Layers of shale in the U.K. that may meet decades of domestic gas demand when drilled are well below water aquifers, minimizing the risk of contamination.

A study by the British Geological Survey and Environment Agency found that 92% of the shale in the Bowland Basin is 800 meters (2,600 feet) under the principal water sources. In the Weald in southern England, the rock lies 650 meters below the water table.

“This would support the industry’s assertion that the chance of contamination of aquifers from shale activity is infinitesimal,” the U.K. Onshore Operators Group, an industry lobby, said in a statement.

The U.K. government is offering tax breaks to shale drillers to spur development of a resource that may meet domestic gas demand for a half-century even if 10% is extracted. The Bowland Basin in northern England may hold as much as 1,300 trillion cubic feet of gas, the BGS said last year.

Opponents of hydraulic fracturing, or fracking, argue that the technique to extract gas and oil from shale rock using a high-pressure mixture of water, sand and chemicals causes quake instability and pollution.

“A positive outcome from this study is that we have been able to identify areas, such as the center of the Weald, where there’s no aquifer over the shale,” John Bloomfield, a hydrogeologist at the BGS, said by phone.

“The BGS survey provides valuable information but it won’t eliminate the risk of water contamination from fracking,” Tony Bosworth, energy campaigner at Friends of the Earth, said in a statement. “Regulation in this area is fundamentally flawed. Better rules would make the industry safer -- but not safe.”

BGS also published new data on methane in groundwater to provide a baseline against which future changes can be measured. Methane occurs naturally in the atmosphere and is commonly found as a dissolved component of groundwater.