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The Project

Impacts & Timeline

How construction occurred

Much of the construction that occurred in the public right-of-way on this two-mile project has been completed in the last three-and-a-half years. Pipe installation, street, sidewalk and landscape renovation is complete on South Henderson Street from Lake Washington west to M.L. King Jr. Way S.

The project alignment begins in the north at the Henderson Pump Station at Seward Park Avenue South and South Henderson Street. It ends on East Marginal Way South near the Duwamish Waterway.

Most of the open-cut sewer installation for the Henderson/ML King CSO Project was completed along South Henderson Street and South Norfolk Street.

Work on the project's six tunnels required heavy construction equipment, installation of open-cut pipelines, tunnel boring, deep shaft excavation and related earth moving.

Click on the image below to view a short description of each major segment of construction and to see sketches of the above-grade tunnel inlet and outlet regulators.

Under way since September 2002, the project was completed in August 2005. The last year of construction consisted primarily of completing the two key regulator stations at each end of the CSO storage tunnel. The project's six tunnels were completed in early 2004, and open-trench work on South Norfolk Street and South Henderson Street was finished in late 2003.

Questions? Contact the project's construction hotline at 206-684-1251 (TTY 711) or e-mail us.

Henderson / M.L. King CSO Project
King Co. Wastewater Treatment Division
201 South Jackson, Suite 503
Seattle, WA 98104

Updated: Oct. 21, 2005