Chapter 9 - The Anatomy of a Bridge
The true freeze hit on the night of November twelfth.
The thermometer outside my study window on Lake Shore Drive read four below zero at midnight, dropping to fourteen below by four in the morning. The wind came off the north basin like a pack of wolves, howling through the steel cables of the suspension bridges, turning the waves of the lake into jagged, mountainous ridges of green ice that slammed against the concrete seawalls.
At five-fifteen, my private line rang.
It was not Calder. It was the commissioner of the Department of Transportation.
“David,” the commissioner said, his voice ragged, competing with the roar of industrial blowers and diesel engines in the background. “The Michigan Avenue bridge. The south leaf won't drop into the lock. The morning commuter traffic is already backed up to Grand Avenue. The mayor’s office is screaming. Your firm signed off on the trunnion overhaul in August—what the hell is holding the pin?”
I stood in my kitchen, wearing my wool robe, looking out at the black, frozen lake.
Beside me, Sophie was sitting on the island stool, her small hands wrapped around a mug of warm milk, her eyes wide in the predawn darkness.
Maren stood by the refrigerator, fully dressed in her heavy field jacket, her work boots laced to the top eyelet, her composition book tucked under her arm.
“Put it on speaker, Mr. Cole,” Maren said.
I hit the button.
“Commissioner,” I said. “Describe the clearance on the south bearing.”
“The bearing is fine!” the commissioner shouted over the phone. “We put two hydraulic jacks on the counterweight rack! It won't budge three-eighths of an inch! The drive motor is pulling double the amperage and the safety clutch keeps tripping!”
Maren stepped up to the counter, her voice cutting through the electronic static like a cold chisel through lead.
“Turn off the jacks,” she said.
A pause on the other end of the line. “Who the hell is that?”
“Turn off the jacks, Commissioner,” Maren repeated, her cadence unhurried, immovable. “You’re driving the pin into the housing. The river temperature dropped eight degrees in the last six hours. The south trunnion shrank 0.4 millimeters, but the limestone balance weight on the upper chord is pulling the shaft three degrees out of true.”
“Who is this?” the commissioner barked.
“It doesn't matter who she is,” I said into the phone. “Listen to her, or you’re going to shear the main drive shaft before six o'clock.”
Maren leaned over the phone.
“Get two propane weed-burners from the track maintenance shanty at the CTA,” she ordered. “Don't heat the pin. If you heat the pin, it expands and locks the bearing permanently. Heat the cast-steel collar on the outer housing. Thirty minutes of continuous heat on the lower quadrant while you spray the inner pin with liquid nitrogen from the utility truck. When the clearance opens two millimeters, the south leaf will fall by gravity. Don't touch the motor.”
Silence hung on the line for five seconds.
“If this doesn't work, David,” the commissioner muttered, “your firm’s bond is forfeit by noon.”
“It will work,” Maren said. “Check your geometry.”
She tapped the red end-call icon on my screen.
The penthouse was silent again.
Sophie looked up from her warm milk, her dark brown eyes reflecting the small amber light from the microwave clock.
“Will it open, Maren?” Sophie asked.
Maren walked over to the island, pulled a stool out, and sat down beside the nine-year-old child. She reached out with her bare, scarred hand and gently turned Sophie’s spiral pad so it was squared with the edge of the granite counter.
“It will open,” Maren said. “The metal doesn't have a choice. It has to obey the heat.”
May you like
She picked up Sophie’s pencil.
“Now,” Maren murmured, tapping the lead against the clean white paper. “Let’s look at the third problem on page ninety-one. The one where they tell you the bridge is impossible.”
