Environmental impact of hydraulic fracturing in the United States

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Schematic depiction of hydraulic fracturing for shale gas, showing potential environmental effects.

Environmental impact of hydraulic fracturing in the United States has been an issue of public concern, and includes the potential contamination of ground and surface water, air pollution, migration of gases and hydraulic fracturing chemicals and radionuclides to the surface, the potential mishandling of solid waste, drill cuttings, increased seismicity and associated effects on human and ecosystem health.[1][2] A number of instances with groundwater contamination have been documented, however in most cases a direct link between hydraulic fracturing and groundwater contamination could not be established.[3] As early as 1987, researchers at the United States Environmental Protection Agency (EPA) concluded that hydraulic fracturing can contaminate and has contaminated groundwater. According to former EPA employees, evidence of the negative environmental impact of fracking was systematically removed from congressional reports to support the energy industry under the direction of the Office of Legal Counsel during the Reagan administration.[4] With the growth of hydraulic fracturing in the United States, "public exposure to the many chemicals involved in energy development is expected to increase over the next few years, with uncertain consequences" per science writer Valerie Brown in 2007.[2]

Air quality[edit]

Methane emissions from wells raise global warming concerns. Other concerns are related to emissions from the hydraulic fracturing chemicals and equipment such as volatile organic compound (VOC) and ozone. In 2008, ozone concentrations in ambient air near drilling sites in Sublette County, Wyoming were frequently above the National Ambient Air Quality Standards (NAAQS) of 75 ppb and have been recorded as high as 125 ppb.[5] In DISH, Texas, elevated levels of disulfides, benzene, xylenes and naphthalene have been detected in the air, emitted from compressor stations.[6] In Garfield County, Colorado, an area with a high concentration of drilling rigs, VOC emissions increased 30% between 2004 and 2006.[2]

On April 17, 2012, the EPA issued cost-effective regulations, required by the Clean Air Act, which include the first federal air standards for natural gas wells that are hydraulically fractured.[7] The final rules are expected to yield a nearly 95% reduction in VOC emissions from more than 11,000 new hydraulically fractured gas wells each year. This reduction would be accomplished primarily through capturing natural gas that escapes into the air, and making it available for sale. The rules also will reduce air toxics, which are known or suspected of causing cancer and other serious health effects, and emissions of methane, a potent greenhouse gas.[7]

Researches from the University of Michigan analyzed the emissions produced form the hydraulic fracturing equipment at the Marcellus Shale and Eagle Ford Shale plays, and concluded that hydraulic pumps accounted for about 83% of the total emissions in the hydraulic fracturing fleet. NOx emission ranged between 3,600–5,600 lb/job, HC 232–289 lb/job, CO 859–1416 lb/job, and PM 184–310 lb/job. If the fuel efficiencies of the hydraulic fracturing pumps are improved than the emissions can be significantly reduced.[8]

Water issues[edit]

Water usage[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.[9][10] An average well requires 3 to 8 million US gallons (11,000 to 30,000 m3) of water over its lifetime.[10][11][12][13] Back in 2008 and 2009 at the beginning of the shale boom in Pennsylvania, hydraulic fracturing accounted for 650 million US gallons per year (2,500,000 m3/a) (less than 0.8%) of annual water use in the area overlying the Marcellus Shale.[11][12][14] The annual number of well permits, however, increased by a factor of five[15] and the number of well starts increased by a factor of over 17 from 2008 to 2011.[16]

According to Environment America, a federation of state-based, citizen-funded environmental advocacy organizations, there are concerns for farmers competing with oil and gas for water.[17] A report by Ceres questions whether the growth of hydraulic fracturing is sustainable in Texas and Colorado as 92% of Colorado wells were in extremely high water stress regions (that means regions where more than 80% of the available water is already allocated for agricultural, industrial and municipal water use) and 51% percent of the Texas wells were in high or extremely high water stress regions.[18] In Barnhart, Texas the aquifer supplying the local community ran dry because of intensive water utilization for hydraulic fracturing.[19] In 2013, the Railroad Commission of Texas adopted new hydraulic fracturing water recycling rules intended to encourage Texas hydraulic fracturing operators to conserve water used in the hydraulic fracturing process.[20]

Consequences for agriculture have already been observed in North America. In some regions of the US that are vulnerable to droughts, farmers are now competing with fracking industrials for the use of water resources.[21] In the Barnett Shale region, in Texas and New Mexico, drinking water wells have dried up due to fracking's withdrawal of water, and water has been taken from an aquifer used for residential and agricultural use.[21] Farmers have seen their wells go dry in Texas and New Mexico as a result of fracking’s pressure on water resources, for instance in Carlsbad, New Mexico.[21] Agricultural communities have already seen water prices rising because of that problem. In the North Water Conservation District in Colorado was organized an auction to allocate water and the prices rose from $22/acre-foot in 2010 to $28 in the beginning of 2012.[21]

Injected fluid[edit]

While some of the chemicals used in hydraulic fracturing are common and generally harmless, some additives used in the United States are known carcinogens.[1] Out of 2,500 hydraulic fracturing products, more than 650 contained known or possible human carcinogens regulated under the Safe Drinking Water Act or listed as hazardous air pollutants".[1] Between 2005 and 2009, 279 products had at least one component listed as "proprietary" or "trade secret" on their Occupational Safety and Health Administration (OSHA) required material safety data sheet (MSDS). The MSDS is a list of chemical components in the products of chemical manufacturers, and according to OSHA, a manufacturer may withhold information designated as "proprietary" from this sheet. Most companies participating in the investigation were unable to name the ingredients of the products they use, leading the committee to surmise these "companies are injecting fluids containing unknown chemicals about which they may have limited understanding of the potential risks posed to human health and the environment".[1] Without knowing the identity of the proprietary components, regulators cannot test for their presence. This prevents government regulators from establishing baseline levels of the substances prior to hydraulic fracturing and documenting changes in these levels, thereby making it more difficult to prove that hydraulic fracturing is contaminating the environment with these substances.[22]

Another 2011 study identified 632 chemicals used in natural gas operations. Only 353 of these are well-described in the scientific literature. The study indicated possible long-term health effects that might not appear immediately. The study recommended full disclosure of all products used, along with extensive air and water monitoring near natural gas operations; it also recommended that hydraulic fracturing's exemption from regulation under the US Safe Drinking Water Act be rescinded.[23] Industry group Energy In Depth, a research arm of the Independent Petroleum Association of America, contends that fracking "was never granted an 'exemption' from it... How can something earn an exemption from a law that never covered or even conceived of it in the first place?”[24]

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 United States Department of Energy (DOE). The site has been met with some scepticism relating to proprietary information that is not included.[25][26] Some states have mandated fluid disclosure and incorporated FracFocus as the tool for disclosure.[27][28] Also in the US, The FracTracker Alliance provides oil and gas-related data storage, analyses, and online and customized maps related to hydraulic fracturing on FracTracker.org.[29][30]

Groundwater contamination[edit]

In 2009, state regulators from across the country stated that they had seen no evidence of hydraulic fracturing contaminating water in their respective jurisdictions.[31] In May 2011 the EPA Administrator Lisa P. Jackson testified in a Senate Hearing Committee stating that the EPA had never made a definitive determination of contamination where the hydraulic fracturing process itself has contaminated water.[32] EPA and other reports released since that time, however, have identified hydraulic fracturing as the likely source of water contamination.[3][33][34][35][36][37] Dr. Robin Ikeda, Deputy Director of Noncommunicable Diseases, Injury and Environmental Health at the CDC testified to congress that EPA had documented contamination at several sites.[38]

Researchers at the University of Texas at Arlington, Arlington, Texas evaluated private well water quality in aquifers overlying the Barnett Shale formation. Arsenic, selenium, strontium and total dissolved solids (TDS) levels in some wells within 3 km of active wells exceeded the EPA's maximum contaminant levels. Levels of arsenic, selenium, strontium, and barium were lower at comparison sites located outside of 3 km from the wells, as well as outside the Barnett Shale region. Methanol and ethanol were found in 29% of samples. Researchers attributed the elevated levels to a variety of factors, including mobilization of natural constituents, the lowering of the water table, and faulty equipment.[39]

In 2006, over 7 million cubic feet (200,000 m3) of methane were released from a blown gas well in Clark, Wyoming and shallow groundwater was found to be contaminated.[40] In 2011 a Duke University study determined that groundwater tended to contain much higher concentrations of methane near hydraulically fractured wells, with potential explosion hazard; the methane's isotopic signatures and other geochemical indicators were consistent with it originating in the fractured deep shale formations, rather than any other source.[41] 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 Marcellus Shale (Middle Devonian) where hydraulic fracturing occurred, and from the shallower Upper Devonian formations.[42] In 2013, Duke University study reported that methane concentrations were six times higher and ethane concentrations were 23 times higher at residences within a kilometer of a shale gas well. Propane was also detected in 10 homes within a kilometer of drilling. The researchers reported that the methane, ethane and propane data, and new evidence from hydrocarbon and helium content, all suggested that drilling has affected the drinking water. They noted that the ethane and propane data were notable because there was no biological source of ethane and propane in the region and Marcellus gas is higher in both than are Upper Devonian gases.[43][44]

Federal regulation of hydraulic fracturing (when it comes to water resources) has its limits. The EPA has a limited capacity in creating and enforcing laws; their power is limited to writing regulations based on laws passed by Congress, and they rely on partnerships with other federal, state, and private organizations to enforce them.[45] Additionally, potential issues include accidental spills, inadequate treatment and storage, lax enforcement of disposal management regulations, lags in disclosure and transparency, as well as small penalties for not following through on regulations.[46] Because of these issues, the safety of hydraulic fracturing on the contamination water resources is a highly contested and widely discussed topic.

However, it is important to note that not every instance of groundwater methane contamination is a result of hydraulic fracturing. Often, local water wells drill through many shale and coal layers that can naturally seep methane into the producing groundwater. This methane is often biogenic (created by organic material decomposition) in origin as opposed to thermogenic (created through "thermal decomposition of buried organic material".[47]) Thermogenic methane is the methane most often sought after by oil and gas companies deep in the earth, whereas biogenic methane is found in shallower formations (where water wells are typically drilled). Through isotope analysis and other detection methods, it is often fairly easy to determine whether the methane is biogenic or thermogenic, and thus determine from where it is produced.[47]

A study was conducted by the center of Rural Pennsylvania to analyze the well water quality before and after drilling the Marcellus shale.[48] The researchers analyzed 48 water wells for methane levels. They were only able to confirm an increase in methane for one well.[48] The researchers also noted that ‘methane did not increase at fracked sites and was not correlated to the distance to the nearest Marcellus well site.’[48]

In 2010 the film Gasland premiered at the Sundance Film Festival. The filmmaker claims that chemicals including toxins, known carcinogens, and heavy metals polluted the ground water near well sites in Pennsylvania, Wyoming, and Colorado.[49] The film was criticized by oil and gas industry group[50] Energy in Depth as factually inaccurate;[51] in response, a detailed rebuttal of the claims of inaccuracy has been posted on Gasland's website.[52] The Colorado Oil and Gas Conservation Commission, a state agency, based on its own investigations, pointed out scientific errors made in the film and on the Gasland website concerning supposed cases of water wells contaminated by hydraulic fracturing.[53]

A 2011 report by the Massachusetts Institute of Technology 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. There is, however, evidence of natural gas migration into freshwater zones in some areas, most likely as a result of substandard well completion practices by a few operators. There are additional environmental challenges in the area of water management, particularly the effective disposal of fracture fluids". This study encourages the use of industry best practices to prevent such events from recurring.[54]

As early as 1987, an EPA report was published that indicated fracture fluid invasion into James Parson's water well in Jackson County, West Virginia. The well, drilled by Kaiser Exploration and Mining Company, was found to have induced fractures that created a pathway to allow fracture fluid to contaminate the groundwater from which Mr. Parson's well was producing. The oil and gas industry and the EPA disagreed regarding the accuracy and thoroughness of this report.[33] Directed by Congress, the EPA announced in March 2010 that it will examine claims of water pollution related to hydraulic fracturing.[55]

In 2009, 13 water wells in Dimock, Pennsylvania were contaminated with methane, while arsenic, barium, DEHP, glycol compounds, manganese, phenol, and sodium were also found in unacceptable levels in the wells.[35] As a result, Cabot Oil & Gas was required to financially compensate residents and provide alternative sources of water until mitigation systems were installed in affected wells.[35] The company denies, however, that any "of the issues in Dimock have anything to do with hydraulic fracturing".[56][57][58] In May 2012 the EPA reported that their most recent "set of sampling did not show levels of contaminants that would give the EPA reason to take further action." Methane was found only in one well.[59] Cabot has held that the methane was preexisting, but state regulators have cited chemical fingerprinting as proof that it was from Cabot's hydraulic fracturing activities.[60] Both Duke University and University of Rochester are conducting studies of the age of the well water to confirm the sources of the various contaminants.[60] The EPA plans to re-sample four wells where previous data by the company and the state showed levels of contaminants.[59]

Complaints about water quality from residents near a gas field in Pavillion, Wyoming prompted an EPA groundwater investigation. The EPA reported detections of methane and other chemicals such as phthalates in private water wells.[36] An EPA draft report dated December 8, 2011 suggested that the ground water in the Pavillion aquifer contains "compounds likely associated with gas production practices, including hydraulic fracturing".[61][62][63] The EPA discovered traces of methane and foaming agents in several water wells near a gas rig, could have come from cleaning products or oil and gas production.[56] Samples of water taken from EPA's deep monitoring wells in the aquifer were found to contain gasoline, diesel fuel, BTEX (benzene, toluene, ethylbenzene, xylene), naphthalenes, isopropanol, and synthetic chemicals (e.g., glycols and alcohols) used in gas production and hydraulic fracturing fluid, and high methane levels. Benzene concentrations in the samples were well above Safe Drinking Water Act standards.[61] The EPA draft report stated concerns about the movement of contaminants within the aquifer and the future safety of drinking water in the context of the area's complex geology. The EPA's sampling of Pavillion area drinking water wells found chemicals consistent with those reported in previous EPA reports, including but not limited to methane and other petroleum hydrocarbons, indicating migration of contaminants from areas of gas production.[61] The draft report also said that contaminants in wells near pits indicated that (frack) pits are a source of shallow ground water contamination. It also said, "Detections of organic chemicals are more numerous and exhibit higher concentrations in the deeper of the two monitoring wells … (which) along with trends in methane, potassium, chloride, and pH, suggest a deep source of contamination." Their observations of chemical reactions in the field led them to suggest that upward migration of chemicals from deep underground is the culprit. They also found that the reports companies filed detailing jobs listed chemicals as a class or as "proprietary," "rendering identification of constituents impossible."[64] The draft report also stated: "Alter­na­tive expla­na­tions were care­fully con­sid­ered to explain indi­vid­ual sets of data. How­ever, when con­sid­ered together with other lines of evi­dence, the data indi­cates likely impact to ground water that can be explained by hydraulic fracturing."[34] The EPA said that the type of contamination found is "typically infeasible or too expensive to remediate or restore."[36] Industry figures rejected the EPA's findings.[34] In 2010 the Agency for Toxic Substances and Disease Registry recommended that owners of tainted wells use alternate sources of water for drinking and cooking, and ventilation when showering. Encana is funding the alternate water supplies.[61] In 2012 the U.S. Geological Survey tested one of two EPA monitoring wells near Pavillion and found evidence of methane, ethane, diesel compounds and phenol,[65] which the EPA had also identified in its 2011 report[66] According to Duke University environmental scientist Rob Jackson, "The stray gas concentrations are very high, not only for methane but especially for ethane and propane. That combination suggests a fossil-fuel source for the gases."[37] An industry advocate, however, says that the USGS found lower concentrations of the particular materials that suggested a fossil-fuel source than the EPA and that what was found could be naturally occurring because of circumstances unique to the area or the testing process.[67] In June 2013, the EPA announced that it was closing its investigation at Pavillion, and would not finish or seek peer review of its preliminary 2011 study. Further investigation will be done by the state of Wyoming.[68]

Not every instance of groundwater methane contamination is a result of hydraulic fracturing. Often, local water wells drill through many shale and coal layers that can naturally seep methane into the producing groundwater. This methane is often biogenic (created by organic material decomposition) in origin as opposed to thermogenic (created through "thermal decomposition of buried organic material").[47] Thermogenic methane is the methane most often sought after by oil & gas companies deep in the earth, whereas biogenic methane is found in shallower formations (where water wells are typically drilled). Through isotope analysis and other detection methods, it is often fairly easy to determine whether the methane is biogenic or thermogenic, and thus determine from where it is produced.[47] The presence of thermogenic methane does not confirm the source of gas. The gas composition and isotopic finger print must be compared by experts with other known sources of gas to confirm a match.[42]


Flowback is the portion of the injected fracturing fluid that flows back to the surface, along with oil, gas, and brine, when the well is produced. An estimated 90% of flowback in the United States is disposed of into deep EPA-licensed Class II disposal wells, with the remaining less than 10% reused, evaporated, used for irrigation, or discharged to surface streams under an NPDES permit. Of nine oil and gas-producing states studied in 2012, underground injection disposal was by far the predominant method in all but Pennsylvania where were only six active waste disposal wells.[69] In California, Virginia, and Ohio there have been instances of illegal dumping of flowback, a precursor to possible contamination of local ground and surface water reservoirs.[46] Discharging oil and gas produced water to surface streams without an NPDES permit is a federal crime.[70] Discharges through water treatment works must comply with the federal Clean Water Act and the terms of their NPDES permits, but the EPA noted that most water treatment works are not set up to treat flowback.[71]

In Pennsylvania, oil and gas produced water had for many years been accepted by licensed water treatment works for treatment and discharge, but the volume expanded greatly with the proliferation of Marcellus Shale wells after 2000. In 2010 the Pennsylvania Department of Environmental Protection (DEP) limited surface water discharges from new treatment plants to 250 mg/l chloride; the chloride limitation was designed to also limit other contaminants such as radium. Existing water treatment plants were "grandfathered," and still allowed higher discharge concentrations, but oil and gas operators were prohibited to send wastewater to the grandfathered treatment plants.[72]

One Duke University study reported that "Marcellus [Shale] wells produce significantly less wastewater per unit gas recovered (~35%) compared to conventional natural gas wells."[73] In Colorado the volume of wastewater discharged to surface streams increased from 2008 to 2011.[74]

Surface water contamination[edit]

Hydraulic fracturing can affect surface water quality either through accidental spills at the wellsite, or by discharge of the flowback through existing water treatment works. Directed by Congress, the EPA announced in March 2010 that it would examine claims of water pollution related to hydraulic fracturing.[55] Christopher Portier, director of the CDC's National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry, argued that, in addition to the EPA's plans to investigate the impact of hydraulic fracturing on drinking water, additional studies should be carried out to determine whether wastewater from the wells can harm people or animals and vegetables they eat.[75] A group of US doctors called for a moratorium on hydraulic fracturing in populated areas until such studies had been done.[76][77]

However, others point out exclusions and exemptions for hydraulic fracturing under United States federal law. Exemptions were made in the Clean Water Act, as part of the Energy Policy Act of 2005, also known as the "Halliburton Loophole." These exemptions included stormwater runoff from gas and oil construction activities which includes "oil and gas exploration, production, process, or treatment operations and transmission facilities" as part of the definition of construction activities.[78] Amendments to the Safe Drinking Water Act involved the definition of underground injection. Underground injection related to hydraulic fracturing was exempted from the Clean Water Act, except if it uses diesel fuel.[79]

The growing of oil and natural gas drilling employing hydraulic fracturing technology is steady around different regions of the United States, but the maintenance of wastewater gathered after the drilling process containing hydraulic fracturing fluids is lagging behind.[80] In Pennsylvania, the DEP reported that the resources to properly regulate wastewater-handling facilities were unavailable, inspecting facilities every 20 years rather than every 2 years as called for by regulation.[80]

The quantity of wastewater and the unpreparedness of sewage plants to treat wastewater, is an issue in Pennsylvania.[81][82] The Associated Press has reported that starting in 2011, the DEP strongly resisted providing the AP and other news organizations with information about complaints related to drilling.[83] When waste brine is discharged to surface waters through conventional wastewater treatment plants, the bromide in the brine usually is not captured. Although not a health hazard by itself, in western Pennsylvania some downstream drinking water treatment plants using the surface water experienced increases in brominated trihalomethanes in 2009 and 2010. Trihalomethanes, undesirable byproducts of the chlorination process, form when the chlorine combines with dissolved organic matter in the source water, to form the trihalomethane chloroform. Bromine can substitute for some of the chlorine, forming brominated trihalomethanes. Because bromine has a higher atomic weight than chlorine, the partial conversion to brominated trihalomethanes increases the concentration by weight of total trihalomethanes.[84][85][86]


Radioactivity associated with hydraulically fractured wells comes from two sources: naturally occurring radioactive material and radioactive tracers introduced into the wells. Flowback from oil and gas wells is usually disposed of deep underground in Class II injection wells, but in Pennsylvania, much of the wastewater from hydraulic fracturing operations is processed by public sewage treatment plants. Many sewage plants say that they are incapable of removing the radioactive components of this waste, which is often released into major rivers. Industry officials, though, claim that these levels are diluted enough that public health is not compromised.[81]

In 2011, the level of dissolved radium in hydraulic fracturing wastewater released upstream from drinking water intakes had been measured to be up to 18,035 pCi/L (667.3 Bq/l),[87] and the gross alpha level measured to be up to 40,880 pCi/L (1,513 Bq/l).[81][87] The New York Times reported that studies by the EPA and a confidential study by the drilling industry concluded that radioactivity in drilling waste cannot be fully diluted in rivers and other waterways.[88] A recent Duke University study sampled water downstream from a Pennsylvania wastewater treatment facility from 2010 through Fall 2012 and found the creek sediment contained levels of radium 200 times background levels.[89] The surface water had the same chemical signature as rocks in the Marcellus Shale formation. The facility denied processing Marcellus waste since 2011. In May 2013 the facility signed another agreement to not accept or discharge wastewater Marcellus Shale formations until it has installed technology to remove the radiation compounds, metals and salts.[90][91] According to the Duke researches the 'waste treatment solids/sludge' have exceeded U.S. regulations for radium disposal to soil.[90] The study by Duke University also found that radium has been "absorbed and accumulated on the sediments locally at the discharge".[90]

The New York Times noted that in 2011 the Pennsylvania DEP only made a "request — not a regulation" of gas companies to stop sending their flowback and waste water to public water treatment facilities.[92] However, the DEP gave oil and gas operators 30 days to voluntarily comply, and they all did.[72] Former Pennsylvania DEP Secretary John Hanger, who served under Gov. Ed Rendell, affirmed that municipal drinking water throughout the state is safe. "Every single drop that is coming out of the tap in Pennsylvania today meets the safe drinking water standard," Hanger said, but added that the environmentalists were accurate in stating that Pennsylvania water treatment plants were not equipped to treat hydraulic fracturing water.[93] Current Pennsylvania DEP Secretary Michael Krancer serving under Gov. Tom Corbett has said it is "total fiction" that untreated wastewater is being discharged into the state's waterways,[94] though it has been observed that Corbett received over a million dollars in gas industry contributions,[95] more than all his competitors combined, during his election campaign.[96] Unannounced inspections are not made by regulators: the companies report their own spills, and create their own remediation plans.[81] A recent review of the state-approved plans found them to appear to be in violation of the law.[81] Treatment plants are still not equipped to remove radioactive material and are not required to test for it.[81] Despite this, in 2009 the Ridgway Borough's public sewage treatment plant, in Elk County, PA, facility was sent wastewater containing radium and other types of radiation at at 275-780 times the drinking-water standard. The water being released from the plant was not tested for radiation levels.[81] Part of the problem is that growth in waste produced by the industry has outpaced regulators and state resources.[81] It should be noted that "safe drinking water standards" have not yet been set for many of the substances known to be in hydrofracturing fluids or their radioactivity levels,[81][not in citation given] and their levels are not included in public drinking water quality reports.[97]

Tests conducted in Pennsylvania in 2009 found "no evidence of elevated radiation levels" in waterways.[98] At the time radiation concerns were not seen as a pressing issue.[98] In 2011 The New York Times reported radium in wastewater from natural gas wells is released into Pennsylvania rivers,[81][99] and compiled a map of these wells and their wastewater contamination levels,[87] and stated that some EPA reports were never made public.[88] The Times' reporting on the issue has come under some criticism.[100][101] A 2012 study examining a number of hydraulic fracturing sites in Pennsylvania and Virginia by Pennsylvania State University, found that water that flows back from gas wells after hydraulic fracturing contains high levels of radium.[102]

Before 2011, flowback in Pennsylvania was processed by public wastewater plants, which were not equipped to remove radioactive material and were not required to test for it. Industry officials, though, claim that these levels are diluted enough that public health is not compromised.[81][82] In 2010 the DEP limited surface water discharges from new treatment plants to 250 mg/l chloride. This limitation was designed to also limit other contaminants such as radium. Existing water treatment plants were allowed higher discharge concentrations. In April 2011, the DEP asked unconventional gas operators to voluntarily stop sending wastewater to the grandfathered treatment plants. The PADEP reported that the operators had complied.[72]

A 2013 Duke University study sampled water downstream from a Pennsylvania wastewater treatment facility from 2010 through 2012 and found that creek sediment contained levels of radium 200 times background levels.[89] The surface water had the same chemical signature as rocks in the Marcellus Shale formation along with high levels of chloride. The facility denied processing Marcellus waste after 2011. In May 2013 the facility signed another agreement to not accept or discharge Marcellus wastewater until it installed technology to remove the radioactive materials, metals and salts.[90][91]

A 2012 study by researchers from the National Renewable Energy Laboratory, University of Colorado, and Colorado State University reported a reduction in the percentage of flowback treated through surface water discharge in Pennsylvania from 2008 through 2011.[74] By late 2012, bromine concentrations had declined to previous levels in the Monongahela River, but remained high in the Allegheny.[103]

Naturally occurring radioactive materials[edit]

The New York Times has reported radiation in hydraulic fracturing wastewater released into rivers in Pennsylvania.[81] It collected data from more than 200 natural gas wells in Pennsylvania and has posted a map entitled Toxic Contamination from Natural Gas Wells in Pennsylvania. The Times stated "never-reported studies" by the United States Environmental Protection Agency and a "confidential study by the drilling industry" concluded that radioactivity in drilling waste cannot be fully diluted in rivers and other waterways.[88] Despite this, as of early 2011 federal and state regulators did not require sewage treatment plants that accept drilling waste (which is mostly water) to test for radioactivity. In Pennsylvania, where the drilling boom began in 2008, most drinking-water intake plants downstream from those sewage treatment plants have not tested for radioactivity since before 2006.[81]

The New York Times reporting has been criticized[100] and one science writer has taken issue with one instance of the newspaper's presentation and explanation of its calculations regarding dilution,[104] charging that a lack of context made the article's analysis uninformative.[101]

According to a Times report in February 2011, wastewater at 116 of 179 deep gas wells in Pennsylvania "contained high levels of radiation," but its effect on public drinking water supplies is unknown because water suppliers are required to conduct tests of radiation "only sporadically".[105] The New York Post stated that the DEP reported that all samples it took from seven rivers in November and December 2010 "showed levels at or below the normal naturally occurring background levels of radioactivity", and "below the federal drinking water standard for Radium 226 and 228."[106] However the samples taken by the state at at least one river, (the Monongahela, a source of drinking water for parts of Pittsburgh), were taken upstream from the sewage treatment plants accepting drilling waste water.[107]

Radioactive tracers[edit]

Radioactive tracer isotopes are sometimes injected with hydraulic fracturing fluid to determine the injection profile and location of created fractures.[108] Sand containing gamma-emitting tracer isotopes is used to trace and measure fractures.[citation needed] A 1995 study found that radioactive tracers were used in over 15% of stimulated oil and gas wells.[109] In the United States, injection of radionuclides are licensed and regulated by the Nuclear Regulatory Commission (NRC).[110] According to the NRC, some of the most commonly used tracers include antimony-124, bromine-82, iodine-125, iodine-131, iridium-192, and scandium-46.[110] A 2003 publication by the International Atomic Energy Agency confirms the frequent use of most of the tracers above, and says that manganese-56, sodium-24, technetium-99m, silver-110m, argon-41, and xenon-133 are also used extensively because they are easily identified and measured.[111] According to a 2013 meeting of researchers who examined low (never exceeding drinking water standards) but persistent detections of iodine-131 in a stream used for Philadelphia drinking water: “Workshop participants concluded that the likely source of 131-I in Philadelphia’s source waters is residual 131-I excreted from patients following medical treatments,” but suggested that other potential sources also be studied, including hydraulic fracturing.[112]


Hydraulic fracturing routinely produces microseismic events much too small to be detected except by sensitive instruments. These microseismic events are often used to map the horizontal and vertical extent of the fracturing.[113] However, 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.[114] While analysis suggested that the increase is "almost certainly man-made", the United States Geological Survey (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.[115] 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).[116]

Induced seismicity from hydraulic fracturing[edit]

The 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 fracking and earthquakes of any concern to society."[117] 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.[118] 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.[119][120]

Induced seismicity from water disposal wells[edit]

Earthquakes large enough to be felt by people have also been linked to some deep disposal wells that receive hydraulic fracturing flowback and produced water from hydraulically fractured wells. Flowback and brine from oil and gas wells are injected into EPA-regulated class II disposal wells. According to the EPA, approximately 144,000 such class II disposal wells in the US receive more than 2 billion US gallons (7.6 Gl) of wastewater each day.[121] To date, the strongest earthquakes triggered by underground waste injection were three quakes close to Richter magnitude 5 recorded in 1967 near a Colorado disposal well which received non-oilfield waste.[122]

According to the USGS only a small fraction of roughly 40,000 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.[123] Although the magnitudes of these quakes has been small, the USGS says that there is no guarantee that larger quakes will not occur.[124] 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.[125] There are also concerns that quakes may damage underground gas, oil, and water lines and wells that were not designed to withstand earthquakes.[124][126]

The 2011 Oklahoma earthquake, the largest earthquake in Oklahoma history (most sources describe it as magnitude 5.7, although the US Geological Survey lists it as 5.6) has been linked by some researchers to decades-long injection of brine.[127] However, the Oklahoma Geological Survey believes that the quake was most likely due to natural causes, and was not triggered by waste injection.[128]

Class II disposal wells receiving brine from Fayetteville Shale gas wells in Central Arkansas triggered hundreds of shallow earthquakes, the largest of which was magnitude 4.7, and caused damage. In April 2011, the Arkansas Oil and Gas Commission halted injection at two of the main disposal wells, and the earthquakes abated.[129]

Several earthquakes in 2011, including a 4.0 magnitude tremor on New Year's Eve that hit Youngstown, Ohio, are likely linked to a disposal of hydraulic fracturing wastewater,[119] according to seismologists at Columbia University.[130] By order of the Ohio Department of Natural Resources, the well had stopped injecting on December 30, 2011. The following day, after the 4.0 quake, Ohio governor John Kasich ordered an indefinite halt to injection in three additional deep disposal wells in the vicinity. The Department of Natural Resources proposed a number of tightened rules to its Class II injection regulations. The Department noted that there were 177 operational Class II disposal wells in the state, and that the Youngstown well was the first to produce recorded earthquakes since Ohio's Underground Injection Control program began in 1983.[131]

Since 2008, more than 50 earthquakes, up to a magnitude of 3.5, have occurred in the area of north Texas home to numerous Barnett Shale gas wells, an area that previously had no earthquakes. No injuries or serious damage from the earthquakes has been reported. A study of quakes near the Dallas-Fort Worth Airport 2008-2009, concluded that the quakes were triggered by disposal wells receiving brine from gas wells.[132]

A two-year study 2009-2011 by University of Texas researchers concluded that a number of earthquakes from Richter magnitude 1.5 to 2.5 in the Barnett Shale area of north Texas were linked to oilfield waste disposal into Class II injection wells. No quakes were linked to hydraulic fracturing itself.[133] Researchers noted that there are more than 50,000 Class II disposal wells in Texas receiving oilfield waste, yet only a few dozen are suspected of triggering earthquakes.[132]

On May 31, 2014, an earthquake registering at a magnitude of 3.4 occurred in Greeley, Colorado. The earthquake occurred in close proximity to two hydraulic fracturing wastewater injection wells that are reportedly close to capacity. One waste injection well is 8,700 feet deep and 20 years old, while the other is 10,700 feet and just two years old. A research team from the University of Colorado Boulder have placed seismographs in the area to monitor further activity.[134][135]

Health effects[edit]

Trace amounts of chemicals used in the drilling process may affect the health of those working on or living near the wells. In Colorado, the U.S. Agency for Toxic Substances and Disease Registry sampled 14 sites, and found high levels of carcinogens such as benzene, tetrachloroethene, and 1-4 dichlorobenzene.[136] In July 2011, the EPA released new emissions guidelines stating that the old standards could have led to an unacceptably high risk of cancers for those living near drilling operations.[136] Pediatric Environmental Health Specialty Units (PEHSU) also found chemical contamination of drinking water near hydraulic fracturing operations in New York and Pennsylvania that involved detectable and harmful levels of benzene toluene, ethyl benzene, xylene, ethylene glycol, glutaldehyde, and other biocides such as hydrochloric acid, and hydrogen treated light petroleum distillates.[137] Human exposure to these chemicals can result in cancer, adverse effects of the reproductive, neurological, and endocrine systems.[137]

Early in January 2012, Christopher Portier, director of the US CDC's National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry, argued that, in addition to the EPA's plans to investigate the impact of fracking on drinking water, additional studies should be carried out to determine whether wastewater from the wells can harm people or animals and vegetables they eat.[75] A week later, a group of US doctors called for a moratorium on fracking in populated areas until such studies had been done.[76][77]

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.[138] In the United States the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) released a hazard alert based on data collected by NIOSH that "workers may be exposed to dust with high levels of respirable crystalline silica (silicon dioxide) during hydraulic fracturing."[139] NIOSH notified company representatives of these findings and provided reports with recommendations to control exposure to crystalline silica and recommend that all hydraulic fracturing sites evaluate their operations to determine the potential for worker exposure to crystalline silica and implement controls as necessary to protect workers.[140]

As of May 2012, the United States Institute of Medicine and United States National Research Council were preparing to review the potential human and environmental risks of hydraulic fracturing.[141][142]

Researchers from the Colorado School of Public Health performed a study in Garfield County, Colorado, regarding potential adverse health effects, and concluded that residents near gas wells might suffer chemical exposures, accidents from industry operations, and psychological impacts such as depression, anxiety and stress. This study (the only one of its kind to date) was never published, owing to disagreements from local health officials and the industry about the study's methods.[143] In 2012, they showed that air pollution caused by hydraulic fracturing may contribute to "acute and chronic health problems" for those living near drilling sites.[144]


A study conducted by Duke University analyzed water from Pennsylvania's Blacklick Creek and after the Josephine Brine Treatment Facility. The researchers were able to find increased levels of bromide in the water downstream of the treatment facility. Theses concentrations decreased as a distance from the treatment facility. According to the researchers, "the overall bromide enrichment in river water could be critical to downstream municipal water treatment plants, given the potential formation of carcinogenic trihalomethane compounds in chlorinated drinking water upon chlorination of water with even slightly enriched bromide".[90]


Researchers have conducted a case study in Colorado analyzing the relationship between the birth outcomes and maternal residential proximity to natural gas sites.[145] The researchers analyzed data from Colorado oil and gas information system to locate sites from 1996 to 2009 and live birth data from Colorado Vital Birth statistics. Using these data sets, they have determined that if maternal residency is in a 10-mile radius of a natural gas site there is an increase chance of having congenital heart defects and neural tube defects.[145]

Effects on livestock[edit]

One study found that hydraulic fracturing fluids in wastewater were strongly implicated in the death, failure to breed, and reduced growth rate of cattle that were exposed to the wastewater. The study examined several cases of cattle exposure to water contaminated with hydraulic fracturing fluids in the states of Colorado, Louisiana, New York, Ohio, Pennsylvania and Texas. In one case, 17 cows died within a single hour of exposure to hydraulic fracturing fluid. In two other cases, parts of a herd of cattle were exposed to wastewater contaminated with hydraulic fracturing fluid and the rest of the herd was kept separate from the wastewater. In both cases the parts of the herds that were exposed to the wastewater had several cows die, deliver stillborn calves or fail to breed while the cattle that were not exposed to the wastewater had no health problems.[146] The researchers recommended requiring disclosure of all hydraulic fracturing fluids, that nondisclosure agreements not be allowed when public health is at risk, testing animals raised near hydraulic fracturing sites and animal products (milk, cheese, etc.) from animal raised near hydraulic fracturing sites prior to selling them to market, monitoring of water, soil and air more closely, and testing the air, water, soil and animals prior to drilling and at regular intervals thereafter.[146]


There are two approaches to regulation. In many States, including almost all US States except Vermont, the UK, Canada or Australia, a risk assessment approach is favored, meaning that fracking is practiced before assessing its risks. However, in other States such as France and Vermont, the precautionary principle as well as the prevention principle invoked in terms of public health, have prohibited the use of fracking until it is proven that it has no impact.[147][148]

Many chemicals used in fracking are known to be carcinogenic but some US States’ regulations allow them to stay “trade secrets” and companies using them in hydraulic fracturing processes do not have to publicize their use to the public. It is for instance the case in Ohio [149] and New Mexico.[149] Criteria of public health in the issuance of drilling permits have also been withdrawn from the EPA's area of regulation, unless diesel fuel is used, in 2005 when fracking was exempted from the Safe Drinking Water Act.[121]

A study conducted on the advisory committees of the Marcellus Shale gas area has shown that not a single member of these committees had public health expertise and that some concern existed about whether the commissions were not biased in their composition.[150] Indeed, among 51 members of the committees, there is no evidence that a single one has any expertise in environmental public health, even after enlarging the category of experts to “include medical and health professionals who could be presumed to have some health background related to environmental health, however minimal”. This cannot be explained by the purpose of the committee since all three executive orders of the different committees mentioned environmental public health related issues. Another finding of the authors is that a quarter of the opposed comments mentioned the possibility of bias in favor of gas industries in the composition of committees. The authors conclude saying that political leaders may not want to raise public health concerns not to handicap further economic development due to fracking.[citation needed]

The NRC and approved state agencies regulate the use of injected radionuclides in hydraulic fracturing in the United States.[110]

The EPA sets radioactivity standards for drinking water.[151] Federal and state regulators do not require sewage treatment plants that accept gas well wastewater to test for radioactivity. In Pennsylvania, where the hydraulic fracturing drilling boom began in 2008, most drinking-water intake plants downstream from those sewage treatment plants have not tested for radioactivity since before 2006.[81] The EPA has asked the DEP to require community water systems in certain locations, and centralized wastewater treatment facilities to conduct testing for radionuclides.[81][152][153] and although water suppliers are required to inform citizens of radon and other radionuclides levels in their water, this does not always happen.[82][154][155] Federal and state nuclear regulatory agencies keep records of the radionuclides used.[110]


Illustration of hydraulic fracturing and related activities

Interviews with the EPA scientists and leaked documents have shown that, since the 1980s, the EPA investigations into the oil and gas industry's environmental impact—including the ongoing one into fracking's potential impact on drinking water—and associated reports had been narrowed in scope[156][157] and/or had negative findings removed due to industry and government pressure.[4][55][158]

Some environmentalists[who?] claim that the industry and governmental pressure have made it difficult to conduct and report the results of comprehensive studies of hydraulic fracturing. The EPA investigations into the oil and gas industry's environmental impact have been narrowed in scope and/or reportedly had negative findings removed due to this pressure.[4] A 2012 Cornell University report noted that it was difficult to assess health impact because of legislation, proprietary secrecy, and non-disclosure agreements that allow hydraulic fracturing companies to keep the proprietary chemicals used in the fluid secret. Pre-drilling tests and other assessments have also found that water supplies—especially private water wells—often suffer from high levels of naturally occurring contaminants, as the US Geological Survey concluded in August 2011.[159] Nonetheless, these particular Cornell researchers recommended requiring disclosure of all hydraulic fracturing fluids, that nondisclosure agreements not be allowed when public health is at risk, testing animals (and their products) raised near hydraulic fracturing sites against animals raised near hydraulic fracturing sites prior to selling them to market, monitoring of water, soil, and air more closely, and testing the air, water, soil, and animals prior to drilling and at regular intervals thereafter. Despite the lack of conclusive data, however, the researchers also wrote that "a ban on shale gas drilling is essential for the protection of public health."[160] The co-chair of the Chemicals Technical Options Committee for the United Nations Environment Program, Dr. Ian Rae, recently[when?] criticized the Cornell researchers' conclusions, saying, "It certainly does not qualify as a scientific paper but is, rather, an advocacy piece that does not involve deep analysis of the data gathered to support its case." Rae added that the Cornell researchers "cannot be regarded as experts" in this particular field. Others have pointed out that the study does still raise important questions, and it echoes similar concerns of some landowners and environmental groups.[161] In addition, after court cases concerning contamination from hydraulic fracturing are settled, the documents are sealed. While the American Petroleum Institute denies that this practice has hidden problems with gas drilling, others believe it has and could lead to unnecessary risks to public safety and health.[33]

The New York Times cited Weston Wilson, the agency whistle-blower, that the results of the 2004 EPA study were influenced by industry and political pressure.[4] An early draft of the study discussed the possibility of dangerous levels of hydraulic fracturing fluid contamination and mentioned "possible evidence" of aquifer contamination. The final report concluded simply that hydraulic fracturing "poses little or no threat to drinking water".[4] The study's scope was narrowed so that it only focused on the injection of hydraulic fracturing fluids, ignoring other aspects of the process such as disposal of fluids and environmental concerns such as water quality, fish kills, and acid burns. The study was concluded before public complaints of contamination started emerging.[162]:780 The study's conclusion that the injection of hydraulic fracturing fluids into coalbed methane wells posed a minimal threat to underground drinking water sources[163] may have influenced the 2005 Congressional decision that hydraulic fracturing should continue to be regulated by the states and not under the federal Safe Drinking Water Act.

The 2012 EPA Hydraulic Fracturing Draft Plan was also narrowed. It does not include studying the effects of radioactive tracer isotopes used in hydraulic fracturing.[164][165][166] Nor does the draft plan include evaluating the impact of wastewater. Christopher Portier, director of the US CDC's National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry, argued that, in addition to the EPA's plans to investigate the impact of hydraulic fracturing on drinking water, additional studies should be carried out to determine whether wastewater from the wells can harm people or animals and vegetables they eat.[75] A group of US doctors called for a moratorium on hydraulic fracturing in populated areas until such studies had been done.[76][77]

Proponents of hydraulic fracturing have claimed in the press and other media that the recent University of Texas Study ("Fact-Based Regulation for Environmental Protection in Shale Gas Development") found that hydraulic fracturing caused no environmental contamination,[167][168] although the study did note that other steps in the drilling process—excepting the actual injection of the fluid—have been sources of environmental contamination.[169] Conflicting interpretations of this study are based on disagreement between industry and the environmental community about what "hydraulic fracturing" actually is: Industry notes that hydraulic fracturing is a specific process, which takes place after the well has been drilled and the drilling equipment has left the pad; the environmental community, however, uses hydraulic fracturing, or "fracking," to describe the entire production phase. The radioactivity of the injected fluid itself was not assessed in the University of Texas study.[169]

Other monitoring resources[edit]

Andrew Revkin identified two web-based resources available to help monitor fracking and its impacts in affected regions.

  • In Pennsylvania, Fracktrack.org was developed "to organize masses of data on drilling permits, violations and other activities related to the natural gas drilling rush in that state". Jamie Serra, developer of the site, set out to provide "a suite of tools to help landowners and citizens of the commonwealth understand what’s happening around them".
  • SkyTruth, drawing on "data that are voluntarily submitted by gas companies to the FracFocus chemical disclosure registry", has created a fracking-chemical data base.

Revkin also provided an EPA video to encourage local infrared video monitoring of methane leakage from gas operations.[170]

See also[edit]

Further reading[edit]


  1. ^ a b c d "Chemicals Used in Hydraulic Fracturing". Committee on Energy and Commerce U.S. House of Representatives. April 18, 2011. 
  2. ^ a b c Brown, Valerie J. (February 2007). "Industry Issues: Putting the Heat on Gas". Environmental Health Perspectives (115(2)) (US National Institute of Environmental Health Sciences). 
  3. ^ a b 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. ^ a b c d e Urbina, Ian (3 March 2011). "Pressure Limits Efforts to Police Drilling for Gas". The New York Times. Retrieved 23 February 2012. "More than a quarter-century of efforts by some lawmakers and regulators to force the federal government to police the industry better have been thwarted, as E.P.A. studies have been repeatedly narrowed in scope and important findings have been removed" 
  5. ^ "Ozone mitigation efforts continue in Sublette County, Wyoming". Wyoming's Online News Source. March 2011. 
  6. ^ 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. 
  7. ^ a b "Oil and Natural Gas Air Pollution Standards". United States Environmental Protection Agency. Retrieved 2013-10-02. 
  8. ^ Rodriguez, Ginna (April 2013). Air Emissions Characterization and Management For Natural Gas Hydraulic Fracturing Operations In the United States (Report). University of Michigan School of Natural Resources and Environment. http://deepblue.lib.umich.edu/bitstream/handle/2027.42/97418/Air%20Emissions%20Hydraulic%20Fracturing_04-23-2013.pdf?sequence=1. Retrieved 4 May 2014.
  9. ^ 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.
  10. ^ 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)"
  11. ^ a b 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.
  12. ^ 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. 
  13. ^ 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"
  14. ^ Satterfield, J; Mantell, M; Kathol, D; Hiebert, F; Patterson, K; Lee, R (September 2008). "Managing Water Resources Challenges in Select Natural Gas Shale Plays". GWPC Annual Meeting. ALL Consulting. 
  15. ^ "Unconventional well drilling permits". Marcellus Center. Marcellus Center, Pennsylvania State University. 2012. Retrieved 2012-09-16. 
  16. ^ "Horizontal drilling boosts Pennsylvania's natural gas production". EIA. 23 May 2012. Retrieved 2012-09-16. 
  17. ^ Ridlington, Elizabeth; John Rumpler (October 3, 2013). "Fracking by the numbers". Environment America. 
  18. ^ Lubber, Mindy (28 May 2013). "Escalating Water Strains In Fracking Regions". Forbes. Retrieved 20 October 2013. 
  19. ^ "A Texan tragedy: ample oil, no water" 11 Aug Guardian
  20. ^ Berner, Daniel P; Grauman, Edward M; Hansen, Karen M; Kadas, Madeleine Boyer; LaValle, Laura L; Moore, Bryan J (May 1, 2013). "New Hydraulic Fracturing Water Recycling Rules Published in Texas Register". The National Law Review (Beveridge & Diamond PC). Retrieved 10 May 2013. 
  21. ^ Cite error: The named reference autogenerated6 was invoked but never defined (see the help page).
  22. ^ Kris Fitz Patrick (November 17, 2011). "Ensuring Safe Drinking Water in the Age of Hydraulic Fracturing". "The most fundamental recommendation is for states to rigorously test their ground water before and after hydraulic fracturing takes place. A major difficulty in proving or disproving contamination in previous cases has been the lack of a baseline sample for the water supply in question. The group also raises a federal policy issue, namely whether fracturing fluids should continue to be exempt from Safe Drinking Water Act regulations. This exemption was an informal one until 2005, when it was codified as part of the Energy Policy Act. A consequence of this exemption is that drilling companies are not required to disclose the chemicals that make up the fracturing fluids, making testing for these chemicals in ground water more difficult." 
  23. ^ 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. 
  24. ^ "FAQ: Hydraulic Fracturing, SDWA, Fluids, and DeGette/Casey". Energy In Depth. Retrieved 27 March 2013. 
  25. ^ Hass, Benjamin (14 August 2012). "Fracking Hazards Obscured in Failure to Disclose Wells". Bloomberg News. Retrieved 27 March 2013. 
  26. ^ Soraghan, Mike (13 December 2013). "White House official backs FracFocus as preferred disclosure method". E&E News. Retrieved 27 March 2013. 
  27. ^ "Colorado Sets The Bar on Hydraulic Fracturing Chemical Disclosure". Environmental Defense Fund. Retrieved 27 March 2013. 
  28. ^ Maykuth, Andrew (22 January 2012). "More states ordering disclosure of fracking chemicals.". Philadelphia Inquirer. Retrieved 27 March 2013. 
  29. ^ Grant, Alison (4 April 2013). "FracTracker monitors shale development in Ohio". The Plain Dealer. Retrieved 28 July 2013. 
  30. ^ Staff. "FracTracker. Exploring data, sharing perspectives, and mapping impacts of the gas industry". FracTracker. Retrieved 28 July 2013. 
  31. ^ "Regulatory Statements on Hydraulic Fracturing Submitted by the States, June 2009". Insterstate Oil and Gas Compact Commission. Retrieved 27 March 2013. 
  32. ^ "Pathways To Energy Independence: Hydraulic Fracturing And Other New Technologies". U.S. Senate. May 6, 2011. 
  33. ^ a b c Urbina, Ian (3 August 2011). "A Tainted Water Well, and Concern There May be More". The New York Times. Retrieved 22 February 2012. 
  34. ^ a b c Susan Phillips (8 December 2011). "EPA Blames Fracking for Wyoming Groundwater Contamination". StateImpact Penn­syl­va­nia. WITF, WHYY & NPR. Retrieved 6 February 2012. 
  35. ^ a b c Fetzer, Richard M. (19 January 2012). Action Memorandum — Request for funding for a Removal Action at the Dimock Residential Groundwater Site (Report). http://www.epaosc.org/sites/7555/files/dimock-action-memo-01-19-12%5B1%5D.pdf. Retrieved 27 May 2012.
  36. ^ a b c DiGiulio, Dominic C.; Wilkin, Richard T.; Miller, Carlyle; Oberley, Gregory (December 2011) (PDF). Investigation of Ground Water Contamination near Pavillion, Wyoming. Draft (Report). EPA. http://www.epa.gov/region8/superfund/wy/pavillion/EPA_ReportOnPavillion_Dec-8-2011.pdf. Retrieved 23 March 2012.
  37. ^ a b Mark Drajem (27 September 2012). "Diesel in Water Near Fracking Confirms EPA Tests Wyoming Disputes". Bloomberg News. Retrieved 28 September 2012. 
  38. ^ Ikeda, Robin (April 26, 2013). "Review of Federal Hydraulic Fracturing Research Activities. Testimony before the Subcommittees on Energy and Environment Committee on Science, Space and Technology U.S. House of Representatives". CDC web site. US Center for Disease Control and Prevention. Retrieved May 11, 2013. 
  39. ^ Fontenot, Brian E.; Hunt, Laura R.; Hildenbrand, Zacariah L.; Carlton Jr., Doug D.; Oka, Hyppolite; Walton, Jayme L. (2013). "An Evaluation of Water Quality in Private Drinking Water Wells Near Natural Gas Extraction Sites in the Barnett Shale Formation". Environ. Sci. Technol. 47 (17): 10032–10040. doi:10.1021/es4011724. PMID 23885945. 
  40. ^ Prevost, Ruffin (2006-08-22). "Blowout brings scrutiny to energy company". Billings Gazette (Casper Star-Tribune). Retrieved 2014-02-23. 
  41. ^ 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. 
  42. ^ 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. 
  43. ^ Jackson, Robert B.; Vengosh, Avner; Darrah, Thomas H.; Warner, Nathaniel R.; Down, Adrian; Poreda, Robert J.; Osborn, Stephen G.; Zhao, Kaiguang; Karr, Jonathan D. (24 June 2013). "Increased Stray Gas Abundance in a Subset of Drinking Water Wells Near Marcellus Shale Gas Extraction" (PDF). Proceedings of the National Academy of Sciences 110 (28): 11250. doi:10.1073/pnas.1221635110. Retrieved 2014-03-30. 
  44. ^ Begos, Kevin (24 June 2013). "Studies find methane in Pa. drinking water". Associated Press. Retrieved 25 June 2013. 
  45. ^ United States Environmental Protection Agency. "Safe Drinking Water Act". United States Environmental Protection Agency. Retrieved March 2014. 
  46. ^ a b Kiparsky, Michael; Hein, Jayni Foley (April 2013). "Regulation of Hydraulic Fracturing in California: A Wastewater and Water Quality Perspective" (PDF). University of California Center for Law, Energy, and the Environment. Retrieved 2014-05-01. 
  47. ^ a b c d Colorado Department of Natural Resources. "Gasland Correction Document". Denver, CO. State of Colorado Oil & Gas Conservation Commission. p. 1. 
  48. ^ a b c Boyer, Elizabeth; Bryan R. Swistock, M.S., James Clark, M.A., Mark Madden, B.S., and Dana E. Rizzo, M.S. (October 2011). The Impact of Marcellus Gas Drilling on Rural Drinking Water Supplies. 
  49. ^ "Gasland". 2010. 
  50. ^ Honan, Edith (2010-06-17). "Film challenges safety of U.S. shale gas drilling". Reuters. Retrieved 2010-06-28. 
  51. ^ Energy in Depth (June 9, 2010). "Debunking GasLand". Retrieved December 17, 2011. 
  52. ^ "Affirming Gasland". July 2010. Retrieved 2010-12-21. 
  53. ^ "Gasland Correction Document". Colorado Oil & Gas Conservation Commission. Retrieved 7 August 2013. 
  54. ^ 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.
  55. ^ a b c "EPA's Study of Hydraulic Fracturing and Its Potential Impact on Drinking Water Resources". EPA. Retrieved 24 February 2010. 
  56. ^ a b Mouawad, Jad; Krauss, Clifford (7 December 2009). "Dark Side of a Natural Gas Boom". The New York Times. Retrieved 3 March 2012. 
  57. ^ Christopher Bateman (21 June 2010). "A Colossal Fracking Mess". VanityFair.com. Retrieved 3 March 2012. 
  58. ^ Jim Snyder; Mark Drajem (10 January 2012). "Pennsylvania Fracking Foes Fault EPA Over Tainted Water Response". Bloomberg. Retrieved 19 January 2012. 
  59. ^ a b Gardner, Timothy (2012-05-11). "Water safe in town made famous by fracking-EPA". Reuters. Retrieved 2012-05-14. 
  60. ^ a b "Dimock, PA Water Testing Results Expected To Impact Fracking Debate". Associated Press. 5 March 2012. Retrieved 27 May 2012. 
  61. ^ a b c d "EPA Releases Draft Findings of Pavillion, Wyoming Ground Water Investigation for Public Comment and Independent Scientific Review" (Press release). EPA. 8 December 2011. Retrieved 27 February 2012. 
  62. ^ "Groundwater Investigation: Pavillion, WY". EPA. Retrieved 6 February 2012. "Pavillion, Wyoming is located in Fremont County, about 20 miles northwest of Riverton. In 2003, the estimated population was 166 residents. The concern at the site is potential groundwater contamination, based on resident complaints about smells, tastes and adverse changes in water quality of their domestic wells."  The report itself is here [1].
  63. ^ Christopher Helman (8 December 2011). "What If Fracking Did Pollute Wyoming Water?". Forbes.com. Retrieved 6 February 2012. 
  64. ^ "EPA Releases Report on Water Contamination By Fracking, As GA Pushes Fee Bills". PhillyNow blog. Philadelphia Weekly. 9 December 2011. Retrieved 6 February 2012. 
  65. ^ Peter R. Wright, Peter B. McMahon, David K. Mueller, and Melanie L. Clark (9 March 2012). Groundwater quality and quality control data for two monitoring wells near Pavillion, Wyoming, April and May 2012. (Report). U.S. Geological Survey. http://pubs.usgs.gov/ds/718/DS718_508.pdf. Retrieved 29 September 2012.
  66. ^ Mead Gruver (12 December 2011). "New Data, but Not Much New in Wyo. Fracking Study". EPA. Retrieved 6 May 2013. 
  67. ^ Keith Mauck (January 1, 2013) The EPA's Tainted Fracking Tests The Wall Street Journal Opinion
  68. ^ US EPA, Region 8, Wyoming to Lead Further Investigation of Water Quality Concerns Outside of Pavillion with Support of EPA, 20 June 2013.
  69. ^ General Accounting Office, Energy-water nexus, p.15-17, 9 Jan. 2012.
  70. ^ U.S. Environmental Protection Agency, Environmental Crimes Case Bulletin, Feb. 2013, p.10.
  71. ^ US Environmental Protection Agency, Natural gas drilling in the Marcellus Shale: NPDES program FAQs, PDF, 16 March 2011.
  72. ^ a b c University of Pittsburgh, Shales Gas Roundtable, p.56, Aug, 2013.
  73. ^ Lutz, Brian; Lewis, Aurana; Doyle, Martin (8 February 2013). "Generation, transport, and disposal of wastewater associated with Marcellus Shale gas development". Environmental Health Perspectives (Water Resources Research) 49 (2): 647–1197. doi:10.1002/wrcr.20096. Retrieved 2013-06-30. 
  74. ^ 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.
  75. ^ a b c Alex Wayne (4 January 2012). "Health Effects of Fracking Need Study, Says CDC Scientist". Businessweek. Retrieved 29 February 2012. 
  76. ^ a b c David Wethe (19 January 2012). "Like Fracking? You'll Love 'Super Fracking'". Businessweek. Retrieved 22 January 2012. 
  77. ^ a b c Mark Drajem (11 January 2012). "Fracking Political Support Unshaken by Doctors' Call for Ban". Bloomberg. Retrieved 19 January 2012. 
  78. ^ "Environmental Defense Center: Fracking". Retrieved 22 April 2013. 
  79. ^ "ENERGY POLICY ACT OF 2005". Authentic Government Information GPO. Retrieved 23 April 2013. "(i) the underground injection of natural gas for purposes of storage; and (ii) the underground injection of fluids or propping agents (other than diesel fuels) pursuant to hydraulic fracturing operations related to oil, gas, or geothermal production activities" 
  80. ^ a b "With Natural Gas Drilling Boom, Pennsylvania Faces an Onslaught of Wastewater". Propublica. 3 October 2009. Retrieved 7 August 2013. 
  81. ^ a b c d e f g h i j k l m n o Urbina, Ian (26 February 2011). "Regulation Lax as Gas Wells' Tainted Water Hits Rivers". The New York Times. Retrieved 22 February 2012. 
  82. ^ a b c Caruso, David B. (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. "...the more than 300,000 residents of the 17 municipalities that get water from the creek or use it for recreation were never informed that numerous public pronouncements that the watershed was free of gas waste had been wrong." 
  83. ^ Kevin Begos (5 January 2014). "4 states confirm water pollution from drilling. Associated Press review of complaints casts doubt on industry view that it rarely happens.". USA Today. Associated Press. Retrieved 6 January 2014. 
  84. ^ Bruce Gellerman and Ann Murray (10 August 2012). "Disposal of Fracking Wastewater Polluting PA Rivers". PRI's Environmental News Magazine (Public Radio International). Retrieved 14 January 2013. 
  85. ^ Sun, M.; Lowry, G.V.; Gregory, K.B. (2013). "Selective oxidation of bromide in wastewater brines from hydraulic fracturing". Water research (Water Res.) 47 (11): 3723–3731. doi:10.1016/j.watres.2013.04.041. PMC 1817691. PMID 23726709. 
  86. ^ Paul Handke, Trihalomethane speciation and the relationship to elevated total dissolved solid concentrations, Pennsylvania Department of Environmental Protection.
  87. ^ a b c White, Jeremy; Park, Haeyoun; Urbina, Ian; Palmer, Griff (26 February 2011). "Toxic Contamination From Natural Gas Wells". The New York Times. 
  88. ^ a b c "Drilling Down: Documents: Natural Gas's Toxic Waste". The New York Times. 26 February 2011. Retrieved 23 February 2012. 
  89. ^ a b Carus, Felicity (2 October 2013). "Dangerous levels of radioactivity found at fracking waste site in Pennsylvania. Co-author of study says UK must impose better environmental regulation than US if it pursues shale gas extraction". The Guardian. Retrieved 10 October 2013. 
  90. ^ a b c d e Warner, Nathaniel R.; Christie, Cidney A.; Jackson, Robert B.; Vengosh, Avner (2 October 2013). "Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania". Environ. Sci. Technol. (ACS Publications) 47 (20): 11849. doi:10.1021/es402165b. PMID 24087919. 
  91. ^ a b Jacobs, Harrison (9 October 2013). "Duke Study: Fracking Is Leaving Radioactive Pollution In Pennsylvania Rivers". Business Insider (Business Insider). Retrieved 10 October 2013. 
  92. ^ Griswold, Eliza (17 November 2011). "The Fracturing of Pennsylvania". The New York Times Magazine. Retrieved 21 November 2011. 
  93. ^ "State Official: Pa. Water Meets Safe Drinking Standards". CBS Pittsburgh. January 4, 2011. 
  94. ^ "Pennsylvania DEP Secretary Defends States' Ability to Regulate Hydraulic Fracturing". PR Newswire. November 17, 2011. 
  95. ^ Don Hopey (February 24, 2011). "Corbett repeals policy on gas drilling in parks". Pittsburgh Post-Gazette. Retrieved April 19, 2011. 
  96. ^ Bill McKibben (8 March 2012). "Why Not Frack?". The New York Review of Books 59 (4). Retrieved 21 February 2012. 
  97. ^ "Annual Drinking Water Quality Report, 2010". Philadelphia Water Department. Spring 2011. Retrieved 7 February 2012. 
  98. ^ a b McGraw, Seamus (27 March 2011). "Is Fracking Safe? The Top 10 Myths About Natural Gas Drilling". Popular Mechanics. Retrieved 27 March 2013. 
  99. ^ Urbina, Ian (7 April 2011). "Pennsylvania Calls for More Water Tests". The New York Times. Retrieved 23 February 2012. 
  100. ^ a b "Natural Gas Drilling, the Spotlight". The New York Times. 5 March 2011. Retrieved 24 February 2012. 
  101. ^ a b Charles Petit (2 March 2011). "Part II of the fracking water problems in PA and other Marcellus Shale country". Knight Science Journalism Tracker. MIT. Retrieved 24 February 2012. 
  102. ^ "Analysis of Marcellus flowback finds high levels of ancient brines" (Press release). Pennsylvania State University. 17 December 2012. Retrieved 31 January 2013. 
  103. ^ Don Hopey, Study finds lower bromide levels in Mon, but not in Allegheny, Pittsburgh Post-Gazette, 13 Nov. 2012.
  104. ^ Urbina, Ian (1 March 2011). "Drilling Down: Wastewater Recycling No Cure-All in Gas Process". The New York Times. Retrieved 22 February 2012. 
  105. ^ Don Hopey (5 March 2011). "Radiation-fracking link sparks swift reactions". Pittsburgh Post-Gazette. Retrieved 23 February 2012. 
  106. ^ Shocker: New York Times radioactive water report is false March 8, 2011 ι Abby Wisse Schachter. Report is from a Rupert Murdoch tabloid, The New York Post
  107. ^ Urbina, Ian (7 March 2011). "E.P.A. Steps Up Scrutiny of Pollution in Pennsylvania Rivers". The New York Times. Retrieved 14 May 2013. 
  108. ^ Reis, John C. (1976). Environmental Control in Petroleum Engineering. Gulf Professional Publishers.
  109. ^ K. Fisher and others, "A comprehensive study of the analysis and economic benefits of radioactive tracer engineered stimulation procedures," Society of Petroleum Engineers, Paper 30794-MS, October 1995.
  110. ^ a b c d Jack E. Whitten, Steven R. Courtemanche, Andrea R. Jones, Richard E. Penrod, and David B. Fogl (Division of Industrial and Medical Nuclear Safety, Office of Nuclear Material Safety and Safeguards (June 2000). "Consolidated Guidance About Materials Licenses: Program-Specific Guidance About Well Logging, Tracer, and Field Flood Study Licenses (NUREG-1556, Volume 14)". US Nuclear Regulatory Commission. Retrieved 19 April 2012. "labeled Frac Sand...Sc-46, Br-82, Ag-110m, Sb-124, Ir-192" 
  111. ^ (PDF) Radiation Protection and the Management of Radioactive Waste in the Oil and Gas Industry (Report). International Atomic Energy Agency. 2003. pp. 39–40. http://www-pub.iaea.org/MTCD/publications/PDF/Pub1171_web.pdf. Retrieved 20 May 2012.
  112. ^ Timothy A. Bartrand and Jeffrey S. Rosen (October 2013). Potential Impacts and Significance of Elevated 131 I on Drinking Water Sources [Project #4486 ORDER NUMBER: 4486] (Report). Water Research Foundation. http://www.waterrf.org/ExecutiveSummaryLibrary/4486_ProjectSummary.pdf. Retrieved 11 November 2013.
  113. ^ Bennet, Les, et.al.. "The Source for Hydraulic Fracture Characterization" (PDF). Oilfield Review (Schlumberger) (Winter 2005/2006): 42–57. Retrieved 2012-09-30. 
  114. ^ 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. 
  115. ^ US Geological Survey, Man-made earthquakes, accessed 22 Sept. 2013.
  116. ^ 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.
  117. ^ Soraghan, Mike (13 December 2013). "Disconnects in public discourse around 'fracking' cloud earthquake issue.". E&E News. Retrieved 27 March 2013. 
  118. ^ Induced Seismicity Potential in Energy Technologies (Report). National Academies Press. 2012. http://dels.nas.edu/Report/Induced-Seismicity-Potential-Energy-Technologies/13355. 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."
  119. ^ a b Kim, Won-Young 'Induced seismicity associated with fluid injection into a deep well in Youngstown, Ohio', Journal of Geophysical Research-Solid Earth
  120. ^ 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) (6142): 164–167. doi:10.1126/science.1238948. 
  121. ^ a b [2], Environmental Protection Agency
  122. ^ USGS, How large are the earthquakes induced by fluid injection?
  123. ^ "How is hydraulic fracturing related to earthquakes and tremors?". USGS. Retrieved 4 November 2012. 
  124. ^ 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. 
  125. ^ Soraghan, Mike (29 March 2012). "'Remarkable' spate of man-made quakes linked to drilling, USGS team says". EnergyWire (E&E). Retrieved 2012-11-09. 
  126. ^ Henry, Terrence (6 August 2012). "How Fracking Disposal Wells Are Causing Earthquakes in Dallas-Fort Worth". State Impact Texas. NPR. Retrieved 9 November 2012. 
  127. ^ Katie M. Keranen, "Potentially induced earthquakes in Oklahoma, USA," Geology, 26 March 2013.
  128. ^ Oklahoma Geological Survey, Prague, Oklahoma earthquake, PDF, 22 March 2013.
  129. ^ Bill Leith, Induced seismicity, US Geological Survey, June 2012.
  130. ^ "Ohio Quakes Probably Triggered by Waste Disposal Well, Say Seismologists" (Press release). Lamont–Doherty Earth Observatory. 6 January 2012. Retrieved 22 February 2012. 
  131. ^ Ohio Department of Natural Resources, Executive Summary, Preliminary Report on the Northstar 1 Class II Injection Well and the Seismic Events in the Youngstown, Ohio, Area, PDF, March 2012.
  132. ^ a b NPR - State Impact Texas, How oil and gas disposal wells can cause earthquakes.
  133. ^ University of Texas, Study finds correlation between injection wells and small earthquakes, 6 Aug. 2011.
  134. ^ Dunn, Sharon (June 5, 2014). "CU research team studying earthquake activity near Greeley". Greeley Tribune. Retrieved 10 June 2014. 
  135. ^ Tomasic, John (June 2, 2014). "Greeley quake adds ammunition to Colorado fracking war". The Colorado Independent. Retrieved 10 June 2014. 
  136. ^ a b Abrahm Lustgarten and Nicholas Kusnetz (2011-09-16). "Science Lags as Health Problems Emerge Near Gas Fields". Propublica. Retrieved 2013-05-06. 
  137. ^ a b PEHSU (August 2011). PEHSU Information Concerning Effects on Children of Natural Gas Extraction and Hydraulic Fracturing (Report). Propublica. http://www.propublica.org/documents/item/250048-pehsu-information-concerning-effects-on-children. Retrieved 2013-05-06.
  138. ^ 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. PMID 22444058. 
  139. ^ "Worker Exposure to Silica during Hydraulic Fracturing". OSHA. Retrieved 15 January 2013. 
  140. ^ Esswein, Eric; Kiefer, Max; Snawder, John; Breitenstein, Michael (23 May 2012). "Worker Exposure to Crystalline Silica During Hydraulic Fracturing". NIOSH Science Blog. United States Center for Disease Control. Retrieved 2012-09-08. 
  141. ^ Mall, Amy (16 May 2012). "Concerns about the health risks of fracking continue to grow". Switchboard: NRDC Staff Blog. Natural Resources Defense Council. Retrieved 2012-05-19. 
  142. ^ Hopkinson, Jenny; DiCosmo, Bridget (15 May 2012). "Academies' NRC Seeks Broad Review Of Currently Ignored Fracking Risks". InsideEPA (Inside Washington Publishers). (subscription required). Retrieved 2012-05-19. 
  143. ^ Schmidt, Charles W. (August 2011). "Blind Rush? Shale Gas Boom Proceeds Amid Human Health Questions". Environmental Health Perspectives 119 (119(1)): A348–53. doi:10.1289/ehp.119-a348. PMC 3237379. PMID 21807583. 
  144. ^ "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. 
  145. ^ a b Mckenzie, Lisa; Ruixin Guo; Roxana Z. Witter; David A. Savitz; Lee S. Newman; John L. Adgate (28 January 2014). "Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado". Environmental Health Perspectives. doi:10.1289/ehp.1306722. 
  146. ^ a b Bamberger, Michelle; Oswald, Robert E. (2012). "Impacts of gas drilling on human and animal health" (PDF). New Solutions: A Journal of Environmental and Occupational Health Policy 22 (1): 51–77. doi:10.2190/NS.22.1.e. Retrieved 2012-12-21. 
  147. ^ />"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"
  148. ^ "Vermont Act 152"
  149. ^ a b "Fracking disclosure rules", Trade Secrets Watch, October 2013
  150. ^ "Missing from the table: role of the environmental public health community in governmental advisory commission related to the Marcellus Shale Drilling", University of Pittsburgh, in Environmental Health Perspectives, Volume 120, Number 4, April 2012
  151. ^ US EPA, are EPA's drinking water regulations for radionuclides? What are EPA's drinking water regulations for radionuclides?, accessed 15 Sept. 2013.
  152. ^ Shawn M. Garvin (7 March 2011). Letter to PADEP re:Marcellus Shale 030711 (PDF). EPA. Retrieved 11 May 2012. "several sources of data, including reports required by PADEP, indicate that the wastewater resulting from gas drilling operations (including flowback from hydraulic fracturing and other fluids produced from gas production wells) contains variable and sometimes high concentrations of materials that may present a threat to human health and aquatic environment, including radionuclides.... Many of these substances are not completely removed by wastewater treatment facilities, and their discharge may cause or contribute to impaired drinking water quality for downstream users, or harm aquatic life ... At the same time, it is equally critical to examine the persistence of these substances, including radionuclides, in wastewater effluents and their potential presence in receiving waters." 
  153. ^ Ian Urbina (7 March 2011). "E.P.A. Steps Up Scrutiny of Pollution in Pennsylvania Rivers". The New York Times. Retrieved 23 February 2012. 
  154. ^ Susan Phillips (2 November 2012). "DEP Employee Says Agency Withholds Water Contamination Information from Residents". StateImpact Pennsylvania. NPR. Retrieved 10 November 2012. 
  155. ^ Sandy Bauers (21 July 2011). "Cancer patients’ urine suspected in Wissahickon iodine-131 levels". Philadelphia inquirer, Carbon County Groundwater Guardians. Retrieved 25 February 2012. 
  156. ^ DiCosmo, Bridget (15 May 2012). "SAB Pushes To Advise EPA To Conduct Toxicity Tests In Fracking Study". InsideEPA. Inside Washington Publishers. (subscription required). Retrieved 2012-05-19. 
  157. ^ Satterfield, John (30 June 2011). "Letter from Chesapeake Energy to EPA". InsideEPA. US Environmental Protection Agency. Retrieved 2012-05-19. 
  158. ^ "The Debate Over the Hydrofracking Study's Scope". The New York Times. 3 March 2011. Retrieved 1 May 2012. "While environmentalists have aggressively lobbied the agency to broaden the scope of the study, industry has lobbied the agency to narrow this focus" 
  159. ^ Joseph D. Ayotte et al. (August 2011). "Trace Elements and Radon in Groundwater Across the United States, 1992-2003". U.S. Geological Survey. Retrieved 25 May 2012. 
  160. ^ Ramanuja, Krishna (7 March 2012). "Study suggests hydrofracking is killing farm animals, pets". Cornell Chronicle Online. Cornell University. Retrieved 9 March 2012. 
  161. ^ Helen Westerman (11 January 2012). "Gas drilling research highlights risk to animals, but more thorough work needed". The Conversation. Retrieved 25 May 2012. 
  162. ^ Dammel, Joseph A. (2011). "Notes From Underground: Hydraulic Fracturing in the Marcellus Shale" (PDF). Minnesota Journal of Law, Science and Technology (University of Minnesota Law School) 12 (2): 773–810. Retrieved 24 February 2012. 
  163. ^ (PDF) Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs; National Study Final Report (Report). EPA. June 2004. http://www.epa.gov/ogwdw/uic/pdfs/cbmstudy_attach_uic_final_fact_sheet.pdf. Retrieved 23 February 2011.
  164. ^ [3] Scott III, George L. (03-June-1997) US Patent No. 5635712: Method for monitoring the hydraulic fracturing of a subterranean formation. US Patent Publications.
  165. ^ [4] Fertl; Walter H. (15-Nov-1983) US Patent No. US4415805: Method and apparatus for evaluating multiple stage fracturing or earth formations surrounding a borehole. US Patent Publications.
  166. ^ [5] Scott III, George L. (15-Aug-1995) US Patent No. US5441110: System and method for monitoring fracture growth during hydraulic fracture treatment. US Patent Publications.
  167. ^ Vaughan, Vicki (16 February 2012). "Fracturing 'has no direct' link to water pollution, UT study finds". Retrieved 3 March 2012. 
  168. ^ Munro, Margaret (17 February 2012). "Fracking does not contaminate groundwater: study released in Vancouver". Vancouver Sun. Retrieved 3 March 2012. 
  169. ^ a b 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.
  170. ^ Revkin, Andrew C., "The Do-It-Yourself Approach to Tracking Gas Drilling", New York Times Dot Earth blog, November 14, 2012. Retrieved 2012-11-14.

External links[edit]