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Consultant gives development go ahead if additional water-storage areas created
Kanata West, a huge proposed development that’s been stalled for years due to questions about possible flooding, can go ahead if the plans add more areas to store stormwater, a consultant said Thursday.
Don Moss, a water resources engineer with Greenland International, said the city needs to get developers in the Kanata West area to create an additional 85,000 cubic metres of water-storage capacity, equal to between five and seven per cent of the total water volume in the Carp River.
Moss said the additional storage capacity would allow for water modeling done for Kanata West to be off by up to 12 per cent. All development approvals for Kanata West have been halted since the city found problems with the modeling for water during potential storms.
As well, Ontario Environment Minister John Gerretsen has taken a personal interest in the proposed development, ordering a number of conditions to be met before Kanata West approvals are issued.
“It’s an insurance policy,” said Moss, of the additional water-storage recommendation. The additional capacity would be phased in among
all developments at Kanata West and would amount to between 100 and 120 cubic metres of water storage per hectare of construction.
Moss said examples of water-storage methods include using gravel on parts of parking lots or reserving areas for vegetation, which would hold water and release it gradually into the river, instead of running rainwater right into the watercourse. If there were 10,000 residences built at Kanata West, and every one had a rain barrel, that would create an additional 10,000 cubic metres of water-storage space.
The 85,000 cubic metres of additional storage space is about equivalent to the capacity of three oil tankers. Moss said that if spilled across all of the Kanata West area, 85,000 cubic metres would be close to an inch deep.
The Carp River and its tributaries are very small watercourses, but they are shallow and could spill into a very flat part of Kanata in the event of a “worst-case” storm, a once-in-a-century event.
A group of about 40 property owners, including the City of Ottawa, have been planning offices, stores and residential neighbourhoods on about 725 hectares around Scotiabank Place for the last eight years.
Moss said that a problem with the water modeling for the Kanata West development is that there were six different software packages used by different development proponents and no single model took into account the total picture for water storage and flow. Missing hydrographs have been accounted for and the models have been updated, according to Greenland.
Moss said that there is no increased risk of flooding at the Queensway as a result of the proposed restoration of the Carp River, which would be done as Kanata West is built.
Rob Mackay, manager of strategic projects for the city, noted that the error in the water-modeling work at Kanata West was “significant” and that it has already resulted in the addition of three stormwater ponds in the design for the area.
Bay Councillor Alex Cullen said the original water-engineering work was flawed and had to be fixed. He was pleased that the problem was caught and he said every developer will have to build some storage capacity.
Kanata North Councillor Marianne Wilkinson said she was relieved that the consultant’s review is done and that developments might soon be winning approvals. She said a church youth centre, a Rona store and three subdivisions have been held up by the development freeze in her ward.
Councillor Eli El-Chantiry, who represents West Carleton-March, said he was pleased with the result. He said the concern over the flooding risk verged on overkill and that the delay in approvals has stopped projects such as a medical centre in the village of Carp. El-Chantiry said the risk of further delays is that people will leave Ottawa for neighbouring communities, such as Almonte.
Ted Cooper, a city water resources engineer who was assigned to Kanata West and then pulled off the file, said there are problems with the Greenland review.
He said the report did not address climate change and the possibility of increased flooding in the future, the way the environment minister had ordered. He said that a big part of the proposed solution is increased stormwater storage and treatment, but the city has been cutting its maintenance of stormwater systems.
City officials at the briefing on the Greenland report said they hope developments in Kanata West might get started by the third or fourth quarter of this year. Planning manager John Moser said there is a backlog of planning applications.
The report must be approved not only by council, but also the Ministry of the Environment and its minister before anything goes ahead. The report goes for committee discussion and public input May 12. It may be read online at ottawa.ca/carpriver
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