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Page 5 4 SUBSURFACE INVESTIGATION ' 4.1 SOIL BORINGS ' On 30 April and 1 May, 1992, Artesian supervised Gregg Drilling &Testing, Inc , in the drilling of three soil bonngs at 1045 West Charter Way in Stockton, California All phases of work were directed by an Artesian geologist under the supervision of a California Registered Geologist The permit from the San Joaquin County Public Health Services is included in Appendix A ' Initially,pilot holes were drilled for all three monitoring wells using eight-inch diameter, continuous flight hollow stem augers (HSA) The three boreholes (B-1, B-2, B-3) were drilled to 45 0, 45 0 and 43 0 feet below ground surface(BGS) respectively All three borings were drilled ' into native material Groundwater was encountered m all the wells at approximately 35 feet below ground surface ' The soils were togged by Matthew H Walraven, Artesian Project Geologist, who is under the supervision of a California-registered geologist Sod samples were collected at least every 5 feet ' and at lithologic changes for lithologic, hydrologic and characterization and possible chemical analysis Boring logs and the Unified Soil Classification System are included in Appendix B One soil sample was obtained from each borehole at the groundwater interface using the standard operating procedure (SOP) for sod sampling outlined in Appendix C The soils were screened with a photoiornzation detector (PID), an instrument to detect organic vapors PID readings ranged from 180 ppm at 26 feet, to 50 ppm at 30 feet and 20 ppm at 36 feet ' below ground surface in B-I PID readings ranged from 10 ppm at 1 I feet to 14 ppm at 16 feet, to 12 ppm at 31 feet and 4 ppm at 36 feet below ground surface in B-2 PID readings ranged from 2 Qpm at 10 feet, to 2 ppm at 16 feet, to 3 ppm at 21 feet to 78 ppm at 26 feet to 20 ppm at 36 feet ' and 8 ppm at 40 feet in B-3 The organic vapor screening method is described using a standard operating procedure outlined in Appendix C ' Drilling equipment was decontaminated between borings using a steam cleaner The nnse water and drill cuttings were stored on site in one, labeled, 55-gallon, DOT 17-H drums in a manner ' consistent with the Regional Air Quality Control Board (RAQCB) and other regulatory agency regulations and guidelines ' All soil samples were labeled and packed on crushed ice for transportation to Chromalab, Inc in San Ramon, a California State certified hazardous materials laboratory The soil samples were analyzed for TPH-g and TPH-d by Method 8015 and BTXE by Method 8020 Chain of Custody documentation (copies attached, see Appendix E) accompanied all samples to the laboratory 100 Shoreline Hwy, Suite 295 B • Mill Valley, CA 94941 • (415)381-6456 FAX (415) 389-0423