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The exposure of people or structures to major geologic hazards such as earthquakes i.; and ground failure; j • Unstable earth conditions or changes in geological substructures; • Disruptions, displacements, or compaction of the soil; ¢ ` A change in topography or ground surface relief features; The destruction, covering, or modification of any unique geologic or physical features; and/or T • Any increase in wind or water erosion of soils either on or off the site. i All Quarry Excavation Alternatives (1 2, and 3) Impact 4.2-1 t Compression or Consolidation of Sediments f Sediments placed as backfill could be subject to compression (sands) or consolidation (clays). If sediments compress, resulting in a decrease in volume, the ground surface i! r above the affected. sediments would settle. Data on the strength and potential for compression of the backfill materials are not available. Information on the texture of the processing sediments and overburden materials indicate that themajority of the sediments i would be silts and clays. The fill thickness would be relatively minor (five feet). Compression of these materials would occur relatively rapidly, probably during placement and possibly in the first couple of years following placement. The fill would be unsaturated and only minor consolidation would be expected. If settlement were to occur, the magnitude would be minor (less than two inches) and would be expected to occur uniformly throughout the project site. Such settlement would not significantly impact the j proposed agricultural end use or proposed drainage system for the project site. This is a i less-than-significant impact. No mitigation is necessary. Alternative 4: No Project Although some minor amount of consolidation and compression of the natural alluvial sediments would occur under the No Project Alternative, the potential for resulting settlement would be less-than-significant. q i` 4 ri Draft Environmental Impact Report 4-15 a ER-9673 k � °f