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625 Cypress Avenue <br />Geotechnical Investigation <br /> <br />Project No. W1895-88-01 - 12 - April 23, 2024 <br />boring B1, indicates that the alluvial soils below the historic high groundwater level could be susceptible <br />to approximately 0.3 inch of total settlement during Maximum Considered Earthquake ground motion <br />(see enclosed calculation sheets, Figures 15 and 16). <br />6.5 Seismically-Induced Settlement <br />Dynamic compaction of dry and loose sands may occur during a major earthquake. Typically, <br />settlements occur in thick beds of such soils. The seismically-induced settlement calculations were <br />performed in accordance with the American Society of Civil Engineers, Technical Engineering and <br />Design Guides as adapted from the US Army Corps of Engineers, No. 9. <br /> <br />The calculations provided herein for boring B1 indicate that the soil above the historic high <br />groundwater level of 35 feet could be prone to approximately 0.14 inch of settlement as a result of the <br />Design Earthquake peak ground acceleration (â…”PGAM). <br /> <br />The calculations provided herein for boring B1 indicate that the soil above the historic high <br />groundwater level of 35 feet could be prone to approximately 0.42 inch of settlement as a result of the <br />Maximum Considered Earthquake peak ground acceleration (PGAM). <br /> <br />Calculation of the anticipated seismically induced settlements is provided as Figures 17 and 18. <br /> <br />6.6 Slope Stability <br />The topography at the site is relatively level and the topography in the immediate site vicinity slopes <br />very gently to the south-southwest. The site is not within an area identified as having a potential for <br />slope stability hazards (City of Santa Ana, 2010) or seismic slope instability hazards (CDMG, 2001). There <br />are no known landslides near the site, nor is the site in the path of any known or potential landslides <br />(USGS, 2024a). Therefore, the potential for slope stability hazards to adversely affect the proposed <br />development is considered low. <br />6.7 Earthquake-Induced Flooding <br />Earthquake-induced flooding is inundation caused by failure of dams or other water-retaining <br />structures due to earthquakes. A review of the Safety Element of the Orange County General Plan <br />(2004) and the City of Santa Ana Seismic Safety Element (2010) indicates that the site is not located <br />within the inundation boundaries of upgradient dams, rivers, creeks, or reservoirs. The probability of <br />earthquake-induced flooding is considered very low.