Officials offer update on massive I-40 repairs

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Officials offer update on massive I-40 repairs

The roller compacted concrete is being layered along the embankment to stabilize the highway. Kyle Perrotti photo

The project to repair the eastbound lanes of I-40 washed away in Haywood County during Hurricane Helene is progressing on-time, but the heavy lift has really just begun. When Helene tore through Western North Carolina in 2024, it inundated the embankment supporting the highway so vital to interstate commerce, washing away about a million cubic yards of rock and dropping the eastbound lanes into the water below.

It was a miracle no lives were lost on that stretch during Helene, but it did leave the state with a lengthy, expensive repair that would require innovative techniques never deployed in a state highway project.

When determining the best design for what has become the biggest project in NCDOT history, hydrologists performed a detailed analysis of not only how high the river peaked but also its flow rate. The magnitude of the flow is the concern in this case and not how high the water goes.

For the first phase of repairs, Wright Brothers Construction and GeoStabilization International shored up what was left of the eastbound lanes and created the temporary safe passage motorists are using now. To stabilize the land under the road, crews installed 128,000 square feet of soil-nail walls anchoring the slopes and are covered with a thick layer of shotcrete. Sensors were installed in the 10 affected areas to detect soil movement under the road. If there’s even the slightest shift, an engineer is alerted via text message and email, and the severity of the problem and whether there are any imminent safety hazards is assessed.

During a media tour of the construction site near the Tennessee state line last week, state officials and project supervisors said the project is scheduled to be completed — or at least close enough to fully open both the eastbound and westbound lanes — by fall 2028. It is expected to come in at about $1.8 billion, 90% of which should be reimbursed by the federal government. Until that point, motorists will see one slow-going, narrow lane in each direction through the gorge.

One of the techniques new to NCDOT is the use of roller compacted concrete. The first step in producing roller compacted concrete is to source the rock. In this case, materials are blasted and drawn from a site just across the river in National Forest Service land and transported across temporary bridges. Project Manager Blake Sobiesky with the contractor RS&H said that using rock just across the river instead of at sites several miles away is saving taxpayers about 30%.

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Engineer Blake Soblesky talks to members of the media. Engineer Blake Soblesky talks to members of the media. Kyle Perrotti photo

Last June, NCDOT announced that out of seven potential spots to dig into the earth, it had selected a 33-acre site from which to draw the rock and a nearby 11.5-acre site where overburden material will be stored. The overburden material — rocks, sand and dirt hauled out of the construction site during the project — can be stored and reused in other phases later on. Soblesky noted that the project is also using a large portion of the 1 million cubic yards of material that fell from the highway and embankment into the river during Helene. These moves mitigate the overall impact of the project on surrounding national forest land.

“That material was used to make our causeway to give us access to the whole project, and some of that material will be used to repair the borrow site when we’re finished, to fill it back in,” Soblesky said. “Additionally, we have around 300,000 cubic yards of overburden soils, loose rocks that aren’t competent and have stripped from the borrow site and stockpiled. That material will then go back in to help reforest, build back the borrow site and build back the slopes.”

The rock sourced from the borrow site, mostly granite and gneiss, is transported via the specially constructed six-mile causeway below the highway to a nearby area replete with heavy machinery affectionately referred to as “rock crusher city.” The rock is processed into a fine material that is turned into the concrete, which is applied and compacted using heavy-duty rollers.

“Depending on the stockpile and how fast you need the material, the rocks can go from the borrow site to the project as final concrete and a day, or it could be stockpiled for continuous use,” Soblesky said.

The process of applying the roller compacted concrete began in February. As of now, about 4%, or 31,000 cubic yards, enough to fill 10 Olympic-size swimming pools, has been used. The roller compacted concrete is laid in 12-inch slabs that will make up sections up to 30 feet thick and 70 feet high. To ensure structural integrity, those sections are installed in 4-foot-tall steps, meaning the embankment will look something like large concrete steps. Once the roller compacted concrete is installed, voids between those structures and the existing embankment will be filled with additional rock from the borrow site.

Rocks brought from the quarry are processed into a gravel pile. Kyle Perrotti photoRocks brought from the quarry are processed into a gravel pile. Kyle Perrotti photo

The advantage of roller compacted concrete is that it’s dense and bonded, meaning unlike the previous rocks — some as big as boulders — that made up the embankment, it won’t be subject to erosion during heavy flow events.

According to NCDOT Construction Engineer Josh Deyton, the next step is to begin installing interlocking pipe piles, which will further shore up steeper embankments. That should begin next month. Deyton noted that the use of roller compacted concrete and interlocking pipe piles are new territory for the state.

“The amount of roller compacted concrete that we’re using on this project is one of the largest roller compacted concrete projects in the US,” he said.

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