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

strength in the deposit of soil so affected. In our opinion, the glacial tili soils at the site will not liquefy under the design earthquake. Earthwork Clearing and Grubbing Areas to be developed or graded should be cleared of surface and subsurFace deleterious matter including any debris, shrubs, trees and associated stumps and roots. Graded areas should be stripped of organic soils. Based on our observations, stripping depths on the order of 6 to 12 inches will be needed to remove organic topsoil materials and subsurface deleterious matter in most areas. Deeper zones of organic soils should be expected in areas of dense vegetation or where large root bulbs are located. The organic soils can be stockpiled and used later for landscaping purposes or may be spread over disturbed areas following completion of grading. If spread out, the organic strippings should be in a layer less than 1-foot-thick, should not be placed on slopes greater than 3H:1V and should be track-walked to a uniformly compacted condition. Materials that cannot be used for landscaping or protection of disturbed areas should be removed from the project site. Concrete debris will be encountered during site clearing and grading. Concrete debris should be removed from the site, unless approved to be crushed and recycled for use as backfill. Recommendations for recycled concrete are provided in the "Structural Fill"section below. Removal of Existing Fill Existing fill located within S feet of final siope grades and below key ways should be removed as described in the "Slope Construction and Regrading" section below. Existing fill should also be removed from below the control building and planned transformer pads. Based on our explorations anticipated depths of existing fill are summarized in Table 1 and are shown on the logs in Appendix A. Suitable existing fill may be reused as structural fill if properly moisture conditioned and compacted. Structural fill placed on the east slope should be benched into existing medium dense to dense till soils. Existing fill containing debris or rubble should not be used as structural fill and should be removed from the site. Subgrade Preparation Control Building We understand that the control building is currently planned to be constructed on shallow foundations near existing site grades. The existing fill soils located below the proposed control building should be removed from below the building and replaced with imported gravel borrow. The fill could be removed and replaced as part of the slope construction earthwork activities. The exposed subgrade should be evaluated during construction. Transformer Pads Loose fill up to 9.5 feet below grade was observed at the proposed location of the north transformer (Boring B-3). The transformer foundations should be founded on structural fill extending down to medium dense to dense native glacial soils. The existing fill should be removed and replaced as part of the earthwork activities for the proposed retaining wall. We anticipate that removal of existing fill under the GEOENGINEER� October24,2014 Page 6 Fle No.0482-027-02