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The wetlands that are supposed to take water draining from new houses on the South March Highlands can hold a lot less water than planners thought when they approved the development, says a report prepared for the city.
Residents in northwestern Kanata opposed to the controversial development hope the revelation will stop subdivisions from being built on the popular natural area; Kanata North Councillor Marianne Wilkinson says actually, there’s a chance that even more trees will be cut down to make way for better drainage works.
The report, completed last fall and recently released to opponents of the development under access-to-information legislation, updates a study done by a different consultant in 2007.
Since then, a large section of the forest on the highlands has been cut down by the land’s owner, KNL Developments – a partnership of developers Urbandale and Richcraft.
The new neighbourhood is partly supposed to drain into nearby wetlands called the Kizell Drain and Beaver Pond, on either side of Goulbourn Forced Road, which crosses the area from roughly the southwest to the northeast.
The difference between the old study (carried out for KNL by engineering consultants IBI Group) and the new one (carried out for the city by another firm, AECOM) is stark: The original calculated that the Kizell Drain could hold about 88,000 cubic metres of water. The new one says the drain’s capacity is more like 12,000 cubic metres.
After that, extra water starts pouring over the road.
The difference isn’t as profound for the larger Beaver Pond, but it holds less water than the first consultants thought, too, with spills over its internal weirs coming at about 180,000 cubic metres rather than 230,000 cubic metres.
“We can already see some of this happening,” said Wilkinson, particularly during spring melts. “The area around Beaver Pond floods, because it’s supposed to, and the water covers the paths we built around that area. That’s OK because they’re designed for it, but the water is starting to reach people’s backyards, which it isn’t supposed to do. – It’s not getting to people’s houses, anything like that, but it’s higher than it’s supposed to be.” A topographical map in the report suggests that at its very fullest, the Beaver Pond would surround several houses on Cecil Walden Ridge, at the northern edge of Kanata Lakes.
Paul Renaud, who posted the study Sunday on his website at renaud.ca, wrote that the difference is big enough to warrant an immediate halt to KNL’s development plans until a new system for dealing with all the water is worked out, and an investigation into how the original consultants got it so wrong. “It is incredible that the planning process in City Hall is so broken as to allow this mess to be created in the first place. The citizens of Ottawa deserve better planning and much more professional engineering work than what has occurred to date in the South March Highlands,” Renaud wrote.
He said Monday the situation indicates a problem with a system that relies on developers to hire engineering consultants to make recommendations on everything from water management to road safety.
“Developers have been hounding the city for years, saying that approvals don’t come fast enough,” he said. “Now we’re relying on developers to police themselves.” Having a city-sponsored report find such flaws with a developer-funded one shows that this doesn’t work, he said.
The new report doesn’t consider the cause of the original findings, though it says that IBI agrees with the new model. Wilkinson said the 2007 study depended on much older figures from when development in the area was first contemplated, so it’s not necessarily IBI’s fault.
Studies like these are done to estimate what will happen in the case of a once-a-century storm. The city’s estimates of how bad such a storm would be has changed since 2007, when the figuring was based on rainfall of 88 millimetres in one day; now, based on more recent severe storms, it’s 107 millimetres. But never mind the models; in 2009, the Kanata area got a downpour that was worse, with 148 millimetres of rain falling in three days, including 122 millimetres on the third day. That’s the rainstorm that led to floods elsewhere in the west end, particularly in Glen Cairn. The hit wasn’t as bad on the South March Highlands, says the newer report, but clearly such rainfalls aren’t just theoretical risks. If one happens, much more water pours into the drainage system than was ever supposed to.
If the system overflows, Wilkinson said, one danger is that water will head north, out of the highlands, and into a district of low-slung buildings holding high-tech companies.
Flooding isn’t the only concern, or even necessarily the major one. One purpose of a stormwater holding system is to capture pollution that rain carries away from lawns, driveways and roads, everything from dog droppings to car oil, and scrub it out before it reaches sensitive waterways like the Carp River and then the Ottawa. In even a moderately serious rainstorm, the new study says, well before the water starts spilling over the roads, it’ll rush out of the ponds and drains and into the waterways a lot faster, before it drops most of its gunk.
Development on the property is partly controlled by an old agreement negotiated between the now-defunct city of Kanata and the land’s previous owners that said 60 per cent of the area could be developed while 40 per cent was retained as open or natural space. The problem, according to Wilkinson, is that stormwater ponds count toward that 40-per-cent requirement, and more such ponds are the probable way to deal with the new understanding of the water situation. (KNL’s spokeswoman Mary Jarvis, the director of planning at Urbandale, said the company is working closely with the city to figure out what stormwater measures the property needs and will be happy to build them.)
“If they have to do stormwater ponds, then it becomes part of the 40 per cent and we’ll lose real natural areas that I’d want to preserve,” Wilkinson said.
All the engineering work now is really about how to develop the property, not about whether it should be developed at all. That ship has sailed, Wilkinson said.
“I’ve told them a thousand times if I’ve told them once,” Wilkinson said. “The only way to stop that subdivision is if somebody buys it.”
That infuriates Renaud, who said he can’t understand why Wilkinson “isn’t representing the people who elected her at city hall. She’s representing the developers and city hall to the people.” He said it’s “symptomatic of groupthink and Kool-Aid-drinking” that afflicts City Hall in general, and an attitude that construction is a good thing in itself.
The Citizen asked for an interview with the city engineer the AECOM report says is assigned to the file, Darlene Conway, but was told that with the number of departments wanting a say in the matter, including the city’s lawyers, it might not be possible to produce any kind of response before today.
dreevely@ottawacitizen.com
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