The property is 425 acres on the north side of the river, west of Clayton Avenue in Empire Township. Cemstone owns the land for gravel mining and would like to sell it while retaining the option of mining it for up to 10 more years.

Dakota County has spent years acquiring conservation easements to prevent future development along the Vermillion, which runs across the middle of the county to the Mississippi River at Hastings. Next year it will begin work on a master plan for the creation of a 100-foot-wide greenway along the river that would include the trail.

With that in mind, county commissioners agreed that securing the option to build a future trail across a mile of the Cemstone property is critical — so important that they considered buying the land just to protect the trail route and reselling most of it.

But the DNR has stepped up to purchase the property as an addition to the adjoining 3,840-acre Vermillion River Highlands area it manages as open land for wildlife habitat and hunting. And, to the county’s relief, the DNR has agreed to permit a trail to cross it, if a key condition is met, said Cynthia Osmundson, DNR regional wildlife manager.

Although trails are typically prohibited in state wildlife management areas because of hunting, the DNR is making a first-of-its-kind exception in this case because Empire Township and Dakota County both have a Vermillion River trail in their future plans, she said.

The condition is that the trail would be permitted to cross the wildlife management area only if it were the last segment needed.

“We have discussed with the county that they would not build a trail across this area until they already had a trail from Farmington and Hastings,’’ Osmundson said.

“This could be 30 or 40 years down the road in terms of the trail going in. Thirty or 40 years from now it could be really significant that this property is set aside as open space with prairie and woods and water,’’ Osmundson said.

The arrangement means that if the trail ultimately becomes a reality, restrictions might be necessary at certain times to avoid hunters and trail users from running into each other, she said.

The purchase of the land by the DNR looks likely.

The Lessard Sams Outdoor Heritage Commission has recommended that the legislature make $4.25 million in legacy funds available to the DNR to buy the property. If the legislature approves, the DNR could buy the land as soon as July.

“We are in the business of providing wildlife habitat and associated recreation that goes with that, primarily hunting,” Osmundson said. “We think this a nice piece to add to that large complex.’’

As proposed, the county would contribute $400,000 to the land purchase, $300,000 of which was granted to the county in Legacy funds, said Al Singer, land conservation manager for the county. “When and if the trail project ever comes to fruition, the final trail alignment would be determined. The easement would be appraised at that time and the county would pay the fair market value.’’

The immediate benefit of the land purchase is the preservation of open land and protection of the river, which is a cool, spring-fed stream known for brown trout. Another plus, Singer said, is that Cemstone would continue mining gravel for up to 10 years and then be required to complete a high-quality habitat restoration at no cost to the state.