Torrential rain left some Moncton streets submerged twice in one week

An engineer with the City of Moncton says the area hasn't seen rainstorms of this magnitude in three years, after some city streets were left flooded twice over the past week.

René Lagacé, director of engineering for the City of Moncton, told Information Morning Moncton the city saw 15 millimetres of rain in 15 minutes on Monday evening. 

"That's quite a short-duration-high-intensity rainfall event," said Lagacé. 

Last week, the city also saw about 50 millimetres of rain over a span of five hours, he said. 

"Our sewer systems can handle that type of rain when it's over a long period, but short duration like that just shocks the system and goes into an overflow," said Lagacé. 

Sewers are only able to handle so much stormwater, he said, and when there's nowhere for any excess to go but onto the street or nearby properties. 

Lagacé said most cities have two types of drainage systems. One is a sanitary system that collects wastewater and sends it to a water treatment facility. The other is a storm sewer system that collects stormwater from rains or snow melt. 

But he said Moncton has a combined sewer system throughout older areas. 

"I guess the engineer at the time didn't see the value in those two systems," said Lagacé. "This means that all stormwater from storm events is going to this one pipe." 

Information Morning - Moncton10:20Torrential rains push Moncton's drainage and sewer system to the limit

René Lagace is the director of engineering with the City of Moncton.

While it's a nuisance having stormwater flowing through city streets, he said, "it's the lesser of two evils than having sewer backups into properties." 

Lagacé said it will take a lot of time and work to replace Moncton's combined sewer system with two separate ones, but the city is doing that bit by bit as it rebuilds streets. 

"You will never hear me say, 'we will avoid stormwater or flooding,' especially now with climate change," he said, "Three years without any events and now two in a week, so it's really unpredictable." 

Lagacé said the city's goal is to keep basements from flooding and it has put measures in place to reduce the risk of future floods.

For example, developers must now build properties at a minimum elevation of 10.5 metres above sea level. 

"Basically, we want to make sure people are not repeating the same mistakes," said Lagacé. 

The city is also working to raise a few streets, including Assumption Boulevard and Robinson Street.

Moncton was hit by two major storms in 1999 and 2009. Since then, the city has spent about $70 million to install larger culverts, separate sewer and stormwater lines and build ponds to hold stormwater.