Environmental Group Calls for Tighter Regulation of Frac Sand

The U.S. shale boom has generated a boom in a related industry: "frac sand." Sand has become an integral component of hydraulic fracturing. Oil companies use sand as a "proppant": after shale formations are injected with water and chemicals, the proppant keeps the newly formed cracks open to allow natural gas or crude oil to escape more easily.

Hydraulic fracturing requires a special kind of sand, which is most commonly found in Wisconsin. This so-called "frac sand" is high quality quartz, which is highly resilient and has spherical grains. It is crush-resistant, and can withstand pressures between 6,000 and 14,000 pounds per square inch. A spike in the demand for frac sand has motivated other states to start producing sand. According to most experts, the best rock units to produce frac sand are the St. Peter Sandstone, Jordan Sandstone, Oil Creek Sandstone and Hickory Sandstone. Wisconsin and Minnesota are the biggest players currently, and have a total of 164