12th Street & I29 Interchange

In early 2006 the SDDOT let the reconstruction of the I-29 and SD Hwy 42 intersection.  The existing configuration was a tight diamond interchange with SD 42 going over I29.  The new designed called for an urban interchange with I-29 going over SD 42.  Through the course of construction traffic would not be shut down, and with an ADT (Average Daily Traffic) of 33,000 it would be no easy task.
In order to accommodate required traffic flows, phased construction was used.  First a detour for SD 42 was built north of the existing alignment and was carried over I-29 on a temporary bridge.  Once traffic was on the detour and the demolition of the 254 foot bridge over the interstate was complete, the work on the North bound lanes structure commenced.

Each bridge was a three span steel girder superstructure, 374 feet long and 56 feet wide.  Each bridge contains 2,000 linear feet of H-Pile, 300,000 lbs of reinforcing steel, 1,200 cubic yards of concrete and 733,000 Lbs of Structural Steel.

The project included the installment of 17,000 square feet of large panel MSE Wall. It also received 2006 South Dakota Transportation Quality Award for Structures Construction.



  • South Dakota Department of Transportation


  • Sioux Falls, SD


  • 9 Months


  • Heavy/Highway and Civil


  • SFC Civil Constructors


  • General Contractor