Pilot Study Data Evaluation: Enhanced Attenuation of PFAS and VOCs in Groundwater
Between 2013 and 2015, thermal remediation of the overburden source zone removed ~500,000 pounds of VOCs and a RCRA cap was installed over the source area in 2016-2017. Expecting these measures would eliminate the need for long-term NTCRA 1 extraction, three valved penetrations were installed through the sheetpile wall, collection and redistribution trenches were constructed on the up- and downgradient sides of the wall, and fill was placed to account for predicted groundwater rise downgradient of the wall.
Despite orders of magnitude VOC concentration reductions in source zone soil and groundwater, and significant ongoing MNA, groundwater within the sheetpile wall remains more impacted than downgradient of the wall. PFOS and PFOA were also detected in NTCRA 1 groundwater at concentrations higher than in NTCRA 2 groundwater. Regulators expressed concern that allowing groundwater flow through the penetrations would degrade the downgradient water quality.
A pilot study was implemented to evaluate using zero-valent iron (ZVI) and PlumeStop® to treat groundwater within the trenches and minimize the potential for adverse downgradient water quality impacts. This presentation will provide an overview of the pilot study approach, summarize the monitoring performed to date, and preliminarily evaluate the materials’ effectiveness at attenuating PFAS migration in groundwater.