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MOUNTAIN MOUSE NEIGHBORHOOD"F"PROJECT INITIAL STUDY Potentially Significant Potentially Unless Less Than Significant Mitigation Significant No Impact Incorporated Impact Impact c) Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on-or off-site landslide, lateral spreading, subsidence, liquefaction or collapse? d) Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code(1994), creating substantial risks to life or property? e) Have soils incapable of adequately supporting the use of septic tanks or alternative waste water disposal systems where sewers are not available for the disposal of waste water? Environmental Checklist Explanations a) Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving. i)Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault? Refer to Division of Mines and Geology Special Publication 42; ii)Strong seismic ground shaking; iii)Seismic-related ground failure, including liquefaction; iv)Landslides? The project site is not within an earthquake fault hazard zone as established by the Alquist-Priolo Earthquake Fault Zoning Act. Therefore ground rupture from faulting is not considered a significant hazard. People and structures at the site could be subject to strong seismic ground shaking because the site is near a number of major active faults capable of generating strong earthquakes. In the Geotechnical Engineering Study--Neighborhood F(Condor Earth Technologies, Inc., 1999), the potential for liquefaction was studied. It was concluded that liquefiable deposits at the project site vary in depth, and are not laterally continuous throughout the site. Liquefaction-induced ground disturbance is not likely to occur because the liquefiable deposits are overlain by a sufficiently thick cap of non-liquefiable soils. Consequently, bearing capacity failure of conventional shallow foundations is very low as a result of liquefaction of soils at depth. Ground settlements resulting from liquefaction of the susceptible deposits encountered during site exploration would average less than 1 inch, with a maximum estimated settlement of about 2.2 inches. It was concluded that the magnitude of lateral spreading is expected to be small at the project site in the event of a major earthquake. However, because of the presence of liquefiable and expansive soils at the site, specific geotechnical recommendations were made. These recommendations address the following: 1)grading and earthwork; 2) foundations; 3) slabs on grade; 4)retaining walls; 5) pavements; and 6) site drainage. The applicant would be required to submit the findings of the Geotechnical Report to the County Building Department which would ensure that all recommendations of the report are implemented. For this reason, the report recommendations have been shown as a Condition of Approval below instead of a mitigation measure. All recommendations of the Geotechnical Engineering Study for Bethany Elementary School (September 1997) shall be implemented by the Lammersville School District at the school site, and would not be the responsibility of the applicant. As for other elements of the project, the County Building Department would ensure that all recommendations of the Geotechnical Engineering Study are implemented. avoass OINM L SnDYwnaat.NMALST DY-PARMoc c7120/00l 88 V.I. GEOLOGY AND SOILS