Large volumes of oil and gas wastewater are ultimately disposed of in underground injection wells (UICs) through a federal program mandated under the Safe Drinking Water Act.
Most of the estimated 180,000 UIC wells nationwide that are designated for oil and gas waste (known as Class II wells) accept wastewater, fluids, and sludges. According to federal estimates, the shale gas and oil boom increased the number of Class II wells 20% from 2005 to 2012.
In addition, an exemption in the Safe Drinking Water Act allows the oil and gas industry to dispose of waste in some aquifers, which threatens potential drinking water supplies with pollution.
