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On the morning of March 25, 2021, a retaining wall failed along an under-construction segment of I-295 southbound in Bellmawr, NJ, that is part of the New Jersey Department of Transportation’s (NJDOT) I-295/I-76/Route 42 Interchange project. The failed structure, designated Wall 22, was a 25-ft (7.6-m) tall Mechanically Stabilized Earth Wall (MSEW) built atop a 27-ft (8.2-m) cut and partially backfilled 2H:1V slope. During construction, the original ground surface was excavated below the planned MSEW base elevation, and Rigid Inclusions (RIs) were installed to provide vertical support for the wall. A Load Transfer Mat (LTM) was placed on top of the RIs, with approximately 5 ft (1.5 m) of sand between the LTM and wall base. The wall failed about 2 years after its initial construction. In response, a post-failure study was completed that included additional geotechnical borings, cone penetration testing, field and laboratory testing, and observations during wall deconstruction. These efforts, along with data from pre-construction geotechnical investigations and construction records, formed the basis for the authors’ analyses of the Wall 22 failure. Independent Limit Equilibrium (LE) slope stability analyses indicate that elevated groundwater levels, higher than those assumed in the original design, contributed significantly to the failure. This finding is consistent with field measurements and observations, as well as a post-failure drone survey that documented wall and slope deformations. To further investigate the failure mechanisms, additional analyses were performed using FLAC, an explicit finite difference continuum modeling program. The numerical model provides a more detailed representation of the wall system, including the RIs, LTM, and MSEW, than can be achieved with LE. The analyses demonstrate that while the unreinforced RIs had adequate axial capacity to support the vertical loads, they provided limited lateral support. Ultimately, the numerical analyses corroborate the conclusion that the wall collapsed due to porewater pressures in the underlying clay foundation soils that were significantly higher than anticipated in the original design. These findings underscore the importance of accurately accounting for groundwater conditions and the complex interactions between geotechnical and structural components in the design and analysis of earth retention systems. The analyses also highlight how LE analyses combined with advanced numerical methods can provide a more complete understanding of wall stability and failure mechanisms than provided by LE analyses alone.