A map shows the proposed tunnel under the Calgary airport. ((City of Calgary))

The federal and provincial governments might help Calgary build an airport underpass by finding ways to lower the cost, Mayor Naheed Nenshi says.

Following last fall's election, Nenshi said building the underpass under a new runway at the Calgary International Airport is a priority.

A new landing strip being built in April 2011 will force the closure of Barlow Trail between 48th Avenue and Airport Road N.E., unless an tunnel is constructed for vehicle traffic.

A cost estimate for the project is being prepared and will come to council for debate on Jan. 24, Nenshi said this week. The new council approved a $250,000 study of the project, with cost estimates, at their first meeting in November.

During the election campaign, the cost was estimated at anywhere from $40 million to $900 million if the underpass is built after the runway is finished.

The federal government controls Transport Canada and could help the city by changing requirements for the underpass to make it less expensive, Nenshi said.

"The design guidelines for this underpass are heavily influenced by Transport Canada and they've been very clear that they're looking for a good, cost-effective and safe solution for us, which may not be the solution that the airport authority had been proposing in years past, which is a very complicated, very expensive solution," Nenshi said.

For its part, the provincial government is looking for ways it can be flexible with its infrastructure financing so the city can use the maximum amount of infrastructure money in paying for the tunnel.

"Problem is, there's not much new money. There's certainly not new money to build the full project," Nenshi said. "We're gonna have to find the resources through funding we've already got."