By CBC News Ottawa, March 21, 2014
A large sinkhole formed on Waller Street when tunnelling for the new LRT line
passed beneath a previously excavated construction pit, according to a technical
memo released by the City of Ottawa on Friday. Ottawa Light Rail Transit
Constructors wrote in the memo that the mining crew noticed "excessive loose and
wet material start to fall" around 9:40 p.m. on February 20. By 1 a.m. on
February 21, the sinkhole reached the surface on Waller Street near Laurier
Avenue, leaving an eight-metre wide opening in the street. via
Downtown sinkhole formed in previously excavated pit - Ottawa - CBC News.