EPA Approves Gallatin River Impairment Designation

State of Montana Can Officially Begin the TMDL Clean-Up Process 

Recent reporting by the Bozeman Daily Chronicle covered the EPA’s approval of an “impairment” determination for the Middle Segment Gallatin River. This segment stretches from Yellowstone National Park downstream to Spanish Creek confluence. 

The decision to list the middle segment Gallatin as impaired came in response to 5 consecutive years of severe algal blooms. As the delegated Clean Water Act authority, the Montana Department of Environmental Quality (DEQ) has a responsibility to use best available science, including both narrative and numeric criteria, to determine whether a waterway is unhealthy and failing to meet is designated uses at law (e.g., capable of supporting fishing, aquatic life, etc). 

EPA’s formal decision approving DEQ’s impairment determination for the middle segment Gallatin River means the river is classified as failing to fully attain two primary river uses – supporting aquatic life and providing for recreation. The impairment determination will be added as an addendum to the 2020 Integrated Report, the biannual list of impaired waterbodies identified in Montana.

“EPA’s approval of the impairment designation is a big win for the Gallatin, as the clean-up process can now officially commence,” said Guy Alsentzer, Executive Director of Upper Missouri Waterkeeper. “A formal impairment determination triggers the mandatory TMDL development process and related pollutant source studies, which will help us identify the pollutants degrading the river and will guide us to an enforceable pollution-reduction plan as necessary to restore the river to health.”

This April 2023 DEQ formally submitted an impairment listing for the Gallatin River to the EPA after making a preliminary finding that the river merits an impairment designation in June 2022. The finding was made in response to a petition submitted by Upper Missouri Waterkeeper and conservation partners in March 2022 along with drone evidence and river-based business narratives demonstrating the negative impacts of severe neon-green algal blooms.

EPA’s approval of the impairment listing officially marks the beginning of the TMDL (total maximum daily load) process. Next steps include DEQ performing scientific studies to identify the pollutants and their sources degrading the river, and developing a TMDL, known as a pollution diet, that includes enforceable limits on existing sources of pollution to reduce pollutant loading to the river. DEQ reports that the process could take up to six years. 

In the meantime, until a TMDL is developed and implemented, federal law prohibits DEQ from authorizing more point source discharges of contributing pollutants to the middle segment Gallatin River. Adding more point source pollution to an unhealthy river system before a clean-up plan would represent a violation of federal CWA requirements. Waterkeeper is pleased to see EPA’s approval, including the agency’s explicit instruction for DEQ to focus on nutrient pollutant sources to the river, and looks forward to participating in the TMDL development process and restoring the health of the Gallatin River.