Date: June 5, 2007
Contacts: Sara Frueh, Media Relations Officer
Sarah Morocco, Media Relations Assistant
Office of News and Public Information
202-334-2138; e-mail <email@example.com>
FOR IMMEDIATE RELEASE
Sediment Dredging Has Fallen Short of Achieving Cleanup Goals At Many Contaminated Sites; Better Monitoring Needed to Assess Suitability and Results
Dredging's ability to achieve cleanup goals depends on a site's characteristics, the report also concludes. If a particular site has one or more unfavorable conditions -- the presence of debris such as boulders or cables, for example, or bedrock lying beneath the contaminated sediment -- then dredging alone is unlikely to be sufficient. The presence or absence of such conditions should be a major consideration in deciding whether to dredge at a site, said the committee that wrote the report.
Contaminated sediments can be found at the bottoms of many
Dredging is effective at removing contaminated sediment mass permanently from the environment, the report says. But removing mass may not be enough to achieve desired cleanup levels or long-term goals for reducing risks, because dredging inevitably leaves residual contamination behind. Dredging alone achieved expected cleanup results at only a few of the sites the committee analyzed. At many others, capping -- placing a layer of uncontaminated material over the tainted sediments -- was also necessary to contain the remaining contamination at acceptable levels. Assessments of the sites also revealed that the dredging process releases contaminants into the water, which in the short term can have adverse effects on fish and other aquatic animals and could potentially raise health risks in people who consume them.
Dredging remains one of the few approaches available for cleaning up contaminated sediments, the report says, and EPA should continue to consider its use among other methods. In locations where buried contaminated sediments could be dislodged by storms, for example, dredging the sediments to prevent them from being transported may reduce risks. If dredging is used, planners need to recognize that residual contamination and releases of chemicals into the water will invariably occur; they should estimate the effects of these processes in advance, and employ best practices to minimize them, the committee said. Using a combination of methods should also be considered, particularly if a site has any characteristics unfavorable to dredging.
The typical Superfund approach, in which EPA conducts an investigation and a feasibility study that establishes a single path to remediation, is not the best way to choose remedies for these sites, the report says. Given the long time frames and many unknowns involved in cleaning up megasites, adaptive management -- which uses monitoring data to review progress and adjust plans when needed -- should be used to select and implement cleanup methods. In addition, dredging and other remediation projects should be designed to meet long-term goals for reducing risks to people and wildlife, instead of objectives not directly related to risk, such as removing a specified amount of sediment.
The report emphasizes that without adequate monitoring before and after dredging, it is impossible to evaluate the degree to which cleanup objectives have been reached. EPA should invest in better and more consistent measurement tools to monitor conditions in the field reliably and efficiently. Monitoring data should also be made available to the public in electronic form, so that evaluations of remedies' effectiveness can be independently verified.
In addition, to help ensure that megasites with contaminated sediments are cleaned up as effectively as possible, EPA should centralize resources, responsibility, and authority for these sites at the national level, the report recommends. Such a shift would help the agency make sure that monitoring is adequate and that adaptive management and best practices are followed.
The report was sponsored by the U.S. Environmental Protection Agency. The National Academy of Sciences, National Academy of Engineering,
Copies of Sediment Dredging at Superfund Megasites: Assessing the Effectiveness will be available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at http://www.nap.edu. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).
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[ This news release and report are available at http://national-academies.org ]
NATIONAL RESEARCH COUNCIL
Division on Earth and Life Studies
Board on Environmental Studies and Toxicology
Committee on Sediment Dredging at Superfund Megasites
Charles O'Melia* (chair)
Abel Wolman Professor of Environmental Engineering and Chair
Department of Geography and Environmental Engineering
G. Allen Burton Jr.
Professor of Environmental Sciences and Director
Institute for Environmental Quality
Department of Fishery and Wildlife Biology
Frank C. Curriero
Departments of Environmental Health Sciences and Biostatistics
Dominic M. Di Toro*
Edward C. Davis Professor of Civil and Environmental Engineering
OA Systems Corp.
Silas H. Palmer Professor and Chair
Department of Civil and Environmental Engineering
Perry L. McCarty
Silas H. Palmer Professor Emeritus
Department of Civil and Environmental Engineering
Management of Environmental Resources Inc.
Katherine N. Probst
Risk, Resource, and Environmental Management
Resources for the Future Inc.
Bettie Margaret Smith Chair of Environmental Health Engineering and Director
Hazardous Substance Research Center/South and Southwest
Louis J. Thibodeaux
Jesse Coates Professor
Donna J. Vorhees
John R. Wolfe
RESEARCH COUNCIL STAFF
Karl E. Gustavson
* Member, National