The furloughs will begin on December 16. Officials told local newspaper the Longview News-Journal that 28 administration workers are being cut along with 26 individuals each from three other mines that will remain in operation due to a collective bargaining agreement.

While no exact impetus for the closure was disclosed, Westmoreland’s decision to close Jewett stemmed from a decision by customer NRG Energy to switch to cleaner burning Powder River Basin (PRB) coal from Wyoming.

Luminant has also been making an effort to shift to other sources for power generation; it purchased two Texas gas-fired facilities earlier this year. Three other Luminant coal mines — Winfield, Thermo and Monticello — have already been closed.

“This has been a very difficult decision, but one that is required to continue to run the business efficiently,” said Tim Bosecker, Martin Lake mines director, in a communication to the Texas Workforce Commission, according to the News-Journal. He added that Oak Hill’s closure will not impact production at the Martin Lake power plant; it will continue to run with both lignite and PRB tonnage.

The 26,000-acre surface site at Oak Hill will be reclaimed in a multiyear project.

Luminant is owned by Dallas-based Energy Future Holdings, which filed for bankruptcy protection in 2014.