The shutdown of the 35-plus-year-old mine has already begun and will wrap up by the end of the year, company general manager Howard Schulz told the Associated Press on Friday. The closure will impact about 365 workers.
“We deeply regret the impact this decision will have on our employees and their families," he added.
According to regional newspaper the Springfield State Journal Register, Texas-based owner ExxonMobil was hoping the sale of the operation would be completed by the year’s end. However, earlier this year spokeswoman Margaret Ross said the company "reserves the right to consider alternative disposition of the property should the ongoing sale negotiations fail to reach closure".
United Mine Workers of America spokesman Phil Smith also told the paper the union "would do whatever it could" to help with a transition from ExxonMobil to a new owner, as it would not like to think of the closure as permanent.
“There is still plenty of coal there left to mine," he said.
Monterey is located in Macoupin County where a second operation, Crown II, closed earlier this year when its owner, Freemen United Coal, was purchased by Springfield Coal.
In October, ExxonMobil received $US332,000 from the state of Illinois as part of a $1.66 million project to install underground mine safety improvements including respirators, a communication system and a miner tracking system to comply with federal regulations.