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Morita Brothers Service Station 17 November 6, 1992 permeability, wet silt with minor fine sand (MLISM) which is presently a perched groundwater aquifer Beneath this is again a consolidated, slight to moderate ' plasticity, medium dense, low permeability, light brown, trace very fine sand, minor silt, clay (CH) to a depth of 65 feet which is the deepest depth penetrated in this investigation A Cross Section has been prepared which integrates the geology, the location of the former tanks and dispensers, and the distribution of gasoline hydrocarbons in the subsurface to yield an interpretation of limit of gasoline hydrocarbons in excess of RWQCB recommended guidelines (Figure 4) 4.2 Hydrology The San Joaquin Valley is filled with up to six vertical miles of sediment Fresh groundwater is produced from wells tapping confined and unconfined aquifers found above and below the Corcoran Clay of the Tulare Formation The Corcoran Clay acts as the main confining layer in the San Joaquin Valley Groundwater with higher salinities can be found both above and below the Corcoran Clay Salinities in the groundwater below the subject sight are within potable drinking water guidelines Groundwater flow is from the valley flanks to the axis and then north towards the Sacramento Delta Locally, the depth to groundwater is approximately 70 feet However a perched groundwater zone is present beneath the property within the interval from 57 to 61 feet below surface grade The general groundwater flow o direction of the regional aquifer is east-northeast This direction is away from the San Joaquin River Delta which is acting as a source of recharge due to the drawing down of the aquifer by municipal water supply wells in the city of Stockton However, the gradient has been observed to switch directions due possibly to seasonal variations in groundwater recharge as well as groundwater extraction This is very important when evaluating the subject property because there is a gasoline service station to the northwest on the north side of Charter Way which has been documented to have impacted the same perched groundwater aquifer with very high concentrations of gasoline hydrocarbons Groundwater monitoring at that gasoline service station has indicated varying directions of groundwater flow including directly towards the Morita Brothers property EB-8101-3 9210-EO55 RPT