Originally published 2/11/2014 updated on 6/13/2014

DULUTH, Minn. - What could be the state's first copper-nickel mine is not even close to being built yet, if it happens at all. But lawmakers want to know now how PolyMet will ensure taxpayers won't foot the bill for long term clean-up at its proposed mine and processing facility on the Iron Range.

How do you plan for something hundreds of years down the road?

It's called financial assurance - like a multi-million dollar security deposit. It's money PolyMet would have to put up to pay for any cleanup after its copper-nickel mine closes or if something goes wrong.

On Tuesday, members of the House natural resources finance committee grilled the DNR to understand what this might look like.

"You have to assume the worst and that is one of the problems in dealing with financial assurance here. We don't know what's going on underground. We don't know how the water's flowing," said DFL Committee Chair Jean Wagenius.

"Will a permit be granted if a financial assurance package is not approved by the DNR?" asked Republican Committee Member Rod Hamilton.

Jess Richards, who is the Director of the DNR's Division of Lands and Minerals answered, "No." By law, PolyMet must put financial assurance in place in order to get a permit to mine.

The DNR also addressed concerns about water quality.

"What the permit to mine would do and then ultimately the financial assurance package, it would be designed to be protective of water quality," said Richards.

When it comes to financial assurance, it would be an amount that reaches potentially hundreds of millions of dollars for, at this point, an unknown amount of time to pay for cleanup.

Opponents are concerned taxpayers might ultimately be on the hook for the any environmental consequences.

The complicated debate showed itself again at the committee hearing Tuesday - environmental concerns balanced with the desire for jobs and economic development on the Iron Range.

PolyMet says it will put up adequate financial assurance, but the details won't be known for some time. That will happen when PolyMet applies for its permit to mine, after the environmental review process is done.

Members of the public have until March 13th to send the DNR comments on a draft environmental study of the PolyMet project.