Billings, MT -

 About one-quarter of the union workers at a coal-fired power plant in Colstrip will be furloughed for up to 90 days after equipment failure shut down one of the generating units.

The Billings Gazette reports PPL Montana is starting mandatory leave for 36 workers on Sept. 14. The furloughs will last at least one month and up to three months.

PPL Montana spokesman David Hoffman said Monday the generating unit isn't expected to be operational until next year. The cause of the failure remains under investigation.

The employees will receive state unemployment benefits, but will still receive their PPL Montana benefits, including health care.

Union business manager Rex Rogers says the International Brotherhood of Electrical Workers Local 1638 agreed to accept furloughs in a May 2012 contract rather than being required to work weekends with no overtime.