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ARROYO LAGO RESIDENTIAL PROJECT <br />ADDENDUM <br /> <br /> <br />FCS 111 <br />Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480036/Addendum/21480036 Arroyo Lago Residential Project Addendum.docx <br />Discussion <br />a-d) Earthquake Hazards; Erosion; Unstable Soils or Geologic Units; Expansive Soils <br />Would the project: a) Directly or indirectly cause potential substantial adverse <br />effects, including the risk of loss, injury or death involving: (i) <br />Rupture of a known earthquake fault, as delineated on the most <br />recent Alquist-Priolo Earthquake Fault Zoning Map issued by <br />the State Geologist for the area or based on other substantial <br />evidence of a known fault; (ii) Strong Seismic Ground Shaking; <br />(iii) Seismic-related ground failure, including liquefaction; or (iv) <br />Landslides? <br />b) Result in substantial soil erosion or the loss of topsoil? <br />c) Be located on a geologic unit or soil that is unstable, or that <br />would become unstable as a result of the project, and <br />potentially result in on- or off-site landsliding, lateral spreading, <br />subsidence, liquefaction, or collapse? <br />d) Be located on expansive soil, creating substantial direct or <br />indirect risks to life or property? <br />Prior FEIR Conclusions <br />Earthquake Hazards (Threshold (a)(i-iv)) <br />The Prior FEIR found that the project site is not located within an Alquist-Priolo Earthquake Fault <br />Zone (EFZ), and no evidence of active or historic faulting was observed on or near the project site. <br />The nearest active fault is the Calaveras Fault, approximately 4.4 miles to the southwest. While the <br />project site is in a seismically active region, the preliminary geotechnical reports concluded that the <br />project site is suitable for development with appropriate design measures. Liquefaction potential is <br />considered negligible due to soil type and groundwater depth (at least 45 feet below ground surface), <br />although Association of Bay Area Governments (ABAG) mapping identifies moderate susceptibility. <br />Landslide risk is low, with no mapped landslides or landslide zones on or near the project site. <br />MM GEO-1 requires a design-level geotechnical study to address site-specific hazards and <br />incorporate recommendations into project design and construction. With respect to Alternative 2, the <br />Prior FEIR determined that soil disturbance and grading would be reduced by approximately 38 acres <br />compared to the County Project, lowering the potential for geotechnical impacts. Required mitigation <br />for geotechnical hazards would still apply, but overall impacts would be less. Therefore, the Prior <br />FEIR concluded that impacts would be less than significant with mitigation incorporated. (Draft EIR, <br />pp. 3.6-17, 6-14). <br />Erosion (Threshold (b)) <br />The Prior FEIR determined that while construction activities could disturb soils and potentially lead to <br />erosion, the County Project would be subject to compliance with the National Pollutant Discharge <br />Elimination System (NPDES) permit requirements. A SWPPP would be implemented, including BMPs