The main pier extension ‘caisson’ has been built in Inchgreen dry-dock on the River Clyde. This unorthodox construction method was chosen to reduce/eliminate any potential negative impact on the routine ferry service running throughout the project. The 4000 tonne concrete and steel structure designed by Wallace Stone Marine Consulting Engineers was built in a period of 12 weeks by RJ McLeod Contractors. This represented a step into the unknown for both the designers and builders with neither company having constructed a caisson before. The emphasis on design was to make the structure float as high as possible to reduce any concern with clearing the dry-dock door on lift off and tow out. Additionally the more freeboard the structure had the better it would behave on the 300 mile voyage to Lochbroom.
Holyhead Towing were contracted to plan and oversee the voyage with the tug Afon Llifon taking the lead and the Stromness based workboat Orcadia bringing up the rear. The 3 vessel convoy followed the inshore route through the Sounds of Islay & Mull before heading through Kylerhea, going under the Skye Bridge on Friday afternoon and arriving in Lochbroom at 6am Saturday. Currently the caisson is berthed on the front of the fishery pier for final fit out before being placed off the end of the ferry pier in mid June. For images of the caisson on its temporary foundation, please click here.