Developing America’s Next-Generation Infrastructure to Power Our Future

Southline Transmission Project

Grid United and Black Forest Partners are co-developing Southline Transmission Project (“Southline”), an approximately 280-mile, double-circuit, high-voltage transmission line and associated substation facilities.

Southline will ultimately connect the electrical transmission systems of the El Paso and Tucson areas in two phases, running from Grant County, NM, to Pima County, AZ, then Grant County, NM, to Dona Ana County, NM. This includes a new transmission line between the Afton substation west of Las Cruces, New Mexico, and the Apache substation in Willcox, Arizona, as well as the upgrade of a Western Area Power Administration transmission line between the Apache substation and Vail substation east of Tucson, Arizona. The design provides the capability to transport power bidirectionally and will enable electricity generated in the Desert Southwest to reach key markets while improving the grid reliability of the region.

Southline has been reviewed under the National Environmental Policy Act and has received federal and state permits.

Benefits

  • Enhancing grid reliability and resiliency in the Desert Southwest, making the power system less vulnerable to price volatility and extreme weather events.
  • Minimizing land and resource impacts by routing along existing infrastructure and upgrading existing transmission lines where feasible.
  • Connecting regions with a variety of energy generation. This allows users of the line to access power in different locations and times that may have better pricing for consumers.
  • Creating hundreds of high-quality construction-related jobs during project construction.
  • Investing approximately $4 million dollars directly in local communities through donations, sponsorships, and partnerships with local organizations.

Benefits

New tax revenue for local governments, communities, and schools: $100 million+

Sponsorships and Donations for local communities: $4 million+

Construction Jobs: 800+

Indirect and induced economic benefits across New Mexico and Arizona: $1 billion+

Enhanced grid reliability and resiliency in the Desert Southwest ➔ a power system that is less vulnerable to price volatility and extreme weather events

Improved interregional transmission ➔ development of new energy generation projects in New Mexico driving hundred of millions in new investment

Routing along existing infrastructure and upgrading existing transmission lines where feasible ➔ minimal impacts to land and resources

Project Location

Extending approximately 280 miles, Southline will ultimately connect the electrical transmission systems of the El Paso and Tucson areas in two phases, running from Pima County, AZ, to Grant County, NM (Phase 1), then on to Dona Ana County, NM (Phase 2). Southline will be an outlet for abundant generation by providing access to new markets for power producers and allowing the export of power during periods of low demand.

Project Schedule

Southline successfully completed an in-depth, multi-year federal and state regulatory process through which major state and federal permits have been obtained. Southline is in the final stages of development, which includes completing detailed engineering, performing pre-construction environmental surveys, and finalizing commercial arrangements.

Southline’s Final Environmental Impact Statement was published in October 2015. The Bureau of Land Management and Western Area Power Administration Records of Decision (RODs) were published in April 2016. The Arizona and New Mexico state siting processes were completed in February 2017 and August 2017, respectively.

Southline expects to begin construction in early 2026. The first phase could be operational by 2028, with the full project online by 2029.

  • Phase 1: Pima County, AZ, to Grant County, NM
  • Phase 2: Grant County, NM, to Dona Ana County, NM
2021

64 miles of Southline sold to Tucson Electric Power (Vail to Tortolita)

2021
2022

Grid United’s Investment in Southline’s remaining 280 miles

2022
2025

Finalized Engineering Design, Private Land Acquired

2025
2026

Bureau of Land Management issues Notice to Proceed, Construction: Staging, Right-of-Way Preparation, and Construction

2026
2028

Commercial Operations of Phase 1

2028
2029

Commercial Operations of Phase 2

2029

Landowner Relations

Our relationships with landowners and communities are at the core of everything we do. Southline worked collaboratively with local landowners to acquire easements for the transmission line and to ensure that land surveys were conducted with respect for private property rights. Southline commits to continuing this collaborative approach beyond development and through construction.