I recommend a very informative interview with Karlis Muehlenbachs, a professor of geochemistry at the University of Alberta who has researched contamination of groundwater by natural gas. Dr. Muehlenbachs states: "The shale gas boom combined with hydraulic fracking will cause wellbores to leak more often than run-of-the-mill conventional wells. The problem is going to get worse, not better."
He also makes a point that NRDC has also been making for a while -- the oil and gas industry has the technical ability to reduce risk: "The biggest problem is that half or more the wells drilled leak due to improper cement jobs or industry is not following best practices."
The oil and gas industry repeatedly states that hydraulic fracturing is safe and has never contaminated groundwater. It's true that, until recently, there have not been scientifically grounded independent investigations that seek to fully understand the role of fracking in most groundwater contamination incidents . One exception is the investigation of the groundwater contamination in Bainbridge Township, Ohio, where the state found that one of the contributing factors was: “the frac communicated directly with the well bore and was not confined within the “Clinton” reservoir.” Others are the current EPA investigation into the groundwater contamination in Pavillion, Wyoming, and the larger EPA study looking into other cases around the country.
Companies can and should be following better standards to reduce the risk to groundwater from fracking. Since they're not, groundwater contamination continues to occur around the country. To protect human health and the environment, it is essential that there are stronger government regulations at both the state and federal level.