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8820101-R COT-3 Figure 2. Selected soil samples were submitted to a laboratory for analysis, which found only one sample to be contaminated. The sample was taken from a depth of 10 feet in Boring B-4 and contained 1,983 mg/kg total petroleum hydrocarbons. The sample taken at 20 feet in Boring B=4 did not detect any hydrocarbons. ASSESSMENT ACTIVITIES . t Boris Well Installation On August 26 and 29, 1988, three borings were adva'nced' at the site and 9 ` completed as monitoring wells. Locations of the b3orings/wells are shown in Figure 2. The general boring/well locations were determined by Thrifty Oil as shown in the appended RFP. Some adjustments were, however, required due to their proximity to sewer lines. San Joaquin County regulations require wells to be at least 50 feet from existing sewer lines (see Figure 2 for sewer locations). Subsequently, Well MW-1 was reliocated slightly to the east of the proposed location,, while MW-3 was moved approximately 40 feet to the east. Well MW-2 was installed at the originally-proposed location. It is assumed that the original well locations were chosen to 3 better define the extent of soil contamination found in B-4, as well as to assess the potential for groundwater contamination beneath the site. Il All borings were advanced using a truck-mounted B-'53 drill rig equipped with 8-inch outside-diameter hollow stem augers, ;Boring MW-3 was drilled. first and completed to a 'depth of 50 feet per thespecifications in the RFP. Although no obvious signs of groundwater were encountered, an increase in soil moisture content was noted at 43. to 46 feet. Soils from both above and below that zone were all characterized as having a low moisture content (i .e. damp). The boring was left open for 1,5 hours, during which time approximately 1.5 feet of water collected in the bottom. Following auger removal, the boring bridged at 25 feet, requiring reinsertion of the augers. At this time, the boring was overdrilled to i i 3 Y