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WP20 Contaminated Harbor and River Sediment
(REV-1117-817180) The use of sediment-profile imaging for contaminated sediment assessment: Pacific Northwest harbor and river examples.
Revelas, E.1, Browning, D.2, 1 Integral Consulting, Inc, Olympia, Wa, USA2 Browning Environmental Services, Olympia, WA, USA
ABSTRACT- Sediment-profile imaging (SPI) provides in-situ information on animal-sediment interactions, stratigraphic properties, geochemical processes, and physical dynamics at the sediment-water interface (0-20 cm depth). Two examples of SPI supporting the interpretation of sediment quality, benthic conditions, and fate and transport at complex contaminated sediment sites are detailed here. The sediment triad approach (sediment chemistry, toxicity, and infaunal community characterization) was used to characterize the Hylebos Waterway CERCLA site (Commencement Bay, Tacoma, WA). SPI data were also collected to provide in-situ information on sediment disturbance patterns in the waterway, which were then related to the triad data. The SPI data provided insights on the natural and anthropogenic processes that confounded interpretation of the triad data. SPI showed that toxicological and benthic infaunal community responses in the waterway were affected by wood product operations, organic loading, and anthropogenic physical disturbances. Two additional waterway characterization benefits provided by SPI were: 1) high resolution disturbance gradient mapping that was used to focus more expensive chemical and toxicological testing, and 2) determining that several adverse benthic responses were due to vessel traffic and accumulations of wood debris from sort/transfer operations rather than contamination. A SPI survey of the Portland Harbor/Lower Willamette River (Oregon) CERCLA site, was conducted as an early step in the remedial investigation of this large, complex, riverine sediment site. SPI was used to define benthic regimes, i.e., broad areas that shared attributes such as sediment texture and depositional/erosional features, geochemical characteristics such as sedimentary methane abundance, and functional infaunal types. The SPI information was used to help: 1) define an ecologically-relevant surface sampling (i.e. mixed layer) depth for the RI and risk assessments; 2) develop a working physical conceptual site model; and 3) optimize an extensive sediment chemical and biological nature and extent sampling program by focusing on regions exhibiting strong benthic gradients.
Key words: sediment-profile imaging, contaminated sediments, site assessment, benthic stressors
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