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

� TABlE 3. INPUT FOR CAISSON COMPUTER PROGRAM Dry Density(Buoyant Coefficient of Rankine Coefficient Bottom of Soil of Lateral Earth Soii Layer Layer t Density below Internal Groundwater) Friction Pressure (feet) (pcf) (deg) Ka KP* Structural Fill properly Placed and See Table 1 125 34 0.26 3.54 Compacted (non-cohesive) Loose to Medium Dense Native Soil See Table 1 120 28 0.33 2.46 (non-cohesive) Medium Dense to Dense Weathered See Table 1 125 36 0.24 4.05 Glacial Till (non-cohesive) Dense Glacially Consolidated Soils See Table 1 130 38 0.22 4.67 (non-cohesive) Notes: t Assumes topsoil and deleterious materials are stripped from site in accordance with our recommendations x Passive coefficient includes a factor of safety of 1.5 $Deepest exploration extended to a depth of 18�/z feet for 115kV yard and 281/2 feet for 230 kV yard If the drilled piers extend below our deepest exploration near the structure, temporary casing or drilling fluid may be required if the piers extend into cleaner sandy zones or into groundwater. We recommend that the drilled pier foundation excavations be observed by the Geotechnical Engineer. Retaining Walls Cast-in-place concrete cantilever walls are planned between the 115kV and 230kV substation levels and along the south side of the 230kV yard adjacent to Scenic Drive. A MSE wall/slope may be constructed in the northwest corner of the site. The walls around the lower 230kV yard will support cuts up to about 10 feet and fill heights up to about 5 feet. The MSE wall is planned to be about 10 feet high and will support new fill. It may be desirable to use a vegetated reinforced slope/wall in the northwest area along the Interurban trail. The following sections provide recommendations for reinforced concrete cantilever wails, MSE �valls, soldier pile walls, and gravity walls. Rockeries, which are not intended as structural retaining walis, may be appropriate for some of the shorter cut sections or in other areas on the site, and are discussed in the "Rockeries"section. Reinforced Concrete Cantilever Walls Reinforced concrete cantilever walls are retaining structures that are economical for walls up to about 10 to 15 feet in height that use readily-available construction equipment. Concrete retaining walls above about 15 feet become less economical than other retaining systems because they require large amounts �f reinforcing steel and concrete to support the earth pressures of the retained soil. GEOENGINEER� October24,2014 Page 16 . Rie No.0482-027-02