What do you do when you need to replace two bridges that are located on one of the busiest stretches of an interstate while minimizing impacts to the environment and the traveling public? If you’re the Vermont Agency of Transportation (VTrans), you rely on VHB’s engineers to help you meet these challenges. When VTrans decided to replace the concrete decks on Bridges 76 North & South over Bay Road and Bridges 77 North & South over Mallets Creek on Interstate 89, our innovative design combined accelerated bridge construction techniques with a precast concrete deck system (AccelBridgeTM) that had never been used in Vermont to finish the project within budget and ahead of schedule.
VHB collaborated with VTrans, the contractor, and the Town of Colchester to bring this project to life. The 76 and 77 three-span continuous bridges are located along one of the heaviest traveled stretches of I-89 in Chittenden County; because of the high traffic volume, VHB knew that a typical crossover approach to traffic management wouldn’t be feasible. Instead, we combined multiple traffic control plans into a single plan that maintained two lanes in the peak commuter direction. Since the contractor was able to demolish half of each bridge deck prior to the bridge closure period, our approach reduced the bridge closure from what could have been up to two weeks to only 59 hours. The result? Two new bridges, a multiple award-winning project, and a new methodology for VTrans the next time they need to replace decks on interstate and high-traffic volume bridges.