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Does Frac Sand Mining Impact Stream Levels?

A multi-year study of groundwater use in Chippewa County, Wis., shows that stream levels can be negatively impacted by frac sand mining and irrigated agriculture, according to researchers from the Wisconsin Geological and Natural History Survey and U.S. Geological Survey (USGS), which partnered with Chippewa County, sand mining companies, farmers and other stakeholders to measure potential impacts to groundwater in the county. The study was based on data gathered between 2011 and 2014, as well as predictive computer modeling.

According to a report by Wisconsin Public Radio, the results show that around 3 billion gal. of water is used each year in western Chippewa County. Of that demand, 70% came from irrigated agriculture, 22% came from public wells and 6% came from existing frac sand mines. That 3 billion gal. demand represented about 2% of the total groundwater flow through the study area.

The causes of these potential impacts were twofold. Mike Parsen of the Wisconsin Geological and Natural History Survey said that while high-capacity wells at mine sites pulled from the aquifer, mining activity itself reduced the amount of rainwater that could make it into the groundwater supply.

"What we found is that early on what you're doing is you're stripping off native vegetation and typically, there's a lot of truck activity, dozers and earthmovers on site that are moving ground as they're working into the mine," said Parsen. "And that tends to decrease infiltration due to compaction and just the change of that land-use cover."

After frac sand mining is completed, companies are required to reclaim their sites by recontouring the land and developing it into either farmland, forest or prairie. Paul Juckem of USGS said he and other researchers focused on prairie restoration and studied how well water penetrated former mine sites.