PART of the £30 million upgrade work on the White Hart roundabout will take longer to finish because of big problems discovered beneath the surface.

The roundabout's road could sink unless the entire structure of the base beneath the carriageway is completely re-done.

Surveys carried out before the work began suggested that the road structure needed repairs - but not a full reconstruction - before new surfacing could be laid on top of it.

While Swindon Borough Council's contractor carried out this maintenance, they raised concerns about the condition and strength of the ground under the road following the repairs of several large potholes.

After carrying out more surveys and taking more samples from a section of the junction between Merlin Way and Oxford Road, they realised the road base was in a far worse condition than they thought and actually needed to be reconstructed.

The maintenance should have been finished by the end of this month but the extra work which is now needed will delay completion to some time in autumn, causing more disruption for motorists.

Councillor Gary Sumner said: "We are doing the right thing for the scheme. If they just replaced the carriageway above the sub-section, it would eventually sink.

"We want the road to have a lifespan of 40 years not two. It would not have been popular if we finished a £30m scheme then had to dig it all up again in a few years because it was full of potholes.

"People living in the area will be familiar with the pothole problem and we have been amazed by how deep some of them were, so this needs to be fixed and now is the best time to do it, before the road needs to accommodate thousands of new homes."

During the planning of this complex project, the council says it considered the possibility of more costly repair work being required due to unforeseen issues and set aside some of the budget just in case this sort of situation happened.

It says this means that the reconstruction effort will not increase the overall cost of the £30m scheme.

An exact date for the autumnal end of the maintenance and reconstruction phase is still being determined and will be known once a final detailed design is hashed out.

Motorists will then be able to use the roundabout fully again while the final part of the scheme is worked on, which will create a new northbound sliproad leading onto the A419.

This work has itself previously been delayed due to a combination of pandemic-related problems and other issues involving the obtaining of possessions from Network Rail to build a new bridge over the railway line.

The scheme - scheduled to finish in February - should make the White Hart junction safer, have more space for traffic flowing onto the busy roundabout and mitigate the impact of the New Eastern Villages development which will bring thousands of new neighbours to the area.

The improvements made to sliproads aim to provide safer and faster connections to the M4 and A419.

A total of £29m in external funding has been awarded from the Department of Transport and Local Growth Fund for this scheme. The remaining million pounds will be obtained from developers’ contributions, which is known as Section 106 funding.