United States
      Environmental Protection
August 1993
      Office of Water
&EPA Combined Sewer
      Overflows In Your

      WHAT  I
Some cities collect both rainwater run-
off and sanitary wastewater in the same
sewer.  These are called "combined
sewers/'  Sometimes when it rains,
combined sewers do not have enough
capacity to carry all the rainwater and
wastewater or the treatment plant is
not large enough to treat the combined
flow. Jn these situations, the combined
wastewater overflows untreated  into
the nearest body of water—streams,
lakes, rivers, or estuaries, creating a com-
bined sewer overflow (CSO).

"CSO  controls protect your community's
 public health and its environment.

 For more  information on CSO strategy,
 policy and guidance, you can contact the
 U.S. EPA Water Management Division in
 your Region or the National Small Flows
 Clearinghouse, P.O. Box 6064, Morgantown,
 West Virginia (Toll Free: 1-800-624-8301).
U.S. EPA Region I
(CT, ME, MA, NH, HI, VT)
JFK Federal Building
Boston, MA 02203
(617) 565-3478

U.S. EPA Region II
(NJ, NY, PR, VI)
26 Federal Plaza
New York, NY 10278
(212) 264-2513
                      U.S. EPA Region VI
                      (AR, LA, TX, OK, NM)
                      1445 Ross Ave., Suite 1200
                      Dallas, TX 75202-2733
                      (214) 655-7101

                      U.S. EPA Region VII
                      (IA, KS, MO, NE)
                      726 Minnesota Avenue
                      Kansas City, KS 66101
                      (913) 551-7030
U.S. EPA Region III       U.S. EPA Region VIII
(DE, MD, PA, VA, WV, DC)   (CO, UT, WY, MT, ND, SD)
841 Chestnut Building      999 18th St., Suite 500
Philadelphia, PA 19107     Denver, CO 80202
(215)597-9410            (303)293-1542
U.S. EPA Region IV
(AL, GA, R, MS, NC, SC, TN, KY)
345 Courtland St., NE
Atlanta, GA 30365
(404) 347-4450

U.S. EPA Region V
(IL, IN, OH, MI, MN, WI)
77 W. Jackson Blvd.
Chicago, IL 60604
(312) 353-2145
                       U.S. EPA Region I
                       (AZ, CA, GU, HI, NV,
                       75 Hawthorne Stree
                       San Francisco, CA 9
                       (415) 744-2125
                       U.S. EPA Region X
                       (AK, ID, OR, WA)
                       1200 Sixth Avenue
                       Seattle, WA 98101
                       (206) 553-1793

The Clean Water Act requires the U.S. EPA and States to issue
permits for controlling discharges from CSOs.  The permit-
tees are responsible for implementing a series of minimum
CSO controls and, if necessary, developing and implement-
ing a long-term CSO control plan.
The minimum CSO controls basically require communities
to (1) fully utilize the existing capacity of wastewater collec-
tion and treatment systems through changes in operational
practices, (2) prevent pollutants from  entering the com-
bined sewers, and (3) install simple devices to remove solids
and floatable materials from the CSOs.  In some communi-
ties, the minimum controls may be adequate to achieve
water quality standards.
                                       bur screens
                                       at CSO
                                                                      When the CSOs are causing serious water pollu-
                                                                      tion, communities will need to take additional
                                                                      actions.  They will need to develop and imple-
                                                                      ment long-term  CSO control plans.

                                                                      These control plans require the identification,
                                                                      evaluation, and  implementation of various CSO
                                                                      control strategies to achieve water quality stan-
                                                                      dards by the communities. The U.S. EPA, State
                                                                      environmental  agencies,  water quality groups,
                                                                      and communities should work together to com-
                                                                      plete the long-term CSO control plans.

                               Separating storm waters from sanitary
                 Using basins or tunnels to store the
                 combined wastewater until the
                 treatment plant can handle it.
      The costs of CSO controls may be high in some
      communities, but low in others. The severity and
      frequency of the CSOs plus the local water quality
      standards will determine the types of CSO controls
      and their costs.
Even though the actual CSO control costs are un-
known for many communities, the U.S. EPA and
State agencies will work with the CSO communities
to find economically achievable solutions that will
improve public health and create a safer environ-
ment for everyone.

   THE   CSOS?
 Combined sewers serve about 43,000,000
 people in an estimated 1,100 communities.
 Most of the CSO communities are located
 in the Northeast and Great Lakes regions.
 More than three-quarters of the communi-
 ties are located in only 11 states.
              HOW  CSOS  AFFECT  YOU
             AND  YOUR  COMMUNITY
                                                           Community control ofCSOs is essential to presetting the public health
                                                             and the ecological balance of our streams, rivers, lakes, and oceans.
During dry weather, combined sewers carry
the community's wastewaters to the treat-
ment facilities. When it rains, however, and
CSOs occur, your health and environment
may be threatened by the untreated waste-
water that is discharged from the combined
sewers to your community's rivers, lakes,
streams, oceans, estuaries, and wetlands.
The main pollutants in CSOs are untreated
human and industrial wastes, toxic materi-
als like  oil and pesticides, and floating
debris washed into the sewer system. These
pollutants can affect your health when you
swim in CSO-polluted water or when you
eat fish  or shellfish contaminated by the
The pollutants in CSOs can cause a variety of diseases, ranging from dysentery to hepatitis. CSO pollutants ar
not just a human health concern. They can damage the environment for fish, shellfish, and other aquatic life