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3.0 LABORATORY ANALYSIS The groundwater samples were transported to Severn Trent Laboratories, Inc. (STL), a state-certified laboratory, located in Pleasanton, California. The groundwater samples were analyzed in accordance ;- with San Joaquin County Environmental Health Department's March 2004 letter as follows: ■ Wells MW-1R, MW-9 and MW-10 were analyzed for the presence of MTBE by EPA Method s- 825013; • Wells MW-2 and MW-5 were analyzed for the presence of MTBE, TAME, and TBA by Method W 826013; ■ Well MW-4 was analyzed for TPH-G (by Method 8015B), BTEX (Method 8021B) as wells as for MTBE(by Methods 8015M-8021B); Copies of the laboratory analytical report and chain of custody record are provided in Appendix C. 4.0 SUMMARY OF RESULTS Based on groundwater elevation data for May 24, 2005 the groundwater flow direction in both the upper and lower aquifers was towards the southeast at gradients of approximately 0.002 feet per foot(ft/ft)and 0.003 ft/ft, respectively (Figures 3 and 4). The groundwater flow directions and gradients noted during this sampling event are consistent with historical trends. ..e TPH-G was analyzed only in MW-4 which samples the lower aquifer; with a concentration level of 50 I-��• BTEX compounds were sampled in MW-4; only toluene was found above the detection limits (concentration of 4.5 µg/L)- &W MTBE was reported in groundwater samples collected from upper aquifer well MW-5 at a concentration of 410 µg/L. MTBE was also reported in lower aquifer wells MW-1R and MW-2 at concentrations of 5.9 gg/L, 8.1 µg/L, respectively. Figures 5 and 6 provide maps of TPH-G, benzene and MTBE concentration distributions in site wells based on the May 24, 2005 sampling event. &' The fuel oxygenate TAME was detected in the groundwater sample collected from MW-5 this quarter at a concentration of 2.8 µg/L. TBA was not detected in any of the groundwater samples collected this quarter. The MTBE concentrations in both lower and upper aquifers have shown an increase in wells MW-1R and MW-5. Concentrations of MTBE in MW-5 have decreased by an order of magnitude since the peak in 1999 and have remained below 500 gg/L since 4s`quarter 2004. TBA concentrations in water samples from MW-5 continue to trend downward significantly between 2004 and 2005 and were below #" detection limits this event. Although there is a reported detection of TAME for MW-5, the current level shows a decline from the last reported detection in March 2004. MW-2 has shown a significant decrease in MTBE since the last sampling event in March 2005 and may indicate in-site degradation of MTBE. Quarterly GW Monitoring Report-2nd Qtr 2005 � "v" �� Quik Stop No. 132 Quik Stop Markets, Inc. * ATC Project No.75.62503.3205 June 13,2005 +•• Page 2 of 4