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Tunnelling suspended in Ottawa following ground collapse

Work on constructing the Light Rail Transit system in Ottawa, Canada has been suspended after ground above the tunnelling work collapsed leaving an 8m wide, 12m deep hole in one of the city’s streets.

In a statement the scheme developer City of Ottawa said: “Tunnelling operations have been suspended at the East Portal due to a roadway collapse on Waller Street. The cause has yet to be determined.”

A spokesperson for the city added: “We were aware of different geotechnical conditions in this vicinity, and before we went out to tender we actually shortened the length of the tunnel, recognising that this type of material would be challenging. Certainly we provided all that geotechnical data [to the contractor].”

Geotechnical engineers from the main contractor Rideau Transit Group are currently assessing the situation but have confirmed that the impact is localized. Nonetheless, the tunnel face has been stabilized and the ground collapse backfilled to ensure the safety of the surrounding area.

The collapse occurred at the eastern end of the 2.5km long tunnelled section of the new Confederation Line, which is being excavated using road headers and sprayed concrete linings. Tunnelling work started in November last year and the Rideau Transit Group had recently announced that it had excavated 10% of the tunnelled route.

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