Nearly 7,000 hydraulic fracturing sites in 27 states were drilled at depths where they could threaten underground drinking water supplies, according to a study published last week in the journal Environmental Science and Technology.
A team led by Robert Jackson of Stanford University reviewed 44,000 publicly recorded sites and found that 16% of them were less than a mile below the surface, at the same level of known aquifers, InsideClimate News reports.
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“You’ll hear from industry all the time that fracking only occurs a mile or two underground,” said University of Colorado geographer Mark Williams, who was not involved with the study. “It’s something they push really hard.”
The “surprising” number of shallow wells “is a concern,” Williams told ICN.
“As concern has grown about fracking’s potential threat to well water in recent years, industry has sought to reassure the public by saying that fracking occurs at depths far below the water table,” Hirji explains. “Consequently, migration of fracking fluid or methane from a frack zone more than a mile underground (deeper than 5,000 feet) to a shallow aquifer (around 1,000 feet) would be nearly impossible, industry contends.”
But “Jackson told InsideClimate News the analysis ‘definitely’ underestimates the practice because of limited reporting to FracFocus, an industry-backed database where companies post drilling information,” and where Jackson’s team found its data. “For most states, company reporting to the online registry is voluntary.”
Jackson noted that some shallow wells are a more serious threat to drinking water than others: the greatest risk involves shallow wells that also use a million gallons of water or more. “Studies have shown that when these high-pressure wells fracture the bedrock, the cracks can extend as much as 2,000 feet upward,” Hirji explains. “This provides an opportunity for the chemical-laced water used in fracking to migrate to the shallower depths of the water table.”
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