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Ms. Carol Oz 4 December 17, 1999 <br /> was detected in groundwater samples obtained from ATC-3 and ATC-5-20'. MTBE was <br /> detected in all groundwater samples except for ATC-4. <br /> SCOPE OF WORK <br /> The proposed scope of work is to further determine the lateral extent of MTBE concentrations in <br /> Lgroundwater downgradient of soil boring ATC-2. The work was requested by the San Joaquin <br /> County Environmental Health Division on April 16, 1999. <br /> 1 INVESTIGATION <br /> ATC retained the services of V & W Drilling of Rio Vista, California for advancing the borehole <br /> and installing the well. The field investigation was performed on November 19, 1999. <br /> Underground Services Alert (USA) was notified of the proposed drilling activities to ensure that <br /> no utility lines were located within the immediate vicinity of the soil boring. Cruz Brothers Sub- <br /> Surface Locators, Inc. of Milpitas, California, provided a subsurface survey of utility lines and/or <br /> other buried objects in and around the borehole location. <br /> One soil boring (MW-8) was advanced to approximately 30 feet bgs. The soil boring location is <br /> shown on Figure 1. Groundwater was encountered at approximately 14 feet bgs. An ATC <br /> geologist under the supervision of a California Registered Geologist logged the soil boring in the <br /> field in accordance with the Unified Soil Classification System (USCS). The soil boring log is <br /> included as Appendix B. <br /> 1 <br /> Undisturbed soil samples were collected from the soil boring at approximately 5-foot intervals. <br /> 1 Soil samples were obtained using a truck mounted drill rig equipped with a California modified <br /> split spoon sampler. The sampler was driven into undisturbed soil ahead of the auger bit using a <br /> 140-pound downhole hammer. The split spoon sampler holds three brass tubes for the collection <br /> of soil samples. <br /> Upon removal of the tubes from the sampler, the lowermost tube was capped with Teflon liners <br /> and plastic caps. The soil samples were properly labeled and placed in a cooler with ice, and <br /> transported to Entech Analytical Labs, Inc., a state-certified laboratory, located in Sunnyvale, <br /> ' California using chain-of-custody protocol. <br /> 1 <br />