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

� This type of retaining structure is relatively settlement-sensitive and suitable foundation support is important. We anticipate that some overexcavation or compaction of the native soils may be required to achieve suitable foundation support, and there may be some areas where this wall type is not suitable due to settlement-prone soils. Construction of this type of wall will require a foundation width approximately equal to 1h of the wall height. If used this type of wall would require temporary cut slopes to construct the walls and the excavated soil may not be suitable for reuse as structural fill depending to the weather conditions and conditioning of the soil. We recommend the following parameters for design purposes: � For conventional concrete walls, use an equivalent fluid density of 35 pcf to calculate active earth pressures acting on the wali; this assumes a level back-slope. For a 2H:1V back-slope, use an equivalent fluid density of 55 pcf to calculate active pressures acting on the wall. For intermediate back-slope inclinations, interpolation can be used between these two values. TrafFic surcharges should be incorporated by using a rectangular earth pressure of 65 psf. ■ Use a rectangular seismic pressure acting over the height of the wall equal to 6H psf, where H is the height of the wall in feet; this assumes a level back-slope. For a 2H:1V back-slope, use a rectangular seismic pressure equal to 14H psf. For intermediate back-slope inclinations, interpolation can be used between these two values. e For footings supported on native glacially consolidated soils or structural fill, use an allowable average soil bearing value of 3,000 psf, with a maximum toe bearing pressure of 4,500 psf. These allowable soil bearing values apply to the total oi dead and long-term live loads and may be increased by up to one-third for seismic loads. ■ Lateral wall loads can be resisted by a combination of friction between the footing and the supporting soil, and by the passive lateral resistance of the soil surrounding the embedded portions of the footings. A coefficient of friction between concrete and soil of 0.45 and a passive lateral pressure of 350 psf may be used for design. We recommend that the upper 2 feet of passive resistance be ignored. The friction coefficient and passive lateral resistance are allowable values and include a factor of safety of 1.5. ■ For level fore-slope, assume an embedment depth of H/20, and for a 11/2H:1V fore-slope, assume an embedment depth of H/5. ■ Drainage measures should be installed as discussed for the Control Building. Mechanically Stabilized Earth Wails MSE walls can be used to retain fill to accommodate grade changes. A MSE wall is a retention system that incorporates reinforcing materials such as metal strips, or geosynthetic soil reinforcement materials such as geogrids that are attached to wall facing elements and embedded in granular fill behind the wall elements. The reinforcing material interacts with compacted granular fill material behind the wall to provide resistance to horizontal loads by creating a gravity structure. MSE walls are typically much less settlement sensitive than reinforced concrete cantilever walls. MSE walls can be constructed with concave and convex face curves. A variety of architectural finishes are available for the wall facing elements (e.g. Keystone, Lock-block, Ultra-block, SierraScape�, Allen Block, etc.). Some wall systems allow for the use of geotextiles/geogrids, which may not attached directly to the facing elements. We recommend that a structurally reinforced slope also be considered for the planned grade change in the GEOENGINEER� October24,2014 Page 17 Fle No.0482-027-02