Consol Energy (CNX) inked a deal on Monday to sell five coal mines in West Virginia to Murray Energy in a deal valued at $3.5 billion as it looks to free up cash for its burgeoning gas business.

The Canonsburg, Pa.-based coal and natural gas producer says it is selling the Consolidation Coal subsidiary so that it can focus on growing in gas exploration and production business at a time when the    U.S. is experiencing a historic shale boom.

"The sale of these five mines – assets that have long contributed to America's economic strength and our company's legacy – was a very difficult decision for our team,” Consol CEO Brett Harvey said in a statement. “In the end, we concluded that the time had come to sell these mature assets to ownership whose strategic direction is more aligned with those mines.”

Murray will pay $850 million in cash as well as future payments amounting to $184 million, and will take on about $2.3 billion of Consol’s balance sheet liabilities.

Consol is expecting to record a $1.3 billion pre-tax gain in its fourth quarter, assuming the transaction closes by Dec. 31, and plans to use the freed up cash to grow its gas production capabilities, including growing annual gas production by 30% in 2015 and 2016. 

The assets being sold are McElroy, Shoemaker, Robinson Run, Loveridge and Blacksville No. 2 mines that together produced 28.5 million tons of thermal coal in 2012. It is only maintaining coal assets that “clearly align” with its long-term goals, including the Bailey, Enlow Fork and soon-to-be-completed BMX mines in Pennsylvania. 

The purchase also gives Murray Energy ownership of roughly 1.1 billion tons of Pittsburg No. 8 seam reserves, as well as Consol’s river and dock operations, including 21 towboats and 600 barges that last year transported 19.3 million tons of coal and other commodities along the upper Ohio River system.

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