UPDATE (7/29/2013, 9:49am EST): EID’s concerns about UTA’s “control” wells (especially the small sample size) were bolstered this weekend when Rob Jackson from Duke University — one of the co-authors of the infamous “Duke studies” linking methane in water to gas drilling — and Terry Engelder from Penn State both made similar observations about the study. According to E&E News (subs. req’d):
But the number of reference wells the scientists used was too small to be statistically relevant, said [Rob] Jackson.
The reference wells were also located outside of the geographic area where the 91 private water well samples were. Ideally, researchers should take reference water samples from wells located in the same geographic area of the Barnett Shale, Jackson said.
Terry Engelder, a geologist at Pennsylvania State University who is a natural gas supporter, said that the reference wells are located in an area that is geologically different from the area where the target wells are located.
—Original post, July 26, 2013—
A new study from researchers at the University of Texas – Arlington (UTA) suggests at least a correlative link between well water contaminants and natural gas development. The researchers took samples from water wells in north Texas that sit atop the Barnett Shale and compared them against historical water quality data from the same counties. Those comparisons, according to the study, suggested an increase in certain compounds after natural gas development in the area began in earnest.
Make no mistake: this new research from UTA could inform better risk management techniques. But there were a few questions that come to mind as we read through this latest study (and the initial news reports about its release).
Question 1: Why is ‘Fracking’ Being Implicated?
In order to determine if the hydraulic fracturing process has contaminated groundwater, samples will usually be tested for benzene, toluene, ethylbenzene, and xylenes – BTEX, for short. The researchers did test for those, and they concluded:
“We found no evidence of BTEX compounds using both LC-UV-MS 192 and GCMS.” (p. 9)
So why, then, did the first story out of the gate put “fracking” in the headline alongside findings of “elevated levels of heavy metals”? The researchers themselves pointed to a variety of different causes (more on that in a moment), which could include increased industrial activity and even changes in the water table due to drought. But apparently, as with the discussion on earthquakes, the obsession around the word “fracking” – and the associated need to include it in every headline – trumped any interest in accuracy.
Question 2: Where’s the Control?
In the study, the researchers included a map of the water wells sampled, which are overlayed on top of an outline of the Barnett Shale, as well as a map of the natural gas wells in the area. A simple scan shows that almost all of the water wells sampled were in close proximity to natural gas wells. Since the researchers did not have baseline samples of these water wells (just historical records of water quality for the same counties), the key comparison for this report would be samples taken close to and far away from natural gas wells.
Indeed, the researchers state that of the 100 total water samples taken, 91 of them were “from areas of active natural gas extraction within the Barnett Shale.” Only nine wells were in non-active extraction areas or outside the Barnett Shale region altogether!
Such a small control sample provides very little data against which to compare the findings from the samples taken near natural gas wells. As such, when the press release says “areas lying outside of active drilling areas or outside the Barnett Shale did not show the same elevated levels for most of the metals,” that’s based on a sample size that is heavily skewed.
Question 3: What Explains the Lack of Uniformity?
This question is actually something of a follow up to the “control” problem identified above. The researchers found elevated levels of certain metals and other contaminants near natural gas well sites, as compared to the (small number of) samples not in close proximity to natural gas wells. But, many of the water samples taken near natural gas well sites fell into their “No Concern” category or the “Below Contamination” threshold. As the researchers themselves observe in the conclusion:
“While our data indicate elevated levels of potentially harmful compounds in private water wells located near natural gas wells, it is important to recognize that there were also a number of private water wells in close proximity to natural gas wells that showed no elevated constituents. This indicates that natural gas extraction activities do not result in systematic contamination of groundwater.” (p. 18)
The researchers also noted that they “are unable to determine” a definitive source of the elevated levels of compounds, owing to a variety of factors:
“To draw definitive conclusions about the origin of elevated constituent levels in these water wells would require a focused study of groundwater before, during, and after natural gas extraction activities. This was logistically impossible as industrial activities have been ongoing for over ten years in this area. Given this limitation, our discussion of the source of elevated constituents is speculative, but we have provided plausible scenarios to explain our data in an effort to increase scientific understanding of this topic and spur future research.” (p. 18)
Also interesting were the findings for total dissolved solids (TDS). Out of 344 samples in historical data from 1989 to 1999 (before Barnett Shale development began in earnest), 61 percent contained TDS levels at or above EPA’s Maximum Contaminant Limit (MCL). Of the 91 samples taken near natural gas wells in this study, only 55 percent registered at or above the MCL. And the nine “control” samples? They registered the highest of all: nearly 78 percent met or exceeded the MCL.
So, what we know from this is that private water wells in and around the Barnett Shale have suffered from poor water quality for decades, and that certain contaminants even declined after shale development began.
Question 4: How Were the Sample Sites Identified?
The researchers actually answer this in the study:
“Private well samples were obtained from a pool of volunteers who responded to a press release calling for study volunteers from 13 counties located in or near the Barnett Shale region (Bosque, Denton, Hamilton, Hood, Hunt, Jack, Johnson, Kaufman, Palo Pinto, Parker, Somervell, Tarrant, and Wise counties; Figure 1).” (p. 6)
It’s worth noting that researchers conducting a study of private water wells need to have permission to access those wells (at least if they don’t want to get arrested!), and thus they need willing participants who own those wells to grant that access. Due to these constraints, issuing a very public press release might be the only way to get a sample size with statistically significant results – although, as mentioned above, the samples themselves are puzzling, to say the least.
But, this also raises other questions: Were any of the respondents known to be opponents of development? When they offered their wells for study, did they offer any opinion on whether the industry should be operating in the region? Perhaps most importantly: had any other investigations of those wells ever occurred, by state regulators or other entities? If so, did they determine a source for the compounds found?
These questions are, in some sense, speculative. But according to the release, the researchers themselves appeared to predict such questions:
“After we put the word out about the study, we received numerous calls from landowner volunteers and their opinions about the natural gas drilling in their communities varied,” Hildenbrand said. “By participating in the study, they were able to get valuable data about their water, whether it be for household or land use.”
As for the source of contaminants, if previous investigations answered that question for any of the wells (including a non-drilling related source), then that would be materially relevant information – especially considering the researchers say the study will “help the scientific community, the natural gas industry, and most importantly, the public, understand the effects of natural gas drilling on water quality.”
Unfortunately, we don’t know the answers to these questions.
As with any study, the purpose is not necessarily to be the end-of-discussion bombshell that answers all questions definitively. But in as much as particular research can help inform better management practices, even limited data can prove useful. The authors of this study appropriately have called for additional research, too.
It’s reassuring to see (once again!) no evidence of the hydraulic fracturing process contaminating groundwater, and it’s worth re-emphasizing that this research shows how shale gas is not inherently destructive to the environment. One of the key contaminants on which the researchers focused was arsenic, and nearly 70 percent of wells sampled in close proximity to natural gas wells registered levels below EPA’s Maximum Contaminant Limit. Nevertheless, in the handful of samples that did have levels above the MCL and any applicable historical average, finding the source of those compounds should remain a top priority.