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Cheaper#76,890 N Main St,Manteca, California <br /> December 22,1995 <br /> Page 12 <br /> . V. Logal and Regional Aydrology <br /> Shallow geology of the study property is recent alluvium, part of the Great Valley <br /> Fan Deposits. Alluvial fans are deposits from a shifting pattern of flowing streams, <br /> occurring where fast-flowing water leaves the hills and enters the plains. This leads <br /> to deposition of sediments and buildup of the stream bed. The stream eventually <br /> shifts position, falling off the elevated stream bed at an upriver spot, leaving the old <br /> bed dry. A new channel of deposition then begins. This radiating pattern of channel <br /> buildup leads to the "fan." Older sediments are dissected or overlain by stream <br /> channel deposits of unconsolidated sand and gravel. These channels act as conduits <br /> for groundwater and help recharge lower aquifers. <br /> Regional groundwater levels appear to fluctuate with the growing season due to <br /> agricultural drawdown, and annual groundwater level averages have generally <br /> been rising since 1987 (Parker, 1991). Average groundwater levels at City of Manteca <br /> Well #8 are between 33 and 35 feet BGS From 1987 to 1992 Groundwater levels at <br /> 890 North Main Street have fallen from 13 feet BGS in 1987 to 29' in 1991, averaging <br /> 24.35 feet BGS <br /> • <br /> Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 <br /> Phone (510) 439-1424 Fax (510) 439-2566 <br />