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

Adapt Engineering Surface Conditions Our surface exploration consisted of a visual site reconnaissance. The existing wood telecommunication tower, proposed to be replaced by a new steel tower, currently resides in the southeast corner of the host parcel. In the vicinity of the proposed tower location,the surface of the gently north-sloped host parcel is primarily overlain by grass and landscaping shrubbery. The existing AT&T equipment facility and adjacent Verizon facility currently reside approximately 90 feet northwest of the tower location. A Snohomish County Public Utility Department(PUD)substation facility resides on the northern half of the host parcel,approximately 100 feet north of the proposed tower location. It should be noted that many public and private underground utilities were identified by public and private utility locating contractors. On-site utilities identified in the vicinity of the proposed tower location included gas, water, power and telecommunication lines. However, non-metallic utility lines may not have been identified. It is encouraged that the exact location of any underground utilities in the vicinity of the future construction footprint are located prior to commencing any subsurface excavation work, to avoid potential underground utility conflict or damage. Subsurface Conditions At the exploration location designated B-1, 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. 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. Seismic Conditions Based on our analysis of subsurface exploration logs and a review of published geologic maps, we interpret the on-site soil conditions to correspond to Site Class D, as defined by Table 20.3-1 within Chapter 20 of ASCE 7 in accordance with the 2012 International Building Code (IBC). The soil profile type for this site classification is characterized by stiff soils with an average blowcount between 15 and 50 within the upper 100 feet bgs. Current (2003) National Seismic Hazard Maps prepared by the U.S. Geological Survey indicate that peak bedrock site acceleration coefficients of about 0.294 and 0.545 are appropriate for an earthquake having a 10 percent and 2 percent probability of exceedance in 50 years (corresponding to return intervals of 475 and 2,475 years, respectively). The IBC mapped spectral AT&T Mobility cio General Dynamics October 10,2016 Adapt Project No.WA16-20654-GEO LDt 2.0