Schematic cross-section of general types of oil and gas resources and the orientations of production wells used in hydraulic fracturing. From U.S. EPA fracking and drinker water study.

It holds the potential to cause problems, but so far hasn’t – that seems to be the thrust of a long-awaited government study on fracking and its impact on drinking water that was released on Thursday.

Going back several years, this has been one of the hot-button issues involving hydraulic fracturing, a key technique that has helped unlock extensive oil and gas resources in the United States in the past decade.

Here are the money paragraphs from the Environmental Protection Agency:

From our assessment, we conclude there are above and below ground mechanisms by which hydraulic fracturing activities have the potential to impact drinking water resources. These mechanisms include water withdrawals in times of, or in areas with, low water availability; spills of hydraulic fracturing fluids and produced water; fracturing directly into underground drinking water resources; below ground migration of liquids and gases; and inadequate treatment and discharge of wastewater.

We did not find evidence that these mechanisms have led to widespread, systemic impacts on drinking water resources in the United States. Of the potential mechanisms identified in this report, we found specific instances where one or more mechanisms led to impacts on drinking water resources, including contamination of drinking water wells. The number of identified cases, however, was small compared to the number of hydraulically fractured wells.

This finding could reflect a rarity of effects on drinking water resources, but may also be due to other limiting factors. These factors include: insufficient pre- and post-fracturing data on the quality of drinking water resources; the paucity of long-term systematic studies; the presence of other sources of contamination precluding a definitive link between hydraulic fracturing activities and an impact; and the inaccessibility of some information on hydraulic fracturing activities and potential impacts. – From the Executive Summary of EPA’s “Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources”