(New throughout, adds details from court filing, background)
By Timothy Gardner
July 14 (Reuters) - Mountain Valley Pipeline LLC asked the U.S. Supreme Court in a filing on Friday to vacate stays imposed by a federal court halting construction of a portion of its West Virginia-to-Virginia natural gas pipeline.
On July 10, an appellate court in Virginia halted construction of the last short section of the 303-mile (488 km)pipeline to run through the federally owned Jefferson National Forest. The court agreed with environmentalists opposed to the project that construction of that section should stop as the court reviewed its federal approvals.
Environmentalists say the project would harm soil and water quality in the forest and increase the use of natural gas, a leading fossil fuel and greenhouse gas emitter.
Approval of the Mountain Valley project has long been supported by conservative Democratic Senator Joe Manchin of West Virginia, a key swing vote in the Senate and one of the largest recipients of in Congress of donations from fossil fuel companies. Approval of Mountain Valley was included in the debt limit deal struck in May between President Joe Biden, a Democrat, and House of Representatives Speaker Kevin McCarthy, a Republican.
The pipeline, which had received authorization from the Federal Energy Regulatory Commission in June to restart construction, is considered key to unlocking more gas supplies from Appalachia, the nation's biggest shale gas-producing basin.
Mountain Valley said in the filing that the appellate court lacked authority to stay the construction because the debt deal approved by Congress said the pipeline was in the national interest and "expressly stripped all courts" of jurisdiction to review decisions by federal agencies over its approval.
Mountain Valley is owned by units of energy company Equitrans Midstream, the lead partner building the pipe; NextEra Energy, Consolidated Edison, AltaGas and RGC Resources.
The project is one of several that have been delayed by regulatory and legal fights with environmental and local groups in recent years. (Reporting by Timothy Gardner; Writing by Richard Valdmanis; editing by Jonathan Oatis and David Gregorio)