Series: Buried Secrets: Gas Drilling's Environmental Threat.
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.