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Z4 Borehole Abandonment <br /> Upon completion of soil and groundwater sample collection activities, boreholes were <br /> abandoned The augers and temporary well casings were removed and the open boreholes <br />' were tremie grouted to grade with a 95% cement, 5% bentonite grout mixture. The top of <br /> each borehole was finished to match the surrounding surface cover. <br /> 2.5 Disposal of Contaminated Materials <br /> Drill cuttings from the boreholes, are currently stored in a 10 yard rolloff bin located in the <br /> tPacific Bell parking lot Decontamination, development and purge liquids from the <br /> monitoring wells have been contained in 55-gallon drums and are stored on-site The <br /> disposable batters and purge lanes from water sampling were placed in the bin with drilling <br /> cuttings and will be disposed of with the soul. Soil samples not selected for analysts were <br /> placed into the bun with drill cuttings to await disposal Used sample sleeves will be disposed <br /> of with the drill cuttings After receipt of the analytical results, all stockpiled cuttings and <br /> water will be properly disposed <br /> 3.0 Results <br /> 3.1 Off-Site Geology <br /> Stratigraphic observation of off-site soils made during the drilling of boreholes indicate the <br />' presence of unconsolidated fluvial sediments varying from clays to sands In three of the soil <br /> borings (SB-1, SB-2, and SB-5) an upper sand layer is noted varying between 9.0 and 28 0 <br /> feet below grade A lower sand unit is encountered in two of these borings (SB-1 and SB-2) <br /> which appears to be the waterbearing unit. The soils observed in the remaining borings <br />' generally consist of clays with varying concentrations of silt to the total depth explored. For <br /> reference, boring logs are contained in Appendix A. <br />' 3.2 Off-Site Hydrogeoâ–ºogy <br /> During drilling of the soil borings, groundwater was encountered at an average depth of 46 <br /> feet below grade. Recent water level measurements collected from on-site monitoring wells <br /> on December 21, 1992, revealed static water to range between 4171 and 45.38 feet below <br /> grade level The average groundwater elevation for December 21, 1992 was 33 feet below <br /> mean sea level with groundwater flowing to the northeast under a gradient of 0 013 ft/ft <br /> (Figure 3) This gradient and flow direction has remained fairly constant over the 1992 <br /> annual cycle (see Table 1 for historical water level information). No free product was <br /> MZ/03-16-93/ENG/93-0034 jf 5 <br />