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 240-mile, 345-kilovolt double-circuit transmission line between the existing substations at Afton, New Mexico, and Apache, Arizona.
  • Upgrade of about 120 miles of WAPA’s existing transmission lines between the Apache and Saguaro substations in Arizona from a 115-kV line to a 230-kV double-circuit line.
    This upgrade would provide up to 1,000 megawatts of capacity.


Jan. 31, 2018: WAPA, Southline sign participation agreement

​WAPA’s Desert Southwest Region and Southline Transmission, LLC, sig​ned a participation agreement committing both parties to developing the Southline Transmission Project–a new critical energy infrastructure effort that will support grid reliability and facilitate renewable energy development in the region. Under the participation agreement, the organizations agreed to a commercial framework that allocates transmission rights on each segment of the project. ​


Since 2012, WAPA has sought input from its transmission customers to define if and how WAPA will participate in this project.

Customer comments: Transmission customers can send questions and comments about WAPA’s proposed involvement in this project to:


WAPA was a joint lead agency with the Bureau of Land Management in preparing the environmental impact statement, or EIS, for the project, which started in April 2012. Based on the Final EIS released in November 2015, both agencies issued separate Records of Decision, or RODs for short. On April 5, 2016, WAPA issued its ROD​ (pdf).

All other environmental review project documents, about the EIS are available through BLM’s Southline Transmission Project web page.


For more information about the project and the EIS, visit:

Last modified on July 5th, 2023