Skip to main content
King County logo

Serving the region since 1956

In 1956, a group of local residents became concerned about the effect of rapid urban growth, especially the decline of water quality in Lake Washington and Puget Sound. Their activism and advocacy led to the formation of a wastewater treatment utility to serve the region.

Today, King County Wastewater Treatment Division provides services to 17 cities, 17 local sewer districts, and more than 1.5 million residents across a 420-square-mile area in King, Snohomish, and Pierce counties. Learn more about our history.