1304 80TH ST SW EVERETT SCHOOL DISTRICT 2018-01-02 MF Import

Subsatface Exploration and Everett Bus Facility Geotechnical Engineering Report Everett, ftshi2gon Design Recommendations lodgement till or new structural fill. An increase of one-third may be used for short-term seismic loading. The vault should not be founded on loose soils or existing fill. Perimeter footings should be a minimum of 12 inches. All footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above loose, organic, or existing uncontrolled fill soils. It should be noted that the area bounded by lines extending downward at II1:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM:D-1557. In addition, a 1.511:IV line extending down from any footing must not daylight as sloughing or raveling may eventually undermine the footing. Anticipated settlement of footings founded on the medium dense to dense lodgement till or approved structural fill placed over these deposits should be on the order of 1 inch or less. Ilowever, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this report. Snohomish County may require such inspections. 10.0 LATERAL WALL PRESSURES Backfill behind vault walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Tully restrained, horizontally backfilled, rigid walls, which cannot yield, should be designed for an equivalent fluid of 50 pounds per cubic foot (pct). If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. In accordance with the 2003 International Building Code (IBC), a seismic surcharge should be included in design of permanent retaining walls. A seismic surcharge represented by a rectangular pressure distribution of 8H psf(where H is the height of the wall) should be included for the at-rest loading conditions. The resultant of the seismic surcharge pressure can be assumed to act at the mid-height of the walls. The lateral pressures presented above are based on the conditions of a uniform backfill consisting of on-site recent alluvium, recessional outwash, or imported soils compacted to 90 percent of ASTM:D-1557. A higher degree of compaction is not recommended as this will increase the pressure acting on the walls. A lower compaction may result in settlement. Thus, the compaction level is critical and must be tested by our firm during placement. Surcharges from adjacent footings, heavy construction equipment, or sloping ground must be added to the above values. November 28, 2005 ASS'OCIAThl)EAR 771 SCIENCF.ti, INC. rrdd_Kraseoms-PmjMx1 6021KE1WP Page 10