There has been huge public interest in this aspect of fracking, popularised by the 2010 film 'Gasland' by Josh Fox. Unfortunately, there is no online link available to the film but the associated website is available here- (http://one.gaslandthemovie.com/whats-fracking). This film clearly falls into the 'anti-fracking camp' but nontheless provides a thoughtful insight into the thousands of lives affected by groundwater contamination.
The most iconic image associated with this film is that of a woman setting her drinking water on fire as it emerges from the tap faucet. This proved to be a very effective method of capturing the attention of world-wide mass media and general public- lets be honest- who isn't shocked by the possibility of setting tap water on fire?
Like 'Gasland', most of the media attention has been focussed on the Marcellus Shale deposits of Pensylvannia, USA; deposited in the Appalachian Basin of Middle Devonian. These deposits consist of well bedded fossiliferous black shale units with high Total Organic Carbon content (1-11%), making it the largest deposit of natural gas trapped in low permeability shale in the USA- and hence the most economically important.
Since 2008 there has been a huge expansion of the drilling operations within the Marcellus Shale; this surge has been implicated as the underlying source of tainted drinking water in the region. Primary research has been conducted by Robert Jackson of Duke University, who undertook methane measurements in drinking water at increasing proximity to fracking wells. The results, as published in Scientific American indicate that : the closer one is situated to a well used for hydraulically fracturing shale for natural gas, the more likely it is that the drinking water is contaminated with methane.
The original report, published online in the Proceeding of the Natural Academy of Sciences is available here:
(http://www.pnas.org/content/108/20/8172.long)
With the sumarising articles of Scientific American avilable here:
(http://www.scientificamerican.com/article.cfm?id=fracking-for-natural-gas-pollutes-water-wells)
(http://www.scientificamerican.com/article.cfm?id=methane-in-pennsylvania-duke-study)
Jackson discovered methane in 115 of the 141 shallow residential drinking water wells, thats a huge 81.56%. Furthermore, homes within a 1 mile radius of the Fracking well showed a 6 fold increase in methane levels than those at futher distances.
Energy companies require unequivocal proof that the methane actually has its source in the Marcellus Shale Formation. This has been evaluated by comparing stable isotopes of carbon in methane from water samples with international standards using del notation:
δ = (Rsample/Rstandard – 1) * 1000.
The systemmatic collection of gas samples has led to a database, allowing 'isotopic finger-printing' of the gas. Jackson discovered that the isotopes are indicative of gas produced by thermal alteration of organic matter due to heat and pressure during burial.
However countering this, energy companies have claimed gas can rise naturally from deep formations through fissures in the rock and enter groundwater independantly of the fracking process. A claim supported in a scientific journal published by the National Groundwater Association which documents cases of flammable drinking water occuring since the 1700's.
A report summary is availbale here, from Energy In Depth:
(http://energyindepth.org/marcellus/study-naturally-occurring-methane-ubiquitous-in-ne-pa-groundwater/).
Cases of methane release are often associated with poor management of the pipe-line. Any ruptures in the metal casing or of the concrete surrounding the pipe can result in methane leaching. This highlights the need for universal supervison of borehole management and production.
Here is a link to providing information on borehole integrity:
(http://www.energyfromshale.org/environment/ground-water-protection)
