Wyoming regulators have rejected an application for underground wastewater disposal linked to a proposed oil and gas project in Natrona and Fremont counties.

According to the Casper Star-Tribune, the Wyoming Oil and Gas Conservation Commission decided in a 5-0 vote on Tuesday to reverse its earlier approval of an aquifer exemption permit that would allow Aethon Energy to inject up to 10 million barrels of wastewater per day into the Madison limestone formation.

Aethon executive assistant Mary Hite said in a statement that the commissioners based their decision on an application submitted by Encana, which Aethon Energy inherited in its recent acquisition of the Moneta Divide field.

Commissioners voted three years ago to allow the project, but this week they said that the analysis presented was insufficient to provide assurance that the wastewater would be confined to one low-lying area within the Madison formation. It would also not contaminate other aquifers used for drinking water, the newspaper reported.

Amber Wilson, environmental quality advocate with the Wyoming Outdoor Council, welcomed the decision and told Public News Service that in the long term it makes sense to protect clean, drinkable water.

“Science points pretty strongly to the fact Wyoming, and the West in general, is facing a drier future,” she said. “And writing off any potential source of groundwater sounds like a pretty big mistake.”

Next, Aethon will review the commissioners’ feedback and determine its strategy for the project, which is currently in the midst of an Environmental Impact Statement process.