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Wastewater Treatment

King County, Washington

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: 206-477-5371
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Get Directions to our office location in Seattle, Washington.

Staff Contacts

South Magnolia CSO Control Project

Project Construction

August 27, 2014 Update -
King County’s contractor is continuing work on 32nd Avenue West to prepare for installation of a new gravity sewer pipeline that is a component of the new CSO facility in the Smith Cove area. Crews are currently preparing for drilling operations scheduled for this fall.

King County’s contractor is waiting for a permit from the City of Seattle to start shoring work to construct the drill pit on the east side of 32nd Avenue West. This work could begin any day and will be noisy. During this work, expect increased construction activity on the street.

Normal work hours begin at 7:00 a.m. and may extend up until 8:00 p.m. Traffic revisions are in place, and people should drive slowly through the project area here and watch for workers, other pedestrians, bikes and cars.

Project area for the South Magnolia CSO control project elements (diversion structure, gravity sewer, storage tank)
South Magnolia CSO basin project area
How will the new CSO facility work? View animation.

Project vicinity map
South Magnolia basin and project location.

Project description

King County is building a new gravity sewer pipeline and an underground storage tank in Magnolia. This facility will store peak combined sewer flows so that discharges of untreated wastewater and stormwater are limited to no more than one per year on a long-term average.

Why does King County need to do this project?

This project is included in a federal consent decree that requires completion by December 2015.

Project schedule

2014-2015 activities

Activities Dates
Pre-construction community meeting - storage January 30, 2014
Pre-construction community meetings - conveyance May 13 & 14, 2014
Construction 2013 - 2015

South Magnolia CSO Control Project Timeline, May 2013
View meeting calendar for upcoming public meetings, and South Magnolia CSO Control Project Timeline (PDF), updated May 2013.

Hotline - South Magnolia CSO Control Project
24/7 Construction Hotline: 206-205-0968
Leave a message, and a project team member will return your call.
Project contact: Monica Van der Vieren, 206-477-5502, or via feedback form.

Project updates

News releases

Related information