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The reclamation of the processing site on the north side of the Mokelumne River <br /> would have only a minimal impact on drainage patterns. Currently, most runoff is <br /> retained on site within the various ponds used to recirculate water to the gravel <br /> processing facility. Drainage would continue to remain on site, primarily in a direction <br /> towards the large stockpond in the southwest corner. The pond currently covers <br /> approximately 60 acres, and would therefore store 60 acre-feet of water per one foot in <br /> depth. This would be more than adequate to contain the runoff from a 10-year storm <br /> event. The pond may also be increased in size during reclamation,by additional land <br /> from the sand recovery area. Potential impacts to drainage in this area are considered <br /> less than significant. <br /> Groundwater holding capacity would be somewhat reduced due to the mining of <br /> sand and gravel, slightly increasing the potential for surface runoff. However, a portion <br /> of the site is intended to be graded to more level contours suitable for agriculture. This <br /> would have the effect of increasing infiltration and reducing runoff. The net effect <br /> would be to cause little change in the quantity of runoff. Potential impact to runoff is <br /> this area is considered less than significant. <br /> The reclamation plan could reduce or increase surface runoff to the existing <br /> wetlands area on site, depending upon grading contours. A reduction in surface runoff <br /> to the wetland area could reduce available wetland habitat. An increase in runoff could <br /> also impact the wetlands by increasing water depth and altering habitat. This is <br /> considered a potentially significant impact. <br /> Groundwater <br /> It is possible that the water levels indicated by the test boring logs are partially <br /> due to a perched water table created by agricultural irrigation. When the farming <br /> activities are removed for the gravel extraction operation, the groundwater level may be <br /> slightly reduced. However, it is likely that the water table fluctuates with the surface <br /> water elevation in the Mokelumne River. Therefore, groundwater may be encountered <br /> at depths as little as 15 to 20 feet below the surface. If the excavated pits are deeper <br /> than the water level in the Mokelumne River and they need to be pumped, then this <br /> would increase the hydraulic gradient from the river to groundwater. <br /> 35 <br />