A new study by Thomas Darrah of Duke University and four colleagues, published in the Proceedings of the National Academcy of Sciences, suggests that there has been significant contamination of the ground water from natural gas drilling in Pennsylvania and Texas, but this contamination is not due to the process of hydraulic fracturing itself. Rather it is caused by leakage of methane, the primary ingredient in natural gas, and other chemicals near the surface due to faulty construction of the well.
The
researchers took 133 water samples from drinking water wells—113 of
them from along the Marcellus Shale in Pennsylvania and 20 from the
Barnett Shale in Texas. Through chemical analysis, they were able to
tell whether each sample was contaminated, and if so, from where the
contimation had come. I'm not knowledgeable enough in chemistry to
understand the testing that was done, so I rely on the fact that this
was a peer-reviewed journal.
They found eight clusters of contaminated wells—seven in Pennsylvania
and one in Texas. The cluster in Texas consisted of five of the
twenty samples they took. They don't say how many samples were
included in the seven Pennsylvania clusters. From eyeballing their
charts, it looks like about 20-25% of their samples were
contaminated. However, the wells were not randomly selected. The
researchers had focused on areas where contamination was suspected.
The
chemical analysis indicated that four of the eight clusters were due
to leakage around the cement used to seal the outside of the well,
three were due corroded or poorly joined steel tubing used to drill
into the ground, and the last was due to “underground mechanical
well failure.”
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| Diagram by Howarth and Engelder (2011) |
In
hydraulic fracturing, or fracking, fracking fluid is forced into the
shale at high pressure in order to release the natural gas contained
in it. The concern is that fracking might create breaks in the
undreground rock formations, through which either natural gas or
fracking fluid might leak upward and contaminate drinking water.
None of the contamination came from far enough below the surface to
indicate that this type of contamination had occurred.
Unlike
last week's study of the correlation between fracking sites and health problems, this study received generous coverage by the corporate media. The general spin seemed to be that “fracking is
safe.” The Pittsburgh Post-Gazette ran
a McClatchy article about the study on the front page. Two days
later, they reprinted a Bloomsberg op-ed entitled “Fracking is not
the threat.” The threat, it seems, is drilling company
carelessness, which can be avoided through government regulations,
regular inspections, and fines for poor performance.
The
coverage is superficial in at least two respects. First, while there
is no evidence that fracking in the narrow sense--that is, hydraulic fracturing, per se--has caused contamination, fracking in a broader sense--the fracking boom--is certainly responsible
for ground water contamination. Regulation and oversight of the
drilling industry will not be accomplished easily, especially in a state like Pennsylvania, where the state government is a wholly-owned
subsidiary of the natural gas industry.
Secondly,
the absence of evidence of leakage due to fracking, per se,
does not necessarily mean that there is none and the process is safe.
Methane and fracking fluid from deep in the shale may simply take a
longer time to reach the surface than chemicals that leak from at or
near the surface. Maybe decades. The Darrah study may simply have
been done too soon.
Meanwhile,
there is accumulating evidence of another problem caused by natural
gas drilling. A new report published in the Bulletin of
the Siesmological Society of America
shows a significant increase in earthquakes in the Raton Basin of
Colorado and New Mexico since 2001. Fracking began there in 1999.
As in previous studies, most of the earthquakes are located within 5
kilometers of waste water injection wells, rather than near sites
where hydraulic fracturing has taken place. I guess that means that
fracking is “safe,” but it doesn't solve the problem of what to
do with the waste water.
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