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FORWARD LANDFILL NON-WATER CORRECTIVE ACTION PLAN 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. 2.2 HYDROGEOLOGIC CONDITIONS The Water Quality Control Plan for the Sacramento River Basin and the San Joaquin River Basin (Basin Plan)places the site in the Duck-Little John Hydrologic Area (31.40) of the San Joaquin River Basin. As a major regional aquifer system, the San Joaquin hydrologic basin is used for industrial, domestic, and agricultural purposes. Most of the production wells in the area are constructed to depths on the order of 500 feet and produce water from the Laguna Formation(see its description in the Geologic Conditions, Section 2.1 above). Although there are no regionally significant fine-grained intervals, by the heterogeneous nature of the Laguna Formation, some localized confinement of groundwater may be present, though typically, groundwater is unconfined or locally semi-confined. It is recognized that the area's heavy reliance on groundwater associated with significant population growth and agricultural needs, has resulted in the basin being overdrafted for at least the past 40 years, and water levels have continued to decrease throughout the region. The uppermost groundwater beneath the Forward Landfill occurs in the unconfined Victor Formation. Historical groundwater measurements in monitoring wells at the Forward Landfill indicate that groundwater occurs at a depth of approximately 50 to 70 feet below the ground surface with seasonal variations in the groundwater depth of as much as 10 feet; the highest M:\2011-0128V'VWFA REPORT.DOCX 3 Geo-Logic Associates