W6 AM Evaluation of Groundwater Communication with Surface Water and Contributions to Sediment Toxicity
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 324-326

(WIL-1122-328301) Ground water vs. surface water influences on sediment toxicity and geochemistry in a Puget Sound estuary.

Williams, L¹, Jacobs, L¹, Staton, M^{2, 3}, ¹ Integral Consulting² SLR International³

ABSTRACT- A thorough analysis of analytical constraints, spatial distributions, and causation relationships is needed to establish a definitive link between groundwater discharge of problem chemicals and impacts to surface water and sediment. Surface water, sediment chemistry, and sediment toxicity data were collected to identify areas potentially affected by petroleum hydrocarbon contamination in ground water associated with a former bulk fuel transfer facility. The facility was built atop coarse fill placed on the natural glacial alluvium in a lowland area along the Puget Sound shoreline. The site is fringed by a freshwater wetland, a small stream, and an estuary that discharge to the sound. Initial data analyses suggested that groundwater may be a source of petroleum in sediment and arsenic in surface water. A more rigorous analysis of spatial trends, sediment toxicity, and analytical limitations determined that groundwater loading was not a concern. Chloride interference with ICP analyses had resulted in a misleading spatial gradient in arsenic that was actually an artifact of a salinity gradient in surface water. Application of appropriate analytical methods demonstrated that a spatial gradient in arsenic was not present. Spatial analysis of petroleum and toxicity of surface sediments demonstrated that observed sediment contamination and toxicity were not due to groundwater, but rather more likely, to storm water runoff.

Key words: ground water, sediment chemistry, sediment toxicity, surface wa