Use of Permeable Reactive Barrier to Bioremediate a Petroleum Hydrocarbon Groundwater Plume

Circa 1980s release of gasoline at a large throughput fueling facility at an Interstate Rest Area produced a groundwater plume which impacted a downgradient wetland area. Previous remediation efforts at the facility sufficiently addressed petroleum impact to the vadose zone but the groundwater plume persisted. Dissolved volatile petroleum hydrocarbons (VPH) were detected in monitoring wells located at a wetland area approximately 200 feet from the sources (underground storage tank systems). The natural reducing conditions at the wetland were exacerbated by the petroleum hydrocarbon groundwater plume resulted in the concentration of arsenic and beryllium in shallow soils. Remediation of the groundwater plume was complicated due to the active fueling operation and presence of approximately 25 feet of fill material [boulders, blast rock, and concrete from the circa 1960s construction of the Interstate highway] overlying the saturated zone. A permeable reactive barrier (PRB) was installed orthogonal to groundwater flow approximately 100 feet up-gradient of the affected wetland to bioremediate the groundwater plume. A mixture of granular activated carbon product (BOS 200®), calcium sulfate, and water was injected throughout the saturated zone to establish the PRB. Post-installation monitoring data indicate that the remedy is performing as designed. The conceptual site model, PRB design and installation data, and approximately 18 months of post-PRB installation performance monitoring will be presented.