A portion of the Brightwater works at the right edge of the panorama below

Brightwater is a regional sewage treatment plant in south Snohomish County, Washington, United States. It serves parts of the Seattle metropolitan area and was opened in 2011. The plant construction and associated tunneling were a five-year megaproject costing $1.8 billion.[1]

Site description

Brightwater is a 114-acre (46 ha) facility at the intersection of State Route 9 and State Route 522 north of Woodinville.[2] The plant itself occupies 114 acres (46 ha); the remainder of the property is used for stormwater treatment and environmental mitigation such as constructed wetlands and stormwater retention.


A 13-mile (21 km), 17.5-foot-diameter (5.3 m)[3] tunnel was built by several tunnel boring machines from the treatment plant to a marine outfall nearly due west on Puget Sound.[4] The outfall is 600 feet (180 m) below the surface.[5] Construction delays were incurred due to unexpected soil conditions causing damage to the boring machines.[3]

The problems with the Brightwater tunnel were considered when planning other large regional tunnel projects, including the Link Light Rail Capitol Hill tunnel and the Alaskan Way Viaduct replacement tunnel.[6]

The tunnel was completed in 2011, and full use of the outfall began on November 2, 2012.[5]


In August 2002, then King County Executive Ron Sims announced that a billion-dollar regional sewage-treatment plant named "Brightwater" would be built in neighboring Snohomish County and provide service for parts of King and Snohomish counties.[7]


Since its proposal, Brightwater has been the subject of numerous lawsuits, including a lawsuit by King County against Snohomish County that was settled when King County agreed to pay $70 million for public safety, habitat protection, and parks in Snohomish County.[8] The project has also had many cost overruns totaling over $272 million.[9] In December 2006, the project had resolved all its lawsuits and only needed building permits from Snohomish County. However, concerns remain over the siting of the project, both from its future neighbors worried about the smells associated with sewage treatment and geologists due to at least one active fault line running through the site, and concerns over whether a new plant was necessary when eliminating stormwater and wastewater from the sewage system.[10] King County countered these concerns by stating the plant will feature advanced odor control, 40 acres (16 ha) of wildlife habitat will be restored, the plant has been designed to withstand a 7.3-magnitude earthquake, and that the project will be paid by new customers.[10]

Public art

The Brightwater plant includes 15 works of public art. The $4.4 million acquisition was funded through the county One Percent for Art construction setaside program.[11]


  1. ^ Denise Whitaker (September 22, 2011). "Brightwater treatment plant set to open Saturday". Archived from the original on December 29, 2011.
  2. ^ "Brightwater Wastewater Treatment Plant project description". King County Wastewater Treatment Division. June 7, 2011. Retrieved 2011-12-15.
  3. ^ a b "2 tunneling machines on Brightwater sewer project are damaged — and 300 feet deep". The Seattle Times. September 8, 2009. Archived from the original (91 m deep) on March 17, 2014. Retrieved 2012-12-15.
  4. ^ Scott Gutierez (August 17, 2011). "Brightwater tunneling completed this week". Seattle P-I. Retrieved 2012-12-15.
  5. ^ a b "Brightwater-to-Sound wastewater conveyance system begins full operation", Press release, King County Natural Resources and Parks, November 15, 2012, retrieved 2012-12-15
  6. ^ Keith Ervin (December 11, 2009). "Deep inside big dig for stalled Brightwater sewage plant". The Seattle Times. Archived from the original on February 2, 2013. Retrieved 2012-12-15. Two giant tunnel-boring machines remain stuck hundreds of feet [100 m] below Bothell and Lake Forest Park, delaying construction of the Brightwater sewer-treatment plant and adding "tens of millions" of dollars to its price tag.
  7. ^ Metro-King County Brightwater proposal
  8. ^ Seattle Times: Deal would end most litigation over Brightwater
  9. ^ Seattle Times: County audit levels criticism at rising Brightwater costs Archived May 24, 2011, at the Wayback Machine
  10. ^ a b Seattle Post-Intelligencer: Brightwater treatment plant nears last hurdle, on track to open in 2010[permanent dead link]
  11. ^ Lawrence W. Cheek (September 26, 2011). "Industrial poetry at the Brightwater treatment plant". Crosscut.com. Archived from the original on June 3, 2012. Retrieved 2012-12-15. There's beauty in those pipes and pumps, as well as in the public art. The real triumph comes from the matching of form and function in a sewage treatment facility

External links

  • Official website
  • Brightwater Center public education facility

Coordinates: 47°47′N 122°08′W / 47.79°N 122.14°W / 47.79; -122.14