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a <br /> t <br /> � f <br /> Subsurface Investigation December 12, 1990 <br /> Former Unocal Station No,2859, Stockton, California AGS 38012-5 <br /> wells were screened from 24 to 54 feet below grade. The methods and materials used for <br /> well construction are detailed in the Appendix to this report. Boring B-b was terminated <br /> at approximately 41 feet below grade, and backfilled with a bentonite/cement slurry. <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 /> On August 28, 1989, we developed, purged, and sampled the two wells; subjectively <br /> analyzed the water samples for hydrocarbons;and measured the ground-water levels. Our <br /> methods for this field work are discussed in the Appendix A. We observed no subjective <br /> evidence of hydrocarbons in the -rater samples. The geologist initiated Chain of Custody <br /> Records which accompanied the samples to the analytical Iaboratories. Copies of those <br /> documents are in Appendix B. <br /> All water purged during monitoring well development and sampling was placed in <br /> Department of Transportation 17E drums and left on the site. At Unocal's request,Armour <br /> Petroleum Service and Equipment Corporation of Vacaville, California removed the drums <br /> and water from the site for disposal after the August 1989 event and each quarterly <br /> monitoring event. <br /> LABORATORY ANALYSES AND RESULTS <br /> Applied GeoSystems submitted soil and groundwater samples from each boring and well <br /> for laboratory analyses. The soil sample selection criteria requested by Unocal was to <br /> ------------- <br /> analyze the soil sample immediately above ground=water if no by rocar on vapors-were- <br /> analyze <br /> apors were- ----- - <br /> detected using a PID. We also analyzed the soil sample collected at 20 feet below grade <br /> lI <br /> AA01 ed OOOSysMemS <br />