SITE INFORMATION AND CORRESPONDENCE

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MEMORANDUM I, I' s. CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL.VALLEY REGION { 3443 Routier Road, Suite Al Phone: (916) 255-3000 Sacramento, CA 95827-8098 CALNET: 8-494-3000 f TO. Gordon Lt\13oggs FROM: �j Elizabeth A. Thayer Undergro Tank Program Manager Associate Engineer DATE: 15 June i SIGNATURE: SUBJECT: REVIEW FOR NO FURTHER ACTION, MAJOR MART, 1235 EAST ALPINE, STOCKTON SAN JOAQUIN COUNTY I1 The former Major Mart is located on the northwest corner of East Alpine Avenue and West Lane. The Kearny-KPF site encompasses a large area southeast of M ajor. Mart, south of Alpine and east of West Lane. No site investigation was conducted between the time the tanks were removed in 1988 to mid- 1991. Since 1991, several environmental consultants have worked at this site. Woodward-Clyde Consultants conducted the investigation between August 1991 and June 1992. Weston Consultants conducted the investigation between July 1992 rand March 1994. Secor has been the consultant since April 1994. INVESTIGATION MILESTONES 1. In April 1988, a 10,000 gallon gasoline tank failed a tigltness�test. 2. In June 1990, three gasoline tanks (6,000, 8,000, and 10,000'gallons) and a 500 gallon waste oil tank were removed by Seibold Corp. Contaminatiori Fwas detected in the soil below the tank. "Simple Green", a detergent, was added to the tank pit! n an unauthorized attempt to remediate contamination. !i ; 3. In June 1991, MW-1, MW-2, and MW-3 were installed. I R 4. In August 1992, MW-4, MW-5, and MW-6 were installed. Also in August 1992, the gas station canopy was demolished and the fuel pipelines were removed,6p to the buildings. Soil was sampled under the pipelines and in the pit. 5. In March 1993, a 150 gallon solvent tank was removed and the 10,000 gallon tank pit was overexcavated. Six hundred cubic yards of soil were removed,to a depth of 32 feet. 6. In April 1994, Secor drilled borings SB-1 and S13-2 to complete the underground tank investigation and SB-3 and SB-4 near the former septic leach field. SOIL CONTAMINATION i3 At the time of tank removal in 1990, soil samples from the Ipit contained up to 1360 ppb benzene, 44,500 ppb toluene, 87,000 ppb ethylbenzene, 313,000 ppb{totaljxylenes, and 5300 ppm TPHg. At the completion of the overexcavation in 1993, after several rounds of excavation and sampling, low levels of TEX and TPHg were detected in soil samples from the excavation side walls and bottom. Benzene was not detected. The highest level of soil contamination in the tank pit was 2.5 ppm TPHg at a depth of 25 feet in the south side wall. '!Soil samples from beneath the solvent tank did not contain TPH, BTEX, or solvents. �',