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Limited Subsurface Environmental Investigation October 3, 1990 <br /> ARCO Service Station No. 6020, Manteca, California AGS 30055-1 <br /> f' <br /> materials consisted predominately of sand and silt. The sand was logged as line-to coarse- <br /> grained. The Log of Borings also indicate a trace amount of fine-grained and coarse- <br /> grained gravel. <br /> Photoionization detector(PID)readings are also included on the Log of Borings. The PID <br /> did not detect hydrocarbons in the soil samples collected. Our staff geologist also did not <br /> note subjective evidence of gasoline hydrocarbons such as soil discoloration or obvious odor. <br /> The geologist initiated Chain of Custody Records which accompanied the samples to the <br /> analytical laboratories. Copies of those documents are in Appendix B. <br /> The bor.ngs were terminated approximately 1 foot below the first encounter of ground water <br /> which was approximately 20 feet below grade in borings B-2 though B-7 and 25 feet in <br /> boring B-1. It is possible we encountered a perched water zone in borings B-2 through B-7 <br /> that was not present in boring B-1. <br /> The borings were backfilled to the ground surface with a neat cement slurry. Cuttings <br /> generated during drilling were placed on plastic, covered with plastic, and left at the site. <br /> io Four soil samples were collected from the drill cuttings and composited into one sample for <br /> laboratory analyses. In addition, and at the request of ARCO, the samples were submitted <br /> to the GS)CUkernFacility-in-ButtbrTwillow-,California for-a-profile-analysis.- <br /> 6 <br /> ana ysis.6 <br /> W <br />