Abstract

 An Integrated Sediment Quality Assessment was conducted to evaluate the ecological risk to aquatic organisms in downstream surface water and sediment due to compounds originating at a contaminated aquifer. The objective for the assessment was to measure specific chemical and biological parameters in an unnamed stream and wetland to evaluate the ecological risk to the aquatic communities downstream of a RCRA Facilities Investigation. The groundwater in the upper aquifer at the facility discharges to an unnamed stream and wetland. A review of the groundwater monitoring data and surface water and sediment quality data were used to characterize the contaminants and to develop a list of contaminants of concern (COC) for the study area. The COC list and the potential for an adverse ecological impact was evaluated using a step-wise tiered approach that assessed the potential for toxicity and/or ecological risk. That screening eliminated many of the chemicals from the COC list including any compounds that bioaccumulate or cause adverse risk to wildlife.
  The potential for the remaining contaminants to cause ecological harm was evaluated by conducting whole sediment toxicity, surface water toxicity, fish and macroinvertebrate community assessments. The intermittent stream whole sediment toxicity assessment and to some extent the intermittent stream macroinvertebrate assessment indicated an adverse impact immediately downstream of the closure site. We correlated the whole sediment toxicity and the macroinvertebrate assessment results with measured concentrations of copper and cyanide, although the results indicated that the test results correlated best with the concentration of copper measured in the water and sediment. We concluded that copper was the principal causative agent and likely responsible for the effects we measured in the intermittent stream. The contamination appeared to be restricted to a relatively small geographical area within the intermittent stream and diminished downstream prior to reaching a river.