Gallatin River

The Gallatin River flows through the mountains Tuesday, Jan. 21, 2020, near Big Sky.

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BIG SKY — A nonprofit organization is laying the groundwork for Gallatin Canyon residents to form a water and sewer district to protect the Gallatin River as development pressure increases.

The Gallatin River Task Force has completed a study on the feasibility, cost and environmental impact of creating a connected system of shared septic tanks, building a wastewater treatment plant or pumping sewage to the Big Sky County Water and Sewer District for treatment.

For any of the three options to become a reality, canyon residents would need to create a water and sewer district, a process that requires a petition or vote.

A canyon district would likely connect buildings near Highway 191 between the Big Horn Shopping Center and Ophir Elementary School with sewer pipes, which would enable wastewater to be treated at a single site and could better protect the Gallatin River from nitrogen pollution than the current network of septic drain fields.

Some Big Sky residents expressed concern at a meeting this week that even if a water and sewer district forms and treats wastewater more robustly, the Gallatin River could still be at risk. They asked for data on how much more nitrogen the Gallatin River can absorb and on how climate change might make the river more vulnerable.

“At the (current) load, we are already seeing signs of impairment,” said Steve Johnson, resort tax board vice chair, adding that the canyon area appears to be approaching the maximum amount of development it can handle.

Mace Mangold, an engineer who worked on the task force’s study, acknowledged the uncertainty in predicting how development affects the Gallatin River.

“Are we a problem right now? We don’t know. But in the future, surely we will be,” he said, explaining that a long-term plan for canyon-area wastewater is necessary to limit harm to the river.

The task force study showed district formation could cost several million dollars because it requires major construction, including the placement of pipelines in challenging topography.

To make the project more feasible, the task force suggested creating the district in stages, starting with an area near the intersection of Lone Mountain Trail and Highway 191 and slowly expanding south.

An upcoming election could help canyon residents build water and sewer infrastructure.

In May, Big Sky voters will decide whether to increase the 3% resort tax to 4% with the additional 1% going toward a water and sewer project that includes a $12 million pipeline system to transport wastewater from the canyon to the treatment plant owned by the Big Sky County Water and Sewer District, which includes landowners in the Meadow Village, Aspen Groves, Spanish Peaks and Lone Moose Meadows.

The 1% tax hike would also provide $27 million of a $35 million upgrade to the Big Sky County Water and Sewer District’s plant. The upgrade would increase the plant’s capacity from 600,000 gallons per day to 910,000 gallons. Some of the new capacity would be earmarked for workforce housing to help address Big Sky’s affordable housing shortage.

The upgrades to the treatment plant would process wastewater to the point that it could be discharged as groundwater and could be used for snowmaking on cross-country ski trails. The ultimate disposal method depends on further analysis, which the Montana Bureau of Mines and Geology is doing.

A handful of conservation groups have said groundwater discharge is unacceptable because that treated wastewater ultimately reaches the Gallatin River and would likely affect water quality. Cottonwood Environmental Law, Gallatin Wildlife Association and Montana Rivers are working to get a section of the Gallatin River designated as an Outstanding Water Resource, which would prohibit treated wastewater from ever reaching the river.

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Perrin Stein can be reached at pstein@dailychronicle.com or at 582-2648.

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