Among Minnesotans who have an opinion on the issue, the largest group supports approval for a controversial copper mine proposed for the northeast corner of the state, according to a new Star Tribune Minnesota Poll.

It found that 46 percent of Minnesotans who were polled want PolyMet Mining Corp.’s proposal to be approved; 21 percent say it should be rejected.

But a whopping one-third say they’re not sure — an indication that many Minnesotans are either uncertain about the trade-offs between economic development and environmental risks to one of the most beautiful parts of the state — or are simply not paying attention to the debate, said J. Brad Coker of Mason-Dixon Polling and Research, which conducted the poll.

“It’s a very high undecided,” Coker said.

PolyMet, a Canadian mining company, has proposed building the first of what could be many copper-nickel mines in the state, in an area just east of the Iron Range and stretching up toward the edge of the Boundary Waters Canoe Area Wilderness. The mining plan has raised hopes of an economic renaissance in northern Minnesota, but its predicted environmental impact, which is now open for public review, has been criticized by environmental watchdog groups and Minnesota Indian tribes, and drawn thousands of Minnesotans to recent public meetings.

PolyMet says it would create as many as 350 long-term mining jobs and hundreds of temporary construction jobs, drawing a groundswell of support among mining advocates. But copper mining also carries different and greater environmental risks to water than taconite mining. PolyMet’s $650 million open pit mine and processing plant would operate for 20 years but would require decades or even centuries of expensive water treatment to protect the lakes and rivers that ultimately drain into Lake Superior.

Some against the risk

Some of the people polled said the risk is not worthwhile.

“In the future, our biggest asset is going to be water,” said John Bode, 71, of Minneapolis. “I don’t think it’s worth taking the chance.”

But 33 percent of people polled were not as certain as Bode, a far higher share compared with the less than 10 percent who described themselves as undecided about such issues as raising the minimum wage and legalizing medical marijuana.

Coker said the difference is that both of those issues are drawing attention across the country — and that many Minnesotans are less likely to care about a mining controversy in a distant part of the state.

Regional differences clear

Regional differences in opinion on copper mining were clearly defined in the results. In northern Minnesota, 69 percent said they thought the state should approve PolyMet’s application.

John Cim, 72, of Cook, is one. He said he worked in the taconite industry for many years, retiring from a management job in 1999. He now lives near Lake Vermilion, which he loves for its clean, clear water, he said.

“I had no qualms about working for a taconite plant, taking resources out of the ground and using them,” he said. Te mining companies and the regulators were careful about protecting the environment, and, he said, PolyMet would be no different.

“This is part of our resources, part of Minnesota,” he said. “We should utilize what we have.”

Even in northern Minnesota, however, one-fifth of respondents said they were not sure about the mine, more than twice the number who said it should be rejected.

In the Twin Cities, a split

In the Twin Cities area as a whole, opinions were equally divided among the three possible answers, while in the suburbs, 45 percent said the mine should be approved. Again, there were significantly more in the suburbs who were not sure, 36 percent, compared with the number who thought the plan should be rejected.

There were few differences among age and income groups, but there was a clear split along gender lines. Men were more likely to approve than women, and more women than men said they were not sure.

“I’m all for bringing jobs to Minnesota,” said Jodi Denzer, 35, of St. Paul Park. “But I don’t think that we should do things that bring harm to our environment. I just don’t know enough about the situation.”

Partisan breakdowns

Republicans were evenly split between approval and “not sure,” with only 3 percent opposing the mine. Democrats said they support the plan, by a small plurality, but that reflects the weight of favorable opinions on the Iron Range, long a DFL enclave, said Coker.

The split among Democratic voters is forcing party leaders to walk a careful line in an election year between their traditional blue-collar base and environmentalists. Gov. Mark Dayton has said that he is keeping an open mind on the issue and plans to wait until he has more information before making a decision, likely late this year at the earliest.

The results were similar to polling that PolyMet and environmental groups have conducted, officials said.

Bruce Richardson, a spokesman for PolyMet, said that the company’s research shows some people are not engaged and are willing to let state regulators manage the decision. Aaron Klemz, communications director for Friends of the BWCA, an advocacy group, said that over time the public’s awareness of the mine and its environmental risks has increased substantially.