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PHASE I HYDROGEOLOGIC YNVESMATION WORK PLAN 4491 West Durham Ferry Road,Tracy,C211fornia DcIta Projcct No.40-91-732 Page 3 2-3 Reglanni Hydrogeolo2y A regional map showing the ground water elevation contours for the unconfined aquifer for spring 1989 prepared by th.;San Joaquin County Flood Control Pnd Water Conservation District shows the direction of ground water flow is towards the north or northeasL Depth to ground water,is expected to be approximately 15 to 20 feet below the ground surface. 3.0 PROPOSED WORK PIAN Delta proposes to drill four additional soil borings and convert two of them into ground water monitoring wells. Two of the soil borings will be drilled directly over the former tank locations to determine whether petroleum hydrocarbons have impacted the soil at these locationG. Ile remaining two soil borings will be drilled and completed as monitoring wells to determine the presence or absence of petroleum constituents as gasoline,in the ground water upgradient of the site and in the direction of the inferred ground water flow. 3.1 Sol]Borings Two soil borings(SB-3 and SB4)will be drilled at the former locadons of the undergrouri storage tanks to a total depill of 15 feet to determine whether the soil at these locations had been impacted of petrolourn hydrocarbons as gasoline. Soil borin locations are shown in Figure 2. 9 3.2 Sol]3ample Callectlon and Screenin A California-modifled split-barret sampler will be used to collect soil samples from the scil borings. Soil samples wiU be collected at S-foot interrals from each soil boring. Soil sampling will be performed in accordance-with ASTM 1586-84 standards, Three&inch brass tubes will be inserted into the California sampler to retain the soil sampke. Upon retrieval of each soil sample, the bottom tube will be capped, sealed, labeled,and stored on ice for transport to a state-certified laboratory for chemical analysis. Suits from the middle tube will be placed in jars and sealed with aluminum foi!for field screening for the presence of orgaiiic vapors with a PID. 3.3 Monitoring Well Installation Two 2-inch-diameter monitoring wells will be constructed to a depth of approximately 30 feet below ground to Surface obtain-,Amterlewl-measurerdents and-itdiind-W�it&��les.---Mottitoring located south of the site along the right-of-way of Durham Ferry Road,and monitoring well MW-3 will be V.