CSO Solutions

by Teresa Austin, Asst. Editor; Civil Engineering Magazine, ASCE World Headquarters, 345 East 47th Street, New York City, NY.,


Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 2, Pg. 56-59


Document Type: Feature article

Abstract: EPA estimates that 1,200 cities have nearly 20,000 combined-sewer-overflow points in areas serving more than 43 million people. Their impact on waterways has become a national problem, yet only 328 cities have abatement plans on the drawing board or under construction. The problem was addressed in 1972's Clean Water Act, but was driven from the limelight by the need for secondary treatment. Now solving the problem could cost more than $100 billion. It was a good idea for its time: Construct an underground conduit system to carry sewage and storm runoff away from 19th century cities and into nearby waterways. Let nature dilute and treat the flow. As cities grew, however, nature was overwhelmed; local water quality dimished. Diversion chambers were then added to divert the sanitary (or dry-weather) flows to plants for treatment. This 20th century solution, however, left the 19th century problem. Treatment plants quickly reach capacity during a heavy storm. The excess, a combination of storm runoff and sanitary sewage, empties directly into public waters. Now EPA says the 1,200 cities with combined sewer overflow outfall must find a better solution for the 21st century.

Subject Headings: Combined sewers | Outfall sewers | Water pollution | Water quality | Environmental issues | Abatement and removal

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