2320 106TH ST SW Geotech Report 2022-10-25

October 14,2015 Project No.T-6116-2 Groundwater We observed minor groundwater seepage at Test Pits TP-2, TP-3, and TP-4 approximately 8.5 to 14 feet below the ground surface. The seepage was occurring from seams of sandier soils contained within the glacial till matrix. Mottling of soils at shallower depths suggests that shallow groundwater seepage develops during the normally wet winter months along the contact between the upper silty sand layer and the unweathered dense glacial till. The occurrence of groundwater seepage will fluctuate seasonally with the highest seepage levels occurring during the normally wet winter to late spring months(November to June). 4.0 GEOLOGICAL HAZARDS 4.1 Seismic Hazards Section 37.0802 of the City of Everett Municipal Code(EMC)defines Seismic hazard areas as"a. Those areas mapped as seismic/liquefaction hazards per the Dames and Moore Methodology for the Inventory,Classification and Designation of Geologically Hazardous Areas,City of Everett, Washington: July 1, 1991. b. Those areas mapped as high and moderate to high liquefaction susceptibility on the Liquefaction mrt sceptibility Map of Snohomish County, Washington, Washington State Department of Natural Resources, —Plalmer, Stephen,et al., September,2004." The site does not fall into the seismic/liquefaction hazards under the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington: July 1, 1991 and the site does not fall under the high and moderate to high liquefaction susceptibility on the Liquefaction Susceptibility Map of Snohomish County, Washington, Washington State Department of Natural Resources, Palmer, Stephen,et al., September, 2004. Therefore,the site is not a seismic hazard site as defined by the EMC. 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. Liquefaction mainly affects geologically recent deposits of fine-grained sand that is 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,eliminating the soil's strength. Based on the soil and groundwater conditions we observed, it is our opinion that the hazard for liquefaction at this site during an earthquake and its associated risk or impacts is negligible. Page No. 3