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June 9,2022 <br /> Page 5 of 15 <br /> Geotechnical Evaluation <br /> b. The city may require larger setback buffer widths under any of the following circumstances: <br /> (1) The land is susceptible to severe erosion and erosion control measures will not effectively <br /> prevent adverse impacts. <br /> (2) The area has a severe risk of slope failure or downslope stormwater drainage impacts. <br /> (3) The increased buffer is necessary to protect public health, safety and welfare based upon <br /> findings and recommendations of the geological assessment. <br /> 3. Unless otherwise permitted as part of an approved alteration,the setback buffers required by <br /> this subsection shall be maintained in native vegetation to provide additional soil stability <br /> and erosion control. If the buffer area has been cleared, it shall be replanted with native <br /> vegetation in conjunction with any proposed development activity. <br /> While the steep slope areas appear stable at this time, their magnitudes are high and surcharge <br /> loads (such as foundations) could de-stabilize the areas. The proposed residence includes a <br /> basement level. We recommend a minimum effective building setback of 7 feet for foundations <br /> closest to the steep slope areas.The effective setback is the horizontal distance measured from the <br /> base of the closest footings to the adjacent slope face. In addition to this setback,we recommend <br /> that foundation elements closest to the east property line be embedded to a depth to create a <br /> minimum iH:iV envelope from the base of the footing to the toe of the slope. This should be <br /> provided in pictorial form on the architectural plans for review. <br /> No buffer is required since the areas have been previously graded. We recommend re-grading <br /> steep slopes into a more stable 2H:1V magnitude in medium dense native soils. These areas could <br /> also be supported with retaining walls. Any finished slopes or yard areas must be fully <br /> landscaped following completion of the grading activities. <br /> C. Permitted Alterations. Unless associated with another critical area, the planning director, <br /> using the review process described in EMC Title 15, Local Project Review Procedures, may <br /> allow alteration of an area identified as a geologically hazardous area or <br /> the setback buffers specified in the IBC if an approved geotechnical report demonstrates that: <br /> 1. The proposed development will not create a hazard to the subject property, surrounding <br /> properties or rights-of-way,or erosion or sedimentation to off-site properties or bodies of water; <br /> 2. The proposal addresses the existing geological constraints of the site,including an assessment <br /> of soils and hydrology; <br /> 3. The proposed method of construction will reduce erosion potential,landslide and seismic <br /> hazard potential,and will improve or not adversely affect the stability of slopes; <br /> 4. The proposal uses construction techniques which minimize disruption of existing topography <br /> and natural vegetation; <br /> 5. The proposal is consistent with the purposes and provisions of this chapter and mitigates any <br /> permitted impacts to critical areas in the vicinity of the proposal; <br /> 6. The proposal mitigates all impacts identified in the geotechnical letter or geotechnical report; <br /> 7. All utilities and access roads or driveways to and within the site are located so as to require <br /> the minimum amount of modification to slopes,vegetation or geologically hazardous areas; and <br /> 8. The improvements are certified as safe as designed and under anticipated conditions by <br /> a geologist. <br /> www.cobaltgeo.com (206)331-1o97 <br />