Feb 25 (Reuters) - U.S. energy regulators on Monday approved TransCanada Corp's request to put part of the company's $3.2 billion Mountaineer XPress natural gas pipeline in West Virginia into service:
* Specifically, the U.S. Federal Energy Regulatory Commission (FERC) authorized TransCanada to commence service on about 21 miles (34 kilometers) of pipeline in Marshall and Wetzel Counties, among other things.
* TransCanada said earlier this month that the Mountaineer pipeline was about 45 percent complete and expected to finish the rest of the project in February and March.
* When TransCanada started work on Mountaineer early last year, it estimated it would complete the project by the end of 2018 at a cost of $2.6 billion.
* The company boosted that cost estimate to $3.0 billion in April 2018 and $3.2 billion in February 2019 due to delays of various regulatory approvals, increased contractor construction costs, and inclement weather throughout construction, among other things.
* In addition, the company has also said it plans to put its $600 million Gulf XPress gas pipeline into service along with Mountaineer.
* The Mountaineer and Gulf projects are two of several pipes designed to connect growing output in the Marcellus and Utica shale basins in Pennsylvania, West Virginia and Ohio with customers elsewhere in the United States and Canada.
* The 2.6-billion cubic feet per day (bcfd) Mountaineer project includes 170 miles of new pipeline in West Virginia, while the 0.88-bcfd Gulf project includes seven new compressor stations in Kentucky, Tennessee and Mississippi.
* One billion cubic feet is enough gas to power about 5 million U.S. homes for a day.
* New pipelines built to remove gas from the Marcellus and Utica have enabled shale drillers to boost Appalachia output to a record 31.6 bcfd in February versus 26.9 bcfd in the same month a year ago.
* That represents about 38 percent of the nation's total dry gas output of 83.3 bcfd in 2018. A decade ago, Appalachia produced just 1.6 bcfd, or 3 percent, of the country's total output.
Reporting by Scott DiSavino Editing by James Dalgleish