By any measure, a new main line railway station is a rare commodity. There has been only a handful over the past 20 years, some linked to regional airports. But the south-east has its own, congestion-easing rail-air interchange at Southend Airport – the work of infrastructure engineers Stobart Rail. Situated just a few minutes up the line from Southend Victoria, the new station will play a key part in the airport’s evolution from a sleepy general aviation base into a busy east-of-London terminal, ready to exploit the influx of visitors expected for the 2012 Olympics.
The vision to develop Southend Airport came from the Stobart Group itself – better known as Britain’s most recognised truck operator but, in reality, a diversified transport company with a well-established rail division, Stobart Rail. “We’ve been working with Network Rail and other rail engineering clients for some years” says the firm’s managing director Kirk Taylor, “but Southend Airport Station is our biggest project yet – a complete design and build from the ground up, with very intricate working conditions on a busy commuter line into London.”
A 40-minute train ride from Stratford’s Olympic Stadium on the line into Liverpool Street, Southend Airport is expected to be handling one million passengers a year soon after opening in 2012, with that figure doubling by 2020. Hence the need for a new station to cope with the one in five passengers expected to take the train into the capital and the Games’ venues, making the station an integral function of the airport.
Stobart Group took control of Southend Airport in the December of 2008, immediately developing ambitious expansion plans including the new rail station and car park, terminal building, air traffic control tower and a 300m runway extension. It has delivered rail infrastructure works through its Stobart Rail division since 1998, completing dozens of major schemes. Typical projects delivered have been bridge reconstructions and refurbishments including track-off, track-on p-way works, track slab installations of both Rheda 2000 and Pandrol Vipa systems which reduce tolerance on the track construction, enabling lines to accommodate larger gauge rolling stock. These and many other projects are precision engineered and have been carried out on major routes throughout the United Kingdom.
“Stobart Rail specialises in time-critical works where minimising disruption to services and delivering a high quality job are vital” says Kirk Taylor. The Southend Airport interchange falls into this category. “This project has enabled us to demonstrate Stobart Rail at its best, delivering a multi-disciplined scheme utilising in-house resource across a broad spectrum of activities.” Speed has certainly characterised the project, with designs commissioned by Atkins Global, smoothed through the planning process and built in just 23 months, all for £12.5 million.
The company plunged into the planning process with the local council as soon as it took control of the airport, knowing that seamlessly integrating the air and rail operations was vital. Hand luggage-only plane passengers should be on the station platform just 15 minutes after touchdown. A high quality design was agreed, featuring metal-clad buildings with an enclosed high-level walkway to link the west and eastbound platforms. “It’s a quality design that pleased the planners and we’ve carried that quality through into the build,” says Taylor.
Stobart consulted with the Southend line’s operator National Express to ensure the finished station would meet with the operational requirements of all the other stations along the route. Additionally the company met with the Office of Rail Regulation as it was the intention to apply for a licence to operate a main line station. The Group Board decided it would prefer to operate the station in-house as it would give greater opportunity to control customer care and satisfaction.
To the casual observer, the bridge and platforms are the obvious signs that Southend Airport has a new station. But the invisible ground works and construction preparations absorbed a great deal of time, resources and planning.
All that started in January 2009 with multiple regulatory site surveys, including unexploded ordnance (none unearthed), archaeology (Iron Age fire pits logged and recorded) and wildlife (150 slow-worms, lizards and rare spiders found and relocated). “The whole of the site footprint had to be fenced off so that specialist contractors could check the wildlife over a three-week period at the start of the build in early 2009,” says project manager Stephen Harker.
Then, before construction of the twin 250m platforms could begin, Stobart had to straighten and level the tracks to ensure the carriages and platforms lined-up correctly, and the platform surfaces were perfectly level to meet Network Rail standards. “It sounds like a simple job but one of our most complex engineering tasks was to realign the tracks to ensure they were co-planar,” recalls Harker.
Procurement of the tamper to align the track could not be made until after the platforms were constructed which differs from normal procedure. Inevitably this would have meant either a two month delay or laser profiling to de-risk the chance of being out of tolerance. Given the tight project timeline, the company couldn’t afford any mistakes so they brought in a laser-levelling machine to perform a gauging analysis and check the kinematic envelope of trains as they passed through the station. “Expensive but essential if we wanted to stay on schedule” insists Harker. To get parallel and co-planar tracks involved Stobart carrying out slews of 125mm and lifts of 75mm.
Built to Network Rail’s latest standards and containing 6,000 building blocks, the coping stones were laid to an accuracy of +5mm and -15mm. All the platform foundations, blockwork, oversailers and brickwork were constructed while trains were running at their usual 20-minute intervals, although much of the key work was scheduled for overnight periods when services stopped and possessions could be taken.
Construction gangs worked a 12-hour day shift, with safety enhanced by an Automatic Track Warning System which gave a 30-second warning of an approaching train. The night shift was shorter at eight hours, but was uninterrupted by the passenger service. “The platform build is traditional but the pressure on time when only limited windows of opportunity are given always presents a challenge” says Harker.
Speedy action was needed on both the realignment and platform build because Stobart’s timetable had no slack in it for booking service disruptions with Network Rail and the line’s operator National Express. “If we’d booked disruptive possessions, the lead time would probably have pushed the project back 12 months and affected the whole redevelopment plan for the airport,” asserts Taylor. So Stobart piggy-backed on other contractors’ possessions which required steely discipline to finish tasks on time. Even the replacement of overhead line equipment (OLE) was completed without booking a disruptive possession. “It piled on the pressure but we got it done” Harker recollects.
As well as these precision activities, there was much earth-moving to be done, with new embankments constructed for each platform requiring 10,000 tonnes of hardcore and earth. Around half of that material came from waste concrete already on site – this was reused to keep local truck movements to a minimum. “Hardly any material has gone off site” says Taylor proudly. “We’ve really minimised waste to landfill.”
When the track was realigned, the OLE also had to be repositioned to match the track and fit around the platforms. Sensibly Stobart retained the existing catenary wiring where possible but installed seven new steel portal structures, complete with concrete foundations, stove pipes, contact and catenary supports with associated wiring and registration equipment. As part of the works, nine existing structures were removed. Among the technical challenges was the electrification equipment’s unusual configuration which is unique to the Southend-Liverpool Street line – a legacy of being one of the first in the UK to be electrified.
Once the platforms, track and OLE hardware were in place, Stobart turned its attention to the station, installing the overhead walkway linking the eastbound platform to the entrance and concourse on the other side of the railway. To simplify the task, all the services to and from the platform were routed under the tracks. That kept the footbridge free of electrical wiring and plumbing etc, therefore there was no reliance on any service feeds should the bridge installation fail. The bridge superstructure was 90% clad before installation so there was no need for contractors to work above the line and therefore no safety-related service disruptions to slow down the construction process.
Steelwork for the walkway was supplied by a British firm and trucked to site as a kit of assemblies to be bolted into a finished structure. Once again, the installation programme left no room for mistakes or serious snags. “There was no Plan B for craning the footbridge into place” grimaces Taylor. “We had a six-hour possession window and no chance for anything to go wrong.” The next available opportunity would be at a minimum of 12 weeks later – a delay that once again would have put a major spanner in the redevelopment works for the airport. To minimise the risk Stobart booked a 500-tonne lifting crane, twice the capacity required for the installation.
Steelwork arrived on site at the beginning of March. The footbridge slotted smoothly into position in the allotted time window and, in doing so, completed the major construction phases of Southend Airport Station. By the end of May, the bridge was fully-clad and waterproofed, with work moving onto the final fit-out.
But there were still dozens of other tasks to be completed including connecting the station to the line’s signalling system. As well as commissioning the driver only operation (DOO) equipment, 12 monitor banks containing up to six flat-screen TFT displays were installed at the 4, 8, and 12-car stops bi-directionally – convenient to see from the driver’s cab – and a communications room festooned with wiring such as broadband links into the BT network. To minimise installation time, all the cables were pre-cut off-site to a plan based on the station’s layout drawings.
“Stobart Rail is all about delivering solutions” says a justifiably satisfied Taylor. “People have come to us for our expertise and this new station project is a clear demonstration of that. We’ve proven we can deliver a complete major project. Now we’re expecting more people to come to us in future for similar schemes.”