2702 59TH ST SW 2024-07-05 - Laserfiche WebLink

Geotechnical Engineering Evaluation Miller Property Slope Stabilization Everett, Washington NGA File No. 1333322 July 1, 2022 Page 11 The repaired slope should be monitored on an on -going basis through visual inspections and monitoring the inclinometer casings, especially during the wet season for signs of instability. The drainage systems should also be monitored on a regular basis. Lawn clippings and any other debris should never be cast over the site slopes. Any future plans for structures near the slope or modifications to the slope should be specifically evaluated by NGA and approved by City of Everett. The soils encountered on this site are considered extremely moisture -sensitive and will disturb easily when wet. We recommend that if possible, repairs take place during periods of dry weather for safety and to keep costs and delays down. We recommend that NGA be retained to review final stabilization plans. We also recommend that NGA be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork and activities comply with plans and specifications. Erosion Control and Slope Protection Measures The erosion hazard for the on -site soils is 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 of the stabilization methods should be protected from erosion. Erosion control measures may include diverting surface water away from the top of slope by using silt fences and/or straw bales to prevent water from leaving the upper portion of the site and flowing over the slope. No material should be stockpiled on this site. Disturbed areas should be planted as soon as practical, and the vegetation should be maintained until it is established. This is discussed further in the Slope Improvements and Drainage subsection of this report. The erosion potential for areas not stripped of vegetation should be low to moderate. Protection of the steep slope areas should be performed as required by City of Everett. After the stabilization methods have been implemented, we recommend that the steep slope not be disturbed or modified through placement of any fill or removal of the existing vegetation. No additional material of any kind should be placed on the slope or be allowed to reach the slopes, 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 except as specifically recommended by NGA and approved by City of Everett. Replacement of vegetation on the slope should be performed in accordance with the City of Everett code. Any future proposed development within or near the steep slope area 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.