Texas environmental regulators on Wednesday issued an air-pollution permit for a power plant expansion, the first coal-fired plant to be approved since the Environmental Protection Agency ruled part of the state's permitting process didn't conform to the Clean Air Act.

Texas Commission on Environmental Quality commissioners approved NRG Limestone's permit for an 800-megawatt expansion at the plant near Jewett, 100 miles south of Dallas. The facility has been opposed by environmental groups who fear increased pollution and plan to ask for a rehearing with the agency.

"The TCEQ needs to rethink this Texas tragedy," said Paul Rolke, an activist with the group Robertson County Our Land Our Lives. "Energy leaders and investors in Texas have to wise up and realize that clean power is the only rational solution. The planet can't stand another coal plant."

Coal-fired plants are a leading source of the pollutants that make up greenhouse gases, and Texas has more of them than any other state. There are 17 such plants in Texas, which also leads the nation in greenhouse gas production.

This Limestone project is part of NRG's $16 billion plan to add 10,500 megawatts in electricity generating capacity over the next 10 years in the rapidly growing state. A megawatt is enough power to serve between 700 and 1,000 homes.

Erik Hendrickson, a technical specialist in the air permits division, said the three TCEQ commissioners looked closely at opposition to the expansion and followed an administrative judge's recommendation in their ruling.

The EPA hasn't reviewed the permit yet so doesn't know if there are any concerns, spokesman Dave Bary said. In September, the EPA ruled the state must rework aspects of its permitting program to improve reporting, record-keeping and monitoring, among other things. Bary said the EPA is working closely with TCEQ and there's been no moratorium placed on permits in the meantime.

The approval came two days after the EPA announced it had found scientific evidence clearly showing carbon dioxide from burning fossil fuels endangers Americans' health so should be regulated under the Clean Air Act. That means the EPA could regulate those gases without the approval of Congress, but those rules have not been finalized.

That ruling couldn't be taken into account in the lengthy approval process, Hendrickson said.

"The process that this permit applicant has gone through is to determine whether or not they're going to meet what's on the books today," he said. "No rules exist today on the books for greenhouse gases."