Examples of Cleanup Approaches
    Fairfield Coal Gasification Plant Site, Fairfield, IA

Site contamination was the result of onsite disposal of waste byproducts generated from the production of coal gas. The waste byproducts, referred to as "coal tar," were disposed on ground or to in-ground containment structures. Thirty chemicals were identified in the risk assessment at the site in both soil and ground water.

The site stratigraphy is fill overlying glacial till consisting of interbedded silty clays and silty sands with minimal sand and gravel lenses. A shale bedrock is found at approximately 77 feet. There are two groundwater systems present in the site area: a localized perched system within the fill and an unconfined system that lies within the underlying silty clays and silty sands above the shale bedrock. (ROD dated 9/21/1990)

The remedial goals at the site were to excavate and treat contaminated source area materials and to clean up contaminated ground water to action levels. EPA established a hierarchy for choosing action levels. The first level to be considered was the EPA negligible risk level (NRL), then the EPA lifetime health advisory level (HAL), and finally MCLs. For the majority of PAHs, method detection limits were chosen as cleanup goals.

Coal tar contaminated soils found during the remedial investigation were excavated and disposed of offsite. Approximately 8,280 tons of contaminated soil that was determined to be non-RCRA hazardous was thermally treated, and 580 tons of RCRA hazardous source material was incinerated. These actions were completed in June of 1995.

A pump-and-treat system was constructed to address the entire zone of contaminated water. The treatment process includes sedimentation, filtration, and activated carbon polishing. The generated sludges are dried with a filter press and disposed of off site. The system came on line in 1989. Institutional controls on land and groundwater use were also implemented at the site.

As a result of the source removal and 12 years of pump and treat, the offsite plume has been consistently below cleanup levels for several years in a row, and the onsite plume has been reduced to levels that may support less expensive, passive remediation using monitored natural attenuation (MNA). Consequently, operation of the pump and treat system was discontinued in July 2001, and an evaluation of MNA was begun. As of June 2004, the pump- and-treat system was still inactive, and MNA was still under evaluation.

Identified source zone areas have been removed, plume extent has been reduced, offsite plume restored to drinking water standards, and onsite plume reduced to levels that may support MNA remediation. Consideration of MNA shows flexibility on the part of Agency.

Record of Decision (53K/26pp/PDF)
1997 Five-Year Review (215K/15pp/PDF)
2002 Five-Year Review (170K/48pp/PDF)