Rideau Street safe after latest hole fixed: official

The City of Ottawa said it is confident that measures taken on Thursday night have fixed an issue that caused a new hole to open on Rideau Street, only a few metres away from where a gaping hole emerged in June 2016.

However, the city has asked the Rideau Transit Group (the conglomerate of companies that is building Ottawa’s light rail transit) to perform a check of Rideau Street to ensure no more holes in the pavement take the city by surprise.

City crews claimed Thursday’s “pothole” was created by shifting sediment around a hydro wire duct that runs the length of the street.

The concrete duct, which houses and protects the high-voltage wires inside, remained in place.

However, sediment underneath it became loose, which allowed the sediment around it and on top of it to shift, creating a pocket under Rideau Street’s asphalt.

The pocket allowed a new hole to open on the street.

“Crews excavated the road in the area of the pothole to investigate. There had been some settlement of material under the concrete duct bank and this left a small void, which allowed material from above to shift slightly downward, causing the pothole at the surface,” said Steve Cripps, director of OTrain construction.

“Crews backfilled the area with concrete. As a temporary measure, steel plates were placed over the excavated area until the concrete gains sufficient strength, at which time the steel plates will be removed and the road repaved.”

The repairs were completed Thursday night.

The city has repeatedly referred to the hole as a “pothole” and not a sinkhole, which is what occurred along that stretch of road in 2016.

The city did not respond to questions about the difference between the two depressions.

However, Transport Quebec, which is regularly dealing with holes in the asphalt around the island of Montreal, describes a “sinkhole” as a hole that originates underground as the soil is eroded from an area, causing a pocket.

When enough soil erodes and the pocket is large enough, the ground or asphalt on top collapses, causing a sinkhole.

A pothole is created at the surface of the roadway due to standing water, aging surface materials or pavement that was installed incorrectly. The damaged road allows water to penetrate through, pushing away the soil underneath, which causes the pothole to continue to expand until it is fixed.

City engineers have inspected the area and have signed off on the measures taken by crews to fix the issue.

“Following the engineer’s signoff of the repairs, the city is confident in the safety of Rideau Street,” said Cripps.

He also said the hole was in no way related to the earlier sinkhole and that, after investigating the new hole, it is not believed to be related to LRT tunnelling.

“It may have been something that was pre-existing that just came to light now,” said Cripps.

“That is why the city has tasked the Rideau Transit Group … to search for any other underground pockets that may exist along Rideau Street that could potentially lead to more potholes.

“There is technology that allows us to make that determination, so we will do so as a precautionary measure.”