West Point Treatment Plant water quality permit now issued

Each municipal wastewater treatment plant in Washington is regulated by their own unique water quality permits from Ecology. These permits ensure that the wastewater treated by these facilities is safe to discharge to the waters of the state, including rivers and Puget Sound. 

Last year, we released a draft water quality permit for the largest wastewater facility in the state, the West Point plant in Seattle, which is operated by the King County Wastewater Treatment Division. We held two public hearings and received over 200 pages of comments on the draft permit. In preparing the final permit, we carefully considered and responded to all comments received and revised some parts of the permit. 

We’ve now issued the final permit. It strengthens protective measures for Puget Sound by updating the permit to match current water quality rules. Some of the most notable changes from the previous permit are:

• Monitoring and controlling sources of PFAS. PFAS is a general term for a family of chemicals that don’t break down naturally in the environment. The permit includes a new focus on identifying and reducing PFAS in industrial wastewater before it enters the sewage system. The final permit also requires King County to monitor for PFAS in the influent (the water coming into the plant), in the treated wastewater from the plant, and in biosolids that the plant produces.
• Best management practices for additional pollutants. We’re requiring King County to expand its long-standing pollution prevention program to specifically address several pollutants, including copper, zinc, PCBs, and 6PPD/6PPD-Q. 
• Elliott West treatment facility. King County is working on upgrading the Elliott West wet weather treatment facility, which treats combined sewer overflows into Elliott Bay near Myrtle Edwards Park. This facility, which began operating in 2005, has issues with treating stormwater flows adequately; at times, its discharge has high levels of bacteria and other pollutants. The permit requires King County to redesign this facility and begin construction of the improved facility. Ecology expects construction completion in 2031, due to the complexity of the upgrade work.
• Henderson/MLK treatment facility. Like Elliott West, the Henderson/MLK facility is designed to treat combined sewer overflows. In the draft permit, we based our pollutant limits on discharge into fresh water, as the facility outfall (discharge pipe) is located where the river transitions between fresh and saltwater conditions. After our review of public comments and additional available data, the final permit applies marine water quality standards to this outfall. This facility can’t currently meet the marine standard for copper, so the permit requires King County to study ways to comply with the standard and implement them by 2031.

In addition to setting limits for the pollutants allowed in treated wastewater that’s discharged into Puget Sound, the permit also describes requirements for operations and maintenance, monitoring and reporting, responding to problems with equipment, planning for the future, engineering design work to improve water quality protections, and controlling industrial wastewater before it enters the sewage system.

The permit is effective on June 1, 2024, for five years. You can find the final permit, the permit's fact sheet, and our responses to public comments in Ecology’s water quality permit database, PARIS.