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4C r7N- Geological Audit Services, Inc j4 . 77r --� 1803 W. March Lane, Suite A•Stockton, CA 95207•(209)956-064�F X (209) 956-070F1 d S�II O CC PROPOSED MITIGATION OF HYDROCARBON CONTAM]AT1JN AT LERNER OIL CO. EALTN ENTAL NViRONMH 521 N. Cherokee Lane ENVIRONMENTAL Lodi, California EXECUTIVE SUMMARY Six underground storage tanks for gasoline and waste oil were excavated and removed from this service station in 1988 . Subsequent soil testing revealed that soil beneath the tanks was contaminated with gasoline. Four soil borings were then drilled around the tank cavity and soil samples were analyzed with a portable photo- ionization detector to help estimate the extent of the contamination. The samples indicated that contaminated soil was present from a depth of about 15 feet down to about 40 feet. The groundwater table was reached at 40 feet, and a water sample was collected from one of the borings. Gasoline was present in the groundwater, and this boring was converted to a monitoring well to monitor fluctuations in the water table and in contamination levels. FALCON ENERGY ASSOCIATES and GEOLOGICAL AUDIT SERVICES, of Stockton, California, have been retained to assess the extent of soil and groundwater contamination and remove it. Two new monitoring wells were drilled in May, 1991. The soil in both wells was contaminated down to the water table at 45 feet, and groundwater is contaminated in one of these. Because gasoline- contaminated groundwater poses a significant risk to public health, the standard first step in the remediation process is to remove the contaminated water. A vacuum truck will be used to pump out the water and gasoline, which will be temporarily stored in 55-gallon drums pending transport to a resource recovery facility for thermal destruction. Depending on the volume of gasoline, this process may take several days. Approximately four to six weeks after transportation, a Certificate of Thermal Destruction will be issued to the generator. The second phase of the cleanup will involve the drilling of additional soil borings to determine the lateral extent of soil contamination. As before, soil samples will be analyzed by a state- certified testing laboratory to determine whether contamination is present. After the extent of the contamination has been identified, a specific plan to remove the contamination will be devised. This may involve the operation of a vacuum-extraction system, which utilizes an internal-combustion engine to volatilize the gasoline and suck the vapor to the surface, where it can be burned in the engine. The engine is equipped with a catalytic converter to minimize air emissions, which are carefully scrutinized by the Air Pollution Control District to insure that air quality standards are met. The system will receive periodic maintainence to insure peak efficiency during the several months that it would be in operation. Environmental Services•Hydrogeology•Geotechnical Services