2721 WETMORE AVE MARQUEE APARTMENTS Geotech Report 2023-06-22

Subsurface Exploration, Geologic Hazard,and 2721 Wetmore Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations As required by the City of Everett, a representative from our firm should observe the subgrades and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. 10.0 FOUNDATIONS Conventional spread footings and column pads, or a mat foundation may be used for building support when founded either directly on the undisturbed, very dense natural sediments, or on a thin crushed rock or CDF mat placed over these materials as discussed subsequently in this section. We recommend that an allowable preliminary foundation soil bearing pressure of 12,000 pounds per square foot (psf) be utilized for design purposes, including both dead and live loads. A mat foundation can be designed assuming a modulus of subgrade reaction of 150 pounds per cubic inch (pci). Foundation areas should be deepened, if necessary, to expose sediments suitable for the support of the recommended bearing pressures. An increase of one-third may be used for short-term wind or seismic loading. We should evaluate the mat foundation soil loading when subject to combined dead and live loads and overturning moments. All footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above loose, organic, or fill soils. Given the high-bearing pressures, footings should not be constructed on fill materials other than a thin (6 inches or less) rock working mat or CDF, as discussed subsequently. It should be noted that the area bounded by lines extending downward at 1H:1V from any footing must not intersect another footing or filled area. In addition, a 1.5H: 1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded on the very dense natural sediments should be on the order of 1 inch or less with differential settlements of approximately one-half of the total. Differential movement from the center to the edge of a mat foundation could approach 1 inch. Most of this movement should occur during initial dead load applications. However, disturbed soil not removed from footing or mat excavations prior to concrete placement could result in increased settlements. All footing areas should be observed 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. Such observation will be required by the City of Everett as part of special inspection requirements. A perimeter foundation May 28,2019 ASSOCIATED EARTH SCIENCES,INC. FSM/Id 190168E001-2 Projects\20190168\KE\WP Page 10