From UniSourceEnergy Services Sept. 2020 Newsletter to the Public (Click to Read PDF Document)

Sept. 24, 6 to 8 p.m. Unisource Energy Hosts VIRTUAL Open House about Rio Rico-Harshaw Line

“The Rio Rico-Harshaw Line will involve the construction of an approximately 20-30 mile, single- circuit 138 kV transmission line mounted on steel monopole structures. The project will interconnect UNSE’s existing 138 kV transmission system to the planned Harshaw Substation through a planned 138 kV switchyard in Rio Rico.”

UniSource wants to hear from you in the early phases for a planned transmission line that will meet growing energy needs and support electric reliability in Santa Cruz County. Please join us at an upcoming virtual public open house meeting to ask questions and learn more about the project.

Virtual Public Open House Meeting Thursday, Sept. 24, 2020 | 6-8 p.m.

Visit for the meeting link and passcode

TO LISTEN VIA TELEPHONE: Call 669-900-6833 Webinar ID: 913 4239 0972 Passcode: 14432319

Learn more at

Excerpts from Unisource Energy Sept. 2020 Newsletter to the Public

“The Rio Rico-Harshaw Line will serve the Hermosa Project, a mine exploration project currently in the pre-feasibility phase, which is owned by Arizona Minerals Inc. (AMI), a subsidiary of South32, located in Santa Cruz County (Hermosa Project). The line also will improve service reliability for all electric customers in the San Rafael Valley, Washington Camp and Lochiel areas of Southern Arizona. The Hermosa Project currently is served by UNSE through an existing 13.2 kV distribution line that is not adequate to support the Hermosa Project’s anticipated energy needs.

Components of the Rio Rico- Harshaw Line project include:

• Rio Rico 138 kV Switchyard: A new switchyard is required to connect to UNSE’s existing 138 kV transmission system. The switchyard will be located east of the Interstate 19 frontage road, about one mile north of Ruby Road.

• Rio Rico-Harshaw 138 kV Line: A new line 20-30 miles long to be constructed between the Rio Rico 138 kV Switchyard and the Harshaw Substation.

• Harshaw Substation: The new line will interconnect with a planned 138/13.2 kV substation located on the privately- owned Hermosa Project site in Santa Cruz County, about 50 miles southeast of Tucson and about nine miles southeast of Patagonia, Arizona.

UNSE plans to build the line with self-weathering steel monopoles 75-110 feet tall. Taller structures may be required at major road or line crossings.

The Rio Rico-Harshaw Line will require approximately 100-foot wide rights-of-way to cross private and government-owned land in Santa Cruz County.


When determining where to locate new electric infrastructure, UNSE considers customers’ projected energy needs, proximity to and potential conflicts with existing infrastructure, project costs, geography, input from the public and other factors.

UNSE developed a project study area based upon the anticipated future energy needs of the Hermosa Project, outage history, existing distribution infrastructure and utility corridors within the area, and the potential point of interconnection to UNSE’s existing 138 kV transmission system. The study area and interconnection points for the Rio Rico-Harshaw Line are shown on the Preliminary Study Area Map


UNSE plans to apply for a special use authorization from the U.S. Forest Service (USFS) to authorize a segment of the Rio Rico-Harshaw Line that is expected to be built on lands within the Coronado National Forest.

Once UNSE submits the application, the company will work with National Forest officials concerning procedures and requirements for obtaining the special use authorization, including environmental reviews as required by the National Environmental Policy Act (NEPA).

Under Arizona law, UNSE also must secure a Certificate of Environmental Compatibility (CEC) from the Arizona Corporation Commission (ACC) before constructing the transmission line.

UNSE expects to file a CEC application in 2021 with the Arizona Power Plant and Transmission Line Siting Committee (Line Siting Committee), which will review the application in a public process that allows neighbors and other stakeholders to provide comments. If the Line Siting Committee grants a CEC, it will be sent to the ACC for final review and approval.

Rio Rico-Harshaw Line’s development timeline will depend in part on the length of the permitting and CEC processes. The transmission line is expected to be in service in 2024.


Public and agency input is an important component of the planning process for the Rio Rico-Harshaw Line, even as UNSE supports public health by practicing social distancing and other guidance from the Centers for Disease Control and Prevention. UNSE will provide information concerning the Rio Rico-Harshaw Line and request public input through virtual presentations, newsletters, interactive survey tools, and other forms of communication, possibly including public open house meetings if they can be conducted safely.

Residents and other stakeholders are always welcome to share their input by:

• Attending the virtual open house meeting listed on the cover of this newsletter

• Mailing a comment form or a letter to: UniSource Energy Services ATTN: Rio Rico-Harshaw PO Box 711 Tucson, AZ 85702

• Sending comments to

• Visiting and filling out an online comment form.

• Calling 1-833-783-0396 and leaving a voicemail message. Learn more at