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Woodward-Clyde V "The large, asymmetrical, northwestward-trending trough of the Sacramento Valley is the principal structure controlling the occurrence and movement of groundwater in the area. Along the flanks of the valley, which are the flanks of the trough, deposits generally are much thinner than those underlying either the topographic axis of the valley or the more westerly structural axis of the trough. In general, most of the confinement of groundwater occurs near the axis of the valley as a result of more extensive confining beds deposited there. Because the flanks of the valley are higher than its axis, recharge from tributary rivers and streams, as well as from irrigation return, has caused heads in the groundwater along the flanks to be higher than those along the axis, so that, overall, groundwater moves from the flanks toward the axis and thence south and westward toward the delta area and V points of ultimate discharge. Since development, some groundwater moves toward large pumping depressions in various parts of the valley." V Typically wells constructed in south-central Sacramento Valley are screened within the �- coarser sediments of flood-basin deposits which are under unconfined storage conditions. Groundwater flow in the Central Valley is strongly influenced by the numerous clay and silty lenses that are present in the aquifer system. Lithologic studies show that the aquifer system contains many isolated lenses of sand, silt, and clay. The fine-grained lenses, although limited in lateral extent, constitute more than 50 percent of the system and have an aggregate u thickness of as much as several thousand feet. Most recent studies show that the Central Valley aquifer system is a single heterogeneous system supported by the presence of V numerous fine-grained lenses and the hydraulic response of the system to pumping (USGS, 1991). V 1.4 PROJECT OBJECTIVE V The purpose of this work was to characterize the lateral and vertical extent of diesel contaminated soil in the vicinity of the former UST at the KJAX site. This included the advancement of soil borings and collection of soil samples and one groundwater sample. The activities were conducted in accordance with Chapter 6.7, Division 20 of the Health and V Safety Code and the California Underground Storage Tank Regulations (Subchapter 16 of Title 23 of the California Code of Regulations). These regulations prescribe the activities required to investigate and cleanup contaminated soil and groundwater resulting from UST V 8054/FEMA/KIAXPMR.M/8-24-95 SAC 1-4 V