The Paducah Gaseous Diffusion Plant (PGDP), located in western Kentucky, is a former uranium enrichment facility owned by the U.S. Department of Energy (US DOE). A previous Remedial Investigation (conducted by others) identified a plume (known as the Southwest Groundwater Plume) at the PGDP. Source area characterization found that the former Oil Landfarm area (Solid Waste Management Unit 1) was contributing to this plume.
The primary groundwater contaminant of concern for the Southwest Groundwater Plume is trichloroethene (TCE). A Record of Decision (ROD) was prepared under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) for the Oil Landfarm area that specified an in-situ treatment using deep soil mixing with interim Land Use Controls. The objective for this project was to design and ultimately implement the Remedial Action for the Southwest Groundwater Plume Oil Landfarm source area.
Geosyntec's Scope of Services
Geosyntec designed the in-situ source treatment for the Oil Landfarm area. The remedial design included the implementation of in-situ soil mixing with large diameter augers (LDA) combined with the introduction of hot air and steam for thermal volatilization and stripping of volatile organic chemicals from the soil and groundwater. The treatment system also included surface vapor recovery and treatment, as well as the addition of a final LDA pass using a zero-valent iron slurry mixture to provide a polishing step for additional treatment.
As part of remedy optimization, Geosyntec developed estimates of the extent and mass of TCE in soils above the Regional Gravel Aquifer using C Tech's Earth Volumetric Studio (EVS). EVS is a three-dimensional volumetric visualization and processing software. Using updated site characterization information, the design was optimized to focus LDA remediation at the source area core to maximize mass removal. Regulator trust was gained by performing sensitivity and uncertainty analyses to evaluate the potential residual mass (presented as a TCE volume) remaining within the proposed optimized treatment footprint. Ultimately, the optimization allowed for the reduction in the number of LDA borings required, resulting in significant cost savings.
Geosyntec worked with the client and regulators to provide an effective, economical and practical design to implement the Remedial Action. An innovative approach to source area remediation resulted in significant cost savings for the project by incorporating a combination of geostatistical modeling and remedial technologies aimed to collectively meet remedial goals in an efficient manner.