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1 Mohr-Fry Ranches 950 Industrial Drive, Stockton, California May 31, 1995 Phase III Remedial Excavation Report Page: 3 Two Iaboratory samples from each pile were composited to give each pile a characterization (Figure 3, Table 2) ' While screening the wall samples with the PID, it was discovered that the sand above the peat layer, and m most places the peat layer, had diesel and oil 1 contamination from 1'/s to 4 feet (Figures 7 & 8, Appendix B) After the tank area was excavated, the sand and peat layer was screened and excavated until they were clean (Figure 5, Table 2) Soil from this part of Excavation 2 were stockpiled as I S-24 (Figure 3) This pile was calculated at ---700 cu yd and was 140 feet long It was marked off in intervals of 20 feet (---100 cu yd each) and four samples were taken and composited from each interval (Table 2) Wall and floor samples were taken at the direction of Mr Steve Sasson, San Joaquin County Public Health Services, Environmental Health Department I [PHS/EBDI (Figure 5) Five (5) of the 23 samples showed residual contamination Two wall samples at the bottom of the peat bed (W-2-5-2 and W-2-5-6) have Motor Oil at 3 7 and 72 mg/kg, respectively The south wall of the tank pit at 10 feet below ground level had 150 mg/kg Motor Oil in sample W-2-10-3 At 15 feet below ground level in the same wall, W-2-15-2 detected Motor Oil at 8 1 mg/kg and Diesel at 11 mg/kg The adjacent east wall sample W-2-15-3 had Motor Oil at 4 5 mg/kg and Diesel at 5 0 mg/kg The tank pit was backfilled with pea gravel to five feet below ground level, and the remainder of Excavation 2 was backfilled with soil and compacted to ongmal grade There was no damage to monitoring well MW-1 3.3 Excavation 3 This area previously had three underground tanks removed, and contamination was believed to be both outside and under the building Excavation started outside the Ibuilding and resulted in an irregularly shaped pit averaging —14 feet wide and 20 feet long (Figure 6) The bottom vaned from 14 to 23 feet deep, with an average depth of 20 feet or -200 cu yd During excavating, dark staining from diesel fuel could be seen in the walls and indicated that the three tanks had leaked in distinct, separate areas With depth, some of the contaminant plumes coalesced This would account for the scattered contaminated areas in MW-2 (Figure 9) Excavation continued until the east wall was undercut below the building wall and between the pier block footings Steel plates were positioned vertically in the excavation between the footings and backfilled on the west side with pea gravel to support the plates Cement grout was placed in the void between the plates and i I 4— e