Sinclair and Dyes Inlet and the Adjoining Bainbridge Basin Marine Sediments Data Summaries, Findings, Publications

Bainbridge Basin

The following table contains links to data summaries. (Click on X to open files. Zip files will need to be extracted into another folder. Shaded boxes indicate summaries not yet available.)

Year Sampled Station Locations Physical Chemical Toxicity Benthic Invertebrates Sediment Quality Triad Indicators
1998 * * * * * *
2009 X X X X X X

*Available upon request.


The Bainbridge Basin Sediment Quality Triad Index (PDF) offers a one-page summary of these findings.

Puget Sound Marine Sediment Indicators is a webpage that describes the Sediment Quality Triad Index, a method to rate the health of marine sediments.


Findings 2009

All our studies assess sediment quality by evaluating chemistry, toxicity, and benthic (sediment-dwelling) invertebrate community structure. Results are compared with those from similar surveys, conducted with the same methods, to determine changes in sediment quality.  

  • Sediments had either minimum or low exposure to chemicals.
  • Concentrations of arsenic, lead, and some polycyclic aromatic hydrocarbons (PAHs) decreased from 1998 to 2009.
  • Concentrations of several metals and multiple PAHs increased from 1998 to 2009.
  • High toxicity was limited to Liberty Bay and moderate toxicity was found in Dyes Inlet and Sinclair Inlet. Low toxicity increased significantly from 1998 to 2009.
  • About half (48%) of the 2009 stations had adversely affected benthic invertebrate communities, a significant increase from 21% since 1998.

Results are rolled up into the Sediment Quality Triad Index, which categorizes sediment quality on a 5-level scale from unimpacted to clearly impacted.  The triad index combines information on measures of exposure (sediment contamination), response (toxicity), and biological effects (benthic invertebrates).

  • From 1998 to 2009 the proportion of the Bainbridge Basin with unimpacted sediment quality decreased significantly and the proportion of area with likely impacted sediment quality increased significantly.
  • Overall sediment quality declined significantly from 1998 to 2009.


Weakland, S., V. Partridge, M. Dutch, E. Long, and K. Welch. 2013. Sediment Quality in the Bainbridge Basin, Changes from 1998 to 2009. Washington State Department of Ecology Publication 13-03-010.

Quality Assurance Project Plan

Dutch, M., V. Partridge, S. Weakland, K. Welch, and E. Long. 2009. Quality Assurance Project Plan: The Puget Sound Assessment and Monitoring Program Sediment Monitoring Component. Washington State Department of Ecology Publication 09-03-121. 98 pp.