John Deere, PING Collaborate for Big Hole-in-One

Hands-On Experience Key to Inspecting N.C. Bridges

Tue September 25, 2007 - Southeast Edition
Taft Wireback -NEWS & RECORD OF GREENSBORO



GRAHAM, N.C. (AP) The tools of Rick Allred’s trade are an extension ladder, a hammer, a measuring tape and two decades of hands-on experience.

If you think anyone who works with such basic tools doesn’t have a very important job, try again: Thousands put their lives in his hands every day.

Allred is a bridge inspector, a 24-year veteran of the state Department of Transportation. He is North Carolina’s main defense against the sort of tragedy that struck Minneapolis, where an Interstate 35 bridge collapsed at rush hour and killed 13 people.

“You always err on the safety side,” Allred said recently, tapping his hammer on the concrete and steel supports beneath a highway bridge over the Haw River. “We never take anything for granted. If I see something serious, we can close this bridge down in a hurry.”

That hasn’t happened often in North Carolina, but in years ahead, who knows? Nearly a third of the state’s bridges are rated subpar for one reason or another, and a large number built in the ’50s and ’60s are near the end of their reliable service lives.

“Water is the No. 1 problem,” Allred said, referring to the rain, snow and ice that attack bridges from top to bottom. “Drainage is the thing, keeping the water moving off the deck.”

Almost 13,000 full-fledged bridges connect here to there in North Carolina. Another 4,000 very large drainage pipes or culverts are classified as bridges and must be inspected with similar intensity.

Inspectors label 31 percent of North Carolina’s bridges “structurally deficient” or “functionally obsolete,” bureaucratic terms that don’t necessarily mean bridges are on the verge of implosion.

They do mean that significant maintenance, shoring-up, widening, redesign or outright replacement is needed, either now, soon or sometime later — all depending on the periodic inspections that Allred and his co-workers give each bridge.

Allred said he has seen only five or six bridges in his time with the DOT that required closure and immediate, drastic repair. One of them was found last week in Rockingham County: a bridge over U.S. 220 with a cracked steel beam.

“You could actually see through the crack,” he said. “They’re going to have to replace that beam.”

The secondary road over U.S. 220 is closed indefinitely at the bridge, pending repair. But the bridge is not an imminent threat to collapse, he said.

The bridge that fell in Minneapolis was a “fracture critical” bridge, prone to failure if just one key component failed, Allred said. Most bridges in the Triad have overlapping support systems, greatly lessening the odds for such catastrophic failure.

“Our bridges have redundancy, which means it would take a whole series of bad things to happen,” he said.

Allred and his partner, Tony Roberts, are one of 18 teams across the state. Their primary role is to examine each bridge in their territory every two years.

The state DOT also has special dive teams for underwater checks where needed.

Allred supervises 1,100 bridges in his district, which includes Alamance, Guilford, Caswell and Rockingham counties. He and Roberts are on a continuous circuit: bridges in Alamance County this week, Rockingham the next, and so on through the cycle, a never-ending slate of bridges due for a 24-month physical.

These days, bridges are built to exacting specifications, using blueprints designed with sophisticated computer technology. They are assembled using gigantic pile-driving and earth-moving equipment, sometimes guided by global positioning satellites.

Yet, once in use, their health and safety is left to a couple of guys using eyesight and basic hand tools?

That’s the way it is, and motorists are no less safe for it, said Don Idol, the state DOT’s bridge-inspection engineer.

“There are some complex tools out there that can be used for bridge inspection,” Idol said. “But for all their expense, they don’t give you much more than that good visual (analysis) and testing by a well-trained inspector.”

One recent weekday, Allred and Roberts started their second day of work on the eight-lane, Interstate 40/85 bridge over the Haw River just east of Graham.

The bridge is a patchwork of construction dating back 40 or 50 years and newer sections added as the road was widened.

The previous afternoon, Allred and Roberts had used their ladder to climb down from the bridge to a pair of catwalks directly over the river, where they could look under the bridge deck.

They found nothing seriously amiss but were concerned about an expansion joint that leaked from the deck to the supports below.

The joint — a flexible seal that lets the bridge expand or contract with changes in temperature — would need to be fixed.

They begin the second day by examining the concrete surface of the bridge, the part motorists drive on. Allred notes that car and truck tires have worn down the concrete deck somewhat, but he determines that it’s mostly normal wear, except for several potholes.

He spots some cracks in the concrete — not enough to be a concern yet. He’d be more troubled if he saw deeper cracking or a lot of “spalling,” pits and deeper scars in the concrete that give motorists a bumpy ride.

The first thing a novice notices standing on the bridge is the incessant traffic, its unceasing noise and the way all the hurtling cars and trucks make the bridge shake.

The DOT sometimes gets calls from people who walk across an interstate bridge for some reason and fear it is about to fall apart because of the shaking, Allred said.

“But bridges are supposed to shake,” he said. It’s the only way a structure can safely deflect all the traffic’s movement and weight.

On the bridge’s eastbound side, Allred checks out a puddle, a place where years of rain have worn an oblong depression into the shoulder near a drainage pipe that opens to the river 30 ft. below.

Allred measures the depression, still a little more than an inch deep, just as it was in 2005, the last time it was inspected.

This bridge had a satisfactory rating back then. So far, Allred said, he’s rating it six out of 10 points or “high fair,” a pretty good mark for a structure under such continually heavy use.

It takes Allred several minutes before there’s a break in traffic long enough for him to cross four lanes and examine the deck on the other side of the bridge’s eastbound half.

Then he waits a similar span of time before recrossing and making some notes on a field report. In his field’s major concession to modern technology, Allred does have a portable computer with access to previous reports on the bridge and a blank form for this year’s assessment.

But the traffic along the interstate is so dangerous and unpredictable, he prefers to be more maneuverable, leaving the computer in his truck and using a paper form to record initial observations.

Next, he and Roberts descend a rock-strewn hillside to the banks of the Haw, where they can look at the bridge’s underbelly and its network of concrete and steel supports.

They enter a dim, cave-like world where the traffic noises are muffled and the air is at least 10 degrees cooler.

This is where Allred uses the hammer, tapping on concrete and steel to check for weak spots.

In the concrete, Allred said, he is concerned about any signs of cracking or other wear. In the steel “H piles,” he looks for signs of rust.

“These piles look real good, no signs of scaling,” he said, referring to the flaking metal that would be a telltale sign of rust on the vertical columns.

He inspects at the water line for signs of “scouring,” damage caused by stream bed erosion that can sap the bridge’s stability.

Allred and Roberts finish their inspection below deck by climbing a ladder to the catwalk, where they can check the bridge’s suspension system. It’s a network of bearing plates, horizontal struts of concrete directly under the bridge that work like a car’s shock absorbers.

The inspectors work through a similar checklist under the bridge on the far bank, again finding nothing beyond normal signs of aging.

They also cast a long, weighted measuring tape from the top of the bridge at several points over the river — the same locations as in previous inspections — to make sure the stream bed has not suffered excessive erosion, which also could suggest dangerous weakening.

The measurements are consistent with previous inspections.

Allred’s new inspection report calls for fixing the leaking expansion joint and filling the potholes on the deck, removing some driftwood that has accumulated on the bridge and continued routine maintenance.

It’s one less bridge for DOT’s growing list of problem structures.

But as Allred knows all too well, that could easily change next time around.