Dozens of groups and individuals filed rehearings requests this week challenging FERC’s certificate orders approving the Atlantic Coast (ACP) and Mountain Valley (MVP) pipelines.

One month after the Federal Energy Regulatory Commission approved the two controversial Appalachia-to-Southeast natural gas pipelines in a rare split decision, challengers flooded both project dockets with rehearing requests calling on the Commission to revisit seemingly every aspect of the orders [CP15-554, CP16-10].

The Appalachian Mountain Advocates, on behalf of a coalition including the Sierra Club, Natural Resources Defense Council and others, filed hundreds of pages detailing FERC’s alleged failures in certificating ACP and MVP. The issues raised in the rehearing requests generally track closely with those brought up throughout the certification process, with the groups claiming, among other things, that FERC failed to properly assess the market need for the pipes and failed to evaluate alternatives.

Contending that FERC’s approvals for ACP and MVP violate the Natural Gas Act, the National Environmental Policy Act and the Constitution, the groups called on the Commission to immediately stay its certificate orders pending rehearing.

“Construction of the project threatens irreparable harm to the environment, intervenors, and their members that far outweighs the exclusively economic harm that the applicant might incur from a stay,” the groups wrote of ACP, mirroring comments submitted to the MVP docket. “Moreover, the public interest lies with the protection of the environment, compliance with federal laws, proper administrative procedure, and the protection of Constitutional rights.”

The groups also highlighted Commissioner Cheryl LaFleur’s dissenting opinion in the MVP and ACP certificate orders, pointing to her concerns about the cumulative environmental impacts from building both pipelines given their similarities.

ACP and MVP each propose crossing mountainous terrain along the Virginia/West Virginia border to make way for Marcellus and Utica shale natural gas delivery to markets in the Southeast and Mid-Atlantic via interconnects with the Transcontinental Gas Pipe Line (Transco). ACP would extend south into North Carolina, with a lateral running to southeastern Virginia.

The 600-mile, 1.5 Bcf/d ACP is a joint venture (JV) of Dominion Energy Inc., Duke Energy, Piedmont Natural Gas and Southern Company Gas. The project is scheduled to enter service in 2019. The 303-mile, 2 million Dth/d MVP, targeting a 4Q2018 in-service date, is a JV between EQT Midstream Partners LP, NextEra US Gas Assets LLC, Con Edison Transmission Inc., WGL Midstream and RGC Midstream LLC.

In the past, FERC has issued tolling orders on rehearing requests filed in opposition to pipeline projects. By extending FERC’s deadline to decide on a rehearing request, the use of tolling orders in the past effectively delayed court challenges while allowing projects to move forward with construction — a practice that has drawn criticism from opposition groups.

Environmentalists have had some success this year challenging FERC’s gas pipeline approvals. The U.S. Court of Appeals for the District of Columbia last week ordered a temporary stay of construction on Transco’s Atlantic Sunrise expansion. In August, opposition groups succeeded in convincing the federal appeals court to toss out FERC’s environmental review of the Sabal Trail Pipeline and two other southeastern expansions, citing inadequate analysis of greenhouse gas emissions.