Interstate 29 Bridge, Road Design, and Grade Raise

Background

The staging pool south of the Fargo-Moorhead Diversion Southern Embankment will impact I-29 during operation of the Diversion. To raise the edge of the roadway above the 500-year pool elevation and maintain mobility throughout the region during large flood events, approximately 4.5 miles of interstate are being raised from south of Cass County Road 18 to south of the existing Wild Rice River crossing south of Fargo.

The Project

The project involves the reconstruction of I-29 in order to raise the grade of I-29 south of the Southern Embankment as well as the replacement of three structures. Two will be at the I-29 crossing over the Diversion Borrow Ditch. The third is the Cass County Road 18 overpass structure.

Given the settlement concerns and the poor soil conditions in the Red River Valley, Houston Engineering, Inc. (HEI) collaborated closely with geotechnical partners to preload the embankment and preconsolidate the area using a surcharge and wick drain system before constructing the roadway and bridges. For the design of the grade raise and the structures, HEI worked in close coordination with the US Army Corps of Engineers, the Metro Flood Diversion Authority, and the North Dakota Department of Transportation to meet their standards and expectations. The project was completed in spring of 2024.

Two 389-foot, three-span prestressed concrete I-beam bridges will provide sufficient waterway area to maintain operation of the Diversion during large flood events. The Cass County Road 18 overpass will be a 293-foot, three-span prestressed concrete I-beam and will maintain a minimum vertical clearance of 16 feet and 6 inches over the interstate.

Due to settlement concerns and poor Red River Valley soils, Houston Engineering, Inc. (HEI) worked closely with our geotechnical partners to preload the embankment and preconsolidate the area with the use of a surcharge and wick drain system prior to construction of the roadway and bridges. For the design of the grade raise and the structures, HEI coordinated closely with the US Army Corps of Engineers (USACE), Metro Flood Diversion

Authority, and the North Dakota Department of Transportation (NDDOT) to ensure their standards and expectations were met.

The project was completed in the spring of 2024.

Winner in the Structural Systems Category, 2025.