CSO treatment facilities
Combined sewer overflow (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.
In addition to the West Point Treatment Plant, King County has four local CSO treatment facilities (and a fifth one under construction). King County has also built a road-side raingarden in West Seattle to control CSOs.
Under construction: Georgetown Wet Weather Station (coming online in 2022).