313 76TH ST SE WESTERN WIRELESS CORPORATION Geotech Report 2018-01-02 MF Import

ADaPT Engineering, Inc. Western Wireless Corporation ADaPTJob No. WA98-993 April I, 1998 Page 5 by the equipment, we recommend the overexcavation extend no deeper than 2-feet below the thickened slab bearing elevation. A layer of gcotextile may be required to separate the structural fill soils from the underlying random materials. Footings should never be cast atop soft, loose, organic, or frozen soils; nor atop subgrades covered by standing water. A representative from AMPT should be retained to observe the condition of footing subgrades before concrete is poured to verify that they have been adequately prepared. Footine Dimensions: We recommend that the thickened edge of the slab be designed as a spread footing and be constructed to have a minimum width of 12 inches. For frost protection, the footings should penetrate at least 18 inches below the lowest adjacent exterior grades. Footings may be supported on structural fill placed on prepared soil subgrade. The horizontal limits of the fill pad below the building or cabinet foundation may be established by extending a line outwards from the base of the thicken.d slab at an angle of I Horizontal: 1 Vertical(I H: I V)down to the upper surface of the bearing horizon. Bearing Pressure: At the location of boring B-1, the near surficial soil should be stripped, excavated to a depth of at least 18 inches below the lowest adjacent grade. The soils at that elcv.tion should be compacted in place if the moisture content allows, resulting in a fine and unyielding subgrade condition. Alternatively, the cabinets could be supported above a maximum thickness of two feet of compacted fill, underlain by a layer of gcotextile (filter fabric), if required. A maximum allowable soil bearing pressure of 1500 pounds per-square-foot can be used for static footing loads. This bearing pressure can be incr_ased by one-third to accommodate transient wind or seismic loads. An allowable base friction coefficient of 0.35 and an allowable passive earth pressure of 250 pounds per cubic foot (pef), expressed as an equivalent fluid unit weight, may be used for that portion of the foundation embedded more than I foot below finished exterior subgrade elevation. Settlements: We estimate that total post-construction settlements of properly designed footings bearing on properly prepared subgrades could approach 1-inch, with differential settlements approaching one-half of the total. Tomer Drilled Pier Foundations Based upon the subsurface soil and groundwater conditions disclosed by our test boring, we recommend that the tower be supported on a drilled pier foundation. llte following recommendations and comments are provided for purposes of drilled pier design and construction: Compressive Capacities: We recommend that the drilled pier penetrate at least 15 feet below the ground surface at the location of boring B-l. For vcnical compressive soil bearing capacity, we recommend using the unit end bearing capacity presented in Table I below. The allowable end bearing capacity,