Officials began the process of shutting down one of the Edmonton City Centre Airport's two runways Tuesday morning, despite protests from a lobby group fighting to keep the strip open.

Edmonton Airports says from now through to the fall, work crews will physically alter runway 16/34 by placing barricades, removing lights and painting signage on its surface. The goal is to ensure pilots know the strip is no longer in operation.

"It is a historic moment," said Traci Bednard with Edmonton Airports.

"We know it is a challenging day for tenants….We're trying to do this in a way that respects that but also recognizes that we have taken a year to make sure that we have prepared properly and have done what we needed to do to make sure this is a safe closure."

The development comes about two-thirds of the way through Envision Edmonton's 60-day campaign to force a plebiscite on whether to close the City Centre Airport. The group says it currently has about 55,000 of the nearly 80,000 signatures needed to make that happen.

In an email sent to CTV News, representatives decried Tuesday's closure with the following statement :

"We are disappointed that the City is ignoring the majority 76.8 per cent of Edmontonians that think they have the democratic right to make this decision regarding the fate of the airport. Closing the runway is a reversible decision. It closed for the Indy and was reopened. We will continue to gather signatures and fight the City on this issue."

CTV News has learned the city may take legal action to challenge the petition drive because it was not launched within two months of council's decision – made on July 8th, 2009 - to close down the airport in phases.

Envision Edmonton spokesperson Chuck Allard argues that would be a bad move so close to October's civic election.

"If they want to try to strip a democratic right that's given under the Municipal Government Act let them go ahead. It sends a strong message to the electorate."

Mayor Stephen Mandel says it's the city's job to move ahead with its own plans for redeveloping the site.

Administration has entered a verbal agreement with STARS Air Ambulance that will allow helicopters to continue using the ECCA while contingency plans are sorted out.

While there is no word when the other runway – known as 12/30 – will shut down, Indy commitments ensure no closure will happen for at least the next three years.

In order to accommodate the transition to a single-strip airport, officials with Edmonton Airports say they completed installation on a GPS navigation system in June.

With Files from CTV's Scott Roberts