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The Facility is generally flat and consists of an office area; an operations area including two truck loading racks and a warehouse; and four areas containing aboveground storage tanks (ASTs). The truck rack, office area, and operations area are asphalt-paved, while the AST areas are generally hard-packed soil covered with gravel. The Facility and area surrounding the Facility is used for heavy industrial purposes. According to the Port of Stockton, land use in the area will continue to be for industrial purposes in the future. Groundwater in the area is not used for drinking water purposes and no drinking water wells were identified within at least a 2-mile radius. 2.2 Historical and Current Site Use The Facility was developed in the 1960s for use as a fuel distribution facility and there are no plans for the use to change. There are currently 21 primary ASTs located within Facility containment areas formed by earthen berms. Most of the piping to the tanks is above grade; however, some of the product pipelines travel for short distances below grade as they pass through earthen berms. The Facility is used to store and distribute refined petroleum products(i.e.,gasoline,diesel, ethanol, aviation gasoline) that are received from the local SFPP pipeline. In addition, small quantities of a proprietary oxygenate formula have been stored in a 1,000-barrel dedicated AST adjacent to the northern truck rack. 2.3 Geology and Hydrogeology Early investigations in the vicinity identified a series of four hydrogeologic zones defined as the A-, B-, C-, and D-zones (SECOR, 2003). The zones have historically been described as being hydrogeologically independent and have been primarily defined in terms of depths encountered. However, the results of the vertical groundwater investigation (Ash Creek, 2009a) suggest two key points: (1) some of the water-bearing zones are not as continuous as previously reported; and (2) a "layer-cake" interpretation of the subsurface stratigraphy is not applicable. As shown in the cross-sectional Figures 3, 4, and 5, stratigraphy underlying the northern portion of the Facility dips to the east, with little to no dip underlying the southern portion of the Facility. Based on the results of the vertical investigation, the water-bearing zones in the southern portion of the leasehold can be summarized as follows: • A/B-Zone—The A/B-zone is comprised of laterally discontinuous and intermittently connected sand and clay layers of various thicknesses. North of the Facility, this unit consists of the separate A-and B-zones described by SECOR (2002). However, beneath and downgradient to the Facility, the A-and B-zones are difficult to distinguish due to the presence of multiple laterally discontinuous sand layers. The A/B-zone underlying the Facility ranges in thickness from 21 to 42 feet and is first encountered at depths of approximately 0 to 5 feet below the ground surface(bgs). Revised Cleanup Plan Page 2 NuStar Stockton Terminal-Stockton,California November 7,2012 1014-12