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�i <br /> ( Subsurface Fxpbration, Geobgic Hauud, and <br /> Sno-lslt SkilLs Center Addition Preliminary Geottchnical Engintering Report <br /> Everett Washingron Preliminary Design Recomrnendorivns <br /> Iretaining wall. Rockeries should not be used to fxa ftlls greater than 4 feet in thickness unless <br /> the fills aze reinforced. <br /> I9.2 Temporarv Cut Sloves <br /> IIn ow opinion, stable consuuction slopes s6ould be the responsibility of the conuactor and <br /> should be determined during construction. For estimacing purposes, however, we anticipate <br /> that temporary, unsupported cut slopes in the fill can be made at a maximum slope of 1.SH:1V <br /> (Horizontal:Verticai) or flatter wlrile unsupported cuu in the lodgement till can be made at a <br /> maximum slope of IH:1V. As is typical wit6 earthwork operations, some sloughing and <br /> � raveling may occur, and cut slopes may have to be adjusted in the field. If ground water <br /> � seepage is encountered in cut slopes, or if surface water is not routed away f:om temporary cut <br /> slope faces, flatter slopes will be required. In addition, WISHA/OSHA regulations should be <br /> Ifollowed at all times. <br /> 93 Site Disturbance <br /> � <br /> ' Some of the on-site soils contain a high percentage of fine-grained material, which makes them <br /> Imoisture-sensitive and subject to disturbance when wet. Most of the shallow soils encountered <br /> � in our explorations were judged to be at or slighdy over their optimum moisture content for <br /> compaction at the time of our study. The contractor must use care during site preparation and <br /> I excavation operations so that the underlying soils aze not softened, particulazly during wet <br /> weather conditions. If disturbance occurs, the softened soils should be removed and the azea <br /> brought to grade with structural fill. Because of the moisture-sensitive nature of the soils, we <br /> I anticipate that wet weather construction would significantly increase the earthwork costs over <br /> dry weather coastruction. <br /> � <br /> 10.0 STRUCTURAL FILL <br /> �, Structural fill may be necessazy to establish desired grades and for utility trench backfill. All <br /> references to structural fill in this report refer to subgrade prepazation, fill type, placement, <br /> , and compaction of materials, as discussed in this sectinn. In those azeas where existing <br /> unconvolled fill is present, we recommend that it be removed and, where suitable, set aside for <br /> reuse. Our recommendations for the placement of swctural fill aze presented in the following <br /> sections. <br /> I <br /> 10.1 Fill Placement <br /> IAfter stripping, planned excavation, and any requ'ved overexcavation has been performed to <br /> the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inc6es of <br /> � exposed ground should be recompacted to at least 90 percent of the modified Proctor mazimum <br /> i <br /> June ll, 2008 ASSOCGTED F.1RTH SCIENCES,INC. <br /> iEGiW-EE08�173A5-AoJeaxISPOB01131EEIWP Page 11 � <br />