6301 36TH AVE W 2016-11-01 - Laserfiche WebLink

June 23, 2014 Project No.T-6241 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, when they contain debris and mud flows, gullying or rifling, immature vegetation, or no vegetation: i. Slopes of 25 to 40 percent in other(not Qva or Qal)geologic units." ' The City of Everett Erosion Hazard, Critical Areas Map 3, dated March 2006, shows the eastern extreme portion of the site is within or adjacent a medium to high erosion hazard area. Based on the site topography available, we estimate that the side slopes of the eastern portion of the site generally range from 20 to 55 percent. Based on our geologic data review and test pits excavated near the top of the slope, the slope is expected to be underlain primarily by Qva soils. Therefore, according to the criteria presented in item (a)(i) and (a)(ii) above, the east slope would be considered a high to very high/severe erosion hazards area. We did not observe indications of significant erosion at the site; however, the site soils will be susceptible to erosion when exposed during construction. In our opinion, the potential for erosion at the site can be adequately mitigated with proper implementation and maintenance of Best Management Practices (BMPs) for erosion and sedimentation control. Erosion protection measures as required by the City of Everett will need to be in place prior to and during grading activity at the site. 4.2 Landslide Hazard Section 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 Everett,Washington: July 1, 1991: i. Very high/severe: slopes greater than 15 percent in the Qtb,Qw, and Qls geologic units and slopes greater than 15 percent with uncontrolled fill. ii. High: slopes greater than 40 percent in all other geologic units(not Qtb,Qw,and 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 percent for Qtb, Qw, and Qls geologic units and uncontrolled fill. ii. Slopes of 25 to 40 percent in all other geologic units. C. Any area with all three of the following characteristics: i. Slopes greater 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. Page No. 4