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Geotechnical Engineering and Geological Hazard Study Lincoln Elementary School Modernization Project Manteca, California Page 6 temporary rise in groundwater levels at the site. For construction planning, and evaluation purposes, we have used a depth to shallow groundwater of 10 feet. 5.3 GEOLOGIC HAZARDS 5.3.1 Faulting No known active or potentially active faults are mapped across the Lincoln Elementary School site, and the site is not located in a Fault -Rupture Hazard Zone as established by the Alquist-Priolo Earthquake Fault Zoning Act (Hart, 1994). Therefore ground displacement from surface rupture is not considered a significant hazard at the site. The site location relative to local faults is shown on Figure 5, Appendix A. 5.3.2 Clays and Cyclic Softening The Site is not within a region where large surface clay deposits are mapped. Therefore expansive soils and cyclic softening are not likely to occur. Silts and sands were encountered in surficial soils in our borings. 5.3.3 Corrosive or Reactive Geochemistry The chemical characteristics of shallow site soils are discussed in Section 11.0, Corrosion Potential. 5.3.4 Hazardous Materials The Site is not within a region where methane, hydrogen sulfide, or tar seeps are considered likely to occur. The closest oil or gas exploration wells are mapped approximately 0.7 miles away and are plugged. See Appendix B for mapped well locations. 5.3.5 Volcanic Eruption The Site is not within a region where volcanic eruptions of magma, ash, mud, or carbon dioxide are considered likely to occur. The closest active volcanic hazard zone is mapped approximately 110 miles away at Mammoth Lakes. 5.3.6 Flooding The site is located at an elevation of approximately 38 feet in a relatively flat area of the north central San Joaquin Valley. The site is approximately three miles uphill and northeast from the San Joaquin River. The San Joaquin River presents a low risk to the site. The site is located near an underground irrigation pipeline. The pipeline is operated and maintained by South San Joaquin Irrigation District and creates a low risk of inundation. Mitigation for the risk of a canal breach is not within the jurisdiction of the school district. While flooding is a potential hazard in the San Joaquin Valley, the site is not currently mapped within the FEMA 100 -year flood zone (I percent chance per year) or within the 500 -year flood zone (0.2 percent chance per year) as shown on Figure 7, Flood Rate Insurance Map, Appendix A. The site is mapped within the New Melones Dam Inundation Zone on maps published by San Joaquin County Public Works (see Appendix B). Potential damage to the site from flooding or dam inundation is likely to be minimal because the site is 40 miles from the dam. Mitigation for the risk of dam inundation would appear to be unwarranted. 5.3.7 Slope Stability The site is located in a generally flat area of the north central San Joaquin Valley. The nearest slopes to the site are located in the Coast Range Mountains approximately 10 miles to the southwest. Review of the USGS topographic quadrangle map indicates that the banks of the San Joaquin River are located