PARENT SESSION
PW11 - Site-Specific Risk Assessments
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P860) Validation of a feasibility study footprint at a sediment site using a weight-of-evidence (WOE) approach.
Holder, J*,1, Michael, D2, Ward, J3, Leather, J4, Gunster, D5, Pound, M6, 1 ENTRIX, Inc, Ventura, CA, USA2 Neptune and Company, Los Alamos, NM, USA3 Battelle Marine Sciences Laboratory, Sequim, WA, USA4 SPAWAR Systems Center San Diego, San Diego, CA, USA5 Battelle, Duxbury, MA, USA6 Southwest Division Naval Facilities Engineering, San Diego, CA, USA
ABSTRACT- The primary objective of this study was to more clearly define the extent of sediments that pose an unacceptable risk to the environment and require evaluation in a Feasibility Study (FS). Three lines of evidence (sediment chemistry, toxicity bioassays, and bioaccumulation studies) were used to validate a preliminary remedial footprint developed for the offshore sediments at this site. Data for the three lines of evidence were evaluated using a WOE framework modified from an approach developed for the State of Massachusetts (Menzie et al. 1996). The WOE approach comprises the following five steps: (1) Determine the weight of the endpoint. This study considered four equally weighted endpoints: sediment chemistry, toxicity to amphipods, toxicity to echinoderm larvae, and bioaccumulation. (2) Determine the nature (i.e., whether the finding is positive or negative) and magnitude of the result. Numeric scores were assigned for various WOE categories based on consensus criteria developed with regulatory agencies. (3) Integrate the weight, finding and magnitude for a given endpoint result. The weight, finding and magnitude for each endpoint result were integrated to determine (a) whether or not the result for that endpoint validates inclusion in the FS footprint, and (b) the level of certainty associated with that conclusion. (4) Integrate all endpoint results for a given sample location. All endpoint results for a given station were integrated to determine if the location (a) should remain in the FS footprint, (b) should be excluded from the FS footprint, or c) required the consideration of additional inputs to make a determination (i.e., the WOE results were equivocal, resulting in a gray area). (5) Map WOE results from Step 4. The WOE results for all stations were mapped to provide an illustration of the preliminary FS footprint.
Key words: Weight of evidence, sediment assessment, ecological risk assessment