Ordinance 2909-06 - Laserfiche WebLink

i. Very High/Severe - Slopes greater than 15% in the Qtb, Qw, and Qls geologic units; and slopes greater than 15% with uncontrolled fill. ii. High - Slopes greater than 40% in all other geologic units (not Qtb, Qw, Qls or uncontrolled fill). 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: i. Slopes less than 15% for Qtb, Qw, Qls geologic units and uncontrolled fill ii. Slopes of 25% - 40% in all other geologic units c. Any area with all three of the following characteristics: i. Slopes greater than fifteen percent; and ii. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock; and iii. Springs, groundwater seepage, or saturated soils. 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 wave 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% 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 composed of consolidated rock. h. Areas that are at risk of landslide due to high seismic hazard. i. Areas that are at risk of landslides or mass movement due to severe erosion hazards. 2. Seismic/Liquefaction hazard areas: 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 Susceptibility Map of Snohomish County, Washington, Washington State Department of Natural Resources, Palmer, Stephen, et. al. September, 2004. 3. Erosion hazard areas: a. Those areas defined as high and very high/severe risk of erosion in the Dames and Moore Methodology 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 - 40% in Qva and Qal geologic units; and slopes of >40% in other (not Qva or Qal) geologic units. 15