ELY — A long-awaited safety project for Highway 169 in northeastern Minnesota has been slowed by environmental concerns — the same type of concerns dogging proposed copper-nickel mines in the region.

At issue is potential water pollution along a five-mile stretch between Ely and the Iron Range. The Minnesota Department of Transportation earlier backed moving the highway about a quarter mile to the south where it could be straighter and less hilly, with wider shoulders. But state and federal environmental regulators then raised concerns, partly because that route would have required blasting millions of tons of rock that’s high in sulfur.

When that rock is exposed to air and water, it creates sulfuric acid which, if not properly managed, can leach heavy metals into nearby waterways. That’s the same basic chemistry underlying much of the opposition to proposed copper-nickel mining in the region.

The current stretch of highway twists through lakes and thick pine forest.

It lacks guard rails where it passes steep ravines, where shoulders are just a couple feet wide.

“It’s a beautiful road, but dangerous,” St. Louis County Commissioner Mike Forsman said.

MnDOT has drawn up a compromise to keep the highway in its existing corridor but straighten out more dangerous curves than an earlier proposal for using the same route. Officials plan to have it ready for public comment next year.