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15 June 1999 AGE-NC Project No. 99-0606 Page 2 of 6 2.2. EXCAVATION OF FORMER TRUCK REPAIR FACILITY On 17 May 1999 the gravel parking lot, formerly the site of the truck repair facility, was excavated to a depth of approximately five feet below surface grade (bsg). The total excavated volume of material was approximately 300 cubic yards. During excavation a possible dry well (vertical injection well) was unearthed. A total of six soil samples were collected during the excavation procedures.Five of the soil samples were located in or around the former repair facility area,and one sample was collected from the center of the possible dry well. Total petroleum hydrocarbons as gasoline (TPH-g) was detected in sample SS-1-3.5 as high as 4.3 milligrams per kilogram(mg/kg). Total petroleum hydrocarbons as diesel (TPH-d) was detected in sample SS-6-1,2 as high as 4,300 mg/kg. Total petroleum hydrocarbons as motor oil (TPH-mo)was detected in sample SS-6-1,2 as high as 11,000 mg/kg. Toluene and Total Xylenes were detected in samples SS-2-6 and SS-6-1,2 as high as 0.024 and 0.021 mg/kg respectively. Analytical results are attached. 2.3. REGIONAL HYDROGEOLOGICAL SETTING The Modesto, Riverbank and Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500-square-mile San Joaquin Valley Ground Water Basin. The basin is drained primarily by the San Joaquin River. The nearest water feature is the Stockton Diverting Canal approximately 4,000 feet northwest of the site. The estimated depth to ground water at the site is approximately 50 feet below surface grade, based on the map titled Lines of Equal Depth to Groundwater Spring 1997 published by the San Joaquin County Flood Control District and Water Conservation District (FCD&WCD). It is inferred from the map titled Lines of Equal Elevation of Groundwater Spring 1997, also published by the FCD&WCD, that the site is in an area where groundwater flows generally toward the south, southeast. Local ground water depths and flow directions can vary based on seasonal rain fall. Ground water depths may vary as great as 10 to 15 feet from previous documented records. 3.0. SCOPE OF WORK The scope of work will initially include the advancement of six soil probe borings to depths of 30 feet below surface grade(bsg).However, if field observations indicate that significant contamination is present at the site, selected probe borings may be advanced to greater depths or additional probe borings may be advanced. Advanced GcoEnviron mental,Inc.