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• • ; KLEINFELDER 2 SITE SETTING 2.1 SITE LOCATION The proposed location for the Linne Estates Subdivision is west of Chrisman Road and south of Bates Road and north of Linne Road in Tracy, San Joaquin County, California(Plate 1). 2.2 CURRENT USE AND SITE CHARACTERISTICS The site consists of approximately 78 acres of undeveloped land. The site is proposed to be developed into a single family residential development. The Package Sewage Treatment Facility is proposed to be located in the central portion of the site west at the intersection of Chrisman and Bates Roads. Kleinfelder previously installed three monitoring wells at the site for baseline quality assessments. In accordance with the proposed package treatment plant location and RWQCB monitoring requirements, two additional monitoring wells were subsequently installed to better assess groundwater quality downgradient of the package treatment plant. 2.3 REGIONAL GEOLOGY AND HYDROGEOLOGY The site lies within the western portion of the Great Valley Geomorphic Province of California. The valley is approximately 400 miles long and averages about 50 miles wide, and comprises about 20,000 square miles. The valley has been filled with a thick sequence of marine and non- marine sediments from the late Jurassic to Holocene. The uppermost strata of the Great Valley represent, for the most part, the alluvial, flood, and delta plains of two major rivers (Sacramento and San Joaquin Rivers) and their tributaries. The valley deposits are derived from the Coast Ranges to the west and the Sierra Nevada to the east. Granitic and metamorphic rocks outcrop along the eastern and southeastern flanks of the valley. Marine sedimentary rocks outcrop along most of the western, southwestern, southern, and southeastern flanks; and volcanic rocks and deposits outcrop along the northeastern flanks of the valley. The valley geomorphology includes dissected uplands, low alluvial plains and fans, river flood plains and channels, and overflow lands and lake bottoms. The majority of the native sediments near the site consist of Miocene to Holocene continental rocks and deposits of a heterogeneous mixture of generally poorly sorted clay, silt, sand, and gravel. Some beds of claystone, siltstone, sandstone, and conglomerate are also present. Review of the California Division of Mines and Geology "Geologic Map of the San Francisco — San Jose Quadrangle," indicates that the site is underlain by Quaternary alluvial fan deposits of the Modesto Formation. Based on previous quarterly groundwater monitoring events, first encountered groundwater in the vicinity of the site is approximately 55 feet below ground surface (bgs) with a groundwater flow direction to the northwest. 34091.E01/ST05R040/JZ:ly Page 2 of 9 ©2005,Kleinfelder,Inc. January 13,2005