U.S. Environmental Protection Agency - October 2007

FY08 - FY10 Compliance and Enforcement National Priority

Clean Water Act, Wet Weather, Sanitary Sewer Overflows

What is the Environmental Problem?

Properly designed, operated, and maintained sanitary sewer systems are
meant to collect and transport all of the sewage that flows into them to
a publicly owned treatment works (POTW) for treatment.  However,
releases of raw sewage from municipal sanitary sewers can occur in these
systems.  These types of releases, called sanitary sewer overflows
(SSOs), may be caused by poor sewer collection system management, and
often pose a substantial risk to public health and the environment.

The main pollutants in raw sewage from SSOs are bacteria, viruses,
pathogens, excessive nutrients, industrial wastes, toxic pollutants such
as oil and pesticides, and wastewater solids and debris.  SSOs are of
special concern to public health because they expose citizens to
bacteria, viruses, intestinal parasites, and other microorganisms that
can cause serious illness such as cholera, dysentery, hepatitis,
cryptosporidiosis, and giardiasis.  Sensitive populations - - children,
the elderly and those with weakened immune systems - - can be at a
higher risk of illness from exposure to sewage from SSOs.

The most common effects of sewage-related illness are gastroenteritis,
which is an infection of the gastrointestinal tract, skin rashes, and
infection of open cuts.  Gastroenteritis affects the entire
gastrointestinal tract, including the stomach and small and large
intestines.  Symptoms typically include abdominal cramps, watery
diarrhea and vomiting which can last from one to ten days, depending on
the severity of the illness and the sensitivity of the individual. 
Infected cuts and rashes can become swollen and red, and in some cases
can result in septicemia or blood poisoning.  Although symptoms can be
treated, no curative medical treatment is available for some
sewage-related illnesses.         

The untreated sewage from SSOs can contaminate waters, in some cases
causing serious water quality problems and threats to public health. 
SSOs may also occur in basements, parks, recreational streams, beaches,
on city streets and backyards, and other areas where people are in close
contact with the overflow.  The public can be exposed to raw sewage from
SSOs through street flooding, recreational contact such as swimming and
fishing, drinking contaminated water and collection system back-ups into
homes.  It is important to note that the threat to public health and the
environment posed by SSOs is not necessarily limited to large volume or
extended-duration overflows.  Some of the greatest threats from SSOs
stem from viruses and pathogens which can present a public health threat
even in small volume, intermittent overflows.

 

Why is EPA Addressing the Problem?

The non-compliance universe of municipal authorities experiencing SSOs
is constantly being updated.  However, empirical data indicate that
there is a significant non-compliance problem.  EPA estimates that
nationally there may be 25,000 to 89,000 SSOs each year.  Further, it is
estimated that there are anywhere from 3 to 10.6 billion gallons of SSO
discharges per year. [The 2004 Report to Congress on the Impacts and
Control of CSOs and SSOs (2004 RTC).] 

Because of the estimated high number of SSOs occurring each year, and
the adverse effects on public health and the environment and the current
level of impaired waterways, the focus on reduction or elimination of
SSOs could result in significant benefits to public health and the
environment.  EPA believes the number of SSOs can be dramatically
reduced through proper management, operation, and renewal of sewer
infrastructure. 

The federal government has an interest in the protection of public
health and in the condition of the U.S. infrastructure of collection
systems and sewage treatment capacity.  Many of the systems were built
with federal dollars.   The federal government has the ultimate
responsibility for writing permits for sewage treatment plant discharges
and must also ensure compliance with the NPDES program and with
individual / general permits.

How Will The Problem Be Addressed?

SSOs have a variety of causes, including but not limited to severe
weather, improper system design and/or inadequate capacity, improper
management, operation and/or maintenance, and vandalism.  Of these
causes, the most common related to SSOs are inadequate capacity,
improper management, and improper operation and maintenance of sanitary
sewer collection systems.  In FY 2008 - FY 2010, EPA and the States will
continue to address these problems using various derivatives of the
capacity, management, operation and maintenance (CMOM) concept which
encourages the use of self-assessments and pro-active correction of
system deficiencies to avoid further deterioration of the sanitary sewer
infrastructure and resultant SSOs.  In some cases, EPA and the States
will use a combination of administrative and civil judicial enforcement
action to achieve these goals.

Highlights from the FY 2005-2007 Planning Cycle

One of the primary goals under the first cycle of the strategy
(FY2005-FY2007) was to protect the public investment in wastewater
infrastructure by ensuring municipal collection systems have sufficient
capacity and use proper asset management, operation, and maintenance
practices.  EPA and the states made a great deal of progress in the
first cycle addressing many of the medium and large municipal
authorities targeted under the strategy.  For example, EPA issued 31
administrative compliance orders for SSOs during the first cycle of the
strategy.  In addition, EPA concluded 16 SSO judicial case settlements
during the first cycle of the strategy.  States have been co-plaintiffs
in the vast majority of these cases.  The injunctive relief required by
three of these judicial case settlements alone will result in the
reduction of SSOs estimated at 290 million gallons annually (Louisville,
KY (218 MG); Los Angeles, CA (46 MG); Washington Suburban Sanitary
Commission, MD (26 MG).    

Final: SSO Summary		October 2007

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