The agreement between BC Hydro and the B.C. and Yukon Territory Building Construction Trades Council is expected to bring labour stability to the project that has already drawn legal challenges from landowners and First Nations.
Under the agreement, BC Hydro will place greater weight on project bids that include union members, while unions have waived the practice of signing project labour deals that restrict other non-affiliated groups from working on the site.
There are also provisions in the agreement prohibiting strikes, lockouts, union raids and organizing on the main work area.
Premier Christy Clark said the compromise ensures an open shop, competition and lower costs but also opportunities for unions.
"I'm not ideological about this," she told reporters. "Recognizing that these sites will have a lot of union workers on them — that's great. We should be happy to embrace that and that's what Hydro did."
Tom Sigurdson, the trade council's executive director, said there's still some convincing to necessary on the unions part to ensure project bids are acceptable to BC Hydro.
"We have a lot of work to do to show those contractors who have not worked with us in the past that we bring value to the work that they hope to do on the site," he added.
He said that during the peak of construction, the dam will need about 1,700 workers.
The union's organized and skilled members may even save contractors money on recruiting costs because they won't have to hire workers by themselves, he added.
"With the relationships with the building trade unions that are going to be signatory in this poly-party agreement, they'll just be able to pick up the phone, call dispatch and workers will be dispatched to the site," he said.
Sigurdson said if workers aren't available in B.C., the group will find them because of its "relationship with other locals in the rest of Canada as well as in the United States."
Jessica McDonald, BC Hydro president and CEO, said in a media release the deal "paves the way" for labour stability and takes steps to ensure that BC Building Trades unions will help construct the megaproject.
The first test of the deal will come soon as contractors bid on moving earth and clearing land, the public utility announced in a news release.
But the Peace Valley Landowner Association and Treaty 8 First Nations have taken the provincial government to court over the project.
The landowners' group wants the court to quash the government's decision to approve the dam, and its lawyer has argued the environmental assessment process was flawed.
Treaty 8 First Nations argue the government ignored the damn's impacts on members and the project infringes on their treaty rights.
The megaproject would see more than 5,500 hectares of land along the Peace River flooded to create an 83-kilometre-long reservoir.
When completed in nine years, Site C is anticipated to produce 1,100 megawatts of power annually, which is enough to power nearly half-a-million homes.
-- with files from Keven Drews in Vancouver