Montana Department of Transportation

Malcolm “Mack” Long, Director

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Public Involvement

MT-81 Bridges

Project Overview

Judith River Bridge Move

The Montana Department of Transportation, Frontier West and Morrison-Maierle made Montana history on October 29, 2020 when the Judith River Bridge superstructure was moved to its permanent home.

The previous bridge structure was constructed in 1948 and had begun to deteriorate. A new bridge needed to be built while still allowing traffic to flow on MT 81 with minimal disruption. A plan was developed to separately build both the new bridge’s substructure and superstructure and then move the entire superstructure after construction. This undertaking was the first new bridge move of its kind in Montana.

A bridge substructure consists of supports under the bridge that provide stability while redistributing the bridge’s weight into the ground. The superstructure is main part of the bridge that spans the area to be crossed; in this case, the Judith River. The superstructure also supports the bridge deck, or the part of the bridge that is driven on.

Bridges Elements Diagram

Temporary supports were built next to the old bridge to allow for the new bridge superstructure and deck to be constructed on top. Once constructed, traffic was transitioned onto the new bridge surface. The former bridge was demolished and a new substructure was built in its place.

Constructed separately from the substructure, the new superstructure had to be moved onto its permanent foundation. The superstructure was hoisted onto a track with a hydraulic jack. Using a very powerful winch, consisting of a chain connected to the bridge and a pully system, crew members hand-cranked a lever that slowly pulled the 1.2 million-pound bridge along the track until it was in place on the substructure.

The bridge was moved approximately 37 feet from where is was constructed to the location of the substructure. The move took 9 hours to complete. Once in place, the superstructure was secured to the foundation and the bridge was reopened to traffic.

This impressive process combined high-tech engineering with good old-fashioned hard work and perseverance. The new bridge will not only convey traffic over the Judith River, but will stand as piece of Montana history for many years to come.

Judith River Bridge Photo

Judith River Bridge Photo

MT-81 Bridges

The bridges on MT-81, otherwise known as Denton Highway, are aging and in need of repair. The bridge over the Judith River was built in 1948; the bridge over Warm Spring Creek dates back to 1935. These bridges are more than 70 years old, attempting to still accommodate the same large weights and vehicles. Though these bridges are currently safe to drive on, it is critical to fix problems before they become too compromised.

Montana Department of Transportation (MDT) is launching the MT-81 Bridges project to replace three aging bridges between Lewistown and Denton. These bridges are located at the Judith River, Warm Spring Creek, and an irrigation canal roughly a mile southeast of Meadow Creek Road. The irrigation canal will be converted from a bridge to a box culvert, a tunnel-like structure that allows water to flow underneath a roadway.

This project will provide safer roadways for residents, agricultural operations, and commercial trucks traveling through the area. For the average person, this project will have a minimal effect – delays for passenger cars will be brief and closures will always be limited to one-lane, making travel through the bridges' construction areas relatively easy. MDT will coordinate with farmers and trucks hauling wide loads to make every reasonable effort to safely route these heavier and wider vehicles through the project area.

Construction is anticipated to kick-off in early April as the weather starts to warm. Weather permitting, the project will wrap up prior to the end of 2020. Construction schedules for each structure are expected to be staggered:

  • Irrigation canal near Meadow Creek Road: April – May 2020
  • Warm Spring Creek Bridge: May – August 2020
  • Judith River Bridge: May – October 2020
MT 81 Bridges project map
Click to view a larger image of the map.

Those who drive this stretch of highway are encouraged to sign up for project updates to stay up to date on construction. The following resources are available:

  • Email updates: Contact us to subscribe.
  • Project hotline: 406-207-4484, Monday - Friday, 8 a.m. - 5 p.m.

Design-Build Construction

While these bridges are currently safe to drive on, they cannot endure additional years of use and need to be reconstructed. Due to the need for a quick solution, the Montana Department of Transportation has nominated this project for “design-build construction,” meaning that project plans will be created, approved, and constructed in an expedited process.

Many projects within Montana Department of Transportation must wait years for funding and design is typically completed while funding is secured. With design-build, Montana Department of Transportation is able to prioritize projects with exceptional needs and identify funding for both design and construction simultaneously. This considerably speeds up the traditional development timeline. With limited funds and many needs across the state, the Montana Department of Transportation must carefully choose projects that qualify for this process.