Ten years ago, Kraemer Mining and Materials could see complications coming at its limestone quarry in Burnsville.
Groundwater seeping into the quarry had to be pumped into the nearby Minnesota River — more than 3 billion gallons a year. The pumping cost money, but more significant was that the company was bumping up against limits set by the Department of Natural Resources for how much it could pump. That put constraints on expansion.
In the meantime, the people supplying drinking water to residents and businesses in the growing cities of Burnsville and Savage also had a problem. They, too, were being constrained by the state in their desire to tap groundwater.
They could see water levels dropping in the Prairie du Chien-Jordan aquifer, and they knew they couldn’t stay on the same path for another 10 or 20 years and continue to plan for growth. What’s more, groundwater pumping was threatening an unusual kind of wetland in the area. Known as a calcareous fen, it and others like it are protected under state law, much like trout streams are.
The result? People in Burnsville and Savage have been drinking quarry water for the past five years. The cities updated the Metropolitan Council on the project last month and expect to renew their partnership soon for another five years.
It’s an example of thinking differently about water and coming up with a solution that both helps preserve a sensitive environmental area and gives some assurance for a long-time supply of drinking water.
“Forget whether you like the fens or not,” said Steve Albrecht, public works director in Burnsville. “If you want to have a long-term supply of water you have to like this. We hit both sides of the aisle.” It’s a reflection of sharing resources, something Albrecht said water officials will need to do increasingly.
Like trout streams, calcareous fens are protected partly to preserve a valued piece of the environment and partly because their status can be a good indicator for what’s going on underground, where we can’t see.
There are about 200 of the fens in Minnesota, fed mainly by groundwater instead of rain or other surface water. They are rich in calcium and harbor a variety of unusual plants. Typically, they are found at the base of escarpments lining the Minnesota and other rivers.
Together, Burnsville and Savage use 3.5 billion gallons of water a year. They now take about a third of that from a Kraemer quarry via a half-mile pipe that feeds the Burnsville water treatment plant. This has allowed the cities to pump less water from underground than they used to, DNR hydrology records show. And that may be allowing a stressed aquifer to rise to previous levels, said Julie Ekman, a DNR manager.
Kraemer executive vice president and chief operating officer Dave Edmunds said the company brought the idea to officials because it knew it was facing potential water management issues. It worked with planners and local officials under the auspices of the Metropolitan Council. It lobbied for state bonding money to help pay for the additional treatment and other equipment needed and kicked in $3 million of its own money.
In the end, the state paid $5.5 million and the cities another $5.5 million to make it happen. The company pays lower fees to the Department of Natural Resources and has to pump less water as a result.
Edmunds said he knew of no other quarry that was being tapped to provide drinking water to people. A handful of communities in northern Minnesota get water from abandoned mine pits, the Minnesota Department of Health says.
One complication in Burnsville is that surface water, even when it has just emerged from underground in the quarry, places different treatment demands on users. Water from the quarry tastes different from the water from Burnsville and Savage wells, resulting in a lot of resident complaints at first.
The city plant always treated water for iron and manganese but had to add an activated carbon filter to get rid of organic material entering the quarry water. As treatment has adjusted, complaints have dropped to just one or two a month, Albrecht said.