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FMS #24 Site Investigation Report <br />California Army National Guard <br />1.0 SITE DESCRIPTION • <br />1.1 Site Location <br />FMS #24 is located in one of four divisional areas at 8010 South Airport Way, Stockton, California, <br />(95206). The divisional areas comprise the Army Aviation and Support Facility (AASF), the <br />Combined Support and Maintenance Shop (CSMS), the FMS, and the Armory. Figure 14 (Appendix <br />A) shows the general site layout and features. <br />1.2 Installation Description and History <br />1.2.1 Stockton AASF, CSMS, FMS, and Armory are a State-owned facility operated by CA ARNG. <br />The post consists of administrative offices, facility engineering, classrooms, training facilities, <br />security facilities, maintenance facilities, gas station (previous), and several equipment, vehicle, and <br />material storage locations/structures. <br />1.2.2 FMS #24 comprises the following: a one-story maintenance building composed of work bays, <br />supply areas, a latrine, and offices; a vehicle inspection rack; various hazardous material sheds; a <br />concrete wash pad with associated holding tank; and a refueling area containing two dispensers at an <br />island and two former UST locations. <br />1.2.3 The two former USTs (one 5,000 -gallon diesel and one 10,000 -gallon gasoline) were removed <br />in April 1996 by Seward Schreder Construction. Soil samples collected during removal and excava- <br />tion of the USTs and associated piping indicated that releases of diesel fuel and gasoline have <br />impacted soil up to 12,000 milligrams per kilogram (mg/kg) for TPHG and 7,100 mg/kg for TPHD. • <br />In addition, BTEX contaminants were detected at concentrations up to 6.2 mg/kg (ethylbenzene) and <br />580 mg/kg (total xylenes) (Versar, Inc., 2004). <br />1.3 Physiographic Setting and Geolo <br />Approximately 90% of the land surface within the FMS is paved. The area around the former USTs <br />is paved. Some grasses, shrubs and trees exist throughout the area due to landscaping and mainte- <br />nance of adjacent properties. The site has been graded and modified to promote surface drainage into <br />storm drain inlets. Catch basins collect rainwater and divert the runoff to the north through under- <br />ground pipes into the adjacent airport storm water system. The system drains approximately 1.5 miles <br />north of the site into Little John Creek, then into French Camp Slough, and finally into the San <br />Joaquin River (Versar, Inc., 2004). <br />1.4 Geology <br />1.4.1 The site lies within the Sacramento Valley. The Sacramento Valley is composed of unconsoli- <br />dated Quaternary sediments from alluvial and lake deposits. The Sierra Nevada Mountains to the east <br />are a source of the alluvium deposits as a result of erosion. Also contributing to the deposits are the <br />Sacramento Valley Coast Ranges to the west. Both ranges consist of a wide variety of rocks and <br />granite, which are metamorphic (ranging widely in age and composition) and sedimentary. In <br />addition, the Stockton Fault, which trends northeast -southwest, is located within the city limits, as <br />well as, the Midland Fault Zone (trending north) located approximately 25 miles northwest of the site <br />(Versar, Inc., 2004). <br />• <br />2 December 2007 <br />