Page 185 - Environment: The Science Behind the Stories

tHE SCIENCE BEHIND tHE StorY

Does Fracking A Pennsylvania homeowner
Contaminate sets fire to her tap water
Drinking Water?

In 2010, gas industry executives testi-
fied to a Congressional panel that no
one had ever proven a single case
of groundwater contamination from
hydraulic fracturing. Yet critics of the
practice maintain that such pollution
is commonplace, and many citizens
living near drilling sites voice concerns
about pollution and health. Moreover,
numerous people are shown setting
their methane-rich tap water on fire in water samples to the lab and analyzed However, when Osborn’s team
the documentary film Gasland. them for their chemical constituents. tested for methane, the main compo-
So, what scientific evidence is Osborn and his colleagues found nent of natural gas, they found that
there on the issue? It’s not a straight- no evidence that well water was being concentrations averaged 17 times
forward question. Determining whether contaminated by chemicals from the higher at wells near natural gas drilling
clean groundwater has become dirty, hydrofracking process or by salty fluids sites than at wells far from drilling sites
what caused any contamination, and rising up from deep underground as (Figure 2). Although methane dissolved
what health impacts might result are a result of fracking. The chemistry of in drinking water is not considered
each complex pursuits. samples near and far from drilling sites toxic to drink, it is an asphyxiating gas
Debate over a 2011 scientific was similar, and these data were also and a hazard for fire and explosions.
paper that documented methane in similar to 124 water samples collected The average methane concentration
drinking water near hydrofracking from nearby regions by other research- these researchers documented in
sites illustrates the degree to which ers in past years. well water near drilling sites fell within
researchers can disagree over data and
interpretations—especially when the
topic is politically charged. The paper,
published in the prestigious scientific
journal Proceedings of the National
Academy of Sciences (PNAS) by
Stephen Osborn and three colleagues New York
from Duke University, elicited so many
queries and critiques that the authors Dimock
set up an online “frequently asked
questions” webpage to address the
barrage of correspondence.
In its research, Osborn’s team Pennsylvania
visited private wells that draw drinking
water from aquifers that lie above the Ohio Marcellus Shale
Marcellus and Utica Shale formations in Utica Shale
Pennsylvania and New York (Figure 1). Marcellus Shale overlying Utica Shale
With homeowners’ permission, they col- Drinking water sample
lected samples of water from 68 wells.
Half the wells were located within 1 km Figure 1 Methane migration was studied in water wells in northeastern Pennsylvania
of active gas drilling sites, while half were and adjacent New York, near the northeastern extent of the vast Marcellus Shale
more than 1 km away from the nearest formation. Data from Osborn, S.G. et al., 2011. Methane contamination of drinking water accompanying
drilling site. The researchers took the gas-well drilling and hydraulic fracturing. PNAS 108: 8172–8176.

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