Phenomenon on the mountain

Intrusive rock, sensitive aquifer and the need for a municipal water source

Preliminary test results from a recent push for water on the mountain have revealed “a phenomenon that seems to have some extent in the Mountain Village,” said Mark Cunnane, environmental consultant and engineer with Western Groundwater Services, LLC. The company was selected to help the Big Sky County Water and Sewer District 363 (BSCWSD) establish test wells in an effort to find production wells for the mountain. Development is not sustainable without water. Using a study from Montana Bureau of Mines Hydrogeologist James Rose and his knowledge of the geographical structure of the area, Cunnane selected nine different sites. Basically, a test well shows early promise but further exploration reveals that although water is found, the aquifer does not sufficiently recover.

Gesturing to graphs during the recent BSCWSD virtual meeting, Cunnane showed the slope of the drawdown line is continuing to decrease.

“So we shut that pump off at the peak and what you see is the recovery falls quite a bit short of getting back to the original aquifer level. It doesn’t need to get quite to that level, but it does need to be pretty close,” he said. “Slope of the drawdown line is continuing to decrease, that is not something we want to see in a well that is going to go into long term use as a public well. That is very telling in the analysis. You generally would not pursue this wellsite as a production well.”

He has seen the same results from other test wells – no stabilization from the draw-down.

“Is there any potential production out of this well, although it won’t be the millions of gallons per minute that we’re looking for?” board member Peter Manka asked.

Cunnane said he will come up with an annual volume and design rate.

Two wells remain from sites selected and there was discussion between Cunnane and BSCWSD Water Superintendent Jim Muscat of potentially placing sensors in some wells to get a better idea of what is happening.

Another option, which is viewed as somewhat of a last resort due to a price tag around $1 million, is drilling deep into the Kootenai aquifer.

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