ARCHIVED REPORTS_2003 FEASABILITY STUDY REPORT AND SITE ASSESSMENT WORK PLAN

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S E C O R • 2003 Feasibility Study Report and Site Assessment Work Plan July 18, 2003 Page 2 The tank farm area, which includes nine ASTs are enclosed by a 3-foot high secondary containment berm. A portion of this berm forms a spill containment area, which is located in the northern portion of the terminal. Fuel lines from the fuel storage tanks run above ground within the secondary containment area as well as below-ground within the tank-truck loading rack area (Figure 2). Retention ponds located on the north side of the terminal are used to store storm water as needed (SECOR, 2003c). Five spills have been documented at the site. The first spill occurred on June 9, 1984 around the Transmix Tank and consisted of 13,000 gallons of gasoline, diesel and heating oil. Soil was excavated immediately in the spill area until no subjective evidence of hydrocarbons remained. The second spill occurred in August of 1990 and consisted of a tank overflow of approximately 300 gallons of gasoline. The third spill occurred in August of 1998 when an unknown volume of gasoline was released as a result tank T-137 being overfilled. The fourth spill occurred in November of 1999 when an unknown quantity of red dye diesel was released from a tanker overfill at the loading racks. The last spill occurred on December 28, 2001 when a flange on a piping manifold, near MW-15A, failed and released less than 10 gallons of red dye diesel at the site (SECOR, 2003a). 2.1 Geology The site is in the Central Valley, which is a structural depression (approximately 400 miles long and 20 to 70 miles wide) extending from Redding to the Tehachapi Mountains. Water-producing deposits in the valley are primarily unconsolidated continental deposits (alluvium) of Pliocene age that extend to depths of up to 3,500 ft(USGS, 1998). Stratigraphy is relatively consistent across the site. The local geology consists of recent unconsolidated alluvial and fluvial deposits to the total depths explored of approximately 60 feet below ground surface (bgs). These sediments are a mixture of gravels, sands, silts and clays and are principal mixtures of sandy-silts and silty-clays. Specifically, lean clay extends from the surface down to approximately 10 feet bgs, which is underlain by silty sand to poorly graded sand to a depth of approximately 30 feet bgs. Records of borings adjacent to TW-5 and TW-6 indicated sandy lean clay extending to approximately 10 feet bgs with silty sand to poorly graded sand to a total explored depth of approximately 30 feet bgs. Generalized geological cross sections are included as Figures 3 and 4 (USGS, 1998). 2.2 Hydrogeology The principle source of groundwater in the area is the Tulare formation. The Tulare formation is separated into three zones, the Upper Tulare Aquifer, the Corcoran Clay Layer, and the Lower Tulare Aquifer (USGS, 1998). The Upper Tulare Aquifer lies from approximately 5 to 200 feet bgs. The Corcoran Clay consists of low permeability silty, diatomaceous clay, is generally encountered at 200 feet bgs, and is approximately 100 feet thick. The confined Lower Tulare Aquifer lies below the Corcoran Clay. No Aquitards or perched aquifers are likely based on regional geology (USGS, 1998). Site assessment activities completed at the site indicate that the Upper Tulare Aquifer is subdivided into the Upper A zone located from 5 to 15 feet bgs, the A zone located from 15 to 35 feet bgs, and I AChevron\1001621\REPO RTS\2003\2003FS\FS_2003_revD.doc