Hours before a federal appellate court was scheduled to issue a formal mandate that would void certificates FERC issued for a trio of Southeast natural gas pipelines, the Commission asked the court to stay issuance of the mandate because it plans to issue an order on remand within 45 days.

In a motion filed Tuesday in the U.S. Court of Appeals for the District of Columbia Circuit, the Federal Energy Regulatory Commission asked the court to stay issuance of a mandate over the proposed Southeast Market Pipelines (SMP) Project for 45 days. SMP includes the Sabal Trail, Hillabee Expansion and Florida Southeast Connection pipeline projects.

FERC told the court that it was working "expeditiously" to comply with the court's ruling last August that the Commission had failed to adequately consider the impact of greenhouse gas emissions (GHG) when it issued a favorable environmental impact statement (EIS) for SMP in December 2015. To help bolster its argument for a stay, FERC issued a final supplemental EIS for the project on Monday.

"Immediate vacatur would revoke the certificates of public convenience and necessity for the projects at issue -- pipelines that are currently providing natural gas to power plants in Florida," FERC said in its motion. "Without such certificates, the pipelines would have to cease operating, at least temporarily. Such an outcome is at odds with the court's affirmance of the Commission's finding that there is a demonstrated need for these pipeline projects."

Attorneys for the project's backers filed a similar motion with the court on Tuesday, asking for a 90-day stay.

"FERC has taken significant steps to comply with the court's [August] decision," wrote attorneys for Sabal Trail Transmission LLC, Florida Southeast Connection LLC, Duke Energy Florida LLC, Florida Power & Light Co., and Transcontinental Gas Pipe Line Co. LLC. "Furthermore, shutting down the pipelines at issue would cause economic and environmental harms, and could interfere with the delivery of reliable electric service at a reasonable price to millions of Florida residents.

"These concerns are not hypothetical," the attorneys said, pointing out that during a cold snap on Jan. 4, the Sabal Trail pipeline was operating at 96% capacity, transporting 800,000 Dth in aggregate. They added that the only two other natural gas pipelines serving Florida were operating at 99% and 100% capacity, respectively, on that day, meaning the other pipelines "could not have met demand in Sabal Trail's absence."

Responses to the two motions for a stay are due by Feb. 16. The court is prevented from taking any action until after that date. The appellate case is Sierra Club et al v. FERC [No. 16-1329].

Eric Huber, an attorney for the Sierra Club, said the environmental group was confident that the court would ultimately reject FERC's request for a stay.

"The court's order was clear: FERC must reanalyze the threats this project poses to our air and climate to determine whether reissuing a certificate is appropriate and on what terms," Huber said Wednesday. "FERC's analysis that concluded the GHG emissions of this project were not significant is not sufficient."

In a separate filing on Monday, the Sierra Club told FERC that it should not issue any new certificates for the SMP project until 30 days after notice of the final supplemental EIS has been published in the Federal Register.

SMP would provide about 1.1 Bcf/d to markets in Florida and the Southeast. The project calls for building 685.5 miles of pipeline and six compressor stations, as well as modifying existing compressor stations in Alabama, Florida and Georgia.

Sabal Trail is a joint venture owned by affiliates of Spectra Energy Partners LP (50% ownership interest), NextEra Energy Inc. (42.5%) and Duke Energy Corp. (7.5%).