THE cables holding up the M48 Severn Bridge are to be opened up for inspection next month as part of work which will see closures put in place on the crossing for eight months.

The work, undertaken by National Highways, is being carried out to monitor corrosion. 

The government-owned company, with its contractors Amey and VolkerLaser, will be inspecting several sections of the two main suspension cables as part of routine investigations to ensure the bridge remains safe for years to come.

To carry out the cable inspections safely, long-term lane closures will be put in place. 

The inspection work will involve the closure of one lane westbound from June 22 and one eastbound from the start of July.

The works are scheduled to last for around eight months.

During the period of lane closures, vehicles of more than 2.9m wide will be prohibited from using the bridge.

The bridge will also be closed totally over three weekends to enable the lifting of inspection gantries to a high level on the suspension cable.

The first full closure is planned for the weekend of June 25 – 26, with motorists being diverted across the M4 Prince of Wales Bridge.


What will the inspection work consist of?

One of the UK’s only parallel strand bridges, there are very small spaces between the 5mm wires that form the bridge cable - these spaces can allow moisture to enter which can then cause corrosion. 

The 511mm diameter main cables are opened up and inspected every five years.

Carried out in three phases, inspections will be focused on the lower central area of the suspended cable midway along the 988m-long main span of the bridge.

Cables are also being checked at the upper levels using two specially designed gantries which will need to be installed using a crane during a full closure of the bridge.

The inspection involves stripping back the cables’ protective sheaths, before removing the original red lead paint to expose the high tensile steel strands which make up the overall main cable. 

Wedges are then hammered into the centre of the cable at eight points around the circumference to separate the strands, enabling the team to inspect the surface for damage and corrosion. 

Chris Pope, project manager for National Highways, said: “Built more than 55 years ago, the M48 is a crucial route across the River Severn and it is imperative we maintain it long into the future.  

“The inspections are vital to allow us to understand the current condition of the suspension cables and confirm the measures that we implemented over the last 15 years have been effective in ensuring the long-term viability of the bridge and the safety of its users. 

“We understand this work may cause some inconvenience and disruption, but we will make every effort to ensure the impact on drivers is kept to a minimum.  

“We are working in conjunction with the Welsh Government and its South Wales Trunk Road Agency to ensure minimum disruption during the closures, and avoiding any major events on either side of the bridge.” 

To minimise any future disruption, maintenance work will also be undertaken during the closures.

This will include:

  • refurbishment and maintenance of expansion joints
  • carriageway surfacing repairs
  • reinstatement of some under bridge gantry bogies and wheels
  • sweeping and litter picking
  • blasting and painting of parapets and lighting column bases
  • weld repairs
  • carriageway inspections
  • gulley and drain cleaning

Scott Millar, Account Director at Amey, said: “The M48 Severn Bridge is an impressive structure requiring our dedicated team of experts to continually inspect and maintain all of its components.  

“This is complex and essential work that will guarantee the long-term integrity of the cables.” 

Over the last 15 years, National Highways have introduced a number of preventative measures to protect the cables, including weight restrictions on lane two in both directions, acoustic monitors to identify any wire breaks and dehumidification on the cables.