The proposed Nogales Interconnection Project (the Project) would be located in southern Arizona within the city of Nogales in Santa Cruz County. The proposed Project would include several components, constructed in two phases:

  • A new, approximately 3-mile-long, overhead double-circuit 138-kilovolt (kV) alternating current (AC) transmission line. The first circuit would originate at an existing pole 1,900 feet west of the existing UNS Electric, Inc. (UNSE) Valencia Substation and terminate at the new Gateway Substation. The existing UNSE 138-kV Vail to Valencia transmission line would be severed and connected to this new line on new double-circuit monopoles, thereby converting the existing Vail to Valencia transmission line to the Vail to Gateway transmission line.

  • Utilizing the same new double-circuit monopoles described above, a second circuit would originate at the Gateway Substation, proceed in an easterly direction, and connect with the existing portion of the above-mentioned UNSE 138-kV Vail to Valencia transmission line, which continues east for 1,900 feet to the existing Valencia Substation. This circuit would constitute the new Gateway to Valencia transmission line.

  • A new, approximately 2-mile-long, overhead, 230-kV AC transmission line extending south from the new Gateway Substation to the proposed international border crossing. For Alternatives 3 and 4, a stretch of the transmission line would include two parallel pole structures, one for the new double-circuit 138-kV line and one for the new single-circuit 230-kV line.

  • Minor modifications to relaying equipment within the existing Valencia Substation to accommodate the connection of the proposed 138-kV transmission line from the Gateway Substation to the Valencia Substation.

  • A new, approximately 11-acre Gateway Substation, located on the Gateway site currently owned by Tucson Electric Power (TEP). The Nogales Gateway Substation and the UNSE Gateway Substation would be located on the Gateway site and referred to collectively as the “Gateway Substation.”

    • On the western portion of the Gateway site, the Nogales Gateway Substation would consist of a direct current (DC) interconnection of up to 300 megawatts (MW). This bi-directional back-to-back high-voltage direct current (HVDC) converter (i.e., DC tie) would allow for an asynchronous interconnection between the electric grids in southern Arizona and Sonora, Mexico. The DC tie would initially be capable of 150 MW of capacity of bi-directional flow between the U.S. and Mexico.

    • The second phase of the proposed Project would involve expanding the DC tie from the initial 150 MW to its full 300-MW capacity within the proposed Gateway Substation. The first phase of construction would begin after all required permits and authorizations are obtained by the Applicant from federal, state, and local agencies. The Applicant would notify DOE before beginning construction of the second phase of construction, the timing of which has not yet been determined.

    • On the eastern portion of the Gateway site, the 138-kV UNSE Gateway Substation would consist of a three bay breaker and a half open air configuration to accommodate the line from Vail, the line to Valencia, the connection to the first phase of the DC tie, the connection to the future second phase expansion of the DC tie, as well as a future UNSE distribution transformer.

The U.S. portion of the proposed Project would cross the U.S.-Mexico border approximately 6 tenths of a mile west of Arizona State Highway 190, just west of the Mariposa Point of Entry. The Comisión Federal de Electricidad (CFE), or Federal Electricity Commission (the Mexican state-owned electric utility), would directly, or via an affiliate, own the transmission assets that would interconnect to the proposed Project in Sonora, Mexico. The Applicant has indicated that CFE (through subsidiaries) would be a market participant in Mexico, entering into wholesale power transactions with U.S.- and Mexican-based entities interested in buying and/or selling power.

Project Map

A general area map, which shows potential route segments for the transmission lines, as well as the location of the existing and newly proposed substations, is shown below.  More detailed mapping was made available in the Draft EA document, which is explained on the Process page.


Banner Image: East-facing view of the proposed Gateway Substation site. Image courtesy of Tucson Electric Power.