Southline Transmission Project

The Southline Transmission Project is a proposed transmission line designed to collect and transmit electricity across southern New Mexico and southern Arizona. The project will consist of two segments:

  • A new approximately 210-mile, 345-kilovolt double-circuit transmission line between the existing substations at Afton, New Mexico, and Apache, Arizona (“New Build Segment”).
  • Upgrade approximately 60 miles of WAPA’s existing transmission lines between the Vail and Apache substations in Arizona from a 115-kV line (“Upgrade Segment”). This upgrade would provide about 1,000 megawatts of capacity.

WAPA’s October 2023 news release on Southline is available on WAPA’s website here.

For the U.S. Department of Energy’s Transmission Facilitation Program October 2023 announcement regarding Southline, see Biden-Harris Administration Announces $1.3 Billion to Build Out Nation’s Electric Transmission and Releases New Study Identifying Critical Grid Needs.

Vail-Tortolita Transmission Project

In 2022, WAPA and Tucson Electric Power (TEP) announced a joint participation agreement to rebuild the westernmost 64 miles of the Southline Project. TEP purchased development rights from Southline, LLC, in 2021 for the project’s western portion.

The project runs through Tucson, Arizona, between the Nogales and Saguaro substations, which are adjacent to TEP’s Vail and Tortolita substations. The Vail to Tortolita Project consists of upgrading WAPA’s existing single-circuit 115-kV line and replacing it with a double-circuit 230-kV line. WAPA will operate one 230-kV circuit and TEP the other. Existing wood pole structures from the 1950s will be replaced with steel monopoles.

WAPA is in the process of preparing a Supplemental Analysis (SA) [DOE/EIS-0474-SA-1] to evaluate the Final EIS [DOE/EIS-0474]. The SA will analyze the changes to the portion of the Southline Project that is now the Vail-Tortolita Project. The SA is expected to be available for public review by summer 2024.

Environmental review process

WAPA served as a joint lead agency with the Bureau of Land Management in preparing the environmental impact statement, or EIS, for the project (DOE/EIS-0474).

Project documents:

Final Environmental Impact Statement DOE/EIS-0474)

Record of Decision

Other project documents

Contact information

For project inquiries, please contact:
Angela Murphy
Project Coordinator, Transmission Asset Planning
Western Area Power Administration, Desert Southwest Region
Phone: (702) 308-1665

Last modified on May 17th, 2024