NCS was subcontracted by Speedie and Associates, Inc. to provide recommendations for the design of ground improvement under the center piers of a new bridge at the Fort Grant Road Traffic Interchange (TI) in Wilcox, AZ.

The Wilcox area has a complex geology, including Playa landforms with salt flats at the surface, and soft clay layers at depth. One or more of the clay layers appears to be underconsolidated. Drilled shaft and spread footings were found to have unacceptable settlements at the pier location of the new bridge, and NCS was tasked with providing ground improvement recommendations.

Deep soil mixing (DSM) was selected as the method of ground improvement, with spread footings to be constructed over the improved subgrade. In late winter to early spring of 2006, Hayward Baker Inc. performed Phase 1 of the DSM. The first half of the new bridge was constructed and brought into service, and the remainder of the old bridge was demolished. In late summer to early fall of 2006, Phase 2 of the DSM was performed and completed.

This proeject has been constructed and is in service.