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Frank C. Alegre Trucking Company, Inc. 4203-173 Former Trucking Facility June 9, 1997 GROUND-WATER MONITORING WELL INSTALLATION Revised July 23, 1997 Page 2 MONITORING WELL INSTALLATION The location of the monitoring well is shown on Figure 2. The well boring was advanced using a truck mounted drill rig equipped with 81/4-inch hollow stem augers. The monitoring well was constructed with 2-inch-diameter PVC casing with flush joints, installed down through the hollow stem auger. Twenty feet of screened casing (0.020-inch slot width) was installed, along with an appropriate length of solid PVC well casing (2-inch-diameter Schedule 40 PVC). The total depth of the monitoring well was 50 feet. A#2/12 sand filter pack was placed from the base of the well to two feet above the top of the screened interval. A 12-inch-thick bentonite seal was placed at the top of the filter pack. The remaining annular space was backfilled with a cement-bentonite grout seal. The well was completed with a raised steel monument and a locking waterproof cap. The monitoring well boring log and construction detail is provided as an attachment. After the cement-bentonite grout had set for 72 hours, the well was developed using a surge block and bailer to produce relatively nonturbid ground water. Approximately 20 casing volumes of water were removed from the well during the development process. The purged water was stored on the site in a Department of Transportation approved drum. Hydrogeologic Conditions Review of the soil boring log for monitoring well MW-1 found approximately 28 feet of sandy import fill material, overlying gray medium sand, gray fine sandy silt and grayish brown silty fine - medium sand. The import fill was placed following on-site overexcavation work conducted in 1996 (Referenced Report). Ground water was encountered at a depth of±38 feet below the ground surface. Based on previous ground-water investigations conducted on the subject property, the calculated direction of ground-water flow is toward the south/southwest. Soil Sampling Soil samples were recovered from the base of the import fill material (±28.5 feet) at approximate five-foot-depth intervals to the base of the well. A photoionization detector was used in the field to screen the soil samples for volatile organic vapors. No significant organic vapors were recorded from the PID screenings. Soil samples from depths of 30, 35 and 40 feet were retained for laboratory analyses. Following recovery,the soil samples were sealed with Teflon sheets tape, and polyethylene caps. The samples were then placed in a cooled ice chest for transportation under documented chain of custody to American Environmental Network Laboratory in Pleasant Hill, California.