Unstable Ground: Lessons from the I-80 New Jersey Sinkhole Saga

In Wharton, New Jersey, a routine repair operation turned into a civil engineering crisis when a new 15-by-15-foot sinkhole suddenly opened on Interstate 80 in mid-March 2025. This was the third such collapse in a matter of weeks—each one revealing a more complex and concerning truth: the ground beneath the highway is unstable, riddled with voids from long-abandoned iron mines dating back over a century.

Initial investigations show that collapsing mine shafts and voids—forgotten relics of New Jersey's industrial past—are the root cause of the ongoing instability. The first sinkhole was reported in late December 2024, with others following in February and March. Each new void triggered closures, emergency repairs, and widespread commuter disruption across Morris County.

With both directions of I-80 closed at Exit 34, traffic has been rerouted through local roads never designed for such heavy use, impacting residents, small businesses, and regional commerce. Meanwhile, engineers are racing to assess the extent of underground risk. According to the NJDOT, testing has identified at least 90 locations along the corridor that now require further inspection and stabilization.

Governor Phil Murphy has declared a state of emergency, and national geotechnical experts have been brought in to support efforts. Congressman Tom Kean Jr. emphasized the need for federal resources, citing massive economic disruptions and safety risks: “We must work across every level of government to reopen I-80 safely and swiftly.”

Sinkholes are not new in civil engineering, but the I-80 incident is a stark reminder of what happens when historical geology meets modern infrastructure. Engineers face the challenge of not only repairing visible damage but understanding the hidden legacy of mining in the area. As repairs unfold, they involve not just surface work but also complex grouting operations, core drilling, and geophysical surveys to detect hidden voids before they collapse.

The interstate, a vital artery for regional and national logistics, is expected to remain closed for months. And while no one was injured in these incidents, the risk of future sinkholes looms large—raising critical questions about how the U.S. manages its aging infrastructure.

Moving forward, this case may serve as a catalyst for other states to revisit how legacy industrial activity influences current-day civil projects. It's a wake-up call for geotechnical engineers, urban planners, and transportation officials alike: sometimes, the most dangerous threats lie beneath the surface.                                                                                                                                  

Check out the following video, discussing the sinkhole crisis over the Route 80 in New Jersey.