ASCE NJB & GTG: NJDOT Rt. 80 Abandoned Mine Subsidence Emergency Response

Speakers:

Dr. Mohab Hussein, PE - NJDOT

Brian Felber, PE - HNTB

Virtual Presentation

On December 26, 2024, a sudden mine subsidence event beneath Interstate 80 at Mile Marker 34 in Wharton, New Jersey, triggered an emergency response to protect public safety and preserve a vital transportation corridor. I-80 is a critical east-west artery in northern New Jersey, carrying more than 114,000 vehicles daily. The closure of both eastbound and westbound lanes—necessitated by three successive subsidence events over a 200-foot stretch—posed significant risks to motorists, disrupted regional mobility, and impacted local communities and commerce.

The New Jersey Department of Transportation (NJDOT) led a rapid multidisciplinary response to assess the threat and

restore safe travel. The site, underlain by the 18th-century Mt. Pleasant mine, presented complex geotechnical challenges due to undocumented mine geometry, deep voids, and glacial overburden susceptible to raveling. Geophysical techniques including ground penetrating radar, microgravity, MASW, and downhole sonar were performed to map subsurface conditions and identify potential failure mechanisms.

With public safety as the top priority, HNTB designed and implemented an emergency stabilization system: a micropile-supported concrete slab spanning the mine-impacted zone. This solution allowed the phased reopening of I-80 within six months, minimizing long-term disruption. In addition, real-time instrumentation including extensometers, tiltmeters, and shape acceleration array were installed to monitor performance and confirm continued safety.

1 PDH pending approval