5828 GLENWOOD AVE CINGULAR WIRELESS ANTENNA Geotech Report 2022-10-25 (2)

Adapt Engineering 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 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 improve or extend the existing access road. Should it be necessary to provide an extension to the existing roadways or to improve the existing access roads,we recommend that the subgrade be prepared in accordance with the Site Preparation 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. Placement and Compaction: Generally,CDF,and lean-mix 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 Minimum Compaction Slab/Footing subgrade 90 percent Gravel drive subgrade(upper 1 foot) 95 percent Gravel drive subgrade(below 1 foot) 90 percent AT&T Mobility do General Dynamics October 10,2016 Adapt Project No.WA16-20654-GEO y'!!!ge'101•01