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— � - <br /> PHASE I HYDROGEOLOGIC INVFSTTGATTON WORK P[AN <br /> 4491 West Durham Ferry Road,Tracy,California <br /> _ Delta Project No.40-9:-732 <br /> Page 3 <br /> t <br /> 2.3 Regional MMgeology <br /> A regional map showing the ground water elevation contours for the unconfined aquifer for spring 1989 <br /> prepared by the San Joaquin County Flood Control and Vater Conservation District shows the direction of <br /> ground water flow is towards the north or northeast. Depth to ground water is expected to be approximately <br /> 15 to 20 feet below the ground surface. <br /> 3.0 PROPOSED WORK PIAN <br /> F' Delta proposes to drill four additional soil borings and convert two of them into ground water monitoring <br /> i wells. Two of the soil borings will be dn7led directly over the former tank Locations to determine whether <br /> petroleum hydrocarbons have impacted the soil at these locations. Tire remaining two soil borings will be <br /> -- drilled and completed as monitoring wells to determine the presence or absence of petroleum constituents <br /> i <br /> as gasoline,in the ground water upgradient of the site and in the direction of the inferred ground water flow. <br /> # 3.1 SoM Boringl <br /> l <br /> Two soil borings(SR-3 and SB-4)will be drilled at the former locations of the underground storage tanks <br /> l <br /> to a total depth of 15 feet to determine whether the soil at these Iocations had been impacted of petroleum <br /> I *-iydtxarbons as gasoline. Soii boring locations are shown in Figure 2. <br /> 3.2 Soil Sample Collection and Screening <br /> A Califibmia-modified split-barrel sampler will be used to collect soil samples from the soil borings. Soil <br /> samples will be collected at 5-foot intervals from each soil boring. Soil sampling will be performed In <br /> ` accordance with AST3vi 1586-84 standards. Three&inch brass tubes will be inserted into the California <br /> € sampler to retain the soil sampI& Upon retrieval of each soil sample, the bottom tube will be capped, <br /> sealed,labeled,and stored on lee for transport to a state-certified laboratory for chemical analysis. Soils <br /> from the middle tube will be placed In jars and sealed with aluminum foil for field screening for the presence <br /> { of organlc wnpors with a PID. <br /> 3.3 Monitoring Well Installation <br /> r TWO 2-inch-diameter monitoring wells will be constt-ucted to a depth of approadmately 30 feet below groz:� <br /> surface to obtain water level measurements and ground water samples. Monitoring well MW-2 will be <br /> i --- —:located south of tbs site along the right-of--way of Durham Ferry Road,and monitoring well MW 3 will be----- ----- <br /> r`: <br /> ii <br />