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

� � Adapt Engineering to displace the water and minimize the risk of contaminating the concrete mix. The Drilled Shaft Manual published by the Federal Highway Administration recommends that concrete be placed by tremie methods if more than 3 inches of water has accumulated in the excavation. Access Driveway Based on available site plans and our site reconnaissance visit, it does not appear necessary to construct a new access road. However, if roadway extensions are necessary, we recommend that the subgrade for any access roadway be prepared in accordance with the Site Preparatzon section of this report. For planning purposes, we anticipate that 6 to 12-inches of "clean" sand and gravel subbase material and a minimum 3-inches of crushed rock surfacing will be required to create a stable gravel roadway surface at this site. Adapt can provide additional subgrade stabilization or gravel road section recommendations based on observed field conditions at the time of construction. Where cuts and fills are required, they should be accomplished in accordance with the recommendations provided in the Site Preparation and Structural Fill sections of this report. Structural Fill The following comments, recommendations, and conclusions regarding structural fill are provided for design and construction purposes. Materials: Structural fill includes any fill materials placed under footings, pavements, driveways, and other such structures. Typical materials used for structural fill include: clean, well-graded sand and gravel (pit-run); clean sand; crushed rock; controlled-density fill (CDF); lean-mix concrete; and various soil mixtures of silt, sand, and gravel. Recycled concrete, asphalt, and glass, derived from pulverized parent materials may also be used as structural fill. Owing to the relatively high groundwater, we recommend the structural fill below the tower mat consist of 2 to 4-inch quarry spalls. Placement and Compaction: Generally, CDF, and lean-rnix concrete do not require special placement and compaction procedures. In contrast, pit-run, sand, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Using the modified Proctor maximum dry density (ASTM: D-1557) as a standard, we recommend that structural fill used for various on-site applications be compacted to the following minimum densities: Fill Application Slab/Footing subgrade Gravel drive subgrade (upper 1 foot) Gravel drive subgrade (below 1 foot) Minimum Comaaction 90 percent 95 percent 90 percent Subgrades and Testing: Regardless of location or material, all structural fill should be placed over firm, unyielding subgrade soils. We recommend that a representative from Adapt be retained to observe the condition of subgade soils before fill placement begins, and to perform a series of in-place density tests AT&T Mobility c/o Ryka Consulting May 5, 2014 Adapt Project No. WA14-18929-GEO Page 11