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4735 Bayview Lane <br />Everet4 Washington Geotechnical Report <br />The attached Site Plan shows the landslide hazard critical areas and their relation to the planned <br />new construction. New additions are located further away from the slope than the existing <br />residence. <br />Seismic Hazards <br />The City of Everett Liquefaction (Seismic) Hazard Map — Critical Areas Map 4 — indicates that <br />there are no liquefaction seismic hazards associated with the property. Seismic hazards are <br />generally defined as lands that, due to a combination of soil and ground water conditions, are <br />subject to risk of ground shaking, lateral spreading, subsidence or liquefaction of soils during <br />earthquakes. These areas are typically underlain by soft or loose saturated soils (such as alluvium) <br />or peat deposits and have a shallow ground water table. Seismically induced landslides may also <br />be considered as a potential seismic hazard. Based on our evaluation of the soil and ground water <br />conditions underlying the site it is our opinion that the risk of lateral spreading, subsidence or <br />liquefaction of soils during earthquakes is low and no mitigation is required. It is also our opinion <br />that, depending upon weather conditions at the time, there is a moderate to high risk of shallow <br />landsliding during an intense seismic event and a low to moderate risk of deep-seated slope <br />movement. However, the recommended 50-foot buffer effectively mitigates this risk. <br />The South Whidbey Island Fault Zone (S WIFZ) is a 4 to 7-mile-wide zone of fault splays that is <br />thought to lie between Old Town Mukilteo and Alderwood Manor which is about 1 to 1.5 miles <br />south of the subject site. The S WIFZ is believed to be capable of producing earthquakes as large <br />as Magnitude 7.5. The recurrence interval on the fault zone is unknown but thought to be in excess <br />of 1,000 years. Ongoing studies in the Puget Sound area may further define the boundaries of the <br />fault zone and its true recurrence interval. The ongoing studies may also identify other previously <br />unknown faults in the area. Due to its location at least a mile from the known fault zone, and the <br />unpredictability of where a ground rupture may ever occur, no mitigation is recommended due to <br />a potential surface rupture. <br />The structure should be properly engineered for potential ground shaking caused by a seismic <br />event. In accordance with the 2015 IBC the site classification is C. <br />Erosion Hazards <br />The steep slope area of the site, which is far removed from the planned construction area, is <br />identified as a high risk erosion hazard area. The remainder of the site is considered to be low risk <br />for erosion due to the gentle slopes and heavy grass cover on the site. There is little to no potential <br />for the planned development to create a hazard to the subject property, surrounding properties or <br />rights -of -way, or to cause sedimentation to surrounding properties or bodies of water. <br />Gary A. Flowers, PLLC <br />5205 23`tl Avenue W Everett, Washington 98203 206-819-4304 <br />