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CSK Auto#4025 GeoTek Project No.:BC 122-4025 <br /> Tracy,California 95376 Page 5 of 20 <br /> March 2,2000 <br /> 3.0 PROPERTY PHYSICAL SETTING <br /> Surface and subsurface drainage are of interest,because the control the movement of <br /> water-born contaminants which could be transported to and from the subject property. <br /> GeoTek reviewed the following information regarding the drainage of the subject <br /> property and immediate surrounding area. <br /> ♦ "Geologic Map of California" by Jenkins dated 1965. <br /> ♦ "Geologic History of Middle California" by Arthur D. Howard, University of <br /> California Press, dated 1979. <br /> ♦ "Ground Water Atlas of the United States Segment 1 (California and Nevada)" <br /> Hydrologic Investigations Atlas 730-A, United State Geological Service (USGS), <br /> dated 1994. <br /> ♦ US Geological Survey (USGS) "Tracy, California" Quadrangle, 7.5-minute series, <br /> topographic map, dated 1981. <br /> 3.1 GEOLOGY <br /> During the second half of the Paleozoic Era (approximately 230 million years ago) the <br /> majority of middle California lay beneath the sea. There was only one vast ocean on the <br /> globe, and one landmass. The sea floor (where the Sierra now lies) there accumulated a <br /> thick assemblage of marine shales, siltstones, sandstones, limestones, and volcanic <br /> deposits. These rocks were crumpled by subduction (early Mesozoic Period) to create the <br /> Sierra Nevada. The sediments were metamorphosed to form slates, phyllites, cherts, <br /> quartzites, marbles, schists, and gneisses. These metamorphic rocks were invaded by <br /> granitic magma during the Triassic Period. <br /> The Paleozoic metamorphic rocks of the ancestral Sierra Nevada are collectively known <br /> as the Calaveras Formation. The Pacific Ocean shoreline during the time of the ancestral <br /> Sierra Nevada Mountains was reportedly within the present day foothills. <br /> During the Triassic, Jurassic, and most of the Cretaceous periods, periodic subduction <br /> revived and accentuated the mountain-building forces, and additional granite magmas <br /> invaded the crust. The deformation process reached a climax in the late Jurassic Period. <br /> During this time, the Triassic and Jurassic seafloor sediments, as well as the volcanic <br /> rocks of an island arc that lay offshore, were mashed against the ancient coast in a <br />