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I8 February 1997 AGE-NC Project No, 97-0301 Page 2 of 3 Joaquin County Flood Control District and Water Conservation District. The prevailing ground water flow direction in eastern Stock-ton is generally toward the northeast, although flow directions may be both locally and seasonably variable. The uppermost ground water flows in an unconfined aquifer. With increasing depth, the aquifer becomes semi-confined, due to the presence of mixed heterogeneous layers of sediments. 3.0. SCOPE OF WORK 3.1 . MULLING AND SAMPLING AGE proposes to advance three angled soil probe borings to depths of approximately 20 feet bs�w and two shallow vertical probe borings to depths of approximately 10 feet bsg. Sol] probe borings will be advanced using a Geoprobe 5400 soil probing unit equipped with 1.125-inch diameter probe rods and an attached 2.15-inch diameter soil sampler. The soil sampler will be loaded with clean 1.125-inch by 6-inch brass sleeves. Probe borings will be advanced near the UST, piping and dispenser areas. Proposed probe boring locations are illustrated on Figure 2. One angled soil probe boring vJ11 be advanced beneath each UST at an angle of approximately 30° from vertical. One shallow vertical soil probe boring will be advanced near each dispenser island area. A description of angles and distances used for calculating sample depths beneath the UST area is depicted in Figure 3 -Prol)osed Angled Soil Probe Borings. Soi] samples will be collected from each soil probe boring at fifteen and twenty feet bsg. If petroleum hydrocarbon-inapacted soil is encountered during probing activities, probe borin�.�s will be advanced to greater depths in an attempt to determine the vertical extent impacted soil. 3.2. EQUIP vIENT DECO;\T Ai INAT10N All probintic, rods, sampling tools and sample liners used for sample collection will be thoroughly rinsed with clean water after washing with a solution of Alconox. 3.3, LABORATORY ANALYSIS Selected soil samples will be analyzed for total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d), volatile aromatics (benzene, toluene, ethylbenzene and xylenes: BTE&X), and methyl tert-butyl ether (MTBE) in accordance with EPA methods 8015m and 80201602. Laboratory reports and sample chain-of-custody documentation will be presented in a report with the findings and recommendations.