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Mohr-Fry Ranches 950lndustrial Drive, Stockton, California August 6, 1996 Site Closure Report Page: 3 ? screened and excavated until they were clean Soil from this part of Excavation 2 were stockpiled as S-2-4 This pile was calculated at -700 cu yd and was 140 feet long It was marked of in intervals of 20 feet (-100 cu yd each) and four samples were taken and composited from each interval Wall and floor samples were taken at the direction of Mr Steve Sasson, PHS/EHD Only five (5) of the 23 samples detected any 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 imported loam soil and compacted to original grade There was no damage to monitoring well MW-1 The Excavation 3 area previously had three underground tanks removed, and contamination was believed to be both outside of and under the building Excavating �-' started outside the building and resulted in an irregular shaped pit averaging —14 feet wide 10 e and 20 feet long The bottom varied 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 soil contaminant plumes coalesced This would account for the scattered contaminated intervals in well MW-2 soil samples Excavating continued until the east I wall of the excavation had undercut the building wall 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 the undercut wall, supporting the building foundation wall along the entire undercut length I nside the building, the concrete floor was saw cut in an area 10 feet wide by 25 feet long and removed The top five feet was excavated and screened with the PID to see how far contaminants had migrated laterally The area next to the grout wall was excavated to 14 feet deep between the pier blocks Approximately 80 cu yd was removed Wall and I floor samples were taken at the direction of Mr Steve Sasson, PHS/EHD After soil samples were taken, the excavation was backfilled with pea gravel to within five feet of grade The remainder was filled with compacted soil and the concrete floor replaced The replaced floor was pinned with rebar, poured under the edge of the building wall and supported by the grout wall below Floor sample F-3-1 at 23 feet below ground level detected residual Diesel of 12 mg/kg Samples F-3-2 and WSI-3-10 were taken specifically to quantify the soils under the building foundation piers that must remain in place F-3-2 had Benzene (1 2 pg/kg), Toluene (7 3 gg/kg), E-Benzene (9 0 gg/kg), Xylenes (48 µg/kg), and ND for Diesel and Motor Oil Sample WSI-3-10 had only Diesel