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.
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.
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.”
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