article: CBC News
The Alberta Regional Council of Carpenters and Allied Workers said in a news release it plans to serve strike notice Wednesday morning to Construction Labour Relations, the umbrella group that negotiates the contract for the workers.
However, under a Alberta labour law, if 19 of the 25 groups in the province's unionized construction industry negotiate a deal with their employers, the remaining groups have to go to arbitration and can't walk off the job.
Right now, 18 have a deal.
Carpenters set to hit picket lines Saturday - The Edmonton Journal
The Contractors trying to head off strike - Calgary Sun