2410 RAILWAY AVE Geotech Report 2023-04-06

Penske Truck Leasing—Proposed Service Facility,2410 Railway Ave, Everett,WA Mar.8,2019/Rev.Feb.25,2020 Geotechnical Engineering Report P1493-T18 Ss= 1.281 g SMs = 1.153 g SDs=0.768 g Si=0.487 g SM1 = 1.169 g SDI=0.779 g Using the 2018 IBC information, MCER Response Spectrum Graph on the USGS Design Summary Report website, Risk Category I/II/III, Sa at a period of 0.2 seconds is 1.15 g and Sa at a period of 1.0 seconds is 1.17 g. The Design Response Spectrum Graph from the same website,using the same IBC information and Risk Category, Sa at a period of 0.2 seconds is 0.77 g and Sa at a period of 1.0 seconds is 0.78 g. 3_6 Liquefaction Potential Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength caused by shear strains, as could result from an earthquake. Research has shown that saturated, loose, fine to medium sands with a fines(silt and clay)content less than about 20 percent are most susceptible to liquefaction. Given the presence of extensive saturated, poorly consolidated soils underlying the proposed improvement area, we interpret the upper site soils as having a moderate to high potential for liquefaction during a large-scale seismic event, which could lead to post-construction settlement. However, we expect that this effect will be attenuated by the overlying fill deposits previously placed on the site and new fills placed to raise existing site grades.In addition,the pre-engineered metal building will accommodate flexing during seismic events. Based on this,we recommend that this structure be designed to accommodate differential settlements of 2 inches over 50 feet without catastrophic collapse. 4.0 CONCLUSIONS AND RECOMMENDATIONS Development plans for this project include the construction of a (4)-Bay Service Facility with an office core and Wash Bay;an associated(2) Lane, (3)-product(gas,diesel,DEF)Fuel Island,and site pavement to support future site activity. If feasible, the project will include underground stormwater quality vaults, underground fuel storage tanks, and sanitary sewer lines. Sewer lines are proposed to be directed first to the City of Everett pressure sewer main, and in the future to a permanent public sanitary sewer system, to be installed to the east side of Railway Avenue. We understand that the flood requirements will require raising site grades between 11/2 and 6 feet across the site including 41/2 to 51/2 feet across the planned office/service building area. We offer these recommendations: • Feasibility: Based on our field explorations, research, and analyses, the proposed improvements appear feasible from a geotechnical standpoint. • Foundation Options: We recommend that the new service facility be supported on structural fill bearing pads with a minimum thickness of 2 feet or on augercast pile foundations. Specific recommendations for spread footings and structural fill are provided in Section 4.3 and 4.9, respectively. Augercast pile recommendations are presented in Section 4.4. Migizi Group, Inc. Page 6 of 17