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BTEX in samples collected from wells MW-4, MW-5, and MW-7. The results of the analyses <br /> r'' = of the samples collected from MW-6 indicate that the ground water underlying that vicinity <br /> remains impacted with TPH-g and benzene analytes above the Maximum Contaminant Levels <br /> (MCLs) set by the California Department of Health Services; the analytes are less prevalent this <br /> _ quarter. With the exception of benzene, detected at 0.4 pg/C, and xylenes, detected at 0.6µg/k, <br /> ;j the sample collected from MW-8 revealed nondetectable analytes; these results are just slightly <br /> higher than the laboratory detection limit of 0.3 ggli. <br /> It should be noted at this time that soil-vapor extraction, augmented by air-sparging of the <br /> ground water, may be the most economical, active remediation methods, but only if deemed <br /> ._� absolutely necessary. The combined technologies could be utilized to clean up the impacted <br /> =� ground water and any affected soil at and below the water table, especially around and <br /> downgradient of MW-6. Soil-vapor extraction was not recommended in the Problem Assessment <br /> --- Report because so little soil left in the backfilled UST excavation may have remained residually <br /> impacted (see Table 1). However, because gasoline contaminant concentrations appear to be <br /> declining in MW-6, Irwin continues to recommend passive remediation and continued ground- <br /> water monitoring under its present contract with The Pegasus Group. <br /> The next ground-water monitoring activity is scheduled for mid-January, 1996. <br /> j <br /> CERTIFICATION <br /> = 7 Should any questions arise regarding the information contained in this report, or if we may be <br /> of further service, please contact our Merced office at (209) 725-2085. W.W. Irwin, Inc. is not <br /> -' responsible for undisclosed or hidden, site-specific information or conditions. <br /> Respectfully Submitted, <br /> �J W.W. Irwin, Inc. <br /> ii),e[) GAO<p <br /> DAYNE L.FRARY (_P4 � 9� NLn <br /> Dayne L. Frary, Merced BranManager No.02980 <br /> Registered Geologist No. 4456 0). No.4456 Q J Expires•&•9 �o <br /> Registered Environmental Assessor No. 02980 �p� 10.31•g7 <br /> SOF CA1-��O ®`OF CAi-IF���`� <br /> =1 <br /> W.W.huiq Inc. <br /> Project No.33016.05 <br /> j -- October 1995 12 <br /> '.J <br /> __' YI <br />