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g PREUMNARY REPORT AND TANK CLOSURO REPORT Tracy Boulevard Shell 3725 Tracy Boulevard,Tracy,California Delta Project No.40.89-012 Page 7 Three 4-inch-diameter monitoring wells(MW-1A,MW-2A,and MW-3A)were installed as replacements for the abandoned wells on August 16, 1990. Monitoring well locations are shown in Figure 2. The wells were constructed with Schedule 40 PVC riser pipe,0.020 slot-size screen,#3 Monterey sand filter pack,and sealed with bentonite pellets and Portland Type I cement grout with 5 percent bentonite. Monitoring well MW-IA was screened from 7 to 22 feet below the ground surface,MW-2A from 6.5 to 21.5 feet,and MW-3A from 7.5 to 22.5 feet. 3.4 Survey of Monitorin Wells On September 26, 1989, monitoring wells MW-1, MW-2, and MW-3 were surveyed to determine the elevations of the riser pipe and the adjacent ground surface with reference to a bench mark with an assumed elevation of 100.0 feet. The bench mark was located on top of the sidewalk at the northeast corner of the station building (see Figure 3). On August 28, 1990, monitoring wells MW-IA. MW-2A,and MW-3A were surveyed to determine the elevations of the riser pipe and the adjacent ground surface with reference to a bench mark with an assumed. r elevation of I00.0 feet. The bench mark was located on top of the fire hydrant located on the east side of Tracy Boulevard,directly east of the site. 3.5 Well Development Monitoring wells MW-I,MW-2,and MW-3 were developed on September 26,1989. Approximately seven well casing volumes of water were removed from each well. Monitoring wells MW-IA. MNV-2A, and MW-3A were developed on August 16, 1990. Fifty-five gallons of water were removed from MW-IA, 30 gallons from MW-2A,and 30 gallons from MW-3A. Water was stored on site in 55-gallon drums and later transported to Shell's refinery in Martinez,California. 3.6 Soil Chemistry A total of 42 soil samples were collected from soil borings SII-I through SB-4, SB-7 through SB-11,and monitoring wells MW-I through MW-3,and MW-IA through MW-3A. Each soil sample was screened for ------------ the presence of petroleum constituents using a portable photoionisation detector(PIIS)equipped with a-10.2--___ eV lamp calibrated for benzene for direct reading in parts per million. The PID indicated that no sample had a reading of greater than 10 ppm. One soil sample from each soil boring was submitted to a state- certified laboratory and analyzed for TPH and BTEX. The laboratory analytical results are presented in Table 5,and the laboratory reports are presented in Appendix E .