In yet another setback for the Mountain Valley Pipeline (MVP), the U.S. Court of Appeals for the Fourth Circuit has rescinded permission for all construction activities in the Jefferson National Forest (JNF) in West Virginia and Virginia.

Responding to cases brought by the Sierra Club, Wild Virginia and Appalachian Voices, the federal appeals court vacated the U.S. Forest Service (USFS) and Bureau of Land Management’s (BLM) decision to allow MVP to cross a 3.5 mile segment of the JNF in Giles and Montgomery counties, VA, and Monroe County, WV, where it would traverse the Appalachian Trail at one spot near the states’ border.

The court sided with the environmental coalition’s arguments that the USFS had improperly concluded that sedimentation and erosion impacts of the pipeline could be mitigated. It also found that the USFS violated its 2012 forest planning rule and that the BLM violated the Mineral Leasing Act by approving a new right-of-way across the JNF.

The Sierra Club said Friday after the decision that MVP should halt work within the forest immediately. It also said the decision could have an impact beyond the 3.5 mile segment running through the JNF.

“Since the same panel of judges is also reviewing the coalition’s same arguments against Virginia’s certification of MVP pursuant to Section 401 of the Clean Water Act, it could mean trouble for MVP’s route in the entirety of Virginia,” the environmental group said. “Furthermore, Sierra Club and Wild Virginia, together with other organizations, have filed a similar challenge regarding the Atlantic Coast Pipeline.” That case is scheduled for a hearing on Sept. 28.

The court has remanded the matter to the federal agencies for further proceedings consistent with the opinion.

The Fourth Circuit’s latest decision comes in addition to another it recently issued that has already delayed the project by three months. The Sierra Club and other opponents are waging that challenge as well.

MVP is a joint venture of EQT Midstream Partners LP (EQM), NextEra US Gas Assets LLC, Con Edison Transmission Inc., WGL Midstream and RGC Midstream LLC. The pipeline had been scheduled to enter service during the fourth quarter. But the Fourth Circuit’s decision last month to stay a crucial water crossing permit issued by the U.S. Army Corps of Engineers has prevented some work from progressing on the 300-mile pipeline.

The project is now targeting a 1Q2019 in-service date. The Army Corps recently filed a motion to lift the stay of the Nationwide Permit 12, which allows contractors to trench through the bottom of streams and rivers, arguing that it’s addressed the issues involved. EQM said Thursday it expects briefing to conclude this month, allowing the court to review and rule on the motion.

MVP would move 2 Bcf/d from West Virginia to Virginia and connect with the Transcontinental Gas Pipe Line to move more Appalachian natural gas to Southeast markets. FERC issued a certificate for the project in October, and it has faced staunch opposition since.