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Balancing winter safety with Gallatin River health



By Alicia DeGroot and Kristin Gardner Blue Water Task Force

GALLATIN CANYON – The drive on Highway 191 from Big Sky to Bozeman along the Gallatin River is awe-inspiring. It’s also one of the most dangerous highways in Montana.

Thankfully, the Montana Department of Transportation is committed to providing winter maintenance there and on Highway 64, the Spur Road up to Big Sky Resort. MDT uses four strategies for winter maintenance:

1. Anti-icing – adding salt to the roadway before a storm to prevent ice and snow from sticking
2. Deicing – adding salt to melt ice and snow already on the roadway
3. Plowing
4. Traction sand application

The mix and match of these different strategies varies and depends on air temperature, road surface temperature, snowstorm intensity, humidity, exposure to sun and weather predictions.

MDT uses two different salts for winter maintenance: magnesium chloride and sodium chloride. Magnesium chloride is a liquid, and sodium chloride is mixed with traction sand. The traction sand provides better grip on the road surface until the salt can melt the snow and ice.

A few years ago, MDT changed the ratio of this mixture by increasing the amount of sodium chloride from 5 to 20 percent, thus reducing the amount of sand applied to roads.

Because of the close proximity of these highways to the Gallatin River and its tributaries, there is a high likelihood for road salt and sand to end up in rivers, streams and aquifers. We know there is a fine line between public safety and the health of the Gallatin River, its tributaries, and near stream vegetation, but we firmly believe that efforts can be made to better protect our water resources from excess sediment and salt.

The salts and sand used for winter maintenance can kill roadside vegetation, degrade soil and leach into groundwater and eventually streams and rivers, where they can kill fish and other aquatic organisms. Excessive salt in the soil reduces the ability of a plant to absorb water and can eventually kill it.

Salts are easily transferred through soils to groundwater and streams, where they can also be lethal to fish and aquatic plant life. However, since most salt loading to our stream occurs during spring run-off, it can be diluted and quickly transported downstream.

Furthermore, most species can tolerate exposure at high concentrations if it occurs in less than three to four days. For these reasons, we are more concerned about the potential impacts of traction sand than salt on the health of the Gallatin River watershed.

Small particles of traction sand can sink and clog the spaces between gravels in stream beds. Such gravel beds are vital for the fish spawning, including trout, and for a diverse population of aquatic insects. Sand that remains suspended in water can clog fish gills. In addition, excess sand and salt in the river affects the density of the water, which can change the water temperature, a serious problem for a cold-water fishery.

Although to date MDT takes no extra precautions near waterways, it has made several efforts to reduce the environmental impact of winter maintenance. A few years ago, MDT began picking up sand after spring runoff; much of the 2011 clean up was sporadic however, and didn’t occur until the fall. MDT has also been replacing its trucks with those that can apply magnesium chloride directly, instead of first being mixed with traction sand. Snowplow drivers receive 40 hours of environmental training each year.

Recent water quality assessments have showed excess sediment in our local rivers and streams, and now, the Blue Water Task Force and MDT are making efforts to more accurately define and address the problem.

BWTF is restructuring its volunteer water quality monitoring program to include indicators of winter maintenance substances, and MDT is conducting a water quality survey on the Gallatin to look for excess chloride and sediment. In addition, over the next year, we’ll work together developing strategies to reduce traction sand and salt loading to our local rivers, streams, and aquifers.

Wondering how you can make a difference? Reduce your speed if you notice fresh sand, salt or liquid being applied to the roads. Vehicles cause sand and salt to be kicked-up into the air and fly off the road. This is especially important on hills and turns, where deicing is most important.

To get involved with the water quality monitoring program on the Upper Gallatin River, contact Kristin at the Blue Water Task Force at, (406) 993-2519, or stop by the office at 50 Meadow Village Dr., Suite 201, in Big Sky.

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