The Channel Island’s Civil Engineering Contractor
Quay Lifeline
Alderney's Commercial quay is the island’s lifeline, receiving everything from food to fuel, building materials and vehicles, as well as providing essential berthing for passenger ferries. Without it, islanders would struggle to survive, which is why this vital part of Braye harbour is undergoing a multimillion pound refurbishment.
The old quay has been facing a growing number of problems. Its two main berths measured just 56m and 61m but serviced cargo vessels 57m and 60m long, with the present tanker fleet set to be replaced by vessels measuring 95m in length. Added to that, new port security procedures also brought health and safety requirements for more space, to allow for segregation of freight and passenger operations.
With inadequate mooring security for oil tankers, a hazardous surface for freight movements and water corrosion damage, the quay was nearing the end of its working life. At over 100 years old it was estimated that only five years working life remained.
Work started on refurbishing the quay in May 2008, when local civil engineering firm Geomarine and marine consulting engineers Beckett Rankine began preparing the groundwork. Ian Gilmour, Managing Director of Geomarine described the project as ‘the sort of civil engineering work that we relish, made even more challenging by Alderney’s demanding marine environment’. He added that it was similar to the work that Geomarine undertook constructing Jersey’s North Quay’.
Geomarine’s ongoing Alderney project team includes a 25-strong workforce, including six divers. The work has involved building a new wall around the old quay, using pre-cast concrete blocks. Once complete, the new structure will form an encasement around the existing quay, increasing its length to accommodate the next generation of shipping.
Work began by cleaning off the existing seabed sand down to sound bed-rock, using a barge-mounted dredger, with final, detailed work undertaken by divers. A steel former was then placed on the seabed and filled with concrete up to the level of the underside of the pre-cast concrete blocks. A structural steelwork skeleton was then erected, to offer temporary support to blocks. The blocks were placed in position up to the low water level by the dive team, whilst work above water was undertaken using conventional, land-based construction techniques.
A complete column of blocks was then anchored to the rock using a 75mm diameter bar, passed through the blocks and drilled 8m into the rock. Anchors within the structure were stressed to 120 tonnes and the temporary structural steelwork removed. Finally, the space between the old and new walls was backfilled.
As part of the overall project, it was necessary for Geomarine to produce cement locally; therefore they built a batching facility nearby. The completed quay will use a total of 842 pre-cast concrete blocks, each weighing 12 tonnes, along with 2500 cubic metres of concrete.
Engineering work in Alderney certainly presents a logistical challenge, being twice removed from suppliers in mainland Britain. A combination of delayed shipping and adverse weather demands detailed planning and organisation if the project is to remain on schedule. Mr Gilmour said that flexibility and a robust sense of humour have also proved useful.
Working underwater is never easy; especially in an area that is wide open to North Easterly winds. Despite these complications, the East Quay has now been finished and handed over, with 50 percent of the work on the North Quay complete. Work has now started on the West Quay.
The project has also had its share of excitement. The quay was used to land tons of munitions during WW11, some of which failed to make it ashore. The construction team has made some interesting finds, including an old, unexploded, seven inch, French artillery shell, along with hundreds of rounds of ammunition.
The new Commercial Quay project is set to be completed this month. To keep up-to-date on progress, including views from the Harbourmaster Cam, visit www.alderneyquay.info
