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Achilles Manufacturing—Axthelm Constructionl7" JN 10076 October 4, 2016 Page 3/ 5—) the area of the proposed structures are not susceptible to seismic liquefaction because of their dense nature and the lack of near-surface groundwater. CONVENTIONAL FOUNDATIONS The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, dense native soil, or on imported rock structural fill placed above this competent native soil. All of the fill beneath the foundations should consist of imported rock spalls compacted with a large plate compactor or a hoepack. See the section entitled General Earthwork and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. Prior to placing structural fill beneath foundations, the excavation should be observed by the geotechnical engineer to document that adequate bearing soils have been exposed. We recommend that continuous and individual spread footings have minimum widths of 12 and 16 inches, respectively. Footings should also be bottomed at least 18 inches below the lowest adjacent finish ground surface. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. An allowable bearing pressure of 4,000 pounds per square foot(psf) is appropriate for footings supported on competent native soil. A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that the total post-construction settlement of footings founded on competent native soil will be less than one inch. Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level structural fill. We recommend using the following ultimate values for the foundation's resistance to lateral loading: Parameter ULTIMATE Value Coefficient of Friction 0.50 Passive Earth Pressure 350 pcf Where:(i)pcf is pounds per cubic foot,and(ii)passive earth pressure is computed using the equivalent fluid density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's resistance to lateral loading,when using the above ultimate values. EXCAVATIONS AND SLOPES Excavation slopes beyond 4 feet are anticipated but should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be made near property boundaries, or existing utilities and structures. Based upon Washington Administrative Code (WAC)296, Part N, the unsaturated, dense glacial till at the subject site would generally be classified as Type A. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an inclination steeper than 0.75:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. For overall slope heights of less than 12 feet, the cut can manifest itself as a 4-foot vertical cut at the toe of a 1:1 (H:V) GEOTECH CONSULTANTS,INC.