Publication Summary

As part of the Urban Waters Initiative, the Department of Ecology′s Environmental Assessment Program is assessing sediment quality throughout urban bays in Puget Sound, beginning with Elliott Bay and adjoining waterways of the lower Duwamish River in 2007. These bay-scale assessments assist environmental managers in determining whether collective localized cleanups and source control improve conditions over a wider area.

Comparisons of the 2007 survey results with similar data collected in 1998 show bay-wide decreases in sediment contamination by numerous toxics, especially PAHs and PCBs. Spatial extent of toxicity decreased significantly from 1998 to 2007, and some measures of benthic infaunal community health improved.

The Appendices for this report are linked below. Data for Appendices D-I and K are linked above as a zip file.

Under the Urban Waters Initiative, the Washington State Department of Ecology (Ecology) is working with local governments near Puget Sound′s urban bays to reduce toxic chemical pollution. As part of the Initiative, Ecology is assessing sediment quality throughout those bays, beginning with Elliott Bay and the adjoining waterways of the lower Duwamish River in 2007.

These bay-scale assessments of sediment-quality status and trends serve as a new effectiveness-monitoring tool, enabling environmental managers to determine whether collective localized cleanups and source control improve conditions over a wider area.

The urban embayment sediment surveys are nested within the ongoing Puget Sound Assessment and Monitoring Program (PSAMP) sediment monitoring sampling design. This probability-based sampling is designed to assess sediment condition on several spatial scales, from bay-wide to regional to Puget Sound-wide. Furthermore, the PSAMP sediment monitoring program has baseline conditions from 1997-2003 surveys against which current Urban Waters Initiative results can be compared.

Comparisons of the 2007 results with similar data collected in 1998 show bay-scale decreases in sediment contamination for numerous toxics, especially polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). However, contamination by a few other chemicals did increase. Spatial extent (percent of area) of toxicity decreased from 1998 to 2007. The majority of measures of benthic invertebrate community health improved, whereas others did not change or indicated degradation.

The PSAMP Sediment Quality Triad Index combines information on measures of exposure (sediment contamination), response (toxicity), and biological effects (benthic invertebrates) to categorize sediment quality on a 4-level scale from high to degraded. In comparison to 1998 conditions in Elliott Bay and adjoining waterways, the 2007 conditions showed positive shifts in sediment quality, especially in harbor and urban areas. Bay-wide, more than 30% of the area had intermediate/degraded to degraded sediment quality in 1998. In 2007, that proportion was less than 20%.