Natural gas production near homes in a Texas subdivision contaminated residents' well water, according to a study published Monday. The discovery was made in a community where the Environmental Protection Agency halted its own investigation two years ago.
In the course of a broader effort to determine the origins of high methane levels in drinking water aquifers near gas wells in Pennsylvania and Texas, scientists found that water in two homes in Parker County, Texas, changed over nine months from containing trace amounts of methane to having high levels.
The newly identified cases "caught this contamination in the act," said Robert Jackson, a study co-author and professor of environmental science at Stanford University.
The discovery poses a challenge to a long-standing assertion by the oil and gas industry that the energy boom sweeping the country has not damaged water supplies. Other studies have found that water wells near natural gas production are at greater risk of containing methane than those farther away. But industry has contended that the methane found in water wells is naturally occurring and was there all along, prior to the start of gas production.
Each of 20 homes tested in Parker County has detectable methane in its well water because of many layers of oil and gas in the ground, the researchers said. Methane that enters homes through drinking water poses an explosion risk if it accumulates in rooms or spaces.
The two homes whose water had negligible amounts of methane in 2012 were tested again in August and November 2013, when they showed far higher levels, the study said. Further, the methane in the homeowners' water no longer had the chemical makeup of the naturally occurring trace gas, according to the study. Instead, it had the same chemical fingerprint as natural gas deposits far below the aquifers, the scientists found.
"All the gas chemistry in the water changed so that it wasn't just higher methane levels but higher methane from a totally different source," said Thomas Darrah, assistant professor of earth sciences at Ohio State University and the study's lead author.
Darrah and his colleagues concluded that the water contamination occurred when natural gas from a lower geological depth migrated higher into drinking water sources because of a faulty cement job around the well.
The researchers believe that in nearly all the cases, the water contamination occurred because poor casing or cementing around the gas wells allowed methane to leak out the sides and into aquifers. Said Darrah, "The good news is that most of the issues we have identified can potentially be avoided by future improvements in well integrity."
The findings of the study, published in the Proceedings of the National Academy of Sciences, spotlight the EPA's controversial decision in 2012 to halt its investigation into possible well-water contamination in Parker County by the energy company Range Resources.
The EPA got involved in 2010 because Range Resources and Texas regulators failed to act immediately on homeowners' complaints of possible drinking water contamination, according to a 2013 report by the EPA inspector general. When the EPA conducted its own tests of well water in some Parker County homes, it found such high levels of methane in the water supply of two homes that it posed a risk of explosion, the report said.
The Justice Department filed a complaint on behalf of the EPA against Range in January 2011 but withdrew it by March 2012. The EPA and Justice Department reversed course because the EPA worried about the costs and legal risks of the case, the inspector general's report said. Texas authorities and Range deny that the company's gas development had contaminated the residents' water.
The two Parker County homes that showed new contamination are near wells drilled by Range in 2009 and sold in 2011 to Legend Natural Gas.
The new contamination was identified as part of a wider study that tested drinking water in 20 wells in the Barnett Shale in Texas and 113 wells in Pennsylvania's Marcellus Shale area.
In Texas, extremely high levels of methane were found in five homes, including the two whose contamination the researchers captured through their testing. In Pennsylvania, high levels of methane were found in 20 homes.
At least one house in Pennsylvania had high levels of methane that was there all along, unrelated to gas production. But for the other homes in the two states, the chemical fingerprint of the methane at high levels in drinking water was the same as natural gas in deeper formations, the study said. The second line of evidence, the chemical fingerprint of gases found with methane in the Texas and Pennsylvania, also indicated the methane came from lower depths, according to the study.
Copyright © 2014, Los Angeles TimesAnda sedang membaca artikel tentang
Natural gas contaminated drinking water in Texas, study says
Dengan url
http://sehatumbuah.blogspot.com/2014/09/natural-gas-contaminated-drinking-water.html
Anda boleh menyebar luaskannya atau mengcopy paste-nya
Natural gas contaminated drinking water in Texas, study says
namun jangan lupa untuk meletakkan link
Natural gas contaminated drinking water in Texas, study says
sebagai sumbernya
0 komentar:
Posting Komentar