The I-15 South Design-Build project stretches from Tropicana Avenue to just south of Silverado Ranch Boulevard in Clark County, Nevada.

The project involves the widening of I-15, the addition of collector-distributor roads, redesigned interchanges, and the delivery of the design of 26 new bridges and more than 40 new retaining wall systems in sixteen (16) months.

Sigma led five different consultant design teams on the preliminary design of more than $100M of bridge structures alone.  Sigma provided oversight of the bridge design activities and led coordination with the roadway, geotechnical, environmental, ITS, drainage, and aesthetic design leads.  Sigma also coordinated the implementation of NDOT design standards and ensured continuity in structures types, geometric improvements, and design efficiencies.

Sigma’s tasks included the design of cast-in-place/post-tensioned concrete box girder bridges, composite steel bridges, curved steel bridges, and railroad underpass structures.  In addition to bridge structures, Sigma led the design of a variety of retaining wall systems ranging from conventional cast-in-place retaining walls, to mechanically stabilized earth walls, soldier pile systems, tie-back walls, and secant pile wall systems.  Unique design solutions were also provided for the modification of existing drainage structures and bridge widenings such as optimized span configurations, reduced structure depths, and in-line railroad bridge replacement.

Finally, Sigma was instrumental in the delivery of project plans and final quantities to the design-builder that were used in the development of the final bid costs.  Close coordination with construction estimating personnel assured that designs were cost effective, efficient, and simple to construct.