It takes ambition, nerve and thorough preparation to start digging around under an airport terminal building. Unfazed at the prospect, BAA has recently completed a 2km-long tunnel that runs between London Heathrow’s Terminals 5, 3 and the new Terminal 2, which also connects to an existing baggage tunnel between Terminals 1 and 4, in order to create a new and vital link for the airport operator’s forthcoming integrated baggage system.

The completion of the tunnel marks a huge achievement for BAA’s project team, which comprised various tunnelling experts that helped contractor Ferrovial Agroman complete this stage of the project on time and without disruption to the airport.

Yet, as BAA’s baggage and flight connections project director Chris Millard is quick to point out, there were a number of considerable challenges to overcome during the excavation period. “To give some scale to the size of the challenge, there are about 250 services to be negotiated including London Underground’s Piccadilly Line and the airport’s fuel farm, alongside 150 stakeholders to engage with. The tunnelling team have worked extremely hard and successfully so that there has been no disruption to any services and the team delivered the project on time,” he says.

Preventing tunnel trouble

“The completion of the Heathrow tunnel’s construction marks a huge achievement for BAA’s project team.”

A £3.3bn tunnel boring machine (TBM) was employed by the team during the excavation. Boring at rate of 15m a day, the TBM created a 5.6m-wide tunnel which was then fitted with 1,800 sections of prefabricated concrete panels. Over the course of five months, 148,000t of earth were removed from the ground. To ensure the TBM ran a precise course, state-of-the-art laser alignment technology was also employed.

“Laser-guided technology was only one aspect of the methods used to make absolutely certain that tunnelling occurred without interruption to airport operations. This technology certainly proved effective in ensuring the TBM remained on course.

Prior to the project, extensive modelling of the airfield was undertaken that took into account expected settlement levels, which was the course mapped out by the lasers,” Millard says. Sorry, there are no polls available at the moment.

“As a testament to the accuracy of these methods, when the team reached the half-way point of the western interface building (WIB) the point was within 0.2mm of the anticipated route. This all happened underneath the world’s busiest international airport without interruption to services and access.”

At over 2km long, 5.6m wide and at depths of up to 35m beneath the airfield, the completed tunnel will eventually be used to transport baggage between the airport’s terminals. This will primarily benefit connecting passengers, whose luggage will be redistributed underground to the relevant terminals.

Currently the airport relies on vans to redistribute transfer baggage around the airport. Given that Heathrow handles approximately a million bags every week or 150,000 departing bags and 100,000 arriving bags a day, of which 50,000 are transfer baggage, the scale of the transferred baggage operation is not to be taken lightly. “The integrated baggage system will help to improve the speed and reliability of the transfer baggage process,” Millard says.

“A £3.3bn tunnel boring machine (TBM) was employed by the team during the excavation.”

“The system will not have an impact on how the passenger checks in their luggage – this will continue as it currently does. Its purpose is to improve the speed and reliability of transferring bags between terminals. The main benefit is making the transfer of bags from one terminal to another much quicker, reducing the journey time of a bag by an average of 20 minutes. This is because the bags will no longer have to be transported into a van and then driven around the airfield to the appropriate terminal.”

Following the recent tunnel boring, the project team must now remove the TBM and the tracks used to transport material inside the tunnel before fitting out the new system and putting it through a lengthy trial period. The tunnels will be furnished with a trolley system comprising 960 carts, which run along a rail capable of handling 3,000 bags an hour. The carts are capable of transporting a single item of luggage at speeds of up to 20mph.

“Another benefit of the integrated system is that the baggage carts will be individually tagged with a radio-frequency identification barcodes, which means we will be able to track bags throughout the system. The function is already operational within Terminal 5’s baggage system and is working well helping to give Heathrow its best baggage performance results to date,” Millard adds.

Going underground

Heathrow’s Terminal 5, of course, was subject to fierce criticism following it’s opening in March 2008, when 28,000 bags infamously failed to travel with their owners during the course of its first ten days of operation. No such problems are likely to occur when the new luggage system goes live in 2012.

“BAA will ensure that there is extensive training when the infrastructure becomes operational. There are over 50 airlines moving as part of the airline relocation plan to enable the rebuilding of Terminal 2 into a world-class facility and several of these have already taken place successfully,” Millard says.

“The completed tunnel will eventually be used to transport baggage between the airport’s terminals.”

“The baggage infrastructure has been designed to be extremely robust to ensure it meets the needs of the world’s busiest international airport. It has been designed for performance and reliability, using proven technology.”

A total of £260m will be invested in the state-of-the-art inter-terminal baggage system, which looks certain to grab the mantle of world’s largest integrated baggage system when it goes live in 2012. The completed underground baggage system will play an integral role in Heathrow’s broader focus on baggage handling systems in the coming years, which will see an investment of £900m eventually lead to the airport handling 110 million bags annually.

Furthermore, a much larger £4bn investment by BAA is also underway to transform the airport for its passengers and airline customers.

“The system is great news for airline customers and passengers as transfer bags will be processed quickly and efficiently between terminals. In addition to the tunnel, the baggage systems in Terminal 3 and 4 are being replaced and the existing baggage tunnel between Terminals 1 and 4 is being refurbished,” says Millard.