Hydraulic fracturing, also known as "fracking," is a drilling process that injects water, sand and chemicals under high pressure to break through underground rock formations. With fracturing technologies becoming more sophisticated, companies increasingly use fracking to access natural gas deposits in deep shale formations. While oil and gas companies claim the process is safe, reports of groundwater pollution are becoming common in areas near drilling operations. The EPA is expected to issue a report on fracking in 2012, following water quality incidents in Alabama, Colorado, Montana, New Mexico, Virginia, West Virginia, Pennsylvania and Wyoming.
The United States contains many large shale deposits of natural gas, including the Marcellus Shale in the eastern U.S. With drilling companies starting to use fracking in more populated regions, the process is becoming more controversial. Hydraulic fracturing can result in the unintended contamination of surrounding groundwater by methane, fracking chemicals and other toxic substances released from the shale layers, including heavy metals. A Duke University study in 2011 found that water wells in the Marcellus Shale region were contaminated by methane from local drilling operations. Fracking also results in large quantities of wastewater, which must be treated at local waste-treatment plants. Inadequate treatment and wastewater spills have resulted in significant surface-water pollution near drilling sites.
Groundwater pollution can occur when oil or gas wells are improperly sealed when extraction is completed. This type of pollution is more common with older abandoned wells. However, 45,000 new wells were drilled in 2010 alone; some newer wells are certain to present problems in the future. Improperly sealed wells can lead to groundwater contamination from oil, gas and brine water. Hydraulic fracturing in new drilling operations can also disturb older wells, leading to increased contamination.
Many drilling processes use large amounts of water. All drilling operations result in produced water, or water that is drawn up along with oil and gas. Generally, as the well ages, the percentage of produced water increases. Hydraulic fracturing is particularly water-intensive, using from 3 to 8 million gallons of water per well, some of which is taken from groundwater. Drilling operations may also use groundwater for a variety of other purposes.