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Monitoring update: May 26, 2017

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. 

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.

During the repairs to restore operations at West Point, monitoring frequency has been increased at four routine offshore sampling sites and one additional offshore sampling site close to West Point has been monitored.

Water Quality Reports. Download complete reports:

Summary: Marine and Environmental Monitoring Results as of May 26, 2017


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.

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

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

For more information

wp sampling mapKing 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.


KSSK02: Offshore site near West Point outfall 

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, and have been open since then. Samples for fecal coliform bacteria were collected at all offshore and beach locations on May 1/2, and at selected offshore and beach locations on May 10th. The figure shows fecal coliform bacteria concentrations measured in surface samples (1 meter) at all offshore stations, as well as historical bacteria concentrations for the month of May. The results indicate:

  • Fecal coliform levels near the West Point Treatment Plant outfall, at other offshore locations, and at most of the beach locations, were all low compared to state standards and similar to typical concentrations measured in May.
  • Fecal coliform concentrations at two beach stations (Golden Gardens and Alki Beach) were slightly elevated above normal, as well as the Enterococcus concentration at the offshore EBO location by West Point, despite no untreated discharges at West Point, or other substantial rainfall/stormwater events occurring during that time.  While the source of these bacteria is unknown, fecal pollution from humans or wildlife are potential sources.  In addition, Entereococcus bacteria can occur naturally in high densities and can survive longer than fecal coliforms in the marine environment. 


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.


KSSK02: Offshore site near West Point outfall

The figure shows ammonia concentrations measured in near-bottom samples at all offshore stations for samples collected on May 1/2 and May 10th, and the results indicate:

  • Ammonia levels at all sites and depths were within normal ranges for May.
  • Low nitrate/nitrite and silica levels at the surface in addition to high chlorophyll-a values indicate the continuance of the regularly-occurring spring phytoplankton bloom which began in mid-to-late April. The timing of the phytoplankton bloom, and the phytoplankton’s subsequent uptake of nutrients for growth, is consistent with historical data.
  • The phytoplankton bloom was more pronounced in the southern portion of the Central Basin during early May and evident at all five stations sampled on May 10th.

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.


KSSK02: Offshore site near West Point outfall

    • Near-bottom dissolved oxygen values were at healthy levels and all sites were above the state water quality standard.
    • Higher dissolved oxygen levels persisted through early May from top to bottom of the water column, reflecting the growth of aquatic plants and algae which produce oxygen. This shows typical spring conditions.