"We're recommending that the project be denied," Chris Severson-Baker, a spokesman for the Pembina Institute, one of three environmental groups in the Oil Sands Environmental Coalition, said Wednesday. "But if the board decides to approve the project, then we identify a number of conditions be imposed."

The environmental coalition is concerned that Suncor's Voyageur project will create new strains on infrastructure and water resources in northern Alberta's oil sands region, and boost greenhouse gas emissions.

The Alberta Energy and Utilities Board began public hearings on whether to approve the project Wednesday in Fort McMurray in the oil sands region. They are expected to last three weeks.

Voyageur will boost production at the oil sands mine near Fort McMurray to as much as 550,000 barrels a day by 2012, more than double current output.

Among the environmental group's requests are that Suncor be forced cut or offset the release of greenhouse gases from the project and reach zero net emissions by 2020.

Voyageur is just one of some C$125 billion worth of projects planned for the region that are expected to triple production to about 3 million barrels a day by 2015.

That boost in output is attracting greater focus on the environmental cost of the massive mines and upgrading refineries located in what a generation ago was nearly untouched wilderness.

In a recent interview with Rolling Stone magazine, former US vice-president and environmental crusader Al Gore said mining the oil sands was "truly nuts" because of the impact on land and the amount of natural gas needed to produce a barrel of oil from the resource.

But Suncor said it has taken the necessary steps to mitigate any environmental damage from the expansion and expects the board to approve it.

"We're confident we have a strong project," said Suncor spokeswoman Darcie Parks. "We've conducted a detailed environmental impact assessment...and we are confident we can move ahead with minimal negative impact to the environment."