skip to main content
Capital improvement projects

For questions about the Wastewater Treatment Division website, please send an e-mail message or contact us at:

King Street Center
201 S. Jackson St., Suite 500
Seattle, WA 98104-3855
Phone: 206-684-1280
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Get Directions to our office location in Seattle, Washington.

Staff Contacts
Puget Sound shoreline next to the West Point Treatment Plant, Seattle

On-site treatment – providing primary treatment for flows exceeding system capacity during large storms

Treat Peak Flows
View handout (PDF file)

Local CSO treatment facilities are built in the vicinity of an existing CSO outfall to treat and disinfect peak flows before they are discharged into Puget Sound.

Key considerations

  • Facility serves a local area
  • High-rate process provides treatment in small footprint
  • Sufficient space is required in vicinity of an outfall
  • Permitting requirements for facility can be rigorous