The city isn't to blame for last summer's sinkhole that opened on Rideau Street, according to a memo from the city's top lawyer.
The memo from Rick O'Connor to mayor and council says "external technical experts" hired by the city weren't able to determine a specific cause, but they are "confident" that it wasn't due to problems with city infrastructure.
The experts' report can't be made public, the memo says, because of any potential future litigation that might arise from the sinkhole.
The sinkhole last June caused a gas leak and nearby buidlings to be evacuated, and took weeks to repair.
That stretch of Rideau Street from Sussex to Dalhousie was also closed for nearly two months until last week as crews injected grouting round-the-clock.
The memo says the effort to find the sinkhole's cause was complicated by the need to immediately stabilize the site, which involved filling the sinkhole with more than 3,000 cubic metres of concrete within 24 hours.
"In light of these circumstances, the City’s external technical experts were unable to pinpoint a singular cause of the event, but are confident, based on their analysis of all the available evidence, that the sinkhole was not precipitated by a failure of City infrastructure," the memo says.
The memo also says businesses affected by the sinkhole have made 31 claims for compensation resulting from the event, which have been referred to the project's insurer.
The city has also claimed $1.5 million in costs arising from the sinkhole.