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• KEI-P91-0202 .R6 January 23 , 1992 Page 5 RECENT FIELD ACTIVITIES On December 16, 17 , 18 , 19 , & 20, 1991, six additional two-inch diameter monitoring wells and two exploratory borings (designated as MW4 through m19 and EBI and EB2 , respectively, on the attached Site Plan, Figure 1) were installed at the site. The wells were each drilled, constructed, and completed in accordance with the guidelines of the Regional Eater Quality Control Board (RWQCB) , and California Well Standards, per Bulletin 74-90 . The subsurface materials penetrated and details of the construction of the wells are described in the attached Boring Logs. The six wells were each drilled and completed to total depths ranging from 79 to 85 feet below grade, except for MW5, which was drilled and completed to a depth of 70 feet below grade. Ground water was encountered at depths ranging from 71. 5 to 75 feet beneath the surface during drilling, except in MW5, where ground water was encountered at a depth of 60 feet below grade. The exploratory borings were drilled to depths of 20. 5 and 21. 0 feet . below grade. Soil samples were taken for laboratory analysis and for lithologic logging purposes at a maximum spacing of 5 foot intervals, at significant changes in lithology, at obvious areas of contamination, and at or within the soil/ground water interface (except for EB1 and EB2 ) , beginning at a depth of approximately 4 to 5 feet below grade and continuing until ground water was encountered. Soil sampling conducted below the ground water table are for lithologic logging purposes only. The undisturbed soil samples were taken by driving a California-modified split-spoon sampler ahead of the drilling augers. The two-inch diameter brass liners holding the samples were sealed with aluminum foil, plastic caps and tape, and stored in a cooled ice chest for delivery to a certified laboratory. Each well casing was installed with a watertight cap and padlock. A round, watertight, flush-mounted well cover was cemented in place over each well casing. The surface of each well cover was surveyed by Kier & Wright of Pleasanton, California to MSL and to a vertical accuracy of 0. 01 feet. All wells were developed on December 26, 27 , 30, and 31, 1991 . Wells MW1 , MW2 , and MW3 were redeveloped as previously recommended by KEI . Prior to development, the wells were checked for the depth to the water table (using an electronic sounder) and the presence of free product (using an interface probe or paste tape) . No free • product was noted in any of the wells. After recording the monitoring data, the wells were purged (with a surface pump) of 50 to 81 gallons, except for wells MW5 and MW6, which were purged of 14 and 24 gallons, respectively (until the evacuated water was