Southline Transmission seeks approval for N.M. portion of approximately 370-mile project

Southline Transmission L.L.C., in a March 3 application filed with the New Mexico Public Regulation Commission, requested that the commission grant location approval for the New Mexico portion of the proposed approximately 370-mile Southline Transmission Project located in southern New Mexico and Arizona.

The company also requested that the commission grant a right of way (ROW) width determination for the proposed line with an ROW greater than 100 feet, as well as any other commission approvals and authorizations that may be legally required.  

The company said that the merchant electric transmission line project includes two sections:

  • A new approximately 249-mile, double-circuit, 345-kV transmission line and associated facilities beginning in Doña Ana County, N.M., and running west into Arizona (the “New Build Section” – the New Mexico portion of the project for which Southline is seeking approval (the “NM Proposed Route”) falls entirely within this section)
  • The upgrade of about 121 miles of two existing 115-kV Western Area Power Administration (WAPA) transmission lines to double-circuit 230-kV lines in Arizona, as well as short segments to interconnect those upgraded lines to existing substations owned by other utilities (the “Upgrade Section”)

The project, which would provide up to about 1,000 MW of bidirectional transmission capacity, addresses four primary regional transmission needs: improved reliability; congestion mitigation; increased regional ability to meet electrical demand growth; and facilitation of renewable generation development, the company said.

The project involves a proposed public-private endeavor between Southline and WAPA, subject to negotiations and approval by WAPA, under which:

  • WAPA would build and continue to own and operate upgrades to its existing transmission lines in the Upgrade Section, which are located wholly within Arizona
  • Southline would build and own the New Build Section, which spans New Mexico and Arizona, and the short segments in the Upgrade Section necessary to interconnect the upgraded WAPA lines to existing Arizona substations
  • WAPA and Southline will work cooperatively with affected landowners to obtain land rights on the New Build Section

After construction is complete, Southline said that it would lease its physical transmission system assets and associated capacity rights to SU FERC, L.L.C.

The project was designed to minimize land and resource impacts by developing a route along existing corridors and by upgrading existing transmission lines where feasible, the company said.

The company said that the NM Proposed Route consists of:

  • About 147 miles of double-circuit, 345-kV transmission line that would start at the existing El Paso Electric (EPE) Afton substation south of Las Cruces and run west to the existing EPE Hidalgo substation northeast of Lordsburg, then continue westerly to the New Mexico/Arizona border
  • A five-mile, double-circuit, 345-kV segment (“Segment P1”) to loop the existing EPE Luna-Diablo 345-kV transmission line into the Afton substation
  • A 31-mile, double-circuit, 345-kV segment (“Segment P3”) running north-south between Interstate 10 and New Mexico State Route 9

The NM Proposed Route – which is not associated with any generation plant – would have a nominal ROW width of 200 feet and would interconnect with the Afton substation, a new “Midpoint” substation near Deming, and the existing EPE Hidalgo substation.

It is anticipated that construction of the Midpoint substation would not be part of the initial construction phase, but would be delayed until needed to serve as yet undetermined generation facilities expected along Segment P3, the company added.

The Bureau of Land Management (BLM) and WAPA each issued a record of decision (ROD) approving the route referred to in the final environmental impact statement (EIS) as the “agency preferred alternative” route. The company added that the NM Proposed Route for which it seeks approval follows the route approved in the agency RODs.

Southline said that it has an executed ROW agreement with the BLM, ROW approval from the New Mexico State Land Office (NMSLO), and plans to begin negotiations with private landowners after obtaining the approvals requested in the application. Specific to New Mexico, the company said that it executed last August an ROW agreement with the BLM covering 43% of the NM Proposed Route. The company also said that it submitted an application to the NMSLO last October to obtain ROW covering 31% of the NM Proposed Route.

Further discussing the location of the line, the company said that the line would be located in Doña Ana, Grant, Hidalgo and Luna counties. The NM Proposed Route would include Segment P1 and a portion of “Segment P2” between the Afton substation and proposed Midpoint substation, which parallels an existing EPE 345-kV transmission line.

From the proposed Midpoint substation, the NM Proposed Route extends west alongside and parallel to existing EPE and Public Service Company of New Mexico (PNM) 345-kV lines, and includes Segment P3, as well as a portion of “Segment P4a” to the existing EPE Hidalgo substation.

The NM Proposed Route then extends west along Segment P4a from the existing Hidalgo substation, connecting to “Local Alternatives LD3a and LD3b” around the north and west sides of Lordsburg Playa. The east-west segment of Local Alternative LD3a parallels an existing EPE/PNM 345-kV line, the company added. Local Alternative LD3b connects to “Segment P5b,” which is located in Arizona.

With regard to the expected date that the transmission line would be online, the company said that it anticipates operations to be phased into service beginning in 2019.

Southline is a wholly owned subsidiary of Hunt Power, L.P.

About Corina Rivera-Linares 3286 Articles
Corina Rivera-Linares was TransmissionHub’s chief editor until August 2021, as well as part of the team that established TransmissionHub in 2011. Before joining TransmissionHub, Corina covered renewable energy and environmental issues, as well as transmission, generation, regulation, legislation and ISO/RTO matters at SNL Financial from 2005 to 2011. She has also covered such topics as health, politics, and education for weekly newspapers and national magazines.