3620 W MUKILTEO BLVD Geotech Report 2025-08-13

Geotechnical Engineering Evaluation Mukilteo Boulevard Development Everett,Washington March 31,2003 NGA File No.366503 Page 8 for importing all-weather material for fill,which could significantly raise earthwork costs. We therefore recommend that earthwork be conducted during the drier summer months. Even during the summer time, great care should be taken not to disturb wet subgrades under construction traffic. Surface water should be diverted around areas to be excavated. If earthwork is to be accomplished during wet weather, we recommend that a blanket of rock spans be placed in the planned access roadway. The thickness of the spall blanket should be based on soil conditions at the time the site is developed,and the performance under heavy equipment. We recommend using a minimum of a 1-foot thickness of spans in traffic areas for estimating additional wet weather costs. Wet weather construction may require increased overexcavation of wet material and importing all- Weather material for fill. Level benches a minimum of 4 feet in width should be created on ground inclining steeper than 20 percent that will receive fill. The benches should help key the new fill into the native material and reduce sliding potential. The level benches could be created as the fill is being placed: Temporary and Permanent Slopes Temporary cuts of up to 12 feet are anticipated for basement walls and detention vault construction. Temporary excavation stability is a function of many factors, such as the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface or ground water. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut-slope geometry. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations, since the contractor is continuously at the job site,able to observe the nature and condition of the cut slopes, and able to monitor the subsurface materials and ground water conditions encountered. This information is provided soley for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates Inc., assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the on-site soils be no steeper than 1.5 Horizontal :1 Vertical (1.5H:1V). If these inclinations are not feasible due to the proximity to existing NELSON GEOTECHNICAL ASSOCIATES INC EXHIBIT # L� PAGER OF2