In-situ biological treatment is one among a number of emerging technologies that may be applied to the remiediation of contaminated soils and groundwater. In 1985, a surface spill of 1, 500 gallons of dielectric transformer oil at the Sandia National laboratories (HERMES II facility) re-sulted in contamination of soil up to depths of 160 feet. The extent of contamination and site characteristics favored the application of in-situ bioremedation as a potential remedial technology. The purpose of this research was to enumerate indigenous microbial populations capable of degrading petroleum hydrocarbons. Microbial enumeration and c haracteriztion methods suitably adapted for hydrocarbon utilizing bacteria were used as an incidator of the presence of viable microbial consortia in excavated oil samples with hydroocargon (TPH) concentrations ranging from 300 to 26,850 ppm. Microbial activity was quantified by direct and streak plating soil samples on silica gel media. Effects of toxicity and temperature were studied using batch cultures of hydrocarbon utilizing bacteria (selectively isolated in an enrichement medium), at temcroorganisms from contaminated soils from depths of 60 to 160 feet, and with oil concentration ranging from 300 to 26,850 ppm. About 62
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