Building a 67-kilometre light-rail network in Montreal could require expropriations, demolition of historic buildings and threaten several species, said the investment group behind the project.

But CDPQ Infra, a subsidiary of the Caisse de dépôt et placement du Québec, also argues its proposed light-rail network will reduce traffic congestion and cut greenhouse gas emissions.

On Thursday, CDPQ Infra released its 2,000-page environmental assessment of the project, which has been submitted to the provincial environmental review agency (better known by its French acronym BAPE).

The electric, fully automated rail line would connect 24 stations stretching from the South Shore to Montreal's Trudeau airport and the West Island. It's projected to cost $5.5 billion.

The Caisse, through CDPQ Infra, has committed to funding $3 billion of the project. The federal and provincial government are expected to pick up the rest, though final financing details are still to be announced.

Pros and cons

In its report to the BAPE, CDPQ Infra acknowledged the rail network will require the expropriation of around 30 homes along the route.

It may also require a partially demolition of the Rodier heritage building in Montreal, and create "pressure" on Parc de l'Anse-à-l'Orme, where the Sainte-Anne-de-Bellevue station will be built.

The report outlines the positive and negative impacts the project will have on its surroundings.

Among the listed positive effects include:

Reduction in road congestion.

Reduction in greenhouse gas emission and other air pollutants.

Reduction in noise pollution from cars, busses and existing commuter trains.

Economic benefits due to creation of jobs and increase in productivity.

The proposed route includes 24 stations, including one at the airport. (CDPQ)

The negative biological effects include:

Possible contamination and decreased water quality in nearby bodies of water such as the Milles-Îles River, Rivière des Prairies and Peel Basin.

Disturbances in fish, reptile and amphibian habitats near the airport, Technoparc and on the South Shore.

Loss of habitats for brown grass snakes and noise disturbance.

Removal of vegetation, prolonged sun exposure and possible swamp drainage in wetlands in Saint-Laurent, Sainte-Anne-de-Bellevue and the South Shore.

45-day consultation period

With the tabling of the CDPQ Infra report, members of the public now have 45 days to consult the document and request an audience if they have concerns.

The consortium has already made a request for a public hearing.

However, Environment Minister David Heurtel can request that the hearings begin after the 30th day of public consultation.

That measure would serve to accelerate the project in order to meet its deadline. It is supposed to be complete by 2020.

Those who want to consult the documents in their entirety can do so on the BAPE website.