2215 MERRILL CREEK PKY NEXTEL ANTENNA 2018-01-01 MF Import

� LSI Adapt, Inc. Surjace Condi�io��s The gcncral site topography within the Icasc arca on thc south side of the cxisting towcr sitc is relativcly Icvel, bounded by the paved parking arca on the wcst side and a roughly 3H:1 V (33 percent) dowmvards slope on the cast sidc. WiAiin the Icasc area, vcgctation consists of low cut grass. Wc obscrvcd no apparcnt cvidcnce of rcccnt surficial soil movcmcnt or sloughing at thc timc of our sitc visit; nor dicl wc observc any standing surfacc watcr. Subsurjace Condi�io�7c The previous subsurface c::ploration (sec enclosed boring log B-1) revcalcd the ncarvsurface soil conditions to consist of about G-inches of grass and topsoil mantling loosc to mcdium dcnsc, silty sand �vitL gravel (Weathered Glacial Till). Bclow thcse surficial soils at a depth of roughly 3.0-fcet bgs, our i 1 boring encountered very densc, silty sand with gravel (Glacial Till), which extcnded the full depth � explored of approximately 29.0-feet bgs. No groundwater scepagc was encountcred at thc time of ' drilling. Throughout the ycar, groundwater Icvcls would likely (luctuate in responsc to changing prccipi�ation pattems, off-site constructiori acti�•ities,and changes in sitc utilization. Seismic Conditio»s Bascd on our analysis of subsurface exploration logs and aur revicw of published geologic maps, wc intcrpret thc on-site soil conditions ro cortespond to seismic soil profilc typc S�, as defined by Table 1 G-J of thc 1997 Chiiforrn lluilding Code and Table 1615.1.1 of the 2000 buernnliaral Building Code. This soil profile is characterized by soft rock or very dcnse soil wilh an average SPT Ulowcount cacecding 50 blows per foot wiihin the upper ]00 feet bgs. Curtent(199G)Natia�al Seismic Na=ard Maps prcpared by tl�e U.S. Geological Survey indicate that a peak bcdrock site acceleration coe�cient of about 0.30 is appropriatc for an carthquakc having u 10-perccnt probability of exccedance in 50 years(corresponding to a return interval of 475 ycars). According to Figure 1 G-2 of the 1997 Unijorm Buildiirg Code, the site lics within Seismic Risk Zone 3. For purposcs of seismic site charactcrization, the obscrved soil conditions were extrapolated bclow the exploration termination depth, based on a rcview of geologic maps and our }:nowledge of regional geology. CONCLUSIONS AND RECOMMENDATIONS Curreni dcvclopmcnt plans call for thc installation af ncw cquipmcnt cabincts on a stcel platform supportcd by drillcd picrs. Provided that thc rccommcndations of this gcotcchnical cnginccring evaluation aze implemented, the project is considered fcasible and is not anticipated to adverscly affect the slopc stability or incrcase the risk of long-tcrm surfacc crosion at thc subjcct site, the nearby stcep slope arws, or adjaccnt properties. Wc rccommcnd that thc drillcd picr foundations for thc cquipmcnt platform be dcsigncd and ir.stalled in accordance with thc recommendations provided below for compressive, uplift and latcral support of drilled pier foundations. Our specific conclusions and rccommcndations conccming sitc prcparation, and cquipmcnt platform foundations, and structurai fill arc prcscntcd in thc follo��ing scelions of diis rcport. Nexte�do Tetra Tech June 25,2004 LSI Adapt Pmject No.WA04-1�499•GEO Page f��