It will take time to determine why the Interstate 35 bridge collapsed, so tragically, during the height of a Minneapolis rush hour on Wednesday night. But investigators will likely find that two factors contributed to its failure: age and heavy use. Bridge 9340 was constructed in 1967, 11 years after the launch of the Eisenhower Interstate System. Until it plunged into the Mississippi River, it served as a transportation lifeline for the growing Twin Cities population, carrying across its 14 spans many of the SUVs, cars and trucks that accounted for the 42 percent rise in Minnesota’s vehicle traffic from 1990 to 2003.
Age and heavy use are by no means isolated conditions. According to a report card released in 2005 by the American Society of Civil Engineers (ASCE), 160,570 bridges, or just over one-quarter of the nation’s 590,750-bridge inventory, were rated structurally deficient or functionally obsolete. The nation’s bridges are being called upon to serve a population that has grown from 200 million to over 300 million since the time the first vehicles rolled across the I-35W bridge. Predictably that has translated into lots more cars. American commuters now spend 3.5 billion hours a year stuck in traffic, at a cost to the economy of $63.2 billion a year.
It is not just roads and bridges that are being stressed to the breaking point. Two weeks ago New Yorkers were scrambling for cover after a giant plume of 200-degree steam and debris shot out of the street and into the air. The mayhem was caused by the explosion of a steam pipe, installed underground in 1924 to heat office buildings near Grand Central station. In January 2007, Kentuckians and Tennesseans woke up to the news that the water level of the largest man-made reservoir east of the Mississippi would have to be dropped by 10 ft. as an emergency measure. The Army Corps of Engineers feared that if it didn’t immediately reduce the pressure on the 57-year-old Wolf Creek Dam, it might fail, sending a wall of water downstream that would inundate communities all along the Cumberland River, including downtown Nashville.
The fact is that Americans have been squandering the infrastructure legacy bequeathed to us by earlier generations. Like the spoiled offspring of well-off parents, we behave as though we have no idea what is required to sustain the quality of our daily lives. Our electricity comes to us via a decades-old system of power generators, transformers and transmission lines—a system that has utility executives holding their collective breath on every hot day in July and August. We once had a transportation system that was the envy of the world. Now we are better known for our congested highways, second-rate ports, third-rate passenger trains and a primitive air traffic control system. Many of the great public works projects of the 20th century—dams and canal locks, bridges and tunnels, aquifers and aqueducts, and even the Eisenhower interstate highway system—are at or beyond their designed life span.
Scary stuff. Read the whole thing.
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