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

1 , Proposed Vew R�dge Subsurfare Erpforation, Geologic Naards, lnfil�rWion Po�ential, Elememary Schoo!Replacement and Preliminary Georerhnical Engineering Report £ve�ett, Washington Prefiminary Desrgn Recommendmions , [hat temporary, unsupported cut slopes in the existing fill can be made at a maximum slope of I.SH:iV (HorizontaL•Vertical) or flatter. Temporary slopes in unsamrated advance outwash , may be planned at 1H:1V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusied in the field. If ground water seepage is encountered in cut slopes, or if surface water is not routed away from temporary cut ' slope faces, Flatter slopes will be requ'ved. In addition, WISHA/OSHA regulations should be followed at all times. Permanent cut and swctural fill slopes that are not intended to be ' exposed to surface water sho�ld be designed at inclinations of 2H:1V or fla[ter. All permanent cut or fill slopes should be compacted to at least 95 percent of the modified Proctor maximum dry densiry, as determined by ASTM:D 1557, and the slopes should be protected from erosion ' by sheet plastic until vegetation cover can be established during favorable weather. 9.7 Frozen Subgrades ' If earthwork takes place during freezing conditions, ail exposed subgrades should be a►lowed to thaw and then be recompacted prior to placing subsequent lifts of structural fill or foundation ' components. Alternanvely, the frozen material could be stripped from the subgrade to reveal unfrozen soil prior to placing subsequent lif�s of fill or foundation components. The frozen soil should not be reused as structural fill until allow�d to thaw and adjusted to the proper ' moisture content, which may not be possible during winter months. , ]0.0 STRUCTURAL FILL ' AI1 references to swcturaf fill in this report refer to subgrade preparation, fill type and placement, and compaction of materials, as discussed in rhis section. If a percentage of compaction is specified under another section of this report, the value given in that section ' should be used. Aker stripping, planned excavation, and any required overexcavation have been performed to ' the satisfaction of the geotechnical engineer, the upper 12 inches of exposed ground in areas to receive fill should be recompacted to 90 percent of the modified Procror maximum density , using ASTM:D 1557 as the standard. If the subgrade contains silty soils and too much moisture, adequate recompaction may be difficult or impossible to obtain, and should probably not be attempted. 1n lieu of recompaction, the area to receive fill should be blanketed with ' washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of ' the free-draining layer by silt migration from below. ' Septemlier 22, 20/0 �� ASSOGATF,D F_ARTH SC/ENCF.S. /NG �, 9WG/!b-KF/�A7ZSSA1 r.��.�r�zaoozssiKF�wr Page 16 � '