A hole has appeared behind the end of the German wall at the eastern side of L'Ancresse, near the slipway.
The States of Guernsey has fenced the area off, and work will start next week to fill it.
Under the latest States resolution, Environment and Infrastructure are to keep repairing the crumbling World War Two defence work for a number of years.
A £150,000 repair plan was agreed in April.
Members of the public are being asked to avoid the area and not pass the barriers.
Guernsey hedge veg owners inaugural meeting
The Hedge Veg Alliance meet for the first time to discuss how to promote and future proof an island favourite.
Guernsey’s Victor Hugo Centre given planning green light
Plans for a new Victor Hugo Centre in Guernsey have been approved.
Stagnant water to remain at Guernsey park
Cleaning and refurbishing the pond at Saumarez Park is cost prohibitive, at an estimated £100,000.
Bailiwick GCSE pass rate exceeds national average by 4.2%
Guernsey's overall GCSE pass rate is 71.2%, fractionally down on last year.
Date set for new vape tax to take effect in Guernsey
Guernsey will follow Jersey and the UK in introducing an excise duty on vaping products in November 2026.
Guernsey's Castle Cornet to close early for bridge replacement
Parking spaces will be lost or be re-designated as £6.2M project is on track to begin in early September.
Guernsey’s Meet the Pilots organiser retires after 20 years
Gary Elson is going travelling, but hopes the legacy of Meet the Pilots, the event he created, will live on.
Prime Guernsey development opportunity sells for £2,555,000
The site of the former Octopus restaurant was sold on the Local Market and now the price paid has been made public.
