Road salt leaving visible effects on the Diefenbaker Bridge

A much-anticipated report with the results of the underwater inspections of the Diefenbaker Bridge’s piers may have put concerns about the structure below the surface.

But one of the conclusions of the report, written by ISL Engineering and Land Services, is raising questions about the piers above the surface of the North Saskatchewan River.

The report notes that the top of the piers have been exposed to salt contaminated water “as the joint in the median above has leaked for a number of years and as a result, delaminated concrete may exist at various piers where water had collected and diffused through the surface.” ISL recommends that the tops of the piers be checked for this failing concrete during the next major inspection.

At Monday’s executive committee meeting, during a discussion of this point in the report, Wes Hicks, who was sitting in as acting public works director, told members of council about the damage resulting from the salt used on the roads. Both the City and the province use salt on the roads.

He said the salt builds up on the splash guards at the side of the road.

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“That’s why you see all that exposed rebar where it has corroded the concrete off and the salt and the gravel fill in all the drain areas and that builds up and starts retaining water, freeze/thaw and it breaks up the concrete on the deck,” he said.

He elaborated on the damaging effects that road salt has, later that week.

“Salt is a very corrosive substance, and when mixed with water and freeze/thaw, it gets under the concrete and once it gets into the concrete and it gets into the rebar and travels through the iron, and it breaks the surfaces of the deck and that’s what you see as a result when you travel across the Diefenbaker Bridge, all the damage along the splash guards.”

Road salt can be tracked onto the bridge by vehicles, and is in the mix spread directly on the bridge by the City. Salt is used to melt the ice on the roads in wintertime, but is only effective to a certain temperature. The sand in the mix is used to help the vehicles’ tires gain traction.

The City uses a sand/salt mixture that contains 10 per cent salt and 90 per cent sand, according to Hicks.

The province uses a similar sand/salt mix on the highways at intersections, as well as pure salt, highways and infrastructure ministry spokesman Joel Cherry said on Friday. He said Saskatchewan uses less salt than some other provinces.

Hicks said the damage caused by the salt can be severe and eventually has to be repaired. He said the damage ISL wrote about in the report to the tops of the piers is the effect of the salt and the water running through the drains of the bridge and running through the membranes from each of the bridge’s sections.

“Some of those have damage to them and then the water gets down underneath. So, it’s something that needs to be repaired,” he said.

The City plans to approach the province’s Urban Highway Connector program with applications to address some of the issues identified in previous bridge inspections.

Hicks said they would then sit down with provincial officials to discuss funding and the priority of those applications.

The Diefenbaker Bridge is covered under the Urban Highway Connector program, Cherry said. “Whether or not we’d provide funding specifically for any sort of corrosion on the deck would depend. We’d have to analyze it once we got the application.”

Council will once again discuss the underwater piers inspection report on Monday evening.

tjames@panow.com

On Twitter: @thiajames