A exclusion zone will be been set up on part of the beach in St Aubin's Bay as drainage work gets underway.
A new surface water pipe and outfall is being created to separate surface water from the sewer system.
The project, by the government's Infrastructure and Environment department, is expected to go on until mid-October.
It includes providing for a new surface water connection to a new hospital at Overdale.
During the works, some some parking in Layby 2 on Victoria Avenue will be suspended, and part of the beach blocked off. Signs and water buoys will be in place, and the public is being asked to observe them.
Cyclists using the promenade might be asked to dismount during some of the work.
Work to clad the outfall with granite will continue after October.
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