There’s always time pressure, isn’t there? It seems to go without saying these days – just a part of modern life and all that. Rail infrastructure projects, complex as they might be, are invariably time constrained and, when those crucial deadlines become threatened by external factors, things can get interesting.

Such was the case during the construction of Blackburn’s new train depot, but it’s said that problems can boost creativity and Network Rail’s main contractor, Buckingham Group Contracting, proved the point. Under plans to improve the railway across the North West, Network Rail is electrifying a number of key routes, including Preston to Blackpool, Manchester to Preston via Bolton and Manchester to Stalybridge. The introduction of electric trains to these routes will require the adaption and enhancement of existing depots. This in turn means the displacement of the existing diesel trains.

Concurrent with this plan, Northern is procuring new Class 195 DMUs, which will allow the withdrawal of its Class 142 and Class 144 Pacer units. Key to the fulfilment of the entire improvement process is the new diesel train depot at Blackburn, which will accommodate the displaced trains and service the new Class 195s.

Tight schedule

To ensure the success of the wider North West Electrification Programme (NWEP), it was crucial that the Blackburn depot scheme met a construction completion date of August 2017 and an entry into service date of November 2017. The Blackpool blockade, forming part of NWEP Phase 3 (Preston to Blackpool electrification), will effectively place the Blackpool diesel train depot off limits. Servicing those trains at Blackburn is, therefore, vital to the successful delivery of NWEP Phase 3.

In addition to this requirement, the rolling stock cascade needs to coincide with a December 2017 timetable change. No pressure then!

Constructed on the site of the disused King Street coal sidings, the six-road depot has been designed for the light maintenance, servicing and stabling of up to thirty diesel train sets. It can also offer additional stabling and servicing facilities in support of the North West Electrification Programme.

A thorough selection process was undertaken prior to choosing the Blackburn site. Already in Network Rail ownership, the adopted location was suitably close to the start/end journey points of the trains that will be stabled there. It also provided sufficient space and an opportunity to develop a neglected urban area.

Experienced

The Blackburn depot project has been delivered by Buckingham Group Contracting (Civils, Rail M&E), acting as the principal contractor, in collaboration with Babcock Rail (signalling) and their respective design consultants Atkins and Arup.

The Buckingham Group’s project team has delivered multiple depots, so lessons learned during these previous projects were embedded into the outline design stage and realised during the detail design and build. Depot flow modelling was used during the design phase, to generate an efficient scheme of operations within the depot whilst at the same time reducing capital expenditure. It was also used to challenge the application of main line standards to the 5mph running operated within the depot.

Enforced delays

The construction programme was planned to commence in July 2016, but prior approval wasn’t granted by Blackburn with Darwen Council until September 2016. Fortunately, the project team was able to identify opportunities that allowed the works programme to be pulled back in line with the target commissioning date and EIS (entry into service) date.

With the construction phase fully underway, Northern announced in January 2017 that it would be acquiring new Class 195 diesel trains. Being built by CAF in Spain from July 2017, these new trains will run as a mixture of two-car and three-car sets. The new depot at Blackburn would therefore need to accept five-car formations.

Because the arrival siding length and the servicing facilities had been designed for four-car units, this necessitated an extensive series of revisions (from four 23-metre cars to five 24-metre cars).

The Class 195 also requires the use of Ad-Blue fuel additive. With construction progressing well on the servicing sidings, the project team had to work collaboratively and quickly to install the necessary storage tank and ducting, at the same time maintaining the existing schedules and budget.

Of course, collaboration between stakeholders is an important feature of all large rail infrastructure schemes these days. For the Blackburn depot project, meeting that vital completion date was always paramount. It was therefore necessary for everyone on site, from the sponsor through to the subcontractors, to be involved in reaching the optimum solutions that would ensure a successful delivery. With design changes and construction activities running in parallel, the challenges of late changes could only be managed through a culture of mutual support and positive attitude.

Efficiency

Blackburn depot is served by a short two-track spur that merges with the existing Down Through siding at Blackburn Bolton Junction. The connecting line swings northwards through almost ninety degrees, passing over the highway at Galligreaves Street on a new precast concrete bridge. Due to restrictions on road closures, the project required a solution that was quick to install and which offered minimal disruption to the public. The bridge design therefore made use of pre-cast, pre-stressed deck beams with integral parapets on pre-cast cills.

Within the depot itself, the six dead-end sidings accommodate a 150-metre long covered fuelling facility, oil and watering systems, carriage cleaning and effluent treatment. Two 40,000 litre aboveground tanks are installed for diesel fuel and there are four 5,000 litre tanks for oils, lubricants and Ad-Blue. The depot also has brick built stores and plant rooms for fuelling and the carriage washer. Accommodation, offices and shunters cabin are of modular construction.

Tested

Earthworks to create new site levels required the removal of 32,000 tonnes of spoil. Previous use of the area as coal sidings had resulted in ground contamination, which required an extensive programme of testing and validation to ensure correct disposal and that on-site construction activities were safe.

The Buckingham Group team also used innovative ground investigation techniques, such as continuous surface wave testing, to determine site-wide ground stiffness profiles. Value engineered solutions were then derived for the track bed and structural foundations.

Two complex drainage systems were installed for the new depot. The surface water drainage system discharges water into a nearby river whilst the foul water system, carrying carriage effluent, discharges to the sewerage system. Both have attenuation tanks, petrol interceptors and hydro-breakers to ensure safe and environmentally friendly discharges.

Slab

Through the fuelling areas and carriage wash facility, use has been made of the Low Vibration Track (LVT) system developed by Sonneville AG. Integrated aprons ensure that all fluids are collected by the special drainage systems. The LVT system consists of reinforced concrete blocks. These are separated from the concrete slab by a specially developed rubber boot that contains a resilient block pad below the concrete block. The elastic support of the blocks by the pads, which are designed especially for each application, gives improved load distribution.

The geographical constrains of the site demanded a complex permanent way design, involving an intricate arrangement of switches and crossings across the site, together with a complete renewal of the tie-in to the existing mainline network.

Precast retaining walls were developed to allow ease of construction whilst also safeguarding the neighbouring land and buildings. These extend to a height of five metres at some parts of the perimeter. Security and safety is provided by three-rail palisade fencing, which also incorporates an anti-burrow strip.

Quiet

Because of its urban location, the project faced challenges to ensure that noise is mitigated during depot operations. Specialised acoustic consultants were used to model future noise levels from trains operating within the depot during the night and to develop measures for reducing the noise levels at various receptors within the vicinity of the site.

One practical solution combines the use of innovative noise absorption material with the security fencing. This reduces noise levels whilst at the same time ensuring minimal visual impact.

The project team also negotiated special operating procedures with the train operators to reduce horn noise within the depot. A trial of this system indicated a reduction in horn soundings from the predicted 200 per week to just two.

Job done

This £28 million multidisciplinary design and build project was delivered on time and under budget and was handed over to Northern in August 2017. Following Northern’s operational learning period, entry into service will take place in November 2017 as planned. The project staff has totalled more than 120, with over 58,000 hours worked and zero accidents.

Buckingham Group attributes its excellent safety record to a number of initiatives, including Network Rail’s Close Call System. In addition, a subcontractor safety forum was set up to share lessons learned and allow issues to be raised. Bi-weekly engagement sessions were held for site staff, during which ‘hot topics’ and safety issues could be discussed. Buckingham Group has also led three Network Rail ‘Step to Safety’ events, during which all staff were stood down to discuss specific safety topics.

It is estimated that the project delivered a £4.5 million efficiency improvement when compared to the outline design estimate, including delivering the increased scope within that value. This saving was returned to the funder for use on other enhancement schemes by Network Rail.

A first class depot and stabling facility has been built which provides a safe working environment for the staff, an efficient train operation for the Northern franchise and a first-class legacy for future train stabling in the North.

Thanks to Will Metcalfe of Buckingham Group for his help with this article.

This article was written by Stuart Marsh.


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