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ENVIROLOGIV TECHNOLOGIES, INC_ appears to be influenced by fluctuating surface water levels associated with a nearby river Flow direction has been observed to range from westerly to easterly ' through the year Site Conditions. Groundwater at this facility has been impacted by BTEX (beri.ene, toluene, ethylbenzene and xylenes) compounds as a result of a gasoline release from an underground storage tank system. It was apparent that very little natural degradation of the contaminant plume was occumng with historical ' analytical data indicating that contaminant concentrations had decreased by less than 37% over a four year period It appeared that the limited natural degradation could be attributed to the oxygen deficient conditions present within the ' contaminant plume Due to the low groundwater flow velocity, the rate of oxygen entering the system was minimal Therefore, Envtrologic designed a source area treatment using ORC to augment natural bioremediation. MATERIALS AND METHODS ORC is a magnesium peroxide powder that, when mixed with water, ' releases oxygen The ORC provides a slow release of oxygen, taking several months to fully complete the reaction The oxygen is delivered to the system ' using the natural groundwater flow system lo deliver the oxygen to the aquifer, the ORC was precast in solid cylinders for installation using hollow stem augers The boring Pattern was focused in areas around the former tank vaults and pump islands in order to concentrate oxygen in the source areas where the highest oxygen demand was expected (refer to r)gure 1) Due to the highly vanable groundwater flow direction at this site the ORC was Positioned so that when the groundwater flow direction changed, a source of ORC would continue to affect the source of groundwater contaminants Cnstinla The ORC powder was mixed at a 2 1 ratio with water to form a slurry The slurry was then poured into 10 2 cm inner diameter, one meter length, PVC ' casing which was capped at one crid to form a casting mold The slurry was allowed to set for approximately 48 hours Once the ORC had formed a solid ' cylinder, the PVC casing and cap were cut away from the ORC for installation into the aquifer ' Instatl:ition. In November and December of 1995, 50 borings were advanced across (lie site The boring were advanced using 10 8 cm inner diameter (ID) hollow stem augers to a depth 3 0 m below the wiater table surface (10 7 m total ' depth) Three one meter length cylinders were then installed through the hollow stem augers into the upper three meters of the aquifer The natural formation was allowed to collapse and surround the ORC cylinder The boring was backfilled to ' grade with cuttings generated during the drilling process The installation of the . ORC cylinders was completed on December 4, 1995 2T • d dTE: = 90 66-t'T -�at7