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2.0 GEOLOGY AND HYDROGEOLOGY <br /> 2.1 REGIONAL GEOLOGY <br /> The Central Valley and surrounding area is the product of a complex series of geologic <br /> events. The Sacramento Valley is a late Mesozoic forearc basin that formed <br /> contemporaneously with, and between the accretionary trench deposits of the Franciscan <br /> Complex to the west, and an eastern magmatic arc complex, the roots of which are <br /> exposed in the Sierra Nevada Mountains. The region has experienced orogenic uplift, <br /> faulting, and subsequent erosion as the valley was inundated by the ancestral Pacific <br /> Ocean. <br /> The exposed granite of the Sierra Nevada mountain range represents the eroded edge of a <br /> tilted block of crystalline rocks known as the Sierra Nevada Batholith. The Sierra <br /> Nevada Batholith is a series of granitic plutons that range in age from Jurassic to <br /> Cretaceous. The plutons intruded sedimentary and volcanic rocks of Ordovician to Late <br /> Jurassic age. <br /> The Sierra Nevada Mountains locally are the bedrock upon which the Great Valley <br /> sequence rests, in other locations, mudflows and lahars of the Pliocene Tuscan Formation <br /> and younger volcanics rocks cover the granitic bedrock, which plunges beneath the Great <br /> Valley sequence at the eastern margin of the Central Valley. <br /> The Great Valley sequence is a very thick accumulation of sediments forming an <br /> asymmetric structural trough or syncline, with the axis of the trough west of the apparent <br /> surface axis of the present valley surface. The trough has been filled with as much as 10 <br /> vertical miles of sediment in the Sacramento Valley (the Great Valley Sequence), and <br /> these sediments range in age from Jurassic to Holocene. The Great Valley sequence rests <br /> on basement rocks consisting of metamorphosed sedimentary and volcanic rocks of <br /> Ordovician to Late Jurassic age. <br /> 2.2 REGIONAL HYDROGEOLOGY <br /> The subject site is located in the Eastern San Joaquin County Groundwater Basin, an area <br /> covering approximately 707,000 acres (1,105 square miles). The San Joaquin Valley <br /> comprises the southernmost portion of the Great Valley Geomorphic Province of <br /> California. The Great Valley is a broad structural trough bounded by the tilted block of <br /> the Sierra Nevada on the east and the complexly folded and faulted Coast Ranges on the <br /> west. The Eastern San Joaquin Subbasin is defined by the areal extent of the <br /> unconsolidated to semi consolidated sedimentary deposits that are bound by the <br /> Mokelumne River on the north and northwest; San Joaquin River on the west; Stanislaus <br /> River on the south; and consolidated bedrock on the east. <br /> 12/22/2009 HANOVER ENVIRONMENTAL SERVICES,INC. 2 <br /> Soil Assessment Report <br /> McHenry Ave Project <br /> 1303 First Street,Escalon <br />