1921 W MUKILTEO BLVD 2018-01-02 MF Import

Preliminary Geotechnical Engineering Evaluation 1919 Mukilteo Boulevard October 20, 2005 NGA File No. 718805 Page 8 Site Preparation and Grading Final grading plans were not available at the time this report was prepared. We do not anticipate large scale grading for this project; however, it is not known whether the existing basement will be filled, or incorporated into the new residence. After erosion control measures are implemented, site preparation should consist of stripping any topsoil or loose soils to expose medium dense or better natives material 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. Only very limited amounts of material should be stockpiled on this site. Stockpiles should be kept away from the top of the steep slope and setback areas. Stockpiles should be covered with plastic. if the ground surface after 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 reworked to structural fill specifications or be over -excavated and replaced with structural fill or rock spalls. If significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed and away from the steep slope, and the exposed subgrades should b,: maintained in a semi -dry condition. If wui conditions are encountered, alternative site stripping and grading techniques might be necessary. These could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted as this could cause further subgrade disturbance. In wet conditions it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around prepared subgrade. Shallow groundwater, if encountered, should be intercepted with cut off drains and routed outside of the planned grading area, or the groundwater should be controlled with sump -pumps or dewatering systems. Structure Setbacks Uncertainties related to building along the top of steep slopes are typically addressed by the use of building setbacks. The purpose of the setback is to establish a "buffer zone" between the structure and NELSON GEOTECHNICAL ASSOCIATES, INC.