There have been a number of reported instances of drinking water contamination in which a link to hydraulic fracturing has been reported. These have been taken seriously enought that the EPA has started a multi-year project funded by Congress to study the problem.
Separately, in response to complaints by domestic well owners regarding objectionable taste and odor problems in wellwater, the U.S. Environmental Protection Agency (EPA) has investigated ground water near Pavillion, Wyoming. The objective of the EPA's investigation was to determine the presence of ground water contamination and to differentiate shallowsource sources (pits, septic systems, agricultural and domestic practices) from deeper sources (gasproduction wells).
The EPA sampled water collected from domestic wells and two municipal wells beginning in March 2009 through April, 2011. Detection of methane and dissolved hydrocarbons in several domestic wells motivated a second round of sampling in January, 2010. The EPA collected additional ground water samples from domestic and stock wells and ground water samples from 3 shallow monitoring wells and soil samples near three known pit locations. Detection of elevated levels of methane and diesel range organics in deep domestic wells prompted the Agency to install 2 deep monitoring wells 233 - 239 meters (MW01) and 293 - 299 meters (MW02) in June 2010 to better evaluate deeper sources of contamination.
Shallow contamination
Detection of high concentrations of benzene, xylenes, gasoline range organics, diesel range organics, and total purgeable hydrocarbons in ground water samples from shallow monitoring wells near pits indicates that pits are a source of shallow ground water contamination in the area of investigation.
Deeper contamination
The EPA says that the determination of the sources of inorganic and organic anomalies in deeper ground water was more complex requiring multiple approaches to detecting contamination. Some the results included
- pH values in MW01 and MW01 are highly alkaline
- Potassium concentration in MW02 and MW01 is between 14.5 and 18.3 times values in domestic wells and expected values in the formation
- Chloride concentration in monitoring well MW02 is 18 times the mean chloride concentration observed in ground water from domestic wells and expected in the formation.
- low calcium, sodium, and sulfate concentrations compared to the general trend observed in domestic well waters.
In addition a number of synthetic organic compounds were detected in MW01 and MW02.
- Isopropanol was detected in MW01 and MW02
- Diethylene glycol was detected in MW01and MW02
- Triethylene glycol was detected in MW01 andMW02
- Tert-butyl alcohol, was detected in MW02
- Benzene, toluene, ethylbenzene, and xylenes (BTEX) were detected in MW02
- Trimethylbenzenes were detected in MW02
- Gasoline range organics were detected in MW01 and MW02
- Diesel range organics were detected in MW01 and MW02
The EPA says that alternative explanations were considered to explain individual sets of data, but when considered together with the other evidence, the data indicates that the "likely impact to ground water that can be explained by hydraulic fracturing."
Methane contamination from gas production wells
Elevated levels of dissolved methane in domestic wells are observed to generally increase the closer they are to gas production wells. The ground water at MW01 which is sampled at a depth typical of deeper domestic wells in the area was saturated with methane. With the exception of two wells, surface casing of gas production wells do not extend below the maximum depth of domestic wells in the area. In addition a number of production wells near MW01 have sporadic bonding or no cement over large vertical instances. The EPA says that it looked at other explanations, but concluded that "enhanced migration of gas has occurred within ground water at depths used for domestic water supply and to domestic wells." As Forbes points out "It’s discomforting to read in the EPA report that at one natural gas well there was no cement liner installed until a depth of 671 meters below the surface."
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