(CNN) One of the energy companies that the new head of the Environmental Protection Agency worked for as a lobbyist is seeking contracts from the agency, raising questions among environmentalists about whether he can put his past behind him as he becomes the nation's top environmental protector.

Since 2009, Andrew Wheeler -- who was announced as the acting leader of the EPA after Scott Pruitt resigned Thursday -- has lobbied for at least 17 companies, including Energy Fuels Inc., the largest supplier of uranium in the US. Wheeler's other clients ranged from companies providing coal, gas and nuclear energy to a mix of clients in the auto and food industries.

As Wheeler prepares to take charge of EPA, the company he once lobbied for is trying to win contracts to clean up abandoned uranium mines, according to EFI's website and its CEO, Mark Chalmers.

Chalmers recently told investors the company is "lobbying very heavily" to get the contracts to help clean up depleted uranium mines on lands in the Four Corners area, including property owned by the Navajo Nation. There are more than 500 abandoned mines, some of which are already part of the EPA's Superfund program. EFI is well situated to do the cleanups as it has the only mill in the area and routinely processes uranium there, he said.

Chalmers told CNN their proposal to the EPA is in its early stages, and in a statement said, "We offer the EPA an established, low-cost option to move material off the Navajo Nation, recycle it into fuel for carbon-free nuclear energy, and dispose of the remnants in existing state-of-the-art facilities. Our understanding is that Mr. Wheeler will not be involved in any decision on this Energy Fuels proposal."

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