Montana Department of Transportation


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Big Sky Bridge Decks

Construction is ongoing Monday through Friday and is anticipated to wrap up this fall.

Drivers can expect single-lane closures for each direction of travel, 24 hours a day, 7 days a week. A traffic signal will be in place to guide travelers through the area.

Call 406-207-4484 with any questions or concerns.

Project Overview

With increasing development and growth of the Big Sky area, roadways are experiencing a surge of truck traffic headed to construction sites and delivering shipments. New residents and tourists add to these volumes all while roadways continue to bear the brunt of travel. Bridges are especially crucial to traffic flow, responsible for carrying the weight of large loads safely through the area.

In 1973, Big Sky Resort opened for its first season, and the bridges over the Gallatin River on US Highway 191 and MT Highway 64 (Lone Mountain Trail) were there to carry skiers and travelers. These same bridges have withstood the growth of the community for nearly 50 years to its current status as a bustling destination. As the community thinks about the next 50 years, strong structures are needed.

The bridges in Big Sky are safe and have undergone regular maintenance for years, but they can no longer be patched for interim fixes. To ensure these structures remain safe for years to come, the Montana Department of Transportation (MDT) is planning the Big Sky Bridge Decks project. Crews will improve three bridges in the area by repairing or replacing each deck and paving over the surface.

Key Information for Travelers

The three structures to be improved during this project are located at:

  • On US 191, two miles north of the turn to Big Sky (Lone Mountain Trail), over the Gallatin River. This bridge deck will be repaired.
  • On MT 64, near the intersection of Lone Mountain Trail and U.S. 191, over the West Fork of the Gallatin River. This bridge deck will be repaired.
  • On MT 64, near the intersection of Lone Mountain Trail and Little Coyote Road, over the West Fork of the Gallatin River. This bridge deck will be fully replaced.
Big Sky Bridge Decks project map
Click to view a larger image.

This work will occur during peak construction season, from May through November, Monday through Friday. There will be three different construction areas with staggered schedules.

Drivers can expect to see single-lane closures with traffic flowing on one side of the bridge. Flaggers will be in-place to stop and guide traffic. Delays of up to 15 minutes can be expected at each area. Drivers are advised to plan extra time to reach their destination, especially during the first few weeks of construction.

About Bridge Decks

A bridge deck is the surface of a bridge for vehicles to drive on. Many travelers do not realize that decks have multiple layers. Asphalt is only the surface-level portion – beneath it is a strong layer of concrete. These decks lay on top of supportive beams that are visible when looking underneath the bridge. A driver might perceive this entire structure as being seamless with the rest of the roadway, since the asphalt is paved and marked similarly. However, bridges are unique and cannot be treated in the same way as roads.

Bridges are regularly analyzed by the Montana Department of Transportation to ensure they are safe for all sizes and weights of vehicles. Once a bridge deck experiences a pothole or crack, crews might fill the area with pavement as a quick repair to ensure the full structure does not degrade further. However, if that damage has permeated the deck layers and is not limited to the top surface, a full repair or replacement of the deck is needed. The underlying layers would not hold the pavement properly, so crews would not be able to simply pave over the top surface.

For this project, workers are repairing the layers of deck in necessary places. They will also mill the top layer, tearing it up, and pave it with new asphalt. One of the decks requires a replacement, meaning that the entire deck with all of its layers will be removed and a new one will be installed.

Stay in the Know

The Montana Department of Transportation understands that many residents regularly commute over these structures. As such, we will make every effort to keep delay times low and to communicate throughout construction. We encourage all to sign up for the weekly update:

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