The Army Corps of Engineers on Oct. 5 suspended a key permit for Mountain Valley Pipeline LLC, halting construction on the 2-Bcf/d gas project at 383 stream crossings and 142 wetland crossings in southwest Virginia.

The corps noted that the U.S. Court of Appeals for the 4th Circuit vacated in its entirety a similar permit that affected four river crossings in West Virginia.

"Because of that order, it is uncertain whether [the permit] will ultimately be available to authorize work for [Mountain Valley] in West Virginia," the Army Corps said in a letter to Mountain Valley developers. "Effective immediately you must stop all activities being done in reliance upon the authorization under the [permit]."

The suspension will stand until the Army Corps decides whether to reinstate, modify or revoke the permit. Without the Army Corps permit, the Federal Energy Regulatory Commission will have stop the pipeline from moving forward, since FERC approval is contingent on the pipeline having all its permits in effect.

The appeals court ruling on Oct. 2 said the corps had overstepped in substituting a particular requirement in lieu of a West Virginia-specific restriction. The ruling was a victory for the Sierra Club and other environmental groups that are against the EQT Corp.-led pipeline project.

FERC approved the project, backed by EQT Midstream Partners LP, NextEra Energy Inc., WGL Midstream Inc., Con Edison Transmission Inc. and RGC Midstream LLC, in an October 2017 order. FERC first authorized construction work Jan. 22. The $4.6 billion project aims to move gas produced in the western Marcellus and to downstream markets in Virginia and points south. (FERC docket CP16-10)