Exact Cause of I-40 Sinkholes Unknown

GARNER, N.C. — State Department of Transportation engineers said Monday that they do not know for certain what caused three sinkholes that shut down a six-mile stretch of Interstate 40 for several days.

Contractors working for the city of Raleigh on a wastewater pump project from Garner to Raleigh noticed on Friday evening that there was a dip in the roadway beneath the eastbound lane of I-40 at mile marker 308, then saw gushing water under the highway.

DOT crews shut down the roadway from U.S. Highway 70 to N.C. Highway 42 to fix two sinkholes discovered Friday. On Sunday, they found a third sinkhole about 25 feet deep, and that delayed I-40's reopening until 5 a.m. Monday.

Raleigh Assistant Public Utilities Director Robert Massengill said Monday that the crew's work involved digging and crossing sewer liners under several roads, but said he did not think workers made a mistake.

"It appears to be related, but we don't know if there was an existing problem already that we exacerbated," he said.

DOT engineer Chris McGee said workers hit something but that road crews did not know exactly what they hit. He also said that just because the contractors found the problem does not mean they caused it.

"It could have been something that's been hiding there for years," McGee said. "It may never have been a problem, or it could have been a problem sometime over the next few years."

McGee said the road is permanently stabilized, and at this point drivers should only notice a slight dip when they cross the uneven pavement.

"There's nothing to be concerned about from a safety standpoint," he said.

The total cost to fix the sinkholes could be more than $20,000, officials said. It is unclear if the DOT or the city of Raleigh will pay for the damage.

"There has not been a whole lot of finger-pointing going on," Massengill said. "So far, it's been mostly proactive in getting it fixed."