Once again, a bridge

  • Article by: JIM FOTI , Star Tribune
  • Updated: September 14, 2008 - 7:26 AM

From afar, it may have looked only like a construction site. But through the seasons, it has been a world unto itself. And soon, it will all vanish.

hide

A giant crane mounted on a barge lifted a 198-ton concrete bridge segment about 60 feet over the river and into place on the south end of the bridge.

Photo: Joel Koyama, Star Tribune

CameraStar Tribune photo galleries

Cameraview larger

Soon it will all vanish.

The cranes and crews. The portable buildings. The power lines and fuel tanks that kept the massive equipment running -- and the concrete curing -- around the clock for nearly a year.

Its inhabitants always knew it was a temporary town, destined to give way to a surge of cars and trucks zipping across the river, most drivers oblivious to the complicated efforts that paved the way for their commute.

Outsiders watching the drama of the Interstate 35W bridge being rebuilt at breathtaking speed may have missed the scenes playing out on a more human scale on and around the emerging structure.

From afar, it may have looked only like a construction site. But through the seasons, it has been a world unto itself.

Fall 2007

The day after Halloween, they started to dig. This was no fertile farm field of winter wheat, no flower bed of bulbs. Enormous drills, some 9 feet across, churned up soil laced with man-made and geologic surprises. The huge augers, like something out of an ice fisherman's dream, contributed a droning bass line to the riverfront's new soundtrack. Wire cutters clicked and power saws whined. The beep-beep-beep of backup alarms was as persistent as crickets chirping. Occasionally, the rushing sound of the nation's most storied river slipped through this cacophony.

Three months earlier, this had been a death scene. The brown water claimed 10 of the 13 lives lost when the Interstate 35W bridge collapsed into the Mississippi River on Aug. 1, 2007.

Specters of that day lurked nearby in remnants of the old bridge's foundation and a crushed rail car. Just downriver, vast amounts of twisted green steel from the old bridge testified to the destructive force unleashed as it fell.

Reminders were not really necessary. Everyone rebuilding the bridge was keenly aware of the tragedy, eager to avoid any hint of repeat, intent on restoring faith in Minnesotans' ability to build. There were hard hats, steel-toed boots, fluorescent vests and even tether cords in case anyone fell down one of the shafts being drilled.

From the start, workers had to think in 360 degrees and three dimensions -- rutted mud pocked with cavernous holes at ground level, cranes and wires above, a forklift to the right, a truckload of rebar approaching from behind.

The earth itself was a big challenge. Water popped up in unexpected places, at unexpected pressures, and became contaminated on its way to the surface. Asbestos, thought to be from a demolished house, turned up in one spot. A former creosote plant was removed. People living near the site were warned to expect odors resembling hot asphalt or mothballs.

There was lots of danger, lots of work to do -- and lots of money to be made.

Winter

Ruddy-cheeked carpenters in flannel and fleece, seeking refuge from the 10-degree January air, tromped into a construction shack on the old 35W roadway near Seven Corners.

The temporary building was the only real refuge from the elements. It was starting to look lived in: a poster for a union-sponsored fishing contest and a wall clock compliments of Biffs, the portable toilet people, adorned the walls, and hints of barbecue sauce from lunch still smeared the table. The biffy just outside sported an electric heater, but that wasn't enough to reach anything like comfort in this weather.

Construction is no longer a three-season affair in Minnesota. The workers just tough it out.

Liquid concrete, on the other hand, needs to be cared for like a newborn baby -- highly sensitive to low temperatures, the formula needs to be just right. Diesel heaters and glimmering ductwork would put the warm air right where it was needed.

But before there could be concrete for the new bridge, there had to be wood, lots of it. Like Dickensian ghosts rattling chains, the carpenters could be heard before they were seen, their clamps, wrenches and hammers clanking together. They hammered and sawed for weeks, building wooden forms to exacting specifications to support thousands of tons of concrete.

Soon the casting yard began to look like a shipyard. Eight wooden ramps, each as wide as a lane of traffic and nearly the length of a football field, were arranged just north of Washington Avenue.

With the speed of a Gold Rush town, more temporary buildings sprang up. Four steel-sided "sheds" the size of mansions were heated to at least 40 degrees. They could be moved along the casting beds to wherever they were needed to protect the concrete from the elements. This is where the main span's 120 pieces -- each a trapezoid with wings -- were born.

Carrie Melius spent her Valentine's Day afternoon in the bracing air, dozens of feet off the snow-covered ground on the east riverbank. She was padded with winter layers, so the only sign that there were women toiling along with men on the bridge was the "Carrie" written across her white hard hat.

She was helping to build a "cage" from rebar coated with green to resist corrosion. Eventually it would be a pier with a fluted shape. Workers nicknamed the form for casting the top the "flowerpot."

Like nearly everyone at the construction site, Melius had a hurried air. Momentarily at ground level, she flipped through a large book of drawings of bridge parts, peering at a diagram indecipherable to an untrained eye. She figured out what type of rebar she needed to put where and quickly headed back up the pier.

Up the bluff, Frank Houle, a carpenter from Farmington, was working on a wooden panel the size of a double garage door. When he was finished, a crane picked up his "door" and began lowering it into the hole where an abutment would be poured. As Houle went down to guide it, the breeze picked up. His eyes fixed upward on the panel and a tether in hand, he looked like a cross between an outfielder and a lion tamer.

Spring

On the cusp of April, the Bohemian Flats area of the river gorge was still sepia-toned -- not a bud or leaf in sight. But the snow was gone. The only whiteness beneath the bare trees was ice from water seeping out of the ground.

"This is beautiful," said John Malz, a mechanic with a crane company, as he gestured across the river on a 47-degree afternoon. "If I had a fishing rod, I'd be over there all day."

He was one of only a few workers at the park, converted into a morgue for steel and concrete remnants of the old bridge and a staging area for pieces of the new.

Next to the river, a giant crane nicknamed Bohemian Blue was being readied to hoist precast concrete segments, which would make their way to the river's edge via truck, then be transported upriver by barge. A second crane -- a red one mounted on barges and dubbed Big Ben -- would do the heavy lifting at the main span. Tugboats Mary Ann and Katie Ann would stabilize the barges.

Up at the bridge site, eight massive concrete piers, their tops still clad in the black plastic that kept the "flowerpot" shape warm during curing, stood stiff as monuments at the water's edge, four on each side of the Mississippi. On both banks, the piers were backed up by platoons of steel poles.

This system of extremely sturdy scaffolding is called falsework. Erecting it is an art. Hammers pinged on the steel with a percussive twang, like some stringed instrument from a faraway land.

The site required a strange choreography from the workers. High above West River Parkway, forms for a 330-foot concrete section of bridge were lined with rebar. Four workers in fluorescent green, carrying rebar at least a dozen yards long, stepped in careful formation, lifting their feet like a child navigating an obstacle course of old tires. They executed a slow, synchronized turn before lowering the rebar into place.

The casting yard was humming. In one shed, the hatches on top were open to the sun, and concrete flowed in through hoses. Gray glop was manipulated with tools as simple as a hand-held trowel and as modern as a wand that used vibrations to knock out any air bubbles. The result: a precast segment.

A week before the fishing opener in early May, office workers at the University of Minnesota stared from their windows transfixed as a 198-ton bridge segment was lowered onto a 64-wheel trailer.

Carpenters, shedding their multiple layers, pounded nails into nearly completed casting beds. Engineers carrying surveying equipment walked past the nearly 6-foot-high wheels of the contraption that lifted the segments.

Segment 2 SB1 EXT rolled out of the yard. Bohemian Blue lifted it off the trailer and onto parkland, where it would await its final ride.

Summer

The bridge had become a tourist destination.

On Memorial Day weekend, hundreds of people peered through the fence on the 10th Avenue bridge trying to figure out how the mix of rods and cables secured each piece.

James Reid knew exactly how it worked.

Each of some two dozen bridge segments came with its own pre-attached piece of scaffolding. That's where Reid was spending his workdays, on a grate dozens of yards above the frothy river. The edges of the bundled cables were sharp enough to rip a shirt or skin. He wore thick gloves as he threaded cables deep into the bridge.

The main span grew from each bank toward the middle, like ever-elongating diving platforms. Thick-necked guys with tattoos bantered and maneuvered powerful jacks on the bridge deck.

Nearby, a silent world existed in the bridge's hollow girders. Within that "tunnel," a worker had, perhaps unintentionally, left a Hollywood-style mark -- two deep boot prints immortalized in concrete.

By early July, the two sides of the northbound bridge were only a few yards apart. A catwalk allowed workers to make a jubilant first crossing of the Mississippi. A few days later, a final wooden form was built in the space over the center of the river, concrete was poured and the two sides were united.

The world created to build the bridge began to shrink.

The bridge deck was still a hive of last-minute activity. Painters soared on 100-foot-long booms attached to barges. A median-making machine crawled along, concrete mush going in one end and a solid wall coming out the other. Anti-icing and lighting systems were installed and tested. Grooves were applied to the surface. Down below, landscapers laid grass on West River Parkway.

The people who built the bridge, and the temporary neighborhood where they often spent 80-hour workweeks, were about to disappear.

In the fraction of a minute it will take to drive across the new bridge, their efforts are worth remembering.

  • related content

  • The year of the bridge

    Saturday September 13, 2008

    It's been a little over a year since the collapse of the 35W bridge over the Mississippi. Starting in November,...

  • get related content delivered to your inbox

  • manage my email subscriptions

ADVERTISEMENT

Connect with twitterConnect with facebookConnect with Google+Connect with PinterestConnect with PinterestConnect with RssfeedConnect with email newsletters

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

 
Close