4110 CLIFF DR 2022-01-26 - Laserfiche WebLink

Geotechnical Engineering Evaluation NGA File No. 1021318 Cliff Drive Short Plat Residence Development February 2, 2018 Everett, Washington Page 6 Erosion Control and Slope Protection Measures The erosion hazard for the on -site soils are listed as low to moderate 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. 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 to moderate. Protection of the site slopes should be performed as required by the City of Everett. Specifically, we recommend that the site slopes not be disturbed or modified through placement of any additional fill or removal of the existing vegetation. No additional material of any kind should be placed on either slope or be allowed to reach the slopes, such as excavation spoils, lawn clippings, and other yard waste, trash, and soil stockpiles. Vegetation should not be removed from the slopes outside the proposed development area. Replacement of vegetation should be performed in accordance with City of Everett code. Under no circumstances should water be allowed to concentrate on the slopes. The clearing of vegetation within the area of the proposed residential developments should not affect slope stability, provided the disturbed areas outside the building are revegetated as soon as practical and protected from erosion. In areas that are disturbed during or after construction, planting, hydro seeding, and/or straw mulching are effective ways to minimize erosion and allow vegetation to be re-established rapidly. 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. Based on our observations, we anticipate stripping depths of one to three feet, depending on the specific locations. However, additional stripping may be required if areas of deeper undocumented fill and/or loose soil are encountered in unexplored areas of the site. 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 NELSON GEOTECHN/CAL ASSOCIATES, INC.