Like a lot of people, perhaps, I was drawn to Rob Jackson’s talk on hydrofracking’s water impacts with visions of those flaming kitchen taps out east.
But the risk to drinking-water wells was only a small part of the troubled landscape surveyed by Jackson, an environmental scientist at Duke and Stanford universities whose background includes degrees in ecology, statistics and chemical engineering.
And though the troubles lie beyond Minnesota’s borders, the Freshwater Society’s concern extends to water problems everywhere — and so, perhaps, should ours.
Some key points from his wide-ranging, fair-minded and highly accessible talk, which was organized by the Freshwater Society and delivered Thursday evening on the University of Minnesota’s St. Paul campus:
Apart from impacts on water quality, fracking is a water-intensive process with potential impacts on water quantity. Considering the energy returned, fracking to produce natural gas uses less water on a unit basis than extracting oil from tar sands, or making electricity from biomass, he said.
But, still, each natural-gas well opened with a combination of horizontal drilling and injection of hydraulic fluids requires water on the order of 1 to 7 million gallons per well, depending on the geology. And only one-third of that water, on average, is ever returned to the surface.
Even in a water-rich state like Pennsylvania, which gets 35 inches of precipitation a year in the area where fracking is producing gas from the Marcellus shale formation, this much pumping of groundwater can create local drawdowns with an appreciable impact on streams and lakes, as well as groundwater supplies.
Around the Eagle Ford fields in east Texas, he said, where annual precipitation is only about 20 inches, the pumping has the potential to draw down aquifers by “feet to tens of feet.”
What the water carries up
Considering what’s in the water that comes back up, though, the low return rate may often be good news.
This “produced water” is being returned at the rate of about 2 billion gallons a day, or roughly a trillion gallons a year, “so the No. 1 thing that oil and gas wells produce isn’t oil and gas — it’s salty, briny water.”
How salty? From the Marcellus wells, typically 10 times saltier than seawater.
Among the other contaminants: toxic elements like barium, selenium, arsenic and lead; bromides, which can interact with methane to produce carcinogenic compounds; elevated levels of natural radioactivity, from naturally occurring but now concentrated substances.
Not to mention the residues of fracking fluids, oil and fuels. Those tend to come back first in a rush after injection ends, Jackson said, to be followed by a longer stream of “nasty, briny wastewater.”
Some 95 percent of this produced water is injected back underground for disposal, which means it’s off our hands. But it’s also out of our supply of available groundwater, essentially forever, and as we all may remember from grade-school earth science, the planet’s water supply is finite.
The 5 percent remaining aboveground becomes an interesting set of disposal problems. Seven states allow the water to be sprayed on land, untreated, or on roads as a de-icing compound, with varying results, many of them undesirable.
In one West Virginia test, he said, some 75,000 gallons of produced water was sprayed on a wooded patch of land to see what would happen; half the trees were dead in a few years.
In the cattle-grazing areas of the arid West, he said, the water is considered by law to have a “beneficial use” if sprayed onto land to create streams that help water the herds.
“These things are just — just dumb,” he said, but alternatives can be tough to arrange. Pennsylvania used to send a lot of produced water through conventional municipal treatment plants, but they weren’t set up to handle the volumes, the chemicals or the radioactivity.
So a new industry has grown up around private water treatment and disposal, using distillation, reverse osmosis and other methods.
Creating radioactive sediments
At one Pennsylvania operation studied by Jackson and colleagues over a period of years, discharges met state and federal standards for certain metals and regulators concluded that “the plant was doing its job.” But levels of salts and radiation remained high.
Though the concentrations of radioactive particles met sampling standards at the discharge pipe, the sheer volume of water moving out of the plant brought river sediments downstream to radiation levels “high enough to where you would have to take them for disposal at a radioactive waste site — you couldn’t dispose of them at a landfill.”
After Jackson’s team published their results, the company supplying the wastewater to the plant announced it would dredge the streambed and haul the sediments away.
On the flip side, Jackson cited several positive developments in terms of fracking’s water impacts, starting with a move toward re-use and recycling of returned water by hauling it from one set of wells to another for re-injection.
On public-health disclosure of fracking chemicals, Jackson said that even though “there’s very often a narrative that the companies don’t disclose the chemicals they use, that’s not true.”
New rules in Wyoming, Texas and elsewhere have brought more transparency, which in turn may lead to a faster phase-out of the worst materials. However, about 20 percent of the chemicals remain hidden behind trade-secret exceptions in the disclosure rules.
Closing up the pits
Meanwhile, there is significant movement away from what used to be the wastewater-disposal method of choice in many areas: retention of returned water in open pits, which invites the problems of failed liners and other leaks that are familiar to Minnesotans who live near certain landfills and feedlot operations. Many of these pits are being converted to enclosed-tank operations or eliminated entirely, he said.
While cautioning that he is not a seismologist, Jackson addressed a subject that has been intermittently high in the headlines for a couple of years now: “induced seismicity,” or the notion that the pressures and volumes of fluids injected in fracking can cause earthquakes.
Based on his reading and conversations with scientists investigating this possibility, he said, “well, literally it’s true — a hydraulic fracture is a tiny, tiny tremor,” an earthquake too small to feel or to be dangerous.
The biggest quakes ever associated with fracking in this country, he said, have been of a magnitude less than 4, “but that’s not where the action is, and that’s not what people should be worrying about.”
“In rare cases, but much more commonly,” he said, it’s re-injection of wastewater that causes seismic activity, because of the sheer volume of material being injected at great depth. (And the problems this causes would happen with any material — say, carbon dioxide being injected for long-term storage.)
According to a study published last year in the journal Science, Jackson said, the rate of earthquakes above magnitude 3 in the midcontinental U.S. has been rising steadily from 21 events a year, on average, with a steep acceleration after 2010 and a peak of 188 events in 2011.
The most powerful event that some scientists think can be attributed to injection approached magnitude 5.6 or 5.7, he said, which is moving into a range that can be dangerous.
In response, the U.S. Geological Survey is working with the industry to come up with protocols for monitoring seismicity and backing off on injection if the earth starts to tremble. Which I guess should qualify as good news, too.
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Jackson’s talk, sponsored by university’s College of Biological Sciences along with the Freshwater Society, can be viewed right here, along with his excellent slides.
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