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Canepa's Car Wash ' 6230 Pacific Avenue, Stockton, California December 30, 1993 Interim Status Report, Phase H Investigation Page• 2 near the vacuum stations And MW4, a two-inch (2") monitoring well, was installed in the alley north of the car wash building in the estimated down gradient direction All four morutonng wells were drilled to 70 feet below ground level and screened from 50 to 70 feet (Appendix B) All soil samples were screened with a portable PID (Photo Ionization Detector) and laboratory samples were taken from MW-3 & 4 at five-foot ' intervals from 20 feet to the water table Samples were selected for analysts by the on-site geologist based on odor, discoloration, and PID readings (Appendix B & Table 1) Stockpiled soil from the soil vapor well area (Figure 3) was sampled and characterized for disposal (Tables 3 & 4, Appendix A) ' 31 Drilling Permits were obtained for all wells before drilling began The soil borings were accomplished using a mobile mounted drilling rig employing the use of a hollow stem flight auger of 8-inch o d All drilling equipment was thoroughly steam- cleaned both before drilling began, to prevent the introduction of contamination from off site, and between borings, to prevent cross contamination The borings were logged under the direct supervision of a registered professional using the Unified Soil Classification System (Appendix H) The color, texture, moisture, plasticity, consistency of the earth materials, pertinent soil or bedrock characteristics and any evidence of contamination were noted All water-beanng zones and the depths at which they were encountered were also noted on these logs ' All bonngs were drilled in such a manner as to prevent cross contatrunation between strata Upon termination, the borings were completed as monitoring wells and backfilled with cement grout, after a bentonite seal had been placed The boring diameters were at least 4-inches greater than the well casing diameters of two and four inches The cuttings from the drilling operation were added to the existing spoils pile on- site and will be disposed of as soon as the pile has been characterized 3.2 Well Construction All materials used in well construction were thoroughly cleaned prior to introduction into the boring Threaded PVC well casing with threaded end caps and factory perforations for placement in the saturated zone was placed in the