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Geotechnical Engineering Evaluation NGA File No. 959616 Watson Residence Addition July 6,2016 Everett, Washington Page 6 The planned earthwork associated with the planned improvement areas should be minor. To lessen the potential impacts of construction on the slopes and to reduce cost overruns and delays, we recommend that foundation preparation take place during dry weather if possible. If earthwork takes place during wet weather, additional expenses and delays should be expected. These extra expenses could include additional erosion control and temporary drainage measures to protect the slope. In any case, the excavation spoils should be hauled off site and not allowed to reach the slope. Also, the vegetation on the slope should not be disturbed. Any disturbed areas should be promptly repaired. Erosion Control and Slope Protection Measures The erosion hazard for the on-site soils is listed as slight to high, but the actual hazard will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped or disturbed areas. Silt fences and/or straw bales should be erected to prevent muddy water from leaving the site or flowing over the steep slope. Stockpiles should be covered with plastic sheeting during wet weather and stockpiled material should be placed no closer than 50 feet from the top of the slope. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential for areas not stripped of vegetation should be low. Protection of the steep slope, setback, and buffer areas should be performed as required by the City of Everett. Specifically, we recommend that the setback as well as the slope, not be disturbed or modified through placement of any fill or removal of the existing vegetation. No material of any kind should be placed on the slope or be allowed to reach the slope, such as excavation spoils, lawn clippings, and other yard waste, trash, or soil stockpiles. Trees or vegetation should not be cut down or removed from the steep slope unless a mitigation plan is developed, such as the replacement of vegetation for erosion protection. Replacement of vegetation should be performed in accordance with the City of Everett code. Any proposed development within the buffer area, other than light decks or patios, should be the subject of a specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slope. NELSON GEOTECHNICAL ASSOCIATES, INC.