Vermont Interstate Project to Use Lateral Slide Construction

Construction is about to begin on the first project in Vermont to use lateral slide construction. The project will build two new bridges over interstate 91 near Burlington, Vermont. The two bridges will be constructed adjacent to the existing bridges and then will be slid into their proper place to finish the project. This relatively new construction method is becoming increasingly popular in highway construction, and the record was recently set for the world’s longest truss slide.

The lateral slide construction method was chosen for the I-91 project because it is significantly safer than the usual bridge replacement process. Lateral slide construction minimizes the impact on commuters by not changing lane configurations multiple times throughout the project, moves the majority of construction work away from traffic, and also greatly reduces the chance of a construction worker being hit by a car. The large amount of space surrounding the two bridges that need to be replaced made the project a perfect candidate for lateral slide construction. 

There are four main steps to lateral slide construction: building new bridge supports under the old bridges, building new bridges next to the old bridges, demolishing the old bridges, and finally sliding the new bridges onto the new supports.  The new pair of 725-ton bridges will be built slightly higher than their supports. Workers will use hydraulic jacks to slide the bridges across steel beams onto bearings on the new supports.

While the lateral slide construction method will make the project safer, it will also increase the project’s final cost. Each bridge will cost $3 million to construct and slide into place. Kristin Higgins, an employee of the Vermont Agency of Transportation, believes the lateral slide construction method will add 10% to 20% to the projects final cost compared to traditional methods, although it is hard to estimate how much the project would cost using the traditional method. It will cost more to design the project, but the lateral slide construction will allow for the project to be completed in one summer instead of two. The lateral slide construction method is expected to increase in popularity moving forward.