July 28, 2020: The terminal condition of Kahn’s Crossing pedestrian bridge stems from deterioration along one of the support beams from water infiltration, according to May 2018 report from borough engineer Maser Consulting.
Brainy Boro Blog obtained the report through an open records request.
Maser recommended closure of the bridge and complete replacement, rather than repair, based on the inspection report. The borough closed the bridge in 2018 and has since been applying for Department of Transportation grants to help fund the $190,000 to replace the bridge.
The cost appears to only include the same type of bridge with galvanized and painted steel, but not removal, erection and installation, the Maser report said.
So what went wrong?
Water was able to infiltrate inside the east support beam which runs under the platform, called a stringer, which did not have closure plates, the report said. That resulted in internal rusting along the length of the east stringer, as well as at the center splice connection along the bottom of the stringer, including on splice plates and splice plate bolts, the report said.
Kahn Pedestrian Bridge Structural Follow-up Report – 5.15.18
Inspectors also found external rusting and deterioration along the west stringer, which was less significant than the internal decay on the east beam, the report said. Though here as well, inspectors found deterioration at the center splice connection.
The original manufacturer of the bridge, Contech Engineered Solutions LLC, also assessed the state of the bridge and came to the same conclusion as Maser.
“Since the rust is occurring on the inside of a closed tube steel, the full extent and degree of the rust cannot be completely seen nor definitively determined,” the report said. “The unknown amount of deterioration and rust on the inside of the stringer’s bottom chord has made the bridge’s structural stability extremely uncertain.”
I’m still not clear what exactly happened to allow water inside the east stringer. Was there a design flaw, construction mistake, simply wear and tear over time? We’ll keep digging.
BTW, there’s apparently been a bridge at the end of Graham Avenue since the 19th Century, after the Lehigh Valley Railroad cut out the land for its railroad. David Thomas, the owner of a large plot of the southwest section of the borough at the time, had the first bridge built at Graham Avenue for his convenience, according to the summer 2007 issue of Nannygoats, the newsletter of the Metuchen-Edison Historical Society.