Sample monopole

Unisource included this sample photo of a steel monopole carrying electrical lines in a presentation about the proposed project.

Eastern county residents asked plenty of questions – and got some answers – at a public meeting last week about a proposed high-power electrical transmission line that would serve the South32 Hermosa mining project.

Three representatives from UNS Electric, the subsidiary of Unisource Energy Services that would build and operate the new line, were on hand to present details of the project and respond to inquiries through a live Zoom meeting, which started at 6 p.m. on Sept. 24.

The plan calls for a 20-to-30-mile long 138-Kilovolt transmission line to run between a pair of new power facilities: a new switchyard would tap into existing UNS transmission lines in the Rio Rico area, the new line would then run to a new substation in the Harshaw area of the Patagonia Mountains.

It’s still not clear exactly where the transmission line would be constructed, and many of the more than 30 questions posed during the meeting centered around the company’s planned route. The power lines would be held up by 75-110 foot tall steel monopoles with up to 50 feet of right-of-way on each side. Company representatives insisted that they didn’t have a specific route in mind, but pointed to a large study area between the planned Rio Rico switchyard and Harshaw substation.

UNS representatives said they would share “some preliminary routes” at a future open house meeting, which they said would probably happen next spring.

A few local residents said they won’t welcome the project if it’s near their homes.

South River Road residents Daniel and Patricia Madril said they didn’t want to see tall electrical poles near their property and that it could take a toll on wildlife near their home. “It’s going to be a hell of an eyesore for me,” Daniel said. Another meeting attendee asked about plans in the area of Flux Canyon Road.

One person asked about a potential hit to property values. A UNS representative responded: “there is no conclusive evidence that transmission lines have any long-term effect on property value.” A few other questions about potential risks were met with similar responses, with company representatives downplaying any health or wildfire dangers related to the lines.

And some meeting attendees questioned why South32 couldn’t generate power on-site or bury the power lines underground. On-site generation would be more expensive and burying high-voltage transmission lines is not a common practice, the UNS representatives said.

Representatives said that South32 would pick up the tab for the construction project, with UNS responsible for ongoing maintenance. They didn’t say how much the project would cost, but noted that a rough estimate for similar projects in the Tucson area is $1 million per mile.

UNS representatives said that the new line would also improve service to 3,000 residential customers in the project area, noting that the existing circuit in the San Rafael Valley, Washington Camp and Lochiel area is “one of the worst performing” circuits.

The new Harshaw-area facility would actually include two transformers, the representatives said. One would be owned by and serve South32, located on that company’s land. The other would be owned by UNS and would serve residential customers in the area.

Thursday’s meeting was part of the project’s scoping phase and the company said it’s seeking input on the plans. Comments can be submitted by mail to Unisource Energy Services, Attn: Rio Rico-Harshaw, PO Box 711, Tucson, AZ 85702; by email to; by calling 1-833-783-0396 to leave a comment in English; by calling 520-918-8399 to leave a comment in Spanish; or by filling out a comment form on the project website:

A video recording of the meeting was posted to YouTube.

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