FLORENCE – Arizona’s economy has been built historically on the 5 c’s: cotton, citrus, cattle, climate and copper.The state’s mining industry – Arizona makes up 65 percent of copper production in the United States – employs about 11,000 people and generates thousands of jobs in connected industries.
But the industry has been battling permitting issues and environmental concerns, especially in Florence, where residents have been working for eight years to block a copper mine.
The Florence Copper Project is an underground copper recovery site that is in development in Florence. The in-situ copper recovery (ISCR) process occurs between 400 to 1,200 feet underground, where a mixture of 99.5 percent water and 0.5 percent sulfuric acid dissolves copper into the bedrock. Then the copper solution is pumped to the surface and processed into copper cathode sheets.
Florence Copper is one of three ISCR sites under development in Arizona. The others are Gunnison Copper Project near Wilcox and the Van Dyke project in the Globe-Miami district. Gunnison is owned by the Excelsior Mining Corporation and Van Dyke is owned by a subsidiary of Copper Fox Metals Inc. Both companies, and Taseko, which owns Florence Copper, are based in Canada.
In-situ recovery is most commonly used for uranium mining and accounted for 48 percent of the world’s uranium production in 2015, according to the World Nuclear Association.
Florence Copper says the pH of the water and sulfuric acid solution is similar to that of “common household vinegar.” Jess Knudson, public information officer for the town of Florence, says the biggest concern for the town is the use of that acid.
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