2710 14TH ST BLDG A Geotech Report 2023-12-29

■ Shallow Foundations on Glaciolacustrine Deposits: For foundations bearing on competent undisturbed glaciolacustrine deposits, foundations may be designed using an allowable soil bearing pressure of 4,000 psf for isolated spread footings and continuous footings. ■ Shallow Foundations on Structural Fill: For foundations bearing on properly placed and compacted structural fill extending down to dense to very dense glacial soils, foundations may be designed using an allowable soil bearing pressure of 3,000 psf for isolated spread footings and continuous footings. The allowable bearing pressures presented above 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. Overexcavated areas must be backfilled with: (1) CDF having a design strength of at least 200 pounds per square inch (psi) where 6,000 psf bearing pressures are used or, (2) structural fill consisting of suitable on -site soils or imported gravel borrow where 3,000 and 4,000 psf is used, respectively. Where structural fill is placed below footings, the fill should extend beyond the edges of the foundations by the depth of the overexcavation. All footings near below -grade walls should be embedded to a depth that is at least below a 1H:1V (horizontal to vertical) line projected up from the bottom of the closest section of wall, otherwise the below -grade walls need to be designed for lateral loads from the footings. 4.2.2. Settlement Post -construction settlement of shallow footings supported on native soils or on properly compacted structural fill as recommended above should be limited to less than 1 inch, and differential settlement between comparably loaded column footings or along a 25-foot section of continuous wall footing should be less than 1/2 inch. We expect most of the footing settlements will occur as loads are applied. Loose or disturbed soils not removed from footing excavations prior to placing concrete will result in additional settlement. 4.2.3. Lateral Resistance Lateral foundation loads may be resisted by passive resistance on the sides of the footings and by friction on the base of the footings. Frictional resistance may be computed using a coefficient of friction of 0.4 applied to vertical dead -load forces. Passive resistance may be computed using an equivalent fluid density of 350 pcf. The allowable passive resistance is for horizontal soil conditions in front of the footing and is applicable provided that the footings are surrounded by structural fill or constructed neat against native glacial soils. The structural fill should be compacted to at least 95 percent of the maximum dry density (MDD) determined in accordance with ASTM D 1557. Passive pressure resistance should be calculated from the bottom of adjacent floor slabs or below a depth of 1 foot where the adjacent area is unprotected, as appropriate. The allowable frictional resistance and passive resistance values presented above include a factor of safety of about 1.5. If soils adjacent to footings are disturbed during construction, the disturbed soils must be recompacted, otherwise the lateral passive resistance value must be reduced. GMENGINEERs October 30, 2019 Page 7 ' File No. 21288.00200