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• 3.1 Pre-Field Investigation Activities <br /> Versar obtained a permit for the advance of geoprobe borings for environmental investigation <br /> from the San Juaquin County Public Health Services, Environmental Health Division. A copy of <br /> the permit is included in Appendix B. Pior to beginning the field investigation, Versar reviewed <br /> the location of borings with Site personnel to reduce the potential for encountering underground <br /> utilities. <br /> 3.2 Soil Evaluation <br /> The following section discusses the methods and procedures that were used in further evaluating <br /> the condition of the soils at the areas of concern. <br /> 3.2.1 Boring Locations <br /> To assess the presence or absence of impacted soil, a total of 28 borings were drilled at the <br /> locations shown in Figures 3 and 4. The soil borings were drilled using a truck mounted, <br /> hydraulic, direct-push rig or hand-augered if access was limited. All non-dedicated drilling and <br /> sampling equipment was cleaned prior to use. Each boring was drilled to a predetermined depth <br /> as specified in Table 2 of Versar's work plan. The following discusses the boring locations at <br /> each of the areas of concern. <br /> Army Aviation and Support Facility (AASF) <br /> Areas of concern at the AASF include the former secondary clarifier, the former paint spray <br /> booth, and the hazardous materials storage sheds. The original washpad was removed in 1991 <br /> and impacted soil removed in 1992. Versar believes the soils data currently available for the <br /> three former 5,000-gallon USTs, discussed in Section 2.1.1 of this report, is sufficient and no <br /> further investigation was necessary. To evaluate the current conditions at the areas of concern <br /> identified at the AASF, Versar collected soil and soil gas samples as follows: <br /> • Soil and soil gas samples were collected at the location of the former secondary clarifier <br /> (B 1) where soil samples collected in 1990 contained TPH and BTEX. The purpose of <br /> this sampling was to assess the presence, concentration, and maximum depth of <br /> petroleum hydrocarbon and VOC contamination at this location. <br /> • Soil and soil gas samples were to be collected at the location of the discharge point of the <br /> former secondary clarifier (B2) where soil samples collected in 1990 contained TPH, <br /> toluene, ethylbenzene, and xylenes. Discussion with AASF personnel in charge of <br /> hazardous materials found that the location of boring B 1 would address this area of <br /> concern. <br /> • Soil gas samples were collected from beneath unpaved areas near the former paint spray <br /> booth (B3) and adjacent to the hazardous waste storage sheds (B4 and B5) to evaluate <br /> potential contamination in near-surface soils. This sampling was conducted to assess if <br /> • 2187-01/3134-100/MAY26'00 5 <br />