New Jersey transportation officials had concerns about Interstate 80 sinkholes as far back as 2009, when they conducted a construction project to reinforce an abandoned mine near a section of the highway that’s had sinkholes and other problems during the past two months.
The 2009 project was proposed to address sinkholes and collapses in the Huff Mine which a project description said was in the vicinity of Exit 34 in the Wharton area of Morris County.
A state Department of Transportation description said the project was to address cave-ins and other issues in the abandoned iron mine that is in the area of the most recent sinkholes on I-80 East.
“NJDOT had a project that was completed in 2010 that stabilized the right lane and shoulder of I-80 eastbound before Exit 34 and enhanced the foundations for light poles and an overhead sign structure,” said Stephen Schapiro, a DOT spokesperson. “The improvements made in 2010 remain stable.”
According to Mineat, a mine data website, the Mount Pleasant Mine was located at next to I-80 East in Wharton and was identified as the mine that caused the December 2024 sinkholes on the highway.
The website also includes photo of the 2009 DOT project seen from Main Street in Wharton, next to I-80 East. The Huff Iron Mine is located adjacent to I-80 East.
That project was proposed to address “ongoing subsidence” (cave-in) issues related to the abandoned Huff Mine, which is located under I-80, at MP 33.6.,” said a 2009 DOT notice to bidders.
“Numerous mine shafts have been mapped within the area, one of which appears to be undergoing crown pillar failure, which is causing sinkholes and roadway subsidence,” it said. A crown pillar is a section of load-bearing rock in between two mining operations.
The project involved constructing a series of concrete slabs to structurally bridge over an area of 310 feet by 23 feet west of the Main Street underpass structure in Wharton that the I-80 East deceleration and right lanes go over, according to a project information description.
The work also included enhancement of an overhead sign foundation and light pole foundations through the installation of micropiles. They are multiple steel bars or pipes that are 5 to 12 inches in diameter drilled into the ground as deep as 200 feet that can support up to 200 tons of weight.
An electrical resistivity system, consisting of sensors and a wiring loop, was installed under the slab. That system provides the ability for testing if it were required to detect any voids that may develop.
That work was done slightly west of Exit 34 in Wharton. In December, a sinkhole opened up in the right lane and shoulder of I-80 East between Exit 34 and Route 15.
Another depression that was 75 feet away from that site opened into a sinkhole in February, which currently has the eastbound lanes closed.
Those lanes remain closed as DOT crews test for and fill voids detected under the highway with grout, which spreads into any voids and firms up the base of the road.
A significant void identified last week underneath the center lane of I-80 East has been stabilized, officials said. However, additional repair work is needed, and the scope of those repairs is still being determined.
“As the drilling and grouting work continues, we are stabilizing I-80 eastbound and narrowing in on the area that will require a more lengthy repair,” said Francis O’Connor, state Transportation Commissioner. “Once we have a better understanding of the subsurface conditions, we can finalize the design for a repair.”
As of Wednesday, 82 locations have been drilled, and 57 locations have been filled with grout, officials said. These areas are not all voids, but locations requiring investigation. The number of locations that require further investigation may be adjusted as work progresses.
At this time, it is difficult to determine an exact completion date, officials said.
Traffic on I-80 East is still being detoured at Exit 34 in Wharton, and drivers are being asked to get off earlier at Exit 28 to use Routes 46 and 10 as alternates.
Stories by Larry Higgs
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Larry Higgs may be reached at lhiggs@njadvancemedia.com. Follow him on X @CommutingLarry
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