State hopes to avert culvert calamity after man falls into sinkhole

Sergio Marquez fell into a sinkhole in May and lived to tell about it.

With the high waters of the Rio Grande surging below, he hung on for dear life until his rescue from the gaping hole that suddenly opened up in the sidewalk to the Main Street bridge in Los Lunas.

There were no signs that a decades-old culvert under N.M. 6 would fail that day, causing the sinkhole, said New Mexico Department of Transportation drainage bureau chief Burke Lokey.

And that’s got the DOT on a mission to ensure other culverts along the Rio Grande are safe, especially those along the river from about Bernalillo to Socorro.

Lokey said the DOT’s District Three Office is conducting a inventory of “just for those culverts, particularly from U.S. 550 down to U.S. 60 that are anywhere in the vicinity of the Rio Grande where we think there might be the same kind of issue. And we do, we think there’s probably quite a few.”

Locating the culverts is one thing. But inspecting the state’s corrugated metal culverts that are under water pose logistical hurdles and could be potentially costly.

“One of the things we have to figure out how to do is to isolate those culverts so we can inspect and get an idea of that kind of condition they are in. It’s going to be a massive project,” Lokey told the Journal. “I would not be surprised if we wind up spending half a million (dollars) just on that effort.”

Though shaken up by the experience, Marquez sustained an injury to his foot that keeps him from going to work. He and his son had been riding bicycles that evening when the sinkhole opened up.

Lokey said even though no one was killed that day, what happened was “pretty close to one of my worst nightmares.”

At the time of the incident, the DOT had been two years into a three-year project to inventory all the state’s culverts, which could number as many as 65,000 by the time all are tracked.

“I know it’s hard to believe the DOT doesn’t know where its own culverts are,” said Lokey, who became bureau chief in 2019. So far, the state has identified 30,000 or 40,000 separate points and is developing a risk rating system depending on their condition.

Such culverts aren’t required to be included in the state’s biennial bridge inspections. And that “can lead to catastrophic road failures if unmaintained,” according to an online description of the inventory project.

Aside from a partial statewide inventory in 2004, culverts in New Mexico have not been comprehensively inspected nor had their condition assessed, the project description stated.

Lokey said the state of New Mexico’s culverts has been a concern.

“It’s weighing heavily on our mind,” he said.

Aging culverts

After the May 13 incident, the DOT issued a $1.5 million emergency contract to repair the culvert underneath the sidewalk, which is 54 inches in diameter. The original culvert was some 70 years old, with 30-year-old extensions on both ends.

With high river flows and unusually high groundwater levels in the vicinity, the culvert is actually lower than the groundwater levels right now, Lokey said, “and that’s a big part of the problem. We think that’s part of what happened with N.M. 6.”

Crews have been de-watering the area to isolate the failed culvert. A battery of pumps has been pumping water that’s continuously flowing. The pumps are dumping the water over a levee and into the Rio Grande.

The maximum life of a culvert that small is about 50 years, but at that size “if it fails then you develop a big enough void under the roadway that you’ll have that kind of sinkhole condition,” Lokey said.

Concrete culverts will last up to 100 years. “But a lot of our corrugated metal pipes ... we start to see significant problems with them after 30 years. And an estimated 70 percent of the DOT’s culvert inventory is corrugated metal pipes, he said.

“We need to do this inventory and get the entire system set up so that we know where we need to prioritize our dollars.”

Prioritizing inspections

Around the state, there have been other instances where culverts have been the culprit.

In mid-March, the DOT closed N.M. 152, the Geronimo Trail Scenic Byway, due to potential roadway failure. “We had a culvert get blocked and it saturated the road and the road started falling off the the hill. That closed the road for two months,” Lokey said.

The DOT has a test project on New Mexico’s portion of Interstate 10, a 116-mile roadway between the Arizona state line and El Paso. Of 600 culverts identified, half are considered in moderate to severe condition.

“The majority of culverts were put in when they built the freeways, so they’re 50 years old now. When they started building the interstate systems in particular and lot of the road construction, corrugated metal pipe was pretty much least expensive option we could go with.”

Lokey said he hopes to spend the summer planning how to do the physical inspections of the river-area culverts.

“There’s no good technology yet that will let us see if the culvert is competent or structurally failing or to see if there’s corrosion going on. And I’m saying to my consultants, find me an option that will let us do that,” he said.

If not, Lokey said, the state will have to de-water the culverts, “and that’s extraordinarily expensive and hard to do.”

Lokey said less than 1% of culverts managed by DOT may warrant immediate intervention, “which still is a lot, but it’s not going to be the routine situation.”