Fixing local basement flooding problems

City looks to prevent repeat of massive 2005 deluge

Antoinette Cerullo remembers driving through her North York neighbourhood on her way to work and spotting discarded carpets, flooring and furniture scattered by the roadside.

It was late August 2005 and only days earlier a massive storm had wreaked havoc on northwest Toronto, dumping 103 millimetres of rain in one hour. Wind gusts of 72 kilometres an hour, hail and flash flooding accompanied the massive deluge.

Left in the storm’s wake were a reported 4,200 flooded basements, mashed roads, downed hydro lines, and eroded ravines — not to mention a 30-metre long sinkhole on Finch Avenue West, near Black Creek.

“I’ll always remember that,” Cerullo said of the destruction.

Seven years later, Toronto has yet to experience another storm of that scale. However, the rare weather event, commonly referred to as a one-in-100-year storm (a storm that has a one percent statistical chance of occurring in any given year), prompted a multi-year undertaking to protect against basement flooding in areas where it has historically been a problem.

With 32 study areas, the city is now turning its efforts to central North York and parts of North Toronto. In early July, a public consultation was held at Earl Bales Community Centre for residents in the area of Highway 401 and Allen Road —study areas 17, 18 and 19.

Bathurst and Sheppard resident Cerullo said she attended the open house to learn more about what progress the city is making. She said she isn’t convinced that her neighbourhood is well-prepared for another 100-year storm.

“If we get another storm like that, I’m sure the same thing will happen,” she said.

But the city has made strides in several chronic flooding areas where sanitary sewers were historically prone to overloading during bad storms, says Michael D’Andrea, director of water infrastructure management.

In 2008, at council’s direction, D’Andrea’s department was tasked with upsizing infrastructure and upgrading sewer system design standards to withstand 100-year storms, while also finding alternative ways to divert surface flow away from neighbourhoods and into local watersheds.

While new subdivisions are built to do just that, older subdivisions were not. Many were designed on bowl-like topography, which explains why a property owner on high ground may consistently enjoy dry basement, while a neighbour down the street is routinely flooded.

“You will be the hardest hit resident in that neighbourhood because you’re in the low spot,” D’Andrea says.

The water department tackles each neighbourhood by looking at a variety of solutions, ranging from storm and sanitary sewer replacement, catchbasins, underground storage tanks, surface flow diversions like ditches and curb cuts and construction of roads that can absorb water.

“If there’s a park in the area we look at constructing a stormwater pond, to take that extra volume of water that otherwise would have ponded in the neighbourhood.”

While several small and large-scale projects have been completed or are underway, D’Andrea admits that if another storm similar to the 2005 system were to hit today, some neighbourhoods would still be vulnerable.

The 10-year, $740-million Basement Flooding Protection program doesn’t allow for a quick fix.

“We can’t be in all 32 study areas. We’ve had to march forward with the list of priority projects to get them to implementation,” he said, later adding. “We hope to have all the environmental assessments underway by the end of this year.”

In subdivisions near Bathurst and Sheppard, the degree of protection depends on what property owners are doing to reduce the risk of flooding.

Flooded basements aren’t the only symptom of overloaded storm sanitary sewers, D’Andrea points out.

In some cases, surface water enters the basement via cracks in the window seal and foundation walls, which only adds to sanitary sewer overload.

That’s why it’s important that property owners put in safeguards to isolate their homes, including disconnecting downspouts, installing backwater valves and sump pumps, and sealing windows and leaks.

“I think that the public are mindful of the work that is underway,” says D’Andrea. “At the same time, my hope is that they’re also taking measures to help guard themselves as well, that they’re not leaving it up to the city because it may take some time before we get to their neighbourhood to put in the upgrades.”

What you can do to help prevent basement flooding:

• Create a positive grade with earth mounded higher on foundation walls, so it slopes away from the house.

• Protect window wells, seal cracks in foundation walls.

• Disconnect downspouts from sewer system (now required by law) and redirect water to lawns and gardens. Ideally, water should drain out two metres from basement walls.

• Install a backwater valve or sump pump. The city’s Basement Flooding Protection Subsidy Program helps homeowners with costs (up to $3,200) to implement flood prevention measures or install such devices.

• Clear overflowing eavestroughs and downspouts of leaves and other debris that prevent proper drainage.


About this article:

By: Karolyn Coorsh
Posted: Jul 20 2012 2:51 pm
Filed in: NEWS
Edition: Toronto
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