Background and Schedule

Thank you for visiting the project website for the "Interchange and Environmental Study for I-229 Exits 3 and 4". These two studies, one for each exit, are analyzing alternatives developed in the previous I-229 Corridor Major Investment Study (MIS) and developing a preferred concept for each exit. Both studies will also include environmental review and documentation.

Project Update

The project's environmental review process continues to advance with final adjustments to potential environmental impacts reflecting right-of-way modifications, floodplain requirements, and final design changes.

We are nearing the final steps in the environmental approval process for the construction of a temporary bridge on I-229 over Cliff Avenue in preparation for the I-229 / Exit 4 Interchange Project.  If the environmental approvals occur this spring, the construction of the temporary bridge would start this summer (2024). More information will be provided on the temporary bridge construction as soon as it is available.

The I-229 / Exit 4 Interchange Project is also waiting for an environmental approval before it can be scheduled for construction. At this point we are anticipating a public meeting later this year and construction for this project is still tentatively planned for 2025-2026.  More information will be provided for this project as soon as it is available.

Environmental Assessment (EA)

The EAs consider a wide variety of topics that address the human and natural environmental effects of the interchange projects.  Project impacts can be either negative, neutral, or positive, depending on the resource.  Sometimes impacts are labeled in terms of likeliness to affect (either adversely or not) the affected resource.  The project must show compliance with all applicable federal, state, and local laws, Executive Orders, regulations, and ordinances and follow a prescriptive process, depending on the resource, to avoid, minimize, or mitigate unavoidable impacts to affected resources. 

Examples of human environment resources that may be affected by the project include people and their residential areas and places of work, school, and play; roadway traffic and noise; park and recreation areas; views to and from the project area, and cultural resources such as archaeological sites and historic places.  Examples of natural environmental resources that may be affected by the project include wetlands and other water resources (rivers, creeks, and streams), floodplains, threatened and endangered species of plants and animals, groundwater, and air quality.

The environmental documentation for the EA is being completed for both interchanges separately.  This is required to allow for potential reevaluations of environmental topic areas if needed and allow for corrections so that both interchanges can proceed on coordinated construction schedules.   The EA drafts are currently under review by SDDOT and FHWA. 

Study Documents

Interchange Modification Justification Reports (IMJR)

• IMJR I-229 Exit 3

• IMJR I-229 Exit 4

Please check back periodically for additional project updates, or sign up for project updates and meeting notifications.

For additional information on the previous "Major Investment Corridor Study", visit the website at i229study.com

You may also visit the South Dakota Department of Transportation website at dot.sd.gov