I-15; MP 8 Interchange Reconfiguration (DDI) Design-Build - St.George, UT

Substantial cost savings for the project were achieved by using a fast-track design-build project delivery method for design and construction. The design-build process resulted in final costs that were approximately 20% less than the engineer’s estimate and reduced project construction risks for UDOT.

Wilson & Company served as Lead Designer for Wadsworth Brothers Construction Company, Inc. to reconfigure the existing I-15 diamond interchange at St. George Boulevard (MP 8) in St. George, Utah to a Diverging Diamond Interchange (DDI).

The existing diamond interchange configuration, combined with the close proximity of adjacent intersections at 1000 East and River Road/Red Cliffs Drive, restricted traffic capacity and caused traffic backing for several blocks along St. George Boulevard and adjacent roadways.

Innovative techniques employed to complete the project in 6 months and reduce project costs:

• Pre-cast girders and deck panels were used for the bridge widening, resulting in a reduced construction duration as well as minimized closures and impacts to traffic during construction
• The roadway design was optimized to eliminate retaining walls, resulting in schedule savings as well as increased project life and reduced maintenance