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CV7 o ASS O C I ATE S I N C . Equal Elevation of Groundwater, Fall 1997). The groundwater gradient was calculated to be approximately 0.0013 feet per foot or 7 feet per mile. Groundwater monitoring data are presented in Table 1. Monitoring wells MW 1, MW2, MW3, MW4, and MW5 were purged a minimum of three well volumes until the electric conductivity, pH, and temperature stabilized. Subsequent to purging, groundwater was sampled and transferred to appropriate sample containers, using a clean, disposable bailer with a bottom-emptying device to reduce volatilization. Sample containers were then labeled with sample identification, placed on ice, and shipped under chain-of-custody to Argon Laboratories. Field development/purge logs are presented in Attachment 1. Laboratory Analysis The groundwater sample from wells MW1, MW2, MW3, MW4, and MW5 were analyzed by Argon Laboratories (DHS Cert. No. 2359) for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Methods 8015/8020. Oxygenate fuel additives which include methanol, ethanol, t-butanol (TBA), methyl-t-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl-t-butyl ether (ETBE), t-amyl methyl ether (TAME), 1,2- dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) were analyzed by EPA method 8260. • Laboratory Results TPHg, benzene, ethyl benzene, toluene, and xylenes were not detected above their respective laboratory method detection limits. Oxygenate fuel additives, including MTBE were not detected above their respective laboratory method detection limits. Analytical results are summarized in Table 2. Laboratory data sheets and chain-of-custody documentation are provided in Attachment 2. DISCUSSION Based on past analytical results and field observations, soil and groundwater beneath the location of the former 500-gallon gasoline UST was moderately impacted by petroleum hydrocarbon constituents. The results from the past four monitoring events indicate that petroleum hydrocarbons have been reduced to nondetectable levels in the groundwater. The observations detailed in this report do not show that lateral migration of petroleum hydrocarbon impacted groundwater has occurred. In the judgment of ATC, the site should be granted closure. If San Joaquin County Environmental Health Department is in concurrence with ATC's recommendation, ATC will submit a workplan and permit application for well abandonment. w:lw0rdpro\17292.0002Veportsli grnr 2002.doe