Ashleigh Contracts were appointed by Dong Energy and Scottish Renewals to carry out the seabed protection repairs at the D1 offshore Wind Facility in Belfast Harbour.
This 500m long deepwater berthing facility had been utilised to service the construction of the West of Duddon Sands offshore wind farm and the vessels using the berth had included heavy jack-up vessels operating alongside the quay to transfer loads to and from the onshore assembly areas. The heavy jacklegs loadings from the transfer vessels caused depressions to be formed in the quayside scour protection stone. In all up to 14No depressions were formed in the seabed ranging in plan size up to 30m x 12m and up to 2m in depth.
In order to maintain the design depth at the berth and to regularise the seabed profile for future similar vessels using the berth, these individual depressions had to be repaired.
Ashleigh also undertook the airlifting of any deposited silts from within each repair area ahead of repair stone placement. This was undertaken using a specially adapted airlift attachment mounted on the Hitachi ZX650 long reach excavator operating from the spudleg Barge.
Ashleigh Contracts placed approx. 5,000T of repair stone of graded 17kg to 60kg stone into each depression – with placement and levelling being controlled by Prolec PCX 3D GPS machine control guidance. The repair stone was loaded out by long reach excavator from the quayside into a Hopper Bin on the Ashleigh 1 spudleg barge with the Hitachi ZX750 long reach placing the stone into the repair areas.