25 metres of the Castle Emplacement walkway will be closed off to the public until early December.
Guernsey Ports began working on the site in July (2023) after it discovered a defective surface water drainage system had damaged the sea wall.
The company said the condition of the section has deteriorated over the years.
A new walkway will be built with reinforced concrete foundations and a new granite wall with improved surface water drainage.
Project Manager Joe Armstrong says good progress is being made:
“The damaged section of the wall has been demolished, reinforced concrete piles have been installed and a reinforced concrete ground beam is currently being constructed.
The reconstruction project has been designed and managed by Guernsey Ports’ Commercial & Infrastructure Team. The works are being undertaken by local contractors following a competitive tender process at a cost of around £400,000."

He says there will be minimal disruption for the public:
"This section of the top walkway is closed off, fortunately, the public can use a section of steps next to the nearby bunker to come down and walk along. The parking wise - that's unaffected. So it's really just the rowing boats that we've had to temporarily move around 50 metres to the west."

Blue Islands cancels upcoming flights as airline ceases trading
Simon Calder: 'To lose one airline is unfortunate, two looks like carelessness'
Guernsey creative David Robilliard awarded Blue Plaque
Guernsey Conservation Volunteers win King's Award
Winners pick up awards for providing Guernsey's best customer service
Guernsey Water unveils £130M plan to transform island infrastructure
St Martin’s Point in Guernsey gets a solar upgrade
Guernsey's Alex Scott won't make England debut against Serbia