Improving Dredged Material Management Decisions with Uncertainty Analysis

The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. The findings of this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents. Improving dredged material management decisions with uncertainty analysis / by Donna J. ISSUE: Federal laws and regulations require the U.S. Army Corps of Engineers (USACE) and U.S. Environmental Protection Agency (USEPA) to assess the potential for dredged material management activities to have significant undesirable effects on human health or the environment. The USACE and USEPA have developed an evaluation process for making dredged material management decisions to protect against such effects. Uncertainty regarding the ecological and human health risks associated with dredged material disposal alternatives can lead to delayed, costly, and unwise decisions. Uncertainty about the likelihood for unacceptable impacts can result from the lack of knowledge about critical elements or processes contributing to risk or natural variability in the same elements or processes. RESEARCH: The objective was to discuss the importance of uncertainty in environmental decision making through specific reference to the dredging program. The approach taken included the following steps: q Describing in detail the uncertainty sources within the tiered evaluation process. q Ranking sources of uncertainty within the tiered evaluation process by degree of contribution. q Making preliminary recommendations for further refinement of the ranking. SUMMARY: The most significant sources of uncertainty within the tiered evaluation process included identification of the contaminants of concern, the selection and use of reference sediments , trophic transfer of sediment-associated contaminants, the potential for chronic toxicity and the use of chronic sublethal bioassays, definition of assessment and measurement end points during the conduct of an environmental risk assessment, the use of contaminant fate and transport models, tissue-based measures of toxicity , dose-response models for human receptors , and the toxicity of complex mixtures. Specific recommendations for the need for more extensive field validation for many of the components in the tiered evaluation process were made.