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r i Mr Kyle Christie Project 0805-142 003 July 28, 1995 Page 2 GROUNDWATER MONITORING: SECOND QUARTER 1995 EMCON was contracted by ARCO to monitor the groundwater monitoring wells previously Installed at the site Field work included measuring depths to water and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the gradient and direction of groundwater flow beneath the site On May 16, 1995, a technician from EMCON measured depths to water and collected groundwater samples from wells MW-1 through MW-3 for subjective and laboratory analyses Floating product or product sheen was not noted in samples from the wells (see Table 1) Sampling and analysis procedures are presented in Attachment A The well head elevations of the monitoring wells at the site were previously surveyed by Tom O Morrow The surveyed elevations and the depth to groundwater measurements (summarized in Table 1) were used to evaluate the potentnometric surface beneath the site The groundwater flow direction on May 16, 1995, was to the south with a hydraulic gradient of 0 001 (see Figure 3) Groundwater elevation data are presented on Figure 3 and in Table 1 Groundwater elevations increased approximately 2 24 feet from the previous sampling event (February 1995) 1 Groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPHG), total petroleum hydrocarbons as diesel (TPHD) using Environmental Protection Agency (EPA) Method 5030/DHS LUFT, total oil and grease (TOG) using EPA Method 5520 B and F, and benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Methods 5030/8020 These samples were analyzed at Columbia Analytical Services, Inc , in San Jose, California. The results of these analyses are summarized in Table 1 Copies of the chain-of custody records and laboratory analysis reports are presented in Attachment B TPHG concentrations were detected in all wells, concentrations ranged from 130 parts per billion ([ppb] well MW-3) to 240 ppb (well MW-1) Concentrations of benzene were not detected at laboratory detection lumts in all wells TOG was not detected in groundwater samples collected from all wells TPHD was detected in well MW-1 at a concentration of 107 ppb The sample contained components that eluted in the diesel range, but the chromatogram did not match the typical diesel fingerprint (see Attachment B) TPHD was not detected at laboratory detection limits in the other wells TPHG and benzene concentrations are shown on Figure 2 ACTIVITIES PERFORMED DURING THE SECOND QUARTER • EMCON performed quarterly groundwater sampling • EMCON compiled and evaluated groundwater monitoring data SACIN\PJft80M9051420 3BL-95 PAS 3