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06 August 2003 AGE-NC Project No. 03-1045 Page 2 of 6 valley(Olmsted and Davis, 1961);the site itself is located on unconsolidated and semi-consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977).Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basin 5-22).The estimated depth to ground water at the site is approximately 20 to 25 feet below surface grade(bsg)based on information obtained from wells installed and sampled by AGE, located immediately south of the subject property on the Comfort Air facility. Ground water flow direction is generally toward the southeast. However, this may be greatly modified by local recharge and discharge patterns. 2.2. UNDERGROUND STORAGE TANK REMOVAL One 1,000-gallon leaded gasoline UST was removed in October 1987; the SJCEHD noted hydrocarbon odor and soil discoloration at the time of removal. Soil samples were collected at 15 feet below surface grade (bsg) and analyzed for gasoline, diesel, kerosene, motor oil, benzene, toluene, ethyl benzene, xylene (BTEX) and lead; the analytical results showed non-detect for all analytes except lead (5.5 mg/kg). The chain of custody was never submitted, and because of the missing documentation and the discrepancy between the SJCEHD evaluation and the analytical results the case was not closed. 2.3. PREVIOUS SITE ASSESSMENTS An Unauthorized Release Report (UAR) was issued by the SJCEHD in March 1994 to facilitate further site assessment. One soil boring was advanced through the former tank excavation to a depth of 15 feet bsg on 04 June 1996. However, the SJCEHD was notified that the sample had been lost and the site was resampled on 20 June 1996 at a depth of 16 feet bsg. The analytical data for the 20 June 1996 sampling indicated non-detect for gasoline,BTEX and the fuel oxygenate MTBE.The laboratory quality assurance procedures were questioned by the SJCEHD and resolved in December 1996. The property was given a"no further action"letter and"closed by the SJCEHD in May 1997. Advanced GeoEnvironmcntal,Inc.