Upper Missouri Waterkeeper has filed a new lawsuit against the Montana Department of Environmental Quality (DEQ) to defend Montanans’ constitutional rights to meaningful public participation opportunities in government decision-making, and to demand comprehensive environmental reviews for significant public sewage infrastructure decisions.
This case challenges DEQ’s quiet approval of a major new sewer pipeline in Big Sky without any public notice or public participation opportunities, and without any environmental review.
This lawsuit seeks to clarify that regional wastewater infrastructure projects with the potential to affect Montana’s rivers must be considered through open, transparent public processes, not behind closed doors.
What Happened
For over a dozen years Upper Missouri Waterkeeper has tracked the issues of wastewater pollution and sprawl development in the community of Big Sky, and the related decline of the Gallatin River and continued impairment of the W Fork Gallatin River. As part of this work the organization has consistently advocated for best-available wastewater treatment and requiring all development projects pay-it-forward and prove they will not cause and contribute to chronic river health challenges. Sadly, state regulators have a poor track record of voluntarily disclosing what projects are being proposed, even ones that may appear positive, such as sewage infrastructure.
For these reasons Upper Missouri Waterkeeper files regular Right to Know Requests to develop an understanding of what decisions our environmental regulators are considering, and to ensure mandatory public participation opportunities are provided. Waterkeeper filed such an information request in Fall 2025 concerning the general plans for wastewater infrastructure in Big Sky’s Canyon Area; DEQ provided a suite of documentation in November 2025 detailing, for the first time, that the agency is already making decisions on what is being called the Gallatin Canyon Sewer Project.
Specifically, last June 2025, DEQ approved a deviation application for a new sewer pipeline in Big Sky that would transport sewage and treated effluent between the canyon and meadow, alongside Highway 64 and stretches of the West Fork of the Gallatin River. DEQ approved the deviation without any opportunity for the public to learn about the project or comment on it, and without any environmental analyses.
The Montana Constitution guarantees the public the right to Know, and to meaningful public participation, in government decisions. Likewise, the Montana Environmental Policy Act requires the government to disclose the environmental impacts, and alternatives, to state-authorized projects as a means to fully inform decisionmakers and the public of potential impacts, before decisions are made. Upon receipt of the November records request, it became plan that DEQ was segmenting its approval of the Gallatin Canyon Sewer Project into individual projects, and not providing for either public participation or a comprehensive environmental review, despite intimate knowledge of the entire game plan.
Doing so was illegal and contrary to Montanan’s constitutional rights. For these reasons Waterkeeper was forced to quickly file a lawsuit to correct DEQ’s legal errors and to chart a correct, and better, path forward for full public participation in Big Sky’s generational investment in regional sewage infrastructure.
Why This Matters
The Pipeline Project is not a minor engineering proposal; it is a central piece of a larger regional wastewater conveyance and disposal system that would sanction hundreds of thousands of gallons of wastewater per day to be moved through the canyon and disposed of nearby the Gallatin River in the Canyon Area. The Pipeline Project relies on public tax-dollars, and has obvious potential impacts, yet the public is ironically being shut out of the decision-making process.
As we all know, the Gallatin River already possesses an EPA-approved impairment designation for harmful algal blooms. Algal blooms create harmful water quality conditions for fish and wildlife, causing harmful dissolved oxygen levels and pH fluctuations, and degrade otherwise world-class recreational opportunities. Because nutrient pollutants are disproportionately found in wastewater, and nutrients are the keystone fertilizing agent that allow algal blooms to occur, there is enormous importance in understanding the Gallatin River’s assimilative capacity for any additional pollution, including a plan for reduction of pollution inputs beyond the status quo.
Recent groundwater studies from the Montana Bureau of Mines and Geology confirm clear connections between groundwater and surface water in the Upper Gallatin watershed, raising serious concerns about nutrient pollution from any new municipal-scale wastewater disposal reaching the river.
Creating further uncertainty is the disconnect between the level of treatment offered at the new Big Sky wastewater treatment plant and how nutrient loads from a new discharge permit in the Canyon Area could allow exponentially more potent pollution to the Gallatin River than it can accept without causing more algal blooms. Unfortunately, DEQ failed to conduct environmental reviews, so no one – not DEQ, decision-makers,or the public – can responsibly understand the potential impact that this pipeline could have on nearby water resources, or the thousands of Montanans, local businesses and economies, agriculture, outdoor recreation, fish and wildlife that depend upon a healthy Gallatin River.
Common-sense, and the law, demands that we “look before we leap” into a predetermined approval of new regional wastewater infrastructure for Big Sky and the Gallatin River.
How DEQ Failed To Do It’s Job & Violated the Law
DEQ appears to have made an informal determination that the Pipeline Project was “nonsignificant” and exempt from MEPA review, based on the misconception that projects meeting engineering standards do not require environmental analysis. Doing so was both illegal, and a logical fallacy.
Article II, Sections 8 & 9 guarantee Montanans the right to be informed of government decisions, and be allowed a meaningful public participation opportunity, before decisions are rendered. When DEQ failed to engage and inform the public about the Pipeline Project it violated Montanans’ constitutional right to know and right to participate in government decisionmaking.
Similarly, the Montana Environmental Policy Act exists to, among other things, ensure decision-makers and the public are informed about the consequences – and alternatives – to proposed projects requiring state approval. The Montana Supreme Court has consistently held that MEPA implements the constitutional right to a clean and healthful environment, and requires DEQ to take a hard look at environmental impacts – and disclose those impacts to the public – on the vast majority of its decisionmaking. Importantly, MEPA requires the performance a robust investigation of potential impacts, including cumulative impacts, through an Environmental Impact Statement when a project is likely to significantly affect the quality of the human environment, including where there is significant public interest.
The generational investment of millions of tax-payer dollars in a regional wastewater system, much less the decision to sanction a new discharge permit adjacent to the Gallatin River, necessarily requires a comprehensive environmental review with robust public participation. Here, DEQ has failed to connect the dots and provide any such review process despite having full knowledge of the entire plan, a plan of infrastructure development that it has kept secret from the public since at least 2023.
What the Lawsuit Seeks
This lawsuit challenges DEQ’s pattern of approving major water infrastructure projects without MEPA review or public participation.
Waterkeeper is asking the court to require:
- Conduct a comprehensive Environmental Impact Statement (EIS) under MEPA;
- Reverse the Pipeline Project approval and provide for meaningful public participation opportunities;
- Require all connected wastewater infrastructure and permits together, rather than piecemeal
- Declare DEQ must evaluate wastewater engineering projects through public processes and MEPA review
How You Can Help
This case has implications far beyond the community of Big Sky. Across the state, DEQ is approving major water infrastructure projects without public participation or environmental reviews. The more this continues, the more the public loses their constitutional rights and voice to speak up for our waterways, or to ensure our government is doing its job of protecting our water, our wildlife, and our outdoors heritage.
Litigation is one of the few tools available to enforce government transparency, uphold our constitutional rights, and ensure state agencies are following the law. But litigation requires significant time and money. Please consider joining Upper Missouri Waterkeeper as a member.
Your membership directly supports our work holding the government accountable, defending the public’s right to participate in decisions that affect our environment, and protecting Montana’s waterways. Please consider making a donation to help fund this lawsuit and future legal actions that protect Montana’s rivers and communities.