Simultaneous Replacement of 3 Housatonic Railroad Bridges Using Accelerated Bridge Construction

August 28th, 2019

AI Engineers recently finished inspecting and administering 3 simultaneously running sites on the Housatonic Railroad performed within a 9-Day closure window running 24-hour work schedules. Thanks to the efforts and commitment of Northern Construction Services, along with cooperation and teamwork by the Connecticut Department of Transportation and the Housatonic Railroad, the work was completed and track was restored one day ahead of schedule. AI Engineers and Garg Consulting Services provided inspection and project management services throughout the accelerated construction project.

On the left is Site 1 in New Milford: The contractor was originally tasked with jacking approximately 80 lf. of 72 in. RC pipe to replace the existing 48 in. corrugate metal pipe. The contractor proposed an alternative to install the pipe via traditional cut-and-cover excavation methods using a slide rail support of excavation system. This proposed change was accepted as it reduced the contractor’s schedule risks and the Department’s risks related to unforeseen conditions. On the right is Site 4 in Canaan: The contractor replaced an existing 71 ft. timber trestle bridge with a 100 ft. steel girder bridge. The new bridge was installed via traditional, stick-build methods with many elements in pre-erected sections. Work included new 8.5 ft. deep girders, precast backwalls, bridge waterproofing, and new slope protection.

Not shown, due to a freak wind storm that caused a tree to fall and crush the camera, is Site 2 in Kent: The contractor replaced an existing culvert with a new, precast, twin-cell box culvert and precast wingwalls. The work required a steel sheeting cofferdam and extensive water handling to complete the work.