Environmental

Site 10

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Site 10: Former Trichloroethene Still and Plant Production Wells A and C

 

Background

Site 10 (formerly designated as Site Production Well A [PWA]) is an 8-acre area located in the south-central area of the developed portion of Plant 1 at ABL. The Site consists of the area that includes the former trichloroethene (TCE) still adjacent to Building 157, former PWA, and former Production Well C (PWC).

Previous investigations identified contamination in groundwater attributed to historic activities at Building 157 that involved distillation of used degreasing solvents from the former TCE still that operated adjacent to the Building during 1959 and the early-1960s. Because volatile organic compounds (VOCs) were detected in the PWA well as early as 1980, the use of PWA as a water source was discontinued.

Site 10 is being managed as two separate Operable Units (OUs). An Interim Record of Decision (ROD) document for Site 10 groundwater (OU-5) was signed in August 1998. The selected interim remedy for Site 10 groundwater was “hot-spot” groundwater extraction with subsequent treatment and discharge of treated water to the river. A treatment facility was designed and constructed near Site 1 to remove hazardous constituents from the extracted groundwater. The implementation of the interim remedial action at Site 10, which initially included three extraction wells connected to the Site 1 treatment plant, was completed in February 1999.

Subsequent to the implementation of the interim remedial action, aquifer testing and modeling indicated the need for additional extraction wells for the bedrock aquifer at Site 10 to adequately contain contaminated groundwater at Site 10. These changes to the extraction system were implemented in February 2003. This expanded groundwater extraction system was selected as the final remedial alternative for Site 10 groundwater in a ROD signed in September 2005. The fifth Five-Year Review for ABL, finalized in 2018, determined that the groundwater remedy at Site 10 is protective of human health and the environment. However, the Five-Year Review recommended improvement to the existing groundwater remediation system effectiveness. As such, a pilot study began in July 2020 to evaluate the groundwater VOC plume while the extraction system is shut down. Groundwater extraction and long-term monitoring (LTM) continue at Site 10. LTM activities include groundwater sampling every five years, and the results are documented in progress reports.

A Vapor Intrusion (VI) investigation was completed in January 2016. Based on this investigation, a human health risk screening was conducted in 2017 and additional investigations at select buildings to further assess VI is expected to be completed in 2020. Results of the VI investigation will be presented in a forthcoming risk assessment.

Evaluation of soil data concluded that soil at Site 10 does not present an unacceptable risk to human health or the environment. A No Further Action ROD document was signed for Site 10 soil (OU-6) in 2007.

Detailed information from previous investigations conducted at Site 10 is available in the Administrative Record.

 

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