Fracking chemicals could poison water: expert

A protest march against fracking in the Karoo. File picture

Some chemicals used for shale gas fracking could contaminate or poison water far from the original drilling site, an expert warned on Monday.

"Before any chemical company is granted a licence to frack it must prove that the chemicals used in fracking cocktails are safe," the Free State University ground water research unit's Prof Gerrit van Tonder said.

He said positive perceptions of fracking and the shale gas it could unlock needed to be balanced by the potential risks involved.

"Other more green options are available, even if fracking is considered," Van Tonder said in an interview.

The danger was that large, watery, underground caverns, which exist even in the arid Karoo, could be polluted by the chemicals used for fracking.

Noxious chemicals leaking into water at one drill site could spread the contamination by either lateral or upward movement of the water.

Aquifers -- from the Latin words aqua, meaning water, and fer, meaning bearing -- could be conduits for the spread of these pollutants.

Ample evidence indicated that, in some circumstances, water welled up from deep sources, such as in the case of hot water springs. Van Tonder said the impacts and risks of fracking fluid reaching fresh water aquifers depended on the number of well pads.

One company had indicated it would need one such pad for every 260 hectares, with up to 10 boreholes per pad.

This meant that if only half of the nine million hectares, as per licence applications, were developed, there would be 17,300 boreholes.

"The integrity of just one borehole failing can be disastrous for surrounding borehole users and the environment within a year," he said.

It was possible that the contaminants could move slowly, spreading to other boreholes over decades, or within a matter of days along dolerite sills and faults.

These included annuli, the ring of material round fracking cement or grouting seals, he said.

Such events had been found to be major contributors of groundwater pollution in the United States and Australia.