Ecological Assessments And Development Of Mitigation Measures At Superfund Sites: Case Studies

The assessment of environmental effects resulting from hazardous waste (Superfund) sites requires both chemical and biological analyses to estimate potential exposure and biological effects. While chemical analysis is an essential first step of hazardous waste site characterization, ecological data also is needed to: 1) assess impacts of the site on living resources; 2) develop cleanup levels and remedies with appropriate mitigative measures to protect and restore natural resources: 3) allow future monitoring of cleanup effectiveness: and 4) meet the information needs of the trustee agencies responsible for addressing natural resource issues. Representatives from the U.S. Environmental Protection Agency @PA) and Federal natural resource trustee agencies have formed a Bioassessment Work Group that provides technical recommendations to Superfund project managers on ecological studies that may be needed at Superfund sites. As a result of this interaction, ecological evaluation has been incorporated into several different phases of the remedial process, from remedial investigation to development of remedial alternatives and mitigative measures. Case histories of ecological evaluations involving the use of several bioassessment methodologies recommended by the Region IJI Bioassessment Work Group are discussed in this presentation. The examples, Army Creek Landfill (Delaware), Chisman Creek (Virginia), and Wildcat Landfill (Delaware) demonstrate how bioassessment can be used effectively from the early site characterization in the Remedial Investigation/Feasibility Study (RI/FS) process to the development of cleanup monitoring. The major objectives of these ecological assessments were to delineate wetlands; to determine the extent of contamination and toxicity in surface water and sediments of freshwater and estuarine habitats; to determine potential impacts and bioaccumulation pathways in wildlife communities: and to generate information necessary to determine remedies needed to eliminate or mitigate the impacts at the site. Information from the biological studies of the Army Creek Landfill site is being used to establish cleanup levels for groundwater treatment and mitigative measures for a capping remedy as it affects the Army Creek wetland. The remedial investigation (RI) conducted by the U.S. Fish and Wildlife Service (USFWS) at the request of EPA assessed the environmental impacts of hazardous substances deposited in borrow pits at the Chisman Creek site. Information from this study was applied to the relocation of a stream, to developing cleanup criteria, and to the use of mitigation strategies to minimize the effects of the remedial activity. The Wildcat Landfill site is a former estuarine wetland partially destroyed by a landfill containing hazardous wastes. Results of the terrestrial and aquatic biological assessment conducted by USFWS for EPAs RWS were used to drive a remedy addressing the specific area, a ponded wetland, where significant environmental impacts were detected. Using these ecological evaluations and technical recommendations from rhe Bioassessment Work Group, the EPA Superfund staf f can better ensure that the remedial design and the monitoring programs will be both cost-effective and protective of the environment.