ABOUT THIS SERIES

Frac Sand Fever is a periodic Star Tribune series on the sand mining boom in Minnesota and Wisconsin as "hydro-fracking" revolutionizes the nation's oil and gas industry.

Sep. 30: A $55 million sand processing plant could make St. Charles the gateway to Minnesota's new mining frontier.

Today: Sand companies are hiring away local regulators, leaving counties short-staffed in the midst of a land rush and raising ethics questions.