Contaminated Sediments - Bioavailability

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The U.S. Environmental Protection Agency estimates that approximately 10% of the sediment underlying our nation’s surface water is sufficiently contaminated with toxic pollutants to pose potential risks to fish and to humans and wildlife that eat fish. This represents roughly 1.2 billion cubic yards of contaminated sediment. According to current average costs for managing contaminated sediments, this volume of material could cost several trillions of dollars to dredge.

One important question that the ITRC Contaminated Sediments – Bioavailability 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., developing a conceptual site model) and understanding bioavailability of chemical constituents in sediments can aid in selecting a remedial process and developing a management plan that best minimizes exposure. The principal objective of bringing bioavailability considerations into sediment risk management is to reduce the extent of cleanup required while still being protective of human health and the environment. In addition, incorporating bioavailability information in the calculation of risk can be an important factor in balancing the risks caused by remedial action with those addressed by the remedial action.

The Contaminated Sediments – Bioavailability Team has developed a website entitled “Incorporating Bioavailability Considerations into the Evaluation of Contaminated Sediment Sites” (CS-1). This site provides technical and regulatory guidance to assist state regulators and practitioners in understanding and incorporating fundamental concepts of bioavailability in contaminated sediment management, including communicating risk and the need for potential remedial action(s) to the public and other parties involved in the decision-making process. The online guidance document offers a compilation of the existing concepts, tools, and measures for assessing bioavailability. Case studies and examples of how these tools and measures have been used in decision making are also included. The intended users of this guidance are individuals who have a working knowledge of contaminated sediment management but seek additional information about bioavailability. The team expects this guidance to be used by responsible parties, state and federal regulators, practitioners, consultants, and public and tribal stakeholders as a tool to understand how bioavailability can be useful in managing risk to ecological and human receptors at contaminated sediment sites.