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LM events . The importance of the above soil properties is that when they exist at depth they significantly contribute to a site' s ability to attenuate the impacts of any past releases of petroleum fuels . Any lead released to these soils from gasoline &. would most likely be rapidly adsorbed onto the clay particles, and the high moisture holding capacity of these soils would likely cause soil voids to be continuously filled with water such that vapor transmission of the solvent portions of the gasoline would likely be impeded. It appears this site may have soils of this type below the lowest portion of the removed tanks . ti.. Deeper lithology and site geology is related to the surface soils . The site is mapped by the U.S. Geological Survey as "basin deposits . " Basin deposits have lithologic profiles dominated by fine-textured materials . However, intercalating layers of coarser textured materials are common and usually �. capable of freely releasing water. Municipal water wells drilled in the general area penetrate through alternating clays and sands to a depth of 250 feet or more before intentionally extracting LO water (i .e. California Water Service wells TINR6E 2M and Q) . Drillers logs of the area indicate the surface clays extend to depths ranging from 50 feet to 27 feet in Section 2 and 3 TINR6E MDB & M, before reaching a coarser material that is saturated (DWR Central District data) . The closest surface stream to the site is Mormon Slough, one mile to the south. The municipal water wells operated by California Water Service Company and mentioned above are in the same section LM but are not on or close to the site under investigation. Furthermore, the wells are sealed to a depth of 250 feet or more. The piezometric level of ground water has been reported to be between 40 and 50 feet below the surface at the site (San Joaquin County Flood Control and Water Conservation District, 1988 data) . However, poor quality first water is probably encountered within 35 feet of the surface (estimate based on driller' s logs) . Municipal wells seal off the first 250 feet because the upper zones of saturation do not meet quality standards or do not +� provide sufficient quantity to be developed (Bulletin 146, California Department of Water Resources, 1967 ) . Therefore, it is highly unlikely the fuel components at this site have affected 1.0 or will affect drinking water supplies . LW -5- LM