8215 BROADWAY 2016-01-01 MF Import

�r with gravel. �Vc intcrpretcd this near surface layer as possible fill materials. A laycr of inedium dcnse, moist, brown silty sand with little gravel and trace af orangc mottling was encountcred betwcen 3 and l3- fect bgs. IIelow 13-fcet bgs, soils were logged as vcry densc, moist, gray-brown, silty sand with trace gravel (Till) wi�ich extended to the full explored depth, approximately 28.5-fcct bgs. Based on the observed soil density and texture encountered �t the location of boring B-1 and our review of the Soil Survcy of Snohomish County published by United States Department of Agriculture, Soil Conservation Scrvice, wc interpret these very dense soils to be glacial till. Glacial till, and all soil urtiu below the till, havc becn compressed by the weight of the glacial ice mass. Accordingly, the till is vcry dense and relative incomprcssiblc. Hard drilling conditions were encountered �etween 13 and 28.5-feet bgs. Groundwatcr �'+as not encountered at this sitc during drilling. A Vace of orange mottling was encountercd within the upper portion of thc cxploratory soil boring. Mottling is a good indication of intcrmittent saturation iluctuating ground�vatcr levels. We intctpret thc site conditions ro be conducive to "perched" groundwatcr conditions. It should be recognized that groundwater levels could fluctuate duc to factors such as seasonal changes, precipitation or future site utilization. Seumic CondiNons According to the Seismic Zone Map of the United States containcd in Figure 1G-2 of the 1997 Uniform Building Codc (UBC), thc projcct site lies within Seismic Risk Zone 3. Based on our subsurface exploration, we interpret the site conditions to most closely correspond to a seismic Soil Profile type Sp, lor Stiff Soil Profile, as defincd by Table 16-J of the 1997 Unifo�m Building Code. This classification is based on the oUserved range of Standard Penetration Test (SPT) blow counts for the soil types cncountered in the soil boring B-1. Thc shallow soil conditions vwcre assumcd to bc represcntative Cor site conditions beyond the depths explorcd. CONCWSIONS AVD RECOMb1FtiUA7'IONS Current deve(opment plans call Cor conshvetion of a monopole a�d associated equipment building or cabinets. Based on the subsurface condilions encountered in our bonng, we recommend that the proposcd tower bc supported on a drilled pier foundation. Design criteria for crmpressive, uplift and latcral support of drilled pier foundations arc presentcd below. A conventionai mat toundation could be uscd lo support a to��er of this type but the depth to competent bcaring soils excecds 12 fect bgs. We undcrstand that VoiceStream Wircless prefers to utilize drilled picrs for towcr foundations as a construction expedicnt. We should bc contactcd to providc (oundation design recommendation: for a mat foundation, if desired, for this sitc. Our specific recommendations concerning site preparation, equipment pad foundatians, too cr foundations, and structural fill arc presented in thc following sections: M11ay 13,:000 \'oicc5trcam Wircicss pagc 3 ADaPT Projcci No, \VA00-0014