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IN-SITU AND EX-SITU BIOREMEDIATION PROJECTS:
4. Gasoline spill from underground storage tanks - Conoco, Inc.

LOCATION:  Watsonville, California
PROJECT DATE:  July, 1987 to July, 1988
CLIENT:  Conoco, Inc.

BACKGROUND: A gasoline spill from underground storage tanks at a service station in Watsonville was discovered. Approximately 1,500 gallons were lost to the shallow aquifer of low permeability. Physical recovery operations were not possible. The California Regional Water Quality Control Board (Central Coast) directed that recovery operations continue until groundwater samples were proven to contain less than 0.7 parts per billion (ppb) benzene.

ACTION TAKEN: A bioreclamation program was chosen as the most cost effective remediation technique with the capability to meet the stringent state cleanup requirements. Nutrient and oxygen formulations were added to infiltration wells in batches. Hydrogen peroxide was used as the oxygen source for this project. Producing wells were used to control ground water flow at the site.

EFFECTIVENESS: This was the first bioremediation project in the state of California that was successfully closed under the tough new cleanup guidelines.