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Electric charge

Integrating two distinct station construction activities was the key to completing the complex London Bridge Station on Contract 104.

Paul Gover took over as senior supervising engineer two years ago to shift the emphasis of the project management towards the electrical and mechanical work. He has been with the project a great deal longer however and spent three years prior to this heading up Drake & Scull's two linewide electrical contracts, 205 and 206.

His task was to follow the tricky and time-consuming civils tunnelling work and take a firm grip of the huge station fit out programme. This meant controlling and organising numerous designated subcontractors and marrying their work into the remaining civils activities.

The contract was one of those most affected by the Heathrow Express tunnelling collapse. Contractor Costain-Taylor Woodrow's plans to construct tunnels with shotcrete had to be substantially revised to use cast iron segments and whole sections of the station layout, particularly the ventilation and escape tunnels, were revised to simplify construction.

Despite continuous refinement of the programme and operations, it was inevitable that time would be lost. And while he accepts that it is never good to finish a job late, Gover insists that long term benefits of the JLE will outweigh any inconvenience in the short term.

'When you see passengers on the trains you realise that the project has been a success,' he says. 'It will be in use for 100 years or more - a few months delay must be seen in this context. Besides, on public funded projects there is always pressure to give a fixed end date - who is to say that thisone was ever truly realistic?'

Civils work at London Bridge was always divided into two distinct areas - construction of the new Jubilee Line station and reconstruction of the Northern Line station to create a new central concourse and bring the station up topost King's Cross fire standards.

This work was always going to be very difficult as it required a huge oval shaped step-plate junction to tie the new southbound Northern Line platform into the existing running tunnel. This was directly under the River Thames with just 5.5m of soft clay separating the tunnel soffit from the river.

Site investigations had revealed that the clay had been disturbed by timber piles during the construction of the original Rennie-designed London Bridge. Further investigations showed this to be much worse than predicted and plans had to be altered at the end of 1995 to reduce the risk of flooding the Tube system.

The solution was radical and meant the southbound Northern Line had to be shut from July to September - at some inconvenience to the travelling public - while a smaller direct connection was made. Early options to stabilise the tunnel by filling it with foamed concrete or using compressed air were eventually felt unnecessary.

Meanwhile, in the JLE station, approval to continue using shotcrete was given the go ahead on the condition that the two platform tunnels and central concourse were not constructed simultaneously. In addition pilot tunnels had to be constructed first to prove the ground in advance of the tunnel enlargement. Using these safeguards it was possible to construct an 11.7m diameter concourse tunnel using shotcrete support, but for many of the smaller tunnels the original Engineer-designed cast iron lined tunnels were constructed.

While credit for the highly complex tunnel construction at London Bridge must go to a large extent to construction manager Marcus Karakashian, once completed in 1997 the responsibility for the job was passed to Gover as the E&M expert.

In contrast to the civils work, when the two areas remained virtually unconnected, when it came to the fit out stage Gover decided that the most effective strategy was to treat the two areas as one and allow the E&M works to dictate the pace.

'We had to refocus the project at London Bridge to make everyone aware of the E&M needs,' he explains. 'While we still had a large number of civil engineers working on the job there was no doubt that the E&M contractors had to come to the fore.'

'We sorted out a target programme when I arrived and we have stuck to it,' he says. 'The priority has always been on areas that had to open first and we have worked with the contractors to make it happen.'

Gover insists that constant communication has enabled the difficult job to hit targets. Discussion with the Health & Safety Executive from a very early stage has allowed the contract to avoid some of the unexpected last minute changes visible on other parts of the project.

He accepts that recent industrial action by the electricians has had a negative effect on the project but insists that arrangements now in place mean that work is back on track. However he is unable to shed any light on how much Drake & Scull is paying or being paid to get on with the job.

'My responsibility is to get the production right - I have absolutely no input on the commercial side,' he insists.

Bechtel's arrival, for Gover, has been a positive step for the job. 'Bechtel came in to re-emphasise the commissioning phase and I think that they have achieved that,' he says. 'But we have always had very close working on this contract between all the parties and have run the job on a team basis. Success will always come down to personalities.'

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