Skip to main content
King County logo

April 2019

Following initial water quality monitoring in Puget Sound after the West Point Treatment Plant flooding event on February 9, 2017, King County voluntarily collected bottom sediments and marine organisms from different areas of the sound in 2017 and 2018 to evaluate any changes in chemical concentrations. The results of this sediment and marine organism monitoring effort will be presented in a series of five individual technical reports to be completed in 2019. A final summary report of the overall impacts of the West Point flooding event on chemical concentrations in the marine environment will be prepared to interpret the collective results and provide an overall conclusion. The final summary report will incorporate input from scientists specializing in regional contamination from the Washington Department of Fish & Wildlife and other agencies who will peer review the technical reports.

The first technical report completed in February 2019, West Point Flooding Event Intertidal Sediment and Clam Tissue Report, presents results of metals monitoring conducted for intertidal sediments and butter clams at six beaches between Carkeek and Alki Beach Parks.

Staff performing analysis in the laboratory

Follow WTD on social media
The separate technical reports are listed below.

West Point Flooding Event Intertidal Sediment and Clam Tissue Report , February 2019

The first technical report, West Point Flooding Event Intertidal Sediment and Clam Tissue Report, presents results of metals monitoring conducted for intertidal sediments and butter clams at six beaches between Carkeek and Alki Beach Parks. The following are key preliminary findings of the report:

  • All metal levels in sediment and clam samples were well below applicable Washington regulatory standards. 
  • Compared to historical data, copper levels in both sediment and clams were elevated at one site near the West Point outfall, while lead levels at this site were only elevated in clams. There are no regulatory limits for these metals in clams or other marine organisms. 
  • Elevated copper and lead levels were observed in effluent discharged from the main West Point outfall during the three-month period of reduced treatment at the plant. These conditions may have contributed to elevated metal levels detected in sediment and clam tissue.
  • All sampling sites were located near the West Point outfall where discharges from the flooding event and subsequent recovery period were expected to be the most impactful. These sites are in areas that are closed to public and private shellfish harvesting. Therefore, no shellfish from these areas are commercially available for public consumption.

map of Intertidal Sediment & Clam sampling stations

Subtital Sediment Report

To be published in 2019.

Crab Tissue Report

To be published in 2019.

Zooplankton Tissue Report

To be published in 2019.

English Sole Tissue Report

To be published in 2019.

Summary Sediment and Tissue Report

To be published in 2019.