The continuous mining operations of the mine will also be reduced to a five-day work week.
Officials said they could not project how long longwall production would be suspended.
“Consol Energy is responding to market conditions primarily as a result of increased inventories and decreased international demand for its metallurgical coal,” it said, confirming that the shrunken schedule would result in an estimated production decrease of approximately 295,000 tons per month.
As a result of the second longwall idle, Consol updated its first-quarter guidance to reflect no changes in its estimate of 1 million ton low-volatility metallurgical and 1Mt high-vol met coal sales but a drop in thermal coal sales of “a few hundred thousand tons” below prior guidance of 13.2Mt.
The producer will also update its full-year production and sales guidance but plans to release the details at a later date.
In the meantime, officials said they would continue to monitor market demand and respond accordingly.
No one will be laid off at the 778-worker Buchanan mine but Consol confirmed that overtime and other non-essential work would be postponed.
The complex will also continue to work on its safety and compliance efforts.
Late last month, the Pennsylvania-based miner announced the idle of the longwall at its Blacksville operation in West Virginia.
Continuous mining crews will also work on a reduced four-day work week.
The 585-worker mine will also retain its entire staff during the slowdown, which Consol confirmed would result in a production shortfall of about 400,000 tons per month.
Blacksville No. 2, in the Pittsburgh 8 seam, produced 4.3Mt with a single longwall and three continuous miners in 2011.
Buchanan had 4.5Mt of low-vol met output and 500,000t of steam coal production last year from its longwall and CMs, which extract from the Pocahontas 3 seam.