5010 DOVER ST Geotech Report 2025-07-31

August 22nd 2022 G-5756 Ben Erickson Page 3 Hand Auger 2(HA-2),was observed to be the same,hard silt that was observed in HA-1 directly below a 2-inch layer of grass and jute netting.This silt was hard directly below the surface at approximately 6 inches and probed less than half an inch. We interpret these dense soils to be hard Transitional Bed deposits that were overridden by ice in the last glaciation and dense to very dense. For a more detailed description of the soils encountered,please refer to the boring logs in Appendix A. CRITICAL AREAS The project site is located within a potential landslide geologic hazard area as mapped by the City of Everett Plate 3—Hazardous Areas Map. As part of our geotechnical engineering study for the proposed development,we evaluated the potential landslide hazard onsite.The majority of the site is mapped as a landslide hazard, sloping to the west where Phillips Creek is located. The existing footprint of the house is in this critical area, as well as the proposed addition which will extend 4 feet to the west,further than the current footprint, into the slope. The soils onsite are mapped to be dense Transitional Bed silts less than a foot below the ground surface in the location of the proposed addition. The slope was observed to be well vegetated beyond the proposed addition location, sloping down into a drainage area with a creek at the bottom. The percent grade of the slope in the location of the proposed development was approximately 10- 20%based on observations from site reconnaissance.No topographic survey has been provided and thus this estimate of percent grade near the project site is based on our onsite observation and past experience. From our subsurface investigation,we observed that the soils are dense to very dense and no signs of creep or instability were observed onsite. In our opinion, as long as our recommendations for proper drainage are applied the risk of a potential slide in the project area is low because of the dense to very dense soils. CONCLUSIONS AND RECOMMENDATIONS The site is underlain with hard, Silty soils that we interpret to be dense native soils,no groundwater was observed. We recommend the proposed addition be supported on conventional concrete footing foundations that bear on dense native soils or on structural fill that is placed on a subgrade of dense native soil. Based on the findings from our investigation,bearing soils are anticipated at depth of approximately 1 foot below the existing ground surface.Detailed recommendations regarding geotechnical aspects of the project are presented in the following sections of this report. GEO Group Northwest,Inc.