2000 TOWER ST ARTS AND SCIENCES BLDG 2018-01-02 MF Import

and shoring must comply with the provisions of Title 296 WAC, Part N, "Excavation, Trenching and Shoring" The excavations for first and second floor levels of the building will be completed primarily in dense to very dense glacial till deposits. The following sections summarize the general excavation recommendations. If conditions allow, the entire excavation for the proposed building may be accomplished using temporary cut slopes. However, depending on the final building layout and site constraints temporary shoring may also be needed. Temporary shoring appropriate for the soil conditions at the site may include soldier pile and timber lagging walls. Temporary - 'wining walls must account for groundwater seepage in their design and during construction. In the following sections we provide a brief description of soldier pile and timber lagging walls. Temporary Cut Slopes For planning purposes, temporary unsupported cut slopes more than 4 feet high for the first and second floor levels may be inclined at 3/4H:1 V maximum steepness within the dense to very dense glacial till. If significant seepage is present on the cut face f the dense to very dense till then the cut slopes may have to be flattened. However, temporary cuts sho•.-a be discussed with the gcotechnical engineer during final design development to evaluate suitable cut slope inclinations for the various portions of the excavation. Steeper cut slopes up to 1/2H:1 V are possible based on observations made by GcoEngineers during construction. The contractor should scale the cut slopes if I/2H:1 V maximum slopes are allowed. The above guidelines assume that surface loads such as traffic, construction equipment, stockpiles or building supplies will be kept away from the top of the cut slopes a sufficient distance so that the stability of the excavation is not affected. We recommend that this distance be at least' feet from the top of the cut for temporary cuts made at III: IV or flatter. Temporary cut slopes should be planned such that they do not encroach on a IHAV influence line projected down from the edges of nearby or planned foundation elements. New footings planned for the second floor level and in temporary cut slope areas for the basement should extend through wall backfill and be embedded in native soils. Water that enters the excavation must be collected and routed away from prepared subgrade areas. We expect that this may be accomplished by installing a system of drainage ditches and sumps along the toe of the cut slopes. Some sloughing and raveling of the cut slopes should be expected. Temporary covering, such as heavy plastic sheeting with appropriate ballast, should be used to protect these slopes during periods of wet weather. Surface water runoff from above cut slopes should be prevented from flowing over the slope face by using berms, drainage ditches, swales or other appropriate methods. If temporary cut slopes experience excessive sloughing or raveling during construction, it may become necessary to modify the cut slopes to maintain safe working conditions. Slopes experiencing problems can be flattened, regraded to add intermediate slope benches, or additional dewatering can be provided if the poor slope performance is related to groundwater seepage. 0) C, C U F '. F i n c c r s I I Filc Nc. 58364012.00/040204