Environmental groups are challenging a final regional haze plan for Texas developed by the U.S. Environmental Protection Agency, which the groups assert could actually lead to an increase in haze-forming pollution in the state.

The new litigation is the latest in a decade-long battle to enforce the regional haze rule in the state and will add to a separate lawsuit running concurrently in a different federal appeals court.

Earthjustice filed suit in the U.S. Court of Appeals for the 5th Circuit on Dec. 15, representing the National Parks Conservation Association, Sierra Club and Environmental Defense Fund. The petition for review was short on details, but in a conference call with media held Dec. 18, the groups said the plan was unlawful because it was adopted without following notice and comment requirements and because the EPA failed to provide a rational basis for abandoning a previous approach to the rule put forward under the Obama administration.

The Obama-era plan set technology requirements and emissions limits for a handful of power plants in Texas, which would have reduced sulfur dioxide pollution that causes visibility concerns in national parks inside and outside of the state's borders. The new plan would implement an intrastate trading program.

Stephanie Kodish, an attorney with the National Parks Conservation Association, said the original plan, proposed in December 2016, would have restored "miles and miles" of visibility in natural areas such as the Big Bend and Guadalupe Mountains National Parks in Texas; and the Wichita Mountains National Wildlife Refuge in Oklahoma.

Kodish said the EPA "did an about face" in abandoning the December 2016 plan, which the agency's new leadership released in October as part of an ongoing court challenge in the U.S. Court of Appeals for the District of Columbia Circuit. Sierra Club Attorney Elena Saxonhouse said her group analyzed the emissions credits that would be doled out as part of the EPA's new plan, and found that they would grant more emissions than what the plants collectively emitted in 2016. The plan is "quite obviously antithetical to the Clean Air Act mandate and the opposite of what park visitors are looking for when they come to these places," she noted. Kodish also noted that the EPA did not properly justify its selection of a trading plan under the regional haze rule.

Outside of the new litigation, the environmental groups have also asked the EPA formally to reconsider the plan, arguing that the EPA adopted it without fulfilling notice and comment requirements.

"EPA cannot credibly claim that its trading program is just a clarification of the ... proposed rule," a petition for reconsideration explains. "In order to adopt its wholly different trading program, EPA had to add dozens of pages of regulatory and explanatory text that appeared nowhere in the ... proposal."