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The top of each well will be secured to prevent unauthorized entry and incursion by surface waters. The two onsite wells will be completed with 6-inch diameter locking steel casing that extends approximately 2.5 feet above the ground surface. The wells in both El Dorado Street and Harding Way will be completed with water-tight, threaded traffic boxes that can only be opened with a special wrench. A tag indicating the well number, well type,depth, perforated interval and the diameters of the boring and casing will be placed in each well. The elevations of the ground surface and the top of casing will be surveyed for vertical location and tied to the previously installed wells. The depths to ground water will be gauged and the elevation of the top of ground water will be calculated in order to determine the direction of flow and establish a hydraulic gradient. 4.2 INSTALLATION OF VAPOR EXTRACTION WELLS Five vapor extraction wells (VW 1, VW2, VW3, VW4, and VWS, Figure 3) will be installed around and within the former tank field at former Chevron SS 9-1918. The vapor extraction wells will be installed for future hook-up to a vacuum and treatment system for inplace remediation of gasoline contaminated soil. The soil borings will be drilled in a manner similar to that for the monitoring wells except that the borings will be 6-inch in diameter. The borings will be terminated just above the water table, approximately 35 to 40 feet below ground surface. The wells will be completed as vapor extraction wells by installing 2-inch diameter,flush-threaded, schedule 40 PVC casing. Screen with a slot size of 0.010 inch will be installed from a depth of approximately 15 feet below ground surface approximately 35 below ground surface. The annular space around the casing will be packed with Lone Star number 3 sand. The five vapor extraction wells will be completed above ground in temporary, steel protective casing until being configured for hook-up to the VETS system. 4.3 SAMPLING AND ANALYSIS OF SOILS AND GROUND WATER Undisturbed soil samples will be collected at each five feet of drilling depth with a modified California split spoon sampler lined with brass liners. The sampler and brass liners will be scrubbed with detergent and rinsed with tap water and then with deionized water before use at each sampling interval. The split spoon sampler is fitted with three brass liners. One soil filled brass liner will be immediately lined with aluminum foil and capped with plastic 9