UPDATE: A Show Cause hearing is set for Thursday, June 12, 2025, at 9 a.m. before Hon. Judge Mike Menahan.
Lawsuit challenges DEQ’s refusal to apply numeric nutrient water quality pollution standards for impairment designations after five years of data
Last week, Upper Missouri Waterkeeper filed a complaint in the Montana First Judicial District Court against the Montana Department of Environmental Quality (DEQ) for failing to apply legally-binding water quality standards in its denial of a petition seeking to declare the Big Hole River impaired by nutrient pollution.
“DEQ’s refusal to apply the laws on the books is a violation of a clear legal duty, and a disservice to one of Montana’s most cherished rivers,” said Guy Alsentzer, Executive Director of Upper Missouri Waterkeeper. “Montanans rely on DEQ to follow best available science and the law, not to bend to political pressure or selectively ignore its own rules.”
The lawsuit comes after DEQ sent a letter to the Big Hole River Foundation and Upper Missouri Waterkeeper denying the petition the organizations submitted requesting the Big Hole River be declared impaired by nutrients. Despite the extensive supporting data from five years of water quality monitoring on the river, DEQ rejected the petition, citing the “narrative standards” set by the Montana Legislature in 2021, which were subsequently rejected by the Environmental Protection Agency (EPA) for failure to comply with the Clean Water Act.
“The law is clear that numeric nutrient criteria must guide agency decision-making under the Clean Water Act,” Alsentzer noted. “This lawsuit is about protecting the headwaters of Missouri and all the beneficial uses in Montana that need clean water.”
More than a third of assessed surface waters in Montana are polluted and unable to support their designated uses. Two of the most common causes of impairment are excessive nitrogen and phosphorus, two pollutants for which the State has adopted numeric standards, making the determination of healthy or unhealthy far easier. Montana’s numeric nutrient standards apply to most wadeable streams in western Montana, including the Big Hole River.
Science-based numeric standards are necessary to help inform strategies that reduce existing pollution and stop new pollution from further degrading Montana’s waters. Separate from numeric standards are open-ended “narrative” standards, which have already been rejected by the EPA as too speculative, subjective, and unprotective of waterway health. In the case of the Big Hole petition, the measured concentrations of nutrient pollution exceeds levels necessary to maintain robust aquatic life and river health. When too much nutrient loading goes into a river, it often causes nuisance algal blooms and other excessive aquatic plant growth. These unnatural plant and algal blooms suck oxygen from the water column, raise water temperatures, and negatively impact food sources and breeding for Montana’s famed trout and the insects that support them.
While SB 358, a bill rolling back Montana’s numeric nutrient criteria, was signed by the Governor on April 30, 2021, the Environmental Protection Agency must approve a state’s revisions to water quality standards before any change is effective. In response to a complaint filed by Waterkeeper, on May 10, 2022, the EPA disapproved of DEQ’s attempt to eliminate numeric nutrient criteria, leaving numeric nutrient criteria as the legally-binding water quality standards for all Clean Water Act purposes. The EPA disapproval letters struck down most portions of Senate Bill 358 for any Clean Water Act purpose, meaning the state law was declared invalid and DEQ was prohibited from using it as a basis for making pollution control decisions.
In response to DEQ’s letter refusing to apply numeric nutrient criteria and denying the petition, Upper Missouri Waterkeeper sent a letter to DEQ reiterating the need to consider all available scientific data in determining the Big Hole’s impairment status under the Clean Water Act, and called on DEQ to reevaluate its decision given the clear legal requirement to use numeric nutrient standards when assessing water quality impairments. To date, DEQ has not responded, prompting the new court challenge.
The Big Hole River is not only an iconic river and trout fishery but also supports Montana’s outdoor economy, local businesses, local communities, and wildlife. An impairment designation would bring the attention needed to resolve the nutrient pollution problems along with additional resources and funding needed to help restore the river’s health.