By Ashley Burke, CBC News Ottawa, December 6, 2016
Six months after a gaping sinkhole suddenly turned one of Ottawa's busiest downtown streets into a chaotic danger zone of hissing gas and gushing, brown water, neither the city nor the light rail construction consortium tunnelling below know what caused the catastrophe.
Both the city and Rideau Transit Group are endeavouring to find out how the June 8 Rideau Street road collapse happened, and the results of their separate investigations should be available in a matter of weeks, according to the city's director of the rail office, Steve Cripps.
http://www.cbc.ca/news/canada/ottawa/ottawa-sinkhole-cause-investigation-1.3882044