Emboldened by an Aug. 22 court ruling that FERC’s analysis of greenhouse gas (GHG) emissions from Sabal Trail and two other natural gas pipelines was inadequate, the Sierra Club is using that case to challenge the proposed Mountain Valley (MVP) and Atlantic Coast (ACP) pipelines.

In separate filings Monday, the Sierra Club, representing a coalition of environmental groups, called on the Federal Energy Regulatory Commission to prepare supplemental environmental impact statements (EIS) for both projects in light of the August ruling handed down by the U.S. Court of Appeals for the D.C. Circuit.

In that case, a three-judge panel concluded that FERC’s environmental review failed to adequately consider GHG emissions as a reasonably foreseeable indirect effect of authorizing the related Sabal Trail, Florida Southeast Connection and Hillabee Expansion projects. The court ordered FERC to prepare a new EIS for the projects.

With the ruling in its back pocket, the Sierra Club is going after the recently completed environmental documents FERC prepared for ACP and MVP, two major greenfield Appalachian-to-Southeast natural gas pipelines that expect to receive certificates from the Commission any day now.

“FERC should repoen the evidentiary record for the purpose of taking additional evidence regarding greenhouse gas emissions and climate impacts, and issue a Supplemental EIS,” the Sierra Club wrote. Both the ACP EIS and MVP EIS have similar flaws to the Sabal Trail EIS, according to the Sierra Club.

Of MVP, Sierra Club wrote, “Although FERC attempted to estimate downstream GHG emissions, it failed to provide an analysis that would meaningfully inform the public or decisionmakers about this indirect effect — including its scope, significance, cumulative impact, or potential mitigation alternatives.”

As for ACP, the group criticized FERC for concluding that no “scientifically accepted methodology” was available to link specific amounts of GHG to discrete environmental impacts. FERC drew a similar conclusion in the Sabal Trail EIS, the Sierra Club wrote.

“These assertions do not justify FERC’s failure to provide any analysis of the severity of the project’s climate impacts,” the group wrote. “At least one tool exists for doing so: the social cost of carbon protocol. FERC was aware of the social cost of carbon protocol when it prepared the ACP EIS, but arbitrarily refused to apply it.”

The Sierra Club recently referenced the Sabal Trail decision in a failed bid to prevent the Atlantic Sunrise project from moving forward with construction.

FERC issued a final EIS for MVP in June, with the ACP EIS arriving in July.

Both ACP and MVP have faced significant pushback over the last few years, but they plan to begin construction this fall. The projects were filed with FERC around the same time and follow similar paths, transporting Marcellus and Utica shale gas from starting points in West Virginia to markets in the Southeast.

The 304-mile, 42-inch diameter MVP would transport about 2 Bcf/d from West Virginia to an interconnect with the Transcontinental Gas Pipe Line in Pittsylvania County, VA. EQT Midstream Partners LP plans to operate MVP as part of a joint venture with NextEra US Gas Assets LLC, Con Edison Transmission Inc., WGL Midstream and RGC Midstream LLC.

The 600-mile, 1.5 Bcf/d ACP would start in West Virginia and travel through Virginia and into North Carolina, serving heating and electric generation demand in the Southeast. ACP is a joint venture of Dominion Energy Inc., Duke Energy, Piedmont Natural Gas and Southern Company Gas.

MVP is targeting a 4Q2018 in-service date, with ACP scheduled to enter service in 2019.