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KEI-P88-1013 .R2 • July 15, 1992 Page 6 RECENT FIELD ACTIVITIES - MONITORING WELL INSTALLATION On April 8 , May 20 and 21, 1992 , four additional two-inch diameter monitoring wells (designated as MW10 through MW13 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 Water Quality Control Board (RWQCB) and the Califo-rnia 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 four wells were each drilled and completed to total depths ranging from 70 to 72 . 5 feet below grade. Ground water was encountered at depths ranging from 64 to 69 feet beneath the surface during drilling. Soil samples were collected for labora- tory analysis from each well boring, except MW13 , and for litho- logic logging purposes at a maximum spacing of 5 foot intervals, at significant changes in lithology, at obvious areas of contamina- tion, and near the soil/ground water interface, beginning at a depth of approximately 5 feet below grade until ground water was encountered. A representative saturated soil sample was collected from the well MW13 boring at a depth of 65 feet below grade.. The sample was submitted to Harlan Tait Associates in San Francisco for particle size analysis for verification of casing slot size and filter pack design (see attached Plate 1) . Soil sampling conducted below the ground water table was for lithologic logging purposes only. The undisturbed soil samples were collected 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 Mean Sea Level (MSL) and to a vertical accuracy of 0. 01 feet. The wells were developed on June 2 , 1992 . Prior to development, the wells were checked for depth to water table by the use of an electronic sounder, and the presence of free product (by the use of an interface probe or paste tape) . No free product was noted in any of the four wells (MW10 through MW13) . After recording the monitoring data, between 85 to 100 gallons of water were purged from each well with a surface pump until the evacuated water was clear and free of suspended sediment. Monitoring and well development data are summarized in Table 1.