CERCLA Feasibility Assessment Gary, Indiana

Situation

An uncontrolled landfill, part of a federal enforcement action, had released numerous non-aqueous phase liquids (NAPL), including hydrocarbons and halogenated solvents. Both soils and groundwater were highly contaminated. A slurry wall installed by the EPA as an interim remedial measure exacerbated the problem because of rainfall accumulating within the slurry wall. The final remedy in the Record of Decision (ROD) stipulated removal of half a million cubic yards of soil, with 90,000 cubic yards being incinerated. The client was faced with a potential cleanup bill approaching $100 million. Hydro Geo Chem was retained to develop a source reduction alternative to incineration, and gain EPA concurrence for modification of the ROD.

Hydro Geo Chem's Approach

Hydro Geo Chem conducted numerical simulations to evaluate the feasibility of soil vapor extraction (SVE) using horizontal drains to accomplish source reduction. The computer models were modified to include the effects of NAPL on cleanup efficiency. We then conducted pre-design field work and a SVE-bioventing pilot test to evaluate contaminant distributions, to collect site specific data on soil-gas distribution coefficients, and to determine soil properties important to SVE evaluation. The system design includes the use of vapor-phase tracers to assess vapor extraction system performance and the potential impact of bioremediation.

Results

Our source reduction alternative using SVE and bioremediation was accepted by EPA, who modified the ROD accordingly. The costs to the client totaled less than 5 percent of the original cleanup estimate. The full-scale system has been installed and is currently in operation by the client.