U.S. Environmental Protection Agency - October 2007

FY08 – FY10 Compliance and Enforcement National Priority

Clean Water Act, Wet Weather, Combined Sewer Overflows

What is the Environmental Problem?

Combined sewer systems (CSSs) are designed to collect storm water
runoff, domestic sewage, and industrial wastewater in the same pipe and
transport it to a sewage treatment plant, where it is treated and then
discharged to a water body.  During periods of rainfall or snowmelt,
however, the wastewater volume in a combined sewer system can exceed the
capacity of the sewer system or treatment plant.  When the capacity of
the system or the treatment plant is exceeded, the excess wastewater
overflows directly into nearby streams, rivers, or other water bodies,
typically causing the receiving water not to meet water quality
standards.  Combined Sewer Overflows (CSOs) are primarily caused by wet
weather events, when the combined volume of wastewater and storm water
entering the system exceeds the capacity of the CSS or treatment plant. 
Overflow frequency and volume varies from system to system and from
outfall to outfall within a single CSS.  Discharges from a CSS during
dry weather, referred to as dry weather overflows, are prohibited under
the NPDES program.  

Annual untreated discharges from CSOs are estimated to be 850 billion
gallons.  When full implementation of the measures described in EPA’s
1994 Combined Sewer Overflow Control Policy is achieved, the Office of
Water estimates that approximately 160 billion gallons of untreated CSOs
would be discharged annually from CSSs.  This is a volume reduction of
approximately 80%. Typical pollutants found in CSOs include total
suspended solids (TSS), metals, bacteria, viruses, nutrients,
oxygen-demanding compounds and other pollutants washed from city streets
and parking lots.  CSO impacts include adverse human health effects
often due to recreational exposure, (e.g., gastrointestinal illness),
beach closures, shellfish bed closures, toxicity for aquatic life, and
aesthetic impairment.  

There are approximately 836 permits for an estimated 772 CSS
communities.  Affected communities are located in 32 states (including
the District of Columbia), primarily concentrated in the Northeast and
Midwest, and serve approximately 46 million people.  Of these systems,
181 are located in population centers greater than or equal to 50,000
(representing approximately 22% of the total number of CSO permits).  

Why Are We Addressing this Problem?

EPA’s 1994 Combined Sewer Overflow Control Policy (59 FR 18688) (CSO
Policy) provides a comprehensive national strategy to ensure that CSO
communities, NPDES permit authorities, water quality standards
authorities, EPA and the public engage in a coordinated planning effort
to achieve cost-effective CSO controls that ultimately meet the
requirements of the CWA.  The CSO Policy establishes objectives for CSO
communities:  (1) to implement the nine minimum controls (NMCs) and
submit documentation on NMC implementation; and (2) to develop and
implement a long-term control plan (LTCP).  CSS operators were expected
to implement the NMCs and to submit appropriate documentation no later
than January 1, 1997.  The 2004 Report to Congress on the Impacts and
Control of CSOs and SSOs (2004 RTC) stated that 94% of the active CSO
permits required implementation of the NMCs.   In addition to
implementing the NMCs, CSO communities are expected to develop and
implement an LTCP that includes measures to provide for attainment of
water quality standards.  LTCP implementation schedules are expected to
include project milestones and a financing plan for design and
construction of necessary controls as soon as practicable.  The 2004 RTC
indicates that implementation of enforceable LTCPs has not been achieved
for the vast majority of combined sewer systems nationally.  Thus,
OECA’s focus is to increase the universe of CSO communities
implementing enforceable LTCPs.

How is OECA Addressing the Problem?

OECA’s primary focus for the FY08-FY10 CSO Performance-based Strategy
is to ensure that communities representing significant population
centers are making appropriate progress towards addressing their CSO
problems and violations.  In addition, CSO communities in non-compliance
and causing environmental or human health risks warranting Federal
attention need to be addressed.  Appropriate EPA actions to achieve
compliance with the CSO Policy include taking appropriate, enforceable
steps to address combined sewer overflow problems and violations through
implementation of enforceable LTCPs.  Critical steps to achieving these
goals include:  (1) targeting violators posing significant risks and
conducting effective compliance monitoring activities and
investigations; (2) using the appropriate administrative or judicial
enforcement forum to achieve compliance and associated environmental
improvements; and, (3) effectively providing compliance assistance.  

Because enforcement actions involving CSO violations are often highly
complex and resource-intensive for EPA and authorized states, this
strategy also emphasizes the need for effective coordination of Federal
and state resources.  In 2005, EPA and a group of interested states
formed a joint workgroup to provide clarity on when the federal
government would pursue enforcement actions in CSO and SSO cases.  These
guidelines for Federal involvement include situations where:  (1)
significant environmental impact is occurring due to noncompliance and
has not been addressed adequately; (2) CSO violations have occurred
which may impact watersheds that cross state or international
boundaries; (3) violations of EPA orders or consent decrees exist; and
(4) a state requests that EPA take an enforcement action.

Highlights from the FY 2005-2007 Planning Cycle

  SEQ CHAPTER \h \r 1 Since EPA issued its Combined Sewer Overflow (CSO)
Control Policy on April 19, 1994, it has focused its attention on
bringing communities with combined sewer systems designed to collect
storm water runoff, domestic sewage, and industrial wastewater into
compliance with the Clean Water Act, through judicial and administrative
enforcement, and through compliance assistance.  As a result of EPA’s
actions during FY 2005 and FY 2006, an estimated 51.6 million pounds of
pollutants have been reduced, treated or eliminated, and 50 sewage
outfalls within 1 mile proximity of a drinking water intake have been
addressed so that drinking water is protected from waterborne pathogens
known to spread serious diseases, including gastroenteritis, cholera,
and typhoid.  In the judicial arena, States have often participated as
co-plaintiffs, and EPA intends to continue to work closely with States
in bringing enforcement actions.  The more significant of the six
federal judicial settlements (Judicial Consent Decrees) concluded in FY
2005 and FY 2006 include decrees in the District of Columbia, (District
of Columbia Water and Sewer Authority), (entered in March 2005), and
Louisville, Kentucky, (entered August 2006).  In FY 2007, the
settlements in CSO cases include decrees in the following cases: 
Indianapolis, Indiana, (entered December 2006), Greater Lawrence
Sanitary District (GLSD), Massachusetts, (entered January 2007), and
Sanitation District of Northern Kentucky, (entered April 2007). 

Final: CSO Summary		October 2007

 PAGE   

 PAGE   1 

