Mining company settles over 2010 pipeline spill

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Silver Bell Mining, LLC has agreed to pay a $60,000 penalty and perform preventive actions worth $50,000 as part of a consent judgment to resolve water quality violations caused by a June 2010 spill from a pipeline at its Silver Bell Copper Mine near Marana in Pima County.

Arizona Department of Environmental Quality officials said Tuesday that Silver Bell Mining agreed to prevent future spills from pipelines by drafting and implementing a pipeline operations and maintenance manual covering more than 20 miles of pipelines; performing periodic pipeline physical inspections, tests and repairs; and training employees on proper procedures for fusing pipe segments together.

About 70,000 gallons of highly acidic solution, containing about 4,000 pounds of sulfuric acid and dissolved metals, escape into a dry wash on Silver Bell property through a rupture in a welded pipeline seam, the ADEQ said in a news release.

The solution moved nearly one mile before it was captured by a storm water impoundment, also on mine property. Pollutants in the discharge exceeded Arizona aquifer water quality standards for fluoride, arsenic, beryllium, cadmium, chromium, nickel and selenium, according to ADEQ officials.

Silver Bell Mining workers contained the discharge on the property, recovering 13,000 gallons of liquids and removing 650 cubic yards of contaminated soil, according to the release.

Silver Bell also reduced the radius of curvature in bends in its pipelines, installed equipment to decrease pipeline operating pressures and changed the surface grades around pipelines to direct any future flows away from washes and into lined impoundments.

"This was a serious spill but Silver Bell reacted responsibly to contain it and clean it up and developed a plan to keep this from happening again," said ADEQ Director Henry Darwin.

The consent judgment is subject to court approval, the ADEQ said.   

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