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San Joaquin County Community Environmental Setting,Impacts,and Mitigation Measures <br /> Development Department P P Geology,Soils,and Seismicity <br /> Impact GEO-3: Potential Structural Damage and Injury <br /> from Development on Materials Subject to Liquefaction <br /> (Less than Significant) <br /> Based on the excessively coarse and fine composition of the soils and sediments <br /> and lack of proximity to groundwater,the susceptibility of soils and sediments to <br /> liquefaction in the project area is low. This impact is considered less than <br /> significant.No mitigation is required. <br /> Impact GEO-4: Potential Accelerated Runoff, Erosion, <br /> and Sedimentation from Grading and Mining Activities <br /> (Less than Significant) <br /> Grading, excavation,removal of vegetation cover, and loading activities <br /> associated with construction and mining activities could temporarily increase <br /> erosion and sedimentation. Construction and mining activities could also result <br /> a. in soil compaction and wind erosion effects that could adversely affect soils and <br /> reduce the revegetation potential. However,as part of the Environmental <br /> Commitments outlined in Chapter 2,"Project Description,"on-site drainage <br /> ` would be retained in the settling ponds and reclaimed lake. Erosion or runoff <br /> control measures would be implemented near processing facilities to prevent off- <br /> site sedimentation. Furthermore, inactive topsoil stockpiles would be sloped at <br /> IH:I V or flatter and would be located at least 15 feet from active mining. <br /> Erosion control and weed control measures would also be implemented as <br /> needed. This impact is considered less than significant.No mitigation is <br /> required. <br /> Impact GEO-5: Potential Erosion of Slopes after <br /> Reclamation (Less than Significant) <br /> During reclamation, 165 acres would be reclaimed to agricultural use. <br /> Equipment associated with mining would be removed from the site. Haul roads <br /> that would not be used after project completion and other heavily compacted <br /> areas such as the plant site would be ripped to at least 12 inches. The site would <br /> be graded and topsoil reapplied to a depth of 18 inches. No revegetation would <br /> be conducted because the majority of the site would be cultivated. The South Pit <br /> would be backfilled to its pre-mining elevation. <br /> r. <br /> Rainfall and inflowing surface water may erode the reclaimed slopes of Stages I <br /> and II of the North Pit and the above water slopes of the Stage III agricultural <br /> water storage basin after mining operations cease, after reclamation,and during <br /> post-reclamation use. However,rainfall in the area is relatively low(9.94-12.21 <br /> inches annually),and the flat surrounding land and the presence of major <br /> drainage channels (the rivers)largely preclude inflowing surface water. <br /> ` Therefore,the potential for erosion during and after reclamation is minimal, <br /> except under flood conditions. Soil that does erode would be deposited in the <br /> DeSilva Gates Quarry Project <br /> Draft Environmental Impact Report 31-13 <br /> JSS 05105.05 <br /> r <br />