WASHINGTON — An environmental group announced plans Monday to sue the federal government over billions in cleanup costs at polluted mine sites in the West and around the country.

Earthjustice said it was filing a notice to sue the Environmental Protection Agency on behalf of four conservation groups in states riddled with abandoned hard-rock mining sites contaminated by lead, arsenic, mercury and other toxins.

The groups are the Idaho Conservation League, Nevada's Great Basin Mine Watch, the Illinois chapter of the Sierra Club, and Amigos Bravos in New Mexico.

The Earthjustice lawsuit aims to force EPA to issue regulations under a 1980 federal Superfund law that would require mining companies to post bonds to pay for cleaning up their sites.

As of 2004, EPA was listing 63 hard-rock mining sites as Superfund sites with an estimated $7.8 billion in cleanup costs, of which $2.4 billion was expected to come from taxpayers, Earthjustice said.

"The lack of financial assurance at mines has caused incredible shortfalls in the ability of mining companies to clean up waste generated at their sites," Earthjustice attorney Lisa Evans said.

EPA spokeswoman Jennifer Wood said the agency was "committed to holding polluters accountable" and would "continue to use all available tools to ensure that bankrupt companies remain responsible for their environmental liabilities."

A spokeswoman for the National Mining Association, Carol Raulston, said mining companies already post cleanup bonds under different federal laws and that additional requirements were not necessary.

"I'm a little perplexed by what they're doing because current law already requires both for hard-rock and coal-mining for you to post a bond that will cover the cost of an outside party — not just you — to reclaim the land you mine," Raulston said.

Evans said current law has proved to be insufficient to cover the enormous costs of cleaning up working and abandoned mine sites. In one example, she said, cleanup costs at a phosphate mining Superfund site in Idaho called the Smoky Canyon mine have been estimated at well over $150 million but the reclamation bond is $8.6 million.

Another example is a company called Asarco, which declared bankruptcy in 2005, leaving behind 94 Superfund sites in 21 states, with total cleanup costs estimated at $1 billion. The cleanup trust established by the company was $62 million, Earthjustice said.

The lawsuit by Earthjustice comes several days after the House of Representatives approved legislation that would require hard-rock mining companies to pay federal royalties for the first time on minerals they extract from public lands.