Adaptive Design to Complete Remediation of Cr(VI)-Impacted Groundwater to Drinking Water Standards

Site-wide remediation services were performed under a fixed-price contract to achieve regulatory closure where former industrial operations resulted in chromium impacts to soil and groundwater. The initial groundwater remedy implemented from 1994 to 2007 consisted of a network of up to 14 extraction wells situated throughout the plume. While the initial extraction system achieved hydraulic containment, the design did not significantly achieve concentration reductions or plume footprint contraction. Full-scale in-situ groundwater remediation was conducted at the site from April 2008 to September 2017 over 10 operational phases over two hydrostratigraphic units. Cr(VI) concentrations have been reduced from baseline concentrations greater than 10,000 micrograms per liter (µg/L) in the source area to below cleanup goals (10 µg/L) throughout the plume. Successful remediation of Cr(VI) in groundwater was achieved through adaptive operation that enhanced groundwater gradients and associated mass flux within discrete treatment cells, established robust in situ reactive zones capable of in-situ Cr(VI) reduction, and proactively optimized system operation in response to treatment performance. The adaptive approach employed in this case study can be applied to achieve substantial reduction in lifecycle costs for groundwater remediation of a broad range of contaminants amendable to enhanced extraction and biogeochemical fixation through in-situ remediation.