Wastewater/CSO History
Rainwater runoff in urban areas creates water quality problems related to both quantity and quality. Acres of impervious roofs, roads, driveways, and parking lots cover or replace vegetation and soil through which rainwater used to either soak directly into the ground or run slowly off into the streams of the watershed. Today, rain that falls on these surfaces usually makes its way into storm drains. For the parts of Bremerton served by a combined sewer system, rainwater from roof and storm drains enter the combined sewer system. The additional volume of stormwater will exceed the hydraulic capacity of the sewer system and cause a Combined Sewer Overflow (CSO). The CSO is discharged into the Port Washington Narrows in the Puget Sound.
The City's combined sewer collection system is over 75 years old in many areas and provides sewer service to approximately 40,000 people. Wastewater is collected from residential, commercial, and the Puget Sound Naval Shipyard. In 1997 the City of Bremerton discharged 122 million gallons of CSO, of which an estimated 10% was wastewater. That is around 12 million gallons of raw sewage with the other 110 million gallons coming from stormwater runoff from roof drains, driveway drain drains and from streets. A roof from a single home can discharge around 1,500 gallons of rainwater into the combined sewer system during a 1" rainfall event.
The City of Bremerton has 16 CSO sites, which discharge into Dyes Inlet, Port Washington Narrows, and Sinclair Inlet in Puget Sound. A key component to reducing Bremerton's CSO discharges is to disconnect roof downspouts that are now directly connected to the combined sewer system.
The City of Bremerton is an older city, constructed from the early 1900's on, where most of the residences and businesses were built before the 1960's. Since the 1980's City ordinances have prevented the connection of stormwater systems to the buildings sanitary sewer service lateral. The City has collected reliable CSO flow data since 1994, when the CSO Flow Monitoring System went on-line. It was soon apparent that there were points in the combined sewer system that received excessive amounts of roof drainage from private properties.
The City has been smoke testing and documenting connections (both private and municiple) to its combined and separate sewer systems. Connections consist from foundation, driveway, roof and various yard drains that were connected to the combined system when these houses were built back in the 30's to the 60's are the point of concern for this application. This grant/loan presents an opportunity to reduce water pollution by diverting downspouts from the combined and separated sewer collection systems to separate storm drains, surface systems, and/or subsurface systems. This will reduce CSO volume and the number of events per year and help to improve water quality around these sites.
