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

� Adapt Engineering allowable displacement for design, based on the specific requirements of the communication equipment mounted on the tower. Table 4 Recommended Horizontal Subgrade Reaction Values Depth Interval nn k� (feet) (pci) (pci) 0-2 0 N/A 2-5 20 N/A 5-35.5 30 N/A Coefficient of Horizontal kh= nh(z/B) kh=k�/(1.5B) Subgrade Reaction (pci) (Sand & Soft Clay) (Stiff Clay) Construction Considerations: Our explorations revealed the near-surface soil conditions below the 2 to 3- inch thick asphalt surfacing material consist of roughly 3 to 6-inches of fine to coarse sand with gravel, interpreted to be fill material used as a grading course, mantling crushed rock and rock spalls, also interpreted to be fill material. Below these surficial soils, at a depth of approximately 5.0-ft bgs, we encountered alternating zones of very dense fine to coarse sand with silt and cobbles and very dense silty gravel with sand and cobbles, which generally extended to the full explored depth of approximately 35.5- feet bgs. The presence of cobbles and potential presence of boulders was noted during advancement of our test boring. The occurance of erratics (cobbles and boulders) is common in glacial sediments, and was generally observed at relatively shallow depths; the contractor should anticipate for the possibility of difficult drilling conditions and presence of large particles. Perched groundwater seepage was encountered within our test boring near 25.0-ft bgs, at the time of drilling. Dewatering may be required depending on the actual depth and time of year of drilled pier construction. The foundation-drilling contractor should be prepared to case the excavation to prevent caving and raveling of the pier shaft sidewall, if necessary due to unexpected soil or excessive groundwater seepage conditions. Should heavy groundwater inflow be encountered in the drilled pier excavation, it may be necessary to pump out the accumulated groundwater prior to concrete placement, or to use a tremie tube to place the concrete from the bottom of the drilled pier excavation, thereby displacing the accumulated water during concrete placement. Alternatively, the use of bentonite slurry could be utilized to stabilize the drilled pier excavation. Drilled Pier Excavation Conditions: The drilling contractor should be prepared to clean out the bottom of the pier excavation if loose soil is observed or suspected, with or without the presence of slurry or groundwater. As a minimum, we recommend that the drilling contractor have a cleanout bucket on site to remove loose soils and/or mud from the bottom of the pier. If groundwater is present and abundant within the pier hole, we recommend that the foundation concrete be tremied from the bottom of the hole AT&T Mobility c/o Ryka Consulting May 5, 2014 Adapt Project No. WA14-18929-GEO Page 10