Demand for silica sand has grown with the rise of hydraulic fracturing, or fracking, in oil and gas production in western North Dakota and other states. Drillers mix the sand with water and other chemicals and pump it down into wells, propping open cracks so that oil and natural gas can flow out. The hills and bluffs of western Wisconsin and southeastern Minnesota hold easy-to-mine deposits of highly pure silica sand that is the ideal size, shape and hardness for fracking.

Caron, of Tiller Corp., said his company started mining silica sand in 2010 as a way to expand struggling sales.

The "sand rush" has been roaring in Wisconsin for several years. Opponents of the silica mining industry said lawmakers need only look east to see the cost of not stepping in.

Pat Popple said the silica mines are "not a pretty scene" in Chippewa Falls, Wis., where she lives. She urged Minnesota lawmakers to ensure they know enough about the environmental and economic costs of the mines.

The documented dangers of workplace exposure to fresh silica dust include silicosis and lung cancer. But opponents said there hasn't been enough research into the potential health effects of silica dust on everyday citizens â¿¿ not just from the mines themselves, but from processing and transport facilities, too.

Local governments don't have the resources or expertise to do that kind of research, said David Williams, a township supervisor for Preble Township in Fillmore County.

"The conflict is real and it is growing," said Lynn Schoen, who is on Wabasha's City Council. She said she worries about the impact on the city's tourism industry from increased truck traffic â¿¿ as many as 600 trips a day, in and out of the silica sand mine, she said.

The experience in Wisconsin shows that mining operations generate heavy truck traffic that affects communities.

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