SITE INFORMATION AND CORRESPONDENCE_FILE 1

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of the Calaveras River. The only well to the north of the site (Well I ) was apparently destroyed many years ago. The site location and the sediments immediately underlying it suggest that the shallow saturated zone is the Victor Formation — (Table 1 ) . Sediments of this formation are poorly sorted sand, gravel, silt, and clay, and have moderate-to-low permeability; they range in age from Pleistocene to Recent. Available well logs indicate that the sediments are mostly clays and sandy clays in the western part of Stockton ( DWR 1955 ) . Ground water in this formation is generally unconfined. The yields to domestic and irrigation wells are low. (During development the monitoring well yielded 4-7 gpm) . This shallow — water, is of poor quality and subject to saltwater intrusion in the western part of Stockton (DWR 1967 ) . — The two nearest public wells to the site, located at distances of 2, 500 and 2 ,900 feet to the south, are screened at intervals from 144 to 456 feet below the surface and pump water from the deeper water-bearing zone. The lithology of this deeper zone is very similar to that of the Laguna Formation, which underlies the Victor Formation and provides ground water to the eastern part of _ the San Joaquin Valley. The static water table in these public wells ( 3101 -2701 ) stabilizes between 63 and 73 feet below the surface, which is between 5 and 10 feet elevation (msl ) . — 1 .4 PRINCIPLES OF SOIL VAPOR CONTAMINANT ANALYSIS The soil vapor survey, or SVCA, technique takes advantage of the — behavior of hydrocarbon mixtures and the physicochemical proper- ties of the individual components in the subsurface. Following a _ subsurface gasoline release, free product will migrate downwards towards the ground water, some of the gasoline will volatilize, and some will adsorb to the soils. In the case of a spill of sufficient volume to exceed the soil binding capacity, free 6