Historical industrial processes resulted in hexavalent chromium impacts to soil and groundwater at a former manufacturing facility in the Northeast United States. Groundwater remediation was conducted as part of several environmental remedies for various sections and depths at the site, including soil excavation, soil mixing, pump and treat, and in situ chemical reduction. For several areas within the lower overburden groundwater plume, as an interim remedial measure (IRM), installation of a viscous slurry reactant (FerroBlack®, a mackinawite structured iron sulfide) was chosen to reduce hexavalent chromium to trivalent chromium.
Here, a viscous slurry was installed in a silty-sand unit and a glacial till unit at significant depth without using soil mixing or hydraulic fracturing. This transect application was a contemporary modification to conventional source treatment and permeable reactive barrier (PRB) options and was preferred for this phase of the project compared to other alternatives, such as excavation and direct mixing.