Environmental groups maintain that this activity can cause tiny earthquakes and that the toxic chemicals used in fracking may contaminate groundwater.

Under some conditions, certain herbicides can be transported via leaching or surface runoff to contaminate groundwater or distant surface water sources.

With the contaminated groundwater levels rising rapidly, scientists have speculated on what will happen when the deadly pollutant reaches the surface.

It contaminated groundwater and caused the water table to rise, making the soil saline and unproductive.

Plans by gas companies to hydraulically fracture, or frack, gas have attracted protests from environmentalists, who argue that the practice risks contaminating groundwater.