PROJECT DATE: July, 1972 to January, 1974
CLIENT: Sun Oil Company
BACKGROUND: A pipeline break spilled an estimated 3,186 barrels of high octane gasoline into an aquifer composed of a highly fractured dolomite. The gasoline was contained by pumping nearby wells. Physical recovery of the gasoline continued until no longer productive an estimated 1,000 barrels (42,000 gallons) remained.
ACTION TAKEN: The gasoline-utilizing microbial population was stimulated by the addition of nitrogen, phosphorus, and dissolved oxygen. Dissolved oxygen was supplied by sparging air into wells with diffusers connected to paint sprayer-type compressors. Ground water flow was controlled by a series of injection and withdrawal wells.
EFFECTIVENESS: Estimates based on the amount of nitrogen and phosphate retained in the aquifer suggested that from 744 to 944 barrels of gasoline were degraded. The amount of free gasoline in the wells declined as the nutrient addition program continued. The levels of gasoline in the produced water were not reduced during the period of nutrient addition, but no gasoline was found in the produced water ten months later. Bacterial levels increased greatly in the ground water. The biostimulation programs met its objective of removing the hydrocarbons from the ground water to the satisfaction of the governmental agency overseeing the project.