Ex-situ Groundwater
The ROD identifies ex-situ treatment of the 1,4-dioxane and VOC plume as a remedial component of the RD/RA. Due to the mobility of 1,4-dioxane and an inherit threat to a downgradient municipal well, USEPA elected to accelerate the cleanup efforts through a Non-Time Critical Removal Action for Groundwater (GW NTCRA), effective July 2016. In order to isolate the plume and cutoff the migration towards Assabet 1A supply well, a temporary treatment system was installed in May 2017 and operated through May 2019.
Operations of the temporary system proved that pumping the extraction well at ~20 gallons permit successfully achieved hydraulic containment of the plume and cutoff migration of contaminated groundwater downgradient to the extraction well. The final groundwater treatment system was designed to operate at the same extraction rate and includes an innovative Advanced Oxidation Process (AOP) that successfully treats 1,4-dioxane and VOCs to non-detectable concentrations. The final groundwater treatment system has been in operation since April 2019 and will continue in perpetuity until site remedial goals in overburden are met.