If approved, a 1,200-kilometre natural gas pipeline would be built through the Northwest Territories' Mackenzie Valley from the Beaufort Sea to a hub in northwestern Alberta. (CBC)

Proponents of the Mackenzie Valley pipeline gave their final pitches on Monday to the National Energy Board, which must decide whether to approve the $16.2-billion proposed natural gas project in the Northwest Territories.

The NEB, an independent federal agency that regulates part of Canada's energy sector, is hearing final arguments on the pipeline proposal this week in Yellowknife. The board will also hold hearings next week in Inuvik, N.W.T.

Lawyers for Calgary-based Imperial Oil, the leader of a consortium of companies behind the 1,200-kilometre pipeline, spent Monday afternoon trying to convince the board that the pipeline would be in the public interest.

"When you consider the evidence and when you balance the positive economic and social impacts against any negative social or environmental impacts, the scale tips heavily to the positive side," Imperial Oil lawyer Don Davies, who spoke for the consortium, told the board.

"The MGP [Mackenzie Gas Project] is in the overall public good of Canada."

The pipeline consortium wants to build the natural gas pipeline from the Beaufort Sea, through Inuvik, N.W.T., and down the Northwest Territories' Mackenzie Valley to northwestern Alberta, where it would connect with existing networks.

In addition to Imperial Oil, the consortium also includes ExxonMobil Corp., ConocoPhillips, Royal Dutch Shell PLC and the Aboriginal Pipeline Group.

More than adequate consultation: lawyer

Davies disputed criticism on Monday that the proponents did not properly consult aboriginal groups, arguing that the companies went well beyond adequate consultation about the pipeline.

"There have been hundreds of open houses and workshops and group meetings, and thousands of one-on-one meetings and discussions. Traditional knowledge studies have been done. A socio-economic agreement has been concluded with the government of the Northwest Territories," he said.

"I could go on and on here, but frankly to even try to summarize the consultation that has been undertaken, in my submission, does an injustice to the effort."

The National Energy Board can approve or reject the Mackenzie pipeline, or approve it with conditions. The board is expected to issue a decision in September.

Proponents have lobbied the board against including potential cumulative impacts in its decision-making process, which is something environmental and social justice groups like Alternatives North have been calling for.

'Protect people in the North'

At a news conference earlier on Monday, Alternatives North spokesman Kevin O'Reilly said the NEB is ruling on a pipeline that could handle natural gas from future developments.

"The NEB has said, 'We're not going to deal with those recommendations. That's off in the future; we can't sort of prejudice the way we're going to deal with future applications,' " O'Reilly said.

"We think the NEB has the authority to do that now, and indeed it's obligated to do it to protect people in the North and our environment."

The organizations want the board to reject the pipeline proposal or at least impose stringent conditions to mitigate negative environmental and social impacts.

The Sierra Club of Canada wants strict conditions on the natural gas that would flow through the pipeline — specifically on how that gas would be used after it connects with other gas networks in northern Alberta.

"We have to make sure that that gas is used wisely so that it is used, for example, to replace coal," Sierra Club ecojustice lawyer Keith Ferguson said.

"That could help reduce Canada's greenhouse gases, as opposed to having that gas go to the Alberta oilsands, for example, where it will increase Canada's greenhouse gases."

Alternatives North and the Sierra Club, along with other interveners, are expected to make their presentations to the board on Tuesday afternoon.