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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

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

Wastewater tutorial

Current wastewater system



 existing system


  • King County has over 250 miles of pipes and two treatment plants that serve most of the urban parts of King and south Snohomish Counties.

  • The wastewater system was built to follow natural drainage systems, so King County's system serves south Snohomish County as well.
History | Current Wastewater System | The Problem
The Solution | The Future