The Americhem site in Mason, Michigan is located on one of the longest (22 miles) eskers in the United States. Groundwater within this unique and highly-permeable depositional feature has been impacted by chlorinated solvents, which have migrated approximately 0.5 miles from the source area at velocities of up to 23 feet/day. While intrinsic anaerobic bacterial processes have largely degraded the plume’s primary contaminant, trichloroethene (TCE), elevated concentrations of dichloroethene isomers (DCE) and vinyl chloride remain.
Based on its demonstrated success in the biological remediation of a similar TCE contaminant plume at the Federal-Mogul Corporation site in St. Johns, the Michigan Department of Environmental Quality (MDEQ) awarded ECT a contract to design and implement a remediation plan to stimulate indigenous halorespiring bacteria insitu. The overall objectives were to accelerate the existing degradation process to non-toxic ethene and mitigate threats to a downgradient creek.
ECT collaborated on the design, installation, and successfully operation of a pilot test nutrient delivery system that is almost entirely trailer-based, with the only on-site components being the delivery and performance monitoring wells. Mobilized for regular (one day) feeding events, the initial system achieved approximately 80 percent degradation of chlorinated ethenes within six months of startup.
Based on this demonstration, the MDEQ subsequently authorized ECT to address the full plume width with this technology. The resulting system has been designed and in operation since June 2011. Still entirely operated out of a trailer, the system treats approximately 300 gpm of groundwater per mobilization, and effectively addresses a plume width of roughly 200 feet. Notably, DCE and vinyl chloride reductions of greater than 90 percent are being achieved, and plume contraction is evident, even in monitoring wells located 350 feet downgradient of the delivery points.