1010 N BROADWAY EVCC 2018-01-01 MF Import

PROPOSED LIBERTY HALL,EVERETT COMMUNITY COLLEGE^-- Everett,Washington flattened. However, temporary cuts should be discussed with the geotechnical engineer during final design development to evaluate suitable cut slope inclinations for the various portions of the excavation. 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 5 feet from the top of the cut for temporary cuts made at 1.5H:1V or flatter. Temporary cut slopes should be planned such that they do not encroach on a 1H:1V influence line projected down from the edges of nearby or planned foundation elements. Water entering excavations 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. Foundation Support • The site contains variable ground conditions that include fill and compressible silt/clay soils. These soils may induce settlement under building loads under certain conditions. Static loads from the building will compress and subsequently induce settlement of the native silt/clay soils and the looser fill soils. Settlements in the native silt/clay soils are a significant concern at the site. Based on the proposed building layout and finished floor of Elevation 84 feet,dense glacially consolidated soils will underlay the west end of the building and up to 12 feet of compressible native silt/clay and fill soils underlay the east end of the building. Due to the variable ground conditions under the building,the building footprint is divided into four zones as shown in Figure 3. We estimate that up to 4 inches of settlement may occur where heavily-loaded column footings are located over these compressible silt/clay soils, if not properly mitigated. To mitigate potentially damaging settlement we recommend that the building foundations be supported either on a pad of imported structural fill, aggregate piers, small diameter pipe piles, or a combination of these systems as described below. Shallow Foundations Shallow Foundation Design We anticipate that it will be most economical to support the building on conventional spread footings supported on (1)dense to very dense native glacially consolidated soils within Zone 1, and (2) a structural fill pad following partial overexcavation and removal of compressible silt/clay GEOENGINEERLO June 10,2010 Page 11 File No.5836-010-00