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06 January 2003 AGE-NC Project No. 02-0896 Page 2 of 7 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 between 55 and 60 feet below surface grade (bsg) based on information from Lines of Equal Depth of Water Wells Fall 1999,published by the San Joaquin County Flood Control District and Water Conservation District- FCD&WCD. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1999 also published by the San Joaquin County FCD&WCD, the site is in an area where ground water flow direction appears to be east-northeast.One domestic well is located on the property,at approximately 80 feet northwest of the USTs location. 2.2. UNDERGROUND STORAGE TANK REMOVAL According to SJCEHD records, two underground storage tanks (USTs) were removed from the property on 30 November 1989. Tank No. 1, a 1,000-gallon unleaded gasoline UST, and Tank No. 2, a 2,000-gallon regular gasoline UST, were located in a common excavation east of the former office building. Two soil samples were collected from the floor of the excavation beneath each UST(a total of four samples). The samples were analyzed at a laboratory for total volatile hydrocarbons (TVH) and volatile aromatics(benzene, toluene, ethyl benzene and xylenes; BTEX)using EPA Method 8020. Petroleum hydrocarbons were not detected in the samples collected beneath the USTs.However,an Official Inspection Report prepared by the SJCEHD indicated that"odd odor noted in backfill like paint thinner" and "vapors were rising off soils". Copies of the analytical results are included as Appendix A; a copy of the Official Inspection Report is included as Appendix B. Based upon noted"odors"by the SJCEHD, two additional soil samples (one beneath each former UST location) were collected on 22 March 1990 (re-sampling). The Official Inspection Report prepared by the SJCEHD indicated that"no odor was detected during sampling,no discoloration was noted either".The two soil samples were submitted to a laboratory and analyzed for Volatile Organic Compounds using EPA Method 8240, and TVH and BTEX using EPA Method 8020. No VOCs or TVH were detected in either"re-sample"soil sample. However, 0.035 milligrams per kilogram (mg/kg) of toluene was detected in the sample collected beneath the 1,000-gallon (southern)UST. Advanced GeoEnviron mental,Inc.