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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

North Beach CSO Control Project

Project Construction

December 18, 2014 Update 

The contractor had a successful concrete pour on Monday. They poured about 300 cubic yards of concrete, forming a part of the combined sewer overflow (CSO) tank base. The contractor had approval from the City of Seattle to work until 8 p.m., but crews were able to complete the pour within regular construction hours. The contractor arranged concrete deliveries earlier in the day, and thanks to nice weather and efficient work, were able to complete the pour quicker than planned.

Reminder: Work until 8 p.m. on December 23

View construction update (December 18, 2014).

View from inside the North Beach CSO storage tank in December 2014. Concrete will be poured into the metal framework to form the base of the tank.
View from inside the North Beach CSO storage tank in December 2014. Concrete will be poured into the metal framework to form the base of the tank. View more photos.


What progress have we made? What's next?
Download the Winter 2014 newsletter (PDF).

Intersection to remain closed

Intersection closure area in orange. Traffic pattern on NW 100th Street and NW Neptune Place.
King County, the Seattle Department of Transportation, and the County’s contractor have worked together to find an option for uninterrupted work in the right-of-way on the North Beach CSO Control Project. The street will remain closed until early 2015, when a temporary reopening is scheduled for three months. Learn more on the Work in the right-of-way page. 

Keep up to date on construction plans and activities
• Work in the right-of-way
• Work on King County’s property
• Traffic control

Project vicinity map
Project vicinity

North Beach Pump Station
North Beach Pump Station, located on King County property next to Blue Ridge Park, is built on the footprint of the former City of Seattle treatment plant.

Project description

King County is designing and building an underground storage tank in the right-of-way in N.W. Blue Ridge Drive and Triton Drive N.W. This facility will be able to store to 380,000 gallons of untreated water during peak flows when the North Beach Pump Station reaches maximum capacity.

Learn more about the project area and elements.

Why does King County need to do this project?

In 2008, King County reported that the North Beach combined sewer overflow facility had 10 overflows per year on long-term average that discharge a total of 2.2 million gallons into Puget Sound off North Beach. At North Beach, King County is working to meet current regulations set by the Washington Department of Ecology require no more than one untreated discharge per year on a long term average.

23 untreated discharges of stormwater and sewage at North Beach by the end of October 2014.
King County appreciates your patience as we continue building this mandated project.  

Construction schedule

This construction schedule is proposed and subject to change. Detailed construction schedules are being developed by King County’s contractor for the project, Stellar J Corporation.

Project schedule
Project schedule (updated December 2014).

Understanding the sewer system in North Beach

The North Beach Pump Station has provided wastewater service for the area since 1962 by collecting flows from the City of Seattle’s local sewer system. These flows are conveyed to the Carkeek Wet Weather Facility where they are either pumped to the county’s West Point Treatment Plant or, in large storm events, treated on site. The North Beach Pump Station is built on the footprint of what was once a City of Seattle treatment plant. The walls and foundation are from the original treatment plant.

Learn more: download Understanding the sewer system in North Beach, Winter 2014

Did you know?

  • The North Beach Pump Station is built on the footprint of what was once a City of Seattle treatment plant. The walls and foundation are from the original treatment plant.
  • When Metro was created by voters in 1958 to provide regional wastewater conveyance and treatment, local treatment facilities like the one in North Beach were considered for conversion to pump stations to bring flows to regional treatment facilities.
  • The current service area for the North Beach Pump Station is 633 acres. Wastewater from additional areas within Blue Ridge are conveyed by gravity to the North Beach force main, where they combine with pumped flows to the Carkeek Wet Weather Facility.
  • The North Beach Pump Station is largely built underground with access hatches and ventilation equipment above ground. Four pumps are used to convey up to 3 million gallons per day (mgd) of wastewater to Carkeek.
  • The CSO facilities include a deepwater outfall upgraded in the 1970’s from the outfall that served the original treatment facility. Discharge to a second outfall, which usually conveys stormwater, helps to prevent backups into homes in large storms.
  • The new CSO facility will introduce odor control at the North Beach site. Currently there is no odor control associated with the North Beach Pump Station. King County has not received odor complaints about this facility.

Construction photos
View construction photos.

North Beach CSO Control Project construction hotline
24/7 Construction Hotline: 206-296-7372
Leave a message, and a project team member will return your call.
Project contact: Monica Van der Vieren, 206-477-5502, Monica.vandervieren@kingcounty.gov or via feedback form.

Project updates

New releases

Related maintenance activities 

Find out if a CSO is occurring in North Beach

Related information

For more information