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King Street Center
201 S. Jackson St., Suite 500
Seattle, WA 98104-3855
Phone: 206-684-1280
Fax: 206-684-1741
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Puget Sound shoreline next to the West Point Treatment Plant, Seattle

How King County controls odors at West Point Treatment Plant

Aerial photo of West Point Treatment Plant, 1999
West Point Treatment Plant, 1999

Aerial photo of West Point Treatment Plant, 1974
West Point Treatment Plant, 1974 (note sludge lagoons on the South Beach at Discovery Park)

The look–and smell–of West Point Treatment Plant has changed a lot since the plant was first dedicated in 1966. Processes like solids settling were once carried out in sludge lagoons on the South Beach at Discovery Park. Today, treatment processes are enclosed and covered, and the area surrounding the treatment plant has been restored for public use and enjoyment.

Odor monitoring and control requirements

Although odors can be a problem in wastewater systems, King County works hard to be a good neighbor by monitoring and controlling odors at our facilities and making long-term improvements to odor control systems.

Both regulations and policies require King County Wastewater Treatment Division to monitor and control odors. West Point Treatment Plant is in compliance with odor control regulations established by Puget Sound Clean Air Agency and the City of Seattle.

King County's 1999 Regional Wastewater Services Plan (RWSP) includes policy guidance to prevent and control nuisance odor occurrences at all treatment plants and associated conveyance facilities and to carry out an odor prevention program that goes beyond traditional odor control. Odor complaints are summarized in the RWSP annual report.

In 2003, the King County Council passed legislation requiring upgrades of odor control systems at both of King County’s regional wastewater treatment facilities. A phased plan for odor improvements was developed for each treatment plant, with a monitoring and evaluation period between phases. Phase I odor improvements were completed at West Point Treatment Plant in 2009, evaluation was completed, and some elements of Phase II are being implemented at this time.

Odor control scrubbers at West Point Treatment Plant
Odor control scrubbers at West Point Treatment Plant

Being a good neighbor by controlling odors

Being a good neighbor by controlling odors is a part of the normal operation of our treatment facility. We work to limit odors at West Point in a variety of ways:

  • Continuously monitor operations at our existing treatment plants
  • Conduct routine odor monitoring at the plant perimeter
  • Add chemicals to neutralize odor in the conveyance system seasonally, before wastewater arrives at the treatment facility
  • Use covers, ventilation, and odor scrubbers to limit potential odors from some processes
  • Modify maintenance schedules and practices to reduce the potential for odors and impacts to park users
  • Chlorinate wastewater entering the treatment plant on a seasonal basis
  • Respond to odor reports promptly and follow up with citizens after investigation

For odor concerns or complaints, call WPTP odor control hotline at 206-263-3840

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