Gary/Chicago International Airport and Canadian National Railway have reached a preliminary agreement on moving railroad tracks that block expansion of its main runway, which remains one of the last hurdles to beginning construction.

"This is a huge, huge step," said Leigh Morris, chairman of the Northwest Indiana Regional Development Authority on Friday. "This could have been a show stopper, if we were not able to come to agreement on this."

Canadian National wants to come to a final agreement on moving the tracks within 90 days, according to a June 23 letter from the railroad to Airport Director Chris Curry.

Curry gave a rough estimate of $30 million to $35 million for the project. That is at least $10 million less than estimates for the cost of moving the tracks under a previous preliminary agreement that involved three railroads.

Curry and his predecessor at the airport, Paul Karas, have been negotiating with railroads for more than half a decade over moving the tracks. Those negotiations were complicated recently when the tracks were sold by the EJ&E Railway to Canadian National.

The estimated cost of the current project is less because it does not contain enhancements for other railroads, some of which would have occurred miles from the Gary airport, Curry said.

Morris said the RDA expects the airport to seek partial funding for the project from his organization. The RDA was directly involved in the airport's negotiations with Canadian National on the deal.

The letter from Canadian National states its final approval is contingent on completion of a definitive agreement and detailed engineering plans.

If final negotiations and engineering on the project go well, construction on new tracks could begin by spring, Curry said.

The agreement with Canadian National includes a new alignment for the tracks, which will require the purchase of about 25 more acres of land, Curry said. The airport has already purchased about 160 acres to make way for runway expansion.

The only remaining hurdle to expanding the runway is obtaining an environmental permit for the runway expansion. That process has been slowed by a dispute with the Gary Community School Corp. over rare dune and swale habitat the airport wants to buy to replace those at the airport.

The school corporation has rejected a $375,000 offer from the airport as too low. The Gary Board of Public Works recently voted to initiate eminent domain proceedings against the school corporation to obtain the land for the airport.