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- •...., rivvL vL %1WL1%,%,rL aL LLL , LL�,LU 1k..vc1 waa aLaneveQ in ule VV ULCU100 LCSL, !L remained necessary to show efficacy in an actual groundwater pollution scenario. Soil and ground water contamination, due to release of gasoline from an underground storage tank, was initially identified and investigated at the Jennifer Mobile Home Park by the North Carolina Division of Environmental Management. Additional site characterization was completed by the Civil Engineering Department of North Carolina State University for further definition of the plume and to design the oxygen barrier system. The following describes the environmental conditions, remedial action and results of oxygen barrier installation, within the 137 day investigative period. The plume, which was the target of remediation efforts, was characterized at a point 150 feet downgradient of the source. At this point, BTEX concentrations were 8 ppm in a region 120 feet wide and 10 feet deep. The oxygen concentration within the plume was zero and the redox potential was -50 mV. Outside the zone of contamination oxygen levels were 1-4 ppm in a +50 mV redox background. The conductivity of the aquifer is approximately 76 feet/day; velocity was approximately .9 feet per day. The influent BTEX levels rose during the course of the experiment by a factor of three to five times. OXYGEN BARRIERS were constructed intersecting the plume 150 ft downgradient from the source. The permeable barrier system consists of 22 fully screened PVC wells 5 feet on center in a line perpendicular to the plume. The wells were 6 in. in diameter and 10 ft. in depth from the water table. The ORC was mixed in concrete to from briquets and was installed in filter fabric socks that were hung inside the PVC wells. Monitoring wells were installed upgradient and downgradient of the barrier. Groundwater samples were monitored for dissolved oxygen, BTEX concentration, pH, - redox potential, and other parameters at various times over 137 days. The ORC Oxygen Barrier reduced BTEX contamination from source levels of>20 mg/L to <0.1 mg/L in 137 days; B was reduced to within <1% of standard (8000 ppb to 34 ppb) and T, E and X were below standard. Oxygen levels in source well were maintained between 9 and 17 ppm. In must be noted that the ratio of oxygen to carbon was only 2:1 and the wells were only loaded to partial capacity. Also, incoming BTEX levels tripled during the course of the trial, and at the end of the experiment, free hydrocarbon product was found in one of the wells. This raised the possibility that other similar zones may have existed downgradient between the barrier wells and the monitoring points. The current product consisting of a sand/ORC mixture in a polyester sock is both denser and made to occupy more of the available well diameter. Along with some ORC quality improvements it can deliver three times the oxygen as was delivered in this early experiment. The oxygen barrier was replenished with the current product and results will be completed and published in early 1996.