&EPA
Policy, Planning
And Evaluation
(PM-221)
230-R-92-006
March 1992
Evaluation of
Wet Weather Design Standards
for Controlling Pollution from
Combined Sewer Overflows
Storm Water Dry Weather Flow Drops to Interceptor
.Excess Wet Weather Flow
to Overflow Point
Combined Sewer Overflow
nnted on R>
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EVALUATION OF
WET WEATHER DESIGN STANDARDS
FOR CONTROLLING POLLUTION FROM
COMBINED SEWER OVERFLOWS
Final Report
Water Policy Branch
Office of Policy Analysis
Office of Policy, Planning and Evaluation
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
March 1992
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ACKNOWLEDGEMENTS
This report was prepared under the direction of Christine Ruf and Jamal Kadri, Water Policy
Branch, Office of Policy Analysis, Office of Policy, Planning and Evaluation, U.S. Environmental
Protection Agency. Ms. Ruf and Mr. Kadri were assisted in its preparation by Industrial Economics,
Incorporated (lEc) of Cambridge, Massachusetts (Work Assignment 16, EPA Contract 68-W1-0009).
Additional technical assistance was provided by Douglas Rae, an independent consultant to lEc; Eugene
Driscoll of HydroQual, Inc.; and Joan Kersnar of Woodward-Clyde Consultants.
The information presented herein is based in part on research begun for EPA by Jeff Albert,
currently at Brown University. The authors gratefully acknowledge his assistance and contribution. In
addition, we extend our thanks to Mike Mitchell and Atal Eralp of EPA's Office of Water, both of whom
provided valuable comments and suggestions on our research, and to Mark Luttner of the Office of
Water, who granted permission to incorporate into this report material originally prepared for inclusion
in a separate Water Office document.
For additional copies of this report or further information on the issues addressed, please contact:
Jamal Kadri
Water Policy Branch
Office of Policy Analysis
Office of Policy, Planning and Evaluation
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
Telephone: (202) 260-3848
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ES-1
Introduction ES-1
Purpose and Findings ES-1
INTRODUCTION AND BACKGROUND INFORMATION ON CSO ISSUES CHAPTER 1
Introduction 1-1
Purpose and Findings 1-1
Organization 1-3
Number, Location, and Other General
Information on Combined Sewer Systems 1-4
Location of the Systems and Population Served 1-5
Number of Outfalls 1-5
Drainage Area Served 1-6
Population Served 1-6
Urban vs. Rural 1-6
Receiving Water for CSS Discharges 1-7
Adverse Impacts of CSO Discharges 1-7
Pollutants from Combined Sewer Overflows 1-7
The Impacts of CSOs on Water Quality 1-10
Fish Kills, Shellfishing
Restrictions, and Beach Closures 1-12
Adverse Effects on Human Health 1-14
Regulatory and Legislative Initiatives 1-15
The National CSO Strategy 1-15
Proposed Legislation 1-18
EPA's Expedited CSO Control Program 1-19
STATE APPLICATIONS OF CSO WET WEATHER DESIGN STANDARDS CHAPTER 2
Introduction 2-1
State Combined Sewer Overflow Standards 2-1
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TABLE OF CONTENTS
(continued)
California 2-3
Illinois 2-3
Massachusetts 2-4
Michigan 2-5
Oregon 2-5
Rhode Island 2-6
Washington 2-7
Wisconsin 2-7
Vermont 2-8
DATA ON RAINFALL EVENTS CHAPTER 3
Introduction 3-1
Storm Parameters 3-1
Collection and Maintenance of Rainfall Data 3-2
Analyzing the Characteristics of Storm Events 3-3
Typical Rainfall Patterns 3-3
Analysis of Storm Frequency 3-3
Rainfall Frequency/Duration Data 3-5
ALTERNATIVE CSO STANDARDS CHAPTER 4
Introduction 4-1
Caveats 4-2
Design Storm Standards 4.3
Frequency/Duration Design Standard 4.3
Depth/Duration Design Standard 4.4
Evaluation of Design Storms as a CSO Control Standard 4-5
Factor of Dry Weather Flow 4_g
Overflow Frequency 4_9
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TABLE OF CONTENTS
(continued)
Interrelationships 4-10
Flow Control Requirements 4-10
Volume Control Requirements 4-11
Comparison and Conclusions 4-11
COMMUNITIES WITH COMBINED SEWER SYSTEMS:
DATA FROM THE 1980 NEEDS SURVEY'S SUPPLEMENTARY DATABASE . . . APPENDIX A
INFORMATION SOURCES FOR STATE CSO WET WEATHER STANDARDS . APPENDIX B
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LIST OF TABLES
State Combined Sewer Wet Weather Design Standards Table 2-1
Annual to Partial-Duration Series Conversion Factors Table 3-1
Approximate Depth of Selected
Frequency/Duration Storms: Cleveland Table 4-1
Average Intensity of Selected
Frequency/Duration Storms: Cleveland Table 4-2
Approximate Return Period of Selected
Depth/Duration Storms: Chicago Table 4-3
Average Intensity of Selected Depth/Duration Storms Table 4-4
The Effect of Variation in the l-Year/6-Hour Storm
on CSO Control Requirements Table 4-5
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LIST OF EXHIBITS
CSS Facility and Population Data
by EPA Region and State Exhibit 1-1
Distribution of Combined Sewer Systems by EPA Region Exhibit 1-2
Population Served by Combined Sewer Systems by EPA Region Exhibit 1-3
Portion of Population Served by CS Systems, By State Exhibit 1-4
Distribution of Combined Sewer Discharge Points
by State and EPA Region Exhibit 1-5
Area Drained by Combined Sewer Systems Exhibit 1-6
Distribution of CS Systems by Population Served Exhibit 1-7
Distribution of CSSs by System Size Exhibit 1-8
Distribution of Population Served by CSSs by System Size Exhibit 1-9
Distribution of CSSs: Urban vs. Non-Urban Areas Exhibit 1-10
Population Served by Urban & Non-Urban CS Systems Exhibit 1-11
Distribution of CSSs by Primary Receiving Water Exhibit 1-12
Contribution of CSOs to Impaired Water
Quality in the United States Exhibit 1-13
Shellfish Harvest-Limited Areas Exhibit 1-14
Beach Closures or Advisories Due to
High Bacteria Count Exhibit 1-15
Status of State CSO Strategy Approvals Exhibit 1-16
Sample Hourly Rainfall Data Exhibit 3-1
Example of Lognormal Distribution Exhibit 3-2
Frequency Distribution of Storm Even Volumes Exhibit 3-3
Rainfall Frequency/Duration Map Exhibit 3-4
Magnitude of the l-Year/6-Hour Storm, By State Exhibit 4-1
Return Period for the 2-Inch/6-Hour Storm, By State Exhibit 4-2
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EXECUTIVE SUMMARY
INTRODUCTION
As Congress begins to consider reauthorization of the Clean Water Act, it is expected to
focus considerable attention on the problem of combined sewer overflows (CSOs). Despite progress
under the Act in reducing pollution from other point sources, pollution from CSOs continues to
impair water quality and habitat nationwide. Hearings on proposals to address this problem,
including significantly strengthening the Act's CSO control requirements, have recently been held.
In conjunction with these hearings, the Environmental Protection Agency (EPA) is reevaluating its
CSO control strategy and exploring a range of options for reducing CSO pollution.
Among the alternatives for reducing CSO pollution are several proposals to mandate a
uniform national technology-based standard for all municipal combined sewer systems (CSSs). A
common element of many of these proposals is a requirement that all CSSs provide sufficient
storage and/or treatment capacity to prevent the discharge of untreated wastewater under most wet
weather conditions. There are several ways to express such a standard, each of which has particular
advantages and disadvantages. To date, however, these options have not been well defined and
explored, and the debate has been clouded by confusion over basic data and technical concepts.
PURPOSE AND FINDINGS
The purpose of this report is twofold. Its first objective is to provide basic information on
the number, location, and other characteristics of CSSs, to describe in general terms the adverse
impacts of CSOs, and to summarize the current regulatory status of CSOs. Its findings in this regard
include the following:
o There are approximately 1,100 CSSs nationwide, the majority of
which are located in the Northeast and Great Lakes regions.
Approximately 84 percent of the systems are located in EPA Regions
1, 2, 3, and 5.
o Approximately 62 percent of combined sewer systems serve 10,000
people or less. Only seven percent of the systems serve populations
greater than 100,000. These large systems, however, account for 70
percent of the approximately 43 million people served by CSSs.
o According to States' 1990 water quality assessments, CSOs are known
to contribute to the inability of 503 square miles of estuary and 132
shore-miles of coastal waters to meet designated uses. In addition,
CSOs contribute to water quality violations in the Great Lakes (93
shore-miles impaired), other freshwater lakes (21,360 lake-acres
impaired) and rivers and streams (5,163 river-miles impaired).
o According to the National Oceanic and Atmospheric Administration
(NOAA), CSOs are a major source of pollutants that adversely affect
ES-1
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shellfish beds, contributing to prohibitions, conditions or restrictions
on 597 thousand acres of shellfish harvesting areas. CSOs also
contribute to fish kills and are a principal cause of beach closures.
The report's second objective is to help illuminate the debate over CSO control by (1)
defining alternative regulatory approaches for setting a wet weather design standard, (2) examining
relationships between the different standards, and (3) evaluating the potential advantages and
disadvantages of each approach. To address this goal, the report first describes CSO design
standards developed by several states, focusing in particular on the rationale each state has employed
in formulating regulations, policies, or permits for CSO control. It then discusses design storm
concepts, the collection and maintenance of rainfall data, and the use of such data in analyzing the
characteristics of storm events. Finally, it describes and evaluates the following approaches to
establishing a CSO wet weather standard, each of which has been employed in at least one state:
(1) Basing the standard on a frequency/duration design storm (e.g., the
l-year/6-hour storm);
(2) Basing the standard on a rainfall depth/duration design storm (e.g.,
a 2.5-inch/24-hour storm);
(3) Requiring control of wet weather discharges up to some multiple of
dry weather flow, such as a factor of 10 (the "10X" standard); and
(4) Specifying a direct limit on the frequency of CSO discharges (e.g.,
two overflows per year).
The evaluation of these approaches identifies underlying factors that are likely to influence
the advantages and disadvantages of each, and uses these insights to describe how the implications
of each approach are likely to vary for different regions or different types of systems. The
evaluation also compares the ease of implementing and enforcing the alternatives. Its principal
conclusions are as follows.
Administratively, the four alternatives analyzed are quite similar. Each would be
implemented and enforced as a design standard. Each would require detailed study to demonstrate
compliance, although the analysis needed to demonstrate compliance with an overflow frequency
limit might prove more complex and statistically sophisticated than that required under the other
approaches. Because CSO projects in general already rely on detailed facility plans, these
requirements seem unlikely to pose a significantly greater analytic burden on CSO permittees. The
implementation of a uniform national standard, however, is likely to increase the degree of
regulatory oversight exercised by the States and EPA. To date, oversight of the recommendations
proposed by permittees in facilities plans has been very limited, and in the absence of specific
guidance or design criteria the CSO controls adopted have varied greatly. Implementation of a
uniform national standard for CSOs would ensure greater consistency in CSO abatement, but would
require EPA and state regulators to devote substantial time to review facility plans, request changes,
and certify compliance.
Operationally, the four regulatory approaches evaluated fall into two general categories. The
first category consists of alternatives that would consistently limit the frequency of overflows across
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systems regardless of likely differences in compliance costs; it includes a frequency/duration design
storm or an overflow frequency limit. The second category consists of alternatives that would
require comparable wet weather storage and treatment capacity for systems that are otherwise
similar but, because of differences in rainfall and/or runoff, might differ markedly with respect to
the frequency of overflows. It includes approaches that would specify a depth/duration design storm
or set control requirements based on a factor of dry weather flow. Thus, these two categories reflect
fundamentally different means of defining a "uniform" wet weather design standard. The first would
set a standard that aims to achieve uniform performance, as measured by the frequency of untreated
overflows. The second would set a standard that tends to equalize control capacity and, hence,
compliance costs, regardless of resulting differences in the frequency with which untreated discharges
would occur.
Ultimately, the choice need not be limited to the four options this report describes. One
alternative is to continue to rely on best professional judgment to establish technology-based
requirements for CSOs on a permit-by-permit basis. While this approach to date has not
satisfactorily addressed the CSO problem nationwide, EPA's renewed efforts under the National
CSO Strategy suggest that progress will be made. Another alternative ~ albeit inconsistent with the
standard NPDES approach of the Clean Water Act ~ would be to forego a technology-based
standard entirely, and instead tailor CSO permit requirements on a case-by-case basis according to
the level of control needed to comply with water quality standards. In theory, this approach would
offer the greatest economic efficiency in achieving water quality goals. In practice, however, setting
CSO control standards based solely on water quality requirements has proved to be quite difficult,
and the lack of a technology-based requirement for CSOs has been and remains a major factor in
making their regulation complicated and their abatement elusive. Moreover, it is likely to be
administratively infeasible to set water quality-based permit limits for each of the thousands of
combined sewer outfalls nationwide. In light of these concerns, the establishment of a state or
national technology-based standard that relates to water quality goals could prove to be essential to
timely progress.
Should Congress or EPA determine that it is necessary to set a design standard for CSOs,
the issue remains how best to balance cost, administrative feasibility and other concerns against
environmental goals. One means of doing so would be to consider a targeted, risk-based approach
that combines aspects of the alternatives described above. For example, the stringency of the design
standard might be linked to the aquatic resources affected by CSOs: discharges to high priority or
high use waters (e.g., discharges that damage a shellfish bed or swimming beach) could be
prohibited, while discharges to lower priority waters could be held to a non-zero overflow frequency
limit. Such a combined approach might prove a viable means of establishing a technology-based
standard without (1) ignoring situations in which the cost of meeting that standard is
disproportionately high relative to water quality benefits, or (2) imposing similar treatment
requirements regardless of need. Such targeted flexibility could help make a technology-based
standard for CSOs more efficient, equitable, and affordable.
ES-3
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INTRODUCTION AND BACKGROUND
INFORMATION ON CSO ISSUES CHAPTER 1
INTRODUCTION
As Congress begins to consider reauthorization of the Clean Water Act, it is expected to
focus considerable attention on the problem of combined sewer overflows (CSOs). Despite progress
under the Act in reducing pollution from other point sources, pollution from CSOs continues to
impair water quality and habitat nationwide. Hearings on proposals to address this problem,
including significantly strengthening the Act's CSO control requirements, have recently been held.
In conjunction with these hearings, the Environmental Protection Agency (EPA) is reevaluating its
CSO control strategy and exploring a range of options for reducing CSO pollution.
Among the alternatives for reducing CSO pollution are several proposals to mandate a
uniform national technology-based standard for all municipal combined sewer systems (CSSs). A
common element of many of these proposals is a requirement that all CSSs provide sufficient
storage and/or treatment capacity to prevent the discharge of untreated wastewater under most wet
weather conditions.1 There are several ways to express such a standard, each of which has
particular advantages and disadvantages. To date, however, these options have not been well
defined and explored, and the debate has been clouded by confusion over basic data and technical
concepts.
PURPOSE AND FINDINGS
The purpose of this report is twofold. Its first objective is to provide basic information on
the number, location, and other characteristics of CSSs, to describe in general terms the adverse
impacts of CSOs, and to summarize the current regulatory status of CSOs. Its findings in this regard
include the following:
o There are approximately 1,100 CSSs nationwide, the majority of
which are located in the Northeast and Great Lakes regions.
1 For example, one proposal would require municipalities to treat all wet weather flows up to
and including that associated with the one-year/six-hour storm.
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Approximately 84 percent of the systems are located in EPA Regions
1, 2, 3, and 5.
o Approximately 62 percent of combined sewer systems serve 10,000
people or less. Only seven percent of the systems serve populations
greater than 100,000. These large systems, however, account for 70
percent of the approximately 43 million people served by CSSs.
o According to States' 1990 water quality assessments, CSOs are known
to contribute to the inability of 503 square miles of estuary and 132
shore-miles of coastal waters to meet designated uses. In addition,
CSOs contribute to water quality violations in the Great Lakes (93
shore-miles impaired), other freshwater lakes (21,360 lake-acres
impaired) and rivers and streams (5,163 river-miles impaired).
o According to the National Oceanic and Atmospheric Administration
(NOAA), CSOs are a major source of pollutants that adversely affect
shellfish beds, contributing to prohibitions, conditions or restrictions
on 597 thousand acres of shellfish harvesting areas. CSOs also
contribute to fish kills and are a principal cause of beach closures.
The report's second objective is to help illuminate the debate over CSO control by (1)
defining alternative regulatory approaches for setting a wet weather design standard, (2) examining
relationships between the different standards, and (3) evaluating the potential advantages and
disadvantages of each approach. To address this goal, the report first describes CSO design
standards developed by several states, focusing in particular on the rationale each state has employed
in formulating regulations, policies, or permits for CSO control. It then discusses design storm
concepts, the collection and maintenance of rainfall data, and the use of such data in analyzing the
characteristics of storm events. Finally, it describes and evaluates the following approaches to
establishing a CSO wet weather standard, each of which has been employed in at least one state:
(1) Basing the standard on a frequency/duration design storm (e.g., the
l-year/6-hour storm);
(2) Basing the standard on a rainfall depth/duration design storm (e.g.,
a 2.5-inch/24-hour storm);
(3) Requiring control of wet weather discharges up to some multiple of
dry weather flow, such as a factor of 10 (the "10X" standard); and
(4) Specifying a direct limit on the frequency of CSO discharges (e.g.,
two overflows per year).
The evaluation of these approaches identifies underlying factors that are likely to influence
the advantages and disadvantages of each, and uses these insights to describe how the implications
of each approach are likely to vary for different regions or different types of systems. The
evaluation also compares the ease of implementing and enforcing the alternatives. The evaluation
concludes that:
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o As design standards, implementation and enforcement of the four
approaches analyzed would be quite similar. Each would require
detailed advanced study to demonstrate that any planned
improvements would comply with the national standard. Because
CSO projects in general already rely on detailed facilities plans, these
requirements seem unlikely to impose a significantly greater analytic
burden on CSO permittees. EPA and State regulators, however,
would need to exercise additional regulatory oversight to ensure
compliance with a national standard.
o Operationally, both a frequency/duration design storm and an
overflow frequency limit could lead to significant inter-regional
variation in compliance costs, due to underlying variation in rainfall
conditions; however, the level of control achieved, as measured by the
frequency of uncontrolled overflows, would be relatively uniform
across systems.
o In contrast, a depth/duration design storm or a factor of flow
approach would impose relatively similar costs on similar systems,
regardless of underlying differences in regional rainfall; however, the
frequency of uncontrolled overflows across systems could vary
considerably.
To balance cost concerns against environmental goals, regulatory authorities may wish to
consider a targeted approach that combines certain aspects of the alternatives analyzed. Such an
approach could provide flexibility in the wet weather standard to take into account situations in
which the cost of meeting the standard is extraordinarily high; for example, less stringent overflow
frequency limits might be set for small communities or for systems whose compliance costs exceed
a certain threshold, provided that the anticipated overflows would not impair the designated uses
of the receiving waters. Conversely, the stringency of the wet weather standard might be linked to
the aquatic resources affected by CSOs: discharges to high priority or high use waters (e.g.,
discharges that would damage a shellfish bed or recreational beach) could be prohibited, while
discharges to lower priority waters could be held to a non-zero overflow frequency limit. Such an
approach might prove a viable means of establishing a national wet weather control standard whose
costs are proportional to resulting water quality benefits.
ORGANIZATION
The remainder of this chapter provides background information on CSO issues. It first
discusses the number, location, and other general characteristics of CSSs. It then describes the
adverse impacts of CSOs, outlines EPA's CSO strategy and elaborates on legislative efforts to date
to strengthen CSO controls. Subsequent chapters are organized as follows:
o Chapter 2 describes the CSO design standards developed and used
by several states to control CSO discharges.
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o Chapter 3 discusses design storm concepts, the collection and
maintenance of rainfall data, and the use of such data to analyze the
characteristics of storm events.
o Chapter 4 describes and evaluates the four alternative CSO wet
weather design standards listed above.
NUMBER, LOCATION, AND OTHER GENERAL
INFORMATION ON COMBINED SEWER SYSTEMS
There are approximately 1,100 combined sewer systems nationwide, serving a population of
some 43 million. These systems, most of which are located in the Northeast and Midwest, carry
sanitary sewage, industrial process wastes and storm water runoff to a publicly owned treatment
works (POTW) prior to discharge to receiving waters. During a storm, a system's interceptor sewers
collect runoff and channel it to the POTW for treatment. In many systems, however, storm flow
frequently exceeds the capacity of the interceptors and/or the POTW. To prevent overloading the
system -- which could lead to backup and flooding or interference with POTW operations — built-in
regulators direct the excess flow to overflow points for discharge. The discharge from these outfalls
consists of an untreated mixture of sanitary sewage, industrial wastewater, and storm water runoff.
The following discussion of CSS characteristics draws primarily on the published results of
the 1980 Needs Survey and on a database containing disaggregated 1980 Survey data, which was
provided to us by the Office of Wastewater Enforcement and Compliance (OWEC).2 Because the
supplementary database contains the preliminary results of the 1980 Needs Survey, not its final
results, there are some discrepancies between the database and the published findings. For example,
the final report for the 1980 Needs Survey indicates that there are 1,118 combined sewer systems
nationwide. In contrast, the supplementary database consists of 1,191 records, each containing
information on a sewage system that has at least some combined sanitary and storm drainage. While
we have no information that explains or resolves these discrepancies, we believe that the published
data are more reliable.3 We therefore employ the published data whenever possible, using it to
describe the number of CSS facilities in each state; the populations served by CSSs in each state;
and the primary receiving water (PRW) class for CSS discharges. All other information from 1980
is drawn from the supplementary database. Appendix A lists, by state and municipality, each of the
combined sewer systems identified in the supplementary database, along with additional information
on each community's population, the populations reported to be served by the CSS, and the primary
body of water to which the system discharges.
The degree to which the 1980 data are representative of current conditions is unknown.
More current information would clearly be preferable, but little exists beyond more current counts
2 This database is an interim product of an ongoing Agency effort to create a comprehensive
database on combined sewer systems.
3 It is likely that the information presented in the published report underwent additional review
and quality control. Many of the records in the supplementary database are incomplete. In
addition, the database appears to contain a small number of typographical errors.
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of CSSs. That information suggests that at least in this respect, the 1980 data are reasonably
representative of conditions today.
Location of the Systems and Population Served
Exhibit 1-1 summarizes 1980 Needs Survey data on the distribution of CSSs and the
populations they serve by state and EPA Region. Exhibits 1-2, 1-3 and 1-4 present this information
graphically. As these exhibits show, the northeast and midwest report the greatest number of CSSs.
Of the 1,118 systems reported in the 1980 Needs Survey, 941 (84 percent) are located in EPA
Regions 1, 2, 3, and 5.
The number of people served by CSSs is even more heavily concentrated in these Regions.
The 1980 data indicate that over 36.6 million (86 percent) of the 42.4 million people served by CSSs
live in Regions 1,2,3, and 5. Note that although Region 2 ranks fourth in number of systems, it
ranks second in population served, reflecting the high concentration of large, urban systems in the
Region.4
Exhibit 1-4 indicates the percentage of each state's population served by CSSs.5 Again, the
midwest and northeast show the greatest reliance on CSSs.
Number of Outfalls
While the supplementary database for the 1980 Needs Survey includes information on the
number of outfalls associated with combined sewer systems, this information is so sporadically
reported that tabulations based upon it would likely be unreliable.6 EPA's 1992 summary of the
status of State CSO Strategies, however, provides information on the number of CSO discharge
points in each state and region. Exhibit 1-5 presents this information. As the exhibit shows, the
status report indicates that there are at least 10,770 combined sewer outfalls nationwide. Over 92
percent of these outfalls are located in Regions 1, 2, 3, and 5. The data contained in the report also
4 As shown in Appendix A, the population served by a municipality's combined sewer is
frequently less than the total municipal population. In other cases the population served by CSSs
exceeds the municipal population, suggesting that the system serves parts of other communities or
unincorporated areas beyond the primary municipality's boundaries. Depending upon the methods
used to finance sewer system improvements, this may suggest a broader funding base than the
population served by CSOs would indicate.
5 In creating Exhibit 1-4, we obtained data on state populations from the 1980 Census. The 1980
Needs Survey reports similar information, but relies on 1979 population estimates. The small
difference in population statistics does not affect the general results.
6 The 1980 database also reports that a single system in Sandusky, Ohio has more than 50,000
discharge points. If this information were correct, this single system would account for roughly five
times as many discharge points as all other systems combined. In light of this discrepancy, we
assume the entry is a typographical error.
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suggest that the average number of outfalls per CSS nationwide is ten, but are insufficient to
characterize the distribution of CSSs by the number of discharge points. The averages calculated
for each state, however, suggest that systems are likely to vary significantly in this regard. The sole
CSS in South Dakota, for example, reports only two discharge points; in contrast, the Washington,
DC system reports 55.7
Drainage Area Served
Exhibit 1-6 shows the distribution of CSSs by the area they drain, according to the 1980
supplementary database. The exhibit shows that most of the systems contained in the database drain
less than 1,000 acres. Conversely, approximately 5 percent of the systems drain an area greater than
10,000 acres.
Population Served
Exhibit 1-7 shows the distribution of CSSs in the supplementary database by population
served.8 The distribution ranges widely, from 19 (Rice Lake, WI) to close to 2l/i million (W-SW
Chicago, IL). Most facilities, however, serve between 1,000 and 50,000 customers.9
Using the 1980 data, we have grouped CSSs into three classes based on the number of
people served - under 10,000 (small); 10,000 to 100,000 (medium); and over 100,000 (large).
Exhibit 1-8 shows the number of systems in each class, while Exhibit 1-9 shows the total number of
people served by systems in each class. Despite there being many more small systems than large
(62.1 percent vs. 6.7 percent), the larger systems serve far more people (69.9 percent vs. 5.1 percent).
Urban vs. Rural
According to the 1980 data, under one-third (29.1 percent) of CSSs are located in areas
classified as urban by the U.S. Bureau of the Census (Exhibit 1-10).10 Urban CSSs, however, serve
7 For consistency's sake, the averages reported in Exhibit 1-5 were calculated using the 1992
report's data on the number of CSSs in each state. As noted previously, these data differ slightly
from the 1980 data.
8 Population served by CSS was reported for 1,145 of the 1,191 systems in the database.
9 It is important to note that the database reports information by facility, not sewage authority.
Thus, facilities operated by the same authority are reported separately; the New York City system,
for example, is listed as ten separate facilities. As a result, Exhibit 1-7 suggests a slightly different
size distribution than would data reported by authority.
10
The criteria for classification as an urban area are:
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84.0 percent of the national CSS population (Exhibit 1-11). Due to the higher percentage of
impervious surface in urban areas, these systems may be more susceptible to overflows.
Receiving Water for CSS Discharges
The primary receiving water (PRW) for CSS discharges was recorded in the 1980 Needs
Survey for 918 (82.1 percent) of the 1,118 systems. PRW designations are based on EPA
classifications detailed in the Survey. As shown in Exhibit 1-12, the majority of systems discharge
into streams (45.3 percent) or rivers (26.2 percent). Smaller percentages discharge to estuaries (5.4
percent), lakes (3.8 percent), or oceans (1.3 percent).
It is important to note that the data on primary receiving waters do not necessarily represent
the distribution of receiving waters that CSOs affect. It is possible, for example, that discharges to
a river or stream may adversely affect an estuary downstream. As a result, these data probably
understate the potential effects of CSOs on downstream lakes, estuaries and coastal waters.
ADVERSE IMPACTS OF CSO DISCHARGES
Pollution from combined sewer overflows can pose health risks, degrade the ecology of
receiving waters, and impair the beneficial use of water resources. The following discussion
describes the pollutants associated with CSOs. It then summarizes data on the extent to which
CSOs impair water quality, force beach closures, and contribute to limits on shellfishing. Finally,
it discusses the adverse health effects that may be caused by CSO discharges.
Pollutants from Combined Sewer Overflows
Combined sewer overflows discharge a mixture of domestic sewage, industrial wastewater,
and stormwater runoff. Included in these flows are pathogens associated with human and animal
fecal material, oxygen-demanding pollutants that deplete the concentration of dissolved oxygen in
the aquatic environment, suspended solids that increase turbidity and damage benthic communities,
nutrients that cause eutrophication, toxics that may persist and bioaccumulate through the food web,
and floatable litter that may both harm aquatic fauna and become a health and aesthetic nuisance
to swimmers and boaters. In addition, high peak volumes of CSO discharges can cause a variety of
adverse impacts on surface water hydrology and the viability of aquatic habitats. The following
discussion briefly outlines the health or environmental concerns associated with CSO discharges.
o A central city with a population of at least 50,000, or twin cities with a
combined population of at least 50,000, with the smaller of the twin cities
having at least 15,000 inhabitants.
o Closely settled surrounding territory, meeting specific criteria outlined in the
Needs Survey.
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Pathogens
Discharges from combined sewer systems include human and animal fecal wastes from
sanitary sewers and urban runoff that may contain pathogens. Any pathogens that live in the human
intestinal system may cause illness or disease through inadvertent ingestion of contaminated waters
during swimming or other recreational activities, or via ingestion of contaminated seafood. These
pathogens include viruses, bacteria, and protozoa that cause a wide range of diseases and illnesses.
Viruses are believed to account for many water-borne diseases, including gastroenteritis,
poliomyelitis infectious hepatitis, and other gastrointestinal infections. Bacterial diseases, such as
cholera and typhoid fever, and parasitic diseases, such as amoebic dysentery and parasitic diarrhea,
can also be transmitted by direct or indirect contact with untreated discharges.
Biological and Chemical Oxygen Demand
The domestic and industrial wastewaters and urban runoff discharged by CSOs may also
contain high concentrations of oxygen-demanding substances. Domestic sewage and urban runoff
include human and animal wastes that consume oxygen through organic decomposition. Industrial
wastewaters that contain organic materials also consume oxygen as these materials oxidize.
When discharged in large quantities, as may occur during overflow events, oxygen-demanding
pollutants can cause oxygen sags in receiving waters, posing the risk of fish kills. These pollutants
can also exacerbate eutrophication and pose aesthetic problems, such as unpleasant odors. These
conditions may persist for short periods of time, but recur as storm events cause combined sewers
to overflow.
Suspended Solids
A wide variety of solids find their way into domestic and industrial wastewaters, which, when
combined with sediments from urban runoff, may result in high CSO loadings of suspended solids.
Sedimentation alters aquatic environments primarily by increasing turbidity. Increased turbidity
impairs the ability of aquatic organisms to obtain dissolved oxygen from the water by interfering with
gill movement and water circulation. In addition, turbidity inhibits the penetration of light, greatly
reducing plant production. Sedimentation also changes heat radiation and, by blanketing stream
bottoms, can smother or otherwise create unfavorable conditions for benthic organisms.11
Other effects of sedimentation include the accumulation and resuspension of pollutants.
Many toxic substances are attached to suspended solids and settle out and accumulate in bottom
sediments. Some substances are broken down in sediments, but others are retained for many years
and continue to serve as a source of toxics to the water body and to aquatic organisms.12 These
11 Novotny, V. and G. Chesters, Handbook of Nonpoint Pollution Sources and Management.
New York: Van Nostrand Reinhold Company, 1981.
12 U.S. Environmental Protection Agency, National Water Quality Inventory. 1988: Report to
Congress. Office of Water, EPA 440-4-90-003, 1990.
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pollutants may be released as sediments are resuspended during periods of high flow and local scour,
further affecting aquatic life. In addition, many navigational waterways must be continually dredged
to remove accumulated sediments. This process causes additional water quality and aquatic life
impacts as sediments and their associated pollutants are resuspended.13
Nutrients
Combined sewers contribute to overall loadings of nutrients (nitrogen and phosphorus),
which are the main cause of eutrophication - an alteration of ecology characterized by excessive
growth of aquatic weeds and algae. The growth of aquatic vegetation requires both nutrients; in
fresh water, however, plant growth typically is controlled by phosphorus input, while in marine
waters, plant growth typically is controlled by nitrogen input. In either case, addition of the
controlling pollutant results in greater plant growth.
Eutrophication is of particular concern in lakes, estuaries and slow-moving rivers. In
addition to the obvious aesthetic problems associated with algae blooms and excessive plant growth,
eutrophication typically reduces dissolved oxygen levels, raises water temperatures, and reduces the
amount of light that reaches plant communities, altering the aquatic environment and threatening
its ability to support sensitive species. Under certain conditions the decay of plant material
associated with eutrophication can significantly deplete oxygen levels, leading to fish kills and the
loss of benthic communities.14
Toxics
Municipal sewage systems receive toxics discharged by both domestic and industrial users.
Industry typically accounts for the largest percentage of organic and inorganic toxics. Pretreatment
standards limit the amount of toxics that can be discharged into municipal sewer systems, but urban
areas typically generate large quantities of toxic effluents, including a wide variety of metals, such
as mercury, lead, copper, chromium, and nickel, and organics from industrial and chemical process
waters. Stormwater runoff also contains metals, lawn herbicides, and other pollutants that contribute
to CSO discharges of toxic substances.
The discharge of toxic substances in toxic amounts poses an immediate threat to aquatic
environments. Moreover, some toxics, such as metals and PCBs, persist in sediments for an
extended time and bioaccumulate in higher predators, such as game fish. Ultimately, the
bioaccumulation of toxics may require the closure of fishing and shellfishing areas or the issuance
of health advisories that recommend limiting consumption of fish and shellfish from contaminated
waters.
13
Novotny and Chesters, op. cit.
14 U.S. Environmental Protection Agency, Report to Congress to Identify Stormwater Discharges
and Determine the Nature and Extent of Pollutants in Stormwater Discharges. Office of Water,
October 1, 1989 (Draft).
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Floatables and Plastics
Litter and plastics found on land, if not removed, eventually are flushed, blown or swept
down storm sewers, where they may be discharged along with sewage effluents in combined sewer
overflows. Such pollutants degrade slowly, increasing the amount of time they remain in receiving
waters. These conventional pollutants degrade the aesthetic quality of receiving waters, limiting
recreational uses and damaging property values. In addition, wildlife is threatened by ingestion of
or entanglement in plastic debris.
The amount of floatables that wash up on beaches in the Northeast has increased greatly
over the last decade. The problem is attributed to CSOs, the ocean disposal of solid wastes, and
other sources. It has become sufficiently severe in the New York City area that New York and New
Jersey have developed a floatables action plan that includes tracking debris slicks in the New
York/New Jersey harbor area, harvesting debris with nets, and notifying beach operators of the
impending landfall of debris slicks."
Temperature
Combined sewer discharges during warmer seasons generally have higher temperatures than
receiving waters, and therefore raise water temperatures. In addition, discharges from storm water
management devices that impound effluents in unshaded areas for long time periods can increase
receiving water temperature. Increased temperature has both direct and indirect detrimental effects
on fish. For example, some cold water fish species and stream insects are fatally affected by
sustained water temperatures greater than 70 degrees. Indirectly, warmer water holds less oxygen,
affecting habitat and increasing the risks associated with the discharge of oxygen demanding
substances.
Hydrological or Habitat Modification
High peak volumes of CSO discharges -- which include storm water runoff -- can have a
variety of adverse impacts on surface water hydrology and the viability of aquatic habitats. High
volumes of discharge can cause stream scouring, which degrades aquatic and riparian habitat, widens
stream channels, and increases erosion.
The Impact of CSOs on Water Quality
One measure of the adverse effects of CSO pollution is the extent to which CSOs contribute
to the failure of receiving waters to support their designated uses. State 305(b) reports, which are
submitted to EPA biennially, are the primary source of national data on this issue. These reports
document State water quality assessments and indicate whether CSOs, among other sources of
pollution, contribute to use impairment. They do not, however, attribute water quality problems to
15 U.S. Environmental Protection Agency, Region II, Assessment of the Floatables Action Plan:
Summer 1989. New York, NY, December, 1989.
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a single, exclusive cause, nor do they provide sufficient detail to determine the degree to which
CSOs contribute to a specific cause of impairment, such as excess oxygen demand. Instead, they
simply indicate whether CSOs are a major or moderate/minor cause of water quality violations. The
following discussion presents this information, relying on preliminary data from the 1990 305 (b)
T*ansiv*to 16
reports.
Rivers and Streams
In their draft 1990 305 (b) reports, 46 states indicated the degree to which 647,066 assessed
river miles support designated uses.17 The states reported that 63 percent of the assessed miles
fully support such uses. Of the 177,792 impaired river miles for which detailed information on
causes of impairment was available, combined sewer overflows had a major impact on 3,521 miles,
and a moderate to minor impact on 1,642 miles, or 2.9 percent of the total.18 Exhibit 1-13
summarizes this information.
Lakes
Data from the draft 1990 305(b) reports indicate that of the 18.5 million lake acres (not
including Great Lakes) assessed by 46 states, about 30 percent fully support their designated uses.
Causes of use impairment are reported for approximately 4 million lake acres. As shown in Exhibit
1-13, combined sewer discharges account at least in part for less than 1 percent of this total.
The draft 1990 data also indicate that only 85 of the 4,857 assessed Great Lakes shoreline
miles support designated uses. This high rate of impaired use is due in large part to fish
consumption restrictions in the near-shore waters of the lakes. The most extensive causes of
nonsupport include synthetic organic chemicals, nutrients, and toxic contamination of sediments.
Illinois, Indiana, New York, and Wisconsin identified the major sources of use impairment for 1,235
shoreline miles. As shown in Exhibit 1-13, these states reported that CSOs contributed to
impairment of 93 shore miles, or 7.5 percent of those for which information on the cause of
impairment is presented.
Estuaries and Coastal Waters
Of the 26,693 square miles of estuaries assessed by 20 states and the District of Columbia
in the draft 1990 305(b) reports, 44 percent do not fully support designated uses. Sixteen states
16 The quality of the 305(b) reports can vary considerably across states. In general, most states
have not assessed all waters to determine whether they support designated uses. As a result, the
available data may understate the extent to which waters are impaired by CSOs or other sources.
17 Data were not reported for Alaska, Idaho, New Jersey, or Virginia, but included the District
of Columbia and Puerto Rico.
18 Information on the cause(s) of impairment is not available in all cases.
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provided information regarding the sources of use impairment. Of the 7,693 square miles impaired
in these 16 states, combined sewer discharges had a major impact on 269 and a moderate to minor
impact on 234, which together accounts for 6.5 percent of the total.
The draft 1990 305 (b) reports contain information from twelve states that assessed water
quality in coastal waters. Of the 4,230 coastal miles assessed by these states, 89 percent fully support
their designated uses. Only four states (Florida, Mississippi, New Jersey, and New York) provided
information regarding the sources and causes of non-attainment of designated uses in coastal waters.
Of the 361 impaired miles in these 4 states, CSOs had a major impact on 12 miles and a moderate
to minor impact on 120 miles, which together constitutes 36.6 percent of the total.
Exhibit 1-13 summarizes the data on use impairment in estuaries and coastal waters.
Fish Kills, Shcllfishing
Restrictions, and Beach Closures
The preceding discussion offers a sense of CSOs' contributions to water quality problems
nationwide. The following discussion expands upon the implications of these problems by describing,
to the extent available data permit, CSOs' role as a contributing cause of fish kills, shellfishing
restrictions, and beach closures.
Fish Kills
When discharged in excessive amounts, oxygen demanding pollutants like those discharged
by CSOs can deplete dissolved oxygen concentrations below those required to support fish. The
discharge of toxic pollutants, which may be contained in CSOs, can also cause fish kills. In EPA's
1988 National Water Quality Inventory. 38 states reported 996 fish kill incidents. Twenty-four of
those states reported the number of fish killed -- a total of 36 million. Of the incidents reported,
605 were caused by conventional pollutants (primarily oxygen demanding substances), while 135 were
caused by toxic pollutants. Sixteen states reported municipal facilities, which may include combined
sewer overflows, as a source of fish kills. Additional information on the number or severity of such
incidents, however, was not reported.19
Shellfishing Restrictions
Pathogens discharged by CSOs to receiving waters can contaminate shellfish. Bivalve
mollusks, such as oysters, clams, and mussels, are filter feeders. These shellfish strain food and
particulate matter that is carried by currents. They filter large volumes of water relative to their
size, concentrating pollutants and pathogens that may be present in the water. Bacterial or viral
pathogens may then be passed to humans through consumption. To protect public health, shellfish
19 U.S. Environmental Protection Agency, National Water Quality Inventory: 1988 Report to
Congress. Office of Water, EPA 440-4-90-003, 1990.
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harvest is not permitted in areas that are near potential pollution sources or that contain high levels
of indicator bacteria.
Studies conducted by the National Oceanic and Atmospheric Administration indicate that
discharges by combined sewers are a major source of pollutants that adversely affect shellfish
harvesting areas.20 Exhibit 1-14 shows that in 1990, 6.4 million of 18.7 million total acres of
shellfish beds were harvest-limited. Combined sewer overflows contributed to prohibitions,
conditions or restrictions on 597 thousand acres, or 9.4 percent of the total harvest-limited
acreage.21
Beach Closures
Exposure to pathogens discharged by combined sewers is a potential cause of illness and
disease. Recreational swimmers, boaters, and others who engage in full body contact recreation may
be exposed to pathogens in fecal material that can cause a wide variety of illnesses, ranging from
hepatitis to gastro-intestinal problems.
State and county health boards attempt to minimize exposures to pathogens by testing
beaches and closing them or posting swimming advisories whenever concentrations of indicator
bacteria exceed threshold limits. In some areas, beaches are automatically closed following a storm
event, and reopened only when test results indicate that concentrations of indicator bacteria meet
state or local criteria.
The presence of plastics and other floatable waste or debris, which in some cases can be
traced to CSOs, may also prompt health authorities to close public beaches or issue beach advisories.
The floatables problem has become particularly acute in some urban areas, particularly in the vicinity
of New York City.
A recent report published by the Natural Resources Defense Council (NRDC) provides data
on beach closings and advisories attributable to high counts of indicator bacteria.22 The report
covers 10 states and the years 1989 and 1990. Exhibit 1-15 summarizes the data from this study.
As the exhibit shows, the report documents 1,753 days of beach closures or advisories in 1989, and
1,467 days of closures or advisories in 1990. In both years, Connecticut, New York and New Jersey
account for over 70 percent of the reported days on which beach closures or advisories were in
20 National Oceanic and Atmospheric Administration, The 1990 National Shellfish Register of
Classified Estuarine Water. U.S. Department of Commerce, Rockville, MD, July 1991.
21 More than half of the shellfishing area reported to be limited due to CSO discharges is along
the Gulf Coast. This result is surprising, since relatively few combined sewer systems serve this area.
To date we have been unable to determine the explanation for this apparent discrepancy.
22 Kassalow, Jennifer, et al., Testing the Waters: A Study of Beach Closings in Ten Coastal
States. Natural Resources Defense Council, August 1991.
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effect.23 The report does not specifically link closures or advisories to CSOs or any other cause,
but CSOs are implicated as an important contributor to sewage effluent loadings.
Adverse Effects on Human Health
Despite the efforts of health authorities to minimize exposures to CSO pollution, health risks
remain. Pollutants from sewage overflows may affect human health through at least three exposure
routes: dermal contact, inadvertent ingestion of contaminated water while swimming, and ingestion
of contaminated fish and shellfish. Exposure through consumption of contaminated drinking water
is also a possibility, but in most cases disinfection and other practices typically employed to treat
drinking water should significantly reduce any risks attributable to pollution from CSOs.
As described above, CSOs may discharge a variety of pollutants that pose risks to human
health, including heavy metals and other toxic compounds. Some of the compounds that may be
discharged by CSOs are known or suspected carcinogens; others may cause kidney ailments,
developmental retardation, or other problems. Many of these effects are only likely to develop after
chronic exposure, but acute effects as a result of exposure to high concentrations of pollutants are
also possibile. Of particular concern, however, is the bioaccumulation of toxic compounds in fish
and shellfish, which can pose significant health risks. In 1988, for example, 39 states reported
finding concentrations of toxic substances in fish tissue high enough to warrant fish bans or fish
consumption advisories. The data, however, do not uniformly indicate whether bans or advisories
were attributable to CSOs, although in one case, in Lake Champlain, they suggest that CSOs may
contribute to elevated concentrations of PCBs in trout.24 This is consistent with the general lack
of information on toxics in CSOs, and with the consequent lack of information on related health
risks.
The health risks associated with pathogens discharged by CSOs are also of particular
concern. Disease-carrying microbes and parasites in ineffectively treated wastewater effluent can
be transmitted to humans via several pathways. Transmission most commonly occurs via one of
three exposure routes: (1) ingestion of aquatic food species (fish and shellfish) infected with
pathogens; (2) ingestion or dermal absorption of contaminated water during recreational activities;
and (3) ingestion of contaminated drinking water.
The potential for human exposure via these different pathways depends on the activity in
question. For example, ingestion of pathogen-contaminated water is likely while swimming and can
23 The NRDC report indicates that in 1989, five New York beaches were under advisories for
the entire summer; in 1990, three New York beaches were under season-long advisories. For
purposes of Exhibit 1-15, we assume that each of these advisories was in effect for 90 days.
Similarly, the NRDC report indicates that in 1990, one beach in Maine was under an advisory for
six weeks; for Exhibit 1-15, we have converted this to 42 days.
24 U.S. EPA, National Water Quality Inventory: 1988 Report to Congress. Office of Water,
Washington, DC, April 1990, pp. 108-111. The data indicate that six states reported fishing
restrictions due to urban runoff and three reported restrictions due to municipal facilities, but a
separate listing for CSOs is not provided.
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lead to gastroenteritis and other water-borne disease. Wading or boating results in dermal exposure
and can lead to skin rashes and secondary infections of wounds.
Shellfish are especially susceptible to pathogen contamination, and the discharge of untreated
sewage to shellfish harvesting areas poses a serious public health threat.25 In contrast, the
discharge of undisinfected wastewaters to surface waters used as public drinking water supplies
generally does not pose significant risks, since chlorine disinfection occurs in the treatment of public
water supplies. However, problems may exist in waters where pathogen levels exceed those that can
be adequately treated by water supply facilities.26 Such may be the case with CSOs.
REGULATORY AND LEGISLATIVE INITIATIVES
CSOs are point sources subject to the limitations on point source discharges set forth in the
Clean Water Act. The Clean Water Act of 1977 mandated that by July 1, 1977, all point sources
must meet discharge limits consistent with the Best Practicable Technology (BPT) then available.
The Water Quality Act Amendments of 1987 set a deadline of March 31, 1989 for all point sources
to comply with more stringent standards, based upon the best conventional pollutant control
technology (BCT) and best available technology economically achievable (BAT). These technology-
based requirements represent minimum standards of control; under the Act, more stringent water
quality-based controls are required whenever technology-based limits are insufficient to comply with
state water quality standards. The statutory deadline for compliance with water quality standards
was July 1, 1977.
Action to bring CSOs into compliance with Clean Water Act requirements has lagged well
behind the Act's statutory deadlines. Most communities with CSSs have not begun to implement
improved CSO controls, and many have not undertaken facilities planning efforts to evaluate control
strategies. Recently, both EPA and Congress have initiated efforts to redress the situation. EPA
has published a national CSO control strategy, while Congress is considering several bills to
strengthen existing standards and set firm schedules for CSO compliance. In response to these
legislative initiatives, EPA is implementing an expedited CSO control program. The following
discussion outlines these efforts, providing additional detail on both EPA and Congressional action.
The National CSO Strategy
EPA's National Combined Sewer Overflow Control Strategy, released on August 10, 1989,
described for the first time EPA policies for bringing CSO discharges into compliance with the
requirements of the Clean Water Act. The Strategy defined combined sewer overflows as:
...flows from a combined sewer in excess of the interceptor or regulator capacity that
are discharged into a receiving water without going to a publicly owned treatment
works (POTW). CSOs occur prior to reaching the headworks of a treatment facility
25 U.S. EPA, "Notice of Policy on Municipal Wastewater Disinfection," 1989.
26 Ibid.
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and are distinguished from bypasses, which are "intentional diversions of waste
streams from any portion of a treatment facility" (40 CFR 122.41 (m)).27
The Strategy affirmed that CSOs are point sources subject to National Pollution Discharge
Elimination System (NPDES) permit requirements, and stipulated that all CSO discharges must be
brought into compliance with the CWA's technology-based and water quality-based standards. It
clarified, however, that CSOs are not subject to the secondary treatment requirements that apply
to POTWs.28
The Strategy set forth the following objectives:
(1) To ensure that if CSO discharges occur, they are only as a result of wet
weather;
(2) To bring all wet weather CSO discharge points into compliance with the
technology-based requirements of the Clean Water Act and applicable State
water quality standards; and
(3) To minimize water quality, aquatic biota, and human health impacts from wet
weather overflows.
To achieve these goals, the Strategy called for States and Regions to develop plans that would
enable them to issue NPDES permits to all CSOs. Implementation of the Strategy included:
o Identifying and categorizing the permit status of each CSO discharge
point;
o Setting permitting priorities;
o Issuing permits, using system-wide permits when possible;
o Establishing compliance schedules consistent with the Clean Water
Act;
o Establishing minimum technology-based requirements;
o Requiring additional control measures as needed to meet water
quality standards;
o Setting compliance monitoring requirements; and
o For certain limited cases, modifying state water quality standards.
The CSO Strategy called on both States and EPA Regions to develop BPT, BCT, and BAT
limits based on best professional judgment (BPJ).29 The strategy specified the following minimum
technology-based requirements for compliance with BCT/BAT:
27 U.S. Environmental Protection Agency, National Combined Sewer Overflow Control Strategy.
August 10, 1989, p. 1.
28 Ibid., p. 2.
29 Ibid., p. 2.
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(1) Proper operation and regular maintenance programs for the sewer
system and combined sewer overflow points;
(2) Maximum use of the collection system for storage;
(3) Review and modification of pretreatment programs to assure CSO
impacts are minimized;
(4) Maximization of flow to the POTW for treatment;
(5) Prohibition of dry weather overflows;30 and
(6) Control of solid and floatable materials in CSO discharges.31
The Strategy also called for CSO control programs to incorporate best managment practices
and other low-cost operational methods whenever possible, and to incorporate more expensive
control measures only if necessary to meet water quality standards. The strategy specifically
identified the following control measures that should be considered to bring wet weather CSOs into
compliance: improved operation and maintenance; best management practices; system-wide storm
water management programs; supplemental pretreatment program modifications; sewer ordinances;
local limits program modifications; identification and elimination of illegal discharges; monitoring
requirements; pollutant specific limitations; compliance schedules; flow minimization and hydraulic
improvements; direct treatment of overflows; sewer rehabilitation; in-line and off-line storage;
reduction of tidewater intrusion; construction of CSO controls within the sewer system or at the
CSO discharge point; sewer separation; and new or modified wastewater treatment facilities.32 If
additional permit limits proved necessary to protect State water quality standards, the Strategy
directed the permittee to choose the most cost-effective control measures that would ensure
compliance.
EPA Headquarters oversees implementation of the National CSO Strategy. Through this
oversight, EPA seeks to ensure that actions taken by the Regions and States are consistent with the
National Strategy, and that the Agency as a whole makes progress toward meeting the requirements
and water quality objectives of the CWA. The National Strategy required the States and Regions
to develop statewide permitting strategies that are consistent with the national approach. Such
strategies were to have been developed no later than January 15,1990 and approved by the Regions
30 The Strategy defined dry weather flow as the flow in a combined sewer that results from
domestic sewage, industrial wastes and ground water infiltration, with no contribution from storm
water runoff or storm water induced infiltration. Wet weather flow was defined as a combination
of sanitary flow, industrial flow, infiltration from ground water, and storm water flow, including
storm water induced infiltration and snow melt.
31 U.S. EPA, National Combined Sewer Overflow Control Strategy. August 10, 1989, p. 6.
32 Ibid., p. 6.
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no later than March 31, 1990.33 As of January 16, 1992, 30 States (including the District of
Columbia) had submitted strategies. Twenty-six of these strategies had been unconditionally
approved, two had been conditionally approved, and two had yet to be approved.34 The 21 States
that have not submitted strategies are not required to do so, either because they have no combined
sewer systems or because they report no overflows from such systems. Exhibit 1-16 summarizes the
status of state CSO strategies for each state.
Proposed Legislation
While EPA's National CSO Strategy promised progress in resolving the CSO problem,
several members of Congress have remained concerned that legislative action is needed to ensure
adequate and consistent efforts to control CSOs nationwide. In 1990, Senators Mitchell (ME),
D'Amato (NY), Moynihan (NY), Bradley (NJ), Lautenberg (NJ), Chaffee (RI), and Pell (RI)
sponsored the Coastal Protection Act (S. 1178), which contained a provision requiring the control
of discharges from combined sewer overflows. Section 207 of that bill required the elimination of
discharges from CSOs for all storm events up to and including the l-year/6-hour storm. This 1990
legislation did not reach the Senate floor, but its proposed CSO control requirements have become
part of subsequent proposals.
In April 1991 members of the Senate Environment and Public Works Committee introduced
a Clean Water Act reauthorization bill entitled the Water Pollution Prevention and Control Act (S.
1081). Among its provisions, the bill would require municipalities to implement programs that
would eliminate all CSO discharges caused by rainfall events up to a l-year/6-hour design storm.
In May 1991 the Senate Public Works Committee held hearings on this bill. The committee's
majority staff is currently circulating a revised draft of the bill; this draft retains the l-year/6-hour
standard. Hearings on the revised bill are expected to be held in the spring of 1992.
Several other bills that would affect CSOs have been filed or are under development. For
example, the CSO Partnership, a coalition of sewer authority interests, has developed legislation
recently introduced by Congressman Olin as H.R. 3477. The bill stresses the site-specific nature of
CSO problems and the need for flexibility and cost-effectiveness in implementing CSO controls. It
also calls for Federal grants to fund CSO improvements, to be awarded on the basis of financial
need and water quality benefit. The bill would require localities with CSOs to provide EPA and the
State with information on their systems, complete a CSO study, develop a CSO control plan, file an
NPDES permit application, and comply with the permit when issued. Permits would be issued in
two phases. Phase 1 permits would require the elimination of dry weather overflows, proper
operation and maintenance of the system to minimize wet weather overflows, maximum use of the
existing system's capacity, and implementation of the study and planning requirements. Phase 2
permits would incorporate the technology-based and water quality-based requirements set forth in
the bill. The bill specifies two levels of technology-based controls, and requires compliance with
water quality standards as soon as possible, but specifies no deadline for compliance. The bill also
33
Ibid., pp. 2-3.
34 Office of Water, U.S. Environmental Protection Agency, "Status of Strategy Approvals,"
January 16, 1992.
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provides for the development of wet weather water quality standards, and a variance from water
quality-based requirements when certain criteria are met.
A bill introduced by Congressman Manton (H.R. 2126) would require EPA, in consultation
with NOAA, to issue regulations setting forth permit requirements for CSO discharges to estuarine
and marine waters. In addition, the bill would prohibit EPA from issuing permits to CSOs after
1999 unless the Agency determines that the permittee has undertaken reasonable efforts to eliminate
dry weather discharges and minimize wet weather discharges. The bill would also authorize EPA,
as an enforceable condition of a permit, to require permittees to budget and expend funds to
improve CSO control.
Senator Moynihan's staff has also developed CSO legislation. This bill, which we understand
to be in draft form, would authorize, over five years, demonstration studies that would evaluate
methods to address the adverse impacts of CSOs. Each study would evaluate CSO problems and
impacts, the financial and economic implications of complying with water quality standards, and
innovative techniques to remedy water quality concerns. These studies would in turn support the
development of water quality management strategies for each area, and a Report to Congress
detailing study findings and recommendations. The Moynihan bill also calls for the development,
over six years, of a Federal strategy on the optimal expenditure of Federal funds to minimize the
impacts of CSOs on the nation's waters. This strategy is to include an inventory of combined sewer
systems, with an emphasis on regional, demographic and historical similarities and differences; an
analysis of the relationship between hydrologic and hydraulic variables and pollutant loadings; a
model to optimize Federal investment in CSO control infrastructure; an analysis of the costs of
improving this infrastructure; and recommendations on how current water quality standards could
be improved to provide more flexibility to address CSO discharges.35
EPA's Expedited CSO Control Program
In response to continuing concerns about inadequate and inconsistent national progress on
CSO abatement, EPA has undertaken actions to accelerate the implementation of its CSO Strategy.
The Office of Wastewater Enforcement and Compliance (OWEC), Office of Water, is coordinating
several workgroups that are pursuing a better understanding of CSO issues and impacts, with the
intention of developing an accelerated permitting and enforcement program for CSOs. This
approach calls for EPA to target CSO facilities that cause the greatest harm to water quality.
Targeting would occur in two phases:
o Identifying the five percent of CSSs in each Region that cause the
most severe water quality impacts.
o Identifying all remaining CSSs that cause significant water quality
problems, as well as those causing less severe impacts.
35 The discussion of the Olin, Manton and Moynihan bills is taken from a series of handouts
prepared for a September 9,1991 meeting of EPA's CSO Workgroup and/or from a November, 1991
progress report on EPA's expedited CSO control plan.
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Each group would be subject to CSO control requirements in a phased approach designed
to bring about compliance with the National Strategy. The following are the major components of
the expedited strategy:
(1) Ensure that all CSO dischargers have enforceable permits that
include the following three compliance phases
First, require the discharger to meet the minimum
technology-based requirements of the National
Strategy;
Second, require the discharger to design and construct
the facilities needed to meet the designated uses of
the receiving waters; and
Third, require the discharger to design and construct
the facilities needed to fully compy with the CWA's
technology- and water quality-based standards.
(2) Provide enforcement support
In conjunction with permit issuance, determine which
CSO facilities have insufficient permit limits,
unpermitted CSOs, or CSOs in violation of permit
conditions;
For those with insufficient limits, require submission
of a facilities plan to correct deficiencies, thus
enabling the permit writer to modify or reissue the
permit;
For those with unpermitted CSOs or CSOs in
violation of permit conditions, issue compliance
orders to evaluate and address violations;
Negotiate an enforceable schedule to implement
corrections; and
Monitor permitting and enforcement schedules for
compliance.
(3) Assess and review water quality standards and technology-based
requirements
Review current State approaches for establishing and
implementing water quality-based CSO controls,
analyze current CSO control requirements, and
1-20
-------
evaluate existing flexibility to develop wet weather
water quality controls;
Within three years, revise State standards based on
the results of the above assessment; and
Review the National CSO Strategy's minimum
technology requirements for effectiveness and
appropriateness, and revise them if necessary.36
This approach would be similar to that taken by EPA in developing the Agency's National Municipal
Policy, through which the Agency set strict deadlines and pursued sanctions against municipalities
that failed to comply with sewage treatment requirements.
36 The description of the expedited permitting and enforcement strategy presented above is taken
from a series of handouts prepared for a September 9, 1991 meeting of EPA's CSO Workgroup.
1-21
-------
Exhibit 1-1
CSS FACILITY AND POPULATION DATA
BY EPA REGION AND STATE
EPA Region
1
10
State
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
New Jersey
New York
Puerto Rico
Subtotal
Subtotal
Delaware
District of Columbia
Maryland
Pennsylvania
Virginia
West Virginia
Subtotal
Florida
Georgia
Kentucky
North Carolina
Tennessee
Subtotal
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
Texas
Iowa
Kansas
Missouri
Nebraska
Subtotal
Subtotal
Subtotal
Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
California
Alaska
Idaho
Oregon
Washington
Subtotal
Subtotal
Subtotal
TOTAL
Number of
Facilities
14
61
34
22
2
31
164
30
74
1
105
5
1
11
113
12
47
189
1
8
17
1
3
30
117
131
86
17
119
13
483
±
1
19
3
14
3
39
5
16
8
10
1
1
41
5
5
2
14
11
34
61
Percent of
Total
Facilities
1.25%
5.46%
3.04%
1.97%
0.18%
2.77%
14.67%
2.68%
6.62%
0.09%
9.39%
0.45%
0.09%
0.98%
10.11%
1.07%
4.20%
16.91%
0.09%
0.72%
1.52%
0.09%
0.27%
2.68%
10.47%
11.72%
7.69%
1.52%
10.64%
1.16%
43.20%
0.09%
0.09%
1.70%
0.27%
1.25%
0.27%
3.49%
0.45%
1.43%
0.72%
0.89%
0.09%
0.09%
3.67%
0.45%
0.45%
0.18%
1.25%
0.98%
3.04%
5.46%
Population
Served
415,217
390,776
1,865,156
283,156
190,550
128,312
3,273,167
2,268,782
9,595,263
600,000
12.464,045
90,068
489,093
53,886
4.175,996
537,350
435,050
5,781,443
4,370
473,018
768,556
8,000
150.500
1,404,444
5,651,169
2,808,981
2,614,925
251,855
3,133,923
627,347
15,088,200
35,000
35,000
404,264
464.000
874,301
199,405
1,941,970
152,341
130,416
34,249
90,991
3,818
14,645
426,460
852,119
852,119
4,860
46,012
397,001
706,821
1,154,694
Percent of
National CSS
Population
0.98%
0.92%
4.40%
0.67%
0.45%
0.30%
7.72%
5.35%
22.62%
1.41%
29.38%
0.21%
1.15%
0.13%
9.84%
1.27%
1.03%
13.63%
0.01%
1.12%
1.81%
0.02%
0.35%
3.31%
13.32%
6.62%
6.16%
0.59%
7.39%
1.48%
35.57%
0.08%
0.08%
0.95%
1.09%
2.06%
0.47%
4.58%
0.36%
0.31%
0.08%
0.21%
0.01%
0.03%
1.01%
2.01%
2.01%
0.01%
0.11%
0.94%
1.67%
2.72%
Percent of
State Population
Served by CSS's
13.36%
34.73%
32.51%
30.76%
20.12%
25.09%
30.80%
54.65%
18.77%
15.15%
76.61%
1.28%
35.20%
10.05%
22.31%
0.04%
8.66%
21.00%
0.14%
3.28%
49.45%
51.16%
28.23%
6.18%
29.02%
13.33%
0.25%
13.87%
19.63%
17.78%
12.70%
5.27%
16.58%
5.25%
13.17%
0.26%
3.12%
3.60%
1.21%
4.87%
15.08%
17.10%
1118
100.00%
42,421.542
100.00%
Sources: 1980 Needs Survey
1980 Census
-------
CD
4-J
C/D
CD
_Q
E
13
Exhibit 1 -2
DISTRIBUTION OF COMBINED SEWER SYSTEMS
BY EPA REGION
1980 NEEDS SURVEY
600-t
10
EPA Region
-------
0
0
c
Q.
O
CL
Exhibit 1-3
POPULATION SERVED BY COMBINED SEWER SYSTEMS
BY EPA REGION
1980 NEEDS SURVEY
16
1
4567
EPA Region
-------
Exhibit 1-4
PORTION OF POPULATION SERVED BY CS SYSTEMS, BY STATE
1980 NEEDS SURVEY
10%
i 15%
20%
25%
30%
40%
50%
60%
-------
Exhibit 1-5
DISTRIBUTION OF COMBINED SEWER DISCHARGE POINTS
BY STATE AND EPA REGION
EPA
REGION STATE
OUTFALLS
PERCENT OF MEAN OUTFALL
TOTAL OUTFALLS PER CSS
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
SUBTOTALS
New Jersey
New York
SUBTOTALS
Delaware
District of Columbia
Maryland
Pennsylvania
Virginia
West Virginia
SUBTOTALS
Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
SUBTOTALS
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
SUBTOTALS
Arkansas
Louisiana
New Mexico
Oklahoma
Texas
SUBTOTALS
Iowa
Kansas
Missouri
Nebraska
SUBTOTALS
242
351
388
164
95
169
1409
281
1200
1481
38
55
74
1260
155
700
2282
0
0
31
206
0
0
0
49
286
1015
1100
594
105
1593
275
4682
NA
0
0
0
0
0
82
17
91
23
213
2.25
3.26
3.60
1.52
0.88
1.57
13.08
2.61
11.14
13.75
0.35
0.51
0.69
11.70
1.44
6.50
21.19
0
0
0.29
1.91
0
0
0
0.45
2.66
9.42
10.21
5.52
0.97
14.79
2.55
43.47
NA
0
0
0
0
0.00
0.76
0.16
0.84
0.21
1.98
18.62
5.75
14.92
7.45
31.67
5.45
9.03
10.04
13.33
12.55
12.67
55.00
10.57
9.00
38.75
14.00
11.13
NA
NA
6.20
9.36
NA
NA
NA
16.33
9.53
7.52
7.80
6.99
17.50
14.61
137.50
9.79
NA
NA
0
NA
NA
0.00
4.32
5.67
6.50
7.67
5.46
-------
Exhibit 1-5
(continued)
DISTRIBUTION OF COMBINED SEWER DISCHARGE POINTS
EPA
REGION
8
9
10
STATE
Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
SUBTOTALS
Arizona
California
Hawaii
Nevada
SUBTOTALS
Alaska
Idaho
Oregon
Washington
SUBTOTALS
BY STATE AND EPA
OUTFALLS
6
NA
0
2
0
0
8
0
39
0
0
39
0
0
100
270
370
REGION
PERCENT OF MEAN
TOTAL OUTFALLS
0.06
NA
0
0.02
0
0
0.07
0
0.36
0
0
0.36
0
0
0.93
2.51
3.44
OUTFALL
PER CSS
6.00
NA
NA
2.00
NA
NA
4.00
NA
19.50
NA
NA
19.50
NA
NA
25.00
24.55
24.67
TOTALS
10770
100.00
10.26
Source: U.S. EPA, "Status of Strategy Approvals,1 January 16, 1992.
-------
Exhibit 1 -6
AREA DRAINED BY COMBINED SEWER SYSTEMS
1980 Supplementary Database
1- under 500 acres, (44.8%)
2- from 500 to 999 acres, (14.7%)
3- from 1,000 to 2,499 acres, (14.8%)
4- from 2,500 to 4,999 acres, (9.7%)
5- from 5,000 to 9,999 acres, (5.7%)
6- over 10,000 acres, (5.4%)
7- no response, (5.0%)
-------
CO
CO
o
>*
n
-o
-------
Exhibit 1 -8
DISTRIBUTION OF CSSs BY SYSTEM SIZE
1980 SUPPLEMENTARY DATABASE
80 Systems 46 Systems
(6.7%)
(3.9%)
325 Systems
(27.3%)
740 Systems
(62.1%)
small- fewer than 10,000 customers served by combined sewers
medium- between 10,000 and 100,000 customers served by combined sewers
large- more than 100,000 customers served by combined sewers
-------
Exhibit 1 -9
DISTRIBUTION OF POPULATION SERVED BY CSSs
BY SYSTEM SIZE
1980 SUPPLEMENTARY DATABASE
2,173,896 customers
(5.1%)
29,549,963 customers
(69.9%)
10,552,263 customers
' (25.0%)
small- fewer than 10,000 customers served by combined sewers
medium- betweem 10,000 and 100,000 customers served by combined sewers
large- more than 100,000 customers served by combined sewers
-------
Exhibit 1-10
DISTRIBUTION OF CSSs: URBAN vs. NON-URBAN AREAS
1980 SUPPLEMENTARY DATABASE
No Response (3.1%)
Non-Urban (67.8%)
Urban (29.1%)
The criteria for classification as an urban area are:
o A central city with a population of at least 50,000 or twin cities with a combined population of at least 50,000, with the smaller of the twin cities
having at least 15,000 inhabitants.
o
Closely settled surrounding territory, meeting specific criteria outlined in the Needs Survey.
-------
Exhibit 1 -11
POPULATION SERVED BY URBAN & NON-URBAN CS SYSTEMS
1980 SUPPLEMENTARY DATABASE
No Response (0.3%) -\
Non-Urban (15.7%)
The criteria for classification as an urban area are:
Urban (84.0%)
A central city with a population of at least 50,000 or twin cities with a combined population of at least 50,000, with the smaller of the twin cities
having at least 15,000 inhabitants.
Closely settled surrounding territory, meeting specific criteria outlined in the Needs Survey.
-------
Exhibit 1 -12
DISTRIBUTION OF CSSs
BY PRIMARY RECEIVING WATER
1980 NEEDS SURVEY
Unidentified
Stream
Stream
River
Lake
Estuary
Ocean
Unidentified
45.3%
26.2%
3.8%
5.4%
1.3%
17.9%
River
Note: These data do not necessarily represent the distribution of receiving waters that CSOs
-------
Exhibit 1-13
CONTRIBUTION OF CSOs TO IMPAIRED WATER
QUALITY IN THE UNITED STATES
(1990 305(b) Data)
Water
Rivers
(miles)
Lakes
(acres)
Great Lakes
(shore-miles)
Estuaries
(square miles)
Oceans
(shore-miles)
Assessed
647,066
18,488,636
4,857
26,693
4,230
Impaired Waters
for which Sources
of Impairment are
Identified
177,792
3,971,330
1,235
7,693
361
Source: 1990 State Section 305(b) Reports, as docui
Congress (Draft), Office of Water, Washing
CSOs a Major
Source of
Impairment
3,521
7,967
0
269
12
CSOs a
Moderate or
Minor Source
of Impairment
1,642
13,393
93
234
120
CSO-Impaired
Waters as a Percent of
all Waters for which
Sources of Impairment
are Identified
2.9%
0.6%
7.5%
6.5%
36.6%
nented in U.S. EPA, National Water Quality Inventory: 1990 Report to
ton, DC, 1991.
-------
Exhibit 1-14
SHELLFISH HARVEST-LIMITED AREAS
Region
North Atlantic
Middle Atlantic
South Atlantic
Gulf Coast
Pacific Coast
Total
Approved
Acres
(1,000)
2,014
4,426
2,092
3,434
338
12,304
Harvest-
Limited
Acres
(1,000)
396
1,181
830
3,662
306
6,375
Source: National Oceanic and Atmospheric Administration,
Classified Estuarine Water. U.S. Department of Coi
Acres
Limited
Due to CSOs
(1,000)
20
229
0
348
0
597
Acres Limited
Due to CSOs as a
Percentage of Total
Limited Area
5.1%
19.4%
0%
9.5%
0%
9.4%
The 1990 National Shellfish Register of
nmerce, Rockville, MD, July 1991.
-------
Exhibit 1-15
BEACH CLOSURES OR ADVISORIES DUE TO
HIGH BACTERIA COUNTS
(Days)
State
Maine
Massachusetts
Rhode Island
Connecticut
New York
New Jersey
Delaware
Maryland
Florida
California
Total:
1989
1
60
0
103
923
266
62
0
N/A
338
1,753
1990
72
59
0
218
581
228
11
0
234
64
1,467
Source: Kassalow, J., et al., Testine the Waters: A Study of Beach Closings in Ten Coastal States,
Natural Resources Defense Council, August 1991.
-------
Exhibit 1-16
STATUS OF STATE CSO STRATEGY APPROVALS
STATE STRATEGY SUBMITTED
NO STRATEGY
REQUIRED
EPA
REGION
1
2
3
4
5
6
7
8
9
10
STATE
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
New Jersey
New York
Delaware
District of Columbia
Maryland
Pennsylvania
Virginia
West Virginia
Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
Arkansas
Louisiana
New Mexico
Oklahoma
Texas
Iowa
Kansas
Missouri
Nebraska
Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
Arizona
California
Hawaii
Nevada
Alaska
Idaho
Oregon
Washington
CONDITIONAL!/
NO ACTION APPROVED APPROVED
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
If
NOCSSs
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
wrracsss
X
X
X
X
X
TOTALS
26
16
Source: EPA, "Status of Strategy Approvals," January 16, 1992.
-------
STATE APPLICATIONS OF CSO
WET WEATHER DESIGN STANDARDS CHAPTER 2
INTRODUCTION
While the Federal government is considering the need for and possible form of a national
technology-based design standard for controlling combined sewer overflows, several states have
already implemented wet weather CSO design standards. Knowledge of state approaches to setting
these standards is of obvious interest in designing a Federal approach. With this in mind, this
chapter describes CSO regulations or policies in selected states.
The review of CSO policies presented here is based primarily upon telephone contacts with
state regulators; Appendix B gives a complete list of state contacts and source documents.1 This
research suggests that states have employed a range of logic in developing CSO standards;
consequently, the policies they have adopted vary significantly. As described below, many standards
have been developed as ad hoc responses to a particular CSO problem. As a result, the
development of the state CSO standards reviewed here provides limited guidance for the selection
of a Federal approach. Nevertheless, simply by illustrating the broad range of CSO wet weather
standards currently in place, this review provides a starting point for defining practical alternatives.
STATE COMBINED SEWER OVERFLOW STANDARDS
We have identified nine states that have taken steps to control CSOs through regulations,
policies, or permitting actions that include wet weather design standards. Table 2-1 summarizes
these actions. As the table shows, one state, Illinois, has adopted a factor of flow standard, requiring
primary treatment for all flows up to 10 times the dry weather flow (the state also requires that
treatment for the "first flush" of storm flows meet applicable effluent standards; the "10X" approach
extends primary treatment requirements beyond the first flush). Three other states have developed
standards based upon design storm concepts: Michigan and Rhode Island have developed CSO
control policies based on a frequency/duration design storm, while Vermont specifies a
depth/duration (2.5-inch/24-hour) design storm. Four others -- California (for San Francisco),
1 Initial interviews were conducted by Jeff Albert under separate contract to EPA. Additional
interviews, including some follow-up interviews, were conducted by Douglas Rae, an independent
consultant to lEc. Appendix B lists all individuals interviewed.
2-1
-------
Massachusetts, Washington, and Wisconsin (for Milwaukee) -- have set overflow frequency standards
that expressly limit the number of overflows per year, while one state, Oregon (for Portland), has
used a hybrid approach that specifies an overflow limit with reference to a design storm. Each of
these approaches is described below; where available information allows, the discussion also includes
the rationale underlying selection of the standard.
Table 2-1
STATE COMBINED SEWER WET WEATHER DESIGN STANDARDS
State Type of Standard Standard Legal Form
California
(San Francisco)
Illinois
Massachusetts
Michigan
Oregon
(Portland)
Rhode Island
Washington
Wisconsin
(Milwaukee)
Vermont
Overflow Frequency
Limit
Factor of Flow
Overflow Frequency
Limit
Frequency/Duration
Design Storm
Overflow Frequency
Limit*
Frequency/Duration
Design Storm
Overflow Frequency
Limit
Overflow Frequency
Limit
Depth/Duration
Design Storm
8 untreated overflows
per outfall per year
(weighted average)
10 times dry
weather flow
4 untreated overflows
per outfall per year
1 -year/1 -hour for
secondary treatment;
10-year/l-hour for
primary treatment
1 untreated overflow
every 10 years in
summer; 1 every
5 years in winter
l-year/6-hour storm
1 untreated overflow
per outfall per year
1.7 untreated
overflows per outfall
per year
2.5-inch/24-hour
storm
System Permit
State Regulation
State Policy
State Policy
System Permit
State Policy
State Policy
System Permit
State Regulation
*As noted in the text, the standard that Oregon is applying to Portland may also be
interpreted as a design storm limit.
Source: Industrial Economics, Incorporated
2-2
-------
There are three combined sewer systems in California, operated by San Francisco, the East
Bay Municipal Utility District, and Sacramento, respectively. The state has received conditional
EPA approval for a CSO policy governing these systems. The policy includes the following
minimum technology-based limitations:
1) proper operation and regular maintenance for the sewer system and CSO
points;
2) maximum use of the collection system for storage;
3) maximization of flow to the POTW for treatment;
4) prohibition of dry weather overflows;
5) control of solid and floatable materials in CSO discharges; and
6) review and modification of pretreatment programs to ensure that CSO
impacts are minimized.
The stale's policy, which is to be implemented by Regional Water Quality Control Boards (WQCBs),
does not include a wet weather design standard; however, the permit requirements for San
Francisco's system specify overflow frequency limits.
The San Francisco Bay Region WQCB has issued three NPDES permits for San Francisco's
CSOs: one for a wet weather treatment plant, one for CSOs discharging to San Francisco Bay, and
one for CSOs discharging to the Pacific Ocean. These permits limit overflows to an average of eight
per year to the Pacific Ocean, and to an average of one, four or ten per year in San Francisco Bay,
depending on "relative receiving-water sensitivity and cost of controlf.]" The WQCB established
these limits based upon an analysis of the cost-effectiveness of CSO control undertaken in the late
1970s. The analysis examined alternative standards of 2, 4, 6, 8,10, and 16 overflows per year. The
study indicated that for overflows to the Pacific, control costs under standards more stringent than
eight overflows per year increased rapidly, with little commensurate beneficial impact on water
quality. Control costs varied for CSOs discharging to the Bay, as did the sensitivity of receiving
waters near the outfalls. The varying design standards for San Francisco Bay reflect the effort to
establish cost-effective limits consistent with the sensitivity and beneficial uses of the receiving
waters.
ois
Illinois' Water Pollution Regulations (Section 303.305: Treatment of Overflows and
Bypasses) require all combined sewer overflows and treatment plant bypasses to be given sufficient
treatment to prevent pollution or the violation of applicable water quality standards. Unless an
exception for an alternative treatment program is granted, sufficient treatment is defined as follows:
2-3
-------
(a) All dry weather flows, and the first flush of storm flows as determined by the
[State], shall meet the applicable effluent standards; and
(b) Additional flows, as determined by the [State] but not less than ten times the
average dry weather flow for the design year, shall receive a minimum of
primary treatment and disinfection with adequate retention time; and
(c) Flows in excess of those described in subsection (b) shall be treated, in whole
or in part, to the extent necessary to prevent accumulations of sludge
deposits, floating debris and solids...and to prevent depression of oxygen
levels.
Illinois' approach requires CSSs to treat the "first flush" of storm flows in accordance with applicable
effluent standards because pollutant loadings from CSSs are likely to be greatest in a storm's early
stages, when wet weather flow acts to scour deposits of sewage and other matter that may have
accumulated in the system. The requirement that primary treatment be provided for wet weather
flows up to ten times the dry weather flow is an extension of this concept, and was based on an
analysis of empirical data that indicated that flows above "10X" were often so diluted with storm
water that the water quality impacts were less severe than at lower flows.
Massachusetts
The Massachusetts Department of Environmental Protection (DEP) released its
"Implementation Policy for the Abatement of Pollution from Combined Sewer Overflows" on May
24, 1990. EPA Region I has conditionally approved this policy, pending resolution of a
disagreement over the wet weather design standard the policy employs.
DEP's policy establishes a design standard based on "a three month design storm as a
minimum technology-based effluent limitation" that "will result in untreated overflows on an average
of four (4) times a year." Massachusetts' rationale for this proposal rests on an analogy to the
suspension of state water quality standards under dry weather, low flow conditions. Like most states,
Massachusetts determines whether a discharge to a river or stream requires a water quality-limited
permit by analyzing whether operation under technology-based limits during low flow conditions
would lead to a violation of state water quality standards. For the purpose of such analyses,
Massachusetts uses 7Q10 (the lowest stream flow for seven consecutive days over a 10 year period)
as its low flow condition. Statistically, flows lower than 7Q10 occur on average about four days per
year, or about one percent of the time. On this basis, Massachusetts argues that wet weather
discharges should also be allowed to violate water quality standards about one percent of the time;
hence, the state proposes a wet weather standard of four overflows per year.
2-4
-------
EPA Region 1 has questioned the logic underlying Massachusetts' policy, arguing that the
analogy to low flow conditions does not hold because one overflow may cause water quality
standards to be violated for many days. This disagreement has yet to be resolved.2
Michigan
Michigan's CSO policy recommends (1) storage for secondary treatment of all CSO flows
up to the 1-year/1-hour storm and (2) equivalent primary treatment (skimming, 30 minutes of
sedimentation, and disinfection with 30 minutes of contact time) of all CSO flows up to the 10-
year/1-hour storm. This standard is coupled with a provision that alternative treatment meeting
Michigan water quality standards is permissible.
Michigan's choice of the 1-year/l-hour storm and the 10-year/l-hour storm as design
standards was based on regulatory precedent and typical sewer system design. In the early 1970s,
a number of storm water detention facilities were built in Michigan. Permits established at that time
on the basis of Best Professional Judgment stipulated the 1-year/1-hour storm as the design standard.
When the Michigan Department of Natural Resources (DNR) was developing its CSO policy, DNR
considered it reasonable to apply this limit as the secondary treatment flow standard for combined
sewer systems as well. The selection of the 10-year/l-hour storm as the design standard for wet
weather flows requiring equivalent primary treatment was based at least in part on the fact that
many Michigan sewer systems were designed to convey flows up to this magnitude; the policy now
requires that these flows receive at least primary treatment.
Oregon
Oregon's CSO Policy was developed by the state's Department of Environmental Quality
(DEQ) in response to EPA's National CSO Policy, and evolved in part from a 1981 policy requiring
that:
"Sewerage Construction programs should be designed to eliminate raw sewage
bypassing during the summer recreation season (except for a storm event greater
than the 1 in 10 year 24 hour storm) as soon as practicable. A program and
timetable should be developed through negotiation with each affected source.
Bypasses which occur during the remainder of the year should be eliminated in
accordance with an approved longer term maintenance based correction program.
More stringent schedules may be imposed as necessary to protect drinking water
supplies and shellfish growing areas." (OAR 340-41-034(3)(f))
2 EPA Region I has established its own CSO guidance policy. Among other features, this policy
calls for the elimination of CSO discharges from critical use areas (e.g., beaches and shellfishing
areas) and implementation of sufficient treatment to comply with water quality standards whenever
technically and economically feasible. The policy does not stipulate a technology-based wet weather
standard.
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The current CSO policy, which was adopted in February 1991, specifies that CSOs will be required
"to meet the minimum technology-based limitations as set forth in the National CSO Control
Strategy." The policy also states that "the Department will require whatever level of controls
including separation of sewers is necessary to achieve water quality standardsf,]" including a fecal
coliform limit of 200/100 ml, to be met at the end of the pipe with no mixing zone. Although the
CSO policy statement does not mention a wet weather design standard, only storms with rainfall
greater than the 10-year event are expected to be sufficient to dilute raw sewage fecal coliform levels
(about 8,000,000/lOOml) to the 200/100 ml limit.3
The DEQ currently is applying this policy in an enforcement order against the City of
Portland, where 60 percent of the sewer system is combined. This order will require elimination of
all discharges that violate applicable water quality standards for
o all flows between May 1 and Oct. 31 up to the 10-year storm event, and
o all flows between Nov. 1 and April 30 up to the 5-year storm event.
Since the 10-year storm event will cause an overflow on average every ten years, this standard is
equivalent to one permitting untreated overflows to occur an average of once every ten summers.
Similarly, the standard would permit untreated overflows to occur an average of once every five
winters.
Rhode Island
In March of 1990 the Rhode Island Department of Environmental Management (DEM)
established a CSO policy requiring primary treatment for all flows equivalent to that associated with
the l-year/6-hour storm event (DEM, "Combined Sewer Overflow Policy", March 1990). Rhode
Island defines primary treatment as 50 percent removal of total suspended solids and 35 percent
removal of BOD loadings, or 100 percent removal of all settleable solids, whichever provides the
greater improvement in water quality. The policy is flexible in that it allows municipalities to
provide storage for less than the l-year/6-hour flow provided that overall treatment is sufficiently
stringent to achieve a reduction in pollutant loadings equivalent to the standard defined above.
In developing its policy, DEM analyzed an available set of data on the 300 largest storms in
Rhode Island from 1949 to 1982. The depth of both the mean and median storms was
approximately that of the state's 1-year/12-hour storm. The average duration of these storms was
six hours. DEM chose the l-year/6-hour storm rather than the 1-year/12-hour storm as its design
standard after discussions with the regulated community suggested that the larger volume of rain
associated with a 1-year/12-hour standard would make storing combined sewage prohibitively
expensive, and therefore would compel communities to employ relatively less effective pass-through
treatment technologies (e.g., swirl concentrators and chlorination). Under the l-year/6-hour storm
standard, it would be more feasible to store wet weather flows off-line until treatment capacity at
POTWs - where a higher degree of control could be attained -- became available.
3 The "ten-year event" refers to the greatest amount of rain expected, on average, from any one
storm over a ten-year period. Such events are defined without reference to duration.
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Washington
In Washington, a 1986 state law requires the "greatest reasonable reduction of CSOs at the
earliest possible date," which the state's Department of Ecology (DOE) has defined in regulations
as an average of one overflow per outfall per year. The selection of this standard was based on an
analysis, completed in the late 1970s, of the impact of Seattle's CSOs on Lake Washington. This
study suggested that a standard of one overflow per outfall per year would be sufficiently stringent
to achieve the fishable/swimmable goals of the Clean Water Act.
Wisconsin
Wisconsin has not developed a uniform statewide CSO standard, but has developed a
standard likely to be included in an NPDES permit for Milwaukee, the state's largest city. This
standard would limit Milwaukee to an average of 1.7 overflows per year. This limit was arrived at
post hoc, and has its origins in the design of improvements to Milwaukee's sewer systems.
In the 1970s the state of Illinois sued the City of Milwaukee and the Milwaukee
Metropolitan Sewer District over CSO pollution of Lake Michigan and degradation of water quality
in Illinois waters. An initial Federal court ruling favored Illinois and required Milwaukee to
eliminate overflows from both its separate and combined sewer systems.4 An appeal to the U.S.
Supreme Court overturned the lower court ruling. The Wisconsin Department of Natural Resources
(DNR) then interceded in the dispute, requiring Milwaukee in a stipulated agreement to attain zero
discharge of its separate storm sewers. No agreement was reached on the level of protection for
combined sewers; instead, a third party, the Southern Wisconsin Regional Planning Commission
(SWRPC), was charged with studying water quality problems in the receiving waters and
recommending a level of protection.
Construction began in the mid-1980s on a deep tunnel to provide 650 acre-feet of storage
to handle overflows from the separate storm sewer system. This volume of storage was considered
adequate to prevent overflow from the "worst storm on record in the last 40 years." A decision not
to line the tunnel with concrete, coupled with the use of a larger tunnel bore than originally planned
(smaller boring equipment was unavailable), increased the tunnel's storage capacity to 1140 acre-
feet. Studies of the combined sewer overflow problem indicated that this additional storage would
be sufficient to limit combined sewer overflows to an average of 1.7 per year, and the SWRPC
recommended that this standard be adopted. Wisconsin DNR has conditionally approved the
standard in a permit, although the DNR has not approved the water quality study conducted by the
SWRPC.5
4 Approximately seven-eighths of the Milwaukee system consists of separate storm and sanitary
sewers; the remaining eighth of the system consists of combined sewers.
5 The cost of the Milwaukee project is estimated at $500 million for control of separate sewer
overflows and $300 million for control of combined sewer overflows.
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Vermont
Vermont's State Water Quality Standards (revised April 1990) propose elimination of CSO
discharges to Class A (drinking water without filtration) and B waters (full body contact and
drinking water with filtration/disinfection) and require that all water quality standards be met for
all CSO discharges to Class C waters for all flows up to the 24 hour/2.5 inch rainfall. This standard
embodies the approach developed to resolve CSO problems in Burlington, Vermont's largest city.
Burlington's combined sewer overflows frequently violated state bacteria standards, forcing Lake
Champlain beaches to close (Class B waters). Pressure from citizen's groups, EPA, and the U.S.
Attorney's Office led to a consent decree in 1989 requiring control of CSOs. The facilities plan
developed under this decree includes separation of some combined sewers and consolidation of
some CSOs, with capacity for treatment and discharge through an extended outfall to Class C waters
beyond the city's Lake Champlain breakwater.
As with Massachusetts, reference to the 7Q10 low flow condition guided Vermont's selection
of a CSO wet weather standard. Analysis of 4,974 rainfall events at the Burlington airport indicated
that only one percent of area storms exceed 2.0 inches; therefore, Vermont concluded, the
probability of a storm that exceeds the depth of the 2.5-inch/24-hour event (less than one percent)
is comparable to the probabilty of experiencing a low flow (7Q10) event (also less than one percent).
It is interesting to note that although both Vermont and Massachusetts draw an analogy to
7Q10 in defining CSO standards, they come to different conclusions about the implications of this
analogy. In Vermont, a 2.5-inch storm event occurs on average only once in two years; therefore,
storms greater than the design storm - those that would cause uncontrolled overflows ~ are likely
to occur on average only once every two years. In contrast, the Massachusetts standard would allow
uncontrolled overflows to occur eight times as frequently. This difference is a result of differing
interpretations of rainfall data and the 7Q10 analogy.
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DATA ON RAINFALL EVENTS CHAPTER 3
INTRODUCTION
An understanding of design storm concepts and of the implications of alternative wet
weather standards for controlling CSOs requires an understanding of the underlying rainfall data.
This chapter briefly discusses key storm parameters, the collection and maintenance of rainfall data
to describe these parameters, and how the data are used to analyze the characteristics of storm
events.1
STORM PARAMETERS
Many structures, such as dams and storm sewers, must be designed with sufficient capacity
to withstand or operate during severe storms. As a consequence, an important branch of
meteorology concerns itself with the analysis of so-called "extreme rainfall events." The
characteristics commonly used in describing such events are:
o Depth - the amount of rain that falls during a storm, typically measured in
inches.
o Duration storm length, typically measured in minutes or hours.
o Intensity - the amount of rain that falls in a given time, typically measured
in inches per hour.
o Frequency - the average number of storms of a given characteristic (e.g.,
depth or duration) that occur within a specified period of time at a particular
location; alternatively, frequency can be expressed as the return period
(average interval between expected occurrences) of a given rainfall event.
1 This chapter is based upon Eugene D. Driscoll and Joan M. Kersnar, Woodward-Clyde
Consultants, "The 1-Year, 6-Hour Design Storm and its Use in Legislative and/or Regulatory
Approaches for Controlling Pollution from Combined Sewer Overflows," August 20, 1991.
3-1
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Note that these characteristics are measured and defined with reference to a particular place (where
the measurements are made). The depth, duration, or intensity of a given storm may vary
significantly at different locations in the storm's path.
COLLECTION AND MAINTENANCE OF RAINFALL DATA
The U.S. Department of Commerce's National Weather Service operates thousands of
weather monitoring stations nationwide. Since 1910, the Service or its predecessor, the U.S.
Weather Bureau, has maintained 200 stations that record rainfall for periods ranging from 30
minutes to 24 hours. In addition, the Service or Bureau has collected data since approximately 1910
at more than 1400 sites where rainfall readings are made once every 24 hours. In combination, this
network of over 1600 stations provides the Weather Service with 80 years of rainfall data from across
the U.S., giving weather researchers a foundation for analyzing the characteristics of relatively rare
storm events.
In the 1940s, the Weather Bureau established an additional network of over 2000 recording
gauges, each of which provides hourly data on rainfall events. This network has now gathered over
40 years of hourly readings, providing comprehensive national coverage and a firmer basis for
analyzing and understanding variations in rainfall parameters within relatively fine time intervals.2
The accuracy of the Weather Service's data is limited to some extent by the methodology
used to gather the data. Rainfall events often overlap clock hour or calender day intervals; however,
some stations record data only within these intervals. A more precise record is required to ensure
that storm duration and intensity are accurately described.3 Since 1948, many weather stations have
recorded rainfall data in 15-minute increments, thereby increasing the precision with which events
are measured and characterized.
The National Climatic Data Center (NCDC) maintains all weather data collected by the
Weather Service. Data from the Weather Service's rain gauge network are available for analysis in
computer-readable form.4
2 Some cities also maintain local rain gauge networks.
3 For example, a storm that begins on March 31 at 23:30 and ends on April 1 at 00:30 would be
recorded under a strict clock/calender system as two 30 minute storms. Under a duration system,
the same storm would more accurately be recorded as a one-hour storm.
4 NCDC's electronic data base contains data from approximately 17,000 previously and 8,000
currently operating stations throughout the 50 states. These data include hourly rainfall records
from over 5,500 stations, and 15-minute data from over 2,700 stations.
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ANALYZING THE CHARACTERISTICS OF STORM EVENTS
The rainfall data collected by the Weather Service provide the basis for determining national
patterns of rainfall depth, duration, intensity, and frequency. These patterns form the basis for
describing "typical"storm events for a given location.
The following discussion describes how the rainfall data are used to analyze and characterize
storm events.
Tical Rainfall
Exhibit 3-1 illustrates typical data from an hourly rain gauge. This particular plot shows the
pattern of rainfall for three separate storm events. As the exhibit shows, for each clock hour in
which a measurable amount of rain falls, the quantity is recorded. 5 Each bar on the plot indicates
both the amount of rain recorded in that hour (in inches), and the average intensity of rainfall
during that hour (in inches per hour). The plot also illustrates the duration of each storm and the
interval between storms (in hours). The total depth for each rainfall event is the sum of the
individual hourly values, and the average intensity of each storm is this sum divided by the storm's
duration. Note that a storm's intensity at any given time may vary considerably from its average
intensity.
A plot of storm depths at a particular site, showing the relative frequency of each depth,
tends to follow a log-normal distribution. As illustrated in Exhibit 3-2, such a distribution is skewed
to the right, where the extreme rainfall events fall. Transforming these data into logarithms yields
a normal distribution, which has more attractive statistical properties. Because statistical analysis
is simplified by working with a normal distribution, engineers, hydrologists and meteorologists
typically work with rainfall data in logarithmic form.
Analysis of Storm Frequency
Exhibit 3-3 shows data on all rainfall events for a site in the San Francisco Bay area over a
39-year period, transformed to logarithmic form and converted to a cumulative frequency
distribution. Distributions like this are employed to analyze the probability that a storm of a given
depth is likely to occur, and to calculate storm return periods. In the distribution shown,
approximately five percent of the rainfall events on record exceed 1.3 inches. Thus, the probability
that a storm will exceed 1.3 inches is 0.05. Given a total of 827 storms in the 39-year period, one
would expect 41.4 storms (.05 x 827) to equal or exceed 1.3 inches, an average of about one per
year. The "1-year storm" for this location is therefore approximately 1.3 inches. Working in the
opposite direction, one can similarly determine the depth of the 2-year storm. Recognizing that
approximately 19.5 such storms (39/2) will occur in a 39-year period, the probability that any given
storm will equal or exceed the 2-year storm is approximately 0.02 (19.5/827), or two percent.
5 The minimum measurable quantity of rain in any hour is usually 0.01 inches.
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Referring again to the cumulative frequency distribution, about two percent of all storms equal or
exceed two inches. Thus, the 2-year storm for this location is approximately two inches.6
Annual vs. Partial-Duration Series
Engineers employ two methods to evaluate storm frequencies: the use of annual data series
and partial-duration data series. Annual series select the largest rainfall event of a given duration
in each year and rank the resulting set of events by depth. A partial-duration series ranks all rainfall
events of a given duration by their depth, regardless of the year in which they occurred; this
approach recognizes that the largest storm in some years may be smaller than the secondary storms
in others. Before the widespread use of computers, the analysis of a complete set of rainfall events
was generally impractical. As a result, annual series were commonly used. Today, the availability
of computers has made use of partial-duration series more common.
The largest storm in a partial-duration series will be the same as the largest storm in an
annual series taken from the same set of data; however, the tenth-ranked storm of the partial-
duration series is likely to exceed the equivalent storm of the annual series, and the magnitude of
such differences is likely to increase as one proceeds down the ranking to storms that occur more
frequently. To correct this possible source of error, standard multipliers have been developed to
convert findings based on annual series to a partial-duration equivalent. Table 3-1 lists several of
these conversion factors.
Table 3-1
ANNUAL TO PARTIAL-DURATION
SERIES CONVERSION FACTORS
Return Period
2
5
10
Year
Year
Year
Conversion Factor
1.14
1.04
1.01
General Method for Calculating Return Periods
Once rainfall events for a given location are ranked by depth, one can use the following
formula to estimate return periods for different size storms:
Return Period = (Years of data + l)/Ranking.
6 The analysis above includes data on all storms, regardless of the storm's length. Hence, the
1-year or 2-year storm is described without reference to duration.
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Thus, if there are 39 years of data, the largest rainfall event is the 40-year storm, the second-largest
is the 20-year storm, and the 40th largest is the 1-year storm. Through regression analysis, analysts
can also use these data to project the depth of 100- and 200-year events.
General Method for Calculating the
Probability of Experiencing the N-Year Storm
It is important to emphasize that storms with a given return period will not necessarily occur
within that period. The return period (n) merely indicates that a storm of a given depth is likely
to occur, on average, once every n years. For storms with a return period of more than one year,
the probability of occurrence within the return period (e.g., the probability that the two-year storm
will occur in the next two years) can be calculated using the following formula:
P = 1 - (1 l/n)°,
where P is the probability of occurrence and n is the return period, in years. Thus, the probability
of experiencing a storm within two years that is greater than or equal to the two-year storm is 0.75.
For longer return periods the probability declines until, as n becomes very large, P approaches a
limit of 0.632.7
Rainfall Frequency/Duration Data
Employing the procedure described above to calculate return periods for rainfall events of
a given duration -- and repeating the procedure for many locations -- makes it possible to create
maps that define rainfall contours (isopluvials) for specified storm frequencies and durations across
a geographic area. In the 1950s, the U.S. Army Corps of Engineers' demand for information to
support flood-control planning led to analysis of long-term rainfall data to develop isopluvial maps
for the entire United States. The Weather Bureau and the Soil Conservation Service published the
results of this analysis in the Rainfall Frequency Atlas of the United States for Durations from 30
Minutes to 24 Hours and Return Periods from 1 to 100 Years (Hershfield, Technical Paper No. 40,
1961). This publication includes maps for return periods of 1,2, 5, 10, 25, 50, and 100 years and
durations of 0.5,1, 2, 3, 6, 12, and 24 hours. Exhibit 3-4 shows an example, illustrating isopluvials
for the l-year/6-hour storm in the 48 contiguous states. Subsequent publications cover Puerto Rico,
Hawaii, and Alaska, and provide additional detail on rainfall in mountainous regions. Although
somewhat dated, these documents continue to serve as primary references for information on the
frequency and depth of extreme rainfall events throughout the U.S.
7 Thus, if you live to be 100, you have only a 63.2 percent chance of experiencing the 100-year
m.
storm
3-5
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Exhibit 3-1
SAMPLE HOURLY RAINFALL DATA
CD
.C
o
c
<
cr
0.0
TIME (clock-hour)
Exhibit 3-2
EXAMPLE OF A LOGNORMAL DISTRIBUTION
-------
Exhibit 3-3
FREQUENCY DISTRIBUTION OF STORM EVENT VOLUMES
c/)
0)
.c
o
c
LU
D
O
I-
Z
LU
LU
DC
O
h-
co
MEDIAN= 0.41
COV = 0.94
MEAN = 0.56
99.9
99
.1
Percent of Events with Rain Volumes
Equal or Greater than Indicated Value
-------
Exhibit 3-4
RAINFALL FREQUENCY/DURATION MAP
1-YEAR 6-HOUR RAINFALL (INCHES)
Reduced copy from Hershfield, DM 1961. Rainfall Frequency Atlas ol the United States
lor Durations from 30 Minutes to 24 Hours and Return Periods from 1 to 100 Years.
Technical Paper 40. Weather Bureau. U.S. Department ot Commerce, Washington. D.C.
-------
ALTERNATIVE CSO STANDARDS CHAPTER 4
INTRODUCTION
The debate over regulatory or legislative initiatives to improve CSO control has focused to
date on proposals to reduce the frequency with which untreated discharges occur. In some
instances, including Senate Bill 1081 (filed in the Spring of 1991), these proposals call for a standard
that would require communities to design and construct facilities to control wet weather discharges
for all storm events smaller than a specified design storm. Other approaches under discussion would
expressly limit the number of untreated CSO discharges that would be permitted each year, or would
require control of wet weather flow up to a specified multiple of dry weather flow.
This chapter describes and compares four general approaches that have been proposed in
Congress or employed by States or Regions to set CSO control standards:
(1) Requiring control of wet weather discharges based on a
frequency/duration design storm, such as the l-year/6-hour event
proposed in S. 1081;
(2) Requiring control of wet weather discharges based on a
depth/duration design storm, such as a 2.5-inch/24-hour event;
(3) Requiring control of wet weather discharges up to some multiple of
dry weather flow, such as a factor of 10 (the "factor of flow"
standard); and,
(4) Specifying an average or maximum number of allowable overflows
per system or outfall each year.
Evaluation of the advantages and disadvantages of these wet weather standards requires
careful consideration of a variety of factors, including their cost, relative effectiveness, enforceability,
administrative feasibility, and resulting ecological, human health, and welfare benefits. In the
absence of specific, detailed proposals and more complete information on the charateristics of the
nation's combined sewer systems, these factors cannot be fully evaluated. For each general
approach, however, it is possible to identify the underlying conditions likely to influence its practical
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impacts, and to use these insights to compare the implications of the approaches for different
regions or different types of systems. This chapter develops such a comparison.
The following discussion focuses in particular on the effect of alternative approaches on
three parameters:
(1) The frequency of uncontrolled overflows;
(2) The volume of wet weather discharge that must be controlled; and
(3) The wet weather flow for which treatment must be provided.
We focus on the frequency of uncontrolled overflows as an indicator of the potential environmental
benefits of a wet weather standard. All other things equal, approaches that reduce the frequency
of uncontrolled overflows more than others would be expected to provide greater environmental
benefits.1 We focus on the design standards' volume and flow management requirements as
indicators of potential CSO control costs.2 CSS's may employ a range of techniques to reduce
pollutant discharges from overflows. A design standard is unlikely to influence the cost of some of
these approaches (e.g., reducing infiltration and inflow, or repairing regulators to avoid dry weather
overflows). A design standard, however, has direct implications for the cost of treatment devices,
which are sized on the basis of flow, and for the cost of storage devices, which are sized on the basis
of volume. All other things equal, the greater the wet weather volume and/or flow that must be
controlled, the greater the expected cost of compliance.
CAVEATS
We emphasize that the conclusions we reach in analyzing alternative CSO design standards
frequently rest on the implicit or explicit assumption, "all other things equal." A wide range of
factors may influence the cost or effectiveness of a particular approach in a specific locale. For
example, differences in the proportion of rainfall that ultimately enters a CSS as storm water runoff
may cause compliance costs for two otherwise identical cities ~ subject to the same standard and
to identical rainfall conditions - to differ significantly. Many other site-specific factors can have
similar effects. The use of the assumption "all other things equal" is not meant to imply that no
local variation exists; rather, it is employed specifically to control for the important influence of such
factors, allowing us to illustrate the practical similarities and differences among alternative standards
and to demonstrate more clearly how the impact of a particular standard may vary due to underlying
differences in a specific parameter of interest.
1 The actual benefits of any wet weather design standard would also depend upon such factors
as the nature of the receiving waters, the pollutants present in the combined sewer discharge, and
the quality of treatment provided.
2 The terms flow and volume are not interchangeable. Volume refers to the total quantity of
wet weather discharge for which storage and treatment must be provided, and is typically measured
in gallons. Flow refers to the volume of wastewater per unit of time for which conveyance and
treatment systems must be designed, and is typically measured in gallons per minute.
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DESIGN STORM STANDARDS
A design storm standard for CSOs would require combined sewer systems to be modified
to control wet weather discharges associated with storms smaller than or equal to the design event.
To enable engineers to determine the volume and flow of runoff associated with a design storm, at
least two of three storm parameters -- depth, duration, and frequency -- must be defined. It is then
possible to determine the value of the third, unspecified parameter, and ultimately -- given data on
local runoff and combined sewer system conditions -- to calculate the associated wet weather volume
and flow the system must control. The following discussion describes two approaches for specifying
a design storm: a frequency/duration standard and a depth/duration standard.
Frequency/Duration Design Standard
Design storms can be defined with respect to frequency and duration. Specification of such
a standard would require combined sewer systems to control wet weather discharges during all
events smaller than or equivalent to the design event -- e.g., events smaller than or equal to the 1-
year/6-hour storm, the greatest amount of rainfall, on average, expected to occur during six
contiguous hours in a 365-day period.
The impact of a frequency/duration standard on the control of combined sewer overflows
would depend upon the storm frequency and duration specified. Table 4-1 indicates, for the
Cleveland area, how changes in storm frequency and/or duration affect rain depth. As the table
shows, rain depth increases as the return period or duration of the design storm increases. This
relationship suggests that the greater the duration or return period of the design storm, the greater
the volume of rain that must be controlled.
Table 4-1
APPROXIMATE DEPTH OF SELECTED
FREQUENCY/DURATION STORMS: CLEVELAND
(INCHES)
Duration
2 Hours
6 Hours
24 Hours
Return Period
1 Year
1.2
1.5
2.0
25 Years
2.5
3.0
4.0
Increases in design storm return period and duration have conflicting effects on storm intensity.
Using Cleveland once again as an example, Table 4-2 shows that the average intensity of design storms
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increases as the return period increases, but decreases as the duration of the storm increases.3 These
relationships suggest that increasing a design storm's return period (e.g., from 1 year to 25 years) would
require CSSs to develop capacity to treat larger wet weather flows, but that increasing the design storm's
duration (e.g., from 6 hours to 24 hours) would have the opposite effect on the treatment capacity
required.
Table 4-2
AVERAGE INTENSITY OF SELECTED
FREQUENCY/DURATION STORMS: CLEVELAND
(INCHES PER HOUR)
Duration
2 Hours
6 Hours
24 Hours
Return Period
1 Year
0.60
0.25
0.08
25 Years
1.25
0.50
0.17
Depth/Duration Design Standard
Design storms can also be characterized by depth and duration; e.g., the 2.5-inch/24-hour storm.
Specification of such a standard would require combined sewer systems to control wet weather discharges
during all events smaller than or equal to a 2.5-inch/24-hour storm.
For a given location, the frequency with which a depth/duration design storm would occur varies
with the depth and duration specified. Table 4-3 illustrates this effect, using Chicago as an example.4
As the table indicates, return periods lengthen as the specified depth increases, indicating that for a given
duration, the greater the depth of the design storm, the less frequently it will occur. For example, in
Chicago, a 2-inch/2-hour storm would occur on average once in 5 years, but a 2.5-inch/2-hour storm
would occur on average only once in 25 years. From the standpoint of CSO control, this suggests that
for a given duration (e.g., 2 hours), the greater the depth of the design storm specified, the greater the
storage and/or treatment capacity required to comply with the standard, and the lower the frequency of
untreated overflows. Conversely, increasing the duration of a depth/duration design storm while holding
depth constant shortens the return period. In Chicago, for instance, moving from a 2-inch/2-hour storm
to a 2-inch/6-hour storm reduces the expected return period from 5 years to 1.5 years. This suggests that
3 In other words, the shorter the design storm (for a given return period), the greater its
intensity.
4 The return periods shown in Table 4-3 are estimates that we have developed based upon a
review of the rainfall frequency/duration maps presented in Hershfield's Rainfall Atlas. The precise
values for Chicago may differ slightly from these estimates.
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the longer the duration of a depth-duration design storm, the less stringent the level of control achieved
and the greater the expected frequency of uncontrolled CSO discharges.
Table 4-3
APPROXIMATE RETURN PERIOD OF SELECTED
DEPTH/DURATION STORMS: CHICAGO
(YEARS)
Duration
2 Hours
6 Hours
24 Hours
Rain Depth
2 Inches
5
1.5
<1
2.5 Inches
25
2
1
3 Inches
50
10
3
The intensity of rainfall associated with a depth/duration design storm will also vary with the
parameters employed. As Table 4-4 shows, increasing the depth of the design storm while holding
duration constant increases not only the total amount of rainfall, but also the average intensity of the
event. Thus, increasing the design storm's depth increases not only the volume but also the flow of rain
that must be controlled. In contrast, increasing the design storm's duration while holding depth constant
decreases the average intensity of the event. Such a change has no effect on the total volume of rain that
must be controlled, but does reduce the average wet weather flow for which conveyance and treatment
capacity must be provided.
Table 44
AVERAGE INTENSITY OF SELECTED
DEPTH/DURATION STORMS
(INCHES PER HOUR)
Duration
2 Hours
6 Hours
24 Hours
Rain Depth
2 Inches
1.00
0.33
0.08
2.5 Inches
1.25
0.42
0.10
3 Inches
1.50
0.50
0.13
Evaluation of Design Storms as a CSO Control Standard
Because of variation in regional rainfall, the use of a design storm as a national CSO wet weather
standard would likely have different cost or pollution control implications for systems in different parts
4-5
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of the country. The nature of these differences would depend upon whether a frequency/duration or
depth/duration design standard were employed.
As described in Chapter 3, the amount of rain associated with a given frequency/duration event
varies with location. Exhibit 4-1 illustrates the extent of this variation for the l-year/6-hour storm.3 As
the exhibit indicates, the l-year/6-hour storm ranges from less than 0.5 inches in parts of the Southwest
to greater than 3.5 inches along the Gulf Coast; in the Northeast and Midwest, where most CSSs are
located, the range extends from roughly 1.0 to 2.0 inches. This variation indicates that the storage,
conveyance and treatment capacity necessary to meet a frequency/duration standard is likely to differ
somewhat from state to state, and therefore that systems located in states subject to larger storms probably
would face higher compliance costs. This standard, however, would offer inter-regional consistency in
controlling the frequency of combined sewer overflows, since the likelihood of experiencing a storm
greater than a specified frequency/duration storm is roughly similar in all parts of the country. Thus,
all other factors being equal, systems complying with the same frequency/duration standard should
experience roughly the same number of uncontrolled overflows.
Table 4-5 further illustrates how control requirements might vary under a frequency/duration
standard. The table shows that both the volume and rate of runoff from an impervious acre increase in
proportion to the depth of the l-year/6-hour storm. As a result, control requirements — measured either
with respect to the storage volume or the treatment capacity required to control the runoff from an
impervious acre - also increase proportionately. Thus, all other things equal, a l-year/6-hour design
storm would require some cities, such as Savannah and Wilmington, North Carolina, to provide greater
wet weather control capacity than others, such as Boston and Buffalo.
In contrast to a frequency/duration standard, a depth/duration design storm would impose similar
control capacity requirements on CSSs nationwide, but could in turn lead to wider variation in the
frequency of uncontrolled overflows. Under a depth/duration standard, all systems would be required
to provide capacity to control the runoff from a storm of the same depth and duration (and, therefore,
the same average intensity). Although site-specific hydrologic and system conditions would influence the
ultimate combined sewer volume and flow associated with a given depth/duration storm, this approach
to setting a national CSO standard would imply less inter-regional variation in storage and treatment
requirements than would a frequency/duration standard; therefore, it would imply greater similarity in
compliance costs.6 Because of inter-regional variations in rainfall, however, this approach would yield
differences in the frequency with which untreated discharges would occur. Exhibit 4-2 gives some sense
of the possible degree of variation, showing the return period for a 2-inch/6-hour storm in each of the
48 contiguous states. As this exhibit suggests, a standard depth/duration storm is likely to be exceeded
5 The exhibit includes data for the 48 contiguous states covered by Hershfield's Rainfall Atlas.
6 This conclusion holds only under the assumption that all other factors that may influence
compliance costs are equal. In practice, of course, complicating factors would likely lead to
differences among systems. It may be the case, for example, that systems in areas with higher
rainfall will require less additional construction than systems in areas with lower rainfall, as the
systems in wetter areas already may be designed with relatively greater capacity to manage excess
wet weather flow. Without a more detailed understanding of the particular systems in question, such
relationships are not easily deduced.
4-6
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with greater frequency in some states than others, leading to a disparity in the frequency of untreated
discharges from combined sewer systems.
Table 4-5
THE EFFECT OF VARIATION IN THE 1-YEAR/6-HOUR STORM
ON CSO CONTROL REQUIREMENTS
Depth
(inches)
1.5
2.0
2.5
Runoff per Impervious
Acre
Volume
(cubic feet)
5,445
7,260
9,075
Rate
(cfs)
0.25
0.34
0.42
Control Capacity
Required
Storage
(gallons/acre)
40,731
54,309
67,886
Treatment
(MGD/acre)
0.16
0.22
0.27
Example
CSO Cities
Boston;
Buffalo;
Cleveland;
Detroit;
Milwaukee
Des Moines;
Louisville;
Nashville;
New York;
Philadelphia;
Washington
Savannah;
Wilmington,
North
Carolina
As the discussion above suggests, specification of a uniform national design storm standard would
not ensure uniformity in CSO control costs and performance. All other things equal, a frequency/
duration standard (e.g., the l-year/6-hour storm) would tend to equalize the frequency of uncontrolled
overflows from different systems, but would likely impose higher costs in rainier regions. In contrast,
establishing a depth/duration standard (e.g., the 2.5-inch/24-hour storm) would tend to equalize wet
weather capacity requirements - and hence, control costs ~ across systems, but would do so while
allowing variations among systems in the frequency with which uncontrolled discharges occur.
Regardless of how it is specified, a design storm standard would be implemented and enforced
as part of the development, review, and approval of CSS facility plans. To demonstrate compliance with
the standard, combined sewer operating authorities would need to characterize hydrologic conditions
throughout the system's service area and describe in depth the calculations employed to determine the
storage and treatment capacity needed under design storm conditions. EPA and state regulators would
4-7
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probably require substantial time to review these plans and calculations, request changes, and certify
compliance.
FACTOR OF DRY WEATHER FLOW
An alternative to the design storm approach to establishing a CSO standard is to specify the wet
weather flow to be controlled as a multiple of the CSS's dry weather flow (i.e., the flow in the system
due to sanitary, commercial, and industrial waste water). As described in Chapter 2, Illinois has adopted
this approach, requiring primary treatment of all flows up to 10 times the design dry weather flow (the
" 10X" approach). Illinois' selection of this standard was based upon (1) the state's interest in controlling
the "first flush" from CSOs during storm events, which typically contains the highest concentrations of
pollutants, and (2) a state analysis that indicated that wet weather flows greater than ten times the dry
weather flow tend to dilute pollutant concentrations to such an extent that water quality impacts are less
severe than occur at lower flows. This section examines the implications of the factor of flow approach
as a CSO control standard.
The practical implications of setting a CSO standard as a factor of dry weather flow would vary
by location, depending on design flows, system characteristics, and hydrology. All other things equal,
a higher multiplier would imply more stringent regulation, higher compliance costs (due to the need for
greater storage and/or treatment capacity), and a higher standard of environmental protection. In
practice, however, systems differ considerably. As a result, compliance costs and the standard of control
achieved under a single multiplier would likely differ for different systems and regions.
Under a factor of flow approach, the cost of compliance is likely to vary with conditions that
influence base flow, such as population and the mix of residential, commercial, and industrial dischargers
a system serves. Consider, for example, two systems subject to identical rainfall and runoff, each serving
small towns with identical populations and drainage areas. Due to the presence of a single industrial user
— e.g., a food processing plant — System A receives twice the dry weather flow of System B. Under the
factor of flow approach, System A would be required to provide twice the wet weather control capacity
of System B, despite the fact that each system is subject to identical runoff volumes and flows. As a
result, compliance costs would likely be higher for System A.
The degree of control offered by the factor of flow approach would vary with rainfall conditions.
Again, consider two systems, A and B, each receiving identical dry weather flows and each serving
identically-sized areas with identical surface runoff conditions. Because their base flows are identical,
the systems would be required to provide similar wet weather storage and treatment capacity. If,
however, System A were located in a rainier area, it would experience more frequent uncontrolled wet
weather discharges than would System B. The compliance requirements for the two systems would be
identical, but the practical standard of control achieved would differ.
The factor of flow approach would not explicitly tie wet weather storage and treatment
requirements to receiving water quality. It would, however, control the first flush of pollutants and
guarantee that uncontrolled discharges from combined sewer systems would be diluted by some minimum
percentage of runoff; for example, a 10X factor of flow standard would ensure that the ratio of storm
water to base flow in any uncontrolled discharge would be at least ten to one. If this ratio were sufficient
under most circumstances to avoid water quality violations from CSOs, and also could be shown to be
economically achievable, the approach might prove an attractive alternative for a uniform national
4-8
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standard. However, variation in receiving waters and in the concentration of pollutants in both base flow
and runoff would make it difficult to derive a uniform, environmentally acceptable and economically
achieveable standard. Moreover, attempting to set a standard based on a dilution factor would ignore the
potential long-term build-up of persistent and bioaccumulative pollutants in aquatic ecosystems.
Like the design storm approach, implementation of a factor of flow approach would require
engineers to modify facilities to control and treat a given quantity of runoff. As under the design storm
approach, implementation and enforcement would entail the development and review of detailed facilities
plans. In contrast, however, these plans would not require detailed analysis to predict the volume and
flow of runoff associated with a rainfall event; instead, greater attention would be devoted to quantifying
the system's dry weather flow, the factor that ultimately would determine wet weather storage and
treatment requirements. Specification of storage and treatment requirements might be simplified if the
standard were based on design rather than actual dry weather flow, since information on design flow may
be available from historical records. Determination of actual dry weather flow would likely require some
form of monitoring and development of mutually agreed upon procedures for averaging variations in
actual flow.
OVERFLOW FREQUENCY
A fourth approach to setting a CSO standard is to directly specify a limit on the number of
overflows that a system would be allowed in a given time period; e.g., four overflows per year. As
noted in Chapter 2, several states have adopted some form of overflow frequency limit. This approach
is similar to the use of a frequency/duration design storm in that both would tend to equalize the level
of control across systems, but would likely cause compliance costs to vary with differences in regional
rainfall. In contrast to a frequency/duration standard, however, an overflow frequency limit expresses
the wet weather standard in terms that are likely to be less subject to debate and confusion. The relative
stringency of alternative overflow frequency limits can be readily compared and understood by laymen,
while the stringency of alternative design storms ~ e.g., a 5-year/2-hour storm versus a l-year/6-hour
storm ~ cannot be discerned without reference to rainfall data. In addition, an overflow frequency limit
lends itself more readily to flexible application. It would be possible, for example, to set overflow limits
on an outfall-by-outfall basis, depending upon the nature of the waters to which the outfalls discharge.
Because some years will be rainier than others, we assume that an overflow frequency design
standard would be specified as a long-run average, rather than as a maximum never to be exceeded in
any year (it would be statistically impossible to demonstrate perfect compliance with a standard that made
no allowance for chance variations in rainfall). It would be necessary, however, to specify whether the
limit applies to the entire system or to each outfall; in the latter case, the standard would also need to
state whether it is necessary to demonstrate compliance outfall-by-outfall, or whether it is permissible to
average the predicted number of overflows across all outfalls.
The cost of complying with a uniform overflow frequency limit would vary across regions.
Holding other factors constant, systems located in regions with greater rainfall would probably face
greater compliance costs. Other factors that affect runoff to combined sewer systems, such as the runoff
coefficient in the drainage area, would also influence costs. In contrast, however, the approach would
provide a consistent standard of performance, since all systems would be held to the same overflow limit.
4-9
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As with the approaches previously discussed, an overflow frequency limit would be implemented
and enforced at the design stage.7 Under this approach, however, facilities plans would be required to
focus particular attention on the relationship between rainfall events and overflows. Demonstrating
compliance could possibly require sophisticated modeling of system performance under a range of storm
conditions. As with the other approaches, development, review and approval of this analysis could prove
time-consuming.
Like the other approaches, an overflow frequency limit would be incorporated as part of a
minimum technology-based standard for CSOs. More stringent limits, including the prohibition of all
uncontrolled overflows, could still be mandated for situations in which technology-based requirements
proved inadequate to achieve applicable water quality standards.
INTERRELATIONSHIPS
Given detailed information on a specific location's meteorology, hydrology, and sewer system,
it would be possible to compare the stringency of specific CSO regulatory alternatives, both with respect
to the frequency of overflows allowed and the costs of compliance. Such a detailed analysis is beyond
the scope of this report. It is possible, however, to develop a simple comparison of the relative
stringency of some alternatives. For purposes of this discussion, we define the stringency of the options
according to the wet weather volume and flow they would require to be controlled. If on-line flow-
through treatment (e.g., screening, filtration, etc.) is the preferred technological option, the flow
requiring treatment determines the stringency of the standard. If storage prior to treatment is the
preferred control technique, the volume of water that must be controlled is the primary indicator of the
standard's stringency.
The following discussion compares the stringency of alternative CSO design standards for a city
on the Ohio River. The standards compared include a l-year/6-hour storm, a 10X factor of flow, and
a 2.5-inch/24-hour standard. Due to the lack of detailed information needed to translate each of these
standards to an estimate of the number of uncontrolled overflows, no quantitative comparison of these
standards with an overflow frequency limit is possible.
Flow Control Requirements
In the city chosen for our example, the l-year/6-hour storm yields about two inches of rainfall.
Therefore, the storm's average intensity is 0.33 inches per hour. Assuming a runoff coefficient of 0.7,
this translates to a runoff rate of approximately 105 gallons per acre per minute. In comparison, the
estimated dry weather flow for the city's system is approximately 150 gallons per capita per day.
Assuming a population density of 15 persons per acre, this per capita flow translates to about 1.6 gallons
per acre per minute. Thus, for this city, the flow associated with the l-year/6-hour design storm is about
7 While it is theoretically possible to impose an overflow frequency limit as a performance
standard, such an approach would be impractical. Given the detailed study and large, long-term
investment in sewers and treatment plants that may be required to address the CSO problem, it is
difficult to justify any standard that would not be enforced at the design stage, before construction
begins.
4-10
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67 times the dry weather flow, or roughly seven times greater than the flow subject to treatment under
the 10X factor of flow standard.8
In comparison to the city's l-year/6-hour storm, a 2.5-inch/24-hour design storm is much less
intense ~ only 0.1 inches per hour. Using the same assumptions employed above, the runoff rate for
this storm would be approximately 33 gallons per acre per minute, or about 21 times the dry weather
flow. Thus, for this location, a 2.5-inch/24-hour design storm would prove roughly twice as stringent
with respect to flow as the 10X factor, but only a third as stringent as the l-year/6-hour storm.
Volume Control Requirements
As noted above, the parameter of interest for evaluating wet weather storage requirements is the
volume of water that must be controlled. The implications of a factor of flow standard for storage
requirements is unclear, since the standard is articulated solely with respect to flow. It is possible,
however, to compare the relative stringency of the two design storms with respect to volume, simply by
comparing rain depth for the two storms: the quantity of rain that falls in a 2.5-inch/24-hour storm is
25 percent greater than the 2 inches that fall in the city's l-year/6-hour storm. Thus, for the sample site,
a 2.5-inch/24-hour design storm implies more stringent storage requirements than a l-year/6-hour design
storm.
COMPARISON AND CONCLUSIONS
As noted earlier in this report, in the absence of specific CSO design proposals it is difficult to
compare in detail the relative cost, effectiveness, and environmental benefits of alternative CSO design
standards. As described below, however, the preceding discussion offers some general insights regarding
administrative and operational similarities and differences among the four approaches.
First, from an administrative perspective, the four alternatives analyzed above are quite similar.
Each would be implemented and enforced as a design standard. Each would require detailed study to
demonstrate compliance, although the analysis needed to demonstrate compliance with an overflow
frequency limit might prove more complex and statistically sophisticated than that required under the
other approaches. Because CSO projects in general already rely on detailed facility plans -- technical
documents that include data on CSO frequency, volume, duration, and pollutant loads; evaluations of
receiving water impacts; and assessments of the cost and effectiveness of CSO pollution abatement
alternatives — these requirements seem unlikely to pose a significantly greater analytic burden on CSO
permittees. The implementation of a uniform national standard, however, is likely to increase the degree
of regulatory oversight exercised by the States and EPA. To date, oversight of the recommendations
proposed by permittees in facilities plans has been very limited, and in the absence of specific guidance
or design criteria the CSO controls adopted have varied greatly. Implementation of a uniform national
8 In practice, the multiplier employed in the factor of flow approach could be applied to the
system's design dry weather flow, rather than the average dry weather flow used in these
calculations. If design flow were greater than average flow, a factor of flow standard would control
a correspondingly larger wet weather flow than our calculations indicate.
4-11
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standard for CSOs would ensure greater consistency in CSO abatement, but would require EPA and state
regulators to devote substantial time to review facility plans, request changes, and certify compliance.
Second, from an operational standpoint, the four regulatory approaches evaluated fall into two
general categories. The first category consists of alternatives that would consistently limit the frequency
of overflows across systems regardless of likely differences in compliance costs; it includes approaches
that would specify a frequency/duration design storm or an overflow frequency limit. The second
category consists of alternatives that would require comparable wet weather storage and treatment capacity
for systems that are otherwise similar but, because of differences in rainfall and/or runoff, might differ
markedly with respect to the frequency of overflows. It includes approaches that would specify a
depth/duration design storm or set control requirements based on a factor of dry weather flow. Thus,
these two categories reflect fundamentally different means of defining a "uniform" wet weather design
standard. The first would set a standard that aims to achieve uniform performance, as measured by the
frequency of untreated overflows. The second would set a standard that tends to equalize control capacity
and, hence, compliance costs, regardless of resulting differences in the frequency with which untreated
discharges would occur.
Ultimately, the choice need not be limited to the four options this chapter describes. One
alternative is to continue to rely on best professional judgment to establish technology-based requirements
for CSOs on a permit-by-permit basis. While this approach to date has not satisfactorily addressed the
CSO problem nationwide, EPA's renewed efforts under the National CSO Strategy suggest that progress
will be made. Another alternative ~ albeit inconsistent with the standard NPDES approach of the Clean
Water Act - would be to forego a technology-based standard entirely, and instead tailor CSO permit
requirements on a case-by-case basis according to the level of control needed to comply with water
quality standards. In theory, this approach would offer the greatest economic efficiency in achieving
water quality goals. In practice, however, setting CSO control standards based solely on water quality
requirements has proved to be quite difficult, and the lack of a technology-based requirement for CSOs
has been and remains a major factor in making their regulation complicated and their abatement elusive.
In general, the development of water quality-based permits has been hampered by:
(1) The lack of comprehensive monitoring data on CSO discharges;
(2) Lack of detailed analysis relating CSO discharges to the nature and
extent of water quality violations;
(3) Extreme difficulty and uncertainty in translating water quality criteria and
standards into numeric effluent limits for CSOs;9
9 A particular difficulty in developing water quality-based permits for CSOs is the stochastic
nature of the storm events that trigger CSO discharges. Given the narrative criteria prohibiting
discharges of floatables, oil and grease, solids, etc., a strict interpretation of most state water quality
standards would hold that any untreated CSO discharge -- even overflows caused by the 100-year
storm - would constitute a violation. Compliance with this strict interpretation would in all
probability require communities to separate their sewer and storm water systems. As an alternative,
some states (Indiana, New Hampshire, North Carolina, Vermont, and the District of Columbia) have
included provisions in their water quality standards that allow for exceedences if caused by CSOs
during specified high flow conditions.
4-12
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(4) The lack of adequate water quality criteria for nutrients, many toxic
pollutants, and contaminated sediments; and,
(5) Inconsistent water quality standards from state to state, particularly for
pathogens.
These obstacles have slowed improvements in CSO control substantially, and in the absence of a national
technology-based standard could continue to do so. Moreover, it is likely to be administratively infeasible
to set water quality-based permit limits for each of the thousands of combined sewer outfalls nationwide.
In light of these concerns, the establishment of a state or national technology-based standard that relates
to water quality goals could prove to be essential to timely progress.
Should Congress or EPA determine that it is necessary to set a design standard for CSOs, the
issue returns again to how best to balance cost, administrative feasibility and other concerns against
environmental goals. One means of doing so would be to consider a targeted, risk-based approach that
combines aspects of the alternatives described above. For example, the stringency of the design standard
might be linked to the aquatic resources affected by CSOs: discharges to high priority or high use waters
(e.g., discharges that damage a shellfish bed or swimming beach) could be prohibited, while discharges
to lower priority waters could be held to a non-zero overflow frequency limit. Such an approach might
prove a viable means of establishing a technology-based standard without (1) ignoring situations in which
the cost of meeting that standard is disproportionately high relative to water quality benefits, or (2)
imposing similar treatment requirements regardless of need. Such targeted flexibility could help make
a technology-based standard for CSOs more efficient, equitable, and affordable.
4-13
-------
Exhibit 4-1
MAGNITUDE OF THE 1-YEAR/6-HOUR STORM, BY STATE
State
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
SUBTOTALS
New Jersey
New York
Puerto Rico
Virgin Islands
SUBTOTALS
Delaware
Dist. of Columbia
Maryland
Pennsylvania
Virginia
West Virginia
SUBTOTALS
Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
SUBTOTALS
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
SUBTOTALS
Number of
Combined Sewer Systems
13
61
26
22
3
31
156
28
90
NA
NA
118
3
1
7
140
4
50
205
0
0
5
22
0
0
0
3
30
135
141
85
6
109
2
478
l-Year/6-Hour Rainfall
Low
finches)
1.50
1.00
1.50
1.00
1.50
1.00
1.00
1.50
1.00
NA
NA
1.00
2.00
2.00
1.50
1.50
1.50
1.50
1.50
2.00
2.50
2.00
1.50
2.00
1.50
2.00
1.50
1.50
1.50
1.50
1.00
1.00
1.50
1.50
1.00
High
Cinches')
1.50
1.50
1.50
1.50
1.50
1.50
1.50
2.00
2.00
NA
NA
2.00
2.00
2.00
2.00
2.00
2.00
1.50
2.00
3.50
3.50
2.50
2.00
3.50
2.50
3.00
2.00
3.50
2.00
2.00
1.50
1.50
1.50
1.50
2.00
-------
Exhibit 4-1
(continued)
l-Year/6-Hour Rainfall
EPA
Region State
6 Arkansas
Louisiana
New Mexico
Oklahoma
Texas
SUBTOTALS
7 Iowa
Kansas
Missouri
Nebraska
SUBTOTALS
8 Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
SUBTOTALS
9 Arizona
California North
South
Hawaii
Nevada
SUBTOTALS
10 Alaska
Idaho
Oregon East
West
Washington
SUBTOTALS
Number of
Combined Sewer Systems
1
0
1
0
0
2
19
3
14
3
39
1
1
0
1
0
0
3
0
1
1
0
0
2
0
2
0
4
11
17
Low
(Inches')
2.00
2.50
0.75
1.00
0.75
0.75
1.50
1.00
2.00
1.00
1.00
0.75
0.75
1.00
1.00
0.50
0.75
0.50
0.75
1.00
0.50
NA
0.50
0.50
NA
0.75
0.50
0.75
0.50
0.50
High
(Inches)
2.50
3.50
1.00
2.50
3.00
3.00
2.00
2.00
2.00
2.00
2.00
1.00
1.00
1.00
1.50
0.75
1.00
1.50
1.25
3.00
2.00
NA
0.75
3.00
NA
1.00
0.75
3.00
3.00
3.00
US TOTALS
1050
0.50
3.50
Sources: EPA, "Status of Strategy Approvals," January 16,1992.
Hershfield, D.M., "Rainfall Frequency Atlas of the US," Weather Bureau
Technical Paper No. 40, Washington, DC, GPO, 1961.
-------
Exhibit 4-2
RETURN PERIOD FOR THE 2-INCH/6-HOUR STORM, BY STATE
State
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
SUBTOTALS
New Jersey
New York
Puerto Rico
Virgin Islands
SUBTOTALS
Delaware
Dist. of Columbia
Maryland
Pennsylvania
Virginia
West Virginia
SUBTOTALS
Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
SUBTOTALS
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
SUBTOTALS
Number of
Combined Sewer Systems
13
61
26
22
3
31
156
28
90
NA
NA
118
3
1
7
140
4
50
205
0
0
5
22
0
0
0
3
30
135
141
85
6
109
2
478
2-Inch/6-Hour Storm
Return Period (years)
2
2-50
2
2-25
2
5
2-50
2-25
1-2
NA
NA
1-25
1-2
1-2
1-2
2-5
1-2
2-5
1-5
1
1
1-2
1
1-2
1
1-2
1-2
1-2
5-50
2-50
2-25
2-5
1-50
-------
EPA
Region State
6 Arkansas
Louisiana
New Mexico
Oklahoma
Texas
SUBTOTALS
7 Iowa
Kansas
Missouri
Nebraska
SUBTOTALS
8 Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
SUBTOTALS
9 Arizona
California North
South
Hawaii
Nevada
SUBTOTALS
10 Alaska
Idaho
Oregon East
West
Washington
SUBTOTALS
Exhibit 4-2
(continued)
Number of
Combined Sewer Systems
1
0
1
0
0
2
19
3
14
3
39
1
1
0
1
0
0
3
0
1
1
0
0
2
0
2
0
4
11
17
2-Inch/6-Hour Storm
Return Period (years)
1
<1
5-50
1-2
1-50
<1-50
1-2
1-5
1
2-25
1-25
5-50
10-50
5-50
2-25
25-100
10-50
2-100
5-50
1-100
1-100
NA
25-100
1-100
NA
25-100
10-100
1-50
100
1-50
US TOTALS
1050
< 1-100
Note: The return periods shown above are approximate. They have been estimated based on the maps
presented in the "Rainfall Frequency Atlas of the US."
Sources: EPA, "Status of Strategy Approvals," January 16,1992.
Hershfield, D.M., "Rainfall Frequency Atlas of the US," Weather Bureau
Technical Paper No. 40, Washington, DC, GPO, 1961.
-------
Appendix A
COMMUNITIES WITH COMBINED SEWER SYSTEMS:
DATA FROM THE 1980 NEEDS SURVEY'S
SUPPLEMENTARY DATABASE
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
AK CORDOVA
AK JUNEAU
CA BLYTHE
CA BRAWLEY
CA SACRAMENTO
CA SAN FRANCISCO
CA SAN FRANCISCO
CO DELTA
CO GRAND JUNCTION
CO LA JARA
CO PUEBLO
CO SPRINGFIELD
CO TRINIDAD
CT BRIDGEPORT
CT DERBY
CT GRISWOLD
CT HARTFORD
CT MIDDLETOWN
CT NEW HAVEN
CT NORWALK
CT NORWICH
CT PORTLAND
CT SHELTON
CT STAFFORD SPRINGS
CT THOMPSONVILLE
PRIMARY
RECEIVING WATER
PRINCE WILLIAM SOUND
GASTINEAU CHANNEL
CITY STP POND
NEW RIVfR
SACRAMENTO RIVER
SAN FRANCISCO BAY
PACIFIC OCEAN
COLORADO RIVER
ARKANSAS RIVER
PURGATOIRE RIVER
BRIDGEPORT HARBOR
HOUSATONIC R
QUINEBAUG R
CONNECTICUT R
COGINCHAUG R
NEW HAVEN HARBOR
NORWALK HARBOR
THAMES R
CONNECTICUT RIVER
HOUSATONIC RIVER
WILLIMANTIC RIVER
CONNECTICUT R
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
60
4,800
11,000
14,000
96,119
473,000
258,000
4,500
37,600
781
107,800
1,660
0
50,000
11,000
3,250
110,000
8,014
84,300
15,800
23,000
150
8,800
80,056
9,900
2,110
26,751
8,428
18,923
369,365
723,959
723,959
3,789
29,034
725
98,640
1,475
8,580
141,686
12,199
10,384
139,739
42,762
130,474
78,331
37,391
5,645
35,418
4,100
8,458
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
CT WATERBURY
CT WEST HARTFORD
DC WASHINGTON
DE WILMINGTON
DE BRIDGEVILLE
DE LEWES
DE MILFORD
DE SEAFORD
FL SANFORD
GA ALBANY
GA ATLANTA
GA ATLANTA
GA ATLANTA
GA AUGUSTA
GA COLUMBUS
GA ROME
GA SAVANNAH
IA ADEL
IA ALBIA
IA BURLINGTON
IA CLINTON
IA COUNCIL BLUFFS
IA DAVENPORT
PRIMARY
RECEIVING WATER
NAUGATUCK RIVER
CONNECTICUT RIVER
POTOMAC RIVER
BRANDYWINE CREEK
NANTICOKE RIVER
LEWES-REHOBOTA CANAL
MISPILLION RIVER
NANTICOKE RIVER
LAKE MONROE
FLINT RIVER
UTOY CREEK
SOUTH RIVER
CHATAHOOCHEE RIVER
SAVANNAH RIVER
CHATAHOOCHEE RIVER
COOSA RIVER
VERNON RIVER
NORTH RACCON RIVER
CEDAR CREEK
MISSISSIPPI
MISSISSIPPI
MISSOURI
MISSISSIPPI RIVER
1980CSO
POPULATION
SERVED (1)
6,947
4,000
489,093
80,368
1,400
2,820
4,880
600
4,370
60,000
195,775
51,900
63,900
54,863
22,970
5,400
18,210
675
1,300
32,645
34,000
62,397
60,000
1990 TOTAL
CITY POPULATION (2)
108,961
60,110
606,900
71,529
1,210
2,295
6,040
5,689
32,387
78,122
394,017
394,017
394,017
44,639
178,681
30,326
137,560
3,304
3,870
27,208
29,201
54,315
95,333
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IA DES MOINES
IA EAGLE GROVE
IA FORT MADISON
IA GOWRIE
IA KEOKUK
IA MONTROSE
IA MOUNT PLEASANT
IA MUSCATINE
IA OLIN
IA OTTUMWA
IA RINGSTEAD
IA SIOUX CITY
IA WASHINGTON
IA WEBSTER CITY
ID BLACKFOOT
ID BONNERS FERRY
ID BOVILL
ID GENESEE
ID IDAHO FALLS
ID MOUNTAIN HOME
ID NEW PLYMOUTH
ID OROFINO
ID PRIEST RIVER
ID RUPERT
ID SPIRIT LAKE
ID ST ANTHONY
ID ST MARIES
PRIMARY
RECEIVING WATER
DES MOINES RIVER
BOONE RIVER
MISSISSIPPI
WEST BUTTERICK CREEK
MISSISSIPPI
MISSISSIPPI RIVER
BIG CREEK
MAD CREEK
WALNUT CREEK
DES MOINES RIVER
BLACK CAT CREEK
MISSOURI RIVER
W FORK CROOKED CREEK
BOONE RIVER
SNAKE RIVER
KOOTENAI RIVER
POTLATCH RIVER
COW CREEK
SNAKE RIVER
PAYETTE RIVER
PAYETTE RIVER
CLEARWATER RIVER
PEND OREILLE RIVER
SNAKE RIVER
SPIRIT LAKE
HENRYS FORK
STJOESPH RIVER
1980CSO
POPULATION
SERVE D(1)
1990 TOTAL
CITY POPULATION (2)
100,000
4,519
15,500
1,294
14,091
838
7,303
24,083
700
30,000
50
4,000
3,675
8,488
3,716
2,700
358
741
31,500
0
1,089
2,000
286
482
75
2,810
20
193,187
3,671
11,618
1,028
12,451
957
8,027
22,881
663
24,488
481
80,505
7,074
7,894
9,646
2,193
256
725
43,929
7,913
1,313
2,868
1,560
5,455
790
3,010
2,442
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
ID WALLACE
IL ADDISON
IL ALTON
IL ASSUMPTION
IL AURORA
IL BATAVIA
IL BEARDSTOWN
IL BELLEVILLE
IL BENLD
IL BLOOMINGTON
IL BLUE ISLAND
IL BRADLEY
IL BRADLEY
IL BUREAU JUNCTION
IL BYRON
IL CAIRO
IL CANTON
IL CARLINVILLE
IL CARMI
IL CASEY
IL CHARLESTON
IL CHICAGO
IL CHICAGO
IL CHICAGO
IL CHICAGO
IL CHICAGO
IL CHRISMAN
PRIMARY
RECEIVING WATER
COVER D'ALENE RIVER
SALT CREEK
WOOD RIVER
BIG GEORGE CREEK
FOX RIVER
FOX RIVER
ILLINOIS RIVER
RICHLAND CREEK
CAHOKIE CREEK
SUGAR CREEK
KANKAKEE RIVER
KANKAKEE RIVER
ILL & MISS CANAL
ROCK RIVER
OHIO RIVER
SPOON RIVER
MACOUPIN CREEK
LITTLE WABASH RIVER
TRIB TO EMBARRAS RIVE
TRIB TO KICKAPOO CRK
LITTLE CALUMET RIVER
NORTH SHORE CHANNEL
CHICAGO SAN & SHIP CA
WILLIAM HIGGINS CRK
SALT CREEK
BROUILLETTS
1980CSO
POPULATION
SERVE D(1)
235
3,000
39,700
1,500
60,000
4,760
6,700
39,709
1,780
11,200
0
10,276
5,000
420
1,900
6,500
15,000
5,765
780
300
26,403
563,344
1,406,255
2,423,431
66,200
0
850
1990 TOTAL
CITY POPULATION (2)
1,010
32,058
32,905
1,244
99,581
17,076
5,270
42,785
1,604
51,972
21,203
10,792
10,792
350
2,284
4,846
13,922
5,416
5,564
2,914
20,398
2,783,726
2,783,726
2,783,726
2,783,726
2,783,726
1,136
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IL CLINTON
IL COWDEN
IL DALZELL
IL DECATUR
IL DIXON
IL DOLTON
IL DWIGHT
IL EARLVILLE
IL EAST ST LOUIS
IL EDWARDSVILLE
IL EFFINGHAM
IL ELGIN
IL ELLSWORTH
IL FAIRBURY
IL FARMER CITY
IL GALESBURG
IL GALESBURG
IL GEORGETOWN
IL GIBSON
IL GRANITE CITY
IL HARRISBURG
IL HARTFORD
IL HAVANA
IL HIGHWOOD
IL HINSDALE
IL JACKSONVILLE
IL JERSEYVILLE
IL JOLIET
PRIMARY
RECEIVING WATER
SALT CREEK
KASKASKIA RIVER
SPRING CREEK
STEVENS CK/SANGAMON
ROCK RIVER
GOOSEBERRY CREEK
INDIAN CREEK
MISSISSIPPI RIVER
CAHOKIA CREEK
TRIE TO SALT CREEK
FOX RIVER
TRIB TO SANGAMON RIV
INDIAN CREEK
SALT CREEK
CEDAR FORK CREEK
CEDAR FORK CREEK
LITTLE VERMILLION
DRUMMER CREEK
MISSISSIPPI RIVER
MIDDLE FORK CREEK
MISSISSIPPI RIVER
ILLINOIS RIVER
LAKE MICHIGAN
FLAGG CREEK
MAUVAISTERRE CREEK
DEARCY CREEK
DES PLAINES RIVER
1980 CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
7,604
517
20
40,000
6,800
0
650
1,400
70,169
4,000
10,000
40,600
25
2,450
1,211
30,000
30,000
4,100
1,000
13,333
9,500
2,300
4,450
0
12,000
5,500
6,240
12,000
7,437
599
587
83,885
15,144
23,930
4,230
1,435
40,944
14,579
11,851
77,010
224
3,643
2,114
33,530
33,530
3,678
3,396
32,862
9,289
1,676
3,610
5,331
16,029
19,324
7,382
76,836
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IL JOLIET
IL KANKAKEE
IL KENILWORTH
IL KINCAID
IL LA SALLE
IL LADD
IL LEMONT
IL LEROY
IL LINCOLN
IL LITCH FIELD
IL LOCKPORT
IL LOMBARD
IL MARSHALL
IL MARSHALL
IL MASON
IL MATTON
IL METROPOLIS
IL MINONK
IL MOMENCE
IL MONMOUTH
IL MORRIS
IL MORRISON
IL MORTON GROVE
IL MT OLIVE
IL MTVERNON
IL NORTH UTICA
IL OGLESBY
IL OLNEY
PRIMARY
RECEIVING WATER
HICKORY CREEK
KANKAKEE RIVER
SO FORK SANGAMON RIV
ILLINOIS RIVER
SPRING CREEK
CHGO SAN & SHIP CANAL
SALT CREEK
SALT CREEK
LAKE LOU YAEGER
DEEP RUN CREEK
E BRANCH-DUPAGE RIV
LITTLE CREEK
EAST MILL CREEK
SALT CREEK
KICKAPOO CREEK
OHIO RIVER
LONG POINT CREEK
KANKAKEE RIVER
CEDAR CREEK
NETTLE CREEK
ROCK CREEK
UNNAM TRIB - SUGAR CR
CASEY FORK
ILLINOIS RIVER
VERMILLION RIVER
FOX RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
71,000
15,000
3,000
1,500
1,000
1,400
5,120
2,630
21,700
7,340
6,437
32,000
1,079
1,066
3,000
13,500
2,100
2,366
2,000
14,000
9,000
42,000
0
1,533
20,000
1,100
4,000
1,000
76,836
27,575
2,402
1,353
9,717
1,283
7,348
2,777
15,418
6,883
9,401
39,408
3,555
3,555
2,323
18,441
6,734
1,982
2,968
9,489
10,270
4,363
22,408
2,126
16,988
848
3,619
8,664
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
ll_ OREGON
IL OTTAWA
IL PARIS
IL PEKIN
IL PEORIA
IL PEOTONE
IL PERU
IL PLAINFIELD
IL PONTIAC
IL QUINCY
IL RANKIN
IL ROCK ISLAND
IL ROCKDALE
IL ROSSVILLE
IL RUSHVILLE
IL SAUGET
IL SHEFFIELD
IL SHELBYVILLE
IL SPRING VALLEY
IL SPRINGFIELD
IL SPRINGFIELD
IL ST ANNE
IL STAUNTON
IL STERLING
IL STREATOR
IL TAYLORVILLE
IL TAYLORVILLE
IL THORNTON
PRIMARY
RECEIVING WATER
ROCK RIVER
ILLINOIS RIVER
SUGAR CREEK
ILLINOIS RIVER
ILLINOIS RIVER
BLACK WALNUT CREEK
ILLINOIS RIVER
DUPAGE RIVER
VERMILION RIVER
MISSISSIPPI RIVER
PIGEON CREEK
MISSISSIPPI RIVER
I & M CANAL
N FORK OF VERMILION R
CRANE CREEK
MISSISSIPPI RIVER
COAL CREEK
KASKASKIA
ILLINOIS RIVER
SUGAR CREEK
SPRING CREEK
LITTLE BEAVER CREEK
CAHOKIA CREEK
ROCK RIVER
VERMILION RIVER
PANTHER CREEK
PANTHER CREEK
THORN CREEK
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
3,700
18,048
10,000
29,000
77,000
600
11,300
3,300
1,250
50,288
750
47,000
1,600
1,340
3,300
200
1,000
5,000
5,605
60,000
15,000
1,300
500
7,000
15,000
11,182
12,000
375
3,891
17,451
8,987
32,254
113,504
2,947
9,302
4,557
11,428
39,681
619
40,552
1,709
1,334
3,229
197
951
4,943
5,246
105,227
105,227
1,153
4,806
15,132
14,121
11,133
11,133
2,778
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IL TOLUCA
IL VANDALIA
IL VENICE
IL VILLA PARK
IL WASHINGTON
IL WATSEKA
IL WAUKEGAN
IL WELLINGTON
IL WENONA
IL WESTVILLE
IL WHITE HALL
IL WILMETTE
IL WOOD RIVER
IL YORKVILLE
IN AKRON
IN ALBANY
IN ALBION
IN ALEXANDRIA
IN ANDERSON
IN ANGOLA
IN ATTICA
IN AUBURN
IN AVILLA
IN BERNE
IN BLUFFTON
IN BRAZIL
IN BUTLER
PRIMARY
RECEIVING WATER
NO BR CROW CREEK
KASKASKIA RIVER
MISSISSIPPI RIVER
SALT CREEK
TRIB TO FARM CREEK
SUGAR CREEK
LAKE MICHIGAN
GAY CREEK
SANDY CREEK
GRAPE CREEK
WOLF RUN CREEK
MISSISSIPPI RIVER
FOX RIVER
CHIPPEWANUK CREEK
MISSISSINEWA RIVER
CROFT DITCHOOOOOOO
PIPE CREEK
WHITE RIVER
MUD CREEK
HONEY CREEK
CEDAR CK
KING LAKE
HABEGGER-DITCH
WABASH RIVER
UNNAMED CREEK WABASHR
BIG RUN CREEK
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,200
3,000
4,600
15,000
946
7,202
1,320
321
1,100
5,450
3,000
0
13,000
1,000
1,776
2,350
1,780
3,000
67,080
0
707
8,000
1,438
2,988
9,000
192,000
2,475
1,315
6,114
3,571
22,253
10,099
5,424
69,392
294
950
3,387
2,814
26,690
11,490
3,925
1,001
2,357
1,823
5,709
59,459
5,824
3,457
9,379
1,366
3,559
9,020
7,640
2,601
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IN CHESTERFIELD
IN CHESTERTON AND PORTER
IN CICERO
IN CLARKSVILLE
IN CLINTON
IN COLFAX
IN COLUMBUS
IN CONNERSVILLE
IN CRAWFORDSVILLE
IN CROTHERSVILLE
IN CROWN POINT
IN DECATUR
IN DUNKIRK
IN DYER
IN EAST CHICAGO
IN EAST GARY
IN EATON
IN EDINBURG
IN ELKHART
IN ELWOOD
IN EVANSVILLE
IN FAIRMOUNT
IN FLORA
IN FORT WAYNE
IN FORTVILLE
IN FOWLER
IN FRANKFORT
IN FRANKLIN
PRIMARY
RECEIVING WATER
WHITE RIVER
LITTLE CALUMET RIVER
MORSE RESERVOIR
CANE RUN TO OHIO RIVE
WABASH RIVER
WITHE DITCH
EAST FK,WHITE RIVER
WEST FK WHITEWATER R
SUGAR CREEK
MUSCATATUCK RIVER
BEAVER DAM DITCH
ST MARYS RIVER
DU LI KIRK-DRAIN
PLUM CREEK(HART DITCH
GRAND CALUMET RIVER
L CALUMET RIVER
MISSISSINEWA RIVER
BIG BLUE RIVER
ST JOSEPH RIVER
DUCK CREEK
PIGEON CREEK
BACK CREEK
BACHELOR RUN
MAUMEE RIVER
FLAT FORK CREEK
HUMBERT DITCH
PRAIRIE CREEK
YOUNG'S ~ "CREEK
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
2,580
21,504
1,378
14,000
1,740
0
26,457
42,840
5,029
0
4,020
10,440
3,354
6,985
45,483
30,000
1,594
4,063
44,000
27,000
50,425
3,600
2,000
177,671
2,000
2,631
20,000
11,411
2,730
9,124
3,268
19,833
5,040
727
31,802
15,550
13,584
1,687
17,728
8,644
2,739
10,923
33,892
0
1,614
4,536
43,627
9,494
126,272
3,130
2,179
173,072
2,690
2,333
14,754
12,907
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IN FRANKTON
IN GARRETT
IN GARY
IN GAS CITY
IN GENEVA
IN GOSHEN
IN GREENFIELD
IN GREENTOWN
IN GREENTOWN
IN GREENWOOD
IN GRIFFITH
IN HAMMOND
IN HARTFORD CITY
IN HARTFORD CITY
IN HIGHLAND
IN HOBART
IN HUNTINGTON
IN INDIANAPOLIS
IN INDIANAPOLIS
IN JASPER
IN JEFFERSONVILLE
IN JONESBORO TOWN OF
IN KENDALLVILLE
IN KOKOMO
IN LA GRANGE
IN LAFAYETTE
IN LAPORTE
IN LIBERTY
PRIMARY
RECEIVING WATER
PIPE CREEK
GARRETT CITY DITCH
LAKE MICHIGAN
MISSISSINEWA RIVER
LOBLOLLY CREEK
ELKHART RIVER
BRANDYWINE CREEK
WILDCAT CR
WILDCAT CREEK
PLEASANT RUN CREEK
CALUMET RIVER
LITTLE CALUMET
BIG LICK CREEK
LITTLE LICK CREEK
CALUMET RIVER
DEEP RIVER
LITTLE RIVER
WHITE RIVER WEST FORK
WHITE RIVER
PATOKA
OHIO RIVER
MISSISSINEWA RIVER
HENDERSON LAKE
WILDCAT CREEK
FLY CREEK
WABASH RIVER
TRAVIS DITCH
TOWN RUN
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,584
7,800
300,000
6,000
1,100
48,000
10,000
0
4,236
7,680
1,500
28,054
3,789
4,418
13,000
26,160
16,500
323,557
205,516
1,000
25,200
0
750
70,000
2,100
47,805
28,000
1,831
1,736
5,349
116,646
6,296
1,280
23,797
11,657
2,172
2,172
26,265
17,916
84,236
6,960
6,960
23,696
21,822
16,389
731 ,327
731,327
10,030
21,841
2,073
7,773
44,962
2,382
43,764
21,507
2,051
10
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IN LIGONIER
IN LINN GROVE
IN LOGANSPORT
IN MARION
IN MARKLE
IN MERRILLVILLE
IN MICHIGAN CITY
IN MIDDLETOWN
IN MILAN
IN MISHAWKA
IN MONTICELLO
IN MONTPELIER
IN MTVERNON
IN MUNCIE
IN MUNSTER
IN NAPPANEE
IN NEW CARLISLE
IN NEW CASTLE
IN NEW HAVEN
IN NOBLESVILLE
IN NORTH LIBERTY
IN NORTH VERNON, VERNON
IN OAKLAND CITY
IN OLDENBURG
IN OSSIAN
IN OTTERBEIN
IN OXFORD
IN PATOKA
PRIMARY
RECEIVING WATER
ELKHART RIVER
TRIE UPPER WABASH
WABASH RIVER
MISSISSINEWA RIVER
WABASH RIVER
TURKEY CREEK
TRAIL CREEK
SUGAR CREEK
SOUTH HOGAN CREEK
ST JOSEPH RIVER
LAKE FREEMAN
SALAMONIE RIVER
OHIO RIVER
WHITE RIVER
L CALUMET RIVER
BERLINCOURT DITCH
HIESPOOZIANCY DITCH
BIG BLUE RIVER
MARTIN DITCH
WHITE RIVER
POTATO-CREEK"
MUSCATTATUCK R VERNON
TURKEY CREEK
HARVEY DITCH
EIGHT MILE CREEK
OTTERBEIN DITCH
MUD PINE CREEK
PATOKA RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
3,000
0
18,500
47,052
1,029
26,000
35,000
2,267
1,210
25,900
5,074
2,800
6,914
162,960
7,600
415
1,434
20,825
5,877
45,000
1,259
7,457
1,800
150
1,735
0
1,200
0
3,443
3,559
16,812
32,618
1,208
27,257
33,822
2,333
1,529
42,608
5,237
1,880
7,217
71,035
19,949
5,510
1,446
17,753
9,320
17,655
1,366
370
2,810
715
2,428
1,291
1,273
704
11
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IN PENDLETON
IN PERU
IN PLAINFIELD
IN PLYMOUTH
IN PORTLAND
IN REDKEY
IN REMINGTON
IN RENSSELAER
IN RICHMOND
IN ROANOKE
IN ROSSVILLE
IN RUSHVILLE
IN SALEM
IN SCOTTSBURG
IN SEYMOUR
IN SHERIDAN
IN SHIRLEY
IN SOUTH BEND
IN SOUTH WHITLEY
IN SPEEDWAY
IN SULLIVAN
IN SUMMITVILLE
IN TERRE HAUTE
IN THORNTOWN
IN TIPTON
IN TOWN OF LAPEL
IN UNION
IN VALPARAISO
PRIMARY
RECEIVING WATER
FALL CREEK
WABASH RIVER
WHITE LICK CREEK
YELLOW RIVER
SALAMONIE RIVER
REDKEY RUN
CARPENTER CREEK
IROQUOIS RIVER
WHITEWATER RIVER
LITTLE RIVER
SILVERTHORN CREEK
FLAT ROCK CREEK
WEST FORK BLUE RIVER
STUCKER FORK
EAST FORK]WHITE RIVER
SYMONS DITCH
SIX MILE CREEK
ST JOSEPH RIVER
EEL RIVER
EAGLE CREEK
BUSSERON CREEK
MUD CREEK
WABASH RIVER
PRAIRE CREEK
CICERO CREEK
STONY CREEK
LITTLE MISSINEWA
SALT CREEK
1980 CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
3,600
14,000
8,650
4,175
7,700
840
343
4,000
5,500
0
1,004
8,340
780
3,800
13,352
4,800
360
100,000
1,600
9,000
7,860
1,000
40,860
1,399
5,300
2,616
3,401
20,544
2,309
12,843
10,433
8,303
6,483
1,383
1,247
5,045
38,705
1,018
1,175
5,533
5,619
5,334
15,576
2,046
817
105,511
1,482
13,092
4,663
1,010
57,483
1,506
4,751
1,742
3,612
24,414
12
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
KS
KS
KS
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
VINCENNES
WABASH
WAKARUSA
WASHINGTON
WATERLOO
WEST LAFAYETTE
WESTERN-WAYNE-RSD
WESTFIELD
WHITING
WOLCOTTVILLE
YORKTOWN
ATCHISON
KANSAS CITY
TOPEKA
ASHLAND
BROMLEY
CARROLLTON
FRANKFORT
HARLAN
HENDERSON
JACKSON
LOUISVILLE
LOUISVILLE
LOYALL
MAYSVILLE
MORGANFIELD
PRIMARY
RECEIVING WATER
WABASH RIVER
WABASH RIVER
WERNTZ DITCH
HAWKINS CREEK
CEDAR CREEK
WABASH RIVER
W FORK WHITEWATER R
COAL CREEK
GRAND CALUMET RIVER
NORTH BRANCH ELKART
W FL WHITE RIVER
MISSOURI RIVER
MISSOURI RIVER
KANSAS RIVER
OHIO RIVER
OHIO RIVER
KENTUCKY RIVER
KENTUCKY RIVER
CUMBERLAND RIVER
OHIO RIVER
N FORK KENTUCKY RIVER
OHIO RIVER
OHIO RIVER
CUMBERLAND RIVER
OHIO RIVER
OHIO RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
29,376
11,300
1,323
12,000
1,584
22,000
1,240
0
7,200
800
1,277
5,000
339,000
120,000
0
177,000
5,475
18,700
0
25,150
800
457,450
13,110
3,000
7,650
2,625
19,859
12,127
1,667
10,838
2,040
25,907
2,091
3,304
5,155
879
4,106
10,656
149,767
119,883
23,622
1,137
3,715
25,968
2,686
25,945
2,466
269,063
269,063
1,100
7,169
3,776
13
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
KY OWENSBORO
KY PADUCAH
KY PIKEVILLE
KY PINEVILLE
KY VANCEBURG
MA BOSTON
MA AMESBURY
MA BROOKLINE
MA CAMBRIDGE
MA CHELSEA
MA CHICOPEE
MA ERVING
MA FALL RIVER
MA FITCHBURG
MA GLOUCESTER
MA GREAT BARRINGTON
MA HATFIELD
MA HAVERHILL
MA HOLYOKS MASS
MA HULL
MA HUNTINGTON
MA LAWRENCE
MA LEOMINSTER
MA LUDLOW
MA MONTAGUE
MA NEW BEDFORD
MA NORTHAMPTON
PRIMARY
RECEIVING WATER
OHIO RIVER
OHIO RIVER
LEVISA FORK
CUMBERLAND RIVER
OHIO RIVER
MERRIMACK RIVER
CHARLES R
CHARLES R
MYSTIC R
CONN - CHICOPEE RIVER
MILLERS RIVER
MOUNT HOPE BAY
NASHUA RIVER
GLOUCESTER HARBOR
HOUSATONIC RIVER
CONNECTICUT RIVER
MERRIMACK RIVER
CONNECTICUT RIVER
MASSACHUSETTS BAY
WESTFIELD RIVER
SPICKETT RIVER
NASHUA RIVER
CONNECTICUT RIVER
CONNECTICUT RIVER
BUZZARDS BAY
CONNECTICUT RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
33,600
14,400
3,821
4,125
1,650
692,200
8,800
58,200
55,000
30,600
31,020
367
92,600
41,800
15,500
4,500
1,500
44,600
22,000
4,500
800
45,000
35,000
8,000
6,500
104,000
22,000
53,549
27,256
6,324
2,198
1,713
574,283
12,109
54,718
95,802
28,710
56,632
1,372
92,703
41,194
28,716
2,810
1,234
51,418
43,704
10,466
1,987
70,207
38,145
0
8,316
99,922
29,289
14
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
MA NORTHFIELD
MA ORANGE
MA PALMER
MA SOMERVILLE
MA SOUTH DARTMOUTH
MA SOUTH HADLEY
MA SPENCER
MA SPRINGFIELD
MA TAUNTON
MA WARREN
MA WEST SPRINGFIELD
MA WESTFIELD
MA WORCESTER
MD CAMBRIDGE
MD CENTREVILLE
MD CUMBERLAND
MD ELKTON
MD FROSTBURG
MD HAVRE DE GRACE
MD MILLINGTON
MD POCOMOKE CITY
MD SALISBURY
MD SNOW HILL
MD WESTERNPORT
ME ANSON
ME AUBURN
PRIMARY
RECEIVING WATER
CONNECTICUT RIVER
MILLERS RIVER
CHICOPEE RIVER
MYSTIC R
BUZZARDS BAY
CONNECTICUT RIVER
CRANBERRY BROOK
CONNECTICUT RIVER
TAUNTON RIVER
QUABOAG RIVER
CONNECTICUT RIVER
WESTFIELD RIVER
BLACKSTONE RIVER
CHOPTANK RIVER
GRAVEL RUN
NORTH BR OF POTOMAC
BIG ELK CREEK
WILLS-CREEK
SUSQUEHANNA RIVER
CHESTER RIVER
POCOMOKE RIVER
N BR WICOMICO RIVER
POCOMOKE RIVER
NTH BR-OF POTOMAC RV
CARABASETT RIVER
ANDROSCOGGIN R
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
2,000
2,750
19,400
80,890
2,000
16,180
4,500
160,000
24,200
260
28,289
20,200
182,000
2,100
2,000
16,000
7,000
7,330
11,000
475
3,825
900
456
2,800
740
19,000
1,322
3,791
4,069
76,210
0
16,685
6,306
156,983
49,832
1,516
27,537
38,372
169,759
11,514
2,097
23,706
9,073
8,075
8,952
409
3,922
20,592
2,217
2,454
2,382
24,309
15
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
ME AUGUSTA
ME BANGOR
ME BAR HARBOR
ME BATH
ME BELFAST
ME BIDDEFORD
ME BREWER
ME BRUNSWICK
ME BUCKSPORT
ME CALAIS
ME CAMDEN
ME CAPE ELIZABETH
ME CARIBOU
ME CORINNA
ME DANFORTH
ME DEXTER
ME DOVER FOXCROFT
ME EASTPORT
ME ELLSWORTH
ME FALMOUTH
ME FORT KENT
ME GARDINER
ME GORHAM
ME HALLOWELL
ME HOWLAND
ME KENNEBUNK
ME KINGFIELD
ME KITTERY
PRIMARY
RECEIVING WATER
KENNEBEC R
PENOBSCOT R
ATLANTIC OCEAN
KENNEBEC ESTUARY
ATLANTIC OCEAN
ATLANTIC OCEAN
PENOBSCOT R
ANDROSCOGGIN RIVER
PENOBSCOT R
ST CROIX R
ATLANTIC OCEAN
ATLANTICOOCEAN
AROOSTOOK RIVER
SEBASTICOOK R
BASKAHEGAN STREAM
SEBASTICOOK RIVER
PISCATAQUIS RIVER
ATLANTIC OCEAN
UNION BAY
ATLANTIC OCEAN
FISH RIVER
KENNEBEC RIVER
PRESUMPSCOT RIVER
KENNEBEC RIVER
PISCATAQUIS RIVER
MOUSAM RIVER
CARRABASSETT RIVER
PISCATAQUA R
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
41,000
25,000
2,775
9,500
600
12,000
8,900
9,700
2,150
3,000
4,000
5,400
750
1,000
105
2,700
2,500
1,500
3,000
340
750
4,700
100
2,500
1,300
5,000
200
1,100
21,325
33,181
2,768
9,799
6,355
20,710
9,021
14,683
2,989
3,963
4,022
8,854
9,415
2,196
710
2,650
3,077
1,965
5,975
1,708
2,123
6,746
3,618
2,534
1,304
4,206
1,114
5,151
16
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
ME LEWISTON
ME LINCOLN
ME LISBON FALLS
ME LIVERMORE FALLS
ME MACHIAS
ME MARS HILL
ME MECHANIC FALLS
ME MEDWAY
ME MILFORD
ME MILLINOCKET
ME NEWPORT
ME OAKLAND
ME OLD ORCHARD BEACH
ME OLD TOWN
ME PITTSFIELD
ME PORTLAND
ME PRESQUE ISLE
ME RANDOLPH
ME RICHMOND
ME ROCKLAND
ME SACO
ME SANFORD
ME SKOWHEGAN
ME SO BERWICK
ME SOUTH PARIS
ME SOUTH PORTLAND
ME STRONG
ME THOMASTON
PRIMARY
RECEIVING WATER
ANDROSCOGGIN R
PENOBSCOT RIVER
ANDROSCOGGIN RIVER
ANDROSCOGGIN RIVER
MACHIAS RIVER
PRESTILE STREAM
LITTLE ANDROSCOGGIN R
PENOBSCOT RIVER
PENOBSCOT RIVER
MILLINOCKET STREAM
SEBASTICOOK RIVER
MESSALONSKEE STREAM
ATLANTIC OCEAN
PENOBSCOTT RIVER
SEBASTICOOK R
ATLANTIC OCEAN
AROOSTOOK RIVER
KENNEBEC RIVER
KENNEBEC ESTUARY
ROCKLAND HARBOR
SACO RIVER
MOOSAM RIVER
KENNEBEC R
SALMON FALLS RIVER
LITTLE ANDROSCOGGIN R
ATLANTIC OCEAN
VALLEY BROOK
ST GEORGE RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
32,300
3,500
5,100
2,180
3,000
200
1,550
0
600
800
1,300
3,000
875
6,500
150
58,000
9,000
1,600
12,000
6,675
7,500
14,900
5,000
200
2,700
14,000
21
750
39,757
3,399
4,674
1,935
1,773
1,717
2,388
1,922
2,228
6,922
1,843
3,510
7,789
8,317
3,222
64,358
10,550
1,949
1,775
7,972
15,181
10,296
6,990
0
2,320
23,163
1,217
2,445
17
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
ME VAN BUREN
ME VEAZIE
ME WASHBURN
ME WATERVILLE
ME WESTBROOK
Ml ADRIAN
Ml ALPENA
Ml ALPENA
Ml ARMADA
Ml BAY CITY
Ml BELDING
Ml BELLEVILLE
Ml BENTON HARBOR
Ml BERKLEY
Ml BESSEMER
Ml BIG RAPIDS
Ml CAPAC
Ml CASPIAN
Ml CHEBOYGAN
Ml COOPERSVILLE
Ml CROSWELL
Ml CRYSTAL FALLS
Ml DAVISON
Ml DETROIT
Ml DETROIT
Ml DOWAGIAC
Ml DUNDEE
PRIMARY
RECEIVING WATER
ST JOHN RIVER
PENOBSCOT RIVER
SALMON BROOK STREAM
KENNEBEC R
PRESUMPSCOT R
RAISIN RIVER
THUNDER BAY
LAKE HURON
COON CREEK
SAGINAW RIVER
FLAT RIVER
HURON RIVER
ST JOSEPH RIVER
RIVER ROUGE
BLACK RIVER
MUSKEGON RIVER
LEMON DRAIN
IRON RIVER
CHEBOYGAN RIVER
DEER CREEK
BLACK RIVER
PAINT RIVER
BLACK CREEK
DETROIT RIVER
ROUGE RIVER
DOWAGIAC CREEK
RAISIN RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
3,565
200
600
22,000
3,500
20,400
2,988
3,100
2,688
25,000
0
1,152
62,000
21,879
820
13,875
260
384
3,228
1,000
957
0
24,434
1,017,880
458,320
6,880
500
2,759
33,181
1,880
17,173
16,121
22,097
11,354
11,354
1,548
38,936
5,969
3,270
12,818
16,960
2,272
12,603
1,583
1,031
4,999
3,421
2,174
1,922
5,693
1,027,974
1 ,027,974
6,409
2,664
18
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
Ml EAST LANSING
Ml EATON RAPIDS
Ml ECORSE
Ml ESSEXVILLE
Ml FARMINGTON
Ml FERNDALE
Ml FLINT
Ml FRANKFORT
Ml GLADWIN
Ml GRAND RAPIDS
Ml GROSSE ISLE
Ml HANCOCK
Ml HART
Ml HOUGHTON
Ml HUBBELL
Ml HUDSON
Ml HUNTINGTON
Ml IMLAY
Ml IRON RIVER
Ml IRONWOOD
Ml ISPHEMING
Ml KINGSFORD
Ml LAINGSBURG
Ml LAKE LINDEN
Ml LANSING
Ml LAPEER
Ml LESLIE
Ml MANCHESTER
PRIMARY
RECEIVING WATER
RED CEDAR RIVER
GRAND RIVER
ECORSE CREEK
SAGINAW RIVER
UPPER ROUGE RIVER
RIVER ROUGE
FLINT RIVER
BETSIE LAKE
CEDAR RIVER
GRAND RIVER
DETROIT RIVER
PORTAGE LAKE SHIP CAN
S BRANCH PENTWATER Rl
PORTAGE LAKE SHIP CAN
PORTAGE LAKE
BEAN CREEK
BELLE RIVER
IRON RIVER
MONTREAL RIVER
CARP RIVER
NENOMINEE RIVER
TORCH LAKE
GRAND RIVER
FLINT RIVER
HUNTOON CREEK
RIVER RAISEN
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
35,000
1,560
16,000
5,000
5,000
30,850
2,400
1,800
1,926
25,789
2,100
4,977
0
6,904
1,425
1,000
0
100
2,694
2,818
8,800
24,000
1,050
2,464
50,000
4,735
2,400
2,880
50,677
4,695
12,180
4,088
10,132
25,084
140,761
1,546
2,682
189,126
9,781
4,547
1,942
7,498
1,174
2,580
6,419
2,921
2,095
6,849
7,200
5,480
1,148
1,203
127,321
7,759
1,872
1,753
19
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
Ml MANISTIQUE
Ml MARINE CITY
Ml MARLETTE
Ml MARQUETTE
Ml MARSHALL
Ml MARYSVILLE
Ml MIDLAND
Ml MILAN
Ml MONROE
Ml MORENCI
Ml MOUNT CLEMENS
Ml MT CLEMENS
Ml NEGAUNEE
Ml NEW HAVEN
Ml NILES
Ml NORWAY
Ml OAK PARK
Ml OAKLAND
Ml PALMER
Ml PLEASANT
Ml PONTIC
Ml PORT HURON
Ml RICHMOND
Ml ROYAL OAK
Ml SAGINAW
Ml SAGINAW
Ml SANDUSKY
Ml SAULT STE MARIE
PRIMARY
RECEIVING WATER
MANISTIQUE RIVER
BELLE RIVER
DUFF DRAIN
LAKE SUPERIOR
KALAMAZOO RIVER
ST CLAIR RIVER
TITTABAWASSEE RIVER
SALINE RIVER
RAISEN RIVER
BEAN CREEK
CLINTON RIVER
CLINTON RIVER
CARP RIVER
SALT RIVER
ST JOSEPH RIVER
WHITE CREEK
DETROIT RIVER
CLINTON RIVER
WARNER CREEK
DETROIT RIVER
UPPER RIVER ROUGE
LAKE HURON
COON CREEK
RIVER ROUGE
SAGINAW RIVER
TITTABAWASSEE RIVER
DWIGHT CREEK
ST MARYS RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
4,550
1,920
1,706
21,800
40,440
6,000
7,200
540
2,500
2,135
4,608
20,300
5,165
184
13,000
1,440
36,762
222,480
690
3,989
26,920
588
960
0
90,000
2,710
240
14,200
3,456
4,556
1,924
21,977
6,891
8,515
38,053
4,040
22,902
2,342
18,405
18,405
4,741
2,331
12,458
2,910
30,462
71,166
0
2,775
71,166
33,694
4,141
65,410
69,512
69,512
2,403
14,689
20
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
Ml
Ml
Ml
Ml
Ml
Ml
Ml
Ml
Ml
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
MN
SHEPHERD
SOUTH RANGE VILLAGE
SOUTHFIELD
ST CLAIR
ST CLAIR SHORES
STOCKBRIDGE
TRENTON
TROY
WYANDOTTE
AITKIN
APPLETON
BIRD ISLAND
BRAINERD
BRAINERD
BUFFALO LAKE
CARLTON
DANUBE
HECTOR
HERON LAKE
MAHNOMEN
NEW ULM
RED WING
RICHMOND
ST CLOUD
ST PAUL
ST PETER
WATSON
PRIMARY
RECEIVING WATER
LITTLE SALT RIVER
DETROIT RIVER
ST CLAIR RIVER
LAKE ST CLAIR
PORTAGE CREEK
DETROIT RIVER
DETROIT RIVER
DETROIT RIVER
MISSISSIPPI RIVER
POMME DE TERRE RIVER
BUFFALO CREEK
MISSISSIPPI RIVER
MISSISSIPPI RIVER
BUFFALO CREEK
ST LOUIS RIVER
BEAVER CREEK
BUFFALO CREEK
HERON LAKE
WILD RICE RIVER
MINNESOTA RIVER
MISSISSIPPI RIVER
SAUK RIVER
MISSISSIPPI RIVER
MISSISSIPPI RIVER
MINNESOTA RIVER
CHIPPEWA RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,723
193
46,080
3,600
49,510
1,047
2,688
3,840
63,600
40
1,400
1,400
13,900
0
0
884
0
1,178
777
1,313
4,800
8,000
866
4,000
204,913
6,375
200
1,413
745
75,728
5,116
68,107
1,202
20,586
72,884
30,938
1,698
1,552
1,326
12,353
12,353
734
923
562
1,145
730
1,154
13,132
15,134
965
48,812
272,235
9,421
211
21
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
MN WHEATON
MO
MO
MO
MO
MO
MO
MO
MO
MO
MO
MO
MO
MO
MO
MS
MS
MS
MT
MT
MT
MT
MT
MT
MT
CAPE GIRARDEAU
CHILLICOTHE
CHULA
JEFFERSON CITY
KANSAS CITY
KANSAS CITY
MACON
MOBERLY
MOBERLY
POPLAR BLUFF
SAINT JOSEPH
SEDALIA
ST LOUIS
ST LOUIS
PASCAGOULA
SUMNER
WEBB
ALBERTON
BAINVILLE
BRIDGER
CULBERTSON
EKALAKA
FORT BELKNAP
FORT BENTON
PRIMARY
RECEIVING WATER
MUSTINKA RIVER
CADE LACROUIX CREEK
GRAND RIVER
NEDECINE CREEK
MISSOURI RIVER
MISSOURI RIVER
BLUE RIVER
MIDDLEFORK SALT RIVER
ELK FORK SALT RIVER
SWEET SPRING CREEK
BLACK RIVER
MISSOURI RIVER
MUDDY CREEK
MISSISSIPPI RIVER
MISSISSIPPI RIVER
EAST PASCAGOULA RIVER
CASSIDY BAYOU
CASSIDY BAYOU
CLARK FORT RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
MISSOURI RIVER
2,009
3,500
8,296
25
4,500
92,000
200,000
5,500
8,670
4,700
22,500
78,750
240
336,000
109,620
18,000
500
600
428
214
0
849
619
0
2,000
1,615
34,438
8,804
183
35,481
435,146
435,146
5,571
12,839
12,839
16,996
71,852
19,800
396,685
396,685
25,899
368
605
354
165
692
796
439
422
1,660
22
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
MT
MT
MT
MT
MT
MT
MT
MT
MT
MT
MT
NC
NC
NC
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
GLASGOW
GLENDIVE
GREAT FALLS
HAVRE
HAVRE
HELENA
LODGE GRASS
MALTA
PLENTYWOOD
SIDNEY
WHITEFISH
LUMBERTON
WARSAW
WILMINGTON
CITY OF FARGO
EDGELEY
ELM CITY
ENDERLIN
FAIRMOUNT
FORBES
GRAFTON
GRAND FORKS
LIDGERWOOD
STARKWEATHER
WEST FARGO
PRIMARY
RECEIVING WATER
MILK RIVER
YELLOWSTONE RIVER
MISSOURI RIVER
MILK RIVER
MILK RIVER
PRICKLY PEAR CREEK
LITTLE BIG HORN RIVER
MILK RIVER
BIG MUDDY CREEK
YELLOWSTONE RIVER
WHITEFISH RIVER
LUMBER RIVER
OATHA CREEK
CAPE FEAR RIVER
RED RIVER
MAPLE CREEK
BOIS DE SIOUX RIVER
PARK RIVER
RED RIVER
DRAINAGE DITCH
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
5,302
6,272
62,006
10,683
10,683
27,123
675
2,243
2,241
4,736
5,700
8,000
3,675
29,450
2,300
890
900
1,133
203
72
6,450
11,280
966
200
15,500
3,572
4,802
55,097
10,201
10,201
24,569
517
2,340
2,136
5,217
4,368
18,601
2,859
55,530
197
680
0
997
427
56
4,840
49,425
799
197
12,287
23
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
NE OMAHA
NE OMAHA
NE PLATTSMOUTH
NH CENTER HARBOR
NH COLEBROOK
NH CONCORD
NH CONCORD
NH EXETER
NH FRANKLIN
NH GORHAM
NH G RON/ETON
NH LANCASTER
NH LEBANON
NH LINCOLN
NH LITTLETON
NH MANCHESTER
NH MILFORD
NH MILTON
NH NASHUA
NH NEWBURY
NH PLYMOUTH
NH PORTSMOUTH
NH SOMERSWORTH
NH WALPOLE
NH WHITEFIELD
NH WINCHESTER
NH WOODSVILLE
PRIMARY
RECEIVING WATER
PAPILLION CREEK
MISSOURI RIVER
MISSOURI RIVER
LAKE WINNIPESAUKEE
MOHAWK RIVER
MERRIMACK R
MERRIMACK R
SQUAMSCOTT RIVER
MERRIMACK RIVER
ANDROSCOGGIN RIVER
UPPER AMMONOOSOC RIV
CONNECTICUT RIVER
MASCO MA RIVER
PEMIGEWASSET RIVER
AMMONOOSUC RIVER
MERRIMACK RIVER
SOUHEGAN RIVER
SALMON FALLS RIVER
MERRIMACK RIVER
SUNAPEE LAKE
PEMIGEW ASSET RIVER
PISCATAQUA RIVER
SALMON FALLS RIVER
CONNECTICUT RIVER
ST JOHNS RIVER
ASHUCLOT RIVER
CONNECTICUT RIVER
1980CSO
POPULATION
SERVED (1)
24,000
167,505
7,900
200
300
3,700
16,000
9,080
500
2,550
1,550
2,000
9,000
1,300
5,400
84,400
6,250
540
54,400
60
2,076
16,000
65,000
400
1,450
500
1,200
1990 TOTAL
CITY POPULATION (2)
335,795
335,795
6,412
996
2,444
36,006
36,006
9,556
8,304
1,910
1,255
1,859
12,183
1,229
4,633
99,567
8,015
3,691
79,662
1,347
3,967
25,925
11,249
3,210
1,041
1,735
1,122
24
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
NJ BAYONNE
NJ CAMDEN
NJ CAMDEN
NJ CLIFFSIDE PARK
NJ ELIZABETH
NJ GLOUCESTER
NJ GUTTENBERG
NJ HOBOKEN
NJ JERSEY CITY
NJ JERSEY CITY
NJ LIBERTY CORNER
NJ LITTLE FERRY
NJ NEW BRUNSWICK
NJ NEWARK
NJ PAULSBORO
NJ PERTH AMBOY
NJ RAHWAY
NJ SOUTH KEARNY
NJ TRENTON
NY
NY ALBANY
NY AMSTERDAM
NY ANDS
NY ASTORIA
NY AUBURN
NY BALDWINSVILLE
PRIMARY
RECEIVING WATER
KILL VAN KULL
DELAWARE RIVER
NEWTON CREEK
ELIZABETH RIVER
LITTLE TIMBER CREEK
HUDSON RIVER
HUDSON RIVER
NEWARK BAY
HUDSON RIVER
DEAD RIVER
HACKENSACK RIVER
LOWER RARITAN RIVER
UPPER NEW YORK BAY
DELAWARE RIVER
RARITAN RIVER
ARTHUR KILL
HACKENSACK RIVER
DELAWARE RIVER
HUDSON RIVER
MOHAWK R
HUDSON RIVER
UPPER EAST RIVER
OWASCO LAKE OUTLET
SENECA RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
72,000
17,000
86,500
0
115,000
15,000
18,551
83,120
91,313
157,914
8,000
106,467
54,500
539,731
33,230
40,000
31,000
19,000
105,600
13,000
91,600
25,872
98,747
680,000
36,800
0
61,444
87,492
87,492
20,393
110,002
12,649
8,268
33,397
228,537
228,537
6,597
9,989
41,711
275,221
6,577
41,967
25,325
34,874
88,675
1,753
101,082
20,714
4,333
7,322,564
31,258
6,591
25
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
NY BEACON
NY BINGHAMTON
NY BOONVILLE
NY BROOKLYN
NY BROOKLYN
NY BROOKLYN
NY BROOKLYN
NY BUFFALO
NY CANASTOTA
NY CANTON
NY CARTHAGE
NY CASTLETON-ON-HUDSON
NY CATSKILL
NY COHOES
NY COXSACKIE
NY ELMIRA
NY ELMIRA
NY ENDICOTT
NY ENDICOTT
NY FORT EDWARD
NY GLEN FALLS
NY GOUVERNEUR
NY GRANVILLE
NY GREEN ISLAND
NY HUDSON
NY HUDSON FALLS
NY HUNTS POINT
NY JOHNSON CITY
PRIMARY
RECEIVING WATER
HUDSON RIVER
SUSQUEHANNA RIVER
MILL CREEK
ROCKAWAY INLET
UPPER BAY
HENDRIX CANAL
XDST RIVER
NIAGARA RIVER
COWASELOW CREEK
GRASSE RIVER
BLACK RIVER
HUDSON RIVER
HUDSON RIVER
HUDSON RIVER
HUDSON RIVER
CHEMUNG RIVER
CHEMUNG RIVER
SUSQUEHANA RIVER
SUSQUEHANA RIVER
HUDSON RIVER
HUDSON RIVER
OSWEGATCHIE RIVER
HUDSON RIVER
HUDSON RIVER
HUDSON RIVER
UPPER EAST RIVER
SUSQUEHANNA RIVER
1980CSO
POPULATION
SERVED (1)
11,200
64,123
2,200
600,000
800,000
350,000
275,000
762,768
18,200
0
0
2,400
5,317
18,635
3,095
81,500
37,500
46,000
46,000
3,750
17,000
4,600
0
3,297
9,000
8,000
750,000
19,000
1990 TOTAL
CITY POPULATION (2)
13,243
53,008
2,220
7,322,564
7,322,564
7,322,564
7,322,564
328,123
4,673
6,379
4,344
1,491
4,690
16,825
2,789
33,724
33,724
13,531
13,531
3,561
3,561
4,604
2,646
2,490
8,034
7,651
7,322,564
16,890
26
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
NY KINGSTON
NY LEWISTON
NY LEWISTON
NY LOCKPORT
NY MASSENA
NY MEDINA
NY NEW YORK
NY NEW YORK
NY NEWBURG
NY NIAGARA FALLS
NY NORTH TONAWANDA
NY OGDENSBURG
NY ONEONTA
NY OSWEGO
NY OWEGO
NY PLATTSBURG
NY POTSDAM
NY POUGHKEEPSIE
NY QUEENS
NY RENSSELAER
NY ROCHESTER
NY SALAMANCA
NY SAUGERTIES
NY SCHENECTADY
NY SIDNEY
NY STATEN ISLAND
NY STOCKPORT
NY SYRACUSE
PRIMARY
RECEIVING WATER
RONDOUT CREEK
NIAGARA RIVER
EIGHTEEN MILE CREEK
GRASS RIVER
OAK ORCHARD CK
EAST RIVER
HUDSON RIVER
HUDSON RIVER
NIAGARA RIVER
NIAGARA RIVER
ST LAWRENCE RIVER
SUSQUEHANNA RIVER
OSWEGO RIVER
SUSQUEHANNA RIVER
SARANAC RIVER
RAQUETTE RIVER
HUDSON RIVER
EAST RIVER
HUDSON RIVER
GENESEE-RIVER
ALLEGHENY R
ESOPUS CREEK
MOHAWK RIVER
SUSQUEHANNA RIVER
KILL VAN KULL
HUDSON RIVER
ONONDAGA LAKE
1980CSO
POPULATION
SERVED (1)
25,000
312
43,000
0
14,000
14,800
1,250,000
156,390
26,000
85,400
49,000
14,500
17,000
24,000
4,800
30,000
13,000
33,270
1,500,000
25,220
166,500
8,000
4,100
71,332
4,800
155,000
625
288,000
1990 TOTAL
CITY POPULATION (2)
23,095
3,048
3,048
24,426
11,719
6,686
7,322,564
7,322,564
26,454
61,840
34,989
13,521
13,954
19,195
4,442
21,255
10,251
28,844
7,322,564
8,255
231,636
6,566
3,915
65,566
4,720
7,322,564
8,034
163,860
27
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
NY
NY
NY
NY
NY
NY
NY
NY
NY
NY
NY
NY
NY
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
TROY
TROY
TUPPERLAKE
UTICA
UTICA
VILLOFWEEDSPORT
WADDINGTON
WATERFORD
WATERFORD
WATERLOO
WATERTOWN
WATSRVLIET
YONKERS
ADA
AKRON
ALLIANCE
ANSONIA
ARCANUM
ASHTABULA
AUSEON
AVON LAKE
BEDFORD
BELLAIRE
BLOOMVILLE
BLUFFTON
BRADFORD
PRIMARY
RECEIVING WATER
HUDSON RIVER
HUDSON RIVER
RAQUETTE POND
MOHAWK RIVER
MAHAWK RIVER
COLD SPRINGS BROOK
HUDSON RIVER
MOHAWK RIVER
BLACK RIVER
HUDSON RIVER
HUDSON RIVER
POE DITCH
GRASS RUN CREEK
LITTLE CUYAHOGA RIVER
MAHONING RIVER
NORTH FORK STILLWATER
SYCAMORE DITCH
LAKE ERIE
BRANCH DITCH
LAKE ERIE
TINKERS CREEK
OHIO RIVER
HONEY CREEK
RILEY CREEK
BALLINGER RUN
1980CSO
POPULATION
SERVE D(1)
1990 TOTAL
CITY POPULATION (2)
174,200
174,200
5,604
130,000
142,402
3,000
0
17,188
2,340
0
32,037
12,464
130,000
24,000
6,300
254,000
625
1,053
2,996
2,160
5,945
13,000
384
10,000
967
2,400
2,300
54,269
54,269
4,087
68,637
68,637
1,996
944
2,370
2,370
5,116
29,429
11,061
188,082
8,348
949
223,019
23,376
1,279
1,953
21,633
364,040
15,066
505,616
6,028
949
3,367
2,005
28
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OH BRIDGEPORT
OH BROOKSIDE
OH BRYAN
OH BUCYRUS
OH CAMPBELL
OH CINCINNATI
OH CINCINNATI
OH CINCINNATI
OH CITY OF WILLARD
OH CLEVELAND EASTERLY AREA
OH CLEVELAND SOUTHERLY AREA
OH CLEVELAND WESTERLY AREA
OH CLYDE
OH COLUMBUS GROVE
OH COLUMBUS JACKSON PIKE
OH COLUMBUS SOUTHERLY
OH CONTINENTAL
OH CONVOY
OH CRESTLINE
OH DEFIANCE
OH DELPHOS
OH DELTA
OH ELMORE
OH ELYRIA
OH ERIE
OH EUCLID
OH FAYETTE
OH FINDLAY
PRIMARY
RECEIVING WATER
WHEELING CREEK
OHIO RIVER
PRAIRIE CREEK
SAN DUSKY RIVER
MAHONING RIVER
OHIO RIVER
OHIO RIVER
OHIO RIVER
JACOBS CREEK
LAKE ERIE
CUYAHOGA RIVER
LAKE ERIE
UNNAMED CREEK
PLUM CREEK
SCIOTO RIVER
SCIOTO RIVER
COUNTY DITCH # 322
HAGERMAN CREEK
PARAMOUR CREEK
MAUMEE RIVER
JENNINGS CREEK
BAD CREEK
PORTAGE RIVER
BLACK RIVER
HURON RIVER
LAKE ERIE
DEER CREEK
BLANCHARD RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
2,000
939
6,954
13,000
250
146,000
30,000
358,100
5,965
255,000
223,000
151,600
4,930
2,000
227,500
122,500
1,200
1,100
3,300
9,500
7,639
2,880
1,300
25,400
694
5,376
1,200
10,980
2,318
703
8,348
13,496
10,038
364,040
364,040
364,040
4,297
505,616
505,616
54,875
5,776
2,231
632,910
2,849
1,214
1,200
4,934
16,768
7,093
2,849
1,334
56,746
1,953
54,875
3,557
35,703
29
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OH FOREST VILLAGE OF
OH FOSTORIA
OH FREDRICKTOWN
OH FREMONT
OH GENOA
OH GIBSONBURG
OH GREEN SPRINGS
OH GREENWICH
OH HASKINS
OH HICKSVILLE
OH HURON
OH IRONTON
OH KENTON
OH KINGSTON
OH LAKEWOOD
OH LANCASTER
OH LIMA
OH LINDSEY
OH * LISBON
OH MARIETTA
OH MARION
OH MARSHALVILLE
OH MARTINS FERRY
OH MARTINS FERRY-BELLAIRE
OH MAUMEE
OH MCCOMB
OH MCCONNELSVILLE
OH MIDDLEPORT
PRIMARY
RECEIVING WATER
TRIB BLANCHARD RIVER
EAST BRANCH PORTYAGE-
KOKOSING RIVER
SANDUSKY RIVER
TOUSSAINT CREEK
PORTAGE RIVER
FLAG RUN CREEK
VERMILLION RIVER
MAUMEE RIVER
MILL CREEK
HURON RIVER
OHIO RIVER
SCIOTO RIVER
BLACKWATER CREEK
ROCKY RIVER
HOCKING RIVER
AUGLAIZE RIVER
MUDDY CREEK
LITTLE BEAVER CREEK
OHIO RIVER
OLENTANGY RIVER
RED RUN
OHIO RIVER
OHIO RIVER
MAUMEE RIVER
ALGIRE CREEK
MUSKINGUM RIVER
OHIO RIVER
1980 CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,155
1,700
2,000
39,600
2,000
2,648
1,350
1,500
647
3,900
1,700
15,700
6,000
1,400
40,000
36,000
55,200
675
3,500
6,960
39,357
255
1,100
27,500
159
1,500
3,000
1,716
2,443
14,983
1,442
17,648
2,262
2,579
1,446
1,442
549
3,664
7,030
12,751
8,356
1,153
59,718
34,507
21,633
529
3,037
15,026
34,075
3,367
7,990
6,028
15,561
1,544
1,804
2,725
30
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OH MIDDLETOWN
OH MILAN
OH MILFORD
OH MINGO JUNCTION
OH MONROEVILLE
OH MONTPELIER
OH NAPOLEON
OH NEW BOSTON
OH NEW BREMEN
OH NEW LEXINGTON
OH NEWARK
OH NEWTON FALLS
OH NILES
OH NORTH BALTIMORE
OH NORWALK
OH OAK HARBOR
OH OHIO CITY
OH PANDORA
OH PAULDING
OH PAYNE
OH PEMBERVILLE
OH PERRYSBURG
OH POME ROY
OH PORT CLINTON
OH PORTSMOUTH
OH PORTSMOUTH
OH ROCKFORD
OH ROSSFORD
PRIMARY
RECEIVING WATER
MIAMI RIVER
HURON RIVER
LITTLE MIAMI RIVER
CROSS CREEK
HURON RIVER
ST JOSEPH
MAUMEE RIVER
OHIO RIVER
WIERTH DITCH
LITTLE RUSH CREEK
LICKING RIVER
MAHONING RIVER
MAHONING RIVER
ROCKY FORD CREEK
RATTLESNAKE CREEK
PORTAGE RIVER
PRAIRIE DITCH
RILEY CREEK
FLATROCK CREEK
FLATROCK CREEK
PORTAGE RIVER
MAUMEE RIVER
OHIO RIVER
LAKE ERIE
OHIO RIVER
LAWSON RUN
ST MARY RIVER
MAUMEE RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
14,724
1,300
75,000
5,200
1,500
3,360
5,850
2,500
2,500
4,500
42,000
6,000
500
3,200
13,500
3,000
630
1,300
3,300
1,350
1,400
9,500
600
7,400
3,300
11,400
960
200
46,022
1,464
5,660
4,297
1,381
4,299
8,884
2,717
2,558
5,117
44,389
4,866
21,128
3,139
14,731
2,637
899
1,009
2,605
1,244
1,279
12,551
2,259
7,106
22,676
22,676
1,119
5,861
31
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OH SANDUSKY
OH SPRINGFIELD
OH STEUBENVILLE
OH STOCKPORT
OH STRUTHERS
OH SWANTON
OH TIFFIN
OH TOLEDO
OH TORONTO
OH UPPER SANDUSKY
OH VAN WERT
OH VILLAGE OF PUT IN BAY
OH WAPAKONETA CITY OF
OH WARREN
OH WASHINGTON
OH WESTON
OH WILLISTON
OH WILSHIRE
OH WOODVILLE
OH WOOSTER
OH YOUNGSTOWN
OH ZANESVILLE
OR
OR ALBANY
OR ASTORIA
OR AUMSVILLE
OR COOS BAY CITY
PRIMARY
RECEIVING WATER
SANDUSKY BAY
MAD RIVER
OHIO RIVER
MUSKINGUM RIVER
MAHONING RIVER
Al CREEK
SANDUSKY RIVER
MAUMEE RIVER
OHIO RIVER
SANDUSKY RIVER
TOWN CREEK
LAKE ERIE
AUGLAIZE RIVER
MAHONING RIVER
PAINT CREEK
TONTOGANY CREEK
ST MARY RIVER
PORTAGE RIVER
KILLBUCK CR
MAHONING RIVER
MUSKINGUM
COQVILLE RIVER
WILLAMETTE RIVER
YOUNGS BAY
BEAVER CREEK
COOS BAY
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
38,000
95,000
133,000
56
28,000
3,000
24,000
196,000
5,353
18,000
11,300
430
3,650
35,000
12,910
1,146
17,405
720
1,520
6,800
46,075
3,330
1,200
2,971
6,103
213
3,553
34,507
70,487
22,125
462
12,284
3,557
18,604
332,943
6,127
5,906
10,891
2,605
9,214
4,866
12,983
1,716
0
15,026
1,953
22,191
95,732
26,778
163
29,462
10,069
1,650
15,076
32
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OR CORVALLIS
OR COTTAGE GROVE
OR CRESWELL
OR DALLAS
OR GERVAIS
OR GLADSTONE
OR GRANTS PASS
OR HUNTINGTON
OR INDEPENDENCE
OR JEFFERSON
OR KLAMATH FALLS
OR LA GRANDE
OR LEBANON
OR MCMINNVILLE
OR MONMOUTH
OR MYRTLE CREEK
OR MYRTLE POINT
OR NEWPORT
OR NORTH BEND
OR ONTARIO
OR OREGON CITY
OR PENDLETON
OR PORTLAND
OR ROSEBURG
OR SALEM
OR SILVERTON
OR ST HELENS
OR THE DALLES
PRIMARY
RECEIVING WATER
WILLAMETTE RIVER
WILLAMETTE RIVER
CAMAS SWALE
RICKREALL CREEK
PUDDING RIVER
WILLAMETTE RIVER
ROGUE RIVER
BURNT RIVER
ASH CREEK
SANTIAM RIVER
LAKE EWAUNA
GEKELER SLOUGH
SOUTH SANTIAM RIVER
SOUTH YAMHILL RIVER
NORTH FORK ASH CREEK
MYRTLE CREEK
COQVILLE RIVER
PACIFIC OCEAN
COOS BAY
MALHEUR RIVER
WILLAMETTE RIVER
MCKAY CREEK
WILLAMETTE RIVER
SOUTH UMPQUA RIVER
WILLAMETTE RIVER
SILVER CREEK
COLUMBIA RIVER
COLUMBIA RIVER
1980CSO
POPULATION
SERVED (1)
5,684
1,197
104
1,529
177
1,501
3,492
270
1,061
165
2,759
367
883
1,462
495
900
750
3,252
2,243
2,190
6,276
1,032
317,574
7,800
60,187
384
2,166
439
1990 TOTAL
CITY POPULATION (2)
44,757
7,402
2,431
9,422
992
10,152
17,488
522
4,425
1,805
17,737
11,766
10,950
17,894
6,288
3,063
2,712
8,437
9,614
9,392
14,698
15,126
437,319
17,488
107,786
5,635
15,076
17,894
33
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
OR
OR
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
WOODBURN
WOODBURN
CALIFORNIA
ALLENPORT
ALTOONA
AMBRIDGE
APOLLO
ARCHBALD
BALDWIN
BARNESBORO
BEAVER FALLS
BELLE VERNON
BENTLEYVILLE
BERWICK
BLAIRSVILLE
BRIDGEPORT
BROWNSVILLE
CENTRAL CITY
CENTRALIA
CHARLEROI
CHESTER
PRIMARY
RECEIVING WATER
MILL CREEK
PUDDING RIVER
LEGHIGH- RIVER
TOWANDA CREEK
QUEMAHONING CREEK
OIL CREEK
QUEMAHONING CREEK
MONONGAHELA RIVER
MONONGAHELA RIVER
LITTLE JUNIATA RIVER
OHIO RIVER
KISKIMENTAS RIVER
LACKAWANNA RIVER
SEE NOTE
W BR SUSQUEHANA RIVER
BEAVER RIVER
MONONGAHELA RIVER
SEE NOTE
SUSQUEHANNA RIVER
CONEMAUGH RESERVOIR
SCHUYLKILL RIVER
MONONGAHELA RIVER
DARK SHADE CREEK
BIG MINE RUN CREEK
MONONGAHELA RIVER
DELAWARE RIV ESTUARY
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,425
1,189
6,300
1,310
1,600
7,331
1,600
12,036
7,800
6,417
45,000
11,324
40,546
210,255
27,000
4,882
13,867
1,496
714
12,274
4,447
5,700
10,000
600
1,089
8,536
35,926
13,404
13,404
481 ,479
481,479
481,479
(1)
21,923
479
5,748
595
51,881
8,133
1,895
6,291
21,923
2,530
10,687
1,213
2,673
10,976
3,595
4,292
3,164
1,246
63
5,014
7,216
34
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
PA CLAIRTON
PA COKEBURG
PA CONFLUENCE
PA CONNELLSVILLE
PA CORAOPOLIS
PA CORRY
PA COUDERSPORT
PA CREIGHTON
PA CREIGHTON
PA CRESSON
PA DAWSON
PA DRAVOSBURG
PA DUQUESNE
PA EASTON
PA EDGEWORTH
PA ELIZABETH
PA ELLSWORTH
PA ELLWOOD CITY
PA ERIE
PA FARRELL
PA FAYETTE CITY
PA FRANKLIN
PA FREELAND
PA GALETON
PA GALLITZIN
PA GREENSBURG
PA HARRISBURG
PA HAZELTON
PRIMARY
RECEIVING WATER
MONONGAHELAKRIVER
SEE NOTE
YOUGHIOGHENY RIVER
YOUGHIOGHENY RIVER
OHIO RIVER
HARE CREEK
ALLEGHENY RIVER
ALLEGHENY RIVER
SEE NOTE
LITTLE CONEMAUGH RIVE
YOUGHIOGHENY RIVER
MONONGAHELA RIVER
MONONGAHELA RIVER
DELAWARE RIVER
SEE NOTE
MONONGAHELA RIVER
SEE NOTE
CONNOQUENESSING CREEK
PRESQUE ISLE BAY
SHENANGO RIVER
MONONGAHELA RIVER
ALLEGHENY RIVER
POND CREEK
WEST BRANCH PINE CR
BRADLEY RUN
SEWICKLEY CREEK
SUSQUEHANNA RIVER
N BR SUSQUEHANA RIVER
1980CSO
POPULATION 1990 TOTAL
SERVED (1) CITY POPULATION (2)
19,870
45
954
9,600
8,435
6,835
3,000
14,256
2,081
2,412
1,500
2,216
11,410
8,000
2,200
2,100
733
10,857
129,231
8,200
1,000
14,600
3,960
1,552
2,406
20,388
69,350
18,800
9,656
724
873
9,229
6,747
7,216
2,854
0
(1)
2,003
535
2,377
8,525
26,276
1,670
1,387
1,048
8,894
108,718
6,841
713
7,329
3,909
1,370
2,003
16,318
52,376
24,730
35
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
PA HAZELTON
PA HAZLETON
PA HUNTINGDON
PA IRWIN
PA JEANNETTE
PA KANE
PA KEISER
PA LANCASTER
PA LANCASTER
PA LATROBE
PA UEETSDALE
PA LIGONIER
PA LILLY
PA MANOR
PA MARIANNA
PA MARYSVILLE
PA MCKEESPORT
PA MEYERSDALE
PA MIDLAND
PA MONACA
PA MONONGAHELA
PA MOOSIC
PA MOOSIC
PA MOUNT CARMEL
PA MT PLEASANT
PA NESQUEHONING
PA NEW BETHLEHEM
PA NEW KENSINGTON
PRIMARY
RECEIVING WATER
SEE NOTE
SEE NOTE
JUNIATA RIVER
BRUSH CREEK
BRUSH CREEK
KINZUA-CREEK
SHAMOKIN CREEK
CONESTOGA CREEK
CONESTOGA CREEK
LOYALHANNA CREEK
OHIO RIVER
LOYALHANNA CREEK
LITTLE CONEMAUGH RIVE
BRUSH CREEK
TEN MILE CREEK
SUSQUEHANA RIVER
MONONGAHELA RIVER
CASSELMAN RIVER
OHIO RIVER
OHIO RIVER
MONONGAHELA
SEE NOTE
LACKAWANNA RIVER
SHAMOKIN CREEK
SHOPE RUN
NESQUEHONING CREEK
RED BANK CREEK
BIG PUCKETAS
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
31,500
3,092
11,000
4,200
15,809
5,000
970
45,815
1,187
612
1,862
2,408
1,436
1,700
850
2,370
74,991
3,000
5,300
7,350
2,840
4,400
40,993
17,300
3,537
3,700
1,300
6,095
24,730
24,730
6,843
4,604
11,221
4,590
7,196
55,551
55,551
9,265
1,387
1,638
1,162
2,627
616
2,425
26,016
2,518
3,321
6,739
4,928
5,339
5,339
7,196
4,787
3,364
1,151
15,894
36
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
PA NEWPORT
PA NORRISTOWN
PA OAKMONT
PA OIL CITY
PA OLD FORGE
PA OSBORNE
PA PHILADELPHIA
PA PITTSBURGH
PA PITTSBURGH
PA PITTSBURGH
PA PITTSBURGH
PA POTTSVILLE
PA PUNXSUTAWNEY
PA ROCHESTER
PA ROCKWOOD
PA SCOTTDALE
PA SCRANTON
PA SEWICKLEY
PA SHAMOKIN
PA SHEFFIELD
PA SHINGLEHOUSE
PA SLIGO
PA SOUTH BETHLEHEM
PA ST CLAIR
PA STROUDSBURG
PA SUNBURY
PA THROOP
PA UNIONTOWN
PRIMARY
RECEIVING WATER
JUNIATA RIVER
SCHUYLKILL RIVER
ALLEGHENY RIVER
OIL CREEK
LACKAWANNA RIVER
SEE NOTE
DELAWARE RIVER
ALLEGHENY RIVER
OHIO RIVER
OHIO RIVER
SEE NOTE
SCHUYLKILL RIVER
MAHONING CREEK
OHIO RIVER
CASSELMAN RIVER
JACOBS CREEK
LACKAWANNA RIVER
OHIO RIVER
SHAMOKIN CREEK
TIONESTA CREEK
OSWAYO- CREEK
LICKING CREEK
RED BANK CREEK
MILL CREEK
BRODHEADS CREEK
SHAMOKIN CREEK
LACKAWANNA RIVER
REDSTONE CREEK
1980CSO
POPULATION
SERVED (1)
3,000
4,800
2,265
15,033
29,335
579
1,926,176
7,900
193,860
518,300
12,036
27,000
7,700
8,255
1,019
2,900
88,000
8,439
22,500
1,564
1,324
800
500
5,000
1,100
12,703
35,449
16,280
1990 TOTAL
CITY POPULATION (2)
1,568
30,749
6,961
11,949
8,834
565
1,585,577
369,879
369,879
369,879
369,879
16,603
6,782
4,156
1,014
5,184
81,805
1,821
11,591
1,294
1,243
706
479
3,524
5,312
11,591
4,070
12,034
37
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
PA
PA
PA
PA
PA
PA
PA
PR
Rl
Rl
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
VERSAILLES
VINTONDAUE
WEST HAZLETON
WEST NEWTON
WILKES-BARRE
WILLIAMSPORT
WINDBER
PUERTO NUEVO
PAWTUCKET
PROVIDENCE
ARTESIAN
CRESBARD
GROTON
HIGHMORE
HURON
LEAD
LEMMON
LENNOX
PINE RIDGE
REDFIELD
SIOUX FALLS
TYNDALL
WAGNER
TN
BRISTOL
PRIMARY
RECEIVING WATER
MONONGAHELA RIVER
S BRANCH BLACKLICK CR
SEE NOTE
YOUGHIOGHENY
SUSQUEHANA
W BR SUSQUEHANA RIVER
CONEMAUGH-RIVER
SAN JUAN BAY
BLACKSTONE R
PROVIDENCE R
JIM CREEK
SNAKE CREEK TRIB.
MUD CREEK
BRANCH OF WOLF CREEK
JAMES RIVER
WHITEWOOD CREEK
CEDAR CREEK.TRIB. OF
WHITE RIVER
TURTLE CREEK
BIG SIOUX FALLS
MISSOURI RIVER TRIB
TRIB. OF CHOTEAU CK
SOUTH FORKHOLSTONRIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
2,754
795
6,200
3,700
23,508
35,000
10,000
600,000
77,000
113,550
277
224
1,200
1,000
14,245
9,063
1,950
1,700
3,000
2,840
80,000
0
1,800
1,821
582
4,136
3,152
31,933
31,933
4,756
0
72,644
160,728
217
185
1,196
835
12,448
3,632
1,614
1,767
2,596
2,770
100,814
1,201
1,462
34,000
23,421
38
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
TN CHATTANOOGA
TN NASHVILLE
TX BEAUMONT
UT EUREKA
UT TREMONTON
VA ALEXANDRIA
VA ASHLAND
VA BRISTOL
VA CLIFTON FORGE
VA COVINGTON
VA HOPEWELL
VA LYNCHBURG
VA NEWPORT NEWS
VA RADFORD
VA REMINGTON
VA RICHMOND CITY
VA WAYNESBORO
VT ALBURG
VT BARTON VILLAGE
VT BELLOWS FALLS
VT BENNINGTON
VT BETHEL
VT BRANDON
VT BURLINGTON
PRIMARY
RECEIVING WATER
TENNESSEE RIVER
CUMBERLAND RIVER
NECHES RIVER
MALAD RIVER
POTOMAC-RIVER
SOUTH ANNA RIVER
BRISTOL CITY
COWPASTURE-RIVER
JACKSON RIVER
POYTHRESS CREEK
JAMES RIVER
JAMES RIVER
NEW RIVER
RAPPAHANNOCK RIVER
JAMES RIVER
SOUTH RIVER
LAKE CHAMPLAIN
BARTON RIVER
CONNECTICUT RIVER
WALLOOMSAC RIVER
SAVH
LAKE CHAMPLAIN
1980 CSO
POPULATION 1990 TOTAL
SERVED (1) CITY POPULATION (2)
15,600
100,900
35,000
918
3,818
13,440
4,275
8,600
5,100
9,760
1,250
85,800
51,600
3,000
450
352,775
1,300
530
1,050
3,505
12,460
87
2,700
20,000
152,466
488,374
114,323
562
4,264
111,183
5,864
18,426
4,679
6,991
23,101
66,049
170,045
15,940
460
203,056
18,549
436
908
3,313
9,532
1,866
1,902
39,127
39
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
VT
WA
WA
WA
ENOSBURG FALLS
ESSEX JUNCTION VILLAGE
FAIRHAVEN
HARDWICK
HYDE PARK
LUDLOW
LUNENBURG
LYNDON
MIDDLEBURY
MONTPELIER
NEWPORT
NORTHFIELD
ORLEANS
POULTNEY
RANDOLPH
RICHFORD
RUTLAND
SOUTH ROY ALTON
SPRINGFIELD
ST ALBANS
ST JOHNSBURY
WILDER
WINDSOR
WINOOSKI
PRIMARY
RECEIVING WATER
MISSISQUOI RIVER
WINOOSKI R
POULTNEY- RIVER
LAMOILLE RIVER
LAMOILLE RIVER
BLACK RIVER
CONNECTICUT RIVER
PASSUMPSIC RIVER
OTTER CREEK
WINOOSKI RIVER
LAKE MEMPHREMAGOG
DOG RIVER
BARTON&WILLOUGHBY RVR
POULTNEY RIVER
THIRD BRANCH OF WHITE
MISSISQUOI RIVER
OTTER CREEK
WHITE RIVER
BLACK RIVER
STEVENS BRANCH
PASSUMPIC RIVER
CONNECTICUT RIVER
CONNECTICUT RIVER
WINOOSKI RIVER
YAKIMA RIVER
SULFUR CREEK
WILLAPA RIVER
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
1,266
4,000
2,200
1,500
318
1,800
400
4,080
2,000
8,609
4,664
4,995
1,047
1,874
1,400
75
20,000
80
6,532
8,200
7,000
1,000
2,940
2,000
0
0
0
1,350
8,396
2,432
2,964
457
1,123
1,176
1,255
6,007
8,247
4,434
1,889
806
1,731
4,764
1,425
18,230
0
4,207
7,339
6,424
1,576
3,714
6,649
491
491
(D
40
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
WA
WA ABERDEEN
WA ANACORTES
WA BELLINGHAM
WA BLAINE
WA BREMERTON
WA CARBONADO
WA CATHLAMET
WA CHENEY
WA EDMUNDS
WA ELLENSBURG
WA EVERETT
WA EVERETT
WA FERNDALE
WA GOLDENDALE
WA GRAND COULEE
WA GRANITE FALLS
WA HOQUIAM
WA ILWACO
WA KALAMA
WA LACEY
WA MARYSVILLE
WA METAUNE FALLS
WA MONROE
WA MOSES LAKE
WA MOUNTVERNON
WA MUKILTEO
WA OLYMPIA
PRIMARY
RECEIVING WATER
STILLAGUAMISH RIVER
CHEHALIS RIVER
GUEMES CHANNEL
BELLINGHAM BAY
DRAYTON HARBOR
PUGETSOUND
CARBON RIVER
COLUMBIA RIVER
YAKIMA RIVER
SKYKOMISH RIVER
SNOHOMISH RIVER
NOOKSACK RIVER
LITTLE KLICKITAT RIV
CRESCENT BAY
PILCHUCK RIVER
CHEHALIS RIVER
BUDD INLET
EBEY SLOUGH
SKYKOMISH RIVER
MOSES LAKE
SKAGIT RIVER
PUGETSOUND
BUDD INLET
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
502
10,539
918
3,998
814
9,616
400
695
6,820
21,600
1,585
264
31,680
38
0
490
600
1,000
1,200
1,200
10,817
1,300
350
2,400
3,500
6,000
770
6,500
491
16,565
11,451
52,179
2,489
38,142
495
508
7,723
30,744
12,361
69,961
69,961
5,398
3,319
984
1,060
8,972
815
1,210
19,279
10,328
210
4,278
11,235
17,647
7,007
33,840
41
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
WA PASCO
WA PORT TOWNSEND
WA PT ANGELES
WA PUYALLUP
WA REARDON
WA ROSLYN
WA SEATTLE
WA SNOHOMISH
WA SPOKANE
WA SUMNER
WA TACOMA
WA VANCOUVER
WA WALLA WALLA
WA WENATCHEE
Wl CHIPPEWA FALLS
Wl CLINTONVILLE
Wl EAU CLAIRE
Wl KENOSHA
Wl MARINETTE
Wl MILWAUKEE
Wl NEKOOSA
Wl OCONTO CITY
Wl OSHKOSH
Wl RACINE
Wl RICE LAKE
Wl SHOREWOOD
Wl SUPERIOR
PRIMARY
RECEIVING WATER
SACAJAWEA LAKE
ST OF JUAN DE FUCA
ST OF JUAN DE FUCA
PUGET SOUND ET.AL
SNOHOMISH RIVER
SPOKANE RIVER
WHITE RIVER
PUYALLUP RIVER
MILL CREEK
CHIPPEWA RIVER
PIGEON RIVER
CHIPPEWA RIVER
LAKE MICHIGAN
MENOMINEE RIVER
LAKE MICHIGAN
WISCONSIN RIVER
OCONTO RIVER
LAKE WINNEBAGO
LAKE MICHIGAN
RED CEDAR RIVER
LAKE MICHIGAN
LAKE SUPERIOR
1980CSO
POPULATION
SERVED (1)
1990 TOTAL
CITY POPULATION (2)
689
137
6,116
25,881
490
1,421
330,000
5,500
160,700
1,080
999
44,000
23,000
17,450
7,378
7,500
45,900
21,000
6,200
366,000
150
2,500
3,150
118,000
19
4,300
30,100
20,337
7,001
17,710
23,875
482
869
516,259
6,499
177,196
6,281
176,664
46,380
26,478
21,756
12,727
4,351
56,856
80,352
11,843
628,088
2,557
4,474
55,006
84,298
7,998
14,116
27,134
42
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
Wl WISCONSIN
WV BARBOURSVILLE
WV BECKLEY
WV BELINGTON
WV BENWOOD
WV BETHANY
WV BLUEVILLE
WV CAMERON
WV CHARLESTON
WV CHESTER
WV CLARKSBURG
WV CLENDENIN
WV EAST BANK
WV ELKINS
WV FOLLANSBEE
WV HANDLEY
WV HINTON
WV HUNTINGTON
WV HURRICANE
WV KENOVA
WV KEYSER
WV MALDEN
WV MARLINGTON
WV MARMET
WV MARTINSBURG
WV MCMECHEN
WV MONONGAH
PRIMARY
RECEIVING WATER
WISCONSIN RIVER
MUD RIVER
PINEY CREEK
TYGART RIVER
OHIO RIVER
BUFFALO-CREEK
TYGART RIVER
GRAVE CREEK
KANAWHA RIVER
OHIO RIVER
WEST FORK RIVER
ELK RIVER
CHELYAN
OHIO RIVER
KANAWHA RIVER
NEW RIVER
OHIO RIVER
OHIO RIVER
NORTH BRANCH POTOMAC
KANAWHA RIVER
GREENBRIAR RIVER
KANAWHA RIVER
OPEQUON CREEK
OHIO RIVER
WEST FORK RIVER
1980CSO
POPULATION 1990 TOTAL
SERVED (1) CITY POPULATION (2)
15,300
2,279
25,000
1,567
1,866
650
6,433
1,537
69,956
4,000
30,137
1,000
1,465
9,170
3,450
450
4,400
76,815
0
5,000
7,000
12,000
1,500
3,500
14,626
2,080
1,200
0
2,774
18,296
1,850
1,669
1,139
5,524
1,177
57,287
2,905
18,059
1,203
892
7,420
3,339
334
3,433
54,844
4,461
3,748
5,870
0
1,148
1,879
14.073
2,130
1,018
43
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
STATE COMMUNITY
WV MONTGOMERY
WV MORGANTOWN
WV MOUNDSVILLE
WV NEW CUMBERLAND
WV NITRO
WV NUTTER FORT
WV PARKERSBURG
WV PARSONS
WV PENNSBORO
WV PETERSBURG
WV PHILIPPI
WV POINT PLEASANT
WV RICHWOOD
WV RIDGELEY
WV ROWLESBURG
WV SCOTT DEPOT
WV SHINNSTON
WV SISTERSVILLE
WV SMITHERS
WV SOUTH CHARLESTON
WV SPENCER
WV SUMMERSVILLE
WV TERRA ALTA
WV WAYNE
WV WHEELING
WV WHITESVILLE
WV WILLIAMSON
PRIMARY
RECEIVING WATER
KANAWHA RIVER
MONONGAHELA RIVER
OHIO RIVER
OHIO RIVER
KANAWHA RIVER
ELK CREEK
OHIO RIVER
SHAVERS FORK
BUNNELLS RUN STREAM
S BRANCH POTOMAC RIVE
TYGART RIVER
OHIO RIVER
CHERRY RIVER
N BR POTOMAC RIVER
CHEAT RIVER
KANAWHA RIVER
WEST FORK RIVER
KANAWHA- RIVER
KANAWHA RIVER
SPRING CREEK
ARBUCKLE-CREEK-
SNOWY CREEK
TWELVE POLE CREEK
OHIO RIVER
BIG COAL RIVER
TUG FORK OF BIG SANDY
1980CSO
POPULATION
SERVE D(1)
1990 TOTAL
CITY POPULATION (2)
2,275
35,250
25,000
575
6,449
2,379
0
1,250
1,614
2,395
3,600
6,350
4,000
1,112
2,000
1,398
2,516
2,821
2,000
17,050
3,800
4,000
1,500
750
54,000
781
5,700
2,449
25,879
10,753
1,363
6,851
1,819
33,862
1,453
1,282
2,360
3,132
4,996
2,808
779
648
0
2,543
1,797
1,162
13,645
2,279
2,906
1,713
1,128
34,882
486
4,154
44
-------
COMMUNITIES WITH COMBINED SEWER SYSTEMS
1980CSO
PRIMARY POPULATION 1990 TOTAL
STATE COMMUNITY RECEIVING WATER SERVED (1) CITY POPULATION (2)
WY SHERIDAN GOOSE CREEK 14,645 13,900
US TOTAL (3) 42,289,122 44,308,986
(1) Source: 1980 Needs Survey, U.S. EPA
(2) Source: 1990 U.S. Census of Population, Bureau of the Census.
(3) Double counting has been eliminated in city total.
Note: Service area of sewer utility for named community does not necessarily correspond with
Census area associated with named community.
-------
Appendix B
INFORMATION SOURCES FOR STATE CSO WET WEATHER STANDARDS
GENERAL INFORMATION
Work performed by Jeff Albert of The Bruce Company under separate contract to EPA provided
general information for all of the state policies. Mr. Albert provided further information in a July
1991 telephone conversation (Natural Resources Defense Council, San Francisco, California, (415)
777-0220).
CALIFORNIA
State Water Resources Control Board, State of California Combined Sewer Overflow Control
Strategy. State of California, Sacramento, California.
Stephen A. Hill, Environmental Specialist, California Regional Water Quality Control Board, San
Francisco Bay Region, Oakland, California, (510) 464-0433. Telephone conversation, July 1991.
"City and County of San Francisco Wastewater Facility Improvements - Status Report," internal
memorandum from Stephen Hill to Steven R. Ritchie, California Regional Water Quality Control
Board, San Francisco Bay Region, August 23, 1991.
ILLINOIS
Tom McSwiggin, Manager, Water Pollution Permits Section, Illinois Environmental Protection
Agency, (217) 782-0610. Telephone conversation, 1991.
MASSACHUSETTS
"Massachusetts Water Quality Standards: Implementation Policy for the Abatement of Pollution
from Combined Sewer Overflows," May 24, 1990.
Glen Haas, Massachusetts Department of Environmental Protection, (617) 292-5500. Telephone
conversations, 1991.
MICHIGAN
Jim Beaver, Water Administrator, City of Grand Rapids, Michigan, (616) 456-3257. Telephone
conversation, July 1991.
Paul Blakesly, Michigan Department of Natural Resources, Lansing, Michigan, (517) 322-5755.
Telephone conversation, December 1991.
B-l
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OREGON
"Oregon's Strategy for Regulating Combined Sewer Overflows (CSOs)," State of Oregon Department
of Environmental Quality, February 28,1991.
"Department of Environmental Quality of the State of Oregon v. City of Portland," Stipulation and
Final Order No. WQ-NWR-91-75, before the Environmental Quality Commission of the State of
Oregon.
Barbara Burton, Department of Environmental Quality, State of Oregon, Salem, Oregon, (503) 229-
6099. Telephone conversations, 1991.
RHODE ISLAND
"Combined Sewer Overflow Policy," Rhode Island Department of Environmental Management,
Division of Water Resources, March 1990.
Save the Bay, Providence, Rhode Island, "A Raw Deal: Combined Sewer Overflow Pollution in
Narragansett Bay," Draft.
Kevin Brubaker, Save the Bay, Providence, Rhode Island, (401) 272-3450. Telephone conversation,
July 1991.
Jay Manning, Rhode Island Department of Environmental Management, (401) 277-3961. Telephone
conversations, 1991.
WASHINGTON
Ed O'Brien, Supervisor, Storm Water/Municipal Unit, Water Quality Program, Washington
Department of Ecology, (206) 438-7037. Telephone conversation, 1991.
WISCONSIN
Wayne Saint John, Milwaukee Metropolitan Sewage District, (414) 225-2141. Telephone
conversation, July 1991.
Jim Koster, Sewer Services Engineer, Department of Street and Sewer Maintenance, City of
Milwaukee, (414) 278-2160. Telephone conversation, July 1991.
VERMONT
Brian Kooiker, Chief of Direct Permits Section, Department of Environmental Conservation,
Vermont Agency of Natural Resources, (802) 244-5674. Telephone conversation, July 1991.
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