MT 21 Bridges - Elk Creek and Hogan Slough logo

Project Overview

In 2020, the Montana Department of Transportation (MDT) upgraded seven water crossings on Montana Highway 21 (MT 21) between mile markers nine and 20. During the project, MDT and its construction partner LHC Inc. replaced three wooden bridges with culverts and flattened the side slopes, eliminating the need for guardrail. Additional work included upgraded guardrails on one concrete bridge and new bridge decks on three wooden bridges.

The engineering design for the Elk Creek, Elk Creek Overflow, and Hogan Slough structures began in early 2021. The construction schedule is tentatively scheduled for 2026. MDT will continue informing the public of project updates as they become available.

Design Overview

The Sun River and its system of creeks and sloughs are prone to flooding. This puts major pressure on the adjacent MT 21. Preventing flooding on the highway can be difficult due to factors, such as changing river flows, weather events, and funding availability. As funding has become available, the MDT has made upgrades to better serve the local community, and travelers. In 2020, MDT widened three bridges, upgraded an existing bridge, and installed three culverts on MT 21 as part of the Highway 21 Bridges: Simms to Augusta project. The next project for this area, MT 21 Bridges: Elk Creek and Hogan Slough, is in the design phase, and will replace the existing Elk Creek, Elk Creek Overflow, and Hogan Slough structures between mile markers zero and one. Construction on this phase is currently expected to begin in 2026, depending on completion of design and availability of funds.

Roadway Improvements and Safety

The Montana Department of Transportation is committed to transportation infrastructure that not only reduces the probability of crash frequency and severity but that provides value, economic benefits, and is environmentally sensitive. Serving Montanans and its commuters is the cornerstone of this mission. The MT 21 Elk Creek and Hogan Slough bridge project supports MDT’s Vision Zero goal of ensuring that Montana’s road systems are built and maintained with safety as the first concern.


The estimated construction cost for MT 21 Bridges Elk Creek and Hogan Slough project has not been determined.

Staying in the Know

The Montana Department of Transportation recognizes the impacts on residents and travelers. We are committed to mitigating those challenges by involving the public in the decision-making process for detour timing and delivering timely updates through a variety of avenues.

For project updates:Email your comment, question, or request updates to Laura Langdon.
Call Laura Langdon at 406-447-3354