CALGARY - Marijauna growing is an industry believed to be worth tens of billions of dollars in Canada. In Nov. 2004, police in Barrie, Ont. busted what was considered the largest and most sophisticated grow-op in Canadian history. But smaller operations are hidden in almost every city across the country. "You have to realize there's so many of these we don't have the resources to extend the surveillance on every one of them to firmly establish who lives there and what not. We deal with such a high volume," said Staff-Sgt. Birnie Smith.