OTTAWA -- The federal Liberals will accept nearly 100 changes the Senate has made to a bill overhauling the federal environmental-assessment process for major construction projects but are rejecting dozens more, including nearly all of those proposed by Conservative senators.

Conservative Sen. David Tkachuk said he is "appalled" at the government's decision.

"If you think Saskatchewan and Alberta are going to take this lying down, I think the country's got another thing coming," he said.

Environment Minister Catherine McKenna says she thinks some of the Senate's proposals made the bill much stronger, including those that reduce the authority of the minister of the environment to interfere with timelines or the make-up of review panels, and some that clarify rules to ensure the same project won't have to go through both a regional and a national review.

She said she is certain the new review process for national-scale resource and transportation projects, like pipelines, mines and highways, will be clear and timely. She said it will allow for as many as 100 new resource projects worth $500 billion to be proposed and examined over the next 10 years.

"This is a system that will attract investment," McKenna said. "This is a system that Canadians, that Canadian businesses should be proud of. We can go and tell everyone that Canada is open for business."

McKenna is rejecting 90 per cent of the amendments made by Conservatives, including some which would have allowed a new Impact Assessment Agency to decide not to consider the impacts on Indigenous people or climate change when assessing a project. She also is rejecting changes that would have put strict limits on who can participate in an assessment hearing, as well as make it harder to challenge a project approval in court.

Environment groups hailed the government's decision as a win for the planet, ensuring climate change in particular is taken into consideration.

Conservatives, however, are warning their fight against Bill C-69, which they say is a threat to national unity, has barely begun.

Alberta Premier Jason Kenney is pondering a constitutional challenge, saying the bill infringes on provinces' rights to control their own natural resources and that it will kill what is left of Alberta's oil-and-gas sector.

"Without the Senate's amendments, this bill will drive away more jobs and investment from Canada," Kenney said. "It is not too late for the federal government, the House and the Senate to do the right thing and sustain the Senate's amendments."

Kenney led six premiers -- five conservative provincial leaders and one non-partisan territorial leader -- to write to Prime Minister Justin Trudeau Monday asking him to accept all the amendments in the name of national unity. Trudeau called it irresponsible to raise the spectre of tearing the country apart just because the premiers weren't getting everything they wanted from Ottawa.

Kenney has tried to bring Quebec Premier Francois Legault, who leads the right-leaning Coalition Avenir Quebec, into the group of premiers declaring a threat to national unity. The Alberta premier was in Montreal Wednesday to meet with Legault and invoked a "historic alliance" between the two provinces during the 1982 talks on patriating the Constitution.

Legault won't sign the letter. He does not like the parts of C-69 that he says infringe on provincial jurisdiction but thinks the other premiers want to cut back too much on environmental protections.

McKenna said conservative premiers, MPs and senators, as well as the oil-and-gas lobbyists, wanted a bill that would guarantee every pipeline proposed would be approved, rather than an environmental-assessment process to ensure only good projects that help the economy while protecting the environment go ahead.

"They want us to copy and paste recommendations written by oil lobbyists that would block court challenges, that would make it easier for future governments to ignore the views of Indigenous Peoples, that would limit Canadians' input and shut Canadians out of the process, and that would increase political interference in decision-making," McKenna said.

She said the government listened to the concerns of the provinces and accused the Conservatives of polarizing the country by changing the law in 2012 to favour the oil industry at the expense of the environment and Indigenous rights.

The House of Commons must debate and then vote on the government motion responding to the Senate amendments but the Liberals' majority virtually guarantees that the government will get its way. Then the Senate gets another shot at the bill. Thus far, the independent senators have tended to defer to the elected House of Commons when the House rejects Senate amendments.

Early indications from independent senators, who are a majority in the Senate, suggest that will be the case with Bill C-69, too.

Sen. Yuen Pau Woo, the head of the Independent Senators Group (a loose affiliation of senators who work together for procedural purposes), said he is disappointed the government didn't accept more of the Senate's suggestions but thinks the ones McKenna is accepting do address three key issues raised by industry, environmental groups and First Nations.

Those include clarity and predictability about the timelines for a review, the assessment criteria, reducing ministerial discretion, and a more explicit recognition of the importance of economic considerations in an impact assessment.

--With files from Christopher Reynolds in Montreal

