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

Adapt Engineering accelerations for short periods at the subject site(Ss and Si; Site Class B)are 122.8 and 43.6(expressed in percent of gravity)at 0.2 and 1.0 second periods,respectively with 2 percent probability of exceedance in 50 years. In accordance with Tables 1613.5.3(1) and 1613.5.3(2), Site Coefficients, Fa and F,,, are 1.009 and 1.564,respectively for a Site Class D. Therefore the adjusted MCE ground motions are SMs=1.239g and SMI=0.682g. For purposes of seismic site characterization, the observed soil conditions were extrapolated below the exploration termination depth, based on a review of geologic maps and our knowledge of regional geology. CONCLUSIONS AND RECOMMENDATIONS Current development plans call for the construction of a new steel telecommunication tower and associated equipment building or cabinet pad within the proposed lease area. Based on the subsurface conditions revealed by our field exploration, we recommend that the proposed tower be supported on a drilled pier foundation. A drilled pier can provide a cost-effective foundation for communication tower structures, provided that adequate embedment depths can be achieved with the drilled pier augering equipment,that the site is accessible to the drill rig,and that drilled pier contractors are available within a reasonable distance from the site. Alternatively, a reinforced concrete mat foundation may be selected if difficult drilling conditions are anticipated due to the presence of shallow bedrock or boulders, provided that the proposed lease area can accommodate the generally larger excavation plan area required for a mat foundation. Given the size and orientation constraints of the tower and distant equipment lease area, it does not appear likely that a mat foundation could be used. For planning purposes, we have therefore provided design criteria for compressive, uplift and lateral support of a drilled pier foundation option below. Our specific recommendations concerning site preparation,equipment building or cabinet foundations,tower foundation,access driveway,and structural fill are presented in the subsequent sections. If further consideration of a mat foundation is warranted, Adapt may be contacted for design criteria Site Preparation Preparation of the lease area for construction should involve clearing, grubbing,stripping, cutting,filling, dewatering,and subgrade preparation.We provide the following comments and recommendations relative to site preparation. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence, and contractor's methods,fmal decisions regarding drainage systems are best made in the field at the time of construction. Nonetheless, we anticipate that curbs, berms, or ditches placed along the uphill side of the work areas will adequately intercept or divert surface water runoff away from the work area. Clearing and Stripping: After surface and near-surface water sources have been controlled, the construction areas should be cleared and stripped of all vegetation, topsoil, and debris. Our site AT&T Mobility do General Dynamics - October 10;2016 Adapt Project No.WA16-20654-GEO