For more than a year, people in New Jersey have wondered what caused a large retaining wall at a construction site along Interstate 295 to partially collapse. Now, they’re finally getting answers.
A report commissioned by the New Jersey Department of Transportation and released this week indicates that inadequate building materials and “a history of slope instabilities” years in the making contributed to the collapse of the roughly 30-foot-tall and 19-foot-wide wall in March 2021.
“The report lays out the contributing factors behind the collapse and we have been assured by the New Jersey Department of Transportation that steps are being taken to address these issues before rebuilding Wall 22, which we understand is expected to be completed by the Summer of 2023,” New Jersey U.S. Rep. Donald Norcross and Assemblyman Bill Moen said in a joint written statement Thursday.
The forensic engineering report was done by the Hardesty & Hanover infrastructure engineering firm. It details several problems that led to the collapse of the wall – referred in the report as Wall 22 – in Bellmawr.
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Wall 22 was supposed to support an elevated section of the roadway. According to the report, the wall sat on a layer of sand. The section of roadway rested on another layer of sand in front of the wall.
However, predesign data showed that the conditions underneath the surface of the wall had “inadequate strength to support the anticipated elevated roadway embankment.”
To make up for that lack of strength, the design employed a system of columns underneath the sand. The columns were supposed to help hold up the weight of everything above them.
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The unreinforced concrete columns, though, “were not adequate to withstand the vertical and horizontal loads from the elevated roadway embankment,” the layer of sand and the wall, the report found.
Construction of Wall 22 began in December 2018, but the slope on which it was built had problems years before that.
The report notes that large fissures appeared on the slope as early as 2016. According to the report, the wall was built directly on top of that slope, which itself was already “soft and saturated with numerous zones of running water.”
Then, in 2019, construction of the wall had to be paused “for several weeks” when several of its panels shifted.
Two years later, around March 11, just days before the collapse, workers noticed the first cracks in the pavement above the wall. The cracks were reexamined five days later, the report notes, but no changes were reported. However, on March 23 – roughly a day or two before the collapse – workers noticed “a significant settlement” of the pavement, according to the report.
“Discussion with NJDOT personnel who observed paving in this area recall observing ‘soft spots’ in the subbase which indicates that some distress may have existed months before the cracks were noticed for the first time around March 11, 2021,” the report notes. “This distress, along with observations during the paving process, further validates that the system exhibited signs of instability before failure occurred.”
The wall finally did collapse on March 26, 2021.
The collapse further set back a $900 million project that was conceived in 1985 and designed to seamlessly unite I-295 with Route 42 and Interstate 76. Construction finally began in 2013 and is expected to wrap up in 2027, but the final contract of the project isn’t even expected to be up for bidding until 2024.