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hn KLEINFELDER 2 SITE SETTING 2.1 SITE LOCATION The site is located in Township 2 South, Range 4 East, Section 21, approximately in Subsection G, Mount Diablo Baseline and Meridian according to the 1953 (photorevised 1980) U.S. Geological Survey"Midway, California"7.5-Minute Topographic Quadrangle Map. According to this map the site area is located at an elevation of approximately 160 feet above mean sea level(msl). 2.2 CURRENT SITE USE AND VICINITY CHARACTERISTICS The project site is currently a disked fallow field located at 23577 Mountainhouse Parkway northwest of the intersection Mountainhouse Parkway and I-205. The site has previously been used for agricultural fields. A farmhouse and associated structures are located on east of the assessment area at the property. Surrounding areas area mostly agricultural. Three pipelines trend through the assessment area including two PG&E transmission lines and a Chevron transmission pipeline. 2.3 REGIONAL GEOLOGY The site lies near the western boundary 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. According to the California Division of Mines and Geology, San Francisco-San Jose Quadrangle Map No. 5A, 1991, the subject site is underlain by Quaternary alluvial fan deposits from Coast Range source rock. Alluvial fan deposits included silt, sand, gravel and clay. 44843.T03/ST04R1025 Page 3 of 16 Copyright 2004 Kleinfelder,Inc. August 6,2004