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III. Environmental Setting, Impacts,and Mitigations <br /> K. Hydrology, Geohydrology, and Water Quality <br /> Impact KA. Uncontrolled erosion from soil stockpiles and landfill surfaces,or inadvertent <br /> spills of refuse or other substances on-site could contaminate surface water. <br /> (SIGNIFICANT) <br /> Little Johns Creek would be relocated and lined to limit the potential for water contamination due <br /> to groundwater intrusion. However,cover soil would be trucked across the bridge to the site, and <br /> the stormwater management approach would include relocating the perimeter ditches and berms <br /> in phases. Therefore, although the landfill surfaces should be adequately protected by the use of <br /> the perimeter ditches,sediment could enter the stream channel on-site,particularly in the vicinity <br /> of the bridge crossing. Periodically there could be grading and exposed soils along relocated <br /> berms and ditches that are not stabilized. <br /> The project would develop and implement procedures to protect the final cover and prevent <br /> s <br /> erosion,in compliance with CCR Title 14(see Section 1.5.7). Proposed erosion control <br /> measures for the final cover and intermediate covers are outlined in Section II,Project <br /> Description. No specific measures have been identified to prevent contaminants,including <br /> sediment,from entering the channel in the vicinity of the bridge crossing. <br /> Mitigation Measure K.4. <br /> Identified by this EIR <br /> (a) The final bridge design should include structural controls to prevent spilled or tracked <br /> sediment from entering the stream channel, and shall be regularly cleared of accumulated <br /> sediment and refuse. Accumulated material should be properly disposed of in the landfill. <br /> (b) Additional measures described in Section III.G, Air Quality, Mitigation Measure G.1., <br /> would also minimize dust impacts. <br /> Implementation of the above measures would reduce this impact to a less-than-significant level. <br /> Impact K.5. Groundwater contamination would result if the liner and leachate collection <br /> system for the expansion failed. (SIGNIFICANT) <br /> The maximum depth of the liner,with exception of the leachate collection trenches and sumps,is <br /> 20 feet MSL. This elevation would provide a minimum separation of 32 feet between the waste <br /> liner and groundwater(Meinfelder, 1988). However,prior contamination in the vicinity has <br /> demonstrated the sensitivity of the upper aquifer and illustrated that contaminants can move <br /> HI.K.15 <br />