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Mr Kyle Christie Project 0805-114 04 August 7, 1995 ' Page 3 ' GROUNDWATER MONITORING: SECOND QUARTER 1995 EMCON was contracted by ARCO to conduct the field work at the site Field work included measunng depths to water and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the direction and gradient of groundwater flow beneath the site On May 19, 1995, a technician from EMCON measured depths to water and collected groundwater samples from wells MW-1 through MW-8 and MW-10 for subjective and ' laboratory analyses Floating product or product sheen was not noted in samples from the wells (see Table 1) Sampling and analyses procedures are presented in Appendix A ' The wellhead elevations of the monitoring wells at the site were previously surveyed by Morrow Surveying of West Sacramento, California. The surveyed elevations and the depth to groundwater measurements, summarized in Table 1, were used to evaluate the potentiometric surface beneath the site The groundwater flow direction on May 19, 1995, was to the east, with a hydraulic gradient ranging from 0 001 to 0 003 (see Figure 3) The groundwater flow direction in the past has generally been towards the east to southeast Groundwater elevation data are presented on Figure 3 and in Table 1 Groundwater elevations increased 190 feet from the previous sampling event performed in February 1995 Groundwater samples collected from wells MW-1 through MW-8 and MW-10 were analyzed for TPHG, and benzene, toluene, ethylbenzene, and total xylene isomers using California Department of Health Services (DHS) LUFT Method and Environmental. Protection Agency (EPA) Method 5030/8020, respectively These samples were analyzed ' at Columbia Analytical Services, Inc , in San Jose, California The results of analyses are summarized in Table 2 Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix B. ' TPHG and benzene were not detected at laboratory detection limits in wells MW-4 and MW-7 Dissolved hydrocarbons were detected in wells MW-1 through MW-3, MW-5, ' MW-6, MW-8, and MW-10 TPHG concentrations ranged from below detection limits in wells MW-4 and MW-7 to 400 ppb in well MW-2 Benzene concentrations ranged from below detection limits in wells MW-3, MW-4, and MW-6 through MW-8 to 23 ppb m well MW-2 TPHG and benzene concentrations are shown on Figure 2. SAC/N�pjW805\08051140 4cs-95 pas 1