Freight railroads have played a crucial role in America's development, particularly in the state of New Jersey. Its proximity to major ports in Philadelphia and New York and abundant natural resources made it an ideal place for railroad development. The industrial town of Paulsboro, situated along the banks of the Delaware River, remains a key link in Conrail's busy Penns Grove Secondary line, which serves southern New Jersey. Built in 1917, the former structure which carried the line over Mantua Creek was a historically significant 'A-frame' swing bridge; a structure that was once common among other rail lines in the region. During the early morning hours of Friday, November 30, 2012, seven freight train cars derailed at the Paulsboro Bridge over the Mantua Creek (also known as the East Jefferson Street railroad bridge). Conrail turned to trusted bridge experts Modjeski and Masters to assist with restoring safe operations of the railroad.
Following an emergency field response and inspection
, Modjeski and Masters worked with Conrail to reopen the formerly movable bridge as a fixed structure. This temporary fix ensured safe operation of the railroad until a more permanent movable structure could be constructed. This new structure would need to be constructed on the same alignment and with as little interruption to rail traffic as possible. Modjeski and Masters was again tasked with finding solutions.
Our problem solvers determined that a new vertical lift bridge with a lift span length of 70’ would be the optimal design for this location. The new structure features: a vertical clearance of 25’; a stringer, floorbeam, thru-girder lift span system with an open tied deck to minimize lift weight; and, was designed to accommodate a slight increase in rail traffic speed. To facilitate construction and minimize railway disruption, our approach was to fabricate, assemble and test the lift span, tower and counterweight off-site while the new substructure units were installed on-site. The lift span was floated into place. The tower, counterweights and ropes were installed with the new lift span in place and rail traffic restored. M&M provided construction support throughout the construction process.
For more information, see our project documentary film on YouTube: https://youtu.be/DsycbgUZm5o