The chemicals transform the fluid into a frictionless mass that works its way deep into the earth, prying open tiny cracks that can extend thousands of feet. The particles of sand or silicon wedge inside those cracks, holding the earth open just enough to allow the gas to slip by.
Gas drilling is often portrayed as the ultimate win-win in an era of hard choices: a new, 100-year supply of cleaner-burning fuel, a risk-free solution to the nation's dependence on foreign energy. In the next 10 years, the United States will use the fracturing technology to drill hundreds of thousands of new wells astride cities, rivers and watersheds. Cash-strapped state governments are pining for the revenue and the much-needed jobs that drilling is expected to bring to poor, rural areas.
Drilling companies assert that the destructive forces unleashed by the fracturing process, including the sometimes toxic chemicals that keep the liquid flowing, remain safely sealed as much as a mile or more beneath the earth, far below drinking water sources and the rest of the natural environment.
More than a year of investigation by ProPublica, however, shows that the issues are far less settled than the industry contends, and that hidden environmental costs could cut deeply into the anticipated benefits.
The technique used to extract the gas, known as hydraulic fracturing, has not received the same scientific scrutiny as the processes used for many other energy sources.
For example, it remains unclear how far the tiny fissures that radiate through the bedrock from hydraulic fracturing might reach, or whether they can connect underground passageways or open cracks into groundwater aquifers that could allow the chemical solution to escape into drinking water. It is not certain that the chemicals--some, such as benzene, that are known to cause cancer--are adequately contained by either the well structure beneath the earth or by the people, pipelines and trucks that handle it on the surface. And it is unclear how the voluminous waste the process creates can be disposed of safely.
"This is a field where there is almost no research," said Geoffrey Thyne, a former professor at the Colorado School of Mines and an environmental engineering consultant for local government officials in Colorado. "It is very much an emerging problem."
The lack of scientific certainty about hydraulic fracturing can be traced in part to the drilling industry's success in persuading Congress to leave regulation of the process to the states, which often lack manpower and funding to do complex studies of underground geology. As a consequence, regulations vary wildly across the country and many basic questions remain unanswered.
ProPublica has uncovered more than 1,000 reports of water contamination from drilling across the country, some from surface spills and some from seepage underground. In many instances, the water is contaminated with compounds found in the fluids used in hydraulic fracturing. ProPublica also found dozens of homes in Ohio, Pennsylvania and Colorado in which gas from drilling had migrated through underground cracks into basements or wells.
But most of these problems have been blamed on peripheral problems that could be associated with hydraulic fracturing--like well failures or leaks--without a rigorous investigation of the entire process.
ProPublica has also found that drilling procedures that can prevent water pollution and sharply reduce toxic air emissions--another frequent side effect--are seldom required by state regulators and are mostly practiced when and where the industry wishes.
Another uncertainty arises from the enormous amounts of water needed for "fracking." The government estimates that companies will drill at least 32,000 new gas wells annually by 2012. That could mean more than 100 billion gallons of hazardous fluids will be used and disposed of each year if existing techniques, which often involve 4 million gallons of water per well, are used.
Proposals for new regulations that might prevent many of these problems almost always lead to a fight. And more often than not, that fight devolves into stark, overdrawn choices between turning on the lights or having clean drinking water--getting rich or staying poor.
Energy lobbyists portray skeptics as hysterical and would-be regulators as over-reaching. Environmentalists cast the dangers as more proven than is the case and as unsolvable.
In less contentious settings, even the industry acknowledges the lack of science on key issues.
In a conference call with reporters this spring, American Petroleum Institute Senior Policy Adviser Richard Ranger, an industry expert who has spoken frequently on the fracturing issue, was asked for evidence that fracturing is without environmental risk:
"Have there been any recent studies done on the safety of this?" a reporter asked.
"The issue of where do these fracking fluids go, the answer is based on the geology being drilled," Ranger said. "You've got them trapped somewhere thousands of feet below with the only pathway out being the well bore.
"I'm just not sure that that study is out there," Ranger said.
"To be clear, we are saying this is a totally safe technology but we can't point to any recent studies that say this is a safe technology?" the reporter asked.
"Or that says it is unsafe," Ranger replied.
ProPublica reporters have posed similar questions to more than 40 academic experts, scientists, industry officials and federal and state regulators. No one has yet provided a more definitive response.
ProPublica's reporting over the last year points to four looming questions:
Where are the gaps in the environmental science and what will it take to address them?
How will the wastewater be safely disposed of?
Are regulations in place to make sure the gas is extracted as safely as possible?
And are state and federal regulatory agencies equipped to keep up with the pace of drilling?
"Most likely there are not a lot of win-win propositions," said David Burnett, a scientist at Texas A&M University's Global Petroleum Research Institute who specializes in industry practices to reduce environmental harm. But, he said, there is opportunity for compromise on enough issues "so that everybody wins sometimes."