8525 EVERGREEN WAY BURGER KING 2021-05-10

Geotechnical Engineering Evaluation NGA File No. 998317 Burger King Restaurant Development August 2,2017 Everett,Washington Page 4 The site is located within the South Whidbey Island Fault Zone (SWIFZ): an active, shallow region of seismicity within central Puget Sound stretching from the Strait of Juan de Fuca to North Bend. Information published in 2013 by the Washington State Department of Natural Resources suggests the SWIFZ last ruptured less than 2,700 years ago, and that the fault zone can produce a M7.5 earthquake. In our opinion,the hazard of ground rupture within this site is low within the expected life of the structure. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the dense glacial till soils interpreted to underlie the site at depth have a low potential for liquefaction or amplification of ground motion. Erosion Hazard The criteria used for determination of the erosion hazard for affected areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey of the Snohomish County Area, Washington, by the Soil Conservation Service (SCS), was reviewed to determine the erosion hazard of the on-site soils. The surficial soil on site is mapped as Alderwood-Urban land complex, 2 to 8 percent slopes. The erosion hazard for this material is listed as moderate. All undisturbed, vegetated areas should have a low to moderate erosion hazard depending on how surface water is controlled on the site. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion from a geotechnical standpoint that the site is compatible with the planned commercial restaurant development provided all recommendations provided in this report are incorporated into the development plans and implemented during construction. Our explorations indicated that the site was underlain by surficial undocumented fill soils with medium dense or better native glacial soils at relatively shallow depths. The competent native glacial till deposits were encountered at approximately 2.0 to 3.0 feet below the existing ground surface where explored. We should note that localized areas of deeper unsuitable soils and/or undocumented fill could be encountered at this site and exposed at the proposed foundation subgrade elevations depending on final site grading and development plans. These unsuitable soils would likely be associated with previous grading activities and/or the installation of the existing utilities within the vicinity of the property. This condition would require additional excavations in foundation, slab,and pavement areas to remove the unsuitable soils. The underlying medium dense or better native soils should provide adequate support for the planned structure. NELSON GEOTECHNICAL ASSOCIATES, INC.