Laserfiche WebLink
GEOTECHNICAL INVESTIGATION <br />EVERETT, WASHINGTON <br />December 5, 2019 <br />COBALT <br />GEOSCIENCES <br />I Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively <br />impermeable sediment or bedrock; and <br />iii. Springs, groundwater seepage, or saturated soils. <br />d. Any area which has shown movement during the Holocene epoch (from ten thousand years ago to the <br />present) or which is underlain or covered by mass wastage debris of that epoch. <br />e. Any area potentially unstable as a result of rapid stream incision, stream bank erosion or undercutting <br />by wave action. <br />f. Areas of historic failures, including areas of unstable, old and recent landslides or landslide debris <br />within a head scarp, and areas exhibiting geomorphological features indicative of past slope failure, such <br />as hummocky ground, slumps, earthflows, mudflows, etc. <br />g.. Any area with a slope of1. forty percent, or steeper and with a vertical relief of fifteen or more feet, <br />except:th.ose manmade slop11 es created under the 1.design and inspection of a geotechnical professional, <br />or slopes composed o f consolidated rock: <br />h. Areas that are at risk of landslide due to high seismic hazard. <br />i. Areas that are at risk of landslides or mass movement due to severe erosion hazards. <br />B. Protective Requirements. <br />1. Geotechnical Assessment Requirements. Development proposals on or within two hundred feet of any <br />area designated as or which, based on site -specific field investigation, the city has reason to believe are <br />geologically hazardous areas shall submit a geological assessment as required by subsection F of this <br />section. <br />2, The setback buffer requirement shall be based upon information contained in a geological <br />assessment, and shall be measured on a horizontal plane from a vertical line established at the edge of the; <br />geologically hazardous area limits (both from the top and toe of slope). In the event that a specific setback <br />buffer.is not included in the recommendation of the geological assessment, the setback buffer shall be. <br />based upon the standards contained in Chapter fg 18 of the International Building Code (IBC), or as the <br />IBC is updated and amended.. <br />It is our opinion that the proposed locations of the residences are suitable. They are currently set back <br />at least 40 feet from the top of the steep slope areas (Figure 2). We recommend a minimum building <br />setback of 25 feet from the top of the steep slopes. We recommend a minimum buffer of 15 feet for <br />vegetation from the top of the slope. <br />a. If the geological assessment recommends setback buffers that are less than the standard buffers that <br />would result from application of Chapter 1g.18 of the IBC, the specific rationale and basis for the reduced <br />buffers shall be clearly articulated in the geological assessment. <br />b. The city may require larger setback buffer widths under any of the following circumstances: <br />i. The land is susceptible to severe erosion and erosion control measures will not effectively prevent <br />adverse impacts. <br />ii. The area has a severe risk of slope failure or downslope stormwater drainage impacts. <br />4 <br />PO Box 82243 <br />Kenmore, WA 98028 <br />cobaltgeo (a)gmail. com <br />2o6-331-1097 <br />