There could be as many as 62 former garbage dumps on the Island of Montreal that are now buried beneath parks and residential lots, a CBC/Radio-Canada investigation has shown.

A list of these old dumping grounds, dated 1994, was obtained through an access-to-information request to the City of Montreal.

According to that list, of the 62 locations, 24 are certified former landfills and 38 are possible landfills and dumps.

Slightly more than half of them are located in areas that are now zoned residential. Twenty former dumps are located on public land, and some are beneath municipal parks.

Explore the map below to see more details of Montreal's former landfills and dump sites.

landfill map legend

On a mobile device? Tap here for the map.

'A bombshell,' says developer

The former Villeray landfill now has hundreds of homes built on top of it.  The old De Lorimier quarry near Rosemont Park is another former dump where 13 apartment buildings now stand.

"This is a bombshell," said Angelo Renda, an engineer and vice-president of Axnor Developments, a property development firm.

"This kind of data is available but hidden from the public, so residences were built on top, but property owners don't have the information."

City says it didn't know of list's existence

After Radio-Canada's initial report on the old dumps, Montreal's current administration said it never knew about the list, and it has promised to publish updated information.

"We will produce a map with the quarries that became dump sites. It will be on our website," said Réal Ménard, the Montreal executive committee member responsible for the environment.

Condo project axed, property seized

Renda was personally affected by this hidden information.

He bought a property that he did not know was built on an old landfill. 

A study he read before making the purchase showed the soil on the property was clean. But when he wanted to tear down the house to build condominiums, he was told to test for contamination. 

It turned out the property was contaminated to a depth of 10 metres.

That's when he learned the land's true history. 

Incinérateur des Carrières archive

The des Carrières garbage incinerator was opened in 1929 and closed in 1993. Waste from incinerators like this were dumped in old quarries then covered up. (City of Montreal)

Renda's financial backer won't pay for the decontamination, and the house has been seized.

"I feel cheated and robbed, because we paid good money for this house," Renda said.

"The city polluted it because they had the incinerator, they had their own landfill here. They should pay for everybody."

Montreal officials have now said they'll conduct tests on the contaminated sites to see if they represent any hazard.

What the city won't commit it to is providing financial help to owners whose homes were built on old dumps to help them decontaminate their property.

With reporting by Benoît Giasson of Radio-Canada and Raffy Boudjikanian of CBC.