Time to release Nipigon River Bridge reports
In early January, the Nipigon River Bridge in northwestern Ontario failed after one end rose a couple of feet. The bridge was closed to traffic, cutting off the only highway link between eastern and western Canada.
A couple of days later, after weights were added to restore alignment with the Trans-Canada Highway, the bridge was partially reopened to car and truck traffic. By the end of February, satisfactory temporary repairs were accepted by the authorities and the bridge was back in service.
There are many ways of spanning highways over rivers; this variety of suspension bridge — a cable-stayed bridge — is usually picked, not for its economy, ($106 million probably represents the most expensive option for this situation), but for its visual or esthetic value, or perhaps for public political considerations. In the computer age, it is relatively easy to design and to analyze the effects of temperature differentials on the design. Extremely cold weather would be a critical part of the criteria for anchoring the cables.
The cause of the failure under extreme cold could immediately be concluded to be one of the following: a material failure of the tie down bolts; a construction error; an error in the design; or a combination of these. The design adequacy could have been established within days, and we can assume that it was, by the fact the bridge was quickly put back in service. Which means the bolt material, the number of bolts or the anchorage of the bolts was the problem. That the hold down of the bolts was the problem can be further inferred from the decision to repair it by using another system for holding down the anchor end of the bridge.
The Ministry of Transportation said on July 4 it had received two independent reports on the bridge’s bolts but will not make the reports public until the fall, after government bridge engineers finish their own analysis and the government also receives a fourth report, from an independent engineering consultant with expertise in cable-stayed bridges.
When Transportation Minister Steven Del Duca is quoted this month saying about the Nipigon River Bridge: “From my perspective, releasing limited information in piecemeal fashion prior to having all the facts does not help us get to the root cause of the bridge failure,” we should find this perspective questionable and misleading.
It is clear, and has been since February, that the hold down by the bolts were the root cause of the failure. Earlier, the ministry said, in looking for solutions, “Each option proposes a different connection method and location to connect the bridge deck to the foundation.”
The Ministry of Transportation in its July 4 release reported, “As well, the monitoring of the temporary repair that was installed in January shows it continues to function as expected and the bridge remains safe for use by all.” The release also states, “The bolt study provided us with only a partial answer about the bridge, and as such we think it’s premature to discuss it on its own at this time.” Why is not clear to this engineer. If the bolt study and the “different connection method and location to connect the bridge deck to the foundation” now in use have not resolved the engineering issues, this should be very troubling to the 1,300 trucks that cross the bridge every day, carrying about $100 million worth of goods.
The minister needs to reveal what he and his department know and why it is premature to discuss it at this time. What facts are missing? What do the final reports on the bolts conclude? What is limited about the information he has, and what is he waiting for that will complete “the comprehensive investigation that is ongoing?”
There is some political sensitivity to questions about expensive spending decisions, and a bridge failure is a public black eye to its owners. It is also a matter of considerable public safety, and political expediency needs to yield to public safety.
We don’t need a public inquiry, we just need to be trusted to not panic if there are unresolved issues that winter may induce. There needs to be more valid and convincing reasons for withholding from the public the reports on what caused a vital public bridge to fail.