7710 EVERGREEN WAY NEW CINGULAR WIRELESS ANTENNA 2016-09-26

� Adapt Engineering Suberade Conditions: The prepared bearing subgrade soils should consist of firm and unyeilding, native, very dense fine to coarse sand with silt. Exposed mat foundation subgrades should be compacted to a firm, unyielding state, as described in the Site Preparation section of this report. Subgrade Verification: Mat foundations, footings, or slabs-on-grade should never be cast atop soft, loose, organic, or frozen soils; nor atop subgrades covered by standing water. A representative from Adapt should be retained to observe the condition of footing subgrades before concrete is poured to verify that they have been adequately prepared. Bearing Pressures: For mat footings bearing on the native, very dense fine to coarse sand with silt at a minimum depth of about 4-feet bgs, we recommend an ultimate static bearing pressure of 7,500 psf. This static bearing pressure does not incorporate a factor of safety, in accordance with the provisions of the EIA/TIA 222-G code. Uplii Capacitv: We expect that uplift loads will be resisted by the dead load of the mat foundation, as well as the weight of soils covering the mat. Native soils used to cover the mat and compacted to a minimum of 90 percent of the inodified Proctor maximum dry density could be assumed to have a unit density of 125 pcf. Lateral Resistance: Lateral loads on the foundation caused by seismic or transient loading conditions may be resisted by a combination of passive soil pressure against the side of the foundation and base friction resistance. We recommend using an ultimate foundation base friction coefficient of 0.67 for the native, very dense fine to coarse sand with silt. A passive earth pressure of 450 pounds per-cubic-foot (pc�, expressed as an equivalent fluid unit weight, may be used for that portion of the foundation embedded more than 1-feet below finished exterior subgrade elevation. These lateral resistance values do not incorporate a safery factor, in accordance with the provisions of the E[A/T[A 222-G code. Gradin� and Ca�ping: Final site grades should slope downward away from the structure at a minimum gradient of 2 percent so that runoff water will flow by gravity to suitable collection points, rather than ponding near the structure. Ideally, the area surrounding the structure should be capped with concrete, asphalt, or compacted low-permeability (silty) soils to reduce surface-water infiltration into the subsoils adjacent to/below the foundation. Settlements: We estimate that total post-construction settlements of properly designed mat foundation bearing on properly prepared subgrades could approach 1 inch, with differential settlements approaching one-half of the total. Tower Drilled Pier Foundations The subsurface soil and groundwater conditions observed in our site exploration are also considered to be generally suitable for the use of a drilled pier foundation to support the proposed tower. The following recommendations and comments are provided for purposes of drilled pier design and construction. AT&T Mobility c/o Ryka Consulting May 5, 2014 Adapt Project No. WA14-18929-GEO Page 7