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w • A S S O C I A T E S I N C Vaipor Wells Results of laboratory analyses indicated dissolved TPH& TPHd, and BTEX constituents were detected in the samples from vapor wells VW-1, VW-2d, and VW-5d Well VW-3 remained nondetect Concentrations reported in wells VW-1 and VW-5d were relatively low and have generally decreased since the two previous sampling events Benzene exceeded the MCL in well VW-5d Concentrations in well VW-2d remain elevated MTBE was not detected in any of the samples from wells VW-1, VW-2d or VW-3, however the detection level for the sample from VW-2d was elevated due to dilution factors The groundwater sample from vapor well VW-5d contained MTBE at 80 1 ppb Results of laboratory analyses are summarized in Table 2 SUMMARY The groundwater flow direction and gradient were consistent with those evaluated during previous events Dissolved gasoline hydrocarbons were detected in the samples from groundwater well MW-I and vapor wells VW-1, VW-2d, and VW-5d Dissolved hydrocarbons in the diesel range were detected in the samples from groundwater wells MW-1 and MW-3 and vapor wells VW-1, VW-2d, and VW-5d during the reporting period BTEX constituents were detected in wells MW-1, VW-1, VW-2d, and VW-5d MTBE was detected only in the sample vapor well VW-5d, however detection limits were elevated for the samples collected from MW-1 and VW-2d Concentrations have generally remained the same in the groundwater wells and generally remained the same or decreased in the vapor wells since they were last sampled If you have any questions with this project, please call our Modesto office at (209) 579-2221 Respectfully submitted, ATC Associates Inc JIB HONISE Jeanne Hornsey No. G0W4410 CA Registered Civil Engineer No 47410 UP CIVIL cc James Giottonim, City of Stockton ,, Marty Hartzell, CRWQCB Central Valley Region • Attachments