The front lawn of the headquarters of SNC Lavalin is seen on November 6, 2014 in Montreal. Shares SNC-Lavalin Inc. plummeted to the lowest level in nearly 15 years Tuesday a day after its largest shareholder, the Caisse de depot et placement du Quebec, warned that the embattled engineering firm had to move to emergency mode to improve its project execution. THE CANADIAN PRESS/Paul Chiasson