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sections of the drill casing were added to extend the drilling depth. After the boring <br /> termination depth was reached, the drill casings were removed by hydraulic jacks and the <br /> borehole backfilled with cement grout. Soils encountered in the borings were classified <br /> _ according to the Unified Soil Classification Systems and recorded in the field logs. A copy of <br /> the boring logs and the boring log legends are presented in Appendix B. <br /> Representative soil samples were collected from the soil deposits in the sample buckets at the <br /> desired depths. Soil samples were contained in 6-inch long by 2-inch diameter pre-cleaned <br /> brass tubes. Both ends of the sample tube were first wrapped with teflon sheets, capped by <br /> plastic end caps, and then sealed with silicon tape. The sealed sample tubes were labeled and <br /> placed in an ice chest filled with crushed ice for temporary field storage. Each soil sample was <br /> field screened by an organic vapor meter (OVM) equipped with a photo-ionization detector <br /> (PID). The readings of the OVM were also recorded on the boring logs. <br /> The collection of undisturbed soil samples were also attempted by driving a Standard <br /> Penetration Test (SPT) split-spoon sampler through the center of the casing. A hydraulic <br /> activated automatic sampling hammer, with a 140-pound hammer weight and a 30-inch hammer <br /> drop, was employed to drive the SPT sampler 18 inches into the subsurface soils beneath the <br /> casing tip. The number of hammer blows needed to drive the SPT sampler for each 6-inch <br /> penetration was recorded to correlate the density of subsurface soils. Undisturbed soil samples <br /> were retained in 6-inch long by 1.5-inch diameter brass tubes that lined the interior of the SPT <br /> sampler. Due to the gravelly nature of site soils, only three SPT samples were successfully <br /> collected. <br /> r <br /> B. Generalized Subsurface Conditions <br /> Field investigation data revealed that the surface soils at the subject property were mostly sandy <br /> gravels and gravelly sands. Intermittent silt and clay layers, varying in thickness from less than <br /> a foot to over 5 feet, existed between the sand and gravel strata. Generally, a layer of light <br /> brown sandy gravel was encountered at the ground surface that extended to a depth about 4 <br /> feet. A darker brown silty sand to sandy silt layer underlain the surficial gravel stratum and <br /> extends to depths between 8 and 16 feet. Below the silty sand layer were tan to light brown <br /> sandy gravels to more than 80 feet below ground surface. <br /> _ Two clayey layers were encountered within the gravelly strata. The upper clayey layer was a <br /> brown sandy silty clay at depths between 73 and 77 feet. The lower clayey layer was a brown <br /> silty sandy clay at the termination depth of boring location B-5, about 88 to 90 feet below <br /> ground surface. A cross section of the idealized subsurface condition between boring locations <br /> B-2 and B-4 is presented on Figure 4. <br /> Petroleum odors and distinctive discolorations were noted in the near surface silty sand layer at <br /> boring locations B-1, B-7 and B-8. This apparent contamination zone generally existed to <br /> depths between 5 and 15 feet. No free groundwater was encountered in any of the soil borings <br /> during this investigation. The groundwater table depth is reportedly more than 100 feet deep at <br /> the subject property. <br /> 4 <br />