Special report on rail: Unblocking 'The Drain'

Metronet's decision to completely close the Waterloo & City line enabled Balfour Beatty Rail to refurbish the track in just 19 weeks. Helen McCormick took a walk through the tunnel.

Jumping off a Tube platform onto the track below and heading into the dark tunnel on foot is a bizarre experience that most London commuters will never have.

Passengers want their journeys to be as brief and easy as possible, and only consider the infrastructure that makes it possible when something goes wrong - which, on the somewhat dilapidated Waterloo & City Line, it frequently did. The line was in such poor state that it suffered frequent signal failures and speed restrictions.

Those using the newly refurbished trains on the line nicknamed 'The Drain', which will reopen next week after a five-month closure, will be whisked along at a brisk 55km/hr, completing the journey from Waterloo to Bank in less than 10 minutes.

Making the 2.4km journey on foot takes rather longer, as the Balfour Beatty Rail workers who made the daily trudge along the tunnel - which can only be accessed at the Waterloo end for health and safety reasons - know all too well.

The upgrade work was originally intended to be completed by March 2007, with work undertaken during 87 weekend closures and others ranging in length from four to 30 days, a common working structure under the huge Underground PPP contract. Instead, Tube maintenance firm Metronet took the decision to pay £3m to London Underground to fully close the line, thus avoiding any disruption to Monday morning services.

It appears to have been money well spent, as this approach has ensured the project met its deadlines, no doubt to the relief of the 40,000 City workers who have had to make alternative travel arrangements over the summer.

The full closure, which compressed nearly two years' worth of temporary work, was possible because the 107-year-old line has a convenient depot at the Waterloo end, which was once a coal-fired power station. As parts of the depot have not been used for some years, track had to be realigned and worn components replaced along the road that sits below the shaft used to lift in and out the rolling stock and the machinery required for the works. These included four battery-powered locos, used to haul materials and plant along the line (and named Walter, Lou, Anne and Kitty in honour of the line) and a special self-propelled track trolley formation, used for lifting, delivering and lowering pairs of 60ft rails.

Most importantly, the route is wholly underground and physically isolated from the rest of the network, making it one of the few lines suitable for complete closure.

"This is not a panacea for the Tube network, although it has to be a safer and more efficient way of working than temporary closures," says Balfour project director Adam Stuart. "You need a depot for trains and materials. I believe less than a third of the network is suitable. Not to mention the fact you have no personal life for 19 weeks."

All change

There was a lot of work to do. Balfour's £40m contract has seen it replace and realign the two running rails and conductor rail in both directions. Some 3,800t of spoil, 2,515 timber sleepers, 9,000m of old rail and 4,500m of old conductor rail had to be removed and replaced with 5,650 sleepers, 9,076m of rail, 1,482m of check rail (used on small radius curves to prevent derailment) and 4,450m of third rail.

The contractor continuously deployed staff 24 hours a day in three shifts, seven days a week, with 240 staff on site in a 24-hour period. This constant workforce meant some shift tweaks were necessary. "The morning changeover is at 7am, to allow the lads to get the tube in to work, and again at 11pm for the same reason," says Stuart.

When Contract Journal visited the site in June, much of the old concrete had been removed, ready for the laying of new track. Travelling at rather less than normal walking pace, due to the uneven ground and sections of raised sleepers that must be clambered over, you appreciate how sharp the curves are compared with most Tube tunnels.

"Some of them are 90m radius curves, as tight as anywhere on the Underground," says Stuart. "Welding 60ft rails is tricky, but we've cracked it."

The bends are the result of the layout of the Square Mile directly overhead, as Stuart explains. "The line was built after most of the landmark City of London infrastructure. Property owners didn't want their foundations tunnelled under, so the tunnel more or less follows the line of the road above. Some areas have a double curve, which is unheard of on most railways."

The bulk of Balfour's work was concerned with upgrading the track in the eastbound and westbound tunnels. This included re-railing the track and and re-sleepering areas that required check rails to hold the train to the curve. Some of the old sleepers were longitudinal, an unusual formation, and replacing these will allow trains to travel much faster on the bends.

A drop of the hard stuff

Concreted sections were also reconditioned. Most were fairly straightforward to remove, although it was an incredibly hot and noisy operation in the cramped tunnels. One section, however, had been previously repaired with an extremely hard concrete, which required tungsten-tipped drills to remove. "Normal ones just bounced off," says Stuart.

At first, the new concrete was mixed in-house, which Stuart is happy to admit was a mistake. "The concrete pour is not that massive, so we took the view that being able to concrete whenever we needed was worth it. It was the wrong decision, we did it twice that way and it was arduous, so we made arrangements with a local supplier instead."

Balfour used Tecroc, a super-hard form of concrete. "We needed to run vehicles on it very soon after it was laid, and it's possible to do so just eight hours later," says Stuart. "The drawback is that it's 10 times more expensive than readymix.

"Time is also pretty tight. It's two-hour concrete with a two-hour retarder, so we have four hours. But it takes half an hour to get it here from our suppliers at Battersea and King's Cross, and half an hour to get it in the tubs and down to the tunnel, leaving us just three hours."

The tubs were lowered into the tunnel using a 1.5t Pelloby crane. "We decided to spend £50,000 on our own crane, which was definitely the right decision," says Stuart. "It's been a great buy, incredibly useful for all sorts of tasks, and it would have cost something like £400,000 to hire a crane 24/7 for 19 weeks."

Go with the flow

The old Waterloo & City Line suffered frequent signal failures due to water ingress. A new open drainage channel has been formed under the sleepers to take the water to the pumping station at the mid-point under the Thames, which should prevent this happening in future. Due to varying gradients, it is filled with shingle to sleeper-level between Bank and the pumping station to slow the flow of water, but left open with solid covers spanning between the sleepers for the remainder to Waterloo. This should make future drainage inspections easy to carry out.

Balfour also undertook signalling modifications to reduce the headway between trains, increase the maximum speed at which the crossover between the two running lines at Bank can be negotiated, and reduce turnaround time at Waterloo. Equipment rooms at Bank and Waterloo have been rewired and signalling relays renewed or refurbished.

Bombardier Transportation is supplying a new control room system that should allow up to five trains to operate at the same time, compared with the previous system's four. It is due to be commissioned in early 2007 following completion of Phase 2 of the project.

Another advantage of completely closing the line was that both stations could be spruced up with a lick of paint and some new tiles and signage. Back in June, Bank station looked like a scene from the Blitz, with a heavy covering of dust. This eerie atmosphere was heightened by the fact that no one had turned off the station announcements. Every few minutes a well-spoken female voice reminded us to take all personal belongings with us, and warned that there was no service in either direction. The trains themselves were also removed and sent away for a refit.

The thousands of stockbrokers and bankers making the short hop across the Thames should from now on have little cause to ponder the mechanics of their journey, which is exactly what Metronet and London Underground intended.

History of 'The Drain'

Designed by WR Galbraith and James Henry Greathead, the Waterloo & City Line was opened in 1898 as part of the London and South Western Railway. It served as an extension of the main line into Waterloo, which had originally been intended to run to the City, but was prevented from doing so by the 1846 ban on surface railways running through the central area of London.

It was London's second deep-level Tube, became part of the Southern Railway in 1923 and was subsequently nationalised with the mainline railways in 1948. It did not become part of London Underground until 1994, when it was bought for a nominal £1.

There are three main theories for the line's nickname 'The Drain': some believe it relates to the smell of the marshy ground on which Waterloo is built, while others believe it relates to the drain-like round deep-level tunnels. Some suggest that the depiction of the line on the Underground map resembles a drainage pipe leading out of The City. However, the truth is more prosaic, and probably has more to do with its initials WC.

[Contract Journal, 6 September 2006, p 30]