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10711 d 's'Y- R+--+ •'-ISEE�� r rl:_,; -"--+ Fwd ''�' _3 e 'a„• ` . �` r.Y gmF %bA CHAPTER 2 FIELD METHODS w During April 23, 1990, through May 10, 1990, five groundwater monitoring wells, one groundwater extraction well, and eight vapor extraction wells were installed. In addition, one groundwater monitoring wall was abandoned and a step-pumping test was performed an the extraction well. The boreholes were drilled by Wayne Drilling Company, using two CME-55 li. drilling rigs equipped with hollow-stem augers. Locations of the wells installed, W-1 A, W-9, i W-10,W-1 I,W-12,E-1, V-1, V-2,V-3,V-4,V-5,V-6, V-7,and V-8,are shown on Figure 2-I. Table 2-1 describes the construction and purpose of each of these wells. The work was performed under San Joaquin County special permit numbers 90-866 and 90-867. All grouting r i was inspected by a San Joaquin County representative. Groundwater Monitoring Wells Each monitoring well borehole was advanced to approximately 80 feet, or about 20 feet below the groundwater surface, using 8-inch hollow-stem augers. For Well W-9, samples for fr laboratory analyses were collected at 5-foot intervals. For the remaining mcnitoring wells, W-lA, W-10, W-I1, and W-12, soil samplinb was conducted only if field evidence of contamination was observed. Each monitoring well borehole was continuously cored for lithologic classification with the exception of W-lA. The borehole for W-1A was not logged because it was a replacement for well W-1 which had previously been logged. Drill cuttings '-' were screened using an organic vapor meter(OVM)or threshold limit value (TLV) meter. Soil showing evidence of organic vapors of 100 parts per trillion (ppm) or mom were considered contaminated, and samples were collected every 5 feet, or until no evidence of contamination was found. Table 2-1 describes the samples taken for each monitoring well. Soil samples were collected using an 18-inch-long by 2-inch-diameter Modified California- type sampler with 6-inch-long brass tube liners. The drive sampler was driven ahead of the auger ., into undisturbed soil. Soil samples were screened in the field for organic vapors using an OVM or TLV and the measurements recorded. The ends of the tubes were covered with foil and a plastic cap taped to the tube. The samples were stored on ice from collection through delivery to Brown and Caldwell's state-certified analytical laboratory in Emeryville, California. Monitoring wells W-9,.._W-10,.-.W-1.1,-and W.-12_.were-.continuously..cored using-a-5-foot-long. ------ ----- - 3-inch-diameter core barrel in order to accurately describe the lithnlogy of the borehole. Each borehole was logged froth the continuous cores and/or the samples taken at 5-foot intervals, and F the drill cuttings, using the Unified Soil Classification system. Borehole logs are presented in Appendix A. 1 U �e