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According to an industry website the process of Hydraulic Fracturing (or "fracking") is safe. According to an article in the Huffington Post the process is not safe. At least, there is evidence the process is not safe. Have any independent studies been done on the issue?
Related question: Does "fracking" cause earthquakes?
The EPA studied the subject in 2005, and produced a report which, according to this article in Environmental Health Perspectives:
In 2005 Congress exempted fracking from regulation under the Safe Drinking Water Act partly on the basis of the EPA report Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs. The authors of this report wrote that hydraulic fracturing poses “minimal threat” to drinking water and that “additional or further study is not warranted at this time.” However, the study involved no direct monitoring of water wells but instead relied on existing peer-reviewed literature and interviews with industry and state and local government officials. It also was strictly limited to one specific type of drilling and did not address the effects in substrates other than coalbeds.
Since the process of fracking has become more common and is used in many contexts other than coalbeds, the EPA is revisiting the issue with a new study that is scheduled to be released in late 2012 (Cite: http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/index.cfm).
Fracking undoubtedly contains substances that are hazardous to human health - the question really revolves around whether those substances reach surface or ground-water, then to humans... it seems like there are some ways for this to happen, and earlier fracking studies may have looked at properly-protected wells and less at the field epidemiology around the wells.
The draft of an EPA investigation of fracking in Pavillion, Wyoming has just been released. It's not yet peer-reviewed, this will happen after the draft has been available for 45 days for public comment.
They measured an unusually alkaline pH level, which could be caused by strong base used during fracking
The high pH measured in the deep monitoring wells was unusual and unexpected. [...] Presence of hydroxide alkalinity suggests strong base addition as the causative factor for elevated pH in the deep monitoring wells.
They also found high concentrations of methane, which they determined to be of thermogenic origin. Thermogenic means it was produced under conditions of high heat and pressure, as opposed to biogenic methane produced directly by bacteria.
The monitoring wells produce ground water near-saturated in methane at ambient pressure, with concentrations up to 19.0 mg/L.
Similarity of δ 13 C values for methane, ethane, propane, isobutane, and butane between gas production and monitoring wells and plots of δ 13 C-CH4 versus δD -CH4 (Figure 18b) and δ 13 C-CH4 versus C1/(C2 + C3) (Figure 18a) indicate that light hydrocarbons in casing and dissolved gas in deep monitoring wells are similar to produced gas and have undergone little oxidation or biodegradation. These observations combined with radiocarbon analysis of CH4 (< 0.2% percent modern carbon) obtained from gas in casing of both MW01 and MW02 indicate that methane in deep monitoring wells is of thermogenic origin.
Those are only two points of evidence in the report, there is more in the full report. Based on these observation they state in their conclusion
While each individual data set or observation represents an important line of reasoning, taken as a whole, consistent data sets and observations provide compelling evidence to support an explanation of data. Using this approach, the explanation best fitting the data for the deep monitoring wells is that constituents associated with hydraulic fracturing have been released into the Wind River drinking water aquifer at depths above the current production zone
The report presents some convincing evidence that components of the fracking fluids are released, though the authors state:
However, further investigation would be needed to determine if organic compounds associated with hydraulic fracturing have migrated to domestic wells in the area of investigation.
The contents of this report are also nicely summarized in the article "How the EPA linked "fracking" to contaminated well water" from Scott K. Johnson at Ars Technica.
