5900 36TH AVE W PRE APP 015 - 032 - SOUNDVIEW BUSINESS CAMPUS - VERITAS Geotech Report 2025-04-22

Veritas Construction Inc ES-4011.03 June 17, 2016 Page 7 Revised June 22, 2016 With respect to the subject site, the areas meeting the definition of a "medium to high" landslide hazard (15 to 40 percent or greater slopes) are located mostly in the southwest corner and along the west and north margins of the site. It should be noted, during our fieldwork and reconnaissance of the surrounding slope areas, we did not observe signs of deep seated slope instability. Dense and competent till soils are prevalent throughout the upland and surrounding slope areas of the site. Mass gradingactivities will involve fills on the order of roughly 20 to 40 feet to establish design 9 Y 9 grades near areas characterized as a landslide hazard. Based on review of the preliminary site ' plan, slopes to be constructed on the north margin of the proposed development are expected to be sloped no steeper than three horizontal to one vertical (3H:1V); the base of the slope is ' expected to be set back 25 feet from the north property line. Slopes to be constructed on the west and other surrounding areas of the proposed development are expected to be sloped no steeper than two horizontal to one vertical (2H:1V). A storm water detention vault will be constructed on the north area of the site but, to the east of an existing ravine located in the northwest area. During construction of the detention vault, an ESNW representative should observe the slopes of the excavation and surrounding areas for signs of instability and landslide ' potential. During our subsurface exploration, native soils observed at test pit locations near the area of the site designated as landslide hazards consisted of medium dense to dense silty sand with gravel (SM) generally in the upper three to seven feet below existing grades underlain by very dense "unweathered" glacial till. These soils generally do not exhibit excessive instability. Per EMC 37.080C (Permitted Alterations), alterations within designated landslide hazard areas can only occur if the planned development will not create a hazard to the site and surrounding properties. Based on our review and investigation, it is our opinion that stability will be maintained and the potential for a landslide should be characterized as low provided our geotechnical recommendations are incorporated into final design. In addition, ESNW prepared a Stability Assessment letter, dated October 6, 2015, relating to the proposed stormwater detention vaults located on the north margin of the subject property. Slope stability analysis was completed as part of an overall evaluation for the proposed detention vaults in the referenced letter demonstrating acceptable stability for the static and seismic conditions is satisfied. Minimal Risk Statement ' Based on our understanding of the proposed development, in our opinion the proposed development will not increase the potential for soil movement, and the risk of damage to the proposed development or adjacent properties from soil movement will be minimal. This estimate does not cover unforeseen or changed conditions. I Earth Solutions NW, LLC