First phase of sediment TIE optimization study wraps up

Posted July 28, 2017
SCCWRP’s Liesl Tiefenthaler prepares sediment samples collected from a site in Los Angeles Harbor for a toxicity identification evaluation (TIE) study. SCCWRP is working to optimize the design of sediment TIE studies to improve confidence in the results.

SCCWRP has completed the first phase of a two-year project exploring how to optimize the design of toxicity identification evaluation (TIE) studies to improve confidence in the results.

The project, initiated in 2016, involves oversampling in Consolidated Slip, an area of the Los Angeles Harbor with high sediment toxicity levels, and then using statistical principles to develop best-practices recommendations for TIE study design.

The TIE optimization study is intended to close knowledge gaps about the degree of variability in TIE results across time and space, and to determine how many samples are needed to produce reliable TIE assessments. The study also is examining how seasonal variation in sediment toxicity can influence TIE results.

Existing guidance for optimizing the design of TIE studies is limited, even as environmental managers devote considerable resources to conducting TIEs and interpreting the findings.

For the first phase of the project, researchers conducted field sampling across Los Angeles and Long Beach Harbors to identify an appropriate site for the study. Once Consolidated Slip was selected, researchers sampled 10 stations at the site in both April and June.

For the second phase of the project, researchers will analyze multiple possible sources of variability in the results to determine the confidence associated with TIE results, and conduct statistical analyses to optimize sampling design for future TIE studies.

The project is expected to wrap up in fall 2017.

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