Estimating the aquatic ecological benefits of reductions in metals` concentrations in streams impacted by mining

The authors demonstrate how the Water Environment Research Foundation`s (WERF) Methodology for Aquatic Ecological Risk Assessment can be used to estimate the aquatic ecological benefits of reductions in metals` concentrations in streams impacted by mining. Ecological benefits are estimated as the reduction risk to the aquatic community that should result from the predicted decrease in concentrations of metals from wastewater treatment or site-remediation. The methodology has two tiers: Tier 1 identifies candidate chemicals of potential concern and their relative risk, and Tier 2 quantifies the risk of those chemicals at the community-level with respect to the percent of species affected by acute and chronic toxicity. Both Tier 1 and Tier 2 can assess risks for single chemicals or the combined effects of multiple chemicals. The case study example is a segment of Clear Creek, CO, which has been affected by historical mining activities. The authors apply the methodology to Clear Creek and evaluate how well it estimates risks by comparing the estimate to instream data on benthic macroinvertebrates. Ecological benefits are estimated for two scenarios. The first is for clean-up to background concentrations of metals, the second is for clean-up to concentrations equal to EPA`s water quality criteria. The methodologymore » is shown to provide realistic estimates of actual effects.« less