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Modernisation of Bath Spa station

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It’s an exciting time for the rail industry. Network Rail has recently embarked on a £50 billion Railway Upgrade Plan across the national network, designed to address, not only the significant increase in demand that exists today, but also what is projected for the future. There is talk and evidence about a more intelligent railway based on digital technology that will, undoubtedly, slowly transform everything that we do.

In addition, decision-making is being devolved to Route businesses that, it is considered, are better placed to generate effective change which will benefit the customer.

To cater for all this change and re-balancing within the industry, some tough decisions have had to be made. One decision that readers will be aware of is the deferral of electrification for the Great Western main line (GWML) through Bath and Bristol. The Government remains committed to delivering the benefits to passengers of improved services while ensuring maximum value for the taxpayer. Electrification between London Paddington and Cardiff has been prioritised, with Bristol Parkway due to be electrified by December 2018.

As readers will be aware, a significant amount of engineering work has already been completed over the last few years, including the track lowering and renewal throughout the length of Box Tunnel and similar work alongside the Grade II Georgian gardens, known as Sydney Gardens, close to the station.

Focus on Bath Spa station

Extensive upgrade work has been focused on Bath Spa Station, with the core of the work being carried out during a possession from 8 to 23 April – a period of 16 days. Mike Jones was the Network Rail project manager for the work and he explained how this carefully planned and important part of the overall project was carried out in and around a Grade ll* listed building in the Georgian city of Bath, a UNESCO World Heritage Site.

Mike pointed out that this possession was in fact the third TPOD (Temporary Period of Disruption) in the area and, as with the previous planned TPODs, Network Rail was determined to maximise the use of the period available, given that the team had devoted more than 18 months to negotiate and finalise the arrangements with the affected TOCs involved. In summary, TPODs are very expensive and, as always, the cost needs to be justified.

The Easter 2017 TPOD started at 01:30 on 8 April, with hand back at 05:30 on 23 April as planned. However, just to make life a little more exciting, one line remained open to traffic on weekdays over the two-week period. ‘No train’ periods were confined to the weekends and bank holidays to reduce the impact on the travelling public. In total, there were 62 different work sites in operation within the possession and a total of 37 engineering trains used.

Careful preparation

Nearly 70,000 hours were worked and 879 workers had to be inducted before the start of the project. Network Rail took great care to minimise extra traffic through the city and disruption as a result of the works, setting up a staff compound at the old Gas Works site with staff commuting to the works by minibus. The site included welfare facilities but, because the station area would have over 150 people working there at any one time, additional welfare facilities were set up on land adjacent to the station.

Being a Grade ll* listed building, the work at the station itself required a considerable amount of forethought. Architectural consultant Acanthus, along with Tony Gee & Partners, developed a package of work that required approval from English Heritage, Bath & North East Somerset Council and Historic England. The challenge was to produce a design that would slightly straighten the curve running through the station to increase platform capacity and reduce the stepping distances between trains and the platform. The design needed to be future proof, preparing the way for the installation of overhead electric cables at a later date, and doing so in a way that ensured sufficient distance between the cables and the listed station canopies to be compliant with regulations.

Protecting our heritage

Fortunately, there is a very generous gap between the two tracks that pass through the station, so it was decided to exploit this space, increasing the width of Platform 1 to Bristol by up to 1.2 metres and the Up platform to London by up to 1.8 metres. This solution not only added capacity to the station platforms to reduce overcrowding in the face of growing passenger numbers, but also meant it will be possible to place single stanchions down the middle of the realigned tracks in the future. As a result, when it comes to electrification through Bath Spa, the platform canopies can remain untouched.

Of course, this design meets the compliance requirements for the live wires but, as it worked to preserve Bath’s heritage as well, the controlling bodies were able to agree Listed Building Consent for the work.

Hochtief UK Construction was assigned as the principal contractor for the work. The majority of the platforms are supported on a brick viaduct, so ground investigation work started nine months before the April start date. Producing a design that kept any additional loading to a minimum was imperative and the solution adopted used a high-density polystyrene new front wall for the platforms. It is a design that has recently been used by Network Rail at Peterborough, Cambridge North and Abergele stations.

MegaTech Projects was employed as a specialist supplier to construct the polystyrene wall. Following the profile of the widened platforms, a compacted 50mm thick sand bed was laid. The polystyrene units, approximately 400mm wide, were placed on the sand with precast concrete coping stones placed on top, bridging back to the original platform. To maintain the look of the station, the polystyrene was faced with brickwork to reproduce the existing features. The platforms were then resurfaced.

Lightweight design

The realignment of the two tracks through the station was carried out by Babcock Rail. The design increased the radius, thereby improving the new alignment. In addition, the ballast depth was increased, helping to distribute loading onto the brick arches. This, combined with the widening of the platforms, mean that passengers benefit from a reduction in the stepping distance from train to platform edge by more than 50 per cent.

In May, the Government confirmed that all the new rolling stock ordered for the Great Western line was to be bi-mode, meaning it can run on diesel as well as electric power. The twenty- one Class 801 trains were originally due to be entirely electric, but the change was made in response to the deferral of electrification, as outlined earlier. These trains will be supported by 36 bi-mode Class 800 trains, due to begin operation from 2017-18.

To accommodate these new, longer trains, both platforms will have to be extended at the Bristol end of the station in due course.

A 55-metre cantilevered walkway extension is being designed for Platform 1. This will be integrated into the Grade ll listed Skew Bridge, which spans across the River Avon at a 28 degree angle, hence the name. Further strengthening work will also be required to support the extension to Platform 2, which will involve refurbishing an existing currently disused length of platform using the same approach as for the work on the platforms during the Easter TPOD – installing precast concrete coping stones over polystyrene supports.

Maximising track access

As well as realigning the track through the station, Babcock Rail also used the possession to lower a section of track west of Bath at Newton Rd and Cross Post overbridges, ready for electrification in the future. Colas Rail was brought in to carry out an extensive programme of drainage works at Bathampton Jn, Box Ashley and at Sydney Gardens. Work at Keynsham station was also completed during the two- week period, correcting the gradient (crossfalls) of the platforms and resurfacing them, as well as installing drainage.

If that’s not enough, an aqueduct at Corsham was also demolished by Hochtief UK at the end of the possession and, as you would expect, the local maintenance team are taking every opportunity to carry out detailed inspections, replacing S&C crossings and repair drainage systems throughout the possessions.

A huge amount of work has taken place over the 16 days. Mike has estimated that the value of the work is in the order of £16 million. It is another TPOD and one that has been fully utilised to upgrade the railway in this part of the world, helping to lay the foundations for full electrification of the Great Western main line in the future.

Written by Collin Carr