Major works to the M8 Woodside Viaducts have been delayed once again and are now set to be completed four years behind schedule - further demonstrating the UK's ageing assets plight.
Works started on the complex project in 2021, with the initial end date already pushed back from 2023. However, the work on the busy motorway is now not expected to be fully completed until 2027.
Amey, which is carrying out the project on behalf of Transport Scotland, said it expects the temporary repair to the Woodside Viaduct to have traffic management removed from the Eastbound carriageway in Autumn 2026, with the Westbound carriageway scheduled for the second half of 2027.
Transport Scotland said the contractor faces 'previously unknown challenges at the site, coupled with ongoing work to control previously known risks'.
'Most significantly, an existing sewer, adjacent to the SPT tunnel [Strathclyde Partnership for Transport’s subway tunnels] at the western end of the viaducts, was found to be in a different location than expected. This has slowed progress to the temporary propping in this location and, despite mitigation measures already in place, is impacting the completion of the Westbound viaduct propping,' the national transport agency said.
On top of this, the strengthening of the triangular crossheads which support the viaducts at their western end and the associated propping steelwork have been 'more complicated than anticipated'.
Also, the need to avoid loading the SPT tunnels has introduced 'an unusual level of complexity and has resulted in delays to propping both the Eastbound and Westbound viaducts', Transport Scotland said in a press statement.
Director of major projects at the transport authority, Lawrence Shackman, said: 'Transport Scotland continues to robustly engage with the contractor, Amey, to deliver the work as quickly and safely as possible, whilst keeping the motorway open to the 150,000 vehicles that use it daily.
'Despite facing significant challenges, the project has made substantial progress with temporary props installed at 13 pier locations out of 23. In addition, 10 of the temporary props have been jacked to assist with supporting the carriageway and taking the load.
'The location of the motorway through a busy, built-up city has meant this project has always been technically complex and presented a number of challenges, notwithstanding dealing with 23 supports that all require individual propping designs to take account of the varying column heights, span lengths and widths. The project has been continuously hampered by inaccurate records of utility apparatus as well as the recent discovery of an uncharted sewer buried deep underground leading to delays and additional work.'
The cost range for the project is between £126m and £152m.
The Woodside Viaducts were built between 1969 and 1971, with the westbound carriageway being widened in the 1990s.
A planned refurbishment of the structures in 2021 originally found that the viaduct crossheads were in a worse condition than expected.
Early the following year, it was announced that the job would be completed in November 2023. This date has been subject to a series of delays. Previous issues to cause delays include damage to support beams caused by water ingress and winter salt treatment leading to structural concerns.
