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Deeper lithology and site geology is related to the surface soils The site is mapped by the U S <br /> ' GeologicaI Survey as "basin deposits " Basin deposits have lithologic profiles dominated by <br /> fine-textured materials However, intercalating layers of coarser textured materials are common <br /> ' and usually capable of freely releasing water Municipal water wells drilled in the general area <br /> penetrate through alternating clays and sands to a depth of 250 feet or more before intentionally <br /> ' extracting water Municipal wells are sealed off for the first 250 feet because the upper zones <br /> of saturation do not meet quality standards or do not provide sufficient quantity to be developed <br /> (Bulletin 146, California Department of Water Resources, 1967) Therefore, it is highly <br /> unlikely the fuel components at this site have affected or will affect drinking water supplies <br /> Two main waterways run within 1 /z miles of the site, the San Joaquin River to the southeast and <br /> ' the Calaveras River to the north Both of these rivers are in hydrogeologic continuity with the <br /> local groundwater system <br /> There are three irrigation wells on the subject property One irrigation well is located 65 feet <br /> south of the former tank locations (IRR2), the other two are located 650 feet north (IRR3) and <br /> 550 feet south (IRR1) of the former tank locations All water for the site, including sinks and <br /> ' restrooms in the office 7s supplied by the irrigation wells, except for drinking water, which is <br /> bottled Also, a septic tank/leach field system is located to the southwest of the tank area One <br /> ' irrigation well is shown on Figure 2 (the others are north and south of MWI, MW2, and MW3 <br /> and are located off the map) <br /> 1 <br /> First groundwater has stabilized in MW 1 at approximately 65 feet below grade Natural <br /> ' Groundwater gradient direction would be expected to be north-northwesterly, towards the <br /> Calaveras River A long history of groundwater use in the Stockton area, however, has resulted <br /> in significant local variations in gradient Groundwater gradient direction at nearby sites ranges <br /> from northeasterly to southerly <br /> ' R 052992 LF 4 <br />