The City of Bremerton's Combined Sewer Overflow Reduction program was completed at the end of 2009. Overflow frequency reduction of more than 99% (from 600+/- events per year to less than 5) was achieved by evaluating every possible aspect of the operating sewer system. CSO reduction projects eliminated 4 overflow sites, installed separate stormwater sewers, increased pump station size and efficiency, and added system and treatment capacity. The remaining 15 sites are in compliance with regulations.
The downspout separation program, also known as the "Cooperative Approach to CSO Reduction" (Program)," focuses on reducing the amount of stormwater entering the sanitary sewer from private property. The City will continue to work with property owners and citizens of Bremerton to reduce the potential for CSOs and reduce sources of stormwater pollution. The Program was supported by a Washington State Department of Ecology (DOE) Centennial Clean Water Fund (CCWF) Grant and matching funds from the City of Bremerton. The Program also had a separate fund, from the Wastewater Utility, that provided financial incentives to residential property owners. This fund allowed the Program to pay residential property owners for separating their downspouts, up to an amount established by City Council Resolution and identified by a site assessment.
Why is it so important to separate stormwater from the sanitary sewer system?
Storm water entering the sanitary sewer system will cause the system to fill up beyond its capacity and can cause a CSO to occur. A CSO is a discharge of untreated, mixed wastewater and storm water that flows directly to Sinclair Inlet or Port Washington Narrows. A CSO only occurs when it rains and lasts for several minutes to several hours, depending on location, intensity and duration of the rain. By separating storm water from the sanitary sewer system and reducing infiltration of ground water and rainfall-induced infiltration into the system, we can eliminate CSOs from our community.
Click here to view animations that show how the sewer system operates during dry weather and during rain storms. These animations were created in an effort to provide a clear understanding of how the City's wastewater and stormwater sewer systems operate.
What has the City done to reduce CSOs?
The City has been reducing CSOs since 1987 when the United States Environmental Protection Agency (EPA) first required reduction of this source of water pollution. In 1992 the City completed its first CSO Reduction Plan and in 1994 the first major CSO reduction project began. The City completed all CSO Reduction Projects in 2009 at a cost of approximately $50 million. The City has achieved a 99% reduction in CSO volume from improvements which addressed storm water runoff in the City street rights-of-way and many residential and commercial properties.
What do private property owners need to do?
A Citywide sewer system assessment, completed in 2000, found that 60% to 80% of the remaining storm water entering the sanitary sewer system is from private property. To reduce the potential for a CSO event it is necessary to disconnect all possible storm water connections to the sanitary sewer system.
Why do private property owners need to be involved at all?
With one inch of rain, roof drainage from an average residential building alone can deliver approximately 1,500 gallons of rainwater to the sanitary sewer system. This has a very significant impact on the sanitary sewer system, and when there are 10 or 20 houses this extra water can easily exceed the design capacity of that sewer system and cause a CSO event.