* Propane and ethane also detected in water
* Scientists suggest leaky natural gas wells are the cause
* Industry group disputes study's findings
By Environment Correspondent Deborah Zabarenko
WASHINGTON, June 24 Elevated levels of methane,
ethane and propane gases were found in drinking water wells in
Pennsylvania, close to operations that shake natural gas loose
from underground shale formations in a process known as
fracking, scientists reported on Monday.
Detection of contaminated drinking water suggests the gas
wells are leaking, according to Robert Jackson of Duke
University, lead author of a study published in the Proceedings
of the National Academy of Sciences. An industry group disputed
these findings, saying that methane occurs naturally in water in
The United States has the world's biggest natural gas
reserves, followed by China, Argentina and Algeria. With the
advent of horizontal drilling and fracking, formally called
hydraulic fracturing, U.S. oil and natural gas production has
soared in the last decade.
The Obama administration supports fracking-derived natural
gas as an alternative to coal, which emits more climate-warming
carbon dioxide than natural gas. President Barack Obama is
expected to call for cuts in carbon dioxide emissions from
coal-fired power plants in a speech on Tuesday.
However, environmental advocates have questioned whether
fracking, in which water and chemicals are injected at high
pressure into rock deep underground to blast out the natural
gas, interferes with water quality at the surface.
Jackson's study suggests that it does, in some cases.
Based on analysis of 141 drinking water wells in northern
Pennsylvania that sit atop a natural gas-rich underground
formation called the Marcellus shale, Johnson and his colleagues
found 82 percent of drinking water samples contained methane,
with concentrations six times higher for homes within .62 miles
(1 km) of natural gas wells than for homes farther away.
Ethane concentrations were 23 times higher for homes close
to natural gas wells; propane was detected in 10 drinking water
wells, also within .62 miles of a natural gas well.
"We found much higher concentrations of methane, ethane and
propane in people's drinking water within one kilometer of the
shale gas wells," Jackson said by telephone. "What that means to
me is that those gases are leaking out of the wells and into the
He noted that no fracking chemicals or radioactivity were
detected in drinking water wells.
"The researchers found methane in virtually every water well
they sampled, irrespective of its proximity to gas drilling.
They suggest a link to Marcellus gas wells, but pre-drill
testing in the same part of the state directly contradicts
them," Steve Everley of Energy in Depth said in an email
response to questions about the study.
Energy in Depth is a program of the Independent Petroleum
Association of America that focuses on shale and fracking.
Fracking operations in the Marcellus shale - which takes in
Pennsylvania, New York, Ohio and West Virginia - are often more
than a mile deep, while aquifers are only a few hundred feet
underground, Everley said.
This indicates, he said, that there is no direct leak from
where the gas is being extracted up through the rock. Instead,
it is more likely that in some cases, the wells are leaking
closer to the shallower drinking water sources.
Jackson said little is known about long-term health effects
from methane and other gases in drinking water, and the
Environmental Protection Agency does not regulate methane in
(Editing by Steve Orlofsky)