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September 2020

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 and 2020. 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.

The second technical report completed in November 2019, West Point Flooding Event Subtidal Sediment Report, presents results of an assessment of subtidal sediments and sediment-dwelling (benthic) organisms surrounding West Point’s two outfalls: the shallow Emergency Bypass Overflow (EBO) and the deeper main outfall.

The third technical report completed in February 2020, West Point Flooding Event Dungeness Crab Tissue Report, presents results of an assessment of contaminant concentrations in Dungeness crab tissues in locations near West Point including Shilshole Bay marina and the northern part of Elliott Bay.

The fourth technical report completed in August 2020, West Point Flooding Event Zooplankton Tissue Report, presents the results of an assessment of contaminant concentrations in zooplankton tissues in two locations in the Puget Sound Central Basin.

View technical reports.

Staff performing analysis in the laboratory

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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

Subtidal Sediment Report , November 2019

The second technical report, West Point Flooding Event Subtidal Sediment Report, presents results of an assessment of subtidal sediments and sediment-dwelling (benthic) organisms surrounding West Point’s two outfalls: the shallow Emergency Bypass Overflow (EBO) and the deeper main outfall. The following are key findings of the report:

  • The flooding of the West Point treatment plant in 2017 did not alter the physical properties of the sediment or seriously damage sediments or benthic invertebrate communities in the surrounding area
  • Remote operated vehicle (ROV) surveys of sediments surrounding the EBO after the second  discharge event indicated little visual evidence of recent deposition or impacts to benthic organisms.
  • Modeling evaluated the potential effect of effluent discharges on sediments near the EBO. Results indicated that no chemicals were expected to exceed Washington’s Marine Sediment Management Standards nearest the outfall and, therefore, not likely to negatively impact benthic organisms. Concentrations of most chemicals would have been minimally elevated over background levels. 
  • Near the main outfall, where reduced treatment effluent was discharged for three months:
    • No surface sediment enrichment was indicated in June 2017 sampling after treatment processes were restored, nor did the flooding event alter the physical properties of the sediment.
    • Extensive testing found metals and organic compounds in sediment near the main outfall to be within regulatory limits, or only temporarily exceeded criteria. 
    • Benzoic acid temporarily exceeded criteria at four of eight stations in September 2017. Elevated concentrations were seen elsewhere in Puget Sound during that year, thus indicating the occurrence was not likely associated with the flooding. Follow-up sampling in April 2018 indicated that concentrations returned below criteria. 
    • Benthic invertebrate communities remained robust and diverse after the event and were similar to those of past monitoring events indicating that the flooding event did not harm benthic invertebrate communities in the surrounding area.

plants-outfalls

2017-sed-sampling-stations

West Point Flooding Event Dungeness Crab Tissue Report , February 2020

The third technical report, West Point Flooding Event Dungeness Crab Tissue Report, presents results of an assessment of contaminant concentrations in Dungeness crab tissues in locations near West Point including Shilshole Bay marina and the northern part of Elliott Bay. The following are key findings of the report:

  • Six metals observed at higher concentrations in West Point effluent during the period of reduced treatment were also higher in crab collected in May 2017 at Shilshole Bay area compared to historic conditions. The data analysis suggested four of these metals may have been influenced by the West Point flooding event. The increased concentration of these metals in crab tissues were temporary. Data for other contaminants in crab collected from Shilshole Bay area were either not detected or did not suggest increases related to the flooding event.
  • Crab collected from the northern area of Elliott Bay did not suggest increases in contaminants related to the flooding event. 
  • Existing Washington Department of Health seafood consumption advisories for crab collected and consumed from the Central Basin of Puget Sound would not have changed based on the West Point flooding event.
  • Overall the lack of available long-term contaminant crab tissue datasets for these areas limit the ability to definitively attribute changes in contaminant tissue concentrations to an event like West Point flooding event because of environmental variability. In addition, stormwater discharges from above normal rainfall between February and April 2017, also contributed contaminants to the Central Basin of Puget Sound that could have influenced crab tissue contaminant levels.

map of crab sampling locations

Zooplankton Tissue Report , August 2020

The fourth technical report, West Point Flooding Event Zooplankton Tissue Report, presents the results of an assessment of contaminant concentrations in zooplankton tissues collected in the spring and late-summer of 2017 and 2018, from two locations north and south of West Point in Puget Sound: the North Central Basin (NCB) and Mid-Central Basin (Mid-CB; see figure).

The evaluation of zooplankton contaminant data for this monitoring effort was qualitative based on a number of confounding factors, including challenges in collecting sufficient tissue mass for robust analyses, a lack of sufficient historical data for comparison, and some sample quality control issues. In addition, several physical and biological factors, such as unusually high spring precipitation, strong phytoplankton bloom conditions, and other factors, may have influenced contaminant concentrations in the water and accumulated by zooplankton in the Central Basin during the time of the West Point flooding event. With these caveats in mind, the following are key findings of the report:

  • Zooplankton collected did not suggest increases in metals or polychlorinated biphenyls (PCBs) related to the West Point flooding event.
  • Concentrations of polybrominated diphenyl ethers (PBDEs), which are flame retardant chemicals, were substantially higher in zooplankton tissue samples collected from both Central Basin locations in the spring of 2017. However, PBDE concentrations were an order of magnitude lower by late summer 2017, and concentrations continued to remain lower in 2018. Therefore, the increased concentration of PBDEs in zooplankton tissues during the spring of 2017 appeared to be temporary.
  • The timing and temporary nature of the increased PBDE concentrations in zooplankton suggest wastewater inputs, including discharges from the West Point flooding event and to a lesser degree increased stormwater runoff, may have contributed to the elevated total PBDE levels in the spring 2017 zooplankton samples.

map displaying sampling locations

English Sole Tissue Report

Pending

Summary Sediment and Tissue Report

Pending