Publication Summary

The Department of Ecology analyzed sediments using chronic bioassays at 11 sites across northern Lake Union and at two reference sites on Lake Washington. Chemical concentrations in the test sediments were not analyzed. All Chironomus tentans bioassay results document sediment toxicity above the cleanup screening level criteria as defined in Ecology′s Sediment Management Standards. One of the test stations also had a cleanup screening level exceedance for Hyalella azteca. Results indicate that toxicity extends beyond the limits of this investigation, and comparisons with six historic bioassay stations suggest that no changes in sediment toxicity have occurred.

The Washington State Department of Ecology analyzed sediments using chronic bioassays at 11 sites across northern Lake Union. This analysis was conducted to determine the nature and extent of sediment contamination associated with prior coal and oil gasification and other industrial activities nearby. Two reference sites on Lake Washington also were sampled.

The 11 Lake Union sites were located across a projected gradient of contaminant concentrations to attempt to describe the magnitude and limits of toxic effects associated with the area; however, the actual chemical concentrations in the test sediments are unknown.

All of the Chironomus tentans bioassay results document sediment toxicity above the cleanup screening level criteria as defined in Ecology′s Sediment Management Standards. One of the test stations also had a cleanup screening level exceedance for Hyalella azteca. Results indicate that sediments in the vicinity of Gas Works Park are toxic and probably adversely impact the benthic community.

Link to EIM data for User Study ID RJAC005