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25 May 2001 <br /> AGE-NC Project No. 95-0100 <br />' Page 3 of 4 <br /> 3.2. GROUND WATER ANALYTICAL RESULTS <br />' During the February 2001 sampling MTBE was detected in both MW-I and MW-3 by EPA method <br /> 8020 at 200 micrograms per liter (µg11) and 52-4g/1, respectively. MTBE was confirmed in each <br />' sample by EPA method 8260 INIodified at concentrations of 150,ugll and 74 ,ug/1, respectively. <br /> During the May 2001 sampling MTBE was detected in both MW-I and MW-3 by EPA method 8020 <br /> at 12 µg/l and 9.1 ugh, respectively. MTBE was confirmed in each sample by EPA method 8260 <br /> Modified at concentrations of 12 µg/1 and 7.2 µg/1, respectively. <br /> ' No other fuel oxygenated compounds were detected above the laboratory reporting limits. Analytical <br /> results of ground water samples are summarized in Table 2. The laboratory reports (Me Campbell <br /> ' Analytical Laboratory ID 60117 to 60179 and 66933 to 66935), quality assurance and quality control <br /> (QA/QC) data and chain-of-custody forms are attached in Appendix B. <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> ' • Based on the findings of this and previous investigations, AGE concludes the following: <br /> • The ground water flow direction was toward the northwest during bath sampling event. The <br /> ' ground water elevation decreased approximately 1.3 feet between November 2000 and <br /> February 2001 and ground water elevation increased approximately 0.5 feet between . <br /> February and May 2001. <br /> • MTBE was detected in samples from monitoring wells MW-1 and MW-3. <br /> • The MTBE concentrations exceeded the State of California maximum contaminant level <br /> ' (MCL) of 13 µg/l during the February 2001. sampling event, however, the MTBE <br /> concentrations decreased to a level below the MCL during the May 2001 sampling event. <br /> 5.0. RECOMMENDATIONS. <br /> Based on the results of this investigation,AGE recommends: that quarterly monitoring be continued. <br /> _Continued_quarterly_..ground water_monitoring._The_next.quarterly_monitoring.,and_sampling. _. <br /> ' event is tentatively scheduled for August 2001. <br /> ' Installation of deep-screened ground water monitoring wells to define and monitor the <br /> vertical extent of the ground water plume. <br /> • • . <br /> _ <br /> Installation.ofadditional shallow ground water wells to define_and monitor the lateral down_ <br /> ' Advanced Geo Environmental,Inc. <br /> 1 <br />