A new study has raised
fresh concerns about the safety of gas drilling in the Marcellus Shale,
concluding that fracking chemicals injected into the ground could
migrate toward drinking water supplies far more quickly than experts
have previously predicted
More than 5,000 wells were
drilled in the Marcellus between mid-2009 and mid-2010, according to the
study, which was published in the journal Ground Water two
weeks ago. Operators inject up to 4 million gallons of fluid, under
more than 10,000 pounds of pressure, to drill and frack each well.
Scientists have theorized that impermeable layers of rock would keep the fluid, which contains benzene and other dangerous chemicals, safely locked nearly a mile below water supplies. This view of the earth's underground geology is a cornerstone of the industry's argument that fracking poses minimal threats to the environment.
But
the study, using computer modeling, concluded that natural faults and
fractures in the Marcellus, exacerbated by the effects of fracking
itself, could allow chemicals to reach the surface in as little as "just
a few years."
"Simply put, [the rock layers] are not impermeable," said the study's author, Tom Myers, an independent hydrogeologist whose clients include the federal government and environmental groups.
"The
Marcellus shale is being fracked into a very high permeability," he
said. "Fluids could move from most any injection process."
The
research for the study was paid for by Catskill Mountainkeeper and the
Park Foundation, two upstate New York organizations that have opposed
gas drilling and fracking in the Marcellus.
Much of the debate about the environmental risks of
gas drilling has centered on the risk that spills could pollute surface
water or that structural failures would cause wells to leak.
Though
some scientists believed it was possible for fracking to contaminate
underground water supplies, those risks have been considered secondary.
The study in Ground Water is the first peer-reviewed research evaluating
this possibility.
The study
did not use sampling or case histories to assess contamination risks.
Rather, it used software and computer modeling to predict how fracking
fluids would move over time. The simulations sought to account for the
natural fractures and faults in the underground rock formations and the
effects of fracking.
The
models predict that fracking will dramatically speed up the movement of
chemicals injected into the ground. Fluids traveled distances within 100
years that would take tens of thousands of years under natural
conditions. And when the models factored in the Marcellus' natural
faults and fractures, fluids could move 10 times as fast as that.
Where
man-made fractures intersect with natural faults, or break out of the
Marcellus layer into the stone layer above it, the study found,
"contaminants could reach the surface areas in tens of years, or less."
The
study also concluded that the force that fracking exerts does not
immediately let up when the process ends. It can take nearly a year to
ease.
As a result, chemicals
left underground are still being pushed away from the drill site long
after drilling is finished. It can take five or six years before the
natural balance of pressure in the underground system is fully restored,
the study found.
Myers'
research focused exclusively on the Marcellus, but he said his findings
may have broader relevance. Many regions where oil and gas is being
drilled have more permeable underground environments than the one he
analyzed, he said.
"One would
have to say that the possible travel times for a similar thing in
Arkansas or Northeast Texas is probably faster than what I've come up with." Myers said
No comments:
Post a Comment