5801 23RD DR W Geotech Report 2025-07-29

I I October 22,2007 Project No.T-5922-1 iii4.2 Landslide Hazard ISection 19.37.080(A)(1)of the EMC defines landslide hazard areas as: a. Those areas defined as high and very high/severe risk of landslide hazard in the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of IEverett,Washington:July 1, 1991: i. Very high/severe: slopes greater than 15 percent in the Qtb, Qw,and Qls geologic units; and I ii. slopes greater than 15 percent with uncontrolled fill. High: slopes greater than 40 percent in all other geologic units (not Qtb,Qw, and Qls or uncontrolled fill). I b. Those areas defined as medium risk of landslide hazard in the Dames and Moore Methodology for Inventory, Classification and Designation of Geologically Hazardous Areas,City of Everett,Washington: July 1, 1991,when combined with springs or seeps, immature vegetation,and/or no vegetation: Ii. Slopes less than 15 percent for Qtb, Qw,and Qls geologic units and uncontrolled fill. ii. Slopes of 25 percent to 40 percent in all other geologic units. c. Any area with all three of the following characteristics: i. Slopesgreater than 15 percent. ii. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock. iii. Springs,groundwater seepage,or saturated soils. I d. Any area which has shown movement during the Holocene epoch (from ten thousand years ago to the present)or which is underlain or covered by mass wastage debris of that epoch. e. Any area potentially unstable as a result of rapid stream incision, stream bank erosion,or undercutting by Iwave action. f. Areas of historic failures, including areas of unstable, old and recent landslides or landslide debris within a head scarp, and areas exhibiting geomorphological features indicative of past slope failure, such as $ hummocky ground,slumps,earthflows, mudflows,etc. g. Any area with a slope of 40 percent or steeper and with a vertical relief of 15 or more feet, except those manmade slopes created under the design and inspection of a geotechnical professional, or slopes I composed of consolidated rock. h. Areas that are at risk of landslide due to high seismic hazard. Ii. Areas that are at risk of landslides or mass movement due to severe erosion hazards. I The sideslopes of the Narbeck Creek drainage ravine in the eastern portion of the site are steeper than 40 percent, and are underlain primarily by Qva soils. Therefore, according to the criteria presented in item (a)(ii) above, the steep ravine slopes are considered high-risk Iandslide hazard areas. As discussed, we did not observe indications I of deep-seated instability or persistent groundwater seepage on or above the slope face, and much of the slope supports growth of relatively-straight mature coniferous trees. I Page No.5