What is a CSO? A combined sewer is built to convey dry weather sanitary flow and both sanitary and storm water during a wet weather period. Surface water flows into a storm drain lateral (A) with wastewater from a sanitary lateral (B) to a combined sewer (C). The "first flush" is diverted to the interceptor sewer by a weir (D) and flows to the wastewater treatment plant. The overflow (E) goes to a lake, river or stream, where a large volume of water dilutes it.

Diluting sanitary/storm overflows by discharging them into a large volume of fresh water, such as Lake Erie, was a practical means of disposal in the 1960s. But in the 70s, the discharge from combined sewer overflows and industry began to noticeably pollute the environment, and congress, responding to the public outcry, passed the Clean Water Act in 1972 to regulate the levels of discharge into the nation’s rivers, lakes and streams.

Avon Lake’s Combined Sewer Overflow, Long Term, Control Plan
Anticipating further regulation, the City of Avon Lake and Avon Lake Municipal Utilities immediately began to separate the combined sewers and by 1974 had a City Master Sewer Plan in effect that would eliminate dry weather CSOs. By 1994 congress established a CSO Control Policy to provide guidance and authorize states to issue permits limiting the levels of overflow cities could discharge into the environment. It also ensured the public would be involved in the implementation of CSO management practices and controls.

In May of 2001, Avon Lake City Council authorized the City Engineer to begin requesting engineering service proposals for the design and construction of the Avon-Belden Road Combined Sewer Separation. The following March, the Municipal Utilities began negotiating a contract with Brown & Caldwell, a nationally recognized engineering firm specializing in CSO control planning, to develop a long term plan required by the State of Ohio EPA and USEPA.

Avon Lake’s Long Term Control Plan was introduced to the public at a meeting in the community library in January 2003. Sewer separation began in June on Moore Rd. Chief Utilities Executive John Kniepper observed that Avon Lake still has a number of Lake Erie outlets impacted by the discharge of overflows. "Every time it rains sewage goes into Lake Erie," he said.

Designed to meet present requirements of the Clean Water Act, the plan will lessen future impact of overflows on the environment. It has a phased approach that considers the financial burden to the community. The plan is site-specific to Avon Lake, addressing the sensitive areas at Heider Ditch, the beach, and the water plant’s intake in Lake Erie. Alternative measures to sewer separation, such as storage/treatment, infiltration/inflow reduction, floatables control, and increasing treatment at Avon Lake’s Water Pollution Control Center, are also being considered. The WPCC presently has capacity to receive and treat any additional flow generated by the plan.

Scope of the work involved creating a computerized hydraulic model, collecting and calibrating data, projecting flows in wet weather conditions, developing size and cost/performance alternatives, and weighing the advantages and disadvantages to a site-specific plan.

Thanks to the foresight of the Board of Municipal Utilities and the City Council Sewer Committee, Avon Lake has a Master Sewer Plan in effect that is way ahead of the requirements for CSO Control.

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