MT 21 Bridges (Simms – Augusta) project logo

Project Overview

Coronavirus Response

The Montana Department of Transportation together with its construction contracting partners continue to take the COVID-19 pandemic very seriously. Construction projects on Montana’s roads and bridges are considered an “essential” operation and will continue moving forward as scheduled in 2020. Construction workers will continue several measures to help keep employees, contractors and the public safe during the construction season. Some of the measures include following social distancing and good hygiene guidelines, and not reporting to work if showing symptoms of illness. For more information visit

Work Zone Safety

When traveling during construction season, watch for the "cone zone" and for workers on the highway. These workers spend their days working a short distance from fast moving vehicles, and while they make every effort to work safely, they are counting on you to pay attention, slow down and be careful as you pass through a work zone. Learn more at

The construction project was awarded to L.H.C. Incorporated for $2,951,725. Construction will begin in mid-April of 2020. The highway will be closed to all traffic at MP 9.2 (Dry Creek) and MP 19.8 (Simms Creek) for 35 days between July 5 and August 22. Advance signs will be placed to warn motorists of the detours and closures. Drivers will experience slower speeds on the detours and should allow additional travel time for driving alternate routes during the closure period.

2020 Project Overview

STPB-BH-BR 81022(2)
UPN 7938000

View Project Updates

The project includes 11 locations on Montana-21 between MP 19.8, west of Simms, and 0.1, east of Augusta, in Cascade and Lewis & Clark Counties. These bridges and stockpasses were built in the 1930s and are too narrow to meet modern design standards.

Three wooden bridges can be replaced with culverts and the recovery zone can be flattened to eliminate the need for guardrail. Guardrail will be upgraded on one concrete bridge and three wooden bridges that will be re-decked. Right-of-way acquisition and utility relocation will be required. The public can anticipate seeing construction starting in 2020. In order for the Montana Department of Transportation to deliver these improvements, construction will result in detours and road closures. Drivers may experience some delays.

Due to recent flood events, the work type and schedules for the three bridges closest to Augusta (mileposts 0.1 Elk Creek, 0.2 Elk Creek Overflow and 0.8 Hogan Slough) are being re-evaluated.

Purpose and Need

  • The project has been nominated to address safety concerns based on bridge width and guardrail blunt ends. The scope is to rehabilitate, widen and overlay the decks and upgrade the guardrail or replace bridges with culverts.
  • These stock passes and bridges are nearing the end of their useful life.
  • The current bridges are only 21' wide and the blunt end guardrail and lack of guardrail are safety problems.
  • The removal of bridges and blunt end bridge rail and replacing with culverts and a wider finished surfacing, as well as slope flattening will enhance safety along this route. Widening the bridge deck and placing new guardrail will provide an increased level of safety for the traveling public.
  • Rehabilitating the bridges to increase width or replacing with culverts is a cost-effective option that utilizes fewer resources than reconstruction. The existing wooden/paved decks will be replaced with corrugated steel decks and paved with plant mix.