Minn. cities launch system to treat water underground

The process is called aquifer storage and recovery, and it involves capturing water during times of plenty, storing it underground and pulling it out later when its needed. Its a strategy used a lot in the western and southeastern parts of the country, where drought and water shortages are common. There are hundreds of these storage wells operating in the United States; the project in St. Michael is the first in Minnesota.

This is the first year where the project has been fully up and running, said Kelly Daleiden, project manager for Veolia Water, which operates the well and other joint water efforts for the three cities. The water will be pumped out of the aquifer this summer, when residents want it for lawn watering and drinking. Its interesting, she said. The water comes out just like it went in for the most part.

People across the country are managing groundwater differently as drought, contamination and other factors cause supplies to dwindle. Even in Minnesota, where aquifers were once thought to be limitless in their bounty, cities and regulators are bumping up against limitations and, by necessity, developing new systems.

In St. Michael, Albertville and Hanover, the problem wasnt a strained aquifer, but rather a strained water-treatment plant. In the winter, water demand is just over a million gallons a day. But during the summer lawn-watering season, demand spikes to between 6 and 8 million gallons, near the limit of what the plant can produce. City leaders looked at their rapidly growing communities the population in St. Michael rose 80 percent between 2000 and 2010 to 16,000 and considered building an additional plant.

But then they talked with a consulting company with offices in Iowa, a state with several underground storage systems, and realized that instead of spending $5 million or more on a new treatment plant and related wells and tower, the cities could spend just around $2 million to build a system that would store treated water in a bubble underground.

When we were looking at the best bang for our buck, building another treatment plant to sprinkle lawns didnt seem like the logical thing to do, said St. Michael city administrator Steve Bot. Thats whats great about (underground storage). We already have a plant that can produce well above our winter usage. We have all this extra capacity in the plant you are only using during the summertime. Now, we are able to use that capacity.

Here is how the process works:

Water is filtered and treated, with manganese and iron removed and fluoride and a type of bleach added. Then the water is injected 500 feet underground, via a stainless-steel tube, into the Mount Simon aquifer, where it displaces existing water and remains pretty much in one place until needed. The sandstone aquifer is akin to a bucket of sand and rocks that have been cemented by time. Water there moves slowly, perhaps only several feet per year. When its pulled back out, all it needs is a little added bleach and its ready for consumption.

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Minn. cities launch system to treat water underground