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c�PRXOX.. FAIR CHAPTER 2 FIELD METHODS During the week of April 6, 1987, three groundwater monitoring wells were installed. Soil boreholes were drilled by P.C. Exploration, Inc., with a truck-mounted drilling rig equipped with 1 . 4-inch inside-diameter and 8-inch outside-diameter hollow-stem augers. P.C. Exploration, Inc. , ha, a C-57 contractors license. Locations of the three monitoring wells are shown on Figure 2-1. Each borehole was advanced to approximately 70 feet, or about 20 feet below the groundwater surface. Soil samples for lithologic '! classification and potential laboratory analyses were collected at ie 5-foot intervals by using an 18-inch-long by 2-inch-diameter Idodified California type sampler with 6-inch-long brass tube liners. The s drive sampler was driven ahead of the auger into undisturbed soil. Each borehole was logged from the samples taken at 5-foot intervals, r using the Unified Soil Classification system. Borehole logs are presented in Appendix C. Soil samples were screened in the field for G organic vapors with a photoionization detector (PID) , and those samples that contained organic vapors were retained for potential laboratory analyses. The ends of the tubes were covered with foil ! ± and a plastic cap taped to the tube. These samples were stored on I-A ice from collection through delivery to the Brown and Caldwell State certified analytical laboratory in Emeryville, California. Cuttings from each borehole were containerized and sealed in 55-gallon drums and_ '' tests temporarily stored on site pending results of the analytical �h A monitoring well was then installed in each borehole by i inserting 2-inch inside-diameter, Schedule 40 polyvinyl chloride (PVC) casing with 30 feet of 0.020-inch slotted well screen (0.020 F4xa inch slots) attached to the 'bottom. The perforated casing extends approximately 20 feet below the water table and 10 feet above the water table in order to accommodate water table fluctuations and to 5 +�, detect free floating product. A bottom plug was installed at the bottom of the perforated interval. +4+. To gravel pack the well, coarse aquarium sand was poured directly # through the augers as the augers were gradually removed from the L.s borehole. A bentonite seal was placed immediately above the gravel e _ anau -pack dthers--were--then—removed--from -tile bThe - -__- F g _orehole.T + remaining annular space of each well was filled with concrete on April ;8 and 9, 1987. Each well was completed at grade with a f watertight utility box. The construction details for each well are included in Appendix D.