Background

The Chrome Plating Shop Facility at the Rock Island Arsenal operated from after World War II through the 1980s until it was required to close under the Resource Conservation and Recovery Act (RCRA). Contaminants in the concrete, soil and groundwater included chromium, cadmium and chlorinated solvents. Complex hydrogeology—including three distinct formations, fracture flow, karst features and a nearby water supply well—made characterization and conceptualization especially challenging.

Approach

Investigation provided a more thorough understanding of the island’s hydrogeology. The resulting conceptual site model has been used by Foth and other investigators for sites on the island, including two risk investigation/feasibility studies under the installation restoration program and Comprehensive Environmental Response, Compensation, and Liability Act.

Our remedial action plan for the former chrome plating shop utilized a risk-based corrective action approach. Hazardous concrete and soil removal was conducted on the interior of the historic building, coupled with bulk sodium lactate application in the excavations to further reduce and dechlorinate the contaminants. We also developed and conducted an innovative pilot groundwater remediation system using sodium lactate injection in wells and an infiltration galley. This work used a turnkey approach which, while conducted as a pilot study, provided significant remediation to the entire site.

Results

A clean RCRA closure has allowed the Army to re-use the historic site, and Foth’s turnkey groundwater treatment provided a cost-effective solution for our client. In addition, significant hexavalent chromium reduction resulted in all geologic formations, including fractured bedrock in the Silurian Formation. Significant amounts of chlorinated solvents were also destroyed through dechlorination, and hazardous hexavalent chromium and TCE groundwater concentrations were treated by in situ reduction and dechlorination.