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CAMBRIA region of the site will provide additional groundwater data to help delineate the western extent of gasoline constituents in groundwater beneath the site CONCLUSIONS AND RECOMMENDATIONS The petroleum hydrocarbon and MTBE concentrations in groundwater samples collected from the shallow wells this quarter are within the historical norm for this site Wells MW-5 and RW-IA continue to contain the highest levels of hydrocarbons and MTBE, however it appears that GWE efforts have reduced these concentrations somewhat MTBE was detected in well MW-14 at a concentration of 17 parts per billion (ppb) during the quarterly sampling event (September 16, 2003) The well was resampled on October 8, 2003 to determine if the first MTBE detection was an anomaly MTBE was detected in MW-14 on October 8, 2003 at a concentration of 0 62 ppb These concentrations are below the California Maximum Contaminant Level for MTBE of 5 ppb However, we initiated monthly sampling of this well and the domestic well at 2452 Country Club Boulevard to better evaluate groundwater quality in the vicinity of MW-14 Preliminary findings for monthly sampling conducted in • November and December 2003, and January 2004, indicate that no MTBE has been detected in MW-14 or in the domestic well at 2452 Country Club Boulevard These findings will be reported with the first quarter 2004 monitoring report It is possible that the low level detections of MTBE in these two samples are due to laboratory contamination issues or field contamination issues Since historical groundwater flow direction at the subject site has been either northeasterly or southwesterly, it appears unlikely that MTBE could migrate from this site, crossgradient, toward MW-14 Furthermore, if MTBE were to migrate from the site toward MW-14 we would expect to first find it in wells MW-13 and/or MW-11 Well MW-13 has never contained MTBE and MW-11 has had only one sampling event where it contained MTBE at 10 ppb We will continue monthly sampling of these wells to monitor this situation Cambria recommends continued operation of the GWE system (as soon as we obtain an NPDES permit) and continued monitoring and sampling of site monitoring wells to evaluate concentration trends at the site As mentioned above, Cambria recommends installing an additional monitoring well at the site, and will submit a work plan to San Joaquin County Environmental Health Department for review and approval • 0783 3