12906 19TH AVE SE FRED MEYER FUELING STATION 2018-01-02 MF Import

Gemechnical Engineering Report 2 June 27, 2008 Fred A1eyer Fueling Facility Project H2008-217 Walgreens Store, and to the cast by Bothell-Everelt Highway (State Route 527). The site is relatively flat with overall elevation differences of less than three feet. 3.2 Soils The soils cncounlcrcd in the test borings are relatively consistent in the project area. 'rile typical soil profile includes up to 4 feel of fill overlying dense to very dense silty SAND with some to trace gravel (glacial till). The fill consists ofdense silly sandy GRAVEL. Our review of the Geologic Map of Sunlicial Deposits in the Seaule 30' by 60' QuacG•angle, Washinglan by .lames C. Yount, cl a1. (1993) indicated that the native soils were mapped as Vashou till (Qvt). The native soils include light to dark gray, nonsortcd, nonstralified mixture of clay, silt, sand and gravel up to boulder -size. 'These descriptions are generally similar to the findings in our field exploration. More detailed descriptions of the subsurface conditions encountered are presented on the Test Boring Logs, Figures A-2 and A-3 in Appendix A. 3.3 Groundwaler Groundwater seepage was encountered at 4.0 feet bgs in the test boring 1.3-1 during our field exploration. The groundwater seems to be perched over the dense glacial till. Fluctuations in static and perched groundwater levels should be expected on a seasonal and annual basis. The levels will be highest during the extended periods of heavy seepage in the wet winter months. 3.4 Scismic Considerations Based on 2003 International Building Code (IBC), the site soil is Class C from 'Table 1615.1.1. The earthquake spectral response acceleration at shot periods (Ss) is 126.4%g and at I -second period (Si) is 43.2%g. Liquefaction Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil's strength. We reviewed the soil conditions encountered during field exploration and assessed the potential for liquefaction of the site's soil during an earthquake. Glacial till is generally considered not subject to liquefaction during an earthquake. Therefore, Riley believes that the site liquefaction potential during an earthquake is minimal. The Riley Group, Inc.