NJDOT Report Reveals Potential Early Red Flag Behind Wall Collapse In I-295 Connector Project, Engineering Expert Says
BELLMAWR, N.J. (CBS) -- A forensic engineering report, commissioned by the New Jersey Department of Transportation, found inadequate construction materials and heavy rainfall, among other elements, contributed to the March 2021 collapse of a retaining wall in the I-295 Connector project in Bellmawr.
Through a records request, Eyewitness News obtained a copy of the forensic engineering report on May 27 and asked Temple University College of Engineering Associate Professor Joseph Thomas Coe, Jr., Ph.D. to review the 700-page report.
According to the forensic engineering report, the ground underneath the collapsed retaining wall, known as Wall 22, had a history of instability because of chronic groundwater on site.
"When we're building retaining walls, water is definitely our enemy," Coe said.
Coe explained engineers can design ways to get around those conditions, but investigators said the concrete columns and sandy material used in Wall 22 were inadequate for the area.
Coe pointed to one section of the report that he described as a potential early red flag.
Photos and inspection notes revealed during construction between November 2018 and August 2019, water was seeping into the wall's site.
"When you start seeing actual water flow through your system, where you didn't anticipate that it would be there, that could definitely raise some red flags," Coe said.
In June 2019, two months before crews completed the wall's construction, monitoring equipment in the earth recorded unusual data, including an abrupt drop in pressure, which, the report noted, appeared to be indicators of instability in the wall's system.
About 14 days before the collapse, construction crews noticed cracks that formed on the road surface.
The report said heavy rainfall on March 24, 2021, was the tipping point, which led to the wall's collapse the next day.
Coe said this report is an example of a lesson he frequently imparts to his students: an engineer's design is based on ground conditions, and if those conditions change, the design may need to be reexamined.
"When we see evidence of things being different, that we need to pivot to potentially a new design or consider the fact that our design may no longer be adequate," Coe said.
Assemblymember Bill Moen, Jr. has introduced legislation to require construction projects to conduct groundwater testing closer to the start date of construction.
He said groundwater testing for the area around Wall 22 occurred 10 years ago.
"[The bill is] to make sure that it's done better in the future," Moen said. "So that we have projects that are done safely and efficiently."
New Jersey DOT expects Wall 22 to be repaired by Summer 2023, and the entire I-295 Connector project is expected to be finished by 2027.
New Jersey DOT declined to comment to Eyewitness News.
