CHEYENNE, Wyo. >> Federal officials withdrew a proposed requirement for companies to clean up groundwater at uranium mines across the U.S. and will reconsider a rule that congressional Republicans criticized as too harsh on industry.

The plan that the U.S. Environmental Protection Agency put on hold Wednesday involves in-situ mining, in which water containing chemicals is used to dissolve uranium out of underground sandstone deposits. Water laden with uranium, a toxic element used for nuclear power and weapons, is then pumped to the surface. No digging or tunneling takes place.

The metal occurs in the rock naturally but the process contaminates groundwater with uranium in concentrations much higher than natural levels. Mining companies take several measures to prevent tainted water from seeping out of the immediate mining area.

Even so, underground leaks sometimes occur, though most of the mines are not near population centers. No in-situ uranium mine has contaminated a source of drinking water, the industry and its supporters assert.

Along with setting new cleanup standards, the rule would have required companies to monitor their former mines potentially for decades. The requirement was set for implementation but now will be opened up for a six-month public comment period, with several changes.

Those include allowing the Nuclear Regulatory Commission or states to determine certain cleanup standards on a site-specific basis. The EPA decided to resubmit the rule and seek additional public input after reviewing earlier comments, agency spokeswoman Monica Lee said.

Wyoming’s Republican U.S. senators, John Barrasso and Mike Enzi, praised the EPA’s decision to reconsider, saying the rule was unnecessarily burdensome for the uranium industry.

Wyoming has five active in-situ uranium mines and is the top uranium-producing state. Other mines are active in Nebraska and Texas.

“In-situ uranium recovery has been used in the United States for decades, providing valuable jobs to Wyoming and clean energy to the nation,” Enzi said in a news release. “I rarely say this about the EPA, but the agency made the right decision.”

Environmentalists and others say uranium-mining companies have yet to show they can fully clean up groundwater at a former in-situ mine. Clean groundwater should not be taken for granted, they say, especially in the arid and increasingly populated U.S. West.

“We are, of course, disappointed that this final rule didn’t make it to a final stage,” said Shannon Anderson with the Powder River Basin Resource Council. “It was designed to address a very real and pressing problem regarding water protection at uranium mines.”

The EPA rule is scheduled for further consideration in President-elect Donald Trump’s administration.

In-situ uranium mining surged on record prices that preceded the 2011 Japanese tsunami and Fukushima nuclear disaster. Prices lately have sunk to decade lows, prompting layoffs.