6307 36TH AVE W Geotech Report 2025-07-29

I I August 13,2008 Project No.T-6241 At the two borings advanced in the western portion of the site, we observed loose to medium dense weathered silty sand overlaying very dense glacial till with pockets of fine to coarse grained sand at Boring B-1 and outwash I sediments at Boring B-2. Boring B-1 is situated immediately south of Test Pit TP-11 while Boring B-2 is situated immediately west of Test Pit TP-12. I Detailed descriptions of the subsurface conditions observed in the test pits and borings are presented on the Test Pit and Boring Logs in Appendix A. The approximate test pit and boring locations are shown on Figure 2. I The Distribution and Description of Geologic Units in the Mirkilteo Quadrant, Washington, by James P. Minard, 1982, shows soils in the vicinity of the site consist of Vashon Till (Qvt) with Advanced Outwash (Qva) in the sites eastern extent. The soils we observed in the test pits are consistent with outwash sediments as well as Iweathered and unweathered horizons of glacial till. I3.3 Groundwater We observed moderate groundwater seepage in Test Pit TP-4, located in the southeast portion of the site. The I seepage appeared to be perched within sand deposits at depth of approximately ten feet below existing surface grade. I We observed that the soils near the contact between the weathered and unweathered deposits were mottled, which is an indication that a perched groundwater table develops at times in that zone. The development of perched groundwater is typical for sites underlain by till. Perched groundwater volumes and seepage rates will I fluctuate seasonally, and typically reach their highest levels during and shortly following the winter and spring months(October through May). 4.0 GEOLOGIC HAZARDS Section 19.4.020 of the Everett Municipal Code (EMC) defines geologically hazardous areas as "areas susceptible to erosion,landslide,seismically induced soil failure, or other geological events." 4.1 Erosion Hazard Section 19.37.080(A)(3)of the EMC defines erosion hazard areas as: a. Those areas defined as high and very high/severe risk of erosion in the Dames and Moore Methodology I for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington: July 1, 1991: i. High erosion hazard areas include slopes of 25 to 40 percent in Qva and Qal geologic. units; and slopes of greater than 40 percent in other (not Qva or Qal) geologic units. ii. Very high/severe erosion hazard areas include slopes of greater than 40 percent in Qva and Qal geologic units. Page No. 3 I