Freeways After People
We built the freeways to serve our needs but they also need us.
Can you imagine life without freeways? How about life with freeways but without people? This is the premise behind the History Channel’s program, “Life After People,” which examines what would happen to various systems if there were no humans to interact with them.
For a segment airing in February, the channel interviewed District 7 Director Doug Failing to find out what exactly would happen to the freeways without vehicles to ride on them and Caltrans to take care of them.
“Freeways are not built to last 1,000 years,” Failing said. “Pavement is designed to last about 20 years, retaining walls and bridges are generally designed to last 60 years and major structures, such as the Vincent Thomas Bridge, are built to last at least 100 years.”
But, he qualified, that assumes Caltrans is constantly maintaining the system. “No piece of roadway, or anything that we build or own, is expected to survive without our continuous attention.”
Another element is the fact that our roadways were designed for vehicles. An obvious statement, but vehicles literally prolong a road’s life by, among other things, keeping weeds down. Otherwise, within a year, leaves would begin to build up along the freeway corridors, deteriorate, become mulch, and turn back into dirt. Roadways are also “great seed corridors,” Failing said. Wind drives the seeds, which settle in pavement cracks, are watered by rain, germinate and, without our intervention, very soon would become weeds, tall grasses and trees.
And don’t even ask what would happen if Caltrans wasn’t around after an earthquake hit. Our structures are built with a lot of reinforced steel to hold the concrete in place. Vertical steel inside the concrete sways during an earthquake, cracking the concrete but retaining the structure’s internal strength. However, the steel is then exposed and if we don’t come out and repair it, the steel starts to rust and lose its strength.
“Our freeways are designed not to collapse during an earthquake,” Failing said. “That’s our main design criteria.” However, it is assumed they will be damaged and that Caltrans will come to their immediate rescue. If we weren’t around, rain would invade the cracked concrete and rust the steel bar. When the second earthquake hit, the steel would ber weaker and less able to hold the structure up. “By the time you get to the third one, you can pretty much expect everything to come down,” he said.
Moving on to the Vincent Thomas Bridge, Failing explained the suspension system and how vital it is that the bridge be maintained and painted daily. If the paint were to peel off, salt and water would attack the steel and “within a couple of years, you’d be looking at those steel cables starting to snap.” After the first one goes, it puts more pressure on the others, so that within three-to five years, the entire bridge could collapse. And how long after the first cable snapped would the center span fail? “I think it would be a matter of months,” Failing said. “Personally, I’d make sure that cable was replaced immediately. If not, I’d turn and run.”
But a lot of what keeps the freeway system going happens underground. A number of our freeways are built below grade, so it’s critical that water flowing onto them be removed before it has a chance to collect. For that, we rely on a series of drainage inlets along the side of the road going down into a system of pipes that pull water away from the freeway. The pipes feed into to a pump house,containing up to five very large pumps, which work in sequence.
“As long as there’s electricity, they’ll continue to work,” Failing said. When the pumps finally break down, water will turn to lakes, which will promote plant growth and draw small animals. Freeways will, in fact, become animal corridors, as predators come to take advantage of prey and the great circle of life rolls on. Meanwhile, he added, “the concrete will continue to crumble until eventually it’s just a fine white layer over the dirt.”