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2.0 SITE BACKGROUND <br /> 2.1 Site Location and Description <br /> The project site is located at the Department of Forestry. Castle Rock Forest Fire Station, 34580 <br /> Corral Hollow in Tracy, California. The site is situated within a relatively rural area of <br /> California, and is bordered to the south of Livermore National Laboratories. A cluster of fve <br /> monitoring wells is located to the west of the project area that are associated with activities at <br /> Livermore National Laboratories. An unnamed ephemeral stream occurs south of the site. The <br /> location of the site with respect to major roads and intersections is presented in Figure 1. <br /> The project area involves the former location of a 550-gallon diesel UST. Specifically, the UST <br /> was located adjacent to a storage shed, in an unpaved area of the Fire Station. Figure 2 presents <br /> the former location of the UST. <br /> 2.2 Subsurface Conditions <br /> Based on information provided by an adjacent property owner (Livermore National <br /> Laboratories), the uppermost subsurface soil at the site consists primarily of unconsolidated <br /> alluvium, consisting of gravelly, cobbly sand. The alluvial sediments are underlain by bedrock at <br /> 20 feet below ground surface. Based on recent measurements of the on-site monitoring wells, <br /> depth to first groundwater at the site has been reported at approximately 10 to 15 feet below <br /> Lground surface. Groundwater gradient has been been reported to flow in the east direction. <br /> 3.0 SUMMARY OF PREVIOUS SITE ACTIVITIES <br /> 3.1 Removal of 550 Gallon Diesel Tank <br /> Based on information provided by the DSA, one 550-gallon diesel UST was removed from the <br /> Forest Fire Station on June 29, 1993 by Tank Protect Engineering. Available analytical results <br /> indicate that two samples(N-1, S-1)were collected from the tank excavation and one sample was <br /> collected from the soil stockpile (SP-1) at the time of removal. Samples were analyzed for Total <br /> Petroleum Hydrocarbons (gasoline & diesel fractions) by EPA Method M8015, BTEX (benzene, <br /> toluene, ethylbenzene, and total xylenes) compounds by EPA Method 8020, ethylene dibromide <br /> by EPA 8240 and Total Lead. <br /> TETRA TECH:Castle Rock Forest Fire Station,Revised Technical Work Plan Page 2 <br />