Bridge project will debut innovative construction methods
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The Vermont Agency of Transportation (VTrans) will replace two highway bridges over US Route 5 on Interstate 91 at exit 11 in White River Junction, approximately one half mile north of the junction of Interstate 91 and Interstate 89. Planning and design for the project will occur in 2014 with construction during 2015.
The bridge replacement will be fast-tracked through VTrans’ Accelerated Bridge Program (ABP). Typically, fast track bridge projects use innovative techniques and are completed in approximately half the time that it would take by conventional construction, often in just one construction season.
A construction method known as a lateral slide, will be used to replace the Interstate 91 Hartford Bridges for the first time in Vermont. The slide will take place over two weekends, one for each bridge. Road closures on Interstate 91 will be limited to these two weekends, minimizing inconvenience to travelers. US Route 5 will remain open while the two bridges are moved into place.
Here’s how the lateral slide will work:
1: Building the foundation…beginning spring 2015
- A new foundation (piers and abutments), otherwise known as a substructure, will be built for each new bridge underneath the existing bridges.
- The new superstructure (bridge deck and support beams) for two bridges will be constructed on temporary supports right next to the existing highway bridges.
- Traffic along Interstate 91 over the existing bridges will flow as usual while construction is going on underneath and next to the bridges.
- Travel lanes on US Route 5 will be reduced from three lanes to two, but traffic will flow in both directions throughout construction.
2: Moving the new bridges in place…summer 2015
- The superstructure for each bridge will be moved over one weekend at a time for each structure. One side of the highway will be shut down and traffic will be rerouted onto a detour to allow the bridge to be connected to its new foundation while the other side of the highway remains open.
- The foundation and deck of the old bridge will be demolished.
- Hydraulic jacks are used to push or slide the bridge in place – thus the name “Slide-in Bridge Construction
- Once the first new bridge is installed and related work is complete, the bridge will be reopened to traffic and the process will be repeated for the second bridge on another weekend.
- US Route 5 will remain open during the lateral slide.
- Plans for handling Interstate 91 traffic when the Interstate is shut down are being developed. Northbound traffic is expected to be detoured off the Interstate at the Exit 11 Northbound off-ramp and make a quick re-entry onto the highway by the northbound on-ramp across US Route 5 Southbound. Interstate 91 traffic detours have not been finalized.
3. Completing construction & restoring site…fall 2015
- Install pavement markings, guardrails
- Pave US Route 5, reinstall islands and install pavement markings
- Seed and mulch construction area