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• 1.0 INTRODUCTION <br /> Versar,Incorporated (Versar), on behalf of the California Army National Guard (CA ARNG), <br /> has prepared this Preliminary Assessment/site Investigation(PA/SI) report for the CA ARNG's <br /> facility in Stockton, California(Site). Versar's workplan for the PA/SI was submitted to the <br /> Central Valley Regional Water Quality Control Board(CVRWQCB) on August 13, 1999. The <br /> work plan was verbally approved by Mr. Robert Pierce of the CVRWQCB. <br /> Versar reviewed the files for the Site at the San Joaquin Public Health Services (SJPHS), the <br /> Central Valley Regional Water Quality Control Board (CVRWQCB), the State of California <br /> Real Estate Services Division (RESD), and the CA ARNG. Following review of the files, <br /> Versar conducted two Site visits, at the request of the CA ARNG, including interviews with Site <br /> personnel to discuss the concerns identified in the file reviews as well as issues not identified <br /> during the file review. The purpose of this investigation is to characterize the condition of soils <br /> in areas of concern identified during the file review and Site visits. The Stockton facility is <br /> divided into four divisions: 1) the Army Aviation and Support Facility (AASF); 2) the Combined <br /> Support and Maintenance Shop(CSMS); 3) the Operation and Maintenance Shop (OMS); and 4) <br /> the Armory. Environmental concerns were not identified at the Armory, and this division was <br /> not included in the PA/SI investigation. The Site Location and Layout are shown on Figures 1 <br /> and 2, respectively. <br /> 1.1 Scope of Work <br /> • The objective of the proposed work is to collect Site-specific information necessary for the <br /> evaluation of the areas of concern at the AASF, CSMS, and OMS. To meet this objective, <br /> Versar interviewed Site personnel and identified potential discharge points and sumps associated <br /> with sanitary and storm sewers at the facility, and evaluated if the discharge points were used for <br /> disposal of contaminants or hazardous substances. Versar included in the interviews questions <br /> regarding the new Hazardous Materials Storage Area, located north of the New Shop Building 3 <br /> in the CSMS area, to determine if uncontained hazardous waste spills have occurred at this <br /> location. Based on our interviews and Site visits, soil borings were drilled and soil and soil <br /> vapor samples collected and submitted for chemical analysis. Three existing groundwater <br /> monitoring wells were also sampled to evaluate groundwater conditions for consideration of <br /> closure by the RWQCB and the SJPHS for the underground storage tank release at this location. <br /> A detailed discussion of the investigation activities is included in Section 3.0 Site Investigation. <br /> Figures 3 and 4 include sanitary and storm sewer locations derived from file records, personnel <br /> interviews and Site visits. <br /> 1.2 Geology <br /> The Site is located in the central portion of the Sacramento Valley. The Sacramento Valley is <br /> composed of unconsolidated Quaternary sediments from alluvial and lake deposits. This <br /> alluvium is the result of the erosion of the foothills of the Sierra Nevada mountain to the east. <br /> The Sierras are composed of a wide variety of rocks, including granitic, metamorphic, and <br /> 2187-01/3134-100/MAY26'00 1 <br />