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Site Background Information: Former Ocampo Property Page 2 of 6 PREVIOUS SITE SUBSURFACE INVESTIGATIONS November 1998: A soil boring was advanced at the site on November 25, 1998 by Upgradient Environmental Consultants; petroleum hydrocarbons were detected in soil samples collected from the boring. Analytical results of the samples are included in Table 1. Due to the detection of contamination, a work plan addendum was prepared by Upgradient Environmental Consultants,and a revised addendum prepared by AGE forthe site in 1999, to advance four soil borings and install three ground water monitoring wells. The revised addendum was approved by the San Joaquin County Environmental Health Department (EHD) by correspondence dated 19 May 1999. October 2002: On 17 October 2002, three soil probe borings (131 through 133) were advanced at the site as part of site assessment activities. A total of three soil samples were submitted to McCampbell Analytical, Inc (MAI), a State of California Department of Health Services (DHS)-certified analytical laboratory, for analysis. Petroleum hydrocarbons and volatile organic compounds were not detected in any of the samples analyzed. Laboratory results of selected soil samples detected barium and chromium in soil samples collected from borings B1, B2, and B3 at maximum concentrations of 120 milligrams per kilogram(mg/kg) (B2-10) and 27 mg/kg (131-10), respectively. Lead was detected in soil samples collected from borings B1 and B2 at a maximum concentration of 6.7 mg/kg (61-10). Arsenic was detected in soil samples collected from borings B1 and B3 at a maximum concentration of 3.4 mg/kg (63-10). On 17 October 2002, soil boring B4 was advanced at the site and the data was held for future reporting. On 17 and 18 February 2004, 135 and 66 were advanced for the collection and analysis of soil and 'grab' groundwater samples. The probe borings B4, B5, and B6 were advanced to depths of 47 feet, 54 feet, and 57 feet bsg, respectively. TPH-g was detected in all soil samples collected from B5 and one sample from B4. Concentrations ranged from 2.2 mg/kg in sample B4-35 to 16,000 mg/kg in sample B5-33. The most significant concentrations of hydrocarbons in soil in boring B5, located at the former UST area,were at depths greater than 30 feet bsg and concentrations are elevated in samples to the total depth of the boring. TPH-d was detected in the samples collected from B5, at concentrations ranging from 640 mg/kg to 11,000 mg/kg. However, the MAI laboratory report notes the diesel concentrations are typical of aged or 'weathered' gasoline patterns. One or more BTEX compounds were detected in the following soil samples, B4-35, 66-45, 66-55, and all samples from B5, at the following maximum concentrations: 50 mg/kg benzene (65-33), 1,800 mg/kg toluene (65-18), 2,100 mg/kg ethylbenzene (B5-18)and 3,690 mg/kg total xylenes(B5-18). 1,2-DCA was detected in the Advanced GeoEnvironmenta4 Inc.