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News - 24/09/14

September breakwater build update

Construction news: The past month has seen CHC’s contractors Boskalis Westminster complete installation of the gravel pre-load on the new breakwater as scheduled, having deposited a total of 51,000m3 to bring the crest of the gravel core up to between 3.7 and 4.4 metres above chart datum.

Five settlement beacons were also installed on the breakwater for on-going monitoring during a four to six week initial resting period prior to the gravel pre-load being reshaped up to 5.0m above chart datum this autumn; the settlement beacons will remain in place until spring 2015.

Boskalis plan to return on 6th October, for approximately two weeks, to reshape the breakwater core using gravel stored on the breakwater sides; this will be achieved using an excavator and a floating spud-legged barge. (STOP PRESS: Boskalis Westminster now plan to resume work on the breakwater on 13th October, weather permitting.)

A consolidation period of eight months will then follow over the winter to allow settlement along the breakwater footprint and strength increase of the subsoil. The placement of rock armour and reshaping of the breakwater to its final profile will take place in 2015.

The breakwater is already proving a popular spot for wildlife, especially birds, as can be seen in a few of our latest photos of the new Cowes breakwater!

Birds on the breakwater gravel core

Navigational information: All vessels and plant associated with the breakwater build have been removed from the Construction Zone for the time being, this has enabled CHC to further reduce the size of the Exclusion Zone as detailed in Cowes Local Notice to Mariners No 26(T) of 2014. The breakwater is now marked with five yellow lights on the gravel core itself, as well as two additional buoys marking the western and eastern ends of the breakwater.

Breakwater cardinal mark

Tidal flow modelling carried out before construction of the breakwater predicted certain changes to the tidal rates and directions within the harbour. Local Notice to Mariners No 25 of 2014 provides the latest observed changes to the tidal system at Mean High Water Springs (4.2m). Tides above MHWS may result in higher tidal flows than predicted. All harbour users should take these tide flows into account when navigating in the harbour. Further detailed tidal flow monitoring will be carried out in November to ascertain precise flow rates and directions.

View of breakwater gravel core looking towards East Cowes