A leaking process discharge line at the Energy Systems Testing Area at NASA’s Johnson Space Center (JSC) resulted in the release of 1,1,2-trichloro-1,2,2-trifluoroethane (chlorofluorocarbon 113 or CFC- 113) and trichloroethene (TCE) into two hydrostratigraphic units from the 1960’s through the 1980s. Contaminants migrated through deposits of interbedded clay and saturated sand to a depth of 80 feet below ground surface. Historically, the co-mingled plumes contained CFC-113 and TCE concentrations of up to 90 milligrams/liter (mg/L) and 0.05 mg/L, respectively. The level of TCE in groundwater exceeded the maximum contaminant level (MCL) in isolated locations within the shallow saturated sand zone (SS-1) at 10 to 20 feet below ground surface and a lower saturated sand zone (SS-2) at 60–80 feet below ground surface. Though CFC-113 concentrations did not exceed the MCL, JSC desired that both CFC-113 and TCE be treated. A groundwater pump and treat system installed in the early 1990s controlled migration of the affected groundwater but did not reduce the TCE concentrations to below the MCL in a timely fashion.

To attain JSC’s objective of reducing TCE concentrations to below the MCL and to reduce CFC-113 concentrations to the maximum extent practicable in an expedited manner, in situ chemical oxidation (ISCO) using sodium permanganate in groundwater was investigated and tested at the site. Few studies exist in the literature describing the effectiveness of permanganate oxidation of CFC-113. Some evidence indicates that high concentrations of CFC-113 might interfere with the direct oxidation of TCE. Bench-scale ISCO treatability studies using batch reactors and column tests indicated that sodium permanganate completely mineralized low concentrations of TCE in the presence of CFC-113, which itself was partially mineralized. The presence of high concentrations of CFC-113 did not inhibit the oxidation reaction at a TCE concentration of 0.1 mg/L.

Pilot injection tests in both affected saturated zones confirmed bench-scale results that ISCO is effective at oxidizing both the CFC-113 and TCE. The initial results of the pilot tests indicated that TCE was oxidized to concentrations below the MCL within both saturated zones, while the CFC-113 concentrations were reduced from 50 to 65 percent in these zones. These results indicate that sodium permanganate is effective at remediating a co-mingled plume of CFC-113 and TCE.

Unnumbered Figure. Groundwater monitoring conducted during pilot oxidant injection test. The purple color in the purging lines indicates the presence of the oxidant in groundwater.

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