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Morita Brothers Service Station 12 November 6, 1992 <br /> a <br /> Underlying this is a zone of consolidated, slight to moderate plasticity, medium dense, <br /> low permeability, gray brown, silty, organic clay (OHlML) to a depth of 53 feet This <br /> clay zone was underlain by consolidated, slight to moderate plasticity, medium dense, <br /> low permeability, light brown, trace very fine sand, minor silt, clay (CH) to a depth <br /> of 56 feet which is the deepest depth penetrated in the soil investigation A Cross <br /> ' Section was prepared which integrates the geology, the location of the former tanks <br /> and dispensers, and the distribution of gasoline hydrocarbons in the subsurface to <br /> yield an interpretation of limit of gasoline hydrocarbons in excess of RWQCB <br /> recommended guidelines (Figure 4) <br /> The San Joaquin Valley is filled with up to six vertical miles of sediment Fresh <br /> groundwater is produced from wells tapping confined and unconfined aquifers <br /> found above and below the Corcoran Clay of the Tulare Formation The Corcoran Clay <br /> acts as the main confining layer in the San Joaquin Valley Groundwater with <br /> higher salinities can be found both above and 'below the Corcoran Clay Salinities in <br /> the groundwater below the subject sight are within potable drinking water <br /> ' guidelines Groundwater flow is from the valley flanks to the axis and then north <br /> towards the Sacramento Delta Locally, the depth to groundwater is approximately 70 <br />' feet and general groundwater flow direction is east-northeast This direction is away <br /> from the San Joaquin River Delta which is acting as a source of recharge due to the <br /> drawing down of the aquifer by municipal water supply wells in the city of Stockton <br /> 3.0 GROUNDWATER ASSESSMENT <br />' 3. 1 Drilling <br /> ESE proposed to drill and install three 2" groundwater monitoring wells Prior to <br />' drilling, Underground Service Alert (USA) was notified in advance drilling activities <br /> A total of three borings were drilled within this phase of groundwater <br />' characterization One soil boring (MW-3) was drilled in a presumed up gradient <br /> position and completed as a groundwater monitoring well Two soil borings (MW-2 <br /> and MW-3) were drilled down gradient of the former underground storage tanks and <br />' dispensers, both of which were converted into groundwater monitoring wells <br /> E13-$101-3 9210-EO55 RPT <br />■ <br />