Technical Integrity / Collaboration / Exceptional Results

Sedimentation Analysis, Source Identification, Stormwater Runoff Analysis, Chemical Fingerprinting, and Expert Testimony, Thea Foss Waterway

Thea Foss WaterwayIntegral scientists prepared an expert report and provided expert witness testimony in a U.S. District Court bench trial regarding the contribution of a former manufactured gas plant (MGP) to sediment contamination in the Thea Foss Waterway, adjacent to downtown Tacoma, Washington. This contribution resulted from construction of a highway underpass through the former MGP site and consequent drainage into storm sewers that feed the waterway.Integral developed site-specific signatures of PAHs from three PAH sources to the waterway sediments: coal tar contamination from the former MGP site, petroleum releases, and urban stormwater runoff (which varied over time). Integral was then able to develop a historical reconstruction that showed that the history of releases from the former MGP site matched the chemical fingerprint of PAHs in waterway sediments. This signature could be distinguished from other petroleum releases to the waterway and the time-dependent fingerprint of urban runoff to the waterway. The PAH fingerprints and their variation through time were established using existing, standard sediment PAH analytes from RI/FS data without having to rely on the expensive collection and analysis of samples for alkylated PAH compounds. Finally, Integral evaluated sediment transport and resuspension in the waterway to assess any role that these processes may have on sediment composition and site liability.Integral prepared an expert report and a rebuttal expert report detailing the analyses conducted and the opinions reached from those analyses. Integral also provided consultation on the preparation of trial exhibits and assisted in deposition preparation. Testimony was provided at trial on the expert report. Integral’s analysis and testimony provided evidence leading the court to conclude that contributions from the MGP site added to remedial costs in waterway sediments.

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