202 ALDER ST Geotech Report 2018-01-02 MF Import

, , Proposed View Ridge Subsurface Ezp[oration, Geologic Nazards, /nj"ilrration Potential, Elemeruary School Repfacement and Prelimiwry Geotechnical Engineenng Repon Evereu, Washingmn Preliminary Design Recommendmions ' planne�l finished grade with compacted structural fill. Subgrade preparation and selection, placen.ont, and compaction of structural fill should be performed under engineering-controlled , conditions in accordance with the project speci�ications. 9.4 Overexcavation/Stabilizatiun I ' Construction during extended wet weather periods could create the �ed to overexcavate ' exposed soils if they become disturbed and cannot be recompacted due to elevated moisture content and/or weather conditions. Even during dry weather periods, soft/wet soils, which may need to be overexcavated, may be encountered in some portions of the site. If ' overexcavation is necessary, it should be confirmed through continuous observation and testing by Associated Earth Sciences, Inc. (AESI). Soils that have become uns[able may require remedial measures in the form of one or more of the following: , 1. Drying and recompaction. Selective drying may be accomplished by scarifying or windrowing surficial material during extended periods of dry and warm weather. , 2. Removal of affected soils to expose a suitable beazing subgrade and replacement with compacted swcturaJ fill. ' 3. Mechanical stabilization with a coazse-crushed aggregate compacted into the subgrade, possibly in conjunction with a geotextile. ' 4. Soi1/cement admixture stabilization. , 9.5 Wet Weather Conditions ' If conswction proceeds during ar. extended we[ weather conswction period and the moisNre- sensitive site soils become wet, they will become unstable. Ti�c.efore, the bids for site grading operations should be based upon the time of year that construction will proceed. It is expected , that in wet conditions, additional soils may need to be removed and/or other stabilization methods used, such as a coarse crushed-rock working mat to develop a stable condition if silry subgrade soils are disturbed in Ihe presence of excess moisture. The severity of construction ' disturbance will be dependent, in part, on the precautions that are taken by the convactor to protect the moisture- and disturbance-sensitive site soils. If overexcavation is necessary, it should be confirmed through continuous observation and testing by a representative of our firm. ' 9.6 Temporary and Permanent Cut Slopes ' In our opinion, stable construction slopes should be the responsibiliry of the contractor and should be determined during construction. For estimating purposes, however, we anticipate ISep�embei 22. 20/0 ASSOCI�ITF,D F.ARTH SGENCES, MC. xwcnc Keimus�a r.o�rn:•swouzss,��wr Page 15 1