Story updated at 10:30 a.m. EST

Sen. Lisa Murkowski (R-Alaska) is questioning U.S. EPA efforts to impose financial assurance requirements on hardrock mining operations under the Superfund law.

In a letter to Interior Secretary Ken Salazar and Agriculture Secretary Tom Vilsack, Murkowski asked whether EPA was overstepping its bounds. She said the Bureau of Land Management and the U.S. Forest Service have long required financial assurances for hardrock mines on federal land.

"Despite the maturity and effectiveness of existing financial assurance programs implemented by your agencies and the states, EPA is considering new regulations that may unnecessarily duplicate or preempt them," Murkowski said in the letter.

Murkowski, the top Republican on the Senate's Energy and Natural Resources Committee, is asking Salazar and Vilsack about their dealings with EPA on the issue. She is also seeking more information about current rules.

"The EPA has repeatedly sought to duplicate or supplant the jurisdictional activities of other federal agencies and the states," Murkowski said in a statement about the letter. "In this case, either the EPA has failed to look at the facts, agencies with existing programs have failed to provide those facts, or both."

Murkowski described EPA's actions as an "intrusion." The press release about the letter also accused the agency of a "power grab."

"I believe the EPA plays a critical role in protecting the environment, but it is important to ensure that such protection is achieved by competent administration of sufficient authorities and not by burying projects in duplicative and expensive regulatory programs that restrict their ability to come to fruition," Murkowski's letter read.

Last July, EPA identified the hardrock mining industry as a priority for developing new financial assurance requirements, which the agency said would protect taxpayers from footing the bill for environmental cleanup. The agency plans to propose a rule by early next year.

The agency said it focused on hardrock mining first because of the "sheer size" of the mines and their negative effects on the environment, the press release said.

EPA's actions follow a federal court order in a lawsuit involving the Sierra Club.

"EPA has a court order issued by the United States District Court to identify priority industries for establishing financial assurance requirements," the agency said in a statement. "EPA is consulting with BLM, other federal agencies and states to evaluate their existing financial assurance requirements to minimize duplication."

"Hardrock mining sites are among the most expensive sites on the EPA's National Priority List," Ed Hopkins, the Sierra Club's environmental quality program director, said in a statement about Murkowski's letter. "When Sierra Club became involved in this litigation, roughly five years ago, 63 hardrock mining sites on the NPL list had estimated cleanup costs of $7.8 billion. Of that, $2.4 billion was going to have to come from taxpayers. Almost another 100 sites were being considered for the NPL at that time."

Stakeholder positions

Murkowski's letter echoes arguments from mining industry advocates.

In 2009, National Mining Association CEO Hal Quinn issued a statement accusing EPA of ignoring federal and state laws and using outdated mine information.

Quinn said the mines on Superfund's National Priorities List "are nearly all 'legacy' sites that were operated and abandoned long before the advent of detailed regulation at the federal and state level, including the requirement for financial assurance for closure and reclamation."

Environmental groups have long said the hardrock industry -- which mines for resources like gold, copper and uranium -- needs to bear a greater financial burden for cleanup and environmental protection efforts.

"It's essential to have financial assurances standards for hardrock mining and other industries to ensure that they do not skip out on costly cleanups by declaring bankruptcy, leaving taxpayers to foot the bill," Hopkins said. "Financial assurances standards result in better environmental protection because they provide an important incentive for industries to behave responsibly."

Hardrock mining operators have been fighting on several fronts in recent years. Environmental groups want to overhaul the Mining Act of 1872, which they say is too lenient on the industry. President Obama's budget blueprint includes a new fee on hardrock mineral production to help pay for the reclamation of abandoned hardrock mines. And the Interior Department is considering setting aside up to 1 million acres from new hardrock mineral exploration around the Grand Canyon for 20 years (E&E Daily, March 3).

Click here to read Murkowski's letter.

Story updated to include response from U.S. EPA.