Posted Aug 23, 2019, 2:12 PM
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Join Date: Mar 2012
Location: Ottawa
Posts: 28,793
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Good piece on the tunnel by Jon Willing. Only significant omission is the shifting of Rideau Station east to William Street.
Quote:
How Ottawa ended up with a 2.5-km rail tunnel under its downtown
JON WILLING Updated: August 22, 2019
Postmedia
One tunnel for incoming trains and another for outgoing between the MSF Connector and the St. Laurent Station. JULIE OLIVER / POSTMEDIA
There were two ways the city could get electrified trains through the downtown core when it was planning its east-west light rail system more than 10 years ago: build rail lines on the road surfaces or dig a rail tunnel.
A 2007 report from a task force appointed by former mayor Larry O’Brien, whose council cancelled a north-south LRT contract, recommended a downtown rail tunnel as the best way to breathe life into the core and get rid of the daily traffic bottleneck.
Digging a tunnel through the core of the nation’s capital would be expensive, but there was potential to reduce the operating costs of OC Transpo by taking diesel-guzzling buses off the roads and removing any barriers to getting through a busy downtown at rush hour.
The 2008 transportation master plan included a downtown tunnel as the backbone for the “phase one, increment one” of an LRT system, part of a larger vision to expand rapid transit across Ottawa.
Eleven years later, the city has a 2.5-kilometre tunnel running through the downtown just blocks from Parliament Hill, and the city is preparing to remove hundreds of bus trips from the core, thanks to a $2.1-billion crosstown electrified rail line.
Going from west to east, trains will enter the tunnel after leaving Pimisi Station on LeBreton Flats. The west portal is just before Bronson Avenue and the tunnel runs a straight course under Queen Street, passing through Lyon and Parliament stations before making a slight turn north at Elgin Street. The tunnel dips under the Rideau Canal and then under Rideau Street to Rideau Station. After passing the Rideau Centre, the tunnel bends south and trains will exit the eastern portal just past Laurier Avenue at the University of Ottawa.
The downtown Ottawa transit tunnel project (the DOTT project, as it became known before the city branded it as the Confederation Line) originally called for a 3.2-kilometre tunnel with four underground LRT stations as part of the 12.5-kilometre, 13-station rail line.
Geotechnical studies in 2010 convinced the city to shorten the length of the tunnel in the area of the University of Ottawa, eventually leading to the final design of a 2.5-kilometre tunnel with an east portal short of uOttawa Station, which would be built above-ground rather than be carved out as a tunnel station.
Jim Watson took over as mayor on Dec. 1, 2010 as the city was trying to figure out how to thread a deep tunnel through the core while protecting its $2.1-billion estimate for the entire LRT line.
Armed with a mandate to keep annual property tax increases capped at 2.5 per cent, Watson’s first move was to get staff scrutinizing budget estimates for the LRT project and the larger transit program. About seven months after he moved into city hall, the city announced a new “better-value alignment” that shifted the tunnel north.
Originally, part of the tunnel was to be constructed under Albert Street with a diagonal alignment between Kent and Rideau streets. The city received criticism for planning a tunnel that would require lengthy descents and ascents for transit users between the surface and the underground stations. There was also the fear that private-sector construction bidders would be nervous about the financial risk in building such a deep tunnel (as much as 40 metres below the surface in the area of O’Connor Street) under a fixed-price contract.
Former councillor Peter Clark received credit for suggesting a shallower tunnel route under a city street. Running the tunnel under a narrow Queen Street corridor, now with a maximum depth of 16 metres in that O’Connor Street location, became a cheaper option. The city had a better shot to land a fixed-price construction contract to build increment one of LRT.
Of the $2.1-billion estimate for the entire LRT line, the city pegged the cost of tunnel construction at nearly $500 million. The contract competition began and the Rideau Transit Group (RTG) consortium of companies won the project with a council vote in December 2012.
RTG started mining the tunnel in fall 2013 using a method called sequential excavation. Twenty-metre-long “roadheaders” chipped away limestone, clay and sand as miners installed steel supports and sprayed concrete in behind the tunnelling machines, which advanced about three metres per day on average.
The average depth of the tunnel is 15 metres below the surface. When transit customers are waiting for trains at Rideau Station, they will be at the deepest part of the tunnel, 26.5 metres underground. Transporting people between the street level and the Rideau Station platform has required the installation of the longest escalator on a Canadian transit system. The escalator is 35.3 metres long.
First responders leave the LRT area at Laurier and Waller after a piece of shotcrete fell in the tunnel in Ottawa, November 10, 2016. JEAN LEVAC / POSTMEDIA NEWS
Construction of the tunnel was far from perfect.
A sinkhole appeared on Waller Street near Laurier Avenue, near the east tunnel portal, on Feb. 21, 2014.
And everyone knows about the massive sinkhole that opened above the tunnel on Rideau Street on June 8, 2016, swallowing a van and construction equipment.
On Nov. 10, 2016, three tunnel workers spraying concrete were trapped on a lift about 100 metres from the east portal. Then, a crane flipped over trying to lift a truck at the east tunnel portal on April 26, 2017.
No serious injuries were reported in the mishaps, but the Ontario Ministry of Labour has been keeping tabs on construction. At one point, the local labour council wasn’t convinced that the tunnel project was safe for workers.
Inspection reports on the tunnel construction revealed there were problems with some of the concrete pours and deficiencies with the waterproofing. Other reports described clogged pipes in at least one tunnel station.
Now that RTG has built the underground rail, its affiliate, Rideau Transit Maintenance, will look after the tunnel under a 30-year maintenance contract with the city.
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