I have called the picture of tap water exploding in fire the most powerful picture in energy policy. It is great television and is run many times, even with little reason to do so. No doubt the picture and its repetitious showing raised public concerns about fracking more than anything else and by a lot.
Tap water on fire is a picture that is worth many more than a thousand words. The picture, however, poses questions, requiring the separation of fact from fiction.
Methane in water that catches fire can come from methane that existed prior to drilling or methane that migrated as a result of poor drilling practices. No doubt exists that a substantial number of water wells in gas producing areas have always had biogenic or natural methane in them. No doubt also exists that mistakes in gas drilling and casing also can cause methane to migrate and to reach water wells.
In the absence of pre-drilling water testing, as was the case in Dimock, determining whether gas existed in tap water before or after drilling is a guaranteed dispute, though a number of ways exist, including examination of the gas in the water, to make reasoned judgments.
As distinguished from poor drilling and casing, hydraulic fracturing itself does not cause methane to be present in tap water. This point is typically not understood or is lost in the public debate.
More good discussion of this topic is desperately needed and Susan Phillips has authored a helpful article. See http://stateimpact.npr.org/pennsylvania/2011/12/19/flaming-taps-methane-migration-and-the-fracking-debate/.