1921 W MUKILTEO BLVD 2018-01-02 MF Import

I� Preliminary Geotechnical Engineering Evaluation 1919 Mukilteo Boulevard !� October 20, 2005 1 NGA File No. 718805 Page 7 Under no circumstances should water be allowed to flow over or concentrate on the site slopes, both during construction and after construction has been completed. We recommend that stormwater runoff from the roof drains, paved areas, and yard drains be tightlined to a suitable discharge point. The steep slopes should be protected from erosion MVP rP-ommend that vegetation on and near the steep slope be maintained and that any disturbed areas be replanted to re-establish vegetation as soon as possible. Stormwater runoff should not be allowed to concentrate and flow over the slope. Specific recommendations for erosion control are presented in the Erosion Control and Slope Protection Measures subsection of this report. Erosion Control and Slope Protection Measures The erosion hazard for the on -site soils is considered 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 or straw bales should be erected to prevent muddy water from leaving the site. Stockpiles should be covered with plastic sheeting during wet weather. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential of areas not stripped of vegetation should be low. Protection of the setback and steep slope areas should be performed as required by the City of Everett. Specifically, we recommend that the setback area and top of 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, and soil stockpiles. Trees should not be cut down or removed from the 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 Everett Municipal code. Any proposed development within the setback 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 slopes. NELSON GEOTECHNICAL ASSOCIATES, INC.