Publication Summary

Ecology's Environmental Assessment Program has conducted a multi-phase study of Salmon Bay sediments to facilitate cleanup efforts by Ecology′s Toxics Cleanup Program. Phase I and Phase II examined physical characteristics and toxic contaminants of Salmon Bay sediments on a broad geographical scale. Objectives of this Phase III study were to assess toxicity of sediments, delineate boundaries of highly contaminated areas, and confirm sediment contamination found during the Phase II study.

Ecology's Environmental Assessment Program has conducted a multi-phase study of Salmon Bay sediments to facilitate cleanup efforts by Ecology′s Toxics Cleanup Program. Phase I and Phase II examined physical characteristics and toxic contaminants of Salmon Bay sediments on a broad geographical scale. Objectives of this Phase III study were to assess toxicity of sediments, delineate boundaries of highly contaminated areas, and confirm sediment contamination found during the Phase II study.

Bottom sediments were collected from 27 locations throughout Salmon Bay and two reference locations in Lake Washington. Samples were analyzed for conventional parameters, metals, semivolatile organics, and butyltins. Polychlorinated biphenyls (PCBs) were sampled in areas of known contamination. Toxicity was assessed through Hyalella azteca survival, Chironomus tentans growth and survival, and Microtox. Potential toxicity of the sediments was assessed by comparing chemistry to Freshwater Sediment Quality Values (FSQVs) and the Puget Sound Dredge Disposal Analysis screening level (SL) for tributyltin (TBT).

Results confirmed widespread chemical contamination in Salmon Bay found during the Phase II study. TBT, mercury, bis(2-ethylhexyl)phthalate, indeno(1,2,3-cd)pyrene, and carbazole appear to be the most pervasive problem chemicals based on comparisons to the SL and FSQVs. Zinc, copper, arsenic, lead, chromium, and polycyclic aromatic hydrocarbons also exceeded FSQVs. At least one chemical was detected above FSQVs in 23 of the 27 samples. TBT concentrations were above the SL in 26 of the 27 Salmon Bay sediments.

Ninety percent of the Salmon Bay samples were toxic to at least one bioassay organism. The Chironomus growth test was the most sensitive bioassay, followed by Microtox, Hyalella survival, and Chironomus survival. Results suggest that the number of organic chemicals exceeding FSQVs was more closely related to toxicity than to the degree of metals contamination.

The distribution of contaminants in Salmon Bay could be characterized by "hot-spots" generally occurring near shore, with cleaner sediments toward the channel center. In most cases, hot-spots detected during Phase II were verified by this survey. However, the sample coverage was too thin to delineate hot-spot boundaries. Therefore, it is recommended that future sampling be designed to delineate hot-spots by focusing on the most contaminated Phase III stations individually.

Link to EIM data for User Study ID SBAYPH3