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10 two,5, a- n 4 - ax EVAX Project 2260-03 6 May 1991 Drilling of Borings West Hazmat Drilling Corporation (Hazmat; C-57 License $54979) of Rancho — Cordova, California was retained by EVAX to drill the soil borings and construct the vapor extraction wells. Soil borings were drilled on March 28, 1991 with a Mobile CME 75, truck mounted drill rig equipped with continuous flight, hollow stem augers of 8-inch diameter. The augers were steam cleaned before drilling each boring. The boring for MW-25 was drilled near the west side of the station uuilding and to a total depth of 77.0 feet below ground surface. MW-25 was designed as both a vapor extraction and groundwater monitoring well. The boring for VW-26 was drilled near the east side of the station building and to a total depth of 60.5 feet below ground surface. VII-26 was designed as a vapor extraction well . A hand operated auger was used to test for possible shallow underground piping in the areas drillad. Soil Sampling -. A geologist supervised the drilling and sampling of soils from the borings. Soil samples from the boring of MW-25 were taken at 5.0 foot intervals starting at a depth of 5.0 feet beluw the ground surface. In the boring of VW-26, soil samples were taken at 10.0 foot intervals ` starting at a depth of 10 feet below the ground surface. Samples were ;., retrieved with a California modified, split-spoon sampler" loaded with 3 steam cleaned, brass sleeves each of 6.0-inch length and 2.0-inch diameter. Sampling involved advancing the boring to a point just above the sampling depth, sliding the sampler through the hollow stem of the augers, and driving the sampler I8 inches into relatively undisturbed i, soils below the base of the boring. A standard 140-pound hammer dropped repeatedly 30 inches was used to drive the sampler into the soils. The j number of blows needed to drive the sampler each successive 6.0-inch increment wa> recorded by the geologist. x The sampler was then retrieved from the boring and soils were evaluated by the geologist following the Unified Soil Classification System.. Soils �.y were also field screened with an Organic Vapor Meter (OVM), a photo- ionization detector that qualitatively measures organic vapor s concentrations. The ends of one of the soil-packed brass sleeves from each sampling interval were sealed with aluminum foil, plastic caps, and tape following retrieval of the sampler from the boring. These soil samples were then labeled and placed in iced storage. Geological and other data are summarized in the logs of borings, Appendix B. - 2. -