Each year, oil and gas companies employ "fracking" at more than 25,000 wells around the United States — injecting water and chemicals deep underground at high pressures to crack open shale rock and extract fuel. This has led to a huge boom in oil and gas production. But it's also spurred concern that gas or chemicals might leak into nearby water supplies.
Now the Environmental Protection Agency has weighed in with a massive new study on the water question. After a four-year investigation, the EPA says it found no evidence that the recent rise of hydraulic fracturing has caused "widespread, systematic" harm to the nation's drinking water.
However, the report did note that certain aspects of the fracking process could potentially threaten nearby water supplies. And the EPA found a small number of cases where contamination has actually occurred — due to, say, gas leaking from of poorly constructed wells, or to improper handling of the wastewater that flows out after fracking is completed.
Crucially, the agency also said that it lacked data to say conclusively how often water supplies have been affected. Here's the key section:
From our assessment, we conclude there are above and below ground mechanisms by which hydraulic fracturing activities have the potential to impact drinking water resources. These mechanisms include water withdrawals in times of, or in areas with, low water availability; spills of hydraulic fracturing fluids and produced water; fracturing directly into underground drinking water resources; below ground migration of liquids and gases; and inadequate treatment and discharge of wastewater.
We did not find evidence that these mechanisms have led to widespread, systemic impacts on drinking water resources in the United States. Of the potential mechanisms identified in this report, we found specific instances where one or more mechanisms led to impacts on drinking water resources, including contamination of drinking water wells. The number of identified cases, however, was small compared to the number of hydraulically fractured wells.
This finding could reflect a rarity of effects on drinking water resources, but may also be due to other limiting factors. These factors include: insufficient pre- and post-fracturing data on the quality of drinking water resources; the paucity of long-term systematic studies; the presence of other sources of contamination precluding a definitive link between hydraulic fracturing activities and an impact; and the inaccessibility of some information on hydraulic fracturing activities and potential impacts.
The oil and gas industry is hailing this study as a major victory, arguing that it proves fracking is broadly safe. Sure, there have been a few problems, but those can be tackled with proper safeguards. "Today’s draft study affirms that hydraulic fracturing does not present systemic impacts on drinking water," said Marty Durbin, CEO of America's Natural Gas Alliance, in a statement.
Environmental groups, however, are emphasizing the fact that the study found troubling instances when fracking can go awry. They're also playing up the study's limitations: according to a previous investigation by Neela Banerjee of Inside Climate, the EPA struggled to procure cooperation from oil and gas companies that would help establish appropriate baselines for truly assessing water contamination.
"The report, while limited, shows fracking can and has impacted drinking water sources in many different ways," said Amy Mall of the Natural Resources Defense Council in a statement. But, she added: "This study is missing some critical elements, hamstringing its comprehensiveness. Among other things, there are reports industry has not cooperated in providing important information."
The EPA said it hoped the report would help policymakers decide “how best to protect drinking water resources now and in the future.” Right now, fracking is largely regulated at the state level, and different states have taken very different approaches. North Dakota and Texas have taken a permissive stance — and fracking for oil and gas is booming there. By contrast, New York State has banned fracking altogether, in part over concerns about air and water pollution.
How fracking works — and how it might harm water supplies
To better understand the water issue, let's first take a look at how energy companies actually employ hydraulic fracturing (and horizontal drilling) to extract natural gas from shale rock. Here's a sample operation in the Marcellus Shale in Pennsylvania:
1) First, a well needs to be drilled all the way down to the layer of gas-rich shale. This shale layer can sit more than 5,000 feet underground, and drilling can take as long as a month. The well is typically lined with cement and a steel casing to prevent any leakage into groundwater near the surface.
2) Once the drill reaches all the way down to the shale layer, it slowly turns and begins drilling horizontally, for a mile or more along the rock.
3) A "perforating gun" loaded with explosive charges is lowered to the bottom of the well and punctures tiny holes in the horizontal section of the casing that's deep down in the shale layer.
4) Now comes the actual "fracking," or "completion," stage: a mixture of water, sand, and chemicals is pumped into the well at extremely high pressures and goes through the tiny holes in the casing. The fluids crack open the shale rock. The sand holds those cracks open. And the chemicals help the natural gas seep out.
5) The "flowback" stage: The water and chemicals flow back out of the well and are taken for disposal or treatment.
6) Finally, natural gas begins flowing from the shale and up out of the well, where it's eventually shipped to consumers via pipeline. A typical well can produce gas for 20 to 40 years, pumping out thousands of cubic feet of gas each day.
Now, there are lots of different points during the above process that could affect nearby water supplies, as the EPA illustrates in this graphic:
Some examples:
1) Fracking requires a lot of water: It takes a lot of water to crack open that shale rock, between 1 and 5 million gallons per well. Nationwide, the EPA study estimates, the fracking industry used some 44 billion gallons of water in 2011 and 2012. That was only 1 percent of the nation's freshwater, but in areas like western Texas, the fraction was far higher — and, in these areas, better water management may be needed.
2) Poorly constructed wells can leak methane or chemicals: This is one potential source of contamination of water supplies near the surface. In recent years, fracking wells have blown out in states like North Dakota. In another incident, thousands of gallons of fracking fluid leaked out of a storage tank in Dimock, Pennsylvania. And poorly constructed wells with cement problems can allow fluids or gas to migrate upward.
The EPA study notes that this is a particular concern for older wells that were drilled before they were repurposed for fracking. "Although new wells can be designed to withstand the stresses associated with hydraulic fracturing operations, older wells may not have been built or tested to the same specifications and their reuse for this purpose could be of concern," the study notes.
3) Wastewater pollution: A separate issue is what happens with all that water after it has been used to crack open shale and is pumped back up to the surface. The oil and gas industry produces billions of gallons of this murky wastewater each year, which typically contains chemicals that were added for the fracking process.
In many states, this wastewater is pumped back underground into separate "injection wells." But when there aren't enough injection wells available, the water is either stored in tanks and holding ponds or sent off to treatment plants. That raises the risk of either accidental spills or improper treatment. In 2013, three treatment plants in Pennsylvania were fined for dumping waste into the Allegheny River.
The EPA notes that accidents are relatively rare, but they can be destructive: "The EPA characterization of hydraulic fracturing-related spills found that 8% of the 225 produced water spills included in the study reached surface water or ground water. These spills tended to be of greater volume than spills that did not reach a water body. A well blowout in Bradford County, Pennsylvania spilled an estimated 10,000 gal (38,000 L) of produced water into a tributary of Towanda Creek, a state-designated trout fishery."
Ultimately, the EPA did not find evidence that these incidents add up to "systematic" or "widespread" harm to America's drinking water supplies. But they're certainly worth addressing on their own.
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