Environmental impact of hydraulic fracturing

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Illustration of hydraulic fracturing and related activities

Environmental impact of hydraulic fracturing includes the potential contamination of ground water, risks to air quality, noise pollution, the potential migration of gases and hydraulic fracturing chemicals to the surface, the potential mishandling of waste, and the health effects of these.[1][2] Many cases of suspected groundwater contamination have been documented.[3][4] Most of the studies on the environmental impact of hydraulic fracturing have been conducted in the United States.[citation needed] This is due to the fact that the US has not adopted a precautionary approach and therefore has decided to use fracking, conducting ex-post risk assessment, which allows to see the impacts of hydraulic fracturing on the environment. Countries that have adopted a precautionary approach like France [5] cannot evaluate such impacts since they do not undergo the potential hazards of fracking. Nevertheless, studies also exist for the North of England, Canada and Australia too, whose approach is close to the American one.

Air emissions[edit]

The main hydraulic-fracturing-related air emissions are methane emissions from the wells during fracturing and emissions from hydraulic fracturing equipment, such as compressor stations. Whether natural gas produced by hydraulic fracturing causes higher well-to-burner emissions than gas produced from conventional wells is a matter of contention. Some studies have found that hydraulic fracturing has higher emissions due to gas released during completing wells as some gas returns to the surface, together with the fracturing fluids. Depending on their treatment, the well-to-burner emissions are 3.5%–12% higher than for conventional gas.[6]

A debate has arisen particularly around a study by professor Robert W. Howarth finding shale gas significantly worse for global warming than oil or coal.[7] Other researchers have criticized Howarth's analysis,[8][9] including Cathles et al., whose estimates were substantially lower."[10] A 2012 industry funded report co-authored by researchers at the U.S. Department of Energy's National Renewable Energy Laboratory found emissions from shale gas, when burned for electricity, were "very similar" to those from so-called "conventional well" natural gas, and less than half the emissions of coal.[11]

This has led to saying shale gas could be a “transitionel fuel” to help reaching greenhouse gas emissions diminution in order to fight climate change and global warming.[12] Nevertheless, studies have demonstrated that the argument did not empirically hold in the UK. Indeed, a study conducted in 2011 by Broderick et al. said that “If the UK Government is to respect its obligations under both the Copenhagen Accord and Low Carbon Transition Plan, shale gas offers no meaningful potential as even a transitional fuel.”[13] Moreover, the 2012 Tyndall Center report stated that the US have known an increase in coal consumption that has gone on rising. They thus conclude, saying “without a meaningful cap on global emissions, the exploitation of shale gas reserves is likely to increase total emissions.” [14]

Several studies which have estimated lifecycle methane leakage from shale gas development and production have found a wide range of leakage rates, from less than 1% of total production to nearly 8%.[15][16] According to the Environmental Protection Agency's Greenhouse Gas Inventory a methane leakage rate is about 1.4%.[17] The American Gas Association, an industry trade group, calculated a 1.2% leakage rate.[18] The most comprehensive study of methane leakage from shale gas to date, initiated by the Environmental Defense Fund and released in the Proceedings of the National Academy of Sciences on September 16, 2013, finds that fugitive emissions in key stages of the natural gas production process are significantly lower than estimates in the EPA's national emissions inventory. The study reports direct measurements from 190 onshore natural gas sites, all hydraulically fractured, across the country and estimates a leakage rate of 0.42% for gas production.[15]

Also transportation of necessary water volume for hydraulic fracturing, if done by trucks, can cause high volumes of air emissions, especially particulate matter emissions.[19]

Water consumption[edit]

Hydraulic fracturing uses between 1.2 and 3.5 million US gallons (4,500 and 13,200 m3) of water per well, with large projects using up to 5 million US gallons (19,000 m3). Additional water is used when wells are refractured.[20][21] An average well requires 3 to 8 million US gallons (11,000 to 30,000 m3) of water over its lifetime.[21][22][23][24] According to the Oxford Institute for Energy Studies, greater volumes of fracturing fluids are required in Europe, where the shale depths average 1.5 times greater than in the U.S.[25]

Concern has been raised over the increasing quantities of water for hydraulic fracturing. Use of water for hydraulic fracturing can divert water from stream flow, water supplies for municipalities and industries such as power generation, as well as recreation and aquatic life.[26] The large volumes of water required for most common hydraulic fracturing methods have raised concerns for arid regions, such as Karoo in South Africa,[27] and in Pennsylvania,[28][29] and in drought-prone Texas, and Colorado in North America.[30] It may also require water overland piping from distant sources.[23]

Some producers have developed hydraulic fracturing techniques that could reduce the need for water.[31] Using carbon dioxide, liquid propane or other gases instead of water have been proposed to reduce water consumption.[32] After it is used, the propane returns to its gaseous state and can be collected and reused. In addition to water savings, gas fracturing reportedly produces less damage to rock formations that can impede production.[31] Recycled flowback water can be reused in hydraulic fracturing.[6] It lowers the total amount of water used and reduces the need to dispose of wastewater after use. The technique is relatively expensive, however, since the water must be treated before each reuse and it can shorten the life of some types of equipment.[33] Also, fracking converts millions of gallons of water into toxic wastewater each year, taking this water out of the water cycle and the possibility of further use, except in fracking itself after recycling.[34]

New data shows that water saved by using natural gas combined cycle plants instead of coal steam turbine plants saves 25–50 times more water than the amount of water needed to extract the gas using hydraulic fracturing.[35]

Water contamination[edit]

Although local groundwater contamination resulting from fracking has been documented, the American Environmental Protection Agency has launched a comprehensive study whose results will be released in 2014 to know if there is a general impact of hydraulic fracturing on groundwater contamination.[36]

Injected fluid[edit]

Hydraulic fracturing fluids may cause contamination both as it is injected under high pressure into the ground and as it returns to the surface.[37][38] To mitigate the effect of hydraulic fracturing on groundwater, the well and ideally the formation itself should remain hydraulically isolated from other geological formations, especially freshwater aquifers.[6]

The type of chemicals used in hydraulic fracturing and their properties vary. While most of them are common and generally harmless, some chemicals used in the United States are carcinogenic.[1] Out of 2,500 hydraulic fracturing additives, more than 650 contained known or possible human carcinogens regulated under the Safe Drinking Water Act.[1] Another 2011 study identified 632 chemicals used in United States natural gas operations, of which only 353 are well-described in the scientific literature.[39]

The European Union regulatory regime requires full disclosure of all additives.[40] In the US, the Ground Water Protection Council launched FracFocus.org, an online voluntary disclosure database for hydraulic fracturing fluids funded by oil and gas trade groups and the U.S. Department of Energy.[41][42]

Flowback[edit]

As the fracturing fluid flows back through the well, it consists of spent fluids and may contain dissolved constituents such as minerals and brine waters.[43][44] In some cases, depending the geology of formation, it may concentrate uranium, radium, radon and thorium.[45] Estimates of the amount of injected fluid returning to the surface range from 15-20% to 30–70%.[44][46] Additional fluid may return to the surface through abandoned wells or other pathways.[47]

Approaches to managing these fluids, commonly known as produced water, include underground injection, municipal and commercial wastewater treatment and discharge, self‐contained systems at well sites or fields, and recycling to fracture future wells.[11][44][48][49] The vacuum multi-effect membrane distillation system as a more effective treatment system has been proposed for treatment of flowback.[50] However, the quantity of waste water needing treatment and the improper configuration of sewage plants have become an issue in some regions of the United States. Part of the wastewater from hydraulic fracturing operations is processed there by public sewage treatment plants, which are not equipped to remove radioactive material and are not required to test for it.[51][52]

A 2011 report by the MIT Energy Initiative addressed groundwater contamination, noting "there has been concern that these fractures can also penetrate shallow freshwater zones and contaminate them with fracturing fluid, but there is no evidence that this is occurring".[53]

Surface spills[edit]

Surface spills related to the hydraulic fracturing occur mainly because of equipment failure or engineering misjudgments.[54][55]

Volatile chemicals held in waste water evaporation ponds can to evaporate into the atmosphere, or overflow. The runoff can also end up in groundwater systems. Groundwater may become contaminated by trucks carrying hydraulic fracturing chemicals and wastewater if they are involved in accidents on the way to hydraulic fracturing sites or disposal destinations.[56]

Methane[edit]

Groundwater methane contamination has adverse effect on water quality and in extreme cases may lead to potential explosion.[57] A scientific study conducted by researchers of Duke University found high correlations of gas well drilling activities, including hydraulic fracturing, and methane pollution of the drinking water.[57] According to the 2011 study of the MIT Energy Initiative, "there is evidence of natural gas (methane) migration into freshwater zones in some areas, most likely as a result of substandard well completion practices i.e. poor quality cementing job or bad casing, by a few operators."[53] A 2013 Duke study suggested that both faulty construction (defective cement seals in the upper part of wells and faulty steel linings within deeper layers) and peculiarity of local geology may be allowing methane and injected fluid to seep into waters.[38] Abandoned gas and oil wells also provide conduits to the surface.[47]

However, methane contamination is not always caused by hydraulic fracturing. Drilling for ordinary drinking water wells can also cause methane release. Most recent studies make use of tests that can distinguish between the deep thermogenic methane released during gas/oil drilling, and the shallower biogenic methane that can be released during water-well drilling. While both forms of methane result from decomposition, thermogenic methane results from geothermal assistance deeper underground.[58][59] A study by Cabot Oil and Gas examined the Duke study using a larger sample size, found that methane concentrations were related to topography, with the highest readings found in low-lying areas, rather than related to distance from gas production areas. Using a more precise isotopic analysis, they showed that the methane found in the water wells came from both the formations where hydraulic fracturing occurred, and from the shallower formations.[58] The Colorado Oil & Gas Conservation Commission has found some wells containing thermogenic methane due to oil and gas development upon investigating complaints from residents.[59] A review published in February 2012 found no direct evidence that hydraulic fracturing actual injection phase resulted in contamination of ground water, and suggests that reported problems occur due to leaks in its fluid or waste storage apparatus; the review says that methane in water wells in some areas probably comes from natural resources.[60][61]

Seismology[edit]

Hydraulic fracturing causes induced seismicity called microseismic events or microearthquakes. These microseismic events are often used to map the horizontal and vertical extent of the fracturing.[62] The magnitude of these events is usually too small to be detected at the surface, although the biggest micro-earthquakes may have the magnitude of about -1.6 (Mw). However, as of late 2012, there have been three instances of hydraulic fracturing, through induced seismicity, triggering quakes large enough to be felt by people: one each in the United States, Canada, and England.[63][64] In England, two earthquakes that occurred in April and May 2011 of a magnitude of respectively 1.5 and 2.3 on the Richter scale were felt by local populations. The UK Department of Energy and Climate Change said the “observed seismicity in April and May 2011 was induced by the hydraulic fracture treatments at Preese Hall”, in the North of England.[12] The injection of waste water from gas operations, including from hydraulic fracturing, into saltwater disposal wells may cause bigger low-magnitude tremors, being registered up to 3.3 (Mw).[65]

A 2012 US Geological Survey study reported that a "remarkable" increase in the rate of M ≥ 3 earthquakes in the US midcontinent "is currently in progress", having started in 2001 and culminating in a 6-fold increase over 20th century levels in 2011. The overall increase was tied to earthquake increases in a few specific areas: the Raton Basin of southern Colorado (site of coalbed methane activity), and gas-producing areas in central and southern Oklahoma, and central Arkansas.[66] While analysis suggested that the increase is "almost certainly man-made", the USGS noted: "USGS's studies suggest that the actual hydraulic fracturing process is only very rarely the direct cause of felt earthquakes." The increased earthquakes were said to be most likely caused by increased injection of gas-well wastewater into disposal wells.[67] The injection of waste water from oil and gas operations, including from hydraulic fracturing, into saltwater disposal wells may cause bigger low-magnitude tremors, being registered up to 3.3 (Mw).[65]

Induced seismicity from hydraulic fracturing[edit]

The United States Geological Survey (USGS) has reported earthquakes induced by hydraulic fracturing and by disposal of hydraulic fracturing flowback into waste disposal wells in several locations. Bill Ellsworth, a geoscientist with the U.S. Geological Survey, has said, however: “We don't see any connection between hydraulic fracturing and earthquakes of any concern to society.”[68] The National Research Council (part of the National Academy of Sciences) has also observed that hydraulic fracturing, when used in shale gas recovery, does not pose a serious risk of causing earthquakes that can be felt.[69] In 2013, Researchers from Columbia University and the University of Oklahoma demonstrated that in the midwestern United States, some areas with increased human-induced seismicity are susceptible to additional earthquakes triggered by the seismic waves from remote earthquakes. They recommended increased seismic monitoring near fluid injection sites to determine which areas are vulnerable to remote triggering and when injection activity should be ceased.[63][70]

A British Columbia Oil and Gas Commission investigation concluded that a series of 38 earthquakes (magnitudes ranging from 2.2 to 3.8 on the Richter scale) occurring in the Horn River Basin area between 2009 and 2011 were caused by fluid injection during hydraulic fracturing in proximity to pre-existing faults. The tremors were small enough that only one of them was reported felt by people; there were no reports of injury or property damage.[71]

A report in the United Kingdom concluded that hydraulic fracturing was the likely cause of two small tremors (magnitudes 2.3 and 1.4 on the Richter scale) that occurred during hydraulic fracturing of shale in April and May 2011.[72][73][74] These tremors were felt by local populations. Because of these two events, seismicity is impact mostly related to hydraulic fracturing in the UK's public opinion.[12]

Induced seismicity from water disposal wells[edit]

According to the USGS only a small fraction of roughly 30,000 waste fluid disposal wells for oil and gas operations in the United States have induced earthquakes that are large enough to be of concern to the public.[67] Although the magnitudes of these quakes has been small, the USGS says that there is no guarantee that larger quakes will not occur.[75] In addition, the frequency of the quakes has been increasing. In 2009, there were 50 earthquakes greater than magnitude 3.0 in the area spanning Alabama and Montana, and there were 87 quakes in 2010. In 2011 there were 134 earthquakes in the same area, a sixfold increase over 20th century levels.[76] There are also concerns that quakes may damage underground gas, oil, and water lines and wells that were not designed to withstand earthquakes.[75][77]

Several earthquakes in 2011, including a 4.0 magnitude quake on New Year's Eve that hit Youngstown, Ohio, are likely linked to a disposal of hydraulic fracturing wastewater,[63] according to seismologists at Columbia University.[78] A similar series of small earthquakes occurred in 2012 in Texas. Earthquakes are not common occurrences in either area.[79]

Health risks[edit]

Concern has been expressed over the possible long and short term health effects of air and water contamination and radiation exposure by gas production.[45][80][81] Health consequences of concern include infertility, birth defects and cancer.[82][unreliable medical source?][83][84][unreliable medical source?] There are reports of health problems around compressors stations[85][unreliable medical source?] or drilling sites,[86] although a causal relationship was not established for the limited number of wells studied[86] and another Texas government analysis found no evidence of effects.[87]

Trace amounts of chemicals used in the drilling process may affect the health of those working on or living near the wells. In 2012, researchers from the Colorado School of Public Health showed that air pollution caused by hydraulic fracturing may contribute to "acute and chronic health problems" for those living near drilling sites.[88] A 2012 study concluded that risk prevention efforts should be directed towards reducing air emission exposures for persons living and working near wells during well completions.[89] A study conducted in Garfield County, Colorado and published in Endocrinology suggested that natural gas drilling operations may result in elevated endocrine-disrupting chemical activity in surface and ground water.[83]

Richard A. Muller, a Principal of the China Shale Fund, argues that the benefits from shale gas made available by hydraulic fracturing, by displacing harmful air pollution from coal, far outweigh their combined environmental costs.[citation needed] In a 2013 report for the Centre for Policy Studies, Muller writes that air pollution, mostly from coal burning, kills over three million people each year, primarily in the developing world. The report does not reference any studies on air pollution associated with gas produced through hydraulic fracturing.[90]

Safety issues[edit]

An additional concern is that oil obtained through hydraulic fracturing contains chemicals used in hydraulic fracturing, which may increase the rate at which rail tank cars and pipelines corrode, potentially releasing their load and its gases.[91][92]

Scientific debate[edit]

There are two main approaches to regulation that derive from a scientific debate over the value of risk assessment. Social sciences have raised two main critiques of risk assessment. Firstly, it takes scientific issues out of the public debate since there is no debate on the use of a technology but on its impacts. Secondly, it does not prevent environmental harm from happening since risks are taken then assessed instead of evaluated then taken as it would be the case with a precautionary approach to scientific debates. The relevance and reliability of risk assessments in fracking communities has also been debated amongst environmental groups, health scientists, and industry leaders. The risks, to some, are overplayed and the current research is insufficient in showing the link between fracking and adverse health effects, while to others the risks are obvious and risk assessment is underfunded.[12]

Different regulatory approaches have thus emerged. In France and Vermont for instance, a precautionary approach has been favored and fracking has been banned based on two principles: the precautionary principle and the prevention principle.[5][93] Nevertheless, some States such as the U.S. have adopted a risk assessment approach, which had led to many regulatory debates over the issue of hydraulic fracturing and its risks.

In the UK, the regulatory framework is largely being shaped by a report commissioned by the UK Government in 2012, whose purpose was to identify the problems around fracking and to advise the country's regulatory agencies. Jointly published by the Royal Society and the Royal Academy of Engineering, under the chairmanship of Professor Robert Mair, the report features ten recommendations covering issues such as groundwater contamination, well integrity, seismic risk, gas leakages, water management, environmental risks, best practice for risk management, and also includes advice for regulators and research councils.[94][95] The report was notable for stating that the risks associated with fracking are manageable if carried out under effective regulation and if operational best practices are implemented.

Anti-fracking movement[edit]

An anti-fracking movement has emerged both internationally with involvement of international environmental organizations and nation states such as France and locally in affected areas such as Balcombe in Sussex where the Balcombe drilling protest was in progress during summer 2013.[96]

See also[edit]

References[edit]

  1. ^ a b c (PDF) Chemicals Used in Hydraulic Fracturing (Report). Committee on Energy and Commerce U.S. House of Representatives. April 18, 2011. http://democrats.energycommerce.house.gov/sites/default/files/documents/Hydraulic-Fracturing-Chemicals-2011-4-18.pdf.
  2. ^ Brown, Valerie J. (February 2007). "Industry Issues: Putting the Heat on Gas". Environmental Health Perspectives (US National Institute of Environmental Health Sciences) 115 (2): A76. doi:10.1289/ehp.115-a76. PMC 1817691. PMID 17384744. Retrieved 2012-05-01. 
  3. ^ Mall, Amy (19 December 2011). "Incidents where hydraulic fracturing is a suspected cause of drinking water contamination". Switchboard: NRDC Staff Blog. Natural Resources Defense Council. Retrieved 23 February 2012. 
  4. ^ Lustgarten, Abrahm (November 2008). "Incidents where hydraulic fracturing is a suspected cause of drinking water contamination". ProPublica. Retrieved 20 March 2012. 
  5. ^ a b "LOI n° 2011-835 du 13 juillet 2011 visant à interdire l'exploration et l'exploitation des mines d'hydrocarbures liquides ou gazeux par fracturation hydraulique et à abroger les permis exclusifs de recherches comportant des projets ayant recours à cette technique"
  6. ^ a b c IEA (2011). World Energy Outlook 2011. OECD. pp. 91; 164. ISBN 978 92 64 12413 4. 
  7. ^ Howarth, Robert W.; Santoro, Renee; Ingraffea, Anthony (13 March 2011). "Methane and the greenhouse-gas footprint of natural gas from shale formations" (PDF). Climatic Change (Springer) 106 (4): 679–690. doi:10.1007/s10584-011-0061-5. Retrieved 2012-05-07. 
  8. ^ Cathles, Lawrence M.; Brown, Larry; Taam, Milton; Hunter, Andrew (2011). "A commentary on "The greenhouse-gas footprint of natural gas in shale formations"". Climatic Change. doi:10.1007/s10584-011-0333-0. Retrieved 7 August 2013. 
  9. ^ Stephen Leahy (24 January 2012). "Shale Gas a Bridge to More Global Warming". IPS. Retrieved 4 February 2012. 
  10. ^ Howarth, Robert W.; Santoro, Renee; Ingraffea, Anthony (1 February 2012). "Venting and leaking of methane from shale gas development: Response to Cathles et al." (PDF). Climatic Change (Springer). doi:10.1007/s10584-012-0401-0. Retrieved 4 February 2012. 
  11. ^ a b Logan, Jeffrey (2012) (PDF). Natural Gas and the Transformation of the U.S. Energy Sector: Electricity (Report). Joint Institute for Strategic Energy Analysis. http://www.nrel.gov/docs/fy13osti/55538.pdf. Retrieved 27 March 2013.
  12. ^ a b c d Williams, Laurence, John "Framing fracking: public responses to potential unconventional fossil fuel exploitation in the North of England", Durham thesis, Durham University, 2014
  13. ^ "Shale gas: an updated assessment of environmental and climate change impacts", Tyndall Center, 2011
  14. ^ Broderick, Anderson "Has US Shale Gas Reduced CO2 Emissions?", Tyndall Center, 2012
  15. ^ a b Allen, David T.; Torres, Vincent N.; Thomas, James; Sullivan, David W.; Harrison, Matthew; Hendler, Al; Herndon, Scott C.; Kolb, Charles E.; Fraser, Matthew P.; Hill, A. Daniel; Lamb, Brian K.; Miskimins, Jennifer; Sawyer, Robert F.; Seinfeld, John H. (16 September 2013). "Measurements of methane emissions at natural gas production sites in the United States" (PDF). Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1304880110. Retrieved 2013-10-02. 
  16. ^ Trembath, Alex; Luke, Max; Shellenberger, Michael; Nordhaus, Ted (June 2013) (PDF). Coal Killer: How Natural Gas Fuels the Clean Energy Revolution (Report). Breakthrough institute. p. 22. http://thebreakthrough.org/images/main_image/Breakthrough_Institute_Coal_Killer.pdf. Retrieved 2 October 2013.
  17. ^ Bradbury, James; Obeiter, Michael (2013-05-06). "5 Reasons Why It's Still Important To Reduce Fugitive Methane Emissions". World Resources Institute. Retrieved 2013-10-02. 
  18. ^ "The Importance of Accurate Data". True Blue Natural Gas. Retrieved 27 March 2013. 
  19. ^ Fernandez, John Michael; Gunter, Matthew. Hydraulic Fracturing: Environmentally Friendly Practices (PDF). Houston Advanced Research Center. Retrieved 2012-12-29. 
  20. ^ Andrews, Anthony et al. (30 October 2009) (PDF). Unconventional Gas Shales: Development, Technology, and Policy Issues (Report). Congressional Research Service. pp. 7; 23. http://www.fas.org/sgp/crs/misc/R40894.pdf. Retrieved 22 February 2012.
  21. ^ a b Abdalla, Charles W.; Drohan, Joy R. (2010) (PDF). Water Withdrawals for Development of Marcellus Shale Gas in Pennsylvania. Introduction to Pennsylvania’s Water Resources (Report). The Pennsylvania State University. http://pubs.cas.psu.edu/FreePubs/pdfs/ua460.pdf. Retrieved 16 September 2012. "Hydrofracturing a horizontal Marcellus well may use 4 to 8 million gallons of water, typically within about 1 week. However, based on experiences in other major U.S. shale gas fields, some Marcellus wells may need to be hydrofractured several times over their productive life (typically five to twenty years or more)"
  22. ^ Ground Water Protection Council; ALL Consulting (April 2009) (PDF). Modern Shale Gas Development in the United States: A Primer (Report). DOE Office of Fossil Energy and National Energy Technology Laboratory. pp. 56–66. DE-FG26-04NT15455. http://www.netl.doe.gov/technologies/oil-gas/publications/EPreports/Shale_Gas_Primer_2009.pdf. Retrieved 24 February 2012.
  23. ^ a b Arthur, J. Daniel; Uretsky, Mike; Wilson, Preston (May 5–6, 2010). "Water Resources and Use for Hydraulic Fracturing in the Marcellus Shale Region" (PDF). Meeting of the American Institute of Professional Geologists. Pittsburgh: ALL Consulting. p. 3. Retrieved 2012-05-09. 
  24. ^ Cothren, Jackson (PDF). Modeling the Effects of Non-Riparian Surface Water Diversions on Flow Conditions in the Little Red Watershed (Report). U. S. Geological Survey, Arkansas Water Science Center Arkansas Water Resources Center, American Water Resources Association, Arkansas State Section Fayetteville Shale Symposium 2012. p. 12. http://ar.water.usgs.gov/Fayetteville_Shale/abstracts.pdf. Retrieved 16 September 2012. "...each well requires between 3 and 7 million gallons of water for hydraulic fracturing and the number of wells is expected to grow in the future"
  25. ^ Faucon, Benoît (17 September 2012). "Shale-Gas Boom Hits Eastern Europe". WSJ.com. Retrieved 17 September 2012. 
  26. ^ Upton, John (August 15, 2013). "Fracking company wants to build new pipeline — for water". Grist. Retrieved August 16, 2013. 
  27. ^ Urbina, Ian (30 December 2011). "Hunt for Gas Hits Fragile Soil, and South Africans Fear Risks". The New York Times. Retrieved 23 February 2012. "Covering much of the roughly 800 miles between Johannesburg and Cape Town, this arid expanse – its name [Karoo] means "thirsty land" – sees less rain in some parts than the Mojave Desert." 
  28. ^ Janco, David F. (3 January 2008). PADEP Determination Letter No. 352 Determination Letter acquired by the Scranton Times-Tribune via Right-To-Know Law request. Order: Atlas Miller 42 and 43 gas wells; Aug 2007 investigation; supplied temporary buffalo for two springs, ordered to permanently replace supplies (Report). Scranton Times-Tribune. http://scrantontimestribune.com/waterproject/352.pdf. Retrieved 27 December 2013.
  29. ^ Janco, David F. (1 February 2007). PADEP Determination Letter No. 970. Diminution of Snow Shoe Borough Authority Water Well No. 2; primary water source for about 1,000 homes and businesses in and around the borough; contested by Range Resources. Determination Letter acquired by the Scranton Times-Tribune via Right-To-Know Law request. (Report). Scranton Times-Tribune. http://scrantontimestribune.com/waterproject/970.pdf. Retrieved 27 December 2013.
  30. ^ Staff (16 June 2013). "Fracking fuels water battles". Politico. Associated Press. Retrieved 26 June 2013. 
  31. ^ a b "Texas Water Report: Going Deeper for the Solution". Texas Comptroller of Public Accounts. Retrieved 2014-02-11. 
  32. ^ Bullis, Kevin (2013-03-22). "Skipping the Water in Fracking". MIT Technology Review. Retrieved 2014-03-30. 
  33. ^ Sider, Alison; Lefebvre, Ben (20 November 2012). "Drillers Begin Reusing 'Frack Water.' Energy Firms Explore Recycling Options for an Industry That Consumes Water on Pace With Chicago". The Wall Street Journal. Retrieved 20 October 2013. 
  34. ^ Ridlington, Rumpler "Fracking by the numbers: key impact of dirty drilling at the state and national level", Environment America, October 2013
  35. ^ Scanlon, Bridget R; Duncan, Ian; Reedy, Robert C (2013). "Drought and the water–energy nexus in Texas" (PDF). Environmental Research Letters 8 (4). doi:10.1088/1748-9326/8/4/045033. Retrieved 2014-03-30. 
  36. ^ [1], Environmental Protection Agency
  37. ^ Staff (26 February 2011). "Drilling Down: Documents: Natural Gas's Toxic Waste". The New York Times. Retrieved 23 February 2012. 
  38. ^ a b Ehrenburg, Rachel (25 June 2013). "News in Brief: High methane in drinking water near fracking sites. Well construction and geology may both play a role". Science News. Retrieved 26 June 2013. 
  39. ^ Colborn, Theo; Kwiatkowski, Carol; Schultz, Kim; Bachran, Mary (2011). "Natural Gas Operations from a Public Health Perspective" (PDF). Human and Ecological Risk Assessment: an International Journal (Taylor & Francis) 17 (5): 1039–1056. doi:10.1080/10807039.2011.605662. 
  40. ^ Healy, Dave (July 2012) (PDF). Hydraulic Fracturing or 'Fracking': A Short Summary of Current Knowledge and Potential Environmental Impacts (Report). Environmental Protection Agency. http://www.epa.ie/pubs/reports/research/sss/UniAberdeen_FrackingReport.pdf. Retrieved 28 July 2013.
  41. ^ Hass, Benjamin (14 August 2012). "Fracking Hazards Obscured in Failure to Disclose Wells". Bloomberg News. Retrieved 27 March 2013. 
  42. ^ Soraghan, Mike (13 December 2013). "White House official backs FracFocus as preferred disclosure method". E&E News. Retrieved 27 March 2013. 
  43. ^ Sandy McSurdy & Radisav Vidic (25 June 2013) (PDF). Sustainable Management of Flowback Water during Hydraulic Fracturing of Marcellus Shale for Natural Gas Production (Report). National Energy Technology Laboratory, US Department of Energy. http://www.netl.doe.gov/technologies/oil-gas/Petroleum/projects/Environmental/Produced_Water/00975_MarcellusFlowback.html. Retrieved 29 June 2013.
  44. ^ a b c Arthur, J. Daniel; Langhus, Bruce; Alleman, David (2008) (PDF). An overview of modern shale gas development in the United States (Report). ALL Consulting. p. 21. http://www.lexisnexis.com/documents/pdf/20100210093849_large.pdf. Retrieved 2012-05-07.
  45. ^ a b Weinhold, Bob (19 September 2012). "Unknown Quantity: Regulating Radionuclides in Tap Water". Environmental Health Perspectives. NIEHS, NIH. Retrieved 11 February 2012. "Examples of human activities that may lead to radionuclide exposure include mining, milling, and processing of radio­active substances; wastewater releases from the hydraulic fracturing of oil and natural gas wells... Mining and hydraulic fracturing, or "fracking", can concentrate levels of uranium (as well as radium, radon, and thorium) in wastewater..." 
  46. ^ Staff (PDF). Waste water (Flowback)from Hydraulic Fracturing (Report). Ohio Department of Natural Resources. http://www.ohiodnr.com/Portals/11/pdf/wastewater-fact-sheet.pdf. Retrieved 29 June 2013. "Most of the water used in fracturing remains thousands of feet underground, however, about 15-20 percent returns to the surface through a steel-cased well bore and is temporarily stored in steel tanks or lined pits. The wastewater which returns to the surface after hydraulic fracturing is called flowback"
  47. ^ a b Detrow, Scott (9 October 2012). "Perilous Pathways: How Drilling Near An Abandoned Well Produced a Methane Geyser". StateImpact Penn­syl­va­nia. NPR. Retrieved 29 June 2013. 
  48. ^ Hopey, Don (1 March 2011). "Gas drillers recycling more water, using fewer chemicals". Pittsburgh Post-Gazette. Retrieved 27 March 2013. 
  49. ^ Litvak, Anya (21 August 2012). "Marcellus flowback recycling reaches 90 percent in SWPA.". Pittsburgh Business Times. Retrieved 27 March 2013. 
  50. ^ "Monitor: Clean that up". The Economist. 2013-11-30. Retrieved 2013-12-15. 
  51. ^ David Caruso (2011-01-03). "44,000 Barrels of Tainted Water Dumped Into Neshaminy Creek. We're the only state allowing tainted water into our rivers". NBC Philadelphia. Associated Press. Retrieved 2012-04-28. 
  52. ^ Urbina, Ian (26 February 2011). "Regulation Lax as Gas Wells' Tainted Water Hits Rivers". The New York Times. Retrieved 22 February 2012. 
  53. ^ a b Moniz, Ernest J. et al. (June 2011) (PDF). The Future of Natural Gas: An Interdisciplinary MIT Study (Report). Massachusetts Institute of Technology. http://web.mit.edu/mitei/research/studies/documents/natural-gas-2011/NaturalGas_Report.pdf. Retrieved 1 June 2012.
  54. ^ New Research of Surface Spills in Fracking Industry. (2013). Professional Safety, 58(9), 18.
  55. ^ name= savannahb022
  56. ^ Energy Institute (February 2012) (PDF). Fact-Based Regulation for Environmental Protection in Shale Gas Development (Report). University of Texas at Austin. p. ?. http://www.scribd.com/doc/82147814/Fact-Based-Regulation-for-Environmental-Protection-in-Shale-Gas-Development-by-The-Energy-Institute-at-the-University-of-Texas-at-Austin-February-201. Retrieved 29 February 2012.
  57. ^ a b Osborn, Stephen G.; Vengosh, Avner; Warner, Nathaniel R.; Jackson, Robert B. (2011-05-17). "Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing" (PDF). Proceedings of the National Academy of Sciences of the United States of America 108 (20): 8172–8176. doi:10.1073/pnas.1100682108. Retrieved 2011-10-14. 
  58. ^ a b Molofsky, L. J.; Connor, J. A.; Shahla, K. F.; Wylie, A. S.; Wagner, T. (December 5, 2011). "Methane in Pennsylvania Water Wells Unrelated to Marcellus Shale Fracturing". Oil and Gas Journal (Pennwell Corporation) 109 (49): 54–67. 
  59. ^ a b "Gasland Correction Document". Colorado Oil & Gas Conservation Commission. Retrieved 7 August 2013. 
  60. ^ "Fracking Acquitted of Contaminating Groundwater". Science 335: 898. 24 February 2012. doi:10.1126/science.335.6071.898. 
  61. ^ Erik Stokstad (16 February 2012). "Mixed Verdict on Fracking". Science. 
  62. ^ Bennet, Les, et al.. "The Source for Hydraulic Fracture Characterization" (PDF). Oilfield Review (Schlumberger) (Winter 2005/2006): 42–57. Retrieved 2012-09-30. 
  63. ^ a b c Kim, Won-Young 'Induced seismicity associated with fluid injection into a deep well in Youngstown, Ohio', Journal of Geophysical Research-Solid Earth
  64. ^ Begley, Sharon; McAllister, Edward (12 July 2013). "News in Science: Earthquakes may trigger fracking tremors". ABC Science (Reuters). Retrieved 17 December 2013. 
  65. ^ a b Zoback, Mark; Kitasei, Saya; Copithorne, Brad (July 2010) (PDF). Addressing the Environmental Risks from Shale Gas Development (Report). Worldwatch Institute. p. 9. http://efdsystems.org/Portals/25/Hydraulic%20Fracturing%20Paper%20-%20World%20Watch.pdf. Retrieved 2012-05-24.
  66. ^ Ellsworth, W. L.; Hickman, S.H.; McGarr, A.; Michael, A. J.; Rubinstein, J. L. (18 April 2012). "Are seismicity rate changes in the midcontinent natural or manmade?". Seismological Society of America 2012 meeting. San Diego, California: Seismological Society of America. Retrieved 2014-02-23. 
  67. ^ a b "Man-Made Earthquakes Update". United States Geological Survey. 2014-01-17. Retrieved 2014-03-30. 
  68. ^ Soraghan, Mike (13 December 2013). "Disconnects in public discourse around 'fracking' cloud earthquake issue.". E&E News. Retrieved 27 March 2013. 
  69. ^ "Induced Seismicity Potential in Energy Technologies". National Academies Press. Retrieved 27 March 2013. "The process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events." 
  70. ^ van der Elst1, Nicholas J.; Savage, Heather M.; Keranen, Katie M; Abers, Geoffrey A. (12 July 2013). "Enhanced Remote Earthquake Triggering at Fluid-Injection Sites in the Midwestern United States". Science (ACS Publications). 341 (6142): 164–167. doi:10.1126/science.1238948. 
  71. ^ "Fracking causes minor earthquakes, B.C. regulator says". The Canadian Press (Canadian Broadcast Company — British Columbia). 6 September 2012. Retrieved 2012-10-28. 
  72. ^ "Shale gas fracking: MPs call for safety inquiry after tremors". BBC News. 8 June 2011. Retrieved 22 February 2012. 
  73. ^ "Fracking tests near Blackpool 'likely cause' of tremors". BBC News. 2 November 2011. Retrieved 22 February 2012. 
  74. ^ de Pater, C.J.; Baisch, S. (2 November 2011) (PDF). Geomechanical Study of Bowland Shale Seismicity (Report). Cuadrilla Resources. http://www.cuadrillaresources.com/wp-content/uploads/2012/02/Geomechanical-Study-of-Bowland-Shale-Seismicity_02-11-11.pdf. Retrieved 22 February 2012.
  75. ^ a b Rachel Maddow, Terrence Henry (7 August 2012). Rachel Maddow Show: Fracking waste messes with Texas (video). MSNBC. Event occurs at 9:24 - 10:35. 
  76. ^ Soraghan, Mike (29 March 2012). "'Remarkable' spate of man-made quakes linked to drilling, USGS team says". EnergyWire (E&E). Retrieved 2012-11-09. 
  77. ^ Henry, Terrence (6 August 2012). "How Fracking Disposal Wells Are Causing Earthquakes in Dallas-Fort Worth". State Impact Texas. NPR. Retrieved 9 November 2012. 
  78. ^ "Ohio Quakes Probably Triggered by Waste Disposal Well, Say Seismologists" (Press release). Lamont–Doherty Earth Observatory. 6 January 2012. Retrieved 22 February 2012. 
  79. ^ "EPA Underground Injection Control Program". Retrieved 2012-04-13. 
  80. ^ McHaney, Sarah (21 October 2012). "Shale Gas Extraction Brings Local Health Impacts". IPS News (Inter Press Service). Retrieved 2012-10-21. 
  81. ^ Colborn, Theo; Kwiatkowski, Carol; Schultz, Kim; Bachran, Mary (2011). "Natural gas operations from public health perspective". Human and Ecological Risk Assessment: an International Journal 17 (5): 1039–1056. doi:10.1080/10807039.2011.605662. 
  82. ^ Banerjee, Neela (16 December 2013). "Hormone-disrupting chemicals found in water at fracking sites". Los Angeles Times. Retrieved 24 December 2013. 
  83. ^ a b Kassotis, Christopher D.; Tillitt, Donald E.; Davis, J. Wade; Hormann, Annette M.; Nagel, Susan C. (March 2014). "Estrogen and Androgen Receptor Activities of Hydraulic Fracturing Chemicals and Surface and Ground Water in a Drilling-Dense Region". Endocrinology 155 (3). doi:10.1210/en.2013-1697. Retrieved 24 December 2013. 
  84. ^ McMahon, Jeff (24 July 2013). "Strange Byproduct Of Fracking Boom: Radioactive Socks". Forbes. Retrieved 28 July 2013. 
  85. ^ Biello, David (30 March 2010). "Natural gas cracked out of shale deposits may mean the U.S. has a stable supply for a century – but at what cost to the environment and human health?". Scientific American. Retrieved 23 March 2012. 
  86. ^ a b Schmidt, Charles (1 August 2011). "Blind Rush? Shale Gas Boom Proceeds Amid Human Health Questions". Environmental Health Perspectives 119: a348–a353. doi:10.1289/ehp.119-a348. Retrieved 23 March 2012. 
  87. ^ "DISH, TExas Exposure Investigation". Texas DSHS. Retrieved 27 March 2013. 
  88. ^ "Study shows air emissions near fracking sites may have serious health impacts". @theForefront. Colorado School of Public Health. 19 March 2012. Retrieved 25 April 2012. 
  89. ^ McKenzie, Lisa; Witter, Roxana; Newman, Lee; Adgate, John (2012). "Human health risk assessment of air emissions from development of unconventional natural gas resources". Science of the Total Environment 424: 79–87. doi:10.1016/j.scitotenv.2012.02.018. 
  90. ^ Why Every Serious Environmentalist Should Favour Fracking, 2013 report by Richard A. Muller and Elizabeth A. Muller of Berkeley Earth
  91. ^ Jim Efstathiou Jr. and Angela Greiling Keane (13 August 2013). "North Dakota Oil Boom Seen Adding Costs for Rail Safety". Bloomberg. Retrieved 19 January 2012. 
  92. ^ Gebrekidan, Selam (11 October 2013). "Corrosion may have led to North Dakota pipeline leak: regulator". Reuters. Retrieved 31 December 2013. 
  93. ^ "Vermont Act 152"
  94. ^ [2]
  95. ^ Royal Society
  96. ^ Jan Goodey (Undated, but July, 2013). "The UK's anti fracking movement is growing". The Ecologist. Retrieved July 29, 2013.