In The News

Pinal Central: Mining process will occur 'A to Z' in Florence

October 23, 2017


FLORENCE — When previous Florence Copper Project owner BHP tested the in-situ process here 20 years ago, they brought in solvent solution from their San Manuel mine. After dissolving copper ore in the ground, they trucked the leach solution back to San Manuel for processing.

This time, current owner Taseko Mines Ltd. plans to do everything here.

“We’re going to do everything from A to Z right on the property,” including manufacturing about 1.5 million pounds of copper, Florence Copper Vice President and General Manager Dan Johnson said. “… So this is truly a pilot prove-out production test facility.”

Critics of BHP’s 94-day test noted the presence of radioactive particles or “radionuclides.” Johnson said this was the result of using solvent solution or “raffinate” from San Manuel. Using existing raffinate helped them begin the test quickly. “It takes time to marinate the solution, to react with the mineralized copper-bearing rock,” Johnson said.

The in-situ process dissolves chrysocolla copper oxide deep underground, then pumps the solution back to the surface to be plated into 100-pound sheets of 99.999 percent pure or “cathode” copper. Florence Copper plans to use a “lixiviant,” or “liquor” of 99.5 percent water and .5 percent sulfuric acid to dissolve copper oxide.

Johnson said they don’t expect to be dissolving a lot of other things they don’t want.

“Radionuclides came from the BHP raffinate when they did the test in 1998,” Johnson said. “That actually concentrates over time from the San Manuel ore body, not from Florence Copper’s ore body. We have a very clean copper deposit here; Mother Nature has been very kind to us.

“… It’s a very clean, weathered copper deposit. Most of those impurities have been weathered out over millions and millions of years. They’re not present in our ore body today. There’s no impurities in it – there’s no lead, zinc, nickel, all the impurities Mother Nature has basically dissolved out,” Johnson said.


Taseko announced a month ago that its board of directors had given approval to proceed with the testing phase, or “production test facility” (PTF). But months of construction and preparation are ahead, and the wells won’t actually begin operating until probably July, 2018.

It takes 180 to 200 days for the copper-bearing solution to reach maturity, and the project will produce its first copper cathode around Thanksgiving or early December, 2018. The test will run around the clock for 12-14 months. The company will then rinse the ore body for six to nine months to restore natural water quality conditions.

All told – with construction, operation and closure programs – “we’re spending $40 million to make $1.5 million (worth of copper) … to verify the reliability and safety of the process to everyone involved: the community, the regulatory agencies and all the other stakeholders,” Johnson said in an interview at the Florence Copper Project off Hunt Highway.

This test phase will consist of four injection wells (pumping the lixiviant into the ore) and nine recovery wells (pumping the copper solution back to the surface). There will also be seven observation wells, six supplemental monitoring wells, and eight operational monitoring and “point of compliance” wells to check whether contaminants are migrating offsite.

The entire project at this time will be located on 160 acres of state land. The town of Florence, which continues to oppose the project, has refused to give the company zoning to use the rest of its property. The town and other opponents, such as Johnson Utilities, Pulte Homes and neighboring landowner Southwest Value Partners, are unconvinced the project can operate without contaminating the town’s groundwater.

If and when the mine proceeds to full production, it will have 200 wells running at a time. Once a section of the mine is exhausted, the well field will move to a new area. Over the 20-year life of the mine, approximately 2,000 wells will be drilled. Johnson said the company will spend over $500 million to build and run the full-size commercial operation.

The number of wells won’t multiply to full production overnight. Florence Copper will have to apply for and receive new state and federal permits and go through another public comment process before full-scale production can begin.

“We’re doing the PTF to show the regulatory agencies it’s reliable and safe. If we don’t do that, they’re not going to approve the next phase of permitting for commercial operations,” Johnson said.

First of its kind

Florence Copper is believed to be the first in-situ copper project in the world to begin as a stand-alone project, and not an auxiliary or offshoot of a traditional mine. Another in-situ project, Excelsior Corporation’s Gunnison Copper Project in the Dragoon area southeast of Tucson, hopes to go straight to commercial-level production sometime next year.

But first, Florence Copper wants to demonstrate the safety and efficiency of its process on a smaller scale. The local staff will increase from six to about 40 for the PTF.

“There’s going to be a lot of good training opportunities for the local folks to do the different tradesmen-type of jobs – drilling, welding, electrical, mechanical, pipefitting,” Johnson said. “Over 80 percent of our workforce will be tradesmen-type of opportunities, and high-paying jobs.

“So we’re just looking forward to getting people on board … and being a significant economic driver in the community.”

There will be three drill rigs, with 40 to 50 people, working around the clock to begin the project. Their shifts will be staggered so as not to add to traffic when Pinal County government and local correctional workers are commuting, Johnson said. The noise audible from Hunt Highway will be low, he said.

“The unique conditions of the Florence deposit make it possible to extract copper in one of the most environmentally responsible ways possible,” Rebecca Rios, Florence Copper’s senior government and community affairs advisor, said in a statement. “There is no blasting, no large open pits, no waste piles – none of the environmental impacts people normally associate with mining. The land disturbance is minimal. Although people call us the Florence copper mine, we’re simply water wells extracting copper in the middle of the desert.”

Company officials claim their state permit is the most comprehensive and stringent one ever issued by the Arizona Department of Environmental Quality (ADEQ).

Florence Copper has offered tours of the property for years, and Johnson said tours will continue during the PTF.

“Absolutely. We want to make sure we’re transparent. We’re confident that the general public will see that we’re going a good job out here.” Stacy Gramazio, manager of communications and public affairs, said not only locals, but industry professionals from around the world are looking to see how things go in Florence.

Johnson agreed, “All the largest copper companies have called us, very interested in this process. … They’re very eager to implement this technology in their operations around the world.”

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