Natural gas fracking can make local well water explosive

Natural gas fracking can make local well water explosive by John Timmer, Arstechnica, May 2011
How did the methane get there? The simplest answer would be that the casings of the new wells are simply not sealed properly, allowing gas to leak out. Alternately, there are many old and abandoned drill sites in the area, and fracking may have opened a pathway for gas to escape into these wells. Finally, the authors suggest that the fracking process may open up natural fractures in the overlying rock formations. At this point, it’s impossible to distinguish between these possibilities…they conclude, “we believe that long-term, coordinated sampling and monitoring of industry and private homeowners is needed.” [Emphasis added]