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5 – Effects Found Not To Be Significant Draft Environmental Impact Report February 2021 14800 W. Schulte Road Logistics Center 5-5 Ground Failure Soil liquefaction is a seismically induced form of ground failure. Liquefaction is a process by which water-saturated granular soils transform from a solid to a liquid state because of a sudden shock or strain, such as an earthquake. The Project site’s subsurface is composed of several interbedded layers of medium-density sands and stiff to hard clays and silts to approximately 50 feet below ground surface. Below a depth of 50 feet, the subsurface is primarily composed of stiff to hard clays and silts. Soil samples taken from the Project site as part of the site-specific geotechnical investigation report indicate that on-site soils could potentially experience liquefaction resulting in settlement on the order of 0.25 inches or less. As a result, the geotechnical investigation (CEG 2020) includes engineering specifications to mitigate potential impacts related to liquefaction. Compliance with the CBC and the engineering recommendations in the site-specific geotechnical investigation report, which will be reviewed and verified by County staff, would ensure structural integrity in the event that liquefaction is experienced at the Project site. Therefore, impacts associated with liquefaction would be less than significant. Landslide The Project site is located in an area that is relatively flat and does not contain any slopes that could result in landslides. Although the Project site currently contains various depressions and elevations, the topography of the Project site would be brought to a flat grade as part of grading activities. Upon completion of grading activities, the Project site would be flat, similar to the surrounding area. As such, there is no potential for landslides to occur on or near the Project site. Therefore, impacts associated with landslides would be less than significant. Soil Erosion and Topsoil Loss Short-Term Construction Impacts The Project would involve earthwork and other construction activities that would disturb surface soils and temporarily leave exposed soil on the ground’s surface. Common causes of soil erosion from construction sites include stormwater, wind, and soil being tracked off site by vehicles. To help prevent erosion, Project construction activities must comply with all applicable federal, state, and local regulations for erosion control. The Project would be required to comply with standard regulations, including the provisions of the National Pollutant Discharge Elimination System (NPDES) Construction General Permit. Construction activities subject to this permit include clearing, grading, and ground disturbances such as stockpiling and excavating. The NPDES Construction General Permit requires implementation of a Stormwater Pollution Prevention Plan (SWPPP), which would include construction features for the Project (i.e., best management practices [BMPs]) designed to prevent erosion and protect the quality of stormwater runoff. Sediment-control BMPs may include stabilized construction entrances, straw wattles on earthen embankments, sediment filters on existing inlets, or the equivalent. Therefore, construction impacts associated with soil erosion would be less than significant. Long-Term Operational Impacts Once redeveloped, the Project site would include buildings, paved surfaces, and other on-site improvements that would stabilize and help retain on-site soils. The remaining portions of the Project site containing pervious surfaces would primarily consist of landscape areas. These landscape areas would include a mix of trees, shrubs, plants, and groundcover that would help retain on -site soils while preventing wind and water erosion from occurring. Therefore, operational impacts related to soil erosion would be less than significant