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40 FIELD ACTIVITIES <br /> The following sections detail the methods and procedures used in this soil and <br /> groundwater assessment Field activities included advancing eight testhole bonngs, <br /> collecting soil samples, and completing three groundwater monitoring wells AGI <br /> personnel conducted the field work on July 28 and 29, 1993 <br /> 41 Soil Boring and Groundwater Monitoring Well Locations <br /> Field activities included advancing eight (8) testhole borings to accomplish project <br /> objectives The eight borings were designated TH-1 , TH-2, TH-3, TH-4 TH-4b, TH-5, <br /> TH-6, and TH-6b Exhibit 2 shows the boring locations, while the Boring Logs are <br /> presented in Appendix A The boring locations were modified from the workplan to <br /> accommodate site conditions but retained the same general labeling scheme The <br /> following discussion describes the field activities in the order of drilling and the rational <br /> for the boring placement <br /> Boring TH-1 was advanced in the vicinity east of the former underground storage tanks <br /> #1 and #2, in an area where laboratory analyses indicated sods contained elevated <br /> concentrations of hydrocarbons TH-1 encountered groundwater at a depth of <br /> approximately 29 feet below the surface grade (bsg), and subsequently, drilling was <br /> terminated at approximately 30 5 feet (bsg) <br /> Testhole boring TH-6 was advanced approximately 22 feet northeast of TH-1 to assess <br /> the lateral extent of impacted soils in this direction Field screening techniques <br /> indicated the presence of hydrocarbons, resulting in the termination of drilling at a <br /> depth of approximately 25 5 feet (bsg) TH-fib was relocated to 41 feet northeast of <br /> TH-1 and advanced to a depth of 50 feet (bsg). <br /> Testhole boring TH-4 was advanced in the vicinity west of underground storage tank <br /> #2 at the request of Mary Meays, San Joaquin County Environmental Health Services <br /> Department Drilling advanced to a depth of approximately 30 5 feet (bsg), after <br /> encountering groundwater at approximately 29 feet (bsg) Field screening indicated <br /> soil impacted with hydrocarbons from 20 feet bgs to groundwater in TH-4 As a result, <br /> TH-4b was relocated approximately 18 feet southwest of the TH-4 to assess the lateral <br /> extent of hydrocarbons in this direction and was advanced to a depth of approximately <br /> 45 feet (bsg) <br /> Testhole boring TH-5 was advanced approximately 25 feet to the northwest of TH-4 to <br /> assess petroleum hydrocarbon impacted soils in this direction Drilling was terminated <br /> at a depth of approximately 45 feet (bsg) after encountering groundwater at <br /> approximately 29 feet (bsg) <br /> Boring TH-3 was advanced about 20 feet southwest of TH-1 , to a depth of <br /> approximately 30 5 feet (bsg) Groundwater was encountered at a depth of 29 feet <br /> 6of17 <br />