Oil and gas topsides are colossal offshore structures that can weigh tens of thousands of tonnes, so their safe removal requires specialist equipment and careful planning. Mammoet has been proudly working with Allseas for many years, supporting it to offload some of the world’s biggest topsides from its specialist vessels onto quaysides for disposal. Previously, Mammoet assisted Allseas with the load-in to shore of the Brent, Bravo, Charlie and Delta topsides. In 2025, it managed the skidding of the 15,300-t Heather Alpha and 11,640-t Eider Alpha topsides for decommissioning.