Workers reach final stretch in LRT tunnel
By Jon Willing, Ottawa Sun
First posted: Friday, December 25, 2015 10:49 PM EST | Updated: Friday, December 25, 2015 10:54 PM EST
Humberto Ferrer and his team can almost see the light at the end of a 2.5-kilometre tunnel in downtown Ottawa.
"The morale is very high," Ferrer, the deputy director of the Rideau Transit Group, told the Sun.
"The people are very excited. We're very close to completion. We're in the last six months of excavation and everybody is very motivated."
Just 600 metres more to go and the LRT tunnel between Lebreton Flats and the University of Ottawa will be excavated. It will be a big milestone for Ferrer and workers with RTG, which is the city's contractor on the $2.1-billion rail system, the largest infrastructure project in Ottawa's history.
The 12.5-km Confederation Line LRT is scheduled to open in spring 2018.
The last leg of tunnel to be mined is between the future Parliament and Rideau stations.
The tunnel between the west portal, just west of Bronson Ave., and Parliament station, around O'Connor St., has been carved. Workers are mining the station at Parliament. On the other side of the Rideau Canal, the tunnel between the east portal (Waller St. at Laurier Ave.) and Rideau station is excavated, with workers carving the station cavern.
Planning is already happening for the big photo opportunity, likely in June, when a roadheader tunnelling machine breaks through rock near the Sussex Dr. end of Rideau station, marking the end-to-end excavation.
There will be an earlier milestone in February when the cavern at Parliament station will be fully excavated. The tunnel machines are diving deeper under the surface as they leave the Parliament station cavern, whose roof is about 16 metres below ground. LRT passengers won't be able to fully appreciate the grandeur of the station caverns since walls, pillars and finishes will eventually fill up the cavities.
The tunnel stretch between Parliament and Rideau stations is noteworthy because mining machines will be working near the National Arts Centre and will dive below the Rideau Canal.
Gary Craig, the city's chief of LRT design and construction, said the contractor will make sure there aren't disruptions with performances at the NAC.
"We're going to be working with their schedule a little bit to try and adjust and make sure we're not doing a lot of the heavy use of the bits on the roadheader and creating a potential impact," Craig said.
While the tunnel will pass under a heritage waterway recognized by the United Nations Educational, Scientific and Cultural Organization, the city and RTG aren't required to meet any special protection measures to protect that international status.
That's because the tunnel will be nowhere near the canal. There will be 20 metres of rock between the bottom of the canal and the top of the tunnel when a roadheader starts rumbling below the waterway in April. Ferrer expects it will take seven to 10 days to pass under the width of the canal as workers dig toward Rideau station.
At about 26 metres below the surface, Rideau station will be the deepest part of the entire tunnel.
Crews are already installing tracks east of downtown and Ferrer expects they will begin laying tracks inside the tunnel next October.
The toughest part of the tunnel construction so far has been around Lyon station, Ferrer said. Workers operating the roadheaders had to be extremely precise scraping out rock next to buildings along Queen St. The buildings were a similar depth to the upper portion of the cavern and crews had to be mindful of the load transfer to the lower levels of the buildings.
"We were really mining one metre from the parking (levels)," Ferrer said.
In fact, there was one glitch in July 2014 when a couple of rock bolts used to stabilize the excavation punctured the parking garage at the Sun Life building. There was no risk to the building's integrity and RTG made the repairs.
The only other reported problem with the tunnel construction was on Waller St. when a sinkhole happened in February 2014. No one was hurt and the city chalked it up to an undetected pit of backfill.
The tunnel work started with just seven workers at the western portal. Now there are about 120 workers on different shifts 24 hours a day. They're getting a bit of a break over the Christmas and New Year's holiday period to spend time with family and friends.
While the tunnel expertise has come from international experts, many of the work hands are from the Ottawa area.
Ferrer is from Barcelona, Spain and moved his family to Ottawa in January 2013. They will be here until at least 2018 and potentially much longer, considering the city wants to extend rail in three directions by 2023.
"It's great here," Ferrer said. "It feels like home."
Twitter: @JonathanWilling
About the Confederation Line tunnel
Total span: 2.5 km
Portals: Commissioner St. near Albert St. (west); Waller St. near Laurier Ave. (east)
Built-in stations: Lyon, Parliament, Rideau
Average depth below surface: 15 metres
Tunnelling method: Sequential excavation
Mining machines: Roadheader (3)
Ground material: Limestone (previaling), clay, sands
http://www.ottawasun.com/2015/12/25/workers-reach-final-stretch-in-lrt-tunnel
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