The U.S. Environmental Protection Agency (EPA) said it expects to decide whether to issue a so-called draft underground injection control (UIC) permit to Taseko Mines Ltd. for its Florence copper project where Taseko has proposed in-situ copper mining.

Reuters reported that Taseko Mines Ltd., a Canadian firm, wants to use a process that involves injecting sulfuric acid and water deep underground to break up a mineral deposit. Uranium miners in rural parts of Australia and the United States have used in situ leaching, for decades, but it has rarely been used to extract copper.

Officials in Florence, AZ, which sits atop 2.4 billion pounds of copper have tried unsuccessfully for a decade to block Taseko's project.
A U.S. appeals court this past spring put an end to the town's legal roadblocks, which included an attempt to take the company's land via eminent domain. The EPA is now deciding whether to approve Taseko's plan.

“It’s a very green way of producing copper,” said Stuart McDonald, Taseko’s president, adding the proven technology can safely boost U.S. production of a metal key to President Joe Bidens electrification plans.

Opponents, including environmentalists, worry it could pollute water supplies in the drought-stricken state and may also damage historical sites.
State officials approved Taseko's plan in December.

Vancouver-based Taseko has told investors it expects a decision very soon. 

After the mixture of water and acid is injected and dissolves the copper - at a pressure less than oilfield fracking - the solution is drawn back to the surface where a process similar to electrolysis separates out the metal. Taseko said it aims to produce 85 million pounds of copper annually, enough to make nearly 500,000 electric vehicles.

In situ leaching does not require an openpit mine or a smelter. It also emits less carbon than most copper mines, according to ESG consultancy Skarn Associates. A two-year study by Taseko did not detect any leaks from test wells.

The EPA is studying whether the project complies with regulations designed to "ensure that underground sources of drinking water are protected from contamination by any authorized subsurface injection activities," said spokesperson Joshua Alexander.

When used to extract uranium, in situ leaching can leave behind radioactive elements, requiring nearby aquifers to be rinsed out.

Steve Enders, a mining engineering professor at the Colorado School of Mines, said in situ leaching is better for the environment than traditional mining.

“There's no better way to recover copper if you want to minimize the impact on the environment,” said Enders, who added the process could potentially be used at a few other Arizona copper deposits that are naturally fractured, like Taseko’s.

If the EPA issues a draft UIC, there would be a public comment period before a final permit is issued, though the timing of that decision is unclear, the EPA said.

Taseko said it could be operational within 18 months of receiving its permits.