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feet and at 4,200 mg/kg in sample JL-P-15 in a sand layer at 12 5 feet (Figure 3) No hydrocarbons were detected in samples below the clay layer, and because organic vapor concentrations (PID readings) declined rapidly below this layer, Upgradrent Enviromnental interpreted the clay as a confining layer that inhibited downward migration of gasoline In July 1996, PHS/EHD requested further investigation of the residual contamination that was detected in samples JL-P-13 and JL-P-15 However, no work was performed until Mr Fisk discussed the matter with representatives of the CVRWQCB in mid-2001 These discussions led to the July 2001 request by Mr Marty Hartzell of the CVRWQCB for a drilling investigation work plan 3 0 PROCEDURES V&W Drilling of Rio Vista, California used a Central Mine Equipment CME-55 hollow- stem auger rig to drill the borings Soil samples were collected at 5-foot intervals in JLM- 2, beginning at a depth of 10 feet Oust above the 12 5 feet at which contamination had been detected in sample JL-13 during the remedial work in 1995) Sampling in JLM-1 began at 25 feet in JLM-1 (at the contact between native soil and backfill material) The samples were screened for the presence of organic vapors with a portable photo- ionization detector (PID), preserved in a cooled ice chest for later laboratory analysis, and described on the boring log (Appendix A) Groundwater was encountered at approximately 33 feet in JLM-2, and a disposable plastic bailer was lowered through the augers to collect a water sample A thin zone of groundwater was penetrated in JLM-1 dust above 30 feet, but the soil sample at 30 feet was dry Therefore, this boring was deepened, and a good flow of groundwater was encountered at approximately 36 feet The boring was terminated at 40 feet, and a bailer was lowered through the augers to collect a water sample Both borings were backfilled by pumping cement-bentonite grout through a tremmie pipe Drill cuttings were stored on plastic sheeting near the western property line Eight soil samples and two water samples were transported to Sequoia Analytical Laboratory in Sacramento, where they were analyzed for Total Petroleum Hydrocarbons as gasoline (TPH-g), and benzene,'toluene, ethylbenzene, and xylene (BTEX) One soil sample and one water sample from JLM-1 were also analyzed for Total Petroleum Hydrocarbons in the diesel range (TPH-d) Four soil samples and both water samples were analyzed for gasoline oxygenates, ethylene dzbromide (EDB), and dichloroethane (1,2-DCA) as instructed by CVWRQCB Four soil samples were also analyzed for total lead The laboratory report is included to Appendix B, and the results are discussed in section 4 0 3