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a.. 2.0 Site Geology and Hydrogeology �- 2.1 Existing Soil and Groundwater Conditions The site is located within the San Joaquin Valley, approximately 4.8 krn (3 miles) east of the *- San Joaquin River. The site is located within the Tracy (Stockton) Fault Zone. Generally, surficial soils are comprised of Quaternary-aged unconsolidated sediments that were deposited during flood stages of major streams in areas between natural stream levees and alluvial fans. ` Review of the soil survey indicates that the surficial soils are comprised of Landlow adobe clay *' alluvial deposits within low-lying areas. Typically, these soils are dark, grayish-brown, fine-textured clays resting on a substratum with a thin layer of lime-cemented hardpan. These a.. soils have low erosion and permeability. Based on information obtained from soil borings, the soil beneath the site consists of a fill `W material overlying alluvial deposits. Generally, the fill is a sandy gravel to a silty sand with lenses of sandy silt and sandy clay encountered at depths between 0.9 and 4.5 m(3 and 15 ft) �- bgs. The alluvium is interbedded sandy, clayey silts and clayey sand with minor lenses of silty clays encountered at depths between 4.5 and 18 in (15 and 60 ft)bgs. Silty sand, to poorly graded sand is encountered at depths between 18 and 21 m(60 and 75 ft)bgs. and sandy, clayey silts and clayey sand extends beyond 27 in (90 ft)bgs. Site groundwater is encountered at approximately 15 in(50 ft)bgs with seasonal highs and lows recorded at approximately 15 m (49 ft) and 21 m(68 ft)bgs, respectively. The groundwater flow �., direction is to the east and northeast. During Third Quarter 2001, groundwater was encountered approximately 15 m(50 ft)bgs and was directed to the northeast with a gradient of 0.21 foot per foot. Review of the CVRWQCB Basin Plan indicates that the site is located in the Duck-Littlejohns +- Hydrologic Area of the North Valley Floor Hydrologic Unit of the San Joaquin Hydrogeologic Basin. The Basin Plan further indicates that groundwater occurring within the San Joaquin Hydrogeologic Basin has "designated beneficial' uses for municipal and domestic supply, agricultural supply, and industrial service and supply purposes. A local well survey was performed for the Additional Groundwater Study (URS, 2000), which concluded that there did not appear to be private or public wells within 500 ft of the property +-r boundaries of the site. The HHRA identified one water well approximately 1,000 ft south of the site that is screened at 500 ft bgs. Based on discussion with the local water purveyor, no SacOP,N:ls%DP'MAPR.PPJ8W3W3789".doc 2-1 s Int 020080) i.r