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GEOMATRIX 1 3.2 Exploration Drilling ' Exploration borings will be drilled at seven locations to evaluate subsurface conditions on and in the vicinity of the Facility. Four exploration borings (EXP-4 through EXP-7) will be located upgradient (west) of the Facility, two borings will be located at the downgradient edge of the property owned by 1 San Joaquin Valley Associates (EXP8 and EXP-9), and one boring (EXP-10) will be located cross- gradient(south)of the Facility (Figure 7). At each location, the exploration borings will be advanced using the mud rotary method to a depth of approximately 150 feet bgs. Continuous soil cores will be collected for lithologic logging using the 1 Unified Soil Classification System (USCS). Upon reaching the target depth, the boring will be geophysically logged using point resistivity, spontaneous potential, 6-foot lateral, and natural gamma 1 ray logs. Exploration borings EXP-4 through EXP-7 will then be destroyed by filling with a bentonite/cement grout from the bottom to the surface via a tremie pipe. Exploration borings EXP-8 and EXP-9 will be reamed out and completed as deeper zone monitoring wells. Exploration boring ' EXP-10 will also be reamed out and completed as an intermediate zone monitoring well. Drill cuttings and fluid will be placed in bins and stored at the Facility pending final disposition by GSHI. 1 3.3 Discrete-Depth Groundwater Sampling A second boring will be advanced adjacent to (within 10 feet) each of the exploration borings EXP-4 1 through EXP-7 and EXP-10 for the collection of discrete-depth groundwater samples from apparent water-bearing intervals identified in the exploration boring. Discrete-depth groundwater samples will 1 not be collected from exploration borings EXP-8 and EXP-9. The other borings will be advanced using the mud rotary method to approximately 2 feet above the target intervals. A SimulProbeTmwill then be driven approximately 4 feet into undisturbed soil and opened for collection of groundwater samples 1 from the shallow, intermediate, and deeper water-bearing zones. The SimulProbeTM sampling method sometimes produces limited sample volume. Therefore, ground- water samples will submitted to a laboratory and analyzed for the presence of(in order of decreasing importance) chloride, nitrate (as N), general minerals, and VOCs. The constituents chloride and nitrate 1 are considered indicator parameters because they are the most mobile of the chemicals detected in groundwater beneath the Facility. Additional groundwater sample volumes may be submitted and ' analyzed for ammonia, DBCP, and/or atrazine if sufficient water can be collected from the SimulProbJm. After collecting the final discrete-depth groundwater sample from each boring, the 1 boring will be destroyed or completed as a monitoring well as described above. 3.4 Monitoring Well Installation ' Nine monitoring wells (MW-20 through MW-28, as shown on Figure 7) will be installed at selected locations following completion of the exploration boring program. Two additional monitoring wells ' may also be installed if discrete-depth groundwater sample results indicate that existing background I:V0.01ECTOb3wDOCV!�MVbS?l"I.Eoc 10