New underground drone images show the cause of a sinkhole that has closed part of Perth city centre.
Council bosses sent the devices beneath Canal Street to get a better idea of the task ahead.
They confirm the sinkhole has opened up following the collapse of a culvert which runs above the historic Perth Town Lade.
The repairs will require a specialist contractor with the skills to work in confined spaces.
They will take some time to find.
And so traffic restrictions have been extended until the end of January 2025.
Perth and Kinross Council says one lane of Canal Street will stay closed “to minimise the risk of further incidents”.
The affected section is between Princes Street and Scott Street.
Sinkhole survey involved drone flights beneath Perth streets
The update is contained in a new briefing note for councillors.
It says the council arranged for a specialist contractor, Panton McLeod, to survey the area around the sinkhole.
The checks went ahead last Wednesday after the hole appeared on December 2.
Three drone flights set off from manholes in Canal Street, close to the defect.
The images they brought back appear to show the rest of the masonry above the old lade is in “generally good condition”.
The briefing note says: “Tayside Contracts have now started the process of procuring a specialist sub-contractor with the required capability and knowledge to carry out the necessary stonework reinstatement using confined space entry and working practices.
“Due to the mobilisation time required for any specialist subcontractor, the works will now most likely take place in January 2025.
“The single lane closure and associated traffic management at Canal Street has been extended until 31 January 2025 to facilitate this.”
Hidden history beneath our feet
The centuries-old Perth Town Lade runs for four-and-a-half miles from the River Almond by Huntingtower, to the River Tay.
It used to power a series of watermills.
And parts of it remain open to the elements.
But long stretches have now been covered over by roads and buildings as Perth has developed over time.
The briefing note says further checks will be carried out on the section from Mill Street and South Methven Street to the outfall to the River Tay at Canal Street.
“This will take place in 2025 once the immediate defect has been repaired,” it adds.
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