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hydrocarbon contamination onsite and to assess the extent of offsite migration. A "zero line" for ground water contamination will thus be established. The soil borings will be drilled by Spectrum Exploration Inc. of Stockton, California(C57 license number: 512268)under contract to and direct supervision of EA. The wells willbe installed according to EA's standard protocols which are based on the guidelines outlined in the Environmental Protection Agency's Technical Enforcement Guidance Document (TEGD), September 1986, the California State Water Resources Control Board's California Undereround Storage Tank Regulations,August 1987,and the specific guidelines of San Joaquin Environmental Health. All soil borings will supervised by a qualified EA geologist under the supervision of a California registered geologist and/or a professional civil engineer. The soil borings will be drilled with a rotary drill using a 10 inch outside-diameter, hollow- stem auger. The borings to be completed as ground water monitoring wells will, according to guidelines, be drilled below the static,perennial ground water. The static depth to ground water at this site is between 36 and 37 feet below ground surface, and a thick competent clay occurs immediately below the water-bearing sand. The ground-water monitoring wells will therefore be completed at depths between 42 and 45 feet below ground surface, 1 to 2 feet into this competent clay to prevent the downward migration of contaminants through the monitoring wells. The augers will be steam cleaned between use in each soil boring. The drill cuttings will be contained in barrels and stored within a fenced area on-site until the cuttings can be appropriately disposed of. The wells will be completed as monitoring wells (Figure 4) according to Section 2647 of California Underaround Storage Tank Regulations. Factory-perforated PVC screen (Schedule 40 PVC with 0.010 inch slot and flush threads) will be installed from one foot above the bottom of the boring to a depth of approximately 25 feet below ground surface, 10 feet above the static level of the ground water. Blank PVC casing will be used to complete the well to the ground surface. The bottom end of the casing will be fitted with either a threaded end plug or a slip cap. A filter pack will be created by filling the annular space around the casing with Lone Star No, 2/16 sand. The filter pack will extend from one foot below the screened casing to two feet above the top of the screen, approximately 23 feet below ground surface. The sand will be sealed with a minimum of 3 feet of bentonite pellets,and a surface seal will be created with neat cement grout. The grout will be placed by tremie beginning at the the bentonite seal and rising to the top. 8