Case Studies - MD001 - Pneumatic Fracturing

Navy Facility - Maryland

Enhanced Reductive Dechlorination (ERD) of tetrachloroethene (PCE) was implemented within a fractured bedrock aquifer at the former Naval Facility in Maryland. This project was implemented on behalf of the US Navy as part of a remedial action to mitigate off-site migration of the chlorinated solvents. The remedial action involved “hot spot” in situ bioremediation of groundwater to eventually reduce contaminants within a reasonable timeframe by stimulating biological activity.

Due to the low permeability of the aquifer sediments (saprolite), pneumatic fracturing (PF) was used to increase subsurface permeability and enhance distribution of a emulsified vegetable oil (EVO) within the target treatment zone.  Approximately 10,440 pounds of 60% substrate was injected into forty five boreholes spaced  within a 60,000 square foot treatment area.  The ground water quality results are presented below.

Three existing monitoring wells, located within 30 feet (ft) of the injection points, were used to monitor the distribution and persistence of the substrate and assess the treatment effectiveness of the injections. Groundwater samples collected 3 months following the injections as part of an ongoing performance monitoring program confirmed greater than 99% reduction in the target COC (PCE) has occurred within 3 of the 4 wells being monitored within the treatment area.  Minor increases in cis-1,2 DCE were also observed indicating treatment via sequential reductive dechlorination.

 

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