Thanet Offshore Windfarm – Export Cable Repair
Briggs Marine commenced working on shallow water repair solutions in association with Balfour Beatty T&D. A Briggs survey vessel Solent Guardian was mobilised to site to conduct fault finding and depth of burial assessments to inform the engineering process; enabling a final repair design solution to be formed.
The Solent Guardian located the fault in the inter-tidal zone in the immediate proximity of the inter-tidal joint, an area that was too shallow to work through a 24 hour tidal cycle. This location identification informed the vessel selection for conducting a cable repair.
The Briggs shallow water construction vessel Forth Guardsman was mobilised to site with Briggs divers, de-burial and diamond wire cutting equipment. The team located and cut the cable some three meters deep and prepared the ends whilst the main repair vessel commenced mobilisaiton.
In parallel, the engineering teams scoured the market for a suitable repair platform that could sustain the rigors of grounding on each low tide, accommodate the Briggs cable repair spread, reel of strategic spare cable, personnel and burial tool. The team selected Pontra Maris as a suitable platform with a six-point mooring system and sufficient deck space to accommodate the engineered spread.
The Briggs team worked around the clock to mobilise Pontra Maris with the modular Briggs cable repair spread in Burntisland within a five-day window, and proceeded to site without delay.
The shallow water nature of this repair placed strict weather operating parameters on the project as dictated from the mechanical cable parameters. A seven-day weather window was required to repair the inter-tidal joint and was conducted by Balfour Beatty T&D jointers.
Once the final joint was deployed the system was immediately protected and buried to two meters by the onboard burial tool.
Scope of Work
- Project documentation construction and Engineering
- Fault location
- Cable cutting & recovery
- Deburial of cable
- Mobilisation of repair vessel
- Recovery of faulted Inter-tidal joint
Both joints were successfully completed and the system re-energised and made available to the OFTO.
The Pontra Maris transited to Briggs cable depot in Burntisland to discharge the strategic spare cable reel and demobilise the barge.