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c7 obgkaf rahatcs Inc Page 2 ' Groundwater Monitoring Report Project No 425 2 . Apn127,2006 ' remaining monitoring wells and the three domestic wells sampled during this event were non-detect above laboratory reporting limits for all analyzed constituents A summary of groundwater analytical findings include • MW-1 shows the presence of benzene, ethylbenzene, total xylenes, TPH-G and MtBE ' constituents The well was non-detect above laboratory reporting limits for all other analyzed constituents Overall there appears to be a decrease in contaminant concentrations • MW-2 shows the presence of BTEX, TPH-G and 1,2-DCA constituents MtBE is likely present but not detected due to elevated detection limits The well was non- detect above laboratory reporting limits for all other analyzed constituents • MW-4 shows the presence of benzene, ethylbenzene, TPH-G and 1,2-DCA constituents The well was non-detect above laboratory reporting limits for all other analyzed constituents The plume appears to be stable around MW-4 MW-4 likely represents the southern edge of the plume • MW-5 shows the presence of ethylbenzene, total xylenes, TPH-G, BTEX, MtBE and 1,2-DCA constituents The well was non-detect above laboratory reporting limits for all other analyzed constituents Overall there appears to be a decrease in contaminant concentrations • MW-7 shows the presence of 1,2-DCA and was non-detect above laboratory reporting limits for all other analyzed constituents The levels are gradually increasing with time This may be showing the plume encroachment on this well predicted in this and previous monitoring reports (Section 3 0) • MW-8 shows the presence of ethylbenzene and TPH-G constituents The well was ' non-detect above laboratory reporting limits for all other analyzed constituents MW- 8 likely represents the eastern edge of the plume • MW-106 shows the presence of TPH--G, MtBE and 1,2-DCA The well was non- detect above laboratory reporting limits for all other analyzed constituents ' 1.0 HYDROGEOLOGIC SYSTEM 1.1 Regional Structure ' George's Service (Georges) is located in the northeast quarter of the northeast quarter of the northeast quarter of Section 20, T3S, R6E, related to the Mount Diablo B&M, on the United ' States Geological Survey (USGS) Topographic Map, Vernalis Quadrangle, California, 7 5 minutes series A review of the USGS Topographic Map reveals that the elevation of this site is approximately 83 feet above mean sea level (AMSL) ' The site is located on theaduall sloped floor of the northern San Joaquin Valley The � Y p geologic composition of the area is characterized as fluvial deposits of the San Joaquin -