The U.S. Army Corps of Engineers has granted a request filed by Atlantic Coast Pipeline LLC to suspend the project’s authorization to cross streams and wetlands along the entire 600-mile route under its Nationwide Permit (NWP) 12.

ACP voluntarily made the request after the U.S. Court of Appeals for the Fourth Circuit this month stayed the NWP 12 pending review of a challenge brought by the Sierra Club and others. ACP spokesperson Jen Kostyniuk said the company asked the Army Corps to suspend work authorizations to allow more time to resolve questions raised by the case before the Fourth Circuit.

“We are confident that this issue will be resolved in a timely manner and we do not expect the project schedule to be affected by this voluntary suspension,” she said on Wednesday, a day after the Army Corps granted the request. Referring to other regulatory and legal issues the project experienced earlier this year, Kostyniuk noted that the company “completed West Virginia summer construction with stay provisions in place.” She said ACP expects “fall and winter construction will also proceed in a productive manner in compliance” with the latest stay provisions.

The Army Corps cited the Fourth Circuit’s move to stay the NWP 12 in granting ACP’s request. District offices in Norfolk, VA, Wilmington, NC, and Pittsburgh, PA, all suspended their work authorizations under NWP 12, which allows contractors to trench through the bottom of streams and rivers.

While the suspension affects work at hundreds of stream and wetland crossings in all three states, Kostyniuk said it only stops work on about 15%, or just 86 miles, of the entire project route.

The Sierra Club, West Virginia Rivers Coalition, Appalachian Voices and other environmental groups filed the challenge over the summer. They argue that the project can’t meet certain conditions of the permit intended to prevent construction activities from stopping fish migration. Specifically, the Sierra Club said ACP plans to dam the Greenbrier River in West Virginia for three days. After the court stayed the permit, ACP stopped water-crossing work in West Virginia.

The similarly routed Mountain Valley Pipeline (MVP) has already faced the same challenge. The Fourth Circuit earlier this year stayed its NWP 12 pending a review that eventually led the court to vacate the permit altogether.

That decision prompted the Army Corps to revoke all of MVP’s authorizations under the permit, and by last month it had lost the ability to make all water crossings during construction. Environmental groups also argued in that case that MVP could not meet special conditions included in the permit. MVP expects a new NWP 12 by early next year.

Both projects have pushed parts or all of their in-service dates back and increased their budgets due to regulatory delays and legal challenges. Full service isn’t expected to begin on ACP until mid-2020.

ACP would carry 1.5 Bcf/d of Appalachian natural gas from West Virginia, through Virginia and North Carolina to Southeast markets. The 2 Bcf/d MVP would follow a similar path to serve the Southeast.