Grid United and Black Forest Partners are co-developing Southline. Black Forest Partners initiated development of the Southline Transmission Project in 2008, and Grid United joined the development of the project in 2022.
Black Forest Partners performed detailed surveys of routes, environmental, and cultural resources, conducted stakeholder and one-on-one meetings, held regulatory agency consultations, and filed major state and federal regulatory permits. The Black Forest team has 30 years of investment and development expertise, ties to the local region, and a deep commitment to leveraging existing assets to advance infrastructure that maximizes benefits and minimizes impacts.
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 constructed in phases to address regional transmission capacity needs. The first will connect Pima County, AZ, to Grant County, NM, and the second phase Grant County, NM, to Dona Ana County, NM. Southline will ultimately connect the Tucson and El Paso electrical systems.
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 engineering, concluding federal land acquisition, and finalizing commercial arrangements.
Southline expects to begin construction in 2026. The first phase of the project could be operational by 2028, with the full project online by 2029.
Southline is designed to ultimately connect the electrical transmission systems of the El Paso and Tucson areas. The transmission line will run 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 utilities connected by Southline serve most of the communities across the region.
Southline will be open to all sources of electrical power generation. Regulations governing the grid require the project to carry electricity without preference for any technology.
Southline enables more power, cheaper power, and more reliable power for the Desert Southwest. Improved reliability will help mitigate the financial impact of extreme weather events and the resulting economic damage. By increasing energy options for both Arizona and New Mexico, Southline will help fortify the power grid to accommodate the growing demand for electricity. Additionally, an increase in transmission capacity will enable power flow from low-cost, high-producing areas, so customers may benefit from new sources of generation through lower power prices and added reliability.
Southline will create hundreds of high-quality construction-related jobs during project construction and will also stimulate the creation of jobs resulting from local spending on project materials, professional services, and hospitality. Additionally, Southline is investing approximately $4 million dollars directly in local communities through donations, sponsorships, and partnerships with local organizations. Most importantly, power is a key input for a variety of growing industries, and Southline will make the Desert Southwest more attractive to these industries.
Southline is expected to be owned, operated, and maintained by local utilities. Parties interested in acquiring transmission rights on Southline or otherwise learning more about the allocation of its transmission capacity are encouraged to submit their contact information here.
Transmission line construction typically involves the following steps:
All restoration activities will be coordinated with appropriate landowners. Restoration can include replacing topsoil and reseeding to bring areas of land disturbed during construction back to their normal contour. Any topsoil that is removed during construction would be stored then used during site restoration after construction work is completed. Southline will also avoid or relocate special-status plants, such as the Pima pineapple cactus, in compliance with local ordinances to ensure their conservation during construction.
Southline worked collaboratively with local landowners to acquire easements for the transmission line.
Yes. We have purchased easements, but the land still belongs to the existing landowners and can be utilized for activities such as farming, grazing cattle, and other activities that do not interfere with the operation of the line.
Southline successfully completed an in-depth, multi-year federal and state regulatory process through which major state and federal permits have been obtained.
From the start of the project, Southline sought to minimize impacts to the natural, cultural, and human environment through agency, local, and tribal consultation, and project siting. As part of the multi-year federal and state regulatory processes, the Bureau of Land Management and Western Area Power Administration prepared a detailed environmental impact statement (EIS). The EIS analyzed and considered the potential human and environmental impacts of Southline in detail. The environmental impacts of the project were further considered in the state permitting processes.
The Southline team has actively engaged with local stakeholders for more than a decade. If you would like to get in touch with the Southline team, please don’t hesitate to reach out.
Building America's Next-Generation Infrastructure to Power Our Future.
Black Forest Partners and Grid United are co-developing Southline Transmission Project.
© 2025. Grid United LLC. All Rights Reserved.