1010 N BROADWAY EVCC 2018-01-01 MF Import

PROPOSED LIBERTY HALL,EVERETT COMMUNITY COLLEGE Everett,Washington deposits within Zones II through IV, and/or (3) a 2-foot gravel pad following ground improvement using GeoPiersTM within Zones III and IV. The allowable bearing pressures presented in each section below apply to the total dead and long-term live loads and may be increased up to one-third for short-term live loads such as wind or seismic forces. The ddsign frost depth for the Puget Sound area is 12 inches; therefore, we recommend that exterior footings for the building be founded at least 18 inches below lowest adjacent finished grade. Interior footings should be founded at least 12 inches below bottom of slab or adjacent finished grade. For shallow foundation support, we recommend widths of at least 24 and 36 inches, respectively, for continuous wall and isolated column footings supporting the proposed building. Foundation Design-Zone I For foundations bearing on competent undisturbed dense to very dense glacial soils within Zone I, .the foundations may be designed using an allowable soil bearing pressure of 6,000 pounds per square foot(psf)for isolated spread footings and continuous footings. The depth to dense glacial soils is summarized in Table 1. If existing fill,compressible silt or clay,or unsuitable native soil are observed at the foundation bearing elevation for footings designed for 6,000 psf bearing pressure, we recommend that the contractor remove the material and backfill with lean concrete or control density fill (CDF) having a design strength of at least 200 pounds per square inch (psi). If the foundations within Zone I are designed for 4,000 psf or lower,the overexcavation (if required) may be backfilled with properly compacted imported gravel borrow. Partial Overexcavation and Replacement-Zones II through IV Supporting the building on shallow spread footings will require removing the upper portion of undocumented fill and compressible silt/clay soils from below the footings within Zones II through IV and replacing these materials with properly compacted imported structural fill. This method of partial overexcavation and replacement with structural fill will mitigate the risk associated with excessive settlement under the building. We recommend that the building foundations be overexcavated in Zones II through IV as described in Table 3 below and shown in Figure 3. The lightly loaded perimeter footings should be overexcavated by at least 11 feet. The concrete slabs-on-grade should also be supported on at least a 1.5 foot thick pad of structural fill below the capillary break layer. The overexcavated zones below the building foundations should be backfilled with imported structural fill such as Gravel Borrow per WSDOT Standard Specification 9-03.14. Removal of the existing fill and silt/clay soils should extend beyond the edges of the building foundations a distance equal to the depth of the excavation below planned foundations. The overexcavation can be neat-cut below the footing if lean concrete or CDF is used as backfill. Page 12 I June 10,2010 I GeoEngineers,Inc. File No.5836.010.00