Project Background

The South Dakota Department of Transportation’s recently completed Major Bridge Investment Study has recommended the existing SD44 bridge over the Missouri River (Platte–Winner Bridge) to be replaced. The current alignment of SD44 over the river has experienced numerous landslides, resulting in millions of dollars in repair and mitigation expenses since the bridge opened to traffic in 1966.

This replacement project is anticipated to take place in the mid-2020’s, and a new Platte-Winner Bridge is expected to be built for a 100 year design life. Because of the importance of the SD44 highway route, maintaining continuous traffic flow during construction will be a priority of SDDOT. It is anticipated that a new bridge will be built off of the current alignment and locating the most stable possible location will be a key consideration in project decision-making.

Study Expectations

The need for this study is to address the deteriorated condition of the Platte-Winner Bridge and review the SD44 corridor. Existing and future capacity of the roadway and bridge, along with any identified safety issues will also be addressed. The project will include an emphasis on minimizing environmental and socioeconomic impacts. Due to the scale of the project, a National Environmental Policy Act (NEPA) document will be prepared and is expected to consist of an Environmental Assessment (EA).

This study will meet the following objectives:

  1. Complete a structure location and type study for a new, long-term bridge considering economics, aesthetics, maintenance, and impact to the environment.
  2. Complete the NEPA process necessary to advance the project into final design phase.
  3. Complete a safety analysis of the highway corridor within the study area.
  4. Identify locations on the highway corridor not in compliance with current design standards under both the current and forecasted future traffic conditions.
  5. Create final products for use by SDDOT which will guide the DOT during the design phase of the bridge replacement and corridor improvement project.

Study Area

The SD44/Platte-Winner Bridge over the Missouri River is the centerpiece of a larger project study area that encompasses approximately 100 square miles in Gregory and Charles Mix Counties. The SD44 corridor runs east-west between the communities of Winner and Platte (specifically between SD47 and SD50) and is approximately 25 miles south of the Interstate 90 corridor at this project location.