Completed fall 2012
In response to increased growth in our region, King County has built a new $1.86 billion regional wastewater treatment system called Brightwater to serve the northern portion of the King County service area. Treatment plant operations began in September 2011. The conveyance system and outfall began full operations in fall 2012.
Brightwater Treatment System (PDF). View more detailed 11x17 inches map (PDF).
The new facilities include:
- The Brightwater wastewater treatment plant is located in unincorporated Snohomish County, north of Woodinville. The plant is designed to have the capacity to treat an average of 36 million gallons of wastewater per day (mgd). By 2040, treatment capacity could be expanded to 54 million mgd.
- The conveyance system is the tunnels, pipes, and other facilities that carry wastewater to and from the treatment plant. The Brightwater system includes 13 miles of pipeline built in underground tunnels, shallower connector pipes, and an influent pump station to send wastewater to the plant.
- The marine outfall consists of twin, 5-foot-diameter pipes with a diffuser at the end where highly treated wastewater from the Brightwater treatment plant is discharged into Puget Sound. The mile-long, 600-foot-deep outfall extends off of Point Wells.
Brightwater Treatment Plant opening (September 24, 2011) from King County DNRP on Vimeo.
Background - siting the Brightwater facilities
Beginning in the summer of 2000, the County began searching for and analyzing sites. In May, 2001 the King County Council selected six sites and eight marine outfall sites for further evaluated as “systems” (including a plant site, conveyance system and outfall).
In June 2001, the County began a second round of evaluation. Based on this, the County Council selected two systems - including conveyance options and four marine outfall zones – to continue on into the environmental review process.
King County conducted a formal environmental review of the Brightwater project under the State Environmental Policy Act (SEPA). On November 19, 2003, a Final Environmental Impact Statement (Final EIS) was issued for this project. See Environmental Review for more details.
Project siting decision - on December 1, 2003, the King County Executive made a decision on the location for the Brightwater Treatment System (PDF).
On July 27, 2005 the King County Executive reaffirmed his earlier selection of the Route 9 - 195th Street system alternative for the Brightwater project. To learn more, download the Regional Wastewater Services Plan: Summary of the Executive's Process to Update the Brightwater System Siting Decision, July 2005 (PDF).
In December 2005, King County completed a systemwide mitigation package (PDF).
The following links point to WTD Flickr sets.
The following links point to DNRP Vimeo videos.