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crew were supplied by Soils Exploration Services, Inc (SES) of Benicia, California. During drilling, auger returns were monitored for the presence of organic vapors using a photo- ionization detector (PID. Thermo Environmental 580A, 10 0 eV, calibrated to isobutylene) Soil samples were collected ahead of the drill bit using a split-tube sampler loaded with ' three pre-cleaned 2-inch by 6-inch brass sleeves The samples were collected at five-foot intervals, using a 140-pound hammer to advance the sampler 18 inches. The number of blows required to advance the sampler in 6-inch increments was recorded on the boring logs. To avoid cross-contamination, the sampling equipment was washed in an alconox solution and rinsed twice with water prior to each sampling run. Augers were steam-cleaned between borings For each sample, both ends of the lead tube were covered with aluminum sheets, capped and sealed with tape. The samples were then stored on ice and transported under chain of ' custody to Pan-Ag Environmental Labs, Inc (Pan-Ag) in Madera, California. A water sample was collected from boring B-15 after drilling to the total depth of 35 feet ' The sample was collected by lowering a disposable plastic bailer through the augers to groundwater The sample was field screened for the presence of petroleum hydrocarbons and organic vapors No laboratory analysis of this sample was conducted 3.2 Logging Soil was extruded from the second brass tube and screened for the presence of organic vapors, using a PID, and the readings were recorded on the boring logs The soil was then described in accordance with the Unified Soil Classification System (see Boring Logs, Appendix A). 3.3 Well Completion Boring B-17 was completed as monitoring well MW-7, boring B-16 was completed as MW-8; and boring B-14 was completed as MW-9 Each well was completed using 20 feet of 2-inch diameter PVC casing with 0 020 screen Blank PVC casing was then extended to the surface. The filter pack (#3 Lonestar sand)was installed from total depth to two feet above the screen interval. Bentonite chips were used to make a 2-foot plug in each well and the wells were then grouted to the surface with Portland cement 3.4 Monitoring Well Sampling and Surveying On December 29, 1994, the water levels and product thicknesses in all nine wells were I measured relative to the top of the casing using an interface probe The relative piezometric level in each well and hydraulic gradient were determined by subtracting the depth-to- groundwater from the surveyed casing elevation (Table 2) On March 1, 1995, the casing elevations of MW-7 MW-8 and MW-9 were surveyed relative to monitoring well MW-1 a. S"'�s.-."1- 5 3C-%A 1026, (100 N_w..QRw2 94