St. George Blvd

Phase One:

The $16.3 million project included upgrading the Interstate 15 interchange at Utah Exit 8 to a Diverging Diamond Interchange (DDI), structure rehabilitation, and inclusion of a pedestrian facility. The European design has the lanes narrow and cross over the bridge to channel traffic into the other lane, reducing the traffic signals from six down to two. The two traffic lights are synchronized to turn green or turn red at the same time in the corresponding directions. Pedestrian can cross the bridge directly in the middle, between the eastbound and westbound lanes of travel at the designated crosswalk signals. This interchange type has proved successful at several locations in northern Utah and is a first such structure for Southern Utah.  The modifications are expected to handle traffic demand through the year 2040.

Phase Two:

The project consisted of upgrading the I-15 MP-8 Interchange to a Diverging Diamond Interchange (DDI, structure rehabilitation, and inclusion of a pedestrian facility.  Project limits include I-15 & St. George Blvd from 100 East to the River Road Intersection.  Key elements for the project included: design and construct project within 6 months; widen existing bridge over I-15 at St. George Blvd; re-configuration of the existing MP8 Interchange to a Diverging Diamond Interchange (DDI); accommodate Pedestrian Facility; roadway widening to provide standard 12 foot lanes, along with 12 foot shoulders across the structure; new intersection and interchange signals.

Wadsworth Brothers used accelerated construction techniques to reduce traffic impacts and delays to the public.  These techniques also helped in meeting the project schedule:

  • Partial-depth deck panels reduced the number of nightly lane closures on I-15 and shorten the bridge deck construction time.
  • High-early-strength concrete was used for all the bridge substructure, lighting, and sign structures to help reduce curing times and pick-up valuable schedule time.
  • Maximizing road closures by working on several work elements at the same time assisted in accelerating the project schedule.

In order to meet the Utah Department of Transportation’s aggressive design-build schedule timeline, WBC utilized its expertise in scheduling to develop a design and construction schedule that would maximize the productivity of planned closures, minimize the number of peak period closures required to complete the project, and reduce the overall schedule duration.  By using proven techniques, reliable suppliers, high quality subcontractors WBC was able to beat UDOT’s project schedule goals.



Completion Date

July 2009


Washington County, UT