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Arizona’s Controversal Copper Mine Might Pump Millions Of Pounds Of Sulfuric Acid Into Ground

December 2, 2011

Wisconsin citizens were alerted this week that the Republican controlled legislature is planning to drive a new controversal mining bill through the process come January.  Northern Wisconsin is the proposed site for  a highly contentious iron mine, and the GOP is planning to fashion a bill that will streamline the process to make it easier for Gogebic Taconite to have its way in the Penokee Hills just south of Lake Superior.

But Wisconsin is not the only state to be caught up in mining controversy.  Arizona is also a hotbed of discussion about a copper mine.  In that state the debate is more about how the local economy will be impacted from either a large development project that could house up to 30,000 people, or a copper mine that may pollute ground water.

The mining project, in the desert town of Florence about 60 miles southeast of Phoenix, calls for drilling thousands of wells and pumping millions of pounds of sulfuric acid into the ground to dissolve and extract copper ore. The mine is just a few miles from a master-planned community under development since 2004 known as Merrill Ranch, owned by a number of residential developers, including Pulte Group Inc. and Southwest Value Partners.

The proposed mining facility would be located above underwater aquifers that are Florence’s chief water supply, and would use a method known as in situ—Latin for “in place”—mining that is relatively rare with metals like copper. The process involves pumping hundreds of millions of gallons of water mixed with chemical solvents, including sulfuric acid, to dissolve copper deposits resting on bedrock, then pumping the fluid back up to the surface and converting it into solid sheets of metal.

Curis says the process, which was tested on a small scale in Florence in the late 1990s, is safe, and that the chemical solution is injected several hundred feet below the water table used for drinking water. There are about 2.84 billion pounds of copper under the town of Florence, worth about $10 billion at today’s prices, Curis says.

Although the city council voted unanimously in early November against a zoning change that would have allowed the mine to fully operate, Curis says it will seek the change again next year. Meanwhile, the company is considering the possibility of moving ahead and extracting copper from a portion of the mine that doesn’t require the town’s approval.

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