National Geographic : 2012 Dec
• than twice the methane that's considered an ex- plosion threat. Chesapeake has been supplying her with bottled water ever since, while arguing that the contamination is natural. Meanwhile Vargson's monthly royalty checks have shrunk from more than $1,000 to less than $100, as pro- duction from the gas well has plummeted. e industry's main argument in attempting to reassure a worried public in Pennsylvania and elsewhere has been that shales typically lie thousands of feet below drinking-water aqui- fers. So contamination, whether by shale gas or fracking wastewater---which contains fracking chemicals, salt, heavy metals, and radioactive elements leached from the rock---should be physically impossible. The argument makes intuitive sense, but the jury is still out. Duke University scientists have recently reported evidence that uids---albeit not fracking uids--- have migrated upward from the Marcellus Shale through natural ssures. In an earlier study the Duke researchers sampled 60 private water wells in northeastern Pennsylvania and found no sign of fracking fluids. But they did find that methane levels were on average 17 times higher in wells near drilling sites and that some of the methane had the chemical signature of shale gas. It may have leaked into the shallow aquifers, they said, through faulty casings around the gas wells. e Pennsylvania Department of Environmental Protection (DEP) also blamed faulty casings in 2009 when it ned Cabot Oil & Gas for con- taminating the drinking supplies of 19 homes in Dimock Township, 60 miles east of the Vargson farm. In that case the methane came not from the shale but from shallow deposits traversed by the gas wells. DEP has also ned gas companies for mishandling fracking wastewater and allow- ing spills that polluted creeks and rivers. In Pennsylvania and elsewhere, shale-gas drilling has raced far ahead of e orts to under- stand and limit its impact. So far, however, its impact seems much smaller than that of coal mining---which in Pennsylvania has caused far worse river pollution, in West Virginia has lopped the tops o numerous mountains, and in the U.S. still kills hundreds of miners a year, mostly through black lung disease. e com- parison is relevant because cheap natural gas is reducing coal burning. As recently as 2007, coal generated nearly half of U.S. electricity. Last March its share fell to 34 percent. John Hanger, a Pennsylvania lawyer who helped author the state's renewable-energy standards, ran the DEP from 2008 to early 2011. ough he tightened regulations on the gas in- dustry and handed out substantial nes, he was attacked by opponents who wanted a complete halt to fracking. Hanger believes such critics are missing the big picture. " e massive switching from coal to gas has done more to clean Penn- sylvania's air, and America's air, than probably any other single thing we've ever done," he says. Unlike coal, natural gas burns without spew- ing sulfur dioxide, mercury, or particulates into the air or leaving ash behind. And it emits only half as much carbon dioxide. e greenhouse gas inventory compiled by the U.S. Environmental Protection Agency (EPA) shows that the nation's CO emissions in 2010 were lower than in 2005 by just over 400 million metric tons, or 7 percent. (Preliminary data for 2011 indicate a further de- crease.) Reduced emissions from power plants, mostly because many have switched from coal to gas, accounted for a bit over a third of that. Some environmentalists who once welcomed shale gas with precisely that expectation changed their minds a er watching the boom in Pennsyl- vania. But Hanger hopes it spreads around the world, as it seems likely to. "In China they're sit- ting on potentially huge supplies of shale gas," he says. "It would be an enormous climate bene t if China were to substitute gas for some of its coal burning. And it's an immediate bene t--- you don't have to wait until 2040 or 2050." into the at- mosphere. As U.S. CO emissions fell between 2005 and 2010, methane emissions rose. By 2010, EPA says, the rise was equivalent in global warm- ing potential to around 40 million metric tons of CO annually, which means it o set 10 per- cent of the CO decline. More than half of that SO FAR, THE IMPACT OF SHALE GAS DRILLING SEEMS MUCH SMALLER THAN THAT OF COAL MINING.