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Monitoring update: March 20, 2017

The County’s marine water quality monitoring program collects and analyzes water quality samples at 12 offshore sites and 20 beach locations. This year-round monitoring program has collected data for up to 50 years in some locations, and provides an understanding of water quality throughout the Puget Sound Central Basin.

While repairs are made to restore operations at West Point, we have increased monitoring frequency at four routine offshore sampling sites and added one additional offshore sampling site close to West Point.

Below you will find a current snapshot for three important water quality tests: fecal coliform bacteria, ammonia (nitrogen), and dissolved oxygen.

Download complete Water Quality Report - March 17, 2017 update (1.3MB).

View marine monitoring plan and more information.

King County Wastewater Treatment Division’s mission is built around protecting our region’s waters. For decades, WTD has provided high quality treatment at our regional treatment plants. As part of our commitment to water quality, King County has conducted decades of water quality monitoring in the central Puget Sound basin where our treatment plant outfalls are located.

We take our commitment to environmental stewardship very seriously. On Feb. 9, an incident caused a loss of full performance of the West Point Treatment Plant. We are working to restore full operations at the plant. At this time, the plant is providing limited primary treatment. We recognize that substandard treatment or any untreated emergency bypasses do not meet the stringent requirements of our permits, and we are working around the clock to restore secondary treatment.

During this time, we are increasing the frequency of marine monitoring to evaluate potential effects of reduced level of wastewater treatment. The marine monitoring program is conducted in accordance with scientific protocols of the region-wide Puget Sound Estuary Program (PSEP). King County conducts the marine water quality monitoring program in collaboration with Ecology’s Environmental Assessment Program.

We will update this page as new monitoring reports are available, expected every two weeks.

For more information

170310-Sampling-Map-700King County Marine Water Quality Monitoring Program - Sampling Type and Frequency


For questions or inquiries related to the West Point restoration, please do not call the West Point Treatment Plant.

Contact us:

206-477-5371 (after hours, leave message)

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Fecal bacteria

Two types of fecal bacteria are routinely monitored by King County at marine beaches as well as at offshore stations. Fecal bacteria are found in the intestinal tracts and feces of humans and other animals and tests for the bacteria are used for evaluating the suitability of water for human water contact recreation such as swimming and scuba diving, and shellfish consumption.

Offshore: surface (1 meter) bacteria

Immediately following the West Point flooding and bypass, fecal bacteria levels in beach samples were high and beaches at West Point, Golden Gardens, and Carkeek Park were posted for closure to water contact recreation. Fecal bacteria concentrations declined over several days following the bypass events, and all beaches were re-opened on February 21st. The figure shows fecal coliform bacteria concentrations measured in surface samples (1 meter) at all offshore stations sampled before and after the Feb. 9 West Point incident), as well as historical bacteria concentrations for the month of February. The results indicate:

  • Fecal coliforms near the West Point Treatment Plant outfall, at other offshore locations, and at the monitored beach locations, were all low compared to state standards and similar to typical concentrations measured in February.


Nutrients like ammonia and nitrate are essential elements for aquatic plants. However, excess nutrients can cause a sudden increase in aquatic plants that can lead to unfavorable conditions. High ammonia concentrations can be toxic to aquatic organisms, including fish.

Offshore: surface (1 meter) ammonia

The figure shows ammonia concentrations measured in surface samples (1 meter) at all offshore stations, and the results indicate:

  • Nutrients at all the offshore stations were within normal values based upon past February values.
  • Other nutrients such as nitrate and orthophosphate were within normal ranges for all sites (see technical report ).

Dissolved oxygen

Dissolved oxygen is important for marine life. Aquatic plants and animals require a certain amount of oxygen dissolved in the water to live, and different species have different tolerances. Waters with high concentrations of dissolved oxygen are considered healthy for sustaining many species.

Offshore: near-bottom dissolved oxygen levels

The most recent offshore sample data from February 21st and 22nd show typical conditions for February across King County’s offshore monitoring stations in Central Puget Sound, and all sites show near-bottom oxygen levels above the state water quality standard.