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A new method to harvest copper

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A new method to harvest copper

by Ryan Randazzo - Jun. 19, 2011 12:00 AM
The Arizona Republic

The traditional icons of Arizona miners are picks and shovels, but a new project possibly starting up next year in Florence could harvest copper from deep underground without moving a spade of dirt.

Curis Resources Inc., an affiliate of Canadian mining company Hunter Dickinson Inc., plans to mine the copper with hundreds of pumps that send acid underground to dissolve the copper minerals, then suck the liquid and copper back to the surface.

Unique copper mine in Florence

Despite promises that the procedure is safe, and would mine copper far below the aquifer that Florence residents use for drinking water, nearby landowners have mounted opposition to the project, saying it could affect their plans to build houses in the area.

In-situ copper recovery, or ISCR, is similar to the procedure used to mine uranium in northern Arizona, and it has been used for decades by other copper miners but always as an addition to a larger mine.

Curis would be the first to develop a copper deposit using ISCR exclusively, without a traditional pit or tunnel to dig for ore.

In-situ mining allows miners to recover minerals without piles of waste rock, tailings dams, a smelter or explosives.

"In our view, this is the next generation of copper recovery in Arizona and around the world," project spokesman Rustyn Sherer said.

The project is north of Florence, across the Gila River bed from town, at the foot of Poston Butte.

But an investment group called Southwest Value Partners, co-founded by Phoenix Suns owner Robert Sarver, bought 4,500 acres next to the Curis property for $27.6 million, closing the deal in March 2010.

The company purchased the land as an investment, hoping to sell it for housing, which would rely on the groundwater. Company officials worry Curis could pollute their groundwater and are fighting the project.

"There are a number of wells planned on our property within 1,000 feet of their operation that would provide water to our properties and others in the region," said Justin Merritt of Southwest Value Partners, which helped form a group called Protect Our Water, Our Future along with other nearby property owners opposed the mine.

Technical debate

Curis plans to use in-situ mining because the low-grade ore far below the surface probably wouldn't be profitable to mine with more traditional digging.

If the project works as intended, it will cost Curis about 70 cents to produce a pound of copper, which currently sells for about $4 a pound on the commodities market. The mine could run for about 20 years, with no plans to develop or even explore for more copper in the area.

"We will be the lowest-cost producer of copper in the world," said Mel Lawson, Curis vice president of project development. "You could see a significant drop in the price of copper and this project still would be economical."

Curis is aiming for a band of bedrock that runs from about 400 feet below the surface to 800 feet below the surface. The ore sits under about 216 acres of land, and Curis would need additional acreage for a production facility to take the acid solution laden with copper after it is pumped to the surface and turn it into sheets of copper, called cathodes.

There is a groundwater where the copper is at, but it is not commonly tapped for wells because it doesn't move rapidly through the broken bedrock, Curis officials said.

The deep aquifer is separated by a thick layer of clay from the shallow groundwater that residents in Florence commonly tap for their water, Curis officials said, but Protect Our Water, Our Future officials contend that is not the case.

They are concerned that drilling through the shallow aquifer and clay barrier to pump acid into the lower aquifer will cause problems.

"They have hundreds and hundreds of core holes at the site (drilled to test for copper) dating back to the 1970s," said Ronnie Hawks, an environmental lawyer representing those opposed to the mine. "Many of those can't be located today. Each one represents a potential conduit for this acid to move up and down through the aquifer."

The acid that would be used would be a 0.33 percent solution of sulfuric acid, which Curis officials compared in acidity to lemon juice.

Curis officials said that all of the acid pumped underground would be recovered, but mine opponents worry that the acid and dissolved copper minerals could pollute the aquifer.

Hawks said that the acid could cause health problems, especially with children and the elderly, if it gets into drinking water. He also said that while the initial acid solution is weak, Curis would continue to re-inject the acid and dissolved minerals into the ground at higher concentrations until there was enough metal in the solution to produce copper.

"By that point, it's not lemonade anymore," he said.

To ensure it recovers all of the acid, each pump injecting acid into the ground would be surrounded by four pumps sucking water, acid and copper to the surface. Protective casings would prevent the solution in the lines from leaking into the shallow aquifer, Curis officials said.

And if any of the acid got past the surrounding recovery pumps, the perimeter of the mine would use lime to neutralize the acidity so it didn't leave the site, said Dan Johnson, environment and technology services manager.

The entire site would use about 2,500 wells, with about 400 to 500 operating at once when the mine is in full production, he said.

Economics touted

Curis has promoted the economic benefit the mine would bring to the town, county and state, which makes the mine's opponents fearful it will win the needed permits regardless of its possible impacts on their property.

Curis officials estimate they could produce 74 million pounds of copper a year, and that if the permit process and the ramp up of operations goes smoothly, the facility could begin full commercial operations in 2014.

Curis intends to invest $280 million in the project in the next three years.

The mine would employ about 150 people, and many more than that would be needed to build the project and its copper-production facility.

Curis officials estimate the project annually would create about $11 million in direct economic activity in Florence and $86 million nationwide.

About half of the copper deposit sits below state trust land, which would bring $100 million in royalties to the state during the life of the project.

Hawks said that those economic figures could be persuasive to officials who could have a hand in permitting the mine.

"In this economy, we are fearful the governor and legislature will push for approval of this mine," Hawks said.

Zoning issue

Part of the debate centers on the site's zoning, which would need to be amended by the town of Florence along with the general plan for the town for the mine to proceed.

The mine also will need a bevy of permits from the Environmental Protection Agency, Arizona Department of Environmental Quality, Department of Water Resources and other agencies. But the town meetings on the subject later this year could be the forum that brings out the local opposition.

Curis needs the town-planning changes to accommodate the light industrial work amid the region now zoned for commercial and residential development, even though the site had mining activity dating to the 1960s, when Asarco first explored what was then unincorporated land.

Continental Oil Co., or Conoco, found copper at the site in 1970.

In the early 1990s, Magma Copper Co. bought the project and studied the area for in-situ mining.

Magma was acquired by BHP Copper, which continued test work and a feasibility study on the site. But in 2000, low copper prices shelved the project, and BHP sold the property to an investment firm.

Florence then annexed the land, folding it into the general plan and zoning it for homes and businesses.

In 2009, Hunter Dickinson bought it and formed Curis to develop the mine. Curis went public in November, and the mine is its only project.

Southwest Value Partners officials argue that because the region is zoned for houses, and many have already been developed nearby in a large Pulte Homes development, the mine should not be permitted.

Merritt, of Southwest Value Partners, said that because his company closed its deal shortly after Curis bought the adjacent land, that he did not know of the mining plans.

"Everybody was bound to confidentiality," he said. "We bought from the same broker, and they were not allowed to disclose the buyer. We especially did not know the type of mining and details of what was going on."

Merritt said that his company bought the land based on the town's general plan.

"Curis (also) bought this with that plan already in place," he said. "They knew it was zoned residential when they bought it."

Curis officials said that the land would be restored after the mine has played out, and said that residential development could take place once the pumps are gone.

At town hall in Florence, officials are trying to stay out of the fight.

"The mayor is trying to remain as neutral as possible on this issue," Florence spokesman Jess Knudson said.

The town plans to spend about $25,000 on a hydrogeologist to consult on the project and determine what, if any, effects the mine would have on groundwater, he said.

"He will help us make a determination on outstanding risks to the water aquifer or other environmental concerns," Knudson said. "Essentially we will be asking him to take a look at the permits Curis files with ADEQ and the EPA, and answer some questions the town has about the project and impacts."

He said several residents have voiced concern to town hall.

"It is important for us to have that third-party perspective," Knudson said. "We understand the great benefits tied to the project, but also want to do our due diligence and make sure it would be safe for the community."

Charlie Leight/The Arizona Republic

Curtis Resources Inc. estimates it could produce 74 million pounds of copper at a site in Florence.

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