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KLEINFELDER encountered to a depth of approximately 35 to 40 feet. Ground water was also encountered at approximately the same depth as the sand layer. The sand layer is underlain by silt then sand in MW-1, MW-2 and MW-4 and is underlain by clay in MW-3. Overall it appears that the sediment profile in MW-1 and MW-4 is more silt and sand rich than that in MW-2 and MW-3. In general the geology under the site shows apparent lateral continuity. Minor variations are probably the result of slight changes in the environment at the time the sediment was deposited. For example the sand at the top of MW-2 may have been deposited in a locally faster moving part of the river channel with respect to the surrounding clay rich areas. The coarser nature of the sediment to the southwest and west may be the result of increased proximity to faster currents to the southwest during the time of deposition. The upward decrease in grain size from sand and silt dominated sediment to clay dominated sediment illustrates the gradual decrease in water energy probably due to migration 'of-the river away from the site. Stockton adobe clay covers the J-M Mfg. facility, and is a heavy-textured, dark gray clay formed from alluvial deposits in basins. The Stockton series soil has a strongly developed hardpan, and slow drainage. The hardpan is a thin, lime-capped layer that is generally found at a depth of approximately 30 inches. Regional soil information is presented in the SWAT Proposal. 5.3 GROUND WATER 5.3.1 Existing Monitoring System The ground water monitoring system consists of four monitoring wells (MW-1 through MW-4). Monitoring well locations are shown on Drawing 1. Each well is screened to monitor first encountered ground water. MW-1 is the background well. Ground water monitoring activities to date consist of two semi-annual sampling dates (June 26, 1989 and January 9 and 10, 1990). CR14-92-12 Page 16 of 39 24-220109-1709 Copyright 1992 Kleinfelder, Inc.