(Adds details of lawmakers' requests, new rules, comments from EPA official)
By Valerie Volcovici
WASHINGTON, March 12 (Reuters) - Republican lawmakers on Wednesday launched an investigation into the U.S. Environmental Protection Agency's decision-making process leading up to establishing emissions standards for new power plants.
Leaders of the House of Representatives Energy and Commerce Committee have written to EPA Administrator Gina McCarthy requesting documents they will use to determine whether the agency complied with the law when it developed its proposals for new power plants, announced in September 2013.
The congressmen questioned whether the EPA was correct to assert that technology used to capture and store carbon emissions from power plants had was already viable on a commercial scale.
Under part of the Clean Air Act known as Section 111(b), which forms the basis of the proposed rule, the EPA must set pollution standards using the "best system of emission reduction" that uses "adequately demonstrated" technology.
Opponents of the EPA regulations, such as lawmakers from large coal-producing states, have zeroed in on this argument and are likely to use it to challenge the agency in court once the final rules are handed down.
The EPA official in charge of writing the rule, known as the New Source Performance Standard for new power plants, defended the commercial potential of the technology in an appearance before the House Science Committee on Wednesday.
Janet McCabe, EPA's acting assistant administrator for air and radiation, said regulations under the Clean Air Act have had a history of accelerating newer technologies.
"We are seeing it in the marketplace. This is the way technology develops," McCabe said. "It starts with a few projects and then it grows."
But some lawmakers at Wednesday's hearing - several of whom are skeptical that climate change is caused by human activities - said that the Obama administration's political agenda was behind the EPA rules and taking precedence over science.
"We are rushing this out before it is ready, at the detriment of long term technical advancement and cost decreases," said Randy Hultgren, a Republican from Illinois.
The EPA has extended the public comment period for its rules on new power plants by 60 days, to May 9, due to intense interest in the guidelines. (Reporting by Valerie Volcovici; Editing by Ros Krasny and Cynthia Osterman)