Ecological Risk Assessment Case Study: Impacts to Aquatic Receptors at a Former Metals Mining Superfund Site

An ecological risk assessment (ERA) was conducted as part of the Baseline Risk Assessment of the Remedial Investigation (RI) for the Baxter Springs/Treece subsites, Cherokee County, Kansas Superfund site, a former metals mining site. Chemicals of potential concern were heavy metals associated with mine wastes and with base metal ore deposits that were characteristic of this area. An EPA-approved method was used to developed site-specific ambient water quality criteria. Ecological impacts were assessed using three complimentary approaches. First, potential chronic impacts were assessed by applying the toxicity quotient approach (i.e., a comparison of the measured concentration of site-related metals in surface water with calculated site-specific health-based criteria). Secondly, semi-quantitative comparative ecology data were used to provide a direct measure of impacts to key species. Finally, data on other factors (e.g., acclimation and tolerance evolution) that may affect the bioavailability and toxicity of site-related metals were also considered. Information from these three sources were used to obtain a realistic picture of actual and potential population- and community-level effects associated with exposure to mining-related metals.