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09 October 2000 <br /> • AGE-NC Project No 98-0534 <br /> Page 5 of 6 <br />' MTBE was detected 1n samples MW-3, MW-4, MW-6 and MW-7 at 3 7µg/l, 13 ,ug/l, 350,ug/l and <br /> 2 2 ,ug/l, respectively ETBE was detected at 24 kcg/l in sample MW-6 and TBA was detected at 21 <br /> 4gll in sample MW-4 No other fuel oxygenates were detected In any of the samples <br /> Laboratory results of water samples analyzed for petroleum hydrocarbons are summarized in Table <br /> 4 The Iaboratory reports for the quarterly monitoring event (MAI Laboratory ID No 44332 to <br /> 44339) QA/QC reports and chain-of-custody form are included In Appendix C <br />' 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the findings from this investigation, the following conclusions are presented <br /> • Trace concentrations of hydrocarbons were detected in the soil samples collected from boring <br />' MW6, located in the former UST area MTBE was also detected in this boring at 15 and 20 <br /> feet, however,the shallow depth to ground water (10 feet bsg) at this site indicates that the <br /> detected hydrocarbons in the soil were collected within the saturated zone <br /> Ground water on the site was flowing toward the south-southwest from the former UST with <br /> a nearly flat hydraulic gradient of 0 003 feet/feet or 0 17 degrees <br /> • MTBE was detected in four ground water samples collected, with the highest dissolved <br /> concentrations occurring within the former UST area, at concentrations as high as 350 Ugll <br /> The CV-RWQCB document titled A Compilation of Water Quality Goals, August 2000, lists <br /> the State of California Maximum Contaminant Level (MCL) for MTBE in drinking water <br /> at 13 ,ug/l Figure 5 depicts the 13 gg/l isocontour for MTBE which is defined by the current <br /> monitoring well network <br /> 5.0. RECOMMENDATIONS <br /> Since the MTBE ground water plume has been defined, AGE recommends that quarterly monitoring <br /> continue <br /> Advanced GeoEnviromnental,Inc <br />