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i . rapid development of surface ponding during normal precipitation 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. 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 lithologzc profiles dominated by fine-textured materials . However, intercalating layers of coarser textured materials are common and usually capable of freely releasing water. ti 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 water ( i . e. California Water Service dells TIN, R6E 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 TTN, R6E 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 piezometric level of groundwater in the vicinity of the site 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) . Groundwater was not encountered in borings to 43 feet drilled for this investigation. Municipal wells seal off the first 250 feet because the upper zones of saturation do not meet quality standards or do not provide sufficiant quantity to be developed ( Bulletin 146, Califarnia Department of water Resources, 1967) . Therefore, it is highly unlikely the fuel components at this site have affected or will affect drinking water supplies. 2.7 Proximity of private, municipal and irrigation wells: The municipal water wells operated by California Water Service Company and mentioned above are in the same section but are nor on or close to the site under investigation. Furthermore, the wells are sealed to a depth of 250 feet or more. Well locations within a one-half mile radius have been requested from the Department of Water Resources (DWR) . There is not a well on the subject property. Also, no dry wells or septic systems are present on the property. 4