Vehicle collisions with wildlife are a major concern on US 160 east of Durango, Colorado. With recent growth in communities surrounding Durango and traffic volumes increasing, CDOT Region 5 chose Muller to design three wildlife underpasses along a particularly vulnerable corridor surrounding Dry Creek. The project also improves capacity on US 160 by adding through lanes and climbing lanes.

Based on feedback from wildlife experts, Muller’s engineers selected single span prestressed I‑girder bridges for two of the three locations. Each crossing location consists of separate eastbound and westbound bridges with a gap at the median. This arrangement provides superior visibility and encourages animals to use the crossing. At the westernmost crossing, shallow bedrock presented an opportunity to use shallow foundations for support of a buried structure. In 2016, a precast arch wildlife underpass was constructed as part of a breakout package at this location. The remaining structures are at a final design level, awaiting construction funding.

The Muller team also designed retaining walls to support the widened road while reducing impacts to the adjacent Dry Creek channel and associated wetland areas. The Mechanically Stabilized Earth walls are designed with a loose rock facing retained by galvanized steel baskets. Due to poor underlying soils, significant post-construction settlement is predicted. The rock basket facing can accommodate this settlement, while providing a natural appearance that is in harmony with the rural surroundings.