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Greer Property I S634 Steinegul Road September 9, 2000 Escalon, California Page: 8 • Report of Findings ' Escalon Iles in the Central Valley Physiographic Province of California. The Valley is approximately 50 miles wide It is bounded to the west by the foothills of the Coast ' Ranges, and to the east by the foothills of the Sierra Nevada Range. The Manteca area is nearly devoid of structural geologic features. ' The Valley is floored by unconsolidated Quaternary sediments to depths of at least 400 or more feet in the Manteca area. All of these units can be considered soils in the engineering sense, because they are unconsolidated Quaternary sediments in the ' Central Valley were deposited as a series of coalescing alluvial fans The fans originated where valleys of the major streams which drained the Sierra Nevada Range emptied into the broad expanses of the valley. The coarser sediments which comprise ' the fans are mainly arkosic in composition and were derived from erosion associated with glacial stages in the mountains The finer grained sediments are predominantly composed of rock flour washed out of the former extensive glaciers in the Sierras, ' (Arkley, 1964). ' The axis of the Central Valley Trough was a marshy, wet area throughout much of the Pleistocene Epoch. Lacustrine, flood plain and marshy depositional environments predominated along the axial portions of the trough, in the toe areas of the fans, ' w throughout much of this time period Coarser grained sediments of the upper portions of the fans occasionally prograded over the axial area of the trough in response to major climatic changes in the Sierras. Thus has resulted in a predominance of fine ' grained silts and clays in the subsurface of the area ' 5.1 Local Geology The geology underlying the subject site consists of alternating layers of silty clay and silty sands to an approximate depth of 100' b g 1 The soils underlying the site are relatively dense from 20' to 100' b g h Figure 4 provides a cross-sectional view of the ' hthology underlying this site ' 5.2 Local Hydrology The groundwater underlying this site was found at apprommately 73' below ground ' level I-Iistoncally the groundwater gradient is generally to the East and Southeast During this sampling event on July 24, 2000, the groundwater direction was 5400 E at 0 0367 ft/ft(Figure 5)