PARENT SESSION
PW11 - Site-Specific Risk Assessments
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P859) An Ecological Risk Assessment Using Multiple Lines of Evidence at a Mine Site in Maine.
Harman, Charles*,1, Calhoun, Christy1, 1 AMEC Earth & Environmental, Somerset, New Jersey, USA
ABSTRACT- An Ecological Risk Assessment Using Multiple Lines of Evidence at a Mine Site in Maine. Harman, CR*, Calhoun, C, AMEC Earth & Environmental, Inc., Somerset, NJ. A Screening-Level Ecological Risk Assessment (SLERA) was prepared for an abandoned zinc mine located in southern Maine. The mine had undergone partial closure, but was still contributing metals (primarily copper, lead, and zinc) to a stream bordering the site. The watershed of the stream included two ponds upstream of the site, one adjacent to the site, a beaver pond adjacent to the site, and a pond downstream of the site. The connecting stream flowed through a riparian corridor comprised of high value wetlands. The objective of the SLERA was to evaluate the potential for ecological impacts to sensitive aquatic and wetland receptors from exposure to metals occurring within the system. The SLERA compared metals in sediments and surface water to relevant benchmarks using the Hazard Quotient process, and evaluated benthic invertebrate communities in the ponds and the stream, wetland functional capacities, fish populations and metals uptake by fish. The study did identify significant background concentrations of metals present in the watershed. The SLERA indicated that metals were present in surface water and sediments adjacent to, and downstream of the Site at concentrations that exceeded background levels identified in upstream sections of the watershed, and exceeded conservative ecological screening benchmarks. The results of the benthic invertebrate and fish population studies did not suggest a significant environmental impact, though the conclusions were somewhat ambiguous. The results of fish tissue analysis indicated that tissue residues were not present at concentrations sufficient to impact piscivorous wildlife. It was also concluded that intrusive remedial action within the downstream watershed would probably result in severe ecological perturbations that would far exceed the present effects of the metals.
Key words: ecological risk assessment, metals, mining, wetland and aquatic sytems