4801 HARBOR LN 2018-01-02 MF Import

Geotechnical Engineering 1 ; ort Johnson Residence Addition Everett, Washington Foundation Considerations - Dwelling J-1280 2' February 2002 Page 6 Preliminary design information provided to us by Fred Baxter & Associates (5 February 2002 facsimile transmittal) indicates that perimeter foundation loads for the proposed dwelling addition will be on the order of 3 kips per lineal foot. In our opinion, the use of conventional foundations supported on at least medium dense native granular soils below the soft and loose native and fill soils is feasible from the geotechnical perspective. Foundations constructed to bear within the very loose to loose fill and native soils would be at risk of unacceptable settlement and displacement or undermining in the event of a landslide, in our opinion. Bearing Capaci The depths to at least medium dense native granular soils at the locations of the two explorations advanced for this study are summarized below. It should be noted that the depth to adequate bearing soils will vary across the footprint of the proposed addition. Summary of Depth to Foundation Bearing Soils Exploration Approximate Approximate Depth Approximate Ground Surface to Bearing Horizon Elevation of Bearing Elevation (feet)* feet Horizon feet B-1 93 13 80 HA-1 95 4 91 • Elevations are site -specific and were measured by hand level methods relative to an arbitrary elevation reference point established by ZZA. Elevations do not reflect actual survey. Continucus and column foundations bearing within at least medium dense native granular soils above may be designed for an allowable bearing capacity of 2,500 pounds per square foot (psf). A one-third increase of these bearing pressures may be used for short-term wind or seismic loading. Higher allowable bearing pressures could be achieved if the foundations are constructed to bear within the denser soils at depth. We recommend that the foundations be constructed with at least 18 inches of embedment in the recommended bearing stratum, and at least 18 inches below the lowest adjacent grade. Foundation dimensions should be determined in accordance with UBC criteria once the project structural engineer has determined loading. Foundation Settlement Total settlement of foundations utilizing the 2,500 psf allowable bearing pressure may approach at ;'4-inch, with differential settlement approaching one-half of the total settlement. The potential for foundation settlement can be reduced by placing foundation concrete on non - yielding surfaces that are free of slough, debris, standing water, or deleterious materials. A thin lean concrete "mud mat", or a lift of compacted crushed rock, placed above a moisture sensitive foundation subgrade can reduce the potential for disturbance during form and reinforcing steel installation. We recommend that the condition of foundation subgrades be evaluated by an Zipper Zeman Associates, Inc. 1890533rd AVMue Wat. Suite 117 Lynnwnad. Washington 98036 (425)771.3304