Regulators said on Thursday they will perform water tests at about 60 homes in the small town of Dimock in northern Pennsylvania where residents say natural gas drilling has polluted wells.
The Environmental Protection Agency also plans to truck water to four homes in the town where some households have relied on water deliveries since drilling by Cabot Oil & Gas Corp began there three years ago, it said in a statement on Thursday.
The tests, which will begin in the coming days, are being carried out "to further assess whether any residents are being exposed to hazardous substances that cause health concerns," the EPA said.
The announcement represents a reversal for the EPA, which six weeks ago declared the water in the 1,400-person town safe to drink before receiving more data provided by residents.
It is also the clearest sign yet that regulators are concerned about the effect of drilling on drinking water there.
Dimock, in a busy drilling area above the gas-rich Marcellus shale deposit, has become the center of a national debate over the natural gas extraction technique called fracking, which involves pumping millions of gallons of chemical-laced water into shale rock deep below the ground.
Fracking has unlocked decades of U.S. natural gas supply, but environmentalists say it contaminates water supplies. Energy companies have said fracking, which is being done across the country, poses no threat to drinking water.
Cabot spokesman George Stark said the company has tested and sampled water from more than 2,000 wells in the area over the past several years and does not have data showing drilling is the cause of "alleged health concerns purported by the EPA."
Dimock residents began complaining of cloudy, foul-smelling water in 2008 after Cabot began fracking nearby.
Cabot had trucked water to a dozen Dimock households for three years until November when state regulators agreed it could stop.
Since then, residents have relied on water deliveries arranged by environmental groups including Water Defense and Sierra Club, though the sporadic deliveries have barely been enough. Some have been using pondwater for showers.
"I am very relieved," said Dimock resident Victoria Switzer who has not drank water from her tap in three years. "After the EPA investigation perhaps we will all get relief from this nightmare we have been living for a long time."
FEDS VS STATES
As fracking increases in the United States and contributes to an energy boom, the EPA is conducting a national study to determine its impacts.
A recent EPA draft report showed that harmful chemicals from fracking fluids were likely present in a Wyoming aquifer near the town of Pavillion.
In Pennsylvania, as in Wyoming, state authorities have expressed frustration at the EPA's involvement in local affairs.
An energy policy analyst said the federal tests could push states to beef up oversight . "Every government that oversees shale gas production at the state and municipal level will be looking for ways to prevent this from happening in their producing areas," said Kevin Book, an analyst at ClearView Energy Partners in Washington. "That means local regulation will be ramping up."