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

Adapt Engineering Table 4 Recommended Horizontal Subgrade Reaction Values Depth Interval nh kv (feet) (pci) (pci) 0-2 0 N/A 2-6 3 N/A 6- 15 10 N/A 15 -30 25 N/A 30-41.5 40 N/A Coefficient of Horizontal kh=nn(z/B) kh=kv1(1.5B) Subgrade Reaction(pci) (Sand&Soft Clay) (Stiff Clay) Construction Considerations: Our exploration revealed the near surface soil conditions consist of roughly 12 inches of sandy topsoil with silt and gravel mantling very loose,poorly graded sand with wood debris (interpreted to be possible fill). At approximately 5 feet bgs, the test boring encountered a loose, relic topsoil layer that was approximately 8 inches thick mantling native, medium stiff, sandy silt. The sandy silt graded into medium dense, poorly graded sand with silt and gravel. At an approximate depth of 15 feet bgs, the test boring encountered dense to very dense,poorly graded sand. Hard silt was encountered at approximately 30 feet bgs,which then extended to the full exploration depth of 41.5 feet bgs. The presence of cobbles was not indicated during the advancement of our test boring;however gravel was noted in the site soils and the drilled pier contractor should anticipate the possibility of difficult drilling conditions and presence of large particles commonly encountered in glacially derived soil deposits. It should be noted that heaving conditions were encountered at an approximate depth of 25 feet bgs, which may have influenced blow counts and the retrieved sample. Perched groundwater was encountered at approximately 8 feet bgs which appeared to extend to an approximate depth of 30 feet bgs. It should be noted that throughout the year, groundwater levels will likely fluctuate in response to changing precipitation patterns,off-site construction activities,and changes in site utilization. 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. AT&T Mobility do General Dynamics October 10,2016 Adapt Project No.WA16-20654-GEO ---- --- _;_--------------- � e2io