The U.S. Court of Appeals for the District of Columbia Circuit has turned away a lawsuit filed by the Delaware Riverkeeper Network (DRN) to block FERC’s December 2014 approval of the Transcontinental Gas Pipe Line (Transco) Leidy Southeast expansion.

DRN contended that the Federal Energy Regulatory Commission violated the Clean Water Act because it granted Transco’s request to construct and operate the project before Pennsylvania had issued a water quality certification, and it violated the National Environmental Policy Act by “failing to establish an accurate baseline from which to conduct its environmental review” of the project, according to a decision handed down by the appeals court Tuesday [Delaware Riverkeeper Network v. Federal Energy Regulatory Commission, No. 16-1092].

The plaintiffs argued that FERC misidentified specially protected wetlands and miscalculated their categorization and total acreage.

“We find no merit in these claims and, therefore, reject the petition for review,” the three-judge panel concluded.

The case may influence pipeline projects and environmental objections to them in the future, but its impact on Leidy Southeast was negligible no matter the outcome, since the Transco project was placed into service 18 months ago.

Transco first filed an application for the project in September 2013 with a goal of alleviating severe capacity constraints in the Marcellus Shale while also serving the growing needs of local distribution companies along the Atlantic Seaboard.

An environmental assessment of the $607 million project prepared by FERC staff in 2014 concluded that construction “would not constitute a major federal action significantly affecting the quality of the human environment.” FERC issued a certificate of public convenience and necessity for the project in December 2014.

Environmental groups have fought to block the Leidy Southeast expansion since the earliest days of Transco’s plans.

In March 2015, a stay precipitated by DRN delayed preliminary work on the Leidy Southeast expansion until it was dissolved by a panel of judges in the U.S. Court of Appeals for the District of Columbia Circuit. Last summer, in a case filed by DRN and the New Jersey Conservation Foundation, the U.S. Court of Appeals for the Third Circuit ruled that New Jersey and Pennsylvania regulators did not “act arbitrarily or capriciously” in issuing water quality permits and related authorizations for the project.