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City of San Leandro 2023-2031 Housing Element Update 3-42 will strike the Bay Area region in the next 30 years, and that there is a 31 percent chance that this quake would occur on the Hayward Fault. Major earthquakes may also occur on the San Andreas Fault and the Calaveras Fault which are 15 miles west and 10 miles east of San Leandro, respectively. 28 Ground shaking and liquefaction hazards exist throughout the city and range from high to very severe. Earthquake hazard maps prepared by the Association of Bay Area Governments (ABAG) indicate that a large Hayward Fault quake would trigger very strong shaking throughout the city and a high risk of liquefaction in the Marina Faire/Mulford Gardens and Washington Manor/Bonaire neighborhoods. Pursuant to Public Resources Code (PRC) Sections 2001 to 2815, the California Geological Survey has designated the area immediately adjacent to the Hayward Fault as a Alquist-Priolo earthquake fault zone. This zone overlaps with single-family residential zoned parcels. Before any development may occur in the Alquist-Priolo earthquake fault zone, geologic studies are required to determine the precise location of active fault traces and feasibility of construction. Structures must be set back at least 50 feet from any fault trace and must be engineered to reduce the potential for earthquake damage. The CBC contains specific requirements for structural design, foundations, grading, and seismic loads to reduce the potential for quake damage. More expensive construction methods are required to reduce the risk of earthquake damage, particularly in multi-story buildings.29 The lengthened permitting process and construction requirements may constrain the development of housing but necessary to ensure building safety. San Leandro has many buildings that predate modern building codes and may be susceptible to earthquake damage. The City has implemented a decades-long program to retrofit unreinforced masonry buildings, most of which were located in and around Downtown. The City also focuses on seismically strengthening soft-story buildings, concrete tilt-up structures, and older single-family homes. Soft-story buildings are structures that have a weaker first floor and are unable to carry the weight of the stories above during an earthquake. Soft-story buildings typically have large openings in the perimeter walls of the first floor, such as garages, parking beneath the second floor, or large windows.30 The City will explore the creation of a formal program to retrofit soft-story multi-family buildings in San Leandro to preserve existing housing stock, as specified in Program 2 of Chapter 6, Housing Plan. 3.3.3 Landslides and Erosion Excessive erosion can contribute to landslides, siltation of streams, undermining of foundations, and ultimately the loss of structures. San Leandro has experienced destructive landslides including a 1998 event that required the relocation of two homes and threatened five others. The San Leandro Hills are currently experiencing erosion which is due to the wearing away of the soil mantle by running water, wind, or geologic forces. 31 Earthquake hazard maps produced by ABAG indicate that a large Hayward Fault quake would trigger very strong shaking throughout San Leandro and a high risk of liquefaction in the Washington Manor 28 City of San Leandro Environmental Hazards Element. 2016. Available: https://www.sanleandro.org/civicax/filebank/blobdload.aspx?blobid=26256. Accessed October 28, 2021 29 City of San Leandro Housing Element. 2015. Available: https://www.sanleandro.org/civicax/filebank/blobdload.aspx?blobid=5207. Accessed October 28, 2021 30 Los Angeles Department of Building and Safety. Available: https://www.ladbs.org/services/core-services/plan-check-permit/plan-check- permit-special-assistance/mandatory-retrofit-programs/. Accessed October 27, 2021 31 Ibid.