SITE INFORMATION AND CORRESPONDENCE

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1 No Further Action Required Request Report Tracy Byron Road-Tracy,California December 1,2011 1 2. Site geology and hydrogeology. I The Site is located in the San Joaquin Valley Groundwater Basin, which is divided into nine sub- basins. The Site lies in the Tracy Sub-basin(Groundwater Basin Number 5-22.15), which is defined by the aerial extent of unconsolidated to semi-consolidated sedimentary deposits bounded by the Diablo Range to the west,the Mokelumne and San Joaquin rivers to the north, the San Joaquin River to the east,and the San Joaquin-Stanislaus county line to the south. The I Tracy Sub-basin is located adjacent to the San Joaquin Sub-basin to the east and the Delta- Mendota Sub-basin to the south(California Department of Water Resources [DWR], 2003). 1 The Tracy Sub-basin is comprised of continental deposits of late Tertiary to Quaternary age, which includes the Tulare Formation,Older Alluvium, Flood Basin Deposits, and Younger Alluvium. The thickness of these formations ranges from a few hundred feet in the western I foothills to about 3,000 feet near the eastern margin of the basin. The Tulare Formation consists I of semi-consolidated, poorly sorted,discontinuous deposits of clay, silt, and gravel. The Corcoran Clay is situated near the top of the Tulare Formation, separating groundwater in the basin in what has been reported as two primary aquifers. The upper aquifer is reported at 15 to 250 feet bgs and the lower aquifer is reported at 600 feet bgs. Given the location of the site within the Tracy Sub-basin, it is likely immediately underlain by Younger Alluvium, Older I Alluvium, and/or Flood Basin Deposits. Groundwater near the site has been documented at approximately 15 to 20 feet bgs(DWR,2003). Regional groundwater flow-direction information and local topography on the relevant United , States Geological Survey(USGS)topographic map indicates that the inferred groundwater flow in the vicinity of the site is to the northeast(DWR,2006; USGS, 1982). During SAIC's investigations, soils encountered in the Site vicinity appeared to be a laterally discontinuous mixture of fine-grained unconsolidated sediments consisting mainly of clays, silts, and sands. 3. Sensitive potential receptors including water supply wells and surface water. On June 26, 2003, SAIC conducted a search of DWR files to review well driller logs for domestic, irrigation, or municipal water-supply wells within 2,000-feet of the centerline of Byron Road. The well search covered portions of Township 2-South, Range 4-East, and 5-East; Sections 13, 19, 20, 24, 29, and 30. A site vicinity map with the location of the water-supply well identified in the DWR file search is shown on Figure 1. Well details are provided in Table 2. The nearest surface water body is an irrigation canal located approximately 0.5 mile southwest (up gradient) of the Site. No other potential ecological, human,or environmental sensitive receptors are known. 4. Provide a map showing the location of all water supply wells used for municipal, domestic, agricultural, industrial and other uses within 2,000 feet of the site. Provide well details and distances in a table. A site vicinity map with the location of the water-supply well identified in the DWR file search is shown on Figure 1. Well details are provided in Table 2. 6 I SAIL I