May 2006 ISSUE

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KEYSER FILE

A Closer Look At Bridge Wear

BY TOM KEYSER
Freelance Columnist

We’re quick to point the finger at provincial government departments when we suspect they’re lying down on the job. So it’s only fair to acknowledge good work when it comes to our attention, right?
Don Hamilton, P.Eng., certainly feels that way.

He does concede a bias — one of Mr. Hamilton’s clients, Alberta Infrastructure and Transportation, has saved provincial residents a bundle in tax dollars by taking a proactive approach to highway bridge maintenance.
Apparently the Consulting Engineers of Alberta agree. CEA judges presented an Award of Merit to Mr. Hamilton and the Edmonton-based bridge deck testing crew at CH2M HILL for their proficiency at spotting corrosion in bridges around the province.

As project manager, Mr. Hamilton is poised to lead his five-member crew back to the field, under terms of a three-year contract with the transportation ministry. He and his team will evaluate some 120 bridges between mid-May and Labour Day.

It may be restating the obvious, but Mr. Hamilton notes: “During the winter, we dump an awful lot of salt on our roads and bridges. And when those chlorides seep through the concrete and interact with the rebar, that’s when we get corrosion.”

Solution: systematic evaluations that enable the deck testers to examine as many as 600 concrete bridges every five years by means of copper sulphate electrode testing, among other methodologies.

Beating up bridges Being a bridge is a tough job — and CH2M HILL knows that finding corrosion early is a great money saver.

Seeing the Unseeable
These methods are remarkably efficient. They allow the engineers to accurately forecast the extent of deterioration years in advance. Such techniques also enable the experts to pinpoint optimum times for bridge deck maintenance and rehabilitation.

“We can detect problems before any visible signs appear on the bridge,” says Mr. Hamilton. “That makes it an economical fix.”

As Mr. Hamilton reasons, an ounce of prevention is worth a pound of cure. No question, this regimen of early detection and repair saves the province millions. It’s much more cost-effective to implement relatively minor repairs than to tackle the job after more serious deterioration has been given time to set in.

In the words of CH2M HILL’s submission to the CEA judging panel: “The life of numerous bridge decks throughout the province can be extended for the cost of a major deck rehabilitation of a single bridge.”
Using the copper sulphate method, Mr. Hamilton’s crew is able to detect and measure minuscule voltage levels created when invading chlorides generate a chemical reaction, or rusting, in the bridge’s steel rebar.

“We electrically connect to the imbedded rebar by means of a deck joint, for example,” Mr. Hamilton says. “Then we measure the voltage and create contour maps to identify areas of high corrosion potential. You can see at a glance exactly what’s happening.”

Roots in the 1970s
The technology isn’t new. Paul Carter, P.Eng., Mr. Hamilton’s long-time associate, was among the first to embrace it when it emerged during the 1970s. At the time, Mr. Carter was employed by the Alberta Transportation Department, which enthusiastically backed his team’s proposals for proactive bridge remediation strategies.

A technical specialist with a superb international reputation, Mr. Carter helped train Mr. Hamilton as a university student. Both men moved over to the private sector in 1996 and have been working together since. Field supervisor Jason Saly is another important member of the bridge-deck testing squad.

In Mr. Carter’s view, the Alberta strategy is superior to those applied in other provinces, as well as more cost-efficient.

He gives Alberta Infrastructure and Transportation high marks for including so many bridges in the program, as well as for the frequency of their evaluation.

“Over the years, we’ve developed a database to track all the information we’ve recorded,” Mr. Carter says. “We’ve used that data to develop accurate prediction models to forecast deterioration based on specific site conditions. And we’ve developed a number of efficiencies so that the overall cost is always quite reasonable.”

This summer, Mr. Hamilton’s crew will tour Alberta, assessing corrosion from Calgary’s Calf Robe Bridge to the viaduct that spans the Athabasca River on Highway 43 at Whitecourt.

No doubt they’ll be giving their province a good financial name, along the way.

Cutline for Keyser Bridge.jpg