Disturbed soft soil from tunnel work played part in sinkhole, report says
Ottawa Citizen

By Jon Willing, Ottawa Citizen, April 5, 2017

A root cause report makes it clear that LRT tunnelling work in soft ground likely contributed to the massive sinkhole forming on Rideau Street last June.

Wet, sandy conditions and groundwater pressure above the top of the tunnel pushed soil down on June 8, 2016, after workers below constructed a reinforcing “pipe umbrella” support system, which had disturbed the soil, the report says. A watermain broke as the supportive soil washed away.


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