Nutrient Data Indicate the Need for Impairment Designation and Pollution Clean-Up Plan
Upper Missouri Waterkeeper and the Big Hole River Foundation filed a petition with the Montana Department of Environmental Quality (DEQ) requesting a Category 5 impaired waterway designation of the Big Hole River under Section 303(d) of the federal Clean Water Act (CWA). Five years of monitoring data indicating clear exceedances of nitrogen and phosphorus water quality standards signal the need for pollution control planning to reduce nutrient discharges and restore water quality in the Big Hole. The DEQ must respond to the request with a preliminary determination within 60 days, or by April 14, 2025.
“There’s no disputing that there’s a nutrient pollution problem on the Big Hole River, with neon-green algal blooms fueled by nutrients cropping up each summer. Thanks to five years of state-verified data, we have proof that nutrient levels are well beyond the legal limit [for impairment],” said Guy Alsentzer, Executive Director of Upper Missouri Waterkeeper. “Thankfully, the State of Montana has the tools to restore rivers impaired by nutrients, like the Big Hole. We now need to hold the State accountable for taking the necessary steps to designate the river as impaired, develop a pollution diet, and work to reduce pollutant sources that are causing degradation.”
Since 2020, the Big Hole River Foundation has been conducting water quality monitoring for chemical data at 10 sites on the mainstem Big Hole and primary tributaries based on a Sampling and Analysis Plan approved by DEQ. Key parameters measured included total nitrogen and total phosphorus, both of which are naturally occurring chemicals that in some concentrations help maintain healthy aquatic ecosystems. However, too much nitrogen and phosphorus can harm fish and insect communities, degrade aquatic habitat, and contaminate drinking water.
Data collected over the past five years revealed exceedances of water quality standards at the majority of sites, with some doubling or tripling the numeric threshold for nitrogen and phosphorus. Sampling sites near Wisdom, Jackson, and Mudd Creek exceeded standards nearly every time sampling occurred, indicating a persistent nutrient pollution problem that warrants attention and action.
“Our science indicates that nutrient pollution in the Big Hole River is exceeding legal water quality standards that are designed to protect aquatic life,” says Big Hole River Foundation Executive Director Brian Wheeler. “Now that we know this, we need the State of Montana to step in and help address the problem to ensure a healthy future for Big Hole, its fisheries, wildlife, and the community.”
When a waterbody fails to meet designated uses (aquatic life, drinking water, agricultural uses, etc.) or is exceeding water quality standards, the state is obligated to list the waterway as “impaired” under Section 303(d) of the CWA and develop a Total Maximum Daily Load (TMDL). A TMDL, or “pollution diet” is a calculation of the maximum number of pollutants that can enter a waterway while still achieving water quality standards, and is used as a planning tool for reducing the various pollutant sources and their contributions. A TMDL is an enforceable mechanism that will bring forth the necessary resources, funding, and DEQ staff to study the problem and develop long-term solutions.
“The Big Hole is suffering blow after blow – extremely low flows prompting mid-season fishing closures, and miles-long algal blooms,” said Wade Fellin, Program Director of Save Wild Trout. “We must do what we can now to make measurable improvements for the river, and that should start with an official impairment determination to clean up the nutrient pollution that is degrading water quality and aquatic habitat.”
Under state and federal law, DEQ must respond to an impairment petition within 60 days. If the department agrees with petitioners, it will publish a notice of intent to list the Big Hole River as an impaired waterway and open a 60-day public comment period. At the close of the public comment period, DEQ will consider comments received and make a preliminary determination, which must be approved by the Environmental Protection Agency. Upon EPA approval, the Big Hole would be formally listed as impaired at law and the state would have a duty to develop a TMDL to address the contributing pollution.