The Southline Transmission Line Project consists of two sections: the New Build and the Upgrade sections. The New Build Section is approximately 240 miles of new double-circuit 345-kilovolt (kV) transmission line along with substation expansions, access roads and associated infrastructure. The Upgrade Section is approximately 120 miles of Western Area Power Administration’s (Western’s) existing 115-kV transmission line that is being upgraded to a double-circuit 230-kV transmission line as well as substation expansions, access roads, and associated infrastructure.
In the New Build Section, Southline will construct and operate approximately 240 miles of new double-circuit 345-kilovolt (kV) transmission line in a new 200-foot-wide ROW between the Afton Substation, south of Las Cruces, New Mexico, and the Apache Substation, south of Willcox, Arizona. In the New Build Section, one new substation, the Midpoint Substation, will be constructed in Luna County, New Mexico; two existing substations in New Mexico and one in Arizona will be expanded. In the Upgrade Section, Southline will upgrade approximately 120 miles of Western’s existing Saguaro–Tucson and Tucson–Apache 115-kV transmission lines in a 100-foot-wide existing ROW to a double-circuit 230-kV transmission line from the Apache Substation to the Saguaro Substation northwest of Tucson, Arizona. In some places along the existing ROW, up to an additional 50-foot ROW will be needed. Approximately 2 miles of new-build double-circuit 230-kV electric transmission line would be needed to interconnect with the existing Tucson Electric Power Company Vail Substation, located southeast of Tucson and just north of the existing 115-kV Tucson-Apache line. Twelve substations in Arizona will be expanded to accommodate new equipment associated with the upgrade; in some cases, expansion may require a separate yard.
A notice of intent (NOI) to prepare the EIS for the Project was published in the Federal Register on April 4, 2012. The notice of availability (NOA) for the Draft EIS was published on April 11, 2014 in the Federal Register. The NOA for the Final EIS was published on November 10, 2015 in the Federal Register. The Record of Decision (ROD) was signed by the BLM Las Cruces District Manager on April 21, 2016.
The project begins at the Afton Substation southwest of Las Cruces, New Mexico, and traverses approximately 360 miles west where it terminates at the Saguaro Substation northwest of Tucson, Arizona.