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Groundwater in Pavillion, WY contaminated by hydraulic fracturing through multiple subsurface pathways

Briana Mordick

Posted December 9, 2011

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The Environmental Protection Agency (EPA) released a draft report of its investigation of groundwater contamination near Pavillion, WY.  It appears likely that groundwater in Pavillion was contaminated by the hydraulic fracturing process itself, rather than by surface spills or leaks of chemicals. EPA determined that hydraulic fracturing chemicals and methane could have reached groundwater by migrating through the annular space of poorly constructed wells, through subsurface formations due to lack of a lithologic barrier (a.k.a. confining zone), or through fractures generated or enlarged by hydraulic fracturing.

NRDC has advocated that wells that will be hydraulically fractured be located in a geologically suitable location such that a suitable confining zone is present, any potential contamination pathways – including improperly constructed or abandoned wells – must be identified and remediated, and properly constructed wells, baseline testing, and site characterization are crucial to preventing contamination of USDWs. EPA’s findings from Pavillion underscore the need for these critical protections.

The principle findings of the study are:

  • Water samples taken from two EPA monitoring wells had anomalously high pH values (highly alkaline). Chemical analyses and modeling indicated this elevation in pH could have been caused by small additions of potassium hydroxide (KOH). Potassium hydroxide was a constituent of two hydraulic fracturing chemicals used in oil and gas wells in the area.
  • Groundwater from the Wind River formation in the two EPA monitoring wells had inorganic geochemical compositions distinct from both shallow groundwater and the typical geochemical composition of Wind River formation water. Both wells had elevated potassium levels and one well had elevated chloride levels. The compositions of both samples were out of equilibrium with regional trends. Potassium and chloride were constituents of multiple hydraulic fracturing chemicals used in oil and gas wells in the area. 
  • A number of synthetic organic chemicals were detected in samples from both monitoring wells, including isopropanol, diethylene glycol, and triethylene glycol. Each of these was a constituent of one or more hydraulic fracturing chemicals used in oil and gas wells in the area. In addition, tert-butyl alcohol (TBA), which is a known break-down product of chemicals used in hydraulic fracturing, was detected in one well. Although Material Safety Data Sheets (MSDS) did not indicate that those chemicals were used in the area, EPA noted that MSDS, “do not contain proprietary information and the chemical ingredients of many additives” and that TBA would not be expected to occur naturally in groundwater.
  • Petroleum hydrocarbons including BTEX, trimethylbenzenes, and naphthalene were detected in one monitoring well and diesel range organics (DRO) and gasoline range organics (GRO) were detected in both wells. Each of these was a constituent of one of more hydraulic fracturing chemicals used in oil and gas wells in the area.
  • Reviews of well completion reports for oil and gas wells showed that in some cases surface casing did not extend below the deepest domestic wells, production casing was not fully cemented to surface, there were multiple instances of poor cement bonding behind production casing, and hydraulic fracturing occurred in or near zones with inadequate cement.
  • This area lacks a suitable confining zone to separate formations that are hydraulically fractured from groundwater.
  • While some migration of gas into groundwater would be expected above gas fields such as Pavillion, isotopic chemical evidence, methane concentrations, well construction practices, and the timing of citizen complaints relative to the timing of hydraulic fracturing indicate that gas migration has been enhanced by natural gas production activities.

EPA considered multiple alternative explanations for the presence of each of the contaminants but in each case concluded that hydraulic fracturing chemicals were the most likely source.

These findings led EPA to reach two important conclusions:

  1. Groundwater near Pavillion, WY has been contaminated by chemicals used in hydraulic fracturing, and;
  2. Those chemicals most likely reached groundwater through subsurface pathways.

The report is still in draft form and will undergo peer review and public comment before being finalized. These are important steps in validating EPA’s research and findings. If EPA’s conclusions are confirmed through this process, there can no longer be a question as to the serious threat that hydraulic fracturing can pose to our drinking water. As EPA stated, “Ground water contamination with constituents such as those found at Pavillion is typically infeasible or too expensive to remediate or restore.”

While the environmental risks from an industrial activity like oil and gas production can never be completely eliminated, adopting best practices can help to reduce those risks. When oil and gas companies choose not to adopt best practices voluntarily, they must be required by regulation. As noted by my colleague Amy Mall, federal regulation of hydraulic fracturing under the Safe Drinking Water Act is imperative to ensuring that groundwater everywhere is protected.

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Comments (Add yours)

TexDec 12 2011 02:59 PM

Those wells were only 1,200ft deep. Even if there were no wellbore integrity issues, it is not surprising that the aquifer could have received some of the frac fluid. This example is a poor analogue to the oil and gas fields in the country where the reservoir being frac’d is 4,000-12,000ft deep.

John DoeDec 13 2011 05:13 PM

Encana Oil & Gas (USA) Inc., a subsidiary of Encana Corporation, strongly disagrees with the U.S. Environmental Protection Agency’s (EPA) preliminary conclusions in its draft report related to the groundwater study in the Pavillion natural gas field of Wyoming. The EPA’s data from existing domestic water wells aligns with all previous testing done by Encana in the area and shows no impacts from oil and gas development. Of most concern, many of the EPA’s findings from its recent deep monitoring wells, including those related to any potential connection between hydraulic fracturing and Pavillion groundwater quality, are conjecture, not factual and only serve to trigger undue alarm.
Encana is especially disappointed that the EPA released its draft report, outlining preliminary findings, before subjecting it to qualified, third-party, scientific verification. This precipitous action runs counter to the cooperative approach that Encana and other state, federal and local participants in the Pavillion Working Group took in working alongside the EPA in its investigation for more than three years.
“These preliminary conclusions do not stand up to the rigor of a non-partisan, scientific-based review and that is of paramount importance to every natural gas producing community, every citizen and business that relies on natural gas and every industry worker,” said Eric Marsh, Encana’s Executive Vice-President, Natural Gas Economy & Senior Vice-President, USA Division. “Safe and responsible natural gas development is vital to North America’s energy security, and hydraulic fracturing is an important, necessary and safe part of natural gas development.”
Numerous discrepancies exist in the EPA’s approach, data and analysis. A few of these discrepancies are:

The EPA report ignores well-known historical realities with respect to the Pavillion field’s unique geology and hydrology.

*The EPA drilled two deep monitoring wells (depth range: 783 – 981 feet) into a natural gas reservoir and found components of natural gas, which is an entirely expected result. The results in the EPA deep wells are radically different than those in the domestic water wells (typically less than 300 feet deep), thereby showing no connection. Natural gas developers didn't put the natural gas at the bottom of the EPA’s deep monitoring wells, nature did.

*There is unacceptable inconsistency between EPA labs’ analysis for numerous organic compounds reported to have been found in the EPA deep monitoring wells. Data is not repeatable and the sample sets used to develop these preliminary opinions are inadequate.

*Several of the man-made chemicals detected in the EPA deep wells have never been detected in any of the other wells sampled. They were, however, detected in many of the quality control (blank) samples – which are ultra purified water samples commonly used in testing to ensure no contamination from field sampling procedures. These two observations suggest a more likely connection to what it found is due to the problems associated with EPA methodology in the drilling and sampling of these two wells.

*The EPA’s reported results of all four phases of its domestic water well tests do not exceed federal or state drinking water quality standards for any constituent related to oil and gas development.
Conclusions drawn by the EPA are irresponsible given the limited number of sampling events on the EPA deep wells and the number of anomalies seen in the data. At the same time, the EPA repeatedly attempts to link limited instances of localized shallow groundwater contamination from historical production pit locations to its broader investigation. In 2005, Encana identified and self-reported these pit locations and entered them into a voluntary remediation program administered by the State of Wyoming.
Given the numerous flaws contained in this report, Encana believes genuine, qualified third-party review is essential. Unfortunately, Encana does not believe that the EPA has subjected any of its data to a qualified, truly independent third party for peer review. We urge EPA and other government officials to ensure that such an independent review is made.
Encana employs a collaborative stakeholder engagement practice to address stakeholder concerns, including hydraulic fracturing. Since some of the residents of Pavillion first expressed concerns about potential impacts from natural gas development on their drinking water, Encana has taken their concerns very seriously.
“We have and continue to work extensively with Wyoming regulators and independent laboratories to determine whether natural gas development is affecting the community’s water quality. To date, all studies found no connection. We care about the impacts of energy development on the environment and we are committed to working to ensure our operations do not impact groundwater,” Marsh said.

John LiffeeDec 13 2011 07:05 PM

Gee, Mr. "Doe," you wouldn't happen to be on the Encana payroll, would you?

John DoeDec 14 2011 09:06 AM

As a matter of fact I'm not.

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