Client: States of Guernsey Harbour Commission
Contractor: Concrete Repairs Ltd
Duration: 17 weeks
Date posted: 19-01-2015
Following MMC Diving Services appointment by CRL on the first phase of Guernsey Berths works in 2013, 2014 saw the team return to site to carry out and complete the second phase of the commercial works on dock gate 4, to renovate the pier in preparation for the installation of two new cranes.
Due to the local chamber being closed down in the Channel Islands, diving operations were limited to very small windows around the low water tides and the harbor authority would only allow a maximum dive depth to 10 metres. MMC sourced a chamber and supplied chamber operators to maximise the productivity and move the project forward.
MMC cleaned back the steel piles in preparation for the welding with an underwater scrabbler and a needle gun. All prepared steel plate was thickness checked using an underwater thickness gauge (NTD) and then thirty 120 kilo anodes were welded to all the fender piles.
Phase 2 consisted of lowering fifteen 1/2 tonne pile brackets onto the seabed, for wet storage, using lift bags. MMC divers floated the brackets just off the seabed, walked them into position and clamped them in place.
Using underwater breakers the divers had to break away the concrete above the pile clamps to expose the reinforced steel inside the legs; later welding contact brackets connecting the anodes to the reinforced steel and finally filling the break out gap with underwater mortar. Six large anodes were also attached to the crane base.
The final phase of the project for the divers was working on the steel knuckle. After burning off old bolts, cleats and excess metal with underwater Brocco, thirty 120 kilo anodes were welded in place, and the sheet piles were repaired by welding patches on the damaged areas and made good ready for the new fender installation.
All documents were reviewed and audited by Halcrow, an independent global consultant prior to every new task. To ensure the quality of the welds MMC Diving Services has developed a weld procedure through weld trials undertaken in a controlled tank by our divers. Quality Assurance procedures such as a recorded Inspection and a Test Plan have been developed and implemented.