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411 • <br /> January 9,2019 <br /> Page 2 of <br /> Liii—utEilGeologic Evaluation <br /> Geologic Hazards <br /> Most critical area ordinances designate slopes with magnitudes greater than about 4o percent and <br /> vertical relief of at least 10 feet as potentially geologically hazardous (steep slope/landslide <br /> hazards). <br /> The site contains slopes with magnitudes of up to 25 percent and relief of about 35 feet. There are <br /> mapped steep slope areas (greater than 33 percent) approximately 3o feet east of the property. <br /> Slope areas within the property appear stable at this time with no evidence of shallow sloughing, <br /> spring activity,erosion,or large-scale movement. <br /> It is our opinion that property does not contain slopes that meet the criteria in the Everett <br /> Municipal Code as landslide hazards. The site slope areas are stable at this time and resistant to <br /> local and global instability. <br /> The near surface soils have a moderate to severe erosion potential in a disturbed (exposed) state; <br /> however,typical erosion control devices,when properly installed and maintained, should prevent <br /> site soils and runoff from leaving the construction area. <br /> Conclusions&Recommendations <br /> It is our opinion that the site is stable and resistant to global instability. We did not observe areas <br /> consistent with landslide hazard areas as defined by the City of Everett Municipal Code. <br /> There is a chance that temporary excavations utilized for basement construction could experience <br /> sloughing depending on the groundwater conditions during construction and slope angles <br /> utilized. The following section includes recommendations for temporary excavations. <br /> Temporary Excavations <br /> Based on our understanding of the project,we anticipate that the grading could include local cuts <br /> on the order of approximately 8 feet or less for basement foundation placement. Excavations <br /> should be sloped no steeper than 1.5H:1V(Horizontal:Vertical)in loose native soils and 1H:1V in <br /> medium dense to dense native soils. If an excavation is subject to heavy vibration or surcharge <br /> loads,we recommend that the excavations be sloped no steeper than 2H:1V,where room permits. <br /> Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part <br /> N,Excavation,Trenching, and Shoring. Temporary slopes should be visually inspected daily by a <br /> qualified person during construction activities and the inspections should be documented in daily <br /> reports. The contractor is responsible for maintaining the stability of the temporary cut slopes <br /> and reducing slope erosion during construction. <br /> Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, <br /> and the slopes should be closely monitored until the permanent retaining systems or slope <br /> configurations are complete. Materials should not be stored or equipment operated within 10 feet <br /> of the top of any temporary cut slope. <br /> In the case of temporary cuts, the existing soil conditions may not be completely revealed until <br /> the excavation work exposes the soil. Typically, as excavation work progresses the maximum <br /> inclination of temporary slopes will need to be re-evaluated by the geotechnical engineer so that <br /> supplemental recommendations can be made. Soil and groundwater conditions can be highly <br /> variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated <br /> conditions,so that the project can proceed and required deadlines can be met. <br /> www.cobaltgeo.com (206)331-1og7 <br />