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Posted: June 2012

Lovell-Yellowtail: Needed transmission upgrade begins in Rocky Mountain

by Lisa Meiman, public affairs

A Western contractor installs a wood frame H-structure during the Lovell-to-Yellowtail transmission line rebuild. 

The structure has been completed and is ready for installation. 

Rebuilding Rocky Mountain’s Lovell-to-Yellowtail No. 1 and No. 2 115-kilovolt transmission lines, that run between Lovell, Wyo., and Yellowtail Dam near Fort Smith, Mont., is underway for one Western contractor.

The project, broken into three phases, is currently concentrating on the lines that cross the National Park Service Big Horn National Recreation Area in Big Horn County, Wyo. The project will replace the existing H-frame wood poles with new ones.

The construction requires at least one line to remain in service at all times to continue reliable service in the area and allow RM Maintenance crews to schedule Yellowtail generation south into Wyoming.

Once the 94 circuit-miles of lines are upgraded, Western will see improved reliability and easier access for maintenance. The largest benefit is that Western’s share of the Yellowtail South path will increase from 225 megawatts to 300 MWs, giving Western the ability to schedule the entire output of the Yellowtail generation south into the RM region.

“The wood H-frame lines were originally built in 1956 and 1966, respectively, and they have exceeded their expected life,” said RM Project Manager Travis Anderson. “Many of the existing poles are in immediate need of replacement.”

Wood pole testing is conducted about every 10 years to ensure the health of the lines. The Lovell-to-Yellowtail No. 1 and No. 2 lines were last tested in 1996. Thirty-one percent of the No. 1 poles did not meet strength requirements while the No. 2 transmission line had a seven percent rejection rate.

During the rebuilds, the contractor will install a higher capacity wire that will increase the power flow capability of the transmission lines.

“The extra capacity will improve the operational flexibility of RM’s use of Yellowtail generation by increasing the scheduling capability,” said Anderson. “This will prevent Western from having to purchase transmission service in order to schedule Yellowtail generation in the future.”

Western also expects about 12.6 acres of unused access roads to be reclaimed by NPS within the Big Horn National Recreation Area. With the rebuild project, these maintenance roads will not be needed.

Finally, the contractor will install overhead optical ground wire on the two transmission lines, to improve communications capabilities on the system and decrease the number of maintenance calls and costs to remote communication sites in the area.

Western worked closely with the NPS, the Crow Creek Tribe and the Montana Department of Environmental Quality to produce an environmental assessment, finding of no significant impact and environment mitigation plan in 2011. Landowners, the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service also participated in the assessment. The three phases for the project include:

  • Rebuilding about 15 miles of each transmission line (or 30 circuit miles) on NPS land. This phase is expected to be completed in September.
  • Rebuilding about 16 miles of each transmission line (or 32 circuit miles) north and south of NPS land. Phase II is expected to be complete in fall 2013.
  • Rebuilding about 16 miles of each transmission line (or 32 circuit miles) on the Crow Reservation. Phase III will begin fall 2013 and is expected to be completed in fall 2014.