Highway 96 and 35W Diverging Diamond

Challenge

The Highway 96 bridge over Interstate 35W in Ramsey County had structural deficiencies and required replacement. In addition, mobility, ADA accessibility, and safety improvements were needed to accommodate the redevelopment of a 430-acre former military site adjacent to the road. The existing bridge could not handle added traffic volumes due to increased developments in the area. Other challenges included gaining public buy-in, as residents and travelers were wary of the new design, upholding regional trail connection accessibility, and the obligation to maintain full access along Highway 96 during the construction process. 

The suggested diverging diamond interchange (DDI) layout posed a difficulty in public outreach and education efforts due to the absence of local examples and its unfamiliar reversal of left and right driving lanes which was challenging for many to comprehend.   

Solution

In collaboration with multiple project partners and under an extremely aggressive schedule, SEH assisted the County in evaluating multiple interchange designs before deciding on an innovative DDI configuration. The SEH team designed a four-lane DDI to replace the existing two-lane bridge. This design accommodates local and regional travelers, commuters, bicyclists, and pedestrians while enhancing traffic flow and allowing access to nearby developments. The DDI layout includes dedicated lanes for entering and exiting the highway, as well as pedestrian and bicycle crossings, resulting in a more efficient and safe interchange that can handle larger traffic volumes than traditional interchanges. 

The project also involved bituminous and concrete paving, installation of traffic signals, storm sewer, lighting, and ADA compliance improvements. SEH conducted public and agency outreach, completed environmental documentation, submitted an interstate access modification request, prepared geometric layouts, and completed final construction documents. Significant agency coordination, public outreach, and creative construction staging were critical factors in the project's success. 

Awards

• 2016 Grand Award - American Council of Engineering Companies, Minnesota Chapter (ACEC/MN)
• 2017 American Council of Engineering Companies – Minnesota Chapter’s (ACEC-MN) Engineering Excellence Grand Award