The walkway along the Castle emplacement has reopened to pedestrians after repairs to part of the retaining wall.
A 25-metre section has been reconstructed after surface water drainage issues.
The number of gullies has been increased from one to five to better prevent flooding.
Guernsey Ports project manager Joe Armstrong says the walkway had deteriorated significantly in recent years, caused in part by a defective surface water drainage system.
"The capacity of the surface water drainage system has been increased by over 200% with a new, larger diameter pipe installed through the seawall."
Mr Armstrong said the new system has performed well to drain away rainfall and wave overtopping.
“In the past, this would have ponded at the base of the wall and that may well have contributed to the wall’s deteriorating condition."
"The retaining wall was reconstructed on top of a reinforced concrete ground beam, which itself sits on piles driven into bedrock.
“This is a more suitable foundation to what was there before.
"Previously, it was comprised of fill material from the land reclamation project to construct the Castle Emplacement in the mid 19th Century.”
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