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1 <br /> The hydraulic gradient in the area of the Exxon site was to the east-northeast, along Rose <br /> Mane Lane, until 1984, when it changed to the northeast, as the water table depression <br /> under the city developed further to the north. Values of the gradient have fluctuated between <br /> 0.0015 and 0.0035 feet/feet. <br /> There is no evidence during the past 40 years of any unusual changes in groundwater flow <br /> direction, groundwater usage, or climatic conditions which could, even for a short penod of <br /> time, reverse groundwater flow direction in this area because rain and flooding affects <br /> primarily the areas where the water table is shallow and/or close to the surface water. <br /> Rebuilding the depression under the city and reversing regional groundwater flow will take <br /> several years of unusually heavy precipitation and a drastic decrease of groundwater pumping <br />' in the area, replenishment of a widely developed aquifer, consisting of interbedded alluvial <br /> deposits of sands silts and clays, is a slow process regulated by a vertical and horizontal <br /> hydraulic conductivity of the deposits Low vertical permeability of the clayey confining <br />' lenses and the urban development minimize the direct aquifer recharge from the surface, and <br /> the underlying aquifer is mostly recharged by the infiltration through the outcrops area in the <br />' Sierra Foothills and underflow. <br /> Based on all the available data on regional geology and groundwater elevations in the area <br />' and the results of soil and groundwater investigations at former Exxon RS 7-3942, there is <br /> no evidence that the groundwater gradient has been reversed which would indicate that fuel <br /> loss at former Exxon RS 7-3942 could migrate into the area of the Shell service station <br /> located west of the Exxon site. <br /> I <br /> 73942(1)/9492/TX 4 4 <br />