Ordinance 3676-19 - Laserfiche WebLink

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,or as revised through best available science: i. High erosion hazard areas include slopes of twenty-five to forty percent in Qva and Qat geologic units; and slopes of greater than forty percent in other(not Qva or Qal)geologic units. ii. Very high/severe erosion hazard areas include slopes of greater than forty percent in Qva and Qal geologic units. b. Those areas defined as medium 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,or as revised through best available science,when they contain debris and mud flows,gullying or rifling, immature vegetation, or no vegetation: i. Slopes of twenty-five to forty percent in other(not Qva or Qal) geologic units. 4. Other areas which the city has reason to believe are geologically hazardous. I B. Geologically Hazardous Slope Setbacks and Slope ProtectionProtectivc Requirements. 1. Geotechnical Assessment Requirements. Development proposals on or within two hundred feet of any area designated as or which, based on site-specific field investigation, the city has reason to believe are geologically hazardous areas shall submit a geological assessment as required by subsection F of this section. 2. The setback buffer requirement shall be based upon information contained in a geological assessment, and shall be measured on a horizontal plane from a vertical line established at the edge of the geologically hazardous area limits (both from the top and toe of slope). In the event that a specific setback buffer is not included in the recommendation of the geological assessment,the setback buffer shall be based upon the standards contained in Chapter 19.18 of the International Building Code (IBC),or as the IBC is updated and amended. a. If the geological assessment recommends setback buffers that are less than the standard buffers that would result from application of Chapter 19.18 of the IBC,the specific rationale and basis for the reduced buffers shall be clearly articulated in the geological assessment. b. The city may require larger setback buffer widths under any of the following circumstances: i. The land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse impacts. ii. The area has a severe risk of slope failure or downslope stormwater drainage impacts. iii. The increased buffer is necessary to protect public health, safety and welfare based upon findings and recommendations of the geological assessment. 3. Unless otherwise permitted as part of an approved alteration,the setback buffers required by this subsection shall be maintained in native vegetation to provide additional soil stability and erosion control. If the buffer area has been cleared, it shall be replanted with native vegetation in conjunction with any proposed development activity. 4. The city may impose seasonal restrictions on clearing and grading within two hundred feet of any geologically hazardous areas. C. Permitted Alterations. Unless associated with another critical area, the planning director, using the review process described in EMC Title 15, Local Project Review Procedures, may allow alteration of an area identified as a geologically hazardous area or the setback buffers specified in the IBC if an approved geotechnical report demonstrates that: EMC Title 19.37 (Critical Areas) Page 24