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t .rte Analytical results of the soil samples revealed that elevated levels of Total Purgeable Hydrocarbons as gasoline (TPH-g) and total extractable petroleum hydrocarbons as diesel (TEPH-d), volatile aromatics benzene, toluene, ethylbenzene, xylenes (BTEX), and lead were :-j present in the samples collected from the excavation and from the stockpile. The overexcavation of the former tank pit was initiated on July 16, 1993 by equipment operator - Mark Burns and a W.W. Irwin, Inc. staff geologist as requested and contracted by the Pegasus Group. The work was periodically supervised by Mr. Michael Collins, San Joaquin County ' Public Health Services - Environmental Health Division (SJCPHS-EHO) Registered =' Environmental Health Specialist. As the excavation proceeded, soil samples were collected for Iithologic analysis and organic vapor analysis (OVA) meter readings were taken in order to -i direct the excavation by determining the level of contamination and the direction of migration. The excavation was expanded slightly in all directions from the original tank pit to an area --, approximately 35 square feet and to a depth of approximately 18 to 20 feet below surface grade - bs The excavation was halted when the excavator reached the limits of its extension and the k- northern-- northern wall became inaccessible. Ground water was not encountered. An estimated 260 cubic yards of newly-excavated soil were removed from the tank pit and stored at a location on the south side of the property, and separately from soil stockpiled during the i tank removal operation. Upon completion of the excavation activities, two bottom samples and 1 four sidewall samples were gathered in the excavator bucket as directed by Specialist Collins. Each sample was analyzed for TPH-g by EPA Method 8015, BTEX analytes by EPA Method 8020, and organic lead per the California Leaking Underground Fuel Tank manual (State Water Resources Board, 1989). The analytical results are listed in Table 1. Hydropunch' Sampling - April 8, 1994 Under the supervision of Specialist Collins, three HydropunchTm boreholes (HP-1, HP-2, and HP- 1 3 shown on the Site Sketch, Figure 2 and the Ground-Water Gradient Map, Figure 3) were drilled near the north, east, and west flanks of the overexcavation. Borehole soil samples were logged at five-foot intervals by the W.W. Irwin, Inc. field geologist; the samples were chilled and retained for laboratory analyses, but the analyses were not required by the SJCPHS-EHD. Ground water was encountered at an average depth of 23.7 feet below surface grade (bsg). -j When analyzed, the ground-water samples collected from HP-1 and HP-2 revealed BTEX analytes in nondetectable or fractional concentrations; the sample from HP-1 exhibited 86 µg/f of TPH-gasoline. When analyzed, the sample collected from HP-3 exhibited TPH-g at 360 lAglf,, and a benzene concentration of 160 tcg/f,, prompting the SJCPHS-EHD to order the completion of three monitoring wells for ground-water direction and gradient determination, and possible definition of the contaminant migratory path. See Table 2 for analytical results. W.W. Irvin, Inc. Project No. 33016.07 December 1995 2