Ignoring its own scientific study, the Environmental Protection Agency said on Tuesday that dumping debris from coal mining into mountain streams doesn't conflict with the Clean Water Act -- a reversal that clears the way for a new Bush administration rule that critics call a gift to mining interests.

In its waning days, the administration is rushing to approve scores of rule changes to leave its stamp on government. The controversy over environmental damage from mountaintop mining -- blasting off the tops of mountains to more easily get at coal -- has raged for years, with environmentalists and the EPA at odds with the industry about the dangers to water quality from dumping debris nearby.

The new rule would make it easier for mining companies to dispose leftover rock and dirt near or on top of streams. EPA approval was needed before the Department of the Interior, under Secretary Dirk Kempthorne, could finalize the rule before Bush leaves office next month.

Why EPA changed its stance remains a mystery. The agency declined to explain beyond releasing a letter (PDF) from Administrator Stephen Johnson to Kempthorne asserting that "nothing in the regulation is inconsistent with the provisions of the Clean Water Act."

"With this about-face, the Bush administration has hammered one more nail into the coffin of a lot of these Appalachian communities," said Vernon Haltom, a co-director of Coal River Mountain Watch, a West Virginia-based environmental group. "The water here is already polluted, homes are threatened by flooding and we have regulatory agencies that look the other way and pretend we don't exist."

At least twice previously, EPA has said discarding debris into streams can violate the Clean Water Act or kill wildlife. It came to this conclusion once in a 2006 study and again in a legal filing. The study and the brief were cited in comments (PDF) opposing the Interior rule that were submitted to EPA by a group of environmental lawyers.

The EPA study says water tested downstream from mining debris had high levels of hazardous chemicals constituting a "violation of water quality standards" in the Clean Water Act.

EPA's legal brief, submitted in conjunction with several other federal agencies as part of a 2001 lawsuit, said that "valley fill," a term used to describe the mining debris, can cause "adverse environmental effects, as it eliminates aquatic life that inhabits those stream segments."

An EPA spokeswoman declined to address the contradiction, instead pointing to a portion of Johnson's letter stating that the agency worked with Interior to include requirements that "no mining activities may occur in or near streams that would violate Federal or State water quality standards."

But the agency has not released those requirements, nor has it responded to questions about whether it will release enforcement guidelines. Johnson's letter went on to suggest that the rule will help meet President Bush's goal of promoting "the increased use of clean coal technology in order to reduce our reliance on foreign oil."

For its part, the Interior Department claims the new rule will help protect streams because it asks companies to "minimize" the environmental impacts of waste disposal. But environmentalists said that nothing in the rule specifies how mining operations can achieve that goal.

In October, a coalition of environmental groups met with the White House Office of Management and Budget and DOI officials and urged them to consider the government's own research before finalizing the rule, warning that the proposed change was "inappropriate, unwise and illegal" (PDF).

Five days later, OMB met with members of the National Mining Association, a trade group that lobbies on behalf of mining companies.

A spokesperson for OMB did not respond to questions about the meetings.

Carol Raulston, spokeswoman for the National Mining Association, said she could not provide details about the OMB meeting. She said the association strongly supports the rule because mountaintop removal is an important way to supply America's energy needs and preserve safe jobs for Appalachian states where mountaintop mining takes place.

"You cannot access that coal by going underground in a traditional way. It's not safe for miners; it's not a safe mining practice," said Raulston. "Proper engineering of valley fills can be done in a way that does not harm water."

Previously, mining companies had to obtain a permit to dump mining waste into streams. But the coal-mining industry and the Bush administration have waged a years-long campaign to eliminate the permits. The permit rule wasn't always enforced: One government study shows that 535 miles of streams were buried between 2001 and 2005.

Environmental groups that were successfully using the rule to challenge mountaintop removal in court were also hoping that the Obama administration would actually enforce permitting. Now, they are scrambling to determine their next steps.

"The simplest thing I can say is that we are going to work with local, state, regional and national government groups and look at what we can do in the courthouse," said Vivian Stockman, of the Ohio Valley Environmental Coalition, which lobbied against the rule change. "We are going to try to influence the incoming administration and look at our legal options. It just seems that EPA can't concur with this rule change and follow its own duties."

The Obama transition team had no comment. Previously, Obama has called for "more environmentally sound ways of mining coal than simply blowing off the tops of mountains."

The rule change will be in effect by the time he takes office. Overturning it would require starting the rulemaking process all over again, which could take years and prompt legal challenges.

"The Obama people could propose to rescind or modify the rule," said David Vladeck, an administrative law professor at Georgetown University. "But every coal company is going to fight it tooth and nail. It's going to be a huge rumble."