Increasing CSO treatment capacity

CSO treatment facilities are designed to provide primary treatment (physical settling of solids), disinfection (usually chlorination), and dechlorination of CSOs. They are built to directly serve the area where they are located. Unlike the West Point Treatment Plant, these facilities operate only during heavy rainfall. King County CSO treatment facilities include the Alki CSO Treatment Plant, the Carkeek CSO Treatment Plant, the Denny Way/Lake Union CSO Control System, and the Henderson/MLK Way/Norfolk CSO Control System. Many of King County's local CSO treatment facilities include a CSO storage tank or tunnel.

 
Elliot West CSO Treatment Facility

 
Carkeek CSO Treatment Facility