Buried Steel Bridge Protects Wildlife and Motorists in New Mexico DOT Project

Article provided by Contech Engineered Solutions and the National Corrugated Steel Pipe Association

The New Mexico DOT I-25 Raton project involved creating two animal passages using two deep corrugated structural plate buried bridges. One goes under the Northbound lanes and one goes under the Southbound lanes.

The Raton pass portion of I-25 is 21.8 miles long, linking the cities of Raton in Colfax County in northeastern New Mexico and Trinidad in Las Animas County, Colorado.

This area of the country is well known for its beautiful scenery and its ecosystem that is home to many species of wildlife.

Wildlife Safety and the Corridors Act

The Wildlife Corridors Act directs the New Mexico State Department of Transportation (NMDOT) and the New Mexico Department of Game and Fish to work together to prioritize wildlife-vehicle collision hot spots and critical wildlife corridors for the purposes of improving driver safety and maintaining habitat connectivity for elk, deer, black bear, bighorn sheep, pronghorn, and mountain lion.

Wildlife can create life-threatening hazards on roadways. In the United States, there are more than a million automobile accidents per year involving wildlife, racking up more than $8 billion in medical costs and vehicle repairs annually and also endanger the wildlife and ecosystem.

Steel Structural Plate Design Advantages

Instead of using conventional bridges with long term maintenance and ice issues on this dangerous stretch of highway, NMDOT decided to use custom size BridgeCor structures that met the wildlife openness ratio for the animal crossings under I-25 at Raton Pass and offered a savings over conventional bridges while protecting both drivers and especially the black bear population in the area.

Construction and Specifications

Although the project bid in late 2020 the construction of the first bridge under the Southbound lanes didn’t begin until the Fall of 2021. The buried bridges are both identical structures in terms of span, rise, gage, and corrugation pattern.

The Southbound lane bridge is 64′ long and the Northbound lane bridges is 70′ long. The structures are 32′ 10″ span x 11′ 7″ rise, 7 gage, Deep Corrugated Steel Structural Plate Box Culverts meeting AASHTO M 167 with 15″ x 5.5″ corrugations.

Since the span of the structures is in excess of 20′, this designates them as “bridges” and they are now on the New Mexico bridge inventory list as Bridges 9789 and 9790. Finite Element Analysis designed the structure using CANDE software. The structure, headwalls and wingwalls were all made from galvanized steel. They are Steel Structural Plate with 6″ x 2″ corrugations. The Northbound lanes structure was completed in the Fall of 2023.

View Original Article