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c <br /> 5 <br /> September 21, 1987 Page 2 Project 195-1.1. <br /> One exploratory soil boring was drilled adjacent to each of the four areas <br /> f (DH-1 through DH-4). The locations of the soil borings are shown on the <br /> i Sketch Site Plan, Figure 1. Borings were drilled using a truck mounted <br /> drill rig equipped with eight inch diameter hollow stem augers. Relatively <br /> undisturbed soil samples were obtained from each boring using a modified <br /> `; California sampler. Soil samples were taken in clean, two inch diameter by <br /> ! four inch long, brass liners, and sealed with aluminum foil, non-reactive <br /> caps and tape. Samples were taken at one foot depth, five foot depth, and <br /> r:a then at five foot intervals to the total depth of each boring. DH-1 was <br /> terminated at a depth of 25 feet, DH-2 was terminated at a depth of 20 feet, <br /> DH-3 and DH-4 were both terminated at a depth of one foot (i.e. after the <br /> first sample). Logs of borings DH-1 and DH-2 are presented in Appendix A. <br /> All drilling and sampling equipment was steam cleaned between borings and <br /> I € between sampling drives to reduce the possible transfer of contamination. <br /> All soil cuttings generated during drilling were placed in 55-gallon drums. . <br /> Ground water was encountered at a depth of 15 feet in DH-1, and at a depth <br /> of 9.5 feet in DH-2. Permit No. 87-3008 was obtained from the San Joaquin <br /> �o Local Health District to allow the installation of shallow ground water <br /> monitoring wells (MW-1 and MW-2) in borings DH-1 and DH-2. <br /> MW-1 was constructed by installing 25 feet of two inch diameter, Schedule 40 <br /> PVC, threaded monitoring casing. The lower 15 feet of the casing was <br /> 3 factory slotted (slot size 0.020 inch) to allow the inflow.of ground watF,r. <br /> A coarse sand filter pack was placed in the annular space around the slotted <br /> I� interval of the casing, to a depth of 8 feet below ground surface. A <br /> �e bentonite seal 2.25 feet thick was placed above the sand pack, and the <br /> remaining annular. space was. sealed with a cement/bentonite grout. A locking <br /> vault was set in the cement surface seal to prevent unauthorized access to <br /> the well. <br /> I:a <br /> MW-2 was constructed by installing 18.5 feet of two inch diameter, <br /> !� Schedule. 40 PVC, threaded.monitoring casing. The lower 10 feet of the <br /> iA casing,was factory slotted (slot size 0.020 inch) to. allow the inflow of <br /> ground water. A coarse sand filter pack was placed in the annular space <br /> � R around the slotted interval of the casing, to a depth of 6.5 feet below <br /> t7 ground surface. A bentonite seal 2 feet thick was placed above the sand <br /> pack, and the remaining annular space was sealed with a cement/bentonite <br /> i � grout. A locking vault was set in the cement surface seal to.prevent <br /> 1ti unauthorized access to the well. <br /> After allowing the surface seals of bot-h monitoring wells to set, the wells. <br /> were developed using a down-hole, positive displacement bladder pump. Each <br /> ty well was pumped until the discharge water was relatively clear of sediment, <br /> and until pH and EC readings of the discharge water had stabilized. A <br /> r_ -_ground_water_sample_was-then-obtained-from each-well-_using-the=-num <br /> equipment. All well developing and sampling equipment was steam cleaned <br /> before sampling each well to reduce the potential for transfer of <br /> t . <br /> contamination. <br /> Sa <br /> 93etar-Associates .. <br />