For carloads of Michigan families, an April weekend in 2003 began like any other. Their bags had been packed, and they were headed north on I-75, the major roadway leading from Detroit to the resort towns along Michigan’s northern coasts.
For some, that’s how the weekend seemed likely to end, as traffic on the freeway unexpectedly slowed to a crawl and began to back up.
Highway workers, meanwhile, were scrambling up ahead to deal with an emergency that many had never before experienced. A set of twin 73-in. by 55-in. corrugated metal arch pipes that crossed beneath the interstate near the town of Prudenville had
collapsed, first bringing one lane of the freeway down and then the other with it. The northbound lanes were closed for more than a week, and traffic had to be detoured along nearby roads while the culverts were replaced.
It wasn’t the first such drainage pipe that passed under a road to reach the end of its life, but the timing and enormity of the collapse put the spotlight on a hidden epidemic affecting roadways throughout Michigan and around the country. You might call it “culvert-itis.”
Age takes its toll
The culverts most vulnerable to collapse today are those constructed in the 1950s and 60s in conjunction with the Interstate Highway System. These culverts serve an important purpose. In Michigan, for example, they help prevent flooding in the state’s drainage basins by transporting rainwater runoff to Lake Michigan.
But now they’re collectively getting older. And as they have aged, many have grown corroded and developed leaks, especially in places where soils and groundwater are acidic. That segment of I-75, passing through the Backus Creek wetlands in Roscommon County, was one such place. When the soil enveloping the culvert enters these deteriorated pipes, it creates a void between the pipe and the road that, as demonstrated along I-75, can ultimately lead to catastrophic collapse.
In the April 2003 collapse, the Michigan Department of Transportation (MDOT) had little choice but to detour traffic, remove and replace the collapsed culvert and repair the roadway above it. It was a disruptive proposition that came with a hefty price tag—more than $100,000, not including the cost of delays.
“It was an emergency situation,” explained Chris Rupinski, pavement management engineer for the MDOT’s North Region. “We needed to act quickly. But we also needed to keep it from happening again.”
Scoping out the problem
Like its counterparts in many other states, the MDOT had no real way of knowing just how big a problem it was facing. Michigan has 83 counties, which its DOT groups into seven relatively autonomous regions, each of which is responsible for its own maintenance.
Any investigation of the condition of the state’s culverts would have to be performed on a regional basis. Even then, such an investigation would be a substantial undertaking, according to Jason Latham, region planning manager for the MDOT’s Southwest Region.
“We have thousands of miles of roads that are 40, 50 and 60 years old,” Latham said.
In the six counties making up the I-75 corridor in the northern part of lower Michigan, for example, inspectors videotaped hundreds of aging culverts to assess their condition. Along that one 12-mile stretch of freeway alone, investigators had already identified dozens of culverts that appeared to be approaching the end of their useful lives.
The inspectors’ findings raised more questions: What could the MDOT do to prevent another emergency? How would it pay for it, considering there was no established budget for such repairs?
“Our number one maintenance priority has traditionally been the upkeep of the pavement to ensure a smooth, safe driving surface,” Rupinski said.
Other maintenance dollars go toward tree trimming, guard rail replacement and other safety-related maintenance. Major culvert replacements, he explained, typically enter the picture during a complete highway reconstruction project, which involves tearing out the road’s sub-base and starting over, beginning with drainage. In those cases, designers typically call for the old culverts to be torn out and replaced with new ones.
Given the potential size and scope of its current problems, MDOT officials knew they needed a more economical, less disruptive alternative.
In some parts of the state, MDOT workers already had some success in repairing culverts using pipebursting and sliplining technologies. With pipebursting, the old culvert is shattered as a new pipe is pulled through it, with the pieces displaced into the surrounding soil. With sliplining, a new liner pipe is pulled into the existing pipe.
While generally effective on smaller diam. culverts—those 12 in. in diameter or less—these technologies proved to be less workable on the more critical, large diameter and elliptically shaped lines. For those lines, Rupinski, who had spent several years working in the Detroit area, had another plan.
“While working in Detroit, I became familiar with a cured-in-place pipe (CIPP) lining system called the ‘Insituform process,’” Rupinski recalled.
Developed by St. Louis-based Insituform Technologies Inc., the technology is used primarily by the wastewater industry to rehabilitate sewer pipes. It involves inverting a resin-filled tube into a deteriorated pipe. Hot water or steam is then circulated through the tube, curing the thermosetting resin into a new structurally sound pipe within a pipe.
Insituform’s CIPP technology, which had already been used to rehabilitate millions of feet of pipes throughout the world, appealed to the MDOT for several reasons. For one thing, the technology could be installed without major impacts on the road traffic above. It also could be applied to culverts of virtually any shape or size. That was especially important in Michigan, where any solution would need to meet the stringent environmental standards set by the state’s Department of Environmental Quality (DEQ).
The Michigan DEQ, for example, contends that a culvert’s original corrugated shape must be maintained so that native fish are able to travel through the pipe more easily. Because it molds to the original pipe, CIPP technology meets that objective.
Equally important, the technology can be installed rapidly; a typical segment could be completed in a day, and at a lower cost than what it would take to replace the existing culvert.
Getting down to business
The MDOT believed it had found the answer it was looking for. Just months before the April 2003 collapse, designers from the department’s Grayling Transportation Service Center had used maintenance inspections to develop a proposal for rehabilitating nearly 8,900 linear ft of culverts of varying shapes and ranging 15 to 73 in. in diam. under both the northbound and southbound lanes of I-75 in Roscommon County.
All they needed was the funding to implement it. That help came shortly after the collapse, when $3 million in funding was secured to proactively line the 73 deteriorated culverts that remained along this route.
Meanwhile, more trouble was brewing farther south along I-196 near South Haven, a popular tourist destination. The interstate was a four-lane freeway that ran along the state’s western coast; its traffic surged each weekend as vacationers made their way to summer cottages.
As the summer of 2005 approached, a maintenance crew noticed something peculiar. They patched a hole in the pavement one day. The next day, the hole had returned.
“The crew realized that there had to be a void beneath the roadway,” recalled Latham. “The question was: How big was it?”
The answer: Very big.
Twin 7-ft elliptical-shaped culverts crossed beneath the expressway at the point where the pavement was showing signs of distress. Further investigation showed that the culverts had become corroded, with water coming through the sides of the pipe.
“The fear was that, in a major rain or storm event, the road might completely collapse,” Latham said.
In a region that relied heavily on tourism, a road collapse could spell economic disaster. But so might the traffic backups and delays that a major repair effort might create.
To complicate matters, the culvert was located 15 to 20 ft beneath the roadway amid wetlands, raising additional environmental issues and questions about site access.
“We wondered how we could stage and construct this project so we would not impact the traffic above and the stream and wetlands below,” Latham said.
The answer, as it turned out, was by using the Insituform CIPP process to restore the structural integrity of the existing culverts.
After hydrology studies were conducted on the stream’s flow characteristics, the DEQ issued the emergency permit needed to make the repairs. Once the custom-made 7-ft liners were complete and transported to the site, work progressed rapidly. It took just three days for an Insituform crew to rehabilitate the twin culverts, with minimal disruption to the traffic passing overhead.
“Had we chosen to replace the culverts, we would have been required to build a temporary bypass bridge,” Latham said. “The entire process would have stretched on for months, and cost substantially more.”
The emergency repair proved to be good for the environment as well. Surveys completed after the culverts had been rehabilitated showed that the new culverts passed the DEQ’s design flows, with no increase in water backups.
Today, regional managers of the MDOT continue to identify potential candidates for culvert rehabilitation. In fact, many now consider it an important and necessary part of their preventive maintenance program.
“Like everywhere else in the country, there’s never enough money to do everything we’d like,” Rupinski said. “But when we can be proactive in identifying potential problem areas and making these repairs, it is always money well spent.”