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Mr. Kyle Christie Project 0805-152.03 June 14, 1995 Page 3 PREFIELD ACTIVITIES • Obtain a drilling permit from the San Joaquin County Public Health Services. • EMCON will notify Underground Service Alert of its intent to drill at least 48 hours before drilling to identify the location of underground utilities. FIELD OPERATIONS • Observe drilling of three 8-inch-diameter soil borings southeast of the site, on the property south of Patterson Pass Road. One boring will be drilled southeast of boring B-26 to evaluate the extent of gasoline hydrocarbons south of the site and the other two borings will be used to evaluate the lateral distribution of hydrocarbons southwest and east of boring B-26. However, if evidence of residual gasoline hydrocarbons are detected in the first boring, EMCON will drill another boring further to the southeast. The borings will be drilled to a minimum depth of approximately 60 feet bgs and terminated when photoionization detector readings of less than 10 parts per million by volume are obtained in two consecutive samples. We estimate a maximum drilling depth of 115 feet bgs. Locations of the proposed borings are shown on Figure 2. • Observe the installation of up to four 4-inch-diameter vapor extraction wells in the off-site borings if field evidence indicates hydrocarbons are present. The screened interval of the vapor extraction well will be based on field evaluation of the extent of soil affected by hydrocarbons and the subsurface material. • Collect undisturbed soil samples for classification and laboratory analyses at 5-foot intervals or soil changes from the ground surface to the total depth of the borings. The soil samples will be classified using visual and manual methods according to the Unified Soil Classification System. • Drill cuttings will be stored at the ARCO site and will be placed on and covered with visqueen. Collect four soil samples from the drill cuttings to be composited into one sample at the laboratory for evaluation of disposal options. • Submit approximately 20 soil samples (five per boring) from the borings and the composite sample to an approved laboratory certified by the state of California. The samples will be analyzed for TPHG and benzene, toluene, ethylbenzene, and total xylene isomers by modified Environmental Protection Agency (EPA) Methods 8015 and 8020, respectively. In addition, the samples collected from the SACW:\PJO\0805\08051520.3AL-94\drt :I