Cairn Cross Civil Engineering Limited and Airquick Limited, working in partnership and on behalf of Network Rail and Arriva Trains Wales, have successfully completed the UK’s most advanced carriage wash system.

This multidisciplinary design and build project was awarded to Cairn Cross Civil Engineering through the development of innovation and value engineering. One of the aspects of value engineering that helped Cairn Cross become the preferred contractor was the use of existing assets and minimising the disruption to day-to-day depot operations.

There were many considerations the design team had during the design phase of this project, including passive provision for overhead line electrification and waste water separation to conform with recycling targets.

Airquick carriage wash

The carriage wash installation at Holyhead is unique in that the specification called for a front and rear cab-end cleaning facility that can operate during a single pass of the train through the wash. The cab-end cleaner has to cater for varying stock from a vertical front to a sloped front of varying angles. Added to the complication is the passive provision of an overhead line running through the wash which excluded the option of a gantry type unit.

The carriage wash machine is a single pass unidirectional unit which incorporates 12 full-body-side brushes on pneumatically operated fully retractable C-frames to allow for the varying stock profiles. High-density polyethylene brushes of varying diameter are fitted to each shaft to ensure the profiles of the various carriages are washed efficiently, each being driven by helical worm gear motors with a rotational speed in excess of 200rpm.

The relatively narrow footprint of the wash required the installation to be as compact as possible whilst still achieving the required cleaning standard demanded by Network Rail.

Also featured on the wash is the use of a partial water-reclaim system that recycles the wash water and rinse water for the pre-wet and main wash sprays, thus improving efficiency and conservation of water. The reclaim unit also incorporates biocide injection to minimise the possibility of microbiological growth within the system.

The wash discharges wash/rinse water to an above ground three-stage interceptor, with a total capacity of eight cubic metres, where the settled water is drawn from the third chamber of the interceptor into the recycling plant.

The pre-wet and detergent water is not returned to the recycling plant, it is captured and discharged to a separate drainage system.

Detergent and final rinse water is provided directly from the mains water storage tank to ensure that cleaning standards are met.

Unipart Rail TrackPan

The TrackPan system is a pollution control measure which ensures all contaminants are disposed of or recycled correctly. It can be installed at any location where there is a risk of a spill of diesel, gasoline, chemicals, oils, contaminated water, effluent or any other liquid polluting the underground and surrounding environment.

Custom-fit to the design of the carriage wash shed, this modular system not only assists in the partial water reclaim system but also removes the requirement for the lifting and relaying of existing rail track following a spill, therefore mitigating any disruption to potential depot movements.

The use of GRP material removes any concerns about interactions with OLE. The TrackPan integrated floor mesh provides a flat, even, anti-slip surface within the wash reducing the potential of any slips, trips or falls.


With a design life of 20 years, this robust product is ideal for use in demanding depots. When compared to traditional concrete and steel solutions, it provides Network Rail and the operator with a cost- effective low-maintenance solution for environmental issues relating to contaminant spills, along with providing easier access for rail inspection.

Any requirement to relocate this system is achievable due to its modular design and assembly.

Network Rail

Peter Caulfield, project manager with Network Rail Infrastructure Projects in Wales, said: “It’s been a pleasure working with Cairn Cross Civil Engineering to deliver this multidisciplinary design and build project.

“The new automatic and manual- control carriage wash plant was housed within a clad portal frame building. The scope also included full modernisation of the electrical and water distribution system to ensure recycling and sustainability were considered and achieved.

“The TrackPan system proved to be extremely versatile and provided a great surface within the wash to carry out any maintenance.

The team at Network Rail was impressed with the ease of installation, simplicity of use and maintenance along with overall performance.

“Throughout the project, there has been a proactive ‘can do’ attitude to push the project forward to complete within time and budget with no safety incidents. The project team has engaged in a professional manner with all stakeholders.”

Star Lite Award

During the course of this project, Cairn Cross Civil Engineering was awarded the Star Lite Award for the standard of safety displayed throughout. This was presented to site manager Aaron Morgan who said: “It’s a great achievement for the project team to be awarded with the Star Lite Award. The acknowledgement of all the hard work that the project team has put in to ensure the highest levels of health and safety are met is fantastic”.

Cairn Cross Civil Engineering is delighted to have handed over the UK’s most advanced carriage wash facility to Network Rail and Arriva Trains. Innovation and value engineering are imperative to providing the client with the best possible solution.