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CASPER, Wyo. — A water-monitoring program in Sublette County recently detected pollutants exceeding state standards in three water wells near a large nearby natural gas field.

But state and federal officials say pollutants detected in the area have actually dropped significantly over time.

In a March report to the federal Bureau of Land Management, the Sublette County Conservation District reported that three non-drinking water wells out of about 250 tested showed either diesel-range organics or benzene — both of which are considered pollutants and are commonly associated with oil or natural gas extraction — exceeding state standards.

All three wells were industrial wells south of New Fork River and west of Boulder, according to Merry Gemper, a physical scientist for the BLM.

Each was completed about 500 feet farther below ground than a standard domestic or livestock drinking well, and each is pumped at a much higher capacity. Gemper said each well was also upgradient from Boulder, meaning detected velocities show that the water would move away from the town.

Whether the detections present any cause for concern is unclear. Gemper said the BLM has for years been working on a more thorough test of Sublette County water and possible contamination sources, and that more information will become clear when that study is complete.

“At this point in time, we are undertaking more in-depth studies,” she said when asked about what the ongoing test results mean to residents. “Until we’re able to work with those data results, I can’t speak to that.”

Oil and natural gas operators whose wells exceed base standards are given a chance to voluntarily solve the problem in cooperation with the Wyoming Department of Environmental Quality. Gemper said all three well operators whose wells exceeded standards in 2012 were already working to solve the problem.

The results were detected as part of an ongoing study of water conditions in the Pinedale Anticline Project Area, a western Wyoming area home to massive natural gas development.

As part of the project area’s final regulatory approval, operators in the area were charged with annually testing water wells within a mile of natural gas wells. The county conservation district was later chosen to perform the work, which began in 2004.

According to both the district and the BLM, early results were much more troubling than what came back in 2012.

“Over the years, I couldn’t say how many detections we’ve found, but the number of detections seems to be decreasing,” Eric Peterson, manager for the conservation district, said.

A past report by the district showed that at least 27 wells in which hydrocarbon constituents had been detected — both exceeding and below drinking-water standards — in 2012 showed no detection of the same materials.

The area has also struggled with air quality. In 2012, the U.S. Environmental Protection Agency deemed the Upper Green River Basin as a “non-attainment area,” meaning it exceeded federal air quality standards for too long.

The basin had tested too high for ozone, a pollutant attributed to natural gas development. The state has until 2015 to reduce ozone levels.

In 2006, tests showed diesel-range organics and gasoline-range organics occurring commonly in wells. Gemper said the results — which were later tied to backflow from vehicles using the wells — led the state and federal regulators to undertake a more thorough effort, much of which is still underway.

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Scientists have reviewed and analyzed water sources in the area and have studied underground water flows, all as part of a study to determine where a contaminant could move in the case it leaked into the system.

The BLM is also collecting samples from potential contamination sources such as evaporation ponds and drilling mud from natural gas sites and natural sources such as the shale underfoot to gain a better understanding of what chemicals exist in each source.

Gemper said the data would aid a “process of elimination” approach to determining where a potential contaminant came from.

The result of the study could reshape the water monitoring system, both in the area and statewide.

“Point is to redesign our monitoring program to target potential impacts,” Gemper said. “It would give us a more timely way to identify if an impact is occurring, and a way (to) respond more timely.”

Gemper added that, depending on its results, the study could also be used to evaluate and influence other water monitoring systems around the state.

One such water-monitoring system is already moving forward as part of Gov. Matt Mead’s energy strategy. A draft of the rules are expected at the Wyoming Oil and Gas Conservation Commission’s June meeting.

“This is a very unique situation because we’re responding to a specific problem,” Gemper said. “We’re not looking to rush into anything here.”

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