Unisource outlines multi‑phase plan to add second transmission line serving Nogales area

Representatives from Unisource Energy Services and Tucson Electric Power briefed the Nogales City Council on April 2 about the Santa Cruz Reliability North (SCR North) project, a multi‑phase effort to add a second transmission connection into Santa Cruz County and the Nogales area.

Clark Bridal, Unisource manager for siting outreach and engagement, described the problem the project intends to solve: Santa Cruz County and Nogales today rely predominantly on a single transmission path to deliver high‑voltage power into the area. That single path leaves the region vulnerable to long outages and limits the utility’s ability to take equipment out of service for maintenance. Bridal said the SCR North project would establish redundancy so that if one transmission line is out of service, power can flow via the other line with no interruption to customers.

Unisource has divided the work into three phases. Phase 1 (the SCR North project) would create a second connection into the regional grid, illustrated on Unisource slides as originating at Tucson Electric Power’s Canoa Ranch substation in the Green Valley area and connecting to the Cantor substation near the Pima–Santa Cruz county line. Phase 2 would allow rebuilding of a constrained segment of the existing line (a constraint Bridal said could not be fixed while that line remained the only supply path). Phase 3 would build a second transmission route from Cantor down to the Nogales area; Unisource said routing for phase 3 will begin public outreach in May and the company plans to seek a hearing before the Arizona Power Plant and Transmission Line Siting Committee in late 2025 with Arizona Corporation Commission decisions to follow.

Bridal said the project requires a Certificate of Environmental Compatibility issued through the Arizona Corporation Commission permitting process; that process includes public hearings, opportunity for intervention and environmental review. He described a multi‑step siting study with iterative public outreach to identify and screen routes and reduce impacts for natural resources and community concerns. Phase 1 siting study work is underway; Unisource held a second round of public meetings in Green Valley and Amado in March and expects construction of phase 1 to begin in 2027 with service in 2028 if permitting and schedule proceed as planned.

The company emphasized that the SCR North project is separate from, and not driven by, a nearby transmission line being built to serve the South32 Hermosa mine; Bridal said the mine project may realize some reliability benefit from the SCR North but that the SCR North project stands on its own reliability case.

Council members asked whether Unisource has built similar projects in Arizona (the company said it has done several in the Tucson area recently), about the proposed timeline’s sensitivity to delays, and about likely community resistance where routes cross private property. Bridal said the schedule is an ideal timeline and could be extended if hearings or siting encounters cause delays; he also said federal grant funding tied to portions of the project creates a completion target that will accelerate work if all approvals and land access proceed.

No council vote or formal action occurred during the briefing; Unisource requested local engagement and said it would return with public meetings during route selection for phase 3. Bridal provided a project web address and a QR code for additional information and said outreach will expand as the company refines route alternatives and begins the formal Certificate of Environmental Compatibility process.