As tourists, commuters, ranchers and shoppers await the promised partial opening of the Blue Mesa bridge by July 4, “what-ifs” and “how-comes” continue floating around about the abrupt closure of the bridge 10 weeks ago.

The 1,500-foot-long span known as the Middle Bridge was closed when inspectors, acting on directives from the Federal Highway Administration, found a significant crack in a crucial weld on a bridge girder.

The bridge was closed to traffic that same day, creating commuter chaos among people who had to chose between detours of six or seven hours to travel between Montrose and Gunnison, a trip that takes about 75 minutes when U.S. 50 is open. Parents were separated from their school-age children, workers from their jobs and patients from their medical caregivers.

As surprising as the closure was for those U.S. 50 drivers, state and federal highway officials had known for decades that there could be problems with bridges, like Middle Bridge, that were constructed with a certain kind of high-strength steel that was welded on bridges using a technique that turned out to be faulty.

The FHWA in 1978 created a “fracture control plan” for such bridges and in 1995 made new welding methods a standard for all highway bridge construction. But the bridges stayed open in a sort of watch-and-wait mode.

In 2011, the FHWA issued a technical advisory warning about “fracture critical” bridges after the Sherman Minton Bridge over the Ohio River between Kentucky and Indiana suffered extensive cracking that year. The bridge was closed for more than five months for repairs.

That cracking on a major bridge sparked an awareness that bridges across the country built with the steel called T-1 might pose unique safety problems. The Middle Bridge was in that category.

The advisory to states pointed out that all bridges built with T-1 steel should be inventoried and regularly inspected using ultrasound to look inside the welds that were most prone to cracking. Those inspections identified another bridge with dangerous cracks in 2021. The Hernando de Soto Bridge across the Mississippi River in Memphis, Tennessee, had to be closed for about 2½ months for repairs.

Those major bridge closures led to more focus on T-1 steel, which turned out to be truly high-strength after it was developed in the 1960s, but to also have a previously unknown problem with brittleness. Welded joints on T-1 constructions tend to develop problems with cracking because hydrogen was introduced into the welds during construction — a practice that is no longer acceptable today. Hydrogen gas can build up in the metal of a weld, forcing breakdowns in the structure.

Nowadays, that problem is understood and mitigated with hydrogen control measures and test welds during bridge constructions.

Why was CDOT behind on inspections?

The Hernando de Soto Bridge problem prompted the Federal Highway Administration to follow its earlier advisory with a more strongly worded memorandum issued Dec. 13, 2021. That message directed all state highway departments to identify potentially problematic T-1 bridges by the end of March 2022.

Testing on those bridges and reports on the results of those tests were required to be complete by the end of March 2024.

Colorado missed those deadlines in spite of the memorandum stating, “these actions are critical to maintaining safety, avoiding similar closures of important structures, and the major disruptions that follow.” 

The highway administration granted Colorado an extension, according to a FHWA spokesperson, because federal law requires the agency to give states an opportunity to address noncompliance issues.

The spokesperson, who did not want to be identified, said “Colorado is currently doing that.”

There were reasons why Colorado slipped into noncompliance in the 2½ years since the memorandum was issued, according to Colorado Department of Transportation communications director Matt Inzeo.

The state agency initially had to wade through state and federal transportation requirements as bridge engineers went on the hunt for problematic bridges, Inzeo said. Meeting those enhanced requirements took place outside the scope of the state’s normal bridge inspection schedule.

CDOT completed an initial review of all 8,450 bridges in the state in early 2022.

After bridges that potentially used T-1 steel were identified, CDOT then had to sift through the detailed construction documentation to determine if they could be eliminated from the list that would require further testing.

That meant digging into details of how bridges were welded together and if they were constructed using the methods that are no longer considered safe. They found five potentially problematic T-1 bridges.

Further inspection showed there were three that fit the federal criteria for further action — two over Blue Mesa Reservoir and one in Bent County. The Bent County bridge is small and low to the ground and was easily and quickly inspected. It was deemed to be safe in 2023.

The Blue Mesa bridges were a whole other matter. Doing the extensive federally mandated testing required extraordinary measures for the Middle Bridge. The Middle Bridge is 1,500-feet long and has 12-foot-high girders that are as long as football fields. The bridge sits over some of the deepest water in the state.

Initially, the department had to conduct load analysis on the U.S. 50 bridges to determine what kind of weight the semitrucks, tourist trailers, timber flatbeds and regular traffic were placing on the structures. Load requirements for the bridges have increased since they were built.

A full phase of testing on the Middle Bridge was approved in September 2023. That was planned to include stripping paint and peering into the bridge structure with ultrasound devices — in the same way a doctor might examine a damaged joint.

CDOT could not do the specialized inspecting and testing in-house. It contracted with Benesch, a Denver engineering firm, for that. That took six months to get underway. Benesch was not able to inspect the critical butt welds on the bridges until April because it was not possible to carry out the testing during the bitter, blustery winters that Blue Mesa is notorious for.

The ultrasound equipment that uses gels to conduct the sound waves through the metal would not work in frigid temperatures. Workers dangling from the sides of the bridge would not be safe in winter storms.

Chaos or success?

Inspections finally began April 8. Ten days later, when a Benesch employee found the now-infamous 3-inch crack that spelled big trouble, the bridge that had stood for 61 years with its questionable construction was deemed by state and federal highway authorities to be dangerous enough to warrant an immediate closure.

Highway authorities who have seen the test results have not argued with that decision.

But critics of the response, who asked not to be identified, called CDOT’s early response “chaotic.”

CDOT brought in Kiewit Construction to handle planning and to carry out the bridge repair work as well as help with detours. Michael Baker Engineering was hired to design the bridge repairs that Kiewit is constructing.

John Cater, a division administrator for the FWHA, said even though Colorado did not meet the deadline for T-1 bridge inspections, once the problem was identified, “I think they moved pretty aggressively to address it.”

Cater noted that the Blue Mesa bridge has presented “a unique challenge” because of its size and its location over deep water.

“In some ways this is a success story,” Cater said. “The crack was found, and it was closed before anything happened.”

Inspectors for CDOT are still in search of cracks. Initial testing has been done on Blue Mesa’s Lake Fork Bridge, but more in-depth testing will not take place until after the Middle Fork Bridge, 2 miles to the west, is patched up with giant steel plates and partially opened.

CDOT Region 3 director Jason Schmidt said testing may require some shutdowns on the Lake Fork Bridge, but he expects it to move much faster using techniques learned under duress on the Middle Bridge. He said if significant cracks are found, CDOT will be ready to quickly do repairs.

The department is also getting ahead of a possible Lake Fork Bridge shutdown by preparing a county road as a detour. That road would be in addition to the county road that is serving as a detour for the Middle Bridge.

The Colorado Transportation Commission has already approved $20 million for all the testing and repairs on the two bridges as well as work on dirt-road detours. CDOT has requested another $10 million.

Once the T-1 bridges are fixed, Colorado has hundreds of other bridges in need of repairs. A Federal Highway Administration listing of poor-condition bridges shows that Colorado has 437. Another 5,370 out of 8,954 bridges in the state are considered to be only in fair condition.

“We have to continue to be vigilant,” Cater said.

Inzeo also has a silver-lining attitude toward the devastating U.S. 50 bridge closure.

“The anomalies in the welds have existed since the bridge was originally constructed, and we have 61 years of lived experience and bridge use without issues,” he said. “Still, we are grateful that the inspections have identified these issues before any incident occurred, and the fixes that are now underway will restore the ability of these bridges to carry the traffic that they did before.”

No highway authorities contacted for this article would say that — if the Middle Bridge problem had been found 13 years ago when T-1 steel welds were first definitely identified as a danger, or 2½ years ago when states were put on alert to find and fix T-1 bridges — the crippling closure could have been avoided. They are focused on being thankful that there were no calamitous failures.