The fatal collapse of a bridge isn't an isolated incident. Over time, the infrastructure of America just plain wears out.
"We just don't have enough inspectors and inspections," said William Ibbs, a professor of civil engineering at the University of California at Berkeley. "It didn't surprise me. It is a tragedy, but unfortunately it doesn't surprise me."
At least 79 people are injured and 4 have been confirmed dead after a bridge spanning the Mississippi River in Minnesota collapsed on Wednesday, according to several reports. Several cars were also trapped in the rubble.
To a large degree, the difficulty of adequately maintaining infrastructure is caused by the sheer scope of the task. "Did you know that there are over 600,000 bridges in the U.S.?" Ibbs said. "And there are also pipelines, roads, dams, schools."
More than during the 1990s, he said. Some were sudden, spectacular failures of commuter bridges that involved fatalities. The majority, however, were out-of-the-way bridges that often failed slowly, or at least in an observable way that gave people advance warning of danger.
But age and budget shortfalls are also factors.
"The age of the infrastructure in the U.S. is old. A lot of the highways and bridges are 30 to 35 years old," said Essam Zaghloul, CEO of Fiber Optic Systems Technology, also known as Fox-Tek. "The roads are old, and they aren't always safe." (The type of bridge that collapsed in Minnesota, an arch bridge, was popular in the 1950s, said Ibbs, but it was phased out when engineers came up with new designs that were cheaper to construct.)
The Toronto-based Fox-Tek has created a fiber-optic sensor system that monitors the health of steel structures. It primarily sells its systems--which can cost tens of thousands of dollars--to oil companies that want to prevent leaks in oil pipelines, or to other private sector clients. It has sold systems to monitor bridges and other public works, but has largely backed out of pursuing more of this business because most government agencies don't have the budgets to fund such projects.
"They try to manage the best they can with the funds they have," Zaghloul said.
The Fox-Tek system detects minute changes in the strain of a structure due to internal corrosion or other factors. The changes in the strain are forwarded via a fiber link to a ground station near the sensor. The data gathered is then converted mathematically into a predicted rate of failure.
The data then lets building owners schedule preventive maintenance.
It isn't just big structures such as bridges that have people worried. In Massachusetts in the last two weeks, officials have been scrutinizing manhole covers and storm drains after a driver was badly injured by a grate dislodged by a truck. Other incidents have since been reported in the greater Boston area, and crews are scrambling to weld the metal elements in place.
And it's not just public infrastructure that's at risk. Private facilities break too. BP got into hot water last year after pipeline leaks in Alaska. The leaks were attributed to corrosion and led to a multimillion-dollar cleanup.