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Monitoring Well Installation Workplan Page 2 of 6 Our Project Number: LES080548 July 10, 2008 fine-grained alluvial fans. In recent times sediments in this area were deposited mostly from stream channels and alluvial fans (Bailey, 19661). The geosyncline has a regional southwest tilt, with the longitudinal axis located off center to the west. This area ranges in elevation from slightly below sea level to about 400 feet at its north and south ends. The valley is bounded to the east by the Sierra Nevada and the west by the Coast Ranges. It is about 400 miles long and 50 miles wide. The rock sequences of the Great Valley can be divided into two sections. The first is a belt along the west base of the Sierra; this includes minimally deformed alluvial fans and lake deposits that feather east onto the Sierran basement. The second is a linear belt from 10 to 20 miles (16-32 km) wide at the east base of the Coast Range; this is composed of deformed Mesozoic and Cenozoic rocks that dip east beneath the valley. The sedimentary cover of gravels and sands is thinner in the western belt. Although unconfirmed, the contact at depth between Sierran and Coast Range basements is presumed to be a fault. Nearer the Coast Range margin, the contact between the two basement units has been definitely located (Norris and Webb, 1990). 1.4.2 Local Geology According to the Geologic Map of California` ', the subject property is located within a region of "alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated." 1.4.3 Hydrogeology The groundwater flow direction in the local area appears to be west. The depth to groundwater is indicated to be 10 to 15 feet below the ground surface2. 1.5 Proposed Monitoring Well Location The City of Manteca and the county of San Joaquin has asked for a workplan for the installation of one (1) Temporary Groundwater Monitoring Well. The proposed placement of the groundwater monitoring well is illustrated on the Site Plan (see Plate 1). Groundwater in the area appears to occur at an approximate depth of between 10 and 15 feet, depending on location and seasonal variations. 1 Bailey, Edgar H., ed., 1966. Geology of Northern California, California Division of Mines and Geology Bulletin 190. 508p. 4Jennin. gs, Charles W., 1969-1973. Geologic Map of California, Scale 1:750,000. 2 Lines of Equal Elevation of Groundwater, Spring 1999, San Joaquin County Flood Control and Water Conservation District. A 902 Industrial Way • Lodi, CA 95240 - 209.367.3701 • Fax 209.369.4228 ©2008 Neil 0. Anderson & Associates, Inc