101 E MARINE VIEW DR SEPA 018 - 011 Geotech Report 2025-04-15

I r Geotechnical Engineering Evaluation NGA File No.988017 East Marine View Drive Warehouse May 19,2017 Everett,Washington Page 3 Within Boring 1, we generally encountered, approximately 75.0 feet of very loose to dense, gray to dark brown, fine to medium sand with varying amounts of silt, gravel, organic content including wood debris. From 75.0 feet to 86.5 feet,we generally encountered very soft gray to gray-blue, silt with fine sand. We interpreted these soils to be native alluvial soils. Boring B-1 was terminated within native alluvial soils at a depth of 86.5 feet below the existing ground surface. In Boring 2, we generally encountered very loose to very dense, gray to gray-brown, fine to medium sand with varying amounts of silt, gravel and organic content along with very soft gray brown silt with fine sand, organics, and wood debris. We interpreted these soils to be native alluvival soils. Boring B-2 was terminated within the native alluvial soils at a depth of 91.5 feet below the existing ground surface. Hydrogeologic Conditions Moderate to heavy groundwater seepage was encountered within Borings 1 and 2 at approximately 5.0 feet below the existing ground surface. The groundwater is interpreted to be part of the regional groundwater regime for the area. We do not expect significant variation in groundwater conditions throughout the year. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2012 International Building Code (IBC) for seismic site classification for this project. Since medium dense sand with silt and gravel was encountered underlying the site at depth, the site general conditions best fit the IBC description for Site Class D. The hazard associated with seismicity for sites underlain by valley sediments is primarily liquefaction. The type of soil that is most susceptible to liquefaction during an earthquake is a saturated, loose, fine-to medium-grained sand deposit. A loose saturated sand deposit, when subjected to vibration, tends to compact and decrease in volume. If the sand deposit does not drain,the pore water pressure increases. If the pore water pressure is allowed to build up by continuous vibration, a "quick" condition will be reached when the pore pressure equals the effective overburden pressure at some depths. Under this condition,the sand is temporarily transformed into a liquid state and loses its load bearing capacity. We do not expect significant lateral spreading of the subsurface soils due to the flat surface of the site. The risk to the structures on site would be differential settlement in case liquefaction takes place. It has been found that fine-grained soils (materials passing the No. 200 sieve) within the soil matrix, can significantly reduce the potential for liquefaction. Thus, a silty sand or silt would not liquefy as easily as a clean sand would under a given seismic event. The majority of the site soils is composed of medium NELSON GEOTECHNICAL ASSOCIATES, INC.