The City of Bremerton Combined Sewer Overflow (CSO) reduction program seeks to reduce discharges of sewage into the Puget Sound from our combined sewer system. Older cities were constructed with combined sanitary and stormwater conveyance systems that were designed to handle typical sewage and stormwater flows. However, during heavy rainfall events, stormwater entering the system exceeds the capacity, resulting in an overflow to the Puget Sound at a CSO outfall. The City has 15 designated CSO outfalls located throughout the City where CSO discharges can occur.
The City began planning for CSO reduction in 1989 to comply with WAC 173-245. In 1992, the Department of Ecology (Ecology) approved the City’s first CSO Reduction Plan. Over the following two decades, the City spent approximately $50 million separating the collection system, eliminating inflow and infiltration, reducing stormwater discharges on private properties into the system, and upgrading pump stations. Ecology determined that in February 2011, the City had fulfilled the obligations of the CSO Reduction Plan. Overall reduction by volume and frequency of events is 99% and compliance has been obtained at all 15 sites.
The City has continued to reduce CSO events by eliminating discharges to the sanitary sewer system when they are discovered, improving the collection system through cure-in-place-pipe lining of old sewer mains, and removing sewer lateral connections in the marine environment. Each year, the City submits a CSO Annual Report to Ecology which describes our ongoing monitoring activities, CSO events that have occurred that year (volume, location, and duration), and any activities that we have performed to reduce CSO events.