Freeport plans Sierrita mine cleanup

Mining giant Freeport McMoran Copper and Gold wants to spend $81 million to stabilize and pump out pollution underlying its Sierrita mine northwest of Green Valley.

The copper company says that plan is the most cost-effective of five alternatives it has studied for easing the sulfate pollution known to have tainted the area's groundwater since the early 1980s.

It's also evaluating the possibility of building a new stack of mine tailings west of its existing tailings. That will help the company solve two problems at once: water pollution underneath the tailings and dust pollution blowing from them, said a retired geology professor who has served as a neutral observer working with a community group that has been monitoring the studies for the cleanup.

The company's consultants outlined the alternatives, costing $71.7 million to $208 million, to generally positive reviews Friday at a meeting of community activists and a state environmental official. One Freeport consultant, Stuart Brown of the Bridgewater Group, said the cleanup will be a large, complex undertaking that will last a long time.

If the state approves Freeport's proposal, cleanup work could start two to three years later, a consultant's study said. That doesn't include the time it takes to buy land for new tailings, do environmental studies, and obtain permits to build a new tailings impoundment. Those steps could take until 2016 to finish, said the study.

The proposal calls for pumping out contaminated groundwater at the edge of the mine's pollution plume to keep it from advancing toward drinking wells. More intensive pumping would occur in the heart of the polluted groundwater.

The pumped-out water would be shipped over to the mine for mining operations. The pumping would continue well into the middle of the 21st century, since the mine is expected to keep producing until about 2042, according to the consultant's report.

Sulfates — sulfur-based compounds that come from copper production — can harm the stomach and intestines, the State Department of Environmental Quality has said.

"I think, 'yay,' " was Green Valley activist Nancy Freeman's reaction to the Freeport proposal Friday.

Terming the plan "a miracle," she said the company goes well beyond what it needed to do to meet a 2006 agreement Freeport signed with the state. That agreement said Freeport must produce a plan to prevent pollution from contaminating drinking wells within a mile of the edge of the polluted groundwater.

"I was really determined that something positive like this was going to happen," said Freeman, director of the Groundwater Awareness League, a non-profit group in Green Valley. "I feel like the mining management has really listened to the community."

Cynthia Campbell, ADEQ's water quality compliance manager, told the group her department likes this alternative.

But because the idea of building a new tailings impoundment is "very speculative, we'd probably like to see another alternative as a fallback," Campbell said.

Building the new tailings stack would require Freeport to buy a considerable amount of adjoining state land. That is never a sure thing because by law, the State Land Department must reap maximum revenue from the sale of its land for public schools. Because no roads or other infrastructure exists in that area, the area may not prove alluring for private developers; Freeman called the area "the backside of nowhere."

Still, "we like the idea of a fallback because without it, if this alternative fails off the table, you've got nothing," Campbell said.

Two other alternatives call for pumping only from the pollution plume's edge, with or without a new tailings stack. A fourth alternative would pump the bulk of the sulfate pollution — without a new tailings impoundment.

The fifth proposal, costing $173 million, would allow the pollution to be naturally eased by mixing with cleaner groundwater. Authorities would drill wells to monitor nearby drinking supplies. If they got contaminated, the company would provide alternative supplies, treat the drinking water or blend polluted water with clean water.

If the new tailings impoundment is built, that would help groundwater pollution because the new tailing site would be lined to prevent leaks, unlike the current one, and include a collection system to pipe out tainted water, said John Sonderegger, a Green Valley resident and a retired professor of hydrogeology at the Montana School of Mines. The new tailings stack would also ease dust problems because the dust pollution increases as the impoundment grows, he said.

"They did a thorough look at the relative value of these projects," Sonderegger said. "The simplest thing to do is to do the alternative with no cleanup — that would have met the state guidelines. It has the lowest cost at the early stages, but you pay big at the back end. By hitting it hard early, they wind up actually doing a better job and saving money later, and it's better for the environment."