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i <br /> monitoring wells (Figure 2-2). The purpose of the soil borings and samples was to <br /> ( assess the potential vertical and horizontal extent of petroleum hydrocarbons and im- <br /> prove the understanding of the local stratigraphy. <br /> f <br /> The soil borings and shallow monitoring wells were drilled by Spectrum Exploration, <br /> Inc. (Spectrum), using CME-55' and CME-75 drill rigs equipped with 8-inch-outside <br /> diameter hollow-stem augers. <br /> The seven soil borings in the vicinity of the former Disco tanks were drilled to depths <br /> between 61 and 76 feet bgs and sampled at approximately 5-foot intervals. Soil <br /> samples collected during the installation of Monitoring Well MW-DIS-2, -3, -4, -5, and <br /> -7S were obtained at 5-foot intervals between 55 and 75 feet bgs. <br /> Soil samples were collected at 5-foot intervals from each of the borings by driving a <br /> split-spoon sampler with brass liners. Immediately after each soil sample was collected, <br /> one brass tube was sealed with Teflon tape and polyethylene end caps, labeled,-and <br /> placed in an ice-filled cooler. Remaining soil in the sampler was visually classified and <br /> logged and field -screened for volatile organic compounds using an HNU meter. Boring <br /> logs are attached to this report as Appendix B. At the end of each 'field day the <br /> sample coolers were shipped via overnight courier to the CH2M HILL Analytical <br /> Laboratory in Redding, California. <br /> Ali soil samples were analyzed for the volatile aromatic hydrocarbons benzene, toluene, <br /> f, ethylbenzene, and xylenes (BTEX), total petroleum hydrocarbons as gasoline (TPH- <br /> gas), and lead. Grain-size analyses were performed on five samples. One soil sample <br /> was also analyzed for phosphate, ammonia, nitrate, pH, and organic content. <br /> ( Groundwater Monitoring Wells <br /> Well Installation <br /> Eight groundwater monitoring wells were installed as MW-DIS-1, -2, -3, -4, -5, -6, -7S, <br /> and -7D (Figure 2-2). Seven of the eight wells (MW-DIS-1, -2, -3, -4, -5, -6, and -7S) <br /> were screened approximately 10 feet below and 10 feet above the current water table <br /> ` as "shallow wells." Monitoring Well MW-DIS-7D was screened as a "deep well" at 60 <br /> to 70 feet below the current water table. Table 2-1 summarizes well construction data. <br /> 1, <br /> SF031604\RP1003.51 2-3 <br />