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3. RESULTS 3 . 1 SITE HYDROGnOLOGY The site is underlain by alluvial, nonconsolidated sediments of the victor Formation (see Figure '2 ) . The southern part of the site (wells EA1 and EA2 ) is unde:-lain by coarser sediments, con- sisting mainly of silt interfingeii.ng with sandy and gravelly lenses. The northern part (EA3, EA4, MW1 , MW2, MW3 ) consists mainly of silty or sandy clay with sandy lenses (Figure 4 ) . The depth to ground water from the top of well casings was between 44 . 53 and 46.88 feet on 11 February 1988 and between 44 .62 and 46. 92 on 17 February. The most recent gauging, on 8 April, showed that water level had dropped approximately one foot during the previous two months, to between 46.23 and 48.0 feet. The direction of around-water flow appears to have shifted from northwest on 11 February ( Figure 5 ) to south-southwest on 17 February and west-southwest on 8 April (Figure 6 ) . The old wells were excluded from the determination of flow direction, because they do not have watertight covers and their Christy boxes were filled with surface water . In addition, these wells are shal- lower and have higher ground-water elevations, creating a mound around them when they were included in the construction of the hydrogeological map. The higher ground-water elevation in the shallower wells indicates a downward component of ground--water flow in the area, suggesting that this i� a recharge zons for an underlying aquifer. The shifts in ground-water direction are probably caused by near- by domestic wells, particularly one located about 250 feet south- west of the site. On the basis of a prel+ i-nus investigation (GTI 1987 ) and data available from the San Joaquin County Flood Control and Water Conservation District (FCWCD 1985, 1986 ) , the . regional ground-water flow direction is north-northeast. c23/72g2 7