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July 21, 2014 <br /> Two Single-Family residences <br /> L&A Job No. 14-065 <br /> Page 8 <br /> deposit on the toe of the hillside portion of the site may experience lateral spreading of <br /> soil in strong earthquakes. This hazard may be mitigated by the conslruction of a <br /> retaining wall as discussed above. The proposed new residences should be designed for <br /> seismic forces induced by strong earthquakes. Based on the soil conditions encountered <br /> by the test pits; it is our opinion that Seismic Use Group I and Site Class D should be used <br /> in the seismic design of the proposed residences in accordance with the 2012 <br /> International Building Code (IBC). <br /> DISCUSSION AND RECOMMENDATIONS <br /> GENERAT, <br /> Based on the soil condition encountered by the test pits excavated on the site, it is our <br /> opinion that the site is suitable for the proposed development from the geotechnical <br /> engineering viewpoint, provided that the recommendations in this report are fully <br /> implemented and observed during construction. Conventional footing foundations <br /> constructed on or into the underlying hard Whidbey formation silt deposit or the medium- <br /> dense advance outwash sand deposit may be used to support the proposed residences. <br /> Driveway may be constructed on proof-rolled weathered soil after surticial topsoil and <br /> weak soil in root zone are tripped. Collected storm runoff may be disposed onsite with <br /> inf ltration trenches into advance outwash sand deposit per recommendations in this <br /> report. The toe of steep hillside is quite sensitive. Cut and regarding of the toe of hillside, <br /> if required, must be carried out and completed in dry season. Temporary shoring and <br /> dewatering may be required to stabilize toe cut. <br /> LIU & ASSOCIATES, INC. <br />