This report is a minor update of report 484 (1) published in 2010. The work was undertaken to provide technical input to the five-yearly review (in 2018) of OSPAR’s categories of offshore structures for which derogation from the general prohibition of dumping of disused offshore installations (including leaving wholly or partially in place) may be granted. The report provides a complete synopsis of the global distribution of CBGS and discusses options for disposal of the structures when they come to the end of their operational life. The review takes into account engineering, environmental, safety and cost challenges associated with decommissioning this class of structure.