Culvert Grouting: How Two Culverts Benefited from Polyurethane Grouting

In 2016, Hurricane Matthew left a path of destruction in its wake up the East Coast. North Carolina was hard hit by storm-related flooding. Waters continued to rise in the days after the storm as flood waters receded elsewhere, draining to lower points. That included Lumberton, North Carolina, located 70 miles southeast of Wilmington, in the coastal plains region of the state.


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Approximately six miles north of Lumberton, there is a triple barrel box culvert under I-95. Each barrel is 12 ft x 12 ft, so essentially there is a 36-ft wide culvert under the highway. Storm-related flooding caused a major washout underneath the inlet end, leaving a huge void, threatening the culvert’s integrity. That, in turn, would lead to a compromised highway in the long run. The North Carolina Department of Transportation (NCDOT) completely shut down I-95 there for a time due to flooding. When flood waters receded, just one lane opened; the lane above the void remained closed.

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Finding a Solution

NCDOT tried filling the void in-house with cementitious grout over a weekend, which was not successful. That Monday, NCDOT officials hired, Applied Polymerics, of Mt. Airy, North Carolina, to solve the problem. The contractor opted to fill the void with Prime Flex 985 LX20 Fast, a highly expansive two-component polyurethane. The Fast formulation reacts in 12 seconds vs. 68 to 70 seconds and reaches full rise at 65 to 85 seconds.

“We needed to use LX20 Fast because we needed it to set up quickly, otherwise the water current would have just washed it away,” said Scott Kammerer, director of Applied Polymerics’ Infrastructure Division. “We like 985 because of its structural capabilities.”

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Applied Polymerics lived up to its promise: “Whatever It Takes.” That evening one of its crews picked up material from Prime Resins, which was just east of Atlanta, Georgia, and started work on Tuesday morning with a second crew.

injecting grout

A crew member injects grout into a void.

Complicating Factor

The flood level of the water created a nearly impossible work site, essentially an underwater grouting job. To preserve as much material as possible and to ensure the grouting technicians didn’t have to work in chest-high water, Applied Polymerics installed a cofferdam of corrugated pipe and secured the pipe with joists against the culvert ceiling and sealed it at the bottom.

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RELATED: Culvert Rehab Passes Hurricane Matthew Test

“We worked closely with the DOT,” said Kammerer. “We worked with their dive team on the cofferdam and the DOT provided a crane. Crew members from the DOT were there nearly all the time we were. It was a good partnership.”

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Crews worked around the clock Tuesday until Friday. An NCDOT engineer allowed both lanes to open for the weekend and give crews a respite. Officials closed one lane again Monday afternoon so grouting work could continue. Crews worked around the clock again until completion on Wednesday.

The void was more than double the originally estimated 80 cubic yards. In the end, it measured between 180 to 200 cubic yards. Prime Resins ensured crews had the material they needed when they needed it.

“The manufacturer came through with material as needed — it was always there on time,” said Kammerer.

Crews filled the void and NCDOT officials opened I-95 to normal traffic.

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Issues of wash-out under culverts are a common occurrence. Another customer of Prime Resins had a similar problem requiring culvert repair in a tidal creek. Again, the wash out underneath the culvert created a need for soil stabilization and void filling. This was also solved using Prime Flex 985 LX20.

Winchester Creek flows through a box culvert running underneath U.S. Highway 101 along the Oregon coast. The seal had broken away from a joint about 70 ft down the culvert and the creek was washing the soil from behind the culvert. This erosion was undermining the road bed.

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A.C.C. owner Andrew Kuperstein and his crew drilled holes through the culvert wall and injected Prime Flex 985 LX 20 through 6-ft pipes to fill the voids, stabilize the soil and prevent future erosion. The 985 is a two-component polyurethane that expands and cures to form a closed cell structural foam with excellent compressive strength needed under the highway.

RELATED: North Carolina Utility Engages in Award-Winning Rehab and Bypass Project

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The site is on a tidal estuary, so work could only be done during low tide, which meant starting at 5 a.m. for a few hours and again at 7 p.m. for a few hours. An added wrinkle was a generator malfunction that prevented them from using their pump for part of the job. Fortunately, the Prime Flex 985 is a versatile product that they could batch mix and pour into the joint.

“The product worked like it’s supposed to,” said Kuperstein. “It’s a nice product to work with; it’s nice that it doesn’t have to go through the equipment.” The job was a success and Kuperstein has been asked to go back in the summer and seal a crack he discovered on the other side of the culvert that is starting to wash out. For that project he’ll use Prime Flex 900 XLV and the activated oakum technique to seal the crack.

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Kevin Anthony is with Prime Resins.

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