Fracking fracas

Print Friendly
Fracking fracas

In New York and Pennsylvania, a technique that splits rock so natural gas can flow is pitting environmentalists against industry and neighbor against neighbor.

ENLARGE

Rectangular swatch of land is covered in gravel, lined with trailers, trucks and equipment, and a drill tower sits at one end

Photo: University of Pittsburgh Graduate School of Public Health’s Center for Healthy Environments and Communities
When opponents talk about an “industrial landscape,” this is what they have in mind. This equipment, in Pennsylvania, will be moved after drilling and fracking is finished.

In areas distant from the surge of natural gas drilling that has swept western states over the past 20 years or so, high-pressure fracturing, or “fracking,” has raised a fundamental question: Can a huge supply of deep natural gas be developed without harming rural landscapes and poisoning the groundwater that most people drink?

See the Classroom Activity Page for this story.

Nationwide, fracking is now used not only to liberate gas from shale, but also to boost production in the majority of oil and gas wells. In an era of energy shortages, it’s difficult to dismiss a massive new supply of natural gas, the cleanest fossil fuel, and the gas industry is quick to position fracking as a key to jobs, prosperity and energy security.

According to an American Petroleum Institute website: Hydraulic fracturing, or “fracking,” is a proven and well-regulated technology. First used in the 1940s, hydraulic fracturing has unlocked massive new supplies of oil and clean-burning natural gas from dense deposits of shale — supplies that increase our country’s energy security and improve our ability to generate electricity, heat homes and power vehicles for generations to come. Fracking has been used in more than one million U.S. wells, and has safely produced more than seven billion barrels of oil and 600 trillion cubic feet of natural gas.

But critics charge that fracking pollutes water and causes excess noise, truck traffic and health hazards. They reject the conversion of rural landscapes into what they call “industrial landscapes.”

Update Dec. 9, 2011: On Dec. 8, the Associated Press reported on an Environmental Protection Agency finding “that compounds likely associated with fracking chemicals had been detected in the groundwater beneath Pavillion, a small community in central Wyoming where residents say their well water reeks of chemicals.” Despite the differences in geology and fracking technology between Wyoming and the eastern gas deposits, the finding adds fuel to the contention that fracking can harm groundwater. End update.

The middle ground on the fracking debate seems as lonely as the far side of moon. But could both sides have some valid arguments? And if so, where do we go from here?

Context for the contest

Natural gas was once flared off as junk at oil wells, but it began to enter the energy markets in the 1920s. By now, it’s one of the big three sources of energy in the United States, alongside coal and oil.

Ten or 15 years ago, rising prices heralded a shortage of natural gas, a clean fossil fuel containing mostly methane that has become a major energy source for electricity and home heating over the past 50 years or so.

Those prices helped spark a two-legged technological revolution composed of fracking and horizontal drilling. Fracturing rock allows gas to flow. Horizontal drilling allows one well to tap a profitable volume of a thin, gas-rich wafer of deep shale.

ENLARGE

Man and woman stand in front of white milk truck holding protest signs against fracking and urging passage of laws on fracking

These protesters in Philadelphia don’t want fracking in the U.S. energy future. But is the pollution they oppose due to the fracking stage of gas development, or to the entire process of gas extraction?

The power of this combination is evident in the frenzy to lock up land above the Marcellus shale, a rock body that underlies parts of Pennsylvania, New York, Ohio and West Virginia, and in the rising estimates for future gas production.

At the same time, “fracking” has become the “brand name” for more generalized opposition to gas drilling, and the debate is confused by the fact that many people use “fracking” as shorthand for new gas development rather than the process that breaks rock so gas can flow. This matters: Although fracking fluids can pose a hazard to groundwater, many gas wells contain other fluids that may carry radiation or other nasties that must be removed before the gas is shipped to its destination.

This “produced water” can be hazardous in its own right.

Down Pennsylvania way

Today, the biggest shale-gas development is in the Barnett Shale, around Fort Worth, Texas, site of more than 10,000 wells. But the hottest political debate concerns the Marcellus shale. The Marcellus was consolidated from mud about 390 million years ago into a fine-grained sedimentary rock that trapped methane produced during the decay of organic matter. The low-oxygen conditions protected the methane from oxidation.

The lay of the shale-gas play

Plays and basins shown through Rocky Mountains, in southern California, from Iowa south to Texas and Louisiana, in Illinois, Michigan and Indiana, and through Ohio, West Virginia, New York, Pennsylvania and Kentucky

“Plays” are regions with available gas or oil. Fracking and horizontal drilling have vastly expanded the fossil-fuel landscape.

World demand in the “Golden Age of Gas” scenario

Line graph shows 2035 projections by energy source. Natural gas line starts at 1200 Mtoe in 1980 and rises to 4200 Mtoe in 2035

Graphic: IAE, 2011
Hydrofracturing plays a major role in projections for a steady increase global in gas production in this scenario from the International Energy Agency. The increases are due to “a more ambitious policy for gas use in China, lower growth of nuclear power, greater production of unconventional gas [such as shale gas] and lower gas prices.” Mtoe = million tons of oil equivalent

The Marcellus shale lies an average of two kilometers deep, far below the groundwater that feeds home and municipal water wells. With an average thickness of about 30 meters, the Marcellus contains an estimated 295 to 2,700 trillion cubic feet of natural gas.

If 10 percent of that gas can be recovered, this amounts to one to 10 years of supply for the United States, which used 21 trillion cubic feet in 2006. 1

Fracking has been dividing communities in the East, which has seen little of the vast energy development of the West. While some landowners and businesses profit from leases and economic activity related to gas development, others fear for the safety of their well water, streams and air.

Today, much of the concern about fracking focuses on drinking water. According to Food & Water Watch, toxic chemicals in fracking fluid can contaminate water via spills, accidents, improper disposal or poor well construction. Natural gas has entered drinking water, the group notes, during “more than 1,000 documented cases of water contamination near drilling sites around the country.”

A platform at the base of a drill tower sits at the edge of cement ditch, which is surrounded by mesh fence and gravel

This drill worked in Dimock, Penna.

In areas with many gas wells, groundwater pollution cannot easily be traced to a particular well, and it takes some effort to trace the pollution to gas drilling itself. But widespread groundwater pollution can also be virtually impossible to reverse.

One of the more notorious cases occurred in Dimock, a Marcellus-shale town in northeastern Pennsylvania. After drilling started in 2008, 18 private water wells became polluted with methane and other chemicals, turning dishes brown and, according to a press report, residents reported getting sick from drinking the water, or even showering under it.

On Dec. 15, 2010, Cabot Oil and Gas Corp. signed a consent agreement with the Pennsylvania Department of Environmental Protection regarding 18 polluted water wells in Dimock. Cabot agreed to suspend drilling, plug and abandon three gas wells, supply drinking water to 18 houses, test home well water, and “comply with all applicable environmental laws and regulations” when it resumed drilling and fracking in the area.

The Department concluded, but Cabot disputed, that the company had engaged in “unlawful conduct.”

Let a thousand wells bloom!

Photo 1: SkyTruth.org and DamascusCitizens.org. Photo 2 (rollover): DamascusCitizens.org, assembled from GoogleEarth images
Three- to five-acre drill pads dot the landscape in Jonah, Wyo. Roll over for a satellite view of drill pads in DISH, Texas.

New York City continues to oppose fracking in its prized watershed in the Catskill Mountains. And fracking opponents scored a victory on Nov. 18, when the Delaware River Basin Commission declined to move forward on a decision to allow fracking in the Basin. Opponents had warned that up to 20,000 gas wells in the area would threaten water supplies for millions.

Many billions are at stake in the debate over shale gas, which ConocoPhillips expects to account for almost half of U.S. natural gas production by 2035. The petroleum giant credits shale gas for a 110 percent rise in U.S. natural gas reserves and resources between 2000 and 2009.

What is fracking?

Hydrofracturing, or fracking, is a stage of “well completion” that follows drilling. Briefly, drillers bore through the surface, insert steel casing and concrete to seal the hole against groundwater, and drill deeper into the rock, repeatedly adding pipe and cement if needed to seal the well from the surrounding rock.

As the drill approaches the gas-bearing shale, it is “steered” into a horizontal direction, then forced through the source rock for hundreds of meters or more. Once the drilling is completed, holes are punched in the lower casing and millions of gallons of frack fluid are pumped into the well at roughly 1,000 times atmospheric pressure.

After some of that frack fluid is withdrawn, production can begin, as gas rises under the influence of the immense pressure belowground. At the surface, produced water and frack fluid are removed before the gas is piped to market.

The fracking process

Well drills below 7,000 feet, then turns horizontal. At well's end are fissures in rock. Smaller diagram shows fissure with sand inside and how gas enters well.

Diagram: ProPublica

Fracking in the history books?

The gas industry often meets questions about the environmental aspects of fracking by asking, essentially, “What’s new?” “The history of fracturing technology’s safe use in America extends all the way back to the Truman administration, with more than 1.2 million wells completed via the process since 1947,” says the industry group Energy in Depth.

But fracking “was a rare process” at first, says Geoffrey Thyne of the Enhanced Oil Recovery Institute at the University of Wyoming. For 20 years it usually used water measured in the tens of thousands of gallons (not millions like today) and sometimes sand, says Thyne. But in the 1990s, drillers in Wyoming “did a giant frack. Suddenly the amount of [frack] fluid jumped 10 or 20 times, and suddenly a whole class of resources that was labeled unconventional became accessible.”

Let’s do the definitions:

Conventional gas and oil rise over the eons until being trapped under a “cap rock” that prevents further ascent. These deposits tend to be rich with hydrocarbons.

Unconventional gas is found in geological formations that do not allow such flow.

Nations with great shale gas potential

Proved reserves and technically recoverable are highest for U.S. and China, followed by Argentina, Mexico, South Africa, Australia, Canada and Poland.

Data source: U.S. Energy Information Administration
In fossil fuels, you have to watch your numbers. Resources may be huge, but not all economically relevant.

Thyne notes that in contrast to conventional gas, shale gas requires “a lot more development, more wells and infrastructure, to get the same bang for the buck, and that creates a lot of friction with landowners.”

Jonah, an unconventional gas field in Wyoming “has a well on every 10 acres,” says Thyne, who teaches petroleum geology and hydrogeology. “If you flew over it, it looks like a moonscape, there’s an incredible amount of development. If you bring that into areas that have not had development, people are going to be put back on their heels: ‘What the heck?'”

As the economic benefits of fracking were proven, it became the rule for oil and gas. Over the last 20 years, Thyne says, “we went from a period where one well in 100 would be fracked, maybe one time each, to now, where 90 percent of all gas and oil wells are fracked, and the number of frackings per well has gone from one to as many as 25, done over a period of several months.”

But that growth is both normal and desirable, says Felmy. “Absolutely, it’s been a wonderful development of technology, and like all technology, it takes time to ramp up. Fortunately, [as a result] a bright spot for consumers is the low price of natural gas today.”

Let the debate begin

The impact of fracturing and horizontal drilling is evident in a new estimate from the U.S. Department of Energy, which places the national gas resource at 110 years of current consumption (although by definition not all of a fossil-fuel “resource” can be recovered).

“Proved natural gas reserves” are known to exist with reasonable certainty;

“Technically recoverable shale gas resources” includes discovered and undiscovered gas that can be recovered with existing technology, without regard to cost or profit. The U.S. quantity shown here includes about 827 trillion cubic feet of unproven shale gas.

U.S. Natural Gas Supply, 1990 – 2035

Shale gas supply is at 14% in 2009 and grows to 46% in 2035.

Graphic: U.S. EIA, Annual Energy Review, October 2011
Will rising natural gas production improve national security and reduce the emphasis on access to Middle-Eastern oil?

Projections about future production are inherently debatable because the economical amount of any energy resources depends on future prices. Internal emails from the U.S. Energy Information Administration have suggested that estimates of production and profit in the shale-gas boom exhibit signs of “irrational exuberance.”

In 1996, Alan Greenspan, then chairman of the Federal Reserve, used that to describe the “dot-com market bubble.

Natural gas has environmental benefits over coal and oil, including a reduced greenhouse-warming impact. To release the same amount of heat, oil and especially coal release more carbon dioxide than methane.

We have seen an April, 2011 study claiming heavy releases of heat-trapping methane from fracking and drilling make natural gas worse than coal for the climate. Although critics have questioned the study on the ground that the massive releases are both dangerous and uneconomical, methane is clearly entering the atmosphere at some gas operations.

Ozone, which damages the lungs and triggers asthma attacks, forms when sunlight strikes hydrocarbons released from a gas or oil well. The Environmental Protection Agency is studying ozone and smog at a gas field in Wyoming.

In a tight economy, jobs and taxes are big allures of gas drilling. Some landowners have profited mightily by leasing land to gas firms. In 2009, an industry-financed study reported that 622,000 people are directly involved in the discovery, extraction and distribution of natural gas in the United States, and the industry had an estimated, direct economic impact of $170 billion.

Concerns and open questions

There are plenty of concerns about the intensified gas extraction enabled by hydro-fracturing. Beyond the worries about noise, traffic, and the “industrial landscape,” there are other concerns.

Seven hours after fracturing began, more than 50 shallow earthquakes occurred within 3.5 kilometers of a gas-drilling operation in Oklahoma, in January, 2011. According to the Oklahoma Geological Survey, “The strong correlation in time and space as well as a reasonable fit to a physical model suggest that there is a possibility these earthquakes were induced by hydraulic-fracturing,” but added that this is “impossible to say with a high degree of certainty… “

ENLARGE

A huge pile of sand towers over a dump truck. Two silos and a conveyor belt stand in the background.

Courtesy Jason Smathers, Wisconsin Center for Investigative Journalism
Fracking has sparked a surge in mining for the silica sand that props open pores created by the fracking pressure. Wisconsin has no shale gas, lots of silica sand, and some neighbors who worry that blowing sand will cause lung disease.

Fluid chemistry

Frack fluid, the liquid used to pressurize and crack underground rocks, is a major concern about fracking. Water, an incompressible liquid, and sand, used to hold open the fractures created by the immense pressure, are said to comprise more than 99 percent of fracking fluid. But the fluid can also contain hundreds of other chemicals to fight bacteria or rust, or to change how the water flows.

Some of the additives are common and low-toxicity, but others, like diesel fuel, are poisonous.

And many are unknown, held as trade secrets. According to an April, 2011 report from Democrats on the House Committee on Energy and Commerce, “Between 2005 and 2009, the 14 oil and gas service companies used more than 2,500 hydraulic fracturing products containing 750 chemicals and other components. Overall, these companies used 780 million gallons of hydraulic fracturing products – not including water added at the well site – between 2005 and 2009.”

The safer components of frack fluid included salt and citric acid, the Democrats wrote, but some components “were extremely toxic, such as benzene and lead.” Methanol, a hazardous air pollutant and human poison, was “the most widely used chemical … used in 342 hydraulic fracturing products.”

To counter suspicion about these chemicals, the industry recently established Frac Focus, a public database on chemicals used in particular wells. Participation is voluntary.

ENLARGE

A drill tower perches on a hill amid a rolling forested landscape, a road and house in foreground

Photo: Ruhrfisch
How many drilling rigs will appear in Pennsylvania and New York shale country? This one is along route 118 in Lycoming County, Penn.

Wastewater disposal

Used fracking fluid needs safe disposal. “We are talking a substantial volume, millions of gallons per well,” Thyne says, “and one-half to one-third of the fracking fluid comes back, and has to be disposed of.”

Gas from many wells contains a second liquid, called “produced water,” that also needs disposal.

“In classic, conventional petroleum, they can reinject everything back into the reservoir,” says Thyne, “but they can’t do that with unconventional gas [because the rock formation is not porous], so we have a sudden surge in material that has to be treated and disposed of; that’s been a real challenge.”

Some of the liquids have been trucked to municipal wastewater plants, which are designed to remove biological waste, not the components of frack fluid.

One of those components, naturally occurring radioactivity, has sparked a flurry of interest among Pennsylvania and federal environmental regulators. The source is radium in the deep rocks; the hazard occurs if this water is released into surface water or groundwater.

Yet as so often in the fracking fracas, much remains in dispute, including whether radioactivity is elevated in rivers that receive fracking wastewater.

Contaminated water emerging from gas wells is often stored in a wastewater pit near the well site, and these pits have been linked to groundwater pollution, as EPA Administrator Lisa Jackson said in June, 2011. “It gets put in these ginormous huge pools and sits there, and that is a source of contamination all by itself, and so we need to determine how to stop that from happening.”

ENLARGE

Aerial of two houses with green lawns and a rectangular pond with murky water behind them.

Photo: University of Pittsburgh Center for Healthy Environments and Communities
These wastewater pits are a particular cause for concern about drinking-water quality.

Wasted by the water

In some states, this wastewater can be spread on land, but a 2011 study2 demonstrated that the practice can kill plants.

When 303,000 liters of fracking fluid were spread on 0.2 hectares of experimental forest, tree leaves started to brown and curl within 10 days, and 56 percent of the trees were dead within two years. Every surviving tree was harmed.

The research suggested that high levels of salts – calcium and sodium chlorides – was causing the damage. Several states, including Colorado and West Virginia, permit land application, and the test application was below West Virginia’s limits.

Industry is starting to recycle fracking fluid to reduce environmental contamination, but that’s no panacea, Thyne says. “You can recycle to a certain extent, once or twice. By that time, you’ve got to treat the water to get it back to where it was before you put in new additive. Recycling buys you a little time, but it’s not an end game.”

Mad about methane

Although industry argues that not a single case of water contamination has been conclusively attributed to fracking, methane and other contaminants are appearing in drinking water and near-surface geology after the drill-and-frack sequence.

State investigators traced a house explosion in 2007 in Geauga County, Ohio, to a faulty cementing job on a nearby gas well. After the well was fractured, gas pressure built up inside it and nearby rock formations before being released into basements. One house was seriously damaged and 19 were evacuated, but there were no injuries.

ENLARGE

Mustached man holds jug of murky water in one hand and small bottle of murky water in other hand

Photo of Dimock, Penna ©Riverkeeper.org
This man holds water from his well, which started to bubble methane after a gas well was fracked near his home. He now drinks water delivered by the fracking company.

In a 2011 study 3 of 68 residential wells in Marcellus shale in Pennsylvania and New York, Robert Jackson of the Center on Global Change at Duke University found, on average, more than 17 times as much methane in wells that were located within one kilometer of a natural-gas well.

As many as 1 million Pennsylvania households rely on private wells for water, the study noted, and in general, the wells are unregulated and untested.

Jackson says the study found no evidence that fracking fluid had contaminated the water wells. “But we see the gas as a warning sign. If methane is leaking, chances are that other things are leaking too.”

The Jackson study was flawed by “a lack of baseline data,” according to Reid Porter, a spokesperson for the American Petroleum Institute. “Most critical: The authors don’t have hard data to show how much methane surfaces on its own in northeastern Pennsylvania. They cite ‘historical sources’ but don’t say how far back those sources go or exactly what the sources are. … Without more data it’s impossible to distinguish between methane emitted naturally and/or from coal mining and methane released by fracturing.”

A baseline would be nice, but the Jackson study did succeed in finding a significant elevation in methane levels closer to gas wells, and isotopic analysis traced that methane to the Marcellus shale, rather than decay of biomass at shallow levels.

Finding a way

So how is methane reaching water wells from deep shale? It could be rising thousands of feet through existing or newly stimulated cracks in the rock, Jackson says, “but the most likely explanation is poor well construction, cementing or casing.”

Petroleum expert Thyne agrees with that explanation, which “means it’s a mechanical issue that can be dealt with.”

Here, at least, API is in agreement. “The energy industry recognizes that well construction is key to community safety,” Porter wrote us. “That’s why API members have developed five documents that specifically and proactively address well construction and environmental protection practices during hydraulic fracturing.”

A red barn sits in the foreground, a white silo sits behind it, the top of a drilling tower is close behind both.

Photo of Dimock, Penn.: ©Riverkeeper.org

When API maintains that fracking groundwater has never been polluted by fracturing fluid, it cites two studies:

a 1998 survey by the Groundwater Protection Council of state regulators on the use of hydraulic fracturing for extracting methane from coal deposits, not from shale. One complaint about groundwater quality surfaced in one state, and regulators could not confirm any relationship to fracturing.

a 2004 Environmental Protection Agency study that “confirmed no direct link between hydraulic fracturing operations and groundwater contamination.” That study concerned the disposal of fracturing fluids in deep wells after fracturing was complete; it did not look at the fracturing process itself.

Industry is fond of quoting EPA administrator Jackson telling Congress that there has never been a documented case where fracking polluted drinking water, but she implied in June, 2011 that such certainty had not been possible: “There are chemicals in the frack water, and until recently, even today, companies don’t have to disclose them, and we at EPA are exempt from regulating them, except for diesel.”

Because gas wells are much deeper than shallow aquifers, Jackson said groundwater pollution can be prevented by attention to the details of drilling, casing, cementing and closing. “If you get a bad operator, someone who is not responsible, who is not seeing how important it is to get this right, they can contaminate an aquifer … so there need to be some standards.”

Is the enemy fracking, gas drilling — or neither?

The gas industry fears legislation that would ban fracking, says Felmy, and it also believes that some of the opposition comes from “anti-fossil-fuel folks who have discovered that a tenet of their opposition, that we are running out of fossil fuels, is suddenly not true. With the technology developments we have, we can produce a vast amount.”

As the reports on water pollution add up, the gas industry has made some moves to address public concerns. Are they enough?

Yet behind all the protest and controversy, there is some constructive movement. Pennsylvania passed an improved well casing standard in February, 2011, so “it’s quite possible that that will go a long way to fixing problems in newer wells,” says Jackson of Duke. New York has not decided whether or how to allow hydraulic fracturing.

In November, the U.S. EPA announced plans for a study of any relationship between hydraulic fracturing and drinking water, with initial results due in 2012. That’s in addition to ozone studies related to gas extraction.

Some changes are likely in the shale-gas industry, Thyne says. “It’s got a lot of newcomers, it’s very much a gold-rush mentality where the profit margins are low. As the industry matures, it will shake out and the big boys will tend to self-regulate both production and environmental standards.”

Oil and gas are secretive industries, and the voluntary website listing chemicals in fracking fluid is a step toward openness. “The public said, ‘If this is not a problem, why won’t you tell us?'” says Thyne. “I sometimes feel the [energy] companies treat the public a bit like children: ‘You don’t want all these details, you just want to put gas into your car.’ But when the well is in your backyard, you want that information. Half the problem will be going away if they are transparent.”

Porter, of the American Petroleum Institute, says, “Disclosure is something we are very much in favor of.”

In deep water?

Just 19 months ago, the Deepwater Horizon drilling rig exploded and sank in the Gulf of Mexico, killing 11, releasing 4.9 million barrels of crude oil, and reminding us that fossil-fuel development can go horribly wrong. Stories from the gas fields remind us that polluted groundwater is difficult or impossible to clean up, even when money is available. Houses atop polluted aquifers are difficult or impossible to sell.

And so the choice is simple: ban fracking, and accept a rising price for energy, or do gas production right, even if that takes more time.

It’s trite but true: Time is money when you are running a gas drilling rig, but haste makes waste. “The Deepwater accident happened because people were in a hurry,” says Jackson of Duke. “I think there is tremendous pressure to move drilling rigs along in the Marcellus. There aren’t enough drill rigs … . The cause of problems here is likely the same as it was with BP: haste.”

Best management practices and standards are important, says Jackson, “but people have to follow them day after day in the field, when they are in a hurry and when nobody is watching, and that does not always happen.”

– David J. Tenenbaum

4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

Terry Devitt, editor; S.V. Medaris, designer/illustrator; Jenny Seifert, project assistant; David J. Tenenbaum, feature writer; Amy Toburen, content development executive

Bibliography

  1. A Critical Evaluation of Unconventional Gas Recovery from the Marcellus Shale, Northeastern United States, Dae Sung Lee et al, KSCE Journal of Civil Engineering (2011) 15(4):679-687
  2. Land Application of Hydrofracturing Fluids Damages a Deciduous Forest Stand in West Virginia; Mary Beth Adams, J. Environ. Qual. 40:1340–1344 (2011); doi:10.2134/jeq2010.0504, Posted online 26 Apr. 2011
  3. Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing, Stephen G. Osborn et al, PNAS ? May17, 2011 ? vol.108 ? no.20 ? 8173
  4. U.S. Energy Information Administration’s natural gas resources.
  5. Modern shale gas development in the US: a primer.
  6. The Future of Natural Gas study.
  7. The gas-rich Utica shale is below the Marcellus.19
    20Interactive fracking diagram.
  8. Natural gas explained.
  9. How much natural gas/a> exists?
  10. U.S.G.S. national oil and gas assessment.
  11. What the frack?
  12. Frac focus chemical database.
  13. Congress’ report on fracking chemicals.
  14. American Petroleum Institute’s resources on fracking.
  15. ProPublica’s long-term investigation of fracking.
  16. A fracking mystery story.
  17. NY Times: Natural gas archive.
  18. England quakes from fracking.