Pondera County, Montana, and environmental and conservation organizations have appealed a U.S. Environmental Protection Agency (EPA) decision allowing industrial wastewater injections into the Madison Aquifer west of Valier.

The Sept. 30 appeal to the Ninth Circuit Court of Appeals challenges EPA’s May 1 decision to expand an existing aquifer exemption for two injection wells operated by Montalban Oil & Gas Operations Inc. The exemption covers approximately 6.6 square miles and would allow the wells to receive industrial wastewater generated by Montana Renewables’ renewable-fuels production.

The Jody Field 34-1 and Jody Field 34-2 wells were previously permitted for wastewater associated with oil and gas production. Montalban sought to convert the wells to Class V injection wells to handle wastewater from Montana Renewables, which processes feedstocks including vegetable oils, animal fats, distillers corn oil and used cooking oil.

The petitioners argue that the EPA decision could compromise a potential future drinking water source and that the agency did not adequately evaluate the potential for injected fluids to migrate beyond the exemption area. EPA modeling projected that injected fluids could travel approximately two miles downgradient over 10,000 years, leading the agency to establish the 6.6-square-mile exemption.

The Madison Aquifer is a regional groundwater resource that supplies drinking water to communities in Montana and other states. EPA determined that the affected portion would not be a practical future drinking water source because of its depth, development costs and treatment requirements.

Petitioners dispute that assessment and also point to concerns about the area’s geology and groundwater movement. They argue that previous work on the wells found confining layers were not present as regulators had previously assumed, raising questions about potential pathways for injected wastewater.

The appeal also raises concerns about groundwater monitoring and potential effects on private wells, springs, livestock water and irrigation supplies. Petitioners are asking the Ninth Circuit to vacate EPA’s aquifer exemption, arguing the agency’s analysis did not adequately support its decision under the Safe Drinking Water Act and Administrative Procedure Act.

The filing represents the petitioners’ arguments and does not constitute a court ruling on the dispute.