1707 SCENIC DR SNO CO PUD Geotech Report 2022-10-25

Perman�nt Sio�es ■ Permanent cut and fill slopes should be constructed no steeper than 2H:1V(horizontal:vertical). ■ All topsoil, fill, and looser native soils on existing slopes where fill will be placed should be removed to expose medium dense to dense glacial soils. ■ Structural fill placed on existing slopes should be benched into the slope (see "Slope Construction and Regrading"below). Slope Construction and Regrading Existing fill located within the outer 8 feet (horizontal distance) from finished grade of new or regraded fill slopes should be removed and replaced with structural fill. The bottom of the fill zone should be keyed into the existing soils by at least 3 feet below the lowest adjacent grade. The key should be at least 6 feet wide. The structural fill material should be benched at least 5 feet into the existing slopes. Temporapy Cut Slo�es Temporary cut slopes should be cut no steeper than 1.5H:1V in fill and loose to medium dense native weathered till and 1H:1V in dense to very dense native glacial till. Con�rol Building The proposed building may be supported on shallow spread foundations bearing on structural fill consisting of imported gravel borrow extending down to medium dense to dense glacial till. Removal of existing fill soils is anticipated to require excavation depths of approximately 5 to 9 feet below existing site grades below the control building. The foundation design may be based on an allowable bearing value of 3,000 pounds per square foot(psf)for properly supported footings. Concrete slabs-on-grade should be supported on a 4-inch-thick capillary break layer overlying structural fill extending down to medium dense to dense glacial till. A subgrade modulus of 100 pounds per cubic inch (pci) may be used for design of the slab-on-grade, if properly supported. Footing drains should be incorporated in the design of the building foundation. N1at Foundations Equipment, such as the transformers, may be supported on mat foundations founded on structural fill extending down to competent native glacial till. Mat foundations may be designed with an allowable bearing value of 3,000 psf when supported on properly placed and compacted structural fill. A subgrade modulus of 75 pounds pci may be used for the design of mat foundations supported on at least 3 feet of structural fill. Due to the existing sloping ground condition under the planned northern transformer, we recommend that all existing fill and otherwise unsuitable soil be removed from below the mat foundation in this area (boring B-3). The slope in this area consists of undocumented fill extendingto depths of up to 9.5 feet. We recommend that existing fill be removed beyond the edges of the mat foundation by the depth of the excavation. We anticipate that the future south transformer pad will require a shallower excavation to remove existing fill soils. GEOENGINEER� October24,2014 Page ES-2 Fle No.04S2-027-02