Water System

The City owns its water supply system, fed by two pristine reservoirs in the Cascade Mountains. From 1910 to 1997, the Water Department oversaw the water system before the agency’s absorption by Seattle Public Utilities. The Engineering Department constructed, and the Department of Streets and Sewers managed, Seattle's drainage and sewage infrastructure from 1896 to 1936. The Engineering Department assumed sole management from 1936 to 1997 (except for the transfer of sewage treatment facilities to METRO in 1961), and Seattle Public Utilities took over in 1997.

Water Supply

After the Great Fire of 1889, citizens voted to fund the creation of a municipally-owned water system. The City purchased private suppliers that drew primarily on Lake Washington and ground water sources. As these sources became increasingly inadequate and unsanitary, Seattleites financed the purchase of the upper Cedar River Watershed and construction of a gravity-powered water transport and storage facilities. Fifty years later, demand exceeded Cedar River supply, and the City purchased and built a second Cascades supply in the Tolt River Watershed. Seattle supplies fresh water to over 1.35 million people in the greater metropolitan area, either directly or through surrounding cities and water districts.

Cedar River Pipeline Number 1 under construction on hill east of Renton, 1899 (Item 7261)
Seattle built a 28.5 mile pipeline that delivered Cedar River water to the Volunteer Park and Lincoln Reservoirs on Capitol Hill.



Aerial of Masonry Dam, 2009
The Masonry Dam diverts water from Masonry Pool to the City Light plant 620 feet below at Cedar Falls for hydroelectric generation.




City Water testing laboratory, 1948 (Item 41114)

In-City Facilities

Seattle built and maintains an extensive network of pipelines and water mains, tunnels, reservoirs, and water towers within the city limits and in adjoining suburban communities to the north and south.



Lincoln Park pumping station, 1929 (Item 6911)

Replacing wooden water main with concrete on Federal Avenue, 1957 (Item 54263)




Standpipe and gate house in Volunteer Park, 1910 (Item 52058) 

Sewers and Drainage

Prior to 1890, Seattle relied on a haphazard assortment of sewers and cesspools that, at best, drained into surrounding lakes and salt water. Faced with recurring threats of waterborne diseases including typhoid and cholera, City Engineer Benezette Williams designed the Seattle's first centralized combined sewage system plan in 1891. This plan sought to remove as much city sewage as possible into the salt water of Elliott Bay and the Puget Sound with more limited drainage into the fresh water of Lake Washington. Although originally untreated, the City undertook a succession of steps starting in the late 1910's to remove solids, begin primary sewage treatment, and eventually separate storm water from raw sewage. Metropolitan King County took over the City's wastewater treatment responsibilities in the 1960's, but Seattle continues to manage its network of storm sewers.

North trunk sewer siphon tunnel, 1913 (Item 6229)

Holly Street Outfall extended into Lake Washington, 1930 (Item 47035)

Lake City water treatment plant, 1955 (Item 52379)

Sewer break at 5th & Washington, 1921 (Item 12950)