Contaminated Sediments Team Leader Kimberly Ward 609-584-4277 Kim.Ward@dep.state.nj.us

The U.S. Environmental Protection Agency estimates that approximately 10 percent of the sediment underlying our nation’s surface water is sufficiently contaminated with pollutants to pose potential risks to fish and to humans and wildlife that eat fish. This represents about 1.2 billion cubic yards of contaminated sediment out of the approximately 12 billion cubic yards of total surface sediments (upper five centimeters) where many bottom dwelling organisms live, and where the primary exchange processes between the sediment and overlying surface water occur.

Based on current average costs for managing contaminated sediments, this volume of material could cost several trillions of dollars to dredge. Primary risk pathways include drinking water supplies, food chain effects, fish consumption, and direct contact.

The relationship between contaminant concentration in sediments and risk from exposure is not a simple linear relationship. Attempts to evaluate the relationship between contaminant concentrations in sediments and risk from exposure are problematic. No guidance for this evaluation exists. Procedures to determine the potential effect of sediment contamination on human or ecological health are normally based on total concentrations in the bulk sediment. Over the past fifteen years, research has shown that the availability of many of these contaminants to receptors is much less than the total amount.

However, the bioavailable fractions of the contaminants may provide a more accurate characterization of potential harmful effects to receptors. There are a variety of approaches to determine sediment contaminant bioavailability that are at varying stages of development. The characterization of sediment contamination in freshwater, estuarine, and marine settings should emphasize assessing the bioavailability of these contaminants to humans and ecological receptors using valid and acceptable measurement tools.

One important question that the Contaminated Sediment Team received from State agencies is: “How can we effectively manage and limit exposure to contaminated sediments (i.e., capping)?” Accurately characterizing potentially contaminated sediments (i.e., development of a Site Conceptual Model) and understanding bioavailability of chemical constituents in sediments can aid in the selection of a remedial process and the development of a management plan that best minimizes exposure.

The team intends to develop a Technical Regulatory Guidance document that describes the contaminated sediment investigative processes including the three-dimensional delineation of source term and characterization of exposure term using tools to evaluate bioavailability.