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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

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Staff Contacts

North Beach CSO Control Project

Project Construction

July 9, 2015 Update 
Crews are making preparations for the initial paving of the north end of the site (shown in orange on the map). They will install final utility connections and level out this area of the site this week. Work will continue to connect wastewater infrastructure elements on-site, including the new combined sewer overflow (CSO) tank to the North Beach Pump Station, and to install new manholes. Crews will be working Saturday, July 11.

Paving sequence as of July 2015.
In a nutshell, we expect the road to be reopened in August, shifting two weeks later than previous dates. Below is an update on the work sequence plan between now and the end of September. We will continue to keep you up to date with the latest in our weekly project emails.

Please let us know if you have any questions. We are happy answer your questions via email, over the phone, or in person. Here’s an overview of upcoming major activities:

Street work and repaving
-- Utility restoration is expected to wrap up on the north end of the site (by the Blue Ridge Park entrance) around mid-July; the last piece of work involves restoring the street light that was removed to construct the tank.
-- On Wednesday, July 15, and Thursday, July 16, the contractor will begin repaving the north end of the site (shown in orange on the map above). They will install the first of two paving layers in this area.
-- The site will remain fenced off with traffic still detoured, as the contractor still needs this space for staging as they continue work on the south end of the site.
-- On Monday, August 3, full paving of the south end of the site (shown in yellow on the map above), and the final layer on the north end is scheduled to begin. This activity is expected to take one week.
-- The contractor will then complete final roadway restoration (striping, curbs, permanent signage, etc.).

Road reopening and bus route restoration
-- Full road reopening for vehicle, pedestrian, and bicycle traffic is scheduled for Monday, August 10.
-- All bus stops on 24th Avenue NW and 28th Avenue NW will be reopened, except for the stop by King County’s North Beach Pump Station on Triton Drive NW. Metro will set up a temporary stop in the area until the new stop is installed.
-- Temporary single-lane closures will be required for final restoration and landscaping. Flaggers and traffic signage will be used to safely direct vehicles, pedestrians, and cyclists around the work area. We will let you know in advance of any single-lane closures.

Commissioning the new facility and final restoration
-- Before completing a new facility, the contractor has to test each part of the system, then carry out full system testing, training, and finally, commissioning.
-- The North Beach CSO Control Project includes the flushing and drain vaults, storage tank, and new odor control facility. Testing these components will occur from mid-July to mid-August.
-- After the new facility is online, the sewer bypass, which has been carrying sewage throughout construction, will be disconnected and the system allowed to operate as designed.
-- The last section of landscape restoration will take place on King County’s site and along the Blue Ridge Park frontage, including installing fences, paving, and landscaping.
-- Due to the hot, dry summer, the contractor will install landscaping and plantings in early September to support better plant survival (pending approval).

View construction update (July 9, 2015) and construction photos.

Questions? Comments? Concerns?

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,

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 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

View construction update (in yellow box at top of page) for latest schedule.

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, 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