Rail Industry Focus

The station over the Thames

With all the major civil engineering work now done, the team behind the complex Blackfriars rebuild can give themselves a huge pat on the back. The project’s leaders, including Network Rail’s project manager for Blackfriars Rob Lines, and Balfour Beatty Civil Engineering project director Chris Evans, briefed RTM on the challenges they’ve faced to get this far.

Most civils and stations projects on the railways involve working in restricted spaces and dealing with logistical challenges.

But few recent projects can match the Blackfriars upgrade for that sort of complexity, with work being done over the River Thames, over and next to live Tube and national rail lines, and busy roads.

But three years later, as Rob Lines, Network Rail’s project manager for Blackfriars, puts it: “It’s starting to look like the artist’s impressions – it’s really quite magnificent.”

The key parts of the upgrade have been the overhaul of the Underground station, platform widening and extensions to allow frequent Thameslink 12-car running and higher passenger flows, a new station entrance on the south bank of the Thames, and major changes to track alignment, including shifting the through lines from the west side of the bridge to the east.

It has been a 24/7 worksite since early 2009, but now the ‘Thameslink baton’ is being passed over to the London Bridge team – hardly a small project itself, of course.

Passenger benefits

First Capital Connect, which has waited patiently as the work was being done, while dealing with the disruption as it affected passengers, drivers and staff, is thrilled with the results, now that the track is available again at nights and weekends. FCC can run eight-car trains at weekends, increase service frequencies, and offer a better weekend service on the Wimbledon/Sutton loop and for passengers from East Croydon. The station is also now ready to accommodate the full 12-car, 24 train-per-hour Thameslink services from 2018.

FCC’s Roger Perkins said: “Blackfriars is back on the Tube map: that’s made a big, big difference to our customers, and will shorten their journeys. It makes Blackfriars a more attractive proposition as a station to use, and what people are slowly waking up to is the fact we have this new south station. Along with Network Rail, we have started to really push this.

“Commuters love it; immediately, it’s 10 minutes knocked off their walking time to work, if they work south of the river. It’s also really perfect for Bankside: for Shakespeare’s Globe, and, further down the river, the South Bank attractions.”

He said 75,000 passengers used the new southern station entrance in March, double the December 2011 figure. He added: “I’m not sure if we realised it was going to be as popular as it is.”

Looking back

Reflecting on some of the major civil engineering challenges along the way, Chris Evans, project director for Balfour Beatty, spoke first about the need to isolate the live Underground lines at Blackfriars, the Circle and District lines, from the construction site.

This involved a solid steel, 350-tonne Track Protection Structure (TPS), which “effectively put the Underground tracks in a tunnel”, as Evans put it. The structure had to be put in place in 39 separate sections in April 2009, with each part slid along steel beams, because of the small size of the access available from above. Evans said: “It was a ‘steel shield’ completely hiding the railway from us, while we demolished the station.”

Most of the old station was demolished during summer 2009, while the subway connecting platforms 4 and 5 was replaced by a temporary footbridge.

In December 2009, during a major Christmastime track possession, the team undertook the so-called ‘bridge slide’, when the existing bridge was dismantled, removed and replaced with a new prefabricated structure that was slid into place in three days. Everything possible was done before the possession to ensure it went smoothly, with meticulous planning, as the team had only one shot to ensure it was a success – and all the subsequent works depended on it.

Evans said: “With the bridge slide, there was a massive sequence of events that all had to happen concurrently to allow the overall programme to move ahead.

“Originally, the through lines went down the west side of the bridge. When we were finished, they had to go down the east side of the bridge. In the north, there were a number of two-span independent steel beams that supported the railway line. The track was parallel to those bridge beams. In the finished lay-out, the track has to go diagonally across those bridge beams, which meant the bridge beams structurally just could not do it.

“So we had to put in a new trapezoidal bridge deck to accommodate the new track alignment. When we put the deck into place, we hadn’t finished the bridge deck at that stage, so we couldn’t put the track in this alignment. So we slid the bridge deck in, put the track back, in that position, but on the new deck, so that we already had the bridge deck in place, so that when we wanted to switch the track it was there and waiting for us.”

Widening the bridge

In early 2010, the first new rib arches were installed, as part of the widening of the bridge – it was extended 3 metres on its east side, and 6 metres on the west. The team made a virtue of the river access: each 45-tonne rib was delivered by barge, after close consultation with the Port of London Authority, who were “extremely positive and helpful”, Evans said.

Lifting in the arch ribs was a complex engineering challenge, which Evans was closely involved in due to his own experience with marine projects.

It involved a tandem lift from a floating barge – it was “very technical”, as Evans put it.

He added: “Widening the west side of the bridge was quite a challenge, because we had to put a piece of concrete onto the old foundation.

“The cranes would not have anywhere near the capacity to lift the pieces of pre-cast concrete, and casting it in situ would be unrealistic because of the tidal constraints. So, we cast a lump of pre-cast concrete weighing some 38 tonnes, five metres above where it finally needed to be. We made a platform five metres up in the air, suspended it on a steel frame and cables, took the platform away and lowered it down into its final position. That avoided the need for tubular piles in the river.”

The bridge widening on the western side made virtue of the old piers next to the existing bridge, which used to support the St Pauls railway bridge until it was demolished in the 1980s – fortunately a decision was taken at the time, on cost grounds, to leave the piers in place. On the eastern side, new concrete shoes were added to the bases of the existing piers.

Even more milestones

In July 2010, the first section of the new roof spine was installed. It is supported 5.8 metres above the deck level, on columns – it couldn’t be any higher for planning reasons regarding unobstructed views of St Paul’s.

Then in Christmas 2010 came the next key milestone: the track switch. Moving the tracks from the west side of the bridge to the east during the six-day blockade allowed the west side bridge deck to be replaced.

Another major logistical exercise was removing the massive truss that used to support the outside edge of what was platform 5. Concurrent road, rail and river span possessions/closures were required to lift the truss out.

In April 2011, the new escalators were delivered to the station as single units, and the roof trusses were installed, while the removal of the TPS was planned for the same months. A full Underground and road possession had been planned far in advance: but then with two months to go, the project team was told it had lost the road closure, due to the Royal Wedding happening the same weekend. It required quite the lobbying effort to ensure the removal could still go ahead, Evans said.

The south station opened in December and the Underground station reopened in February 2012, able to accommodate more than 40,000 passengers a day.

The major engineering works and nearconstant weekend/evening blockades finished in May, when the new bay platforms opened. FCC’s improved services began running from May 19.

Some bridge works have been carrying on and will do after the Olympics, but none of these will impact passengers: these include painting the underside of the bridge, for example.

The solar panel array on the station roof across the Thames, as explained in the last edition of RTM, will be switched on this summer, providing half of the station’s energy needs.

The works over the last three and a half years have happened on time, though have dug into the Thameslink contingency budget. Network Rail spokesman David Wilson said: “The Thameslink programme is running totally on budget; Blackfriars is using some contingency from Thameslink – it’s an immensely complicated project and we’ve come up against difficulties.”

Tell us what you think – have your say below, or email us directly at [email protected]