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It appears that petroleum hydrocarbons in soil are primarily contained within a limited area beneath <br /> the former UST complex and along portions of the former product piping (3 fbg). Petroleum <br /> hydrocarbons were not detected in unsaturated soils analyzed from Borings MW-3, B-6, GEOI, and <br /> GEO4, located down-gradient from the former UST location. Petroleum hydrocarbons were not <br /> detected in unsaturated soils analyzed from up-gradient wells MW-1 and MW-2, Borings B-2, B-5, <br /> and GEO3. Petroleum hydrocarbons were also not detected in unsaturated soils analyzed from the <br /> new USTs location; Borings B-1, B-9, B-10, B-11, B-12, B-13 and B-14. <br /> Additional site investigation activities were conducted in July and September 1997, including drilling <br /> four soil boring (SB-1 through SB-4) and installation of Wells MW-4 through MW-7. Borings SB <br /> through SB-4 completed vertical and lateral delineation of petroleum hydrocarbons and oxygenate <br /> compounds in the area of the dispenser islands. 519'1 * 56-,5 }V 0.5 61b aMly <br /> Wells MW-4 and MW-7 contained Total Purgeable Petroleum Hydrocarbons (TPPH) concentrations <br /> ranging from 1,300 to 31,000 ppb, benzene concentrations ranging from 9.1 to 1,900 ppb, and <br /> methyl-tertiary-butyl-ether (MTBE) concentrations ranging from 12 to 170 ppb. These wells have <br /> been added to the quarterly monitoring and sampling program in place at this site. <br /> TECHNICAL RATIONALE FOR PROPOSED SCOPE OF WORK <br /> • Cross-section A-A' (Plate 3) was prepared to evaluate the soil analytical data collected from <br /> several phases of investigation conducted at this site. The cross-section indicates that <br /> vertical delineation of petroleum hydrocarbons and oxygenate compounds in the vicinity of <br /> the southwest corner of the former UST complex (Boring B-3) is incomplete. <br /> • Cambria proposes to drill a soil boring at the southwest corner of the former UST complex to <br /> delineate the vertical extent of petroleum hydrocarbons and oxygenate compounds. <br /> • Additional down-gradient delineation of petroleum hydrocarbons and oxygenate compounds <br /> in ground water is proposed by the installation of a ground water monitoring well southeast of <br /> the subject site in the center of Pacific Avenue. <br /> WORK TASKS <br /> Permits: An appropriate permit for drilling will be obtained from SJCPHS and an encroachment <br /> permit will be obtained from the City of Stockton for the proposed well in Pacific Avenue. <br /> Health and Safety Plan: A site-specific Health and Safety Plan will be prepared for field work. <br /> 240-0854 3 <br />