Hydraulic Fracturing and the Water Environment

Hydraulic fracturing to obtain oil and natural gas has had a very positive impact on making the United States energy independent.  However, there are water related issues associated with the hydraulic fracturing process such as: water withdrawals; groundwater contamination associated with well drilling and production; wastewater management; truck traffic and its impacts on water quality; surface spills and leaks; and stormwater management.  Two of the most critical issues are water withdrawals and wastewater management.

Water Withdrawals:  Each wellhead requires about one million gallons of fresh water for the fracking process. This results in many billions of gallons of water being used every year. For example, just the Bakken Shale play in Eastern Montana and Western North Dakota alone used approximately six billion gallons of fresh water during 2013.  Many of the shale gas plays are in water stressed regions of the United States where the use of water for fracking is competing with water needs for food production (agriculture and ranching), such as in the Eagle Ford, Barnett Shale, and Permian Basin plays in Texas.  With either insufficient river water supplies or regulatory restrictions, some fracking operations are now purchasing water from private sources, thus increasing costs. For example, the Army Corps of Engineers recently mandated against withdrawing water from the Missouri River for use by fracking operations so operators in those regions must find other sources of fresh water.  Even in water rich areas such as Pennsylvania, there are concerns about water use and the impact on drinking water sources.  The Susquehanna River Basin Commission has stated that the Marcellus Shale play can use up to eight million gallons of water in a single week as the number of wells increase.    Although the volume of water being withdrawn seems extremely large, it is relatively small when compared to the amount of water being used and consumed annually.  According to US-EPA, about 44 billion gallons of water were withdrawn for fracking operations during the period from 2011 to 2012, but this represented only about 1% of the total annual water use and consumption for that same period. However, water withdrawals can result in high competition for water and increased potential for conflicts among various stakeholders in certain locations.

Wastewater Management:  Wastewater generated from the wells is also a major problem.  Flowback from the well typically represents about 60% of the water initially injected into the well and in addition, each well can produce as much as 100,000 gallons per day of wastewater during its operation.   This wastewater must be stored, treated, or disposed of in some way.   Fracking wastewater tends to be high in salinity (represented as total dissolved solids-TDS) and can contain metals and natural occurring radionuclides.  In addition, it contains chemical additives that make up the fracking fluid and excess proppant, as well as residual petroleum products.  As noted by US-EPA, since these constituents are not typical of municipal influent wastewater, fracking wastewater disposed at a municipal treatment plant can be discharged, untreated to surface waters, can disrupt the operation of the treatment plant (for example, by inhibiting biological treatment), can accumulate in biosolids (sewage sludge) limiting their use, and can facilitate the formation of harmful disinfection by-products. In addition, many of the chemicals used in fracking fluids are unknown making it difficult to assess the fate of these chemical through a municipal treatment plant, their impact on water quality of the receiving water, and their potential impact on drinking water sources.  Municipal treatment plant operators are reluctant to allow fracking wastewater to be discharged to their facilities so fracking wastewater is typically disposed of by deep well injection, centralized treatment facilities, and/or reused by the fracking operations.

Although deep well injection is a common way of disposal, it can also result in environmental problems with potential contamination of groundwater as a drinking water source.  In some areas there are insufficient deep wells available resulting in wastewater being transported long distances for deep well injection at other locations.  For example, some fracking companies in Pennsylvania ship wastewater to deep well injections sites in Ohio with trucks driving several hundreds of miles to these sites.

Centralized wastewater treatment (CWT) plants are facilities designed to remove many of the components in the fracking wastewater. The effluent from these treatment facilities can be sent to a municipal wastewater facility for further treatment, or reused by the well operators.  According to an EPA report, the use of CWTs for hydraulic fracturing wastewater is greater in the Marcellus Shale region than other parts of the country most likely due to the lack of deep well injection sites and the high cost of trucking water for disposal. However, these CWTs cannot remove TDS so any effluent that is not reused cannot be discharged to surface water without further treatment.  The amount of water reused by fracking operators varies by location with about 70 to 90% being reused in the Marcellus Shield and little to none in Bakken Shield in North Dakota no water is reused.

Hydraulic fracturing has played a major role in making the US energy independent and providing more economical energy.  The issues associated with water withdrawal and wastewater treatment are solvable issues.  There are many research projects currently underway to developing solutions.   It is important that there is open communication and cooperation between fracking operators, companies producing fracking additives, and researchers so that the most efficient treatment technology is developed to ensure that fracking wastewater can be entirely reused.  Additionally, studies must continue to identify both short-term and long-term environmental risks and impact on drinking water quality and quantity allowing for the development of methods to mitigate these risks.