The sinkhole that opened up on Rideau Street in Ottawa 10 months ago is still causing headaches for city officials, as an engineering assessment that was made public yesterday ruled that the cause of the cavity was due to previous excavation efforts.
Rideau Street had to be closed for six months for repairs following the incident that occurred June 08, 2016.
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“The loss of ground likely occurred very rapidly because the ground had previously been disturbed and loosened” by the installation of a pipe and excavation for a tunnel entrance, a report prepared by engineering consultant McMillen Jacobs Associates read.
The consultant further explained in its report that once the ground beneath the watermain moved, there was nothing to support the pipe from bursting. When it finally burst, the water that gushed out flushed away the surrounding soil, causing the subsequent “catastrophic rupture” of the roadway.
CBC confirmed that there was indeed tunneling work being performed around the area – near the intersection of Rideau and Sussex Drive – by light rail construction crews employed by Rideau Transit Group around the time of the roadway’s collapse. The sinkhole grew quickly after the road gave way, swallowing a van and three lanes of traffic. It took weeks for Rideau Transit Group to pump water out of the tunnel.
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A previous leak in the Rideau watermain could be to blame for why city consultants initially ruled out water leakage as the cause of the collapse. The earlier leak occurred in November 2015, which caused water to bubble up on to the surface of the pavement.
Although that earlier leak was repaired the same day it was detected, no cause for the leakage was determined. In the days leading up to the sinkhole incident, none of the clues that would suggest a watermain leak were reported.
“In fact, groundwater levels in the vicinity of the sinkhole dropped ... six meters in response to west running tunnel construction activity in the days leading up to the sinkhole,” a city report said.
“There’s certain evidence that presents itself [with a watermain leak],” rail office director Steve Cripps told CBC. “None of those things presented themselves this time around. So that allowed the consultant to compare one against the other and say there’s really no evidence that city infrastructure contributed to the sinkhole.”
In a memo to councillors last December, Ottawa’s solicitor said that the city’s infrastructure was not to blame for the sinkhole. The actual report prepared for this explanation, however, was kept confidential for over three months; city officials argued that the document could prejudice the insurance claim or any potential lawsuits if it was disclosed.
Compounding matters, the city did not hire third party investigators to address the cause of the sinkhole, electing to use the same experts working on the LRT project.
Ottawa had submitted $2 million worth of claims to its insurer to cover costs related to the collapsed road. Rideau Transit Group is in the process of filing a claim, having incurred millions of dollars in repairs costs.
CBC reported that over 30 businesses have written notices demanding the city pay for damages and loss of business resulting from the sinkhole.
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