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certain designated wastes (ash, petroleum hydrocarbon contaminated soil, and asbestos). WMU A covers approximately 8 acres where designated wastes and hazardous waste sludge were placed between the late 1970s and 1984. WMU A was closed and capped in 1989. Waste disposal at the Austin Unit began in 1954 along the northern side of the unit, before landfill liner requirements were implemented. Engineered lined containment systems have been constructed in the remaining waste cells FU -03, FU -04, FU -05, FU -06, FU -08, FU -10, FU -13 continuing in an easterly direction. Waste disposal at the Austin Unit has been limited to non- hazardous solid waste, inert waste, and certain designated wastes (ash, petroleum hydrocarbon contaminated soil, and asbestos). The geology and hydrogeology of the Forward Landfill have been detailed in several reports including Kleinfelder & Associates (1991, 1997, 1999), CH2M Hill (1992), California Department of Water Resources (2003), and Beta Associates (1988). These studies confirm that geologic and hydrogeologic conditions at the Forward Landfill are consistent with regional conditions. 2.1 Geologic Conditions The Forward Landfill is located approximately 7 miles southeast of Stockton, California, near the center of the Great Valley Geomorphic Province in the region locally referred to as the northern San Joaquin Valley. The Great Valley is an elongated asymmetrical structural trough bounded on the east by the Sierra Nevada and on the west by the Coastal Range. In the northern San Joaquin Valley, nearly 8000 feet of sediments have accumulated within the basin, including an accumulation of about 5250 feet of marine clays, silts and sands followed by approximately 2500 feet of unconsolidated terrestrial sediments. The uppermost portion includes the Pleistocene age Victor Formation. In the northern San Joaquin Valley this unit includes 100 feet of fine-grained clays and silts with interbedded coarser -grained sediments deposited in a meandering fluvial environment. At the site, the uppermost sediments of the Victor Formation have been divided into three subunits based on lithologic logs for borings and monitoring wells that identified logical groupings of gross lithology and pervasive color distinctions. The upper 28 to 40 feet consist of highly interbedded sandy silt, clayey silt, silt, and clay. Most of these sediments have an oxidized appearance and an orange brown color. Below this subunit is a 25 - to 35 -foot -thick, gray -brown interbedded sand, silty sand, and minor clay subunit. The third subunit occurs to a depth of about 110 feet and is generally light brown to yellow brown dominated by fine to medium -grained sand, with some coarse-grained sand and gravelly layers and a few silt and clay interbeds. Contacts between these three subunits are not distinct and are therefore subject to interpretation. As fluvial deposits, by their nature these sedimentary units interfinger and on an individual basis are discontinuous. The Victor Formation is underlain by the Laguna Formation of Plio-Pleistocene age (two million years ago). The Laguna Formation consists of discontinuous lenses of stream laid sand and silt with lesser amounts of clay and gravel. This formation thickens to about 1000 feet in the Stockton area. D:\2014-0012\FA finassur.doa 2 3/10/2014, Rev. 0