The Dakota Aggregates mine that is chipping away at an 1,800-acre stretch of land in Rosemount is expected to be fully operational within a few months.

The mine is part of the University of Minnesota's 5,000-acre UMore Park and includes active mining on up to 160 acres. Mining began in June 2014, and facilities for processing asphalt and concrete have cropped up over the past several months.

"To build a mine site of this size, it takes a little bit of time and effort," said Tim Becken, senior vice president at Cemstone. The company partnered with Ames Construction to form Dakota Aggregates.

In a metro area scattered with glacial deposits that fed mining for decades, the Rosemount site is the last major trove of high-quality aggregate, Becken said.

It's also a deep cut in both the U's land and the city around it. University researchers whose work is based at UMore Park are concerned about the mine's steady expansion, as are those who live close enough to see and hear the 24/7 operation.

For years, the U had plans for an eco-friendly community at UMore Park. But this winter, officials said those plans are off the table. The mining may bring the U about $90 million over the course of its 40-year lease with Dakota Aggregates.

The mining site stretches across 1,800 acres, and 160 acres are actively worked on at one time.

Dakota Aggregates invited the public to see the mine Thursday, attracting everyone from municipal employees to curious residents. As trucks came and went, dust rising from their open beds, visitors gathered in a bright white tent filled with tables holding bouquets of flowers.

Trolleys carried visitors to the deep gravel pit and the 5,000-foot conveyor belt running from it. Becken said there's enough aggregate to outlive the 40-year lease. And for the time being, there's plenty of construction in the metro area — and plenty of demand for aggregate.

"It's been significantly better than what it was a few years ago," Becken said.

But one day, when the mining is done, the pit will be filled with sand and topped with dirt, said production manager Stacey Hannover. Grass may be planted and houses may be built, and it'll seem as if the mine was never there at all.

Emma Nelson • 952-746-3287