Intrinsic Bioremediation of Fuel Contamination in Ground Water at a Field Site

A spill of gasoline occurred at an automobile service station in 1986. Oily phase residue in the subsurface has, for the past eight years, continued to release water soluble fuel hydrocarbons into the aquifer. The site was characterized for implementation of intrinsic remediation. The subsurface was a beach sand with sea shell fragments. The water table was near 1.3 meters below ground surface. Surface dimensions over the plume were about 200 meters downgradient and 60 meters in width. Three points to coincide with direction of ground water flow were selected in the plume for water quality assessments. Both methane and trimethylbenzene were used as surrogate tracers to normalize loss of contaminants. Aerobic respiration and methanogenesis accounted for most biodegradation obtained. Assimilation capacities of dissolved oxygen, ferrous iron, and methane distributions when compared to BTEX concentrations showed that the ground water has sufficient capacity to degrade all dissolved BTEX before the plume moves beyond 250 meters downgradient. Evidence obtained from loss of contaminants, geochemistry and microbial breakdown chemicals showed that intrinsic bioremediation technology would be a viable option to restore the site.