Santa Cruz Reliability Project South

UniSource initiated a comprehensive planning and siting analysis in early 2025 to evaluate potential transmission line routes for the project. The study area, as well as opportunities and constraints, were presented to the public during the in-person and virtual open houses held in May 2025.

Since May, UniSource reviewed the identified Opportunities for construction feasibility before developing a set of preliminary segments.  These segments could ultimately be pieced together to form a complete route.  The preliminary segments were each evaluated for their suitability, which considered input from the community, including Constraints, visual resources, archaeological resources, historic properties, environmental and land use considerations such as special status, species habitat and proximity to residential properties. As a result of the assessment, UniSource removed 53 preliminary segments from consideration. The remaining 73 segments are illustrated on the included map, together with the eliminated segments. An interactive map is also available on the project webpage to view these refined segments in greater detail.

A new segment that was not previously presented to the public during the May 2025 open houses (Segment 123) has been added for consideration. This segment was added to provide additional route possibilities and has been subject to the same evaluation as other preliminary segments.

The Santa Cruz Reliability Project is designed to reduce the potential for a major, sustained outage in Santa Cruz County by providing UniSource with another way to deliver power to the substations that serve residents, businesses, service providers and other customers in Santa Cruz County.

Power outages would be less frequent and shorter because UniSource could supply energy from more than one direction to the substations that support service to residents, businesses, service providers and other customers in the area.

Santa Cruz Reliability (SCR) Project South is designed to strengthen the local energy grid by building a new 138 kilovolt (kV) transmission line to interconnect its Kantor Substation in Amado to the Valencia Substation in Nogales through the planned Gateway Substation west of Interstate 19 and West Mariposa Road. This project would improve service reliability for customers by completing the process of converting the current radial line configuration to a looped transmission system.

The new single-circuit transmission line would be installed in rights-of-way on weathering steel monopoles.

The Santa Cruz Reliability Project South will provide several benefits to customers in the area. The project would:

• Improve the reliability and resiliency of the electrical transmission system serving Santa Cruz County.
• Reduce the frequency and duration of outages affecting residents, businesses and industries, including hospitals, schools, ports of entry and federal facilities.
• Expand energy capacity in the area to meet current and future energy needs without impacting service to existing customers.
• Support economic growth.

• Study Area Map (PDF)
• Interactive Map

Under state law, UniSource must secure a Certificate of Environmental Compatibility (CEC) to construct the transmission line between the Kantor and Gateway substations. UniSource plans to file a CEC application with the Arizona Power Plant and Transmission Line Siting Committee, which reviews CEC applications in a public process that allows neighbors and others to provide comments. UniSource anticipates this hearing will occur in February 2026.

The Arizona Corporation Commission must review and approve the CEC before UniSource can begin construction.

UniSource also applied for special use authorization from the U.S. Forest Service for potential transmission line segments that could be located within the Coronado National Forest (CNF). This process could require environmental reviews under the National Environmental Policy Act (NEPA).

Public input is an important part of UniSource’s planning process.

UniSource will host several open houses and other public engagement opportunities throughout the year.  The first of these opportunities will occur in May.

Identifying a suitable location for new transmission facilities involves several phases, each informed by public input. Area residents and other stakeholders can provide insight to help UniSource identify opportunities and constraints, areas to avoid and specific route segments.

Residents and other stakeholders can also help UniSource to evaluate and prioritize the importance of the criteria used to assess potential routes. Alternative route segments will be identified using multiple criteria, including some required by law and others deemed important by area residents and other stakeholders. These criteria will support the development of a preferred transmission line route.

We encourage area residents, property owners, businesses and other stakeholders to ask questions and share their input by:

• Filling out an online comment form
• Sending email comments to scrsouth@uesaz.com
• Calling 520-917-6637 and leaving a voicemail message
• Mailing a letter with comments to:
  ATTN: Santa Cruz Reliability - South
  P.O. Box 711
  Mail Stop CB200
  Tucson, AZ 85702

Newsletters

• Newsletter No. 1 – May 2025

Open House – May 13, 2025

• Posters
• Presentation
• FAQs

Open House – Sept. 3, 2025

• Posters
• Presentation