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10 September 2004 AGE-NC Project No 04-1129 Page 2 of 7 from both marine and non-marine sediment, and are generally formed in alluvium denved from ' mixed rock sources The Modesto,Riverbank,Turlock Lake Formations and overlying recent alluvium are the principal sources of domestic groundwater in the 13,500-square-mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water feature in the vicinity of the property is the Old River,approximately 2 5 miles west of the property 2 2 ,UNDERGROUND STORAGE TANK REMOVAL AND OVER-EXCAVATION In November 2002,two USTs(UST-1 and UST-2)were discovered during excavation of debris and hydrocarbon-impacted soil The two USTs were single-walled and appeared to be constructed of redwood with steel banding, the tanks were contained in separate brick vaults with concrete floors Each tank had an approximate capacity of 15,000 to 20,000 gallons Upon discovery of the tanks, the San Joaquin County Environmental Health Department(EHD)was notified and the tanks were removed under permit Based on analytical results of soil samples collected from beneath the tanks, it appears that the tanks contained diesel Total petroleum hydrocarbons quantified as diesel(TPH-d) fwas detected in each of the soil samples collected from beneath UST-1 and UST-2 and in the stockpile soil sample at concentrations ranging from 1,400 mg/kg(UST-2)to 28,000 mg/kg(UST-1) ' Sample UST1-001 was collected in a shallow sand zone between the bottom of UST-1 and the concrete floor supporting UST-1 and UST-2 None of the other target analytes were detected in the samples collected ' On 26 and 27 November 2002, the two USTs were removed under permit Approximately 2,000 cubic yards of material was excavated from the UST area (Figure 2) Tank material (wood, steel ' banding, impacted soil and concrete) was stockpiled on plastic sheeting at the site for disposal Following excavation of the tank material, additional impacted soil was removed from beneath the former UST locations (approximately 20 to 25 feet bsg),and segregated into a separate stockpile ' On 05 March 2004, approximately 372 4 tons of petroleum impacted-soil and petroleum-impacted UST material (wood, steel banding and mortar/brick) were disposed of at Forward Landfill in ' Manteca, California Copies of landfill manifests are included in Appendix B Following removal of the UST material, soil excavated from the UST pit was spread at the site The ' UST excavation was backfilled utilizing soil excavated from other locations at the site unrelated to the UST investigation ' Advanced Geo Environmental,Inc I