The Rideau Station Cavern of Ottawa's Recently Opened Confederation Line

Thursday, November 14th, 2019

The Confederation line is an electrically powered light rail line crossing Canada’s capital from west to east and opened to the public on September 14, 2019. It was the largest infrastructure project in the history of the City of Ottawa and took approximately six years to build, costing approximately $ 2.1 billion CAD. The Confederation line included the design and construction of three mined underground stations located in the centre of the city: Lyon, Parliament and Rideau.

Ottawa’s light rail transit map (

Lyon and Parliament stations were constructed in limestone and shale bedrock, and the Rideau station was partially constructed in the glacial till and glaciofluvial deposits overlying the bedrock.

Rideau station cavern construction transition from bedrock to soil

The 20.8 m wide and 16.5 m high Rideau station cavern is likely to be the largest of its kind built in North America to date.

Rideau station cavern completed and construction of the running tunnel towards Parliament station in progress

The soil mainly comprising glacial till was dewatered before cavern construction started, pipe roof pre-support was installed over the full length of the cavern in soil, and a double side wall drift SEM excavation and support sequence was employed. The initial cavern lining was of 500 mm thick sprayed concrete and included two layers of mesh reinforcement.

Final cavern lining installation in progress

The waterproofing of the cavern comprised a tanked sheet waterproofing membrane system.

Fully fit out Rideau station cavern