Owners of dragon boat company 22Dragons on the Lachine Canal said they've been forced to close twice this summer because of sewage overflows into the water. (CBC)

The owners of a dragon boat company on the Lachine Canal said they're upset with the city's practice of dumping sewer overflow into the canal.

Matt Robert, co-owner of 22Dragons boat club on St. Patrick Street near Monk Boulevard, said this is the second time he has had to shut down this summer because of raw sewage coming out of a pipe about four kilometres west of his club.

Roberts said he was forced to move his boats to Pointe-Claire for an event because the canal was temporarily closed.

"Sometimes it's a bigger volume than others. When it's a huge volume, well, you can imagine what sewage water looks like," Robert said, adding that when the water is dirty, no one can rent his boats.

Robert said he's also worried about the health risks to others who use the canal.

"Whether they close it or not, people had contact with that water today."

Waterworks officials said the overflow is caused by heavy rain. On Wednesday night, a nearby sewer collector became overwhelmed and the outlet pipe gushed sewage into the canal for 45 minutes.

"We've had pretty wicked storms over the last few days. And what’s particular about them is that they’re very localized," said Richard Fontaine, who is in charge of Montreal's wastewater treatment.

"As soon as the network can retake what we've had in terms of storms, the overflow stops," said Fontaine.

He said the solution would be to build an underground basin that could hold excess water until it could be sent for treatment. He said studies are underway but the basin would cost about $50 million. In the meantime, Fontaine confirmed the canal would continue to close for three days after each sewer overflow.