UNS Electric Inc, (UNSE) a subsidiary of Unisource Energy Services, has announced its plans to install a new electric transmission line, named “Rio Rico-Harshaw Line”, funded by South32 because of the mining company’s anticipated needs of future exploration in the Patagonia mountains. The current electricity provided to South32’s Hermosa project according to the UNSE “is not adequate to support the Hermosa Project’s anticipated energy needs.” 

UNSE’s September e-newsletter outlined their plan to construct “approximately 20-30 mile, single-circuit 138 kV transmission line mounted on steel monopole structures.” The new switchyard “will be located east of the Interstate 19 frontage road, about one mile north of Ruby Road and a new line 20-30 miles long will be constructed between the Rio Rico 138 kV Switchyard and the Harshaw Substation,” located on the privately-owned Hermosa Project site, about nine miles southeast of Patagonia, AZ.” UNSE employee projected the cost of $1 million per mile of new line installed.

UNSE plans to “build the line with self-weathering steel monopoles 75 to 110 feet tall. Taller structures may be required at major road or line crossings.” The new transmission line “will require approximately 100-foot wide rights-of-way to cross private and government-owned land in Santa Cruz County.”

The Rio Rico-Harshaw Line will need a special use authorization from the U.S. Forest Service and “a Certificate of Environmental Compatibility from the Arizona Corporation Commission before constructing the transmission line.” The Rio Rico-Harshaw Line’s construction timeline will depend on the permitting process. UNSE expects the line to be in service in 2024 if the Forest Service gives their proposal a Finding of no Significant Impact (FONSI). 

UNSE hosted a virtual public meeting in Sept. 2020. The presentation and recording are available online www.uesaz.com/rio-rico-to-harshaw/