According to a report issued by the Wyoming Department of Environmental Quality on Monday, over 10 years of research has has determined that oil and gas development did not pollute water wells near the town of Pavillion.

DEQ spokesman Keith Guille said that "We just have not been able to find [contaminants] in those domestic wells that would be connected to hydraulic fracturing."

In 2008, residents with water wells east of the town became vocally concerned about contamination.

This led to an investigation from the U.S. Environmental Protection Agency who indicated in 2011 that hydraulis fracturing which uses high pressured water and chemicals to dislodge minerals could be polluting the wells.

A more recent report and one that builds on prior research, disputes that.

In 2016, an unpublished report by the DEQ did not find unsafe levels of about 20 varying contaminants, said Guille, adding that researchers wondered how much lower detection measurements they would need go to find them.

The DEQ sampled water both after the irrigation season in 2017 as well as before the irrigation season in 2018, he said.

"That's why it's taken a bit longer; we wanted to collect some more data."

However, the DEQ has worked with the affected Pavillion residents, Guille said including sharing data about some contaminants such as sulfides and bacteria that are naturally occurring. But they have been decreasing in recent years, he said.

"It's their wells, it's their water quality; they need to know what's there."

There are additional problems according to the report; gas in the upper Wind River Formation has migrated into the sands in the area.

Guille also said that another problem has been the lack of a base line for comparing water quality.

As oil and gas development in the area occurred in the 1950s and 1960s and no water samples were taken before that, there is no way to compare the original water quality with current water quality, said Guille.

However, The Wyoming Oil and Gas Conservation Commission now requires taking pre-development water samples, he went on to say.

The DEQ also gave advice about how to treat their wells and have good water quality, and in 2013, the state appropriated about $1 million for residents in the area to install cisterns, he added.

According to the recommendations from the report, the state is not finished yet either.

"There is additional investigation work that is happening from the Oil and Gas Conservation Commission on these old pits from the oil and gas development, so it's like production water or whatnot they'd pour into these pits," he said.

The DEQ is reclaiming those pits, he added.

A copy of the report can be found here.