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Sector
Rail
Location
Northern Wales
Services
Bridge and Tunnel Structural Inspections
Specialist Access Support
Our partnership with Network Rail
Project overview
XEIAD were appointed by Network Rail as part of the CEFA rail structures examination programme to undertake a Detailed Examination of the bores, portals and shafts of Severn Tunnel.
This also included the confined space entry into the drainage and ventilation headings. Severn Tunnel is a single bore tunnel situated on the Bristol to South Wales Line.
The challenge
The Severn Tunnel is 7,670 yards long and runs beneath the River Severn estuary.
It has a circular arch profile with curved sidewalls and an invert is present throughout. The lining to the arch and sidewalls is in brickwork and the portals are constructed in stone. With the ongoing South Wales electrification works still being completed, this resulted in a lack of normal track access opportunities.
Therefore, the main examination works were planned to be completed during the 2020 Easter blockade which unfortunately coincided with the UK being at the height of the Covid-19 national lockdown, when so many additional and unforeseen restrictions were quickly coming into place. Six shifts had been planned to complete the examination. With the restrictions, it was agreed that two teams of four Engineers working back-to-back would be the most effective approach, leaving some contingency time in the blockade if works overrun.
Welfare and personnel access was also a key factor to consider due to the length of the tunnel, therefore a ‘people carrier’ including welfare facilities was used to move our team in and out of the tunnel to maximise examination time.
The solution
The examination was completed utilising a Road Rail Vehicle (RRV) MEWP to facilitate access to all aspects of the tunnel bore. Due to other works in the vicinity, our access arrangements were meticulously planned alongside several contractors to ensure that the most efficient use of time was achieved.
This resulted in our teams mobilising from both the English and the Welsh ends of the tunnel as well as accessing from the central pumping station at Sudbrook. To maximise the effectiveness of the possession opportunities and to minimise the number of high priority defects arising from the examination, a maintenance team followed our Engineers with their own access to carry out repairs as instructed by our lead Tunnel Engineer (STE6/STE2 with delegated STE1 authority).
Numerous mitigation measures were employed to reduce the risk of Covid-19 transmission – the most effective being the use of Versaflo personal respiratory systems which allowed our examiners to undertake critical examination work within 2m of other staff and contractors.
On completion of the tunnel bore examination, our teams continued with the works completing the inspection of over a dozen other complex assets in and around the Severn Tunnel infrastructure. This included a confined space entry into the many ventilation and drainage headings which run throughout Sudbrook Pumping Station, English Pump Shafts and 14m Shaft.
It’s a credit to our highly skilled, competent, hardworking, and motivated Engineers and Examiners that these works were so successful. Despite working long shifts, over the bank holiday, and during such difficult times, our examinations were carried out to an exceptionally high standard and with no safety issues to report.
The results
Completed detailed examination of bores, portals and shafts, including confined space entry into drainage and ventilation headings, despite challenges of COVID-19 lockdown and limited track access.
- Used Road Rail Vehicle (RRV) MEWP to facilitate access to all aspects of the tunnel bore.
- Co-ordinated with other contractors to ensure efficient use of time.
- Deployed a maintenance team to follow engineers and carry out repairs as instructed.
- Employed numerous mitigation measures to reduce the risk of COVID-19 transmission.
- Completed the works to an exceptionally high standard and with no safety issues to report.
Overall, XEIAD’s work on Severn Tunnel was a success, despite the challenging circumstances. The team was able to complete the detailed examination of the tunnel bore and other complex assets, while also ensuring the safety of their personnel and other contractors.
Key figures
Completed complex examination under challenging conditions.
Completed all work safely and to the highest standards.
Minimised COVID-19 transmission risk.
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