1901-1919 N Fairview St - Soils Report

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603284-001 3.2.6 Seiches and Tsunamis Tsunamis are long wavelength seismic sea waves (long compared to the ocean depth) generated by sudden movements of the ocean bottom during submarine earthquakes, landslides, or volcanic activity. A seiche is an oscillation (wave) of a body of water in an enclosed or semi-enclosed basin that varies in period, depending on the physical dimensions of the basin, from a few minutes to several hours, and in height from several inches to several feet. A seiche is caused chiefly by local changes in atmospheric pressure, aided by winds, tidal currents, and occasionally earthquakes. Based on the site elevation (approximately 99 to 101 feet msl) and inland location of the site (approximately 10 miles from Pacific Ocean), the potential for damage due to either a tsunami or seiche is low. 3.2.7 Ground Lurchina Ground lurching is defined as movement of low density soil materials on a bluff, steep slope, or embankment due to earthquake shaking. Since there are no significant slopes at the site, it is our opinion that the potential for ground lurching as a result of nearby or distant seismic events is low. 3.3 Flooding Hazards According to a Federal Emergency Management Agency (FEMA) flood insurance rate map (FEMA, 2008), the site is located within a flood zone. In addition, based on our review of dam inundation and topographic maps, the site is located within a dam inundation area from the Prado Dam. Flood zones located in the site vicinity are shown on Figure 9, Flood Hazard Map. 3.4 Expansive Soils Based on our geotechnical exploration, the near surface soils are generally granular with localized sandy silt to clay layers. Two near surface bulk soil samples (B-1 and B-4) were tested for expansion potential. The results indicate that the near surface soils have low expansion potential. -15- Leighton