A new front has opened in the legal battle against a 430-mile natural gas pipeline planned through the Texas Hill Country, this time focusing on how the project will impact the endangered golden-cheeked warbler.

Hays County, the Travis Audubon Society and private property owners say they plan to file what is called a “notice of intent to sue.” The paperwork is a first step in a federal lawsuit.

The group argues pipeline company Kinder Morgan has not obtained the necessary federal permit from the U.S. Fish and Wildlife Service to allow to potentially harm the endangered birds.

“I think everyone agrees that golden-cheeked warblers will be adversely impacted by the pipeline. The question is: If you’re going to adversely impact ... you need to get a permit for it,” said David P. Smith, the lawyer representing the plaintiffs.

Instead of getting that permit, the plaintiffs argue, Kinder Morgan used a work-around agreement with the Army Corps of Engineers in violation of the Endangered Species Act.

Kinder Morgan has long maintained it went above and beyond its legal responsibilities in planning the project.

“There’s a regulatory process in place that we are following,” Allen Fore, Kinder Morgan's VP of public affairs, told KUT in late May. “In the middle of the game, some want to change the rules.”

Under federal law, plaintiffs must file a “notice of intent” to sue 60 days ahead of actually suing. Smith said the U.S. Fish and Wildlife Service, Kinder Morgan and the Army Corp of Engineers will all be named in the suit.

He said he hopes Kinder Morgan will reroute the pipeline project to avoid a federal lawsuit.

This is the second lawsuit filed against the company. The first, a state constitutional challenge, is under appeal after a Travis County District Court Judge found in favor of Kinder Morgan.