Fracking, the controversial technique for exploiting underground supplies of shale gas, does not appear to result in the contamination of groundwater supplies, according to an independent investigation carried out in the US.
The study found little evidence to support widespread fears in Britain and the US that fracking – in which shale gas is extracted by deliberating fracturing underground rock with toxic chemicals – can result in groundwater being contaminated. However, the American university scientists who carried out the investigation said they could not give fracking an entirely clean bill of health as the long-term effects of the process are so poorly understood.
They have particular concerns about the possibility of disturbing toxic substances such as arsenic that are naturally present in the environment, which could result in serious groundwater contamination. The authors of the report said they wanted to separate fact from fiction in the intense debate over fracking that has arisen since huge shale-gas reserves have been identified in the US and Britain. The fears were heightened by the film GasLand, which showed methane gas coming out of water taps in areas close to fracking sites.
The report says that natural substances such as methane are often present in water sources before fracking operations began and are "mobilised" by vibrations and pressure pulses due to drilling rather than the fracturing of rock.
"The immediate concern about shale gas development and hydraulic fracturing is that fracturing several thousand feet below the surface would put chemicals into the groundwater that people drank and that would be very bad for health," said Charles Groat, associate director of the Energy Institute at the University of Texas in Austin, who led the inquiry. "A major part of our study was to see if there was any verifiable evidence that hydraulic fracturing itself was producing contaminated waters that ended up in groundwater," he told the American Association for the Advancement of Science in Vancouver.
"Our preliminary finding is that we have found no demonstration that that has happened. That doesn't mean that there aren't ways for fracture fluids or produced waters or flowback waters to get into the groundwater supplies."