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Despite Progress, Sewer Overflows Still Pose Health and Environmental Concerns, EPA Reports

Release Date: 08/26/2004
Contact Information:

Contact: John Millett 202-564-7842 /

(Washington, D.C. - August 26, 2004) In a comprehensive report to Congress, EPA finds that further control of sewer overflows is vital to reducing risks to public health and protecting the environment from water pollution. EPA concludes that adequate funding, integrated local and regional watershed protection programs, improved water quality monitoring and reporting, and stronger partnerships among all levels of government, industry, and citizens will be needed to make further progress.

Report to Congress: Impacts and Control of CSOs and SSOs focuses on two types of discharges from municipal wastewater systems – combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs) – and summarizes what is known about the characteristics of CSOs and SSOs, the human health and environmental impacts of CSOs and SSOs, and the resources spent and technologies used by municipalities to reduce the impacts of CSOs and SSOs.

Since passage of the Clean Water Act in 1972, EPA, states and local water pollution control agencies have undertaken numerous actions and initiatives to reduce CSOs and SSOs. A combination of regulations, standards, federal funding, technical guidance and policies are currently in place. In April 1994, EPA issued the CSO Control Policy – a national strategy to achieve cost-effective CSO controls that meet health and environmental objectives and requirements. Under the Clean Water Act, SSOs that reach waters of the United States are prohibited unless authorized by federal or state permitting authorities. SSOs, including those that do not reach waters of the United States, may indicate improper operation and maintenance of the sewer system, and may also violate federal or state permits.

Sewer overflows are environmental enforcement priorities for EPA. Since 1998, EPA has concluded 15 CSO enforcement cases and 25 SSO enforcement cases, including more than $14 million in civil penalties and $11 billion in injunctive relief to protect public health and the environment. CSO and SSO enforcement against seven major municipalities alone has resulted in the elimination of approximately 14 billion gallons of sewage overflows per year, more than $10.8 million in fines and more than $75 million in environmental improvement projects. Since 2002, EPA has settled sewer overflow cases with Los Angeles, Calif., Baltimore, Md., Baton Rouge, La., and Hamilton County/Cincinnati, Ohio.

CSOs occur at combined sewer systems that were built in the late 19th and early 20th centuries in U.S. cities located mainly in the Northeast and the Great Lakes region. These systems were designed to discharge directly into rivers, streams or coastal waters when the combined volume of sewage and storm water exceeds the capacity of the system. Sanitary sewer systems do not combine storm water with wastewater. SSOs have a number of causes: blockages, pipe breaks, defects that allow storm water or groundwater to enter the system, inadequate operation and maintenance, equipment or power failures, and vandalism.

CSOs and SSOs contribute to beach closures, shellfish bed closures, contamination of drinking water supplies, and other environmental and public health concerns because they discharge untreated wastewater that contains microbial pathogens, suspended solids, toxics, nutrients, trash, and pollutants that deplete dissolved oxygen. For the first time with this report, EPA used currently available data and health effects modeling methods to estimate the number of gastrointestinal illnesses linked to sewer overflows. For beaches that are regularly monitored, EPA estimates that about 3,500 to 5,500 gastrointestinal illnesses per year are caused by CSOs and SSOs. This data is available for only coastal and Great Lakes beaches. EPA cannot calculate a national estimate of the human health impacts of CSOs and SSOs because sufficient water quality and health effects data is not currently available for all recreational swimming areas in the United States.

In 31 states and the District of Columbia, 772 combined sewer systems annually discharge an estimated 850 billion gallons of untreated wastewater and storm water, according to the report. There are about 19,000 municipal sanitary sewer collection systems in the United States. These systems serve 160 million people in the United States, roughly 58 percent of the nation’s population. EPA estimates that between 23,000 and 75,000 SSOs occur annually, discharging a volume of three to 10 billion gallons. Municipal treatment facilities annually collect and discharge more than 11 trillion gallons of treated wastewater. According to EPA’s 2000 Clean Water Needs Survey (, over the next 20 years, approximately $50.6 billion will be needed to reduce CSO volume by 85 percent, and $88.8 billion will be required to control SSOs.

In addition to fulfilling a 2000 congressional request for information on CSO and SSO health and environmental impacts, resources spent, and overflow control technology, the report provides extensive new information to guide EPA, state and municipal efforts to further reduce sewer overflows. For more information and a copy of the report, go to: .