'The jetty is in a very exposed section of the harbour, near the mouth of Milford Haven and always catches the worst of the weather. It means we suffer the large ocean swells and high waves when the winds blow. The worst condition is when we have long, widely spaced swells which cause the greatest movement on the barges, ' says project director Mathieu Dechamps.
Last autumn heavy storms stopped work for three weeks.
To make up time and exploit good weather to the full, many operations now run 24 hours a day.
Anchorage and jacking points for every barge must be located carefully to avoid bearing onto the red maerl. Where anchorage has to lie within the coral beds, engineers must liaise with the Countryside Council for Wales to ensure they have minimal impact on the environment.
Making the project even more difficult, small vessels are still allowed to sail between piers, ships are constantly passing close by and there is a well used public path which runs under the jetty near the shoreline.