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<br />3-16 <br /> <br /> <br /> <br />3.3 Flood Causal Event <br />Flooding is a reasonably foreseeable causal event. Flooding can be caused by storms, heavy rains, changes <br />in the landscape due to fires or development, or failure of engineered flood control systems such as levees <br />or dams. Other than failure of a levee or dam, unusually intense rainfall such as the 1,000-year, 24-hour <br />storm, is typically the cause of flooding. <br />The BMP for the flood as a causal event is: <br /> Flooding is not considered a reasonable foreseeable causal event if the landfill is not located <br />in the 500-year flood zone. <br /> For the purposes of determining corrective action, any landfill located within the 500-year <br />flood zone needs to assess the potential damage resulting from the 500-year flood. <br />A review of the Federal Emergency Management Agency (FEMA) flood insurance rate maps (FIRM) for the <br />area indicates the site is located outside the 500-year flood zone. A copy of the FEMA FIRM map is <br />contained in Appendix C. <br />3.4 Tsunami Causal Event <br />A tsunami is a sea wave that may be generated by an earthquake, landslide, volcanic eruption, or a large <br />meteor hitting the ocean. The California coast has experienced several tsunamis, some causing significant <br />damage. It is anticipated that the types of damage caused by a tsunami would be like those resulting from <br />a flood. <br />The BMP for the tsunami as a causal event is: <br /> Tsunamis are not considered a reasonably foreseeable causal event if the landfill is in an area <br />that is not designated to be prone to be inundated by a tsunami by the Department of <br />Conservation or local emergency response agency. <br /> For landfills located in an area that is prone to be inundated by a tsunami, the corrective action <br />plan needs to address the potential impacts and damage that may result. <br />A review of the United States Geological Survey (USGS) tsunami inundation zone maps indicates the site <br />is not located in an area susceptible to inundation by a tsunami. The site is in San Joaquin County, <br />approximately 65 miles east (inland) of the affected USGS quads in the adjacent Contra Costa County. A <br />copy of the relevant USGS tsunami inundation zone map is provided in Appendix D. <br />3.5 Seiche Causal Event <br />A seiche is a wave on the surface of a lake or landlocked bay caused by atmospheric or seismic <br />disturbances and may be defined as an occasional rhythmic oscillation of water above and below the <br />mean level of lakes or seas, lasting from a few minutes to an hour or more. Seiches are uncommon but <br />have been known to have occurred on Lake Tahoe. Damages anticipated to result from a seiche would <br />be like those from a flood or tsunami. <br />The BMP for a seiche as a causal event is: <br /> A seiche is not a reasonably foreseeable causal event, if the landfill is located greater than ½ <br />mile away from a lake or a landlocked bay. <br /> A landfill that is located within ½ mile of a lake or landlocked bay needs to identify the height <br />of the wave and evaluate if the wave will inundate the landfill and cause any damage.