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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GEOLOGY, SOILS, AND SEISMICITY <br />TABLE 4.5-1 SAN LEANDRO GENERAL PLAN GOAL AND POLICIES <br />Goal/Policy <br />Number Goal/Policy Text <br />Chapter 6, Environmental Hazards <br />Goal 29 Mitigation of Natural Hazards: Reduce the potential for injury, property damage, and loss of life resulting <br />from earthquakes, landslides, floods, and other natural disasters. <br />Policy 29.01 Risk Management: Minimize risks from geologic, seismic, and flood hazards by ensuring the appropriate <br />location, site planning, and design of new development. The City's development review process, and its <br />engineering and building standards, should ensure that new construction is designed to minimize the <br />potential for damage. <br />Policy 29.02 Earthquake Retrofits: Strongly encourage the retrofitting of existing structures to withstand earthquake <br />ground shaking, and require retrofitting when such structures are substantially rehabilitated or <br />remodeled. <br />Policy 29.04 Code Revisions: Revise and update construction codes and regulations to incorporate the latest <br />available information and technology related to earthquake hazards. <br />Policy 29.05 Public Awareness: Promote greater public awareness of earthquake hazards, along with incentives and <br />assistance to help property owners make their homes and businesses more earthquake -safe. <br />Source: San Leandro General Plan, 2002, Chapter 6, Environmental Hazards <br />4.5.1.2 EXISTING CONDITIONS <br />Geology and Soils <br />Regional Geology <br />The Project site is in the northern portion of the Coast Ranges geomorphic province of California, which is <br />characterized by northwest -trending mountain ranges and valleys that generally parallel the major <br />geologic structures such as the San Andreas and Hayward faults. The oldest widespread rocks in the <br />region are highly deformed sedimentary, metamorphic and volcanic rocks of the Franciscan Assemblage, <br />which formed during the Mesozoic Era (225 to 65 million years ago). These rocks are in fault contact with <br />similar age sedimentary rocks of the Mesozoic Great Valley Sequence. The Mesozoic rocks are, in turn, <br />overlain by a diverse sequence of Cenozoic Era (younger than 65 million years) sedimentary and volcanic <br />rocks. Since their deposition, the Mesozoic and Cenozoic rocks have been extensively deformed by <br />repeated episodes of folding and faulting. The Bay Area experienced several episodes of uplift and faulting <br />during late Tertiary Period (approximately 25 million to 2 million years ago), that produced the region's <br />characteristic northwest -trending mountain ranges and valleys, which include the eastern San Francisco <br />Bay hills and San Francisco Bay. <br />Worldwide climate fluctuations during the Pleistocene age (approximately 1.8 million to 11,000 years ago) <br />resulted in several distinct glacial periods. A lowering of sea level accompanied each glacial advance as <br />water became stored in vast ice sheets. Melting of the continental glaciers during warm intervals caused <br />corresponding rises in sea level. High sea levels favored rapid and widespread deposition in the bay and <br />surrounding floodplains. Low sea levels during glacial advances steepened the gradients of streams and <br />rivers draining to the sea, thereby encouraging erosional down -cutting. The most recent glacial interval <br />ended approximately 11,000 years ago. Evidence suggests that during the maximum extent of this latest <br />glaciation, sea level was approximately 300 to 400 feet below its present elevation and the valley now <br />occupied by San Francisco Bay drained to the Pacific Ocean more than 30 miles west of the Golden Gate. <br />PLACEWORKS 4.5-3 <br />