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Sediment Quality Triad Index

Through the efforts of the PSAMP/NOAA 1997-1999 Puget Sound Sediment Monitoring Program, a Sediment Quality Triad Index was developed as a weight-of-evidence approach that combines the results of the sediment chemistry, toxicity, and benthic infaunal analyses generated in this study to classify the overall quality of the sediment samples. Four categories of sediment quality were generated to define each sediment monitoring station, including:

• High Quality – no degradation detected in any of three test parameters.
• Intermediate/High Quality – degradation detected in one of three test parameters and the study area as a whole.
• Intermediate/Degraded Quality – degradation detected in two of three test parameters.
• Degraded Quality – degradation detected in all three test parameters.

The spatial extent of impacted sediment quality for each index category was then calculated for the defined Puget Sound study regions, strata, and the entire 1997-1999 study area (see Sediment Quality Triad Index in Puget Sound).  This information was later updated to include the 2002-2003 study years.

These values will be used as a baseline and compared with similar values generated by the PSAMP Sediment Component in the future to determine changes in sediment condition over time throughout Puget Sound.