The B.C. Green caucus will visit the Peace River valley on Tuesday to examine the $8.8-billion hydroelectric project they want to stop.

Green Leader Andrew Weaver was once a champion of the project. A photo of the event where the Site C dam project was launched, on April 19, 2010, shows his smiling face several rows behind then-premier Gordon Campbell. Mr. Weaver was invited to attend the splashy event as a renowned climate scientist who endorsed this massive clean energy project – one of dozens of guests who were flown to Hudson's Hope near the proposed dam site to applaud Mr. Campbell's construction pledge.

Even before then, Mr. Weaver, as a member of Mr. Campbell's climate action advisory team, advocated for the dam. In a 2009 interview with The Globe and Mail, he urged Mr. Campbell's government to dust off the project, which had been shelved in the 1980s.

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"I cannot see what is stopping Site C," Mr. Weaver said eight years ago. At the time, Mr. Campbell was launching an ambitious climate-action agenda and Mr. Weaver concluded it was time for BC Hydro to get back in the business of mega-projects to produce more emissions-free energy. "They should be carving out their niche with the Site C dam," he said.

Today, he has his wish. There are more than 2,200 workers on site, and BC Hydro has spent close to $2-billion to date on construction.

When he visits the project on Tuesday, however, Mr. Weaver will be drawing attention to the reasons to cancel the project.

He'll be meeting with some of the most outspoken opponents of the project. Mr. Weaver and his caucus members, Adam Olsen and Sonia Furstenau, will visit an Indigenous grave site that is earmarked to be paved over, they'll participate in a sweat-lodge ceremony hosted by the West Moberly and Prophet River First Nations, and they will meet with the two families who are being forced from their homes to make way for the dam.

Today, as a politician holding a powerful lever in the B.C. legislature, Mr. Weaver is exerting all the pressure he can to halt the project he now regards as a white elephant.

Mr. Weaver has signed a pact with the NDP that aims to bring down the governing Liberals, and as part of that deal, the Greens insisted on a short, independent review of the project that they believe will justify ending construction.

"What has changed is the economics," he said in an interview.

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In 2009, he was convinced the hydroelectric project would help British Columbia meet aggressive targets to reduce greenhouse gas emissions. He also believed that with a construction budget of $6-billion, Site C was the most economic way to generate more greenhouse gas-free electricity.

"This, at the time, was the cheapest way of getting clean energy," he said. "There is no question, this is clean energy."

However, he said it didn't take long for the math to fall apart. The cost of wind and solar has dropped dramatically, while the construction cost of the dam has climbed. As well, the increased demand that BC Hydro forecast has not materialized – in fact, domestic demand has declined since 2008. And, a federal environmental review panel brought to light the negative impact on the rights of Indigenous peoples in the valley.

"To be blunt, one of the things I didn't consider back when I was a climate scientist, thinking about nothing but climate science, was the issue of First Nations' rights and title," he said.

He said another unintended consequence of the project is that it has squeezed out private-sector investments in clean energy which, back in 2009, seemed poised to take off. He pointed to wind farm projects that have been cancelled because, with Site C in construction, Crown-owned BC Hydro didn't need to buy private power.

"We've killed this nascent industry that was ready to take off here. These were producers who work in partnership with First Nations in British Columbia."

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The Site C dam would produce 1,100 MW megawatts of power capacity – enough electricity to power about 450,000 homes.

With the Greens' support, the NDP hope to defeat the Liberal government on a vote of confidence, expected later this month. While the NDP oppose the project, NDP Leader John Horgan has said construction should continue until a review by the independent regulator is complete.