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(Mckinney Drilling Co., 1989). The groundwater at this depth may be due to both <br /> perched irrigation water from local farming activities, and to water table fluctuations <br /> coincident with the stage of the Mokelumne River. <br /> The Mokelumne River is primarily an influent stream and it should be expected <br /> that the groundwater table slopes down, away from the river. The water table most <br /> likely fluctuates with changing river stages, gaining water with increasing river flows <br /> (influent conditions), and losing water with decreasing flows (effluent conditions). <br /> A single well at the existing processing facility is the source for the water (1,500 <br /> gallons per minute) used for processing and dust control. Most of the water is recycled <br /> through a series of settling ponds on site. <br /> 3.2.2 Impacts <br /> The level of significance of hydrology and water quality impacts addressed in <br /> this section of the report are based on the level of impact that changes in runoff, <br /> percolation, drainage and erosion would have on other resources such as fisheries, <br /> vegetation, and soils. Impacts that have a reasonable likelihood of impacting these <br /> resources are considered potentially significant and require mitigation. <br /> Channel Stability and Flooding <br /> The operation of Camanche Reservoir has significantly reduced the discharge and <br /> area of inundation during peak streamflow events in the Mokelumne River. A <br /> maximum release of 5,000 cfs under COE operating procedures has been maintained by <br /> EBMUD since the reservoir was installed. Uncontrolled releases, that discharge greater <br /> than 5,000 cfs, are possible depending upon extreme precipitation conditions and <br /> antecedent reservoir levels. <br /> An intermediate regional flood (100 year flood) was expected to have a discharge <br /> of 9,700 cfs at Lodi (U.S. Army Corps of Engineers, 1970). The 100 year discharge <br /> event has been revised as of 1988 to 16,000 cfs at Lodi and 18,000 cfs at Clements <br /> (Hatch, D., Pers. conim.). However, the return interval for the peak 1986 storm was <br /> estimated to be, on average, 200 years within the Mokelumne River drainage above <br /> Camanche Reservoir and only resulted in a 5,000 cfs release from the reservoir (Stein, <br /> 31 <br />