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CAMBRIA. <br /> • Table 1.Site Conceptual Model,Smell-branded Service Station,2494 East Fremont Street,Stockton,California <br /> 2 9 Stratigraphy and Hydrogeology The site is underlain primarily by fine-grained sediments(clay and silt) <br /> with lesser amounts of coarse-grained sediments (sand and gravel) The <br /> coarse-grained sediments primarily occur at three depth intervals (with <br /> varying thicknesses) 10 to 30 fbg, 70 to 85 fbg, and 105 to 115 fbg The <br /> coarse-grained sediments have not been found in every boring at these <br /> depths so it may be that they are not laterally continuous beneath the site <br /> 2 10 Preferential Pathways Analysis No analysis has been performed However, due to groundwater depth (a <br /> least 46 fbg), it is highly unlikely that any utility trenches would act as a <br /> preferential pathway for groundwater migration <br /> 211 Other Pertinent Issues Groundwater has risen significantly in the vicinity of the site since the <br /> 1970s Historical depth to water information for the area suggests <br /> groundwater levels may have been 70 to 80 fbg during the 1970s It <br /> appears that the release at this site maybe an old release Since fuel <br /> oxygenates (most notably MTBE) have not been detected at significant <br /> concentrations at this site, this indicates the release occurred prior to the <br /> introduction of fuel oxygenates into gasoline In addition, since TPHg <br /> and BTEX have been detected at depths of 70 to 80 fbg,this suggests <br /> the release may have occurred when groundwater level was lower than it <br /> is today These components of gasoline have a specific gravity less than <br /> that of water and typically do not migrate downward <br /> A former service station was present on the property to the north <br /> (upgradient) of the subject site This former service station property has <br /> not yet been investigated However, grab groundwater samples from <br /> boring SB-18, drilled south of this property, contained TPHg, benzene, <br /> and 1,2-DCA These data suggest the former service station may have <br /> had a release <br /> 0955 Page 3 of 5 Date Modified 12/16/2004 <br />