United States
             Environmental Protection
  Offioi of Water
EPA 832-F-94-002
April 1994
 ^_ ^^_       &.*fUK*i~
OCrA   Combined Sewer Overflow Control Policy:
             A Consensus Solution Ito Improve Water Quality

       The U.S. Environmental Protection
  Agency (EPA) is issuing a "Combined Sewer
  Overflow Control Policy" which establishes
  a national framework and provides guidance
  to communities and State/Federal officials
  for controlling combined sewer overflows
  (CSOs). The Policy calls for communities
  with CSOs to take immediate and long-term
  actions to address their CSOs. Rather than
  a one-size-fits-all mandate, the Policy
  provides communities with the flexibility to
  develop a workable, cost-effective solution
  to a major environmental problem.

       Given the high control cost and
  serious nature of CSOs, EPA decided to
  pursue a negotiated dialogue with all
  interested stakeholders in developing the
  Policy. Representatives of communities with
  CSOs, State officials, plus environmental
  and other interest groups joined EPA at the
  table and helped develop the consensus
  Policy. Endorsements have come from
  municipal and environmental groups alike.

        President Clinton's Clean Water
  Initiative recommends that the 1994
  amendments to the Clean Water Act (CWA)
  endorse the final CSO Policy.

  What are CSOs?

        CSOs are a remnant of the country's
  early infrastructure.  In the past, cities built
  sewer systems to collect both storm water
  and sanitary wastewater in the same sewer.
  These are called "combined sewers."
    CSOs are discharges of raw
       sewage, industrial and
   commercial wastes, and storm
  water. About 1100 communities,
    mostly in the Northeast and
    Great Lakes, have CSOs that
   serve a population of about 43
      During dry weather, combined sewers
carry wastewater to treatment facilities.
However, when it rains, combined sewers
may not have the capacity to carry all the
storm water and wastewater, or the
treatment plant may not be large enough to
treat  all of the combined flow.  In these
situations, some of the combined wastewater
overflows untreated into the nearest body of
water -- streams, lakes, rivers, or estuaries -
creating a combined sewer overflow
(CSO). These CSOs may pose risks to
your  health and environment.

Why are CSOs a problem?

      Since CSOs are comprised of raw
sewage, commercial and industrial wastes,
and storm water runoff, many different types
of pollutants may be present. The main
constituents of CSOs are untreated human
and industrial wastes, toxic materials like oil
and pesticides, and floating debris washed
Into the  sewer system from streets and their
drainage area. These pollutants can affect
your health when you swim in CSO-polluted
water or eat fish or shellfish contaminated
by CSOs.  CSO impacts on water quality are
unique to each location and may be
responsible for beach closures, shellfish bed
closures, fish kills, and other water quality
degradation in your community.

How are CSOs regulated?

      CSOs are considered to be "point
sources" of pollution under the Clean Water
Act (CWA). The CWA requires EPA and
States to issue permits for controlling point
sources, including discharges from CSOs.
National Pollutant Discharge Elimination
System  (NPDES) permits must be issued to
address CSOs.

      Permits are written to meet the water
quality standards for a particular
waterbody. Water quality standards are
State-adopted or Federally-promulgated
rules that serve as the goals for the
waterbody and the legal basis for NPDES
permit requirements under the CWA.

      For example, a waterbody may be
designated for a variety of recreational
activities (e.g., swimming, boating, fishing,
etc.), and standards are developed
 What are the key components
 of the Policy?
      EPA's CSO Policy ensures that
municipalities, permitting and water quality
standards authorities, and the public
engage in a comprehensive and
coordinated planning effort to achieve cost-
effective CSO controls and ultimately
comply with the Clean Water Act. The
Policy recognizes the site-specific nature of
CSOs and their impacts, and provides the
necessary flexibility to tailor controls to local
situations. Key components include:

      Municipalities should  immediately
      implement the nine minimum
      controls (see box on next page);
      Municipalities should  use a
      targeted approach, giving the
      highest priority to environmentally
      sensitive receiving waters;
      Municipalities, in cooperation
      with EPA, States, environmental
      agencies, and water quality
      groups, must develop long-term
      CSO control plans. These plans
      should identify and evaluate various
      control strategies, and lead to
      selection of an approach that is
      sufficient to meet water quality
      States may decide to review and
      revise, as appropriate, State water
      quality standards during the CSO
      long-term planning process.
      The financial capability of
      municipalities may be considered
      when developing schedules for
      implementation of CSO  controls.
      Public participation is  essential
      throughout all CSO planning and
      implementation efforts.

      The Policy also provides flexibility to
accommodate^jpgoing or completed CSO
projects, the special needs of small
communities, and watershed planning.

How expensive are CSO control

      Past CSO proposals have carried
national price tags as high as $160 billion or
more. The negotiated Policy has reduced
that cost to $41 billion, a substantial
savings. CSO costs may be high in some
communities, but low in others. The severity
and frequency of CSOs, plus the local water
quality standards, will determine the types of
controls that are neecjed and their costs.

      EPA recognizes that financial
considerations are often a major factor
affecting the implementation of CSO
controls. For that reason, the Policy allows
consideration of a community's financial
capability in connection with the long-term
CSO control planning effort, water quality
standards review, and enforcement actions.
However, communities are ultimately
responsible for aggressively pursuing
financial arrangements for implementation of
the minimum controls and the long-term
CSO control plan.

      EPA and State agencies will work
with CSO communities to find/economically
achievable solutions that will improve public
health and create a safer environment for

How will the Policy be enforced?

      Elements of the Policy will be
incorporated into National Pollutant
Discharge Elimination System (NPDES)
permits or other appropriate enforceable
      The enforcement portion of the Policy
indicates EPA's intent to commence an
enforcement initiative immediately against
municipalities that have CSOs that occur
during dry weather.  It also provides
guidance on the enforcement of the wet-
weather elements of the Policy.
 Nine Minimum Controls

      Communitfes should immediately
 Implement the Mowing minimum controls:
 1.    Proper operation and regular
      maintenance programs for the
      sewer system and CSOs;
 2..    Maximum use of the collection
      system for storage^
 3,    Review and modification of
      pretreatment requirements to
      assure CSO impacts are minimized;
 4,    Maximization of flow to the
     -'municipal sewage treatment plant
      for treatment;:
 5.    Prohibition of CSOs during dry
 ft*    Control of solid and floatable
      materials in CSOs;
 ?l    Pollution prevention,*
 8.    Public notice to ensure that the
      public receives adequate
      notification of CSO occurences
      and impacts; and
 9.    Monitoring to effectively
      characterize CSO impacts and the
      efficacy of CSO controls.
 For more information
       For copies of the CSO Control
 Policy, please contact the Office of Water
 Resource Center in Washington, DC, at
 (202) 260-7786. Or write:
       Office of Water Resource Center
       US EPA, Mailcode RC-4100
       Washington, DC 20460

            Diagram of a Combined Sewer System

           T%          During Wet Weather

This diagram shows how domestic wastewater (sewage),
industrial and commercial wastes and storm water are
collected in the same sewer pipes in a combined sewer
system. During dry weather, all of this wastewater should
be carried to the wastewater treatment plant for treatment.
But when it rains, some of the combined wastewater
overflows untreated into the nearest receiving water,
causing a combined sewer overflow.
                                         Industrial Wastswate
      Domestic Wastewater
                                                     Catch Basin
                                                             Excess Wet Weather Flow
                                                                  to Overflow Point
                Storm Water and Dry Weather Row
                Drops to Interceptor
                                               Combined Sewer Overflow