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Geotechnical Engineering Evaluation NGA File No. 1033518 Larsen Property Garage May 8,2018 Everett,Washington Page 7 Erosion Control and Slope Protection Measures The erosion hazard for the on-site soils are interpreted to be slight to moderate for exposed soils, 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 slopes. Stockpiles should be covered with plastic sheeting during wet weather and stockpiled material should be kept at least 35 feet away from the top of the steep 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 site slope areas should be performed as required by the City of Everett. Specifically, we recommend that the setback area and site slopes not be disturbed or modified through placement of any fill or removal of the existing vegetation outside of the proposed development area. No additional material of any kind should be placed on either slope or be allowed to reach the slope, such as excavation spoils, lawn clippings, and other yard waste, trash, and soil stockpiles. Vegetation should not be removed from the slope. Replacement of vegetation should be performed in accordance with City of Everett code. Any proposed development within the slope setback area should be the subject of a specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slope. Site Preparation and Grading After erosion control measures are implemented, site preparation should consist of stripping any loose soils and undocumented fill to expose medium dense or better native soil in foundation, slab-on-grade, and pavement areas. The stripped materials should be removed from the site or stockpiled for later use as landscaping fill. Stockpiles should be kept at least 35 feet away from the top of the steep slopes and should be covered with plastic. If the ground surface, after site stripping, should appear to be loose,it should be compacted to a non- yielding condition. Areas observed to pump or weave during compaction should be over-excavated and replaced with properly compacted structural fill or rock spalls. If loose soils are encountered in any slab areas, the loose soils`should be removed and replaced with rock spalls or, granular structural fill: If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed,and the exposed subgrades should be maintained in a semi-dry condition. NELSON GEOTECHNICAL ASSOCIATES,INC.