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The borings were drilled using a truck-mounted CME 55 rig. The drill rig and two-man crew were supplied by Soils Exploration Services, Inc. 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. 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 McCampbell Analytical Inc. in Pacheco, California (MAI). 3.7 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 C). 3.8 Well Completion Borings MW-1, MW-2 and MW-3 were completed as groundwater monitoring wells using 2-inch diameter PVC casing with 0.020 inch screen from 20 to 5 feet. The filter pack (#3 Lonestar sand)was installed from 20 feet to 3.5 feet. A surge block was used to set:the sand pack. Bentonite chips were used to make a 1-foot plug and the wells were grouted to the surface with Portland cement. 3.9 Monitoring Well Purge Procedures On October 24, 1994, the water levels in monitoring wells MW-1, MW-2 and MIN-3 were measured relative to the top of the casing using a Solinst water level meter. The relative piezometric level in each well and hydraulic gradient were determined by subtracting the depth to groundwater from the relative casing elevation (Table 5). After water levels were measured, a 2-stage submersible purge pump was used to surge and purge each well. Between 7 and 9 gallons of water were removed from each well to stabilize temperature, pH and conductivity (Appendix E). Stabilization parameters were measured at one-gallon intervals using an ICM water analyzer. Pumping was then continued to develop the wells. Approximately 35 gallons of water were removed from MW-1 and approximately 20 gallons were removed from MW-2 and MW-3. The purge water was stored in 55-gallon drums on-site. 0-1bs d A.&S. kw,I- 9 CA{DWM...w/79lA-93 .J