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e • s <br /> i <br /> Limited Environmental Investigation July 16, 1990 <br /> ARCO Service Station No. 6100,Tracy, California AGS 30041-1 <br /> i <br /> Soil samples were collected during drilling at approximately 5-foot intervals and were <br /> _ classified according to the Unified Soil Classification System (Plate P .. Descriptions of <br /> materials encountered are presented in the Logs of Boring(Plates P-4 through P-14). The <br /> ! materials consisted predominately of silt and clay. <br /> The boring,were terminated when(1)photoionization detector(PIA)readings of less than <br /> 50 parts per million by volume (ppmO were obtained in two consecutive samples, and (2) <br /> ,w other additional subjective evidence of gasoline hydrocarbons such as soil discoloration or f <br /> obvious odor was not noted. Boring B-1 was terminated 56 feet below surface grade,boring <br /> B-2 was terminated 41 feet below grade, and boring B-3 was terminated 26 feet below <br /> grade. The total depth of borings B-4 and B-5 was 31 feet below grado. <br /> The Logs of Boring for B-1 and B-3 show saturated sediment was present in a 6-inch sample <br /> k IIr i <br /> I from approximately 19-1/2 to 20 feet below grade and between 14-1/2 and 15 feet below <br /> grade in boring B-4. Ground water was not detected at these depths using a water level <br /> indicator. The.bottom 6-inch samples collected from each boring in the 18-inch split spoon <br /> sampler were logged as damp or dry. All soil samples collected below the saturated sample <br /> were logged as damp or dry. Saturated sediment was not sampled in borings B-2 and B-5. <br /> E � <br /> ti <br /> ARRAO ' Ge0Systems <br />