Protecting Our Waters program library
King County CSO Control Program documents and resources
Protecting Our Waters is King County’s program to prevent pollution caused by excess stormwater in the sewer system on rainy days. Relief points called combined sewer overflows (CSOs) are built into sewer systems that carry sewage and stormwater in the same pipe.
CSOs can release polluted water into waterways during heavy rains. They are needed to prevent sewer backups and flooding. A controlled CSO overflows no more than one time each year, on long-term average.
Below are a number of documents, reports, studies, maps, and resources related to the Protecting Our Waters CSO Control Program.
Protecting Our Waters documents
King County’s Wastewater Treatment Division (King County) prepares an annual report on its combined sewer overflow (CSO) control program and what happened at each of King County’s 38 CSOs over the past year. This report is submitted to the Washington State Department of Ecology (Ecology) and the U.S. Environmental Protection Agency (EPA).
Reports are available dating back to 1987.
Protecting Our Waters projects are planned and prioritized years in advance. The County reviews the program and updates the plan every 5 years.
In 2013 King County signed an agreement with the U.S. Department of Justice and the Environmental Protection Agency (EPA). This agreement, called a “consent decree,” requires King County to complete its CSO control plan by 2030.
Additional studies and reports
This report documents the quality of the water released from each of King County’s CSOs and the quality of the underwater soils near them.
|Comprehensive Sediment Quality Summary Report for CSO Discharge Locations||Dec 2009||22.8MB|
|Effluent quality||Dec 2009||10.1MB|
|Sediment quality||Dec 2009||3.8MB|
|Effluent and sediment quality||Dec 2009||1.5MB|
This study was completed in 1998 with help from a large stakeholder group and the Water Environment Research Foundation and describes the effects of CSOs on the Duwamish River and Elliott Bay. A new Water Quality Assessment and Monitoring Study began in 2013.
|Volume 1: Overview and Interpretation||Feb 1999||8.4MB|
Appendix B1, subappendices G through K are available upon request
|Volume 2: Public Information Document||Aug 1999||4.2MB|
|Volume 3: Stakeholder Committee Report||Jan 1999||224KB|
|Volume 4: WERF Peer Review Committee Report (not available online)|