Combined Sewer Overflows (CSOs) are an overflow of sewage and stormwater into Puget Sound. They occur as a direct result of stormwater entering the sanitary sewer system. Stormwater entering the sanitary sewer system uses the available system capacity and as the pipes fill and wastewater pump stations reach their capacity a CSO event can occur.
Bremerton completed its CSO Reduction program in 2009 with an investment of more than $50 million that achieved a 99.9% reduction in CSO events and volume. The city continues to improve the combined sanitary sewer system in an effort to eliminate CSOs and reduce operating costs. The following animations demonstrate how a single property can impact the sanitary sewer system when stormwater is allowed to enter.