After 63 years of service, the coal-fired units at the Wabash River Generating Station in West Terre Haute, Indiana, have been shut down, according to the Indianapolis Star.

Under a 2013 settlement with environmental groups, Duke Energy agreed to retire the plant over issues with air permits for Duke’s coal gasification plant in Edwardsport, Indiana. The plant was shut down last week, a few days before the plant’s air permits were scheduled to expire.

Units 2, 3, 4 and 5 will be decommissioned. Unit 6 may be converted to cleaner-burning natural gas. That decision will be announced later this year, a company spokesman told the Star.

Duke was already planning to retire the plant because of new emission limits under the Environmental Protection Agency’s Mercury and Air Toxics Standard, better known as the MATS rule. The MATS rule, which became effective in 2015, established the first limits on mercury, arsenic and acid-gas emissions from coal-fired power plants.

Larry Slater, 54, who has worked at the plant for 18 years, told the Star that the retirement of the power station “is almost like a divorce for some of the older guys, a bad divorce. I think we could turn around and (cry) at any minute.”