2505 57TH ST SW Geotech Report 2022-10-25

August 29, 2019 Mr. Jeff Davis G-4971 Page 6 A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads against the building foundations can be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter case, the foundations must be poured "neat" against the existing undisturbed soil or be backfilled with compacted structural fill. Our recommended parameters are as follows: - Passive Pressure (Lateral Resistance) 350 pcf, equivalent fluid weight, for structural fill or competent undisturbed native soil - Coefficient of Friction (Friction Factor) 0.35 for structural fill or competent undisturbed native soil Slab -on -Grade Floors Slab -on -grade floors should be constructed on a firm, unyielding subgrade. During preparation of the slab subgrade, any areas of the subgrade that have been disturbed by construction activity should be either re -compacted or excavated and replaced with compacted structural fill. We recommend that structural fill placed below slab -on -grade floors conform to the earthwork and grading recommendations provided in this report. To avoid moisture build-up on the subgrade, floor slabs should be placed on a capillary break, which is in turn placed on the prepared subgrade. The capillary break should consist of a layer, at least 6 inches thick, of free -draining crushed rock or gravel containing no fines and no more than five percent material finer than a No. 4 sieve. A vapor barrier should be placed over the capillary break to reduce upward transmission of water vapor through the slab, if such transmission is undesirable. Surface Drainage We recommend that storm water drainage from impervious areas be collected into one or more tight -line systems which convey the water to an approved discharge location. Storm water should not be permitted to develop into concentrated flows on the ground surface, because GEO Group Northwest, Inc.