Half of the concrete for the new Airport Trail tunnel has now been poured, the city says.

The walls and roof of the 620-metre tunnel — which will link Airport Trail (96th Avenue N.E.) on the west side with 36th Street N.E. on the other side — are being poured in 50 sections.   As of Friday, 26 of the sections had been poured, the city announced on Monday.

Construction of a new runway at the airport forced the closure of Barlow Trail between 48th Avenue and Airport Road N.E. in April last year.

The plan to tunnel under the runway was hotly debated in the 2010 municipal election. Mayor Naheed Nenshi, who campaigned in favour of it, said the tunnel will improve the city’s transportation network.

"This is a significant milestone in the completion of the tunnel," he said.

Once the tunnel’s walls and roof are complete by the fall, the city will hand over that portion of the project to the Airport Authority so that runway construction can start, the city said.

"Project management and work crews have done an outstanding job so far in meeting the tight construction schedule and maintaining budget," said Ward 3 Ald. Jim Stevenson.

Each tunnel section requires 850 cubic metres of concrete which takes 80 trucks to deliver in a 12-hour period.

More than 22,000 cubic metres of concrete has been poured since late February.

Most of the work on the roadways will be done next year. The entire project is slated to be done by May 2014.

The project is being constructed in three stages. Stage one consists of:

  • Construction of the tunnel under the new runway.
  •  Widening Airport Trail between Deerfoot Trail and Barlow Trail to six lanes.
  • Extending Airport Trail through the tunnel to 36th Street N.E.

The estimated cost of the first stage is $280 million. In 2011 council approved a budget of $294.8 million for the six-lane transit-way.

Stage two will include the construction of interchanges along Airport Trail at Barlow Trail and 19 Street N.E. as well as extending Airport Trail to Metis Trail. The City will pay $50 million and the airport will contribute $20 million to the cost of the stage two interchanges.

In stage three the city and the airport will split the cost of building upgraded interchanges to improve access from Airport Trail to the airport when traffic levels warrant, which is expected to be decades from now, the city said last year.