150,000 gallons of tailings pour from pipeline

Workers at the Phelps Dodge Sierrita Mine in Green Valley worked Wednesday and Thursday to clean up a 150,000-gallon tailings spill outside their processing facility.

The spill occurred around 7:10 p.m. Tuesday, spokesman Richard Ducote said, after a break in a 36-inch, above-ground pipeline from the concentrator. Federal and state reports said the incident on West Duval Mine Road posed no public danger. No employees were evacuated.

Production was not affected because the pipeline from the plant to the tailings dam splits into two segments, Ducote said. Only one was broken.

Material from the mining pit goes into a concentrator, where copper and molybdenum are extracted. Solid wastes, or tailings, are sent to a tailing dam for storage. Water is recycled.

“During production, instruments showed a sudden drop in pipeline pressure,” Ducote said. “The spill included about 75,000 gallons of solid material and 75,000 gallons of liquid, mostly water. We are picking up the solid material.”

The spill ran for 3,000 feet on the Phelps Dodge property, down a berm and into Demetrie Wash. If it were not picked up, the waste would break down and seep into the ground, Ducote said, or it could be blown or pushed off the property by thunderstorms.

“When we have a spill, the responsible thing to do is clean it up, whether it’s toxic or not,” Ducote said. “This was not a dangerous spill. But we want everyone to know it’s being cleaned up. We were on it instantly.”

The spill was reported to the Pima County Department of Environmental Quality and the Arizona Department of Environmental Quality, Ducote said.

Francis Dominguez, Pima County DEQ’s media liaison, said the spill also was reported to the U.S. National Response Team, which coordinates emergency preparedness and response for oil and hazardous substance incidents for 16 federal agencies. The analysis came back “non-hazardous,” she said.

A federal report said 9.3 pounds of lead escaped during the incident, just below the reportable threshold of 10 pounds.

Phelps Dodge was acquired in March by Freeport-McMoRan Copper & Gold Inc. It is one of the world’s leading producers of copper and a world leader in the production of molybdenum. It is also the largest producer of molybdenum-based chemicals and continuous-cast copper rod.

jbennett@gvnews.com | 547-9770