A team of experts from Delhi has arrived at the Kolkata airport to review whether a crane that has a 30m arm and is meant to be used for the construction of a Metro line can cause safety hazards for flights and, if it does, how to resolve the tangle and build the corridor.
Work on the airport-New Barrackpore Metro project has stalled for several months and airport and Metro officials said the proposals offered by both agencies to each other were not viable.
“The Airports Authority of India (AAI) has sent a team of seven experts to review the situation. They are supposed to stay till Friday,” a Kolkata airport official said on Tuesday. The committee, he said, will submit the report to the AAI headquarters in Delhi.
The crane in question is now lying idle off Jessore Road, along the perimeter wall of the airport. It was brought there by the Metro Rail authorities for the construction of the diaphragm wall of the underground tracks from the airport to New Barrackpore, further north. The construction will be adjacent to the airport’s boundary wall.
The crane will pick up pre-fabricated iron cages, raise them to a height of 30m above the ground and then lower them into the excavated pit below, said officials.
However, since last year, work has remained stalled because of the objections raised by the airport authorities. They had said the crane’s arm could cause safety hazards for flights operating in and out of the airport.
Metro Railway general manager Uday Kumar Reddy said on Tuesday that discussions were still on. “Talks are on with the civil aviation ministry and the Kolkata airport authorities. Nothing concrete has come out yet and various options are being explored,” Reddy said.
On Tuesday, an airport official said the Metro authorities had proposed that flight operations be stalled for several hours when the crane would be operated. “Work will go on for several months,” said the official.
“Kolkata is an international airport and stalling flight operations for several hours every day for months is not possible,” a senior airport official said.
The alternative will be to use another method of construction.
Now, the construction is planned according to the cut-and-cover method. The other proposal is to use a tunnel-boring machine and drill a hole underground. But the cost of the project will go up sharply if a tunnel-boring machine is used.
“No underground tunnelling is possible. Any other method except cut-and-cover is not viable,” a senior Metro official said on Thursday.
“In the cut-and-cover method, a pit is first dug and then the pre-fabricated structures are lowered into it,” said a Metro engineer. It will take 23 hours for one diaphragm wall to be constructed in the cut-and-cover method.
“Each diaphragm wall will be 31m high. It will take four months to complete all the diaphragm walls between the airport and New Barrackpore,” said the Metro engineer.
Several rounds of meetings have taken place between the Metro and airport authorities.
“Now, it is being dealt with by officials of the railway and civil aviation ministries,” said an airport official. Soon, another meeting will take place to review the project, sources said.
The Telegraph reported in January that airport officials had alleged that the railways had not taken clearance from them for the use of a tall crane. Two pilots had complained about the crane while landing, following which the construction was stopped.
According to officials, if the crane’s arm is raised to 30m, there could be problems in the functioning of communication, navigation and surveillance equipment in and around the airport. Also, the touchdown point, where the wheels of a plane touch the runway while landing, can be pushed further away from the edge of the runway.
Already, because of Jessore Road, the touchdown point is 1,400ft from the starting point of the main runway. Pushing the point further would mean the space on the runway that the pilots will get to slow down will shrink even more, officials said.
The airport-Barasat Metro project, already delayed by several years, was commissioned in January 2011 but never got going because of land logjams. In 2013, the contractor, Larsen & Toubro, withdrew from the project on the ground that there was “no clear site in a substantial patch”.
In 2018, it was decided that the tracks would be constructed till New Barrackpore because there was no land hurdle till there.