Green Line boss makes pitch for 1 tunnel through downtown Calgary, not 2

When it comes to putting an LRT tunnel under Calgary's downtown, the guy in charge of the project says one big tunnel could be better than two smaller, parallel ones.

The idea was put before the city's transportation and transit committee on Thursday.

A large tunnel boring machine will be brought to Calgary for the construction of the four-kilometre-long underground section through the city's core.

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The machine will be a large one. The city is looking at one that's 14-metres in diameter.

The managing director of the Green Line project, Paul Giannelia, said there would be significant benefits to boring a bigger, single tunnel to hold both tracks versus smaller, twin tunnels that would each holda single LRT track.

"What a single tunnel eliminates is the need for deep, open-cut stations because the tunnel itself becomes the station," said Giannelia.

That meansless disruptions at the surface for neighbouring buildings and businesses. He said it also saves costs related to underground utility relocations.

A single tunnel also potentially saves money because there would be less construction around each station.

"During construction, there'll be less impact with the travelling public, whether it's pedestrian or vehicular," said Giannelia. "That's a big plus, a big gain."

By December, he said they'll have a sense of how much could be saved by switching to a single tunnel.

Among his goals for the Green Line is to deliver Stage 1 of the $4.6-billion mega-project on time and at the lowest possible cost.

Changes to access

The move to a single tunnel could result in changes in how people can access the four underground stations which will be located at 16th Avenue N., SecondAvenue S.W., SeventhAvenue S.W.and Centre Street at 12th Avenue S.E.

Coun. Druh Farrell said she's worried less about single versustwin tunnels than she is about what that decision could mean for areas above the stations.

"What I'm concerned about,certainly communities are concerned about,is deviating from the approved plan, which is to develop a train plus the areas around the train," said Farrell.

More information is expected to come to city council in December.

Preparation work for the Green Line is continuing. Landfills are being removed next to the future HighfieldStation,utilities are being relocated and properties are being acquired.

Construction on the Green Line is projected to start in 2020.

The first 20 kilometres of the line,which will ultimately stretch across the city north to southeast,are scheduled to go into service in 2026.

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