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' 4 26 May 1995 AGE-NC-95-0124 Page 2 of 3 In April 1994, approximately 200 cubic yards of impacted soil were removed from the former UST excavation. Final dimensions of the excavation were approximately 15 feet in width and 20 feet in length; the excavation was 22 feet in depth at the west end and 28 feet in depth near the east end. TPH-g was not detected in soil samples collected from the north, south and east sidewalls, as well as the floor of the excavation. 'However, hydrocarbons were detected in a sample from the west sidewall, indicating that contamination extends beneath the on-site building.. The excavated soil was transported and disposed at a licensed landfill and the excavation was backfilled. 3.0. SCOPE OF WORK In a letter dated 6 September 1994, the PHS-EHD.states that "the remaining contamination beneath the building must be defined laterally and vertically. Sufficient data to estimate the mass of the remaining contamination shall be obtained. The estimate sliall be used as the basis of a feasibility study for removing the remaining contamination or a risk appraisal of leaving the contamination in place." Therefore, AGE proposes to drill one soil boring to a-depth of 40 feet approximately 30 feet, west of the former UST excavation, inside the on-site structure (see Figure 2). 4.0. PROCEDURES Details of the proposed drilling and sampling procedures are as follows:. 1) Notify the San Joaquin County PHS-EHD 48 hours prior to field work. 2) Drill one soil boring using a limited access truck-mounted drill rig equipped with. continuous-flight, 8-inch diameter hollow-stem augers. 3) Obtain discrete soil samples at five-foot intervals, using a split-spoon sampler loaded with three brass sample sleeve. 4) Decontaminate sampling equipment in a,phosphate-free solution and rinse .twice with water prior to each sampling run. 5) Preserve soil samples in the lead brass sleeve by covering both ends with aluminum foil, capping, and sealing with tape.