Network Rail has begun a major upgrade of the Severn Tunnel’s overhead power infrastructure in a project designed to improve reliability and reduce maintenance across one of the UK rail network’s most challenging environments.
The programme will see Network Rail and contractor ARQ replace the tunnel’s existing overhead line equipment with a new system specifically engineered to withstand the corrosive conditions created by moisture and saltwater beneath the Severn Estuary.
Stretching 4.35 miles between South Wales and England, the Severn Tunnel has long posed maintenance challenges due to its harsh operating environment. Since electrification, the overhead power system has experienced ongoing corrosion and electrical wear, resulting in increased maintenance requirements and occasional disruption to services.
To address the issue, Network Rail’s Wales and Borders team has developed and trialled a new overhead line system using a single seven kilometre copper contact wire supported by modified bridge arms. The design is intended to eliminate many of the corrosion problems associated with previous infrastructure while improving operational performance.
The technology will now be deployed across the full length of the tunnel in what Network Rail describes as a world first installation at this scale.
Extensive infrastructure renewal programme
The wider programme of works includes replacing 838 bridge arms that support the overhead electrification system and renewing 9,000 metres of overhead wiring within the tunnel.
Additional track, drainage and infrastructure improvements will also be carried out in the Bristol and Patchway areas.
Alongside the tunnel upgrade, Network Rail is progressing railway improvements linked to the new Bristol Brabazon station, being developed on the former Filton airfield site. The station is expected to open later this year and will restore passenger rail services to the Henbury line for the first time since 1964.
Nia Watkins, Regional Asset Manager for Network Rail Wales and Borders, said the project is essential to the long term reliability of the route.
“Running beneath the Severn Estuary, the 4.35 mile Severn Tunnel is one of the most challenging environments on the UK rail network, making this work essential to maintain safe, reliable services and support its long term future,” she said.
“Using an innovative solution developed by our teams at Network Rail, this complex and highly coordinated upgrade is being delivered at a world first scale across the tunnel’s full length, making the railway more resilient and reducing the risk of future disruption for passengers and freight.”
Watkins added that the wider improvements would also support regional connectivity and economic growth.
Passenger disruption during upgrade works
The project will require temporary closures of the railway between Newport and Bristol Parkway, with replacement bus services operating during parts of the work programme.
Marcus Deegan, GWR’s Station Manager at Bristol Parkway, acknowledged the disruption but said the long term benefits would be significant.
“This investment to improve and maintain the Severn Tunnel will make a real difference to the reliability and resilience of the route for many years ahead,” he said.
“The wider work taking place will also allow us to introduce train services to Bristol Brabazon later this year, and in time to Portishead and Pill, reconnecting people to rail and providing a vital economic catalyst across the area.”
GWR said its teams are supporting passengers during the disruption and advised customers to check journeys in advance.
The rail operator’s Growing Places research estimates stations across the South West could contribute £14 billion in economic value and support 238,000 new jobs by 2036.
