The improvements will be carried out primarily at night until February 2018, with the M4 scheduled to be closed between junctions 25A and 26 from 8pm to 6am on up to five nights per week.
Commenting on the essential works, Economy and Infrastructure Secretary Ken Skates said:
“The M4 is of vital importance to the Welsh economy and this maintenance to the Brynglas Tunnels forms part of our ongoing commitment to improving the motorway. The timing of this work is designed to ensure that it’s carried out safely and as quickly as reasonably possible, with minimal possible disruption to road users.
“Whilst such work will always be necessary, it’s clear that improvements to the current M4 alone will not resolve the wider, long term issues surrounding the congestion on the M4 around Newport. I’d like to be very clear that tackling these wider long term issues remains a top priority and I hope to be in a position to make an announcement to this end soon.”
The section of the M4 around Newport was constructed in the 1960s and elements of the tunnels and river bridge now require work to maintain the safety and serviceability of this major artery into Wales. This work is irrespective of, and would complement, any M4 Corridor around Newport project.
The refurbishment of the tunnels is required in order to upgrade the Mechanical and Electrical (M&E) systems, as well as the carriageways, drainage and tunnel linings in order to provide resilience in the tunnel systems for the foreseeable future. Whilst this work is undertaken additional and necessary refurbishment work will be undertaken to the River Usk Bridge and Malpas Viaduct structures, with work generally being undertaken via access from underneath the structures allowing normal trafficking.
Closures on the M4 will primarily be put in place in one direction only, with the Southern Distributor Road in Newport (the A48) being utilised as the dedicated diversion route for all eastbound or westbound traffic. The diversion will be in place between junctions 24 and 28 of the M4, however local traffic will be allowed to travel up to junctions 25a and 26 in order to access local routes. Closure of both bores may be needed to be put in place for a short period of time for safety reasons.