Pittsburgh --

A landmark federal study on hydraulic fracturing, or fracking, shows no evidence that chemicals from the natural gas drilling process contaminated drinking water aquifers at a western Pennsylvania drilling site, the Department of Energy said.


Although the results are preliminary - the study is still ongoing - they are the first independent look at whether the potentially toxic chemicals pose a threat to people during normal drilling operations.

Drilling fluids tagged with unique markers were injected more than 8,000 feet below the surface but were not detected in a monitoring zone at a depth of 5,000 feet. That means potentially dangerous substances stayed about a mile away from drinking water supplies, which are usually at depths of less than 500 feet.


The boom in gas drilling has led to tens of thousands of new wells being drilled in recent years. That's led to major economic benefits but also fears that the chemicals used in the drilling process could spread to water supplies.


"Very few people think that fracking at significant depths routinely leads to water contamination," said Scott Anderson, a drilling expert with the Environmental Defense Fund. "But the jury is still out on what the odds are that this might happen in special situations."