There are several potential environmental impacts of hydraulic fracturing in addition to those associated with conventional oil and gas exploration and production. Water and air quality impacts will be emphasized here, but seismic events, noise and socioeconomic impacts are additional concerns receiving attention.

WATER

Water quality impacts are the most publicized of potential environmental impacts of hydraulic fracturing. Water contamination can occur due to:

1. lack of integrity of the steel and cement barriers to wellbore-groundwater aquifer communication (refer to What is hydraulic fracturing?). This possibility can materialize, as the case of groundwater contamination in Pavillion, WY demonstrates. The Environmental Protection Agency’s draft report of this instance of contamination, details how inadequate cementing of several wellbores likely led to contamination of drinking water.

2. propagation of induced fractures from the production zone to groundwater aquifers (refer to What is hydraulic fracturing?). This possibility is less likely to occur because production zones are typically several thousand feet deep, whereas groundwater aquifers are usually located at depths of just a few hundred feet. A 2011 study by investigators from Duke University found no evidence of migration of either fracturing fluid or production zone constituents such as naturally-occurring radioactive materials from the production zone to drinking water wells in several locations in the Marcellus Shale. They did, however, find evidence of migration of methane, the principal component of natural gas, from the production zone to drinking water wells. These investigators speculated that pre-existing fractures in the formations overlying the production zone formation permitted this upward migration of methane and that hydraulic fracturing facilitated this migration. This study is published in the peer-reviewed journal Proceedings of the National Academy of Sciences USA and can be accessed here.

3. lack of integrity of surface pits. In addition to disposing of produced water by recycling or injection into UIC Program injection wells, produced water can be held in surface pits to permit evaporation of water (with subsequent treatment of remaining solids at a hazardous waste facility). If the lining of a surface pit is of insufficient integrity, contamination of groundwater aquifers can occur. In the Pavillion, WY case mentioned above, this source of contamination was also implicated.

Water use is also of concern, especially in more arid Western U.S. states. While the volumes of water required for hydraulic fracturing operations are seemingly large (1-5 million gallons), they currently constitute a small fraction of total water use. For example, in Colorado less than 0.1% of state water use in 2010 was for fracturing. Water use projections remain relatively low through 2015, as discussed in the Colorado Oil and Gas Conservation Commission report.

AIR

Air quality impacts comprise another category of potential environmental impacts associated with hydraulic fracturing. The additional equipment required to conduct a fracturing operation results in additional emissions of:

2.

3.

4.

Some of these air pollutants also have produced water (refer to What is hydraulic fracturing?) as a source. Although all are of concern due to their association with chronic diseases such as cardiovascular and respiratory disorders and cancer, methane is of particular concern for another reason. Methane is a greenhouse gas of much greater potency than carbon dioxide; currently, much of this air pollutant escapes capture prior to the production phase of a natural gas well. Recently-promulgated regulations by the Environmental Protection Agency are intended to limit emissions of these air pollutants. Click here to access the regulations.

OTHER

Other potential impacts of hydraulic fracturing include seismic events, noise and socioeconomic impacts. Of these possibilities, seismic events are of perhaps greatest interest. A recent National Research Council report concluded that, in the U.S., no seismic events could be unequivocally linked to fracturing operations. The same report did conclude that two U.K. seismic events, of magnitudes 2.5 and 1.7 on the Richter scale, could be linked to hydraulic fracturing. For reference, the San Francisco Earthquake of 1906 was of magnitude 8-9. The authors of this report postulated that an imbalance between fluid addition and withdrawal may precipitate seismicity; fracturing operations tend to have equal additions and withdrawals of fluid (refer to What is hydraulic fracturing?). Injection of produced water into Class II injection wells would therefore be predicted to have some associated risk of seismic activity. Click here to access the National Research Council report.