16).
Bioretention
Bioretention facilities (or rain
gardens) typically consist of
engineered, shallow, vegetated
depressions that are used to
manage stormwater runoff from
impervious surfaces including
rooftops, streetscapes, and
parking lots. Bioretention
facilities provide stormwater
quantity control through runoff
capture, infiltration, and
evapotranspiration.
Bioretention designs can vary
significantly by size, depth,
engineered soil characteristics,
plant selection, and the
presence and location of any
subsurface drainage structures.
Performance is highly site
dependent and is affected by
design parameters and local
conditions, including topography
and the infiltration capacity of
surrounding soils. Local zoning
and building codes should be
consulted for any guidance on
bioretention facility
specifications.
Line18 - Number of
bioretention facilities being
installed. Enter number of
bioretention retrofits expected to
be installed over the previously
established planning horizon to
manage runoff from existing
directly connected impervious
areas.
Line 19 - Average directly
connected impervious area
(sq ft) being managed by each
bioretention facility. The size
and design of bioretention
facilities can vary significantly,
thus influencing the size of the
drainage area managed. Most
bioretention facilities are sized
and designed according to the
available space and the
drainage area to be managed.
Depending on the
characteristics of the drainage
area, the bioretention facility
footprint is typically 5 to 15
percent of the contributing
impervious area being
managed. In general, a
bioretention facility drainage
area should not exceed 3 to 5
acres. Given all those
considerations, enter a value
that is characteristic of each
bioretention facility impervious
drainage area in the sub-
sewershed(s).
Line 20 - Average
bioretention runoff reduction
rate. The runoff reduction
potential of a bioretention facility
depends on a number of site-
specific factors, including the
topography and infiltration
capacity of local soils. On the
basis of a general
understanding of the local
conditions in the sub-
sewershed, select a runoff
reduction rate from Table 3 and
enter it on Line 20. The
permittee can use a runoff-
reduction rate that is higher than
those listed in Table 3 only if it is
appropriately documented.
Line 21 - Runoff to CSS
eliminated due to bioretention
facility installation. Multiply 24-
hour rainfall (inches) (Line 9) by
number of bioretention facilities
expected to be installed (Line
18) by average directly
connected impervious area (sq
ft) being managed by each
bioretention facility (Line 19) by
average bioretention runoff
reduction rate (Line 20). Multiply
that product by 0.5922 (that
factor includes the unit
conversion to gallons as well as
the impervious area runoff
coefficient of 0.95).
Line 22 - Bioretention runoff
reduction volume (MG). Divide
runoff to CSS eliminated
because of bioretention facility
installation (Line 21) by
1,000,000 to convert from
gallons to MG.
Line 23 - Unit cost per square
foot for bioretention
installation. Unit costs for
bioretention facility installations
can vary significantly. Enter a
cost that reflects local conditions
or use the default value of $7
per square foot.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 24 - Fraction of publicly
owned or subsidized
bioretention facilities being
installed. Determine the
number of publicly owned
bioretention facilities expected
to be installed and add to it any
privately owned bioretention
facilities that are expected to be
partially or wholly subsidized
with public funds. For private
installations, count only the
portion of the total bioretention
facility installation cost that is
publicly funded (i.e., if a public
subsidy pays for 10 percent of a
typical installation, count only 10
percent of that installation). The
permittee might also need to
consider the incentive cost for
bioretention facility in the public
property and any related cost for
future maintenance.
Line 25 - Estimated public
cost of cumulative
bioretention installation.
Some of the costs of
bioretention will be borne by
private citizens or corporations
and will not be borne by the
permittee. To determine the cost
to the permittee, multiply
number of bioretention facilities
expected to be installed (Line
18) by average directly
connected impervious area (sq
ft) being managed by each
bioretention facility (Line 19) by
unit cost per square foot for
bioretention installation (Line23)
by fraction of publicly owned or
subsidized bioretention facilities
being installed (Line24). Divide
that product by 10 to account for
the relationship between the
impervious drainage area size
and the bioretention facility size.
Vegetated Swales
Vegetated swales (or bioswales)
are shallow, open channels with
vegetation covering the side
slopes and channel bottom.
They are primarily designed to
collect and convey runoff to
downstream discharge locations
as alternatives to curbs, gutters,
and stormwater pipes. They can
be used to manage stormwater
runoff from any number of
impervious surfaces, including
rooftops, streetscapes, and
parking lots. While their primary
function is conveyance and
water quality management, they
can actually provide significant
water quantity management as
well via infiltration and
evapotranspiration.
Vegetated swales are linear
features that can typically
manage runoff from larger areas
than can bioretention facilities
(although the quantity
management effectiveness will
likely not be as high). As with
bioretention facilities, vegetated
swale designs can vary
significantly by size, depth,
engineered soil characteristics,
and plant selection.
Performance is highly site
dependent and is affected by
design parameters, as well as
by local conditions, including
topography and the infiltration
capacity of surrounding soils.
Local zoning and building codes
should be consulted for any
guidance on vegetated swale
specifications.
Line 26 - Cumulative directly
connected impervious area
(sq ft) expected to be
managed by vegetated
swales. Most vegetated swales
are sized and designed
according to the available space
and the type and configuration
of the contributing drainage area
to be managed. In general, a
vegetated swale drainage area
should not exceed 10 acres.
Following an evaluation of the
potential for vegetated swale
installation, enter the existing
cumulative directly connected
impervious area within the sub-
sewershed(s) that is expected to
be managed by vegetated
swales over the planning
horizon.
Line 27 - Cumulative footprint
area (sq ft) of vegetated
swales. Depending on the
characteristics of the drainage
area, the vegetated swale
footprint is typically 3 to 5
percent of the contributing
impervious area being
managed. Given that, enter the
cumulative footprint of
vegetated swales that are
expected to be installed over the
planning horizon to manage the
drainage area provided on Line
26.
Line 28 - Average vegetated
swale runoff reduction rate.
The runoff reduction potential of
a vegetated swale depends on a
number of site-specific factors,
including the slope and
infiltration capacity of local soils.
On the basis of a general
understanding of those local
conditions in the sub-
sewershed, select a runoff
reduction rate from Table 3 and
enter it on Line 28. The
permittee can use a runoff
reduction rate that is higher than
those listed in Table 3 only if it is
appropriately documented.
Line 29 - Runoff to CSS
expected to be eliminated due
to vegetated swale
installation. Multiply 24-hour
rainfall (inches) (Line 9) by
cumulative directly connected
impervious area (sq ft) being
managed by vegetated swales
(Line 26) by the average
vegetated swale runoff
reduction rate (Line 28). Multiply
that product by 0.5922 (this
factor includes the unit
conversion to gallons as well as
the impervious area runoff
coefficient of 0.95).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 30- Vegetated swale
runoff reduction volume (MG).
Divide runoff to CSS eliminated
because of vegetated swale
installation (Line 29) by
1,000,000 to convert from
gallons to MG.
Line 31- Unit cost per square
foot for vegetated swale
installation. Unit costs for
vegetated swale installations
can vary significantly. Enter a
cost that reflects local conditions
or use the default value of $15
per square foot.
Line 32- Fraction of publicly
owned or subsidized
vegetated swales being
installed. Determine the
fraction of vegetated swales
expected to be installed that are
to be publicly owned or partially
or wholly subsidized with public
funds. For private installations,
count only the portion of the
total vegetated swale installation
cost that is publicly funded (i.e.,
if a public subsidy pays for 10
percent of a typical installation,
count only 10 percent of that
installation). The permittee
might also need to consider the
incentive cost for vegetated
swales in the public property
and any related cost for future
maintenance.
Line 33- Estimated public
cost of cumulative vegetative
swale installation. Some of the
costs of vegetated swales will
be borne by private entities and
will not be borne by the
permittee. To determine the cost
to the permittee, multiply
cumulative footprint area (sq ft)
of vegetated swales (Line 27) by
unit cost per square foot for
vegetated swale installation
(Line 31) by fraction of publicly
owned or subsidized vegetated
swales expected to be installed
(Line 32).
Permeable Pavement
Permeable pavement (also
referred to as pervious or
porous pavement) can be used
in lieu of traditional impervious
pavements in applications that
do not receive excessive
vehicular loads (including
parking lots, sidewalks,
playgrounds, parking lanes,
driveways, and such).
Permeable pavement includes a
range of materials that allow the
water to move through the
paving material, including
permeable asphalt, permeable
concrete, paving stones,
interlocking pavers, and
reinforced turf, among others.
Permeable pavement provides
stormwater quantity control
through runoff capture and
infiltration. Designs can vary by
paving material, depth of sub-
base materials, and the
presence and location of any
subsurface drainage structures.
Performance is highly site
dependent and is affected
primarily by the infiltration
capacity of surrounding soils.
Local zoning and building codes
should be consulted for any
guidance on permeable
pavement specifications.
Line 34 - Cumulative area (sq
ft) of directly connected
pavement expected to be
replaced with permeable
pavement. Most permeable
pavement retrofit applications
are installed as complete or
partial replacements of existing
impervious pavement.
Permeable pavement
applications typically are not
designed to accept runoff from
other vegetated or non-
impervious areas. Enter the
existing cumulative directly
connected impervious pavement
within the sub-sewershed(s) that
is expected to be replaced with
permeable pavement over the
planning horizon.
Line 35 - Average permeable
pavement runoff reduction
rate. The runoff reduction
potential of permeable
pavement depends on a number
of site specific factors, including
the topography and infiltration
capacity of local soils. On the
basis of a general
understanding of those local
conditions in the sub-
sewershed, select a runoff
reduction rate from Table 3 and
enter it on Line 35. The
permittee can use a runoff
reduction rate that is higher than
those listed in Table 3 only if it is
appropriately documented.
Line 36 - Runoff to CSS
expected to be eliminated due
to permeable pavement
installation. Multiply the 24-
hour rainfall (inches) (Line 9) by
the cumulative area (sq ft) of
directly connected pavement
replaced with permeable
pavement (Line 34) by the
average permeable pavement
runoff reduction rate (Line 35).
Multiply that product by 0.5922
(this factor includes the unit
conversion to gallons as well as
the impervious area runoff
coefficient of 0.95).
Line 37- Permeable pavement
runoff reduction volume (MG).
Divide the runoff to CSS
eliminated due to permeable
pavement installation (Line 36)
by 1,000,000 to convert from
gallons to MG.
Line 38- Unit cost per square
foot for permeable pavement
installation. Unit costs for
permeable pavement
installations can vary
significantly. Enter a cost that
reflects local conditions or use
the default value of $7 per
square foot.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 39- Fraction of publicly
owned or subsidized
permeable pavement
installations. Determine the
fraction of permeable pavement
applications being installed that
are to be publicly owned or
partially or wholly subsidized
with public funds. For private
installations, count only the
portion of the total permeable
pavement installation cost that
is publicly funded (i.e., if a public
subsidy pays for 10 percent of a
typical installation, count only 10
percent of that installation)
Line 40- Estimated public
cost of cumulative permeable
pavement installation. Some
of the costs of permeable
pavement will be borne by
private entities and will not be
borne by the permittee. To
determine the cost to the
permittee, multiply the
cumulative area (sq ft) of
traditional pavement expected
to be replaced with permeable
pavement (Line 34) by the unit
cost per square foot for
permeable pavement installation
(Line 38) by the fraction of
publicly owned or subsidized
permeable pavement
installations (Line 39).
Rain Barrels and Cisterns
Rain barrels and cisterns are
storage devices that can be
used to manage rooftop runoff
from residential, commercial
and industrial buildings. Both
rain barrels and cisterns
typically include connection to a
rooftop downspout, an overflow
pipe, and a drainage spigot at or
near the bottom. Rain barrels
are more likely to be used in
residential settings, because
they are typically smaller (50-
150 gallons). Cisterns are
generally larger (typically
between 1,500 and 10,000
gallons) and can be placed
above ground or underground.
With either device, stored water
can be used for irrigation or
other non-potable uses. Local
zoning and building codes
should be consulted for any
guidance on rain barrels or
cistern specifications.
Line 41 - Number of buildings
with rain barrels/cisterns
expected to be installed. Enter
the number of existing directly
connected buildings where rain
barrels or cisterns are expected
to be installed over the
previously established planning
horizon.
Line 42 - Average volume
(gallons) of the rain
barrels/cisterns. Enter the
average volume in gallons of the
rain barrels and cisterns that will
be installed.
Line 43 - Average rain
barrel/cistern runoff reduction
rate. The runoff reduction
potential of a rain barrel or
cistern depends on the capacity
and how often it is emptied.
Select a runoff reduction rate
from Table 3 and enter it on
Line 43. The permittee can use
a runoff reduction rate that is
higher than those listed in Table
3 only if it is appropriately
documented.
Line 44 - Runoff to CSS
eliminated due to rain
barrel/cistern installation.
Multiply number of buildings
with rain barrels and cisterns
expected to be installed (Line
41) by the average volume
(gallons) of the rain barrels and
cisterns (Line 42) by the
average rain barrel and cistern
runoff reduction rate (Line 43).
Line 45- Rain barrel/cistern
runoff reduction volume (MG).
Divide runoff to CSS eliminated
because of rain barrel/cistern
installation (Line 44) by
1,000,000 to convert from
gallons to MG.
Line 46- Unit cost per rain
barrel/cistern capacity
(gallons). Unit costs for rain
barrels and cisterns vary by size
and type. Enter a cost per gallon
that reflects local conditions or
use the default value of $1.25
per gallon.
Line 47- Fraction of publicly
owned or subsidized rain
barrels/cisterns. Determine the
fraction of rain barrels and
cisterns being installed that are
to be publicly owned or partially
or wholly subsidized with public
funds. For private installations,
count only the portion of the rain
barrel or cistern cost that is
publicly funded (i.e., if a public
subsidy pays for 10 percent of a
typical installation, count only 10
percent of that installation)
Line 48- Estimated public
cost of cumulative rain
barrel/cistern installations.
Some of the costs of rain
barrels/cisterns will be borne by
private entities and will not be
borne by the permittee. To
determine the cost to the
permittee, multiply number of
rain barrels/cisterns expected to
be installed (Line 41) by the
average volume of each rain
barrel and cistern (Line 42) by
the unit cost per rain
barrel/cistern (Line 46) by the
fraction of publicly owned or
subsidized rain barrel/cistern
installations (Line 47).
Cumulative Runoff
Reduction Check
This section provides a check to
ensure that the number and
combination of green
infrastructure practices selected
above meet the retention
standard or goal set on Line 6.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 49 - Runoff reduction
volume (MG) derived from
retention standard. Enter from
Line 8.
Line 50- Runoff reduction
volume (MG) derived from
sum of individual practices.
Add Lines 14,22, 30,37, and
45.
Line 51 - Planning Check.
This calculation is meant to
serve as a check for the
permittee to show how realistic
it will be to achieve the runoff
retention standard or goal using
green infrastructure.
Divide runoff reduction volume
(MG) derived from sum of
individual practices (Line 50) by
runoff reduction volume (MG)
derived from retention standard
(Line 49). If this value is greater
than or equal to 1.00 and less
than 1.05, the number and
combination of selected green
infrastructure practices are
sufficient to meet the runoff
retention standard or goal.
If this value is less than 1.00,
either the runoff retention
standard or goal is set too high
or the number and combination
of selected green infrastructure
practices is too low. If the value
is greater than 1.05, either the
runoff retention standard is set
too low or the number and
combination of selected green
infrastructure practices is too
high. Adjust the values
associated with the runoff
retention standard or goal or the
green infrastructure practices
until the value falls into the
acceptable range if this is
possible.
Runoff Recalculation
Because the green
infrastructure practices
evaluated in the previous
sections of this schedule reduce
runoff before it gets to the
collection system, the volume of
runoff calculated in Schedule 4-
CSO VOLUME will need to be
recalculated.
Line 52 - Original volume of
runoff (MG). Enter the original
volume of runoff calculated in
Schedule 4-CSO VOLUME for
each sub-sewershed in the CSS
(Line 13 on Schedule 4-CSO
VOLUME. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 53 - Runoff reduction
volume (MG). Enter the runoff
reduction volume in MG
calculated using the retention
standard or goal for each sub-
sewershed (Line 8). If you are
using the electronic version of
the form, this value will have
been filled in automatically).
Line 54 - Revised volume of
runoff (MG). Subtract the runoff
reduction volume (MG) on Line
53 from the original volume of
runoff (MG) on Line 52 to obtain
the revised runoff volume.
Line 55 - Runoff reduction
factor. Divide the revised runoff
volume on Line 54 by the
original runoff volume on Line
52 to obtain the runoff reduction
factor.
Peak Wet-Weather Flow
The relationship between the
original runoff volume and the
revised runoff volume (the runoff
reduction factor) is used to
modify the peak wet-weather
flow rates that influence the
overflow fraction and diversion
fraction that was calculated in
Schedule 4-CSO VOLUME.
Line 56 - Original peak runoff
rate (MGD). Enter the original
peak runoff rate (MGD)
calculated in Schedule 4-CSO
VOLUME for each sub-
sewershed in the CSS (Line 6
on Schedule 4-CSO VOLUME.
If you are using the electronic
version of the form, this value
will have been filled in
automatically).
Line 57 - Revised peak runoff
rate (MGD). Multiply the original
peak runoff rate (MGD) on Line
56 by the runoff reduction factor
on Line 55 to obtain a revised
peak runoff rate for each sub-
sewershed.
Line 58 - Dry-weather flow
rate (MGD). Enter the dry-
weather flow rate (MGD) from
Schedule 4-CSO VOLUME for
each sub-sewershed in the CSS
(Line 7 on Schedule 4-CSO
VOLUME. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 59 - Revised peak flow
rate (MGD). The peak flow rate
is the sum of the peak runoff
rate and dry-weather flow in
MGD. Add Lines 57 and 58 and
enter the sum for each sub-
sewershed area on Line 59.
Revised Overflow
Line 60 - CSO hydraulic
control capacity (MGD). Enter
the CSO hydraulic control
capacity in MGD for each CSO
sub-sewershed area on Line 60
(Line 11 b on FORM LTCP-EZ. If
you are using the electronic
version of the form, this value
will have been filled in
automatically).
Line 61 - Revised ratio of
CSO hydraulic control
capacity to peak flow rate.
Enter 1.0 on Line 61 if Line 60 is
greater than Line 59. Otherwise,
divide Line 60 by Line 59 and
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
enter the quotient (result) on
Line 61.
Line 62 - Revised overflow
fraction of combined sewage.
This is a recalculation of the
overflow fraction of combined
sewage within the sub-
sewershed. It is based on the
ratio of CSO hydraulic control
capacity to peak flow rate. Take
the square of (1 minus the value
on Line 61) and enter it on Line
62. For example, if the ratio of
CSO hydraulic control capacity
to peak flow rate on Line 10 is
0.15, the overflow fraction is (1
- 0.15)2, or 0.7225.
Line 63 - Volume of dry-
weather flow (MG). This is the
total dry-weather flow in MG for
the 24-hour design rainfall
period. It was previously
calculated in Schedule 4-CSO
VOLUME (Line 14 on Schedule
4-CSO VOLUME. If you are
using the electronic version of
this form, this value will have
been filled in automatically).
Line 64 - Revised total
volume of flow (MG). This is
the total volume of flow in MG
within each sub-sewershed for
the 24-hour design rainfall
period. Add Lines 54 and 63
and enter the sum on Line 64.
Line 65 - Revised volume of
excess combined sewage at
individual CSO hydraulic
controls during 24-hour
rainfall period. This is the
recalculated CSO volume at the
CSO hydraulic control and is the
combined sewage that exceeds
the diversion capacity
determined by the CSO
hydraulic control in each sub-
sewershed. Multiply Line 62 by
Line 64 and enter the product
on Line 65.
Revised Diversion
Line 66 - Diversion fraction of
combined sewage. This is the
fraction of runoff within each
sub-sewershed that is collected
and diverted to the WWTP over
the 24-hour design storm
period. The diversion fraction is
based on the ratio of CSO
hydraulic control capacity to
peak flow rate and conveyance.
It was previously calculated in
Schedule 4-CSO VOLUME.
Determine the diversion fraction
of combined sewage again
using the revised value on Line
61 along with Table 2, and enter
it on Line 66.
Line 67 - Revised volume of
runoff diverted to WWTP. This
is the recalculated volume of
runoff within each sub-
sewershed that is collected and
diverted to the WWTP over the
24-hour design storm period.
Multiply Line 54 by Line 66 and
enter the product on Line 67.
Line 68 - Revised total
volume of combined sewage
conveyed to WWTP during 24-
hour rainfall period (MG). Add
Lines 63 and 67 and enter the
sum on Line 68.
Revised Conveyance
Line 69 - Revised peak rate of
collected combined sewage
diverted to the WWTP within
sub-sewersheds. Identify the
smaller of Line 59 and Line 60
within each sub-sewershed and
enter the peak rate in MGD on
Line 69.
Line 70 - Revised peak rate of
combined sewage conveyed
to WWTP (MGD). This peak
rate represents the sum of the
peak rates of collected
combined sewage diverted to
the WWTP from individual sub-
sewersheds in MGD. Add up
sub-sewershed values on Line
69 and enter the sum on Line
70.
Line 71 - Peak rate of sewage
from non-CSO areas (MGD).
Enter the peak rate of sewage
conveyed to the WWTP from
non-CSO areas in the
community in MGD on Line 71.
(Line 22 on Schedule 4-CSO
VOLUME. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 72 - Peak rate of sewage
from satellite communities
(MGD). Enter the peak rate of
sewage conveyed to the WWTP
from satellite communities in
MGD on Line 72. (Line 23 on
Schedule 4-CSO VOLUME. If
you are using the electronic
version of the form, this value
will have been filled in
automatically).
Line 73 - Revised peak rate of
sewage conveyed to the
WWTP (MGD). This is the
recalculated peak rate of
sewage flow in MGD received at
the WWTP from the CSS and
adjacent non-CSO areas in the
community and satellite
communities. Add Lines 70, 71
and 72 and enter the sum on
Line 73.
Treatment
Line 74 - Primary treatment
capacity (MGD). Enter the
primary treatment capacity in
MGD on Line 74 (Line 4a on
FORM LTCP-EZ. If you are
using the electronic version of
the form, this value will have
been filled in automatically).
Line 75 - Revised ratio of
primary treatment capacity to
peak rate of sewage conveyed
to WWTP. Enter 1.0 on Line 75
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
if Line 74 is greater than Line
73. Otherwise, divide Line 74 by
Line 73 and enter the quotient
(result) on Line 75.
Line 76 - Revised fraction of
combined sewage untreated
at WWTP. This is the fraction of
sewage delivered to the WWTP
during the 24-hour rainfall
period that does not received
primary treatment. It is based on
the ratio of primary treatment
capacity to peak rate of sewage
conveyed to the WWTP. It was
previously calculated in
Schedule 4-CSO VOLUME.
Recalculate it by taking the
square of (1 minus the value on
Line 75) and enter it on Line 76.
For example, if the ratio of
primary treatment capacity to
peak rate of sewage conveyed
to the WWTP on Line 26 is 0.80,
the overflow fraction is (1 -
0.80)2, or 0.04.
Line 77 - Revised sum of
combined sewage conveyed
to WWTP during 24-hour
rainfall period (MG). Add up
the sub-sewershed values in
MG on Line 68 and enter the
sum on Line 77.
Line 78 - Volume of sewage
from non-CSO areas during
24-hour rainfall period (MG).
The volume of sewage from
non-CSO areas during the 24-
hour rainfall period was
previously calculated in
Schedule 4-CSO VOLUME.
Enter Line 30 from Schedule 4-
CSO VOLUME. If you are using
the electronic version of the
form, this value will have been
filled in automatically.
Line 79 - Volume of sewage
from satellite communities
during 24-hour rainfall period
(MG). The volume of sewage
from satellite communities
during the 24-hour rainfall
period was previously calculated
in Schedule 4-CSO VOLUME.
Enter Line 32 from Schedule 4-
CSO VOLUME. If you are using
the electronic version of the
form, this value will have been
filled in automatically.
Line 80 - Revised total
volume of sewage during 24-
hour rainfall event (MG). Add
Lines 77, 78, and 79 and enter
the volume in MG on Line 80.
Line 81 - Revised volume of
combined sewage untreated
at WWTP (MG). This is the
recalculated CSO volume at the
WWTP. If Line 74 is greater
than Line 73, enter 0.0 on Line
81. Otherwise, multiply Line 80
by Line 76 and enter the volume
in MG on Line 81.
CSO Volume Recalculation
The revised CSO volume that
needs to be stored, treated or
eliminated is recalculated.
Those CSO volumes are
identified within individual sub-
sewersheds at CSO hydraulic
controls, and at the WWTP.
Line 82 - Revised volume of
combined sewage overflows
at CSO outfalls (MG). This
represents the volume of excess
combined sewage in MG that is
discharged at CSO outfalls.
Sum all sub-sewershed volumes
in MG on Line 65 and enter the
value on Line 82
Line 83 - Revised volume of
combined sewage overflow at
WWTP (MG). This represents
the volume of excess combined
sewage in MG that is collected
and conveyed to the WWTP that
does not receive at least
primary treatment. Enter the
value from Line 81 on Line 83.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Instructions: Schedule 5B - CSO Network and WWTP Control
(Network and WWTP Controls)
Schedule 5A focused on controls that reduce runoff before entering the collection system. Schedule 5B
focuses on CSO controls within the collection system.
Three general methods for pipe network CSO control are considered in this schedule. They are as
follows:
Conveyance and treatment at the WWTP
Sewer separation
Off-line storage
Permittees should evaluate these controls in the order presented. Using more than one CSO control in an
LTCP is common. Using other controls not described herein is valid but would have to be documented
separately in a similar effort to what is presented in this schedule.
Both Schedule 5A and 5B - CSO CONTROL should be used iteratively to identify the most appropriate
mix of CSO controls with respect to CSO reduction and cost. For Schedule 5B-CSO NETWORK AND
WWTP CONTROL, the volumes of combined sewage at CSO outfalls and at the WWTP that need to be
controlled (Lines 82 and 83 on Schedule 5A - CSO RUNOFF CONTROL) serve as the reduction targets
for this schedule.
Conveyance and Treatment at the WWTP
Maximizing treatment at the existing WWTP is emphasized in the CSO Control Policy, and it is an
important feature of many LTCPs. In some CSO communities, combined sewage conveyed to the WWTP
exceeds the primary capacity of the WWTP. The presence of this condition is assessed in Schedule 4 -
CSO VOLUME, and the use of additional storage or treatment capacity at the WWTP is included in this
schedule. The schedule is not set up to evaluate the opposite situation, where the WWTP has excess
primary treatment capacity. Permittees with that situation could make use of available primary treatment
capacity at the WWTP by adjusting CSO hydraulic controls, increasing interceptor conveyance capacity,
or increasing pumping capacity. This analysis must be documented separately and attached to this
schedule.
Sewer Separation
Sewer separation is the practice of replacing the single pipe system of a CSS with separate pipes for
sanitary and stormwater flows. Sewer separation is highly effective and widely used. However, it can be
expensive relative to other CSO controls. While sewer separation can be implemented on a broad basis
across an entire CSS, it is most often implemented in selective portions of the CSS where localized
circumstances make it less disruptive and more economical. Note that while sewer separation can help to
mitigate CSO issues, it can increase the burden on the storm sewer system.
Off-Line Storage
Off-line storage is a phrase used to describe facilities that store combined sewage in added tanks, basins,
tunnels or other structures. During dry weather, wastewater is passed around, not through, off-line
storage facilities. During wet weather, combined sewage flows are diverted from the CSS to the off-line
facility by gravity drainage or with pumps. The stored combined sewage is temporarily detained in the
storage facility and returned to the CSS once conveyance and treatment capacity become available.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Off-line storage facilities can be expensive relative to other CSO controls. Near-surface storage facilities
probably have the most utility in small communities because space could be more readily available than
in large cities. Design, construction and O&M costs are less with near-surface storage than with deep
underground tanks and tunnels.
Cost of CSO Control
Generalized cost information for CSO controls is provided. Background information or the derivation of
this cost information is in Appendix C. Permittees should realize that CSO control costs are highly
variable and dependent on site-specific conditions. Using actual or local cost data is always preferable
where it is available. Permittees should verify the appropriateness of default cost values where they are
used. Permittees should also note that cost estimates are for the construction of facilities. Additional
operational costs and treatment costs are not expressly included in cost estimates for controls where
primary capacity is added or where combined sewage is temporarily stored on-site at the WWTP or off-
line and released for treatment following the rainfall event.
Summary
More information is at EPA's CSO control technology description at
http://www.epa.gov/npdes/pubs/csossoRTC2004 AppendixL.pdf.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Conveyance and Treatment
at the WWTP
This section of Schedule 5 -
CSO CONTROL considers
conveyance and treatment of
combined sewage at the
WWTP. Additional treatment or
storage can be added at the
WWTP if the volume of
combined flow to the WWTP
exceeds primary capacity.
Conversely, excess primary
capacity at the WWTP provides
an opportunity to maximize flow
of combined sewage to the
WWTP for treatment.
If you are not evaluating control
alternatives at the WWTP, skip
to Line 10.
Line 1 - Peak rate of sewage
conveyed to WWTP (MGD).
Enter the peak rate of sewage
conveyed to the WWTP in MGD
on Line 1 (If Schedule 5A-CSO
RUNOFF CONTROL has been
completed, use Line 73 on
Schedule 5A-CSO RUNOFF
CONTROL. Otherwise use Line
24 on Schedule 4 - CSO
VOLUME. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Line 2 - Primary treatment
capacity (MGD). Enter the
primary treatment capacity in
MGD on Line 2 (Line 25 of
Schedule 4 - CSO VOLUME. If
you are using the electronic
version of the form, this value
will have been filled in
automatically).
Line 3 - Difference between
primary treatment capacity
and peak rate of sewage
conveyed to WWTP (MGD).
Enter the combined sewage
untreated at the WWTP in MGD
(Line 32 on Schedule 4 - CSO
VOLUME. If you are using the
electronic version of the form,
this value will have been filled in
automatically).
Untreated combined sewage at
the WWTP can be controlled by
adding additional treatment
capacity (Line 4) or by adding
storage (Line 7) to allow
collected combined sewage to
be retained temporarily until
treatment capacity becomes
available following the rainfall
event. Permittees can estimate
costs for both options and
determine which is most
appropriate for their facility.
Note: If Line 2 is greater than
Line 1, the difference represents
primary treatment capacity that
could be available for treatment
of combined sewage.
Maximizing flow to the WWTP
should be pursued under such
circumstances. This could be
done iteratively in Schedule 4 -
CSO VOLUME by adjusting
hydraulic control capacities or
assessed in worksheets to
supplement the Green LTCP-EZ
Template.
Line 4 - Additional primary
treatment capacity required
(MGD). Additional primary
treatment capacity can be
added to the system to treat the
combined flows that reach the
WWTP during wet weather. Line
3 represents the minimal
additional primary treatment
capacity that will be required to
treat the flows. Permittees can
either enter the value from Line
3 on Line 4 or enter a larger
number if they want to increase
primary treatment capacity even
further.
Line 5 - Unit cost of primary
treatment per MGD. The unit
cost of primary treatment varies
greatly. Enter a cost that reflects
local site-specific conditions, or
use the default value of
$2,000,000 per MGD.
Line 6 - Estimated cost of
new primary treatment
capacity at WWTP. Multiply the
unit cost on Line 5 by the
additional capacity required on
Line 4.
Line 7 - Volume of storage
required at WWTP (MG). The
volume of storage required is
determined by converting the
flow rate in MGD on Line 3 to a
volume in MG by multiplying
Line 3 by 24 hours. Enter this
value on Line 7.
Line 8 - Unit cost of
additional storage at WWTP.
The unit cost of storage varies
greatly. Enter a cost that reflects
local site-specific conditions, or
use the default value of
$1,000,000 per MG.
Line 9 - Estimated cost for
storage at WWTP. Multiply the
additional storage volume
required on Line 7 by the unit
cost on Line 8.
Sewer Separation
Sewer separation is the practice
of separating the single pipe
system of a CSS into separate
pipe systems for sanitary and
stormwater flows. Sewer
separation is widely used as a
CSO control. It is often applied
opportunistically in small
subareas to minimize disruption.
Some small communities also
invest in sewer separation on a
system-wide basis.
Line 10 - 24-hour design
rainfall (inches). Enter the 24-
hour design rainfall in inches on
Line 10 (Line 12 on Schedule 4
- CSO VOLUME. If you are
using the electronic version of
the form, this value will have
been filled in automatically).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 11- Sub-sewershed area
to be separated (acres). Enter
the area to be separated in each
sub-sewershed.
Line 12- Runoff coefficient of
area to be separated. Enter the
runoff coefficient entered on
Line 3 on Schedule 4 - CSO
VOLUME.
Line 13 - Runoff to CSS
eliminated due to sewer
separation (Gal.). Multiply
Lines 10, 11, and 12. Multiply
the product by 27,156 to convert
to gallons.
Line 14 - Volume reduction
(MG). Enter the volume
reduction achieved through
sewer separation. Divide Line
13 by one million.
Line 15 - Unit cost of sewer
separation per acre. The unit
cost of sewer separation is
highly variable. Estimates range
from less than $10,000 to more
than $200,000 per acre. Enter a
cost that reflects local site-
specific conditions.
Line 16 - Estimated cost of
sewer separation. Multiply the
number of acres to be
separated on Line 11 by the unit
cost on Line 15 and enter on
Line 16.
Off-Line Storage
The use of storage facilities to
store and attenuate peak
combined sewage flows is
widely used as a CSO control.
Off-line storage is the term used
to describe facilities that store
excess combined sewage in
tanks, basins, tunnels, or other
structures adjacent to the CSS.
Line 17 - Volume reduction to
be achieved with storage
(MG). Enter the proposed
volume of storage in each sub-
sewershed. This can be
established as the revised
volume of excess combined
sewage at individual CSO
hydraulic controls (Line 65 on
Schedule 5A - CSO VOLUME)
minus reductions achieved
through sewer separation.
Line 18 - Unit cost per MG of
storage. The unit cost of off-line
storage is highly variable and
ranges from less than $100,000
per MG to several million dollars
per MG. Enter a cost that
reflects local site-specific
conditions.
Line 19 - Estimated cost of
storage. Multiply Line 17 by
Line 18.
Summary of Controls and
Costs
The final CSO control
alternatives selected on this
schedule (and on supporting
analysis if used) represent the
CSO controls proposed for the
draft LTCP. The level of CSO
control proposed must be
consistent with the CSO
volumes determined to require
control on Line 23 and 24 of
Schedule 4 - CSO VOLUME.
Complete the following
summary of recommended CSO
controls and costs below and on
FORM GREEN LTCP-EZ.
Line 20 - Volume reduction
from CSO controls in sub-
sewersheds (MG). Add Lines
14 and 17.
Line 21- Cost of CSO controls
in sub-sewersheds. Add Lines
16 and 19.
Line 22 - Total volume
reduction in sub-sewersheds
(MG). Add up volumes across
Line 20.
Line 23 - Total cost of CSO
controls in sub-sewersheds.
Add up costs across Line 21.
Line 24 - Total cost of
additional treatment or
storage at WWTP. Add costs
on Line 6 and Line 9. If no
additional control is planned at
the WWTP, enter 0.0.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Instructions: Schedule 6 - CSO Financial Capability
The CSO Control Policy recognizes the need to address the relative importance of environmental and
financial issues when negotiating an implementation schedule for CSO controls. The ability of small
communities to afford CSO control influences control priorities and the implementation schedule.
Schedule 6 - CSO FINANCIAL CAPABILITY uses EPA's financial capability analysis approach to
develop a financial capability indicator for the community. The financial capability indicator is not to be
interpreted as an indicator of whether communities can afford CSO controls; rather, the financial
capability analysis is used as part of the planning process to determine the potential burden on the
community for implementing the controls over a specific schedule. Thus, one of the primary uses of the
financial capability analysis is in the negotiation of the CSO control implementation schedule. The
financial capability analysis standardizes the determination of financial burden by using standard big-
picture measures of a community's financial capability (e.g., property tax rates, median household
incomes, bond ratings). Once the overall financial capability is determined for a community, it can be
used in discussions with regulators to determine a realistic schedule for implementing CSO controls that
takes into account the financial burden to the community in implementing those controls.
This schedule presents a two-phase approach to assessing a permittee's financial capability. The first
phase identifies the combined effects of wastewater and CSO control costs on individual households. The
second phase examines the debt, socioeconomic, and financial conditions of a permittee. The results of
the two-phase analysis are combined in a Financial Capability Matrix.
Phase I determines a Residential Indicator. This indicator is the permittee's average costs per household
(CPH) for WWT and CSO controls as a percentage of the local median household income (MHI). It
reflects the residential share of current and planned WWT and CSO control needs to meet the
requirements of the CWA. A value for this indicator characterizes whether costs will impose a low, mid-
range, or high financial effect on residential users.
Phase II develops the permittee's Financial Capability Indicators. Six indicators are used to evaluate the
debt, socioeconomic and financial conditions that affect a permittee's financial capability to implement the
CSO controls. The indicators serve as the basis for a second phase analysis that characterizes the
permittee's financial capability as weak, mid-range, or strong. Schedule 6 - CSO FINANCIAL
CAPABILITY is based on Combined Sewer Overflows-Guidance for Financial Capability Assessment and
Schedule Development (EPA 1997).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Phase I Residential
Indicator
In Phase I of the analysis of the
permittee's financial capability, a
Residential Indicator is
calculated. The Residential
Indicator measures the financial
effect of the current and
proposed WWT and CSO
controls on residential users.
Developing this indicator starts
with determining the current and
proposed WWT and CSO
control costs per household
(CPH). Next, the service area's
CPH estimate and the median
household income (MHI) are
used to calculate the Residential
Indicator. Finally, the
Residential Indicator is
compared to financial impact
ranges to determine whether
CSO controls will produce a
possible high, mid-range, or low
financial impact on the
permittee's residential users.
The first step in developing the
CPH is to determine the
permittee's total WWT and CSO
costs by summing the current
costs for existing WWT
operations and the projected
costs for any proposed WWT
and CSO controls. The next
step is to calculate the
residential share of the total
WWT and CSO costs. The final
step is to calculate the CPH by
dividing the residential share of
total WWT and CSO costs by
the number of households in the
permittee's total wastewater
service area.
The permittee's latest financial
reports should be used to
develop the current WWT
operations costs. To comply
with accounting requirements,
most permittees develop a
combined statement of
revenues, expenses, and
changes in fund balance. Such
reports should be available
directly from the accounting or
financial departments in the
permittee's community, or, in
some states, from central
records kept by the state auditor
or other state offices (many
states conduct audits and
generate financial reports, i.e.,
balance sheet, statement of
revenues, expenses, changes in
fund balances, and statement of
cash flows, for each permittee).
Projected costs and the number
of households in the wastewater
service area should be available
through planning documents.
The U.S. Census Bureau Web
site (http://factfinder.census.gov/
home/saff/main.html? lang=en)
has data that can be used to
estimate the number of
households in a specific service
area. The Consumer Price
Index rate (CPI) is used in
several calculations. The value
used should be the average rate
for the previous 5 years. The
CPI is available through the
Bureau of Labor Statistics (BLS)
Web site at
http://www.bls.gov/cpi/.
The first step in developing the
Residential Indicator is to
determine the CPH of total
WWT and CSO costs. To do
this, permittees must first
calculate current WWT and
CSO costs, and then projected
costs of future WWT and CSO
treatment. These steps are
completed in Lines 1-17 below.
Current Costs
Current WWT costs are defined
as current annual wastewater
O&M expenses (excluding
depreciation) plus current
annual debt service (principal
and interest). That is a fair
representation of cash
expenses for current WWT
operations (expenses for funded
depreciation, capital
replacement funds, or other
types of capital reserve funds
are not included in current WWT
costs because they represent a
type of savings account rather
than an actual O&M expense).
Line 1 - Annual operations
and maintenance expenses
(excluding depreciation).
Enter the annual O&M costs
including all significant cost
categories, such as labor,
chemicals, utilities,
administration, and equipment
replacement. Do not include
depreciation.
Line 2 - Annual debt service
(principal and interest). Enter
the annual debt service paid on
WWT debts.
Line 3 - Current costs. Add
together the annual O&M
expenses from Line 1 and the
annual debt service from Line 2
and enter the sum on Line 3.
Projected Costs (Current
Dollars)
Estimates of projected costs are
made for proposed WWT
projects and for CSO controls.
Any concerns about including
specific proposed WWT projects
or CSO controls in the projected
costs, or the length of the
planning period, should be
discussed with the appropriate
NPDES permitting and
enforcement authorities. Such
costs should include projected
O&M expenses plus projected
debt service costs for any
proposed WWT and CSO
controls. The residential or
household costs (Lines 12-17)
exclude the portion of expenses
attributable to commercial,
governmental, and industrial
wastewater discharges. The
costs are adjusted to current
dollars (i.e., deflated).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 4 - Projected annual
operations and maintenance
expenses (excluding
depreciation). Enter the
projected annual WWT and
costs for new CSO-related
facilities.
Line 5 - Present value
adjustment factor. The present
value adjustment factor can be
calculated using the formula
presented below. The formula
converts projected costs to
current dollars using the
average annual national CPI
inflation rate (available from the
BLS Web site at
http://www.bls.gov/cpi/) for the
past 5 years. The CPI is used
as a simple and reliable method
of indexing projected WWT
costs and household income.
For example, if the most recent
5-year average CPI is 4 percent,
and the projected annual O&M
and debt service costs will begin
in 2 years, calculate the
adjustment factor as follows:
Adjustment Factor =
1 _ =
borrowing term of the permittee.
Calculate the factor using the
following
formula:
CPI)
1
years
= .925
(1 + .04
Line 6 - Present value of
projected costs. Multiply the
projected annual O&M
expenses on Line 4 by the
present value adjustment factor
on Line 5 and enter the result on
Line 6.
Line 7 - Projected costs. Enter
the projected debt costs for the
proposed WWT projects and
CSO controls on Line 7.
Line 8 - Annualization factor.
Enter an annualization factor
(AF) that reflects the local
borrowing interest rate (IR) and
AF=
IR
+IR)years-<\ +
Line 9 - Projected annual
debt service (principal and
interest). Multiply the projected
debt cost on Line 7 by the
annualization factor on Line 8,
and enter the result on Line 9.
Line 10 - Projected costs. Add
the present value of projected
costs on Line 6 to the projected
annual debt service on Line 9,
and enter the result on Line 10.
Line 11 - Total current and
projected WWT and CSO
costs. Add the current costs on
Line 3 to the projected costs on
Line 10. Enter the result on Line
11.
Cost Per Household
Line 12 - Residential WWT
flow (MGD). Enter the portion of
wastewater flow (including I/I) in
MGD attributable to residential
users.
Line 13 - Total WWT flow
(MGD). Enter the total
wastewater flow at the
WWTPinMGD.
Line 14 - Fraction of total
WWT flow attributable to
residential users. Divide the
residential flow on Line 12 by
the total flow on Line 13 and
enter the result on Line 14. The
result should be between 0
andl.
Line 15 - Residential share of
total WWT and CSO costs.
Multiply the total current and
projected WWT and CSO costs
on Line 1 1 by the fraction of
total WWT flow attributable to
residential users on Line 14,
and enter the result on Line 15.
Line 16- Number of
households in service area.
Enter the number of households
associated with the residential
flow.
Line 17 - Cost per household
(CPH). Calculate the CPH by
dividing the residential share of
total WWT and CSO costs on
Line 15 by the number of
households in the service area
on Line 16. Enter the result on
Line 17.
Median Household Income
(MHI)
The second step in developing
the Residential Indicator is to
determine the adjusted MHI for
the permittee's entire
wastewater service area.
MHI is available for most
communities from the latest
census. In the few cases where
a local jurisdiction's MHI is not
available, the surrounding
county's MHI might be sufficient.
Each state has a state data
center that serves as a local
source of census data for public
use.
Line 18 - Census Year MHI.
Enter the MHI value from the
most recent census year for the
service area. The Census
Bureau's designated MHI areas
generally encompass most
permittees' service areas. If the
permittee's service area
includes more than one
jurisdiction, a weighted MHI for
the entire service area could be
needed. Additional instructions
on developing a weighted MHI
is in EPA's previously
referenced Combined Sewer
OverflowsGuidance for
Financial Capability Assessment
and Schedule Development.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 19 - MHI adjustment
factor. The MHI adjustment
factor converts the MHI from the
latest census year to current
dollars on the basis of the CPI
inflation rate from the latest
census year to the present. The
MHI adjustment factor can be
taken from Table CAF-3 (from
EPA 1997) or calculated using
the formula below:
MHI Adjustment Factor =
f-\ + pp ^Current Year -Census Year
For example, if a permittee's
MHI was taken for the 1990
census year, the average
annual CPI since 1990 was 4
percent and the current year is
1992, the adjustment factor
would be 1.0816:
MHI Adjustment Factor =
(1+.04)1992-1990=1.0816
Line 20 - Adjusted MHI.
Multiply the Census Year MHI in
Line 18 by the MHI adjustment
factor in Line 19, and enter the
result in Line 20.
Residential Indicator
Line 21 - Annual WWT and
CSO control CPH as a percent
of adjusted MHI. Divide the CPH
on Line 17 by the adjusted MHI
in Line 20, and then multiply by
100. Enter the result on Line 21.
Line 22 - Residential
Indicator. Enter the appropriate
Financial Impact according to
the value of CPH as percent
MHI in Line 21. The appropriate
Financial Impacts are defined
below:
CPH as % of
MHI
<1
1 to 2
>2
Financial
Impact
Low
Mid-Range
High
Analyzing the Residential
Indicator
The Residential Indicator is
used to help permittees, EPA,
and state NPDES authorities to
negotiate a reasonable and
workable long-term CSO and
WWT control schedules.
The Residential Indicator is
used with the financial impact
ranges that reflect EPA's
previous experience with water
pollution control programs.
When the Residential Indicator
is less than 1, between 1 and 2,
and greater than 2, the financial
impact on residential users to
implement the CSO and WWT
controls will be characterized as
low, mid-range, and high,
respectively. Unless there are
significant weaknesses in a
permittee's financial and
socioeconomic conditions,
second phase reviews for
permittees that have a low
residential indicator score (CPH
as percent of MHI less than 1)
are unlikely to result in longer
implementation schedules.
In situations where a permittee
believes that there are unique
circumstances that affect the
conclusion of the first phase, the
permittee can submit
documentation of its unique
financial conditions to the
appropriate state NPDES and
EPA authorities for
consideration.
Phase II Permittee
Financial Capability
Indicators
In Phase II of the analysis of the
permittee's financial capability,
selected indicators are
assessed to evaluate the
financial capability of the
permittee. Such indicators
examine the permittee's debt
burden, socioeconomic
conditions, and financial
operations. The second-phase
review examines three general
categories of financial capability
indicators for the permittee.
Debt Indicators - Assess
current debt burden of the
permittee or the communities
in the permittee's service
area and their ability to issue
additional debt to finance the
WWT and CSO control
costs. The indicators
selected for this purpose are
as follows:
o Bond Ratings (General
Obligation or Revenue
Bond Fund or both)
o Overall Net Debt as a
Percent of Full Market
Property Value
Socioeconomic Indicators
-Assess the general
economic well-being of
residential users in the
permittee's service area. The
indicators selected for this
purpose are as follows:
o Unemployment Rate
o MHI
Financial Management
Indicators - Evaluate the
permittee's overall ability to
manage financial operations.
The indicators selected for
this purpose are as follows:
o Property Tax Revenue
Collection Rate
o Property Tax Revenues
as a Percent of Full
Market Property Value
Even though the financial
capability analysis reflects
current conditions, pending
changes in the service area
should be considered when
developing the second phase
indicators. For example, if the
current unemployment rate is
high, but there is a new industry
opening that will stimulate
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
economic growth, the
unemployment indicators for the
service area would need to be
modified to reflect the projected
impact of the new plant. The
permittee should submit
documentation of such
conditions to the appropriate
EPA and state NPDES
authorities for consideration.
When the permittee is a sanitary
district, sewer authority or
similar entity, the second phase
indicators related to property
values and tax revenues might
not be applicable. In such
circumstances, the permittee
can simply use the remaining
indicators or submit other
related documentation that will
help assess its financial
capability to implement the CSO
controls.
Debt Indicators
The debt indicators described
below are used to assess the
current debt burden conditions
and the ability to issue new
debt. Such indicators are the
bond rating and overall net debt
as a percent of full market
property value (MPV). When
those indicators are not
available for the permittee, other
financial data that illustrates
debt burden and debt issuing
capacity can be used to assess
the permittee's financial
capability in this area.
Bond Rating
Recent bond ratings summarize
a bond rating agency's
assessment of a permittee's or
community's credit capacity.
General obligation (G.O.) bonds
are bonds issued by a local
government and repaid with
taxes (usually property taxes).
They are the primary long-term
debt funding mechanism in use
by local governments. G.O.bond
ratings reflect financial and
socioeconomic conditions
experienced by the community
as a whole.
Revenue bond ratings, in
comparison, reflect the financial
conditions and management
capability of the wastewater
utility. They are repaid with
revenues generated from user
fees. Revenue bonds are
sometimes referred to as water
or sewer bonds. In some cases,
the bonds might have been
issued by the state on behalf of
local communities.
Bond ratings normally
incorporate an analysis of many
financial capability indicators.
Such analyses evaluate the
long-term trends and current
conditions for the indicators.
The ultimate bond ratings reflect
a general assessment of the
current financial conditions.
However, if security
enhancements such as bond
insurance have been used for a
revenue bond issue, the bond
rating might be higher than
justified by the local conditions.
Many small and medium-sized
communities and permittees
have not used debt financing for
projects and, as a result, have
no bond rating. The absence of
bond rating does not indicate
strong or weak financial health.
When a bond rating is not
available, this indicator can be
excluded from the financial
analysis.
Municipal bond reports from
rating agencies (e.g., Moody's
Bond Record, Standard &
Poor's Corporation) provide
recent ratings.
Line 23a - Date of most
recent general obligation
bond. Enter the date of
issuance for the permittee's
most recent G.O. bond.
Line 23b - Rating agency.
Enter the name of the rating
agency for the most recent G.O.
bond.
Line 23c - Rating. Enter the
rating provided by the rating
agency for the most recent G.O.
bond.
Line 24a - Date of most
recent revenue (water or
sewer) bond. Enter the date of
issuance for the permittee's
most recent revenue obligation
bond.
Line 24b - Rating agency.
Enter the name of the rating
agency for the most recent
revenue bond.
Line 24c - Bond insurance.
Indicate whether bond
insurance was required.
Line 24d - Rating. Enter the
rating provided by the rating
agency for the most recent
revenue bond.
Line 25 - Bond rating. For the
more recent of the bonds
entered in Lines 23 and 24,
enter a bond rating benchmark
according to the schedule
below:
If the rating agency is Moody's
Investor Services, enter Strong
for a rating of AAA, AA, or A;
Mid-Range for a rating of Baa;
and Weak otherwise.
If the rating agency is Standard
& Poor's, enter Strong for a
rating of AAA, AA, or A; Mid-
Range for a rating of BBB; and
Weak otherwise.
Note: this information is also
used in Line 48a of Schedule 6-
FINANCIAL CAPABILITY
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Overall Net Debt
Overall net debt is debt repaid
by property taxes in the
permittee's service area. It
excludes debt that is repaid by
special user fees (e.g., revenue
debt). This indicator provides a
measure of the debt burden on
residents in the permittee's
service area, and it assesses
the ability of local governmental
jurisdictions to issue additional
debt. Net debt includes the debt
issued directly by the local
jurisdiction and debt of
overlapping entities such as
school districts. This indicator
compares the level of debt owed
by the service area population
with the full market value of real
property used to support that
debt, and it serves as a
measure of financial wealth in
the permittee's service area.
Line 26 - Direct net debt (G.O.
bonds excluding double-
barreled bonds). Enter the
amount of G.O. debt
outstanding that is supported by
the property in the permittee's
service area. G.O. bonds are
secured by the full faith and
credit of the community and are
payable from general tax
revenues. This debt amount
excludes G.O. bonds that are
payable from some dedicated
user fees or specific revenue
source other than the general
tax revenues. These G.O.
bonds are called double-
barreled bonds.
Debt information is available
from the financial statements of
each community. In most cases,
the most recent financial
statements are on file with the
state (e.g., state auditor's
office). Overlapping debt might
be provided in a community's
financial statements. The
property assessment data
should be readily available
through the community or the
state's assessor office. The
boundary of most permittees'
service areas generally
conforms to one or more
community boundaries.
Therefore, prorating community
data to reflect specific service
area boundaries is not normally
necessary for evaluating the
general financial capability of
the permittee.
Line 27 - Debt of overlapping
entities (proportionate share
of multijurisdictional debt).
Calculate the permittee's service
area's share of any debt from
overlapping entities using the
process described. For each
overlapping entity, do the
following:
1. Identify the total amount of
tax-supported outstanding
debt for each overlapping
entity in Column A and enter
it in Column B. Money in a
sinking fund is not included
in the outstanding debt
because it represents
periodic deposits into an
account to ensure the
availability of sufficient
monies to make timely debt
service payments.
2. Identify the percentage of
each overlapping entity's
outstanding debt charged to
persons or property in the
permittee's service area and
enter it in Column C. The
percentage is based on the
estimated full market value of
real property of the
respective jurisdictions.
3. Multiply the total outstanding
debt of each overlapping
entity by the percentage
identified for the permittee's
service area (Column B x C).
4. Add the figures and enter
them in Column D to arrive at
the total overlapping debt for
the permittee's service area.
Line 28 - Overall net debt.
Add the direct net debt on Line
26 to the overlapping entities
debt on Line 27.
Line 29 - Full market property
value (MPV). The MPV reflects
the full market value of property
in the permittee's service area.
It is possible that the tax
assessed property value will not
reflect the full market value. This
occurs when the tax
assessment ratio is less than
one. In such cases, the full MPV
is computed by dividing the total
tax assessment value by the
assessment ratio (the
assessment ratio represents the
percentage of the full market
value that is taxed at the
established tax rate), For
example, if the assessed value
is $1,000,000 and the
assessment ratio is 50 percent,
the full market value of real
property is $1,000,000 / 0.50 =
$2,000,000.
Line 30 - Overall net debt as a
percent of full market value of
property. Divide Line 28 by
Line 29, then multiply by 100,
and enter the value on Line 30.
Line 31 - Net debt
benchmark. If the value in Line
30 is greater than 5, enter
Weak. If the value is less than 2,
enter Strong. Otherwise, enter
Mid-Range. Note: this
information is also used in Line
48b of Schedule 6- FINANCIAL
CAPABILITY
Socioeconomic Indicators
The socioeconomic indicators
are used to assess the general
economic well-being of
residential users in the
permittee's service area. The
indicators used to assess
economic conditions are
unemployment rate and MHI.
When the permittee has
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
additional socioeconomic data,
it might want to submit the data
to the appropriate EPA and
state NPDES authorities to
facilitate a better understanding
of the permittee's unique
economic conditions. Several
examples of this type of
socioeconomic data would be
poverty rate, population growth,
and employment projections.
Unemployment Rate
The unemployment rate is
defined as the percent of a
permittee's service area
residents on the unemployment
rolls. The BLS maintains current
unemployment rate figures for
municipalities and counties with
more than 25,000 people.
National and state
unemployment data are also
available for comparison
purposes.
Line 32 - Unemployment rate
for permittee service area.
Enter the unemployment rate for
the permittee's service area. Be
sure to use the correct value to
represent the percentage. The
spreadsheet interprets the
number entered as that percent,
so the permittee would enter 6
for 6 percent, and so on. If doing
the calculations by hand, use
0.06 for6 percent. Please
indicate the source in the line
below the question.
Line 33 - Unemployment rate
for permittee's county. Enter
the unemployment rate for the
permittee's county. Be sure to
use the correct value to
represent the percentage. The
spreadsheet interprets the
number entered as that percent,
so the permittee would enter 6
for 6 percent, and so on. If doing
the calculations by hand, use
0.06 for6 percent. This will be
used only when the
unemployment rate for a
permittee's service area is not
available. Indicate the source in
the line below the question.
Line 34 - Average national
unemployment rate. Enter the
current average national
unemployment rate. Be sure to
use the correct value to
represent the percentage. The
spreadsheet interprets the
number entered as that percent,
so the permittee would enter 6
for 6 percent, and so on. If doing
the calculations by hand, use
0.06 for 6 percent. Indicate the
source of this number on the
line below the question.
Line 35 - Unemployment Rate
Benchmark. If the local
unemployment rate is 1 percent
or more below the national
average, enter Strong. If the
local rate is 1 percent or more
above the national average,
enter Weak. Otherwise, enter
Mid-Range.
For example, if the national
average unemployment rate is 6
percent and the unemployment
rate for the permittee service
area is 7 percent, the
unemployment rate benchmark
would be weak. If the
unemployment rate for the
permittee service area is 5
percent, the unemployment rate
benchmark would be strong.
Note: This information is also
used in Line 48c of Schedule 6-
FINANCIAL CAPABILITY.
Median Household Income
MHI is defined as the median
amount of total income dollars
received per household during a
calendar year in an area. It
serves as an overall indicator of
community earning capacity.
Line 36 - Median household
income - permittee. Copy the
value already entered in Line
20.
Line 37 - Census Year
national MHI. Enter the most
recent census value for National
MHI. The national average MHI
in 2004 was $44,389 (Author
year)(http://www.census.gov/
Press-Release/www/releases/
archives/income_wealth/005647
.html).
Line 38 - MHI adjustment
factor. Copy the value from
Line 19.
Line 39 - Adjusted MHI.
Multiply the national MHI from
Line 37 by the MHI adjustment
factor in Line 38.
Line 40 - MHI Benchmark. If
the permittee MHI in Line 36 is
less than 75 percent of the
adjusted national MHI in Line
39, enter Weak. If the permittee
MHI is more than 125 percent of
the adjusted national MHI, enter
Strong; otherwise, enter Mid-
Range. Note: this information is
also used in Line 48d of
Schedule 6-AFFORDABILTY.
Financial Management
Indicators
The financial management
indicators used to evaluate a
permittee's financial
management ability is property
tax revenue as a percent of full
MPV and property tax revenue
collection rate.
Property Tax Revenues as a
Percent of Full MPV
This indicator can be referred to
as the property tax burden
because it indicates the funding
capacity available to support
debt on the basis of the
community's wealth. It also
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
reflects the effectiveness of
management in providing
community services.
The property assessment data
should be readily available
through the community or the
state's assessor office (see
instructions for Line 29).
Property tax revenues are
available in communities' annual
financial statements.
Occasionally, the assessment
and tax revenue data of
communities partially serviced
by the permittee may need to be
prorated to provide a clearer
picture of the permittee's
property tax burden.
Line 41 - Full market value of
real property. Copy the value
from Line 29.
Line 42 - Property tax
revenues. Enter the most
recent year's property tax
revenue. General fund revenues
are primarily property tax
receipts.
Line 43 - Property tax
revenues as a percent of full
MPV. Divide Line 42 by Line 41,
then multiply by 100, and enter
the result on Line 43.
Line 44 - Property Tax
Benchmark. If the value in Line
43 is above 4 percent, enter
Weak. If the value is below 2
percent, enter Strong.
Otherwise, enter Mid-Range.
Note: this information is also
used in Line 48e of Schedule 6-
FINANCIAL CAPABILITY .
Property Tax and
Collection Rate
The property tax revenue
collection rate is an indicator of
the efficiency of the tax
collection system and the ability
of the community to support the
tax levels.
Property taxes levied can be
computed by multiplying the
assessed value of real property
by the property tax rate, both of
which are available from a
community's financial
statements or the state
assessor's office. Property tax
revenues are available in
communities' annual financial
statements. Occasionally, the
assessment and tax revenue
data of communities partially
serviced by the permittee might
have to be prorated to provide a
clearer picture of the permittee's
property tax revenue collection
rate.
Line 45 - Property taxes
levied. Enter on Line 45 the
property taxes levied.
Line 46 - Property tax
revenue collection rate. Divide
Line 42 by Line 45, and then
multiply by 100 to present the
collection rate as a percentage.
Enter the value on Line 46.
Line 47 - Collection Rate
Benchmark. If the value in Line
46 is below 94, enter Weak. If
the value is above 98, enter
Strong. Otherwise, enter Mid-
Range. Note: this information is
also used in Line 48f of
Schedule 6-AFFORDABILTY.
Matrix Score: Analyzing
Permittee Financial
Capability Indicators
This section describes how the
indicators in the second phase
can be used to generate an
overall picture of a permittee's
financial capability. The
indicators are compared to
national benchmarks to form an
overall assessment of the
permittee's financial capability
and its effect on implementation
schedules in the LTCP or on
long-term plans for WWT.
In situations where a permittee
has unique circumstances that
could affect financial capability,
the permittee can submit
documentation of the unique
financial conditions to the
appropriate EPA and state
NPDES authorities for
consideration. The purpose of
additional information is to
clarify unique circumstances
that are not adequately
represented by the overall
scores of the selected
indicators. An example of a
unique financial situation might
be where a state or community
imposes restrictions on the
property taxes that are used to
fund sewer service.
Line 48 - Scoring of Financial
Capability Benchmarks. For
each benchmark completed in
this form, enter the benchmark
and the corresponding score
(Weak = 1, Mid-Range = 2,
Strong = 3), then sum the
scores and enter the value on
Line 48g. Each line is described
below.
Line 48a - Bond Rating. Enter
the bond rating on Line 48a
(Line 25 on Schedule 6 -
FINANCIAL CAPABILITY. If you
are using the electronic version
of the form, this value will have
been filled in automatically).
Line 48b - Net Debt. Enter the
net debt on Line 48b (Line 31
on Schedule 6 - FINANCIAL
CAPABILITY. If you are using
the electronic version of the
form, this value will have been
filled in automatically).
Line 48c - Unemployment
Rate. Enter the unemployment
rate on Line 48c (Line 35 on
Schedule 6 - FINANCIAL
CAPABILITY. If you are using
the electronic version of the
form, this value will have been
filled in automatically).
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Line 48d - Median Household
Income. Enter the MHI on Line
48d (Line 40 on Schedule 6 -
FINANCIAL CAPABILITY. If you
are using the electronic version
of the form, this value will have
been filled in automatically).
Line 48e - Property Tax. Enter
the property tax on Line 48e
(Line 44 on Schedule 6 -
FINANCIAL CAPABILITY. If you
are using the electronic version
of the form, this value will have
been filled in automatically).
Line 48f- Collection Rate.
Enter the collection rate on Line
48f (Line 47 on Schedule 6 -
FINANCIAL CAPABILITY. If you
are using the electronic version
of the form, this value will have
been filled in automatically).
Line 48g - Sum. Enter the total
by adding 48a through 48f
together.
Line 49 - Permittee indicators
score. Divide the result in Line
48g by the number of
benchmarks completed to
determine the average financial
capability score.
Line 50 - Permittee Financial
Capability Indicators
Descriptor. If the value in Line
49 is less than 1.5, enter Weak.
If the value is greater than 2.5,
enter Strong. Otherwise, enter
Mid-Range.
Line 51 - Permittee
Residential Indicator
Benchmark. Copy from Line
22.
Line 52 - Financial Capability.
Using Table CAF-4, cross-index
the Financial Capability
benchmark result in Line 50 with
the Residential Indicator
benchmark result in Line 51 to
determine overall financial
capability.
Table CAF-4. Financial capability
Permittee capability
(socioeconomic, debt,
and financial indicators)
Weak
Mid-Range
Strong
Residential(CPH as %MHI)
Low
Medium
Burden
Low Burden
Low Burden
Mid-Range
High Burden
Medium
Burden
Low Burden
High
High Burden
High Burden
Medium
Burden
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
References
American Society of Civil Engineers (ASCE) and the Water Pollution Control Federation. 1969. Design
and Construction of Sanitary and Storm Sewers (Manual of Practice No. 37). New York, New York.
Huff, Floyd A. and James R. Angel. Rainfall Frequency Atlas of the Midwest. Illinois State Water
Survey, Champaign, Bulletin 71, 1992. (http://www.isws.illinois.edU/pubdoc/B/ISWSB-71.pdf, Date
accessed October 22, 2009.)
MWCOG (Metropolitan Washington Council of Governments). 2001 Combined Sewer Overflow
Rooftop Type Analysis and Rain Barrel Demonstration Project. Metropolitan Washington Council of
Governments, Washington, DC.
Schueler, T.R. 2008. Technical Support for the Bay-wide Runoff Reduction Method. Chesapeake
Stormwater Network, Baltimore, MD.
USEPA (U.S. Environmental Protection Agency). 1994. Combined Sewer Overflow (CSO) Control
Policy. EPA 830-B-94-001. U.S. Environmental Protection Agency, Washington, DC.
(http://www.epa.gov/npdes/ pubs/owm0111 .pdf).
USEPA (U.S. Environmental Protection Agency). 1995a. Combined Sewer Overflows Guidance for
Long-Term Control Plans. EPA 832-B-95-002. U.S. Environmental Protection Agency, Office of
Water, Washington, DC. (http://www.epa.gov/npdes/pubs/owm0272.pdf).
USEPA (U.S. Environmental Protection Agency). 1995b.Combined Sewer Overflows Guidance for Nine
Minimum Control Measures. EPA 832-B-95-003. U.S. Environmental Protection Agency, Office of
Water, Washington, DC. (http://www.epa.gov/npdes/pubs/owm0030.pdf).
USEPA (U.S. Environmental Protection Agency). 1995c.Combined Sewer Overflows Guidance for
Permit Writers. EPA 832-B-95-008. U.S. Environmental Protection Agency, Office of Water,
Washington, DC. http://cfpub.epa.gov/npdes/cso/guidedocs.cfm.
USEPA (U.S. Environmental Protection Agency). 1997. Combined Sewer Overflows: Guidance for
Financial Capability Assessment and Schedule Development. EPA 832-B-97-004. U.S.
Environmental Protection Agency, Washington, DC. (http://www.epa.gov/npdes/pubs/csofc.pdf).
USEPA (U.S. Environmental Protection Agency). 1999. Combined Sewer Overflows Guidance for
Monitoring and Modeling. EPA 832-B-99-002. U.S. Environmental Protection Agency, Office of
Water, Washington, DC. (http://www.epa.gov/npdes/pubs/sewer.pdf).
USEPA (U.S. Environmental Protection Agency). 2004. Report to Congress - Impacts and Control of
CSOs and SSOs. EPA 833-R-04-001. U.S. Environmental Protection Agency, Office of Water,
Washington, DC.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Glossary of Terms
This glossary includes a collection of the terms used in this manual and an explanation of each term. To
the extent that definitions and explanations provided in this glossary differ from those in EPA regulations
or other official documents, they are intended to help you understand material in this manual only and
have no legal effect.
Bioretention Facility - Bioretention facilities, or rain gardens, are landscaping features that are designed
to capture and treat local stormwater runoff. The typical components of a bioretention facility include
vegetation, a mulch-layer, and engineered soil, all of which lie in a depression such that it can capture
local stormwater runoff.
Cause of Impairment - Where possible, states, tribes, and other jurisdictions identify the pollutants or
stressors causing water quality impairment. Such causes of impairment keep waters from meeting the
state-adopted water quality standards to protect designated uses. Causes of impairment include chemical
contaminants (such as PCBs, metals, and oxygen-depleting substances), physical conditions (such as
elevated temperature, excessive siltation, or alterations of habitat), and biological contaminants (such as
bacteria and noxious aquatic weeds).
Class A Waters - A Use Classification that some states use in their water quality standards to designate
high-quality waters.
Combined Sewer Overflow (CSO) - A discharge of untreated wastewater from a combined sewer
system at a point before the headworks of a publicly owned treatment works plant.
Combined Sewer System (CSS) - A combined sewer system (CSS) is a wastewater collection system
owned by a State or municipality (as defined by section 502 (4) of the Clean Water Act) which conveys
sanitary wastewaters (domestic, commercial and industrial wastewaters) and storm water through a
single-pipe system to a Publicly Owned Treatment Works (POTW) Treatment Plant (as defined in 40 CFR
403.3(p)).
Combined Sewage - Wastewater and storm water carried in the same pipe by design.
Consumer Price Index (CPI) - A statistical time-series measure of a weighted average of prices of a
specified set of goods and services purchased by consumers.
CSO Control Policy - EPA published the CSO Control Policy on April 19, 1994 (59 Federal Register
18688). The policy includes provisions for developing appropriate, site-specific National Pollutant
Discharge Elimination System permit requirements for combined sewer systems that overflow as a result
of wet-weather events.
Dissolved Oxygen (DO) - The oxygen freely available in water, which is vital for sustaining fish and
other aquatic life as well as for preventing odors. DO levels are considered one of the most important
indicators of a waterbody's ability to support desirable aquatic life. Secondary treatment and advanced
waste treatment are generally designed to ensure adequate DO in the water that receives WWTP
effluent.
Dry-Weather Flow Conditions - Hydraulic flow conditions in the combined sewer system resulting from
one or more of the following: flows of domestic sewage; groundwater infiltration; and commercial and
industrial wastewaters.
Dry-Weather CSO - An unauthorized discharge from a combined sewer system that occurs during dry-
weather conditions.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
First Flush - The occurrence of higher concentrations of pollutants in stormwater or combined sewer
overflow discharges at the beginning of a storm.
Floatables and Trash - Visible buoyant or semi-buoyant solids including organic matter, personal
hygiene items, plastics, styrofoam, paper, rubber, glass and wood.
Green Infrastructure - stormwater management techniques that use or mimic natural processes to
infiltrate, evapotranspire, or store stormwater or runoff on or near the site where it is generated.
Green Roofs - Vegetated roofing systems that can be installed or retrofitted on commercial, industrial,
and residential buildings of all sizes. They typically consist of a waterproofing layer, a drainage layer, a
root barrier, a water retention layer, and a growth medium layer. Green roofs help manage stormwater by
providing detention storage of incident rainfall and facilitating evapotranspiration of the detained water.
Headworks of a Wastewater Treatment Plant - The initial structures, devices, and processes receiving
flows from the sewer system at a wastewater treatment plant, including screening, pumping, measuring,
and grit-removal facilities.
Hyetograph - A graphical representation of the distribution of rainfall overtime.
Imperviousness - The fraction (%) of a sub-sewershed that is covered by non-infiltrating surfaces such
as concrete, asphalt, and buildings.
Infiltration - Stormwater and groundwater that enter a sewer system through such means as defective
pipes, pipe joints, connections, or manholes. (Infiltration does not include inflow.)
Infiltration/Inflow (I/I) - The total quantity of water from both infiltration and inflow.
Inflow - Water, other than wastewater, that enters a sewer system from sources such as roof leaders,
cellar drains, yard drains, area drains, foundation drains, drains from springs and swampy areas,
manhole covers, cross connections between storm drains and sanitary sewers, catch basins, cooling
towers, stormwater, surface runoff, street wash waters, or other drainage. (Inflow does not include
infiltration).
Interceptor Sewers - A sewer without building sewer connections that is used to collect and carry flows
from main and trunk sewers to a central point for treatment and discharge.
Long-Term Control Plan (LTCP) - A water quality-based combined sewer overflow control plan that is
ultimately intended to result in compliance with the Clean Water Act. As described in the 1994 CSO
Control Policy, LTCPs should consider the site-specific nature of combined sewer overflows and evaluate
the cost effectiveness of a range of controls.
Median Household Income (MHI) -The median amount of total income dollars received per household
during a calendar year in a geographical area.
Million Gallons per Day (MGD) - A rate of flow commonly used for wastewater discharges. One MGD is
equivalent to a flow rate of 1.547 cubic feet per second over a 24-hour period.
National Pollutant Discharge Elimination System (NPDES) - The national program for issuing,
modifying, revoking and reissuing, terminating, monitoring and enforcing permits, and imposing and
enforcing pretreatment requirements, under Sections 307, 318, 402 and 405 of the Clean Water Act.
Nine Minimum Controls (NMC) - The minimum technology-based combined sewer overflow controls
designed to address combined sewer overflow problems without extensive engineering studies or
significant construction costs before implementing long-term control measures. Municipalities were
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
expected to implement the NMC and submit appropriate documentation to NPDES permitting authorities
no later than January 1, 1997.
Permeable Pavement - An alternative to conventional asphalt and concrete surfaces used mostly in
non-street construction such as parking lots, sidewalks, and alleyways. Permeable pavement uses
various types of materials, including permeable asphalt and concrete, and permeable or grass pavers.
Permeable pavement helps manage stormwater by providing retention storage of surface runoff and
allowing infiltration into underlying soil.
Permittee -An entity that holds a National Pollutant Discharge Elimination System permit. In the case of
Green LTCP-EZ, the term should be interpreted to include any users of the Green LTCP-EZ Template.
Permitting Authority - The agency (EPA or the state or Indian tribe) that administers the National
Pollutant Discharge Elimination System permit program.
Primary Treatment - The first steps in wastewater treatment in which screens and sedimentation tanks
are used to remove most materials that float or will settle. Clean Water Act section 301 (h), which
addresses waivers from secondary treatment for discharges into marine waters, defines primary or
equivalent treatment as that adequate to remove 30 percent of biochemical oxygen demand and 30
percent of suspended solids.
Publicly Owned Treatment Works (POTW) - As defined by section 212 of the Clean Water Act, a
POTW is a treatment works that is owned by a state or municipality. This definition includes any devices
and systems used in the storage, treatment, recycling, and reclamation of municipal sewage or industrial
wastes of a liquid nature. It also includes sewers, pipes, and other conveyances only if they convey
wastewater to a POTW plant.
Rational Method - A simple approach for estimating peak discharges for small drainage areas in which
no significant flood storage occurs.
Regulator - A device in combined sewer systems for diverting wet-weather flows that exceed
downstream capacity in the sewer system to a combined sewer overflow outfall.
Runoff-The flow of water from rain, snowmelt, or other sources over the land
Sanitary Sewer System (SSS) - A municipal wastewater collection system that conveys domestic,
commercial, and industrial wastewater and limited amounts of infiltrated groundwater and stormwater to a
POTW. Areas served by SSSs often have a municipal separate storm sewer system to collect and convey
runoff from rainfall and snowmelt.
Satellite Sewer Systems - Combined or sanitary sewer systems that convey flow to a publicly owned
treatment works owned and operated by a separate entity.
Secondary Treatment - Technology-based requirements for direct discharging municipal sewage
treatment facilities. 40 CFR 133.102 defines secondary treatment as 30-day averages of 30 milligrams
per liter (mg/L) BOD5 and 30 mg/L suspended solids, along with maintenance of pH within 6.0 to 9.0
(except as provided for special considerations and treatment equivalent to secondary treatment).
Sensitive Area - An area of environmental significance or sensitivity that could be adversely affected by
combined sewer overflow discharges. Sensitive areas include Outstanding National Resource Waters,
National Marine Sanctuaries, water with threatened or endangered species, waters with primary contact
recreation, public drinking water intakes, shellfish beds, and other areas identified by the permittee or
National Pollutant Discharge Elimination System permitting authority, in coordination with the appropriate
state or federal agencies.
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Green Long-Term Control Plan-EZ Template: A Planning Tool for CSO Control in Small Communities
Sewer Separation - The process of separating a combined sewer system into sanitary and separate
storm sewer systems. It is accomplished by constructing a new pipe system (either sanitary or separate
storm) and diverting the appropriate types of flows (sanitary or storm) into the new sewers while allowing
the existing sewers to carry only the other type of flow (storm or sanitary).
Source of Impairment - Where possible, states, tribes, and other jurisdictions identify from where
pollutants or stressors (causes of impairment) are coming. Such sources of impairment are the activities,
facilities, or conditions that generate the pollutants that keep waters from meeting the state-adopted
criteria to protect designated uses. Sources of impairment include, for example, municipal sewage
treatment plants, factories, storm sewers, combined sewer overflows, modification of hydrology,
agricultural runoff, and runoff from city streets.
Sub-Sewershed Area - An area within a combined sewer system that drains to one combined sewer
overflow outfall.
Tier III Waters - Federal guidance establishes three levels or tiers of nondegradation, which is the model
states are to use when adopting nondegradation provisions. Tier III provides the highest level of
protection from pollution to waters specifically identified as very high quality, important recreational
resources, ecologically sensitive, or unique.
Total Suspended Solids (TSS) - A measure of the filterable solids present in a sample of water or
wastewater (as determined by the method specified in 40 CFR Part 136).
Vegetated Swales (sometimes called grassed swales) - Open-channels designed specifically to treat
and attenuate stormwater runoff. Unlike traditional drainage ditches, the vegetation in a vegetated swale
slows runoff to allow sedimentation and infiltration into the underlying soils.
Wastewater Treatment Plant (WWTP) -A facility containing a series of tanks, screens, filters, and other
processes by which pollutants are removed from water.
Water Quality Standards - Standards established by regulatory agencies that consist of the beneficial
use or uses of a waterbody, the numeric and narrative water quality criteria that are necessary to protect
the use or uses of that waterbody, and an antidegradation statement.
Wet-Weather Event - A discharge from a combined sewer system that occurs in direct response to
rainfall or snowmelt.
Wet-Weather Flow - Dry-weather flow combined with stormwater introduced into a combined sewer
system.
Wet-Weather Flow Conditions - Hydraulic flow conditions within the combined sewer system resulting
from a wet-weather event.
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Appendix A. One-Hour, 3-Month Rainfall Intensities, Schedule 4 - CSO
Volume
A-1
-------
1hr-3mo
State County (in.)
CT Fairfield 0.87
CT Hartford 0.87
CT Litchfield 0.87
CT Middlesex 0.87
CT New Haven 0.87
CT New London 0.87
CT Tolland 0.87
CT Windham 0.87
DE Kent 0.87
DE New Castle 0.87
DE Sussex 0.87
DC DC 0.87
IL Adams 0.84
IL Alexander 0.90
IL Bond 0.81
IL Boone 0.78
IL Brown 0.76
IL Bureau 0.78
IL Calhoun 0.79
IL Carroll 0.78
IL Cass 0.79
IL Champaign 0.74
IL Christian 0.79
IL Clark 0.77
IL Clay 0.79
IL Clinton 0.81
IL Coles 0.77
IL Cook 0.76
IL Crawford 0.77
IL Cumberland 0.77
IL DeWitt 0.76
IL DeKalb 0.76
IL Douglas 0.77
IL DuPage 0.76
IL Edgar 0.77
IL Edwards 0.79
IL Effingham 0.77
IL Fayette 0.77
IL Ford 0.74
IL Franklin 0.79
IL Fulton 0.76
IL Gallatin 0.90
IL Greene 0.79
IL Grundy 0.76
IL Hamilton 0.79
IL Hancock 0.84
IL Hardin 0.90
IL Henderson 0.84
IL Henry 0.78
IL Iroquois 0.74
IL Jackson 0.90
IL Jasper 0.77
IL Jefferson 0.79
IL Jersey 0.79
IL Jo Daviess 0.78
1hr-3mo
State County (in.)
IL Johnson 0.90
IL Kane 0.76
IL Kankakee 0.76
IL Kendall 0.76
IL Knox 0.84
IL LaSalle 0.76
IL Lake 0.76
IL Lawrence 0.79
IL Lee 0.78
IL Livingston 0.74
IL Logan 0.76
IL Macon 0.76
IL Macoupin 0.79
IL Madison 0.81
IL Marion 0.79
IL Marshall 0.76
IL Mason 0.76
IL Massac 0.90
IL McDonough 0.84
IL McHenry 0.76
IL McLean 0.76
IL Menard 0.79
IL Mercer 0.78
IL Monroe 0.81
IL Montgomery 0.79
IL Morgan 0.79
IL Moultrie 0.77
IL Ogle 0.78
IL Peoria 0.76
IL Perry 0.81
IL Piatt 0.76
IL Pike 0.79
IL Pope 0.90
IL Pulaski 0.90
IL Putnam 0.78
IL Randolph 0.81
IL Richland 0.79
IL Rock Island 0.78
IL Saline 0.90
IL Sangamon 0.79
IL Schuyler 0.76
IL Scott 0.79
IL Shelby 0.77
IL St. Glair 0.81
IL Stark 0.76
IL Stephenson 0.78
IL Tazewell 0.76
IL Union 0.90
IL Vermilion 0.74
IL Wabash 0.79
IL Warren 0.84
IL Washington 0.81
IL Wayne 0.79
IL White 0.79
IL Whiteside 0.78
1hr-3mo
State County (in.)
IL Will 0.76
IL Williamson 0.90
IL Winnebago 0.78
IL Woodford 0.76
IN Adams 0.65
IN Allen 0.65
IN Bartholomew 0.74
IN Benton 0.73
IN Blackford 0.69
IN Boone 0.74
IN Brown 0.81
IN Carroll 0.74
IN Cass 0.71
IN Clark 0.74
IN Clay 0.79
IN Clinton 0.74
IN Crawford 0.81
IN Daviess 0.83
IN Dearborn 0.74
IN Decatur 0.74
IN DeKalb 0.65
IN Delaware 0.69
IN Dubois 0.83
IN Elkhart 0.71
IN Fayette 0.69
IN Floyd 0.81
IN Fountain 0.79
IN Franklin 0.74
IN Fulton 0.71
IN Gibson 0.83
IN Grant 0.74
IN Greene 0.83
IN Hamilton 0.74
IN Hancock 0.74
IN Harrison 0.81
IN Hendricks 0.74
IN Henry 0.69
IN Howard 0.74
IN Huntington 0.65
IN Jackson 0.81
IN Jasper 0.73
IN Jay 0.69
IN Jefferson 0.74
IN Jennings 0.74
IN Johnson 0.74
IN Knox 0.83
IN Kosciusko 0.71
IN Lagrange 0.65
IN Lake 0.73
IN LaPorte 0.73
IN Lawrence 0.81
IN Madison 0.74
IN Marion 0.74
IN Marshall 0.71
IN Martin 0.83
1hr-3mo
State County (in.)
IN Miami 0.71
IN Monroe 0.81
IN Montgomery 0.79
IN Morgan 0.74
IN Newton 0.73
IN Noble 0.65
IN Ohio 0.74
IN Orange 0.81
IN Owen 0.79
IN Parke 0.79
IN Perry 0.81
IN Pike 0.83
IN Porter 0.73
IN Posey 0.83
IN Pulaski 0.73
IN Putnam 0.79
IN Randolph 0.69
IN Ripley 0.74
IN Rush 0.74
IN Scott 0.74
IN Shelby 0.74
IN Spencer 0.83
IN St. Joseph 0.71
IN Starke 0.73
IN Steuben 0.65
IN Sullivan 0.83
IN Switzerland 0.74
IN Tippecanoe 0.79
IN Tipton 0.74
IN Union 0.69
IN Vanderburgh 0.83
IN Vermillion 0.79
IN Vigo 0.79
IN Wabash 0.71
IN Warren 0.79
IN Warrick 0.83
IN Washington 0.81
IN Wayne 0.69
IN Wells 0.65
IN White 0.73
IN Whitley 0.65
IA Adair 0.83
IA Adams 0.83
IA Allamakee 0.70
IA Appanoose 0.75
IA Audubon 0.75
IA Benton 0.72
IA Black Hawk 0.70
IA Boone 0.72
IA Bremer 0.70
IA Buchanan 0.70
IA Buena Vista 0.67
IA Butler 0.71
IA Calhoun 0.75
IA Carroll 0.75
A-2
-------
1hr-3mo
State County (in.)
IA Cass 0.83
IA Cedar 0.72
I A CerroGordo 0.71
IA Cherokee 0.67
IA Chickasaw 0.70
IA Clarke 0.75
IA Clay 0.67
IA Clayton 0.70
IA Clinton 0.72
IA Crawford 0.75
IA Dallas 0.72
IA Davis 0.75
IA Decatur 0.75
IA Delaware 0.70
IA Des Moines 0.75
IA Dickinson 0.67
IA Dubuque 0.70
IA Emmet 0.67
IA Fayette 0.70
IA Floyd 0.71
IA Franklin 0.71
IA Fremont 0.83
IA Greene 0.75
IA Grundy 0.72
IA Guthrie 0.75
IA Hamilton 0.72
IA Hancock 0.71
IA Hardin 0.72
IA Harrison 0.75
IA Henry 0.75
IA Howard 0.70
IA Humboldt 0.71
IA Ida 0.75
IA Iowa 0.72
IA Jackson 0.72
IA Jasper 0.72
IA Jefferson 0.75
IA Johnson 0.72
IA Jones 0.72
IA Keokuk 0.75
IA Kossuth 0.71
IA Lee 0.75
IA Linn 0.72
IA Louisa 0.75
IA Lucas 0.75
IA Lyon 0.67
IA Madison 0.75
IA Mahaska 0.75
IA Marion 0.75
IA Marshall 0.72
IA Mills 0.83
IA Mitchell 0.71
IA Monona 0.75
IA Monroe 0.75
IA Montgomery 0.83
1hr-3mo
State County (in.)
IA Muscatine 0.72
IA O'Brien 0.67
IA Osceola 0.67
IA Page 0.83
IA Palo Alto 0.67
IA Plymouth 0.67
IA Pocahontas 0.67
IA Polk 0.72
IA Pottawattamk 0.83
IA Poweshiek 0.72
IA Ringgold 0.75
IA Sac 0.75
IA Scott 0.72
IA Shelby 0.75
IA Sioux 0.67
IA Story 0.72
IA Tama 0.72
IA Taylor 0.83
IA Union 0.75
IA Van Buren 0.75
IA Wapello 0.75
IA Warren 0.75
IA Washington 0.75
IA Wayne 0.75
IA Webster 0.72
IA Winnebago 0.71
IA Winneshiek 0.70
IA Woodbury 0.75
IA Worth 0.71
IA Wright 0.71
KY Adair 0.88
KY Allen 0.88
KY Anderson 0.77
KY Ballard 0.93
KY Barren 0.88
KY Bath 0.77
KY Bell 0.80
KY Boone 0.77
KY Bourbon 0.77
KY Boyd 0.80
KY Boyle 0.77
KY Bracken 0.77
KY Breathitt 0.80
KY Breckinridge 0.88
KY Bullitt 0.88
KY Butler 0.88
KY Galloway 0.93
KY Campbell 0.77
KY Carlisle 0.93
KY Carroll 0.77
KY Carter 0.80
KY Casey 0.88
KY Christian 0.93
KY Clark 0.77
KY Clay 0.80
1hr-3mo
State County (in.)
KY Clinton 0.88
KY Crittenden 0.93
KY Cumberland 0.88
KY Daviess 0.93
KY Edmonson 0.88
KY Elliott 0.80
KY Estill 0.80
KY Fayette 0.77
KY Fleming 0.77
KY Floyd 0.80
KY Franklin 0.77
KY Fulton 0.93
KY Gallatin 0.77
KY Garrard 0.77
KY Grant 0.77
KY Graves 0.93
KY Grayson 0.88
KY Green 0.88
KY Greenup 0.80
KY Hancock 0.93
KY Hardin 0.88
KY Harlan 0.80
KY Harrison 0.77
KY Hart 0.88
KY Henderson 0.93
KY Henry 0.77
KY Hickman 0.93
KY Hopkins 0.93
KY Jackson 0.80
KY Jefferson 0.88
KY Jessamine 0.77
KY Johnson 0.80
KY Kenton 0.77
KY Knott 0.80
KY Knox 0.80
KY Larue 0.88
KY Laurel 0.80
KY Lawrence 0.80
KY Lee 0.80
KY Leslie 0.80
KY Letcher 0.80
KY Lewis 0.80
KY Lincoln 0.77
KY Livingston 0.93
KY Logan 0.93
KY Lyon 0.93
KY Madison 0.77
KY Magoffin 0.80
KY Marion 0.88
KY Marshall 0.93
KY Martin 0.80
KY Mason 0.77
KY McCracken 0.93
KY McCreary 0.80
KY McLean 0.93
1hr-3mo
State County (in.)
KY Meade 0.88
KY Menifee 0.80
KY Mercer 0.77
KY Metcalfe 0.88
KY Monroe 0.88
KY Montgomery 0.77
KY Morgan 0.80
KY Muhlenberg 0.93
KY Nelson 0.88
KY Nicholas 0.77
KY Ohio 0.93
KY Oldham 0.77
KY Owen 0.77
KY Owsley 0.80
KY Pendleton 0.77
KY Perry 0.80
KY Pike 0.80
KY Powell 0.80
KY Pulaski 0.80
KY Robertson 0.77
KY Rockcastle 0.80
KY Rowan 0.80
KY Russell 0.88
KY Scott 0.77
KY Shelby 0.77
KY Simpson 0.93
KY Spencer 0.77
KY Taylor 0.88
KY Todd 0.93
KY Trigg 0.93
KY Trimble 0.77
KY Union 0.93
KY Warren 0.88
KY Washington 0.77
KY Wayne 0.80
KY Webster 0.93
KY Whitley 0.80
KY Wolfe 0.80
KY Woodford 0.77
ME Androscoggin 0.75
ME Aroostook 0.62
ME Cumberland 0.75
ME Franklin 0.75
ME Hancock 0.75
ME Kennebec 0.75
ME Knox 0.75
ME Lincoln 0.75
ME Oxford 0.87
ME Penobscot 0.75
ME Piscataquis 0.75
ME Sagadahoc 0.75
ME Somerset 0.75
ME Waldo 0.75
ME Washington 0.75
ME York 0.75
A-3
-------
1hr-3mo
State County (in.)
MD Allegany 0.75
MD AnneArundel 0.87
MD Baltimore 0.87
MD Baltimore City 0.87
MD Calvert 0.87
MD Caroline 0.87
MD Carroll 0.87
MD Cecil 0.87
MD Charles 0.87
MD Dorchester 0.87
MD Frederick 0.87
MD Garrett 0.75
MD Harford 0.87
MD Howard 0.87
MD Kent 0.87
MD Montgomery 0.87
MD Prince George's 0.87
MD Queen Anne's 0.87
MD Somerset 1.00
MD St. Mary's 0.87
MD Talbot 0.87
MD Washington 0.75
MD Wicomico 0.87
MD Worcester 1.00
MA Barnstable 0.87
MA Berkshire 0.75
MA Bristol 0.87
MA Dukes 0.87
MA Essex 0.87
MA Franklin 0.75
MA Hampden 0.87
MA Hampshire 0.75
MA Middlesex 0.87
MA Nantucket 0.87
MA Norfolk 0.87
MA Plymouth 0.87
MA Suffolk 0.87
MA Worcester 0.87
Ml Alcona 0.51
Ml Alger 0.50
Ml Allegan 0.59
Ml Alpena 0.51
Ml Antrim 0.49
Ml Arenac 0.52
Ml Baraga 0.59
Ml Barry 0.61
Ml Bay 0.52
Ml Benzie 0.49
Ml Berrien 0.59
Ml Branch 0.61
Ml Calhoun 0.61
Ml Cass 0.59
Ml Charlevoix 0.49
Ml Cheboygan 0.51
Ml Chippewa 0.50
1hr-3mo
State County (in.)
Ml Clare 0.56
Ml Clinton 0.61
Ml Crawford 0.51
Ml Delta 0.50
Ml Dickinson 0.59
Ml Eaton 0.61
Ml Emmet 0.49
Ml Genesee 0.56
Ml Gladwin 0.56
Ml Gogebic 0.59
Ml Grand Traverse 0.49
Ml Gratiot 0.56
Ml Hillsdale 0.61
Ml Houghton 0.59
Ml Huron 0.52
Ml Ingham 0.61
Ml Ionia 0.61
Ml losco 0.51
Ml Iron 0.59
Ml Isabella 0.56
Ml Jackson 0.61
Ml Kalamazoo 0.59
Ml Kalkaska 0.49
Ml Kent 0.59
Ml Keweenaw 0.59
Ml Lake 0.53
Ml Lapeer 0.56
Ml Leelanau 0.49
Ml Lenawee 0.56
Ml Livingston 0.56
Ml Luce 0.50
Ml Mackinac 0.50
Ml Macomb 0.56
Ml Manistee 0.49
Ml Marquette 0.59
Ml Mason 0.53
Ml Mecosta 0.56
Ml Menominee 0.59
Ml Midland 0.56
Ml Missaukee 0.49
Ml Monroe 0.56
Ml Montcalm 0.56
Ml Montmorency 0.51
Ml Muskegon 0.53
Ml Newaygo 0.53
Ml Oakland 0.56
Ml Oceana 0.53
Ml Ogemaw 0.51
Ml Ontonagon 0.59
Ml Osceola 0.56
Ml Oscoda 0.51
Ml Otsego 0.51
Ml Ottawa 0.59
Ml Presque Isle 0.51
Ml Roscommon 0.51
1hr-3mo
State County (in.)
Ml Saginaw 0.52
Ml Sanilac 0.52
Ml Schoolcraft 0.50
Ml Shiawassee 0.61
Ml St. Glair 0.56
Ml St. Joseph 0.61
Ml Tuscola 0.52
Ml Van Buren 0.59
Ml Washtenaw 0.56
Ml Wayne 0.56
Ml Wexford 0.49
MO Adair 0.75
MO Andrew 0.76
MO Atchison 0.76
MO Audrain 0.75
MO Barry 0.90
MO Barton 0.90
MO Bates 0.84
MO Benton 0.84
MO Bollinger 0.84
MO Boone 0.75
MO Buchanan 0.76
MO Butler 0.84
MO Caldwell 0.76
MO Callaway 0.75
MO Camden 0.84
MO CapeGirardeau 0.84
MO Carroll 0.76
MO Carter 0.84
MO Cass 0.84
MO Cedar 0.84
MO Chariton 0.76
MO Christian 0.90
MO Clark 0.75
MO Clay 0.76
MO Clinton 0.76
MO Cole 0.84
MO Cooper 0.84
MO Crawford 0.84
MO Dade 0.90
MO Dallas 0.90
MO Daviess 0.76
MO DeKalb 0.76
MO Dent 0.84
MO Douglas 0.90
MO Dunklin 0.90
MO Franklin 0.75
MO Gasconade 0.75
MO Gentry 0.76
MO Greene 0.90
MO Grundy 0.76
MO Harrison 0.76
MO Henry 0.84
MO Hickory 0.84
MO Holt 0.76
1hr-3mo
State County (in.)
MO Howard 0.76
MO Howell 0.84
MO Iron 0.84
MO Jackson 0.76
MO Jasper 0.90
MO Jefferson 0.84
MO Johnson 0.84
MO Knox 0.75
MO Laclede 0.90
MO Lafayette 0.76
MO Lawrence 0.90
MO Lewis 0.75
MO Lincoln 0.75
MO Linn 0.76
MO Livingston 0.76
MO Macon 0.75
MO Madison 0.84
MO Maries 0.84
MO Marion 0.75
MO McDonald 0.90
MO Mercer 0.76
MO Miller 0.84
MO Mississippi 0.90
MO Moniteau 0.84
MO Monroe 0.75
MO Montgomery 0.75
MO Morgan 0.84
MO New Madrid 0.90
MO Newton 0.90
MO Nodaway 0.76
MO Oregon 0.84
MO Osage 0.75
MO Ozark 0.90
MO Pemiscot 0.90
MO Perry 0.84
MO Pettis 0.84
MO Phelps 0.84
MO Pike 0.75
MO Platte 0.76
MO Polk 0.90
MO Pulaski 0.84
MO Putnam 0.76
MO Rails 0.75
MO Randolph 0.75
MO Ray 0.76
MO Reynolds 0.84
MO Ripley 0.84
MO Saline 0.76
MO Schuyler 0.75
MO Scotland 0.75
MO Scott 0.90
MO Shannon 0.84
MO Shelby 0.75
MO St. Charles 0.75
MO St. Glair 0.84
A-4
-------
1hr-3mo
State County (in.)
MO St. Francois 0.84
MO St. Louis 0.75
MO St. Louis City 0.75
MO Ste. Genevieve 0.84
MO Stoddard 0.90
MO Stone 0.90
MO Sullivan 0.76
MO Taney 0.90
MO Texas 0.84
MO Vernon 0.84
MO Warren 0.75
MO Washington 0.84
MO Wayne 0.84
MO Webster 0.90
MO Worth 0.76
MO Wright 0.90
NH Belknap 0.75
NH Carroll 0.87
NH Cheshire 0.75
NH Coos 0.87
NH Grafton 0.75
NH Hillsborough 0.75
NH Merrimack 0.75
NH Rockingham 0.75
NH Strafford 0.75
NH Sullivan 0.75
NJ Atlantic 0.87
NJ Bergen 0.87
NJ Burlington 0.87
NJ Camden 0.87
NJ Cape May 0.87
NJ Cumberland 0.87
NJ Essex 0.87
NJ Gloucester 0.87
NJ Hudson 0.87
NJ Hunterdon 0.87
NJ Mercer 0.87
NJ Middlesex 0.87
NJ Monmouth 0.87
NJ Morris 0.87
NJ Ocean 0.87
NJ Passaic 0.87
NJ Salem 0.87
NJ Somerset 0.87
NJ Sussex 0.87
NJ Union 0.87
NJ Warren 0.87
NY Albany 0.75
NY Allegany 0.75
NY Bronx 0.87
NY Broome 0.75
NY Cattaraugus 0.75
NY Cayuga 0.75
NY Chautauqua 0.62
NY Chemung 0.75
1hr-3mo
State County (in.)
NY Chenango 0.75
NY Clinton 0.62
NY Columbia 0.75
NY Cortland 0.75
NY Delaware 0.75
NY Dutchess 1.00
NY Erie 0.62
NY Essex 0.62
NY Franklin 0.62
NY Fulton 0.75
NY Genesee 0.62
NY Greene 0.87
NY Hamilton 0.62
NY Herkimer 0.62
NY Jefferson 0.62
NY Kings 0.87
NY Lewis 0.62
NY Livingston 0.62
NY Madison 0.75
NY Monroe 0.62
NY Montgomery 0.75
NY Nassau 0.87
NY New York 0.87
NY Niagara 0.62
NY Oneida 0.75
NY Onondaga 0.75
NY Ontario 0.62
NY Orange 0.87
NY Orleans 0.62
NY Oswego 0.62
NY Otsego 0.75
NY Putnam 0.87
NY Queens 0.87
NY Rensselaer 0.75
NY Richmond 0.87
NY Rockland 0.87
NY Saratoga 0.75
NY Schenectady 0.75
NY Schoharie 0.75
NY Schuyler 0.75
NY Seneca 0.75
NY St. Lawrence 0.62
NY Steuben 0.75
NY Suffolk 0.87
NY Sullivan 0.87
NY Tioga 0.75
NY Tompkins 0.75
NY Ulster 1.00
NY Warren 0.62
NY Washington 0.75
NY Wayne 0.62
NY Westchester 0.87
NY Wyoming 0.62
NY Yates 0.75
OH Adams 0.69
1hr-3mo
State County (in.)
OH Allen 0.61
OH Ashland 0.63
OH Ashtabula 0.61
OH Athens 0.61
OH Auglaize 0.65
OH Belmont 0.61
OH Brown 0.70
OH Butler 0.70
OH Carroll 0.61
OH Champaign 0.65
OH Clark 0.65
OH Clermont 0.70
OH Clinton 0.70
OH Columbiana 0.61
OH Coshocton 0.63
OH Crawford 0.60
OH Cuyahoga 0.61
OH Darke 0.65
OH Defiance 0.61
OH Delaware 0.65
OH Erie 0.60
OH Fairfield 0.65
OH Fayette 0.65
OH Franklin 0.65
OH Fulton 0.61
OH Gallia 0.69
OH Geauga 0.61
OH Greene 0.70
OH Guernsey 0.61
OH Hamilton 0.70
OH Hancock 0.61
OH Hardin 0.65
OH Harrison 0.61
OH Henry 0.61
OH Highland 0.70
OH Hocking 0.61
OH Holmes 0.63
OH Huron 0.60
OH Jackson 0.69
OH Jefferson 0.61
OH Knox 0.63
OH Lake 0.61
OH Lawrence 0.69
OH Licking 0.65
OH Logan 0.65
OH Lorain 0.60
OH Lucas 0.61
OH Madison 0.65
OH Mahoning 0.61
OH Marion 0.65
OH Medina 0.61
OH Meigs 0.69
OH Mercer 0.65
OH Miami 0.65
OH Monroe 0.61
1hr-3mo
State County (in.)
OH Montgomery 0.70
OH Morgan 0.61
OH Morrow 0.65
OH Muskingum 0.61
OH Noble 0.61
OH Ottawa 0.60
OH Paulding 0.61
OH Perry 0.61
OH Pickaway 0.65
OH Pike 0.69
OH Portage 0.61
OH Preble 0.70
OH Putnam 0.61
OH Richland 0.63
OH Ross 0.69
OH Sandusky 0.60
OH Scioto 0.69
OH Seneca 0.60
OH Shelby 0.65
OH Stark 0.61
OH Summit 0.61
OH Trumbull 0.61
OH Tuscarawas 0.61
OH Union 0.65
OH VanWert 0.61
OH Vinton 0.61
OH Warren 0.70
OH Washington 0.61
OH Wayne 0.63
OH Williams 0.61
OH Wood 0.61
OH Wyandot 0.60
PA Adams 0.75
PA Allegheny 0.75
PA Armstrong 0.75
PA Beaver 0.75
PA Bedford 0.75
PA Berks 0.87
PA Blair 0.75
PA Bradford 0.75
PA Bucks 0.87
PA Butler 0.75
PA Cambria 0.75
PA Cameron 0.75
PA Carbon 0.75
PA Centre 0.75
PA Chester 0.87
PA Clarion 0.75
PA Clearfield 0.75
PA Clinton 0.75
PA Columbia 0.75
PA Crawford 0.62
PA Cumberland 0.75
PA Dauphin 0.75
PA Delaware 0.87
A-5
-------
1hr-3mo
State County (in.)
PA Elk 0.75
PA Erie 0.62
PA Fayette 0.75
PA Forest 0.75
PA Franklin 0.75
PA Fulton 0.75
PA Greene 0.75
PA Huntingdon 0.75
PA Indiana 0.75
PA Jefferson 0.75
PA Juniata 0.75
PA Lackawanna 0.75
PA Lancaster 0.87
PA Lawrence 0.62
PA Lebanon 0.75
PA Lehigh 0.87
PA Luzerne 0.75
PA Lycoming 0.75
PA McKean 0.75
PA Mercer 0.62
PA Mifflin 0.75
PA Monroe 0.75
PA Montgomery 0.87
PA Montour 0.75
PA Northampton 0.87
PA Northumberland 0.75
PA Perry 0.75
PA Philadelphia 0.87
PA Pike 0.75
PA Potter 0.75
PA Schuylkill 0.75
PA Snyder 0.75
PA Somerset 0.75
PA Sullivan 0.75
PA Susquehanna 0.75
PA Tioga 0.75
PA Union 0.75
PA Venango 0.75
PA Warren 0.75
PA Washington 0.75
PA Wayne 0.75
PA Westmoreland 0.75
PA Wyoming 0.75
PA York 0.87
Rl Bristol 0.87
Rl Kent 0.87
Rl Newport 0.87
Rl Providence 0.87
Rl Washington 0.87
VT Addison 0.62
VT Bennington 0.75
VT Caledonia 0.62
VT Chittenden 0.62
VT Essex 0.62
VT Franklin 0.62
1hr-3mo
State County (in.)
VT Grand Isle 0.62
VT Lamoille 0.62
VT Orange 0.62
VT Orleans 0.62
VT Rutland 0.75
VT Washington 0.62
VT Windham 0.75
VT Windsor 0.75
VA Accomack 1.00
VA Albemarle 1.00
VA Alexandria 0.87
VA Allegheny 0.75
VA Amelia 0.87
VA Amherst 1.00
VA Appomattox 1.00
VA Augusta 1 .00
VA Bath 0.75
VA Bedford 1.00
VA Bland 0.75
VA Botetourt 1.00
VA Brunswick 0.87
VA Buchanan 0.75
VA Buckingham 1.00
VA Campbell 1.00
VA Caroline 0.87
VA Carroll 0.87
VA Charles City 0.87
VA Charlotte 0.87
VA Chesapeake 1.00
VA Chesterfield 0.87
VA Clarke 0.87
VA Colonial Heights 0.87
VA Craig 0.75
VA Culpeper 1.00
VA Cumberland 0.87
VA Dickenson 0.75
VA Dinwiddie 0.87
VA Essex 0.87
VA Fairfax 0.87
VA Fairfax City 0.87
VA Falls Church 0.87
VA Fauquier 1.00
VA Floyd 0.87
VA Fluvanna 1.00
VA Franklin 1.00
VA Frederick 0.75
VA Fredericksburg 0.87
VA Giles 0.75
VA Gloucester 1.00
VA Goochland 0.87
VA Grayson 0.75
VA Greene 1.00
VA Greensville 1.00
VA Halifax 0.87
VA Hampton 1.00
1hr-3mo
State County (in.)
VA Hanover 0.87
VA Henrico 0.87
VA Henry 1.00
VA Highland 0.75
VA Hopewell 0.87
VA Isle of Wight 1.00
VA James City 1.00
VA King and Queen 0.87
VA King George 0.87
VA King William 0.87
VA Lancaster 0.87
VA Lee 0.75
VA Loudoun 0.87
VA Louisa 0.87
VA Lunenburg 0.87
VA Lynchburg 1.00
VA Madison 1.00
VA Manassas 0.87
VA Manassas Park 0.87
VA Mathews 1.00
VA Mecklenburg 0.87
VA Middlesex 0.87
VA Montgomery 0.87
VA Nelson 1.00
VA New Kent 0.87
VA Newport News 1.00
VA Norfolk 1.00
VA Northampton 1.00
VA Northumberland 0.87
VA Nottoway 0.87
VA Orange 1.00
VA Page 1.00
VA Patrick 1.00
VA Petersburg 0.87
VA Pittsylvania 0.87
VA Poquoson 1.00
VA Portsmouth 1.00
VA Powhatan 0.87
VA Prince Edward 0.87
VA Prince George 0.87
VA Prince William 0.87
VA Pulaski 0.75
VA Rappahannock 1.00
VA Richmond 0.87
VA Richmond City 0.87
VA Roanoke 1.00
VA Rockbridge 1.00
VA Rockingham 1.00
VA Russell 0.75
VA Scott 0.75
VA Shenandoah 0.87
VA Smyth 0.75
VA Southampton 1.00
VA Spotsylvania 0.87
VA Stafford 0.87
1hr-3mo
State County (in.)
VA Suffolk 1.00
VA Surry 1.00
VA Sussex 1.00
VA Tazewell 0.75
VA Virginia Beach 1.00
VA Warren 1.00
VA Washington 0.75
VA Westmoreland 0.87
VA Williamsburg 1.00
VA Wise 0.75
VA Wythe 0.75
VA York 1.00
WV Barbour 0.75
WV Berkeley 0.75
WV Boone 0.75
WV Braxton 0.75
WV Brooke 0.75
WV Cabell 0.75
WV Calhoun 0.75
WV Clay 0.75
WV Doddridge 0.75
WV Fayette 0.75
WV Gilmer 0.75
WV Grant 0.75
WV Greenbrier 0.75
WV Hampshire 0.75
WV Hancock 0.75
WV Hardy 0.75
WV Harrison 0.75
WV Jackson 0.75
WV Jefferson 0.87
WV Kanawha 0.75
WV Lewis 0.75
WV Lincoln 0.75
WV Logan 0.75
WV Marion 0.75
WV Marshall 0.75
WV Mason 0.75
WV McDowell 0.75
WV Mercer 0.75
WV Mineral 0.75
WV Mingo 0.75
WV Monongalia 0.75
WV Monroe 0.75
WV Morgan 0.75
WV Nicholas 0.75
WV Ohio 0.75
WV Pendleton 0.75
WV Pleasants 0.75
WV Pocahontas 0.75
WV Preston 0.75
WV Putnam 0.75
WV Raleigh 0.75
WV Randolph 0.75
WV Ritchie 0.75
A-6
-------
State
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
County
Roane
Summers
Taylor
Tucker
Tyler
Upshur
Wayne
Webster
Wetzel
Wirt
Wood
Wyoming
Adams
Ashland
Barron
Bayfield
Brown
Buffalo
Burnett
Calumet
Chippewa
Clark
Columbia
Crawford
Dane
Dodge
Door
Douglas
Dunn
Eau Claire
Florence
Fond Du Lac
Forest
Grant
Green
Green Lake
Iowa
Iron
Jackson
Jefferson
Juneau
Kenosha
Kewaunee
La Crosse
Lafayette
Langlade
Lincoln
Manitowoc
Marathon
Marinette
Marquette
Menominee
Milwaukee
Monroe
Oconto
1hr-3mo
(in.)
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.65
0.67
0.67
0.67
0.59
0.67
0.67
0.59
0.67
0.67
0.68
0.68
0.68
0.68
0.59
0.67
0.67
0.67
0.57
0.59
0.57
0.68
0.68
0.65
0.68
0.67
0.67
0.68
0.65
0.65
0.59
0.67
0.68
0.57
0.67
0.59
0.67
0.57
0.65
0.57
0.65
0.67
0.57
State
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
Wl
County
Oneida
Outagamie
Ozaukee
Pepin
Pierce
Polk
Portage
Price
Racine
Richland
Rock
Rusk
Sauk
Sawyer
Shawano
Sheboygan
St. Croix
Taylor
Trempealeau
Vernon
Vilas
Walworth
Washburn
Washington
Waukesha
Waupaca
Waushara
Winnebago
Wood
1hr-3mo
(in.)
0.67
0.59
0.65
0.67
0.67
0.67
0.65
0.67
0.65
0.68
0.68
0.67
0.68
0.67
0.57
0.59
0.67
0.67
0.67
0.68
0.67
0.65
0.67
0.65
0.65
0.65
0.65
0.59
0.65
A-7
-------
Appendix B. Hydraulic Calculations within Green LTCP-EZ, Schedule 4
CSO Volume, and Schedules 5A and 5B - CSO Control
B-1
-------
Introduction
It is necessary to make several important estimates within Schedule 4-CSO Volume (and again in
Schedule 5A-CSO RUNOFF CONTROL). These estimates are for quantification of the amount of
combined sewage that overflows the amount of combined sewage that is diverted to an interceptor and
transported to the WWTP and, in some instances, the amount of combined sewage that goes untreated
at the WWTP. Continuous simulation hydrology and hydraulic models like the storm water management
model (SWMM) are often applied for these purposes. However, in the spirit of keeping Green LTCP-EZ
easy, simple relationships and equations were used instead of detailed models. This appendix describes
the method used to make these estimations in the Green LTCP-EZ Template.
Overflow Fraction of Combined Sewage
The fraction of runoff volume that overflows at the CSO hydraulic control at the lower end of a sub-
sewershed is dependent on peak flow rate within the sub-sewershed (runoff plus dry-weather flow) and
the hydraulic control capacity. The peak runoff rate (Qp) for the one-hour, 3-month rainfall is calculated
with the rational method. Similarly, the total volume of runoff (Vt) for the 24-hour, 3-month rainfall is also
calculated with the rational method. The peak runoff rate is compared with the capacity of the hydraulic
control to determine whether or not an overflow occurs. The volume of overflow (Vo) depends on the
shape of the runoff hydrograph through the 24-hour rainfall period.
Dimensional reasoning suggests that the ratio of overflow volume to total runoff volume is a function of
the ratio of hydraulic control capacity to the peak runoff rate. It can be shown that, for a triangular
hydrograph, the following relationship holds:
(1)
where V0 = volume of overflow (MG);
Vt = total volume of runoff (MG);
Qr = hydraulic control or pump station capacity (MGD); and
Qp = peak runoff rate (MGD).
The overflow fraction of combined sewage in Schedule 4-CSO Volume is defined as the ratio of overflow
volume to total volume, and is calculated as follows:
(2)
where f0 = overflow fraction of combined sewage [--].
The actual overflow volume is then computed as follows:
V0 = f0*Vt (3)
The situation from which Equation 1 was derived is depicted in Figure B-1. Empirical studies show that
actual runoff hydrographs are likely to be shaped more concave up relative to the triangular assumption,
so that the fraction of overflow volume would be less than that predicted with Equation 1. To test this, the
B-2
-------
RUNOFF block within the SWMM Model was used to generate runoff hydrographs from design storms of
various lengths and for a variety of catchment characteristics. A series of fractional overflow volumes
were then computed from the resulting hydrographs by varying the hydraulic control flow rate, and the
fractional volumes were compared with Equation 1. Three sets of catchments (designated as set A, set B,
and set C) were used. These catchments represent a wide range of CSO sub-sewershed conditions and
are representative of the conditions that would typically be found in a CSO community. Set A consisted of
161 catchments with areas ranging from 2.7 to 174 acres, and ground slopes ranging from 0.0002 to
0.0173. Set B consisted of 161 catchments with areas ranging from 0.3 to 37 acres, and ground slopes
ranging from 0.0024 to 0.129. Set C consisted of 101 catchments with areas ranging from 16 to 4630
acres, and ground slopes ranging from 0.004 to 0.100. The results are depicted in Figure B-2, which
shows that the observed ratios of overflow volume (represented by the individual points) are below the
predicted ratios of overflow volume for all regulator flow/peak flow ratios (represented by the solid line).
This suggests that using Equation 1 will provide conservative estimates of the volume of overflow at a
CSO hydraulic control.
Note that the model results from this test are dependent on the assumed shape of the design storm
hyetograph. This test and the SWMM Model application were based on the third quartile distribution of
heavy rainfall at a point, taken from Table 10 of Rainfall Frequency Atlas of the Midwest (Huff and Angel
19922). Use of rainfall at a point was considered appropriate for the relatively small sewersheds of Green
LTCP-EZ permittees (less than 1,000 acres). The third quartile distribution is specified for storms of 12 to
24 hours.
Diversion Fraction of Combined Sewage
It is intuitive that the volume of runoff diverted to the interceptor and the WWTP is the difference between
the total volume of runoff and the volume that overflows. However, if the estimate of overflow volume is
conservatively high (using Equation 1), calculating diversion by subtraction (that is, 1 - Equation 1) will
tend to underestimate the volume diverted. An alternate approach called the Hyetograph Approach was
developed to determine a better and more conservative estimate of the fraction of runoff diverted to the
interceptor and the WWTP. The Hyetograph Approach is also based on the ratio of hydraulic control
capacity to peak runoff rate. It is recognized that a small degree of double counting occurs when the two
approaches are used together. That is, the total estimated overflow plus the total estimated conveyance
slightly exceeds the total runoff plus dry weather sanitary flow. This is acceptable, however, in that it
provides a conservative estimate for both quantities, rather than forcing one quantity to be conservative at
the expense of the other.
The Hyetograph Approach assumes that the runoff hydrograph has the same shape as the rainfall
hyetograph, and that the total volume diverted is simply the sum of the volumes less than Qr added up
over the course of the storm. This concept is graphically depicted in Figure B-3, and it was tested with a
simple spreadsheet model. The hyetograph is again the third quartile distribution of heavy rainfall at a
point. Fractional volumes were quantified with a simple spreadsheet model for a range of Qr/Qp ratios,
and those results are shown in Figure B-4 as the Hyetograph Approach. Rather than developing a
regression equation from the results, a lookup table was compiled for inclusion in the Green LTCP-EZ
form and reproduced here as Table B-1. For comparison, Figure B-4 also shows the diverted fraction of
runoff that would be calculated on the basis of 1 - Equation 1.
Fraction of Combined Sewage Untreated at WWTP
Similar to what occurs at a CSO hydraulic control, the fraction of combined sewage that overflows at the
WWTP is dependent on the peak rate of sewage delivered to the WWTP and the primary treatment
2 Table 10 in Rainfall Frequency Atlas of the Midwest provides "the median distribution of heavy storm rainfall at a
point." Huff, Floyd A. and James R. Angel. Rainfall Frequency Atlas of the Midwest. Illinois State Water Survey,
Champaign, Bulletin 71, 1992, pgs 20-21. (http://www.isws.illinois.edU/pubdoc/B/ISWSB-71.pdf, Date accessed
October 22, 2009.)
B-3
-------
capacity at the WWTP. The estimate of combined sewage that overflows or is untreated at the WWTP
(Vo) is also based on Equation 1 but with Vt equal to the total volume of sewage conveyed to the WWTP
during the 24-hour rainfall event, Qr equal to primary treatment capacity at the WWTP, and Qp equal to
the peak rate of sewage delivered to the WWTP. Use of Equation 1 for this estimation is also thought to
be conservative in that it might slightly overestimate rather than underestimate the volume of combined
sewage untreated at the WWTP.
^overflow
Figure B-1. Conceptual diagram of triangular runoff hydrograph
B-4
-------
set A set B
setC
equation 1
0.2
0.4 0.6
Qregulator/Qpeak
0.8
Figure B-2. Comparison of SWMM simulated overflow volumes with Equation 1.
Volume conveyed is sum of
gray columns
Qregulator
1 3 5 7 9 11 13 15 17 19 21 23
storm hour
Figure B-3. Conceptual diagram of calculation of fraction diverted
B-5
-------
» hyetograph approach
1 - equation 1
0.2
0.4 0.6
Qregulator/Qpeak
0.8
Figure B-4. Comparison of fraction conveyed by Hyetograph Approach versus Equation 1
B-6
-------
Table B-1. Fraction of total flow diverted to WWTP from 24-hour rainfall
Ratio of hydraulic control
capacity to peak flow rate
0.01 to 0.02
0.02 to 0.03
0.03 to 0.04
0.04 to 0.05
0.05 to 0.06
0.06 to 0.07
0.07 to 0.08
0.08 to 0.09
0.09 to 0.10
0.10 to 0.12
0.12 to 0.14
0.14 to 0.16
0.16 to 0.18
0.18 to 0.20
0.20 to 0.24
0.24 to 0.28
0.28 to 0.32
0.32 to 0.36
0.36 to 0.40
0.41 to 0.50
0.51 to 0.60
0.61 to 0.70
0.71 to 0.80
0.81 to 0.90
0.91 to 1.00
Diversion fraction
0.04
0.06
0.09
0.11
0.14
0.16
0.19
0.21
0.24
0.28
0.33
0.38
0.42
0.47
0.54
0.62
0.68
0.72
0.76
0.81
0.87
0.91
0.95
0.98
0.99
B-7
-------
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A
and 5B - CSO Control
C-1
-------
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A and 5B - CSO Control
This Appendix summarizes some of the cost estimate figures used in the Green LTCP-EZ Template
Schedules 5A and 5B - CSO CONTROLS. Cost information is relative and depends on the location and
market. Localized and/or site-specific costs should be used when they are available, because local values
will give the most reliable results. Permittees should verify the actual cost for a better understanding of
the effective cost analysis. However, EPA recognizes that local data will not always be available and has
provided the information below, which is based on national data. Descriptions of how the cost estimates
were derived are provided below.
SCHEDULE 5A - CSO RUNOFF CONTROLS (Green Infrastructure Runoff Controls)
Line 15 - Unit cost per square foot for green roof installation.
The default value of $20 per square foot was chosen as a median value from the published values below:
Low Impact Development Center- $15 to $20/sq ft
http://www.lid-stormwater.net/greenroofs cost.htm
Green Roofs for Healthy Cities - $5 to $20/sq ft
http://www.qreenroofs.orq/index.php
City of Portland, Bureau of Environmental Services, 2008 Cost Benefit Evaluation of Ecoroofs -
$15.750/sqft
Wetland Studies and Solutions, Inc. - $31.80/sq ft
http://www.wetlandstudies.eom/portals/4/docUpload/WSSI LID 2007.pdf
Line 23 - Unit cost per square foot for bioretention installation.
The default value of $7 per square foot was chosen as a median value from the published values below:
North Carolina State - $2.32 to $4.65/sq ft
Brown and Schueler, 1997 - C = 7.3V099 with V in ft3
The Economics of Stormwater BMPs in the Mid-Atlantic Region: Final Report.
Center for Neighborhood Technology - $7/sq ft
http://www.cnt.org/natural-resources/demonstration-proiects/st-marqaret-marv-church-case-studv')
Bannerman and Considine, 2003 - $11/sq ft
Line 31- Unit cost per square foot for vegetated swale installation.
The default value of $15 per square foot was chosen as a median value from the published values below:
City of Portland, Bureau of Environmental Services - $5.50/sq ft
Willamette Watershed Program - Task Memorandum 4.1 August 2005
Water Environment Research Federation - $15.00/sq ft
Low Impact Development Best Management Practices Whole Life Cost Model 2007
Center for Neighborhood Technology - $24.00/sq ft
http://www.cnt.org/natural-resources/demonstration-proiects/olqh-case-studv
Line 38- Unit cost per square foot for permeable pavement installation.
The default value of $7 per square foot was chosen as a median value from the published values below:
Low Impact Development Center- $5.50/sq ft
http://www.lowimpactdevelopment.org/lid%20articles/biqbox final doc.pdf
C-2
-------
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A and 5B - CSO Control
City of Portland, Bureau of Environmental Services - $6.34/sq ft
Willamette Watershed Program - Task Memorandum 4.1 August 2005
Wetland Studies and Solutions, Inc. - $7.10/sq ft
http://www.wetlandstudies.eom/portals/4/docUpload/WSSI LID 2007.pdf
PlaNYC 2030 Sustainable Stormwater Management Plan - $8.13/sq ft
http://www.nvc.gov/html/planyc2030/html/stormwater/stormwater.shtml
North Carolina Green Building Technology Database - $11.60
http://www.ncgreenbuilding.org
Line 46- Unit cost per rain barrel/cistern capacity (gallons).
The default value of $1.25 per gallon was chosen as a median value from the published values below:
Metropolitan Water Reclamation District of Greater Chicago - $0.72/gal
http://www.mwrd.org/iri/portal/anonymous/rainbarrel
Water Environment Research Federation - $1.45/gal
Low Impact Development Best Management Practices Whole Life Cost Model 2007
SCHEDULE 5B - CSO NETWORK and WWTP CONTROLS (Green Infrastructure Controls
Network and WWTP Controls)
Line 5 -Unit cost of primary treatment per MGD
EPA's document Cosf of Urban Storm Water Control (EPA 600/R-02/021), January 2002, uses the
following equation to estimate construction costs for off-line storage areas:
C = 2980\/062
where
C = construction cost ($ millions), in 1999 dollars
V= volume of storage system, in MG
The document indicates that this calculation is valid where 0.15 MG < volume < 30 MG
In addition to this equation, one cost value was collected from the literature. This cost is summarized
below:
Chamber Creek WWTP $433,500/MG for primary treatment.
http://www.co.pierce.wa.us/xml/services/home/environ/planning/Appendix%20l.pdf
Line 21 - Unit cost for separation per acre
Costs/acre of sewer separated:
Seaford, Delaware: $1,750
Skokie/Wilmette, Illinois: $31,397
St. Paul, Minnesota: $17,730
Portland, Oregon: $19,000
Providence, Rhode Island: $81,000
These costs came from EPA's Report to Congress: Impacts and Control of CSOs and SSOs, August
2004 (EPA 833-R-04-001).
C-3
-------
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A and 5B - CSO Control
Nashville Phase I - $37,910 ($6,634,372 for 175 acres)
http://www.atlantaga.gov/client resources/mayorsoffice/special%20reports-
archive/csositev.pdf
Nashville Phase II - $23,909 ($12,552,277 for 525 acres)
http://www.atlantaga.gov/client resources/mayorsoffice/special%20reports-
archive/csositev.pdf
Boston - ranged from $60,000/acre for partially separated residential neighborhoods to $190,000/acre
for completely combined downtown, http://books.nap.edu/books/0309048265/html/357.html
Atlanta - $41,000/acre.
http://www.atlantaga.gov/client_resources/mayorsoffice/special%20reports-archive/csp.pdf
DCWASA - $360,000/acre.
http://www.dcwasa.com/news/publications/Ops%20Minutes%20Julv%202004.pdf
Summary: Sewer separation costs an average of approximately $40,000/acre. This cost can be higher if
the area to be separated is in a congested downtown.
Sewer separation costs per linear foot of sewer separated:
Harbor Brook and Clinton sewer separation projects, Syracuse, New York, 2000. Cost was $2,311,126
for 3812 feet of separated pipe, or $606/ft. http://www.lake.onondaga.ny.us/olpdf/ol303ad.pdf
Rouge River project - $175-$220/ft (CSO and SSO)
Portsmouth, New Hampshire - ~$500/ft (personal communication with Peter Rice, Portsmouth).
Line 24 Unit cost per MG of storage
EPA's document Cosf of Urban Storm Water Control (EPA 600/R-02/021), January, 2002, uses the
following equation to estimate construction costs for off-line storage areas:
C = 4.546\/0826
where
C = construction cost ($ millions), in 1999 dollars
V= volume of storage system, in MG
The document indicates that this calculation is valid where 0.15 MG < volume < 30 MG.
In addition to this equation, a number of cost values were collected from the literature. These are
summarized below:
EPA's Report to Congress: Impacts and Control of CSOs and SSOs, August 2004 (EPA 833-R-04-
001). Costs per MG of near surface storage ranged from < $0.10 to $4.61/gallon, with an average of
$1.75 gallon.
EPA Combined Sewer Overflow Technology Fact Sheet: Retention Basins (EPA 832-F-99-032).
Costs range from $0.32 to $0.98/gallon.
Decatur McKinley - $1.09/gallon.
http://www.nap.edu/catalog.php7record id=2049#description, pages 362-363.
Decatur 7th Ward - $0.76/gallon.
http://www.nap.edu/catalog.php7record id=2049#description, pages 362-363.
C-4
-------
Appendix C. Cost Estimates for Green LTCP-EZ Template, Schedules 5A and 5B - CSO Control
Rouge River- range from $2.86 to $8.53/gallon of storage for aboveground facilities. The average
was$5.18/gallon.
http://www.rougeriver.com/cso/overview.html
San Francisco - $2.35/gallon.
http://www.swrcb.ca.gov/rwqcb2/Agenda/07-16-03/07-16-03-fsheetattachments.doc
Summary: On average, near surface storage costs $2.00 per gallon of storage.
C-5
-------
Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Appendix D. Green Infrastructure Runoff Controls Fact Sheets and
Additional Information for Schedule 5A - CSO Runoff Control
This Appendix presents fact sheets on the 6 green infrastructure technologies utilized by the Green
LTCP-EZ (plus a fact sheet on the runoff reduction benefits available from tree planting). These fact
sheets are intended to summarize some of the references and resources available to help users better
understand the design, performance and implementation issues associated with green infrastructure.
These resources are not a substitute for local design standards or guidance when available. The cost
information provided in the fact sheets is relative and depends on the location and market. Permittees
should verify the actual costs of these practices for their communities to provide for a more effective cost
analysis.
The 6 green infrastructure technologies are:
Green Roofs
Rain Gardens
Vegetated Swales
Permeable Pavement
Rain Barrels & Cisterns
Constructed Wetlands
Overview and General Information References
EPA Office of Wastewater Management (OWM), Managing Wet Weather with Green Infrastructure
Web site (http://cfpub.epa.gov/npdes/home.cfm7program id=298) - Contains information on EPA
policies, case studies, technical information, and funding sources.
Center for Neighborhood Technology, Green Values Stormwater Toolbox (http://greenvalues.cnt.org/)
- Contains overview technical information and two green infrastructure stormwater calculators that can
be used to estimate costs and benefits of various green infrastructure applications.
Center for Watershed Protection, Stormwater Manager's Resource Center
(http://www.stormwatercenter.net/) - Contains overview technical information, fact sheets, and design
guidelines and manuals.
International Stormwater BMP Database (http://www.bmpdatabase.org/) - Database of hundreds of
BMPs performance studies (including many green infrastructure studies).
Water Environment Research Foundation (WERF), Livable Communities Web site
(http://www.werf.org/livablecommunities/) - Contains communication and implementation tools and
resources and in-depth case studies.
Low Impact Development Center, LID Urban Design Tools Web site, (http://www.lid-stormwater.net/) -
Contains design tools, design examples, and in-depth case studies.
D-1
-------
Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Green Roofs
A green roof is a roof that is partially or completely covered with a layer of vegetation and growth medium
over a waterproofing membrane. The depth of the planting medium, amount of maintenance and planted
material varies depending on the design plan. Extensive green roofs have a thin soil layer and are lighter,
less expensive and require less maintenance. Intensive green roofs are characterized by a deeper soil
layer, are heavier, and have higher capital costs. Intensive green roofs may support an increased
diversity of plants but also have a higher maintenance requirement.1
Construction
Green roofs may be installed on a large or small scale
either as a retrofit, or as part of new construction.2 Prior to
installation, roof structures must be capable of supporting
the weight of an intensive or extensive green roof system.
Once it is verified that the weight load can be
accommodated, construction may begin. Most green roofs
installed in North America consist of four distinct layers:
an impermeable roof cover or roofing membrane, a
lightweight drainage layer consisting of porous media
capable of water storage, a geosynthetic layer to prevent
fine soil media from clogging porous media soil or other
lightweight planting or growth medium, and adapted
vegetation.
Vegetation
Growing Medium
Root Barrier Filter Fabric
Drainage. Aeration, WaterStorage Core
Separation Fabric
Insulation
Roofing Membrane
Structural Support
3,4
AMERGREEN prefabricated drain illustration published with
permission from American Wick Drain Corporation.
Benefits
The primary benefits of green roofs include retention of rainfall, reduction in stormwater quantity, and
overall improvement of water quality.5 Associated benefits may include enhanced stormwater
management, reduced building energy demand associated with insulation of the green roof, reduced
urban heat islands, improved air quality, reduced pollutant loads, and improved structural durability and
roof longevity.6 7 Moreover, green roofs may provide enhanced amenity value and habitat in urban areas.8
For best stormwater management results, green roofs should be used in conjunction with other practices
such as bio-infiltration and rain-gardens, where possible.
Limitations
The greatest limitation to the installation and use of green roofs is cost relative to standard roofing
practices. Estimates indicate that a new green roof may cost approximately $15.52 per square foot and a
retrofit may cost as much as $25.87 per square foot (values inflated to January 2010 dollars).9 Costs for a
green roof are greater than conventional roofs which have construction costs of approximately $10 per
square foot.10 For a 40,000 square foot roof, the increased cost associated for green roof installation
ranges from $220,800 to $634,800 for a new and retrofitted roof, respectively. Despite lasting two to three
times longer than a conventional roof,11 having decreased replacement costs, and paying for itself within
a 20 year roof life12 many property owners remain hesitant to contribute the upfront costs necessary to
install a green roof. However, A recent survey of 300 Brooklyn property owners found that approximately
77 percent of respondents would be willing to install a green roof on their property if cost neutral to a
conventional roof.
13
D-2
-------
Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Climate Considerations
Green roofs are appropriate for use in warm and cold climates given that the proper vegetation is
installed. For example, research at the University of Toronto offers data suggesting that "winter green
roofs," composed of evergreens, juniper shrubs, and thicker soil base, provide heat loss and
environmental benefits associated with standard green roofs.
14
CSO Impact
Stormwater retention by green roofs can vary seasonally and by media. During the summer months, a
study determined nearly 95 percent of the precipitation was retained. During winter, retention was smaller
(<20 percent) and not significant. Seasonally adjusted,
retention was approximately 50 percent of total
precipitation during the study period.15 Depending on
media depth, annual runoff volume reductions can range
from 40 percent (for 2 inch media)16 to in excess of 50
17
The Calhoun School, New York, NY. Courtesy of James D'Addio.
percent for 3 inch media.
A recent report published for New York City suggests that
for every $1,000 invested in new green roof construction,
retrofits, and incentivized green roofs, will result in up to
810 gallons, 865 gallons, and 12,000 gallons of annual
stormwater reductions,
18
Computer modeling for the District of Columbia estimates that installing 20 million square feet of green
roofs, 20 percent of the roof area for all city buildings over 10,000 square feet, over the next 20 years will
result in citywide reduction in runoff of 1 percent and CSO discharges of 15 percent.19 These modeling
results suggest that green roofs are anticipated to retain and store 430 million gallons of rainwater
annually.
20
Maintenance
Maintenance largely depends on the type of green roof system installed and the type of vegetation
planted. Green roof maintenance may include watering, fertilizing and weeding and is typically greatest in
the first two years as plants become established. Roof drains should be cleared when soil substrate,
vegetation or debris clog the drain inlet. Basic maintenance for extensive vegetated covers typically
requires about 3 man-hours per 1,000 square feet, annually.21 Maintenance requirements in intensive
systems are generally more costly and continuous, compared to extensive systems. The use of native
vegetation is recommended to reduce plant maintenance in both extensive and intensive systems. Green
roofs should be inspected frequently for leaks and other functional or structural concerns.
22
Costs
Green roofs cost from $15.52 to $25.87 per square foot to install (January 2010 dollars). Roof retrofits
and intensive roofs with soil deeper than 6 inches will be more expensive.24 Operating and maintenance
costs (January 2010 dollars) are estimated to be approximately $1.74 per square foot per year.25
Although green roof installation costs may be high, relative to other low-impact development BMPs,
substantial cost savings may be observed in relation to decreased cooling and heating demand, avoided
stormwater facility costs, increased roof longevity; and thus decreased life cycle costs.26
D-3
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
1 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
2 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
3 Pennsylvania Association of Conservation Districts (PACD). (1998). Pennsylvania Handbook of Best Management
Practices for Developing Areas. Harrisburg, PA. As cited in USEPA. (2009). Green Roofs for Stormwater Runoff
Control. 81 pp. Available at: < http://www.epa.qov/nrmrl/pubs/600r09026/600r09026.pdf>.
4 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
5 Pennsylvania Association of Conservation Districts (PACD). (1998). Pennsylvania Handbook of Best Management
Practices for Developing Areas. Harrisburg, PA. As cited in USEPA. (2009). Green Roofs for Stormwater Runoff
Control. 81 pp. Available at: < http://www.epa.qov/nrmrl/pubs/600r09026/600r09026.pdf>.
6City of Portland Environmental Services. (2008). Cosf Benefit Evaluation of Ecoroofs. 42 pp. Available at:
.
7 Velazquez, L. S. 2005. Greenroofs.com. Available at: .
8Kloss, C and Calarusse, C. (2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined
Sewer Overflows. Prepared for the Natural Resources Defense Council. 56 pp. Available at:
.
9 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
10 City of Portland Environmental Services. (2008). Cosf Benefit Evaluation of Ecoroofs. 42 pp. Available at:
.
11 Penn State Green Roof Research. About Green Roof Research, Available at:
.
12 Ballensky, D. (2006). Built up roofs are expected to last 20 years. Roofing Life-Cycle Costs Emerge, Buildings.
Available at: .
13 Montalto, F.A., Culligan, P.J., Behr, C.T., (2007). Results of a property owner survey of acceptance of urban low
impact development. In: Montalto, F.A., Culligan, P.J. (Eds.), Innovative Approaches to the Management of
Urban Soil and Water. ASCE Geotechical Practice Publication, in preparation.
14 University Of Toronto. (2005). Green Roofs In Winter Hot Design For A Cold Climate. Science Daily. Available at:
.
15 USEPA. (2009). Green Roofs for Stormwater Runoff Control. 81 pp. Available at:
.
16 Scholz-Barth, K. (2001). Green roofs: Stormwater management from the top down. Environmental Design and
Construction. January/February. As cited in USEPA. (2009). Green Roofs for Stormwater Runoff Control. 81 pp.
Available at: .
17 Miller, C. (1998). Vegetated Roof Covers: A new method for controlling runoff in urbanized areas. Proceedings:
Pennsylvania Stormwater Management Symposium. Villanova University. Villanova, PA. As cited in USEPA.
(2009). Green Roofs for Stormwater Runoff Control. 81 pp. Available at:
.
18 Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp.
Available at: < http://www.riverkeeper.orq/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-
O8.pdf>.
19 Barbara Deutsch, et al. (2005). Re-Greening Washington, DC: A Green Roof Vision Based On Storm Water and Air
Quality Benefits, Casey Tree Endowment Fund and LimnoTech, Inc.,. as cited in Kloss, C and Calarusse, C.
(2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows.
Prepared for the Natural Resources Defense Council. 56 pp. Available at:
.
20 Barbara Deutsch, et al. (2005). Re-Greening Washington, DC: A Green Roof Vision Based On Storm Water and Air
Quality Benefits, Casey Tree Endowment Fund and LimnoTech, Inc.,. as cited in Kloss, C and Calarusse, C.
(2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows.
Prepared for the Natural Resources Defense Council. 56 pp. Available at:
.
21 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
22 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
lew York State Department of Environmental Conservation. (2010). New York State S
Design Manual. 642 pp. Available at: .
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
24 Peck, S. and M. Kuhn. Design Guidelines for Green Roofs. As cited in Plumb, M. (2008). Sustainable Raindrops:
Cleaning New York Harbor by Greening the Urban Landscape. 40 pp. Available at:
.
25 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
:ity of Portland Environmental Services. (2008). Cosf Benefit Evaluation <
.
26 City of Portland Environmental Services. (2008). Cosf Benefit Evaluation of Ecoroofs. 42 pp. Available at:
Additional Resources for Green Roofs:
Green Roofs for Healthy Cities, Green Roofs Tree of Knowledge Web site (http://qreenroofs.org/qrtok/)
Contains searchable database on green roofs research (including design and costs/benefits) and policy.
Green Roofs for Healthy Cities, Green Save Calculator (http://www.qreenroofs.org/index.php/qreensavecalc)
Allows user to compare cost of green roofs with conventional roofing systems.
North Carolina State University, Green Roof Research Web site, (http://www.bae.ncsu.edu/qreenroofs/)
Contains background information and current performance research on green roofs.
Penn State, Center for Green Roof Research Web site, (http://horticulture.psu.edu/cms/qreenroofcenter/)
Contains current performance research data related to green roofs.
Virginia Department of Conservation and Recreation, Stormwater Design Specifications
("http://www.chesapeakestormwater.net/storaqe/first-draft-bavwide-desiqn-
specificationsi/BAYWIDE%20No%205%20GREEN%20ROOF%20DESIGN%20SPECFICATION.pdf).
Contains design specifications for green roofs.
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Rain Gardens
Rain gardens are man-made landscaped depressions designed to collect and store small volumes of
stormwater runoff.1 Rain gardens provide natural infiltration, directing stormwaterto recharge
groundwater rather into storm drains.2
Construction
Rain gardens, commonly used in residential settings,3
are designed as passive filter systems, with or without
an underdrain. Rain gardens typically require an area
of 100 to 300 square feet, where water can collect and
infiltrate.4 Typical design generally include an optional
pretreatment, flow entrance, ponding area, a gravel
drainage layer used for dispersed infiltration, organic
or mulch layer, planting soil and filter media, plant
material, sand bed and/or gravel base.56 Stormwater
directed into the rain garden temporarily ponds in the
system and seeps into the soils over a period of one to
two days. The ideal soil composition for infiltration
typically contains 50 to 60 percent sand, 20 to 30
percent compost, and 20 to 30 percent topsoil.7
Areas in which soils are not permeable enough to
allow water to infiltrate and drain should be amended,
to be closer to the ideal composition, prior to rain garden construction.
5-08.
Rain Garden located at the Berkeley County Judicial Complex in
Martinsburg, West Virginia. 29 April, 2008. Photo Courtesy of:
Sherry Wilkins, WVDE.
Benefits
Rain gardens provide many benefits; the most notable include pollutant treatment, groundwater recharge
augmentation, addition of micro-scale habitat, aesthetic improvement, and transpiration via the planted
vegetation.8
Limitations
Rain gardens are fully functional in most settings. The most notable limitations to rain gardens are design
limitations. For example, rain gardens require relatively flat slopes, augmentation based on soil type may
be necessary to provide appropriate infiltration, and rain gardens cannot be used to treat large drainage
areas including parking lots or roadway runoff.9
Climate Considerations
10
Rain gardens are appropriate for almost every climate in the United States. However, since rain
gardens rely on a successful plant community to stabilize the ponding area, promote infiltration, and
uptake pollutants, plant species must be selected that are adaptable to the given climate.11 For best
results, native plant species are suggested for planting.
CSO Impact
Several studies have demonstrated that the installation of rain gardens can reduce CSO volume. One
residential area model simulation suggested a 36 percent reduction in combined sewer overflow volume
during major storm events, assuming 100 percent implementation of the rain gardens' design plan.12 A
hydraulic modeling study for the Norwood Park sewershed, a neighborhood outside of Chicago, Illinois,
D-6
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
determined that three-inch and six-inch-deep rain gardens installed at each home could reduce total
runoff volume by approximately 4 percent and 7 percent, respectively, for the same six-month or one-year
storm events.
13
Maintenance
Properly designed and installed rain gardens
require regular maintenance. Rain gardens require
living plants; thus pruning and weeding may be
required, particularly during vegetation
establishment. Mulch should be reapplied as
needed when erosion is evident or once every 2 to
3 years. Rain gardens should be inspected at least
two times per year for sediment buildup, detritus,
erosion, etc. Trees and shrubs should be inspected
twice per year to evaluate health.14 During periods
of extended drought, rain gardens may require
watering.
Costs
Trent Street Rain Gardens, Victoria, BC, Canada. Courtesy of Murdoch
de Greefflnc.
Construction costs associated with rain gardens vary depending on installation costs, size, and native
plants selected. A recent study generalized the inflated cost for bioretention construction as follows:15
Construction, design and permitting cost = 7.30 (Volume of water treated by the facility, ft3)099
For self-installed rain gardens, costs inflated to January 2010 dollars generally range between $3.88 and
$6.47 per square foot. Costs associated with hiring a landscaping company to install a residential rain
garden can be in excess of $15 per square foot (January 2010 dollars).1617 Operating and maintenance
costs are estimated at 5.0 to 10.9 percent of the construction costs, annually. Based on a construction
cost of approximately $15, annual operation and maintenance costs (January 2010 dollars) are estimated
to be approximately $1.69/per square feet of drainage.18
1 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
2 Clean Water Campaign. Rain Gardens for Home Landscapes. 2 pp. Available at:
.
3 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
4 Wisconsin Department of Natural Resources. (2003). Rain Gardens: A how-to manual for homeowners. 32 pp.
Available at: .
5 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
6 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
7 Clean Water Campaign. Rain Gardens for Home Landscapes. 2 pp. Available at:
.
8 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
9 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Bioretention (Rain
Gardens). Available at:
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
10 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Bioretention (Rain
Gardens). Available at:
.
11 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
12 The Civic Federation. (2007). Managing Urban Stormwater with Green Infrastructure: Case Studies of Five U.S.
Local Governments. Prepared for The Center for Neighborhood Technology. 56 pp. Available at:
.
13 Kloss, C and Calarusse, C. (2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and
Combined Sewer Overflows. Prepared for the Natural Resources Defense Council. 56pp. Available at:
.
14 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
15Brown, W., and T. Schueler. (1997). The Economics of Stormwater BMPs in the Mid-Atlantic Region. Prepared for
Chesapeake Research Consortium. Edgewater, MD. Center for Watershed Protection. Ellicott City, MD. As cited
in USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Bioretention
(Rain Gardens). Available at:
.
16 The Groundwater Foundation. Rain Gardens 101. Available at .
17Wisconsin Department of Natural Resources. (2003). Rain Gardens: A how-to manual for homeowners. Available
at: .
18 Weiss, P.T., J. S. Gulliver and A. J. Erickson, (2005). The Cost and Effectiveness of Stormwater Management
Practices. Prepared for Minnesota Department of Transportation. Report 2005-23. Available at:
.
Additional Resources on Rain Gardens and Bioretention:
Los Angeles County BMP Design Criteria (http://www.ci.chula-vista.ca.us/Citv Services/
Development Services/Engineering/ PDF%20Files/ StormWaterManual/B-1.pdf) - Contains design
protocols and considerations for bioretention applications
University of Wisconsin - Madison, Civil & Environmental Engineering Department, RECARGA
(http://dnr.wi.gov/runoff/stormwater/technote.htm) - Bioretention sizing tool
North Carolina State University, Bioretention Web site, (http://www.bae.ncsu.edu/topic/bioretention/) -
Contains background information and current performance research on bioretention applications
Prince George's County, Maryland Bioretention Design Specifications and Criteria,
(http://www.princegeorgescountymd.gov/der/bioretention.asp) - Contains siting and design criteria for
bioretention facilities
Virginia Department of Conservation and Recreation, Stormwater Design Specifications
(http://www.chesapeakestormwater.net/storage/first-draft-baywide-design-
specificationsi/BAYWIDE%20No%209%20BIORETENTION%20DESIGN%20SPECIFICATION.pdf)-
Contains design specifications for bioretention facilities
D-8
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Vegetated Swales
Vegetated swales, including the design variations of grassed channels, dry swales, wet swales, biofilters,
and bioswales, are turf-lined open drainage channels designed to slow runoff, promote the infiltration of
stormwater into the soil media, and reduce pollutant loads in the process of conveying runoff.1
Construction
Swales are constructed as broad, shallow, trapezoidal or parabolic, channels and are often heavily
vegetated with close growing, water-resistant, high pollutant removal plants.2 Longitudinal slopes should
be as low as possible, and never more than 4 percent. A small forebay should be used at the front of the
swale to trap incoming sediments.3 Vegetation is typically underlain by at least 24 inches of permeable
soil and/or sand4 to provide significant volume reduction and reduce the stormwater conveyance rate.5
The permeable soil media should have a minimum infiltration rate of 0.5 inches per hour and contain a
high level of organic material to enhance pollutant removal. Swales should be designed to treat runoff
from small drainage areas (less than 5 acres), so that the volume of flow does not overwhelm the filtering
abilities of the BMP.6
Benefits
Swales slow runoff velocity, filter out stormwater
pollutants, reduce runoff temperatures, and under
certain conditions, infiltrate runoff into the ground as
groundwater.7 Since swales may discretely blend in
with existing landscape features, they can also provide
an aesthetic enhancement, particularly if native
vegetation is utilized.
Limitations
Grass Swale constructed in median on MD route 32 near
Savage, MD. Courtesy of: James Stagge & Allen P. Davis,
University of Maryland.
A major concern when designing swales is ensuring
that excessive stormwater flows, slope, and other
factors do not combine to produce erosive flows that may exceed the capacity of the swale. See above
for construction specifications to ensure the most effective use of swales. Swales generally cannot treat
drainage acres over 5 acres.8
Climate Considerations
Swales can be applied in most regions of the United States. In arid and semi-arid climates, however, the
value of installing and maintaining swales should be weighed against the needed to irrigate them.9 If
swales are to be implemented in arid or semi-arid climates, swales should be designed with drought-
tolerant vegetation, such as buffalo grass.
CSO Impact
A study of a recent stormwater management project using bioswales in Portland, OR, estimated that
implantation removed 1 million gallons of stormwater annually from the combined sewer system.10
Reduction in stormwater flow to the combined sewer system may ultimately decrease the occurrence and
severity of CSOs in the surrounding sewershed.
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Maintenance
Compared to otherstormwater management measures, the required upkeep of vegetated swales is
relatively low. Maintenance strategies focus on sustaining the hydraulic and pollutant removal efficiency
of the channel, as well as maintaining a dense vegetative
cover. The following maintenance activities are suggested
annually, and within 48 hours after every major storm
event: inspect and correct erosional problems, damage to
vegetation, and sediment and debris accumulation; inspect
vegetation on side slope for erosion and formation of
gullies; inspect for pools of standing water; mow and trim
vegetation to ensure safety, aesthetics and proper
operation; inspect for litter and remove litter as
appropriate; inspect for uniformity in cross-section and
longitudinal slope; inspect inlet and outlet for signs of
blockage, correct as needed.11 Swales should be
irrigated if implemented in arid or semi-arid climates.
12
Grass Swale constructed in median on MD route 32 near
Savage, MD. Courtesy of: James Stagge & Allen P. Davis,
University of Maryland.
Costs
The cost of installing and maintaining swales varies widely with design, local labor and material rates, real
estate value, and contingencies. In general, swales are considered a relatively low cost control measure13
at an implementation cost of approximately $7.66 per square foot of swale (January 2010 dollars).14
Annual operation and maintenance costs range from 5 to 7 percent of construction costs, or $0.54 per
square foot based on a construction cost of $7.66 per square foot.15
1 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu ofBMPs: Grassed Swales.
Available at:
.
2 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Storm water Best Management Practices Manual. 685 pp. Available at:
.
3 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu ofBMPs: Grassed Swales.
Available at:
.
4 Tredyffrin Township, Chester County Pennsylvania Department of Public Works. Vegetated Swale. 9pp. Available
at: .
5 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Storm water Best Management Practices Manual. 685 pp. Available at:
.
6 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu ofBMPs: Grassed Swales.
Available at:
.
7 Charles River Watershed Association. (2008). Low Impact Best Management Practice (BMP) Information Sheet:
Vegetated Swale. 2pp. Available at: .
8 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu ofBMPs: Grassed Swales.
Available at:
.
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
9 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Grassed Swales.
Available at:
.
10 Kloss, C and Calarusse, C. (2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and
Combined Sewer Overflows. Prepared for the Natural Resources Defense Council. 56 pp. Available at:
.
11 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
12 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Grassed Swales.
Available at:
.
13 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at
.
14 Stormwater Manager's Resource Center. Stormwater management Fact Sheet: Grass Channel. Available at:
.
15 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
Additional Information on Vegetated Swales:
Los Angeles County BMP Design Criteria (http://www.ci.chula-vista.ca.us/Citv Services/
Development Services/Engineering/ PDF%20Files/ StormWaterManual/B-13.pdf) - Contains design
protocols and considerations for vegetated swales
Virginia Department of Conservation and Recreation, Stormwater Design Specifications
http://www.chesapeakestormwater.net/storaqe/first-draft-bavwide-desiqn-
specificationsi/BAYWIDE%20No%203%20GRASS%20CHANNEL%20SPECIFICATION.pdf) - Contains
design specifications for grass channels
University of Florida, Field Guide to Low Impact Development
(http://buildqreen.ufl.edu/Fact sheet Bioswales Vegetated Swales.pdf) - Contains overview and design
considerations for vegetated channels
Indianapolis Sustainlndy, Swale Fact Sheet (http://www.sustainindv.Org/assets/uploads/4.7%20Swales.pdf)
- Contains example of municipal design considerations for vegetated channels
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Porous Pavement and Permeable Pavers
Permeable pavement is a class of paving materials that allow for the movement of water in and around
the paving material. Permeable pavement is designed to infiltrate stormwater runoff through the surface
and has two basic design variations: porous pavement and permeable pavers.1
Construction
Porous pavement, similar in look to conventionally paved surfaces, is constructed from a permeable
surface, generally concrete or asphalt, and has three main design components: surface, storage, and
overflow.2 Porous pavement is underlain by a choke course, open-graded base reservoir, open-graded
subbase reservoir, optional underdrain, optional geotextile liner, and subgrade. An underdrain provides
peak flow control so that water levels do not rise to the
pavement level during large storm events.3 A geotextile
layer may be used to separate the subbase from the
subgrade and prevent the migration of soils into the
aggregate subbase or base.4 As stormwater drains
through the surface, it is temporarily held in the voids of
the paving medium, and then slowly drains into the
underlying, uncompacted soil.5
Permeable pavers, including reinforced turf, interlocking
concrete modules, and brick pavers, do not require the
same level of design intensity when compared to porous
pavement. Permeable pavers are generally not as
extensive in depth, and generally have no underground
stone reservoir.6 However, these systems may provide some level of infiltration through the permeable
surface to the ground and may be an important source of erosion control.
Benefits
Porous pavement can dramatically reduce the rate and volume of runoff by providing temporary
stormwater storage, can recharge the groundwater, promote infiltration, and improve water quality.
Porous pavement has gained acceptance as a construction material for low traffic roads, parking lots,
sidewalks, among others.7 Permeable pavers are gaining acceptance for use in single-family residential
driveways, sidewalks, plazas, and courtyard areas.8 Permeable pavers may also provide aesthetic
improvements in addition to the aforementioned stormwater management benefits.
Limitations
The most significant limitation to use of porous pavement is the higher costs associated with installation
as well as operation and maintenance cost9, relative to standard paving practices. A recent survey of 300
Brooklyn property owners found that approximately 79 percent of respondents would be willing to install
porous pavement if cost neutral to other "gray" practices.10 However, without subsidies, porous pavement
in many areas may still be more expensive than traditional asphalt.11 Additional limitations may be site
specific including unsuitable grade and subsoils, and/or high flow volume sites which may be unsuitable
for implementation of this BMP.
Porous pavement close-up, Aurora, CO. Courtesy of: The
Colorado Association of Stormwater and Floodplain Managers
(CASFM).
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Climate Considerations
Freeze-thaw cycles tend to not adversely affect porous pavement or permeable pavers because water
drains through the surface and into the subsurface bed. In northern climates, porous pavement has less
of a tendency to form black ice, require less plowing, and develops fewer cracks than conventional
asphalt.12 Some regional limitations associated with porous pavement including subsurface soil types,
depths, and underlying soil permeability should be examined prior to implementation.13
CSO Impact
USEPA research recognizes porous pavement as a cost-
effective approach to reducing CSOs and improving urban
water quality.14 In a set of experiments in Athens, Georgia, a
porous parking lot built over low permeability, clay-rich soils
was found to produce 93 percent less runoff than a standard
asphalt lot, as measured during nine different storms each
totaling between 0.3 and 1.85 cm of rainfall.15 Modeling data
suggests maximum implementation of porous pavement
alone may generate CSO reductions of approximately
11 percent. Permeable Pavers at the transit center parking lot in
" Mound, Minnesota. Courtesy of: Julie Westerlund, MN
DNR.
Maintenance
Porous pavement requires extensive maintenance compared with other practices, given the potential for
clogging of the porous surface. To ensure the proper function of porous pavement the following activities
should be completed on a monthly cycle: ensure that the paving area is clean of debris; ensure that the
paving dewaters between storms; ensure that the area is clean of sediment. The surface should be
inspected annually for signs of deterioration. The surface should be vacuum swept as needed to keep it
free of sediment.17 Similar maintenance activities should be considered for permeable pavers. Properly
18
installed and maintained porous pavement has a significant lifespan, in excess of 20 years.
Costs
Porous pavement is significantly more expensive than traditional asphalt. Porous pavement can range
from $3.93 to $5.90 per square foot (January 2010 dollars), depending on the design.19 In comparison 1
conventional pavement, porous pavement can cost $45,000 to $100,000 more per impervious acre
treated.20 Annual operation and maintenance costs are roughly 4 percent of capital costs, or
approximately $2.63 per square foot (January 2010 dollars).21
1 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
2 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
3 USEPA. (2009). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Porous Asphalt
Pavement. Available at:
.
4 USEPA. (2009). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Porous Asphalt
Pavement. Available at:
.
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
5 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
6 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
7 Ferguson, B.K.. (2005). Porous Pavements. Taylor & Francis, Boca Raton, FL, 577 pp. As cited in Montalto, F.,
Behr, C., Alfredo, K., Wolf, M., Arye, M., and Walsh, M. (2007). Rapid assessment of the cost-effectiveness of
low impact development for CSO control. Landscape and Urban Planning. 82:117-131.
8 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
9 The Center for Neighborhood Technology, prepared by The Civic Federation. (2007). Managing Urban Stormwater
with Green Infrastructure: Case Studies of Five U.S. Local Governments. 56 pp. Available at:
.
10 Montalto, F., Behr, C., Alfredo, K., Wolf, M., Arye, M., and Walsh, M. (2007). Rapid assessment of the cost-
effectiveness of low impact development for CSO control. Landscape and Urban Planning. 82:117-131.
11The Civic Federation. (2007). Managing Urban Stormwater with Green Infrastructure: Case Studies of Five U.S.
Local Governments. Prepared for The Center for Neighborhood Technology. 56 pp. Available at:
.
12 USEPA. (2009). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Porous Asphalt
Pavement. Available at:
.
13 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
14 Field, R., Masters, H., Singer, M. (1982). Status of porous pavement research. Water Research. 16: 849-858.
15 Dreelin, E.A., Fowler, L., Carroll, C.R. (2006). A Test of Porous Pavement Effectiveness on Clay Soils During
Natural Storm Events. Water Research. 40: 799-805.
16 Montalto, F., Behr, C., Alfredo, K., Wolf, M., Arye, M., and Walsh, M. (2007). Rapid assessment of the cost-
effectiveness of low impact development for CSO control. Landscape and Urban Planning. 82:117-131.
17 Watershed Management Institute (WMI). (1997). Operation, Maintenance, and Management of Stormwater
Management Systems. Prepared for US EPA Office of Water. Washington, DC.
18 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
19 The Stormwater Manager's Resource Center. Stormwater Management Fact Sheet Porous Pavement. Available
at:
20 The Stormwater Manager's Resource Center. Stormwater Management Fact Sheet Porous Pavement. Available
at:
21 California Stormwater Quality Association. (2003). California Stormwater BMP Handbook: New Development and
Redevelopment: Pervious Pavement. 10pp. Available at:
Additional resources on Porous Pavement and Permiable Pavers:
Los Angeles County BMP Design Criteria (http://www.ci.chula-vista.ca.us/City Services/
Development Services/Engineering/ PDF%20Files/ StormWaterManual/B-10.pdf) - Contains design
protocols and considerations for permeable pavement applications
University of New Hampshire Stormwater Center, Design Specifications for Porous Asphalt Pavement and
Infiltration Beds ("http://www.unh.edu/erq/cstev/pubs specs info/unhsc pa spec posted 06 09.pdf) -
Contains design specifications for permeable asphalt applications
North Carolina State University, Permeable Pavement Research Web site,
(http://www.bae.ncsu.edu/info/permeable-pavement/) - Contains background information and current
performance research on permeable pavement applications
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Virginia Department of Conservation and Recreation, Stormwater Design Specifications
(http://www.chesapeakestormwater.net/storage/first-draft-bavwide-design-
specificationsi/BAYWIDE%20No%207%20PERMEABLE%20PAVERS.pdf) - Contains design specifications
for permeable pavers
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Rain Barrels and Cisterns
Rain barrels and cisterns are on-site rainwater collection systems, des
igned to collect roof stormwater runoff.1
Construction
Rain barrels are generally above ground residential
systems while cisterns are for commercial and/or
industrial sites. Rain barrels can be created from
any water-retaining material from an on-site or pre-
manufactured source.2 Rain barrels often hold
between 55 to 250 gallons with 55 to 75 gallon
barrels being the most commonly used sizes.3
Cisterns are large, underground or surface
containers. Cisterns are generally constructed
from fiberglass, steel, concrete, plastic, or brick. A
typical cistern holds tens of thousands of gallons.4
The basic components of a rain barrel or cistern
include a connection to the gutter downspout,
watertight storage container, secure cover,
debris/mosquito screen, coarse inlet filter with
clean-out valve, overflow pipe, manhole or access hatch, drain for cleaning, hose connection for water
reuse, and extraction system (tap or pump).5 Additional features may include a water level indicator,
sediment trap, or connector pipe to an additional tank for extra storage volume.6
Benefits
Benefits from rain barrels include applications from water re-use and reductions in stormwater volume.
Captured water from rain barrels and cisterns may be re-used for irrigation, landscaping, sidewalk
cleaning, industrial use, firefighting, or, in more elaborate systems, connected to the buildings cooling
towers or plumbing for use in toilets.7 Benefits related to reductions in stormwater volume include
reductions in transportation of pollutants, especially heavy metals, associated with atmospheric
deposition on rooftops into receiving waters and reduced water consumption for nonpotable uses.8
Limitations
The biggest limitation to the installation and use of rain barrels and cisterns is the need for active
management/maintenance and initial capital cost.9 Generally, the ease and efficiency of municipal water
supply systems and the low cost of potable water discourage people from implementing on-site rainwater
collection and reuse systems. Improper or infrequent use of the collection system by the property owner,
such as neglecting to empty the rain barrel between storm events, may result in unintended discharges.
Typical 55-gallon rain barrel. Photo courtesy of Lexington-Fayette Urban
County Government (KY)
10
Climate Considerations
Climate is an important consideration for rain barrel and cistern use as the system should be designed to
account for freezing potential. Rain barrels and cisterns placed on the ground require extra insulation on
the exposed surfaces which may include lining the intake pipe with heat tape and closing the overflow
valve. Water levels must be lowered at the beginning of winter to prevent possible winter ice damage and
provide the needed storage for capturing rooftop runoff from snow melt. The year round use of rain
barrels in cold climates is not recommended since bursting may occur due to ice formation and freezing
D-16
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
temperatures.11 It is recommended that disconnection occur from the roof gutters during winter months.
During the time in which the rain barrel or cistern is disconnected downspout piping must be reconnected
and directed to a grassy area away from the structure to prevent winter snowmelt from damaging building
foundations.
CSO Impact
Rain barrels and the associated stormwater captured can significantly reduce stormwater runoff into
sewers. The City of Milwaukee found that attaching rain barrels to 40,000 houses could decrease runoff
by 273 million gallons per year and decrease water treatment plant operation costs during light rainfall.12
Maintenance
Rain barrel maintenance is not complicated when compared to other green practices. The following
components should be inspected at least twice a year and repaired or replaced as needed: roof
catchment, gutters, downspout, entrance at rain barrel, runoff/overflow pipe, and spigot.13 On a monthly
cycle the rain barrel should be emptied to allow for more rooftop runoff and decrease the likelihood of
algal growth. Once a year the rain barrel should be tipped over and rinsed out with a hose. Leaks in rain
barrels can be repaired with aquarium caulk, or a clear sealant available at most hardware stores.14
Maintenance of cisterns is similar to rain barrels, although on a much larger scale.15 The tank of a cistern
should be cleaned out about once a year if debris is present. Screens should be cleared as necessary
and compacted sediment cleaned out semi-annually.16
Costs
Fifty-five-gallon rain barrels typically cost $50 to $100 for prefabricated units, or $30 for do-it-yourself
kits17 (January 2010 dollars). Costs for large cistern systems are dependent on many site-specific
factors, such as whether excavation is required for underground units. The following table shows cistern
tank costs depending on the tank material and capacity. This table does not take into account the
installation of the tank, site preparation, and other site-specific factors.
Cistern tank cost by type ($/gallon, installation not included)*
Fiberglass
10, 000 gal and up
$1.34
Steel
500-1 5, 000 gal
$2.54
Plastic
50-1 ,500 gal
$1.45
Concrete
2,000 gal and up
$1.68
Source: WERF BMP and LID Whole Life Cost Model, Version 2.0. As cited in Guidance for Federal Land
Management in the Chesapeake Bay Watershed, 2010. *Prices inflated from reported 2009 dollars to
January 2010 dollars.
The operation and maintenance cost burden for rain barrels and cisterns is low.18 Excluding the periodic
operational activity of emptying the rain barrel, the annual maintenance associated with disconnecting
and cleaning the barrel would only take about one hour. Based on annual operation and maintenance
costs associated with fiberglass cisterns being approximately 3 percent of construction costs, a 10,000
gallon cistern would cost about $400 per year to maintain.
1 Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp.
Available at:
< http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-08.pdf>.
2 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
3 USEPA. (2010). Guidance for Federal Land Management in the Chesapeake Bay Watershed. 848 pp. Available at:
.
4 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
5 Water Use and Conservation Bureau, New Mexico Office of the State Engineer. A Waterwise
Guide to Rainwater Harvesting, .
As cited in Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban
Landscape. 40 pp. Available at:
< http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-08.pdf>.
6 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
7Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp.
Available at:
< http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-08.pdf>.
8 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
9 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
10 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
11 Metropolitan Council, (2001). Minnesota Urban Small Sites Best Management Practices (BMP) Manual. Prepared
for Metropolitan Council. 14pp. Available at:
.
12 Karen Sands and T. Chapman, Milwaukee Metropolitan Sewerage District, Milwaukee, Wisconsin. (2003). Rain
Barrels-Truth or Consequences, presented at USEPA National Conference on Urban Stormwater: Enhancing
Programs at the Local Level, p. 390-395. Available at:
. As cited in Plumb, M. (2008). Sustainable
Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp. Available at:
< http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-08.pdf>.
13 Urban Design Tools: Low Impact Development. Rain Barrels and Cisterns. Available at:
< http://www.lid-stormwater.net/raincist maintain.htm>.
14Austin Water Utility Conservation Program. (2008). Rainbarrel Maintenance 101. Available at:
.
15 University of Florida, Program for Resource efficient Communities. (2008). Florida Field Guide to Low Impact
Development: Cisterns/Rain Barrels. Available at: .
16 Fairfax County Government. Cistern Maintenance. Available at:
17 USEPA. (2010). Guidance for Federal Land Management in the Chesapeake Bay Watershed. 848 pp. Available at:
.
18 University of Florida, Program for Resource efficient Communities. (2008). Florida Field Guide to Low Impact
Development: Cisterns/Rain Barrels. Available at: .
Additional Resources for Rain Barrels and Cisterns:
North Carolina State University, Rainwater Harvesting Web site,
(http://www.bae.ncsu.edu/topic/waterharvesting/) - Contains background information and current
performance research on rainwater harvesting techniques
Virginia Department of Conservation and Recreation, Stormwater Design Specifications
(http://www.chesapeakestormwater.net/storage/first-draft-bavwide-design-
specificationsi/BAYWIDE%20No%206%20RAIN%20TANKS%20AND%20CISTERNS.pdf) - Contains
design specifications for rainwater harvesting
Infrastructure Guidance: Cisterns and Rain Barrels
(http://www.sustainindv.Org/assets/uploads/4 03 CisternsandRainBarrels.pdf) - Contains overview and
design considerations for vegetated channels
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Constructed Wetlands
Constructed wetlands (CWs) are engineered systems that have been designed and constructed to utilize
the natural processes involving wetland vegetation, soils, and the associated microbial population to treat
a variety of wastewaters. Constructed wetlands are designed to mimic natural processes and serve as an
alternative stormwater treatment process. Examples of constructed wetlands include shallow wetlands,
extended detention wetlands, pond/wetland, and pocket wetland.1 CWs may be classified according to
the life form of the dominating vegetation into systems with free-floating, rooted emergent and submerged
macrophytes. Further division could be made according to the wetland hydrology (free water surface and
subsurface systems); subsurface flow CWs could be classified according to the flow direction (horizontal
and vertical flow)2.
Construction
Constructed wetlands consist of a basin
that contains water, a substrate, and, most
commonly, vascular plants.3 Substrates
used to construct wetlands may include
soil, sand, gravel, rock, and organic
materials such as compost.4 Constructed
wetlands may be used in conjunction with
other BMP components such as a
sediment forebay, buffer strip, micropool,
berms, and bottom drain pipe.56
Benefits
Constructed Wetland Designed by F.X. Browne, Inc.
Constructed wetlands have considerable ecologic and aesthetic benefits. Under the appropriate
conditions wetlands can provide water quality improvement, flood storage, cycling of nutrients and other
materials, reduction in pollutant loads, habitat for fish and wildlife, and passive recreation, such as bird
watching and photography.7
Limitations
Constructed wetlands require a relatively large amount of space and an adequate source of inflow to
maintain a permanent water surface. Therefore constructed wetlands may have limited applicability in
urbanized, or ultra urbanized areas where the required amount of space is unavailable.8 9 Further,
constructed wetlands may be unsuitable in arid and semi-arid climates where it may be difficult to
maintain a permanent pool10 necessary for normal operation of the system.
Climate Considerations
Constructed wetlands, if planted properly, are designed to tolerate most local conditions. However,
constructed wetlands require a minimum amount of water, and while they can tolerate temporary
droughts, they cannot withstand complete dryness. Freezing of constructed wetland systems is generally
not problematic in temperate regions since microbial activity usually generates enough heat to keep the
subsurface layers from freezing.11
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
CSO Impact
A study examining the efficacy of constructed
wetlands in pesticide removal from tailwaters
in the Central Valley, CA, found that
constructed wetlands reduced the flow volume
by 68 to 87 percent, through percolation and
evapotranspiration in addition to providing
pollutant removal.12 Reductions in flow volume
to the treatment plants may ultimately
decrease the intensity and frequency of CSOs.
Maintenance
Constructed wetlands require maintenance,
particularly during the first two years after
construction. During the first growing season,
vegetation should be inspected every two to three weeks. During the first two years, constructed wetlands
should be inspected at least four times a year and after major storms (greater than two inches in 24
hours). Sediment should be removed every three to seven years before sediment occupies 50 percent of
the forebay. Over the life span constructed wetlands should be inspected semiannually and after major
storms as well as after rapid ice breakup. Undesirable species should be removed and desirable
replacements planted if necessary. Once established, properly designed and installed constructed
wetlands should require little maintenance.13
Courtesy of: Aleksandra Drizo, PhD; Associate Research Professor;
University of Vermont.
Costs
The construction costs of constructed wetlands can vary greatly depending on the configuration, location,
and site-specific conditions. Typical construction costs (January 2010 dollars) range from $0.89 to $1.86
per cubic foot of water stored in the facility.14 Costs are generally most dependent on the amount of
earthwork and the planting. Annual operation and maintenance costs have been reported to be
approximately 2 percent to 5 percent of the capital costs, or approximately $0.09 per cubic foot of storage
provided.15
1New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
2 Vymazal, J. (2010). Review: Constructed Wetlands for Wastewater Treatment. Water 2010, 2(3), 530-549. Available
at: .
3USEPA. (1995). Handbook of Constructed Wetlands: General Considerations: Volume 1. 53pp. Available at:
.
4 USEPA. (1995). Handbook of Constructed Wetlands: General Considerations: Volume 1. 53pp. Available at:
.
5 Clermont County, Ohio. Stormwater Wetland. 4 pp. Available at: .
6 Metropolitan Council. (Minneapolis-Saint Paul, MN). Constructed Wetlands Stormwater Wetlands. 15 pp. Available
at: .
7 USEPA. (1995). Handbook of Constructed Wetlands: General Considerations: Volume 1. 53pp. Available at:
.
8 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
8USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Stormwater Wetland.
Available at:
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
10 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Stormwater Wetland.
Available at:
.
11 USEPA. (1995). Handbook of Constructed Wetlands: General Considerations: Volume 1. 53pp. Available at:
.
12 Budd, R, O'Geen, A., Goh, K.S, Bondarenko, S. and Gan, J. (2009). Efficacy of Constructed Wetlands in
Pesticide Removal from Tailwaters in the Central Valley, California. Available at:
.
13 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
13USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Stormwater Wetland.
Available at:
.
15 Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. (2006). Pennsylvania
Stormwater Best Management Practices Manual. 685 pp. Available at:
.
D-21
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
Tree Planting
Tree planting refers to the activity of planting trees either
in concentrated groupings or, more likely the case in
urbanized settings, in "tree boxes." Tree planting is suited
for all areas including landscaped areas, sidewalk cut-
outs, parking lots, parks, shopping centers or other open
or urbanized spaces.1 The purpose of tree planting is to
reduce stormwater runoff, increase nutrient uptake, and,
where used in riparian zones, to provide bank
stabilization.2
Construction
Street trees with porous pavement, Pier A Park, Hoboken,
New Jersey. Courtesy of: Bruce K. Ferguson.
Tree planting occurs by converting open or paved areas
into planted areas. For planting in open spaces allow for
appropriate planting depth according to tree species and size. In urbanized areas with impervious
surfaces, impervious surfaces must be removed prior to tree planting, and installation generally includes
the use of a "tree box" to protect the tree roots from heavy traffic. The tree box generally includes a 4-foot
by 6-foot precast concrete frame fully capable of supporting traffic loading which surrounds the base of
the tree.3 After tree planting, stormwater may infiltrate naturally into the surrounding soils and
groundwater through physical, chemical, and biological processes.4
Benefits
Planting new trees can reduce stormwater runoff, promote evapotranspiration, increase nutrient uptake,
provide shading and thermal reductions, encourage wildlife habitat, improve aesthetics in neighborhoods
and parks,5 and contribute to the process of air purification and oxygen regeneration.6 For example, one
report in New York City estimates that by adding 300,000 street trees to the 500,000 existing street trees,
over 60 tons of air pollution can be removed each year.7 The report also states estimates the addition of
every 100,000 trees could decrease the city temperature by 1.4 degrees and decrease ozone annually by
12,000 pounds.8
Limitations
Limitations to an effective tree planting program include the costs associated with buying, planting, and
maintaining the planted area.9 Further, unpredictable weather events with high winds, such as hurricanes,
other large storms or droughts, and ice damage/scour may significantly damage newly planted areas.
10
Climate Considerations
Tree planting can be implemented in all climates, although local site characteristics must be considered
when selecting tree species to be planted.11 Depending on climate, tree species planted, and annual
rainfall, watering may be necessary for trees to survive the growing season. For example, each street tree
planted in New York City is estimated to require 20 gallons of water per day during the growing season to
survive.
12
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
CSO Impact
Communities with higher percentages of tree cover have been found to have lower stormwater volumes
and treatment costs.13 Reductions in the amount of treated stormwater can translate into reductions in the
volume and frequency of CSOs. Researchers at the University of California at Davis have estimated that
for every 1,000 deciduous trees in California's Central Valley, stormwater runoff is annually reduced
nearly 1 million gallons.14 Another study
suggests that trees with mature canopies can
mi
Illl
absorb the first half-inch of rainfall.15
Maintenance
Planted trees require minimal maintenance
other beyond routine pruning, weeding, disease
or insect damage inspection, and watering if
applicable. During the first three years,
mulching, watering and protection of young
trees may be necessary. Tree should be
inspected every three months and within one
week of ice storms and high wind until trees
have reached maturity.16
Charlotte, NC. Courtesy of: USDA Forest Service, PSW, Center for Urban
Forest Research.
Construction Costs
Tree planting costs can vary greatly. Tree planting costs include the cost of site preparation, seedlings or
seed, cost of planting, and weed control for three to five years after planting. Low planting costs may be
associated with community action programs that solicit volunteers to plant low priced saplings. Higher
costs may be associated with professional landscape businesses.
minimal given the anticipated maintenance activities stated above.
17
Operation and maintenance costs are
New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
' New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
'Water world. (2008). Tree Filter Systems for Effective Urban Stormwater Management. Available at:
'Water world. (2008). Tree Filter Systems for Effective Urban Stormwater Management. Available at:
' New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
' New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
' Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp.
Available at: < http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-
O8.pdf>.
' Plumb, M. (2008). Sustainable Raindrops: Cleaning New York Harbor by Greening the Urban Landscape. 40 pp.
Available at: < http://www.riverkeeper.org/wp-content/uploads/2009/06/Sustainable-Raindrops-Report-1-8-
O8.pdf>.
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Appendix D. Green Infrastructure Runoff Controls Fact Sheets and Additional Information for Schedule 5A- CSO
Runoff Control
9 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Reforestation
Programs. Available at:
10 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Reforestation
Programs. Available at:
.
12 New York City Department of Parks and Recreation, Caring for Street Trees and Greenstreets. Available
at.
13 Trust for Public Land and American Water Works Association. (2004). Protecting the Source. As cited in USEPA.
(2007). Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices. 37 pp.
Available at: < http://www.epa.gov/owow/NPS/lid/costs07/documents/reducingstormwatercosts.pdf>
14 Rocky Mountain Institute. (2005). Green Development Services: Village Homes Daw's, California,
http://www.rmi.org/sitepages/pid209.phpAs cited in Kloss. C and Calarusse. C. (2006). Rooftops to Rivers:
Green Strategies for Controlling Stormwater and Combined Sewer Overflows. Prepared for the Natural
Resources Defense Council. 56 pp. Available at: .
15 Kloss, C and Calarusse, C. (2006). Rooftops to Rivers: Green Strategies for Controlling Stormwater and
Combined Sewer Overflows. Prepared for the Natural Resources Defense Council. 56 pp. Available at:
.
16 New York State Department of Environmental Conservation. (2010). New York State Stormwater Management
Design Manual. 642 pp. Available at: .
17 USEPA. (2006). National Pollutant Discharge Elimination System (NPDES) Menu of BMPs: Reforestation
Programs. Available at:
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