State environmental regulators gave TXU Corp. the go-ahead Wednesday to build a new coal-fired power plant in Central Texas, overruling two arbitrators who questioned the utility’s claim that the plant won’t make local pollution worse.

Opponents said they would appeal, but if TXU prevails it could salvage at least a portion of its one-time plan to build a fleet of new coal-fired plants.

The Texas Commission on Environmental Quality voted 2-1 to approve an air permit for the two-unit plant in Robertson County, about 100 miles northeast of Austin.

The vote came after a four-hour hearing in the commission’s Austin chambers, which were packed to overflowing with Robertson County residents who favor the plant and its jobs, and environmentalists who fear it will foul Austin’s skies and pump 1,440 pounds of mercury into the air each year.

Two administrative law judges recommended last year that the air permit be denied, saying TXU failed to prove it could meet emissions limits. Much of the concern hinged on the proposed fuel - Texas lignite, a particularly dirty form of coal that comes from three nearby mines owned by TXU.

One of the judges, Thomas Walston, said TXU planned to use technology that hasn’t been used to clean emissions from lignite plants. In a memo, even a TXU expert wrote that ash from the lignite might clog filters.

Commission Chairwoman Kathleen Hartnett White said the judges had set too strict a standard for unproven methods of controlling emissions. She said TXU only needed to show “a reasonable expectation that the technology will work.”

TXU says the plant, and another proposed near Bryan, are needed to meet future energy demand. White said the Oak Grove plant was “tremendous news for the Texas public” and won’t hurt air quality.

But Commissioner Larry Soward said the agency was running roughshod over the decision of two administrative law judges who examined evidence and testimony in the case.

“I’m not sure why we send any of these to a hearing,” Soward complained, adding that once agency staffers favor an applicant like TXU, “the show is over and the monkey is dead.”

The deciding vote was cast by H.S. Buddy Garcia, a former aide to Gov. Rick Perry whom Perry appointed to the commission in January. Without Garcia, the permit would have been rejected on a 1-1 tie.

TXU had planned to build 11 new coal-fired units, but it dropped eight when investors announced a $32 billion buyout of the Dallas-based utility. TXU and the buyers said this week they would equip current coal plants with new emission-control technology.

Both steps were designed to ease environmental opposition to the takeover of TXU by private interests, and they have worked - to a degree; they didn’t stop opposition to Oak Grove.

State Rep. Valinda Bolton, D-Austin, said emissions from Oak Grove would lead to more high-ozone days in which children are urged to stay indoors.

“How do (parents) tell their children that monetary gain trumps health?” she said.

But Robertson County Judge Jan Anderson Roe said opponents of the plant were guilty of “politically motivated environmental hysteria.” She said local officials had met with state regulators, who answered all their questions about pollution side effects.

“Our fears have been assuaged with facts,” Roe said. When she sat down, long-silent supporters of the plant erupted in applause.

After the vote, environmentalists said they would ask for a rehearing - a necessary step before filing a lawsuit against the commission in state or federal court.