Project Description

Location:   Kern County, California
Installed Capacity: 1,346.45 MW
Construction Cost: $500,000,000+
Year Commissioned:   2010 – 2014

The Alta Wind Energy Center, located near Mojave in Kern County, California, is within one of the largest concentrations of wind farms in the world. Phases 2 through 11 of this project included construction of over 450 wind turbine generators. The Alta Wind Energy Center provides approximately 30 percent of California’s wind-generated electrical power.

RRC was involved with numerous aspects and phases of the Alta project.

RRC’s geotechnical services included conventional soil borings, continuous rock coring, in-situ geophysical surveys, geological hazard studies, slope stability evaluations, and geotechnical engineering/analysis. Collapsible cohesionless soils were encountered in our investigations, requiring remediation measures to reduce the risk of hydro-consolidation at some turbine sites. Portions of the project site are located within the California Alquist-Priolo (AP) Earthquake Fault Zone; therefore, geological fault investigation was conducted to establish appropriate setback distances from active traces of Garlock Fault. In-situ and laboratory thermal resistivity testing was conducted for design of underground electrical cables.

RRC provided extensive foundation designs for the development based upon various configurations of GE and Vestas turbines. Challenges to the structural design included design for high strength tower versions for seismically controlled locations and a standard tower versions for extreme wind-controlled locations. Adding to the challenge, many foundation sites also required coordination of the design for scour protection as well as measures to protect the subgrade against hydro-consolidation concerns.

As with all projects, RRC provided the most economical design to realize maximum cost savings over the project as well as construction support to keep the project on schedule.