Salerie car park is closed this weekend while surveyors look at what is going on beneath the surface.
The busy car park, which is often used by people living and working in Town, sits on land that was reclaimed from the sea in the late 1980s.
It is thought, over time some of the fill material used to form the car park has been hit by waves causing sunken areas on the surface, which are prone to flooding.
Localised repairs on the surface have been carried out previously in an attempt to tackle the issue, but a survey team is now looking a bit deeper using a ground penetrating radar.
Pictured: The car park is built on land reclaimed from the sea.
The findings will be used alongside a topographical survey of the surface, which was carried out in September last year. It provided a snapshot of the car park to assess the extent of any changes and is being used to monitor reports of subsidence.
"The sub-surface survey being carried out this weekend will supplement the topographical survey carried out last year," said Ports Commercial Manager Doug Wright. "The results should provide a detailed picture of what is going on beneath the car park, to help determine what repairs or additional investigations are required."
The car park is closed until 20:00 on Sunday.
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