MTI, an Atlas company, led this project consisting of 63 wind turbine locations, 6 alternative locations, and five alternative sub-station locations. This geotechnical investigation consisted of Phase II of a pre-existing wind farm. Overlying soils were assessed in the field and in the lab to determine in-situ dry density, soil Standard and Modified Proctors, consolidation properties, Atterberg limits and clay content, direct shear properties, collapsibility potential, moisture content, pH level, sodium sulfate chloride levels, California Bearing Ratio, and soil resistivity properties.
At depths generally varying between 1 to 9 feet in depth, basalt rock was cored for an additional 25 feet. Rock was assessed in the field and in the lab to determined core unit weight, compressive strength, L.A. Abrasion, sodium sulfate soundness, Rock Quality Designation, Rock Mass Rating, and seismic refraction (P and S-wave). In addition to borings, thirty-three test pits were advanced along the power collection lines to assess soil thermal conductivity for backfill material and identify potential basalt quarry locations to be used in construction of access roadway.
Foundation design recommendations including net allowable bearing capacity, skin friction, and subgrade modulus was provided for both substation shallow foundation and deep proprietary P & S pier foundation systems. Design recommendations for crane pad and all-weather access roadway were also provided.
Similar services were also provided for the following wind energy projects: Simco Road Wind Tower Project (two towers) in Elmore County, Idaho and Schwendiman Wind Tower Project (thirteen towers) in Iona, Idaho.