High times are coming to Canada. Sources tell CTV News the Federal Government plans to introduce legislation by April 20th to legalize marijuana, with it becoming legal by Canada Day 2018.

"We do not have legislation tabled yet, so I don't want to prejudge what that legislation is going to look like," said Federal Health Minister Jane Philpot.

The Winnipeg Construction Association will be waiting to see. "The construction industry, I think like any other industry where safety is a real priority, we have concerns about legalization," said Colin Fast.

One of its big concerns is the detection of intoxication. Today, companies like Winnipeg's Intrinsic Analytics have several methods available to detect the presence of marijuana in a person's system, but determining if they're impaired by it is far more difficult.

"It's not a hard and fast rule," said Dr. Waylon Hunt, Intrinsic Analytics CEO. "There's no one level of impairment for everybody."

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Hunt said THC, the active ingredient in marijuana, is stored differently than alcohol. Hunt said it's possible a long-term user could test positive and yet not be impaired.

That's why he said in the United States cut off levels have been established for workplace testing.

"In order to establish that somebody hasn't been exposed environmentally, and also it's been established that there's been observed signs of impairment at those levels."

While legalized pot will soon be new, requiring employees on the job to stay free of the influence of drugs -- legal or otherwise -- isn't.

The City of Winnipeg says should marijuana become legal, this policy would still apply.