Here’s an overview of some of the key concerns: Groundwater contamination: One big concern is whether the chemicals used in fracking or the natural gas itself could contaminate people’s drinking water.
In recent years, fracking wells have blown out in states like North Dakota.
In another incident, thousands of gallons of fracking fluid leaked out of a storage tank in Dimock, Pennsylvania.
The Environmental Protection Agency is currently conducting a big study into this type of contamination and how to prevent it.
A second question is whether chemicals or natural gas could somehow migrate from the fracked shale layer thousands of feet up into the groundwater — even if the wells are perfectly constructed.
Environmental Protection Agency Wastewater pollution: A separate issue is what happens with all that water after it has been used to crack open shale and is pumped back up to the surface.
But when there aren’t enough injection wells available, the water is either stored in tanks and holding ponds or sent off to treatment plants.
That raises the risk of either accidental spills or improper treatment.
Air pollution: Once an area of shale has been fracked, natural gas begins flowing up out of the well.
In 2012, the EPA began requiring oil and gas companies to limit these emissions and capture the escaped gas.