A big strip mine opening in Rosemount will add a major new source of sand and gravel for roads and other construction projects in the Twin Cities, officials say.

Dakota Aggregates will begin work this spring on a 600-acre surface mine, said Eric Zweber, senior city planner. The business, a partnership composed of local firms Cemstone Products and Ames Construction, recently won unanimous project approval from the Rosemount City Council.

The partnership has leased about 1,500 acres above the aggregate deposit, which extends south into Empire Township. Cemstone estimates more than 150 million tons of sand and gravel will be extracted over the next 40 years, said Senior Vice President Tim Becken. When the Rosemount deposit peters out in about 25 years, the partnership plans to mine the same deposit for 15 more years in neighboring Empire Township, he said.

The glacial deposit on UMore Park land owned by the University of Minnesota is one of the largest remaining sand and gravel sources so close to the metro area, Becken said. That reduces construction and fuel costs because trucking the material for long distances often costs more than mining it.

The UMore deposit "may have the biggest potential of remaining [aggregate] resources" in the metro area, said Chuck Howe, chief engineering geologist for the state Department of Transportation, which tracks sand and gravel pits used in highway projects.

In recent years, more than half of aggregate materials mined are used in concrete, asphalt and other products for highways and other public projects, officials say. Other large gravel mines in the metro area include pits in Maple Grove, Elk River, Apple Valley, Burnsville and Lakeland, and Gray Cloud Island in Washington County.

More than half a century ago, much metro-area sand and gravel came from strip mines in Maple Grove, and the city estimates that its mining will last another 10 or 15 years, said Community Development Director Dick Edwards.

He said mining firms have been cooperative in refilling and grading mined areas that underlie the huge Arbor Lakes shopping area. They include some housing and the city's town center, with a big pond and amphitheater, he said.

With the UMore mining approved, most available sand and gravel resources have shifted to the south metro area, said Heather Arends, industrial minerals supervisor for the state Department of Natural Resources. She noted a study done in 2000 estimated metro sand and gravel could be depleted by 2028, but that date has been pushed back because of the UMore project -- and because the recession reduced aggregate demand.

Dakota County is a state leader in providing aggregate materials; gravel taxes collected from mining companies also help to rebuild streets and county roads damaged by heavily laden mining trucks, said Don Hess, Dakota's aggregate tax administrator.

Empire Township led the county with $310,000 in gravel taxes out of Dakota's total of $821,425 paid by about 30 mining firms in 2011, tax records show. Empire was followed by Burnsville, with $184,000 in taxes, nearly all from Kraemer Mining & Materials; and Apple Valley, where Fischer Mining paid more than $94,500.

Kraemer executive Dave Edmunds expects to continue producing limestone gravel west of I-35W and south of the Minnesota River for about 20 years. Pete Fischer said roughly two-thirds of his sand and gravel along County Road 42 has been removed, and he has obtained land in Empire Township for future mining. Part of the mined area in Apple Valley already has been developed for housing and retail stores, including Kohl's and Menards.

Rosemount's mining agreement with Dakota Aggregates brings about 900 acres of leased land onto the city tax rolls that had been tax-exempt because it is owned by the University of Minnesota, said Rosemount Mayor Bill Droste.

The entire 1,500-acre mining site sits inside the western boundary of the 5,000-acre UMore Park, east of Biscayne Avenue and south of County Road 42.

Rosemount spent more than two years developing mining permit conditions that include grading and restoring the mined-out areas for future development. The partnership agreed to provide a 130-acre buffer zone with at least 1,000 feet between the nearest home and the mining work, Droste said. That will protect neighbors from noise and dust caused by mine processing and by trucks hauling sand and gravel.

The partnership also agreed to drill wells to monitor runoff from a large wet-mining pond that will dip into the water table. The wells will ensure that runoff doesn't contaminate drinking water or underlying aquifers, planner Zweber said.

Jim Adams • 952-746-3283