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GeoTest Services, Inc.—Revision 1 April 10, 2020 <br /> Kikuchi Retaining Wall, Everett, Washington Project No. 20-0344 <br /> • Removing wet surficial soil prior to commencing fill placement each day <br /> • Sealing the exposed ground surface by rolling with a smooth drum compactor or rubber- <br /> tired roller at the end of each working day <br /> • Providing up-gradient perimeter ditches or low earthen berms and using temporary <br /> sumps to collect runoff and prevent water from ponding and damaging exposed <br /> subgrades <br /> Seismic Design Considerations <br /> The Pacific Northwest is seismically active, and the site could be subject to movement from a <br /> moderate or major earthquake. Consequently, moderate levels of seismic shaking should be <br /> accounted for during the design life of the project, and the proposed structure should be <br /> designed to resist earthquake loading using appropriate design methodology. <br /> For structures designed using the seismic design provisions of the 2018 International Building <br /> Code, the stiff to very stiff transitional beds underlying the site is classified as Site Class D, <br /> according to ASCE 7-16. The structural engineer should select the appropriate design response <br /> spectrum based on Site Class D soil and the geographical location of the proposed construction. <br /> Summary of Soil Parameters for Design <br /> A summary of recommended soil parameters to be used in the design of the retaining wall is <br /> presented in the following table. The values provided in Table 2 have been established using a <br /> combination of measured field and laboratory data obtained during our March 2020 site visit. <br /> GeoTest is also utilizing published data and our experience with similar soils to establish these <br /> soil parameters. <br /> Table 2. Retaining Wall Design Parameters <br /> Assumed Passive Earth <br /> Assumed Active Soil At-rest Soil <br /> Dry Coefficient of Base Pressure <br /> Soil Type Friction Pressure Pressure <br /> Density Angle (psf) (psf) Friction (pcf) <br /> (pcf) <br /> Existing, 105 30 35 55 Do not put foundations 200 <br /> Uncontrolled Fill on existing fill. <br /> Transitional 120 32 35 55 0.30 250 <br /> Beds <br /> New Structural 135 35 35 60 0.35 325 <br /> Fill <br /> Notes: <br /> -Soil pressure parameters assume drained conditions <br /> -Passive Pressure assumes a factor of safety of 1.5 <br /> -Equipment and/or slope surcharges are not included in the presented pressures. <br /> 16 <br />