Longueuil set to dump raw sewage into river

Longueuil is set to begin dumping raw sewage in the St. Lawrence River on Thursday.

WHY IS THIS BEING DONE?

Longueuil says it must remove and replace two sixmetre-long sections of a sewage pipe at the bottom of the river that carries effluent from the mainland to a water-treatment plant on Île Charron. Workers discovered a leak in the 90-centimetre pipe in June. Installed in 1990, the pipe was supposed to have a lifespan of 60 to 80 years.

WHERE IS THE PIPE?

Close to the Lafontaine bridge-tunnel and Île Charron.

HOW MUCH SEWAGE WILL BE DUMPED?

About 162 million litres. The raw sewage — from Longueuil and Boucherville in an area that straddles Highway 20 — will emanate from 4,700 homes, as well as businesses. Wastewater from toilets, sinks, showers and commercial and industrial drains will go directly into the river. Longueuil says it will capture and remove solid waste.

HOW LONG WILL THIS TAKE?

Seven or eight days, starting Thursday. Much of the work will be done by scuba divers working in shifts that cover 24 hours a day.

HOW MUCH WILL IT COST?

The estimated price tag is $700,000.

WILL IT AFFECT THE QUALITY OF DRINKING WATER?

Longueuil says the discharge will have no impact on drinking water. It is warning the public to avoid contact with water flowing between the Îlesde-Boucherville and the mainland. That includes the stretch of bike path that runs along the shore on the mainland between the Lafontaine bridge-tunnel and Parc des Voiles.

ARE THERE ANY LONG-TERM DANGERS?

Longueuil says there will be “very, very little (environmental) impact on a long-term basis because the river has a very high capacity of dilution.” It says it will test water quality before, during and after the dump, and monitor river banks. After Montreal dumped sewage in the river in 2015, the city said drinking water was unaffected in downstream municipalities. Water quality was back to regular levels within four to 10 days. Fecal coliform levels were 30 times the acceptable limits four days after the discharge but back to normal six days after that.

HOW DOES THIS COMPARE TO MONTREAL’S DUMP?

In 2015, Montreal poured five billion litres of raw sewage into the river so it could repair a sewage collector. If Longueuil dumps the expected 162 million litres, its discharge will be about three per cent the size of Montreal’s.