September 18, 2009
Managing water flow integral to Don Lands revitalization project
The businesses that used to inhabit the 32-hectare West Don Lands are gone, as is most of their ancient sewer and water infrastructure.
In helping to lay the groundwork for Waterfront Toronto’s newest community, R.V. Anderson Associates Ltd. was retained to undertake and implement the necessary municipal infrastructure, including sewer and watermains, roads, street lighting and district energy system.
The new community extends from The Distillery District at Cherry Street to the Don River. Most important in the early stages of site preparation is getting the development levelled and scaped to protect it from flooding, says Peter Langan, Project Director with R.V. Anderson.
“The land used to slope toward the Don River, but in order to protect the West Don Lands from flooding, we’re in the process of changing the way that the water flows.”
An earthwork berm was constructed along the river to direct water toward a new stormwater management system along the extended Bayview Avenue that will release treated stormwater into Lake Ontario to the south.
“We wanted something that would last for a thousand years,” says John Campbell, President and CEO of Waterfront Toronto. “It’s made up of about 420,000 cubic metres of soil that rises about four metres above the river at the south end and a metre-and-a-half on the north and will comprise the six-hectare Don River Park.”
The Don River, as it enters Lake Ontario, is an engineered channel that has been straightened over the years. The berm, which began construction in 2007, is located on the former riverbed, underlaid by a pocket of 13 metres of compressible peat.
“The interesting thing from an engineering point of view was that, because of these soggy spots, it might have taken 10 years or longer to compress,” says Campbell. “We put more soil on the berm than we needed and drilled 30,000 wicks into the soil along a grid, to allow the peat to compress to the height we need in just six months to a year.”
The construction of the berm was preceded by a $20-million river-widening program, which included extending the CN rail bridge crossing the river at Lakeshore Boulevard, to accommodate stormwater run-off.
“We had to proceed with that work first,” says Campbell. “If we’d built the berm right away, we’d have had water on Bay Street.”
Old asphalt was removed from the site this summer to accommodate the new community’s infrastructure.
The first phase of water service will include the installation of 300-mm PVC watermains that will eventually follow about three kilometres of new roads.
“There is no designation for a LEED water system,” says Langan. “To earn supporting LEED points for the development, we’re sourcing local materials and aggregates that require minimal transportation.”
As a brownfield development, some existing site soil was contaminated through industrial use. Approximately 95 per cent of the soil was treated and re-used on site. For the trench where new municipal service infrastructure, including watermains, will be installed, clean fill will be used to a metre below and to 1.5 metres on either side, so construction workers will only come in contact with uncontaminated soil during current construction and future service.
Urban Capital Property Group, Toronto and Redquartz Development, Dublin will develop the first residential phase of West Don Lands. River Square Neighbourhood, which includes 850 units of housing located in an area bounded by King Street in the north to the Don River Park in the south and from St. Lawrence Street in the west to the extension of Bayview Avenue in the east.
“Due to the flood protection requirements and the time required for the compressible fill to settle, it’s put the project a little behind schedule,” says Langan. “But it’s allowed us to advance the construction of the extension of Mill Street from the Distillery District. Mill Street and its sewer and water service is the missing link that will tie the city’s existing infrastructure into the extension of Bayview Avenue, where the first housing will be constructed.”
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