Green Line tunnel under Bow River and downtown seen as best option for new LRT route

The best route for the north-centralportion of Calgary's next majorLRT expansionwould be to tunnel from 20th Avenue North, beneath the Bow River and all the way under downtown, finally emerging in the Beltline, according to the first-stage evaluation of the mega-project.

With an initialballpark estimate of $1.8billion,that was the most expensive option being considered by the city, but also the one that is believed to offer the fastest transit times and create the least disruption to existing traffic patterns.

• Calgary mulls downtown Green Line LRT route options
• Calgary's Green line route to be studied further
• North-central LRT routes through downtown up for debate

The city is also looking at the possibility ofbuilding a new bridge to carry LRT cars over the Bow River, then either carrying the line above grade over downtown or building a shorter tunnel below the city centre.Those optionswere believed to be roughly $500 million less expensive than the full-tunnel option.

The cheapest option under consideration would be to run the LRT line down the middle of the existing Centre Street Bridge, pegged at about $700 million less than the full-tunnel route.

Those cost estimates are from February 2015, however, and they are only rough figures of a project that remains a long way from even getting started.

Monday's announcement that the city is leaning toward the full-tunnel option is just a "first step in designing the downtown segment of theGreenLineLRT," according to project managerJon Lea.

"We're starting to get a sense of what this project could mean for the downtown, and we're looking forward to continuing our work withCalgariansto further shape this new transitline," he said in a release.

In total, the city examined five possible routes through downtown, with various combinations of elevated, street level, and underground routes for the Green Line.

An evaluation of environmental sustainability, technical feasibility, cost, alignment with existing city policies,urban development, and public input led city staff to conclude "Option D"full-tunnel route best met the criteria.

"We hear often with the LRTs we have today: Why didn't you put them underground?" said Coun. Shane Keating.

"It is the most expensive option, but today is not really about the cost, trying to nail it down. It's saying 'What is the best for the City of Calgary?'"

Beltlineroute next to be evaluated

TheGreenLine's route through the Beltlineis still to be determined and could includeunderground, street-level or elevated routeson 10th Avenue, 11thAvenue or 12thAvenue South.

Public input will be sought and more informationcan be found online and at an "interactive installation" the city plans to host atOlympic Plaza April 18 to28, in addition to a series of "pop-up events" over the nexttwo weeks.

The route through the Beltline would connect to the southeast portion of the Green Line, which isfurther along in the planning process, with the route already determined.

The goal of the multi-billion project is to have light-rail transit running all the way from the city's northern edge tothe deep-southeast community of Seton.