Proceedings of the U.S. Geological Survey (USGS) Sediment Workshop, February 4-7, 1997


By Tom Armitage, U.S. Environmental Protection Agency

Contaminated sediment in water bodies of the U.S. has emerged as an ecological and human health issue of national proportions. Contaminated sediment can be associated with acute and chronic effects on aquatic life. Sediments also constitute a major source of persistent bioaccumulative toxic chemicals which may pose threats to ecological and human health even after contaminants are no longer released from point and nonpoint sources. Documented adverse ecological effects of contaminants in sediments include: fin rot, skin lesions, increased tumor frequency, and reproductive toxicity in fish; reproductive failure in fish-eating birds and mammals; and decreased biodiversity in aquatic ecosystems. Threats to human health occur when sediment contaminants bioaccumulate in fish and shellfish tissues consumed by humans. Fish advisories have been issued for more than 1,500 water bodies in 46 states for pollutants such as mercury, dioxins, PCBs, PAHs and pesticides such as chlordane (a banned pesticide) and chlorpyrifos (a pesticide currently registered for use).

More than ten Federal statutes provide authority to many EPA program offices to address the problem of contaminated sediment. These statutes include: the National Environmental Policy Act; the Clean Air Act; the Coastal Zone Management Act; the Federal Insecticide, Fungicide, and Rodenticide Act; the Marine Protection, Research, and Sanctuaries Act; the Resource Conservation and Recovery Act; the Toxic Substances Control Act; the Clean Water Act; the Great Lakes Water Quality Agreement of 1978, and the Comprehensive Emergency Response, Compensation, and Liability Act. A complete summary of EPA statutory authorities for addressing sediment contamination is provided in Contaminated Sediments - Relevant Statutes and EPA Program Activities (U.S. EPA, 1990).

The major goals of EPA programs with authority to address contaminated sediment are reflected in the Agency's Contaminated Sediment Management Strategy published for public review and comment in August, 1994 (U.S. EPA, 1994). These goals are: (1) prevent further sediment contamination that may cause unacceptable ecological or human health risks; (2) when practical, clean up existing sediment contamination that adversely affects the Nation's water bodies or their uses; (3) ensure that sediment dredging and dredged material disposal continue to be managed in an environmentally sound manner; and (4) develop methodologies to enhance the capability for assessment of sediment contaminants. A number of program objectives are being pursued by EPA to meet these goals. These program objectives include:

A comprehensive and well coordinated contaminated sediment research program will support many of these EPA program objectives. Research should be conducted to identify relationships between sediment contaminants and the viability and sustainability of benthic ecosystems. The results of such research can be used to direct cost-effective source control and pollution prevention strategies. Research to address critical uncertainties in the areas of contaminant effects, exposure assessment, and the treatment of sediments can also support risk-based decision making. Four categories of contaminated sediments research needed to support EPA program objectives can be identified as follows.

Extent and severity of sediment contamination. Data from analysis of high quality, representative samples are needed to better understand national and regional trends in concentrations of organic and inorganic sediment contaminants, sediment toxicity, and benthic community composition and abundance.

Methods and data to assess ecological exposure and effects of sediment contaminants. Priority needs include the development of: (a) data on the ecological consequences of sediment contaminants at the population, community, and ecosystem scales ; (b) data on tissue residue thresholds and models for assessing lethal and sublethal effects of bioaccumulative sediment contaminants; (c) data on the fate and transport of contaminants and how these factors influence exposure and bioavailability; (d) field-validated sediment toxicity assessment methods to evaluate impacts on individual test species as well as on populations of benthic organisms; (e) methods for determining the effects of mixtures of contaminants on sediment toxicity; and (f) refined models for determining the fate and transport of sediment contaminants.

Development and validation of chemical-specific sediment quality criteria. Techniques for the derivation of numerical sediment quality criteria for both marine and freshwater systems should be developed and field validated through research activities such as: (a) field and laboratory studies to validate equilibrium partitioning for different classes of contaminants and associated tissue residue approaches for deriving sediment quality criteria; (b) studies to determine the physical and chemical factors in sediments which mediate the bioavailability and toxicity of metals and ionizable organic chemicals; (c) studies to develop food chain models for predicting the exposure of higher trophic level organisms, and (d) studies to evaluate the efficacy of sediment criteria to protect benthic and fish assemblages at the population, community, and ecosystem scales.

Studies are also needed to derive chemical data for development of sediment quality criteria. Research can be conducted to determine octanol/water partition coefficients for hydrophobic organic compounds, investigate sorption-desorption kinetics of organic pollutants, investigate mechanisms by which organic contaminants and medals adsorb to sediment, and to develop and validate models for binding and release of metals to sediments. Research is also needed to develop chemical and biological transformation pathway/kinetic data for ionic and nonionic organic contaminants for development of sediment quality criteria.

Development and evaluation of sediment cleanup methods. Research is needed to develop and evaluate a range of cost-effective remediation technologies for contaminated sediments, with emphasis on in situ containment, biological treatment, and metals treatment. Such research may focus on capping or armoring of sediment for in situ containment, on the use of confined disposal facilities such as large bioreactors to degrade contaminants, and on development of technologies for removal, recovery, and eventual reuse of metals from sediments. Research is also needed to determine the rates of recovery of benthic communities under different environmental conditions and stresses, for use in developing criteria to determine when natural recovery is the appropriate remedial alternative.

In undertaking research to support contaminated sediment program goals and objectives, EPA will benefit from working closely with a number of other Federal agencies and stakeholders to ensure that the methods, tests, and models developed are useful to EPA program offices and other identified users of research products. The Agency's Contaminated Sediment Management Strategy states that EPA can most effectively manage the problem of contaminated sediments by drawing upon the technical expertise available in other government agencies, academia, and industry, and coordinating EPA research and management programs with the ongoing activities of these other agencies and stakeholders.


U.S. EPA. 1990. Contaminated Sediments-Relevant Statutes and EPA Program Activities. EPA 506/6-90/003 U.S. EPA. 1994. EPA's Contaminated Sediment Management Strategy. EPA 823/R/94/001

Workshop Proceedings
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Contribution from the USGS